FIELD OF THE INVENTION 0001 The present invention relates to a surface position detection apparatus and method, and exposure apparatus and device manufacturing method using said exposure apparatus, and more particularly, in an exposure apparatus, to a surface position detection apparatus and method adapted to detecting a location and a tilt of a surface of a wafer with respect to an optical axis of a projective optical system during exposure scan.

BACKGROUND OF THE INVENTION 0002 As the density of VLSI circuits has increased the circuit patterns themselves continue to be miniaturized. This miniaturization of circuit patterns has in turn engendered higher numerical apertures (NA) for the miniaturized projective lens systems used in semiconductor exposure apparatuses, such that the permissible depth of focus of the lens during the process of transferring the circuit pattern has become shallower. At the same time, the area to be exposed by the miniaturized projective lens system during the manufacture of a semiconductor chip has increased. Given these conflicting trends, there is a growing need for a scanner-type semiconductor exposure apparatus capable of enlarging the exposure area and NA while still using a stepper-type lens equivalent. 0003 In a scanner-type exposure apparatus, a common method used to make a good exposure transfer of a circuit pattern across the entire exposure area involves scanning the wafer surface that is to receive the transfer of the circuit pattern on a reticle (hereinafter sometimes referred to as the focus plane of the wafer surface of the miniaturized projective lens system) so as to detect the position and tilt of the wafer surface and continuously adjusting the position and tilt of the focus plane via an autofocus/auto-leveling correction drive operation so as to continuously present the best possible imaging surface to the projective lens. 0004 There are several commonly known methods of detecting the height of the wafer and the position of the wafer surface (i.e., the position and tilt of the wafer surface described above) in such an arrangement. On commonly known method involves using a detection optical system to direct a beam of light onto the wafer surface at an angle thereto and detect a positional deviation in the reflected light as a positional deviation on a sensor. Another commonly known method involves using a gap sensor, such as an air microsensor or an electrostatic capacitance sensor, to scan a plurality of points on the surface of the wafer and determine the exact position of the wafer surface from that scan. 0005 Further, in the methods described above, in order to position the entire wafer exposure area (also called a shot) securely within the permissible depth of focus of the miniaturizing projective lens systema depth of which, as described above, has become shallower with advances in NAthe whole process is closely controlled so as to avoid the local topography beneath the point of scanning detection (or of light reflection), which can give erroneous readings, by using a plurality of positions within the shots as detection points, comparing the readings at the detection points against an optimum focus setting surface, measuring the difference (if any), and offsetting it. 0006 Use of this sort of measurement offset is accomplished by one of two methods. The first method involves measuring the measurement offset itself using a pilot wafer to manage the job. The second method involves using the first wafer after a change in the wafer production lot to obtain the measurement offset, which is then used to process that lot. 0007 However, the convention apparatuses and methods have several problems, which are detailed below. 0008 The scanning speed of a slit-scan-type exposure apparatus is calculated from the apparatus intensity (that is, the illumination intensity within the exposure slit defined by the masking plate) and the wafer surface resist sensitivity so as to yield a best exposure amount. 0009 The intensity of the apparatus can be controlled by the laser output and the laser oscillation frequency, and is set to make the best exposure amount constant in the face of process discrepancies. Here, the term process discrepancies means the phenomenon in which the best exposure amount fluctuates within the same wafer due to unevenness in the resist coating on the wafer surface or unevenness in the high-speed dispersion furnaces used in the after-process baking of the wafers (wafer surface oxidation). 0010 The scanning speed and the intensity of the apparatus are interrelated, insofar as, for a given wafer surface resist sensitivity, the scanning speed increases when the laser output and the laser oscillation frequency increase. Conversely, the scanning speed decreases when the laser output and the laser oscillation frequency decrease. 0011 In other words, in the conventional art, a fixed scanning speed can be made constant for the same job or the same lot by adjusting the best exposure amount using the laser output and the laser oscillation frequency to account for process discrepancies, with the above-described measurement offset obtained for the pilot wafer or the lead wafer in the production lot used in the processing of that lot. 0012 However, since the scanning speed calculated in such a case becomes the lowest of the speeds among which it is possible to select with respect to the process discrepancies, a problem arises in the throughput. The problem is magnified in the case of DRAMs, which tend to have large individual production lots. 0013 Also, when using low-output laser light sources such as Argon-Fluorine (ArF) lasers and F2 lasers, the intensity of the apparatus is insufficient relative to the scanning speed, which is reduced accordingly. As a result, when attempting to control for the best exposure amount using the laser output and the laser oscillation frequency for the process discrepancies, the lack of scanning speed makes improvements in throughput difficult to achieve. 0014 Moreover, even if the scanning speed is increased in order to improve the throughput, the insufficiency of apparatus intensity relative to the scanning speed make it difficult to control the best exposure amount using the laser output and the laser oscillation frequency in the face of process discrepancies. 0015 One measure used to solve the above-described problem involves controlling the best exposure amount for the process discrepancies by changing the scanning speed with each shot and each wafer, thereby making maximum use of the apparatus intensity. However, the time allotted for the operation of detecting and measuring the position and tilt of the wafer surface while being synchronized with the scanning operation is fixed, so the scan area will vary from shot to shot and wafer to wafer if the scanning speed is changed with each shot and each wafer. 0016 If in such circumstances the above-described conventional control methods are used to carry out the measurement offset described above, the size of the scan area will be different for the measurement offset and the exposure, leading to errors in the measurement offset for the optimum focus setting surface. 0017 Conversely, seeking the measurement offset for each scanning speed, although it does not lead to errors in the measurement offset for the optimum focus setting surface, does reduce throughput drastically due to the great frequency with which opportunities arise to seek the measurement offset.

SUMMARY OF THE INVENTION 0018 Accordingly, the present invention is proposed in order to solve the above-described problems of the conventional art, and has as its object to provide quick and accurate detection of the position and tilt of a wafer surface using a measurement offset even when the scanning speed is changed with each wafer and each shot. 0019 The above-described object of the present invention is achieved by a surface position detection apparatus comprising: 0020 measuring means for measuring a surface position of a measurement area on the surface of an object; 0021 detection means for detecting the surface position of a measuring point provided on the surface of the object using the measuring means while relatively scanning the surface of the object; and 0022 determining means for determining drive parameters of the measuring means according to a speed to be employed in the relative scan of the object surface prior to detection of the surface position with the detection means, such that the measuring area for the measuring point assumes a preset size. 0023 In addition, the above-described object of the present invention is also achieved by a surface position detection method comprising: 0024 a detection step of relatively scanning a surface of an object using measuring means for measuring the surface position of a measurement area on the surface of the object and detecting the surface position of a measuring point provided on the surface of the object; and 0025 a determination step for determining drive parameters of the measuring means according to the speed to be employed in the relative scan of the object surface prior to detection of the surface position with the detection means, such that the measuring area for the measuring point assumes a preset size. 0026 Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS 0027 The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention, in which: 0028 FIG. 1 is a partial schematic diagram illustrating a lateral cross-sectional view of an example of a slit-scanner-type projective exposure apparatus according to one embodiment of the present invention; 0029 FIG. 2 is a diagram illustrating the positions of the exposure slit and the measuring points during surface position detection using a detection optical system; 0030 FIG. 3 is a schematic plan view of the disposition of exposure areas (shots) and a sample shot selection example using pre-scan light adjustment and measuring the surface state within the exposure area; 0031 FIGS. 4A-4C are diagrams illustrating the positions of the shot, slit and measuring points (spots) during scanning/measurement; 0032 FIG. 5 is a diagram illustrating the positions of the shot and the spot at the beginning of scanning/measurement in the present embodiment; 0033 FIGS. 6A and 6B are diagrams showing the change in measured area due to differences in scanning speed; 0034 FIGS. 7A and 7B are diagrams illustrating how the difference in measured area due to differences in scanning speed shown in FIGS. 6A and 6B is absorbed by the measurement time interval; 0035 FIG. 8 is a flow chart showing steps in a measurement offset and a surface position correction drive sequence during exposure at the shots using the surface position detection method according to a first embodiment of the present invention; 0036 FIGS. 9A and 9B are flow charts showing steps in a wafer processing sequence using the surface position detection method according to the first embodiment of the present invention; 0037 FIG. 10 is a flow chart showing steps in a measurement offset and a surface position correction drive sequence during exposure at the shots using the surface position detection method according to a second embodiment of the present invention; 0038 FIG. 11 is a partial schematic diagram showing an example of a slit-scan-type projective exposure apparatus using an electrostatic capacitance in surface position detection; 0039 FIG. 12 is a flow chart showing steps in a measurement offset and a surface position correction drive sequence during exposure at the shots using the surface position detection method according to a third embodiment of the present invention; 0040 FIG. 13 is a flow chart illustrating the surface position detection method according to a fourth embodiment of the present invention; 0041 FIG. 14 is a flow chart showing steps in the process of manufacturing a semiconductor device; and 0042 FIG. 15 is a flow chart showing details of the wafer processing operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 0043 Preferred embodiments of the present invention will be described in detail in accordance with the accompanying drawings. 0044 First Embodiment 0045 FIG. 1 is a partial schematic diagram illustrating a lateral cross-sectional view of an example of a slit-scanner-type projective exposure apparatus according to one embodiment of the present invention. 0046 In FIG. 1, reference numeral 1 denotes a miniaturized projective lens system, in which the dot-and-dash line AX indicates the axis of light. The image surface lies perpendicular to the Z-axis of the diagram. Reference numeral 2 denotes a reticle and reference numeral 3 denotes a reticle stage. The reticle 2 is retained atop the reticle stage 3. A pattern on the reticle is reduced to from to or its original size by the scaling of the miniaturized projective lens system and projected onto the image surface, where it forms an image. 0047 Reference numeral 4 denotes a wafer that is coated with a resist, on which a multiplicity of exposure areas (shots) having an identical pattern structure that formed in the exposure step described above are aligned. Reference numeral 5 denotes a stage on which a wafer is placed, the stage 5 consisting of a chuck that suctionally fixes the wafer 4 to the stage 5, an X-Y stage capable of horizontal movement in the direction of the X axis and the direction of the Y axis, a leveling stage capable of movement in the direction of a Z axis that is the optical axis (AX) of projective lens 1 as well rotation about the X axis and Y axis, and a rotary stage capable of rotating about the Z axis. All together, the stage 5 forms a 6-axis correction system for focusing the reticle pattern image onto the wafer. 0048 Reference numerals 10-19 in FIG. 1 denote various constituent elements of a detection optical system of the surface position detection apparatus, provided in order to detect a surface position and tilt of the wafer. Reference numeral 10 denotes a light source, which consists of an illumination unit configured so as to direct light from either a white lamp or a high-intensity LED having a plurality of different peak wavelengths. Reference numeral 11 denotes a collimator lens, which projects beams of light from the light source 10 as parallel beams of light having a substantially uniform cross-sectional intensity distribution. Reference numeral 12 denotes a prism-like slit member, in which the tilted surfaces of a pair of prisms are glued together, with a plurality of apertures (in the present embodiment, nine pin-holes) provided on the glued-together surfaces using a light shielding membrane. The light shielding membrane may be chrome. 0049 Reference numeral 13 denotes a double side telecentric optical system, in which the nine separate beams of light passing through the plurality of pin-holes in the slit member 12 are directed onto nine different measuring points on the surface of the wafer 4. Although FIG. 1 shows only three of the beams of light, each beam of light has three beams of its own, in a direction perpendicular to the surface of the paper. The plane in which the pin-holes are formed and a plane that includes the surface of the wafer 4 are arranged so as to satisfy Scheinmpflug's condition with respect to the optical system. The projector portion of the surface position detection apparatus includes the parts denoted by the foregoing reference numerals 10-14. 0050 FIG. 2 is a diagram illustrating the positions of the exposure slit and the measuring points during surface position detection using a detection optical system. FIG. 3 is a schematic plan view of the disposition of exposure areas (shots) and a sample shot selection example using pre-scan light adjustment and measuring the surface state within the exposure area. 0051 In the present embodiment, the angle of incidence at which the beams of light are directed onto the surface of the wafer 4 from the projector portion (angle between perpendicular line set up on wafer surface (optical axis) and beams of light) is at least 70. As shown in FIG. 3, a plurality of exposure areas (shots) having the same pattern structure is arranged on the surface of the wafer 4 (shown in FIG. 3 as rectangles). The nine beams of light that have passed through the lens system 13 are directed and focused onto mutually independent measuring points of a pattern area like that shown in FIG. 2. (It should be noted that FIG. 2 shows only six of the nine beams of light referred to in the present embodiment, the remaining three beams of light being omitted solely for the sake of simplicity in description.) Also, the nine measuring points are illuminated by the beams of light striking them from a direction rotated away from the X axis (that is, scanning direction 5a) in the X-Y plane by (in this example, 22.5) so as to be mutually independent and observable. 0052 Returning once more to FIG. 1, a description is given of the detection of the beams of light reflected from the wafer 4, that is, of a sensing part composed of assemblies 15-19. 0053 Reference numeral 16 denotes a sensor optical system of a double side telecentric system, which senses the nine beams of light reflected from the surface of the wafer 4 via a mirror 15. A stopper aperture 17 provided within the sensor optical system 16 is common to all nine measuring points, and cuts out high-diffraction light (that is, noise light) generated by the circuit pattern existing on the wafer 4. The axes of the beams of light that pass through the sensor optical system 16 of the double side telecentric system are mutually parallel and are focused onto to a sensor surface of photoelectric converter assembly 19 by nine separate lenses of a correction optical system assembly 18 so as to form nine separate spotlights of identical size. 0054 Parts 16-18 of the sensor described above correct the relative tilt of the measuring points on the surface of the wafer 4 and the sensor surface of the photoelectric converter assembly 19 so that the two are in conjunction. Such tilt correction eliminates fluctuations in the position of the pin-hole image at the sensor surface caused by localized tilting at the measuring points, so that the pin-hole image changes at the sensor surface in response only to changes in the height along the axis of light AX of the measuring points. 0055 In the present embodiment, the photoelectric converter assembly 19 is composed of, for example, nine one-dimensional CCD line sensors. As can be appreciated by those of ordinary skill in the art, however, the same effects of the present invention as described above can be achieved using instead a plurality of two-dimensional position detectors for the photoelectric converter assembly 19. 0056 Next, a description is given of the slit-scan type of exposure system, with reference once again to FIG. 1. 0057 After the reticle 2 shown in FIG. 1 is suctionally attached to the reticle stage 3, the apparatus is correctively driven so as to scan within a plane positioned perpendicular to the axis of light AX of the projective lens 1, in a direction indicated in FIG. 1 by arrow 3a (that is, along the X axis) as well as in a direction perpendicular to arrow 3a (that is, along the Y axis, i.e., in a direction perpendicular to the surface of the paper) at a constant speed, so as constantly to maintain a target coordinate position. 0058 The position of the reticle stage along the X axis and Y axis is constantly measured by directing a plurality of laser beams onto an XY bar mirror 20 fixedly mounted on the reticle stage as shown in FIG. 1. 0059 An exposure illumination optical system 6 uses a light source that generates pulses of light such as an excimer laser, and is composed of at least a beam alignment optical system, an optical integrator, a collimator and a mirror (none of which is shown in the diagram). These members are made of materials which efficiently transmits or reflects the pulse light of the far ultraviolet region. The beam alignment optical system corrects the cross-sectional shape and dimensions of the emitted beams of light to a desired shape and dimensions. The optical integrator equalizes the distribution of luminous intensity of the beams of light so that the reticle 2 is illuminated with uniform illuminance. 0060 A masking blade inside the exposure illumination optical system 6 that is not shown in the diagram sets a rectangular illumination area according to the chip size. A pattern on the reticle 2 that is partially illuminated by this illumination area is projected by the projective lens 1 onto the wafer 4, which is coated with a resist. 0061 A main control unit 27, shown in FIG. 1, exerts overall control of the apparatus, that is, it both synchronizes the reticle 2 and the wafer 4 with the projective optical system as well as projectively exposes the pattern on the reticle 2 onto the wafer 4 through a reductive projective optical system 1, while adjusting the position of the slit image of the reticle 2 within a particular area of the wafer 4 in the X-Y plane (that is, the X, Y position and the angle of rotation _ around the Z-axis) and along the Z-axis (i.e., the angles of rotation _, _ around the X-axis and the Y-axis, as well as the height along the Z-axis). 0062 More particularly, the alignment or positioning of the pattern on the reticle 2 within the X-Y plane is executed by first obtaining position data readings from a reticle interferometer 21 and a wafer stage interferometer 24, as well as position data on the wafer 4 from an alignment microscope not shown in the diagram. The various position data so obtained is then used to calculating control data with which to control a reticle position control system 22 and a wafer position control system 25. 0063 When scanning the reticle stage 3 in the direction indicated by arrow 3a in FIG. 1, the wafer stage 5 is scanned with a speed that is corrected in the direction of arrow 5a in FIG. 1 by an amount equal to the reduction rate of the projective lens. The scanning speed of the reticle stage 3 is set to achieve the best throughput possible, given the width of the masking blade inside the exposure illumination optical system 6 (not shown in the diagram) in the direction of the scan and the sensitivity of the resist that coats the surface of the wafer 4. 0064 FIGS. 4A-4C are diagrams illustrating the positions of a shot 41, slit 40 and six measuring points (spots) on the wafer 4 during scanning/measurement. 0065 As shown in the diagram, there are three spots on each side of the exposure slit 40 in the scanning direction, with three more slots not shown in the diagram disposed within the exposure slit 40 for a total of nine spots. The spots inside the exposure slit 40 are used for slit acquisition measurement. The height of the wafer (i.e., its location on the Z-axis) is measured at a plurality of measuring points (M0, M1, M2, . . . ) in the scanning direction at each spot, in the three channels composed of spots CR1, CR2 and CR3 when the wafer 4 is scanned from right to left as shown in the diagram (in this case the slit 40 scans from left to right), and in the three channels composed of spots CL1, CL2 and CL3 when scanning the wafer 4 from left to right. 0066 The measurements so obtained are then further used as data for focus correction when scanning the wafer 4 further proceeds and the measuring points come to the center of the exposure slit 40. In other words, focus correction is performed by pre-reading focus measurements at measuring points ahead of scanning. 0067 FIG. 5 is a diagram illustrating the positions of the shot and the spot at the beginning of scanning/measurement, that is, of the spots CR1, CR2 and CR3 at a time T0 in the present embodiment. 0068 FIGS. 6A and 6B are diagrams showing the change in measured area due to differences in scanning speed, that is, scanned and measured areas L11, L21, L31 and L12, L22, L32 that the spots CR1, CR2 and CR3 scan and measure during a certain time interval (from T0 to T1) at different scanning speeds S1 and S2. Since the scanning speeds are different (i.e., S1>S2), the measured areas are also different as shown in the diagram. 0069 FIGS. 7A and 7B are diagrams illustrating how the difference in measured area due to differences in scanning speed shown in FIGS. 6A and 6B is absorbed by the measurement time interval, that is, how identical positions (that is, measurement areas of the same size at the same position) of the measurement areas to be scanned and measured by the spots CR1, CR2 and CR3 can be maintained by changing the measurement starting time T0 and the measurement ending times T1, T2 in accordance with the scanning speed. As can be readily appreciated by those of ordinary skill in the art, the measurement starting time T0 is recalculated for each shot in accordance with the scanning speed so that the measurement area is always at the same position. 0070 The wafer position control system 25 positions the pattern on the reticle along the Z-axis (that is, aligns it with the image surface) by controlling the leveling stage inside the wafer stage based on calculation results performed by a surface position detection controller 26 for detecting the height of the wafer 4. In other words, the wafer position control system 25 calculates the tilt of the wafer in a direction perpendicular to the scanning direction and its height along the axis of light AX using height data from the three spotlights (CR1-3 or CL1-3) disposed near the slit in the scanning direction and used to measure the height of the wafer, determine the amount of correction to the optimum image surface position at the exposure position, and corrects accordingly. 0071 In the exposure apparatus shown in FIG. 1, prior to exposing the wafer, the wafer is pre-scanned at a sample shot (that is, a shot 31 with the diagonal lines shown in FIG. 3) under a constant illuminance by the light source 10 to obtain light adjustment data by sensing the reflected light at the detection points with the photoelectric converter assembly 19. The light adjustment data may be signal peaks, for example. The photoelectric converter assembly 19 may be a CCD sensor. From the data so obtained, the exposure apparatus then calculates and stores the setting current value needed to attain an optimum peak value for focusing during scan exposure at each measuring point. By driving the light source 10 at this setting current during exposure of the shots, the shots can be illuminated at a setting current suitable for the reflectance at successive measuring points, and the shape of the waveform to be measured can be held constant regardless of the reflectance. It should be noted that, instead of adjusting the lighting using the setting current of the light source 10 as described above, the lighting may be adjusted by adjusting the gain at the photoelectric converter assembly 19. 0072 By determining the optimum lighting and gain at the detection points in advance of scanning/measurement as described above enables the lighting to be adjusted quickly and accurately so as to provide a uniform measurement time interval, during scanning/measurement, with the result that scanning and surface position measurement can be conducted simultaneously, and, accordingly, providing accurate offset correction and precise surface position detection. 0073 Moreover, the above-described exposure apparatus pre-scans measurement offset values for the purpose of correcting differences in focus measurement readings caused by differences in the surface conditions at the detection points, and corrects the measurements at each successively obtained measuring points during exposure of each shot. 0074 In order to detect deviations in the position of the exposure area of the wafer 4 on the Z-axis, that is, the position (Z) and tilt (_,_) with respect to the image surface position, the surface of the wafer 4 must be accurately measured and, at the same time, the relation between the illumination area shape and exposure area pattern structure (actual topography) must be carefully considered. 0075 Using an optical detection system to achieve the former goal, that is, the object of accurately measuring the surface of the wafer 4, requires considering the detection margin of error factor caused by the effects of interference between the light reflected form the surface of the resist on the wafer 4 and the light reflected from the surface of the substrate of the wafer 4. These effects vary depending on the material used in the substrate surface that is in abroad sense the pattern structure, and with high-reflection wiring materials such as aluminum is too large to be ignored. Also, when using an electrostatic capacitance sensor as the wafer surface position detection sensor, and GaAs (gallium-arsenic) wafers are used as the substrate of high-speed elements or light-emitting diodes, as is common knowledge, unlike with silicon wafers, there are large measurement offsets because such wafers are dielectrics. 0076 With the exposure apparatus shown in FIG. 1, obtaining the measurement offset for correcting for differences in focus measurement readings caused by differences in the surface conditions of the individual detection points is accomplished by pre-scanning sample shots 32-39 indicated by cross-hatched markings in FIG. 3. (Here, the term pre-scanning means detecting the surface position of a plurality of points inside the exposure area while actually scanning.) Then, the exposure apparatus calculates corrections values for correcting the position of the wafer 4 (i.e., the surface position readings indicating the position of the wafer 4) during scan exposure by the distance needed to reach an optimum exposure image surface position (i.e., the margin of error according to the pattern structure) using the surface position detection readings obtained during the scan described above. 0077 It should be noted that the sample shot disposition shown in FIG. 3 is one example, and the number and position of the shots is not limited to that illustrated in FIG. 3. 0078 When calculation of the correction is completed, the position of the wafer is corrected during scan exposure by correcting the surface position detection readings at the detection points that detect the surface position by a correction value corresponding to the pattern structure for those detection points so as to match the area to be exposed to the exposure image surface based on the corrected surface position detection readings. 0079 A description is now given of surface position detection and correction according to a first embodiment of the present invention, with reference to the flow chart of FIG. 8. It should be noted that, in the exposure apparatus of FIG. 1, an LED is used as the light source 10 and a one-dimensional CCD sensor is used as the light sensor. 0080 FIG. 8 is a flow chart showing steps in a measurement offset and a surface position correction drive sequence during exposure at the shots using the surface position detection method according to a first embodiment of the present invention. 0081 When the exposure apparatus receives a start instruction, the process it performs proceeds from a step S101 (START) to a step S102, in which the wafer is placed on the stage and suctionally mounted on the chuck. In a step S103, based on a certain scanning speed and a certain CCD charge time, a reference scan area size is determined according to the following formula: 0082 Reference scan area size (overall length)Measurement spot size(scanning speedCCD charge time) 0083 and stored in the main control unit 27. It should be noted that the addition of the measurement spot size in the formula above is for the purpose of calculating the overall length of the measurement area size. 0084 Next, in a step S104, the exposure apparatus adjusts the lighting at a plurality of measuring points inside the area to be exposed while scanning the sample shot 31 of FIG. 3 at a certain speed and stores a signal peak. This adjustment of the lighting while scanning at a certain speed causes the CCD charge time to change in at least two stages, storing at least two or more adjusted lighting results. In other words, the exposure apparatus conducts a plurality of scans during lighting adjustment, changing the CCD charge time with each scan. The operation of adjusting the lighting according to the exposure scanning speed during the exposure scan to be described later is performed using the lighting adjustment data measured and stored as described above. 0085 Next, the exposure apparatus obtains the measurement offset for eliminating the measurement margin of error factor that is itself determined by the pattern structure (that is, by the actual topography within the area to be exposed and the material of the substrate) from the surface position detection readings gotten during exposure scanning. The ultimate amount of that correction includes this measurement offset. 0086 First, in a step S105, in order to measure the shape of the surface within the area to be exposed of the chip (i.e., a plurality of surface positions), the exposure apparatus detects surface positions at a plurality of points within the area to be exposed while scanning a plurality of sample shots 32-39 as shown of FIG. 3 at a certain speed. The scanning speed and the CCD charge time are the scanning speed and CCD charge time used in the calculation of the reference scan area size described above. In a step S106, the exposure apparatus calculates correction values for correcting surface position detection readings during the exposure scanning, by a distance required to attain an optimum exposure image surface position (that is, a margin of error depending on the pattern structure) using the surface position detection readings (that is, the surface position data) obtained in the preceding step. In a step S107, the correction values so calculated are stored in the main control unit 27. More specifically, in step S107 the detection points and the correction amounts are stored as pairs. 0087 In a step S108, the exposure apparatus calculates the optimum CCD charge time based on the exposure scanning speed for the area to be exposed (the scanning speed being previously set in the apparatus according to the client's own specifications as to energy requirements, etc.) and the reference scan area size recorded in step S103. Based on the CCD charge time so calculated, the exposure apparatus then sets an appropriate measurement starting time and an appropriate measurement ending time for each of the detection points. In other words, the measurement starting time is the time at which the spot arrives at detection position M0 or the like, and the measurement ending time is the measurement starting time plus the calculated CCD charge time. In addition, in a step S109, from the changes in the light adjustment values with the changes in CCD charge time stored in step S104 the exposure apparatus determines the optimum light adjustment value for the CCD charge time calculated as described above. 0088 As described above, the present invention makes it possible to set a constant optimum light amount without increasing the time needed to readjust the light even when the scanning speed changes with each exposure area, and at the same time makes it possible to continuously synchronize the measurement areas used for surface position measurement at the detection points. Accordingly, offset control of the focus measurement values can be conducted with a high degree of accuracy in the offset correction of the focus measurement values because the detection points continuously maintain the identical positions, enabling high-resolution pattern transfers with high throughput. 0089 In a step S110, the exposure apparatus scans with the light adjustment values set in step S109. The surface position detection readings taken from the measurement starting time to the measurement ending time set in step S108 at the detection points that detect the surface positions during such scan exposure are corrected by the correction values corresponding to the pattern structures of the detection points (that is, the correction values that were stored in step S107). Based on these corrected surface position detection readings, the area to be exposed is matched to the exposure image surface and exposed. Steps S108 and S109 are executed for each shot. 0090 The light adjustment data and correction values obtained in the pre-scan measurement operation of steps S103 through S107 depend on the pattern structure (i.e., the actual topography within the area to be exposed and the material of the substrate). Therefore, wafers of the same lot or having completed the same process probably have the same pattern structure, so it is possible to use the light adjustment data and correction values obtained for at least one wafer for succeeding wafers as well. A description of this type of process is given with reference to FIGS. 9A and 9B. 0091 FIGS. 9A and 9B are flow charts showing steps in a wafer processing sequence using the surface position detection method according to the first embodiment of the present invention, that is, a process of pre-scanning a certain number of initial wafers and using the readings thereby obtained to expose succeeding wafers. 0092 In the flow charts shown in FIGS. 9A and 9B, the exposure apparatus performs exposure and pre-scanning for the initial j wafers among the n wafers to be processed. In other words, using a counter i set to 0 in a step S202, steps S102 through S112 are repeatedly executed until the counter i becomes j or more. 0093 When processing of j number of wafers is completed, the exposure apparatus statistically processes (e.g., averages) the pre-scan data obtained for the j wafers in a step S205 and sets the processed pre-scan data to be applied to the remaining wafers. Then, in steps S206 and the steps that follow, the rest of the wafers are exposed using the processed pre-scan data obtained in step S205. 0094 In other words, in step S206, the exposure apparatus increases the counter by 1 and conveys the next wafer to the wafer stage and chucks it thereat in a step S207. In steps S108 through S110, the exposure apparatus performs the same processes as in steps S108-110 described above, but the pre-scan data to be used were set in step S205. When all the shots on the wafer have been exposed in a step S208, the chuck is released and the wafer is carried out in a step S209. The processes of from step S206 to step S209 are executed for all the remaining wafers (in a step S210). 0095 A sequence like that of the flow charts shown in FIGS. 9A and 9B can provide large improvements in throughput. 0096 Second Embodiment 0097 In a second embodiment of the present invention, the exposure apparatus shown in FIG. 1, an LED is used as the light source 10 and a PSD sensor capable of high-speed sampling is used as the sensor. That is, the second embodiment uses a time averaging type sensor that averages a plurality of measurement readings taken in continuous succession to arrive at a single measurement reading. 0098 FIG. 10 is a flow chart showing an exposure processing according to the second embodiment. FIG. 10 shows steps in a measurement offset and a surface position correction drive sequence during exposure at the shots using a surface position detection method according to a second embodiment of the present invention. 0099 When the exposure apparatus receives a start instruction, the process it performs proceeds from a step S301 (START) to a step S302, in which the wafer is placed on the stage and suctionally mounted on the chuck. 0100 Next, in a step S303, the exposure apparatus uses a certain scanning speed and a certain averaged number of times, as well as a sampling clock Hz of the PSD sensor, to determine a reference scan area size according to the following formula: 0101 Reference scan area size (overall length)Measurement spot size(scanning speed(averaged number of times/sampling clock)) 0102 with the result being stored in the main control unit 27. 0103 In a step S304, the exposure apparatus adjusts the lighting and stores the results thereof at the plurality of measuring points inside the area to be exposed as shown in FIG. 5 while scanning the sample shot area 31 of FIG. 3 at a certain speed. As with the first embodiment described above, this adjustment of the lighting while scanning at a certain speed optimizes the amount of light and the gain. Like the first embodiment as well, the exposure apparatus according to the second embodiment executes a plurality of scans at different averaged number of times in order to accommodate a variety of scanning speeds. 0104 Next, the process proceeds to a step S305, in which the exposure apparatus obtains the measurement offset for eiminating the measurement margin of error factor that is itself determined by the pattern structure (that is, by the actual topography within the measurement area to be exposed and the material of the substrate) from the surface position detection readings gotten during exposure scanning. The ultimate amount of that correction includes this measurement offset. 0105 First, in a step S305, in order to measure the shape of the surface within the area to be exposed of the chip (i.e., a plurality of surface positions), the exposure apparatus detects surface positions at a plurality of points within the area to be exposed while scanning a plurality of sample shots 32-39 as shown of FIG. 3 at a certain speed. At this time, the scanning speed and the averaged number of times are the scanning speed and averaged number of times used to calculate the reference scan area size described above. Then, in a step S306, the exposure apparatus calculates correction values for correcting the surface position detection readings measured during exposure scan, by a distance required to attain an optimum exposure image surface position (that is, the margin of error according to the pattern structure) using the surface position detection readings (that is, the surface position data) obtained in the preceding step. In a step S307, the correction values so calculated are stored in the main control unit 27. 0106 In a step S308, the exposure apparatus calculates and sets the measurement starting time for the scanning speed and the optimum averaged number of times based on the scanning speed for the area to be exposed and the reference scan area size recorded in step S303. Based on the lighting adjustment data recorded in step S304, the exposure apparatus determines the appropriate setting current and/or gain for the set averaged number of times. It should be noted that, as with step S108 described above with respect to the first embodiment, the time at which the measuring points M0 . . . etc. arrive at the spots is calculated from the scanning speed and the measurement starting time is set accordingly. 0107 While the exposure apparatus scans the chip in a step S309, the exposure apparatus measures the surface positions at the detection points that detect the surface positions using the measuring starting time and the averaged number of times determined in step S308. 0108 The exposure apparatus then corrects the surface position measurement readings gotten during this exposure using the correction values set for the pattern structure at the detection points (that is, the correction values set in step S307). Based on these corrected surface position detection readings, the area to be exposed is matched to the exposure image surface and exposed. 0109 The light adjustment data and correction values obtained in the pre-scan measurement operation of steps S303 through S306 depend on the pattern structure (i.e., the actual topography within the area to be exposed and the material of the substrate). Therefore, wafers of the same lot or having completed the same process probably have the same pattern structure, so it is possible to use the light adjustment data and correction values obtained for at least one wafer for succeeding wafers as well. As can be readily appreciated by those of ordinary skill in the art, such an arrangement can provide large improvements in throughput. The specific processes involved in such a routine are exactly the same as those described with reference to FIGS. 9A and 9B of the first embodiment, so a description thereof is omitted. 0110 Third Embodiment 0111 Whereas a PSD sensor was used in the second embodiment, it should be understood that the present invention is not limited to such an arrangement. Rather, time-average sensors such as air micro-sensors and electrostatic capacitance sensors may be employed instead, with the result that high-accuracy, high throughput can still be achieved even with the use of such non-optical sensors. Accordingly, a third embodiment of the present invention is described with reference to one such non-optical sensor, i.e., an electrostatic capacitance sensor. 0112 FIG. 11 is a partial schematic diagram showing an example of a slit-scan-type projective exposure apparatus using an electrostatic capacitance sensor in surface position detection. Parts that are the same as or similar to parts shown in FIG. 1 are designated with the same reference characters. 0113 In FIG. 11, reference numerals 50 and 51 denote electrostatic condenser sensors provided in order to detect the surface position and tilt of the wafer 4, with three sensors disposed at each of the proximal and dismal ends of the scanning direction vis-a-vis the exposure slit, in a direction perpendicular to the surface of the sheet of paper on which the drawing appears. Accordingly, the measuring points consist of the six points CL1-CL3 and CR1-CR3 shown in FIG. 4, positioned with respect to the exposure slit as shown in FIGS. 4A, 4B and 4C. 0114 FIG. 12 is a flow chart showing steps in a measurement offset and a surface position correction drive sequence during exposure at the shots using the surface position detection method according to a third embodiment of the present invention. 0115 As shown in FIG. 12, when the exposure apparatus receives a start instruction, the process it performs proceeds from a step S401 (START) to a step S402, in which the wafer is placed on the stage and suctionally mounted on the chuck. 0116 Next, in a step S403, the exposure apparatus uses a certain scanning speed and a certain averaged number of times, as well as a sampling clock Hz of the electrostatic capacitance sensor, to determine a reference scan area size according to the following formula: 0117 Reference scan area size (overall length)Measurement spot size(scanning speed(averaged number of times/sampling clock)) 0118 with the result being stored in the main control unit 27. 0119 It should be noted that the surface position and tilt detection readings obtained by the electrostatic capacitance sensor use the average reading over a certain number of measurements for enhanced accuracy. However, it is also possible to use the average value over a certain time interval as well, in which case the formula to be used is as follows: 0120 Reference scan area sizeMeasurement spot size(scanning speed(averaged time/sampling clock)) 0121 Next, the exposure apparatus measures the measurement offsets (correction values) to be used to eliminate the measurement margin of error factor that is itself determined by the pattern structure (that is, by the actual topography within the measurement area to be exposed and the material of the substrate) from the surface position detection readings gotten during the exposure scan. 0122 First, in a step S404, in order to measure the shape of the surface within the area to be exposed of the chip (i.e., a plurality of surface positions), the exposure apparatus uses the electrostatic capacitance sensors to detect surface positions at a plurality of points within the areas to be exposed while scanning a plurality of sample shots 32-39 as shown of FIG. 3 at a certain speed. At this time, the scanning speed and the averaged number of times are the scanning speed and averaged number of times used to calculate the reference scan area size described above. 0123 Next, in a step S405, the exposure apparatus calculates correction values for correcting the scan exposure surface position detection readings by a distance required to attain an optimum exposure image surface position (that is, the margin of error according to the pattern structure) using the surface position detection readings (that is, the surface position data) obtained in the preceding step S404. In a step S406, the correction values so calculated are stored in the main control unit 27. 0124 Having acquired the pre-scan data as described above, the process proceeds to a step S407, in which the exposure apparatus calculates and sets the measurement starting time for the scanning speed and the optimum averaged number of times based on the scanning speed for the areas to be exposed and the reference scan area size recorded in step S403. (As with step S108 described above, the time at which the measuring points M0 . . . etc. arrive at the spots is calculated from the scanning speed and the measurement starting time is set accordingly.) 0125 In a step S408, the exposure apparatus scans the chip. During the exposure scanning, the exposure apparatus corrects the surface position detection readings taken from the measurement starting time to the averaged scan completion set in step S407 using the electrostatic capacitance sensors at the detection points, by the above-described correction values corresponding to the pattern structures at the detection points. Based on these corrected surface position detection readings, the measurement areas to be exposed are matched with the exposure image surface and exposed. 0126 The corrected readings obtained during the pre-scan operation described in steps S403 through S405 depend on the pattern structure (that is, by the actual topography within the measurement area to be exposed and the material of the substrate). Therefore, wafers of the same lot or having completed the same process probably have the same pattern structure, so it is possible to use the light adjustment data and correction values obtained for at least one wafer for succeeding wafers as well. As can be readily appreciated by those of ordinary skill in the art, such an arrangement can provide large improvements in throughput. The specific processes involved in such a routine follow those described with reference to FIGS. 9A and 9B of the first embodiment, and can be understood by those of ordinary skill in the art, so a description thereof is omitted. 0127 It should be noted that, as noted previously, instead of changing the averaged number of times in conjunction with the scanning speed, it is possible to change the averaged time in conjunction with the scanning speed instead and still achieve the same effect. 0128 Fourth Embodiment 0129 In the embodiments described above, the scan area is determined using a certain scanning speed and CCD charge time and the like. By contrast, a fourth embodiment of the present invention shows an example in which the reference scan area size is set from an external input terminal (i.e., a console) not shown in FIG. 1. 0130 FIG. 13 is a flow chart illustrating the surface position detection method according to a fourth embodiment of the present invention. The difference between FIG. 13 and FIG. 1 is that the former includes, in a step S503, the setting of the size of the scan area using an external input apparatus. 0131 As a result of this use of an external input apparatus to set the size of the scan area, the size of the scan area can be freely selected or specified using the graphic display on the console, making it possible to provide highly reliable measurement area focus for a known shot pattern. 0132 As described above, according to the foregoing embodiments of the present invention the measuring points are maintained at the same position regardless of changes in scanning speed and changes in exposure illuminance with each wafer and/or each shot, thus eliminating the need to reset the measurement offset with no risk of deterioration in the accuracy of the measurement offset. Accordingly, if scan speed is changed by selecting optimum scan speed in accordance with fluctuations of exposure illuminance due to fluctuations of resist sensitivity within a wafer, high accuracy offset correction to focus measurements can be performed, and the surface position detection can be performed with high throughput. 0133 Fifth Embodiment 0134 A description is now given of a fifth embodiment of the present invention, that is, of a method for manufacturing semiconductor devices using the exposure apparatus described above. 0135 FIG. 14 is a flow chart showing steps in the process of manufacturing a miniature semiconductor device. 0136 In a step S1, (circuit design), the circuit is designed. In a step S2 (mask production), a mask is produced on which the designed circuit pattern is formed. In a step S3 (wafer production), a wafer is produced using a material such as silicon. In a step S4 (wafer process), called pre-process, an actual circuit is formed by lithography using the mask and wafer. Next, a step S5 (assembly), called post-process, is the process of making a semiconductor chip using the wafer produced in step S4, and includes assembly (dicing, bonding, etc,), packaging (chip insertion) and so on. In a step S6 (inspection), the operation and durability of the semiconductor device produced in step S5 is tested. The completed and tested semiconductor device is then shipped in a step S7, completing the production process. 0137 FIG. 15. is a flow chart showing details of the wafer processing operation. In a step S11 (oxidation), the surface of the wafer is oxidized. In a step S12 (CVD), an insulating film is laid down over the surface of the wafer. In a step S13 (electrode formation), electrodes are vapor-formed on the wafer. In a step S14 (ion injection), the wafer is injected with ions. In a step S15 (resist process), the wafer is coated with a photosensitizer. In a step S16 (exposure), a circuit pattern is etched (exposed) on the surface of the wafer using the exposure apparatus described above. In a step S17 (development), the exposed wafer is developed. In a step S18 (etching), everything but the developed resist image is scraped away. In a step S19 (resist peeling), the resist, which is no longer needed now that etching is completed, is removed. By repeating these steps, a multi-layered circuit pattern is formed on the wafer. 0138 By using the exposure apparatus described in the first through fourth embodiments above in the method for manufacturing of the fifth embodiment as described above, surface position detection and measurement using measurement offsets can be performed accurately, thus improving throughput. 0139 As described above, the present invention makes it possible to detect surface positions with a high degree of accuracy using measurement offsets even when the scanning speed is changed with each wafer and each shot. Also, according to the present invention, it is possible to utilize the illuminance of the exposure apparatus to the fullest, and achieve high throughput. 0140 The present invention is not limited to the above embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.