TECHNICAL FIELD 0001 Cleaning solutions for photoresist are disclosed which are useful for cleaning a semiconductor substrate in the last step of development when photoresist patterns are formed. More specifically, a cleaning solution for photoresist comprising H2O as a primary solvent, a surfactant of phosphate-alcoholamine salt as an additive and an alcohol compound, and a method for forming patterns using the same are disclosed.

DESCRIPTION OF THE RELATED ART 0002 As semiconductor devices become smaller, the aspect ratio of the photoresist patterns (i.e. the ratio of the thickness of photoresist, or height to the linewidth of formed pattern) increases. 0003 When the height of formed photoresist patterns extends beyond critical height, capillary force exceeds elasticity of photoresist, thereby resulting in collapse of patterns during a cleaning process. 0004 In order to overcome this problem, adhesive force between underlying layers and photoresist is enhanced by increasing inner elasticity of photoresist or decreasing surface tension thereof. 0005 Generally, a method of forming photoresist patterns on semiconductor substrates comprises the steps of: forming an underlying layer on a semiconductor substrate; forming a photoresist film on the underlying layer; and exposing a portion of the underlying layer by exposing and developing processes to form a photoresist pattern. In case of a positive photoresist, the photoresist film of an exposing region is removed by developing solution to form a photoresist pattern. 0006 The last step of the above method is a cleaning process of removing the residual photoresist film by spraying distilled water from spin equipment while the semiconductor substrate is spun. In this process, the pattern is collapsed due to high surface tension of the distilled water. 0007 Conventionally, U.S. Pat. No. 5,374,502 discloses that the collapse of photoresist patterns having high aspect ratios can be prevented by using a cleaning solution including tert-amyl alcohol, 2-methyl-1-butanol, 1-butanol, tert-butyl alcohol, 3-pentanol and isobutyl alcohol. 0008 In addition, U.S. Pat. No. 5,474,877 discloses that the collapse of photoresist patterns can be prevented by using a cleaning solution whose surface tension is lowered by heat. However, neither solution provided by the prior art is ideal and therefore there is a continuing need for improved cleaning solutions that address the problems of high aspect ratio photoresist patterns.

SUMMARY OF THE DISCLOSURE 0009 Accordingly, cleaning solutions for photoresist patterns is disclosed whose surface tension is lowered to prevent collapse of photoresist patterns in the last development process of removing the residual photoresist film. Also, methods for forming patterns using the same are disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS 0010 FIG. 1 is a photograph of a photoresist pattern obtained from Example 9. 0011 FIG. 2 is a photograph of a photoresist pattern obtained from Example 10. 0012 FIG. 3 is a photograph of a photoresist pattern obtained from Example 11. 0013 FIG. 4 is a photograph of a photoresist pattern obtained from Example 12. 0014 FIG. 5 is a photograph of a photoresist pattern obtained from Example 13. 0015 FIG. 6 is a photograph of a photoresist pattern obtained from Example 14. 0016 FIG. 7 is a photograph of a photoresist pattern obtained from Example 15. 0017 FIG. 8 is a photograph of a photoresist pattern obtained from Example 16. 0018 FIG. 9 is a photograph of a photoresist pattern obtained from Comparative Example 2.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 0019 A cleaning solution for photoresist comprises H2O as a solution and a compound represented by following Formula 1 as a surfactant: 2

0020 wherein 0021 R is C2-C20 alkyl or C6-C25 alkyl aryl; 0022 x, y and z individually are an integer ranging from 0 to 10; 0023 a is 2 or 3; and 0024 b is an integer ranging from 2 to 50. 0025 The compound of Formula 1 is water-soluble since which is salt. Also, the compound of Formula 1, which includes both a hydrophilic group such as a hydroxyl group and a hydrophobic group such as an alkyl group having a long chain in one molecule, remarkably lowers surface tension. 0026 Preferably, the compound of Formula 1 which is phosphate-alcoholamine salt is represented by Formula 2 or Formula 3: 3

0027 wherein 0028 R is C2-C20 alkyl or C6-C25 alkyl aryl; 0029 x, y and z individually are an integer ranging from 0 to 10; and 0030 n is an integer ranging from 1 to 49. 0031 In the compound of Formula 2 or Formula 3, R is preferably C6-C14 alkyl or C12-C20 alkyl aryl, and more preferably selected from the group consisting of octyl, octyl phenyl, nonyl, nonyl phenyl, decyl, decyl phenyl, undecyl, undecyl phenyl, dodoecyl and dodecyl phenyl, n is an integer ranging from 5 to 10, and x, y and z individually are an integer ranging from 0 to 2. 0032 More specifically, the compound of Formula 2 is selected from the group consisting of compound wherein R is nonyl, x, y and z are 1, and n is 7; compound wherein R is octyl, x, y and z are 1, and n is 7; compound wherein R is dodecyl, x, y and z are 0, and n is 7; and compound wherein R is octyl phenyl, x, y and z are 1, and n is 3. 0033 Also, the compound of Formula 3 is selected from the group consisting of compound wherein R is nonyl, x, y and z are 1, and n is 7; compound wherein R is octyl, x, y and z are 1, and n is 7; compound wherein R is dodecyl, x, y and z are 0, and n is 7; and compound wherein R is octyl phenyl, x, y and z are 1, and n is 3. 0034 The water of the disclosed cleaning solution is preferably distilled water. 0035 The disclosed water further comprises an alcohol. 0036 The above alcohol comprises C1-C10 alkyl alcohol or C1-C10 alkoxyalkyl alcohol. Preferably, the C1-C10 alkyl alcohol is selected from the group consisting of methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2,2-dimethyl-1-propanol and mixtures thereof, and the C1-C10 alkoxyalkyl alcohol is selected from the group consisting of 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 1-methoxy-2-propanol, 3-methoxy-1,2-propandiol and mixtures thereof. 0037 In the disclosed cleaning solution, the compound of Formula 1, which is a surfactant, is present in an amount ranging from 0.001 to 2 wt % based on the total weight of said solution, and the alcohol is present in an amount ranging from 0 to 20 wt % based on the total weight of said solution. 0038 When the compound of Formula 1 is present in the amount of less than 0.001 wt %, the effect of lowering surface tension is degraded. When the compound of Formula 1 is present in the amount of more than 2 wt %, the effect of lowering surface tension is also degraded, and the residual compound of Formula 1 remains on the wafer. 0039 In addition, when the alcohol is present in the amount of more than 20 wt %, the alcohol dissolves photoresist materials, thereby collapsing patterns. 0040 Specifically, the compound of Formula 2 is present in an amount ranging from 0.001 to 2 wt %, more preferably, from 0.01 to 1 wt % based on the total weight of said solution, and the alcohol is present in an amount ranging from 0 to 20 wt %, more preferably, from 0.01 to 10 wt % based on the total weight of said solution. 0041 The compound of Formula 3, which is a surfactant, is present in an amount ranging from 0.001 to 2 wt %, more preferably, from 0.001 to 1 wt % based on the total weight of said solution, and the alcohol is present in an amount ranging from 0 to 10 wt %, more preferably, from 0.001 to 5 wt % based on the total weight of said solution. 0042 The disclosed cleaning solution is manufactured by filtering the resulting mixture of the distilled water, the compound of Formula 1 and the alcohol with 0.2 m filter. 0043 A method for forming a photoresist pattern comprises: 0044 (a) preparing a semiconductor substrate on which an underlying layer is formed; 0045 (b) coating a photoresist on the underlying layer to form a photoresist film; 0046 (c) exposing the photoresist film to light; 0047 (d) developing the exposed photoresist film; and 0048 (e) cleaning the resulting structure using a disclosed cleaning solution. 0049 The above method further comprises soft baking step before part (c) or post baking step after part (c). Preferably, the bake process is performed at a temperature ranging from 70 to 200 C. 0050 In the above the exposure step, the source of the light is preferably selected from the group consisting of KrF (248 nm), ArF (193 nm), VUV (157 nm), EUV (13 nm), E-beam, X-ray and ion-beam. The exposure step is preferably performed at exposure energy ranging from 0.1 to 50 mJ/cm2. 0051 The above development step (d) is performed with an alkaline developing solution which is preferably TMAH aqueous solution ranging from 0.01 to 5 wt %. 0052 As described above, the collapse of photoresist patterns can be prevented by performing the cleaning process using the disclosed cleaning solution including the compound of Formula 1 which is a surfactant to lower surface tension of the cleaning solution. 0053 Additionally, a semiconductor device manufactured according to the process described above is disclosed. 0054 The disclosed cleaning solution for photoresist will be described in more details referring to examples below, when are not intended to be limiting.

EXAMPLE 1

Preparation of Cleaning Solution and Measurement of Surface Tension 0055 The compound of Formula 2 wherein R is nonyl, x, y and z are 1, respectively, and n is 7 (0.3 g), methanol (1 g) and distilled water (99 g) were stirred for 1 minute. The resulting mixture was filtered through a 0.2 m filter to obtain a disclosed cleaning solution. The surface tension of the disclosed cleaning solution measured by a KRUSS K9 tension meter of measurement equipment was 31N m/m2.

EXAMPLE 2

Preparation of Cleaning Solution and Measurement of Surface Tension 0056 The compound of Formula 2 wherein R is octyl, x, y and z are 1, respectively, and n is 7 (0.3 g), methanol (1 g) and distilled water (99 g) were stirred for 1 minute. The resulting mixture was filtered through a 0.2 m filter to obtain a disclosed cleaning solution. The surface tension of the disclosed cleaning solution measured by a KRUSS K9 was 32N m/m2.

EXAMPLE 3

Preparation of Cleaning Solution and Measurement of Surface Tension 0057 The compound of Formula 2 wherein R is dodecyl, x, y and z are 0, respectively, and n is 7 (0.3 g), isopropanol (1 g) and distilled water (99 g) were stirred for 1 minute. The resulting mixture was filtered through a 0.2 m filter to obtain a disclosed cleaning solution. The surface tension of the disclosed cleaning solution measured by a KRUSS K9 was 28N m/m2.

EXAMPLE 4

Preparation of Cleaning Solution and Measurement of Surface Tension 0058 The compound of Formula 2 wherein R is octyl phenyl, x, y and z are 1, respectively, and n is 3 (0.3 g), isopropanol (1 g) and distilled water (99 g) were stirred for 1 minute. The resulting mixture was filtered through a 0.2 m filter to obtain a disclosed cleaning solution. The surface tension of the disclosed cleaning solution measured by a KRUSS K9 was 29N m/m2.

EXAMPLE 5

Preparation of Cleaning Solution and Measurement of Surface Tension 0059 The compound of Formula 3 wherein R is nonyl, x, y and z are 1, respectively, and n is 7 (0.3 g), methanol (1 g) and distilled water (99 g) were stirred for 1 minute. The resulting mixture was filtered through a 0.2 m filter to obtain a disclosed cleaning solution. The surface tension of the disclosed cleaning solution measured by a KRUSS K9 was 34N m/m2.

EXAMPLE 6

Preparation of Cleaning Solution and Measurement of Surface Tension 0060 The compound of Formula 3 wherein R is octyl, x, y and z are 1, respectively, and n is 7 (0.3 g), methanol (1 g) and distilled water (99 g) were stirred for 1 minute. The resulting mixture was filtered through a 0.2 m filter to obtain a disclosed cleaning solution. The surface tension of the disclosed cleaning solution measured by a KRUSS K9 was 37N m/m2.

EXAMPLE 7

Preparation of Cleaning Solution and Measurement of Surface Tension 0061 The compound of Formula 3 wherein R is dodecyl, x, y and z are 0, respectively, and n is 7 (0.3 g), isopropanol (1 g) and distilled water (99 g) were stirred for 1 minute. The resulting mixture was filtered through a 0.2 m filter to obtain a disclosed cleaning solution. The surface tension of the disclosed cleaning solution measured by a KRUSS K9 was 33N m/m2.

EXAMPLE 8

Preparation of Cleaning Solution and Measurement of Surface Tension 0062 The compound of Formula 3 wherein R is octyl phenyl, x, y and z are 1, respectively, and n is 3 (0.3 g), isopropanol (1 g) and distilled water (99 g) were stirred for 1 minute. The resulting mixture was filtered through a 0.2 m filter to obtain a disclosed cleaning solution. The surface tension of the disclosed cleaning solution measured by a KRUSS K9 was 37N mm2.

Comparative Example 1 0063 Measurement of Surface Tension of Distilled Water 0064 The surface tension of the distilled water as measured by the KRUSS K9 was 73N m/m2.

EXAMPLE 9

Formation of Photoresist Pattern 0065 After an underlying layer was formed on a silicon wafer treated with hexamethyldisilazane (HMDS), a photoresist comprising methacrylate type compound, sold under the designation AX1020P by Clariant, was spin-coated on the silicon wafer at a thickness 2400 to form a photoresist film, and soft-backed at 130 C. for 90 seconds. After soft-baking, the photoresist film was exposed to light using an ArF laser exposer, and then post-baked at 130 C. for 90 seconds. When the post-baking was completed, it was developed in 2.38 wt % aqueous TMAH solution for 30 seconds. While the silicon wafer was spun, the silicon wafer was cleaned by spraying the cleaning solution (30 ml) obtained from Example 1 from the spin equipment and then dehydrated, to obtain 90 nm L/S photoresist pattern (see FIG. 1).

EXAMPLE 10

Formation of Photoresist Pattern 0066 The procedure of Example 9 was repeated using the cleaning solution of Example 2 instead of the cleaning solution of Example 1 to obtain 90 nm L/S photoresist pattern (see FIG. 2).

EXAMPLE 11

Formation of Photoresist Pattern 0067 The procedure of Example 9 was repeated using the cleaning solution of Example 3 instead of the cleaning solution of Example 1 to obtain 90 nm L/S photoresist pattern (see FIG. 3).

EXAMPLE 12

Formation of Photoresist Pattern 0068 The procedure of Example 9 was repeated using the cleaning solution of Example 4 instead of the cleaning solution of Example 1 to obtain 90 nm L/S photoresist pattern (see FIG. 4).

EXAMPLE 13

Formation of Photoresist Pattern 0069 The procedure of Example 9 was repeated using the cleaning solution of Example 5 instead of the cleaning solution of Example 1 to obtain 90 nm L/S photoresist pattern (see FIG. 5).

EXAMPLE 14

Formation of Photoresist Pattern 0070 The procedure of Example 9 was repeated using the cleaning solution of Example 6 instead of the cleaning solution of Example 1 to obtain 90 nm L/S photoresist pattern (see FIG. 6).

EXAMPLE 15

Formation of Photoresist Pattern 0071 The procedure of Example 9 was repeated using the cleaning solution of Example 7 instead of the cleaning solution of Example 1 to obtain 90 nm L/S photoresist pattern (see FIG. 7).

EXAMPLE 16

Formation of Photoresist Pattern 0072 The procedure of Example 9 was repeated using the cleaning solution of Example 8 instead of the cleaning solution of Example 1 to obtain 90 nm L/S photoresist pattern (see FIG. 8).

Comparative Example 2 0073 Formation of Photoresist Pattern 0074 The procedure of Example 9 was repeated using the distilled water instead of the cleaning solution of Example 1 to obtain a photoresist pattern. As a result, the photoresist pattern collapsed (see FIG. 9). 0075 As shown in the above Examples, the collapse of patterns can be avoided by using the disclosed cleaning solution in the last step of the development because the disclosed cleaning solution has a lower surface tension than distilled water which has been used in conventional cleaning solutions. Accordingly, the disclosed cleaning solution may enable stabilization of development processes for forming ultrafine photoresist patterns of less than 130 nm.