204 over the substrate stage 210. For example, planar position encoders 230 and 232 configured to measure positional data (e.g., metrology) of the target substrate 302 and/or the substrate stage 210 may be integrated with the metrology frame 204. A die handler 280 is coupled to or integrated with the metrology frame 204 and configured to retrieve and transport a die 320 from a carrier substrate to the target substrate 302. The die handler 280 is generally configured to vertically transport the die 320 to the target substrate 302. The die handler 280 may alternatively be referred to as a pick-and-place handler. As shown, the die 320 is positioned face-down with respect to a surface 302a of the target substrate 302. The surface 302a may be a front side or a back side of the target substrate 302.

Alternative to the embodiment depicted in FIG. 4, the apparatus 200 may be configured as a double-scanner, having two separate substrate stages for processing two target substrates concurrently. Referring to FIG. 5, for example, an apparatus 200′ is constructed similarly to the apparatus 200 with the exception that the apparatus 200′ includes an additional substrate stage 260 laterally adjacent the substrate stage 210. The substrate stage 260 is provided on the balance mass 208 and includes a coarse stage 262 integrated with a fine stage 264, which are generally analogous to the coarse stage 212 and the fin stage 214. As shown, the substrate stage 260 is loaded with a target substrate 304, which can be processed separately from the target substrate 302. In some embodiments, while the target substrate 302 is loaded, measured, and aligned with the die 320 at the substrate stage 210, the target substrate 304, which has already been aligned with another die or dies, undergoes a bonding process (e.g., operation 114 of the method 100). In this regard, the apparatus 200′ also provides a substrate transfer system (not depicted) between the substrate stage 210 and the substrate stage 260 to facilitate the operation of both scanners.

For purposes of illustration, the subsequent operations of the methods 100 and 150 are described with reference to the target substrate 302 and the substrate stage 210 as a part of the apparatus 200 of FIG. 4. For this reason, depiction of the apparatus 200 has been simplified in subsequent figures to include only the substrate stage 210, the illumination source 220, and the die handler 280.

FIG. 6 illustrates the apparatus 200 with the target substrate 302 loaded onto the substrate stage 210 (depicted as the coarse stage 212 and the fine stage 214). In some embodiments, loading the target substrate 302 includes placing the target substrate 302 onto the fine stage 214 and subsequently aligning the target substrate 302 with the fine stage 214 utilizing alignment marks disposed on both the target substrate 302 and the fine stage 214. For example, referring to FIG. 7, the surface 302a of the target substrate 302 includes a set of alignment marks 402a, 402b, 402c, and 402d (collectively referred to as alignment marks 402a-402d) arranged symmetrically over the target substrate 302, and the fine stage 214 includes a set of alignment marks 412a, 412b, 412c, and 412d (collectively referred to as alignment marks 412a-412d) corresponding to the alignment marks 402a-402d, respectively. The depicted arrangement of these and any subsequent alignment marks is for illustration purposes only with the understanding that other arrangements may also be applicable in the present disclosure. For example, the surface 302a may include more or less of the alignment marks similar to the alignment marks 402a-402d, and that such alignment marks may not necessarily be arranged symmetrically over the surface 302a.

In some embodiments, referring to FIG. 2, the process of aligning the target substrate 302 with the fine stage 214 (i.e., the substrate stage 210) may be implemented by an embodiment of the method 150. For example, the method 150 measures position(s) of one or more of the alignment marks 402a-402d at operation 152 and subsequently measures position(s) of one or more of the alignment marks 412a-412d at operation 154. In some embodiments, positions of the various alignment marks may be measured by a metrology technique, such as an optical method (e.g., using a lens system integrated with the apparatus 200), a diffraction method, scatterometry, interferometry, or combinations thereof. In some embodiments, measuring the positions of the alignment marks may rely on the use of the illumination source 220 to reposition the target substrate 302 or the fine stage 214. In some embodiments, the positions of the alignment marks 402a-402d and the alignment marks 412a-412d are measured using different tools. For example, referring to FIG. 6, an alignment detection module including a detection element 272 and a detection element 274 may be integrated with the apparatus 200 to measure the position(s) of one or more of the alignment marks 412a-412d on the fine stage 214. The alignment detection module further includes the planar position encoders 203/232 coupled with a photodetector 276, which are integrated with the apparatus 200 to measure the position(s) of one or more of the alignment marks 402a-402d on the target substrate 302. The alignment detection module may rely on one or more of the metrology techniques provided herein to measure the positions of the various alignment marks.

Subsequently, based on the measured positions of the alignment marks 402a-402d and 412a-412d, which may be collectively considered as a set of corresponding alignment marks, the method 150 at operation 156 aligns the target substrate 302 with respect to the fin stage 214. In some embodiments, the aligning at operation 156 is implemented by adjusting the position of the target substrate 302, the fine stage 214, or both.

The method 150 at operation 158 measures the resulting positions of the alignment marks 402a-402d and 412a-412d, respectively, after performing an initial alignment process. On the condition that alignment is not detected (“No” at operation 160), the method 150 proceeds to repositioning or realigning the target substrate 302 with respect to the fine stage 214 at operation 162 and subsequently measuring the resulting positions of their respective alignment marks at operation 158. Alternatively, on the condition that alignment is detected (“Yes” at operation 160), the method 150 proceeds to operation 164 to complete the alignment process.

Now referring to FIGS. 1 and 8, the method 100 at operation 104 proceeds to loading a carrier substrate 312 onto a wafer handler 284, where the carrier substrate 312 includes a plurality of dies 320 disposed thereon. In some embodiments, the carrier substrate 312 is loaded with the dies 320 facing downward, i.e., toward the target substrate 302.

Referring to FIGS. 1 and 9, the method 100 at operation 106 proceeds to positioning the carrier substrate 312 for handling by the die handler 280. As shown, because the die 320 faces downward on the carrier substrate 312, the wafer handler 284 is configured to transport and position the carrier substrate 312 at a position over the die handler 280, i.e., between the die handler 280 and the illumination source 220 as depicted.

Referring to FIGS. 1 and 10, the method 100 at operation 108 proceeds to coupling the die 320 with the die handler 280, where the coupling includes aligning a second set of corresponding alignment marks on the die 320 and the die handler 280.

In some embodiments, the die handler 280 is configured as a U-shaped structure, having a segment 280a connected to a segment 280b through a curved segment 280c, where both the segments 280a and 280b are substantially straight (or leveled with a horizontal plane). Accordingly, a space interposed between the segments 280a and 280b is designed to receive the die 320, such that edges of the die 320 directly contact the segments 280a and 280b when coupled. In the depicted embodiments, the die handler 280 couples with the die 320 along a lateral direction (e.g., along the X axis a shown in FIG. 10), allowing the die 320 to fit between the segments 280a and 280b. In some embodiments, the die handler 280 may have a different configuration and may couple with the die 320 from a vertical direction (e.g., along the Z axis as shown in FIG. 10). In some embodiments, the coupling between the die 320 and the die handler 280 may be by means of vacuum suction, where vacuum tracks are provided within the segments 280a and 280b and emerge at an interface between each of the segments and the die 320. An application of negative pressure holds the die 320 in the space between the segments 280a and 280b. Other means of coupling the die 320 to the die handler 280 may also be applicable in the present disclosure.

In some embodiments, coupling the die 320 with the die handler 280 includes aligning the die 320 with the die handler 280 utilizing alignment marks disposed on both the die 320 and the die handler 280. For example, referring to FIG. 11A, the die 320 includes, on its surface 320a, a set of two alignment marks 432a and 432b arranged opposite to one another along a diagonal axis (dashed line in FIG. 11A) of the die 320, and the die handler 280 includes a set of two alignment marks 442a and 442b corresponding to the alignment marks 432a and 432b, respectively. In this regard, an alignment between the die 320 and the die handler 280 is established when the alignment mark 432b is aligned with the alignment mark 442b, while the alignment mark 432a is offset from both the alignment marks 442a and 442b. Referring to FIG. 11B, the die 320 includes a set of three alignment marks 434a, 434b, and 434c on its surface 320a, where the alignment marks 434b and 434c are vertically aligned, and the alignment mark 434a is opposite to the alignment mark 434b along a diagonal axis of the die 320.

In some embodiments, the process of aligning the die 320 with the die handler 280 is similar to the process of aligning the target substrate 302 with the substrate stage 210 and may be implemented by an embodiment of the method 150. For example, referring to FIG. 2, the method 150 measures position(s) of one or more of the alignment marks 432a and 432b (or 434a-434c) at operation 152 and subsequently measures position(s) of one or more of the alignment marks 442a and 442b at operation 154, using one or more of the metrology techniques provided herein.

Subsequently, based on the measured positions of the alignment marks 432a and 432b (or 434a-434c) and 442a and 442b, which may be collectively considered as a set of corresponding alignment marks, the method 150 at operation 156 aligns the die 320 with the die handler 280. In some embodiments, the aligning at operation 156 is implemented by adjusting the position of the die 320, the die handler 280, or both.

The method 150 at operation 158 measures the resulting positions of the alignment marks 432a and 432b (or 434a-434c) and 442a and 442b, respectively, after performing the alignment process. On the condition that alignment is not detected (“No” at operation 160), the method 150 proceeds to repositioning or realigning the die 320 with respect to the die handler 280 at operation 162 and subsequently measuring the resulting positions of their respective alignment marks at operation 158. Alternatively, on the condition that alignment is detected (“Yes” at operation 160), the method 150 proceeds to operation 164 to complete the alignment process.

Referring to FIGS. 1 and 12, the method 100 at operation 110 proceeds to transporting the die 320 to the target substrate 302 using the die handler 280, and subsequently removing the carrier substrate 312 using the wafer handler 284, for example. In some embodiments, transporting the die 320 includes removing the die 320 coupled to the die handler 280 from the carrier substrate 312 and moving the die 320 towards the target substrate 302 using the die handler 280.

Thereafter, referring to FIGS. 1, 13A, and 13B, the method 100 at operation 112 proceeds to coupling the die 320, which is also coupled to the die handler 280, to the target substrate 302, where the coupling includes aligning a third set of alignment marks.

Referring to FIGS. 13