Systems, devices, and methods for compensating for shape variations when using image-based alignment to align bonding pads

1 . A method of aligning a chiplet to a substrate, the method comprising:

obtaining an image of a region on a chiplet;

measuring a deviation from planarity of the region on the chiplet;

estimating a chiplet-position error of the chiplet based on the image of the region and the deviation from planarity of the region, wherein estimating the chiplet-position error comprises:

obtaining an observed alignment error of the region based on the image of the region,

calculating a component of the observed alignment error that is caused by the deviation from planarity of the region, and

calculating an in-plane alignment error by subtracting the component from the observed alignment error; and

controlling at least one of a bonding head that holds the chiplet or a substrate stage that holds the substrate to adjust a relative position of the chiplet and the substrate based on the chiplet-position error.

2 . The method of claim 1 , wherein estimating the chiplet-position error of the chiplet is further based on a reference surface.

3 . The method of claim 2 , wherein the reference surface is an image of a region of a reference chiplet.

4 . The method of claim 2 , wherein obtaining the observed alignment error comprises:

calculating an alignment difference between the image of the region on the chiplet and the reference surface,

wherein the alignment difference includes one or both of a translation difference and a rotation difference.

5 . The method of claim 4 , wherein calculating the component of the observed alignment error comprises:

adjusting the alignment difference based on the deviation from planarity of the region.

6 . The method of claim 5 , wherein adjusting the alignment difference based on the deviation from planarity of the region includes subtracting a component of the alignment difference that is caused by the deviation from planarity of the region.

7 . The method of claim 1 , wherein the chiplet is held by a bonding head.

8 . A system comprising:

one or more processors; and

one or more memories, wherein the one or more processors and the one or more memories are configured to:

obtain an image of a region on a chiplet;

measure a deviation from planarity of the region on the chiplet;

calculate a chiplet-position error of the chiplet based on the image of the region and the deviation from planarity of the region, wherein, to calculate the chiplet-position error, the one or more processors and the one or more memories are configured to:

obtain an observed alignment error of the region based on the image of the region,

calculate a component of the observed alignment error that is caused by the deviation from planarity of the region, and

calculate an in-plane alignment error by subtracting the component from the observed alignment error; and

control at least one of a bonding head that holds the chiplet or a substrate stage that holds a substrate to adjust a relative position of the chiplet and the substrate based on the chiplet-position error.

9 . The system of claim 8 , wherein the chiplet-position error of the chiplet is calculated further based on a reference surface.

10 . The system of claim 9 , wherein the reference surface is an image of a region of a reference chiplet.

11 . The system of claim 9 , wherein, to obtain the observed alignment error, the one or more processors and the one or more memories are configured to:

calculate an alignment difference between the image of the region on the chiplet and the reference surface,

wherein the alignment difference includes one or both of a translation difference and a rotation difference.

12 . The system of claim 11 , wherein, to calculate the component of the observed alignment error, the one or more processors and the one or more memories are further configured to:

adjust the alignment difference based on the deviation from planarity of the region.

13 . The system of claim 12 , wherein, to adjust the alignment difference based on the deviation from planarity of the region, the one or more processors and the one or more memories are further configured to subtract a component of the alignment difference that is caused by the deviation from planarity of the region.

14 . The system of claim 8 , further comprising:

a bonding head, wherein the chiplet is held by the bonding head.

15 . One or more non-transitory computer-readable storage media storing instructions that, when executed by one or more computing devices, cause the one or more computing devices to perform operations comprising:

obtaining an image of a region on a chiplet;

measuring a surface relief of the region on the chiplet;

calculating a chiplet-position error of the chiplet based on at least the image of the region, the surface relief of the region, and a reference surface, wherein calculating the chiplet-position error comprises:

obtaining an observed alignment error of the region based on the image of the region,

calculating a component of the observed alignment error that is caused by the surface relief of the region, and

calculating an in-plane alignment error by subtracting the component from the observed alignment error;

calculating a position-adjustment value for the chiplet based on the chiplet-position error; and

controlling at least one of a bonding head that holds the chiplet or a substrate stage that holds a substrate to adjust a relative position of the chiplet and the substrate based on the position-adjustment value.

16 . The one or more non-transitory computer-readable storage media of claim 15 , wherein calculating the position-adjustment value for the chiplet includes calculating a surface-relief component of the chiplet-position error based on the surface relief of the region, wherein the surface-relief component is caused by a difference between the surface relief of the region on the chiplet and the reference surface.

17 . The one or more non-transitory computer-readable storage media of claim 16 , wherein calculating the position-adjustment value for the chiplet further includes

calculating an in-plane-translation difference and an in-plane-rotation difference of the region, wherein calculating the in-plane-translation difference and the in-plane-rotation difference of the region includes subtracting the surface-relief component from the chiplet-position error.

18 . The one or more non-transitory computer-readable storage media of claim 17 , wherein the in-plane-translation difference and the in-plane-rotation difference define the position-adjustment value.

19 . The one or more non-transitory computer-readable storage media of claim 16 , wherein the reference surface is a surface of a reference chiplet or an ideal planar surface.