Alignment marks

Abstract

In the present invention, a positioning mark comprises at least one tick mark row (111) that is composed of an odd number of a reference tick mark (101), a first tick mark (102), a second tick mark (103), a third tick mark (104), and a fourth tick mark (105). Each tick mark is formed as a trapezoid, the shape of which comprises, as seen in plan view, an upper base and a lower base that is longer than the upper base, the tick marks being of the same height. Relative to the reference tick mark (101), which is disposed in the center of the tick mark row (111), the positions of the upper bases of the first tick mark (102), the second tick mark (103), the third tick mark (104), and the fourth tick mark (105) are shifted in a positioning direction at set regular intervals away from the reference tick mark (101).

Description

[Technical Field]

[0001] The present invention relates to alignment marks. [Background technology]

[0002] The integration of compound optical semiconductors and silicon photonics optical circuits is progressing toward higher speeds, larger capacities, and smaller sizes of optical transceivers for optical communications. Among these, micro transfer printing is attracting attention as a technology that can integrate completed compound optical semiconductor devices and silicon photonics optical circuits with high positional accuracy, high throughput, and low cost.

[0003] In the transfer printing method, as shown in Non-Patent Document 1, the compound semiconductor device to be transferred and the substrate to which it is to be transferred are aligned using visible light and a high-definition camera. Conventionally, this alignment uses a cross mark 201 formed on the substrate side as shown in Figure 4(a) and a cross-shaped cutout mark 202 formed on the device side as shown in Figure 4(b). For alignment, the cross mark 201 is made to overlap the cross-shaped cutout portion of the cutout mark 202. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] J. McPhillimy et al., "Automated Nanoscale Absolute Accuracy Alignment System for Transfer Printing", ACS Applied Nano Materials, vol. 3, pp. 10326-10332, 2020. [Non-patent document 2] N. Ye et al., "High-alignment-accuracy transfer printing of passive silicon waveguide structures", Optics Express, vol. 26, no. 2, pp. 2023-2032, 2018. Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the alignment accuracy required for silicon photonics optical circuits and the like is on the order of sub-micrometers (Non-Patent Document 2). For this reason, it is difficult to achieve the required accuracy with the conventional marks used for the above-mentioned alignment.

[0006] In contrast to the alignment using the marks described above, there is an alignment technique using vernier marks (Non-Patent Document 1). This technique uses a first vernier mark 311 formed on the surface of a substrate 301 and a second vernier mark 321 formed on the upper surface of a device 302, as shown in Fig. 5A. The use of vernier marks enables highly accurate alignment.

[0007] High-precision alignment requires high-magnification observation using an optical microscope, but there is generally a trade-off between the magnification and depth of focus of an optical microscope, and the depth of focus of an optical microscope at the magnification required for sub-micron alignment is shallow, at most a few tens of microns.

[0008] 5B, the surface of substrate 301 on which first vernier mark 311 is formed and the top surface of device 302 on which second vernier mark 321 is formed are at different positions in the focal direction of the observation system. For this reason, a sufficient observation magnification cannot provide a focal depth that brings both marks into focus, and when one mark is in focus, the other mark becomes blurred, making accurate observation impossible and reducing the accuracy of alignment.

[0009] Furthermore, transfer printing can sometimes involve forming a film such as a resist on the surface of the device. When the device surface is covered with a resist film, high-magnification observation is affected by the optical path length, which is the thickness of the resist film, which is on the order of a few microns, and this can easily cause focus shifts and aberrations, hindering accurate observation.

[0010] The above problems can be solved by combining image analysis and confocal techniques such as laser microscopy, but this technique requires time to acquire and combine multiple images with different focuses, which reduces throughput in alignment.

[0011] The present invention has been made to solve the above problems, and has as its object to enable accurate alignment without causing a decrease in throughput. [Means for solving the problem]

[0012] The alignment mark according to the present invention is an alignment mark formed on a substrate, which is used to align a linear alignment portion of the shape of a device in a plan view with a linear alignment position on the substrate, and to place a device on the substrate, and the alignment mark comprises at least one set of scale mark rows made up of an odd number of scale marks, each of which has a trapezoidal shape in a plan view having an upper base and a lower base that is longer than the upper base, and which have the same height, and the scale marks of the scale mark row are arranged in the alignment position within the range of the alignment portion, in a direction perpendicular to the alignment direction of the device, and the scale marks of the scale mark row The upper and lower bases and the arrangement direction are parallel, and the positions of the upper bases of the other scale marks relative to the reference scale mark at the center of the scale mark row are shifted in the alignment direction at a set constant interval as they move away from the reference scale mark, and the other scale marks arranged in one direction relative to the reference scale mark are opposite in direction from the lower base to the upper base, and the direction in which the other scale marks arranged in one direction relative to the reference scale mark are shifted is opposite to the direction in which the other scale marks arranged in the other direction are shifted. [Effects of the Invention]

[0013] As described above, according to the present invention, a scale mark row consisting of an odd number of scale marks, each having a trapezoidal planar shape, is used which is formed on a substrate on which a device is to be mounted, thereby enabling accurate alignment without incurring a decrease in throughput or the like. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a plan view showing the configuration of an alignment mark according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing the configuration of another alignment mark according to the embodiment of the present invention. [Figure 3A] FIG. 3A is a plan view for explaining alignment using an alignment mark according to an embodiment of the present invention. [Figure 3B]FIG. 3B is a plan view for explaining alignment using an alignment mark according to the embodiment of the present invention. [Figure 3C] FIG. 3C is a plan view for explaining alignment using an alignment mark according to the embodiment of the present invention. [Figure 3D] FIG. 3D is a plan view for explaining alignment using an alignment mark according to the embodiment of the present invention. [Figure 3E] FIG. 3E is a plan view for explaining alignment using an alignment mark according to an embodiment of the present invention. [Figure 3F] FIG. 3F is a plan view for explaining alignment using an alignment mark according to an embodiment of the present invention. [Figure 4] FIG. 4 is a plan view showing a conventional alignment mark. [Figure 5A] FIG. 5A is a plan view for explaining alignment using vernier marks. [Figure 5B] FIG. 5B is a side view for explaining alignment using a vernier mark. DETAILED DESCRIPTION OF THE INVENTION

[0015] An alignment mark according to an embodiment of the present invention will be described below with reference to Fig. 1. This alignment mark is formed on the substrate 121 and is used to align a linear alignment portion of the shape of the device in a planar view with a linear alignment position on the substrate 121, thereby placing the device on the substrate 121. The linear portion that serves as the alignment position on the substrate 121 has a length that falls within a range that can be confirmed by an observation system used to perform alignment, for example. The device has, for example, a rectangular parallelepiped outer shape, a rectangular shape in a planar view, and a thickness of several hundred nanometers to several tens of micrometers.

[0016] The alignment marks include at least one set of scale mark rows 111 made up of an odd number of reference scale marks 101, a first scale mark 102, a second scale mark 103, a third scale mark 104, and a fourth scale mark 105. Each scale mark has a trapezoidal shape in plan view, with an upper base and a lower base that is longer than the upper base, and each has the same height.

[0017] The reference scale mark 101, the first scale mark 102, the second scale mark 103, the third scale mark 104, and the fourth scale mark 105 that make up the scale mark row 111 are arranged in the alignment position within the alignment portion in a direction (x direction) perpendicular to the alignment direction (y direction) of the device.

[0018] The reference scale mark 101, the first scale mark 102, the second scale mark 103, the third scale mark 104, and the fourth scale mark 105 have their upper and lower bases parallel to the arrangement direction (x direction).

[0019] Furthermore, with respect to the reference scale mark 101 disposed in the center of the scale mark row 111, the positions of the upper bases of the other first scale mark 102, second scale mark 103, third scale mark 104, and fourth scale mark 105 shift in the alignment direction (y direction) at a set constant interval as they move away from the reference scale mark 101. This interval can be determined based on the required (necessary) alignment accuracy and can be on the order of sub-micron. For example, if the required alignment accuracy is 0.5 μm, 0.5 μm can be set as the constant interval. This interval is known when alignment is performed. Furthermore, the upper base of the reference scale mark 101 is disposed so as to overlap (align) with the linear alignment position on the substrate 121.

[0020] The other first scale marks 102 and second scale marks 103, which are arranged in one direction (-x direction) relative to the reference scale mark 101, and the other third scale marks 104 and fourth scale marks 105, which are arranged in the other direction (+x direction), are arranged in opposite directions (y direction) from the lower base to the upper base.

[0021] Furthermore, the direction in which the other first scale marks 102 and second scale marks 103, which are arranged in one direction (-x direction) relative to the reference scale mark 101, shift is opposite to the direction in which the other third scale marks 104 and fourth scale marks 105, which are arranged in the other direction (+x direction), shift.

[0022] The dimensions of the upper base, lower base, and height of each scale mark can be approximately several micrometers. The intervals between the scale marks can be uniform. The intervals between the scale marks can also be different lengths. In this example, five scale marks form one set of scale mark arrays 111. One set of scale mark arrays 111 can be composed of five or more scale marks. The number of scale marks can be set appropriately depending on the required positional accuracy. Each scale mark can have the same planar shape. The length of the scale mark array 111 in the array direction (x direction) is set, for example, within the range that can be confirmed by the observation system used to perform alignment.

[0023] 2, a first scale mark row 111a and a second scale mark row 111b can be arranged at two alignment portions 122a, 122b that are parallel to each other in a plan view. The first scale mark row 111a is made up of a reference scale mark 101a, a first scale mark 102a, a second scale mark 103a, a third scale mark 104a, and a fourth scale mark 105a. The second scale mark row 111b is made up of a reference scale mark 101b, a first scale mark 102b, a second scale mark 103b, a third scale mark 104b, and a fourth scale mark 105b.

[0024] Each graduation mark can be formed, for example, from a metal pattern. For example, they can be formed by patterning a metal film formed on the substrate 121 using a well-known lift-off method. Alternatively, each graduation mark can be formed from a recess formed in the substrate 121. The recess can be formed by forming a mask pattern having openings at the positions where the graduation marks will be formed using a known photolithography group, and then etching the surface of the substrate 121 using the formed mask pattern as a mask.

[0025] Next, alignment using the alignment mark according to the embodiment when the required alignment accuracy is ±0.5 μm will be described with reference to FIGS. 3A to 3F. The following describes the state confirmed by observation using an observation system for performing alignment. The state used in the following description is a state in which linear alignment portion 122a of the planar shape of device 122 to be aligned and linear alignment position on substrate 121 are aligned parallel to each other in advance.

[0026] As shown in FIG. 3A, when the upper bases of the two scale marks on the right, the third scale mark 104 and the fourth scale mark 105, are not visible and the upper bases of the two scale marks on the left, the first scale mark 102 and the second scale mark 103, are visible, it is possible to determine that the positional deviation (Δ) in the alignment direction (y direction) of the device 122 is in the range of "-0.5 μm<Δ<0 μm."

[0027] Next, as shown in FIG. 3B, when the reference scale mark 101 and the first scale mark 102 are not visible and the upper base of the second scale mark 103 is visible, it is possible to determine that the positional deviation amount (Δ) in the alignment direction (y direction) of the device 122 is in the range of "-1.0 μm<Δ<-0.5 μm."

[0028] Next, as shown in FIG. 3C, when the reference scale mark 101, the first scale mark 102, the second scale mark 103 (and the fourth scale mark 105) are not visible, and the bottom of the third scale mark 104 is visible, it is possible to determine that the positional deviation (Δ) in the alignment direction (y direction) of the device 122 is in the range of "Δ<-1.0 μm."

[0029] Furthermore, as shown in FIG. 3D, when the upper bases of the reference scale mark 101, the first scale mark 102, and the second scale mark 103 are visible but the lower bases are not, and the lower bases of the third scale mark 104 and the fourth scale mark 105 are visible, it is possible to determine that the positional deviation amount (Δ) in the alignment direction (y direction) of the device 122 is in the range of "0 μm<Δ<+0.5 μm."

[0030] Furthermore, as shown in FIG. 3E, when the upper bases of the reference scale mark 101 and the first scale mark 102 are visible but the lower bases are not, the lower base of the fourth scale mark 105 is visible, and the entire third scale mark 104 is visible, it is possible to determine that the positional deviation amount (Δ) in the alignment direction (y direction) of the device 122 is within the range of "+0.5 μm<Δ<+1.0 μm."

[0031] Furthermore, as shown in FIG. 3F, when the upper base of the reference scale mark 101 is visible but the lower base is not, and the second scale mark 103, the third scale mark 104, and the fourth scale mark 105 are entirely visible, it is possible to determine that the positional deviation (Δ) in the alignment direction (y direction) of the device 122 is within the range of "+1.5 μm<Δ".

[0032] In the alignment using the alignment marks according to the above-described embodiment, the scale marks formed on the surface of the substrate are observed in a state where they are hidden by the alignment portion on the bottom surface of the device located on the surface of the substrate. Therefore, the focus of the observation system only needs to be adjusted to the surface of the substrate, and there is no loss of accuracy due to insufficient focal depth, making it possible to observe at high magnification. Furthermore, since complex processes such as confocal observation or depth stacking are not required, real-time alignment can be performed using a simple optical microscope, and there is no reduction in throughput.

[0033] As described above, according to the present invention, a scale mark row consisting of an odd number of scale marks, each having a trapezoidal planar shape, is used which is formed on a substrate on which a device is to be placed, thereby enabling accurate alignment without causing a decrease in throughput or the like.

[0034] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Explanation of symbols]

[0035] 101...reference scale mark, 102...first scale mark, 103...second scale mark, 104...third scale mark, 105...fourth scale mark, 111...scale mark row, 121...board.

Claims

1. An alignment mark formed on a substrate, which is used to align a linear alignment portion of a shape of a device in a plan view with a linear alignment position on the substrate, and to place the device on the substrate, at least one set of scale mark rows is formed of an odd number of scale marks each having the same height and each having a trapezoidal shape in a plan view with an upper base and a lower base that is longer than the upper base, the scale marks of the scale mark row are arranged in a direction perpendicular to the alignment direction of the device within the alignment portion and are disposed at the alignment position; the scale marks in the scale mark row are arranged parallel to the upper and lower bases, the positions of the upper bases of the other scale marks relative to the reference scale mark at the center of the scale mark row are shifted in the alignment direction at a set constant interval as they move away from the reference scale mark; the other scale marks arranged in one direction relative to the reference scale mark and the other scale marks arranged in the other direction are arranged in opposite directions from the lower base to the upper base, The direction in which the other scale marks arranged in one direction relative to the reference scale mark are shifted is opposite to the direction in which the other scale marks arranged in the other direction are shifted. An alignment mark characterized by:

2. 2. The alignment mark according to claim 1, The scale mark rows are arranged at each of the two alignment portions that are parallel to each other in a plan view. An alignment mark characterized by:

3. 2. The alignment mark according to claim 1, An alignment mark characterized in that one set of the scale mark rows is made up of five or more scale marks.

4. The alignment mark according to any one of claims 1 to 3, An alignment mark, wherein each of the scale marks in the scale mark row has the same planar shape.

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