An overlay matching method

Abstract

The present invention provides an overlay matching method, comprising: providing a wafer, forming a first photoresist layer on the wafer; exposing the first photoresist layer using a first photolithography machine, with the remaining first photoresist layer constituting a first alignment mark; forming a second photoresist layer on the wafer, with the second photoresist layer covering the wafer and the first alignment mark; exposing the second photoresist layer using a second photolithography machine, with the remaining second photoresist layer constituting a second alignment mark; obtaining an overlay accuracy between the first alignment mark and the second alignment mark, and adjusting an initial exposure position of the second photolithography machine according to the overlay accuracy. The first and second alignment marks are formed on the wafer by the photoresist layer, thereby achieving overlay matching between photolithography machines while avoiding performing an etching process on the wafer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and in particular to an overlay matching method. Background Art

[0002] The photolithography process is a key step in the manufacture of semiconductor integrated circuits. Specifically, it refers to the fine processing technology that transfers the pattern designed on the mask to the wafer through processes such as exposure, development, and etching, by chemically transforming the photoresist under special wavelengths of light or electron beams. In the production of semiconductor chips, the entire manufacturing process is usually completed through multiple layers of photolithography. The pattern left on the wafer after exposure and development must be aligned with the position of the existing pattern on the wafer. In other words, the pattern on the current layer of the wafer must be aligned with the pattern on the previous layer of the wafer. The overlay accuracy between the upper and lower layers of the wafer must meet the required level to ensure correct connection between the various parts of the semiconductor device. Overlay accuracy greatly affects the yield of semiconductor devices.

[0003] Considering production costs, in actual operation, a high-performance lithography machine is selected to perform the process of critical layers, while a lower-performance lithography machine is selected to perform the process of non-critical layers. This hybrid lithography method can more efficiently utilize the performance of each lithography machine while reducing equipment costs. When using multiple lithography machines to perform lithography on a wafer, it is necessary to first perform overlay matching between the lithography machines to ensure the overlay accuracy of the patterns on the wafer and to achieve lithography on different lithography machines. Summary of the Invention

[0004] The purpose of the present invention is to provide an overlay matching method to achieve overlay matching between different lithography machines.

[0005] In order to achieve the above object, the present invention provides an overlay matching method, comprising:

[0006] providing a wafer, and forming a first photoresist layer on the wafer;

[0007] Exposing the first photoresist layer using a first photolithography machine, so that the remaining first photoresist layer constitutes a first alignment mark;

[0008] forming a second photoresist layer on the wafer, wherein the second photoresist layer covers the wafer and the first alignment mark;

[0009] exposing the second photoresist layer using a second photolithography machine, so that the remaining second photoresist layer constitutes a second alignment mark;

[0010] The overlay accuracy between the first alignment mark and the second alignment mark is obtained, and the initial exposure position of the second photolithography machine is adjusted according to the overlay accuracy.

[0011] Optionally, the overlay accuracy includes a first overlay accuracy along the first direction and a second overlay accuracy along the second direction, the initial position of exposure of the second photolithography machine includes a first initial position along the first direction and a second initial position along the second direction, and the step of adjusting the initial position of exposure of the second photolithography machine according to the overlay accuracy includes:

[0012] The first initial position of exposure by the second photolithography machine is adjusted according to the first overlay accuracy, and the second initial position of exposure by the second photolithography machine is adjusted according to the second overlay accuracy.

[0013] Optionally, the positive and negative properties of the first photoresist layer and the second photoresist layer are the same or different.

[0014] Optionally, after the first photoresist layer is exposed by the first photolithography machine, the remaining first photoresist layer also constitutes an alignment mark, and the second photolithography machine performs alignment through the alignment mark.

[0015] Optionally, after obtaining the overlay accuracy between the first alignment mark and the second alignment mark, the method further includes:

[0016] A stripping process is performed on the wafer to remove the first alignment mark, the second alignment mark, and the alignment mark on the wafer.

[0017] Optionally, when there are multiple second photolithography machines, the degumming process is performed on the wafer after each adjustment of the initial position of the second photolithography machine, and the wafer after degumming is used for overlay matching between the first photolithography machine and the next second photolithography machine.

[0018] Optionally, the first photolithography machine and the second photolithography machine are of the same or different models.

[0019] Optionally, the exposure accuracy of the first photolithography machine is higher than the exposure accuracy of the second photolithography machine.

[0020] Optionally, the first photolithography machine uses a first mask to expose the first photoresist layer, and the first mask has the alignment mark and the first position mark.

[0021] Optionally, the second photolithography machine uses a second mask to expose the second photoresist layer, the second mask has a second alignment mark corresponding to the first alignment mark, and the first alignment mark and the second alignment mark constitute an overlay mark.

[0022] The present invention provides an overlay matching method, comprising: providing a wafer, forming a first photoresist layer on the wafer; exposing the first photoresist layer using a first photolithography machine, with the remaining first photoresist layer constituting a first alignment mark; forming a second photoresist layer on the wafer, with the second photoresist layer covering the wafer and the first alignment mark; exposing the second photoresist layer using a second photolithography machine, with the remaining second photoresist layer constituting a second alignment mark; obtaining an overlay accuracy between the first alignment mark and the second alignment mark, and adjusting an initial exposure position of the second photolithography machine according to the overlay accuracy. Overlay matching between photolithography machines is achieved by using the first alignment mark and the second alignment mark formed on the wafer by the photoresist layer.

[0023] In addition, the present invention does not etch the wafer during the overlay matching process of the lithography machine, which reduces the process steps. After the overlay matching is completed, the wafer can be subjected to a degumming process to achieve the recycling of the wafer, greatly reducing the process cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of an overlay matching method;

[0025] Figure 2 A flowchart of an overlay matching method is provided for an embodiment of the present invention;

[0026] Figures 3-4 A schematic diagram of an overlay mark for an overlay matching method provided in an embodiment of the present invention;

[0027] The accompanying drawings are as follows:

[0028] 100-first alignment mark; 200-second alignment mark. DETAILED DESCRIPTION

[0029] Figure 1 is a flow chart of an overlay matching method, such as Figure 1 As shown, the overlay matching method includes:

[0030] Step S11: providing a standard wafer, wherein the standard wafer has an alignment mark and a first registration mark;

[0031] Step S12: aligning the standard wafer and the photolithography machine to be matched by the alignment mark, and etching the standard wafer using a third mask as a mask to form a second alignment mark on the standard wafer;

[0032] Step S13: measuring the overlay accuracy between the first alignment mark and the second alignment mark, and adjusting the data parameters of the lithography machine to be matched according to the overlay accuracy.

[0033] In the existing overlay matching method, the standard wafer needs to be manufactured first, and the standard wafer needs to be etched when forming the alignment mark, the first alignment mark and the second alignment mark. The manufacturing process is complicated, and the standard wafer cannot be used for other purposes after overlay matching.

[0034] The following is a more detailed description of the specific embodiments of the present invention with reference to schematic diagrams. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are not to exact scale, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention.

[0035] Hereinafter, the terms "first," "second," and the like are used to distinguish between similar elements and are not necessarily used to describe a particular order or chronological sequence. It is to be understood that these terms, when used in this manner, are interchangeable where appropriate. Similarly, if a method described herein comprises a series of steps, the steps presented herein are not necessarily the only order in which the steps may be performed, and some of the steps described may be omitted and / or other steps not described herein may be added to the method.

[0036] Figure 2 A flowchart of an overlay matching method provided in this embodiment is shown in FIG. Figure 2 As shown, the present invention provides an overlay matching method, comprising:

[0037] Step S1: providing a wafer, and forming a first photoresist layer on the wafer;

[0038] Step S2: exposing the first photoresist layer using a first photolithography machine, and the remaining first photoresist layer constitutes a first alignment mark;

[0039] Step S3: forming a second photoresist layer on the wafer, wherein the second photoresist layer covers the wafer and the first alignment mark;

[0040] Step S4: exposing the second photoresist layer using a second photolithography machine, and the remaining second photoresist layer constitutes a second alignment mark;

[0041] Step S5: obtaining the overlay accuracy between the first alignment mark and the second alignment mark, and adjusting the initial exposure position of the second photolithography machine according to the overlay accuracy.

[0042] Specifically, a first mask, a second mask, a first photolithography machine to be matched, and a second photolithography machine are provided. The model or manufacturer of the first photolithography machine and the second photolithography machine may be the same or different, and the first photolithography machine has better stability than the second photolithography machine. The first mask has an alignment mark between the first photolithography machine and the second photolithography machine, and the first mask also has a first alignment mark, and the second mask has a second alignment mark, and the first alignment mark and the second alignment mark constitute an overlay mark.

[0043] A wafer is provided, and a first photoresist layer is spin-coated on the surface of the wafer, with the first photoresist layer covering the wafer. The first photoresist layer is exposed using the first photolithography machine using the first reticle as a mask, and the remaining first photoresist layer after development forms the alignment mark and the first position mark. The wafer is then transferred to a second photolithography machine, and a second photoresist layer is spin-coated on the wafer, with the second photoresist layer covering the alignment mark, the first position mark, and the wafer. The second photoresist layer is exposed using the second reticle as a mask, and the remaining second photoresist layer after development forms the second position mark.

[0044] Figures 3-4 Schematic diagram of the overlay marking of the overlay matching method provided in this embodiment, Figure 3 It is a commonly used box-in-box alignment mark. Figure 4 It is a commonly used bar-in-bar registration mark. Figure 3 and 4 Only the optional embodiments listed in the present invention are Figure 3 and Figure 4 In the embodiment, the second alignment mark 200 is located in the first alignment mark 100 . The present invention does not limit the shape of the overlay pattern, nor does it limit the positional relationship between the first alignment mark 100 and the second alignment mark 200 .

[0045] It should be noted that the photoresist used in the first photoresist layer may be positive or negative, and the photoresist used in the second photoresist layer may be positive or negative. The first and second photoresist layers may have the same or different positive and negative properties. However, considering the exposure and development characteristics of photoresists, and in order to better preserve the alignment marks and the first position mark during exposure and development of the second photoresist layer, thereby forming a more accurate overlay mark, the first and second photoresist layers have different positive and negative properties. That is, when the first photoresist layer is a positive photoresist, the second photoresist layer is a negative photoresist, and vice versa.

[0046] In addition, in order to ensure the overlay accuracy between the overlay marks, the alignment between the wafer and the second photolithography machine needs to be completed through the alignment marks before the exposure and development process of the second photoresist layer. If the thickness of the second photoresist layer is relatively thick, it will be difficult for the second photolithography machine to align with the alignment marks. Therefore, the thickness ratio between the first photoresist layer and the second photoresist layer provided in this embodiment is greater than 1.5:1 to prevent the second photoresist layer from being too thick and completely covering the alignment marks, thereby improving the accuracy of the alignment between the second photolithography machine and the wafer, and thus improving the accuracy of the overlay mark position and reducing errors. The thickness of the second photoresist is 100nm to 140nm.

[0047] After the overlay mark is formed on the wafer, the overlay accuracy between the first alignment mark and the second alignment mark is obtained, and the initial exposure position of the second photolithography machine is adjusted according to the overlay accuracy.

[0048] Specifically, the overlay accuracy includes a first overlay accuracy along the first direction and a second overlay accuracy along the second direction. The initial position of exposure of the second photolithography machine includes a first initial position along the first direction and a second initial position along the second direction. The first initial position of exposure of the second photolithography machine is adjusted according to the first overlay accuracy, and the second initial position of exposure of the second photolithography machine is adjusted according to the second overlay accuracy.

[0049] In addition, the first photolithography machine and the second photolithography machine may be overlaid multiple times until the overlay accuracy reaches a preset value, thereby satisfying the overlay matching requirement between the first photolithography machine and the second photolithography machine.

[0050] After the overlay matching of the lithography machine is completed, the wafer is subjected to a degumming process, and the alignment mark, the first alignment mark and the second alignment mark on the wafer are removed by ashing or other methods. The wafer after the degumming process can also be used for other purposes. The overlay matching method provided by the present invention only performs exposure and development processes on the first photoresist layer and the second photoresist layer on the wafer, and does not etch the wafer. Therefore, when the overlay matching is completed, as long as the photoresist on the wafer is removed, the wafer can be applied to other processes or continue to be used for overlay matching, thereby realizing the recycling of the wafer. Compared with the method of etching the standard wafer in the existing process, it not only reduces the process steps but also greatly saves costs.

[0051] It should be noted that in this embodiment, overlay matching between two photolithography machines is used as an example. In actual operation, when there are multiple second photolithography machines, the stripping process is performed on the wafer after adjusting the initial position of each second photolithography machine, and the initial position of the next second photolithography machine using the same wafer is adjusted. Only one wafer can be used to sequentially achieve overlay matching between each second photolithography machine and the first photolithography machine, thereby minimizing the impact of different wafers on the overlay accuracy. The exposure accuracy of the first photolithography machine is higher than that of the second photolithography machine, and the performance of the first photolithography machine is more stable.

[0052] In other optional embodiments, the first photolithography machine can be used to form a number of wafers with the alignment marks and the first positioning marks, and the second mask is used as a mask on the corresponding second photolithography machine to form respective second positioning marks on the wafers; finally, the overlay accuracy is calculated respectively, and the initial position of the exposure lens of the second photolithography machine is adjusted to achieve overlay matching of multiple photolithography machines with the first photolithography machine.

[0053] In summary, the present invention provides an overlay matching method, comprising: providing a wafer, forming a first photoresist layer on the wafer; using a first photolithography machine to expose the first photoresist layer, and the remaining first photoresist layer constitutes a first alignment mark; forming a second photoresist layer on the wafer, and the second photoresist layer covers the wafer and the first alignment mark; using a second photolithography machine to expose the second photoresist layer, and the remaining second photoresist layer constitutes a second alignment mark; obtaining the overlay accuracy between the first alignment mark and the second alignment mark, and adjusting the initial position of the exposure of the second photolithography machine according to the overlay accuracy. Overlay matching between photolithography machines is achieved by forming the first alignment mark and the second alignment mark on the wafer through the photoresist layer. In addition, the present invention does not etch the wafer during the overlay matching process of the photolithography machine, which reduces the process steps. After the overlay matching is completed, the wafer can be subjected to a de-bonding process to achieve the recycling of the wafer, greatly reducing the process cost.

[0054] The above description is merely a preferred embodiment of the present invention and does not limit the present invention in any way. Any person skilled in the art who, without departing from the scope of the present invention, makes any equivalent substitution, modification, or other changes to the technical solution and technical content disclosed in the present invention shall be deemed to be within the scope of the present invention and still fall within the scope of protection of the present invention.

Claims

1. An overlay matching method, characterized in that: include: providing a wafer, and forming a first photoresist layer on the wafer; exposing the first photoresist layer using a first photolithography machine, so that the remaining first photoresist layer constitutes a first alignment mark; forming a second photoresist layer on the wafer, wherein the second photoresist layer covers the wafer and the first alignment mark; exposing the second photoresist layer using a second photolithography machine, so that the remaining second photoresist layer constitutes a second alignment mark; Obtaining an overlay accuracy between the first alignment mark and the second alignment mark, and adjusting an initial exposure position of the second photolithography machine according to the overlay accuracy; The first photoresist layer and the second photoresist layer have different positive and negative properties; and a thickness ratio between the first photoresist layer and the second photoresist layer is greater than 1.5:

1.

2. The overlay matching method according to claim 1, wherein: The overlay accuracy includes a first overlay accuracy along the first direction and a second overlay accuracy along the second direction, the initial position of exposure of the second photolithography machine includes a first initial position along the first direction and a second initial position along the second direction, and the step of adjusting the initial position of exposure of the second photolithography machine according to the overlay accuracy includes: The first initial position of exposure by the second photolithography machine is adjusted according to the first overlay accuracy, and the second initial position of exposure by the second photolithography machine is adjusted according to the second overlay accuracy.

3. The overlay matching method according to claim 1, wherein: After the first photoresist layer is exposed by the first photolithography machine, the remaining first photoresist layer also constitutes an alignment mark, and the second photolithography machine performs alignment through the alignment mark.

4. An overlay matching method as claimed in claim 3, characterized in that: After obtaining the overlay accuracy between the first alignment mark and the second alignment mark, the method further includes: A stripping process is performed on the wafer to remove the first alignment mark, the alignment mark, and the second alignment mark on the wafer.

5. The overlay matching method according to claim 4, wherein: When there are multiple second photolithography machines, the stripping process is performed on the wafer after each adjustment of the initial position of the second photolithography machine. The wafer after stripping is used for overlay matching between the first photolithography machine and the next second photolithography machine.

6. An overlay matching method according to claim 1 or 5, characterized in that: The first photolithography machine and the second photolithography machine are of the same model or different models.

7. An overlay matching method according to claim 6, characterized in that: The exposure accuracy of the first photolithography machine is higher than that of the second photolithography machine.

8. The overlay matching method according to claim 3, wherein: The first photolithography machine uses a first mask to expose the first photoresist layer, and the first mask has the alignment mark and the first position mark.

9. The overlay matching method according to claim 1, wherein: The second photolithography machine uses a second mask to expose the second photoresist layer. The second mask has a second alignment mark corresponding to the first alignment mark. The first alignment mark and the second alignment mark constitute an overlay mark.

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