Overlay bias compensation method

Abstract

A method for overlay error compensation, comprising: providing a plurality of batches of wafers with a first exposure layer, the first exposure layer having alignment marks thereon; forming a second exposure layer on the first exposure layer; aligning a lithography machine with the alignment marks to obtain a first down value; obtaining a first measurement value, the first measurement value being an offset of the second exposure layer relative to the first exposure layer; obtaining a best down value corresponding to each batch of wafers according to the first down value and the first measurement value; grouping the plurality of batches of wafers according to a plurality of the best down values to obtain a plurality of groups, each group including at least one batch of wafers; and performing iterative compensation of etching errors of the lithography machine for the plurality of batches of wafers in the same group to obtain a plurality of third exposure layers on the second exposure layer. The method has a good in-group compensation effect.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and in particular to a method for compensating for overlay deviations. Background Technology

[0002] Photolithography is a crucial technology in semiconductor manufacturing, enabling the transfer of patterns from a photomask to the surface of a silicon wafer, forming semiconductor products that meet design requirements. In the photolithography process, firstly, through an exposure step, light passes through the transparent or reflective areas of the photomask and illuminates the silicon wafer coated with photoresist, causing a photochemical reaction with the photoresist. Next, through a development step, the solubility of the developer by the photosensitive and unphotosensitive photoresist forms a photolithographic pattern, achieving the transfer of the photomask pattern. Then, through an etching step, the silicon wafer is etched based on the photolithographic pattern formed by the photoresist layer, further transferring the photomask pattern onto the silicon wafer.

[0003] However, the overlay accuracy of the patterns transferred onto the silicon wafer is poor. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a method for compensating for overlay deviations, so as to improve overlay accuracy.

[0005] To address the aforementioned technical problems, the present invention provides a method for overlay deviation compensation, comprising: providing several batches of wafers, each batch of wafers having a first exposure layer, the first exposure layer having alignment marks; forming a second exposure layer on the first exposure layer; aligning a lithography machine with the alignment marks to obtain a first cut-off value; obtaining a first measurement value, the first measurement value being the offset of the second exposure layer relative to the first exposure layer; obtaining an optimal cut-off value corresponding to each batch of wafers based on the first cut-off value and the first measurement value; grouping the several batches of wafers according to several optimal cut-off values ​​to obtain several groups, each group including at least one batch of wafers; performing iterative compensation for etching deviation on the lithography machine of several batches of wafers in the same group to obtain several third exposure layers located on the second exposure layer.

[0006] Optionally, the method for iteratively compensating for etching deviations in lithography machines of several batches of wafers within the same group to obtain several third exposure layers located on the second exposure layer includes: selecting a first batch of wafers within any group, forming a third exposure layer on the second exposure layer of the first batch of wafers; obtaining a second measurement value of the first batch of wafers, where the second measurement value of the first batch of wafers is the offset of the third exposure layer of the first batch of wafers relative to the second exposure layer; compensating the lithography machine of the second batch of wafers based on the second measurement value of the first batch of wafers; after compensating the lithography machine of the second batch of wafers, forming a third exposure layer on the second exposure layer of the second batch of wafers; obtaining a second measurement value of the second batch of wafers, where the second measurement value of the second batch of wafers is the offset of the third exposure layer of the second batch of wafers relative to the second exposure layer; compensating the lithography machine of the third batch of wafers based on the second measurement value of the second batch of wafers; repeatedly obtaining the second measurement values ​​of different batches of wafers until compensation is performed on the lithography machines of several batches of wafers within the same group.

[0007] Optionally, the method for forming a third exposure layer on the second exposure layer of the first batch of wafers includes: forming a third layer to be exposed on the second exposure layer of the first batch of wafers; forming a second photoresist material layer on the third layer to be exposed; exposing the second photoresist material layer to obtain a second photolithographic pattern; and etching the third layer to be exposed using the second photolithographic pattern as a mask to form a third exposure layer on the second exposure layer of the first batch of wafers.

[0008] Optionally, the method for forming a third exposure layer on the second exposure layer of the second batch of wafers includes: forming a third layer to be exposed on the second exposure layer of the second batch of wafers; forming a second photoresist material layer on the third layer to be exposed; compensating the lithography machine with the second measurement value of the first batch of wafers, exposing the second photoresist material layer to obtain a second lithographic pattern; and etching the third layer to be exposed using the second lithographic pattern as a mask to form a third exposure layer on the second exposure layer of the second batch of wafers.

[0009] Optionally, after obtaining the second measurement value of the first batch of wafers, the method further includes: compensating the lithography machine for the second batch of wafers based on the first shipment value and the second measurement value of the first batch of wafers; after obtaining the second measurement value of the second batch of wafers, the method further includes: compensating the lithography machine for the third batch of wafers based on the first shipment value and the second measurement value of the second batch of wafers.

[0010] Optionally, the method for forming a second exposure layer on a first exposure layer includes: forming a second layer to be exposed on the first exposure layer; forming a first photoresist material layer on the second layer to be exposed; exposing the first photoresist material layer to obtain a first photolithographic pattern; and etching the second layer to be exposed using the first photolithographic pattern as a mask to form a second exposure layer on the first exposure layer.

[0011] Optionally, the method for grouping several batches of wafers according to the optimal delivery value to obtain several groups includes: obtaining a two-dimensional distribution scatter plot of the optimal delivery value, wherein the horizontal axis of the two-dimensional distribution scatter plot is a compensation value based on the first measurement value, the sum of the first measurement value and the compensation value is 0, and the vertical axis of the two-dimensional distribution scatter plot is the first delivery value; performing linear fitting on the scatter plot distribution of several optimal delivery values ​​to obtain several straight lines, wherein when the distance between two straight lines is greater than a preset value, the two straight lines correspond to two different groups.

[0012] Optionally, before performing iterative compensation for etching deviations among several batches of wafers within the same group, the method further includes: determining whether the group needs iterative compensation for etching deviations based on the optimal cut-off value.

[0013] Optionally, the method for determining whether the group needs iterative compensation for etching deviation includes: when the optimal cutting value is greater than a preset value, the group needs iterative compensation for etching deviation; when the optimal cutting value is less than the preset value, the group does not need iterative compensation for etching deviation.

[0014] Optionally, the first exposure layer includes parallel fin structures; the second exposure layer includes a gate structure that spans the fin structures; and the third exposure layer includes a metal layer parallel to the gate structure.

[0015] Optionally, it further includes: source / drain doped regions located within the fin structures on both sides of the gate structure, wherein the metal layer is electrically connected to the source / drain doped regions; and a dielectric structure located on the wafer, wherein the gate structure and the fin structure are located within the dielectric structure, and the metal layer is located on the dielectric structure.

[0016] Optionally, the second exposure layer exposes the first exposure layer by developing and etching, and the third exposure layer exposes the second exposure layer by developing and etching.

[0017] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0018] The technical solution of this invention involves statistically analyzing a first measurement value of the offset of the second exposure layer relative to the first exposure layer and a first cutting value for alignment between the lithography machine and the alignment mark to obtain optimal cutting values ​​for several batches of wafers. These optimal cutting values ​​are then grouped into groups, each group including at least one batch of wafers. Iterative compensation for etching deviations is performed between the lithography machines of several batches of wafers within the same group to obtain several third exposure layers located on the second exposure layer. After grouping by the optimal cutting values, only the groups requiring overlay deviation compensation need to perform overlay deviation compensation between different batches of wafers within the group. The differences between different batches of wafers within the same group are small, resulting in more accurate compensation. Furthermore, mutual compensation between batches of wafers within different groups is unnecessary, avoiding uncertainties caused by large differences in batch wafers, thereby improving the accuracy of overlay precision compensation. Attached Figure Description

[0019] Figures 1 to 3 This is a schematic flowchart of the overlay deviation compensation method in an embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram of several batches of wafers grouped in an embodiment of the present invention. Detailed Implementation

[0021] As described in the background section, the overlay accuracy of patterns transferred onto silicon wafers is poor.

[0022] Specifically, the deviation compensation process between different etched layers is as follows: obtain the offset measurement value of the second metal layer relative to the first metal layer; use the offset measurement value to compensate the mask pattern for forming the third metal layer, and obtain the photolithographic pattern for forming the third metal layer.

[0023] In this process, the process of obtaining the offset measurement value of the second metal layer relative to the first metal layer is performed on multiple batches of wafers. The accuracy of the offset measurement value depends on the sampling stability. For example, there will be a large difference when sampling at the center and edge positions of the same batch of wafers, which will make the accuracy of the offset measurement value lower. Therefore, a large number of sampling tests are required to ensure the accuracy of the offset measurement value, which is costly.

[0024] When performing low-cost measurements with a small number of samples, and assuming stable processes, the offset measurement value will have a good effect if the two batches of wafers are very different. However, if the two batches of wafers are very different, the offset measurement value will become noise and affect the prediction results.

[0025] Therefore, a method for overlay deviation compensation is needed to overcome the adverse effects caused by sampling stability and wafer batch variability.

[0026] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] Figures 1 to 3 This is a flowchart illustrating the overlay deviation compensation method in an embodiment of the present invention.

[0028] Please refer to Figure 1 The overlay deviation compensation method includes:

[0029] Step S10: Provide several batches of wafers, each batch of wafers having a first exposure layer, the first exposure layer having alignment marks;

[0030] Step S11: Form a second exposure layer on the first exposure layer;

[0031] Step S12: Align the lithography machine with the alignment mark to obtain the first shipment value;

[0032] Step S13: Obtain a first measurement value, wherein the first measurement value is the offset of the second exposure layer relative to the first exposure layer;

[0033] Step S14: Based on the first shipment value and the first measurement value, obtain the optimal shipment value corresponding to each batch of wafers;

[0034] Step S15: Group several batches of wafers according to several optimal shipment values ​​to obtain several groups, each group including at least one batch of wafers;

[0035] Step S16: Perform iterative compensation for etching deviations on several batches of wafers within the same group to obtain several third exposure layers located on the second exposure layer.

[0036] The method involves statistically analyzing a first measurement of the offset of the second exposure layer relative to the first exposure layer and a first cut-off value for alignment between the lithography machine and the alignment mark to obtain optimal cut-off values ​​for several batches of wafers. These optimal cut-off values ​​are then grouped, with each group containing at least one batch of wafers. Iterative compensation for etching deviations is performed between the lithography machines of several batches of wafers within the same group to obtain several third exposure layers located on the second exposure layer. After grouping by optimal cut-off values, compensation for etching deviations between different batches of wafers within a group is only required for the group requiring overlay deviation compensation. The differences between different batches of wafers within the same group are small, resulting in more accurate compensation. Furthermore, mutual compensation between batches of wafers within different groups is not necessary, avoiding uncertainties caused by large differences in batch wafers, thereby improving the accuracy of overlay precision compensation.

[0037] Next, each step will be analyzed and explained.

[0038] Please continue to refer to this. Figure 1 Step S10: Provide several batches of wafers, each batch of wafers having a first exposure layer, and the first exposure layer having alignment marks.

[0039] The alignment mark is used to continue alignment when forming other upper-layer structures.

[0040] In this embodiment, the first exposure layer includes a plurality of parallel fin structures.

[0041] Please continue to refer to this. Figure 1 Step S11: Form a second exposure layer on the first exposure layer.

[0042] A method for forming a second exposure layer on a first exposure layer includes: forming a second layer to be exposed on the first exposure layer; forming a first photoresist material layer on the second layer to be exposed; exposing the first photoresist material layer to obtain a first photolithographic pattern; and etching the second layer to be exposed using the first photolithographic pattern as a mask to form the second exposure layer on the first exposure layer. In this embodiment, the second exposure layer includes a gate structure that spans the fin structure.

[0043] In this embodiment, the method further includes forming source / drain doped regions within the fin structures located on both sides of the gate structure.

[0044] In this embodiment, the method further includes forming a dielectric structure on a wafer, wherein the gate structure and the fin structure are located within the dielectric structure.

[0045] Please continue to refer to this. Figure 1 Step S12: Align the lithography machine with the alignment mark to obtain the first output value.

[0046] The first value is the offset adjusted after the alignment system of the lithography machine is aligned with the alignment mark.

[0047] The alignment process can be achieved by moving the lens of the lithography machine or by moving the stage on which the wafer is loaded.

[0048] Please continue to refer to this. Figure 1 Step S13: Obtain a first measurement value, wherein the first measurement value is the offset of the second exposure layer relative to the first exposure layer.

[0049] The second exposure layer has a preset position relative to the first exposure layer, and the offset between the actual position of the second exposure layer relative to the first exposure layer and the preset position is the first measurement value.

[0050] The method used to measure the first measured value is a conventional method in this field and will not be described in detail here. Please refer to [link / reference needed]. Figure 1 Step S14: Based on the first shipment value and the first measurement value, obtain the optimal shipment value corresponding to each batch of wafers.

[0051] The optimal unloading value is the sum of the first unloading value and the first measurement value.

[0052] Please continue to refer to this. Figure 1 Step S15: Group several batches of wafers according to several optimal shipment values ​​to obtain several groups, each group including at least one batch of wafers.

[0053] Please refer to Figure 2 In this embodiment, the method for grouping several batches of wafers according to the optimal shipment value to obtain several groups includes:

[0054] Step S191: Obtain a two-dimensional distribution scatter plot of the optimal delivery value. The horizontal axis of the two-dimensional distribution scatter plot is the compensation value based on the first measurement value, and the sum of the first measurement value and the compensation value is 0. The vertical axis of the two-dimensional distribution scatter plot is the first delivery value.

[0055] Step S192: Perform linear fitting on the scatter distribution of several optimal goods values ​​to obtain several straight lines. When the distance between two straight lines is greater than a preset value, the two straight lines correspond to two different groups.

[0056] The preset value is a known value that has been set in advance.

[0057] After grouping the wafers according to their optimal cutting values, only the lithography machines of different batches of wafers within the same group need to be compensated for etching deviations. The differences between different batches of wafers within the same group are small, and the compensation results are more accurate.

[0058] Based on the optimal order value, several batches of wafers are grouped to obtain several groups. Please refer to [reference needed]. Figure 4 As shown, Figure 4 This is a schematic diagram of several batches of wafers grouped together. The horizontal axis X is the compensation value of the first measurement value, the vertical axis Y is the first shipment value, and the scatter plots represent several batches of wafers. G1 is the first group, G2 is the second group, and the spacing between G1 and G2 is greater than a preset value.

[0059] Please continue to refer to this. Figure 1 Before performing iterative compensation for etching deviations between several batches of wafers within the same group, the method further includes: step S17: determining whether the group needs iterative compensation for etching deviations based on the optimal cut-off value.

[0060] The method for determining whether the group needs iterative compensation for etching deviation includes: when the optimal cutting value is greater than a preset value, the group needs iterative compensation for etching deviation; when the optimal cutting value is less than the preset value, the group does not need iterative compensation for etching deviation.

[0061] Please continue to refer to this. Figure 1 Step S16: Iteratively compensate for etching deviations of several batches of wafers in the same group to obtain several third exposure layers located on the second exposure layer.

[0062] Please refer to Figure 3 In this embodiment, the method for iteratively compensating for etching deviations between several batches of wafers within the same group to obtain several third exposure layers located on the second exposure layer includes:

[0063] Step S221: Select the first batch of wafers in any group and form a third exposure layer on the second exposure layer of the first batch of wafers;

[0064] Step S222: Obtain the second measurement value of the first batch of wafers, wherein the second measurement value of the first batch of wafers is the offset of the third exposure layer of the first batch of wafers relative to the second exposure layer.

[0065] Step S223: Compensate the lithography machine for the second batch of wafers based on the second measurement value of the first batch of wafers;

[0066] Step S224: After compensating the lithography machine of the second batch of wafers, a third exposure layer is formed on the second exposure layer of the second batch of wafers;

[0067] Step S225: Obtain the second measurement value of the second batch of wafers, wherein the second measurement value of the second batch of wafers is the offset of the third exposure layer of the second batch of wafers relative to the second exposure layer;

[0068] Step S226: Compensate the lithography machine for the third batch of wafers based on the second measurement value of the second batch of wafers;

[0069] Step S227: Repeat the acquisition of the second measurement value of different batches of wafers multiple times until the lithography machine of several batches of wafers in the same group is compensated.

[0070] The etching deviation between different batches of wafers in the same group is compensated. The difference between different batches of wafers in the same group is small, and the compensation result is relatively accurate.

[0071] In this embodiment, the method for forming a third exposure layer on the second exposure layer of the first batch of wafers includes: forming a third layer to be exposed on the second exposure layer of the first batch of wafers; forming a second photoresist material layer on the third layer to be exposed; exposing the second photoresist material layer to obtain a second photolithographic pattern; and etching the third layer to be exposed using the second photolithographic pattern as a mask to form a third exposure layer on the second exposure layer of the first batch of wafers.

[0072] In this embodiment, the method for forming a third exposure layer on the second exposure layer of the second batch of wafers includes: forming a third layer to be exposed on the second exposure layer of the second batch of wafers; forming a second photoresist material layer on the third layer to be exposed; compensating the lithography machine with the second measurement value of the first batch of wafers, exposing the second photoresist material layer to obtain a second lithographic pattern; and etching the third layer to be exposed using the second lithographic pattern as a mask to form the third exposure layer on the second exposure layer of the second batch of wafers.

[0073] In this embodiment, the third exposure layer is parallel to the second exposure layer.

[0074] In this embodiment, the third exposure layer includes a metal layer parallel to the gate structure. The metal layer is electrically connected to the source / drain doped regions and is located on the dielectric structure.

[0075] The second photolithographic pattern is formed after compensating for etching deviations between photolithography machines of different batches of wafers within the same group. The differences between different batches of wafers within the same group are small, and the compensation result is more accurate, resulting in a smaller difference between the third exposure layer and the first exposure layer, which can form a semiconductor structure with higher dimensional accuracy.

[0076] In this embodiment, the lithography machine for the second batch of wafers is compensated based on the second measurement value of the first batch of wafers; the lithography machine for the third batch of wafers is compensated based on the second measurement value of the second batch of wafers.

[0077] In other embodiments, after obtaining the second measurement value of the first batch of wafers, the method further includes: compensating the lithography machine for the second batch of wafers based on the first shipment value of the first batch of wafers and the second measurement value of the first batch of wafers; after obtaining the second measurement value of the second batch of wafers, the method further includes: compensating the lithography machine for the third batch of wafers based on the first shipment value of the second batch of wafers and the second measurement value of the second batch of wafers.

[0078] In this embodiment, the second exposure layer is developed and etched to expose the first exposure layer, and the third exposure layer is developed and etched to expose the second exposure layer.

[0079] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for compensating for overlay deviation, characterized in that, include: A number of batches of wafers are provided, each of which has a first exposure layer and alignment marks on the first exposure layer; A second exposure layer is formed on top of the first exposure layer; Align the lithography machine with the alignment mark to obtain the first loading value, which is the offset adjusted by the alignment system of the lithography machine after it is aligned with the alignment mark. Obtain a first measurement value, which is the offset of the second exposure layer relative to the first exposure layer; Based on the first shipment value and the first measurement value, the optimal shipment value corresponding to each batch of wafers is obtained, wherein the optimal shipment value is the sum of the first shipment value and the first measurement value; Several batches of wafers are grouped according to several optimal cut-off values ​​to obtain several groups, each group including at least one batch of wafers; Iterative compensation of etching deviation is performed on several batches of wafers in the same group to obtain several third exposure layers located on the second exposure layer, including: selecting the first batch of wafers in any group and forming a third exposure layer on the second exposure layer of the first batch of wafers; The process involves: acquiring a second measurement value for the first batch of wafers, where the second measurement value is the offset of the third exposure layer relative to the second exposure layer of the first batch of wafers; compensating the lithography machine for the second batch of wafers based on the second measurement value of the first batch of wafers; after compensating the lithography machine for the second batch of wafers, forming a third exposure layer on the second exposure layer of the second batch of wafers; acquiring a second measurement value for the second batch of wafers, where the second measurement value is the offset of the third exposure layer relative to the second exposure layer of the second batch of wafers; compensating the lithography machine for the third batch of wafers based on the second measurement value of the second batch of wafers; repeating the acquisition of second measurement values ​​for different batches of wafers multiple times until compensation is performed on the lithography machines for several batches of wafers within the same group.

2. The overlay deviation compensation method as described in claim 1, characterized in that, The method for forming a third exposure layer on a second exposure layer of a first batch of wafers includes: forming a third exposure layer on a second exposure layer of a first batch of wafers; forming a second photoresist material layer on the third exposure layer; exposing the second photoresist material layer to obtain a second photolithographic pattern; and etching the third exposure layer using the second photolithographic pattern as a mask to form a third exposure layer on the second exposure layer of the first batch of wafers.

3. The overlay deviation compensation method as described in claim 1, characterized in that, The method for forming a third exposure layer on the second exposure layer of the second batch of wafers includes: forming a third layer to be exposed on the second exposure layer of the second batch of wafers; forming a second photoresist material layer on the third layer to be exposed; compensating the lithography machine with a second measurement value of the first batch of wafers, exposing the second photoresist material layer to obtain a second lithographic pattern; and etching the third layer to be exposed using the second lithographic pattern as a mask to form the third exposure layer on the second exposure layer of the second batch of wafers.

4. The overprinting deviation compensation method as described in claim 1, characterized in that, After obtaining the second measurement value of the first batch of wafers, the process further includes: compensating the lithography machine for the second batch of wafers based on the first shipment value and the second measurement value of the first batch of wafers; after obtaining the second measurement value of the second batch of wafers, the process further includes: compensating the lithography machine for the third batch of wafers based on the first shipment value and the second measurement value of the second batch of wafers.

5. The overprinting deviation compensation method as described in claim 1, characterized in that, The method for forming a second exposure layer on a first exposure layer includes: forming a second layer to be exposed on the first exposure layer; forming a first photoresist material layer on the second layer to be exposed; exposing the first photoresist material layer to obtain a first photolithographic pattern; and etching the second layer to be exposed using the first photolithographic pattern as a mask to form a second exposure layer on the first exposure layer.

6. The overlay deviation compensation method as described in claim 1, characterized in that, The method for grouping several batches of wafers according to the optimal delivery value to obtain several groups includes: obtaining a two-dimensional distribution scatter plot of the optimal delivery value, wherein the horizontal axis of the two-dimensional distribution scatter plot is a compensation value based on the first measurement value, the sum of the first measurement value and the compensation value is 0, and the vertical axis of the two-dimensional distribution scatter plot is the first delivery value; performing linear fitting on the scatter plot distribution of several optimal delivery values ​​to obtain several straight lines, wherein when the distance between two straight lines is greater than a preset value, the two straight lines correspond to two different groups.

7. The overlay deviation compensation method as described in claim 1, characterized in that, Before performing iterative compensation for etching deviations among several batches of wafers within the same group, the method further includes: determining whether the group needs iterative compensation for etching deviations based on the optimal cut-off value.

8. The overlay deviation compensation method as described in claim 7, characterized in that, The method for determining whether the group needs iterative compensation for etching deviation includes: when the optimal cutting value is greater than a preset value, the group needs iterative compensation for etching deviation; when the optimal cutting value is less than the preset value, the group does not need iterative compensation for etching deviation.

9. The overlay deviation compensation method as described in claim 1, characterized in that, The first exposure layer includes parallel fin structures; the second exposure layer includes a gate structure that spans the fin structures; and the third exposure layer includes a metal layer parallel to the gate structure.

10. The overlay deviation compensation method as described in claim 9, characterized in that, Also includes: The source and drain doped regions are located within the fin structures on both sides of the gate structure, and the metal layer is electrically connected to the source and drain doped regions. A dielectric structure located on a wafer, wherein the gate structure and fin structure are located within the dielectric structure, and the metal layer is located on the dielectric structure.

11. The overprinting deviation compensation method as described in claim 1, characterized in that, The second exposure layer exposes the first exposure layer through development and etching, and the third exposure layer exposes the second exposure layer through development and etching.

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