Technological method for improving photoetching line width uniformity

Abstract

The invention discloses a process method for improving photoetching line width uniformity, which comprises the following steps: S1, carrying out multiple photoetching tests on a wafer to obtain a first function, a second function and a first exposure region S2, providing the wafer, and carrying out photoetching treatment on the current wafer at a first scanning speed and a first exposure quantity to obtain a second function; s3, providing a next wafer, adjusting the scanning speed according to the actual line width uniformity of the first exposure area of the previous wafer, obtaining the corresponding line width at the scanning speed according to a second function, and obtaining the actual line width and the line width uniformity of each exposure area of the current wafer; and S4, adjusting the exposure amount according to the corresponding line width and the first function to compensate the line width of the first exposure area so as to reach the target line width, and obtaining the actual line width and the line width uniformity of each exposure area of the current wafer after photoetching treatment, and repeating the step S3. By means of the mode, the problem that the line width uniformity difference of an exposure area is caused by the scanning speed of a low-order photoetching machine can be solved.

Description

Technical Field

[0001] This invention relates to the field of photolithography processes, and in particular to a process method for improving the uniformity of photolithography linewidth. Background Technology

[0002] As linewidths become increasingly smaller, the requirements for linewidth uniformity in lithography become more stringent. For scanner lithography machines, when scanning along the Y direction during exposure, the linewidth within the exposure area can easily change along the scanning position.

[0003] Advanced lithography machines have linewidth compensation functions in both the wafer and the exposure area (DOMA / IMO). They control the linewidth uniformity of the wafer by adjusting the exposure energy and adjust the linewidth uniformity of the exposure area by controlling the machine hardware. However, for lower-end lithography machines (such as iline / KRF lithography machines), the exposure energy can only be adjusted by the average linewidth value, and the linewidth uniformity compensation of the exposure area cannot be taken into account. Summary of the Invention

[0004] The main technical problem solved by this invention is to provide a process method to improve the uniformity of lithography linewidth, which can solve the difference in linewidth uniformity in the region caused by the inability of low-order lithography machines to take into account the linewidth uniformity compensation of the exposure area.

[0005] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is to provide a process method for improving the uniformity of photolithography linewidth, comprising the following steps: S1: Perform multiple photolithography tests on the wafer to obtain a first function, a second function, and a first exposure area on the wafer; wherein, the first function is a fitting function of exposure amount and actual linewidth, the second function is a fitting function of scan speed and actual linewidth; the first exposure area is the exposure region in each wafer where the actual linewidth varies along the scan direction of the exposure process; S2: Provide a wafer, perform photolithography on the current wafer at a first scanning speed and a first exposure amount, and obtain the actual linewidth and linewidth uniformity of each exposure area of ​​the current wafer, wherein the first exposure amount is the value corresponding to the target linewidth in the first function, and the first scanning speed is the value corresponding to the target linewidth in the second function; S3: Provide the next wafer, adjust the scanning speed according to the actual linewidth uniformity of the first exposure area in the previous wafer to improve the linewidth uniformity of the first exposure area, obtain the corresponding linewidth at the scanning speed according to the second function, adjust the exposure amount according to the corresponding linewidth and the first function to compensate for the linewidth of the first exposure area to achieve the target linewidth, and obtain the actual linewidth and linewidth uniformity of each exposure area of ​​the current wafer after photolithography. S4: Repeat step S3 until the actual linewidth and actual linewidth uniformity of the wafer meet the preset range respectively.

[0006] In S1, the process of obtaining the first function, the second function, and the first exposure area on the wafer includes: Furthermore, photolithography is performed on the wafer at the same initial scan speed but with different exposure levels to obtain the first function; Furthermore, photolithography is performed on the wafer with a first exposure amount and the initial scanning speed to obtain a first exposure area; Furthermore, the first exposure area in the wafer is photolithographically processed with a first exposure amount and different scanning speeds to obtain the second function; Furthermore, the first exposure amount in step S2 is the exposure amount in the first functional relationship corresponding to the target linewidth.

[0007] Furthermore, the first speed in step S2 is the optimal scanning speed under the target linewidth uniformity.

[0008] Furthermore, the exposure process involves scanning from one end of the current exposure area along the Y-axis to the other end.

[0009] Furthermore, the change in line width along the scanning direction means that the line width increases or decreases along the Y-axis after scanning.

[0010] Furthermore, the first functional relationship is: F （X） =ax+b, where x is the actual line width and b is F. （X） Exposure amount, where b is a constant.

[0011] Furthermore, the second functional relationship is: F （y） =ky+c, where y is the actual line width and c is F. （y） The scanning speed, where c is a constant.

[0012] Furthermore, the scanning speed adjustment method in step S3 involves adjusting the scanning speed based on the deviation between the actual line width uniformity and the target line width uniformity, and determining the corresponding line width based on the second functional relationship.

[0013] Furthermore, the exposure adjustment method in step S3 includes, given the adjusted scanning speed and the corresponding line width at that scanning speed, compensating for the exposure based on the corresponding line width and the first functional relationship.

[0014] Furthermore, group control can be implemented, dividing exposure areas with the same scanning speed into the same group. After exposure, the scanning speed corresponding to each exposure area of ​​the wafer is obtained. Exposure areas with a scanning speed error within 10% are classified into a group. It is only necessary to calculate the linewidth uniformity of one exposure area of ​​the current wafer, substitute the actual linewidth of the area into the second function relationship for analysis and adjustment of the scanning speed, and change the exposure amount to compensate based on the linewidth determined by the scanning speed. Thus, the scanning speed and exposure amount of the next wafer corresponding exposure area are determined.

[0015] The beneficial effects of the present invention are as follows: Based on the above process method, for low-order scanner lithography machines (such as iline / KRF lithography machines) and lithography machines in areas where the linewidth of a single exposure area changes with the scanning direction, the linewidth uniformity can be adjusted by the linear relationship between the scanning speed and the linewidth change, which can improve the linewidth convergence and improve the linewidth uniformity by 20-30%. Attached Figure Description

[0016] Figure 1 This is a flowchart of the process steps of the present invention; Figure 2 This is a schematic diagram of the wafer exposure area according to an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the functional relationship between the actual linewidth and exposure amount in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the functional relationship between the actual line width and the scanning speed in an embodiment of the present invention; Detailed Implementation

[0017] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0018] Low-end lithography machines cannot automatically compensate for the linewidth uniformity of each exposed area of ​​the wafer when exposing it. Therefore, it is necessary to manually control the scanning speed to adjust the linewidth uniformity of the exposed area.

[0019] This invention provides a process for improving linewidth uniformity. The process involves first scanning and exposing the exposure area of ​​the wafer using a photolithography machine to collect data. Based on the collected data, a fitting algorithm is used to obtain two linear relationships: the first functional relationship is the linear relationship between linewidth and exposure amount, and the second functional relationship is the linear relationship between the linewidth of the exposure area and the scanning speed. The first functional relationship reflects the relationship between the average line width and the exposure. The second functional relationship reflects the relationship between linewidth and scan speed within a single exposure area; Line width uniformity is directly proportional to scanning speed; The linewidth uniformity of individual exposure areas is controlled by continuously adjusting the scanning speed, and the average linewidth is compensated by adjusting the exposure amount, thereby improving the overall linewidth uniformity. The specific steps are as follows: like Figure 1 The image shows an embodiment of an instrument provided by this invention. The wafer is divided into 102 exposure areas, and the known target linewidth is 49 nanometers. Figure 2 , Figure 3 As shown, the functional relationship between linewidth and exposure at the optimal focal length is known: F （X） =ax + b, where x is the actual line width, and b is F. （x） The scanning speed, where b is a constant, and the known functional relationship between linewidth and scanning speed: F （y） =ky+c, where y is the actual line width, and F is the line width. （y） The scanning speed, where c is a constant, involves exposing the wafer along the Y-axis in each exposure area using a lithography machine at the optimal exposure amount and optimal scanning speed. This yields the actual average linewidth and linewidth uniformity for each area. Taking exposure area 4 as an example, the actual linewidth uniformity is found to be 4. This is achieved through F... （y） The functional relationship =ky+c is used to obtain the linewidth uniformity of the next wafer exposure area 4 at a scan speed of 530 nm, which can be adjusted to 2.8. The linewidth value at a scan speed of 530 nm is determined to be 47.6 nm. Then, based on F... （X） =ax+b. Based on the functional relationship between exposure and linewidth, we know that reducing the exposure by one millijoule can increase it by 0.8 nanometers, thus obtaining an exposure of 46 millijoules for the next wafer exposure area 1. Similarly, the linewidth uniformity of each exposure area is measured, and the scanning speed of 102 exposure areas is obtained through the second functional relationship. Exposure areas with scanning speed errors within 10% are grouped together, with scanning speeds within the same range forming one group, and the exposure compensation within the same group being the same.

[0020] This method is applicable to other low-end lithography machines (such as iline / KRF lithography machines), or lithography machines that do not have DOMA / IMO functionality and whose linewidth varies along the scanning direction within an exposure area; Multiple exposure areas are set on a wafer. The exposure areas are exposed with an initial scan speed and different exposure amounts to obtain a first functional relationship between exposure amount and linewidth. By selecting a target linewidth, the optimal exposure amount under the target linewidth can be obtained through the first functional relationship. It should be noted that the initial scan speed and the optimal exposure amount are determined according to different models. The wafer is exposed using the optimal exposure amount and initial speed. The exposure direction of each region is to expose sequentially from one end of the current exposure region along the Y-axis. The exposure region where the linewidth increases or decreases along the Y-axis is found. These regions are exposed using different scanning speeds with the optimal exposure amount to obtain the second functional relationship between the linewidth and scanning speed in that region. The first functional relationship reflects the relationship between the average line width and the exposure. The second functional relationship reflects the relationship between linewidth uniformity and scanning speed within a single exposure area; The target linewidth and linewidth uniformity are set. Linewidth uniformity refers to the range of fluctuation between the maximum and minimum linewidth values ​​within a single exposure area. An optimal exposure amount and scan speed are selected to expose the wafer, obtaining the average linewidth, maximum linewidth, and minimum linewidth for each area. By comparison, the linewidth uniformity and average linewidth within each area are determined. Since the functional relationship between scan speed and linewidth uniformity varies for different scanner models (the functional relationship may be increasing or decreasing depending on the model), the scan speed within a region is adjusted according to the functional relationship between scan speed and linewidth uniformity for different scanner models to improve the linewidth uniformity within a single region. Because the scan speed is changed, the exposure amount within that region should be appropriately compensated to improve the average linewidth across the entire wafer. Once the linewidth uniformity of a single exposure area is improved, the average linewidth of all areas can be adjusted through exposure compensation, thereby improving the linewidth uniformity of the entire wafer.

[0021] Preferably, group control is added to the process method to divide the exposure areas with the same scanning speed into the same group. After exposure, the actual linewidth uniformity of each exposure area of ​​the wafer is obtained. It is only necessary to calculate the difference between the actual linewidth and the target linewidth of one exposure area of ​​the current wafer. The difference is analyzed with the corresponding function relationship to determine the scanning speed of the next wafer's corresponding exposure area. Exposure areas with scanning speed error within 10% are classified into a group. The exposure compensation corresponding to the same scanning speed is also the same, thereby improving efficiency.

[0022] In summary, this invention experimentally establishes two functional relationships: ① the functional relationship between linewidth and exposure amount, and ② the functional relationship between linewidth and scanning speed. Then, by selecting an optimal exposure amount and optimal scanning speed to expose the wafer, the average linewidth and linewidth uniformity of each exposed region are obtained. By analyzing the actual linewidth uniformity and the target linewidth uniformity, the scanning speed is adjusted. Based on the linewidth value obtained from the scanning speed, the average linewidth of that region is compensated using the exposure amount, thereby improving the linewidth uniformity of the entire wafer. This allows low-order scanner lithography machines (such as iline / KRF lithography machines) or lithography machines without DOMA / IMO functionality where the linewidth varies along the scanning direction within an exposed region to adjust the overall linewidth uniformity using the above method, resulting in better linewidth convergence and an improvement of 20-30% in linewidth uniformity.

[0023] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A process method for improving the uniformity of photolithographic linewidth, characterized in that, Includes the following steps: S1: Perform multiple photolithography tests on the wafer to obtain a first function, a second function, and a first exposure area on the wafer; wherein, the first function is a fitting function of the exposure amount and the actual linewidth, and the second function is a fitting function of the scan speed and the actual linewidth; the first exposure area is an exposure region in each wafer where the actual linewidth varies along the scan direction of the exposure process; S2: Provide a wafer, perform photolithography on the current wafer at a first scanning speed and a first exposure amount, and obtain the actual linewidth and linewidth uniformity of each exposure area of ​​the current wafer, wherein the first exposure amount is the value corresponding to the target linewidth in the first function, and the first scanning speed is the value corresponding to the target linewidth in the second function; S3: Provide the next wafer, adjust the scanning speed according to the actual linewidth uniformity of the first exposure area in the previous wafer to improve the linewidth uniformity of the first exposure area, obtain the corresponding linewidth at the scanning speed according to the second function, adjust the exposure amount according to the corresponding linewidth and the first function to compensate for the linewidth of the first exposure area to achieve the target linewidth, and obtain the actual linewidth and linewidth uniformity of each exposure area of ​​the current wafer after photolithography. S4: Repeat step S3 until the actual linewidth and actual linewidth uniformity of the wafer meet the preset range respectively.

2. The process method for improving the uniformity of photolithographic linewidth according to claim 1, characterized in that, In step S1, the process of obtaining the first function, the second function, and the first exposure area on the wafer includes: Photolithography is performed on the wafer with the same initial scan speed but different exposure levels to obtain the first function; Photolithography is performed on the wafer at a first exposure level and the initial scanning speed to obtain a first exposure area; The first exposure area in the wafer is photolithographically processed with a first exposure amount and different scanning speeds to obtain the second function.

3. The process method for improving the uniformity of photolithographic linewidth according to claim 1, characterized in that, The first exposure in step S2 is the exposure in the first functional relationship corresponding to the target linewidth.

4. The process method for improving the uniformity of photolithographic linewidth according to claim 2, characterized in that, The first speed in step S2 is the scanning speed corresponding to the second functional relationship under the target linewidth uniformity.

5. The process method for improving the uniformity of photolithographic linewidth according to claim 1, characterized in that, The exposure process involves scanning from one end of the current exposure area along the Y-axis to the other end.

6. The process method for improving the uniformity of photolithographic linewidth according to claim 5, characterized in that, The line width changes along the scanning direction because the line width increases or decreases along the Y-axis after scanning.

7. The process method for improving the uniformity of photolithographic linewidth according to claim 1, characterized in that, The first functional relationship is: F （X） =ax+b, where x is the actual line width, and F （X） The exposure amount is given by b, which is a constant.

8. The process method for improving the uniformity of photolithographic linewidth according to claim 6, characterized in that, The second functional relationship is: F （y） =ky+c, where y is the actual line width, and F （y）为 The scanning speed, where c is a constant.

9. The process method for improving the uniformity of photolithographic linewidth according to claim 1, characterized in that, The scanning speed adjustment method in step S3 involves adjusting the scanning speed based on the deviation between the actual line width uniformity and the target line width uniformity, and determining the corresponding line width based on the second functional relationship.

10. The process method for improving the uniformity of photolithographic linewidth according to claim 9, characterized in that, The exposure adjustment method in step S3 includes, given the adjusted scanning speed and the corresponding line width at that scanning speed, compensating for the exposure based on the corresponding line width and the first functional relationship.

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