阅读说明：本技术 监控光刻机晶圆移载台平整度的方法 (Method for monitoring flatness of wafer transfer platform of photoetching machine ) 是由 王建涛 张聪 于 2019-10-17 设计创作，主要内容包括：本发明涉及监控光刻机晶圆移载台平整度的方法,涉及半导体集成电路制造技术,建立一条晶圆移载台平整度检测的流程,利用污染状况良好的光片进行检测,曝光采用任意掩模板进行,同时设定曝光程式里反映平整度的参数上限,采用设定完成的曝光程式对光片进行曝光,获取曝光文件,分析曝光文件得到移载台的平整度信息,如此无需对光刻机进行停机,大大降低成本、提高产能,且单次作业时间较短,可以根据需要设定检测的频率(如每天、每周或每两周等),大大提高了监控频率,实现了对移载台平整度的实时检测,减少离焦缺陷的发生。(The invention relates to a method for monitoring the flatness of a wafer transfer table of a photoetching machine, which relates to the manufacturing technology of a semiconductor integrated circuit, establishes a process for detecting the flatness of the wafer transfer table, utilizes a polished section with good pollution condition to detect, exposes by adopting any mask plate, simultaneously sets the upper limit of a parameter reflecting the flatness in an exposure program, exposes the polished section by adopting the set exposure program, obtains an exposure file, analyzes the exposure file to obtain the flatness information of the transfer table, thus needing no shutdown of the photoetching machine, greatly reducing the cost, improving the productivity, having shorter single operation time, being capable of setting the detection frequency (such as every day, every week or every two weeks) according to the needs, greatly improving the monitoring frequency, realizing the real-time detection of the transfer table flatness and reducing the occurrence of defocusing defects.)

1. A method for monitoring the flatness of a wafer transfer table of a photoetching machine is characterized by comprising the following steps:

s1: generating an exposure program, setting a non-focus region of the wafer edge in the exposure program, and setting an upper limit A of flatness detection in the exposure program;

s2: adding mask plate information for exposure;

s3: generating a monitoring product batch, wherein wafers in the monitoring product batch adopt polished sections;

s4: monitoring the pollution condition of the light sheet in the step S3, and reserving the light sheet of which the pollution condition meets the regulation;

s5: exposing the light sheet generated in the step S4 by adopting the exposure program generated in the step S1 and the mask plate information in the step S2, and generating an exposure file after the exposure is finished; and

s6: and capturing information of points with the flatness exceeding the upper limit value A in the exposure file, defining the points with the flatness exceeding the upper limit value A as abnormal points, and analyzing abnormal point data to obtain the flatness information of the wafer transfer platform.

2. The method of monitoring the flatness of a wafer transfer table of a lithography machine according to claim 1, wherein the non-focus area of the edge of the wafer in the exposure program is set to be less than 3 mm in step S1.

3. The method of claim 2, wherein the unfocused region of the wafer edge in the exposure program is set equal to 0 in step S1.

4. The method of claim 1, wherein the upper limit A is less than the process window B of the product in step S1.

5. The method of claim 4, wherein the upper limit A is less than the process window B of the product minus 10nm and greater than 30nm in step S1.

6. The method of claim 1, wherein in step S2, the mask is a mask of a current in-line product or a mask that has been discarded.

7. The method of claim 1, wherein in step S3, the wafer is directly put into service without any film layer or pattern on the wafer.

8. The method as claimed in claim 1, wherein in step S4, the contamination of the optical sheets is monitored, and the optical sheets with contamination exceeding the specification are removed from the monitored product lot, cleaned, inspected again for contamination, and reused or directly removed.

9. The method of claim 8, wherein the monitoring of contamination comprises detecting a particle condition on a surface of the wafer.

10. The method of claim 9, wherein the polished section with a particle size less than 60nm is considered to be a qualified polished section.

11. The method of claim 9, wherein the number of particles on the sheet of light that are less than 50 is considered to be within the specification.

12. The method of claim 9, wherein the light sheet having a particle size of less than 60nm and a particle count of less than 50 light sheets is considered to be a light sheet meeting the specification.

13. The method of claim 1, wherein in step S6, if there is a special distribution of abnormal points or points with flatness exceeding the process window, the flatness of the wafer transfer stage is considered abnormal; if not, the flatness of the wafer transfer platform is considered to be normal.

14. The method of claim 13, wherein coordinates of outliers and flatness information are captured, and the outliers are mapped according to X and Y coordinates to accurately locate the outliers, check if there is a special distribution of outliers, and simultaneously screen the flatness information and record the maximum value of the flatness information, and if there is a special distribution of outliers or the maximum value exceeds a process window, the wafer stage is considered to have abnormal flatness.

Technical Field

The invention relates to a semiconductor integrated circuit manufacturing technology, in particular to a method for monitoring the flatness of a wafer transfer platform of a photoetching machine.

Background

Photolithography is an important step in the fabrication of semiconductor integrated circuits, which directly affects the yield of semiconductor devices. In order to ensure the quality of the pattern, it is necessary to ensure that the exposure is performed under the optimal condition, and the most important of the photolithography process is the process window (Depth of Focus, DOF) of the product. Currently, as the size of semiconductor devices decreases, the critical dimension becomes smaller, which brings higher demands and challenges to the photolithography process. The process window of the photoetching is greatly reduced, and in order to obtain an accurate pattern, the photoetching exposure is required to be ensured under the optimal focal length, so that the probability of defocusing (defocus) is reduced to the maximum extent.

In order to ensure the optimal focal length (focus) of exposure, the photoetching machine before exposure can carry out flatness detection on the surface of the silicon wafer so as to obtain the appearance of the surface of the silicon wafer, and therefore the data are used for compensating the exposure process so as to ensure the optimal focal length of product exposure. The biggest factor influencing the flatness of the surface of the silicon wafer is the flatness of the wafer moving table, and if the flatness exceeds the allowable range of a process window of a product, a pattern is out of focus (defocus). In the FAB, the flatness monitoring of the wafer stage of the lithography machine has been incorporated into a daily offline monitoring project.

The main method for detecting the flatness of the transfer platform at present is to shut down a photoetching machine regularly and then detect the flatness manually by an engineer in a shut-down state, the method is time-consuming, about 1-2 hours is needed, the productivity is seriously influenced, the detection frequency is too low, and the method has the biggest limitation that the flatness condition of the platform cannot be detected in real time (the detection frequency is too low), so that the abnormal flatness cannot be effectively grasped, and the product yield is reduced.

Disclosure of Invention

The invention aims to provide a method for monitoring the flatness of a wafer transfer table of a photoetching machine, so that the photoetching machine does not need to be stopped for detection, the cost is reduced, the productivity is improved, the monitoring frequency is improved, and the occurrence of defocusing defects is reduced.

The invention provides a method for monitoring the flatness of a wafer transfer platform of a photoetching machine, which comprises the following steps: s1: generating an exposure program, setting a non-focus region of the wafer edge in the exposure program, and setting an upper limit A of flatness detection in the exposure program; s2: adding mask plate information for exposure; s3: generating a monitoring product batch, wherein wafers in the monitoring product batch adopt polished sections; s4: monitoring the pollution condition of the light sheet in the step S3, and reserving the light sheet of which the pollution condition meets the regulation; s5: exposing the light sheet generated in the step S4 by adopting the exposure program generated in the step S1 and the mask plate information in the step S2, and generating an exposure file after the exposure is finished; s6: and capturing information of points with the flatness exceeding the upper limit value A in the exposure file, defining the points with the flatness exceeding the upper limit value A as abnormal points, and analyzing abnormal point data to obtain the flatness information of the wafer transfer platform.

Further, in step S1, the wafer edge non-focus area in the exposure program is set to be less than 3 mm.

Further, in step S1, the unfocused region of the wafer edge in the exposure program is set equal to 0.

Further, the upper limit value a is smaller than the process window B of the product in step S1.

Further, the upper limit A is less than the process window B of the product minus 10nm and greater than 30nm in step S1.

Further, in step S2, the mask plate is a mask plate of the current in-line product or a mask plate that has been discarded.

Further, in step S3, the optical sheet is not grown with any film layer or pattern, and the offline wafer is directly put into use.

Further, in step S4, the optical sheets are monitored for contamination, and the optical sheets with contamination exceeding the specification are removed from the monitored product lot, cleaned, and inspected for contamination, and then put into use again or directly removed.

Further, the contamination monitoring includes detecting the particle condition on the wafer surface.

Further, a light sheet having particles with a diameter of less than 60nm is considered to be a light sheet in conformity with the specification.

Further, a gloss piece having a particle number of less than 50 is considered to be a satisfactory gloss piece.

Further, a light sheet having a particle diameter of less than 60nm and a particle number of less than 50 particles is considered to be a light sheet in conformity with the specification.

Furthermore, in step S6, if there is a special distribution of the abnormal points or there is a point with flatness exceeding the process window, it is determined that the flatness of the wafer transfer stage is abnormal; if not, the flatness of the wafer transfer platform is considered to be normal.

Furthermore, coordinates and flatness information of the abnormal points are captured, the abnormal points are mapped according to X and Y coordinates to accurately position the positions of the abnormal points, whether the abnormal points have special distribution or not is checked, meanwhile, the flatness information is screened, the maximum value of the flatness information is recorded, and if the abnormal points have special distribution or the maximum value exceeds a process window, the flatness of the wafer transfer platform is considered to be abnormal.

The method for monitoring the flatness of the wafer transfer table of the photoetching machine provided by the invention establishes a process (monitor flow) for detecting the flatness of the wafer transfer table, a polished section (bare wafer) with good pollution condition is used for detection, exposure is carried out by adopting any mask plate, meanwhile, the upper limit of a parameter reflecting the flatness in an exposure program is set, the polished section is exposed by adopting the set exposure program, an exposure file is obtained, and the flatness information of the transfer table is obtained by analyzing the exposure file.

Drawings

FIG. 1 is a flowchart illustrating a method for monitoring the flatness of a wafer stage of a lithography machine according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of outlier data obtained by the method for monitoring the flatness of the wafer stage of the lithography machine according to the present invention.

FIG. 3 is a schematic view of the flatness of an actual wafer stage.

Fig. 4 is a schematic view of the flatness of the wafer on the stage shown in fig. 3.

Detailed Description

The technical solutions in the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

In an embodiment of the present invention, a method for monitoring the flatness of a wafer transfer stage of a lithography machine is provided, and specifically, referring to fig. 1, fig. 1 is a flowchart of a method for monitoring the flatness of a wafer transfer stage of a lithography machine according to an embodiment of the present invention, as shown in fig. 1, the method for monitoring the flatness of a wafer transfer stage of a lithography machine includes:

s1: generating an exposure program, setting a non-focus area (focus edge clearance) of the wafer edge in the exposure program, and setting an upper limit A of flatness detection in the exposure program;

specifically, in an embodiment of the present invention, the non-focus area of the wafer edge in the exposure program is set to be less than 3 mm. Namely, the edge of the wafer is less than 3 mm, so that the patterned area of the wafer can be covered, and the flatness condition of the patterned area can be effectively grasped.

Specifically, in one embodiment of the present invention, the unfocused region of the wafer edge in the exposure program is set equal to 0. Therefore, the whole wafer area can be covered when the flatness detection is carried out by exposure, and the flatness condition of all areas of the wafer can be effectively captured.

Specifically, in an embodiment of the present invention, the upper limit a is smaller than the process window B of the product, so as to ensure the process window of the product. Furthermore, the upper limit value a also needs to accurately reflect the flatness of the movable stage and ensure the smooth operation of the FAB production line. For this reason, in one embodiment of the present invention, the upper limit a is preferably less than the process window B of the product minus 10nm and greater than 30 nm. If the process window of the product is about +/-60nm, the upper limit A of the flatness detection in the exposure program is set to 35nm, and it is considered that the points beyond the upper limit A cause the defocusing of the product pattern, which is an abnormal point.

S2: adding mask information for exposure;

in an embodiment of the present invention, the mask plate may be any mask plate, and a mask plate of a current online product or a mask plate that has been discarded may be adopted, so that the cost is greatly reduced.

S3: generating a monitoring product batch (monitor lot), wherein wafers in the monitoring product batch adopt polished wafers (bare wafers);

specifically, in an embodiment of the present invention, no film layer (film) or pattern is grown on the polished section, and the offline wafer is directly used to reduce the interference of the front layer on the flatness detection, so that the flatness detected by the present invention only reflects the flatness information of the wafer moving stage of the lithography machine.

S4: monitoring the pollution condition of the light sheet in the step S3, and reserving the light sheet of which the pollution condition meets the regulation;

specifically, in an embodiment of the present invention, the optical sheets are monitored for contamination, the optical sheets with contamination exceeding the specification are removed from the monitored product batch, cleaned, and inspected for contamination, and then put into use again or directly removed. Specifically, in an embodiment of the present invention, the monitoring of the contamination condition includes detecting a particle (particle) condition on a surface of the wafer, so as to ensure that the wafer in the monitored product lot (monitor lot) does not bring the particle (particle) into the lithography machine. In one embodiment of the present invention, a light sheet with particles less than 60nm in diameter is considered to be a defined light sheet. In one embodiment of the present invention, a light sheet with a particle number of less than 50 particles is considered to be a defined light sheet. Preferably, in one embodiment of the present invention, the light sheet with a particle diameter of less than 60nm and a particle number of less than 50 is considered to be a qualified light sheet.

S5: exposing the light sheet generated in the step S4 by using the exposure program generated in the step S1 and the mask information in the step S2, and generating an exposure file (lot report) after the exposure is finished;

s6: and capturing information of points with the flatness exceeding the upper limit value A in an exposure file (lot report), defining the points with the flatness exceeding the upper limit value A as abnormal points, and analyzing the abnormal point data to obtain the flatness information of the wafer transfer platform.

Specifically, in an embodiment of the present invention, if there is a special distribution of abnormal points or points with flatness exceeding the process window, it is determined that the flatness of the wafer transfer stage is abnormal; if not, the flatness of the wafer transfer platform is considered to be normal.

Specifically, in an embodiment of the present invention, coordinates and flatness information of the singular points are captured, the singular points are plotted according to X and Y coordinates to accurately locate positions of the singular points, whether the singular points have special distributions or not is checked, meanwhile, flatness information is screened, a maximum value of the flatness information is recorded, and if the singular points have special distributions or the maximum value exceeds a process window, the flatness of the wafer transfer stage is considered to be abnormal, and the apparatus is notified to inspect the apparatus.

Specifically, in the semiconductor integrated circuit manufacturing, the special distribution means that the abnormal points can be connected into straight lines, arc lines, Chinese character pin shapes, triangle shapes, annular shapes and the like, or the abnormal points point to the center of a circle and the like. The range of the special distribution can be changed according to the irregular patterns commonly occurring in the industry, so that all the irregular patterns can be included in the method for monitoring the flatness of the wafer transfer platform of the photoetching machine.

Specifically, referring to fig. 2, fig. 2 is a schematic diagram of the abnormal point data obtained by the method for monitoring the flatness of the wafer transfer stage of the lithography machine according to the present invention, as shown in fig. 2, the abnormal points are annularly distributed on the X and Y coordinates and are distributed on the upper edge of the wafer. Referring to fig. 3, fig. 3 is a schematic view of the flatness of the actual wafer transfer stage, and as shown in fig. 3, points 310 with abnormal flatness are also distributed on the upper edge of the transfer stage. Referring to fig. 4, fig. 4 is a schematic view illustrating the flatness of the wafer on the stage shown in fig. 3, and as shown in fig. 4, points 410 with abnormal flatness are also distributed on the upper edge of the stage. Therefore, the method for monitoring the flatness of the wafer transfer platform of the photoetching machine can accurately reflect the flatness information of the transfer platform.

In summary, a process (monitor flow) for detecting the flatness of the wafer transfer stage is established, a polished section (bare wafer) with a good pollution condition is used for detection, exposure is carried out by using any mask plate, meanwhile, the upper limit of parameters reflecting the flatness in an exposure program is set, the polished section is exposed by using the set exposure program, an exposure file is obtained, and the exposure file is analyzed to obtain the flatness information of the transfer stage, so that the photoetching machine does not need to be stopped, the cost is greatly reduced, the productivity is improved, the single operation time is short, the detection frequency (such as every day, every week or every two weeks and the like) can be set according to needs, the monitoring frequency is greatly improved, the real-time detection of the flatness of the transfer stage is realized, and the occurrence of defocusing defects is reduced.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.