Method for determining light intensity threshold during SRAF exposure

Abstract

The present invention provides a method for determining the light intensity threshold for SRAF exposure. The method comprises: selecting a target pattern with an SRAF added to a test pattern; setting an energy-focal length matrix for exposure on a photolithography machine, and exposing the test pattern mask to obtain an exposure pattern matrix; determining whether a first exposure pattern that exposes the SRAF exists in the exposure pattern matrix; if so, obtaining the energy corresponding to the first exposure pattern, and obtaining a curve of the characteristic size of the target pattern versus focal length at the energy level through optical measurement; obtaining a second exposure pattern that exposes the SRAF based on the deviation between the characteristic size of the target pattern and a preset target size, and determining the light intensity threshold for SRAF exposure based on the exposure parameters of the second exposure pattern. The present invention solves the problem of high judgment errors caused by existing manual judgment methods.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for determining a light intensity threshold during SRAF exposure. Background Art

[0002] As integrated circuits evolve from the micron to the nanometer scale, the lithography process window becomes increasingly smaller (especially for patterns with larger feature sizes and smaller pitches). Existing technology increases the process window by adding sub-resolution assist patterns (SRAFs). However, SRAFs cannot be exposed on the wafer. Therefore, OPC engineers need to determine the light intensity threshold for exposing SRAFs to prevent them from being exposed on the wafer.

[0003] Currently, OPC engineers often manually determine whether SRAF is exposed based on the image quality of the exposure energy-focus matrix (FEM). This method leads to a high probability of error in the judgment results. Therefore, how to reduce human error and ensure the accuracy of process conditions is a technical problem we need to solve. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for determining the light intensity threshold during SRAF exposure, so as to solve the problem of many judgment errors caused by the existing manual judgment method.

[0005] To achieve the above and other related objectives, the present invention provides a method for determining a light intensity threshold during SRAF exposure, the method comprising:

[0006] Selecting a target pattern with an SRAF added thereto in the test layout, wherein the SRAF can be exposed on the wafer during exposure;

[0007] Setting the energy-focal length matrix during exposure of the photolithography machine, and exposing the test pattern mask to obtain an exposure pattern matrix;

[0008] determining whether a first exposure pattern for exposing the SRAF exists in the exposure pattern matrix; if so, obtaining an energy corresponding to the first exposure pattern, and obtaining a curve of a characteristic dimension of the target pattern versus focal length at the energy through optical measurement;

[0009] A second exposure pattern for exposing the SRAF is obtained according to a deviation value between the characteristic size of the target pattern and a preset target size, and a light intensity threshold of the SRAF exposure is obtained according to exposure parameters of the second exposure pattern.

[0010] Optionally, a scanning electron microscope or an optical line width meter is used to collect patterns to obtain the exposure pattern matrix.

[0011] Optionally, before obtaining the curve of the characteristic size of the target pattern as a function of focal length under the energy through optical measurement, the method further includes a step of determining a light intensity range according to the exposure pattern matrix.

[0012] Optionally, the light intensity range is determined by measuring the feature size of the target pattern in the exposure pattern matrix using a scanning electron microscope or an optical line width meter.

[0013] Optionally, the method for obtaining a second exposure pattern for exposing the SRAF according to a deviation between the characteristic size of the target pattern and the preset target size includes:

[0014] Obtaining a maximum deviation between the characteristic size in the variation curve and the preset target size by calculation;

[0015] The second exposure pattern is obtained from the exposure pattern matrix according to the maximum deviation value.

[0016] Optionally, when obtaining the light intensity threshold of the SRAF exposure according to the exposure parameters of the second exposure pattern, the exposure parameters include the energy and the focal length.

[0017] Optionally, the target pattern is a semi-dense pattern or a dense pattern, including pattern areas and spacing areas between adjacent pattern areas.

[0018] Optionally, the SRAF is added in the graphics area.

[0019] Optionally, the SRAF is added within the spacer region.

[0020] Optionally, the target graphic is an isolated graphic, and the SRAF is added at a preset distance from the isolated graphic.

[0021] As described above, the method for determining the light intensity threshold for SRAF exposure of the present invention uses an energy-focal length matrix to determine the energy of the exposure pattern for SRAF exposure. Optical measurement is then used to obtain the characteristic dimensions of the target pattern at the same energy and different focal lengths to determine the maximum deviation between the characteristic dimensions and a preset target dimension. Based on this maximum deviation, an exposure pattern is identified that can be used to determine the light intensity threshold, thereby determining the light intensity threshold for SRAF exposure. This method allows for simple and rapid determination of the SRAF light intensity threshold, thereby reducing errors associated with manual determination and improving production capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1FIG. 4 is a flow chart showing a method for determining a light intensity threshold during SRAF exposure provided by the present invention.

[0023] Figure 2 It is a schematic diagram showing a first method of adding SRAF when the target pattern of the present invention is a semi-dense pattern or a dense pattern.

[0024] Figure 3 Display as Figure 2 The cross-sectional structure diagram of the exposure pattern formed on the wafer in the additive manner is shown.

[0025] Figure 4 Display as Figure 2 FIG. 4 is a top view schematic diagram of an exposure pattern formed on a wafer using an additive method.

[0026] Figure 5 Display as Figure 2 Schematic diagram of the light intensity change curve of the target graphic under the addition method shown.

[0027] Figure 6 It is a schematic diagram showing a second way of adding SRAF when the target pattern of the present invention is a semi-dense pattern or a dense pattern.

[0028] Figure 7 Display as Figure 6 The cross-sectional structure diagram of the exposure pattern formed on the wafer in the additive manner is shown.

[0029] Figure 8 Display as Figure 6 FIG. 4 is a top view schematic diagram of an exposure pattern formed on a wafer using an additive method.

[0030] Figure 9 Display as Figure 6 Schematic diagram of the light intensity change curve of the target graphic under the addition method shown.

[0031] Figure 10 It is a schematic diagram showing a method of adding the SRAF when the target pattern of the present invention is an isolated pattern.

[0032] Figure 11 Display as Figure 10 A schematic cross-sectional structure diagram of an exposure pattern formed on a wafer in the additive manner is shown.

[0033] Explanation of Figure Numbers

[0034] 10 SRAF

[0035] 101 shallow groove

[0036] 102 raised lines

[0037] 20 Target Graphics

[0038] 21 Graphics Area

[0039] 211 lines

[0040] 22 spacer

[0041] 221 groove

[0042] 30 mask

[0043] 40 preset areas DETAILED DESCRIPTION

[0044] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0045] See also Figures 1 to 11 It should be noted that the illustrations provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation, the form, quantity, and proportion of each component in actual implementation may be arbitrarily changed, and the component layout may also be more complex.

[0046] like Figure 1 As shown, this embodiment provides a method for determining a light intensity threshold during SRAF exposure, the method comprising:

[0047] A target pattern 20 with an SRAF 10 added thereto is selected in the test layout, and the SRAF 10 can be exposed on the wafer during exposure;

[0048] Setting the energy-focus matrix during exposure of the lithography machine, and exposing the test pattern mask 30 to obtain an exposure pattern matrix;

[0049] Determining whether a first exposure pattern for exposing the SRAF 10 exists in the exposure pattern matrix; if so, obtaining an energy corresponding to the first exposure pattern, and obtaining a curve of a characteristic dimension of the target pattern 20 versus focal length at the energy through optical measurement;

[0050] A second exposure pattern for exposing the SRAF 10 is obtained according to a deviation between the characteristic size of the target pattern 20 and a preset target size, and a light intensity threshold for exposing the SRAF 10 is obtained according to exposure parameters of the second exposure pattern.

[0051] Specifically, the target pattern 20 is a semi-dense pattern or a dense pattern, comprising pattern areas 21 and spacing areas 22 between adjacent pattern areas 21. In this embodiment, the pattern areas 21 are used to form lines 211, and the spacing areas 22 are used to form grooves 221 between the lines. In this case, the characteristic dimension is the sum of the width D1 of the lines 211 and the width D2 of the grooves 221 between the lines 211.

[0052] As an example, the SRAF is added in the graphic area 21 .

[0053] like Figure 2 As shown, the SRAF 10 added to the graphic area 21 is exposed on the wafer through an exposure process, and a shallow groove 101 is formed on the top of the line 211 (the cross-sectional view is shown in FIG. Figure 3 As shown, the top view is Figure 4 In this embodiment, the SRAF 10 is used to increase the process window of the spacer 22. Figure 5 As shown, the light intensity threshold obtained by the method provided in this embodiment is 0.122.

[0054] As an example, the SRAF is added in the spacer 22 .

[0055] like Figure 6 As shown, the SRAF 10 added to the spacer 22 is exposed on the wafer through an exposure process, and a raised line 102 is formed in the groove 221 (the cross-sectional view is shown in FIG. Figure 7 As shown, the top view is Figure 8 In this embodiment, the SRAF 10 is used to increase the process window of the graphic area 21. Figure 9 As shown, the light intensity threshold value obtained by the method provided in this embodiment is 0.531.

[0056] Specifically, the target graphic 20 is an isolated graphic, and the SRAF 10 is added at a preset distance from the isolated graphic.

[0057] like Figure 10 As shown, in this embodiment, the isolated pattern is a line. The SRAF 10 is added at a predetermined distance from the isolated pattern to increase the process window of the isolated pattern. Furthermore, the characteristic dimension is the sum of the width D1 of the line 211 and the predetermined width D4 of the predetermined region 40 surrounding it where the SRAF 10 is added.

[0058] like Figure 11As shown, in this embodiment, the predetermined region 40 is the area where the addition of the SRAF 10 can affect the process window of the isolated pattern. If the SRAF 10 is exposed on the wafer, the predetermined width D4 of the predetermined region 40 changes, causing a deviation in the feature size. The maximum deviation can then be used to determine whether the SRAF 10 has been exposed and to determine the light intensity threshold.

[0059] Specifically, a scanning electron microscope or an optical line width meter is used to collect patterns to obtain the exposure pattern matrix.

[0060] Specifically, before obtaining the curve of the characteristic size of the target pattern as a function of focal length under the energy through optical measurement, the method further includes a step of determining a light intensity range according to the exposure pattern matrix.

[0061] As an example, the light intensity range is determined by measuring the feature size of the target pattern in the exposure pattern matrix using a scanning electron microscope or an optical line width meter.

[0062] Specifically, the method for obtaining the second exposure pattern for exposing the SRAF10 according to the deviation value between the characteristic size of the target pattern and the preset target size includes: obtaining the maximum deviation value between the characteristic size and the preset target size in the change curve by calculation; and obtaining the second exposure pattern from the exposure pattern matrix according to the maximum deviation value.

[0063] In this embodiment, the energy required to expose the SRAF 10 is determined using the first exposure pattern. Exposure patterns at different focal lengths at this energy are then obtained, thereby generating the second exposure pattern used to determine the light intensity threshold. Due to process conditions, the target pattern's feature size may vary when exposed under different exposure parameters. However, this deviation reaches its maximum value when the SRAF 10 is exposed. Therefore, this maximum deviation value can be used to determine whether the SRAF 10 has been exposed. In this embodiment, the preset target size is the feature size of the target pattern 20 when the SRAF 10 is not exposed.

[0064] Specifically, when obtaining the light intensity threshold of the SRAF10 exposure according to the exposure parameters of the second exposure pattern, the exposure parameters include the energy and the focal length. In this embodiment, a change in the focal length will cause a change in the light intensity, so the light intensity can be determined according to the focal length.

[0065] In summary, the present invention's method for determining the light intensity threshold for SRAF exposure uses an energy-focal length matrix to determine the energy of the exposure pattern for SRAF exposure. Optical measurement is then used to obtain the characteristic dimensions of the target pattern at the same energy and different focal lengths to determine the maximum deviation between the characteristic dimensions and a preset target dimension. Based on this maximum deviation, an exposure pattern capable of determining the light intensity threshold is identified, thereby determining the light intensity threshold for SRAF exposure. This method allows for simple and rapid determination of the SRAF light intensity threshold, reducing errors associated with manual determination and improving production capacity. Therefore, the present invention effectively overcomes the shortcomings of the prior art and possesses high industrial value.

[0066] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for determining the light intensity threshold during SRAF exposure, characterized in that: The method comprises: Selecting a target pattern with an SRAF added thereto in the test layout, wherein the SRAF can be exposed on the wafer during exposure; Setting the energy-focal length matrix during exposure of the photolithography machine, and exposing the test pattern mask to obtain an exposure pattern matrix; determining whether a first exposure pattern for exposing the SRAF exists in the exposure pattern matrix; if so, obtaining an energy corresponding to the first exposure pattern, and obtaining a curve of a characteristic dimension of the target pattern versus focal length at the energy through optical measurement; A second exposure pattern for exposing the SRAF is obtained according to a deviation value between the characteristic size of the target pattern and a preset target size, and a light intensity threshold of the SRAF exposure is obtained according to exposure parameters of the second exposure pattern.

2. The method for determining the light intensity threshold during SRAF exposure according to claim 1, wherein: The exposure pattern matrix is ​​obtained by collecting patterns using a scanning electron microscope or an optical line width meter.

3. The method for determining the light intensity threshold during SRAF exposure according to claim 2, wherein: Before obtaining the curve of the characteristic size of the target pattern as a function of focal length under the energy through optical measurement, the method further includes a step of determining a light intensity range according to the exposure pattern matrix.

4. The method for determining the light intensity threshold during SRAF exposure according to claim 3, wherein: The light intensity range is determined by measuring the feature size of the target pattern in the exposure pattern matrix using a scanning electron microscope or an optical line width meter.

5. The method for determining the light intensity threshold during SRAF exposure according to claim 1, wherein: The method for obtaining a second exposure pattern for exposing the SRAF according to a deviation value between the feature size of the target pattern and the preset target size includes: Obtaining a maximum deviation between the characteristic size in the variation curve and the preset target size by calculation; The second exposure pattern is obtained from the exposure pattern matrix according to the maximum deviation value.

6. The method for determining the light intensity threshold during SRAF exposure according to claim 5, wherein: When the light intensity threshold of the SRAF exposure is obtained according to the exposure parameters of the second exposure pattern, the exposure parameters include the energy and the focal length.

7. The method for determining the light intensity threshold during SRAF exposure according to claim 1, wherein: The target pattern is a semi-dense pattern or a dense pattern, including pattern areas and spacing areas between adjacent pattern areas.

8. The method for determining the light intensity threshold during SRAF exposure according to claim 7, wherein: The SRAF is added in the graphics area.

9. The method for determining the light intensity threshold during SRAF exposure according to claim 7, wherein: The SRAF is added within the spacer region.

10. The method for determining the light intensity threshold during SRAF exposure according to claim 1, wherein: The target pattern is an isolated pattern, and the SRAF is added at a preset distance from the isolated pattern.

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