Method for monitoring ghosting effect of lighting system of photoetching machine

Abstract

The invention discloses a method for monitoring a ghosting effect of an illumination system of a photoetching machine, which comprises the following steps: step 1, the illumination system comprises a lens and a measurement platform, and a light intensity uniformity sensor is arranged on the measurement platform; setting a lens area, a peripheral area and a central area on a moving plane of the measuring platform; light leakage of the peripheral area can generate a ghosting effect. Step 2, turning on the illumination system, moving the measurement platform to move the light intensity uniformity sensor to the central area, measuring the first light intensity of the central area, and obtaining a reference value according to the first light intensity; and step 3, moving the light intensity uniformity sensor to a selected position of the peripheral area, and measuring second light intensity at the selected position. And step 4, dividing the second light intensity by the reference value to form a first ratio, and taking the first ratio as a scattered light monitoring value of the ghost effect. According to the invention, the sensitivity can be improved, the monitoring range can be expanded, the measurement period can be shortened, repeated measurement can be realized, measurement errors can be effectively eliminated, and the accuracy is improved.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a semiconductor integrated circuit, and in particular to a method for monitoring the afterimage effect of an illumination system of a photolithography machine. Background Art

[0002] like Figure 1A , which is a schematic diagram of a mask in an existing photolithography process; the mask 101 includes a main graphic area 102 , and a peripheral graphic area 103 is also provided on the peripheral side of the main graphic area 102 .

[0003] The main graphic region 102 has a pattern 104 , and the peripheral graphic region 103 has a pattern 105 .

[0004] In a photolithography machine such as a scanner photolithography machine, the pattern 104 in the main graphic area 102 needs to be transferred to an exposure area (shot) on the wafer during one exposure. However, due to the existence of the peripheral graphic area 103, the scattered light from the light source may pass through the peripheral graphic area 103 and transfer the pattern 105 in the peripheral graphic area 103 to the adjacent exposure area, thereby affecting the pattern in the pattern in the adjacent exposure area, which is the afterimage effect.

[0005] like Figure 1B , which is a schematic diagram of the afterimage effect produced in the existing photolithography process; in the photolithography process, the exposure area 107a is first exposed to form a pattern 104a transferred from the pattern 104 in the main graphic area 102 in the mask 101 in the exposure area 107a.

[0006] Afterwards, the exposure area 107b is exposed, and the pattern 104 is transferred to the exposure area 107b to form the pattern 104b. However, in this process, the light from the light source and through the lens is not only incident on the main graphic area 102, but also scattered light 106 passes through the peripheral graphic area 103, and then the light 106a is incident on the exposure area 107a adjacent to the exposure area 107b. At this time, the pattern 105 in the peripheral graphic area 103 is transferred to the exposure area 107a to form the pattern 105a. Obviously, the pattern 105a will affect the already formed pattern 104a, for example, it will cause the critical dimension (CD) of the pattern in the pattern 104a to change. The effect of the scattered light 106 on the adjacent exposure area 107a to produce the pattern 105a is the afterimage effect.

[0007] The existing method of monitoring the afterimage effect of the lithography machine lighting system uses Figure 1B The double exposure effect in the exposure area 107a shown in FIG. 1 , the existing method for monitoring the afterimage effect of the lithography machine illumination system includes:

[0008] The exposure region 107a is exposed once to form a pattern 104a, and the CD of the pattern in the pattern 104a exposed once is measured.

[0009] Next, the exposure area 107b is exposed. At this time, due to the afterimage effect, the scattered light 106 in the exposure will expose the exposure area 107a for a second time and superimpose pattern 105a on the basis of pattern 104a. Pattern 105a will change the key dimensions of the graphics in pattern 104a. At the same time, the changes in the key dimensions of the graphics in pattern 104a are calculated to calculate the amount of light leakage, thereby monitoring the afterimage effect.

[0010] However, the existing methods for monitoring the afterimage effect of the lithography machine illumination system have the following disadvantages:

[0011] First, specific exposure conditions need to be established to worsen the afterimage effect so that the scattered light intensity reaches a threshold before it can be detected, and the sensitivity is too low.

[0012] Secondly, the range that can be monitored by the existing method is strongly related to the size of the mask 101 itself, and the monitoring range is limited.

[0013] In addition, the existing method indirectly monitors the light leakage by measuring the CD on the wafer, which requires multiple steps such as gluing, exposure, development, and measurement, and the entire cycle is relatively long.

[0014] Finally, CD measurement relies on the principle of electron beam imaging. The stability of the electron beam and measurement problems will interfere with the measurement results and reduce the accuracy of the final results. Summary of the invention

[0015] The technical problem to be solved by the present invention is to provide a method for monitoring the afterimage effect of the illumination system of a lithography machine, which can improve sensitivity, expand the monitoring range, shorten the measurement cycle, realize repeated measurement, effectively eliminate measurement errors and improve accuracy.

[0016] In order to solve the above technical problems, the method for monitoring the afterimage effect of the illumination system of a lithography machine provided by the present invention comprises the following steps:

[0017] Step 1: The illumination system of the lithography machine includes a lens and a measuring platform, and a light intensity uniformity sensor is arranged on the measuring platform.

[0018] A lens area, a peripheral area and a central area are set on the moving plane of the measuring platform; the lens area is located in the inner area of ​​the edge line formed after the edge of the lens is irradiated, the central area is an area selected inside the lens area and the center point of the central area is the center point of the lens area; the peripheral area is located outside the lens area, and light leakage in the peripheral area will produce an afterimage effect.

[0019] Step 2: Turn on the lighting system, move the measuring platform to move the light intensity uniformity sensor to the central area, measure the first light intensity of the central area, and obtain a reference value from the first light intensity.

[0020] Step three: move the measuring platform to move the light intensity uniformity sensor to a selected position in the peripheral area, and measure the second light intensity at the selected position in the peripheral area.

[0021] Step 4: dividing the second light intensity by the reference value to form a first ratio as a scattered light monitoring value of the afterimage effect.

[0022] A further improvement is that, in step 4, the first ratio is multiplied by 100 or 100% to obtain the scattered light monitoring value.

[0023] A further improvement is that the measuring platform moves in a stepping manner along the X direction or the Y direction.

[0024] A further improvement is that the step size of the measurement platform moving along the X direction is the first step, and the size of the first step is preset before step two and is adjustable.

[0025] The step size of the measurement platform moving along the Y direction is the second step size, and the size of the second step size is preset before step 2 and is adjustable.

[0026] A further improvement is to change the coordinates of the selected position in step three, and then repeat steps three and four to obtain the scattered light monitoring values ​​at the selected position with different coordinates.

[0027] A further improvement is that the coordinates of the selected position in step 3 are continuously changed by stepping along the X direction or the Y direction to achieve measurement of the scattered light monitoring value at each position in the sub-area of ​​the peripheral area.

[0028] A further improvement is that the coordinates of the selected position in step 3 are continuously changed by stepping along the X direction or the Y direction, so as to achieve the measurement of the scattered light monitoring values ​​at all positions of the peripheral area.

[0029] A further improvement is that the lighting system further comprises a light source, and the wavelength of the light source comprises: 365 nm, 248 nm or 193 nm.

[0030] A further improvement is that the lithography machine is a scanning lithography machine.

[0031] A further improvement is that the wafer size exposed by the photolithography machine includes: 200nm, 300nm or 450nm.

[0032] A further improvement is that in step 2, the moving direction and distance of the measuring platform are continuously changed by stepping along the X direction or the Y direction to measure the first light intensity at all positions of the central area, and the average value of the first light intensity at each position of the central area is used as the reference value.

[0033] Further improvements include:

[0034] Step 5: Move the measurement platform to move the light intensity uniformity sensor to the lens area outside the central area, so as to measure the third light intensity of the lens area outside the central area.

[0035] A further improvement is that, in step five, the moving direction and distance of the measuring platform are continuously changed by stepping along the X direction or the Y direction to achieve measurement of the third light intensity at all positions of the lens area outside the central area.

[0036] The present invention uses a light intensity uniformity sensor of a lithography machine to monitor the peripheral scattered light leakage ratio of a lens of the lithography machine to reversely deduce the afterimage effect of the illumination system, and can achieve the following technical effects:

[0037] 1. The present invention can improve sensitivity because: in the existing method, it is necessary to compare and calculate the key dimensions of the graphics in the double exposure area and the single exposure area to calculate the amount of light leakage and thus monitor the afterimage effect. However, the existing method requires specific settings of the exposure conditions to worsen the afterimage effect so that the scattered light intensity reaches a threshold value before it can be detected. Therefore, the sensitivity of the existing method is low. In the present invention, the light intensity uniformity sensor itself has a high photoelectric sensitivity, so there is no need to establish specific conditions to achieve monitoring. Therefore, the present invention can improve sensitivity.

[0038] 2. The present invention can expand the monitoring range because: in the existing method, monitoring requires the use of a mask for exposure, and the monitoring range will be limited by the size of the mask itself; in the present invention, no mask is required during the monitoring process, and the light intensity uniformity sensor is installed on a measuring platform with a large movement range. Therefore, the present invention can monitor a wider residual effect area, thereby expanding the monitoring range.

[0039] 3. The present invention can shorten the measurement cycle because: in the existing method, it is necessary to measure the critical dimension (CD) on the wafer for monitoring, which requires multiple steps including gluing, exposure, development and measurement, resulting in a long cycle; in the present invention, a light intensity uniformity sensor is used to directly measure and monitor, so the measurement cycle can be shortened.

[0040] 4. The present invention can achieve repeated measurement, effectively eliminate measurement errors and improve accuracy. The reason is: in the existing method, the measurement of CD on the wafer is measured by means of electron beam imaging principle. The stability and measurement problems of the electron beam will interfere with the measurement results and reduce the accuracy of the results. However, the present invention uses a light intensity uniformity sensor to directly measure and monitor, so it can achieve repeated measurement, effectively eliminate measurement errors and improve accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0042] Figure 1A It is a schematic diagram of a mask in an existing photolithography process;

[0043] Figure 1B It is a schematic diagram of the afterimage effect produced in the existing photolithography process;

[0044] Figure 2 is a flow chart of a method for monitoring the afterimage effect of a lithography machine illumination system according to an embodiment of the present invention;

[0045] Figure 3A It is a schematic diagram of a lens area, a peripheral area and a central area in a method for monitoring an afterimage effect of an illumination system of a lithography machine according to an embodiment of the present invention;

[0046] Figure 3B is a schematic diagram of using a light intensity uniformity sensor to measure light intensity in a method for monitoring an afterimage effect of a lithography machine illumination system according to an embodiment of the present invention;

[0047] Figure 4A It is a schematic diagram of moving a measuring platform along the X-axis direction to perform a light intensity test in a method for monitoring an afterimage effect of an illumination system of a lithography machine according to an embodiment of the present invention;

[0048] Figure 4B Is adopted Figure 4A The light intensity distribution curve is obtained by moving the measuring platform along the X-axis direction to perform light intensity test;

[0049] Figure 5A is a schematic diagram of scanning a sub-area in a method for monitoring an afterimage effect of an illumination system of a lithography machine according to an embodiment of the present invention;

[0050] Figure 5B Yes Figure 5A Light intensity distribution table obtained by scanning the sub-areas in . DETAILED DESCRIPTION

[0051] like Figure 2 As shown, it is a flow chart of a method for monitoring the afterimage effect of a lithography machine illumination system according to an embodiment of the present invention; Figure 3A As shown, it is a schematic diagram of the lens area 201, the peripheral area 203 and the central area 202 in the method for monitoring the afterimage effect of the illumination system of the lithography machine according to an embodiment of the present invention; Figure 3B FIG. 2 is a schematic diagram of using a light intensity uniformity sensor 205 to measure light intensity in a method for monitoring the afterimage effect of a lithography machine illumination system according to an embodiment of the present invention. The method for monitoring the afterimage effect of a lithography machine illumination system according to an embodiment of the present invention comprises the following steps:

[0052] Step 1: The illumination system of the lithography machine includes a lens and a measuring platform 204 , on which a light intensity uniformity sensor 205 is disposed.

[0053] like Figure 3A As shown, a lens area 201, a peripheral area 203 and a central area 202 are set on the moving plane of the measuring platform 204; the lens area 201 is located in the inner area of ​​the edge line 201a formed after the edge of the lens is illuminated, the central area 202 is an area selected inside the lens area 201 and the center point of the central area 202 is the center point of the lens area 201; the peripheral area 203 is located outside the lens area 201, and the light leakage of the peripheral area 203 will produce an afterimage effect.

[0054] Figure 3A In the embodiment, the length of the outer circumference of the outer region 203 is L, and the width is W. The direction of the length L is the X direction, and the direction of the width W is the Y direction.

[0055] In the embodiment of the present invention, the illumination system further comprises a light source, and the wavelength of the light source comprises: 365 nm, i.e., in-line light, 248 nm, i.e., KeF light, or 193 nm, i.e., ArF light.

[0056] The lithography machine is a scanning lithography machine.

[0057] The wafer sizes exposed by the photolithography machine include: 200nm, 300nm or 450nm.

[0058] Step 2: Figure 3B As shown, turn on the lighting system, Figure 3B 2 shows a vertically irradiated light 206 and scattered light 207 at the edge. The scattered light 207 will produce an afterimage effect.

[0059] The measuring platform 204 is moved to move the light intensity uniformity sensor 205 to the central area 202, and the first light intensity of the central area 202 is measured, and a reference value is obtained from the first light intensity. Figure 3B There is only one measuring platform 204 in the figure, but in order to simultaneously indicate that the measuring platform 204 can move to various positions, schematic diagrams showing the measuring platform 204 at two positions are simultaneously shown.

[0060] Step 3: Figure 3B As shown, the measuring platform 204 is moved to move the light intensity uniformity sensor 205 to a selected position of the peripheral area 203 , and the second light intensity at the selected position of the peripheral area 203 is measured.

[0061] Step 4: dividing the second light intensity by the reference value to form a first ratio as a scattered light monitoring value of the afterimage effect.

[0062] In the embodiment of the present invention, the first ratio is multiplied by 100 or 100% as the scattered light monitoring value. The formula is:

[0063] Scattered light = measured value / reference value x 100[%] (1);

[0064] In formula (1), the scattered light is the scattered light monitoring value, and the measured value is the second light intensity.

[0065] The measuring platform 204 moves in a stepping manner along the X direction or the Y direction. Figure 3A As shown, the X direction is the direction of length L, and the Y direction is the direction of width W.

[0066] The step size of the measurement platform 204 moving along the X direction is the first step, and the size of the first step is preset before step 2 and is adjustable.

[0067] The step size of the measurement platform 204 moving along the Y direction is a second step size, and the size of the second step size is preset before step 2 and is adjustable.

[0068] In the embodiment of the present invention, the coordinates of the selected position in step three are changed, and then steps three and four are repeated to obtain the scattered light monitoring values ​​at the selected position with different coordinates.

[0069] In some embodiments, the coordinates of the selected position in step 3 are continuously changed by stepping along the X direction or the Y direction to achieve measurement of the scattered light monitoring value at each position in the sub-area of ​​the peripheral area 203 .

[0070] In some embodiments, the coordinates of the selected position in step 3 are continuously changed by stepping along the X direction or the Y direction to achieve measurement of the scattered light monitoring values ​​at all positions of the peripheral area 203 .

[0071] In some embodiments, the moving direction and distance of the measuring platform 204 are continuously changed by stepping along the X direction or the Y direction to measure the first light intensity at all positions of the central area 202, and the average value of the first light intensity at each position of the central area 202 is used as the reference value.

[0072] In some embodiments, it also includes:

[0073] Step 5: Move the measurement platform 204 to move the light intensity uniformity sensor 205 to the lens area 201 outside the central area 202 to measure the third light intensity of the lens area 201 outside the central area 202 .

[0074] A further improvement is that, in step five, the moving direction and distance of the measuring platform 204 are continuously changed by stepping along the X direction or the Y direction to achieve measurement of the third light intensity at all positions of the lens area 201 outside the central area 202.

[0075] like Figure 4A As shown, it is a schematic diagram of moving the measuring platform along the X-axis direction to perform light intensity testing in the method for monitoring the afterimage effect of the illumination system of the lithography machine according to an embodiment of the present invention; that is, starting from the outer edge of the peripheral area 203, the measuring platform is moved along the X-axis direction using the first step and will continue to move to the lens area 201, and the light intensity at each moving position is tested. Figure 4B As shown, it is adopted Figure 4A From the light intensity distribution curve 301 obtained by moving the measuring platform along the X-axis direction to perform the light intensity test, it can be seen that the peripheral area 203 between the X-coordinates of -13800 and -13200 has a certain light intensity, and the light intensity of the outer area of ​​the coordinate -13800 is basically 0; the area within the coordinate -13200 is the lens area 201, and the corresponding light intensity is the third light intensity.

[0076] like Figure 5A , which is a schematic diagram of scanning a sub-area in a method for monitoring the afterimage effect of a lithography machine illumination system according to an embodiment of the present invention; Figure 5A In the embodiment, the sub-area 209 is the area where the light intensity needs to be scanned and measured, and most of the sub-area 209 is located in the peripheral area 203, and a small part is located in the lens area 201. Figure 5B As shown, it is Figure 5AThe light intensity distribution table obtained by scanning the sub-area 209 in FIG. Figure 5B In the figure, the area shown in the box 302 is located in the lens area 201. It can be seen that in the peripheral area close to the box 302, such as the two first step areas in the X direction and the two second step areas in the Y direction, the light intensity is relatively large; the light intensity value of the other peripheral areas 203 outside is relatively low, which is consistent with Figure 4B It is consistent with the curve 301 in FIG.

[0077] The embodiment of the present invention uses the light intensity uniformity sensor 205 of the lithography machine to monitor the peripheral scattered light leakage ratio of the lens of the lithography machine to reversely deduce the afterimage effect of the illumination system, and can achieve the following technical effects:

[0078] 1. The embodiments of the present invention can improve sensitivity because: in the existing method, it is necessary to compare and calculate the key dimensions of the graphics in the double exposure area and the single exposure area to calculate the amount of light leakage and thus monitor the afterimage effect. However, the existing method requires specific settings of the exposure conditions to worsen the afterimage effect so that the scattered light intensity reaches a threshold value before it can be detected. Therefore, the sensitivity of the existing method is low. In the embodiments of the present invention, the light intensity uniformity sensor 205 itself has a high photoelectric sensitivity, so there is no need to establish specific conditions to achieve monitoring. Therefore, the embodiments of the present invention can improve sensitivity.

[0079] 2. The embodiment of the present invention can expand the monitoring range. The reason is: in the existing method, monitoring requires the use of a mask for exposure, and the monitoring range will be limited by the size of the mask itself; in the embodiment of the present invention, a mask is not required during the monitoring process, and the light intensity uniformity sensor 205 is installed on the measurement platform 204. The measurement platform 204 has a large range of motion. Therefore, the embodiment of the present invention can monitor a wider residual effect area, thereby expanding the monitoring range.

[0080] 3. The embodiment of the present invention can shorten the measurement cycle. The reason is that in the existing method, it is necessary to measure the critical dimension (CD) on the wafer for monitoring, which requires multiple steps including gluing, exposure, development and measurement, so the cycle is long. In the embodiment of the present invention, the light intensity uniformity sensor 205 is used to directly measure and monitor, so the measurement cycle can be shortened.

[0081] 4. The embodiment of the present invention can achieve repeated measurement, effectively eliminate measurement errors and improve accuracy. The reason is: in the existing method, the measurement of CD on the wafer is measured by means of electron beam imaging principle. The stability and measurement problems of the electron beam will interfere with the measurement results and reduce the accuracy of the results. However, the embodiment of the present invention uses the light intensity uniformity sensor 205 to directly measure and realize monitoring, so it can achieve repeated measurement, effectively eliminate measurement errors and improve accuracy.

[0082] The present invention has been described in detail above through specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principle of the present invention, those skilled in the art may also make many variations and improvements, which should also be considered as the protection scope of the present invention.

Claims

1. A method for monitoring the afterimage effect of a lithography machine illumination system, characterized in that , including the following steps: Step 1: The illumination system of the lithography machine includes a lens and a measuring platform, and a light intensity uniformity sensor is arranged on the measuring platform; Setting a lens area, a peripheral area and a central area on a moving plane of the measuring platform; The lens area is located in the inner area of ​​the edge line formed after the edge of the lens is illuminated, the central area is an area selected inside the lens area, and the center point of the central area is the center point of the lens area; the peripheral area is located outside the lens area, and the light leakage in the peripheral area will produce an afterimage effect; Step 2, turning on the lighting system, moving the measuring platform to move the light intensity uniformity sensor to the central area, measuring the first light intensity of the central area, and obtaining a reference value from the first light intensity; Step 3: Move the measuring platform to move the light intensity uniformity sensor to a selected position in the peripheral area, and measure the second light intensity at the selected position in the peripheral area; Step 4: dividing the second light intensity by the reference value to form a first ratio as a scattered light monitoring value of the afterimage effect.

2. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 1, characterized in that: In step 4, the first ratio is multiplied by 100 or 100% to obtain the scattered light monitoring value.

3. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 1, characterized in that: The measuring platform moves in a stepping manner along the X direction or the Y direction.

4. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 3, characterized in that: The step size of the measuring platform moving along the X direction is the first step, and the size of the first step is preset before step 2 and is adjustable; The step size of the measurement platform moving along the Y direction is the second step size, and the size of the second step size is preset before step 2 and is adjustable.

5. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 4, characterized in that: The coordinates of the selected position in step three are changed, and then steps three and four are repeated to obtain the scattered light monitoring values ​​at the selected position with different coordinates.

6. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 5, characterized in that: The coordinates of the selected position in step 3 are continuously changed by stepping along the X direction or the Y direction, so as to measure the scattered light monitoring value at each position in the sub-area of ​​the peripheral area.

7. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 6, characterized in that: The coordinates of the selected position in step 3 are continuously changed by stepping along the X direction or the Y direction, so as to measure the scattered light monitoring values ​​at all positions of the peripheral area.

8. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 1, characterized in that: The lighting system further comprises a light source, and the wavelength of the light source comprises: 365 nm, 248 nm or 193 nm.

9. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 1, characterized in that: The lithography machine is a scanning lithography machine.

10. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 1, characterized in that: The wafer sizes exposed by the photolithography machine include: 200nm, 300nm or 450nm.

11. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 4, characterized in that: In step 2, the moving direction and distance of the measuring platform are continuously changed by stepping along the X direction or the Y direction to measure the first light intensity at all positions of the central area, and the average value of the first light intensity at each position of the central area is used as the reference value.

12. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 4, characterized in that: Also includes: Step 5: Move the measurement platform to move the light intensity uniformity sensor to the lens area outside the central area, so as to measure the third light intensity of the lens area outside the central area.

13. The method for monitoring the afterimage effect of the illumination system of a lithography machine according to claim 12, characterized in that: In step five, the moving direction and distance of the measuring platform are continuously changed by stepping along the X direction or the Y direction to measure the third light intensity at all positions of the lens area outside the central area.

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