A stray light measurement system and its measurement method and device

Abstract

The embodiment of the present invention discloses a stray light measurement system and a measurement method and device thereof, wherein the measurement system comprises: a mask, wherein the mask has a light shielding pattern combination, wherein the light shielding pattern combination comprises a first pattern and a second pattern of the same shape, wherein the outer edge radius value of the first pattern is greater than the outer edge radius value of the second pattern, and the centers of the first pattern and the second pattern have light-transmitting areas of the same shape and size; and a photolithography machine, wherein a substrate to be photolithography is arranged in the photolithography machine, wherein the photolithography machine is used to perform a single exposure of the substrate to be photolithography through the mask, and after the exposure is completed, the exposure parameters of the substrate to be photolithography are measured, and the first stray light ratio is obtained according to the exposure parameters, and the influence distance of the first stray light is greater than or equal to the outer edge radius value of the second pattern. In the embodiment of the present invention, the accuracy of the stray light test is improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to optical testing technology, and in particular to a stray light measurement system and a measurement method and device thereof. Background Art

[0002] Stray light is non-imaging light other than imaging light in an optical system, that is, "unwanted" light flux components outside the spectral bandwidth. For photolithography, stray light in the exposure system refers to other light energy other than the light required for normal exposure. Stray light in the exposure system has an important impact on photolithography resolution and key dimension characteristics.

[0003] According to the difference in the distance of its impact, stray light can be divided into short, medium and long range stray light. The impact distance of short range stray light is less than 5μm, the impact distance of long range stray light is greater than 200μm, and the impact distance of medium range stray light is 5μm to 200μm. Of course, with the continuous improvement of lithography technology, the definition of short, medium and long range stray light is also changing. For example, short range stray light is stray light less than 2μm, and long range stray light is stray light greater than 100μm.

[0004] Stray light at different distances has different effects on the photolithography process. Among them, medium and short-range stray light has the greatest impact on photolithography imaging, making the current measurement method less accurate. Summary of the invention

[0005] The embodiment of the present invention provides a stray light measurement system and a measurement method and device thereof to improve the accuracy of stray light testing.

[0006] An embodiment of the present invention provides a stray light measurement system, including:

[0007] A mask having a light-shielding pattern combination, wherein the light-shielding pattern combination includes a first pattern and a second pattern of the same shape, wherein the outer edge radius of the first pattern is greater than the outer edge radius of the second pattern, and the centers of the first pattern and the second pattern have light-transmitting areas of the same shape and size;

[0008] A photolithography machine, wherein a substrate to be photolithography is arranged therein, and the photolithography machine is used to expose the substrate to be photolithography once through the mask plate, and measure the exposure parameters of the substrate to be photolithography after the exposure is completed, and obtain a first stray light ratio according to the exposure parameters, and the influence distance of the first stray light is greater than or equal to the outer edge radius value of the second pattern.

[0009] Furthermore, the shapes surrounded by the outer edges of the first pattern and the second pattern are both square or circular, and the shape of the light-transmitting area is square or circular;

[0010] The radius of the outer edge of the square is half of the side length of the square.

[0011] Further, the outer edge radius of the second pattern is greater than or equal to 1 μm; and / or,

[0012] The light-transmitting spacing between the first pattern and the second pattern in the light-shielding pattern combination is greater than or equal to 200 μm.

[0013] Furthermore, the exposure layout of the substrate to be photolithographic includes a central area and an edge area surrounding the central area, the mask graphic layout corresponding to the central area is a combination of multiple shading patterns arranged in an array, and the mask graphic layout corresponding to the edge area is a combination of multiple shading patterns evenly distributed in a circle.

[0014] Furthermore, the light-transmitting area includes a shading structure, and the shading structure is composed of M shading strips arranged in parallel, and the extension length of the shading strip is smaller than the minimum size of the light-transmitting area in the extension direction thereof.

[0015] Furthermore, the second pattern is composed of N light-shielding rings surrounding the light-transmitting area, and the center points of the N light-shielding rings overlap with the center point of the light-transmitting area.

[0016] Based on the same inventive concept, an embodiment of the present invention further provides a method for measuring the stray light measurement system as described above, comprising:

[0017] Performing an exposure once using a set exposure dose corresponding to the outer edge radius value of the second pattern, and measuring exposure parameters of first marks corresponding to the first pattern in the substrate to be photolithographic after the exposure is completed, and calculating exposure size errors according to the exposure parameters of each first mark;

[0018] Measuring exposure parameters of a second mark corresponding to the second pattern in the substrate to be photolithographically processed, and calculating an actual exposure size of the second mark and an actual exposure dose corresponding thereto according to the exposure size error and the exposure parameters of the second mark;

[0019] The first stray light ratio is calculated according to the actual exposure dose and the set exposure dose.

[0020] Furthermore, the exposure layout of the substrate to be photolithographic includes a central area and an edge area surrounding the central area, the mask pattern layout corresponding to the central area is a combination of multiple shading patterns arranged in an array, and the mask pattern layout corresponding to the edge area is a combination of multiple shading patterns evenly distributed in a circumference;

[0021] An exposure process includes:

[0022] Exposing the edge area of ​​the substrate to be photolithographic through the mask with the set exposure dose, and at the same time, exposing the middle area of ​​the substrate to be photolithographic through the mask with the set exposure dose as the middle value and using a preset dose step rule;

[0023] The exposure parameters include exposure size and its corresponding exposure dose.

[0024] Further, calculating the exposure size error according to the exposure parameters of each of the first marks includes:

[0025] Calculating an average exposure size of the first marks in the edge region of the substrate to be photolithographically processed according to the exposure sizes of the first marks in the edge region;

[0026] The difference between the exposure size average value and the exposure size of a first intermediate mark is determined as the exposure size error, the first intermediate mark is located in the middle area of ​​the substrate to be photolithographically processed and the exposure dose corresponding to the first intermediate mark is the set exposure dose.

[0027] Furthermore, before calculating the actual exposure size of the second mark and the actual exposure dose corresponding thereto, the method further includes:

[0028] According to the exposure size and exposure dose of each first mark in the middle area of ​​the substrate to be photolithographically processed, the size-dose formula (1) is obtained by fitting:

[0029] y=ax+b (1),

[0030] Where x is the exposure dose, y is the exposure size, and a and b are constants.

[0031] Further, calculating the actual exposure size of the second mark and the actual exposure dose corresponding thereto includes:

[0032] Calculating an average exposure size of the second marks in the edge region of the substrate to be photolithographically processed according to the exposure sizes of the second marks in the edge region;

[0033] The difference between the exposure size average value and the exposure size error is determined as the actual exposure size of the second mark, and the actual exposure dose corresponding to the actual exposure size of the second mark is calculated according to formula (1).

[0034] Further, calculating the first stray light proportion Ls includes:

[0035] Ls=100%*(Ds-D0) / D0, (2)

[0036] Wherein, Ds is the actual exposure dose, and D0 is the set exposure dose.

[0037] Based on the same inventive concept, an embodiment of the present invention further provides a measuring device of the stray light measuring system as described above, comprising:

[0038] an exposure module, configured to perform an exposure once using a set exposure dose corresponding to the outer edge radius value of the second pattern, and after the exposure is completed, measure exposure parameters of first marks in the substrate to be photolithographically processed corresponding to the first pattern, and calculate exposure size errors according to the exposure parameters of each of the first marks;

[0039] a measuring module, configured to measure an exposure parameter of a second mark corresponding to the second pattern in the substrate to be photolithographically processed, and calculate an actual exposure size of the second mark and an actual exposure dose corresponding thereto according to the exposure size error and the exposure parameter of the second mark;

[0040] A calculation module is used to calculate the first stray light ratio according to the actual exposure dose and the set exposure dose.

[0041] In an embodiment of the present invention, the mask used in the stray light measurement system has at least one shading pattern combination, the shading pattern combination includes a first pattern and a second pattern of the same shape, the outer edge radius value of the first pattern is greater than the outer edge radius value d3 of the second pattern, and the centers of the first pattern and the second pattern have light-transmitting areas of the same shape and size; the lithography machine exposes the substrate to be photolithography once through the mask, and obtains the first stray light ratio according to the exposure parameters of the substrate to be photolithography, and the influence distance of the first stray light is greater than or equal to d3. In an embodiment of the present invention, the mask used can realize the measurement of stray light at different distances, which can be completed by only one exposure, reducing the accumulation of machine errors caused by multiple exposures, improving accuracy, and not only quantifying the ratio of stray light at different distances, but also characterizing the influence of stray light on process graphics. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, although the drawings described below are some specific embodiments of the present invention, for those skilled in the art, the basic concepts of the device structure, driving method and manufacturing method disclosed and suggested by the various embodiments of the present invention can be expanded and extended to other structures and drawings, and there is no doubt that these should be within the scope of the claims of the present invention.

[0043] Figure 1 is a schematic diagram of the exposure layout of a substrate to be photolithographically processed in a stray light measurement system provided by an embodiment of the present invention;

[0044] Figure 2is a schematic diagram of a first light-shielding pattern combination in a mask provided by an embodiment of the present invention;

[0045] Figure 3 is a schematic diagram of a second light-shielding pattern combination in a mask provided by an embodiment of the present invention;

[0046] Figure 4 is a schematic diagram of a third light-shielding pattern combination in a mask provided by an embodiment of the present invention;

[0047] Figure 5 is a schematic diagram of a fourth light-shielding pattern combination in a mask provided by an embodiment of the present invention;

[0048] Figure 6 is a schematic diagram of a fifth light-shielding pattern combination in a mask provided by an embodiment of the present invention;

[0049] Figure 7 is a schematic diagram of a sixth light-shielding pattern combination in a mask provided by an embodiment of the present invention;

[0050] Figure 8 is a flow chart of a measurement method of a stray light measurement system provided by an embodiment of the present invention;

[0051] Fig. 9 yes Figure 8 Flow chart of step S1 in the measurement method shown;

[0052] Fig.10 yes Figure 8 Flow chart of step S2 in the measurement method shown;

[0053] Fig.11 It is a schematic diagram of the fitting curve of the exposure size and exposure dose of the first mark. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described through the implementation method with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the basic concepts disclosed and suggested by the embodiments of the present invention, all other embodiments obtained by those skilled in the art are within the scope of protection of the present invention.

[0055] The embodiment of the present invention provides a stray light measurement system for measuring the proportion of stray light above a certain distance in a photolithography process. Figure 1 and Figure 2As shown, the stray light measurement system provided in this embodiment includes: a mask 100, the mask 100 has a shading pattern combination 101, the shading pattern combination 101 includes a first pattern 110 and a second pattern 120 of the same shape, the outer edge radius value d2 of the first pattern 110 is greater than the outer edge radius value d3 of the second pattern 120, and the centers of the first pattern 110 and the second pattern 120 have light-transmitting areas 119 of the same shape and size; a photolithography machine, the photolithography machine is provided with a substrate 200 to be photolithography, the photolithography machine is used to expose the substrate 200 to be photolithography once through the mask 100, and measure the exposure parameters of the substrate 200 to be photolithography after the exposure is completed, and obtain the first stray light ratio according to the exposure parameters, and the influence distance of the first stray light is greater than or equal to the outer edge radius value d3 of the second pattern 120. Among them, Figure 1 The exposure layout of the light shielding pattern combination 101 of the mask 100 on the substrate 200 to be photolithographically processed is shown.

[0056] In this embodiment, one or more shading pattern combinations 101 constitute the mask 100. In the exposure layout of the optional substrate 200 to be photolithographic, the mask graphic layout corresponding to its edge area has at least one shading pattern combination 101, and the mask graphic layout corresponding to its center area has at least one shading pattern combination 101; in other embodiments, the mask can also be selected to have only one shading pattern combination, or the edge area of ​​the mask is distributed with multiple shading pattern combinations and the center area is distributed with multiple shading pattern combinations. Relevant practitioners can reasonably set the pattern of the mask according to product requirements.

[0057] The shading pattern combination 101 includes a first pattern 110 and a second pattern 120 of the same shape. The shape described herein specifically refers to a shape formed by the outermost edges of the pattern. The first pattern 110 and the second pattern 120 of the same shape are the same as the shape formed by the outermost edges of the first pattern 110 and the shape formed by the outermost edges of the second pattern 120. Figure 2 The outer edge radius of the second pattern 120 is d3, and d3 corresponds to the minimum impact distance of the stray light to be measured; for example, d3 is equal to 2 microns, and the mask can be used to detect the proportion of stray light with an impact distance of more than 2 microns in the photolithography process.

[0058] In addition, the outer edge radius value d2 of the first pattern 110 is greater than the outer edge radius value d3 of the second pattern 120, and d2 corresponds to the maximum impact distance of the stray light to be measured, and the distance interval from d3 to d2 is the impact distance range of the stray light to be measured; for example, d3 is equal to 2 microns, and d2 is equal to 200 microns, then the mask can be used to detect the proportion of stray light with an impact distance between 2 microns and 200 microns in the photolithography process. Based on this, relevant practitioners can reasonably set d2 and d3 according to product requirements, for example, d3 = 1 micron, d2 = 300 microns.

[0059] In this embodiment, the center of the first pattern 110 and the second pattern 120 has a light-transmitting area 119 of the same shape and size, that is, the light-transmitting area 119 of the first pattern 110 and the light-transmitting area 119 of the second pattern 120 are exactly the same, and the outer edge radius of the light-transmitting area 119 is equal to d1. It can be understood that d1 is less than d3, but d1 is not specifically limited in the present invention. It should be noted that the areas of the first pattern 110 other than the central light-transmitting area 119 are all light-shielding areas 111, that is, the area between the edge corresponding to d1 and the edge corresponding to d2 in the first pattern 110 is the light-shielding area 111; the areas of the second pattern 120 other than the central light-transmitting area 119 are all light-shielding areas 121, that is, the area between the edge corresponding to d1 and the edge corresponding to d3 in the second pattern 120 is the light-shielding area 121; all areas other than the light-shielding areas 111 and 121 in the mask are light-transmitting areas, for example, the gap between any two adjacent patterns is a light-transmitting area.

[0060] The stray light measurement system also includes a photolithography machine, in which a substrate to be photolithography is placed. The photolithography machine exposes the substrate to be photolithography once through a mask plate 100. After the exposure process is completed, a first mark corresponding to the first pattern 110 is formed on the substrate to be photolithography, and a second mark corresponding to the second pattern 120 is also formed. The exposure process at least includes exposure and development, and the specific process is not repeated here. After the exposure is completed, the photolithography machine measures the exposure parameters of the substrate to be photolithography, specifically, the exposure size of each first mark and the exposure dose corresponding thereto are measured, and the exposure size of each second mark and the exposure dose corresponding thereto are measured. The photolithography machine obtains the first stray light ratio according to the exposure parameters on the photolithography substrate, and the influence distance of the first stray light is greater than or equal to the outer edge radius value d3 of the second pattern 120. The specific calculation process of the first stray light ratio is described in detail in the following measurement method, and is not repeated here.

[0061] In an embodiment of the present invention, the mask used in the stray light measurement system has at least one shading pattern combination, the shading pattern combination includes a first pattern and a second pattern of the same shape, the outer edge radius value of the first pattern is greater than the outer edge radius value d3 of the second pattern, and the centers of the first pattern and the second pattern have light-transmitting areas of the same shape and size; the lithography machine exposes the substrate to be photolithography once through the mask, and obtains the first stray light ratio according to the exposure parameters of the substrate to be photolithography, and the influence distance of the first stray light is greater than or equal to d3. In an embodiment of the present invention, the mask used can realize the measurement of stray light at different distances, which can be completed by only one exposure, reducing the accumulation of machine errors caused by multiple exposures, improving accuracy, and not only quantifying the ratio of stray light at different distances, but also characterizing the influence of stray light on process graphics.

[0062] Exemplarily, based on the above technical solution, the shapes surrounded by the outer edges of the first pattern and the second pattern can be square or circular, and the shape of the light-transmitting area can be square or circular; wherein the radius of the shape of the square outer edge is half of the side length of the square. It is also possible that the shapes surrounded by the outer edges of the first pattern and the second pattern can be other measurement figures, such as ellipse, rectangle, etc., and the shape of the light-transmitting area can be other measurement figures, such as ellipse, rectangle, etc.

[0063] like Figure 2 As shown, the shapes surrounded by the outer edges of the optional first pattern 110 and the second pattern 120 are both circular, and the shape of the light-transmitting area 119 is circular.

[0064] like Figure 3 As shown, the shapes surrounded by the outer edges of the optional first pattern 110 and the second pattern 120 are both circular, and the shape of the light-transmitting area 119 is a square.

[0065] like Figure 4 As shown, the shapes surrounded by the outer edges of the optional first pattern 110 and the second pattern 120 are both square, and the shape of the light-transmitting area 119 is circular.

[0066] like Figure 5 As shown, the shapes surrounded by the outer edges of the optional first pattern 110 and the second pattern 120 are both square, and the shape of the light-transmitting area 119 is a square.

[0067] Optionally, the outer edge radius d3 of the second pattern 120 is greater than or equal to 1 μm; and / or, the light-transmitting spacing d4 between the first pattern 110 and the second pattern 120 in the light-shielding pattern combination 101 is greater than or equal to 200 μm.

[0068] For the photolithography process, stray light in the exposure system refers to other light energy except the light required for normal exposure. According to the difference in its impact distance, stray light can be divided into short, medium and long-range stray light. The impact distance of stray light ranges from 2μm to 200μm. With the continuous improvement of photolithography technology, the definition of short, medium and long-range stray light is also changing. For photolithography processes with higher nodes, short-range stray light is stray light less than 2μm, medium-range stray light is stray light greater than 2μm and less than 100μm, and long-range stray light is stray light greater than 100μm. The impact of stray light at different distances on the photolithography process also decreases in turn. Short-range stray light will cause imaging contrast problems, and long-range stray light will affect the dose during exposure. Medium and short-range stray light has the greatest impact on photolithography.

[0069] The outer edge radius d3 of the second pattern 120 can be set to be greater than or equal to 1 μm, which can be used to measure the proportion of stray light above 1 micron. When the size of the light-transmitting area is greater than or equal to 200 μm, it will no longer be affected by stray light during exposure, so the light-transmitting spacing d4 between the first pattern 110 and the second pattern 120 can be set to be greater than or equal to 200 μm.

[0070] It is understandable that relevant practitioners can reasonably set d1, d2, d3 and d4 according to product requirements, and no specific limitation is made in the present invention.

[0071] like Figure 1 The exposure layout of the optional substrate 200 to be photolithographic shown includes a central area and an edge area surrounding the central area. The mask graphic layout corresponding to the central area is a plurality of shading pattern combinations 101 arranged in an array, and the mask graphic layout corresponding to the edge area is a plurality of shading pattern combinations 101 uniformly distributed on the circumference. In this embodiment, the exposure central area of ​​the substrate 200 to be photolithographic is exposed using a plurality of shading pattern combinations 101 arranged in an array, and the edge area is exposed using a plurality of shading pattern combinations 101 uniformly distributed on the circumference. After exposure, a plurality of edge area marks uniformly distributed on the circumference are formed in the edge area of ​​the photolithographic substrate, and a plurality of center area marks arranged in an array are formed in the center area of ​​the photolithographic substrate. The edge area marks and the center area marks can be compared to facilitate stray light measurement. The specific measurement process is described in the measurement method below and will not be repeated here.

[0072] like Figure 6The optional light-transmitting area 119 shown includes a shading structure, which is composed of M parallel shading strips 112, and the extension length of the shading strips 112 is less than the minimum size of the light-transmitting area 119 in the extension direction thereof. In this embodiment, a special pattern, such as a shading structure such as a shading strip, is set in the light-transmitting area 119 of each pattern, and can also be used to reflect the influence of stray light at different distances on certain main patterns through test results. It can be understood that the special pattern includes but is not limited to the shading strip, and relevant practitioners can reasonably set the pattern in the light-transmitting area according to product requirements.

[0073] like Figure 7 The optional second pattern 120 shown is composed of N light shielding rings 121 surrounding the light-transmitting area 119, and the center points of the N light shielding rings 121 overlap with the center point of the light-transmitting area 119. In this embodiment, the second pattern 120 includes multiple light shielding rings 121, which can also be used to test stray light in a certain range.

[0074] Based on the same inventive concept, an embodiment of the present invention further provides a measurement method of a stray light measurement system, which can be performed by a measurement device, which can be implemented in software and / or hardware and configured in a lithography machine for application. The stray light measurement system provided in this embodiment can be selected from the measurement system described in any of the above embodiments.

[0075] like Figure 8 As shown, the measurement method of the stray light measurement system includes:

[0076] Step S1, performing an exposure once using a set exposure dose corresponding to the outer edge radius value of the second pattern, and measuring exposure parameters of first marks corresponding to the first pattern in the substrate to be photolithography after the exposure is completed, and calculating exposure size errors according to the exposure parameters of each first mark;

[0077] Step S2, measuring the exposure parameters of the second mark corresponding to the second pattern in the substrate to be photolithographically processed, and calculating the actual exposure size of the second mark and the actual exposure dose corresponding thereto according to the exposure size error and the exposure parameters of the second mark;

[0078] Step S3: Calculate the first stray light ratio according to the actual exposure dose and the set exposure dose.

[0079] For the operation of step S1, first, the lithography machine exposes the substrate to be photolithography once through the mask described in any of the above embodiments. After exposure and development, a first mark corresponding to each first pattern is formed on the substrate to be photolithography, and a second mark corresponding to each second pattern is also formed. It can be understood that the exposure dose of the exposure process is based on the set exposure dose. The set exposure dose is not selected arbitrarily, but is a suitable exposure dose selected based on the outer edge radius value d3 of the second pattern. For example, when d3=2μm, the optimal exposure dose is 50mj, and the set exposure dose is selected as 50mj; when d3 changes, the corresponding optimal exposure dose may change, and relevant practitioners can reasonably preset the set exposure dose according to product requirements. A measuring device is integrated in the lithography machine. Secondly, the measuring device measures the exposure parameters of each first mark in the substrate to be photolithography. The exposure parameters of the mark include the exposure size of the mark and the exposure dose when the mark is exposed. Finally, the measuring device calculates the exposure size error according to the exposure parameters of each first mark.

[0080] For the operation of step S2, the measuring device measures the exposure parameters of each second mark in the substrate to be photolithographically processed, and calculates the actual exposure size of the second mark after removing the exposure process error and its corresponding actual exposure dose based on the exposure size error obtained in step S1 and the exposure parameters of each second mark.

[0081] For the operation of step S3, the first stray light ratio is calculated according to the actual exposure dose and the set exposure dose.

[0082] In the embodiment of the present invention, the exposure error can be decomposed by only one exposure and measurement, and the stray light at different distances can be monitored. The whole measurement process is simple and fast. The measurement method is completed by a measurement device integrated in the lithography machine, which avoids the error caused by human testing, reduces the accumulation of machine errors caused by multiple exposures, improves the test accuracy, and can quantify the proportion of stray light at different distances, and can also characterize the impact of stray light on process graphics.

[0083] The exposure layout of the optional substrate to be photolithography includes a central area and an edge area surrounding the central area, the mask graphic layout corresponding to the central area is a combination of multiple shading patterns arranged in an array, and the mask graphic layout corresponding to the edge area is a combination of multiple shading patterns evenly distributed in a circle; one exposure process includes: exposing the edge area of ​​the substrate to be photolithography through a mask with a set exposure dose, and at the same time, exposing the middle area of ​​the substrate to be photolithography through a mask with the set exposure dose as an intermediate value and a preset dose step rule; wherein the exposure parameters include the exposure size and its corresponding exposure dose.

[0084] refer to Figure 1As shown, the exposure edge area of ​​the optional substrate 200 to be photolithographically exposed has 6 shading pattern combinations 101 evenly corresponding to the edge area marks formed after exposure along the circumference, and the mask pattern layout corresponding to the central area is arranged in an array with 4*2 shading pattern combinations 101. It can be understood that Figure 1 The exposure layout of the substrate to be photolithographic is only an example. In other embodiments, the exposure layout of the substrate can also adopt other arrangements, not limited to Figure 1 shown.

[0085] For the edge area in the exposure layout of the substrate to be photolithographic, the lithography machine uses the set exposure dose to expose it during exposure. After the exposure process is completed, a mark combination corresponding to the shading pattern image and 101 is formed in the edge area of ​​the substrate to be photolithographic, and the mark combination includes a first mark and a second mark. Simultaneously, for the central area in the exposure layout of the substrate to be photolithographic, the lithography machine uses the set exposure dose as the middle value and the exposure step as the rule to expose it during exposure. After the exposure process is completed, a mark combination corresponding to each other is formed in the central area of ​​the substrate to be photolithographic.

[0086] For example, if the exposure dose is set to 50mj, the photolithography machine exposes the edge area of ​​the substrate to be photolithography with 50mj through the shading pattern combination 101 of the mask 110; synchronously, with 50mj as the middle value and 1mj as the dose step, the middle area of ​​the substrate to be photolithography is exposed through the shading pattern combination 101 of the mask 110. The exposure doses of the 4*2 shading pattern combinations 101 that can be selected corresponding to the middle area of ​​the substrate to be photolithography include: the exposure doses of the 4 shading pattern combinations 101 from left to right in the first row are 46, 47, 48, and 49, respectively, and the exposure doses of the 4 shading pattern combinations 101 from left to right in the second row are 50, 51, 52, and 53, respectively. It can be understood that the exposure dose difference between two adjacent shading pattern combinations in the same row is the exposure step, and the exposure dose setting of the middle area is not limited to the above example.

[0087] like Fig. 9 The operation of calculating the exposure size error according to the exposure parameters of each first mark in the optional step S1 includes:

[0088] Step S11, calculating an average exposure size of the first marks in the edge region of the substrate to be photolithographically processed according to the exposure sizes of the first marks in the edge region;

[0089] Step S12: determining the difference between the average exposure size and the exposure size of the first intermediate mark as the exposure size error, wherein the first intermediate mark is located in the middle area of ​​the substrate to be photolithographically processed and the exposure dose corresponding thereto is the set exposure dose.

[0090] In this embodiment, after the exposure process is completed, the measuring device integrated in the lithography machine can measure the exposure parameters of the first mark corresponding to the first pattern in the substrate to be photolithography, and the measuring device can be a measuring instrument that can be used to measure size, etc. The measuring device obtains the exposure size of each first mark located in the edge area of ​​the substrate, and then sums and calculates the average value to obtain the average exposure size of the first mark in the edge area of ​​the substrate to be photolithography.

[0091] The middle area of ​​the substrate to be photolithographically processed has a first middle mark, which is formed by exposure using a set exposure dose. Figure 1 As shown, the exposure doses of the 4*2 shading pattern combinations 101 in the middle area of ​​the optional mask include: the exposure doses of the 4 shading pattern combinations 101 in the first row from left to right are 46, 47, 48, and 49, respectively, and the exposure doses of the 4 shading pattern combinations 101 in the second row from left to right are 50, 51, 52, and 53, respectively; when the exposure dose is set to 50mj, the leftmost shading pattern combination in the second row in the middle area of ​​the mask is exposed with the set exposure dose of 50mj. After exposure, the shading pattern combination forms a mark combination in the middle area of ​​the photolithography substrate, and the first mark in the mark combination corresponding to the first pattern is the first middle mark.

[0092] The measuring device calculates the difference between the average exposure size of the first mark in the edge area of ​​the substrate to be photolithographic and the exposure size of the first intermediate mark, and determines the difference as the exposure size error, which is the process error of the photolithography machine.

[0093] Before the operation of calculating the actual exposure size of the second mark and the actual exposure dose corresponding thereto in the optional step S2, the method further includes:

[0094] According to the exposure size and exposure dose of each first mark in the middle area of ​​the substrate to be photolithographic, the size-dose formula (1) is fitted:

[0095] y=ax+b (1),

[0096] Where x is the exposure dose, y is the exposure size, and a and b are constants.

[0097] In this embodiment, after exposure, the middle area of ​​the substrate to be photolithographic has a plurality of mark combinations corresponding to the shading pattern combinations, each mark combination includes a first mark corresponding to the first pattern and a second mark corresponding to the second pattern. The measuring device measures the exposure size of each first mark in the middle area of ​​the substrate to be photolithographic, and the exposure dose of each shading pattern combination in the middle area by the photolithography machine during the exposure process is predetermined, so the measuring device can obtain the exposure size and exposure dose of each first mark in the middle area of ​​the substrate to be photolithographic. Figure 1As shown, a size-dose curve is drawn according to the exposure sizes and exposure doses of the eight first marks in the middle area, and a and b as well as the size-dose formula (1) are obtained by fitting the curve.

[0098] like Fig.10 The operation of calculating the actual exposure size of the second mark and the actual exposure dose corresponding thereto in the optional step S2 includes:

[0099] Step S21, calculating an average exposure size of the second marks in the edge region of the substrate to be photolithographically processed according to the exposure sizes of the second marks in the edge region;

[0100] Step S22: determine the difference between the exposure size average value and the exposure size error as the actual exposure size of the second mark, and calculate the actual exposure dose corresponding to the actual exposure size of the second mark according to formula (1).

[0101] In this embodiment, after the exposure process is completed, the measuring device integrated in the lithography machine can measure the exposure parameters of the second mark corresponding to the second pattern in the substrate to be photolithographic. The measuring device obtains the exposure size of each second mark in the edge area, and then sums and calculates the average value to obtain the exposure size average value of the second mark in the edge area of ​​the substrate to be photolithographic.

[0102] According to step S1, the exposure size error of the lithography machine is determined, and the measuring device calculates the difference between the average exposure size of the second mark in the edge area of ​​the substrate to be lithography and the exposure size error, and determines the difference as the actual exposure size of the second mark. According to formula (1), the actual exposure dose corresponding to the actual exposure size of the second mark can be calculated.

[0103] The operation of calculating the first stray light proportion Ls in the optional step S3 includes:

[0104] Ls=100%*(Ds-D0) / D0, (2)

[0105] Wherein, Ds is the actual exposure dose, and D0 is the set exposure dose. In this embodiment, the actual exposure dose of the second mark is calculated according to step S2, and the set exposure dose is also predetermined, then the first stray light ratio can be calculated according to formula (2). For example, the outer edge radius value of the second pattern d3 = 2μm, and the corresponding set exposure dose is 50mj, then the calculated first stray light ratio Ls is the ratio of stray light above 2μm in the photolithography process.

[0106] The measurement method provided in the above embodiment measures the exposure parameters of the substrate to be photolithographic after a single exposure process. According to the measurement results, the error of stray light can be decomposed and quantified online, and the distribution of stray light can be quickly quantified to determine whether the stray light exceeds the standard, thereby ensuring the performance of the photolithography machine. The measurement process is simple, the data processing efficiency is fast, and the automatic test of the equipment does not require manual recording, thereby avoiding human errors. It should be noted that the measurement method can save time, reduce the number of exposures, and can be interspersed with exposures during mass production, thereby greatly reducing costs.

[0107] The measurement method provided in the above embodiment is specifically described below using multiple examples.

[0108] Example 1: Testing stray light above a certain distance.

[0109] 1. Adoption Figure 2 The mask shown is used for exposure. The radius d2 of the optional first pattern is 200μm, the radius d3 of the optional second pattern is 2μm, the radius d1 of the light-transmitting area of ​​the optional first pattern and the second pattern is 0.24μm, and the area outside the first pattern and the second pattern is the light-transmitting area. The outer edge spacing d4 between any two adjacent patterns in the mask is more than 200μm. It can be understood that according to different test requirements, the mask has a plurality of shading pattern combinations, wherein the shading area of ​​the pattern can be changed according to the stray light test requirements at different distances, such as a shading area with a radius of 10μm can test the amount of stray light above 5μm.

[0110] 2. Place the prepared mask on the photolithography machine and expose a test silicon wafer. The exposure layout is as follows: Figure 1 As shown, the middle area of ​​the silicon wafer is exposed using an exposure dose step mode. The dose step is set according to the equipment accuracy and graphic requirements. The optional dose step is 1 mj. For example, the exposure doses of the eight shading pattern combinations in the middle area are 46, 47, 48, 49, 50, 51, 52, and 53, respectively. The edge area of ​​the silicon wafer is exposed using a fixed exposure dose mode, and the optional fixed exposure dose is 50 mj.

[0111] 3. After the exposure is completed, the exposure dimensions of the eight first marks in the middle area of ​​the silicon wafer are measured. The exposure parameters of the eight first marks are shown in Table 1. Among them, the size errors of the two first marks obtained after exposure at 46mj and 53mj are too large, so these two first marks are not included in the formula fitting. Fig.11 As shown, a CD-Dose curve is drawn according to the effective data in Table 1, and then a linear function y=ax+b is obtained by least squares fitting, wherein y=5.8486x-170.73 is obtained according to Table 1. Table 1 is as follows:

[0112] Dose 46 47 48 49 50 51 52 53 Size CD 105 109.46 115.43 121.4 127.37 134

[0113] 4. Measure the first mark and the second mark of the edge area of ​​the silicon wafer, remove the points with abnormal graphics and CD, and calculate the average exposure size of the first mark of the edge area and the average exposure size of the second mark of the edge area based on the remaining data. The exposure sizes of the first mark and the second mark of the edge area are shown in Table 2 below. Table 2 is as follows:

[0114]

[0115] 5. The CD average value of the first mark in the edge area is recorded as CD1, and the CD value of the first mark in the middle area at the same dose is recorded as CD0. According to Table 1 and Table 2, CD1 = 121.3, CD0 = 121.4. Subtracting CD0 from CD1 is the exposure process error CDerror caused by the silicon wafer or other factors. The unit of CD is nam, CDerror = CD1-CD0 = 121.3-121.4 = -0.1.

[0116] The average CD value of the second mark in the edge area is recorded as CD2, and the actual CD value CDOK of the second mark after removing other process errors is obtained by subtracting CDerror from CD2.

[0117] CDok=CD2-CDerror=124-(-0.1)=124.1nm.

[0118] Substituting CDok into the fitted linear function y=5.8486x-170.73 in step 3, the actual exposure dose Dok corresponding to CDok can be calculated, CDok=5.8486Dok-170.73, then

[0119] Dok=(CDok+170.73) / 5.8486=(124.1+170.73) / 5.8486=50.41mj.

[0120] The dose difference Dstraylight can be obtained by subtracting the actual exposure dose Dok of the second mark from the set exposure dose 50mj, where Dstraylight=Dok-50mj=0.41mj.

[0121] The dose difference is the amount of stray light above 2 μm caused by 50 mj. Dividing this difference by 50 mj gives the percentage of stray light above 2 μm, Ls = 0.41 / 50 = 0.82%.

[0122] Based on the stray light ratio result, it is possible to evaluate whether the stray light amount of the lithography machine is within the qualified range, determine whether the stray light amount will affect the imaging, and determine the impact of the stray light amount on the imaging of isolated holes through the imaging of the graphics.

[0123] Based on the graphic design rules and exposure process of Example 1, simulation is performed, and d1, d2, and d3 can be selected as 0.25μm, 1μm, and 0.55μm, and the calculation is performed according to the above calculation method. Since other process errors are not considered in the simulation, there is no CDerror, so the slope of CD-Dose is a=15.76, where the exposure dose is 22mj, and the calculation process is as follows:

[0124] (1) CD1 = 518.6 nm;

[0125] (2) CD2 = 539.8 nm;

[0126] (3)Dstraylight=(539.8-518.6) / 15.76=1.35mj;

[0127] (4) Ls = 1.35 / 22*100% = 6%

[0128] (5) According to the above calculation results, within the range of 0.55 μm to 1 μm, the proportion of stray light is 6%.

[0129] Those skilled in the art can understand that, with regard to the entire measurement process described above, relevant practitioners can modify the mask layout according to actual needs, and parameters such as exposure dose can also be adaptively adjusted.

[0130] Example 2: Test stray light above a certain distance and within a certain range.

[0131] 1. Adoption Figure 7 The mask shown is used for exposure. Figure 7 As shown, the first mark and Figure 2 The first mark shown is the same, but the second mark is changed according to the test requirements, and a special pattern is added. The design requirements of the special pattern are: d2>d6>d5>d1, d1=0.24μm, d2=200μm, d5=2μm, d6=5μm, and d4 is greater than or equal to 200μm.

[0132] 2. Place the prepared mask on the photolithography machine and expose a test silicon wafer. The exposure layout is as follows: Figure 1As shown, the middle area of ​​the silicon wafer is exposed using an exposure dose step mode. The dose step is set according to the equipment accuracy and graphic requirements. The optional dose step is 1 mj. For example, the exposure doses of the eight shading pattern combinations in the middle area are 46, 47, 48, 49, 50, 51, 52, and 53, respectively. The edge area of ​​the silicon wafer is exposed using a fixed exposure dose mode, and the optional fixed exposure dose is 50 mj.

[0133] 3. After the exposure is completed, the exposure size CD of the 8 first marks in the middle area of ​​the silicon wafer is measured, and the CD-Dose curve is drawn, and the least squares method is used to fit a linear function, such as y=ax+b.

[0134] 4. Measure the first mark and the second mark in the edge area of ​​the silicon wafer, remove the points with abnormal graphics and CD, and calculate the average exposure size CD1 of the first mark and the average exposure size CD2 of the second mark in the edge area based on the remaining data.

[0135] 5. The CD of the first mark at the set exposure dose of 50mj in the middle area of ​​the silicon wafer is CD0. Subtracting CD0 from CD1 is the process error caused by the silicon wafer or other factors, which is recorded as CDerror. Subtracting CDerror from CD2 of the second mark in the edge area is the actual CD value CDOK of the second mark after removing other process errors. Substituting CDOK into the linear function y=ax+b fitted in step 3, the actual exposure dose DOK corresponding to CDOK can be calculated. Subtracting the actual exposure dose Dok of the second mark from the dose 50mj corresponding to CD0 can obtain the dose difference Dstraylight. This dose difference is the amount of stray light of 2μm to 5μm caused by 50mj. Dividing this dose difference by 50mj can obtain the proportion of stray light Ls at this distance of 2μm to 5μm. 2～5 The calculation formula is as follows:

[0136] (1) CDerror = CD1 - CD0;

[0137] (2) CDOK = CD2 - CDerror;

[0138] (3) DOK = (CDOK-b) / a;

[0139] (4) Dstraylight = DOK-50;

[0140] (5)Ls 2～5 =Dstraylight / 50*100%;

[0141] Those skilled in the art can understand that, with regard to the entire measurement process described above, relevant practitioners can modify the mask layout according to actual needs, and parameters such as exposure dose can also be adaptively adjusted.

[0142] Example 3: You can test the proportion of stray light at different distances, and the test results can also reflect the impact of stray light at different distances on certain main graphics.

[0143] 1. Adoption Figure 6 The mask shown is used for exposure. Figure 6 As shown, the central area of ​​the first mark is a light-transmitting area, and a shading strip is arranged in the light-transmitting area. The shading structure formed by the shading strip is the target pattern. The area outside the central area of ​​the first mark, that is, the annular structure with a diameter of d2, is a light-opaque area. The optional central area is a square with a side length of 90nmDL, that is, d1=45nmDL, d2=200μm; the central light-transmitting area of ​​the second mark is exactly the same as the central light-transmitting area of ​​the first mark, d3=2μm.

[0144] 2. Place the prepared mask plate on the photolithography machine and expose a test silicon wafer. The exposure layout can be set according to the needs. The exposure mode can select the exposure dose step mode or the fixed exposure dose mode. The optimal exposure dose of the center area pattern can be selected as 30mj.

[0145] 3. After the exposure is completed, observe and measure under the measuring device, and compare the graphic differences between the light-transmitting areas of the first mark and the second mark. This difference is the imaging problem caused by stray light above 2μm.

[0146] 4. Similarly, according to different test requirements, by changing the target pattern and the opaque area of ​​the second mark, the imaging effect of stray light at different distances on various patterns can be checked.

[0147] Based on the same inventive concept, an embodiment of the present invention further provides a measuring device of the stray light measurement system as described above, the measuring device is used to perform the measuring method described in any of the above embodiments, and the measuring device includes:

[0148] an exposure module, configured to perform an exposure once using a set exposure dose corresponding to the outer edge radius value of the second pattern, and after the exposure is completed, measure exposure parameters of first marks in the substrate to be photolithographically processed corresponding to the first pattern, and calculate exposure size errors according to the exposure parameters of each of the first marks;

[0149] a measuring module, configured to measure an exposure parameter of a second mark corresponding to the second pattern in the substrate to be photolithographically processed, and calculate an actual exposure size of the second mark and an actual exposure dose corresponding thereto according to the exposure size error and the exposure parameter of the second mark;

[0150] A calculation module is used to calculate the first stray light ratio according to the actual exposure dose and the set exposure dose.

[0151] In the embodiment of the present invention, the exposure error can be decomposed by only one exposure and measurement, and the stray light at different distances can be monitored. The entire measurement process is simple and fast. The measuring device automatically performs the test, avoids the error caused by manual testing, reduces the accumulation of machine errors caused by multiple exposures, improves the test accuracy, and can quantify the proportion of stray light at different distances and characterize the impact of stray light on process graphics.

[0152] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A stray light measurement system, characterized in that: include: A mask having a light-shielding pattern combination, wherein the light-shielding pattern combination includes a first pattern and a second pattern of the same shape, wherein the outer edge radius of the first pattern is greater than the outer edge radius of the second pattern, and the centers of the first pattern and the second pattern have light-transmitting areas of the same shape and size; A photolithography machine, wherein a substrate to be photolithography is arranged therein, and the photolithography machine is used to expose the substrate to be photolithography once through the mask plate, and measure the exposure parameters of the substrate to be photolithography after the exposure is completed, and obtain a first stray light ratio according to the exposure parameters, and the influence distance of the first stray light is greater than or equal to the outer edge radius value of the second pattern.

2. The stray light measurement system according to claim 1, characterized in that: The shapes surrounded by the outer edges of the first pattern and the second pattern are both square or circular, and the shape of the light-transmitting area is square or circular; The radius of the outer edge of the square is half of the side length of the square.

3. The stray light measurement system according to claim 1, characterized in that: The outer edge radius of the second pattern is greater than or equal to 1 μm; and / or, The light-transmitting spacing between the first pattern and the second pattern in the light-shielding pattern combination is greater than or equal to 200 μm.

4. The stray light measurement system according to claim 1, characterized in that: The exposure layout of the substrate to be photolithographic includes a central area and an edge area surrounding the central area. The mask graphic layout corresponding to the central area is a combination of multiple shading patterns arranged in an array, and the mask graphic layout corresponding to the edge area is a combination of multiple shading patterns evenly distributed in a circle.

5. The stray light measurement system according to claim 1, characterized in that: The light-transmitting area includes a shading structure, which is composed of M shading strips arranged in parallel, and the extending length of the shading strips is smaller than the minimum size of the light-transmitting area in the extending direction thereof.

6. The stray light measurement system according to claim 1, characterized in that: The second pattern is composed of N light-shielding rings surrounding the light-transmitting area, and the center points of the N light-shielding rings overlap with the center point of the light-transmitting area.

7. A method for measuring stray light according to any one of claims 1 to 6, characterized in that: include: Performing an exposure once using a set exposure dose corresponding to the outer edge radius value of the second pattern, and measuring exposure parameters of first marks corresponding to the first pattern in the substrate to be photolithographic after the exposure is completed, and calculating exposure size errors according to the exposure parameters of each first mark; Measuring exposure parameters of a second mark corresponding to the second pattern in the substrate to be photolithographically processed, and calculating an actual exposure size of the second mark and an actual exposure dose corresponding thereto according to the exposure size error and the exposure parameters of the second mark; The first stray light ratio is calculated according to the actual exposure dose and the set exposure dose.

8. The measuring method according to claim 7, characterized in that: The exposure layout of the substrate to be photolithographic includes a central area and an edge area surrounding the central area, the mask pattern layout corresponding to the central area is a combination of multiple shading patterns arranged in an array, and the mask pattern layout corresponding to the edge area is a combination of multiple shading patterns evenly distributed in a circumference; An exposure process includes: Exposing the edge area of ​​the substrate to be photolithographic through the mask with the set exposure dose, and at the same time, exposing the middle area of ​​the substrate to be photolithographic through the mask with the set exposure dose as the middle value and using a preset dose step rule; The exposure parameters include exposure size and its corresponding exposure dose.

9. The measuring method according to claim 8, characterized in that: Calculating the exposure size error according to the exposure parameters of each of the first marks includes: Calculating an average exposure size of the first marks in the edge region of the substrate to be photolithographically processed according to the exposure sizes of the first marks in the edge region; The difference between the exposure size average value and the exposure size of a first intermediate mark is determined as the exposure size error, the first intermediate mark is located in the middle area of ​​the substrate to be photolithographically processed and the exposure dose corresponding to the first intermediate mark is the set exposure dose.

10. The measuring method according to claim 8, characterized in that: Before calculating the actual exposure size of the second mark and the actual exposure dose corresponding thereto, the method further includes: According to the exposure size and exposure dose of each first mark in the middle area of ​​the substrate to be photolithographically processed, the size-dose formula (1) is obtained by fitting: y=ax+b (1), Where x is the exposure dose, y is the exposure size, and a and b are constants.

11. The measuring method according to claim 10, characterized in that: Calculating the actual exposure size of the second mark and the actual exposure dose corresponding thereto includes: Calculating an average exposure size of the second marks in the edge region of the substrate to be photolithographically processed according to the exposure sizes of the second marks in the edge region; The difference between the exposure size average value and the exposure size error is determined as the actual exposure size of the second mark, and the actual exposure dose corresponding to the actual exposure size of the second mark is calculated according to formula (1).

12. The measuring method according to claim 7, characterized in that: Calculating the first stray light proportion Ls includes: Ls=100%*(Ds-D0) / D0, (2) Wherein, Ds is the actual exposure dose, and D0 is the set exposure dose.

13. A measuring device of a stray light measuring system according to any one of claims 1 to 6, characterized in that: include: an exposure module, configured to perform an exposure once using a set exposure dose corresponding to the outer edge radius value of the second pattern, and after the exposure is completed, measure exposure parameters of first marks in the substrate to be photolithographically processed corresponding to the first pattern, and calculate exposure size errors according to the exposure parameters of each of the first marks; a measuring module, configured to measure an exposure parameter of a second mark corresponding to the second pattern in the substrate to be photolithographically processed, and calculate an actual exposure size of the second mark and an actual exposure dose corresponding thereto according to the exposure size error and the exposure parameter of the second mark; A calculation module is used to calculate the first stray light ratio according to the actual exposure dose and the set exposure dose.

Images