Photoetching machine compensation method based on photomask overlay error

Abstract

The invention provides a photomask overlay error-based photoetching machine compensation method, which comprises the following steps of: manufacturing a photomask, and arranging a plurality of photomask alignment marks on the photomask; the photomask alignment mark is measured; establishing a measurement data model by adopting a feed-forward system and calculating a compensation value of each parameter of a photomask overlay error; and the photoetching machine carries out compensation during actual exposure according to the compensation value. According to the invention, the photomask overlay error is compensated to the photoetching machine through the feed-forward system, so that the overlay error in a final product exposure area caused by a photomask manufacturing process is eliminated in advance, and the pilot run time and cost are saved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor integrated circuits, and in particular to a photolithography machine compensation method based on mask overlay error. Background Art

[0002] The mask overlay error refers to the overlay accuracy of each mask relative to a certain reference mask or a reference data in the database when different masks are produced in the mask factory. It describes the impact of the manufacturing process on the quality of each mask. The mask overlay error is measured by placing mask alignment marks on each mask layout, sampling and measuring all the mask alignment marks placed on the entire mask after the mask production process, modeling the actual mask network, and comparing it with a reference mask or a reference network in the database to obtain the overlay error of the current mask.

[0003] The mask overlay error reflects the overlay error in the exposure area caused by the mask during the final exposure on the wafer. This error will be directly transmitted to the overlay error in each exposure area when the product is exposed. As the critical dimensions of the semiconductor process shrink, the tolerance for the above-mentioned mask overlay error also decreases. However, when receiving the mask, the wafer fab can only obtain the approximate overlay error level of the entire mask through the mask quality inspection report. It is impossible to know the overlay error in each exposure area in advance and effectively correct the overlay error in each exposure area. In the prior art, it is necessary to measure the overlay error (Over lay, the position difference between the alignment marks of the previous layer and the current layer) after the exposure is completed on the wafer before it can be used and the compensation value for post-feedback is generated. This correction method will introduce trial run (pi-run, or trial run) time, resulting in reduced production efficiency and increased costs. Summary of the invention

[0004] The purpose of the present invention is to provide a lithography machine compensation method based on mask overlay error, which compensates the mask overlay error to the lithography machine through a feedforward system to eliminate the overlay error in the exposure area of ​​the final product introduced by the mask manufacturing process in advance, saving trial operation time and cost.

[0005] In order to solve the above technical problems, the present invention provides a lithography machine compensation method based on mask overlay error, comprising the following steps:

[0006] Making a photomask, wherein the photomask is provided with a plurality of photomask alignment marks;

[0007] Measuring the mask alignment mark;

[0008] Using a feedforward system to establish a measurement data model and calculate compensation values ​​for various parameters of mask overlay error; and

[0009] The photolithography machine performs compensation during actual exposure according to the compensation value.

[0010] Optionally, the number of the mask alignment marks provided on the mask is greater than or equal to the number of the mask alignment marks required for compensation by the lithography machine.

[0011] Optionally, the measured number of the mask alignment marks is consistent with the compensation capability of the lithography machine.

[0012] Optionally, the method for calculating compensation values ​​of various parameters of mask overlay error includes: comparing measurement data of the mask alignment mark with standard data to obtain a difference, and determining various compensation parameters of the mask overlay error and compensation values ​​corresponding to the compensation parameters through the difference.

[0013] Optionally, the mask overlay error parameter includes a translation parameter and a rotation parameter, and the method for obtaining the compensation value of the translation parameter and the rotation parameter includes:

[0014] Obtaining a difference value according to the measurement data of the two mask alignment marks and the standard data, wherein the difference value is a vector;

[0015] Obtaining the components of the difference in the X direction and the Y direction respectively;

[0016] Obtaining translation compensation values ​​in the X direction and the Y direction according to the components of the two mask alignment marks in the X direction and the Y direction;

[0017] Obtaining a remaining component of the mask alignment mark after removing the translation compensation values ​​in the X direction and the Y direction, and obtaining a remaining difference value according to the remaining component; and

[0018] A rotation compensation value is obtained according to the remaining difference and the distance between the two mask alignment marks.

[0019] Optionally, the standard data is the designed placement position of the mask alignment mark in the layout database.

[0020] Optionally, the mask alignment mark is formed into a block by four sub-marks, each sub-mark includes a plurality of parallel and spaced bar patterns, and the extension directions of the bar patterns in two adjacent sub-marks are perpendicular, and the extension directions of the bar patterns in two opposite sub-marks are the same.

[0021] Optionally, the width of the sub-logo in the arrangement direction of the bar pattern is greater than the width in the extension direction of the bar pattern.

[0022] Optionally, of two adjacent sub-identifiers, one of the sub-identifiers is identical to the other sub-identifier after being rotated by 90°.

[0023] Optionally, the method for measuring the mask alignment mark includes: measuring each bar pattern in the sub-mark to obtain a center value of the sub-mark; and obtaining a center value of the mask alignment mark according to the center values ​​of four sub-marks.

[0024] Optionally, the method for the photolithography machine to perform compensation during actual exposure according to the compensation value includes:

[0025] The feedforward system transmits the compensation value to the advanced process control system;

[0026] The advanced process control system controls the photolithography machine to perform compensation.

[0027] In summary, in the photolithography machine compensation method based on the mask overlay error provided by the present invention, a mask is first made, and a plurality of mask alignment marks are set on the mask, and then the mask alignment marks are measured, and then a feedforward system is used to establish a measurement data model and calculate the compensation values ​​of various parameters of the mask overlay error, and then the photolithography machine performs compensation during actual exposure according to the compensation values. The present invention compensates the mask overlay error to the photolithography machine through the feedforward system, so as to eliminate the overlay error in the exposure area of ​​the final product introduced by the mask manufacturing process in advance, saving trial operation time and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0029] Figure 1 It is a flow chart of a lithography machine compensation method based on mask overlay error provided by one embodiment of the present invention.

[0030] Figure 2 It is a structural schematic diagram of a mask alignment mark provided by an embodiment of the present invention.

[0031] Description of reference numerals:

[0032] 10 - mask alignment mark; 11 - first sub-marker; 12 - second sub-marker; 13 - third sub-marker; 14 - fourth sub-marker. DETAILED DESCRIPTION

[0033] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0034] As used in the present invention, the singular forms "one", "an", and "the" include plural objects, unless the content clearly indicates otherwise. As used in the present invention, the term "or" is generally used in a sense that includes "and / or", unless the content clearly indicates otherwise. As used in the present invention, the term "several" is generally used in a sense that includes "at least one", unless the content clearly indicates otherwise. As used in the present invention, the term "at least two" is generally used in a sense that includes "two or more", unless the content clearly indicates otherwise. In addition, the terms "first", "second", and "third" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features.

[0035] Figure 1 This is a flow chart of a lithography machine compensation method based on mask overlay error provided by an embodiment of the present invention. Figure 1 As shown, the lithography machine compensation method based on mask overlay error provided in this embodiment includes the following steps:

[0036] S1: manufacturing a photomask, wherein a plurality of photomask alignment marks are provided on the photomask;

[0037] S2: measuring the alignment mark of the photomask;

[0038] S3: Using a feedforward system to establish a measurement data model and calculate compensation values ​​of various parameters of the mask overlay error;

[0039] S4: The photolithography machine performs compensation during actual exposure according to the compensation value.

[0040] The present invention compensates the overlay error of the photomask to the photolithography machine through a feedforward system, so as to eliminate the overlay error in the exposure area of ​​the final product introduced by the photomask manufacturing process in advance, thereby saving trial operation time and cost.

[0041] In step S1, a photomask is produced, and a plurality of photomask alignment marks are arranged on the photomask. The number of the photomask alignment marks arranged on the photomask is greater than or equal to the number of photomask alignment marks required for compensation by the lithography machine.

[0042] In one embodiment of the present invention, a sufficient number of mask alignment marks are placed on each mask layout, and then the mask is produced using the mask layout. A sufficient number of mask alignment marks are set on the produced mask so that the mask overlay error can be fully compensated by the subsequent photolithography machine. In one embodiment of the present invention, the mask alignment marks are placed at set positions, and in one embodiment, they are placed at set positions in a uniformly distributed manner.

[0043] In one embodiment of the present invention, the mask alignment mark is placed in a non-device area of ​​the mask to avoid affecting the preparation of the device and to avoid occupying the wafer space when the mask alignment mark is replicated on the wafer, thereby ensuring the utilization rate of the wafer and maximizing the utilization of the wafer. Preferably, the mask alignment mark is placed in a test area or a dicing area on the mask, and the test area includes a PCM area (including important parameter test areas such as square block resistance, capacitance, hole contact resistance, wire resistance, and transistor turn-on voltage), etc.

[0044] In one embodiment of the present invention, a certain distance is required between the mask alignment marks to effectively avoid the mask alignment marks from overlapping each other and to prevent the mask alignment marks from interfering with each other. Exemplarily, the distance between the mask alignment marks is greater than 50 μm.

[0045] A sufficient number of the mask alignment marks can be placed on the mask without affecting the utilization rate of the wafer and without mutual interference between the mask alignment marks. The number of mask alignment marks placed is linked to the compensation capability of the lithography machine. The more mask alignment marks are placed, the higher the Intra OVL (different small areas within each exposure area) that can be compensated, and the more accurate and effective the compensation value.

[0046] In step S2, the mask alignment mark is measured.

[0047] In one embodiment of the present invention, the mask alignment mark is formed into a block by four sub-marks, that is, the four sub-marks are surrounded by the center of the mask alignment mark to form a block, each sub-marker includes a plurality of parallel and spaced-apart bar patterns, and the extension directions of the bar patterns in two adjacent sub-markers are perpendicular to each other, and the extension directions of the bar patterns in two relative sub-markers are the same.

[0048] Figure 2 This is a schematic diagram of the structure of a mask alignment mark provided in the first embodiment of the present invention. Figure 2As shown, the mask alignment mark 10 is composed of four sub-marks, the first sub-mark 11 includes 4 bar patterns (for example, a rectangular pattern) arranged in parallel and at intervals along the second direction Y, and the bar pattern extends along the first direction X, the second sub-mark 12 includes 4 bar patterns arranged in parallel and at intervals along the first direction X, and the bar pattern extends along the second direction Y, the third sub-mark 13 has the same structure as the first sub-mark 11, and the fourth sub-mark 14 has the same structure as the second sub-mark 12.

[0049] The first sub-identifier 11, the second sub-identifier 12, the third sub-identifier 13 and the fourth sub-identifier 14 are arranged in a block shape around the center of the mask alignment identifier 10, that is, the first sub-identifier 11 is arranged adjacent to the second sub-identifier 12 and the fourth sub-identifier 14, and is arranged opposite to the third sub-identifier 13.

[0050] In this embodiment, the width of the sub-logo in the arrangement direction of the stripe pattern is greater than the width in the extension direction of the stripe pattern. For example, the width of the first sub-logo 11 in the second direction Y is greater than the width in the first direction X, that is, the first sub-logo 11 is a rectangle, but not limited thereto.

[0051] In this embodiment, one of the two adjacent sub-identifiers is identical to the other sub-identifier after being rotated by 90°. For example, the first sub-identifier 11 is identical to the second sub-identifier 12 or the fourth sub-identifier 14 after being rotated by 90°.

[0052] It is understandable that the number of bar patterns in each sub-mark is not limited to 4. The more bar patterns there are, the more accurate the measurement result will be. The structure of the mask alignment mark 10 is not limited to Figure 2 The structure shown may also be other structures known to those skilled in the art.

[0053] In this step, the method for measuring the mask alignment mark includes: measuring the position of each bar pattern in the sub-mark to obtain the center value of the sub-mark, and then obtaining the center value of the mask alignment mark according to the center values ​​of the four sub-marks. For example: measuring the position of each bar pattern in the first sub-mark 11, calculating the center value of the first sub-mark 11 according to the measured value of each bar pattern, sampling the same method to obtain the center values ​​of the second sub-mark 12, the third sub-mark 13 and the fourth sub-mark 14, and then calculating the center value of the mask alignment mark 10 according to the center values ​​of the four sub-marks. The more bar patterns measured in the same direction (the more samples), the more accurate the measurement result.

[0054] In this step, the mask alignment marks are measured, and a sampling measurement or a full measurement can be performed. The number of the mask alignment marks measured is consistent with the compensation capability of the lithography machine. Table 1 is an overlay error parameter in an exposure area that can be compensated by a lithography machine and the corresponding number of mask alignment mark measurements required.

[0055] Table 1

[0056]

[0057]

[0058] X and Y in Table 1 are two perpendicular directions. Figure 2 In Table 1, for example, if the translation in the X direction needs to be compensated, at least one mask alignment mark is required. In this embodiment, the number of mask alignment marks required for compensating the overlay error parameters in Table 1 is measured to compensate for the mask overlay error in subsequent steps.

[0059] In step S3, a feedforward system is used to establish a measurement data model and calculate compensation values ​​of various parameters of the mask overlay error.

[0060] The parameters of the mask overlay error may be the parameters in the above Table 1. A measurement data model is established based on the data measured in step S2 to obtain the relationship between the measurement data and the compensation values ​​of the parameters of the mask overlay error, and to obtain the compensation values ​​of the parameters of the mask overlay error.

[0061] In one embodiment of the present invention, a method for calculating compensation values ​​of various parameters of mask overlay error includes: comparing the measurement data of the mask alignment mark with the standard data to obtain a difference, and determining various compensation parameters of the mask overlay error (see Table 1) and the compensation values ​​corresponding to each compensation parameter through the difference.

[0062] Exemplarily, two mask alignment marks and obtaining the compensation values ​​of the translation parameters and rotation parameters of the mask alignment marks are used as an example for explanation. The method for obtaining the compensation values ​​of the translation parameters and the rotation parameters includes: obtaining a difference according to the measurement data and standard data of the two mask alignment marks, wherein the difference is a vector; obtaining the components of the difference in the X direction and the Y direction respectively; obtaining the translation compensation values ​​in the X direction and the Y direction according to the components of the two mask alignment marks in the X direction and the Y direction; obtaining the remaining components of the mask alignment mark after removing the translation compensation values ​​in the X direction and the Y direction, and obtaining the remaining difference according to the remaining components; and obtaining the rotation compensation value according to the remaining difference and the distance between the two mask alignment marks.

[0063] Specifically, the two mask alignment marks are the first mask alignment mark Mark1 and the second mask alignment mark Mark2. The difference of each Mark, i.e., the mask overlay error, is obtained by measuring the data and the standard data, wherein the difference of Mark1 is OVL1, and the difference of Mark2 is OVL2, and the difference is a vector. Then, the components of OVL1 and OVL2 in the X direction and Y direction are obtained respectively. The components of OVL1 in the X direction and Y direction are X1 and Y1 respectively, and the components of OVL2 in the X direction and Y direction are X2 and Y2 respectively, thereby obtaining the translation Tx in the X direction and the translation Ty in the Y direction. For example: the component X1 of OVL1 in the X direction is 1.5nm, and the component Y1 in the Y direction is 0.5nm, the component X2 of OVL2 in the X direction is 2nm, and the component Y2 in the Y direction is 1nm, so the translation Tx in the X direction is X1=1.5nm, and the translation Ty in the Y direction is Y1=0.5nm.

[0064] Then, after removing the translation Tx in the X direction and the translation Ty in the Y direction, the remaining components of the mask alignment mark in the X direction and the Y direction are obtained, and the remaining difference OVL′ is obtained based on the components, and then the rotation value is obtained based on the difference OVL′ and the distance between the two mask alignment marks. For example: after performing the translation Tx=0.5nm in the X direction and the translation Ty=0.5nm in the Y direction, the overlay error of Mark1 has been compensated, and Mark2 still has a remaining component X2′=2nm-1.5nm=0.5nm in the X direction, and Mark2 still has a remaining component Y2′=1-0.5nm=0.5nm in the Y direction. Then, based on the remaining component of Mark2 in the X direction and the remaining component in the Y direction, the remaining difference of Mark2, that is, the overlay error OVL2′=0.707nm, is obtained, and based on the distance r=15mm between Mark2 and Mark1, the rotation value R=OVL2′ / r of Mark2 centered on Mark1 is obtained. That is, with Mark1 as the center, Mark2 is rotated by R so that the remaining overlay error of Mark2 can be compensated, thereby obtaining the compensation values ​​of the translation parameters and rotation parameters of the two mask alignment marks.

[0065] In this embodiment, the difference between the measured data and the standard data of the mask alignment mark is a vector, which refers to the vector pointing from the actual position of the mask alignment mark to the designed placement position, that is, the mask alignment mark can be moved from the actual position according to the vector to reach the designed placement position of the mask alignment mark.

[0066] The above is the process of establishing a measurement data model and calculating the compensation values ​​of the translation parameters and rotation parameters of the mask overlay error. The remaining parameters of the mask overlay error can also be obtained by a similar method. Of course, the number of mask alignment marks required is also different. Please refer to Table 1.

[0067] In the above embodiment, the extension direction of the sub-marks in the first mask alignment mark Mark1 and the second mask alignment mark Mark2 is the same, that is, the second mask alignment mark Mark2 can be obtained by translating the first mask alignment mark Mark1. When calculating the remaining parameters of the mask overlay error, the required placement positions of the mask alignment marks can be determined according to actual needs, for example, the two mask alignment marks can be obtained by rotating and translating relative to each other.

[0068] In one embodiment of the present invention, the standard data is the designed placement position of the mask alignment mark in the layout database.

[0069] In step S4, the photolithography machine performs compensation during actual exposure according to the compensation value.

[0070] Specifically, the feedforward system transmits the compensation value to an advanced process control system (APC), and the advanced process control system controls the photolithography machine to perform compensation during actual exposure according to the compensation value. That is, the advanced process control system compensates the exposure parameters of the photolithography machine according to the compensation value, and the exposure machine uses the compensated exposure parameters to expose the wafer.

[0071] When the wafer is lithographed using a lithography machine, the mask overlay error has been compensated, thereby eliminating the overlay error in the exposure area of ​​the final product introduced by the mask manufacturing process in advance, saving trial operation time and cost.

[0072] In summary, in the photolithography machine compensation method based on the mask overlay error provided by the present invention, a mask is first made, and a plurality of mask alignment marks are set on the mask, and then the mask alignment marks are measured, and then a feedforward system is used to establish a measurement data model and calculate the compensation values ​​of various parameters of the mask overlay error, and then the photolithography machine performs compensation during actual exposure according to the compensation values. The present invention compensates the mask overlay error to the photolithography machine through the feedforward system, so as to eliminate the overlay error in the exposure area of ​​the final product introduced by the mask manufacturing process in advance, saving trial operation time and cost.

[0073] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A lithography machine compensation method based on mask overlay error, characterized in that: The following steps are involved: Making a photomask, wherein the photomask is provided with a plurality of photomask alignment marks; Measuring the mask alignment mark; Using a feedforward system to establish a measurement data model and calculate compensation values ​​for various parameters of mask overlay error; and The photolithography machine performs compensation during actual exposure according to the compensation value.

2. The lithography machine compensation method based on mask overlay error according to claim 1, characterized in that: The number of the mask alignment marks arranged on the mask is greater than or equal to the number of the mask alignment marks required for the photolithography machine to perform compensation.

3. The lithography machine compensation method based on mask overlay error according to claim 1, characterized in that: The measured number of the mask alignment marks is consistent with the compensation capability of the lithography machine.

4. The lithography machine compensation method based on mask overlay error according to claim 1, characterized in that: The method for calculating compensation values ​​of various parameters of mask overlay error includes: comparing the measurement data of the mask alignment mark with standard data to obtain a difference, and determining various compensation parameters of the mask overlay error and compensation values ​​corresponding to the compensation parameters through the difference.

5. The lithography machine compensation method based on mask overlay error according to claim 4, characterized in that: The mask overlay error parameters include translation parameters and rotation parameters, and the method for obtaining compensation values ​​of the translation parameters and the rotation parameters includes: Obtaining a difference value according to the measurement data of the two mask alignment marks and the standard data, wherein the difference value is a vector; Obtaining the components of the difference in the X direction and the Y direction respectively; Obtaining translation compensation values ​​in the X direction and the Y direction according to the components of the two mask alignment marks in the X direction and the Y direction; Obtaining a remaining component of the mask alignment mark after removing the translation compensation values ​​in the X direction and the Y direction, and obtaining a remaining difference value according to the remaining component; and A rotation compensation value is obtained according to the remaining difference and the distance between the two mask alignment marks.

6. The lithography machine compensation method based on mask overlay error according to claim 4, characterized in that: The standard data is the designed placement position of the mask alignment mark in the layout database.

7. The lithography machine compensation method based on mask overlay error according to any one of claims 1 to 6, characterized in that: The mask alignment mark is formed into a block by four sub-marks, each sub-mark includes a plurality of parallel and spaced bar patterns, and the extending directions of the bar patterns in two adjacent sub-marks are perpendicular to each other, and the extending directions of the bar patterns in two opposite sub-marks are the same.

8. The lithography machine compensation method based on mask overlay error according to claim 7, characterized in that: Of two adjacent sub-identities, one of the sub-identities is identical to the other sub-identity after being rotated by 90°.

9. The lithography machine compensation method based on mask overlay error according to claim 7, characterized in that: The method for measuring the mask alignment mark includes: measuring the position of each bar pattern in the sub-mark to obtain the center value of the sub-mark; and obtaining the center value of the mask alignment mark according to the center values ​​of four sub-marks.

10. The lithography machine compensation method based on mask overlay error according to any one of claims 1 to 6, characterized in that: The method for the photolithography machine to perform compensation during actual exposure according to the compensation value comprises: The feedforward system transmits the compensation value to the advanced process control system; The advanced process control system controls the photolithography machine to perform compensation.

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