Method for monitoring mask plate deformation of photoetching machine caused by fine particles

Abstract

The invention provides a method for monitoring deformation of a mask plate of a photoetching machine caused by fine particles. The method comprises the following steps: step 1, setting six pairs of horizontal alignment marks on two sides of the mask plate from top to bottom; 2, linear deformation of the alignment marks in the X direction and the Y direction is calculated, and four sets of linear deformation data are correspondingly obtained by each pair of alignment marks; 3, calculating the asymmetric variation of the linear deformation of the alignment marks on the two sides of the mask by using the data obtained by implementing the step 2; and 4, judging whether the mask generates nonlinear horizontal deformation caused by fine particles or not according to whether the linear deformation of the alignment mark has jump of asymmetric variation or not. According to the method and the device, the mask deformation of the photoetching machine caused by the fine particles can be effectively found, and the product yield is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and particularly to a method for monitoring the deformation of a lithography mask caused by fine particulate matter. Background Art

[0002] The lithography machine projects the preset pattern on the mask onto the surface of the silicon wafer through a projection lens after reducing it by a certain ratio. In this process, accurately controlling the position of the mask is very important for the quality of the finally generated actual pattern.

[0003] Before starting the exposure, the lithography machine reads the preset alignment marks on the mask to obtain the horizontal position difference between the mask and the silicon wafer and compensates during the exposure, so that the deformation of the actual pattern finally generated on the silicon wafer can be controlled within an acceptable specification.

[0004] As Figure 1A shown, the mask is fixed on the carrier stage by the vacuum generated by the lithography machine. The contact area between the mask and the carrier stage is called the adsorption area (RS Platen). If there are foreign objects in the adsorption area, the mask cannot be fixed well, and the lithography machine will issue an alarm by sensing the vacuum value during adsorption. However, in some cases, the size of the foreign objects in the adsorption area is very small, resulting in no change in the vacuum value, but the mask cannot be fixed flat on the carrier stage. This situation will cause the mask to generate fine deformation, which will include both horizontal and vertical directions. This deformation will be transmitted to the silicon wafer through the projection lens, resulting in horizontal displacement deformation (Overlap) and vertical displacement deformation (Defocus) of the mask pattern formed on the final silicon wafer as Figure 1B shown.

[0005] Most of the currently used lithography machine models cannot detect the deformation of the mask caused by such small foreign objects due to the lack of consideration of this situation in the hardware design, resulting in Overlay and Defocus situations on the products and causing scrapping. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of this application is to provide a method for monitoring the deformation of a lithography mask caused by fine particulate matter, which is used to solve the problem that the prior art cannot detect the deformation of the mask caused by small foreign objects.

[0007] To achieve the above-mentioned purpose and other related purposes, this application provides a method for monitoring the deformation of a lithography mask caused by fine particulate matter, including:

[0008] Step 1, set six pairs of horizontal alignment marks from top to bottom on both sides of the mask;

[0009] Step 2: Calculate the linear deformations of the alignment marks in the X and Y directions. Four sets of linear deformation data are obtained for each pair of alignment marks.

[0010] Step 3: Calculate the asymmetric change amount of the linear deformations of the alignment marks on both sides of the mask using the data obtained in Step 2.

[0011] Step 4: Determine whether the mask has a non-linear horizontal deformation caused by fine particles based on whether there is a jump in the asymmetric change amount of the linear deformations of the alignment marks.

[0012] Preferably, each pair of alignment marks are two alignment marks that are symmetrically distributed about the central axis of the mask and are located on both sides of the mask.

[0013] Preferably, the alignment marks include alignment marks that characterize the displacement, rotation, magnification, and orthogonal difference of the mask pattern relative to the silicon wafer.

[0014] Preferably, the data obtained in Step 2 is recorded in a log file automatically generated when the mask pattern is projected onto the silicon wafer by the lithography machine.

[0015] Preferably, in Step 3, the asymmetric change amount of the linear deformation in the X direction of the alignment marks on both sides of the mask is the difference between the difference in the linear deformation values in the X direction of the two alignment marks at the uppermost and lowermost positions on the right side of the mask and the difference in the linear deformation values in the X direction of the two alignment marks at the uppermost and lowermost positions on the left side of the mask. The asymmetric change amount of the linear deformation in the Y direction of the alignment marks on both sides of the mask is the difference between the difference in the linear deformation values in the Y direction of the two alignment marks at the uppermost and lowermost positions on the right side of the mask and the difference in the linear deformation values in the Y direction of the two alignment marks at the uppermost and lowermost positions on the left side of the mask.

[0016] Preferably, in Step 4, when there is a jump in the asymmetric change amount of the linear deformation in the X direction of the alignment marks on both sides of the mask and the asymmetric change amount of the linear deformation in the Y direction of the alignment marks on both sides of the mask, it is necessary to check for fine particles on the mask.

[0017] As described above, the method for monitoring the deformation of the lithography mask caused by fine particles provided by the present application has the following beneficial effects: It can effectively detect the deformation of the lithography mask caused by fine particles and improve the product yield. Description of the Drawings

[0018] To more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1A Schematic diagram showing the slight deformation of the reticle pattern caused by fine particles;

[0020] Figure 1B Schematic diagram showing the horizontal and vertical displacement deformations in the reticle pattern on the silicon wafer;

[0021] Figure 2 Flowchart showing the method for monitoring the deformation of the lithography reticle caused by fine particles provided by the embodiment of the present application;

[0022] Figure 3 Schematic diagram showing six pairs of horizontal alignment marks arranged from top to bottom on both sides of the reticle;

[0023] Figure 4 Schematic diagram showing the jump of the asymmetric change amount of the alignment marks on both sides of the reticle. Specific Embodiments

[0024] The following illustrates the embodiments of the present application through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] The following will clearly and completely describe the technical solutions in the present application in conjunction with the drawings. Obviously, the described embodiments are some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0026] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0027] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0028] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0029] Since the size of the fine particles is very small, the vacuum value of the mask fixed on the carrier table does not change, and the supporting hardware of the lithography machine cannot issue corresponding alarm prompts by sensing the change of the vacuum value. The fine particles cause local lifting of the mask (as shown in Figure 1A ), and the mask pattern formed on the silicon wafer after projection undergoes horizontal displacement deformation and vertical displacement deformation as shown in Figure 1B , resulting in product defects.

[0030] To solve this problem, the present application provides a method for monitoring the deformation of the lithography machine mask caused by fine particles. Without modifying the hardware of the lithography machine, by using the existing horizontal alignment marks on the mask, it is determined whether the mask has non-linear horizontal deformation by calculating whether there is a jump in the asymmetric change amount of the alignment marks through software. If there is a jump in the asymmetric change amount of the alignment marks, it is necessary to check for the presence of fine particles on the mask.

[0031] Please refer to Figure 2 , which shows the flowchart of the method for monitoring the deformation of the lithography machine mask caused by fine particles provided by the embodiments of the present application.

[0032] As shown in Figure 2 , the method for monitoring the deformation of the lithography machine mask caused by fine particles includes the following steps:

[0033] Step 1: Set six pairs of horizontal alignment marks from top to bottom on both sides of the reticle.

[0034] Step 2: Calculate the linear deformations of the alignment marks in the X and Y directions, and four sets of linear deformation data are obtained for each pair of alignment marks.

[0035] Step 3: Use the data obtained in Step 2 to calculate the asymmetric change amount of the linear deformations of the alignment marks on both sides of the reticle.

[0036] Step 4: Determine whether the reticle has non - linear horizontal deformation caused by fine particles according to whether there is a jump in the asymmetric change amount of the linear deformations of the alignment marks.

[0037] In Step 1, as Figure 3 shown, six pairs of horizontal alignment marks (VRAmark) are set from top to bottom on both sides of the reticle. Each pair of alignment marks consists of two alignment marks that are axially symmetrically distributed with respect to the central axis of the reticle on both sides of the reticle. Among them, the three alignment marks in the upper left part of the reticle are numbered L1, L2, and L3 from top to bottom, the three alignment marks in the lower left part of the reticle are numbered L4, L5, and L6 from top to bottom, the three alignment marks in the upper right part of the reticle are numbered R1, R2, and R3 from top to bottom, and the three alignment marks in the lower right part of the reticle are numbered R4, R5, and R6 from top to bottom.

[0038] As an example, the alignment marks include alignment marks characterizing the displacement (Shift X, ShiftY), rotation (Rotation), magnification (Magnification X, magnification Y), and orthogonality differences of the reticle pattern relative to the silicon wafer. The above - mentioned differences are respectively reflected in the horizontal displacement, overall deflection by a certain angle, size change, and partial topographical distortion of the reticle pattern formed on the silicon wafer surface relative to the preset position.

[0039] In Step 2, calculate the linear deformations of the alignment marks in the X and Y directions to obtain the linear deformation data of the alignment marks. As shown in Table 1, four sets of linear deformation data are obtained for each pair of alignment marks, that is, the linear deformation data (XL, YL) of the alignment marks in the X and Y directions on the left side of the reticle and the linear deformation data (XR, YR) of the alignment marks in the X and Y directions on the right side of the reticle.

[0040] Table 1 Linear deformation data of the alignment marks on both sides of the reticle in the X and Y directions

[0041]

[0042] Each time the lithography machine projects the pattern of the reticle onto the silicon wafer, a log file will be automatically generated, which contains the linear deformation data of the alignment marks on both sides of the reticle in the X and Y directions. Taking Table 1 as an example, it shows a part of the linear deformation data of the alignment marks on both sides of the reticle in the X and Y directions in the log file.

[0043] In Step 3, taking the data in Table 1 as an example, the asymmetric change amount of the linear deformation of the alignment marks on both sides of the reticle in the X direction is (XR1 - XR6) - (XL1 - XL6), that is, the difference between the linear deformation values of the two alignment marks at the uppermost and lowermost positions on the right side of the reticle in the X direction and the difference between the linear deformation values of the two alignment marks at the uppermost and lowermost positions on the left side of the reticle in the X direction. The asymmetric change amount of the linear deformation of the alignment marks on both sides of the reticle in the Y direction is (YR1 - YR6) - (YL1 - YL6), that is, the difference between the linear deformation values of the two alignment marks at the uppermost and lowermost positions on the right side of the reticle in the Y direction and the difference between the linear deformation values of the two alignment marks at the uppermost and lowermost positions on the left side of the reticle in the Y direction.

[0044] In Step 4, as Figure 4 shown, within the range marked by the dashed line, the asymmetric change amount of the linear deformation of the alignment marks on both sides of the reticle in the X direction and the asymmetric change amount of the linear deformation of the alignment marks on both sides of the reticle in the Y direction undergo jumps, that is, the fluctuation range changes significantly. Fine particles will cause local lifting of the reticle, which will inevitably cause displacement of a certain alignment mark, and the displacement amount will be more outlier compared with other alignment marks, resulting in jumps as shown in Figure 4 shown.

[0045] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present application in a schematic manner. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0046] In summary, the method for monitoring the deformation of the lithography machine reticle caused by fine particles provided by the present application can effectively detect the deformation of the lithography machine reticle caused by fine particles and improve the product yield. Therefore, the present application effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0047] The above embodiments only illustrate the principle and its effects of the present application by way of example, rather than limiting the present application. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present application.

Claims

1. A method for monitoring the deformation of a photolithography mask caused by fine particles, characterized in that: The method comprises: Step 1, setting six pairs of horizontal alignment marks from top to bottom on both sides of the mask; Step 2, calculating the linear deformation of the alignment marks in the X and Y directions, and obtaining four sets of linear deformation data for each pair of alignment marks; Step three, using the data obtained from step two to calculate the asymmetric change in the linear deformation of the alignment marks on both sides of the mask; Step 4: judging whether the alignment mark linear deformation mask has nonlinear horizontal deformation caused by fine particles according to whether the alignment mark linear deformation has a jump in asymmetric variation.

2. The method according to claim 1, characterized in that: Each pair of alignment marks is two alignment marks located on both sides of the mask and distributed axially symmetrically with respect to the central axis of the mask.

3. The method according to claim 1 or 2, characterized in that: The alignment marks include alignment marks that characterize the displacement, rotation, magnification and orthogonal difference of the mask pattern relative to the silicon wafer.

4. The method according to claim 1, characterized in that The data obtained by implementing the step 2 is recorded in a log file automatically generated when the photolithography machine projects the pattern of the mask onto the silicon wafer.

5. The method according to claim 1, characterized in that In the step three, the asymmetric variation of the linear deformation of the alignment marks on both sides of the mask in the X direction is the difference between the linear deformation values ​​of the two alignment marks located at the top and the bottom on the right side of the mask and the linear deformation values ​​of the two alignment marks located at the top and the bottom on the left side of the mask in the X direction, and the asymmetric variation of the linear deformation of the alignment marks on both sides of the mask in the Y direction is the difference between the linear deformation values ​​of the two alignment marks located at the top and the bottom on the right side of the mask and the linear deformation values ​​of the two alignment marks located at the top and the bottom on the left side of the mask in the Y direction.

6. The method according to claim 1, characterized in that In step 4, the asymmetric variation of the linear deformation of the alignment marks on both sides of the mask in the X direction and the asymmetric variation of the linear deformation of the alignment marks on both sides of the mask in the Y direction jump, and it is necessary to check for fine particles on the mask.

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