Process monitoring method for stability of focusing depth of exposure light source of photoetching machine

Abstract

The invention discloses a process monitoring method for the focusing depth stability of an exposure light source of a photoetching machine. The process monitoring method comprises the following steps: S1, providing a wafer; s2, coating positive glue; s3, positive photoresist is exposed, mask plate stepping exposure is adopted, stepping exposure is carried out on the surface of the wafer according to rows and columns, in the adjacent continuous grids to be exposed in the corresponding rows to be exposed, the exposure dose of each grid is constant and corresponds to the line width size of the product, the focusing depth is gradually increased from left to right, and the exposure dose of the adjacent continuous grids to be exposed in the corresponding rows to be exposed corresponds to the line width size of the product; the focusing depth is changed by a focusing depth variable in each step, the focusing depth is progressively decreased by the focusing depth variable in the leftward step, the focusing depth is progressively increased by the focusing depth variable in the rightward step, and step exposure is started from the leftmost focusing depth to a negative value until the rightmost focusing depth is a positive maximum set value; s4, developing the positive photoresist by using a positive photoresist developing solution; and S5, the line width scanning electron microscope collects line width sizes corresponding to different focusing depths of each grid so as to determine a focusing depth range corresponding to the line width size of the product.

Description

Technical Field

[0001] The present disclosure relates to the semiconductor field, and more specifically to a process monitoring method for the stability of the focusing depth of an exposure light source of a lithography machine. Background Art

[0002] Photolithography is an important micro-nano manufacturing technology, widely used in integrated circuits, optical devices and other fields. In a photolithography machine, the depth of focus is to accurately focus the light beam on a specific point on the surface of the wafer to form the desired image or pattern. In the photolithography process, focusing is critical to ensuring imaging quality and resolution. If the focus depth range is inaccurate, the light beam may deviate from the target position, resulting in blurred, distorted or misaligned images, which will affect the performance and quality of the final product. Therefore, it is crucial to develop a method to monitor the stability of the focus depth (i.e., the focus depth range). Summary of the invention

[0003] In view of the problems existing in the background technology, an object of the present invention is to provide a process monitoring method for the focus depth stability of the exposure light source of a lithography machine, which can determine the focus depth range corresponding to the product line width size in a workshop environment, so as to perform lithography exposure in the workshop environment through the determined focus depth range, thereby ensuring the stability of the line width size of the product lithography.

[0004] Therefore, a process monitoring method for the focus depth stability of the exposure light source of a lithography machine includes the following steps: S1, providing a wafer as a semiconductor substrate matching a product film layer; S2, applying a positive photoresist on the surface of the wafer; S3, exposing the positive photoresist, using a mask stepping exposure, the stepping exposure is performed on grids arranged in rows and columns on the surface of the wafer, in adjacent and continuous grids to be exposed in the corresponding row to be exposed, the exposure dose of each grid is constant and corresponds to the product line width size, the focus depth increases from left to right, the focus depth changes by a focus depth variable for each step of a grid, the focus depth decreases by a focus depth variable when stepping to the left, and increases by a focus depth variable when stepping to the right, the exposure starts with the focus depth of the leftmost side being a negative value, and then stepping one grid at a time from left to right until the focus depth of the rightmost side is a positive maximum set value; S4, developing the positive photoresist using a positive photoresist developer; S5, using a line width scanning electron microscope to collect the line width size corresponding to different focus depths of each grid to determine the focus depth range corresponding to the product line width size.

[0005] The beneficial effects of the present disclosure are as follows: in the process monitoring method for the focus depth stability of the exposure light source of the lithography machine according to the present disclosure, through steps S1 to S5, the focus depth range corresponding to the product line width size can be determined in a workshop environment, so that the lithography exposure is performed through the determined focus depth range in the workshop environment, ensuring the stability of the line width size of the product lithography, and further ensuring the performance and quality of the final product. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a flow chart of a process monitoring method for the stability of the focusing depth of an exposure light source of a lithography machine according to the present disclosure.

[0007] Figure 2 These are the layout of the grid to be exposed in step S3 of Embodiment 1 and Embodiment 2 and the focus depth of exposure.

[0008] Figure 3A This is a graph showing the relationship between the focus depth and the line width after step S5 of Example 1 is completed when the workshop environment is normal.

[0009] Figure 3B This is a graph of the relationship between the focus depth and the line width after the power outage in the workshop and the restoration of power supply to the workshop and the stabilization of the workshop environment in Example 2 after step S5 is completed. DETAILED DESCRIPTION

[0010] It will be understood that the disclosed embodiments are merely examples of the present disclosure, which may be implemented in various forms, and therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to implement the present disclosure in various ways.

[0011] [Process monitoring method for focusing depth stability of exposure light source of lithography machine]

[0012] Reference Figure 1 and Figure 2 According to the disclosed process monitoring method for the stability of the focus depth of the exposure light source of the lithography machine, the steps include:

[0013] S1, providing a wafer as a semiconductor substrate matching a product film layer;

[0014] S2, coating positive resist on the surface of the wafer;

[0015] S3, expose the positive photoresist,

[0016] The mask is used for step-by-step exposure, and the step-by-step exposure is performed on the wafer surface in a grid arranged in rows and columns (such as Figure 2 As shown, Figure 2 The * in the left figure represents the grid to be exposed). In the adjacent continuous grids to be exposed in the corresponding row to be exposed, the exposure dose of each grid is constant and corresponds to the product line width size. The focus depth increases from left to right. The focus depth changes with the focus depth variable for each step of a grid. When stepping to the left, the focus depth decreases by the focus depth variable, and when stepping to the right, the focus depth increases by the focus depth variable. The exposure starts with the focus depth of the leftmost side as a negative value, and then steps from left to right one grid at a time until the focus depth of the rightmost side is the positive maximum setting value. Figure 2 As shown in the right figure, Figure 2 The numbers in the grid in the right picture are

[0017] Depth of focus;

[0018] S4, developing the positive photoresist using a positive photoresist developer;

[0019] S5, line width scanning electron microscope collects the line width dimensions corresponding to different focusing depths of each grid to determine the focusing depth range corresponding to the product line width dimensions.

[0020] In the process monitoring method for the focus depth stability of the exposure light source of the lithography machine according to the present invention, through steps S1 to S5, the focus depth range corresponding to the product line width size can be determined in a workshop environment, so that the lithography exposure is performed through the determined focus depth range in the workshop environment, ensuring the stability of the line width size of the product lithography, and further ensuring the performance and quality of the final product.

[0021] In one example, in step S1, a wafer is a silicon substrate having Thickness of SiO2 film and Thickness of SiN film layer.

[0022] In one example, in step S2, the positive photoresist is GKR5315, and the coating thickness of the positive photoresist is In step S3, the mask is V0T612-010-BA, the product line width is 350nm, and the exposure dose is 29mj / cm 2 , the focus depth variable is 0.05μm, the leftmost focus depth is -0.1μm, and the rightmost focus depth is 0.35μm; in step S4, the positive photoresist developer is ZX-238, the development time is 60s, and the flushing time is 30s.

[0023] [test]

[0024] Example 1

[0025] Example 1 is carried out when the workshop environment is normal.

[0026] The process monitoring method for the stability of the focus depth of the exposure light source of the lithography machine in Example 1 adopts the following steps:

[0027] S1, providing a wafer as a semiconductor substrate matching the product film layer, the wafer is a silicon substrate with Thickness of SiO2 film and Thickness of SiN film layer;

[0028] S2, apply positive photoresist on the surface of the wafer. The positive photoresist is GKR5315 and the coating thickness is

[0029] S3, expose the positive photoresist,

[0030] The mask of V0T612-010-BA version is used for step-by-step exposure, and the grids arranged in rows and columns on the wafer surface are exposed by step-by-step exposure. Figure 2 As shown, Figure 2 The exposure dose of each grid in the adjacent continuous grids to be exposed in the corresponding row to be exposed is constant at 29 mj / cm 2 And corresponding to the product line width size, the product line width size is 350nm, the focus depth increases from left to right, and the focus depth changes by a focus depth variable of 0.05μm for each step of a grid. When stepping to the left, the focus depth decreases by the focus depth variable, and when stepping to the right, the focus depth increases by the focus depth variable. The exposure starts with the focus depth of the leftmost side being a negative value of -0.1μm, and then one grid at a time from left to right is exposed until the focus depth of the rightmost side is the positive maximum setting value of 0.35μm. Figure 2 As shown in the right figure, Figure 2 The numbers in the grid in the right picture are the depth of focus;

[0031] S4, developing the positive photoresist with a positive photoresist developer, the positive photoresist developer is ZX-238, the developing time is 60 seconds, and the flushing time is 30 seconds;

[0032] S5, line width scanning electron microscope collects the line width dimensions corresponding to different focusing depths of each grid to determine the focusing depth range corresponding to the product line width dimensions.

[0033] Example 2

[0034] Example 2 is carried out after a power outage in the workshop (i.e., a power outage in the workshop, all machines in the workshop are forced to power off) and after the power supply is restored and the workshop environment stabilizes.

[0035] The process monitoring method for the stability of the focusing depth of the exposure light source of the lithography machine in Example 2 is the same as that in Example 1.

[0036] Figure 3A This is a graph showing the relationship between the focus depth and the line width after step S5 of Example 1 is completed when the workshop environment is normal. Figure 3B This is a graph of the relationship between the focus depth and the line width after the power outage in the workshop and the restoration of power supply to the workshop and the stabilization of the workshop environment after the completion of step S5 of Example 2.

[0037] from Figure 3AIt can be seen that when the workshop environment is normal, when the focusing depth is between 0.1-0.25μm, the line width size is stable (that is, close to the product line width size of 350nm, with a deviation in the range of -3.67nm to 1.91nm); when the focusing depth is less than 0.1μm, as the focusing depth decreases, the line width size shows a decreasing trend, and the deviation from the product line width size of 350nm increases; when the focusing depth is greater than 0.25μm, as the focusing depth increases, the line width size shows a decreasing trend, and the deviation from the product line width size of 350nm increases.

[0038] from Figure 3B It can be seen that after the power outage in the workshop and the workshop power supply is restored and the workshop environment is stable, although the process monitoring method for the stability of the focus depth of the exposure light source of the lithography machine is the same as that in Example 1, the control Figure 3A The line width curves of the two line width curves are not consistent. Figure 3B In the test, when the focus depth is between -0.05-0.15μm, the line width is stable, but it is quite different from the product line width of 350nm, with a deviation ranging from -26.26nm to -31.19nm. This indicates that the state of the lithography machine has changed and further adjustments are needed to meet the requirements of the product line width of 350nm.

[0039] The above detailed description is used to describe multiple exemplary embodiments, but this document is not intended to be limited to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined together to form multiple additional combinations that are not shown for the sake of simplicity.

Claims

1. A process monitoring method for the stability of the focusing depth of a photolithography exposure light source, characterized in that: Includes steps: S1, providing a wafer as a semiconductor substrate matching a product film layer; S2, coating positive resist on the surface of the wafer; S3, expose the positive photoresist, Adopting mask stepping exposure, stepping exposure is performed on the wafer surface in grids arranged in rows and columns. In the adjacent continuous grids to be exposed in the corresponding row to be exposed, the exposure dose of each grid is constant and corresponds to the product line width size. The focus depth increases from left to right. The focus depth changes by the focus depth variable for each step of a grid. When stepping to the left, the focus depth decreases by the focus depth variable, and when stepping to the right, the focus depth increases by the focus depth variable. Exposure starts with the focus depth of the leftmost side being a negative value, and then steps from left to right one grid at a time until the focus depth of the rightmost side is the positive maximum setting value. S4, developing the positive photoresist using a positive photoresist developer; S5, line width scanning electron microscope collects the line width dimensions corresponding to different focusing depths of each grid to determine the focusing depth range corresponding to the product line width dimensions.

2. The process monitoring method for the stability of the focusing depth of the exposure light source of the lithography machine according to claim 1, characterized in that: In step S1, a wafer is a silicon substrate having Thickness of SiO2 film and Thickness of SiN film layer.

3. The process monitoring method for the stability of the focusing depth of the exposure light source of the lithography machine according to claim 1, characterized in that: In step S2, the positive photoresist is GKR5315, and the coating thickness of the positive photoresist is In step S3, the mask is V0T612-010-BA, the product line width is 350nm, and the exposure dose is 29mj / cm 2 , the focus depth variable is 0.05μm, the focus depth on the far left is -0.1μm, and the focus depth on the far right is 0.35μm; In step S4, the positive photoresist developer is ZX-238, the developing time is 60 seconds, and the flushing time is 30 seconds.

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