CN119511630A

CN119511630A - Process monitoring method for stability of focusing depth of exposure light source of photoetching machine

Info

Publication number: CN119511630A
Application number: CN202411720069.1A
Authority: CN
Inventors: 王岳; 周红宇; 李海涛
Original assignee: Anhui Guangzhi Technology Co Ltd
Current assignee: Anhui Guangzhi Technology Co Ltd
Priority date: 2024-11-28
Filing date: 2024-11-28
Publication date: 2025-02-25

Abstract

A process monitoring method for the focus depth stability of an exposure light source of a photolithography machine comprises the following steps: S1, providing a wafer; S2, applying a positive resist; S3, exposing the positive resist, adopting 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 with a focus depth variable for each step of a grid, the focus depth decreases with the focus depth variable when stepping to the left, and increases with the focus depth variable when stepping to the right, the exposure starts with the focus depth of the leftmost side being a negative value and the stepping exposure is performed until the focus depth of the rightmost side is a positive maximum setting value; S4, developing the positive resist with a positive resist developer; S5, collecting the line width size corresponding to different focus depths of each grid with a line width scanning electron microscope to determine the focus depth range corresponding to the product line width size.

Description

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

Technical Field

The present disclosure relates to the field of semiconductors, and more particularly to a process monitoring method for stability of depth of focus of an exposure light source of a lithography machine.

Background

The photoetching machine is an important micro-nano manufacturing technology and is widely applied to the fields of integrated circuits, optical devices and the like. In a lithographic apparatus, the depth of focus is the exact convergence of the beam onto a specific point on the wafer surface to form the desired image or pattern. In a photolithography process, focusing is critical to ensure imaging quality and resolution. If the depth of focus range is inaccurate, the beam may deviate from the target position, causing blurring, distortion or misplacement of the image, thereby affecting the performance and quality of the final product. Therefore, it is important to formulate a method of monitoring the depth of focus stability (i.e., depth of focus range).

Disclosure of Invention

In view of the problems existing in the background art, an object of the present disclosure is to provide a process monitoring method for stability of a focusing depth of an exposure light source of a lithography machine, which can determine a focusing depth range corresponding to a line width dimension of a product in a workshop environment, so that lithography exposure is performed in the workshop environment through the determined focusing depth range, and stability of the line width dimension of the product lithography is ensured.

S1, providing a wafer which is matched with a product film layer and is used as a semiconductor substrate; S2, positive photoresist is coated on the surface of a wafer, S3, positive photoresist is exposed, a mask plate is adopted for step exposure, step exposure is carried out on grids arranged on the surface of the wafer according to rows and columns, in adjacent continuous grids to be exposed in corresponding rows to be exposed, the exposure dose of each grid is constant and corresponds to the line width size of a product, the focusing depth is increased from left to right, each step of focusing depth is changed by a focusing depth variable, the focusing depth is decreased by a focusing depth variable when the focusing depth is increased to left, the focusing depth is increased by a focusing depth variable when the focusing depth is increased to right, the exposure is started from the leftmost focusing depth to a negative value, then one grid from left to right is subjected to step exposure until the rightmost focusing depth is a positive maximum set value, S4, positive photoresist is developed by positive photoresist developer, and S5, line width scanning electron mirrors collect line widths corresponding to different focusing depths of each grid to determine the focusing depth range corresponding to the line width size of the product.

The method has the beneficial effects that in the process monitoring method for the stability of the focusing depth of the exposure light source of the photoetching machine, through the steps S1 to S5, the focusing depth range corresponding to the linewidth dimension of the product can be determined in a workshop environment, so that photoetching exposure is carried out in the workshop environment through the determined focusing depth range, the stability of the linewidth dimension of photoetching of the product is ensured, and further, the performance and quality of the final product are ensured.

Drawings

FIG. 1 is a flow chart of a process monitoring method for depth of focus stability of an exposure light source of a lithography machine according to the present disclosure.

Fig. 2 is the layout of the lattices to be exposed and the focus depth of the exposure in step S3 of example 1 and example 2.

Fig. 3A is a graph of depth of focus versus line width after completion of step S5 of example 1 when the shop environment is normal.

Fig. 3B is a graph of depth of focus versus line width after the shop is powered up and the shop environment is stable after the completion of step S5 of example 2.

Detailed Description

It is to be understood that the disclosed embodiments are merely examples of the disclosure, which may be embodied in various forms and, therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the disclosure.

[ Process monitoring method for stability of depth of focus of exposure light source of photoetching machine ]

Referring to fig. 1 and 2, a process monitoring method for the stability of the depth of focus of an exposure light source of a lithography machine according to the present disclosure includes the steps of:

s1, providing a wafer which is matched with a product film layer and is used as a semiconductor substrate;

S2, positive photoresist is coated on the surface of the wafer;

s3, exposing the positive photoresist,

Using mask plate step exposure, wherein step exposure is performed on grids (shown in fig. 2, the grids to be exposed are represented in the left graph of fig. 2) arranged in rows and columns on the surface of a wafer, in 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 line width size of a product, the focusing depth is increased from left to right, each step is changed by a focusing depth variable, the focusing depth is decreased by the focusing depth variable when the step is left, the focusing depth is increased by the focusing depth variable when the step is right, the exposure is started from the leftmost focusing depth to be negative value, then one step exposure is performed from left to right until the focusing depth to be positive is the maximum setting value, as shown in the right graph of fig. 2, and the numbers in the grids in the right graph of fig. 2 are

Depth of focus;

s4, developing the positive photoresist by using positive photoresist developer;

S5, collecting line width dimensions corresponding to different focusing depths of each grid by using a line width scanning electron microscope so as to determine a focusing depth range corresponding to the line width dimensions of the product.

In the process monitoring method for the stability of the focusing depth of the exposure light source of the lithography machine, through the steps S1 to S5, the focusing depth range corresponding to the line width dimension of the product can be determined in the workshop environment, so that the lithography exposure is carried out in the workshop environment through the determined focusing depth range, the stability of the line width dimension of the lithography of the product is ensured, and further the performance and quality of the final product are ensured.

In an example, in step S1, the wafer is a silicon substrate withThickness of SiO ₂ film layerA SiN film layer of thickness.

In an example, in step S2, the positive photoresist has a thickness of GKR a 5315 aIn the step S3, the mask is a V0T612-010-BA plate, the line width size of the product is 350nm, the exposure dose is 29mj/cm ², the focusing depth variable is 0.05 mu m, the focusing depth at the leftmost side is-0.1 mu m, the focusing depth at the rightmost side is 0.35 mu m, and in the step S4, the positive photoresist developer is ZX-238 type, the development time is 60S and the flushing time is 30S.

[ Test ]

Example 1

Example 1 was performed when the plant environment was normal,

The process monitoring method for the stability of the focusing depth of the exposure light source of the photoetching machine in the embodiment 1 comprises the following steps:

S1, providing a wafer which is matched with a product film layer and is used as a semiconductor substrate, wherein the wafer is a silicon substrate and sequentially provided with Thickness of SiO ₂ film layerA SiN film layer with a thickness;

s2, positive photoresist is coated on the surface of the wafer, wherein the positive photoresist is GKR and 5315, and the photoresist coating thickness is

S3, exposing the positive photoresist,

Step exposure is carried out on grids (shown as a figure 2, the grids to be exposed are represented in the left graph of the figure 2) which are arranged in rows and columns on the surface of a wafer by adopting a mask plate of V0T612-010-BA version, the exposure dose of each grid is constant 29mj/cm ² and corresponds to the line width size of a product, the line width size of the product is 350nm, the focusing depth is increased from left to right, the focusing depth of each step is changed by a focusing depth variable of 0.05 mu m, the focusing depth is decreased by a focusing depth variable when the step is left, the focusing depth is increased by a focusing depth variable when the step is right, the exposure is firstly carried out from the leftmost focusing depth of 0.1 mu m, then one step exposure is carried out from left to right on the grids until the focusing depth of the rightmost grid is a positive maximum set value of 0.35 mu m, and the number in the right graph of the figure 2 is the focusing depth;

S4, developing positive photoresist by using positive photoresist developer, wherein the positive photoresist developer is ZX-238 type, and has a development time of 60S and a flushing time of 30S;

Example 2

Example 2 was performed after a plant was tripped (i.e., the plant was powered off, all the stations in the plant were forced to power down) and after the plant restored to the powered plant environment,

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

Fig. 3A is a graph of depth of focus versus line width after completion of step S5 of example 1 when the shop environment is normal. Fig. 3B is a graph of depth of focus versus line width after the shop is tripped and the shop environment is stable after the process of step S5 of example 2 is completed.

As seen from fig. 3A, when the workshop environment is normal, the line width dimension is stable (i.e., close to the product line width dimension of 350nm, with a deviation in the range of-3.67 nm to 1.91 nm) at a depth of focus of 0.1-0.25 μm, when the depth of focus is less than 0.1 μm, the line width dimension decreases with a decreasing trend with a product line width dimension of 350nm, and when the depth of focus is greater than 0.25 μm, the line width dimension decreases with a increasing trend with a product line width dimension of 350nm, and a greater deviation with a product line width dimension.

As shown in fig. 3B, after the power is jumped in the workshop and the environment of the workshop is stable, although the process monitoring method for the stability of the focusing depth of the exposure light source of the lithography machine is the same as that of the embodiment 1, the two line width curves are not consistent, and in fig. 3B, the line width dimension is stable when the focusing depth is-0.05-0.15 μm, but the difference from the line width dimension 350nm of the product is large, and the deviation is in the range of-26.26 nm to-31.19 nm, which indicates that the state of the machine of the lithography machine is changed, and further adjustment is needed to adapt to the requirement of the line width dimension 350nm of the product.

The various exemplary embodiments are described using the above detailed description, but are not intended to be limited to the combinations explicitly disclosed herein. Thus, unless otherwise indicated, the various features disclosed herein may be combined together to form a number of additional combinations that are not shown for the sake of brevity.

Claims

1. A process monitoring method for the stability of the focus depth of an exposure light source of a lithography machine, characterized in that it comprises the steps of:

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. The exposure starts with the focus depth of the leftmost side being a negative value, and then one grid is exposed from left to right 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 The 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, the exposure dose is 29mj/ ^cm2 , 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 developing time is 60 seconds, and the flushing time is 30 seconds.