WO2017114360A1

WO2017114360A1 - Exposure system and exposure method for semiconductor photolithography

Info

Publication number: WO2017114360A1
Application number: PCT/CN2016/112138
Authority: WO
Inventors: 葛亮; 杨志勇
Original assignee: 上海微电子装备（集团）股份有限公司
Priority date: 2015-12-30
Filing date: 2016-12-26
Publication date: 2017-07-06
Also published as: CN106933049A; CN106933049B; TW201734658A

Abstract

An exposure system and an exposure method. The method comprises: arranging a micro-reflector array (4) between a uniform light unit (3) and a reflector (5) to replace a variable slit apparatus; according to the pattern of a mask plate (7) during exposure and the requirements for exposure precision, setting parameters of an exposure field of view; and inputting same into drive software of the micro-reflector array (4), so as to calculate motion parameters of the micro-reflector array (4) during the exposure. During the exposure, a control card continuously sends an instruction to each digital micro-mirror in the micro-reflector according to data in the drive software, and each digital micro-mirror takes a corresponding flipping action each time the instruction is received until the exposure ends. The micro-reflector array (4) has thousands of digital micro-mirrors, so that the exposure field of view, range and dose are changed in real time, thereby avoiding the mechanical vibration generated by a traditional variable slit apparatus when changing the shape of the slit and the requirements for the high acceleration of a slit apparatus drive system, and reducing the complexity of an exposure system mechanical structure and a control system.

Description

Exposure system and exposure method for semiconductor lithography

Technical field

The present invention relates to the field of semiconductor lithography, and more particularly to an exposure system and an exposure method for semiconductor lithography.

Background technique

In the manufacturing process of semiconductor IC integrated circuits, a complete chip usually needs to be lithographically exposed to be completed, and the mask and process requirements corresponding to each lithography will change, when the process requirements are high. It is necessary to concentrate the light intensity and the stray light needs to be occluded. When the pattern area of the mask is complicated, the invalid stray light of some areas needs to be blocked, so as to ensure the precision of the pattern left on the silicon wafer after exposure. When the process requirements are low or the pattern area is relatively simple, and the lithography precision is low, part of the stray light generated by the illumination source with low light intensity can be shielded and the work efficiency can be reduced. Therefore, it is necessary to provide a variable slit between the illumination source and the exposure object, which can adjust the intensity and range of the illumination. The variable slit is responsible for cooperating with each side of the mask, and occluding the dynamic scanning exposure process, possibly illuminating adjacent The illumination of the exposure field. In the latest type of front scanning lithography machine, the variable slit is also used for correction of high-order dose error in the field non-scanning.

The traditional variable slit is realized by the high-speed and high-acceleration motion of the mechanical structure of the knife edge. It is necessary to design a physical motion of up to 5~10G high acceleration in the exposure system, and introduce a large dynamic disturbance to the precise optical system, affecting the final Lighting performance. At the same time, in order to achieve the correction of the high-order dose error in the non-scanning field, the variable slit of the conventional structure needs to make nearly 20 pairs of programmable micro-motion structures on the knife edge, resulting in an extremely complicated system structure and a variable slit. It is a kind of mechanical device, which will inevitably produce vibration shock during the change process. The change also requires the variable slit drive system to have high acceleration function, which makes the engineering reliability and reliability of the entire exposure system low. Therefore, it is necessary to invent an exposure apparatus capable of simply and efficiently carrying the function of a variable slit and improving the achievable exposure system Sex and reliability.

Summary of the invention

In order to solve the above problems, the present invention proposes an exposure system having a micro mirror array in which a micro mirror array replaces the original variable slit device, so that the exposure system not only has the function of a variable slit, but also The vibration shock generated by the mechanical change of the variable slit device and the high acceleration requirement of the drive system are eliminated, and the engineering realization and reliability of the exposure system are improved.

In order to achieve the above object, the present invention provides an exposure system for semiconductor lithography, comprising an illumination source, a collimation beam expanding system, a light homogenizing unit, a mirror, and a relay unit sequentially disposed along an optical path direction, from which The light beam emerging from the unit is used to illuminate a mask, wherein the exposure system further comprises: a micro mirror array disposed between the light homogenizing unit and the mirror; and a light absorbing device located at the optical path In addition, the micromirror array reflects an effective light beam from the illumination beam from the leveling unit onto the mirror and transmits it to the relay unit for illuminating the mask, which will come from the uniform The stray light beam in the illumination beam of the light unit is reflected to the light absorbing device.

Advantageously, said micromirror array comprises a control board and a digital micromirror, said digital micromirror being a microelectromechanical system chip externally a micromirror and connected to said control board.

Advantageously, the control board is provided with drive software for inputting a parameter to control the angle of reflection and the flip speed of each of the digital micromirrors during exposure.

Preferably, the number of the digital micromirrors is more than one thousand, and the number of the digital micromirrors increases correspondingly with an increase in exposure precision.

Preferably, the control board controls the inversion speed of the micro mirror according to the moving speed of the mask, and determines the reflection angle of each micro mirror at each time according to the exposure dose set at the time of exposure.

Preferably, the mask moves during exposure as exposure progresses.

The present invention also provides an exposure method using the above exposure system, comprising the following steps:

Step 1: determining the parameters of the exposure field of view according to the process precision and the pattern of the mask;

Step 2: input the parameters of the exposure field into the driver software of the control board of the micro mirror array. Calculating the flipping speed and flipping angle of each digital micromirror in the micro mirror array at each moment;

Step 3: Turn on the illumination source, and the control board sends a flip instruction to each digital micromirror, and each digital micromirror flips to a corresponding angle after receiving the flip instruction;

Step 4: As the exposure progresses, the control board sends an instruction to each digital micro-mirror at each moment, and each digital micro-mirror changes the angle of the flip after receiving the instruction;

Step 5: After the exposure is completed, the micro mirror array is restored to the initial state.

Preferably, the parameter of the exposure field of view in step 1 refers to the area, range and exposure dose of the field of exposure.

Preferably, the response time of the digital micromirror is proportional to the time when the light source is scanned on the mask. The response time of the digital micromirror is equal to the time when the control board sends the flipping instruction to the digital micromirror, and the digital micromirror receives the command. The sum of the time and the time the digital micromirror makes the flipping action.

Preferably, the response time of the digital micromirror is S _DMD , and

Where S _WS is the time when the light source is scanned on the mask, M _po is the objective magnification, and M _il is the illumination system magnification.

Compared with the prior art, the invention has the beneficial effects that the present invention replaces the conventional variable slit device by providing a micro mirror array between the light homogenizing unit and the mirror, according to the pattern of the mask and the exposure precision during exposure. It is required to set the parameters of the exposure field of view and input into the driving software of the micro mirror array to calculate the motion parameters of the micro mirror array during exposure, and then, during exposure, the control board continues to follow the data in the driver software. Each digital micromirror in the micromirror sends an instruction, and each digital micromirror performs a corresponding flipping action after receiving the instruction at each moment until the end of the exposure. The micromirror array used in the invention has thousands of digital micromirrors changing the field of view, range and dose in real time, avoiding the mechanical vibration generated by the conventional variable slit device when changing the shape of the slit and the variable The high acceleration requirement of the slit device driving system reduces the complexity of the mechanical structure and control system of the exposure system, and has the characteristics of simple and rapid operation, improved system achievability and reliability.

DRAWINGS

1 is a schematic structural view of an exposure system provided by the present invention;

2 is a schematic structural view of a micro mirror array provided by the present invention;

FIG. 3 is a schematic flow chart of an exposure method provided by the present invention.

In the picture: 1-illumination source, 2-collimation beam expander system, 3-homogening unit, 4-micro mirror array, 401-effective beam, 402-stray beam, 5-mirror, 6-relay unit , 7-mask, 8-absorber, 9-workpiece.

detailed description

The above described objects, features and advantages of the present invention will become more apparent from the aspects of the appended claims.

Referring to FIG. 1 , an exposure system provided by the present invention sequentially includes an illumination source 1, a collimating beam expanding system 2, a light concentrating unit 3, a micro mirror array 4, a mirror 5, and a relay unit 6 disposed along an optical path. The light beam emerging from the unit 6 illuminates the mask 7 and then illuminates the workpiece stage 9, and a light absorbing means 8 is provided in addition to the light path. For example, the light absorbing means 8 can be located adjacent to the micro mirror array 4, the light homogenizing unit 3 and the mirror Between 5, the light absorbing device 8 may be disposed at other suitable positions as long as the light absorbing device 8 does not affect the illumination light path and can receive the reflected light from the micro mirror array 4. Thus, the light emitted from the illumination source 1 is sequentially transmitted to the micromirror array 4 through the collimation beam expanding system 2 and the light homogenizing unit 3, and the micromirror array 4 reflects the required light beam onto the mirror 5, and then It is transmitted to the mask plate 7 and the workpiece stage 9 through the relay unit 6, and the unnecessary light beam is reflected to the light absorbing device 8, and is absorbed and processed.

The illumination source 1 is mainly an ultraviolet light source or a visible light source such as a mercury lamp.

The function of the collimation beam expanding system 2 is to enlarge the light beam emitted from the illumination source 1 to form an illumination field of view substantially corresponding to the pattern size of the mask 7.

Referring to FIG. 2, the micromirror array 4 has a rectangular structure as a whole, and is arranged by a plurality of square digital micromirrors. When the light is irradiated to the micromirror array 4, each digital micromirror is formed according to the previous setting. Flip angle, when the beam projected onto the digital micromirror needs to be placed into the exposure illumination When the beam in the field (ie, the effective beam), the digital micromirror is flipped to an angle that can reflect the beam onto the mirror 5, when the beam projected onto the digital micromirror does not need to be placed in the exposure illumination The stray beam in the field either destroys the undesired beam of the exposure process, the digital micromirror is flipped to an angle that can reflect the undesired beam to the light absorbing device 8, so that the entire micromirror array 4 can handle all the needs Each of the light irradiated to the mask 7 is reflected onto the mirror 5, and each of the light that does not need to be irradiated to the mask 7 is reflected onto the light absorbing device 8. Each of the digital micromirrors is mounted on the lower chip socket, and the chip socket is connected to the control board, and the digital micromirror is a microelectromechanical system chip with an external micromirror. The higher the exposure precision requirement, the digital micro The more the number of mirrors.

The control board internally sets the driver software. The driver software is used to input parameters to control the flip angle and flip speed of the digital micromirror during exposure, and sends an instruction to each digital micromirror during exposure to indicate each digital micromirror at each moment. The angle that needs to be flipped, each digital micromirror makes a corresponding flip action after receiving the instruction.

The mask 7 and the workpiece stage 9 are moved during exposure, and the control board controls the inversion speed of the digital micromirror according to the moving speed of the mask 7, and determines the exposure of each micromirror according to the exposure dose set during exposure. The angle of reflection.

The sum of the time that the control board sends the flip command to the digital micromirror, the time the digital micromirror receives the command, and the time the flip action is made is called the response time of the digital micromirror. The response time of the digital micromirror is proportional to the time the light source is scanned on the mask. Specifically:

Where S _DMD is the response time of the digital micromirror, where S _WS is the scanning time of the light source on the mask, M _po is the objective magnification, and M _il is the illumination system magnification. And this response will also bring the corresponding discretization error, which is represented by:

Where F _DMD is the response frequency of the digital micromirror.

For example, the front field of the lithography machine has a field of view of 26 mm × 10 mm, which requires a field size accuracy of 0.1 mm, and a mask synchronization time requirement of 50 ms. The conventional 0.7-inch digital micro-mirror product has a pixel size of 1024×768, and each pixel has a side length of 13.6 μm, and the side length in the field of view is not less than 0.5 mm. The images can be resolved, the response time can reach ms level or higher, and the refresh frequency is 5KHz. Therefore, the micromirror array 4 composed of digital micromirrors can fully meet the response speed required for exposure.

The control board also adjusts the flip angle of each digital micromirror at each moment according to the exposure dose determined by the pattern area of the mask and the accuracy requirement of the exposure process. The exposure dose is represented by the following formula:

DOSE(X,Y,x,y)=A(X,Y)·F(x)·G(y), where X and Y are the coordinates of the center of the exposure field on the silicon wafer, and A(X,Y) is The dose setting value of each exposure field, F(x) is the integrated light intensity in the X direction, and G(y) is the integrated light intensity in the Y direction;

X is the non-scanning direction coordinate of each point in the exposure field, f(x) is the polynomial expression of the scanning intensity in the X direction, F _i is the setting coefficient, ε _x is the control residual, so the integral in the X direction The light intensity is:

i is the order of control precision. The order of this control precision is determined by the precision that the exposure device can achieve. i∈[1,∞), the different f _i (x) corresponding to _i is different, such as when When i=1, f _i (x)=x, and when i=2, f _i (x)=x ² .

Y is the scanning direction coordinate of each point in the exposure field, g(y) is the polynomial expression of the scanning light intensity distributed in the Y direction, G _i is the setting coefficient, and ε _y is the control residual, so the integrated light in the Y direction Strong for:

Similarly, g _i (x) corresponding to different i is different, such as when i=1, g _i (x)=x, and when i=2, g _i (x)=x ² .

For the convenience of calculation, x, y ∈ [-1, 1] in the above polynomial.

The micromirror array 4 can be considered as a discretized representation of DOSE(X, Y, x, y) = A(X, Y)·F(x)·G(y), which is formed by controlling the micromirror array 4 The illumination field of view contour, the workpiece table 9 scanning process is the integration of the illumination profile, and finally the required dose distribution data is formed.

The present invention also provides an exposure method using the above exposure system. Referring to FIG. 3, the following steps are included. Step:

Step 1: Determine parameters of the exposure field of view according to the process precision and the pattern of the mask, such as the area, range and exposure dose of the exposure field of view;

Step 2: Input the parameters of the exposure field of view into the driving software, and calculate whether the beam irradiated onto each digital micro-mirror at each moment is an effective beam that needs to be placed into the illumination field of view, and determine each digital micro-mirror in each The flipping speed and flip angle required at a time;

Step 3: Turn on the illumination source 1, and the control board sends a flip instruction to each digital micromirror, and each digital micromirror flips to a desired angle after receiving the flip instruction;

Step 4: As the exposure progresses, the control board sends an instruction to each digital micro-mirror at each moment, and each digital micro-mirror changes the angle of the flipping immediately after receiving the instruction;

Step 5: After the exposure is completed, the micromirror array 4 is restored to the initial state.

The present invention has been described in the above embodiments, but the invention is not limited to the embodiments described above, and it is obvious that those skilled in the art can make various modifications and changes to the invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of the invention as claimed.

Claims

An exposure system for semiconductor lithography, comprising an illumination source arranged in sequence along an optical path, a collimation beam expanding system, a light homogenizing unit, a mirror and a relay unit, and a light beam emitted from the relay unit is used for illumination A mask, characterized in that the exposure system further comprises:

a micromirror array disposed between the light homogenizing unit and the mirror;

a light absorbing device located outside the light path

The micromirror array reflects an effective light beam from the illumination beam from the leveling unit onto the mirror and transmits to the relay unit for illuminating the mask, from the leveling unit The stray light beam in the illumination beam is reflected to the light absorbing device.
The exposure system for semiconductor lithography according to claim 1, wherein said micromirror array comprises a control board and a digital micromirror, said digital micromirror being a microelectromechanical system having a micromirror externally The chip is connected to the control board.
The exposure system for semiconductor lithography according to claim 2, wherein said control board is provided with driving software for inputting a parameter to adjust a reflection angle of each of said digital micromirrors during parameter exposure With flip speed.
The exposure system for semiconductor lithography according to claim 2, wherein the number of the digital micromirrors is more than one thousand, and the number of the digital micromirrors increases correspondingly with an increase in exposure precision.
The exposure system for semiconductor lithography according to claim 2, wherein the control board controls the flip speed of the micro mirror according to the moving speed of the mask, and determines the exposure according to the exposure dose set at the time of exposure. The angle of reflection of each micromirror at a time.
The exposure system for semiconductor photolithography according to claim 1, wherein the mask is moved as exposure progresses during exposure.
An exposure method using the exposure system according to any one of claims 1 to 6, characterized in that it comprises the following steps:

Step 1: determining the parameters of the exposure field of view according to the process precision and the pattern of the mask;

Step 2: input the parameters of the exposure field into the driving software of the control board of the micro mirror array, and calculate the turning speed and the flip angle of each digital micro mirror in the micro mirror array at each moment;

Step 3: Turn on the illumination source, and the control board sends a flip instruction to each digital micromirror, and each digital micromirror flips to a corresponding angle after receiving the flip instruction;

Step 4: As the exposure progresses, the control board sends an instruction to each digital micro-mirror at each moment, and each digital micro-mirror changes the angle of the flip after receiving the instruction;

Step 5: After the exposure is completed, the micro mirror array is restored to the initial state.
The exposure method according to claim 7, wherein the parameter of the exposure field of view in step 1 refers to an area, a range, and an exposure dose of the exposure field of view.
The exposure method according to claim 7, wherein the response time of the digital micromirror is proportional to the time when the light source is scanned on the mask, and the response time of the digital micromirror is equal to the control card to the digital micromirror. The sum of the time when the flip command is sent, the time the digital micromirror receives the command, and the time the digital micromirror makes the flip action.
The exposure method according to claim 9, wherein the response time of the digital micromirror is S DMD , and
Where S WS is the time when the light source is scanned on the mask, M po is the objective magnification, and M il is the illumination system magnification.