A free pupil illumination control system for a lithography machine

Abstract

A free-pupil illumination control system for a lithography machine includes: an operation center, a control center, a micromirror array control unit, a micromirror array angular position monitoring unit, and a micromirror array. The operation center obtains the target illumination mode of the lithography machine through a host computer, calculates the target angular position and initial driving voltage of each micromirror based on the target illumination mode, and sends the target angular position and initial driving voltage to the control center. The control center sends the initial driving voltage of each micromirror to the micromirror array control unit to drive each micromirror to rotate. The micromirror array angular position monitoring unit monitors the angular position of each micromirror and feeds back the measured angular position to the control center. The control center also performs closed-loop control of each micromirror based on the measured angular position until each micromirror achieves the target illumination mode. This control system is capable of high-speed, synchronous, closed-loop control of multiple micromirrors, providing a precise illumination mode.

Description

Technical Field

[0001] The present invention relates to the technical field of photolithography machines, and in particular to a free pupil illumination control system for a photolithography machine. Background Art

[0002] With the advancement of semiconductor technology, the performance requirements for lithography machines are becoming increasingly stringent. The Rayleigh criterion, which is the basis for improving lithography machine resolution, is: R = k_1·λ / NA, where R is the resolution, k1 is the process factor, λ is the exposure wavelength, and NA is the numerical aperture of the lithography machine system. The formula shows that there are three ways to improve lithography machine resolution: 1. Reducing the lithography machine exposure wavelength λ; 2. Increasing the lithography machine system numerical aperture NA; and 3. Reducing the process factor k1.

[0003] Lithography systems also require resolution within a certain defocus range. Specifically, the greater the depth of focus (DOF), the more consistent the resolution across different etch depths on the wafer. DOF = k²·λ / NA², where DOF is the depth of focus, k² is the process factor, λ is the exposure wavelength, and NA is the numerical aperture of the lithography system. The resolution and depth of focus formula shows that increasing the system's numerical aperture (NA) improves the lithography system's resolution, but the system's depth of focus decreases dramatically.

[0004] To resolve this contradiction, off-axis illumination (OAI) within resolution enhancement technology (RET) can simultaneously improve system resolution and increase depth of focus. It is also the easiest RET technology to implement. Currently, the most commonly used off-axis illumination method utilizes a beam shaping element (DOE) to achieve various illumination modes, including traditional, annular, secondary, and quaternary. However, because a single DOE diffraction element can only implement one type of illumination mode, using DOE off-axis illumination limits the flexibility of switching between different illumination modes within a lithography tool.

[0005] To address the above issues, free-pupil illumination systems that can achieve arbitrary illumination modes are gradually being used in lithography machines at 28nm and below nodes. The micromirror array (MMA) in the free-pupil illumination system contains thousands of micromirrors. How to control these numerous micromirrors at high speed and synchronously is a key issue in the free-pupil illumination system. Summary of the Invention

[0006] In response to the technical problem of how to achieve high-speed and synchronous control of the free pupil illumination system in a lithography machine, the present application provides a free pupil illumination control system for a lithography machine, which can perform high-speed and synchronous control of the micromirrors in the micromirror array, and can also perform closed-loop control of the micromirrors to provide a precise illumination mode for the lithography machine.

[0007] The technical solutions provided by the present invention are as follows:

[0008] The present invention provides a free pupil illumination control system for a lithography machine, the free pupil illumination control system comprising: a computing center, a control center, a micro-mirror array control unit, a micro-mirror array angular position monitoring unit, and a micro-mirror array; the micro-mirror array comprises a plurality of micro-mirrors, and different illumination modes are provided to the lithography machine by controlling each micro-mirror to rotate to different angular positions;

[0009] The operation center is connected to the host computer of the lithography machine and the control center via Ethernet communication, and the micro-mirror array control unit and the micro-mirror array angular position monitoring unit are connected to the control center via optical fiber communication.

[0010] The operation center obtains the target illumination mode of the lithography machine through the host computer, calculates the target angular position and initial driving voltage of each micro-mirror according to the target illumination mode, and sends the target angular position and initial driving voltage of each micro-mirror to the control center;

[0011] The control center sends the initial driving voltage of each micro-mirror to the micro-mirror array control unit to drive each micro-mirror to rotate;

[0012] The micro-mirror array angular position monitoring unit is used to monitor the angular position of each micro-mirror and feed back the monitored measured angular position to the control center;

[0013] The control center is further configured to perform closed-loop control on each micro-reflector according to the measured angular position until each micro-reflector achieves a target illumination mode.

[0014] Further preferably, the control center includes a first DSP unit and a first FPGA unit;

[0015] The first DSP unit is connected to the operation center via Ethernet communication, and receives the target angular position and initial driving voltage sent by the operation center;

[0016] The first DSP unit is connected to the first FPGA unit via SRIO communication, and sends the received initial driving voltage of each micro-mirror to the first FPGA unit;

[0017] The first FPGA unit is connected to the micro-mirror array control unit and the micro-mirror array angular position monitoring unit for optical fiber communication, and the first FPGA unit sends an initial driving voltage of each micro-mirror to the micro-mirror array control unit and sends an angular position detection command to the micro-mirror array angular position monitoring unit;

[0018] The first FPGA unit is further configured to send the measured angular position fed back by the micro-mirror array angular position monitoring unit to the first DSP unit;

[0019] The first DSP unit is further configured to calculate a current driving voltage according to the measured angular position, and to correct the current driving voltage according to the initial driving voltage, so as to perform closed-loop control on each micro-mirror through the corrected driving voltage.

[0020] Further preferably, the micro-mirror array includes 64*64 micro-mirrors, and each micro-mirror is controlled by 4 electrodes.

[0021] Further preferably, the first DSP unit integrates two DSP processors, each DSP processor has 8 DSP cores, and each DSP core performs closed-loop control on 256 micro-mirrors.

[0022] Further preferably, the first DSP unit distributes the received measured angular position data of 64*64 micro-mirrors evenly to each DSP core, so that the 16 DSP cores synchronously perform closed-loop control on the micro-mirrors.

[0023] Further preferably, the micro-mirror array control unit includes: a micro-mirror drive control board, a second DSP unit and a second FPGA unit;

[0024] The micro-mirror drive control board integrates 64 ASICs, with each of the four ASICs being controlled via four chip selects (CS) and one SPI, and each ASIC driving 64 micro-mirrors.

[0025] The second DSP unit is used to receive the driving voltage sent by the first FPGA unit and write the driving voltage into the second FPGA unit;

[0026] The second FPGA unit sends the driving voltage to the 16 ASICs synchronously through the 16-way SPI and the chip select CS according to the driving voltage loading command.

[0027] Further preferably, the second FPGA unit stores the received driving voltage synchronously into 16 BRAMs according to the address, each BRAM corresponds to one SPI, and the memory of each BRAM corresponds to 4 chip select CSs and is divided into 4 memory areas.

[0028] Further preferably, the micro-mirror array angular position monitoring unit comprises: an angular position monitoring control board, a light spot array generating component and an angular position detecting component;

[0029] The angular position monitoring control board includes a third FPGA unit and a third DSP unit;

[0030] After receiving the angular position detection command issued by the first FPGA unit, the third FPGA unit controls the light spot array generating component to generate a focused light spot and irradiate the focused light spot onto the micro-mirrors in the micro-mirror array, controls the angular position detection component to monitor the angular position of the light spot reflected by the micro-mirrors, and sends the measured angular position monitored by the angular position detection component to the third DSP unit;

[0031] The third DSP unit is used to feed back the measured angular position to the first FPGA unit.

[0032] Through the free pupil illumination control system of the lithography machine provided by the present invention, the operation center generates the target angular position and initial driving voltage of each micromirror through the target illumination mode, and the control center sends the received initial driving voltage to the micromirror array control unit to control the rotation of each micromirror. At the same time, the control center also performs closed-loop control of the micromirrors according to the angular position feedback from the micromirror array angular position monitoring unit until the micromirror array achieves the target illumination mode. Furthermore, the micromirror array control unit controls 64*64 micromirrors at high speed and synchronously through 16-channel SPI and 64 ASICs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the schematic diagram of the free pupil illumination control system for the lithography machine;

[0034] Figure 2 This is the schematic diagram of the closed-loop control of the micromirror;

[0035] Figure 3 This is the schematic diagram of the micro-mirror drive control board;

[0036] Figure 4 This is the schematic diagram of the FPGA in the micro-mirror array control unit;

[0037] Figure 5 This is the principle diagram of the optical path for angular position monitoring. DETAILED DESCRIPTION

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without inventive work.

[0039] The present invention provides a free pupil illumination control system for a lithography machine, which aims to solve the technical problem of free pupil illumination control in a lithography machine. The principle diagram thereof is shown in FIG. Figure 1 As shown, it includes: an operation center 100 , a control center 200 , a micro-mirror array control unit 300 , a micro-mirror array angular position monitoring unit 400 and a micro-mirror array 500 .

[0040] The micromirror array 500 is the core component of the free pupil illumination system for photolithography machines. Through the continuous adjustment of the two-dimensional angle of the micromirror array, arbitrary illumination modes can be achieved. The micromirror array 500 includes several micromirrors. The control system provided by the present invention controls the rotation of each micromirror to different angular positions to provide different illumination modes for the photolithography machine. The basic control concept is as follows:

[0041] The operation center 100 is connected to the host computer of the lithography machine and the control center 200 via Ethernet communication, and the micro-mirror array control unit 300 and the micro-mirror array angular position monitoring unit 400 are connected to the control center 200 via optical fiber communication.

[0042] The operation center 100 obtains the target illumination mode of the lithography machine through the host computer, calculates the target angular position and initial driving voltage of each micro-mirror according to the target illumination mode, and sends the target angular position and initial driving voltage of each micro-mirror to the control center 200;

[0043] The control center 200 sends the initial driving voltage of each micro-mirror to the micro-mirror array control unit 300 to drive each micro-mirror to rotate;

[0044] The micro-mirror array angular position monitoring unit 400 is used to monitor the angular position of each micro-mirror and feed back the measured angular position to the control center 200;

[0045] The control center 200 is further configured to perform closed-loop control on each micro-reflector according to the measured angular position until each micro-reflector achieves a target lighting mode.

[0046] In the present invention, the operation center 100 mainly calculates the target angular position and initial driving voltage of each micro-mirror in the micro-mirror array corresponding to the target illumination mode. For example, the operation center 100 finally obtains the driving voltage and angular position of each micro-mirror in the micro-mirror array corresponding to the target pupil in the overall environment of the lithography machine through the angular position generation algorithm and the calibration results of the relationship between the driving voltage of the micro-mirror array and the coherence factor.

[0047] In addition, the operation center 100 can also realize functions such as measurement and calibration, status monitoring exception handling, and initialization.

[0048] Among them, the measurement and calibration functions include calibration of the basic functions of the micro-mirror array in the overall environment of the lithography machine, detection of the basic functions of each micro-mirror in the micro-mirror array (for example, detection of whether the deflection function of the micro-mirror rotation axis is normal); calibration of the relationship between the driving voltage and the coherence factor of the micro-mirror array, mainly to obtain the relationship between the driving voltage of each micro-mirror in the micro-mirror array and the corresponding position coordinates (size and intensity) of the light spot generated, and also to obtain the relationship between the driving voltage of each micro-mirror in the micro-mirror array and the corresponding rotation angle collected from the angular position monitoring unit.

[0049] Status monitoring exception handling is a mechanism for reporting and handling anomalies that occur during the free pupil illumination process. In addition to monitoring for anomalies during communication, the operation center 100 periodically sends status query commands to the control center 200 to check for anomalies. All detected anomalies are reported layer by layer to the IPC, which issues an alarm and performs exception handling.

[0050] Initialization is that the operation center 100 first sets the initialization parameters of each component, such as the deflection voltage setting of the 4096 scanning points of the light spot array generating component, the scanning interval time setting of the light spot array generating component, the laser used by the light spot array generating component, etc.

[0051] The control center 200 implements closed-loop control of the micro-mirror array 500 based on the driving voltage data and micro-mirror angular position sent by the operation center 100 and the feedback from the micro-mirror angular position monitoring unit 400. The principle diagram of the closed-loop control of the micro-mirror is shown in FIG. Figure 2 shown.

[0052] Specifically, the control center 200 includes a first DSP unit 201 and a first FPGA unit 202;

[0053] The first DSP unit 201 is connected to the operation center 100 via Ethernet communication, and receives the target angular position and initial driving voltage sent by the operation center 100;

[0054] The first DSP unit 201 is connected to the first FPGA unit 202 via SRIO communication, and sends the received initial driving voltage of each micro-mirror to the first FPGA unit 202;

[0055] The first FPGA unit 202 is connected to the micro-mirror array control unit 300 and the micro-mirror array angular position monitoring unit 400 via optical fiber communication. The first FPGA unit 202 sends the initial driving voltage of each micro-mirror to the micro-mirror array control unit 300 and sends the angular position detection command to the micro-mirror array angular position monitoring unit 400.

[0056] The first FPGA unit 202 is further configured to send the measured angular position fed back by the micro-mirror array angular position monitoring unit 400 to the first DSP unit 201;

[0057] The first DSP unit 201 is further configured to calculate a current driving voltage according to the measured angular position, and to correct the current driving voltage according to the initial driving voltage, so as to perform closed-loop control on each micro-mirror using the corrected driving voltage.

[0058] The micro-mirror array of the present invention includes 64*64 micro-mirrors, each of which is controlled by 4 electrodes; further, the first DSP unit 201 integrates two DSP processors of model TMS320C6678, each DSP processor includes an 8-core DSP core with a main frequency of 1.25GHz, so there are a total of 16 DSP cores; each DSP core performs closed-loop control on 256 micro-mirrors; the first DSP unit distributes the received measured angular position data of 64*64 micro-mirrors (that is, 4096 micro-mirrors) evenly to each DSP core, so that the 16 DSP cores synchronously perform closed-loop control on the micro-mirrors.

[0059] In the present invention, the 8 cores of the DSP processor use IPC communication; the DSP processors are interconnected using HyperLink / PCIe@5Gbps; and the DSP processor and the first FPGA unit 202 are interconnected using SRIO x4@5Gbps / lane.

[0060] The micro-mirror array control unit 300 of the present invention includes: a micro-mirror drive control board 301, a second DSP unit 302 and a second FPGA unit 303;

[0061] The micro-mirror drive control board 301 integrates 64 ASICs, each of which is controlled by 4 chip selects CS and one SPI, and each ASIC drives 64 micro-mirrors. The schematic diagram of the micro-mirror drive control board 301 is shown in FIG. Figure 3As shown in the figure, if each ASIC is designed to be controlled by one SPI, a total of 64 SPI controls need to be designed. However, the present invention simplifies the 64 SPIs actually required by the driver chip into 4 chip select CSs*16 SPI data lines through a switching circuit and FPGA design. The chip select CS selects 16 SPIs each time and completes the 64-channel SPI control in 4 times of time sharing.

[0062] The second DSP unit 302 is used to receive the driving voltage sent by the first FPGA unit 202 and write the driving voltage into the second FPGA unit 303;

[0063] The second FPGA unit 303 sends the driving voltage to the 16 ASICs synchronously through the 16-way SPI and the chip select CS according to the driving voltage loading command.

[0064] Furthermore, the second FPGA unit 303 stores the received driving voltage in 16 BRAMs according to the address. Each BRAM corresponds to one SPI channel, and the memory of each BRAM corresponds to 4 chip select CSs and is divided into 4 memory areas. The schematic diagram of the second FPGA unit 303 is shown in FIG. Figure 4 shown.

[0065] The micro-mirror array control unit 300 implements high-speed, synchronous control of 4096 micro-mirrors as follows:

[0066] a) The second DSP unit 302 writes the driving voltage data to the address mapped by the second FPGA unit 303 through the GPMC bus;

[0067] b) The second FPGA unit 303 stores the driving voltage data synchronously into 16 BRAMs according to the address, and each BRAM is divided into 4 memory areas;

[0068] c) After receiving the driving voltage data loading command issued by the second DSP unit 302, the second FPGA unit 303 synchronously sends the driving voltage data to the micro-mirror driving control board 301 through the 16-way SPI and chip select CS, and sends the driving voltage data in four rounds, each round lasting 525 μs. Therefore, the driving voltage data of 16,384 electrodes can be sent within 2,100 μs.

[0069] d) After the driving voltage data is sent, the second FPGA unit 303 synchronously sends the driving voltage loading instruction. After CS1, CS2, CS3, and CS4 are synchronously selected, the 4*16-channel SPI communication synchronization error is less than 100ns.

[0070] Ultimately, the second FPGA unit 303 can complete the issuance of 16,384 electrode drive voltage data within 2,100 μs, and the drive voltage loading synchronization instruction error is less than 100 ns, ultimately achieving high-speed and synchronous control of 4,096 micro-mirrors.

[0071] The micro-mirror array angular position monitoring unit 400 of the present invention comprises: an angular position monitoring control board 401, a light spot array generating component 402 and an angular position detecting component 403. The optical path principle diagram of the angular position monitoring unit 400 is shown in FIG. Figure 5 shown.

[0072] The angular position monitoring control board 401 includes a third FPGA unit 4011 and a third DSP unit 4012;

[0073] After receiving the angular position detection command issued by the first FPGA unit 202, the third FPGA unit 4011 controls the light spot array generating component 402 to generate a focused light spot and irradiate it onto the micro-mirrors in the micro-mirror array 500, controls the angular position detecting component 403 to monitor the angular position of the light spot reflected by the micro-mirrors, and sends the measured angular position monitored by the angular position detecting component 403 to the third DSP unit 4012.

[0074] The third DSP unit 4012 is used to feed back the measured angular position to the first FPGA unit 202 .

[0075] The light spot array generating component 402 consists of a laser, a MEMS galvanometer and an F-θ lens; the laser contains a beam shaping element, so that the light beam incident on the MEMS galvanometer is a collimated circular light spot; the F-θ lens focuses the reflected light of the MEMS galvanometer onto the micro-mirrors in the micro-mirror array, and the light-emitting point of the MEMS galvanometer is located on the front focal plane of the F-θ lens. The reflected light of the MEMS galvanometer at different angles passes through the F-θ lens and becomes parallel to each other, forming a telecentric optical path.

[0076] The angular position detection component 403 consists of a Fourier transform lens, a PSD, and a PSD signal processing circuit. Combined with the electromechanical characteristics of the micro-mirror array, after the PSD completes the conversion of the photoelectric signal, the PSD signal processing circuit converts and amplifies the current signal output by the PSD to facilitate signal capture and calculation by the angular position monitoring control board 401.

[0077] The free pupil illumination control system for a lithography machine provided by the present invention can control 64*64 micro-mirrors at high speed and synchronously, and provide a precise target illumination mode for the lithography machine through closed-loop control of the micro-mirrors.

[0078] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. Those skilled in the art can make several simple deductions, modifications or substitutions based on the concept of the present invention.

Claims

1. A free pupil illumination control system for a lithography machine, characterized in that: The free pupil illumination control system includes: an operation center, a control center, a micro-mirror array control unit, a micro-mirror array angular position monitoring unit, and a micro-mirror array; the micro-mirror array includes a plurality of micro-mirrors, and each micro-mirror is controlled to rotate to a different angular position to provide different illumination modes to the lithography machine; The operation center is connected to the host computer of the lithography machine and the control center via Ethernet communication, and the micro-mirror array control unit and the micro-mirror array angular position monitoring unit are connected to the control center via optical fiber communication. The operation center obtains the target illumination mode of the lithography machine through the host computer, calculates the target angular position and initial driving voltage of each micro-mirror according to the target illumination mode, and sends the target angular position and initial driving voltage of each micro-mirror to the control center; The control center sends the initial driving voltage of each micro-mirror to the micro-mirror array control unit to drive each micro-mirror to rotate; The micro-mirror array angular position monitoring unit is used to monitor the angular position of each micro-mirror and feed back the monitored measured angular position to the control center; The control center is further configured to perform closed-loop control on each micro-mirror according to the measured angular position until each micro-mirror achieves a target illumination mode; The control center includes a first DSP unit and a first FPGA unit; The first DSP unit is connected to the operation center via Ethernet communication, and receives the target angular position and initial driving voltage sent by the operation center; The first DSP unit is connected to the first FPGA unit via SRIO communication, and sends the received initial driving voltage of each micro-mirror to the first FPGA unit; The first FPGA unit is connected to the micro-mirror array control unit and the micro-mirror array angular position monitoring unit for optical fiber communication, and the first FPGA unit sends an initial driving voltage of each micro-mirror to the micro-mirror array control unit and sends an angular position detection command to the micro-mirror array angular position monitoring unit; The first FPGA unit is further configured to send the measured angular position fed back by the micro-mirror array angular position monitoring unit to the first DSP unit; The first DSP unit is further configured to calculate a current driving voltage according to the measured angular position, and to correct the current driving voltage according to the initial driving voltage, so as to perform closed-loop control on each micro-mirror through the corrected driving voltage.

2. The free pupil illumination control system for a lithography machine according to claim 1, wherein: The micro-mirror array includes 64*64 micro-mirrors, and each micro-mirror is controlled by 4 electrodes.

3. The free pupil illumination control system for a lithography machine according to claim 2, wherein: The first DSP unit integrates two DSP processors, each DSP processor has 8 DSP cores, and each DSP core performs closed-loop control on 256 micro-mirrors.

4. The free pupil illumination control system for a lithography machine according to claim 3, wherein: The first DSP unit distributes the received measured angular position data of 64*64 micro-mirrors evenly to each DSP core, so that the 16 DSP cores synchronously perform closed-loop control on the micro-mirrors.

5. The free pupil illumination control system for a lithography machine according to claim 2, wherein: The micro-mirror array control unit includes: a micro-mirror drive control board, a second DSP unit and a second FPGA unit; The micro-mirror drive control board integrates 64 ASICs, with each of the four ASICs being controlled via four chip selects (CS) and one SPI, and each ASIC driving 64 micro-mirrors. The second DSP unit is used to receive the driving voltage sent by the first FPGA unit and write the driving voltage into the second FPGA unit; The second FPGA unit sends the driving voltage to the 16 ASICs synchronously through the 16-way SPI and the chip select CS according to the driving voltage loading command.

6. The free pupil illumination control system for a lithography machine according to claim 5, wherein: The second FPGA unit stores the received driving voltage synchronously in 16 BRAMs according to the address, each BRAM corresponds to one SPI, and the memory of each BRAM corresponds to 4 chip select CSs and is divided into 4 memory areas.

7. The free pupil illumination control system for a lithography machine according to claim 1, wherein: The micro-mirror array angular position monitoring unit comprises: an angular position monitoring control board, a light spot array generating component and an angular position detecting component; The angular position monitoring control board includes a third FPGA unit and a third DSP unit; After receiving the angular position detection command issued by the first FPGA unit, the third FPGA unit controls the light spot array generating component to generate a focused light spot and irradiate the focused light spot onto the micro-mirrors in the micro-mirror array, controls the angular position detection component to monitor the angular position of the light spot reflected by the micro-mirrors, and sends the measured angular position monitored by the angular position detection component to the third DSP unit; The third DSP unit is used to feed back the measured angular position to the first FPGA unit.

Images