Exposure control system and control method of direct writing device

Abstract

The present invention discloses an exposure control system and control method of a direct writing device, wherein the control system includes a frequency adjustment circuit, an exposure actuator, a control interface, an exposure file, an output interface, and an exposure status register; the frequency adjustment circuit is used to generate a clock of a specific frequency required for exposure according to the requirements of exposure parameters, as a clock source for the exposure actuator; the exposure file is a pre-generated file, and the exposure file is divided into a main field, a sub-field, and a shape as a hierarchy to form a single or multiple files, and the file contains all the instruction codes for parameter operation and exposure control required for the exposure circuit pattern; the exposure actuator is used to accept the control of the control interface and run the exposure file to complete the exposure of the pattern. The present invention can not only realize the continuous execution of the exposure process and improve the exposure efficiency, but also ensure high-precision control of the exposure time.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of semiconductor manufacturing, and in particular to an exposure control system and a control method for a direct writing device. Background Art

[0002] In the field of semiconductor manufacturing, direct writing equipment controls the deflection and on-off of energy beams (light, electrons, ions, etc.) to engrave patterns on the photoresist above the substrate material, and then goes through subsequent etching, deposition, and development processes to achieve the production of circuit structures.

[0003] Direct writing equipment has no mask template. Its working process is to expose the pattern in the input layout design file. The exposure control of the pattern is generally performed by a pattern generator. Taking electron beam exposure as an example, the specific exposure process is:

[0004] The exposure time of an exposure point in the shape is calculated in advance according to the characteristics, thickness and beam size of the photoresist. Then, when exposing a shape, the following steps are performed in sequence:

[0005] 1. Control the deflection amplifier circuit to deflect the electron beam to the starting point of the shape;

[0006] 2. Open the beam gate to keep the electron beam on;

[0007] 3. Stay at one exposure point for the exposure time;

[0008] 4. Control the deflection amplifier circuit to deflect the electron beam to the next exposure point;

[0009] 5. Repeat steps 3-4 in sequence until a shape is completed;

[0010] 6. Close the brake.

[0011] By moving the workpiece stage and repeating the exposure of all shapes, the exposure of the design layout can be completed.

[0012] From the above process, we can see that the continuity of the exposure process determines the exposure efficiency, and the control accuracy of the exposure time determines the exposure quality.

[0013] In the prior art, such as in the patent application (utility model name: pattern generator; authorization announcement: CN 2598023Y), a pattern generator is disclosed, which is used for exposure machines of charged particles such as electron beams and ion beams, and belongs to the pattern generator hardware of the exposure machine. This utility model provides a pattern generator for exposure machines with fast operation speed, simple interface, low power consumption and diverse functions. It uses a high-speed digital signal processor as the core and realizes communication with the host computer through a universal serial bus interface. The pattern generator can not only meet the exposure format with triangles, rectangles and trapezoids as basic exposure unit patterns, but also adds circles and rings as basic exposure unit patterns, solving the defects in speed and accuracy of integrated grating device processing. The utility model is composed of an interface circuit, a dual-port memory circuit, a digital signal processor circuit, a digital-to-analog conversion circuit, an exposure / mark detection control circuit, a mark detection circuit, a final exposure data register unit and a beam gate control circuit connected to each other.

[0014] The exposure control process in the prior art is: the digital signal processor sets the scanning starting point coordinates, scanning step length and scanning step number in the final exposure data register circuit, selects the scanning frequency, and then the digital signal processor controls the final exposure data register circuit to perform the coordinate point update process until the scanning step number counter is cleared. The above process can perform the scanning of a line segment. To complete the exposure of the pattern, the above process needs to be repeated.

[0015] From the above process, it can be seen that the scanning in the prior art is based on line segments, and the exposure of the entire pattern requires the continuous intervention of the digital signal processor. The exposure process is discontinuous and the exposure efficiency is difficult to improve. In addition, the exposure dose control is achieved by dividing a reference clock, which can only divide into several specific frequencies. The degree of subdivision is not enough, and the exposure dose cannot be accurately controlled. Summary of the invention

[0016] The technical problem to be solved by the present invention is: in view of the technical problems existing in the prior art, the present invention provides an exposure control system and a control method for a direct writing device which can realize continuous execution of the exposure process and improve exposure efficiency.

[0017] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0018] An exposure control system for a direct writing device, comprising a frequency adjustment circuit, an exposure actuator, a control interface, an exposure file, an output interface and an exposure status register;

[0019] The frequency adjustment circuit is used to generate a clock with a specific frequency required for exposure according to the requirements of the exposure parameters, as a clock source for the exposure actuator;

[0020] The control interface is used to control the behavior of the exposure actuator;

[0021] The exposure file is a pre-generated file; the exposure file is divided into main field, sub-field and shape levels to form a single or multiple files, and the file contains all the instruction codes for parameter operation and exposure control required for exposing the circuit pattern;

[0022] The output interface is used to control the controlled adjustable components in the direct writing device;

[0023] The exposure status register includes one or more of exposure frequency, step value, number of steps, resolution, instruction pointer and instruction fetch flag status;

[0024] The exposure executor is used to accept the control of the control interface and run the exposure file to complete the exposure of the pattern.

[0025] The present invention also discloses a control method for an exposure control system based on the direct writing device as described above, comprising the steps of:

[0026] The frequency adjustment circuit generates a clock of a specific frequency required for exposure according to the requirements of the exposure parameters, which serves as a clock source for the exposure actuator;

[0027] The exposure file is a pre-generated file; the exposure file is divided into main field, sub-field and shape levels to form a single or multiple files, and the file contains all the instruction codes for parameter operation and exposure control required for exposing the circuit pattern;

[0028] The exposure executor is controlled by the control interface and runs the exposure file to complete the exposure of the pattern.

[0029] Preferably, the clock source of the frequency adjustment circuit is generated by an external independent oscillator or by the inside of the chip; the output frequency of the frequency adjustment circuit is equal to the multiplication and division of the clock source frequency; select a suitable clock source frequency, calculate the multiplication factor and the division factor according to the value of the exposure frequency in the exposure status register, and obtain the required output frequency.

[0030] Preferably, the instruction code in the exposure file includes instructions and additional parameters; the instructions include one or more combinations of no operation, step unit setting, exposure frequency setting, main field jump X instruction, main field jump Y instruction, sub-field jump X instruction, sub-field jump Y instruction, dual-axis step XY instruction and beam gate control instruction.

[0031] Preferably, the exposure file generates instruction codes with the basic shape as the smallest unit; when the basic shape is a trapezoid, firstly, an exposure frequency setting instruction is generated; then, a no-operation instruction is inserted, and a number of cycles are waited for the frequency to be stable; next, if a new subfield is to be exposed, a main field jump X instruction and a main field jump Y instruction are generated to position the beam to the subfield position; next, a subfield jump X instruction and a subfield jump Y instruction are generated to position the beam to the starting point of the shape; next, a beam gate control instruction is generated to open the beam gate; next, a dual-axis step XY instruction is generated to expose the first line segment of the trapezoid; the dual-axis step XY instruction is repeatedly generated until the trapezoid exposure is completed; finally, a beam gate control instruction is generated to close the beam gate.

[0032] Preferably, the exposure executor is controlled by the control interface and works according to the input clock drive. In the first clock cycle, if the instruction fetch flag is set, the instruction code pointed to by the address in the instruction address register is fetched into the register, and then the instruction address register is incremented and the instruction fetch flag is cleared. The instruction is executed in the second clock cycle and the instruction fetch flag is set according to the specific situation. The above steps are then repeated until the instruction execution is completed or the control interface issues a stop or reset command.

[0033] Preferably, when a no-operation instruction is executed, no operation is performed and the instruction fetch flag is set;

[0034] When executing the step unit setting instruction, the exposure frequency register is set and the instruction fetch flag is set;

[0035] When the main field jump X instruction is executed, the deflection coordinate value is written into the main field X direction DAC and the fetch flag is set;

[0036] When executing the main field jump Y instruction, the deflection coordinate value is written into the main field Y direction DAC and the fetch flag is set;

[0037] When executing the subfield jump X instruction, the deflection coordinate value is written into the subfield X direction DAC and the fetch flag is set;

[0038] When executing the subfield jump Y instruction, the deflection coordinate value is written into the subfield Y direction DAC and the fetch flag is set;

[0039] When executing the dual-axis stepping XY instruction, the DAC values ​​in the subfield X direction and Y direction are incremented by the corresponding step value, the step count register is decremented, and it is determined whether the step count register is zero. If it is zero, the instruction fetch flag is set;

[0040] When the beam gate control instruction is executed, the beam gate is opened or closed according to the parameters in the instruction code, and the instruction fetch flag is set.

[0041] Compared with the prior art, the advantages of the present invention are:

[0042] The exposure process of the present invention is based on the exposure file as a unit, and the exposure executor continuously executes the instruction code in the exposure file until it is completed, without the intervention of other processors in the middle, thereby improving the efficiency of exposure. The present invention transforms the control of exposure time into the control of the operating frequency of the exposure executor, and adopts a control method of frequency doubling and frequency division, which can achieve a higher level of exposure time control compared to a single frequency division method; at the same time, no exposure time counter is required during the exposure process, which simplifies the structure of exposure time control and can achieve a higher operating frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a block diagram of an exposure control system in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0045] like Figure 1 As shown, the exposure control system of the direct writing device according to the embodiment of the present invention includes a frequency adjustment circuit, an exposure actuator, a control interface, an exposure file module, an output interface and an exposure status register;

[0046] The frequency adjustment circuit is used to generate a clock with a specific frequency required for exposure according to the requirements of the exposure parameters, as a clock source for the exposure actuator;

[0047] The control interface is used to control the behavior of the exposure actuator; the output interface is used to control the controlled adjustable components in the direct writing device;

[0048] The exposure status register includes multiple status variables such as exposure frequency, step value, number of steps, resolution, instruction pointer and instruction fetch flag.

[0049] The exposure file is a pre-generated file, which consists of a sequence of instruction codes. The instruction codes in the exposure file include instructions and additional parameters. The instruction types include a combination of exposure frequency setting, step unit setting, no operation, main field / sub-field deflection value setting, sub-field stepping and beam gate control, etc. When the sub-field stepping instruction is executed, the exposure point coordinates will be updated in sequence, that is, the exposure time of a single exposure point is equal to the execution cycle of the instruction. The exposure file is divided into main field, sub-field and shape levels to form a single or multiple files. The file contains all the instruction codes for parameter operation and exposure control required for exposing the circuit pattern. After these instruction codes are executed continuously, the exposure of the pattern can be completed.

[0050] The exposure executor is used to accept the control of the control interface and execute reset, run and stop operations. When running, it runs the exposure file to complete the exposure of the pattern.

[0051] The exposure process of the present invention is based on an exposure file as a unit, and the exposure executor continuously executes the instruction codes in the exposure file until completion, without the need for intervention of other processors in the middle, thereby improving the exposure efficiency.

[0052] In a specific embodiment, the control system is implemented on an FPGA; the frequency adjustment circuit is implemented based on PLL, and the clock source of PLL can be an external independent oscillator or generated inside the chip; a frequency division circuit is inserted into the PLL feedback loop to achieve PLL output frequency multiplication, and a frequency division circuit is added after the PLL output frequency, so that the output frequency of the frequency adjustment circuit can be equal to the multiplication and division of the clock source frequency; a suitable clock source frequency is selected, and the multiplication coefficient and the division coefficient are calculated according to the value of the exposure frequency in the exposure status register to obtain the required output frequency. Because the multiplication coefficient and the division coefficient are both integers, the obtained output frequency may not be completely consistent with the required output frequency. In this case, the multiplication and division coefficient pair whose actual output frequency is closest to the required output frequency shall prevail. Of course, in other embodiments, the frequency adjustment circuit can also be implemented based on a voltage-controlled oscillator.

[0053] The present invention converts the control of exposure time into the control of the operating frequency of the exposure actuator, and adopts a control method of frequency doubling and frequency division. Compared with the single frequency division method, it can achieve more highly subdivided exposure time control; at the same time, no exposure time counter is required during the exposure process, which simplifies the structure of exposure time control and can achieve a higher operating frequency.

[0054] In a specific embodiment, the control interface sends a control instruction to the exposure actuator by hard wiring or communication. When the exposure actuator performs a reset operation, the exposure status register and the output interface of the exposure actuator are set to the initial value; when performing a run operation, the exposure actuator reads the instruction code in the exposure file according to the value of the instruction pointer register to execute the exposure process. During the execution of the instruction, the exposure actuator will operate the exposure status register and the output interface according to the different instruction codes; when performing a stop operation, the operation of the exposure actuator will be suspended.

[0055] In a specific embodiment, the instruction code in the exposure file is aligned to 4 bytes, wherein the instruction occupies 1 byte, and the parameter and padding part occupies 3 bytes. The instruction code includes a no-op, a step unit setting, an exposure frequency setting, a main field jump X instruction, a main field jump Y instruction, a sub-field jump X instruction, a sub-field jump Y instruction, a dual-axis step XY instruction, and a beam gate control instruction, wherein:

[0056] The no-operation instruction code contains a no-operation instruction;

[0057] The step unit setting instruction code includes a step unit setting instruction and a step value;

[0058] The exposure frequency setting instruction code includes an exposure frequency setting instruction and an exposure frequency;

[0059] The home jump X instruction code includes the home jump X instruction and the deflection coordinate value;

[0060] The home jump Y instruction code includes the home jump Y instruction and the deflection coordinate value;

[0061] The subfield jump X instruction code includes a subfield jump X instruction and a deflection coordinate value;

[0062] The subfield jump Y instruction code includes a subfield jump Y instruction and a deflection coordinate value;

[0063] The dual-axis stepping XY instruction code includes dual-axis stepping XY instruction, XY stepping amount and stepping times;

[0064] The beam gate control instruction code includes a beam gate control instruction and a beam gate state.

[0065] The exposure file generates instruction codes with the basic shape as the smallest unit. Taking the trapezoid as an example, the first step is to generate the exposure frequency setting instruction (if it needs to be changed); then insert the no-operation instruction and wait for several cycles until the frequency stabilizes; next, if it is to expose a new subfield, generate the main field jump X instruction and the main field jump Y instruction to position the beam to the subfield position; next, generate the subfield jump X instruction and the subfield jump Y instruction to position the beam to the starting point of the shape; next, generate the beam gate control instruction to open the beam gate; next, generate the dual-axis step XY instruction to expose the first line segment of the trapezoid; repeatedly generate the dual-axis step XY instruction until the trapezoid exposure is completed; finally, generate the beam gate control instruction to close the beam gate.

[0066] In a specific embodiment, the output interface controls the controlled adjustable components in the direct writing device, including a main field deflection amplifier, a sub-field deflection amplifier, a beam gate, a centering coil, a focusing coil, an stigmator, and the like.

[0067] In a specific embodiment, the exposure executor is controlled by the control interface and works according to the input clock drive. In the first clock cycle, if the instruction fetch flag is set, the instruction code pointed to by the address in the instruction address register is fetched into the register, and then the instruction address register is incremented, the instruction fetch flag is cleared, and the instruction is executed in the second clock cycle, and the instruction fetch flag is set according to the specific situation. Then the above steps are repeated until the instruction execution is completed or the control interface issues a stop or reset command.

[0068] The specific instruction execution process is:

[0069] When executing a no-operation instruction, no operation is performed and the instruction fetch flag is set;

[0070] When executing the step unit setting instruction, the exposure frequency register is set and the instruction fetch flag is set;

[0071] When the main field jump X instruction is executed, the deflection coordinate value is written into the main field X direction DAC and the fetch flag is set;

[0072] When executing the main field jump Y instruction, the deflection coordinate value is written into the main field Y direction DAC and the fetch flag is set;

[0073] When executing the subfield jump X instruction, the deflection coordinate value is written into the subfield X direction DAC and the fetch flag is set;

[0074] When executing the subfield jump Y instruction, the deflection coordinate value is written into the subfield Y direction DAC and the fetch flag is set;

[0075] When executing the dual-axis stepping XY instruction, the DAC values ​​in the subfield X direction and Y direction are incremented by the corresponding step value, the step count register is decremented, and it is determined whether the step count register is zero. If it is zero, the instruction fetch flag is set;

[0076] When the beam gate control instruction is executed, the beam gate is opened or closed according to the parameters in the instruction code, and the instruction fetch flag is set.

[0077] The embodiment of the present invention further discloses a control method of an exposure control system based on the direct writing device as described above, comprising the steps of:

[0078] The frequency adjustment circuit generates a clock of a specific frequency required for exposure according to the requirements of the exposure parameters, which serves as the clock source of the exposure actuator;

[0079] The exposure file is a pre-generated file; the exposure file is divided into main field, sub-field and shape levels to form a single or multiple files, and the file contains all the instruction codes for parameter operation and exposure control required for exposing the circuit pattern;

[0080] The exposure executor is controlled by the control interface and runs the exposure file to complete the exposure of the pattern.

[0081] The control method of the present invention is implemented based on the control system as described above, and also has the advantages described above for the control system. It can not only realize the continuous execution of the exposure process and improve the exposure efficiency, but also ensure high-precision control of the exposure time.

[0082] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. An exposure control system for a direct writing device, characterized in that: It includes a frequency adjustment circuit, an exposure actuator, a control interface, an exposure file, an output interface and an exposure status register; The frequency adjustment circuit is used to generate a clock with a specific frequency required for exposure according to the requirements of the exposure parameters, as a clock source for the exposure actuator; The control interface is used to control the behavior of the exposure actuator; The exposure file is a pre-generated file; The exposure file is divided into main field, sub-field and shape levels to form a single or multiple files. The file contains all the instruction codes for parameter operation and exposure control required for exposing the circuit pattern. The output interface is used to control the controlled adjustable components in the direct writing device; The exposure status register includes one or more of exposure frequency, step value, number of steps, resolution, instruction pointer and instruction fetch flag status; The exposure executor is used to accept the control of the control interface and run the exposure file to complete the exposure of the pattern.

2. A control method for an exposure control system based on the direct writing device according to claim 1, characterized in that: Includes steps: The frequency adjustment circuit generates a clock of a specific frequency required for exposure according to the requirements of the exposure parameters, which serves as a clock source for the exposure actuator; The exposure file is a pre-generated file; The exposure file is divided into main field, sub-field and shape levels to form a single or multiple files. The file contains all the instruction codes for parameter operation and exposure control required for exposing the circuit pattern. The exposure executor is controlled by the control interface and runs the exposure file to complete the exposure of the pattern.

3. The control method according to claim 2, characterized in that: The clock source of the frequency adjustment circuit is generated by an external independent oscillator or inside the chip; the output frequency of the frequency adjustment circuit is equal to the multiplication and division of the clock source frequency; select the appropriate clock source frequency, calculate the multiplication factor and the division factor according to the value of the exposure frequency in the exposure status register, and obtain the required output frequency.

4. The control method according to claim 2 or 3, characterized in that: The instruction code in the exposure file includes instructions and additional parameters; the instructions include one or more combinations of no operation, step unit setting, exposure frequency setting, main field jump X instruction, main field jump Y instruction, sub-field jump X instruction, sub-field jump Y instruction, dual-axis step XY instruction and beam gate control instruction.

5. The control method according to claim 4, characterized in that: The exposure file generates instruction codes with the basic shape as the smallest unit; when the basic shape is a trapezoid, the exposure frequency setting instruction is generated first; then a no-operation instruction is inserted, and several cycles are waited for the frequency to stabilize; next, if a new subfield is to be exposed, a main field jump X instruction and a main field jump Y instruction are generated to position the beam to the subfield position; next, a subfield jump X instruction and a subfield jump Y instruction are generated to position the beam to the starting point of the shape; next, a beam gate control instruction is generated to open the beam gate; next, a dual-axis step XY instruction is generated to expose the first line segment of the trapezoid; the dual-axis step XY instruction is repeatedly generated until the trapezoid exposure is completed; finally, a beam gate control instruction is generated to close the beam gate.

6. The control method according to claim 2 or 3, characterized in that: The exposure executor is controlled by the control interface and works according to the input clock. In the first clock cycle, if the instruction fetch flag is set, the instruction code pointed to by the address in the instruction address register is fetched into the register, and then the instruction address register is incremented and the instruction fetch flag is cleared. The instruction is executed in the second clock cycle and the instruction fetch flag is set according to the specific situation. Then the above steps are repeated until the instruction execution is completed or the control interface issues a stop or reset command.

7. The control method according to claim 6, characterized in that: When executing a no-operation instruction, no operation is performed and the instruction fetch flag is set; When executing the step unit setting instruction, the exposure frequency register is set and the instruction fetch flag is set; When the main field jump X instruction is executed, the deflection coordinate value is written into the main field X direction DAC and the fetch flag is set; When executing the main field jump Y instruction, the deflection coordinate value is written into the main field Y direction DAC and the fetch flag is set; When executing the subfield jump X instruction, the deflection coordinate value is written into the subfield X direction DAC and the fetch flag is set; When executing the subfield jump Y instruction, the deflection coordinate value is written into the subfield Y direction DAC and the fetch flag is set; When executing the dual-axis stepping XY instruction, the DAC values ​​in the subfield X direction and Y direction are incremented by the corresponding step value, the step count register is decremented, and it is determined whether the step count register is zero. If it is zero, the instruction fetch flag is set; When the beam gate control instruction is executed, the beam gate is opened or closed according to the parameters in the instruction code, and the instruction fetch flag is set.

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