Beam detection circuit and beam detection method of electron beam exposure machine

Abstract

The invention discloses a beam detection circuit and a beam detection method of an electron beam exposure machine. The detection circuit comprises a beam controller, a beam correction module, a beam detection module, a first switch module, a second switch module and a third switch module, the beam controller is connected with one end of the beam correction module and one end of the beam detection module. The other end of the beam correction module is connected with one end of the first switch module; the other end of the beam detection module is connected with one end of the second switch module; and the other end of the first switch module and the other end of the second switch module are connected with a Faraday cup of the electron beam exposure machine through the third switch module. According to the invention, parameters of the beam detection module can be automatically calibrated conveniently, the automation degree is high, the exposure cavity does not need to be disassembled and assembled back and forth, the stability is better, the efficiency is higher, and the debugging speed and the stability and accuracy of a machine are improved.

Description

Technical Field

[0001] The present invention mainly relates to the field of electron beam technology, and in particular to a beam current detection circuit and a detection method for an electron beam exposure machine. Background Art

[0002] Electron beam exposure machines are mainly used in the field of micro-nano processing. Its biggest features are extremely high resolution, short production cycle, and easy modification. Therefore, it is widely used in the production of photomasks and X-ray masks. It has become the main means of making masks in the microelectronics industry. On the other hand, the electron beam exposure system can achieve extremely high overlay accuracy using mark detection technology, so it can directly draw on the wafer, that is, directly manufacture devices on the wafer without a mask. Therefore, it is used in the development of new devices and new integrated circuits and the production of small batches of devices and integrated circuits.

[0003] The most important indicators of an exposure machine are the beam size and the beam spot size. The larger the electron beam current, the faster the exposure speed, but the larger the beam spot size, the lower the resolution. The larger the beam current, the faster the exposure speed. Of course, the maximum exposure speed is limited by the scanning frequency, and the beam spot of a large beam current will also be larger. It can be seen that accurately measuring the size of the beam current can achieve better exposure. A good beam current detection system can ensure the high-precision and high-stability operation of the electron beam exposure machine.

[0004] The beam detection is usually placed in the exposure chamber. Since the chamber is sealed, it is very troublesome to disassemble and assemble if there is a problem. Many parameters will change, and re-debugging will waste a lot of time. Especially in the debugging stage of a new machine, if the machine is repeatedly disassembled and assembled due to a certain problem, it will affect the debugging progress and the stability of the machine. Based on the above reasons, a beam detection system with calibration circuits and methods has been developed. Before debugging or starting the machine, you only need to calibrate the circuit first, so that you can accurately control the beam of the exposure machine, which is conducive to ensuring the stability and reliability of the machine. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a beam detection circuit and a detection method for an electron beam exposure machine which can improve the debugging speed and the stability and accuracy of the machine.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is: A beam detection circuit for an electron beam exposure machine comprises a beam controller, a beam correction module, a beam detection module, a first switch module, a second switch module and a third switch module; the beam controller is respectively connected to one end of the beam correction module and one end of the beam detection module; the other end of the beam correction module is connected to one end of the first switch module; the other end of the beam detection module is connected to one end of the second switch module; the other end of the first switch module and the other end of the second switch module are connected to a Faraday cup of the electron beam exposure machine via the third switch module.

[0007] Preferably, the first switch module, the second switch module and the third switch module are all relays.

[0008] Preferably, the beam correction module and the beam detection module are both located in an exposure chamber of an electron beam exposure machine.

[0009] Preferably, the beam correction module comprises a voltage reference circuit, a plurality of resistor voltage divider networks and a plurality of plug-in resistors; the voltage reference circuit is connected to the plurality of resistor voltage divider networks, and the plurality of resistor voltage divider networks are connected to corresponding plug-in resistors.

[0010] Preferably, the inserted resistor is a resistor of 1 GΩ.

[0011] Preferably, the third switch module is connected to a Faraday cup of the electron beam exposure machine through a shielded cable.

[0012] Preferably, the beam controller is connected to a pattern generator.

[0013] The present invention also discloses a detection method based on the beam detection circuit of the electron beam exposure machine as described above, comprising the steps of: The beam controller controls the first switch module to be closed, and the second switch module and the third switch module to be disconnected; The beam correction module generates a correction current, and the beam detection module detects the correction current and converts it into a corresponding voltage and transmits it to the beam controller; The beam controller calculates the detection error of the beam detection module under the corresponding working environment at this time according to the correction current generated by the beam correction module and the detection voltage of the beam detection module, and then obtains the correction parameter; The beam controller controls the first switch module to disconnect and the second switch module to close. The beam detection module detects the beam signal of the Faraday cup and converts it into a voltage signal, which is sent to the beam controller. The beam controller calculates the correction parameters with the beam data measured this time to obtain the actual beam size and intensity information, and completes the correction and detection of the beam.

[0014] Preferably, the correction parameter includes a difference between a correction current generated by the beam correction module and a beam current corresponding to a detection voltage of the beam detection module.

[0015] Preferably, when the difference is within a preset threshold, the actually detected beam data is corrected by the difference; when the difference is not within the preset threshold, it indicates that the beam correction module and / or the beam detection module is abnormal.

[0016] Compared with the prior art, the advantages of the present invention are: The present invention can conveniently calibrate the parameters of the beam detection module through the beam correction module each time the machine is turned on and a new machine is debugged. The present invention has a high degree of automation, does not need to disassemble and assemble the exposure chamber, has better stability, higher efficiency, and improves the debugging speed and the stability and accuracy of the machine. The beam controller can save the correction parameters and measurement parameters each time, and provide long-term stable data for future research and improvement of beam measurement accuracy and electron beam control. The beam correction module uses a voltage source to replace the current source to generate a micro power source, and the structure is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a topological structure diagram of a beam detection circuit of an electron beam exposure machine in an embodiment of the present invention.

[0018] Figure 2 It is a block diagram of the beam correction module in an embodiment of the present invention.

[0019] Figure 3 FIG. 4 is a circuit schematic diagram of a beam correction module in an embodiment of the present invention.

[0020] Legend: 1. Pattern generator; 2. Beam controller; 3. Exposure chamber; 4. Beam correction module; 5. First switch module; 6. Beam detection module; 7. Second switch module; 8. Faraday cup; 9. Shielded cable; 10. Third switch module. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the beam detection circuit of the electron beam exposure machine provided by the embodiment of the present invention includes: a pattern generator 1, a beam controller 2, an exposure chamber 3, a beam correction module 4, a beam detection module 6, a first switch module 5 and a second switch module 7, a Faraday cup 8, a shielded cable 9 and a third switch module 10; One end of the beam controller 2 is connected to one end of the beam correction module 4 and one end of the beam detection module 6 respectively, and the other end of the beam controller 2 is connected to the pattern generator 1; the other end of the beam correction module 4 is connected to one end of the first switch module 5; the other end of the beam detection module 6 is connected to one end of the second switch module 7; the other end of the first switch module 5 and the other end of the second switch module 7 are connected to the Faraday cup 8 of the electron beam exposure machine through the third switch module 10; The beam controller 2 receives the control command (including the beam detection and beam correction signals) sent by the pattern generator 1 to control the first switch module 5 to close and the second switch module 7 to open, and the beam correction module 4 generates multiple current values ​​in the range of 1pA-1nA, which are then converted into corresponding voltages by the beam detection module 6 and transmitted to the beam controller 2. The beam controller 2 calculates the detection error of the beam detection module 6 under the corresponding working environment according to the voltage value detected by the beam detection module 6, and saves the corresponding correction parameters; Then the beam controller 2 controls the first switch module 5 to be disconnected and the second switch module 7 to be closed. The beam detection module 6 detects the beam signal of the Faraday cup 8 and converts it into a voltage signal, which is sent to the beam controller 2. The beam controller 2 calculates the correction parameters and the beam data measured this time to obtain information such as the actual beam size and intensity, and then transmits it to the pattern generator 1 to complete the beam correction and detection, and prepare for the next process (etching).

[0023] The present invention can conveniently calibrate the parameters of the beam detection module 6 through the beam correction module 4 at each startup and new machine debugging, with a high degree of automation, without the need to disassemble and assemble the exposure chamber 3, better stability, higher efficiency, and improved debugging speed and machine stability and accuracy. The beam controller 2 can save each calibration parameter and measurement parameter, providing long-term stable data for future research and improvement of beam measurement accuracy and electron beam control.

[0024] Specifically, the first switch module 5, the second switch module 7 and the third switch module 10 are all relays, which use high isolation impedance and a shielding layer to greatly reduce leakage current and ensure measurement accuracy. The shielding layer can prevent the switch action from affecting the process action inside the exposure chamber 3.

[0025] Specifically, the beam correction module 4 and the beam detection module 6 are both located in the exposure chamber 3, the measurement environment is stable, the noise is small, the micro-current measurement conditions are met, and the beam signal can be measured more accurately.

[0026] In specific applications, the current range detected by the beam detection module is 1pA-500nA. Since it is difficult to generate tiny currents and has high material requirements, especially pA-level currents, it is very likely to leak through various channels. This occurs when the voltage method is used to replace the current during current correction, such as Figure 2 As shown, for example, to generate a 1pA current, a high-precision and high-stability voltage reference source can be designed first, and then a 1V voltage is generated through a voltage-dividing resistor, and then a 1mV voltage is generated through a multi-stage resistor voltage divider, and then a 1GΩ resistor with high precision and high stability is connected to the first switch module 5, and then connected to the beam detection module 6 through the first switch module 5. The above circuit is made into a module and calibrated outside first, so that (1mV / 1GΩ=1pA, by changing this flying resistor, different current values ​​can be obtained) the corresponding current can be generated, and then the beam detection module 6 detects the corresponding current value to calibrate the inherent error of the circuit itself, such as the bias current of the operational amplifier.

[0027] The embodiment of the present invention further provides a detection method based on the beam detection circuit of the electron beam exposure machine as described above, and the specific steps are as follows: First, the third switch module 10 is turned off, and the first switch module 5 and the second switch module 7 are turned on. Then, the beam controller 2 controls the beam correction module 4 to generate a corresponding current signal. Then, the beam detection module 6 measures the corresponding current and records it. The difference between the current signal generated by the beam correction module 4 and the detection current of the beam detection module 6 is written into the corresponding register, and then corresponding compensation is made for subsequent beam measurements. Next, the second switch module 7 and the third switch module 10 are turned on, and the first switch module 5 is turned off, so that normal beam current measurement can be performed. Then, the beam current measured by the beam current detection module 6 is added with corresponding compensation to obtain the real beam current data, which is then sent to the pattern generator 1 for corresponding processing.

[0028] Specifically, Figure 2-Figure 3 As shown in the figure, assuming n=3, there can be three current reference points, assuming that they are 1pA, 100pA and 10nA. Since it is difficult to make a micro current source accurately, a voltage source is used instead of a current source. To generate a 1pA current, for example, first a high-precision reference source generates a 1V voltage, and then a high-precision resistor divides the voltage multiple times to generate a 1mV voltage. The 1mV voltage is connected to the relay through a 1G ohm plug-in resistor R6 (insulation resistance is 10 12Ohms or above), and then connected to the beam detection module through a relay. If the beam detection module 6 measures this current as 1pA, it means that there is no problem with the beam detection module 6; if it is greater than or less than 1pA, it means that the beam detection module 6 measures the current inaccurately; if the difference is within the allowable range, the difference between 1pA and the measured value can be recorded as ΔI, and then the corresponding difference can be added to the corresponding range during actual measurement. For example, the 1pA calibration is in the range of 1pA-100pA, and the measured values ​​within this range are all +ΔI The value obtained can be used as the actual beam current value. If the difference is not within the allowable range, it means that the beam detection module 6 is abnormal or the beam correction module 4 is abnormal, and the two modules should be checked accordingly to ensure that the equipment can work normally.

[0029] 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. A beam current detection circuit for an electron beam exposure machine, characterized in that: The invention comprises a beam controller (2), a beam correction module (4), a beam detection module (6), a first switch module (5), a second switch module (7) and a third switch module (10); the beam controller (2) is respectively connected to one end of the beam correction module (4) and one end of the beam detection module (6); the other end of the beam correction module (4) is connected to one end of the first switch module (5); the other end of the beam detection module (6) is connected to one end of the second switch module (7); the other end of the first switch module (5) and the other end of the second switch module (7) are connected to a Faraday cup (8) of an electron beam exposure machine via the third switch module (10).

2. The beam detection circuit of the electron beam exposure machine according to claim 1, characterized in that: The first switch module (5), the second switch module (7) and the third switch module (10) are all relays.

3. The beam detection circuit of the electron beam exposure machine according to claim 1, characterized in that: The beam correction module (4) and the beam detection module (6) are both located in an exposure chamber (3) of an electron beam exposure machine.

4. The beam detection circuit of the electron beam exposure machine according to claim 1, 2 or 3, characterized in that: The beam correction module (4) comprises a voltage reference circuit, a plurality of resistor voltage divider networks and a plurality of plug-in resistors; the voltage reference circuit is connected to the plurality of resistor voltage divider networks, and the plurality of resistor voltage divider networks are connected to corresponding plug-in resistors.

5. The beam detection circuit of the electron beam exposure machine according to claim 4, characterized in that: The inserted resistor is a 1 GΩ resistor.

6. The beam detection circuit of the electron beam exposure machine according to claim 1, 2 or 3, characterized in that: The third switch module (10) is connected to a Faraday cup (8) of an electron beam exposure machine via a shielded cable (9).

7. The beam detection circuit of the electron beam exposure machine according to claim 1, 2 or 3, characterized in that: The beam controller (2) is connected to a pattern generator (1).

8. A detection method for a beam detection circuit of an electron beam exposure machine according to any one of claims 1 to 7, characterized in that: Includes steps: The beam controller (2) controls the first switch module (5) to be closed, and the second switch module (7) and the third switch module (10) to be disconnected; The beam correction module (4) generates a correction current, and the beam detection module (6) detects the correction current and converts it into a corresponding voltage and transmits it to the beam controller (2); The beam controller (2) calculates the detection error of the beam detection module (6) under the corresponding working environment at this time according to the correction current generated by the beam correction module (4) and the detection voltage of the beam detection module (6), thereby obtaining the correction parameter; The beam controller (2) controls the first switch module (5) to be disconnected and the second switch module (7) to be closed; the beam detection module (6) detects the beam signal of the Faraday cup (8) and converts it into a voltage signal, which is then sent to the beam controller (2); the beam controller (2) calculates the correction parameter and the beam data measured this time to obtain information on the actual beam size and intensity, thereby completing the correction and detection of the beam.

9. The detection method according to claim 8, characterized in that: The correction parameter includes the difference between the correction current generated by the beam correction module (4) and the beam current corresponding to the detection voltage of the beam detection module (6).

10. The detection method according to claim 9, characterized in that: When the difference is within the preset threshold, the actually detected beam data is corrected by the difference; when the difference is not within the preset threshold, it indicates that the beam correction module (4) and / or the beam detection module (6) are abnormal.

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