Device and system for compensating direct-current self-bias voltage of electrostatic chuck

Abstract

The invention discloses a device and a system for compensating the direct current self-bias voltage of an electrostatic chuck, and relates to the technical field of semiconductor processing, the device comprises a radio frequency impedance matcher, a numerical value conversion unit and an analog-to-digital conversion circuit, the radio frequency impedance matcher is used for providing intermediate parameters related to process conditions, and the numerical value conversion unit is used for converting the numerical value into the analog-to-digital conversion circuit; the method has the advantages that the problem that the potential difference between the electrode and the wafer is increased due to the direct-current self-bias can be compensated through a series of operations such as acquiring the intermediate parameters, calculating the direct-current self-bias approximate value and feeding back and compensating the voltage, so that the condition that the wafer adsorption effect of the electrostatic chuck is poor is improved, and the service life of the electrostatic chuck is prolonged. According to different process conditions such as radio frequency power, gas types, gas flow, cavity pressure and the like, intermediate parameters are accurately obtained, an approximate value of the direct-current self-bias voltage is calculated through a function relation, then accurate compensation of the direct-current self-bias voltage is achieved, and the accuracy of the direct-current self-bias voltage is improved. And the performance and the efficiency of semiconductor processing equipment are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, specifically to a device and system for compensating for the DC self-bias of an electrostatic chuck. Background Technology

[0002] In semiconductor plasma etching processes, whether it is an inductively coupled etching device or a capacitively coupled etching device, process gas and a high-frequency electric field are introduced into the reaction chamber. The process gas will be ionized to form plasma. Since the electrons and ions in the plasma move at different speeds in the reaction chamber, the electrons, due to their faster speed, will fall onto the wafer surface in large numbers, forming a DC negative bias.

[0003] The wafer is fixed and adsorbed onto the electrostatic chuck by the electrostatic attraction generated between the DC electrode of the electrostatic chuck and the substrate. The existing unipolar electrostatic chuck contains only one DC electrode, which is supplied with high voltage DC by a unipolar DC power supply. When a DC negative bias voltage is generated on the wafer surface, it will increase the potential difference between the electrode and the wafer, break the balance of electrostatic attraction, and affect the adsorption effect of the electrostatic chuck. To this end, we propose a device and system for compensating for the DC self-bias voltage of the electrostatic chuck. Summary of the Invention

[0004] The purpose of this invention is to provide a device and system for compensating for the DC self-bias of an electrostatic chuck.

[0005] To address the problems mentioned in the background art, the present invention provides the following technical solution: a system for compensating for the DC self-bias of an electrostatic chuck, the system comprising an RF impedance matching unit, a numerical conversion unit, and an analog-to-digital conversion circuit. The RF impedance matching unit is used to provide intermediate parameters related to process conditions, including RF power, gas type, gas flow rate, and cavity pressure. The numerical conversion unit and the analog-to-digital conversion circuit are used to process the intermediate parameters and send them to a computer to view the DC self-bias value. By measuring the DC self-bias value on the wafer surface under different process conditions and fitting the DC self-bias value with the intermediate parameters, a functional relationship of the data is obtained, thereby deriving the relationship between the intermediate parameters and the DC self-bias value on the wafer, and completing the calculation of the DC self-bias value.

[0006] As a further aspect of the present invention, the system further includes a control unit for a unipolar DC power supply, the control unit being used to receive a standard I / O signal of DC self-bias and to control the voltage output terminal of the unipolar DC power supply to perform voltage compensation.

[0007] As a further aspect of the present invention: the radio frequency impedance matching device provides intermediate parameters for different process conditions. After being processed by the numerical conversion unit and the analog-to-digital conversion circuit, the DC self-bias voltage value can be converted into a standard I / O signal and fed back to the unipolar DC power supply of the electrostatic chuck to achieve voltage compensation.

[0008] As a further aspect of the present invention: the DC self-bias voltage value of the wafer surface is 1 / 2 of the peak value of the radio frequency voltage. Factors affecting the DC self-bias voltage include the pressure of the cavity, the power of the high-frequency power supply, the type of gas, and the gas ratio of the mixed gas.

[0009] As a further aspect of the present invention: by measuring the DC self-bias voltage value on the wafer surface under different process conditions, the measured DC self-bias voltage value and intermediate parameters are fitted to obtain a functional relationship of the data. This functional relationship is represented by slope and deviation. Based on this functional relationship, the DC self-bias voltage on the wafer is obtained from the intermediate parameters.

[0010] As a further aspect of the present invention: after the radio frequency impedance matching device obtains intermediate parameters, these parameters are processed sequentially through a numerical conversion unit and an analog-to-digital conversion circuit to calculate the value of the DC self-bias voltage, and this value is fed back to the control unit of the unipolar DC power supply as a standard I / O signal to achieve accurate voltage compensation at the power supply voltage output terminal.

[0011] As a further aspect of the present invention: when a DC negative bias voltage is generated on the wafer surface, causing the potential difference between the electrode and the wafer to increase, the system increases the output voltage of the unipolar DC power supply, thereby reducing the potential difference and improving the adsorption effect of the electrostatic chuck. When the DC negative bias voltage decreases, the system reduces the output voltage of the unipolar DC power supply to maintain the balance of electrostatic attraction.

[0012] In addition, the present invention also provides a device for compensating the DC self-bias of an electrostatic chuck. The device includes an RF impedance matching unit, a numerical converter, and an analog-to-digital converter (ADC). The RF impedance matching unit includes an RF impedance matching device, the numerical converter includes a numerical conversion unit, and the ADC internally houses an ADC circuit. The device also includes a unipolar DC power supply and a controller. The controller internally houses a control unit capable of controlling the unipolar DC power supply. The RF impedance matching unit is electrically connected to the numerical conversion unit and the ADC. The RF impedance matching unit transmits intermediate parameters to the numerical conversion unit and the ADC. The numerical conversion unit is connected to the analog-to-digital conversion circuit. After the intermediate parameters are initially processed by the numerical conversion unit, they are then converted by the analog-to-digital conversion circuit. The analog-to-digital conversion circuit is connected to a computer, which sends the processed intermediate parameters to the computer to view the DC self-bias voltage value. The computer is connected to the control unit of the unipolar DC power supply, which transmits the calculated DC self-bias voltage data to the control unit. The control unit of the unipolar DC power supply is connected to the unipolar DC power supply. The control unit controls the voltage output terminal of the unipolar DC power supply to perform voltage compensation based on the received information. The unipolar DC power supply is connected to an electrostatic chuck to provide the required voltage to the electrostatic chuck.

[0013] Compared with the prior art, the beneficial effects of the present invention by adopting the above technical solution are as follows:

[0014] 1. This invention, through a series of operations such as obtaining intermediate parameters, calculating the approximate value of DC self-bias, and feeding back and compensating the voltage, can compensate for the problem of increased potential difference between the electrode and the wafer caused by DC self-bias, thereby improving the poor wafer adsorption effect of the electrostatic chuck and improving the quality and stability of semiconductor processing.

[0015] 2. This invention accurately obtains intermediate parameters based on different process conditions, such as RF power, gas type, gas flow rate, and cavity pressure, and calculates an approximate value of DC self-bias voltage through functional relationships, thereby achieving precise compensation of DC self-bias voltage and improving the performance and efficiency of semiconductor processing equipment. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall system process framework in an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of the DC self-biasing process viewed on a computer in an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram illustrating the relationship between DC self-bias voltage and cavity pressure in an embodiment of the present invention;

[0019] Figure 4This is a schematic diagram illustrating the relationship between DC self-bias voltage and high-frequency power supply in an embodiment of the present invention. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0021] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] Please see the appendix Figure 1 - Appendix Figure 4 This invention discloses a system for compensating for the DC self-bias of an electrostatic chuck. The system includes an RF impedance matching unit, a numerical conversion unit, and an analog-to-digital conversion circuit. The RF impedance matching unit provides intermediate parameters related to process conditions, including RF power, gas type, gas flow rate, and cavity pressure. The numerical conversion unit and the analog-to-digital conversion circuit process the intermediate parameters and send them to a computer to view the DC self-bias value. By measuring the DC self-bias value on the wafer surface under different process conditions and fitting the DC self-bias value with the intermediate parameters, a functional relationship of the data is obtained, thereby deriving the relationship between the intermediate parameters and the DC self-bias value on the wafer, and completing the calculation of the DC self-bias value.

[0023] In one embodiment of the present invention, the system further includes a control unit for a unipolar DC power supply. The control unit is used to receive a standard I / O signal of DC self-bias and control the voltage output terminal of the unipolar DC power supply to perform voltage compensation.

[0024] In one embodiment of the present invention: the radio frequency impedance matching device provides intermediate parameters for different process conditions. After being processed by the numerical conversion unit and the analog-to-digital conversion circuit, the DC self-bias voltage value can be converted into a standard I / O signal and fed back to the unipolar DC power supply of the electrostatic chuck to achieve voltage compensation.

[0025] In one embodiment of the present invention: the DC self-bias voltage value of the wafer surface is 1 / 2 of the peak value of the radio frequency voltage. Factors affecting the DC self-bias voltage include the pressure of the cavity, the power of the high-frequency power supply, the type of gas, and the gas ratio of the mixed gas.

[0026] In one embodiment of the present invention: by measuring the DC self-bias voltage value on the wafer surface under different process conditions, the measured DC self-bias voltage value and intermediate parameters are fitted to obtain a functional relationship of the data. This functional relationship is represented by slope and deviation. Based on this functional relationship, the DC self-bias voltage on the wafer is obtained from the intermediate parameters.

[0027] In one embodiment of the present invention: after the radio frequency impedance matching device obtains intermediate parameters, these parameters are processed sequentially through a numerical conversion unit and an analog-to-digital conversion circuit to calculate the value of the DC self-bias voltage, and the value is fed back to the control unit of the unipolar DC power supply as a standard I / O signal to achieve accurate voltage compensation at the power supply voltage output terminal.

[0028] In one embodiment of the present invention: when a DC negative bias voltage is generated on the wafer surface, causing the potential difference between the electrode and the wafer to increase, the system increases the output voltage of the unipolar DC power supply, thereby reducing the potential difference and improving the adsorption effect of the electrostatic chuck. When the DC negative bias voltage decreases, the system reduces the output voltage of the unipolar DC power supply to maintain the balance of electrostatic attraction.

[0029] This invention also provides a device for compensating for the DC self-bias of an electrostatic chuck. The device includes an RF impedance matching unit, a numerical converter, and an analog-to-digital converter (ADC). The RF impedance matching unit includes an RF impedance matching device, the numerical converter includes a numerical conversion unit, and the ADC internally contains an ADC circuit. The device also includes a unipolar DC power supply and a controller. The controller internally contains a control unit capable of controlling the unipolar DC power supply. The RF impedance matching unit is electrically connected to the numerical conversion unit and the ADC. The RF impedance matching unit transmits intermediate parameters to the numerical conversion unit and the ADC. The numerical conversion unit is connected to the ADC. After preliminary processing by the numerical conversion unit, the intermediate parameters are converted by the ADC. The ADC is connected to a computer, which sends the processed intermediate parameters to the computer to view the DC self-bias value. The computer is connected to the control unit of the unipolar DC power supply, which transmits the calculated DC self-bias data to the control unit. The control unit of the unipolar DC power supply is connected to the unipolar DC power supply. The control unit controls the voltage output terminal of the unipolar DC power supply to perform voltage compensation based on the received information. The unipolar DC power supply is connected to the electrostatic chuck to provide the required voltage.

[0030] Example 1, please refer to the appendix. Figure 1 - Appendix Figure 2 In the semiconductor plasma etching process, the radio frequency impedance matching device acquires intermediate parameters related to the process conditions, such as 100W radio frequency power, Ar and CF4 gas types, 200sccm gas flow rate, and 100mTorr chamber pressure. The numerical conversion unit and analog-to-digital conversion circuit process the intermediate parameters and send them to the computer to calculate that the DC self-bias voltage on the wafer surface is approximately half of the peak-to-peak value of the radio frequency voltage. By adjusting the unipolar DC power supply control unit, the voltage output terminal of the power supply is controlled to perform voltage compensation, which improves the adsorption effect of the electrostatic chuck and ensures that the wafer is stably adsorbed on the electrostatic chuck.

[0031] Example 2, please refer to the appendix. Figure 1 - Appendix Figure 2 The process conditions were set as follows: RF power 150W, gas types He and N2, gas flow rate 180sccm, and cavity pressure 80mTorr. An RF impedance matching unit provided intermediate parameters. After processing by a numerical conversion unit and an analog-to-digital conversion circuit, an approximate value of the DC self-bias voltage was calculated. According to experiments, the higher the cavity pressure, the lower the actual self-bias voltage; the higher the power of the high-frequency power supply, the higher the actual self-bias voltage. Under these conditions, the system accurately calculated the DC self-bias voltage and converted it into a standard I / O signal, which was fed back to the unipolar DC power supply. Voltage compensation was performed by the control unit, which effectively improved the poor wafer adsorption effect of the electrostatic chuck caused by the DC self-bias voltage.

[0032] Example 3, please refer to the appendix. Figure 1 - Appendix Figure 2 The process conditions selected were 200W RF power, Ne and O2 gas types, 220sccm gas flow rate, and 120mTorr chamber pressure. The conversion circuit inside the RF impedance matching circuit provided intermediate parameters. After a series of calculations and conversions, the relationship between the intermediate parameters and the DC self-bias voltage on the wafer was obtained. When the DC negative bias voltage generated on the wafer surface caused the potential difference between the electrode and the wafer to increase, the system increased the output voltage of the unipolar DC power supply to reduce the potential difference and improve the adsorption effect of the electrostatic chuck. When the DC negative bias voltage decreased, the system reduced the output voltage of the unipolar DC power supply to maintain the balance of electrostatic attraction and improve the quality and efficiency of semiconductor processing.

[0033] Specifically, by acquiring intermediate parameters, calculating the approximate value of DC self-bias, and feeding back and compensating the voltage, the problem of increased potential difference between the electrode and the wafer caused by DC self-bias can be compensated, thereby improving the poor wafer adsorption effect of the electrostatic chuck and enhancing the quality and stability of semiconductor processing.

[0034] Specifically, by accurately obtaining intermediate parameters based on different process conditions, such as RF power, gas type, gas flow rate, and cavity pressure, and calculating an approximate value of the DC self-bias voltage through functional relationships, the accurate compensation of the DC self-bias voltage is achieved, thereby improving the performance and efficiency of semiconductor processing equipment.

[0035] Working principle:

[0036] In the semiconductor plasma etching process, the radio frequency power supply provides a high-frequency electric field to the reaction chamber, causing the process gas to ionize and form plasma. Due to the difference in the movement speed of electrons and ions in the plasma, a large number of electrons fall on the wafer surface, forming a DC negative bias voltage. The wafer is fixed and adsorbed on the electrostatic chuck by the electrostatic attraction generated between the DC electrode of the electrostatic chuck and the substrate. The radio frequency impedance matching device obtains intermediate parameters related to process conditions such as radio frequency power, gas type, gas flow rate, and chamber pressure. The intermediate parameter conversion circuit converts these parameters. The numerical conversion unit and the analog-to-digital conversion circuit process the intermediate parameters and send them to the computer. By measuring the approximate value of the DC self-bias voltage on the wafer surface under different process conditions and fitting it with the intermediate parameters, the functional relationship of the data is obtained. Thus, the relationship between the intermediate parameters and the DC self-bias voltage value on the wafer is obtained, and the calculation of the DC self-bias voltage value is completed.

[0037] The DC self-bias voltage on the wafer surface is approximately half the peak-to-peak value of the RF voltage. The higher the cavity pressure, the lower the actual self-bias voltage; the higher the power of the high-frequency power supply, the higher the actual self-bias voltage. The influence of gas type and the proportion of mixed gases on the DC self-bias voltage is analyzed on a case-by-case basis. The obtained DC self-bias voltage is converted into a standard I / O signal and fed back to the unipolar DC power supply of the electrostatic chuck. The control unit of the unipolar DC power supply receives this signal and controls the voltage output terminal of the power supply for voltage compensation. When a DC negative bias voltage is generated on the wafer surface, causing an increase in the potential difference between the electrode and the wafer, the system increases the output voltage of the unipolar DC power supply to reduce the potential difference and improve the adsorption effect of the electrostatic chuck. When the DC negative bias voltage decreases, the system decreases the output voltage of the unipolar DC power supply to maintain the balance of electrostatic attraction, thereby improving the poor wafer adsorption effect of the electrostatic chuck caused by the DC self-bias voltage. This completes the entire workflow.

[0038] The terms "front," "back," "left," "right," "top," and "bottom" all refer to the figures in the accompanying drawings. Figure 1 Based on the perspective of the observer, the side of the device facing the observer is defined as the front, the left side of the observer is defined as the left, and so on.

[0039] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0040] It should be noted that the device structure and accompanying drawings of this invention mainly describe the principle of this invention. In terms of the technical aspects of this design principle, the setting of the power mechanism, power supply system and control system of the device is not fully described. However, under the premise that those skilled in the art understand the principle of the above invention, the specific details of its power mechanism, power supply system and control system can be clearly understood. The control method in the application document is automatic control through a controller. The control circuit of the controller can be implemented by those skilled in the art through simple programming.

[0041] All standard parts used can be purchased from the market, and can be customized according to the instructions and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the existing technology. The machinery, parts and equipment adopt conventional models in the existing technology, and the structure and principle of the components known to those skilled in the art can be known by those skilled in the art through technical manuals or conventional experimental methods.

[0042] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A system for compensating for DC self-biasing of an electrostatic chuck, characterized in that: The system includes an RF impedance matching unit, a numerical conversion unit, and an analog-to-digital conversion circuit. The RF impedance matching unit provides intermediate parameters related to process conditions, including RF power, gas type, gas flow rate, and chamber pressure. The numerical conversion unit and the analog-to-digital conversion circuit process the intermediate parameters and send them to a computer to view the DC self-bias voltage value. By measuring the DC self-bias voltage value on the wafer surface under different process conditions and fitting the DC self-bias voltage value with the intermediate parameters, a functional relationship of the data is obtained, thereby deriving the relationship between the intermediate parameters and the DC self-bias voltage value on the wafer, and completing the calculation of the DC self-bias voltage value.

2. The system for compensating for DC self-biasing of an electrostatic chuck according to claim 1, characterized in that: The system also includes a control unit for a unipolar DC power supply, which receives a standard I / O signal of DC self-bias and controls the voltage output terminal of the unipolar DC power supply to perform voltage compensation.

3. The system for compensating for DC self-biasing of an electrostatic chuck according to claim 2, characterized in that: The radio frequency impedance matching device provides intermediate parameters for different process conditions. After being processed by the numerical conversion unit and the analog-to-digital conversion circuit, the DC self-bias voltage value can be converted into a standard I / O signal and fed back to the unipolar DC power supply of the electrostatic chuck to achieve voltage compensation.

4. The system for compensating for DC self-biasing of an electrostatic chuck according to claim 3, characterized in that: The DC self-bias voltage on the wafer surface is half of the peak value of the radio frequency voltage. Factors affecting the DC self-bias voltage include the pressure of the cavity, the power of the high-frequency power supply, the type of gas, and the gas ratio of the mixed gas.

5. A system for compensating for DC self-biasing of an electrostatic chuck according to claim 5, characterized in that: By measuring the DC self-bias voltage value on the wafer surface under different process conditions, the measured DC self-bias voltage value and intermediate parameters are fitted to obtain the functional relationship of the data. This functional relationship is represented by the slope and deviation. Based on this functional relationship, the DC self-bias voltage on the wafer is obtained from the intermediate parameters.

6. A system for compensating for DC self-biasing of an electrostatic chuck according to claim 5, characterized in that: After the RF impedance matching device obtains intermediate parameters, these parameters are processed sequentially by a numerical conversion unit and an analog-to-digital conversion circuit to calculate the value of the DC self-bias voltage. This value is then fed back as a standard I / O signal to the control unit of the unipolar DC power supply to achieve accurate voltage compensation at the power supply voltage output terminal.

7. A system for compensating for DC self-biasing of an electrostatic chuck according to claim 2, characterized in that: When a DC negative bias voltage is generated on the wafer surface, causing an increase in the potential difference between the electrode and the wafer, the system increases the output voltage of the unipolar DC power supply, thereby reducing the potential difference and improving the adsorption effect of the electrostatic chuck. When the DC negative bias voltage decreases, the system reduces the output voltage of the unipolar DC power supply to maintain the balance of electrostatic attraction.

8. A device for compensating the DC self-bias of an electrostatic chuck, applicable to a system requiring the compensation of DC self-bias of an electrostatic chuck as described in any one of claims 1-7, characterized in that: The device includes an RF impedance matching unit, a numerical converter, and an analog-to-digital converter (ADC). The RF impedance matching unit includes an RF impedance matcher, the numerical converter includes a numerical conversion unit, and the ADC internally houses an ADC circuit. The device also includes a unipolar DC power supply and a controller. The controller internally houses a control unit capable of controlling the unipolar DC power supply. The RF impedance matching unit is electrically connected to the numerical conversion unit and the ADC. The RF impedance matching unit transmits intermediate parameters to the numerical conversion unit and the ADC. The numerical conversion unit is connected to the ADC. After preliminary processing by the numerical conversion unit, the intermediate parameters are converted by the ADC. The ADC is connected to a computer, which sends the processed intermediate parameters to the computer to view the DC self-bias value. The computer is connected to the control unit of the unipolar DC power supply, transmitting the calculated DC self-bias data to the control unit. The control unit of the unipolar DC power supply is connected to the unipolar DC power supply. The control unit controls the voltage output of the unipolar DC power supply for voltage compensation based on the received information. The unipolar DC power supply is connected to an electrostatic chuck to provide the required voltage to the electrostatic chuck.

Images