Plasma processor and heater thereof

Abstract

The invention provides a driving control circuit for a multi-zone heater of a plasma processor. A protection circuit is arranged in each driving circuit, and a protection circuit comprising a high-frequency impedance element and a discharge capacitor is arranged in each protection circuit, so that the output of direct-current heating voltage is realized, and meanwhile, the leakage of a radio-frequency signal is prevented; and abnormal high voltage can be guided to a grounding end through a voltage stabilizing diode and a discharge capacitor, so that the core optical coupler switch is prevented from being damaged. Due to the existence of the high-frequency impedance element, an area which is not interfered by radio-frequency signals exists in the driving circuit, the state detection circuit is arranged in the area, stable temperature measurement can be achieved, and accurate temperature control over all the heating units is further achieved.

Description

Technical Field

[0001] The present invention relates to a plasma processor, and particularly to a temperature control driving device for a multi-zone temperature control base of a plasma reactor. Background Art

[0002] During the production process of semiconductor chips, a large amount of microfabrication is required. Common plasma etching reactors can form various through-holes or trenches with micron or even nanometer-scale dimensions on wafers. By combining other processes such as chemical vapor deposition, various semiconductor chip products can be finally formed. With the increasing requirements for etching processes, the precision requirements for controlling the temperature of wafers or substrates during the plasma treatment process are also getting higher and higher. The existing several independent temperature control regions can no longer meet the process requirements for the temperature difference within the same control region. To further improve the temperature control ability of wafers, the prior art has proposed an array of independently controlled heating units arranged in a matrix, integrated between an electrostatic chuck and a conductive base serving as a lower electrode.

[0003] The patent application CN 111211029 B submitted by the same applicant describes a multi-zone temperature control structure. In the plasma reactor in this patent application, it includes a cavity. The bottom inside the cavity is a conductive base, and the conductive base also serves as a lower electrode and is connected to at least one high-frequency radio frequency power supply. After the plasma above the wafer is ignited, the radio frequency power supply can adjust the plasma concentration or energy. Other radio frequency power supplies can also be provided in the plasma reactor, such as connecting the radio frequency power supply to a gas showerhead at the top inside the reaction chamber, or arranging an inductance coil above the reaction chamber so that the magnetic field generated by the inductance coil enters the reaction chamber to generate and maintain the plasma concentration. The conductive base is fixed to the bottom of the cavity through a support device, where both the cavity and the support device are made of conductors and are electrically grounded to prevent the leakage of the radio frequency electric field to the outside. The conductive base includes an electrostatic chuck made of an insulating material with electrodes for electrostatic adsorption buried inside. Below the electrostatic chuck, there is also a multi-zone heater, and the heater includes a large number of independently controllable heating units. The number of heating units can be 10 * 10 = 100, or 15 * 15 = 225, or even more. The heating power of the power supply enters the heater group controller through the power bus. At the same time, the heater controller is also connected to the process controller through the control signal input line to receive the heating power distribution data required by the process. The controller can convert the received heating power distribution data into a driving signal for the on-time of the driving switch or the duty cycle of the switch.

[0004] In the technical solution described in this patent, each heating unit is driven by a driving circuit, and the driving circuit includes an opto-coupler switch to achieve electrical isolation between the driving signal side and the control signal side. On the driving signal side, the opto-coupler switch is directly connected in series with a heated heating unit. In the actual working environment, since the heating unit is in a radio frequency radiation environment, when the radio frequency power increases resulting in an increase in radio frequency voltage or an arcing phenomenon occurs in the plasma processor, a high voltage will be generated instantaneously. Both of these high voltages will break down the opto-coupler switch, causing the heater to fail. The existing driving circuit structure cannot avoid this problem, so the working stability is extremely poor, and it is necessary to frequently repair and replace components.

[0005] Therefore, it is necessary to propose a new multi-zone temperature-controlled plasma reactor that can prevent the opto-coupler switch from being broken down and improve the reliability of the system. Summary of the Invention

[0006] The present invention provides a heater for a plasma processor. The heater includes a plurality of heating units arranged horizontally, each heating unit is used to heat different regions above, and a plurality of driving circuits, each driving circuit is used to drive at least one of the heating units to heat; the driving circuit includes an opto-coupler switch, and two ports on one side of the opto-coupler switch are used to receive a control signal (S1) from a controller, and the first and second ports on the other side are respectively connected to a DC power supply and one of the heating units; the driving circuit further includes a protection circuit, the protection circuit includes a high-frequency impedance unit connected in series between the second port of the opto-coupler switch and the heating unit, and further includes a discharge capacitor with one end connected to the DC power supply and the other end connected between the high-frequency impedance unit and the heating unit. Wherein the heater further includes a grounding capacitor group connected between the DC power supply and the grounding end, and the grounding capacitor group includes a plurality of capacitors with different capacitance values connected in parallel to conduct abnormal high-voltage currents of different frequencies to the grounding end.

[0007] Optionally, the heater further includes a zener diode connected in parallel between the two output ports of the opto-coupler switch to further protect the opto-coupler switch and prevent it from being broken down by high voltage.

[0008] Wherein the high-frequency impedance unit has an impedance to DC less than 1 / 100, preferably less than 1 / 1000, of its impedance to radio frequency signals, so that radio frequency power will not leak to the opto-coupler switch.

[0009] Optionally, the heater further includes a detection circuit, and the detection circuit includes a sampling resistor connected between the second end of the opto-coupler switch and the high-frequency impedance unit.

[0010] The present invention also provides a plasma processor, which includes a cavity and a pedestal located in the cavity. The pedestal is used to support the wafer to be processed. Above the pedestal, there are the above-mentioned heater and an electrostatic chuck located above the heater. At least one radio frequency power supply outputs radio frequency power into the pedestal.

[0011] The multiple drive circuits in the heater further include a detection circuit. Each detection circuit is used to detect the sampling signal on the drive circuit where it is located. The sampling signal is the voltage signal of a resistor connected in series with the heating unit. After amplifying and processing the sampling signal, the detection circuit transmits the processed signal to at least one input terminal of the controller through a second opto-coupler switch. The controller receives the processed signal through at least one input terminal, calculates the processed signal, and adjusts the control signal output to the drive circuit where the detection circuit is located.

[0012] Optionally, the controller outputs the adjusted control signal to the drive circuits where the detection circuit is located and the surrounding multiple drive circuits to control the heating power of the multiple heating units. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1a 、 1b is a schematic diagram of the drive circuit of the heating unit of the present invention;

[0014] Figure 2 is a schematic diagram of the drive circuit of the heating unit including a temperature measurement circuit of the present invention;

[0015] Figure 3 is a schematic diagram of the drive control circuit of the heater of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] The technical solutions of the present invention will be described in detail below with reference to the drawings. It should be emphasized that this is only an exemplary description and does not exclude other embodiments that utilize the idea of the present invention.

[0017] As shown in Figure 1, the heating unit drive circuit of the present invention includes: a control signal S1 receiving end located on the first side (terminals 1 and 2) of the opto-relay OC1. A capacitor C10 is connected in parallel on the first side of the opto-relay OC1 to form a stable control voltage, causing the second side (terminals 3 and 4) of the opto-relay OC1 to conduct. A zener diode D20 is also connected in parallel between the 3rd and 4th terminals of the opto-coupler switch to protect the opto-coupler switch from being damaged due to excessive voltage. The 4th terminal of the opto-coupler switch is connected to the DC drive power supply Vdc, and the DC drive power supply outputs the current for heating, and the output voltage can be 24V DC or other higher voltages. The DC drive power supply Vdc is connected to the ground terminal GND through a grounding capacitor group, where the grounding capacitor group includes capacitors C21 and C23 connected in parallel. The DC drive power supply Vdc is connected to the heating unit through a discharge capacitor C20. The present invention also includes a micro high-frequency impedance element M1 made of ferrite material. The micro high-frequency impedance element M1 has an impedance of less than 1 ohm to direct current, but has an impedance greater than 1000 ohms to high-frequency signals such as 100Mhz signals, and the volume size of the micro high-frequency impedance element is only millimeter-level and can be installed in large quantities on the drive circuit of each heating unit. As long as the impedance to direct current is less than 1 / 100 of the impedance to radio frequency signals, it can be a single component or a functional circuit composed of multiple components, and all can achieve the purpose of the present invention and belong to the high-frequency impedance element or radio frequency impedance element required by the present invention. The micro high-frequency impedance element M1 is connected between the 3rd terminal of the opto-coupler switch and the heating unit, and one end of each of the zener diode D20 and the capacitor C20 is connected to both ends of the micro high-frequency impedance element M1.

[0018] During operation, the control signal S1 sends a high-level signal for heating, the opto-coupler switch OC1 conducts, and the current flows from the DC power supply Vdc through Figure 1aThe shown current path i1 reaches the heating unit. The heating unit and the entire drive circuit are in a radio frequency radiation environment. Therefore, high-voltage radio frequency signals will flow in the entire drive circuit. Due to the blockage of the micro high-frequency impedance element M1 in the present invention, the radio frequency signals will not flow to the optocoupler switch, but flow with a weak current to C20 with a higher impedance to radio frequency signals and the grounding capacitor banks C21 and C13. The capacitance values of C21 and C23 can be selected to adapt to radio frequency signals of different frequencies, so that the fundamental wave and the additionally generated harmonic frequencies in the plasma reaction chamber can reach the grounding end through appropriate paths. In addition, C20 needs to be selected with a smaller capacitance value to reduce the large leakage of radio frequency power supplied to the plasma processor base through the drive circuit. Only a small amount of radio frequency power will pass through C20, C21, and C23 to reach the grounding end. In the present invention, the above-mentioned micro high-frequency impedance element M1 blocks high-frequency signals from reaching the easily damaged optocoupler switch OC1, and C20 blocks the leakage of radio frequency power required for normal operation. When an abnormal signal mutation (such as arcing) occurs, the pulsed large current generated by the mutation signal can flow through the above capacitors C20, C21, and C23 to the grounding end, realizing the guiding grounding of the destructive current. As Figure 1b The dotted line shown in Figure 1b indicates the flow path of the above-mentioned destructive current i2. It can be seen that the destructive current all flows to the grounding end. Even if there is an indication that the voltage across the capacitor C20 instantaneously exceeds the safety threshold, the current will flow through the high-frequency impedance M1, the voltage stabilizing diode D20, and the capacitors C21 / C23 in sequence to reach the grounding end due to the conduction of the voltage stabilizing diode D20, and finally keep the voltage across the optocoupler switch OC1 within the safe voltage range.

[0019] Since the side of the high-frequency impedance element M1 close to OC1 (the left side in the figure) in the present invention basically blocks the passage of radio frequency signals, while the direct current signal can still pass through, a temperature measurement circuit can be further arranged in this area. As Figure 2Shown is a driving circuit for a heating unit including a temperature measurement circuit. Compared with FIG. 1, a resistor R2 is provided between the first end of the high-frequency impedance element M1 and the zener diode D20. Two signal receiving ends (12, 13) of a comparator B1 are connected to both ends of the resistor R2, and the output end (14) of the comparator B1 outputs to a triode U1 for signal amplification to achieve amplification of the compared signal. Among them, the triode includes a power supply end connected to the DC driving power supply Vdc through a resistor R4. The output end of the triode U1 is connected to the first end of the capacitor C31 and the first end (7) of the second opto-coupler switch OC2, and the other end of the capacitor C31 is connected to the second end (8) of the second opto-coupler switch OC2 and grounded. The two output ends (9, 10) on the other side of the second opto-coupler switch OC2 are respectively connected to both ends of a voltage dividing circuit composed of two series capacitors C31 and C32. The output end 9 is grounded through a resistor R6, where the first end of C31 is connected to the low-voltage DC power supply, and the second end is connected to the capacitor C32 and outputs a feedback signal S2. During the heating process, since the heating unit is composed of a resistance wire, the temperature rise will synchronously cause the overall resistance of the heating unit to increase. By measuring the resistance value of the heating unit, the current temperature of the heating unit can be calculated. The resistor R2 and the heating unit are connected in series with each other, and the resistor R2 is much smaller than the resistance of the heating unit, so the resistance of the heating unit dominates the impedance change of the entire series resistance. By detecting the voltage across R2, the current flowing through R2 and the heating unit can be calculated. Since the driving power supply voltage Vdc is fixed, the actual resistance of the heating unit can be calculated, and thus the actual temperature of the heating unit can be obtained.

[0020] The above temperature measurement circuit does not necessarily need to be configured on each driving circuit. Among a large number of temperature control areas on the base, in the first part of the area, the temperatures of a large number of heating units are relatively uniform. Only a few temperature measurement circuits need to be set in this area to monitor the temperature well. There is also a second part of the area where there are lifting pins or cooling gas holes, or there are other hardware structures that seriously affect the temperature uniformity. A large number of temperature measurement circuits need to be set in this area to accurately control the temperatures of each heating unit and improve the overall temperature uniformity. The number of heating units corresponding to the first part of the area (70%) is much larger than the number of heating units corresponding to the second part of the area (30%). Taking 100 areas as an example, among the 70 heating units located in the first part of the area, only 10 can be set to complete basic temperature monitoring. For the remaining 30 units, 15 - 20 temperature measurement circuits need to be set. Therefore, a total of 25 - 30 temperature measurement circuits are required overall. In this way, the number of temperature measurement circuits can be significantly reduced, and the number of input ports required for the controller 80 can also be saved.

[0021] The above-mentioned drive circuit jointly composed of an optocoupler switch, a protection circuit, and a status detection circuit. Each component in it needs to withstand a relatively high drive voltage and various abnormal high-voltage signals that appear in the plasma processor. On the other side of the two optocoupler switches are the controller 80 and the attached signal processing circuit, which are only used for signal processing and can operate with a relatively low voltage (such as 3 - 5V). Electrically isolating the two areas through the optocoupler can avoid electrical signal interference between the two and also prevent the impact of high-voltage pulses from reaching the low-voltage control circuit area.

[0022] Such as Figure 3 As shown in the figure, it is the drive control structure diagram of the overall heating unit of the present invention. The heating voltage in the external non-radiofrequency radiation environment passes through a filter to supply heating power to a large number of heating units in the plasma processor. The host computer (PC) is set with the process menu for plasma processing by the staff, including the set process temperature, and transmits control signals to the controller 80 located in the radiofrequency environment through an optical transceiver (optical fiber). The controller 80 outputs control signals to the optocoupler switches in each drive circuit through multiple output ports S11 - S1n. After being driven by the optocoupler switch, the heating voltage Vdc reaches each heating unit for heating through the protection circuit. A status detection circuit is connected between the optocoupler switch and the protection circuit. The status detection circuit transmits the electrical signals S21 - S2n detected in the radiofrequency environment back to the controller 80 through the second optocoupler switch. Each optocoupler switch divides the circuit in the radiofrequency environment into a low-voltage control circuit including the controller 80 and its auxiliary circuits, and a high-voltage drive circuit including the status detection circuit and the protection circuit. Such a circuit structure design enables the smooth bidirectional transmission of control signals, drive signals, and feedback detection signals, but also realizes electrical isolation, avoiding the propagation of abnormal high voltages in the entire drive and control circuits and damaging internal components. The low-voltage control circuit and the high-voltage drive circuit of the present invention can be located under the base of the plasma processing device. The base has a coolant channel for temperature control. The control circuit and the drive circuit close to the base are in a low-temperature environment, preventing the control and drive circuits from being damaged by excessive temperature and further improving the long-term stability of the heater control circuit and the drive circuit.

[0023] In addition to the Figure 2 structure shown in the figure, it can also be other circuit structures. For example, the comparator B1 and the triode U1 for signal amplification can be replaced by other circuits that can achieve signal amplification. As long as it is a circuit that can detect the temperature of the heating unit in the radiofrequency environment, it belongs to the variant embodiments of the present invention.

[0024] In the present invention, a protection circuit is provided in the drive circuit. The protection circuit includes a protection circuit including a high-frequency impedance element M1 and a discharge capacitor C20, which realizes the output of the DC heating voltage, prevents the leakage of radio frequency signals, and can also avoid the damage of the core optocoupler switch by draining the abnormal high voltage to the ground terminal through the diode D20 and the capacitor C20. The presence of the high-frequency impedance element M1 makes there be a region in the drive circuit that is not interfered by radio frequency signals. The present invention sets the state detection circuit in this region to achieve stable temperature measurement and further realizes precise temperature control of each heating unit.

[0025] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A heater for a plasma processor, the heater comprising a plurality of heating units arranged horizontally, each heating unit for heating different regions above; a plurality of drive circuits, each drive circuit for driving at least one of the heating units to heat; The drive circuit includes an opto - isolator switch, two ports on one side of the opto - isolator switch for receiving a control signal (S1) from a controller, and a first and a second port on the other side respectively connected to a DC power supply and one of the heating units; The drive circuit further includes a protection circuit, the protection circuit including a high - frequency impedance unit connected in series between the second port of the opto - isolator switch and the heating unit, and further including a discharge capacitor with one end connected to the DC power supply and the other end connected between the high - frequency impedance unit and the heating unit.

2. The heater according to claim 1, characterized in that, The heater further includes a ground capacitance group connected between the DC power supply and the ground terminal.

3. A heater using the one described in claim 1, characterized in that, The ground capacitance group includes a plurality of capacitors with different capacitance values connected in parallel.

4. The heater according to claim 1, characterized in that, The heater further includes a zener diode connected in parallel between the two output ports of the opto - isolator switch.

5. The heater according to claim 1, characterized in that The high - frequency impedance unit has an impedance to DC less than 1 / 100 of its impedance to RF signals.

6. The heater according to claim 1, wherein The heater further includes a detection circuit, the detection circuit including a sampling resistor connected between the second end of the opto - isolator switch and the high - frequency impedance unit.

7. The heater according to claim 6, characterized in that, It further includes a signal processing circuit connected to the sampling resistor, comparing and amplifying the signal on the sampling resistor and then outputting it to a second opto - isolator switch, and the second opto - isolator switch outputs a feedback signal to the controller.

8. A plasma processor, comprising a cavity and a susceptor located within the cavity, the susceptor for supporting a wafer to be processed, above the susceptor including the heater as claimed in claim 1 and an electrostatic chuck located above the heater, and at least one RF power supply outputting RF power into the susceptor.

9. The plasma processor according to claim 8, wherein, The controller is located below the susceptor, and the plasma processor further includes a host computer, and the host computer conveys control signals to the controller through an optical fiber.

10. The plasma processor as claimed in claim 8, wherein the plurality of drive circuits in the heater further include a detection circuit, each detection circuit for detecting a sampling signal on the drive circuit where it is located, the sampling signal being a voltage signal of a resistor connected in series with the heating unit, and the detection circuit amplifies and processes the sampling signal and then transmits the processed signal to at least one input terminal of the controller through a second opto - isolator switch.

11. The plasma processor as claimed in claim 10, wherein the controller receives the processed signal through at least one input terminal, calculates the processed signal, and adjusts the control signal output to the drive circuit where the detection circuit is located.

12. The plasma processor as claimed in claim 10, wherein the controller outputs the adjusted control signal to the drive circuits where the detection circuit is located and the surrounding drive circuits to control the heating power of the plurality of heating units.

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