TW201611177A - Electrostatic clamping system in plasma processing device - Google Patents

Abstract

Provided is an electrostatic clamping system in a plasma processing device, which comprises: a plasma processing chamber and an electrostatic chuck mounted at the bottom of the plasma processing chamber, wherein a wafer is fixed to the electrostatic chuck and the electrostatic chuck is provided therein with at least one adsorption electrode; and an adsorption voltage supply system including a first receiving terminal to receive an adsorption voltage setting value, a second receiving terminal to receive a direct current bias value on the wafer disposed inside the plasma processing device, and an output terminal for outputting the adsorption voltage to the adsorption electrode. The adsorption voltage supply system determines a corrected adsorption voltage value by comparing the received adsorption voltage setting value with the direct current bias value, and adjusts the amplitude and polarity of the output voltage outputted to the adsorption electrode according to the corrected adsorption voltage value.

Description

Electrostatic clamping system in plasma processing equipment

The invention relates to a plasma processing device, in particular to an electrostatic clamping system with a DC bias compensation function in a plasma processing device, and a method for controlling the adsorption voltage thereof.

In recent years, with the development of semiconductor manufacturing processes, the integration and performance requirements of components have become higher and higher, and plasma processes are widely used in the manufacture of semiconductor components. The wafer to be processed in the plasma processing apparatus is first sent to the upper surface of the electrostatic chuck in the plasma processing apparatus, and the electrode in the electrostatic chuck is connected to a high voltage DC power source, and the wafer is adsorbed by the high voltage. On the electrostatic chuck. Conventional techniques generally apply a very high negative voltage to the electrodes of the electrostatic chuck to achieve electrostatic adsorption. The externally applied negative voltage and the negative DC bias generated by the plasma are superimposed, and finally the electrostatic chuck can be made. Stable adsorption. However, this method also has problems, such as the use of negative voltage adsorption, which is easy to cause plasma induced damage to the wafer to be processed. These damages can cause the wafer to be processed and the life of the wafer is shortened, or the performance is weakened or even scrapped. . In order to reduce these damages, it is possible to apply a positive voltage to the electrodes of the electrostatic chuck, which also enables adsorption of the wafer. During the plasma processing, a large amount of electrons in the plasma will accumulate on the wafer to form a negative voltage, that is, a DC bias. The magnitude of the DC bias can be controlled by controlling the power of the RF bias power supply. However, the DC bias formed by the negative charge accumulation on the wafer is opposite to the polarity of the externally applied positive DC high voltage, and the two will cancel each other out, and the DC bias will increase as the RF power applied to the plasma processing device increases. When the DC bias voltage is increased to be greater than or equal to the externally applied DC high voltage, the actual adsorption voltage will be close to zero, and the adsorption force will be significantly reduced. If the externally set DC high voltage (HV setting) setting value is much larger than the DC bias that may occur, the adsorption of the wafer can be ensured, but this will impose a great burden on the DC high voltage power supply circuit, and not only the device withstand voltage requirements but also power consumption. It will also increase, and it will take a longer time to apply a reverse high voltage to remove the charge on the wafer when the wafer needs to be detached from the electrostatic chuck after the plasma treatment, in order to reliably neutralize the charge on the wafer. The reliability and efficiency of wafer detachment is unfavorable. In order to solve the influence of DC bias on the adsorption voltage of the electrostatic chuck, an adsorption voltage control system is required to synthesize the numerical relationship between the externally given high voltage (HV setting) and the DC bias voltage (Vdc), and output a suitable adsorption voltage value, so that The wafer can be stably adsorbed on the electrostatic chuck while reducing the PID damage to the wafer, and further ensure that the wafer can be reliably and quickly detached from the electrostatic chuck after the plasma treatment is completed.

The main object of the present invention is to overcome the defects of the prior art and provide a multi-mode output adsorption voltage control system, which can output different adsorption voltages according to changes in DC bias, thereby ensuring stable adsorption of the wafer and also significantly reducing Damage to devices on the wafer while enabling flexible switching between different voltage output modes.

To achieve the above object, the present invention provides an electrostatic clamping system comprising: a plasma processing chamber and an electrostatic chuck mounted below the plasma processing chamber, the wafer being fixed on the electrostatic chuck, in the electrostatic chuck Included in at least one adsorption electrode; an adsorption voltage supply system that receives the adsorption voltage set value through the first receiving end, a second receiving end for receiving the DC bias value on the wafer in the plasma processing apparatus, and an output end Outputting an adsorption voltage to the adsorption electrode;

The adsorption voltage supply system compares the received adsorption voltage set value and the DC bias value to obtain a corrected adsorption voltage value, and adjusts the amplitude and polarity of the output voltage output to the adsorption electrode according to the corrected adsorption voltage value. The adsorption voltage supply system may further include a comparator that adds the received adsorption voltage set value and the DC bias value to generate and output a corrected adsorption voltage value.

The adsorption voltage supply system may further include an output voltage switching device and a trigger, the trigger receiving the modified adsorption voltage value, and the first mode switching threshold and the second mode switching threshold according to the modified adsorption voltage value The comparison result outputs a first mode switching signal and a second mode switching signal to the output voltage switching device, and the output voltage switching device makes the output voltage according to the received first mode switching signal or the second mode switching signal The polarity is switched between positive and negative. The adsorption voltage supply system further includes a power converter including an output voltage that receives and generates a respective amplitude based on the corrected adsorption voltage value, the output voltage being coupled to the output voltage switching device.

The invention also provides a method for controlling adsorption voltage in a plasma processing apparatus, the plasma processing apparatus comprising a base, an electrostatic chuck on the base and a wafer placed on the electrostatic chuck, the adsorption The voltage control method comprises: introducing a reaction gas, and applying a radio frequency electric field to the plasma processing device to ignite the plasma; providing an adsorption voltage setting value, a first mode switching threshold, a second mode switching threshold; detecting and obtaining the plasma Processing a DC bias value on the wafer in the device; processing the adsorption voltage set value and the DC bias value to obtain a corrected adsorption voltage value, generating an adsorption voltage according to the modified adsorption voltage value; comparing the corrected adsorption voltage value and The first mode switching threshold and the second mode switching threshold select to output a positive adsorption voltage or a negative adsorption voltage to the electrostatic chuck. Wherein the first switching threshold is greater than zero, the second switching threshold is less than zero, and the corrected adsorption voltage is less than the second switching threshold to output a negative adsorption voltage to the electrostatic chuck; the corrected adsorption voltage value is greater than the first switching At the threshold, a positive adsorption voltage is output to the electrostatic chuck. The first switching threshold is less than or equal to 50V, and is equal to the second switching threshold being greater than or equal to -50V.

Wherein the adsorption voltage setting value is greater than 500V, the DC bias value is less than zero, and the corrected adsorption voltage value is a sum of the adsorption voltage set value and the DC bias value.

Where the modified adsorption voltage value is less than the first switching threshold value is greater than the second switching threshold value, the absolute value of the output adsorption voltage is less than 30V to achieve a flexible transition in the output mode transition.

In order to make the content of the present invention clearer and easier to understand, the contents of the present invention will be further described below in conjunction with the accompanying drawings. Of course, the invention is not limited to the specific embodiment, and general replacements well known to those skilled in the art are also encompassed within the scope of the invention.

In the description of the present invention, it should be noted that the terms "connected" and "electrically connected" are to be understood broadly, and may be directly connected or indirectly connected through an intermediate medium, unless otherwise specifically defined and defined. The specific meaning of the above terms in the present invention can be understood in a specific case by those skilled in the art.

1 shows a schematic diagram of a plasma processing apparatus provided by an embodiment of the present invention. As shown in Fig. 1, the plasma processing apparatus of the present invention comprises a plasma reaction chamber 100. The top of the inside of the reaction chamber is a reaction gas injection unit 11, which is connected to the gas source 110 through a pipe and a valve. The bottom of the reaction chamber 100 includes a susceptor 22 including an electrode connected to at least one RF power source via a conductor. After the reaction gas is introduced into the reaction chamber, the plasmon is ignited and maintained by the RF power source, and the amount of negative charge accumulated on the surface of the plasma can be adjusted by the output power of the RF power source, thereby adjusting the DC bias voltage. (Vdc). Above the susceptor 22 includes an electrostatic chuck 21 that includes an electrode 210 on which the wafer 20 to be processed is placed. The plasma processing apparatus preferably includes an edge ring 23 surrounding the wafer and electrostatic chuck 21 to regulate the electric field and temperature distribution at the edge of the wafer. The plasma processing apparatus of the present invention further includes an adsorption voltage control circuit including an adder 30, a power converter 31, an output voltage switching device 32 and a flip-flop 33. The adder 30 includes at least two signal receiving terminals 301 and 302 respectively receiving an externally set set high voltage value and a DC bias voltage (Vdc) obtained by the DC bias detecting system. The DC bias detection system may be a detection circuit connected to the electrode 210. The detection circuit is connected to the electrode 210 through an RF resistor to attenuate the RF power, and then through rectification and integration including a diode and components such as an inductor and a capacitor. The circuit obtains an electrical signal representing the magnitude of the DC bias voltage, and the value of Vdc can be obtained by mathematically processing the electrical signal. The value of detecting Vdc is well known in the art and will not be described herein. The setting of the high voltage value 301 can be optimally selected according to process parameters such as temperature, power, and wafer material structure during plasma processing, and the parameters are selected to ensure that the wafer is reliably adsorbed without damaging the wafer. When the details of the operation of the adsorption voltage control circuit of the present invention are further described below, the high voltage value 301 is set to 700V as an example, but the actual invention can select a wider range such as 500-3000V.

The adder of the present invention adds the set high voltage value 301 and the detected DC bias voltage 302 to obtain a signal HVm representative of the corrected high voltage value, which represents the electrostatic suction force actually generated on the wafer. The electric signal HVm is output to the rear power converter 31. The power converter 31 generates a corresponding DC high voltage output between the output terminals 311 and 312 according to the HVm signal, and the voltage of the DC high voltage is a modified high voltage value. The electric signal HVm representing the corrected high voltage value is also sent to a flip-flop 33, and the trigger outputs a control signal to the output voltage switching device 32 according to the electric signal to control the switching of the internal switch. The output voltage switching device 32 includes at least two inputs connected to 311 and 312, respectively. The two inputs are connected to the output 320 via a switching network, and the output 311 of the power converter 31 is selectively electrically connected through the switching network. Connected to an electrostatic chuck or ground, while the output 312 is selectively grounded or electrically connected to the electrostatic chuck. The output voltage of the power converter can only be positive, and the output voltage value is a modified high voltage value. The output voltage switching device of the present invention can realize the positive or negative modified high voltage output electrode 210 of the electrostatic chuck.

The operation of the flip-flop 33 of the present invention will now be described in accordance with the voltage or voltage signal waveform diagram of FIG. The set high voltage value on 埠 301 in the figure is always fixed at 700V, and the DC bias value detected on 埠 302 varies with time, including at least 5 consecutive stages of A-E.

The amplitude of the DC bias voltage Vdc detected in the phase A is gradually increased from 0 to -650 V, and is processed by the adder 30 to obtain a corrected high voltage value of 50 V, which is output to the power converter 31, and the power converter 31 outputs a voltage of 50 V. The working principle of the flip-flop 33 is described below by taking a Schmitt trigger as an example. The upper limit of the output of the flip-flop 33 is 50V, and the lower limit is -50V. The flip-flop 33 simultaneously receives the corrected high voltage value of 50 V. Since the corrected high voltage value 50 V has not reached the lower limit, the switching signal is not sent to the output voltage switching device 32, and the output voltage switching device 32 is maintained in the positive voltage output state. The output voltage of the final output 320 is gradually reduced from 700 to 50V as shown in FIG.

In the B phase, the DC bias voltage drops below -650V -750 or more. At this time, due to the hardware limitation of the power converter 31, the output voltage cannot be output normally at 50V, so the output voltage of the output terminal 311 is approximately equal to zero, for example, according to the power. The converter 31 is designed differently, the output voltage can be varied between 30-0V or the power converter 31 can be directly turned off, so that the output voltage is zero. At this time, since the DC bias amplitude is much larger than the output voltage amplitude of the power converter 31, the dominant DC bias is adsorbed to the wafer. At the same time, the corrected high voltage value outputted by the adder 30 varies from 50V to -50V, and the trigger 33 does not detect that the corrected high voltage value exceeds the lower limit of the conversion, so the positive output state is maintained. The voltage at which the final output terminal 311 is close to zero is output as an adsorption voltage from the crucible 320 to the electrostatic chuck. Although the output adsorption voltage is zero, since the DC bias is very high (-700±50V), the DC bias can be used to stably adsorb the wafer onto the electrostatic chuck. Since the output voltage of the 埠320 is zero, the current flowing through the switch in the output voltage switching device 32 is also zero, and device damage and electromagnetic field interference caused by thermal switching can be avoided when subsequently switching to other output states.

In the C stage, the DC bias voltage drops below -750V (such as -800V), and the corrected high voltage value -100V exceeds the lower conversion limit of -50V. The power converter 31 also restores the supply of a stable voltage to the outside, and the trigger 33 issues control. The command causes the output voltage of the output voltage switching device 32 to be reversed to a negative voltage, that is, the output voltage of the output terminal 312 is connected to the electrode 210 of the electrostatic chuck, and the other output terminal 311 is connected to the ground terminal. At this time, the output voltage outputted through the output terminal 320 is -100V, the DC self-bias voltage is -800V, and the voltage of the two is still 700V, thus ensuring the stability of the electrostatic adsorption force, and converting from the A phase to the C phase. There is no direct thermal switching with current, and the middle phase includes the B phase of zero current flow, which realizes flexible switching.

In the D phase, the DC bias voltage rises again to -750V or more, and the corrected high voltage value is also below -50V + 50V, and the power converter 31 outputs zero voltage again. However, since the upper limit of the conversion of the flip-flop 33 has not been reached +50 V, the output voltage switching means 32 still does not switch the negative voltage output mode in which the C phase is located.

In the E phase, the DC bias voltage rises above -650V, and the corrected high voltage value is also above +50V, and the power converter 31 resumes outputting the corrected high voltage again. The corrected high voltage value also exceeds the upper switching limit of +50 V, so the flip flop 33 controls the output voltage switching device 32 to switch to the positive voltage output mode, and 320 outputs the positive corrected high voltage to the electrostatic chuck.

In summary, the multi-mode output adsorption voltage control system of the present invention can output different adsorption voltages according to changes in the DC bias voltage, thereby ensuring stable adsorption of the wafer and significantly reducing the on-wafer device. The damage while achieving flexible switching between different voltage output modes. The upper and lower limits of the conversion in the present invention may also be other values such as ±30V or ±20V, and the specific setting of the upper and lower limit values is affected by the specific parameters of the power converter 31, as long as the power converter 31 can still ensure stable power output, It is possible to choose a lower upper and lower limit value.

The adsorption voltage control system of the present invention is composed of an adder, a power converter, a flip-flop, and an output voltage switching device as shown in FIG. 1, and can also be implemented by other circuit structures, for example, the adder and the flip-flop can be integrated into the same In a chip or circuit, the power converter can also be integrated into the corresponding switch to achieve the output of voltages of different polarities. It is within the scope of the invention for those skilled in the art to select different circuits to implement the functions of the present invention.

The present invention has been described in the above preferred embodiments, and the present invention is not intended to limit the scope of the present invention, and is not intended to limit the scope of the invention. A number of changes and refinements may be made, and the scope of protection claimed by the present invention shall be as described in the scope of the patent application.

100‧‧‧reaction chamber
11‧‧‧Reactive gas injection device
110‧‧‧ gas source
20‧‧‧ wafer
21‧‧‧Electrical chuck
210‧‧‧ electrodes
22‧‧‧ pedestal
23‧‧‧Edge ring
30‧‧‧Adder
301, 302‧‧‧ signal receiving end
31‧‧‧Power Converter
311, 312, 320‧‧‧ output
32‧‧‧Output voltage switching device
33‧‧‧ Trigger

1 is a schematic view of a plasma processing apparatus of the present invention; and FIG. 2 is a waveform diagram of an externally applied high voltage, DC bias, and output adsorption voltage received by the adsorption voltage control system of the present invention.

100‧‧‧reaction chamber

11‧‧‧Reactive gas injection device

110‧‧‧ gas source

20‧‧‧ wafer

21‧‧‧Electrical chuck

210‧‧‧ electrodes

22‧‧‧ pedestal

23‧‧‧Edge ring

30‧‧‧Adder

301, 302‧‧‧ signal receiving end

31‧‧‧Power Converter

311, 312, 320‧‧‧ output

32‧‧‧Output voltage switching device

33‧‧‧ Trigger

Claims (9)

An adsorption voltage control method in a plasma processing apparatus, the plasma processing apparatus comprising a susceptor, an electrostatic chuck on a susceptor and a wafer placed on the electrostatic chuck, the adsorption voltage control method comprising: Passing a reaction gas and applying a radio frequency electric field to the plasma processing device to ignite the plasma; providing an adsorption voltage set value, a first mode switching threshold, and a second mode switching threshold; detecting and obtaining a wafer in the plasma processing device a DC bias value; processing the adsorption voltage set value and the DC bias value to obtain a corrected adsorption voltage value, generating an adsorption voltage according to the modified adsorption voltage value; and comparing the corrected adsorption voltage value with the first The mode switching threshold, the second mode switching threshold selects to output a positive adsorption voltage or a negative adsorption voltage to the electrostatic chuck. The adsorption voltage control method according to claim 1, wherein the first switching threshold value is greater than zero, the second switching threshold value is less than zero, and the corrected adsorption voltage value is less than the second switching threshold value to output a negative adsorption voltage to The electrostatic chuck; when the corrected adsorption voltage value is greater than the first switching threshold, a positive adsorption voltage is output to the electrostatic chuck. The adsorption voltage control method according to claim 1, wherein the adsorption voltage set value is greater than 500 V, the DC bias value is less than zero, and the corrected adsorption voltage value is a sum of an adsorption voltage set value and a DC bias value. The adsorption voltage control method according to claim 2, wherein the first switching threshold is less than or equal to 50V, and the second switching threshold is equal to or greater than -50V. The adsorption voltage control method according to claim 4, wherein when the corrected adsorption voltage value is less than the first switching threshold value is greater than the second switching threshold value, the output adsorption voltage is less than 30V. An electrostatic clamping system in a plasma processing apparatus, comprising: a plasma processing chamber and an electrostatic chuck installed under the plasma processing chamber, the wafer is fixed on the electrostatic chuck, and the electrostatic chuck includes at least one An adsorption voltage supply system receives an adsorption voltage set value through a first receiving end, a second receiving end for receiving a DC bias value on a wafer in the plasma processing apparatus, and an output terminal output adsorption voltage And the adsorption voltage supply system compares the received adsorption voltage set value and the DC bias value to obtain a corrected adsorption voltage value, and adjusts an output voltage outputted to the adsorption electrode according to the corrected adsorption voltage value. The magnitude and polarity. The electrostatic chucking system of claim 6, wherein the adsorption voltage supply system comprises an output voltage switching device and a trigger, the trigger receiving the corrected adsorption voltage value, according to the corrected adsorption voltage value and the first The comparison result of the mode switching threshold and the second mode switching threshold outputs a first mode switching signal and a second mode switching signal to the output voltage switching device, and the output voltage switching device switches the signal according to the received first mode or The second mode switching signal causes positive and negative switching of the polarity of the output voltage. The electrostatic clamping system of claim 7, wherein the adsorption voltage supply system further comprises a power converter that receives and generates an output voltage of a corresponding amplitude according to the corrected adsorption voltage value, the output voltage connection To the output voltage switching device. The electrostatic clamping system of claim 6, wherein the adsorption voltage supply system further comprises an adder that adds the received adsorption voltage set value and the DC bias value to generate and output a corrected adsorption voltage value. .