Wafer electrostatic adsorption device and adsorption method

Abstract

The invention discloses a wafer electrostatic adsorption device, which comprises an electrostatic adsorption power supply and an electrostatic chuck, the electrostatic adsorption power supply is used for generating multi-path square wave voltage; the electrostatic chuck comprises an upper electrode layer, a lower electrode layer and a dielectric layer located between the upper electrode layer and the lower electrode layer. The lower electrode layer comprises a plurality of electrodes which are correspondingly connected with multiple paths of voltage output by the electrostatic adsorption power supply respectively; the electrostatic chuck generates polarization charges on the surface of the dielectric layer through multiple paths of voltage and induces charges with opposite polarity on the back surface of the wafer, so that the wafer is adsorbed. The invention also discloses a wafer electrostatic adsorption method, which comprises the following steps of: generating six paths of square wave voltage through the electrostatic adsorption power supply; the six paths of voltages are correspondingly connected to six electrodes of an electrostatic chuck; electric charges with opposite polarities are induced on the surface of a dielectric layer of the electrostatic chuck and the back face of the wafer, and electrostatic adsorption force is generated to adsorb the wafer to the surface of the electrostatic chuck. The wafer fixing device has the advantages of being capable of achieving non-contact, uniform and stable fixing of wafers and the like.

Description

Technical Field

[0001] This invention mainly relates to the field of semiconductor equipment manufacturing technology, specifically to a wafer electrostatic adsorption device and adsorption method. Background Technology

[0002] In the semiconductor manufacturing process, different semiconductor equipment needs to fix and support the wafer. In order to avoid movement and misalignment during processing, the silicon wafer must be placed stably on the process equipment. Traditional clamping technologies (such as Bernoulli chucks, mechanical clamps, etc.) can no longer meet the current process requirements. In particular, mechanical clamps not only reduce product utilization, but also bring a certain amount of metal contamination, which will inevitably affect the process results. Summary of the Invention

[0003] To address the technical problems existing in the prior art, the present invention provides a wafer electrostatic adsorption device and adsorption method for achieving non-contact, uniform and stable wafer fixation.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A wafer electrostatic adsorption device includes an electrostatic adsorption power supply and an electrostatic chuck. The electrostatic adsorption power supply is used to generate multiple square wave voltages and output them to the electrostatic chuck. The electrostatic chuck includes an upper electrode layer, a lower electrode layer, and a dielectric layer located between the two; the lower electrode layer contains multiple electrodes, which are respectively connected to the multiple voltage outputs of the electrostatic adsorption power supply. The electrostatic chuck generates polarized charges on the surface of the dielectric layer through the multi-channel voltage, and induces charges of opposite polarity on the back side of the wafer, thereby adsorbing the wafer.

[0005] Preferably, the electrostatic adsorption power source includes: The signal generation module is used to generate multiple low-voltage square wave signals with a predetermined phase difference; High voltage generating module, used to provide positive and negative high voltage DC operating voltage; The high-voltage amplifier module is used to amplify multiple low-voltage square wave signals into multiple high-voltage square wave voltages.

[0006] Preferably, the signal generation module includes an oscillator, a frequency divider, and a multi-channel analog switch, which are connected in sequence to generate multiple low-voltage square wave signals with a phase difference of 60° and a frequency of 30Hz.

[0007] Preferably, the high-voltage amplifier module includes multiple high-voltage amplifiers, which amplify the low-voltage square wave signal and output a high-voltage square wave signal respectively; each of the high-voltage amplifiers uses two-stage IGBT transistors connected in series, and DC negative feedback is used between the output and the input.

[0008] Preferably, the multi-channel high-voltage square wave voltage is a six-channel high-voltage square wave voltage, and the multi-channel analog switch is a four-channel analog switch.

[0009] Preferably, the electrostatic adsorption power supply outputs six square wave voltages, with A+ and A- being out of phase, B+ and B- being out of phase, and C+ and C- being out of phase, and the phase difference between each pair of channels is 60°; the six electrodes of the electrostatic chuck correspond one-to-one with the six regions on the surface of the electrostatic chuck, wherein the surface of the electrostatic chuck is divided into 6 regions, with region A+ being centrally symmetrical with region A-, region B+ being centrally symmetrical with region B-, and region C+ being centrally symmetrical with region C-.

[0010] This invention also discloses a wafer electrostatic adsorption method based on the wafer electrostatic adsorption device described above, comprising the following steps: Six square wave voltages with a phase difference of 60°, an amplitude of ±1kV, and a frequency of 30Hz are generated by an electrostatic adsorption power supply. The six voltages are respectively connected to the six electrodes of the electrostatic chuck; Charges of opposite polarity are induced on the dielectric layer surface of the electrostatic chuck and the back side of the wafer, thereby generating an electrostatic attraction force that adsorbs the wafer onto the surface of the electrostatic chuck; during the adsorption process, the net charge on the back side of the wafer remains zero.

[0011] Preferably, the electrostatic adsorption force F satisfies the formula: F = εSU² / d²; Where ε is the dielectric constant of the dielectric layer, S is the surface area of ​​the insulating medium, U is the voltage difference between the plates, and d is the thickness of the insulating medium.

[0012] Compared with the prior art, the advantages of the present invention are as follows: This invention achieves non-contact, uniform, and stable wafer fixation through six-phase electrostatic adsorption, effectively avoiding wafer damage, edge contamination, and area loss caused by traditional clamping methods. At the same time, it ensures that the net charge on the back side of the wafer is zero, thereby significantly improving process uniformity, equipment compatibility, and product yield in vacuum and plasma processes. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the electrostatic adsorption power supply in this invention.

[0014] Figure 2 This is a waveform diagram of the output voltage of the electrostatic adsorption power supply in this invention.

[0015] Figure 3 This is a schematic diagram illustrating the electrostatic chuck adsorption principle of the present invention.

[0016] Figure 4 This is a schematic diagram showing the electrode connection between the electrostatic adsorption power supply and the electrostatic chuck of the present invention. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1 As shown, the wafer electrostatic adsorption device provided in this embodiment of the invention is applied to the ion implanter of semiconductor equipment. It mainly includes an electrostatic adsorption power supply and an electrostatic chuck. The electrostatic adsorption power supply generates a six-phase positive and negative 1kV square wave voltage and outputs it to the electrostatic chuck. The electrostatic chuck adsorbs the wafer through electrostatic adsorption. Specifically, the electrostatic adsorption power supply includes a six-phase signal generation module, two high-voltage generation modules, a six-channel high-voltage amplifier module, and a power control module; The six-phase signal generation module generates signals of different phases through an oscillator and a frequency divider circuit; Meanwhile, the high voltage generation module outputs two positive and negative 1500VDC high voltages through the PWM control circuit and the voltage doubler rectifier circuit; The six-channel high-voltage amplifier module amplifies the six square wave voltages output by the six-phase signal generation module, and finally outputs six positive and negative 1kV square wave voltages with a 60-degree phase difference to provide power to the six electrodes of the electrostatic chuck. When the six electrodes of the electrostatic chuck are energized, polarization charges are generated on the surface of their dielectric layer; simultaneously, polarization charges of opposite polarity are generated on the back side of the wafer and the top surface of the electrostatic chuck. Therefore, the wafer is attracted to the surface of the electrostatic chuck.

[0019] Specifically, the six-phase signal generation module includes an oscillator, a 6-divider, a 60° phase shifter, a four-channel analog switch, an amplifier, and an inverter. The six-phase signal generation module generates six square waves that meet the requirements of a 60° phase difference and a certain frequency. The positive and negative amplitudes of the square waves are equal to the input DC control voltage. In addition, the module samples and sums the six-phase load current (i.e., the chuck charging and discharging current) and converts it into a DC signal, which is then sent to the power controller.

[0020] The high voltage generation module consists of two identical high voltage generation circuits that generate ±1500VDC high voltage to provide the high voltage amplifier with a ±1500VDC high voltage DC operating voltage.

[0021] The six-channel high-voltage amplifier module consists of six identical high-voltage amplifiers, each amplifying one of the six low-voltage square wave signals generated by a six-phase signal generation circuit. The output consists of six high-voltage square wave signals with a specific phase difference, providing voltage to the electrostatic chuck. A key feature of the high-voltage amplifier is the use of two IGBTs connected in series to enhance its high-voltage characteristics. DC negative feedback is employed between the output and input of the high-voltage amplifier, resulting in extremely stable amplification.

[0022] like Figure 2 As shown, the electrostatic adsorption power supply outputs six positive and negative 1kV square wave voltages with a voltage output frequency of 30Hz. The phase difference between each channel is 60 degrees, the voltage amplitude uniformity of each channel is less than 1%, and the positive and negative voltage switching time of each channel is 2.5ms ± 0.1ms.

[0023] like Figure 3 As shown, the electrostatic chuck consists of three layers: the top and bottom layers are electrode layers, and the middle layer is a dielectric layer. The bottom electrode layer consists of six electrodes. The dielectric layer has a withstand voltage of 1.5kV, the surface flatness of the dielectric layer of the target plate is <0.1mm, the parallelism of the dielectric layer of the target plate relative to the water-cooled surface is <0.1mm, the insulation resistance between any two electrodes is greater than 11GΩ under a voltage of 1kV, and the insulation resistance between any electrode and ground is greater than 11GΩ under a voltage of 1kV.

[0024] The electrostatic adsorption power supply outputs six 1kV square wave voltages, which are connected one-to-one with the six electrodes of the electrostatic chuck. Therefore, polarized charges are generated on the surface of the dielectric layer, and simultaneously, opposite charges are generated on the surface of the electrostatic chuck and the back of the wafer. The wafer is then adsorbed onto the surface of the electrostatic chuck. The resulting electrostatic adsorption force F is calculated using the following formula: F = εSU² / d²; Where ε is the dielectric constant of the dielectric layer, S is the surface area of ​​the insulating medium, U is the voltage difference between the plates, and d is the thickness of the insulating medium.

[0025] like Figure 4 As shown, the electrostatic adsorption power supply outputs six approximately square wave voltages, where A+ and A- are anti-phase voltages, B+ and B- are anti-phase voltages, and C+ and C- are anti-phase voltages. These six voltages are supplied to the six electrodes of the electrostatic chuck, which correspond one-to-one with six regions on the surface of the electrostatic chuck. The surface of the electrostatic chuck is divided into six regions, where region A+ is centrally symmetrical with region A-, region B+ is centrally symmetrical with region B-, and region C+ is centrally symmetrical with region C-. At any given time, the adsorption force on the wafer in the symmetrical regions is equal. Therefore, the wafer experiences uniform force in all directions, and the number of positive and negative charges on the back side of the wafer is equal, so the net charge of the wafer remains zero.

[0026] During adsorption, the charge polarity on each small piece corresponding to each phase electrode on the silicon wafer changes continuously, but the total charge content on the entire silicon wafer is zero. Therefore, it does not affect parameters such as uniformity and dosage during ion implantation. During voltage phase transition, the total sum of charging and discharging currents is zero, so it does not affect operations that require current injection into the silicon wafer. When the external input voltage drops to zero, the voltage accumulated on the silicon wafer also immediately drops to zero, so no static electricity accumulation occurs.

[0027] This invention achieves non-contact, uniform, and stable wafer fixation through six-phase electrostatic adsorption, effectively avoiding wafer damage, edge contamination, and area loss caused by traditional clamping methods. At the same time, it ensures that the net charge on the back side of the wafer is zero, thereby significantly improving process uniformity, equipment compatibility, and product yield in vacuum and plasma processes.

[0028] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0029] The wafer electrostatic adsorption device of the present invention includes an electrostatic adsorption power supply and an electrostatic chuck; The electrostatic adsorption power supply consists of four main modules: a six-phase signal generation module, a six-channel high-voltage amplifier module, two high-voltage generation modules, and a power control module. The six-phase signal generation module includes components such as frequency dividers, inverters, shift registers, and buffers. The six-phase signal generation board generates six approximate square waves with a phase difference of 60 degrees and a frequency of 30Hz. The positive and negative amplitudes of the square waves are equal to the input DC control voltage. It also has the function of monitoring the current sampling function after the six voltages are loaded. The current samples are summed and converted into DC voltage signals, which are then sent to the external power controller.

[0030] The two high-voltage generating modules of the electrostatic adsorption power supply ( Figure 1 The high-voltage power supply module consists of two identical high-voltage generation circuits that generate ±1500VDC high voltage. The high-voltage generation circuit controls the push-pull circuit and the on / off state of the field-effect transistor through a PWM wave, thereby separating the positive and negative voltages, which are respectively input to the transformer. The transformer outputs a rectangular AC voltage, which is then passed through a voltage doubler rectifier circuit to obtain positive and negative DC high voltages, providing ±1500VDC high-voltage DC operating voltage for the high-voltage amplifier.

[0031] The six-channel high-voltage amplifier module consists of six identical high-voltage amplifiers, each amplifying one of the six low-voltage square wave signals generated by a six-phase signal generation circuit, outputting six high-voltage square waves with a certain phase difference. A key feature of this amplifier is the use of two IGBTs connected in series to enhance its high-voltage characteristics. DC negative feedback between the amplifier's output and input ensures extremely stable amplification.

[0032] The electrostatic chuck system is a three-layer structure, comprising two electrode layers and an intermediate dielectric layer. In practical applications, the wafer serves as the upper electrode layer, while the lower electrode layer and dielectric layer are integrated within the electrostatic chuck structure. The exterior of the electrostatic chuck is a grounded support structure. The lower electrode layer consists of six electrodes connected to the output voltage of the electrostatic adsorption power supply. These six electrodes are A+, A-, B+, B-, C+, and C-, corresponding one-to-one with the six regions on the surface of the electrostatic chuck. The six regions on the surface of the electrostatic chuck are centrally symmetrical about A+ and A-, B+ and B-, and C+ and C-, respectively.

[0033] The electrostatic adsorption power supply outputs six square wave voltages with an amplitude of ±1kV, a frequency of 30Hz, and a phase difference of 60 degrees between each phase. These voltages are A+ and A-, B+ and B-, and C+ and C-, which are inversely phased. These six voltages are supplied to the six electrodes A+, A-, B+, B-, C+, and C- of the electrostatic chuck. After the six electrodes receive the voltage, polarization charges are generated on the dielectric surface of the electrostatic chuck, and an electric field is generated on the upper and lower surfaces of the dielectric. The generated electric field intensifies the polarization charges generated on the back side of the wafer. The charges distributed on the back side of the wafer have opposite polarities to the charges on the upper surface of the electrostatic chuck, thus adsorbing the wafer onto the electrostatic chuck.

[0034] It is now widely used in semiconductor processes under plasma and vacuum environments, such as etching, chemical vapor deposition, and ion implantation. The advantages of this technology are reduced silicon wafer breakage caused by uneven pressure and collisions when using mechanical chucks, increased the area of ​​the silicon wafer that can be effectively processed, eliminated waste caused by edge effects, and the ability to operate in vacuum chambers. The electrostatic adsorption control system and methods are also applied to the electrostatic holding process of wafers in semiconductor equipment—ion implanters—and are a core component of the wafer transport system in ion implanters.

[0035] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A wafer electrostatic adsorption device, characterized in that, Includes electrostatic adsorption power supply and electrostatic chuck; The electrostatic adsorption power supply is used to generate multiple square wave voltages and output them to the electrostatic chuck. The electrostatic chuck includes an upper electrode layer, a lower electrode layer, and a dielectric layer located between the two. The lower electrode layer contains multiple electrodes, which are respectively connected to the multiple voltage outputs of the electrostatic adsorption power supply. The electrostatic chuck generates polarized charges on the surface of the dielectric layer through the multi-channel voltage, and induces charges of opposite polarity on the back side of the wafer, thereby adsorbing the wafer.

2. The wafer electrostatic adsorption device according to claim 1, characterized in that, The electrostatic adsorption power source includes: The signal generation module is used to generate multiple low-voltage square wave signals with a predetermined phase difference; High voltage generating module, used to provide positive and negative high voltage DC operating voltage; The high-voltage amplifier module is used to amplify multiple low-voltage square wave signals into multiple high-voltage square wave voltages.

3. The wafer electrostatic adsorption device according to claim 2, characterized in that, The signal generation module includes an oscillator, a frequency divider, and a multi-channel analog switch. The oscillator, frequency divider, and multi-channel analog switch are connected in sequence to generate multiple low-voltage square wave signals with a phase difference of 60° and a frequency of 30Hz.

4. The wafer electrostatic adsorption device according to claim 3, characterized in that, The high-voltage amplifier module includes multiple high-voltage amplifiers, which amplify the low-voltage square wave signal and output a high-voltage square wave signal. Each high-voltage amplifier uses two-stage IGBT transistors connected in series and employs DC negative feedback between the output and input.

5. The wafer electrostatic adsorption device according to claim 3, characterized in that, The multi-channel high-voltage square wave voltage is a six-channel high-voltage square wave voltage, and the multi-channel analog switch is a four-channel analog switch.

6. The wafer electrostatic adsorption device according to any one of claims 1-5, characterized in that, The electrostatic adsorption power supply outputs six square wave voltages, with A+ and A- being out of phase, B+ and B- being out of phase, and C+ and C- being out of phase, with a phase difference of 60° between each pair. The six electrodes of the electrostatic chuck correspond one-to-one with the six regions on the surface of the electrostatic chuck. The surface of the electrostatic chuck is divided into six regions, with region A+ and region A- being centrally symmetrical, region B+ and region B- being centrally symmetrical, and region C+ and region C- being centrally symmetrical.

7. A wafer electrostatic adsorption method based on the wafer electrostatic adsorption device according to any one of claims 1-6, characterized in that, Includes the following steps: Six square wave voltages with a phase difference of 60°, an amplitude of ±1kV, and a frequency of 30Hz are generated by an electrostatic adsorption power supply. The six voltages are respectively connected to the six electrodes of the electrostatic chuck; Charges of opposite polarity are induced on the dielectric layer surface of the electrostatic chuck and the back side of the wafer, thereby generating electrostatic adsorption force to adsorb the wafer onto the surface of the electrostatic chuck. During the adsorption process, the net charge on the back side of the wafer remains zero.

8. The wafer electrostatic adsorption method according to claim 7, characterized in that, The electrostatic adsorption force F satisfies the following formula: F = εSU² / d²; Where ε is the dielectric constant of the dielectric layer, S is the surface area of ​​the insulating medium, U is the voltage difference between the plates, and d is the thickness of the insulating medium.

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