TW201911363A - Bias modulation method, bias modulation system and plasma processing device - Google Patents

Abstract

The present invention provides a bias modulation method, a bias modulation system and a plasma processing device. The bias modulation method comprises: during loading of a bias power to a base for bearing a workpiece to be machined, increasing an output voltage of a bias radio frequency source, so that the output voltage increases to a target voltage value from an initial voltage value, and so that a negative bias produced on a surface of the workpiece to be machined is kept within a pre-set range during loading of the bias power to the base. Also disclosed is a bias modulation system. The plasma processing device disclosed comprises a bias modulation system provided in the present invention. The bias modulation method, the bias modulation system and the plasma processing device can all prevent the case of a negative bias appearing on the surface of a wafer decreasing during loading of a bias power to a base, so that not only the decrease in plasma processing speed can be avoided and productivity is ensured, but also the surface of a workpiece to be machined can be ensured to be sufficiently processed, enabling the electrical performance thereof to satisfy requirements.

Description

Bias modulation method, bias modulation system, and plasma processing device

The present invention relates to the field of semiconductors, and in particular to a bias modulation method, a bias modulation system, and a plasma processing apparatus.

With the rapid development of semiconductor component manufacturing processes, the requirements for component performance and integration are getting higher and higher, making plasma technology widely used. In a plasma etching or deposition system, the reaction gas is completely dissociated by introducing an external electromagnetic field (direct current or alternating current) by introducing various reaction gases (such as Cl ₂ , SF ₆ , C ₄ F ₈ , O _{2 ,} etc.) into the vacuum reaction chamber. Forming a plasma. The plasma contains a large amount of active particles of electrons, ions (including positive ions and negative ions), excited atoms, molecules, and radicals. These active particles interact with the surface of the wafer placed in the cavity and exposed to the plasma. Various physical and chemical reactions are generated on the surface of the wafer to change the surface properties of the wafer, and process processes such as etching or deposition are completed. In the development of plasma devices for semiconductor manufacturing processes, the most important factors are increased wafer processing capabilities to increase yields, and the ability to fabricate highly integrated device processes.

In a conventional semiconductor manufacturing process, a relatively large-scale semiconductor etching device is used to excite plasma by means of an Inductive Coupled Plasma Emission Spectrometer (ICP), which can obtain high-density electricity at a lower working pressure. Pulp, but also simple in structure and low in cost.

As shown in Fig. 1, it is a schematic structural view of a typical ICP semiconductor etching apparatus. A dielectric window 2 (quartz or ceramic) is disposed on the top of the vacuum chamber 3, and a planar RF antenna 1 is disposed above the dielectric window 2, and the RF energy output from the RF source 8 passes through the RF antenna 1 to In the form of an inductive discharge, energy is coupled into the vacuum chamber 3 to excite the reactive gases within the chamber to produce a high density plasma. The plasma distributed in the vicinity of the dielectric window 2 is diffused from top to bottom to the surface of the wafer 4 for a specific process. In addition, a typical lower electrode structure is provided in the vacuum chamber 3, which includes a stage 6, a metal electrode 5, and a bias RF source 7 and an impedance matching network electrically connected thereto. The carrier 6 is used to carry the wafer 4; the metal electrode 5 is embedded in the carrier 6; the bias RF source 7 provides RF energy through the metal electrode 5 to generate a negative bias on the surface of the wafer, thereby controlling The ion energy bombarded to the surface of the wafer.

However, during the process, since the wafer is not electrically conductive, when the bias RF source 7 supplies RF energy, positive ions accumulate on the surface of the wafer, generating a positive potential, and the generated positive potential reduces the negative bias of the wafer surface. The pressure, which causes the attraction of positive ions in the plasma to be weakened, reduces the number and rate of positive ions reaching the surface of the wafer, thereby reducing the etching rate of the wafer surface, reducing the productivity, and possibly the surface of the workpiece to be processed. A situation that cannot be adequately handled, thereby affecting the electrical performance of the workpiece.

The present invention is directed to the above technical problems existing in the prior art, and provides a bias modulation method, a bias modulation system, and a plasma processing apparatus that can prevent a negative bias of a wafer surface from decreasing during loading of a bias power to a susceptor. In this case, not only can the plasma processing rate be reduced, the production capacity can be ensured, but also the surface of the workpiece to be processed can be sufficiently processed to meet the electrical performance requirements.

The present invention provides a bias modulation method, comprising: increasing an output voltage of a bias RF source during loading of a bias power to a susceptor for carrying a workpiece to be processed, so that the output voltage is increased from an initial voltage value to a target The voltage value is such that the negative bias generated on the surface of the workpiece to be processed is maintained within a preset range during the loading of the bias power to the susceptor.

Optionally, the difference between the target voltage value and the initial voltage value is equal to a negative bias loss value, and the output voltage of the bias RF source is maintained during loading of the bias power to the susceptor. The loss value of the negative bias generated on the surface of the workpiece to be processed when the initial voltage value is constant.

Optionally, the pedestal is loaded with a bias power according to a pulse period; wherein the pulse period includes a pulse turn-on time and a pulse turn-off time, and at the pulse turn-on time, a bias power is applied to the pedestal, and the bias voltage is increased. The output voltage of the RF source is such that the output voltage is increased from the initial voltage value to the target voltage value; at the pulse off time, the biasing power to the pedestal is stopped.

Optionally, the bias power is applied to the susceptor at the pulse turn-on time, and the method includes the following steps: Step S101: detecting and recording the first bias voltage V ₀ generated on the surface of the workpiece to be processed when t= ₀ ; The first bias voltage V ₀ is equal to the initial voltage value; Step S102: detecting and recording a second bias voltage Vn generated on the surface of the workpiece to be processed at time tn of the current pulse-on time; wherein tn=n ( T1/N) N≥100, and N is an integer; 1≤n≤N, and n is an integer; T1 is the length of the pulse on time; when n=N, the output of the bias RF source at time tn The voltage is the target voltage value; Step S103: calculating a difference V between the second bias voltage Vn and the third bias voltage V'n-1; wherein the third bias voltage V'n-1 is completed at the previous time a bias voltage generated on the surface of the workpiece to be processed after the bias compensation; the third bias voltage V ₀ ' is equal to the first bias voltage V ₀ ; Step S104 : the bias voltage source at the time tn of the current pulse turn-on time The output voltage is immediately adjusted to the sum of the output voltage of the bias RF source and the difference V at time tn-1; Step S105: detecting and recording the completion bias a third bias voltage V _n ' generated on the surface of the workpiece to be processed after pressure compensation; step S106: determining whether n is equal to N; if yes, the step ends; if not, replacing n with n+1, and sequentially This step S102 to step S106 is performed.

Optionally, the ratio of the initial voltage value to the target voltage value ranges from 0.1 to 0.9.

Optionally, the output voltage of the biased RF source increases linearly during loading of the bias power to the susceptor.

Optionally, the slope of the output voltage of the bias RF source increases linearly: K=(Vt−Vs)/T1; wherein, Vt is the target voltage value, Vs is the initial voltage value, and T1 is the pulse. opening time.

As another technical solution, the present invention further provides a bias modulation system, comprising: a bias RF source electrically connected to a pedestal for carrying a workpiece to be processed, for biasing the pedestal a power adjustment module, the voltage adjustment module is electrically connected to the bias RF source, and is configured to increase an output voltage of the bias RF source during loading of the bias RF source to the pedestal The output voltage is increased from the initial voltage value to the target voltage value such that a negative bias voltage generated on the surface of the workpiece to be processed is maintained within a predetermined range during which the bias RF source loads the bias power to the susceptor.

Optionally, the bias RF source is a pulse modulation RF source to be capable of loading bias power to the pedestal in a pulse period; wherein the pulse period includes a pulse on time and a pulse off time, and at the pulse on time, The bias RF source loads the bias power to the pedestal, and the voltage adjustment module increases the output voltage of the bias RF source to increase the output voltage from the initial voltage value to the target voltage value; at the pulse off time, The biased RF source stops loading bias power to the pedestal.

Optionally, the voltage adjustment module includes: a clock generator capable of emitting a clock signal synchronized with the bias RF source; and a voltage sensor, wherein the voltage sensor communicates with the clock generator, Detecting a negative bias generated on the surface of the workpiece to be processed during the pulse on time; a digital processor that communicates with the voltage sensor for receiving a transmission from the voltage sensor Calculating an output voltage adjustment value according to the negative bias voltage, and adjusting an output voltage of the bias RF source to the output voltage adjustment value to generate a negative bias voltage on a surface of the workpiece to be processed The preset value is maintained during the loading of the bias power to the susceptor.

Optionally, the voltage sensor detects a first bias voltage V ₀ generated on a surface of the workpiece to be processed when t=0; the first bias voltage V ₀ is equal to the initial voltage value; and detecting the current pulse a second bias voltage Vn generated on the surface of the workpiece to be processed at a time tn of the opening time; wherein tn=n(T1/N) N≥100, and N is an integer; 1≤n≤N, and n is an integer T1 is the length of the pulse on time; when n=N, the output voltage of the bias RF source is the target voltage value at time tn; and detecting and recording the surface of the workpiece to be processed after the completion of the bias compensation A third bias voltage V _n ' is generated.

Optionally, the digital processor receives and records the first bias voltage V ₀ , the second bias voltage Vn , and the third bias voltage V _n ' sent by the voltage sensor, and performs: calculating the second a difference V between the bias voltage Vn and the third bias voltage Vn _-1 '; wherein the third bias voltage Vn _-1 ' is a bias generated on the surface of the workpiece to be processed after the bias compensation is completed at the last time Pressing; V ₀ ' is equal to the first bias voltage V ₀ ; the output voltage of the bias RF source will be immediately adjusted to the output voltage of the bias RF source at time tn-1 at the current pulse on time tn The sum of V; determine whether n is equal to N; if yes, control the voltage sensor to stop detecting operation, and stop adjusting the output voltage of the bias RF source; if not, control the voltage sensor to continue detecting operation, And instantly adjust the output voltage of the bias RF source.

As another technical solution, the present invention further provides a plasma processing apparatus comprising: a susceptor for carrying a workpiece to be processed, and the above-mentioned bias modulation system provided by the present invention, the bias modulation system and the pedestal connection.

Advantageous Effects of Invention: In the technical solutions of the bias modulation method, the bias modulation system, and the plasma processing device provided by the present invention, during the loading of the bias power to the susceptor, the output voltage of the bias RF source is increased to The output voltage is increased from the initial voltage value to the target voltage value. Since the output voltage of the bias RF source is gradually increased, the negative bias generated on the surface of the workpiece to be processed is gradually increased, and the amount of increase in the negative bias can be fully or partially compensated for being gradually accumulated on the surface of the workpiece to be processed. The bias generated by the positive potential generated by the positive ions, that is, although the positive potential reduces the negative bias of the wafer surface, the reduction of the negative bias is substantially the same as the increase of the negative bias, thereby Keeping the negative bias voltage within the preset range can not only avoid the plasma processing rate reduction, ensure the productivity, but also ensure that the surface of the workpiece to be processed can be fully processed to meet the electrical performance requirements.

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the bias modulation method, the bias modulation system and the plasma processing apparatus provided by the present invention are further described in detail below with reference to the accompanying drawings and specific embodiments. Embodiment 1 This embodiment provides a bias modulation method, including:

Increasing the output voltage of the bias RF source during loading of the bias power to the susceptor for carrying the workpiece to be processed, so that the output voltage is increased from the initial voltage value to the target voltage value so as to be on the surface of the workpiece to be processed The resulting negative bias is maintained within a predetermined range during the loading of the bias power to the pedestal.

The so-called preset range refers to the range of fluctuations of the allowable bias power, which satisfies: the positive ions that reach the surface of the workpiece to be processed have a certain number and rate, thereby ensuring that the plasma processing rate is within a suitable process range.

Since the output voltage of the bias RF source is gradually increased, the negative bias generated on the surface of the workpiece to be processed is gradually increased, and the amount of increase in the negative bias can partially or completely compensate for the positive accumulation on the surface of the workpiece to be processed. a bias that is lost by the positive potential generated by the ions, that is, although the positive potential reduces the negative bias on the surface of the wafer, the amount of decrease in the negative bias is substantially equal to the increase in the negative bias, thereby enabling The negative bias voltage is kept within the preset range, thereby not only avoiding the plasma processing rate reduction, ensuring the productivity, but also ensuring that the surface of the workpiece to be processed can be sufficiently processed to meet the electrical performance requirements.

Optionally, the difference between the target voltage value and the initial voltage value is equal to a negative bias loss value, and the output voltage of the bias RF source is maintained during the initial loading of the bias power for the susceptor. The loss value of the negative bias generated on the surface of the workpiece to be processed when the voltage value is constant. With this arrangement, the negative bias that increases the surface of the workpiece to be processed just compensates for the bias that is lost due to the positive potential generated by the positive ions accumulated on the surface of the workpiece to be processed, thereby keeping the negative bias of the surface of the workpiece to be processed constant. The initial voltage level can not only avoid the plasma processing rate reduction, ensure the production capacity, but also ensure that the surface of the workpiece to be processed can be fully processed to meet the electrical performance requirements.

It should be noted that the difference between the target voltage value and the initial voltage value may also be greater than or less than the above-mentioned negative bias loss value, as long as the negative bias voltage of the surface of the workpiece to be processed is kept within a preset range.

In the prior art, the bias RF source outputs a sinusoidal continuous wave. However, when the characteristic dimension of the etching process is below 20 nm, the continuous wave plasma may damage the device during the etching process, affecting the electrical power of the device. performance. A solution to this problem may be to apply bias power to the pedestal in a pulse period. Specifically, the pulse period includes a pulse on time and a pulse off time. At the pulse on time, the bias power is applied to the pedestal, and the output voltage of the bias RF source is increased to increase the output voltage from the initial voltage value to the target voltage. Value; at the pulse off time, stop loading bias power to the pedestal.

Since the bias power is stopped from being applied to the susceptor during the pulse-off time, electrons in the plasma will fall into the surface of the wafer and positive ions accumulated during the pulse-on time, thereby accumulating a positive potential on the surface of the wafer, thereby further reducing the bias voltage. Loss.

The bias RF source is capable of loading bias power to the pedestal in a pulse period, such as a pulse modulated RF source.

In this embodiment, as shown in FIG. 2, the bias RF source is a pulse modulation RF source, wherein the pulse period T includes a pulse on time T1 and a pulse off time T2, and at a pulse on time T1, the bias RF source is The output voltage is increased from the initial voltage value V1 to the target voltage value V2. In this embodiment, as shown in FIG. 3, the bias power is applied to the pedestal at the pulse-on time, which specifically includes the following steps:

Step S101: detecting and recording a first bias voltage V ₀ generated on the surface of the workpiece to be processed when t=0; the first bias voltage V ₀ is equal to the initial voltage value.

Step S102: detecting and recording a second bias voltage Vn generated on the surface of the workpiece to be processed at the time tn of the current pulse-on time; wherein tn=n(T1/N) N≥100, and N is an integer; ≤ n ≤ N, and n is an integer; T1 is the length of the pulse on time; when n = N, at the time tn, the output voltage of the bias RF source is the target voltage value.

Step S103: Calculating a difference V between the second bias voltage Vn and the first bias third bias voltage V'n-1.

Wherein, the third bias voltage V'n-1 is a bias voltage generated on the surface of the workpiece to be processed after the bias compensation is completed at the last time; since the first time loop of n=1 is performed, the last moment is At time t=0, the bias compensation operation is not performed, so that the third bias voltage V ₀ ' is specified to be equal in value to the first bias voltage V ₀ .

Step S104: Immediately adjust the output voltage of the biased RF source at the time tn of the current pulse-on time to the sum of the output voltage of the biased RF source and the difference V at time tn-1.

Step S105: detecting and recording the third bias voltage V _n ' generated on the surface of the workpiece to be processed after the completion of the bias compensation.

Step S106: It is judged whether n is equal to N. If yes, the step ends. If not, n is replaced by n+1, and steps S102 to S106 are sequentially performed.

It can be seen from the above. From n = 1, the steps S102 to S106 are cyclically performed until n = N, and the above step ends, that is, the pulse is turned off. The actual voltage at the moment before the pulse is turned off is the target voltage at the last moment of the pulse-on time. After the pulse is turned off, electrons enter the bottom of the etch tank, neutralizing the positive charge, and restoring the wafer surface bias to 0V.

The above method of applying bias power to the susceptor according to the pulse period can realize real-time dynamic adjustment compensation of the bias voltage generated on the surface of the wafer during the process, so that the surface of the wafer reaches the compensation effect as shown in FIG. Among them, the larger the value of N, the better the compensation effect.

Wherein, the detection and output voltage of the second bias voltage in each of the loops is increased from the initial voltage value to the target voltage value under the same process condition, that is, the detection and voltage increase process is performed at the same pulse. Time, the same pulse power and pulse duty cycle, and the same initial voltage value are performed to ensure that the bias of the surface loss of the workpiece to be processed obtained by the test is exactly equal to the compensation amount of the bias of the surface loss of the workpiece to be processed, thereby The negative bias of the surface of the workpiece to be processed is maintained at a constant initial voltage level, thereby not only avoiding a reduction in the plasma processing rate, but also ensuring the productivity, and ensuring that the surface of the workpiece to be processed can be sufficiently treated to meet its electrical performance.

Alternatively, as shown in FIG. 2, during the loading of the bias power to the pedestal, for example, during the pulse-on time T1, the output voltage of the biased RF source increases linearly. When the pulse waveform output from the bias RF source is a square wave, the positive charge accumulation on the workpiece to be processed has a substantially linear trend. Therefore, by linearly increasing the output voltage of the bias RF source, the linear increase can be correspondingly increased. The charge is cancelled to achieve a desired negative bias level on the workpiece to be processed.

Wherein, the initial voltage value of the output voltage of the bias RF source is Vs, and the target voltage value is Vt. The slope of the output voltage of the bias RF source increases linearly: K = tan θ = (Vt - Vs) / T1; where Vt is the target voltage value, Vs is the initial voltage value, and T1 is the pulse turn-on time. The larger the slope K is, the faster the output voltage of the bias RF source is increased. Conversely, the smaller the slope K is, the slower the output voltage of the bias RF source is increased.

For example, an inductively coupled plasma etching device that biases an RF source output pulse is a novel pulse-modulated RF source that can output a waveform as shown in FIG. The pulse modulated RF source is used to apply a negative bias to the pedestal to create a negative bias on the surface of the wafer to be etched placed on the susceptor to attract plasma to the surface of the wafer to be etched.

As shown in Fig. 4, during the etching process, the pulse modulation RF source output pulse frequency is 50 Hz, the duty ratio is 60%, and the initial voltage value Vs is 300V. When the duty cycle of the pulse is set to 60%, the surface bias of the wafer to be etched during the pulse on and off phases is reduced from 300V to 200V, that is, the bias voltage is lost by 100V. Therefore, in order to compensate for the bias loss of the surface to be etched, the target voltage value Vt of the pulse-modulated RF source output should be increased to 400V to compensate for the above-mentioned loss of 100V bias voltage, that is, the initial voltage value Vs of the pulse-modulated RF source output and The voltage ratio Vr of the target voltage value Vt is 0.75. At this time, the pulse modulation waveform output from the bias RF source and the corresponding negative bias voltage on the surface of the wafer to be etched are as shown in FIG. In the pulse on phase, the output bias voltage is linearly increased from 300V to 400V, and the linear increase slope tan θ = (400V-300V) / 12ms, thereby compensating for the negative bias loss caused by the positive charge accumulation on the surface of the wafer to be etched. The surface bias of the wafer to be etched is maintained at the initial voltage value Vs level, so that the negative bias voltage of the surface of the workpiece to be processed is maintained at a constant initial voltage level, thereby not only avoiding the plasma processing rate reduction, ensuring the productivity, but also ensuring The surface of the workpiece to be processed can be fully treated to meet the electrical requirements.

In the pulse off phase, free electrons enter the etched trench in the surface of the wafer to be etched and the positive charge therein, causing the surface of the wafer to be etched to return to zero potential; It can be seen from Fig. 4 that during the pulse-on time, the pulse is modulated to solve the problem of negative bias drop due to positive charge accumulation on the surface of the wafer to be etched, thereby maintaining the expected etch rate relative to the prior art, thereby ensuring The production capacity of the wafer.

It should be noted that the pulse voltage of the output may also increase nonlinearly during the turn-on time T1 of the pulse. The non-linearly increased voltage can correspondingly cancel the non-linearly increasing accumulated positive charge, thereby achieving a desired negative bias level on the wafer to be processed.

Optionally, as shown in FIG. 2, the ratio of the initial voltage value Vs to the target voltage value Vt ranges from 0.1 to 0.9. Adjusting the ratio of the initial voltage value Vs to the target voltage value Vt within this range can achieve appropriate compensation of the wafer surface bias loss to be processed, thereby enabling processing of the wafer to be processed according to different processing process target requirements of the wafer to be processed. Regulation is carried out to achieve precise control of the wafer processing rate, improve wafer processing quality, and ensure wafer throughput.

In this embodiment, the bias RF source is a pulse-modulated RF source, and the pulse frequency of the output pulse is f=1/(T1+T2), and the pulse frequency f is adjusted in the range of 10 Hz-20 KHz. The duty cycle of the pulse D=T1/(T1+T2) is adjusted from 10% to 90%. The RF frequency of the pulse-modulated RF source is 2MHz, 13.56MHz or 60MHz. The bias modulation method in this embodiment is applicable not only to an inductively coupled plasma processing process (ICP), but also to a capacitively coupled plasma processing process (CCP), a microwave plasma processing process, and a microwave electron cyclotron resonance plasma processing process ( ECR).

In summary, in the technical solutions of the bias modulation method, the bias modulation system, and the plasma processing device provided by the embodiments of the present invention, the output voltage of the bias RF source is increased during the loading of the bias power to the susceptor. So that the output voltage is increased from the initial voltage value to the target voltage value. Since the output voltage of the bias RF source is gradually increased, the negative bias generated on the surface of the workpiece to be processed is gradually increased, and the amount of increase in the negative bias can be fully or partially compensated for being gradually accumulated on the surface of the workpiece to be processed. The bias generated by the positive potential generated by the positive ions, that is, although the positive potential reduces the negative bias of the wafer surface, the reduction of the negative bias is substantially the same as the increase of the negative bias, thereby Keeping the negative bias voltage within the preset range can not only avoid the plasma processing rate reduction, ensure the productivity, but also ensure that the surface of the workpiece to be processed can be fully processed to meet the electrical performance requirements. Example 2:

The present embodiment provides a bias modulation system, as shown in FIG. 5, for modulating a negative bias voltage of a workpiece to be processed placed on the surface of the susceptor 10. The bias modulation system includes a bias RF source 7 and a voltage adjustment module, wherein the bias RF source 7 is electrically coupled to a susceptor 10 for carrying a workpiece to be processed for loading bias power to the susceptor 10 to The surface of the workpiece to be processed is negatively biased. The voltage adjustment module 9 is electrically connected to the bias RF source 7 for increasing the output voltage of the bias RF source during the bias power supply of the bias RF source to the pedestal to increase the output voltage from the initial voltage value. To the target voltage value, such that the negative bias generated on the surface of the workpiece to be processed is maintained within a preset range during the biasing of the bias RF source to the susceptor.

By means of the voltage adjustment module 9, the negative bias generated on the surface of the workpiece to be processed can be gradually increased, and the increase of the negative bias can compensate for the positive or negative generation of the positive ions accumulated on the surface of the workpiece to be processed. The bias voltage lost by the potential, that is, although the positive potential reduces the negative bias of the wafer surface, the reduction of the negative bias is substantially the same as the increase of the negative bias, so that the negative bias can be maintained. Within the preset range, not only can the plasma processing rate be reduced, the production capacity can be ensured, but also the surface of the workpiece to be processed can be sufficiently processed to meet the electrical performance requirements.

The workpiece to be processed is the wafer 4 to be processed.

In this embodiment, as shown in FIG. 5, the voltage adjustment module 9 includes a clock generator 91, a voltage sensor 92, and a digital processor 93, wherein the clock generator 91 can emit a synchronization with the bias RF source. Clock signal. The voltage sensor 92 is in communication with the clock generator 91 to be able to detect a negative bias generated on the surface of the workpiece to be processed during the pulse-on time. The digital processor 93 is in communication with the voltage sensor 92 for receiving a negative bias voltage sent from the voltage sensor 92, and obtaining an output voltage adjustment value based on the negative bias voltage, and biasing the output voltage of the RF source. The output voltage adjustment value is adjusted so that the negative bias generated on the surface of the workpiece to be processed is maintained at a preset value during the loading of the bias power to the susceptor.

Wherein, the voltage sensor 92 detects a first bias voltage V ₀ generated on the surface of the workpiece to be processed when t=0; the first bias voltage V ₀ is equal to the initial voltage value, and detecting the current pulse turn-on time At time tn, a second bias voltage Vn is generated on the surface of the workpiece to be processed; wherein tn=n(T1/N) N≥100, and N is an integer; 1≤n≤N, and n is an integer; T1 is The length of the pulse-on time; when n=N, the output voltage of the bias RF source is the target voltage value at time tn; and the third bias voltage V generated on the surface of the workpiece to be processed after the completion of the bias compensation is detected and recorded _n '.

The digital processor 93 receives and records the first bias voltage V ₀ , the second bias voltage Vn and the third bias voltage V _n ' transmitted from the voltage sensor 92, and performs: calculating the second bias voltage Vn and the third a difference V of the bias voltage V _n-1 '; wherein the third bias voltage V _n-1 'is a bias voltage generated on the surface of the workpiece to be processed after the bias compensation is completed at the previous time; V ₀ ' is equal to the first A bias voltage V ₀ .

Then, the digital processor 93 immediately adjusts the output voltage of the biased RF source at the time tn of the current pulse-on time to the sum of the output voltage of the biased RF source and the difference V at time tn-1.

Thereafter, the digital processor 93 determines whether n is equal to N, and if so, the command voltage sensor 92 stops the detecting operation, and stops adjusting the output voltage of the bias RF source; if not, the control voltage sensor 82 continues the detecting operation. , and instantly adjust the output voltage of the bias RF source.

The clock generator 91 is used to generate a square wave pulse, and the pulse period of the square wave pulse is T1/N. The bias RF source 7 is a novel pulse modulated RF source that can output a waveform as shown in FIG. The square wave pulse generated by the clock generator 91 is input to the voltage sensor 92. Where N is an integer greater than 0, in order to ensure the timeliness and effectiveness of voltage compensation, generally N≥100, the larger the N value, the better the compensation effect. The voltage sensor 92 is responsible for detecting the first bias voltage and the second bias voltage on the surface of the wafer 4. The timing of detecting is controlled by a square wave pulse outputted by the clock generator 91, and can be set to trigger detection of a rising or falling edge of the pulse. Action, where n is the count value of the square wave pulse of the clock generator 91. The digital processor 93 is responsible for receiving, recording and calculating the detection data of the voltage sensor 92, and the result of the operation is fed back to the bias RF source 7, so that the bias RF source 7 can immediately output the pulse voltage according to the result of the feedback. Adjustment.

In this embodiment, the specific process of loading the bias power into the pedestal by the voltage adjustment module 9 in the pulse period is: the bias RF source 7 and the clock generator 92 simultaneously output pulses, assuming a bias RF source 7 The initial output voltage is (Vs)0=V0', and at the beginning (t=0), the voltage sensor 92 detects the first bias voltage V0=(Vs)0=V0' of the surface of the current wafer 4, and transports Record storage is performed in the digital processor 93.

Assuming n is an integer greater than 0, the initial value is 1, and the value of n can be changed and stored in the digital processor 93. When the rising edge/falling edge of the next pulse output from the clock generator 91 comes, that is, t=n*(T1/N) time (n=1), the detection action of the voltage sensor 92 is triggered, and the surface of the wafer 4 is detected. The second bias voltage V1 is sent to the digital processor 93. The digital processor 93 operates on the detection result to obtain V=V1-V0', where V is the voltage to be compensated, and the result V is fed back to the bias RF source 7, and the bias RF source 7 is instantaneous according to the feedback result. Output voltage adjustment (Vs) 1 = (Vs) 0 + V. This cycle is repeated until n=N and the pulse is turned off. The voltage output from the bias voltage source 7 at the moment before the pulse is turned off is the target voltage at the last moment of the pulse turn-on time. After the pulse is turned off, electrons enter the bottom of the etch tank, neutralizing the positive charge, and the wafer 4 is biased back to 0V.

The RF pulse modulation system can realize the instantaneous dynamic compensation of the surface bias of the wafer 4 during the process, and achieve the compensation effect as shown in FIG.

In the bias modulation system of this embodiment, by setting the voltage adjustment module, the negative bias generated on the surface of the workpiece to be processed can be gradually increased, and the increase of the negative bias can be fully or partially compensated due to the gradual accumulation. The bias voltage lost by the positive potential generated by the positive ions on the surface of the workpiece to be processed, that is, although the positive potential reduces the negative bias of the wafer surface, the reduction of the negative bias and the increase of the negative bias It is basically flat, so that the negative bias can be kept within the preset range, thereby not only avoiding the plasma processing rate reduction, ensuring the productivity, but also ensuring that the surface of the workpiece to be processed can be sufficiently processed to meet the electrical performance. Example 3:

The present embodiment provides a plasma processing apparatus including a susceptor for carrying a workpiece to be processed, and the bias modulation system of the above-described Embodiment 2, the bias modulation system being electrically connected to the susceptor.

The plasma processing apparatus further includes a plasma generating device including a coil and an upper electrode RF source connected to the coil, wherein the upper electrode RF source is a continuous wave RF source or a pulse modulated RF source.

By adopting the bias modulation system of the above-described Embodiment 2, the negative bias generated on the surface of the workpiece to be processed can be gradually increased, and the increase in the negative bias can be fully or partially compensated for gradually accumulating to the surface of the workpiece to be processed. The positive ion generated by the positive ion and the bias voltage lost, that is, although the positive potential reduces the negative bias of the wafer surface, the reduction of the negative bias is substantially the same as the increase of the negative bias, thereby The negative bias voltage can be kept within the preset range, thereby not only avoiding the plasma processing rate reduction, ensuring the productivity, but also ensuring that the surface of the workpiece to be processed can be sufficiently processed to meet the electrical performance requirements.

In addition, it is worth noting that the bias modulation method, the bias modulation system, and the plasma processing apparatus including the bias modulation system of the present invention are not limited to the negative bias occurring in the generation of the inductively coupled plasma and the generation of the capacitively coupled plasma. The problem of pressure loss, the above-described inductively coupled plasma or capacitively coupled plasma is merely illustrative of specific embodiments of the invention and is not intended to limit the invention. As long as there is a problem of negative bias loss on the surface of the workpiece to be processed, the bias modulation method of the present invention can be employed, and the bias modulation system and the plasma processing apparatus solve the technical problems.

It is to be understood that the above embodiments are merely exemplary embodiments employed to explain the principles of the invention, but the invention is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and scope of the invention. These modifications and improvements are also considered to be within the scope of the invention.

1‧‧‧RF antenna

2‧‧‧Dielectric window

3‧‧‧vacuum chamber

4‧‧‧ wafer

5‧‧‧Metal electrode

6‧‧‧Slide

7‧‧‧Bias RF source

8‧‧‧Primary RF source

T1‧‧‧ pulse on time

T2‧‧‧ pulse off time

Vs‧‧‧ initial voltage

Vt‧‧‧ target voltage

9‧‧‧Voltage adjustment module

91‧‧‧clock generator

92‧‧‧ voltage sensor

93‧‧‧Digital Processor

10‧‧‧ Pedestal

1 is a schematic structural view of an inductively coupled semiconductor etching apparatus in the prior art; FIG. 2 is a waveform diagram of a modulated pulse-modulated RF source output according to an embodiment of the present invention; and FIG. 3 is a bias diagram of an embodiment of the present invention. FIG. 4 is a schematic diagram of a waveform of a modulated pulse modulated RF source output and an actual negative bias waveform of a corresponding wafer surface according to an embodiment of the present invention; FIG. 5 is a partial embodiment of the present invention Schematic diagram of the pressure modulation system.

Claims (13)

A bias modulation method, comprising: increasing an output voltage of a bias RF source during loading of a bias power to a pedestal for carrying a workpiece to be processed, so that the output voltage is The initial voltage value is increased to a target voltage value such that a negative bias voltage generated on the surface of the workpiece to be processed is maintained within a preset range during loading of the bias power to the susceptor. The bias modulation method according to claim 1, wherein the difference between the target voltage value and the initial voltage value is equal to a negative bias loss value, and the negative bias loss value is loaded on the pedestal During the bias power, the output voltage of the bias RF source maintains the loss value of the negative bias generated on the surface of the workpiece to be processed while the initial voltage value remains unchanged. The bias modulation method according to claim 1 or 2, wherein the pedestal is loaded with a bias power in a pulse period; wherein the pulse period includes a pulse on time and a pulse off time, During the pulse-on time, the pedestal is loaded with bias power while increasing an output voltage of the bias RF source to increase the output voltage from an initial voltage value to a target voltage value; Stop loading bias power to the pedestal. The bias modulation method of claim 3, wherein loading the bias power to the susceptor at the pulse-on time comprises the following steps: Step S101: detecting and recording t=0, in the waiting Processing a first bias voltage V ₀ generated on the surface of the workpiece; the first bias voltage V ₀ is equal to the initial voltage value; Step S102: detecting and recording at the time tn of the current pulse turn-on time, on the surface of the workpiece to be processed Generating a second bias voltage Vn; wherein tn=n(T1/N) N≥100, and N is an integer; 1≤n≤N, and n is an integer; T1 is the length of the pulse on time; =N, at the time tn, the output voltage of the bias RF source is the target voltage value; Step S103: calculating a difference V between the second bias voltage Vn and a third bias voltage V'n-1; The third bias voltage V'n-1 is a bias voltage generated on the surface of the workpiece to be processed after the bias compensation is completed at the previous time; the third bias voltage V ₀ ' is equal to the first bias voltage V ₀ ; Step S104 : The output voltage of the bias RF source will be immediately adjusted to tn-1 at the time tn of the current pulse-on time. Voltage V and the sum of the difference; Step S105: After detecting and generating the bias compensation recording completion workpiece surface to be machined in the third bias V _n '; Step S106: determining whether or not n is equal to N; if so, The step ends; if not, n is replaced by n+1, and step S102 to step S106 are sequentially performed. The modulation method of claim 1 or 2, wherein the ratio of the initial voltage value to the target voltage value ranges from 0.1 to 0.9. The modulation method of claim 1, wherein the output voltage of the bias RF source increases linearly during loading of the bias power to the susceptor. The modulation method according to claim 6, wherein the output voltage of the bias RF source has a linear increase slope: K=(Vt−Vs)/T1; wherein Vt is the target voltage value, Vs is the initial voltage value and T1 is the pulse on time. A bias modulation system, comprising: a bias RF source electrically coupled to a pedestal for carrying a workpiece to be processed for loading bias power to the susceptor; a voltage adjustment module, the voltage adjustment module is electrically connected to the bias RF source, and is configured to increase an output voltage of the bias RF source during the bias power supply of the bias RF source to the pedestal Increasing the output voltage from an initial voltage value to a target voltage value such that a negative bias voltage generated on a surface of the workpiece to be processed is maintained within a preset range during loading of the bias RF source to the pedestal bias power . The bias modulation system of claim 8, wherein the bias RF source is a pulse modulated RF source to enable bias power to be applied to the pedestal in a pulse period; wherein the pulse period includes a pulse turn-on time and a pulse turn-off time, the bias RF source loads a bias power to the pedestal at the pulse turn-on time, and the voltage adjustment module increases an output voltage of the bias RF source to enable the The output voltage is increased from an initial voltage value to a target voltage value; at the pulse off time, the biased RF source stops loading bias power to the pedestal. The voltage modulation module of claim 9, wherein the voltage adjustment module comprises: a clock generator capable of emitting a clock signal synchronized with the bias RF source; and a voltage sensing The voltage sensor is in communication with the clock generator to detect a negative bias generated on the surface of the workpiece to be processed during the pulse on time; a digital processor, the digital processor and the voltage The sensor communicates to receive the negative bias voltage sent from the voltage sensor, and obtains an output voltage adjustment value according to the negative bias voltage, and adjusts the output voltage of the bias RF source to the output. The voltage adjustment value is such that a negative bias generated on the surface of the workpiece to be processed is maintained at a preset value during loading of the bias power to the susceptor. The bias modulation system of claim 10, wherein the voltage sensor detects a first bias voltage V ₀ generated on the surface of the workpiece to be processed when t= ₀ ; the first bias voltage V ₀ is equal to the initial voltage value; and detecting a second bias voltage Vn generated on the surface of the workpiece to be processed at the time tn of the current one pulse on time; wherein tn=n(T1/N) N≥100 And N is an integer; 1≤n≤N, and n is an integer; T1 is the length of the pulse on time; when n=N, at tn, the output voltage of the bias RF source is the target voltage value; And detecting and recording a third bias voltage V _n ' generated on the surface of the workpiece to be processed after the completion of the bias compensation. The bias modulation system of claim 11, wherein the digital processor receives and records the first bias voltage V ₀ , the second bias voltage Vn , and the third signal transmitted from the voltage sensor Bigging V _n ', and performing: calculating a difference V between the second bias voltage Vn and a third bias voltage V _n-1 '; wherein the third bias voltage V _n-1 ' is at the previous moment After the bias compensation is completed, a bias voltage is generated on the surface of the workpiece to be processed; V ₀ ' is equal to the first bias voltage V ₀ ; the output voltage of the bias RF source is immediately adjusted to tn at the time tn of the current pulse-on time -1 the sum of the output voltage of the bias RF source and the difference V; determining whether n is equal to N; if so, controlling the voltage sensor to stop detecting operation, and stopping adjusting the output voltage of the bias RF source If not, the voltage sensor is controlled to continue the detection operation, and the output voltage of the bias RF source is adjusted instantaneously. A plasma processing apparatus comprising: a susceptor for carrying a workpiece to be processed, characterized by further comprising a bias modulation system according to any one of claims 8 to 12, the bias modulation The system is electrically connected to the base.