Plasma processing apparatus and plasma processing method

Abstract

Aspects relate to providing a plasma processing technique capable of facilitating uniform etch results in low power microwave plasma processing applications. A plasma processing apparatus includes: a control unit configured to cause a microwave power supply to output a first microwave pulse having a first power and a first duty cycle to generate uniformly distributed plasma in a plasma processing chamber; the microwave power supply outputs a second microwave pulse with a second power smaller than the first power and a second duty ratio larger than the first duty ratio; the RF bias power supply applies a wafer bias voltage to the substrate table; and the microwave power supply and the RF bias power supply stop the output of the second microwave pulse and the wafer bias voltage.

Description

Technical Field

[0001] The present disclosure relates to a plasma processing apparatus and a plasma processing method. Background Art

[0002] Conventionally, a technique for processing the surface of a semiconductor device by etching the surface of the semiconductor device with plasma is known. As an example, an electron cyclotron resonance (ECR) method is an example of a technique that can be used to etch a semiconductor device using plasma. In the ECR technique, plasma is generated by microwaves in a vacuum container to which an external magnetic field is applied. Electrons perform cyclotron motion due to the magnetic field, and by creating resonance between the magnetic field frequency and the microwave frequency, plasma can be generated.

[0003] In this technology, in order to accelerate the ions incident on the semiconductor device, high-frequency power is applied to the sample (e.g., a wafer) in a substantially sinusoidal continuous waveform. The high-frequency power applied to the sample is called a high-frequency bias. Halogen gases such as chlorine and fluorine are widely used as gases for generating plasma. Etching is performed by the reaction between the free radicals and ions generated by the plasma and the material of the sample. By performing plasma control to select the free radical species and the amount of ions, high-precision etching can be achieved.

[0004] Japanese Unexamined Patent Application Publication No. 2020-17565 (Patent Document 1) is an example of a conventional plasma etching technique.

[0005] Patent document 1 discloses that "a technology capable of controlling a process with high precision is provided. The plasma processing apparatus 1 includes a processing chamber 104 for performing plasma processing on a sample (wafer 112), a first high-frequency power supply (electromagnetic wave generating power supply 109) for supplying a first high-frequency power 161 for generating plasma, a sample stage (sample placement electrode 111) on which the sample is placed, and a second high-frequency power supply (high-frequency bias power supply 114) for supplying a second high-frequency power 162 to the sample stage. In addition, the apparatus includes a pulse generating unit 121 that generates a first pulse for temporally modulating the first high-frequency power 161 and a second pulse for temporally modulating the second high-frequency power 162. The first pulse has an off period, a first period, and a second period, wherein the amplitude of the first period is a finite value, and the amplitude of the second period is greater than the amplitude of the first period. The second pulse is an on period during the second period."

[0006] Reference List

[0007] Patent Literature

[0008] PTL 1: Japanese Unexamined Patent Application Publication No. 2020-17565 Summary of the invention

[0009] Technical issues

[0010] Low-power plasma etching using lower power microwaves is a type of plasma etching that has demand for a range of applications. By using low-power microwaves, a mild plasma can be created that allows for increased etching selectivity while reducing damage to the substrate compared to high-power plasma etching. Low-power plasma etching has applications for micromachining, surface modification, and medical device production.

[0011] However, when plasma etching is performed using low-power microwaves, the generated plasma has a relatively low density and cannot be uniformly diffused to the periphery of the processing chamber, resulting in a non-uniform plasma distribution. Etching performed with such a low-density, non-uniform plasma distribution results in a non-uniform etching result on the sample surface.

[0012] Patent document 1 discloses a technique for performing plasma processing, wherein a microwave output cycle has one off period and two on periods, wherein the microwave output in the second on period has a larger amplitude (microwave power) than the microwave output in the first on period, and a high-frequency bias voltage is applied during the second on period. According to the technique of patent document 1, isotropic etching caused by a period in which high-power microwaves are applied while the high-frequency bias voltage is off can be prevented.

[0013] However, Patent Document 1 does not consider the challenge of non-uniform etching caused by non-uniform plasma distribution in low-power microwave processing applications.

[0014]

[0011] Accordingly, an object of the present disclosure is directed to providing a plasma processing technique that can promote uniform etching results in low power microwave plasma processing applications.

[0015] Solution to the problem

[0016] A representative example of the present disclosure relates to a plasma processing apparatus, comprising: a plasma processing chamber; a substrate stage disposed in the plasma processing chamber and configured to support a substrate; a microwave power supply coupled to the plasma processing chamber and configured to generate a microwave signal; an RF bias power supply coupled to the substrate stage and configured to generate an RF bias signal; and a control unit configured to control the microwave power supply and the RF bias power supply; wherein the control unit enables: the microwave power supply to output a first microwave pulse having a first power and a first duty cycle in a first time period to generate plasma meeting a plasma density distribution standard in the plasma processing chamber; the microwave power supply to output a second microwave pulse having a second power less than the first power and a second duty cycle greater than the first duty cycle in a second time period after the first time period; the RF bias power supply applies a wafer bias voltage to the substrate stage in the second time period; and the microwave power supply and the RF bias power supply stop outputting the second microwave pulse and the wafer bias voltage in a third time period after the second time period.

[0017] Advantageous Effects of the Invention

[0018] According to the present disclosure, a plasma processing technique can be provided that can promote uniform etching results in low power microwave plasma processing applications.

[0019] Problems, configurations, and effects other than those described above will become clear from the description in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [ Figure 1 ] Figure 1 is a schematic configuration diagram of a longitudinal cross section of an ECR type microwave plasma processing apparatus according to an embodiment of the present disclosure.

[0021] [ Figure 2 ] Figure 2 is a flowchart illustrating an example flow of a plasma processing method according to an embodiment of the present disclosure.

[0022] [ Figure 3 ] Figure 3 is a diagram illustrating a graph of microwave power level settings and bias power level settings according to an embodiment of the present disclosure.

[0023] [ Figure 4 ] Figure 4 is a diagram illustrating an example of non-uniform plasma distribution in a plasma processing chamber.

[0024] [ Figure 5 ] Figure 5 is a diagram illustrating an example of uniform plasma distribution in a plasma processing chamber.

[0025] [ Figure 6 ] Figure 6 is a table showing examples of plasma processing parameters and corresponding plasma processing results according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] In this article, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the embodiments described herein are not intended to limit the present invention according to the claims, and it will be understood that each element and combination thereof described for the embodiments is not strictly necessary to implement various aspects of the present invention.

[0027] Various aspects are disclosed in the following description and related drawings. Alternative aspects may be designed without departing from the scope of the present disclosure. Additionally, well-known elements of the present disclosure will not be described in detail or will be omitted to avoid obscuring the relevant details of the present disclosure.

[0028] The words "exemplary" and / or "example" are used herein to mean "serving as an example, instance, or illustration." Any aspect described herein as "exemplary" and / or "example" is not necessarily to be construed as preferred or advantageous over other aspects. Likewise, the term "aspects of the disclosure" does not require that all aspects of the disclosure include the discussed feature, advantage, or mode of operation.

[0029] In addition, many aspects are described in terms of a sequence of actions to be performed by, for example, an element of a computing device. It will be appreciated that the various actions described herein may be performed by a specific circuit (e.g., an application specific integrated circuit (ASIC)), by program instructions executed by one or more processors, or by a combination of the two. Additionally, the sequence of actions described herein may be considered to be implemented entirely within a computer-readable storage medium of any form having a corresponding computer instruction set stored therein, which, when executed, will cause the associated processor to perform the functions described herein. Therefore, various aspects of the present disclosure may be implemented in a variety of different forms, all of which are considered to be within the scope of the claimed subject matter.

[0030] Hereinafter, a detailed description of embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0031] Turning now to the drawings, reference will be made to Figure 1 A schematic configuration diagram of a longitudinal cross section of an ECR type microwave plasma processing apparatus according to an embodiment of the present disclosure is described.

[0032] Figure 11 is a schematic configuration diagram of a longitudinal cross section of an ECR (electron cyclotron resonance) type microwave plasma processing apparatus (hereinafter, referred to as a plasma processing apparatus) according to an embodiment of the present disclosure. In an embodiment, each component of the plasma processing apparatus 1 (e.g., a processing chamber 121, a substrate stage 114, and a wafer 115) may have an axisymmetric shape (e.g., a cylinder, a column, or a disk).

[0033] exist Figure 1 In the embodiment of the present invention, the discharge device 113 is connected to the lower part of the processing chamber 121 inside the vacuum chamber 101 of the plasma processing apparatus 1. The shower plate 102 and the quartz top plate 103 are arranged in the upper part of the interior of the processing chamber 121. The shower plate 102 includes a plurality of holes. The plasma etching gas supplied from the gas supply device 119 is introduced into the processing chamber 121 through the holes of the shower plate 102. The quartz top plate 103 is arranged on the shower plate 102, and a gap 106 for gas supply is provided between the quartz top plate 103 and the quartz top plate 103. The quartz top plate 103 allows the transmission of electromagnetic waves from above and hermetically seals the upper part of the processing chamber 121.

[0034] The substrate stage 114 is arranged below the process chamber 121 to face the quartz top plate 103. The substrate stage 114 supports a wafer 115 (ie, a sample) placed thereon.

[0035] The cavity resonator 104 is arranged on the quartz top plate 103. The upper part of the cavity resonator 104 is open, and is connected to a waveguide 105 composed of a waveguide transformer that combines a vertical waveguide extending in the vertical direction with a curved portion that bends the direction of the electromagnetic wave by 90 degrees. The waveguide 105 and the like serve as an oscillation waveguide for propagating electromagnetic waves, and at the end of the waveguide 105, a microwave power supply 107 for plasma generation is connected via a tuner 108.

[0036] The microwave power source 107 is a power source for plasma generation, and oscillates electromagnetic waves under the control of the control unit 122. As an example, the microwave power source 107 can perform microwave oscillation of 2.45 GHz. The microwave oscillated by the microwave power source 107 is propagated through the waveguide 105, and propagates into the process chamber 121 via the cavity resonator 104, the quartz top plate 103, and the shower plate 102. Magnetic field generating coils 110, 111, and 112 are arranged around the process chamber 121. The magnetic field generating coil is composed of a plurality of coils, and forms a magnetic field in the process chamber 121. The high-frequency power oscillated from the microwave power source 107 generates a high-density plasma 120 in the process chamber 121 due to the interaction between the magnetic field generated by the magnetic field generating coils 110 to 112 and the ECR.

[0037] The microwave pulse unit 109 is connected to the microwave power supply 107. The pulse start signal from the microwave pulse unit 109 enables the microwave power supply 107 to pulse-modulate the microwave at the set repetition frequency. The high-frequency power output from the microwave power supply 107 is called microwave power (hereinafter, also referred to as MW power). The microwave pulse unit 109 can make the microwave power supply 107 output a first microwave pulse having a first power and a first duty cycle in a first time period to generate a uniformly distributed plasma 120 in the plasma processing chamber 121, and output a second microwave pulse having a second power less than the first power and a second duty cycle greater than the first duty cycle in a second time period after the first time period. The microwave power supply 107 can stop the output of the second microwave pulse in a third time period after the second time period.

[0038] In an embodiment, a plasma distribution sensor 125 configured to monitor the plasma density distribution of the plasma 120 may be disposed in the processing chamber 121. The plasma distribution sensor 125 may continuously monitor the plasma density distribution of the plasma 120 in the processing chamber 121. As described herein, the plasma density distribution measurements collected by the plasma distribution sensor 125 may be used to determine when to stop the output of the second microwave pulse and the wafer bias voltage to promote uniform etching results. In an embodiment, the plasma distribution sensor 125 may be implemented using the following: a Langmuir probe configured to measure the plasma density and temperature in the processing chamber 121 by measuring the current collected by a small electrode immersed in the plasma 120, an optical emission spectroscopy that uses a spectrometer to analyze the light emitted by the plasma 120 and determine its composition, a microwave interferometry that uses microwaves to measure the plasma density by analyzing the interference pattern generated by the microwaves passing through the plasma 120, an electrostatic probe configured to measure the plasma potential by measuring the voltage between the small electrode and the plasma 120, etc.

[0039] The RF bias power supply 116 generates high frequency power for ion attraction and supplies the high frequency power to the substrate stage 114. The matching box 117 is connected to the RF bias power supply 116 to match (align) the RF bias. Even when the plasma density is changed by microwave pulse oscillation and the plasma impedance fluctuates rapidly, the matching box 117 plays a role in matching the RF bias. The RF bias power supply 116 can be configured to apply a wafer bias voltage to the substrate stage 114 in a second time period. The RF bias power supply 116 can stop the output of the wafer bias voltage in a third time period after the second time period.

[0040] The control unit 122 is a control device for the plasma processing apparatus 1, and is connected to the microwave power supply 107 and the RF bias power supply (radio frequency bias power supply) 116 to control the output of the microwave power and the RF bias power. In an embodiment, the control unit 122 may be configured to control the first microwave pulse from the microwave power supply 107, the second microwave pulse from the microwave power supply 107, the output of the wafer bias voltage output by the RF bias power supply 116 for the substrate stage 114, the on and off timing of the microwave pulse unit 109, the frequency and duty cycle of the microwave power supply 107, and the delay time of the microwave power supply 107. In addition, the control unit may control the pulse on and off timing in the RF bias pulse unit 118, the repetition frequency and duty cycle of the on and off of the RF bias power supply 116, the delay time of the RF bias power supply 116, and other parameters of the microwave power supply 107 and the RF bias power supply 116. In addition, the control unit 122 may be configured to control etching parameters (e.g., gas flow rate, processing pressure, coil current, sample stage temperature, etching time, etc.) to promote desired etching performance.

[0041] Next, refer to Figure 2 , an example flow of a plasma processing method according to an embodiment of the present disclosure will be described.

[0042] Figure 2 2 is a flowchart showing an example process of a plasma processing method 200 according to an embodiment of the present disclosure. The plasma processing method 200 is a method for using a plasma processing apparatus (e.g., Figure 1 The sample may include a plasma treatment device (shown in Figure 1) to perform a plasma etching process of the sample. As described herein, the sample may include a plasma treatment device (shown in Figure 1) to perform a plasma etching process of the sample. Figure 1 The illustrated plasma processing apparatus 1 includes a wafer disposed on a substrate stage at a lower portion of a vacuum container.

[0043] First, at step S210, the control unit 122 of the plasma processing device 1 causes the microwave power supply 107 to output a first microwave pulse having a first power and a first duty cycle in a first time period to generate a dense, uniformly distributed plasma 120 in the plasma processing chamber 121 of the plasma processing device 1. As an example, the first microwave pulse may have a first power of 1500 watts and a first duty cycle of 5%, but the present disclosure is not limited here, and the first power and the first duty cycle may be adjusted according to the specifications of the etching application. Here, the first time period refers to the time window for outputting the first microwave pulse.

[0044] In certain embodiments, the first power and the first duty cycle can be set to values ​​capable of achieving a desired plasma density distribution as indicated by simulation results. Thus, the first microwave pulse can be used to generate a dense, uniformly distributed plasma 120 in the plasma processing chamber 121 of the plasma processing apparatus 1 .

[0045] Next, at step S220, the control unit 122 of the plasma processing device 1 causes the microwave power supply 107 to output a second microwave pulse having a second power and a second duty cycle in a second time period after the first time period, and causes the RF bias power supply 116 to apply a wafer bias voltage to the substrate stage 114 in the second time period. Here, the second power is less than the first power of the first microwave pulse, and the second duty cycle is greater than the first duty cycle of the first microwave pulse. For example, the second power may be 300 watts, and the second duty cycle may be 15%. However, as described above with respect to the first microwave pulse, the present disclosure is not limited here, and the second power and the second duty cycle may be adjusted according to the specifications of the etching application or based on simulation results.

[0046] As an example, referring to the case of using a wafer having a height of 100 mm and a radius of 150 mm, the ratio of the second duty cycle of the second microwave pulse to the first duty cycle of the first microwave pulse may be set to a value greater than 1, and the first power of the first microwave pulse and the second power of the second microwave pulse may be set to reach 1.48×10 17 ions / m30.95×10 17 It should be noted that ion density ratios greater than this number may be insufficient to achieve the desired ignition and plasma processing power for uniform plasma processing.

[0047] It should be noted that the second microwave pulse and the wafer bias voltage are applied together in the second time period. For example, the second microwave pulse and the wafer bias voltage can be applied substantially simultaneously with each other. In this way, effective etching can be promoted for the sample.

[0048] In addition, it should be noted that when switching from the first microwave pulse to the second microwave pulse having a lower power, the plasma 120 begins to converge toward the center of the plasma processing chamber and the plasma density distribution decreases. Therefore, as described herein, various aspects of the present disclosure are directed to performing etching of a sample before the plasma density distribution falls below a predetermined plasma density distribution standard to achieve uniform etching results.

[0049] In an embodiment, the wafer bias voltage may be associated with a wafer bias delay, and each microwave pulse may be associated with a microwave pulse delay.

[0050] Microwave pulse delay refers to the duration of delaying the output of a specific microwave pulse in a pulsed microwave plasma source. The microwave pulse delay can be set relative to the output of another microwave pulse (e.g., the time interval between the output of the first microwave pulse and the output of the second microwave pulse) or the end of another microwave pulse (e.g., the time interval after the end of the first microwave pulse and before the start of the second microwave pulse). In general, the microwave pulse delay time can have an impact on the characteristics of the plasma (e.g., plasma density, ion energy, and free radical species concentration). A longer delay time between pulses may result in a longer microwave-free power period, which may result in a lower plasma density and a reduced etching or deposition rate. On the other hand, a shorter delay time between pulses may result in a higher plasma density, a higher ion energy, and an increased etching or deposition rate. However, a shorter delay time may also result in increased ion bombardment and damage to the substrate or deposited film. In an embodiment, the microwave pulse delay can be expressed as a percentage of the time of a processing cycle (e.g., a microwave pulse delay ratio). The microwave pulse delay ratio is the ratio of the delay time of the opening period of the microwave pulse to the total time of one cycle of the microwave modulation pulse.

[0051] Wafer bias delay refers to a parameter of the duration of delaying the output of a wafer bias voltage in a pulsed microwave plasma source. Wafer bias delay can be set relative to the output of another microwave pulse (e.g., the time interval between the output of a first microwave pulse and the output of a wafer bias voltage) or the end of another microwave pulse (e.g., the time interval after the end of the first microwave pulse and before the wafer bias voltage application begins). In some cases, during the wafer bias delay, the sample can be exposed to a DC bias voltage before generating plasma. The bias voltage can affect the surface of the substrate by removing any oxide layer and creating a clean and activated surface. This can improve the adhesion and quality of the deposited film and change the surface chemistry of the substrate. However, if the wafer bias delay is too long, it may cause excessive sputtering of the substrate, which may damage the surface and cause a non-uniform etching profile. On the other hand, if the wafer bias delay is too short, the surface of the substrate may not be properly activated, which may result in poor film quality or adhesion. In an embodiment, the wafer bias delay can be expressed as a percentage of the time of a processing cycle (e.g., a wafer bias delay ratio). The wafer bias delay ratio is the ratio of the opening period delay time to one cycle of the wafer bias modulation pulse.

[0052] According to the research of the inventors of the present disclosure, it was found that delaying the output of the second microwave pulse relative to the output of the first microwave pulse by a second microwave pulse delay equal to the first duty cycle (e.g., so that the second microwave pulse starts when the first microwave pulse ends), and delaying the output of the wafer bias voltage relative to the output of the first microwave pulse by a wafer bias delay greater than or equal to the second microwave pulse delay (e.g., so that the wafer bias voltage is output simultaneously with or later than the second microwave pulse) achieves an etching result associated with high uniformity. This is because by starting the plasma process using the second microwave pulse quickly after creating a uniform plasma using the first pulse, etching can be performed at a time when the plasma density distribution is in its most uniform state. As an example, in a case where the first duty cycle is 30% and the second duty cycle is 50%, the second microwave pulse delay can be set to 30% (e.g., equal to the first duty cycle), and the wafer bias delay can be set to 30% or greater (e.g., greater than or equal to the second microwave pulse).

[0053] Next, at step S230, during a second time period, etching is performed on the sample while the plasma distribution sensor 125 provided in the plasma processing apparatus 1 continuously monitors the plasma density distribution of the plasma 120. For example, the plasma distribution sensor 125 may measure the plasma density distribution of the plasma 120 in terms of ions per cubic meter, and compare the measured plasma density distribution value with respect to a predetermined plasma density distribution standard. Here, the plasma density distribution standard is a benchmark, standard or reference for evaluating when the plasma density distribution is reduced below a tolerance threshold. In an embodiment, the plasma density distribution standard may be set to a minimum plasma density distribution value that may achieve satisfactory etching uniformity.

[0054] As an example, referring to the case of using a wafer having a height of 100 mm and a radius of 150 mm, the plasma density distribution standard may be set to 1.48×10 17 ions / m30.95×10 17 This is because at a larger ion density ratio, the ion density may not be sufficient to achieve uniform plasma processing. As another example, the plasma density distribution standard may be set to a value of "0.5×10^17 ions per cubic meter".

[0055] Next, at step S240, in response to determining that the plasma density distribution does not meet the plasma density distribution standard, the plasma processing method 200 may proceed to step S250. In the case where the plasma density distribution meets the plasma density distribution standard, the plasma processing method 200 may return to step S230 and may continue etching until a desired etching result is obtained or until the plasma density distribution does not meet the plasma density distribution standard.

[0056] Next, at step S250, the control unit 122 of the plasma processing apparatus 1 causes the microwave power supply 107 and the RF bias power supply 116 to stop the output of the second microwave pulse and the wafer bias voltage in a third time period after the second time period. Here, the third time period corresponds to the off state. By stopping the output of the second microwave pulse and the wafer bias voltage, the plasma 120 returns to the gas and no longer performs etching. In this way, by stopping the output of the second microwave pulse and the wafer bias voltage once the plasma density distribution does not reach the desired plasma density distribution standard, etching resulting in low uniformity results can be avoided.

[0057] According to reference Figure 2 The described plasma processing method 200 can obtain etching results associated with high uniformity by first outputting high-power microwave pulses to generate a uniformly distributed plasma 120, then outputting low-power microwave pulses together with a wafer bias voltage to promote the etching process, and in response to detecting that the plasma density distribution of the plasma 120 in the plasma processing chamber 121 no longer meets a predetermined plasma density distribution standard, stopping the output of the low-power microwave pulses and the wafer bias voltage.

[0058] Next, refer to Figure 3 , a microwave power level setting and a bias power level setting according to an embodiment of the present disclosure will be described.

[0059] Figure 3 is a diagram illustrating a graph of microwave power level settings and bias power level settings according to an embodiment of the present disclosure.As described herein, aspects of the present disclosure relate to controlling the power of microwaves and wafer bias during plasma processing to promote high uniformity etching results. Figure 3 A microwave power graph 310 and a wafer bias power graph 350 are shown for one cycle of a plasma etching process.

[0060] As shown in the microwave power curve 310, first, during the first time period 301, the control unit 122 causes the microwave power supply 107 to output a first microwave pulse 311 having a first power and a first duty cycle. The first power and the first duty cycle are set to values ​​capable of generating a dense, uniformly distributed plasma 120 in the plasma processing chamber 121 of the plasma processing apparatus. As an example, the first microwave pulse may have a first power of 1500 watts and a first duty cycle of 5%. As shown in the wafer bias power curve 350, it can be seen that during the first time period 301, while the first microwave pulse 311 is output, no wafer bias is applied.

[0061] Next, during a second time period 302 after the first time period 301, the control unit 122 causes the microwave power source to perform a discharge switch from the first power to the second power, and outputs a second microwave pulse 312 having a second power and a second duty cycle. Here, the second power is less than the first power of the first microwave pulse, and the second duty cycle is greater than the first duty cycle of the first microwave pulse. For example, the second power may be 300 watts, and the second duty cycle may be 15%.

[0062] As an example, referring to the case of using a wafer having a height of 100 mm and a radius of 150 mm, the ratio of the second duty cycle of the second microwave pulse to the first duty cycle of the first microwave pulse may be set to a value greater than 1, and the first power of the first microwave pulse and the second power of the second microwave pulse may be set to reach 1.48×10 17 ions / m30.95×10 17 It should be noted that ion density ratios greater than this number may be insufficient to achieve the desired ignition and plasma processing power for uniform plasma processing.

[0063] When switching from the first microwave pulse to the second microwave pulse having lower power, the plasma 120 begins to converge toward the center of the plasma processing chamber 121, and the uniformity of the plasma density distribution decreases.

[0064] Additionally, during the second time period 302, the RF bias power supply 116 applies the wafer bias voltage 352 at the same time as the second microwave pulse 312 is output by the microwave power supply 107. The simultaneous application of the wafer bias voltage 352 and the second microwave pulse 312 facilitates efficient etching of the sample. In this way, etching is performed while the plasma distribution sensor 125 provided in the plasma processing apparatus continuously monitors the plasma density distribution of the plasma 120.

[0065] Next, in response to determining that the plasma density distribution does not meet the plasma density distribution standard, the control unit 122 can cause the microwave power supply 107 and the RF bias power supply 116 to stop the output of the second microwave pulse 312 and the wafer bias voltage 352 in the third time period 303 after the second time period 302. By stopping the output of the second microwave pulse and the wafer bias voltage, the plasma returns to the gas and etching is no longer performed. In this way, by stopping the output of the second microwave pulse and the wafer bias voltage once the plasma density distribution does not meet the desired plasma density distribution standard, etching resulting in low uniformity results can be avoided.

[0066] It should be noted that reference Figure 3 A single cycle of microwave power and wafer bias power for a plasma etching process is described, but multiple such cycles may be repeated until the desired etching results are achieved.

[0067] Next, refer to Figure 4 and Figure 5 , examples of non-uniform and uniform plasma distributions will be described.

[0068] Figure 4 4 is a diagram showing an example of a non-uniform plasma distribution 400. As described herein, according to conventional low-power plasma etching techniques, the generated plasma distribution 400 has a relatively low density and cannot be uniformly diffused to the periphery of the process chamber 121 or cover the entire diameter of the wafer 115. Etching performed with such a low-density, non-uniform plasma distribution 400 may result in non-uniform etching results on the surface of the wafer 115.

[0069] Figure 5 is a diagram showing an example of a uniform plasma distribution 500. As described herein, according to the plasma processing technique based on the present disclosure, a high-power microwave pulse is output to generate a uniform plasma distribution 500 that uniformly extends to the periphery of the processing chamber and covers the entire diameter of the wafer 115. Next, a low-power microwave pulse is output together with a wafer bias voltage to facilitate the etching process, and in response to detecting that the plasma density distribution of the plasma in the plasma processing chamber 121 no longer meets a predetermined plasma density distribution standard, the output of the low-power microwave pulse and the wafer bias voltage is stopped. In this way, by performing plasma etching only when a uniform plasma distribution 500 exists in the processing chamber 121, an etching result associated with high uniformity can be obtained.

[0070] Next, refer to Figure 6 , examples of plasma processing parameters and corresponding plasma processing results according to embodiments of the present disclosure will be described.

[0071] As described herein, the results of a plasma process may be affected by many parameters. For example, with reference to a plasma process according to an embodiment of the present disclosure, it is desirable to adjust parameters (e.g., microwave source power, wafer bias operating frequency, wafer bias delay, wafer bias on time, and wafer bias pulse width) to promote uniform etching results. Therefore, Figure 6 A plasma processing table 600 including plasma processing parameters and corresponding plasma processing results is shown according to an embodiment of the present disclosure.

[0072] like Figure 6 As shown, the plasma processing table 600 includes a set of plasma processing parameters 610 and a set of plasma processing results 650. In the plasma processing table 600, the plasma processing parameters and the plasma processing results are shown for a first experiment, in which the microwave source power is set to 1500 W with a 5% duty cycle for the first microwave pulse and is set to 300 W with a 15% duty cycle for the second microwave pulse, and in the second experiment, the microwave power is set to 300 W with a 20% duty cycle for the first microwave pulse and is set to 1500 W with a 20% duty cycle for the second microwave pulse.

[0073] The set of plasma processing parameters 610 illustrates various parameters that may be controlled or varied to manipulate the properties and behavior of the plasma during plasma processing, and as shown in FIG. Figure 6 As shown, the microwave source power 612 , the wafer bias operating frequency 614 , the wafer bias delay 616 , the wafer bias on time 618 , and the wafer bias pulse width 620 may be included.

[0074] However, it should be noted that although the plasma processing table 600 shows a set of plasma processing parameters 610 that are most relevant to obtaining uniform plasma results for plasma processing techniques according to the present disclosure, the present disclosure is not limited herein and other plasma processing parameters (e.g., gas pressure, gas flow rate, electrode configuration, and gas composition) may also be adjusted appropriately.

[0075] Microwave source power 612 is the amount of microwave energy applied to the plasma in the plasma processing chamber. Changing microwave source power 612 may affect the density and temperature of the plasma, which may affect the etch rate, selectivity, and uniformity. Higher source power may result in higher plasma density and temperature, resulting in faster etch rates, but it may also increase the likelihood of damage to the substrate or etched features.

[0076] As described herein, aspects of the present disclosure involve applying a first microwave pulse having a first power and a second microwave pulse having a second power, wherein the first power is greater than the second power. Figure 6 As shown, the first microwave pulse may have a first power of 1500 W, and the second microwave pulse may have a second power of 300 W. That is, the first power may be five times the second power.

[0077] Additionally, each microwave pulse is associated with a duty cycle. Here, the duty cycle refers to the ratio of the on time of the plasma source (microwave power) relative to the total cycle time. In an embodiment, the duty cycle can be expressed as a percentage, where 100% indicates that a particular parameter or condition is applied continuously or constantly throughout the entire processing cycle. As described herein, various aspects of the present disclosure involve applying a first microwave pulse having a first duty cycle and a second microwave pulse having a second duty cycle, wherein the second duty cycle is greater than the first duty cycle. For example, Figure 6 As shown, the first microwave pulse may have a first duty cycle of 5%, and the second microwave pulse may have a second duty cycle of 15%. That is, the second duty cycle may be three times the first duty cycle.

[0078] Wafer bias operating frequency 614 refers to the frequency at which the wafer bias is turned on and off during the etching process. Changing the operating frequency may affect ion energy and directionality, which may affect etching rate and selectivity. Higher operating frequencies may increase ion energy, resulting in higher etching rates, but may also cause damage or roughness on the substrate surface. As an example, the wafer bias operating frequency for the first microwave pulse may be 100 Hz, and the wafer bias operating frequency for the second microwave pulse may be 500 Hz.

[0079] Wafer bias delay 616 is the time delay between the start of a plasma processing cycle (e.g., output of the first microwave pulse) and the application of a wafer bias voltage. Changing the wafer bias delay may affect surface activation and cleaning, which may affect the adhesion and quality of deposited films or etch characteristics. Longer wafer bias delays may improve surface activation, but may also increase the likelihood of sputtering and damage to the substrate surface.

[0080] As described herein, according to the research of the inventors of the present disclosure, it was found that delaying the output of the second microwave pulse relative to the output of the first microwave pulse by a second microwave pulse delay equal to the first duty cycle (e.g., such that the second microwave pulse starts when the first microwave pulse ends), and delaying the output of the wafer bias voltage relative to the output of the first microwave pulse by a wafer bias delay greater than or equal to the second microwave pulse delay (e.g., such that the wafer bias voltage is output simultaneously with or later than the second microwave pulse) achieves etching results associated with high uniformity. This is because by starting the plasma process with the second microwave pulse quickly after creating a uniform plasma with the first pulse, etching can be performed at a time when the plasma density distribution is in its most uniform state.

[0081] Wafer bias on time 618 refers to the duration of time that the wafer bias voltage is applied during the etching process. Changing the wafer bias on time may affect ion energy and directionality, which may affect etching rate and selectivity. Longer on times may increase ion energy, resulting in higher etching rates, but may also cause damage or roughness on the substrate surface.

[0082] Wafer bias pulse width 620 refers to the duration of each pulse of the wafer bias voltage applied to the wafer. That is, wafer bias on time 618 refers to the total duration during which the wafer bias voltage is applied to the wafer, while wafer bias pulse width 620 refers to the duration of each pulse of the wafer bias voltage applied to the wafer during each cycle. Changing the pulse width may affect ion energy and directionality, which may affect etching rate and selectivity. Longer pulse widths may increase ion energy, resulting in higher etching rates, but may also cause damage or roughness on the substrate surface.

[0083] The collection of plasma processing results 650 shows various parameters that characterize the etching performance of the plasma etching process, and as shown in FIG. Figure 6 As shown, polysilicon (Poly-Si) etch rate 652 , poly-Si uniformity 654 , SiN etch rate 656 , and SiN uniformity 658 may be included.

[0084] However, it should be noted that although the plasma processing table 600 shows a collection of plasma processing results 650 that are most relevant to showing uniformity of etching results for plasma processing techniques according to the present disclosure, the present disclosure is not limited here and other plasma processing results may also be monitored and evaluated.

[0085] The polysilicon etch rate 652 refers to the speed at which polysilicon is removed from the surface of the substrate during the etching process. The etch rate is affected by a variety of factors, including plasma density, gas composition, and substrate bias. Typically, higher plasma density and higher substrate bias will result in higher polysilicon etch rates. However, high etch rates may also result in over-etching or excessive removal of material, which may negatively affect device performance.

[0086] Polysilicon uniformity 654 refers to the uniformity of the etching process across the surface of the polysilicon layer. Non-uniformity may be caused by variations in plasma density, gas composition, or substrate bias, among other things. Non-uniformity may lead to abnormal device performance, reduced device yield, or even device failure. Therefore, achieving high uniformity is a goal in the polysilicon etching process.

[0087] SiN Etch Rate 656 The etch rate refers to the speed at which SiN (silicon nitride) is removed from the surface of the substrate during the etching process. The etch rate is affected by multiple factors, including plasma density, gas composition, and substrate bias. Generally, higher plasma density and higher substrate bias will result in higher SiN etch rates. However, similar to polysilicon etching, high etch rates may also result in over-etching or excessive removal of material, which may negatively affect device performance.

[0088] SiN uniformity 658 refers to the uniformity of the etching process across the surface of the SiN layer. Non-uniformity may be caused by variations in plasma density, gas composition, or substrate bias, among other things. Non-uniformity may lead to abnormal device performance, reduced device yield, or even device failure. Therefore, achieving high uniformity is a goal in the SiN etching process.

[0089] Referring to the set of plasma processing parameters 610 and the set of plasma processing results 650 included in the plasma processing table 600, it can be seen that for a given experiment, the most desirable polysilicon uniformity 654 (16.6, 13.3) and SiN uniformity 658 (14.6, 17.3) were achieved by using the following: a first microwave pulse having a power of 1500 Watts and a duty cycle of 5%, a second microwave pulse having a power of 300 W and a duty cycle of 15%, wafer bias operating frequencies of 100 Hz and 500 Hz, respectively, a wafer bias delay of 5% (e.g., a wafer bias delay equal to the first duty cycle), and wafer bias pulse widths of 0.5 ms and 0.1 ms, respectively. In other words, a first microwave pulse having the following: a power of 5 times the power of the second microwave pulse, a duty cycle of one-third the duty cycle of the second microwave pulse, and a wafer bias delay equal to the first duty cycle promotes uniform etching results.

[0090] As shown in plasma processing table 600, by using a first high power microwave pulse to create a dense, highly uniform plasma in a plasma processing chamber, and then quickly initiating plasma processing using a low power second microwave pulse and an applied wafer bias after creating the uniform plasma using the first pulse, etching can be performed at a time when the plasma density distribution is in its most uniform state, thereby resulting in etching results associated with high uniformity.

[0091] As described herein, aspects of the present disclosure involve first outputting high-power microwave pulses to generate a uniformly distributed plasma, then outputting low-power microwave pulses together with a wafer bias voltage to facilitate an etching process, and in response to detecting that the plasma density distribution of the plasma in the plasma processing chamber no longer meets a predetermined plasma density distribution standard, stopping the output of the low-power microwave pulses and the wafer bias voltage.

[0092] By setting the first microwave power and the first duty cycle to achieve a desired high density, uniform plasma, and setting the second microwave power and the second duty cycle to perform low power plasma etching, a high level of etching selectivity can be achieved while reducing damage and promoting highly uniform etching results.

[0093] In addition, by using a plasma distribution sensor to monitor the plasma density distribution of the plasma in the processing chamber, and in response to detecting that the plasma density distribution of the plasma in the plasma processing chamber detected by the plasma distribution sensor does not meet the plasma density distribution standard, stopping the output of the second microwave pulse and the wafer bias voltage, etching with low density that will result in low uniformity results can be avoided.

[0094] Furthermore, by setting the microwave pulse delay of the second microwave pulse relative to the output of the first microwave pulse to the same value as the first duty cycle of the first microwave pulse (e.g., 5%), and setting the wafer bias delay relative to the output of the first microwave pulse to be greater than or equal to the microwave pulse delay, the second microwave pulse and the wafer bias voltage can be applied at the same time as the end of the first microwave pulse. As a result, the plasma process can be started using the second microwave pulse quickly after the uniform plasma is created using the first pulse, and etching can be performed at a time when the plasma density distribution is in its most uniform state.

[0095] In this way, a plasma processing technique can be provided that can promote uniform etching results in low power microwave plasma processing applications.

[0096] As described herein, aspects of the present disclosure relate to the following aspects.

[0097] (Aspect 1)

[0098] A plasma processing device, comprising:

[0099] Plasma processing chamber;

[0100] a substrate table disposed within the plasma processing chamber and configured to support a substrate;

[0101] a microwave power supply coupled to the plasma processing chamber and configured to generate a microwave signal;

[0102] an RF bias power supply coupled to the substrate stage and configured to generate an RF bias signal; and

[0103] a control unit configured to control the microwave power supply and the RF bias power supply;

[0104] Among them, the control unit enables:

[0105] The microwave power supply outputs a first microwave pulse having a first power and a first duty cycle in a first time period to generate plasma meeting a plasma density distribution standard in the plasma processing chamber;

[0106] The microwave power source outputs a second microwave pulse having a second power less than the first power and a second duty cycle greater than the first duty cycle in a second time period after the first time period;

[0107] The RF bias power supply applies a wafer bias voltage to the substrate stage during a second time period; and

[0108] The microwave power supply and the RF bias power supply stop outputting the second microwave pulse and the wafer bias voltage in a third time period after the second time period.

[0109] (Aspect 2)

[0110] The plasma processing apparatus according to aspect 1, wherein the output of the second microwave pulse is delayed relative to the output of the first microwave pulse by a second microwave pulse delay equal to the first duty cycle.

[0111] (Aspect 3)

[0112] A plasma processing apparatus according to any one of Aspects 1 or 2, wherein the output of the wafer bias voltage is delayed relative to the output of the first microwave pulse by a wafer bias delay that is greater than or equal to a second microwave pulse delay.

[0113] (Aspect 4)

[0114] The plasma processing apparatus according to any one of Aspects 1 to 3 further includes: a plasma distribution sensor configured to monitor a plasma density distribution of plasma in a processing chamber, wherein the control unit is configured to: in response to detecting that the plasma density distribution of plasma in the plasma processing chamber detected by the plasma distribution sensor does not meet a plasma density distribution standard, cause the microwave power supply and the RF bias power supply to stop outputting the second microwave pulse and the wafer bias voltage.

[0115] (Aspect 5)

[0116] The plasma processing device according to any one of aspects 1 to 4, wherein the ion density ratio of the first microwave pulse to the second microwave pulse is greater than 1.48×10 17 Ion ratio per cubic meter: 0.95×10 17 In the case of ions, the plasma density distribution of the plasma in the plasma processing chamber is determined to fail the plasma density distribution standard.

[0117] (Aspect 6)

[0118] The plasma processing apparatus according to any one of aspects 1 to 5, wherein the second duty cycle is three times the first duty cycle.

[0119] (Aspect 7)

[0120] The plasma processing apparatus according to any one of aspects 1 to 6, wherein the first power is five times the second power.

[0121] The present invention may be a system, method and / or computer program product. The computer program product may include one or more computer-readable storage media having computer-readable program instructions thereon that cause a processor to perform aspects of the present invention.

[0122] A computer readable storage medium may be a tangible device that can retain and store instructions used by an instruction execution device. A computer readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above. A non-exhaustive list of more specific examples of computer readable storage media includes the following: a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device (such as a punched card with instructions recorded thereon or a raised structure in a groove), and any suitable combination of the above.

[0123] As used herein, computer-readable storage media should not be interpreted as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through optical cables), or electrical signals transmitted through wires.

[0124] Various aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present invention. It should be understood that each block of the flowchart illustration and / or block diagram and the combination of blocks in the flowchart illustration and / or block diagram can be implemented by computer-readable program instructions.

[0125] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device for producing a machine, so that the instructions (executed via the processor of the computer or other programmable data processing device) create a device for implementing the functions / actions specified in one or more boxes of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium, which can guide a computer, a programmable data processing device, and / or other equipment to work in a specific manner, so that the computer-readable storage medium in which the instructions are stored contains an article of manufacture, which includes instructions for executing various aspects of the functions / actions specified in one or more boxes of the flowchart and / or block diagram.

[0126] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device, so that a series of operating steps are performed on the computer, other programmable apparatus, or other device to produce a computer-implemented process, so that the instructions executed on the computer, other programmable apparatus, or other device implement the functions / actions specified in one or more boxes of the flowchart and / or block diagram.

[0127] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present invention. In this regard, each frame in the flow chart or block diagram can represent a part of a module, segment or instruction, which contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the function recorded in the frame may occur in an order other than the order recorded in the accompanying drawings. For example, the two frames shown in succession may actually be substantially concurrently executed, or the frames may be executed in reverse order at some time, depending on the function involved. It will also be noted that each frame of the block diagram and / or flow chart illustration, and the combination of frames in the block diagram and / or flow chart illustration can be implemented by a system based on special-purpose hardware, which performs a specified function or action, or performs a combination of special-purpose hardware and computer instructions.

[0128] Although the foregoing is directed to exemplary embodiments, other and further embodiments of the present invention may be designed without departing from the basic scope of the present invention, and the scope of the present invention is determined by the appended claims. Descriptions of various embodiments of the present disclosure have been presented for illustrative purposes, but are not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is to explain the principles of the embodiments, practical applications, or technical improvements to the technologies found in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

[0129] The terms used herein are only for the purpose of describing a specific embodiment, and are not intended to limit various embodiments. As used herein, the singular forms "one", "one" and "the" are also intended to include plural forms, unless the context clearly indicates otherwise. "A set of ...", "a group of ...", "a cluster of ..." etc. are intended to include one or more. It will also be understood that the terms "including" and / or "comprising" when used in this specification specify the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof. In the above detailed description of the exemplary embodiments of various embodiments, reference is made to the accompanying drawings (wherein similar reference numerals represent similar elements) forming a part of the various embodiments, and in the accompanying drawings, specific exemplary embodiments that can implement various embodiments are shown in an illustrative manner. These embodiments are described in sufficient detail so that those skilled in the art can implement these embodiments, but other embodiments can be used, and logical, mechanical, electrical and other changes can be made without departing from the scope of the various embodiments. In the above description, many specific details are set forth to provide a thorough understanding of the various embodiments. However, various embodiments can be implemented without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the embodiments.

[0130] Reference numerals list

[0131] 1... plasma processing apparatus, 101... vacuum chamber, 102... shower plate, 103... quartz top plate, 104... cavity resonator, 105... waveguide, 106... gap, 107... microwave power supply, 108... tuner, 109... microwave pulse unit, 110, 111, 112... magnetic field generating coil, 113... discharge device, 114... substrate stage, 115... wafer, 116... RF bias power supply, 117... matching box, 118... RF bias pulse unit, 119... gas supply device, 120... high-density plasma, 121... processing chamber, 122... control unit, 125... plasma distribution sensor.

Claims

1. A plasma processing device, comprising: Plasma processing chamber; a substrate stage disposed in the plasma processing chamber and configured to support a substrate; a microwave power supply coupled to the plasma processing chamber and configured to generate a microwave signal; an RF bias power supply coupled to the substrate stage and configured to generate an RF bias signal; as well as a control unit configured to control the microwave power supply and the RF bias power supply; Wherein, the control unit enables: The microwave power supply outputs a first microwave pulse having a first power and a first duty cycle in a first time period to generate plasma meeting a plasma density distribution standard in the plasma processing chamber; The microwave power source outputs a second microwave pulse having a second power less than the first power and a second duty cycle greater than the first duty cycle in a second time period after the first time period; The RF bias power supply applies a wafer bias voltage to the substrate stage during the second time period; and The microwave power supply and the RF bias power supply stop outputting the second microwave pulse and the wafer bias voltage in a third time period after the second time period.

2. The plasma processing apparatus according to claim 1, wherein: The output of the second microwave pulse is delayed relative to the output of the first microwave pulse by a second microwave pulse delay equal to the first duty cycle.

3. The plasma processing apparatus according to claim 2, wherein: The output of the wafer bias voltage is delayed relative to the output of the first microwave pulse by a wafer bias delay that is greater than or equal to a delay of the second microwave pulse.

4. The plasma processing apparatus according to claim 1, further comprising: A plasma distribution sensor is configured to monitor a plasma density distribution of the plasma in the plasma processing chamber, wherein the control unit is configured to: in response to detecting that the plasma density distribution of the plasma in the plasma processing chamber detected by the plasma distribution sensor does not meet the plasma density distribution standard, cause the microwave power supply and the RF bias power supply to stop outputting the second microwave pulse and the wafer bias voltage.

5. The plasma processing apparatus according to claim 4, wherein: The ion density ratio of the first microwave pulse to the second microwave pulse is greater than 1.48×10 17 Ion ratio per cubic meter: 0.95×10 17 When the number of ions is less than 1, the plasma density distribution of the plasma in the plasma processing chamber is determined to fail the plasma density distribution standard.

6. The plasma processing apparatus according to claim 1, wherein: The second duty cycle is three times the first duty cycle.

7. The plasma processing apparatus according to claim 1, wherein: The first power is five times the second power.

8. A plasma processing method for a plasma processing device, the plasma processing device comprising: Plasma processing chamber; a substrate stage disposed in the plasma processing chamber and configured to support a substrate; a microwave power supply coupled to the plasma processing chamber and configured to generate a microwave signal; an RF bias power supply coupled to the substrate stage and configured to generate an RF bias signal; a control unit configured to control the microwave power supply and the RF bias power supply; as well as a plasma distribution sensor configured to monitor a plasma density distribution of a plasma in the plasma processing chamber; Wherein, the plasma treatment method comprises: The microwave power source outputs a first microwave pulse having a first power and a first duty cycle in a first time period to generate plasma meeting a plasma density distribution standard in the plasma processing chamber; Outputting, by the microwave power source, a second microwave pulse having a second power less than the first power and a second duty cycle greater than the first duty cycle in a second time period after the first time period; applying a wafer bias voltage to the substrate stage by the RF bias power supply during the second time period; measuring, by the plasma distribution sensor, a plasma density distribution value of the plasma in the plasma processing chamber during the second time period; and In response to detecting that the plasma density distribution value of the plasma in the plasma processing chamber detected by the plasma distribution sensor does not meet the plasma density distribution standard, the microwave power supply and the RF bias power supply stop outputting the second microwave pulse and the wafer bias voltage in a third time period after the second time period.

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