Plasma processing apparatus and plasma processing method

Abstract

An aspect relates to providing a plasma processing technique that can promote uniform etching results in the application of low-power microwave plasma processing. The plasma processing apparatus includes a control unit, which causes the microwave power supply to output a first microwave pulse having a first power and a first duty ratio in order to generate plasma uniformly distributed in the plasma processing chamber, causes the microwave power supply to output a second microwave pulse having a second power smaller than the first power and a second duty ratio larger than the first duty ratio, causes the RF bias power supply to apply a wafer bias voltage to the substrate stage, and is configured to stop the output of the second microwave pulse and the wafer bias voltage to the microwave power supply and the RF bias power supply.

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 with plasma is known. As an example, the 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 chamber to which an external magnetic field is applied. Electrons perform cyclotron motion due to the magnetic field, and plasma can be generated by generating resonance between the frequency of the magnetic field and the frequency of the microwaves.

[0003] In this technique, in order to accelerate the ions incident on the semiconductor device, high-frequency power is applied to a 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 proceeds by the reaction between radicals and ions generated by plasma using the material of the sample. High-precision etching can be achieved by performing plasma control to select the radical species and the ion amount.

[0004] Patent Document 1 is an example of a conventional plasma etching technique. 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 in which a sample (wafer 112) is plasma-processed, a first high-frequency power supply (electromagnetic wave generation power supply 109) for supplying a first high-frequency power 161 for generating plasma, a sample stage (sample mounting 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. Further, the device further includes a pulse generation unit 121 that generates a first pulse for time-modulating the first high-frequency power 161 and a second pulse for time-modulating the second high-frequency power 162. The first pulse has an off period, a first period, and a second period. The amplitude of the first period is a finite value, and the amplitude of the second period is larger than the amplitude of the first period. The second pulse becomes an on period during the second period."

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Low-power plasma etching using lower-power microwaves is a type of plasma etching that has demand across various applications. By using low-power microwaves, a gentle plasma can be generated that can increase etching selectivity while reducing damage to the substrate compared to high-power plasma etching. Low-power plasma etching has applications for ultra-fine processing, surface modification, and medical device manufacturing.

[0007] However, when performing plasma etching using low-power microwaves, the generated plasma is of relatively low density and does not spread uniformly over the enclosure of the processing chamber, resulting in a non-uniform plasma distribution. Etching performed with such a low-density and non-uniform plasma distribution leads to non-uniform etching results on the sample surface.

[0008] Patent Document 1 discloses a technique for performing plasma processing having a microwave output cycle 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, it is possible to prevent isotropic etching resulting from the period during which high-power microwaves are applied while the high-frequency bias voltage is off. However, Patent Document 1 does not consider the problem of non-uniform etching resulting from the non-uniform plasma distribution in the application of low-power microwave processing.

[0009] Therefore, an object of the present disclosure is to provide a plasma processing technique capable of promoting uniform etching results in low-power microwave plasma processing applications.

Means for Solving the Problem

[0010] A typical example of the present disclosure includes 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. The control unit causes the microwave power supply to output a first microwave pulse having a first power and a first duty ratio in a first time period to generate plasma reaching a plasma density distribution determination criterion in the plasma processing chamber, causes the microwave power supply to output a second microwave pulse having a second power smaller than the first power and a second duty ratio larger than the first duty ratio in a second time period following the first time period, causes the RF bias power supply to apply a wafer bias voltage to the substrate stage in the second time period, and stops the output of the second microwave pulse and the wafer bias voltage over a third time period following the second time period to the microwave power supply and the RF bias power supply. The present disclosure relates to a plasma processing apparatus.

Advantages of the Invention

[0011] According to the present disclosure, it is possible to provide a plasma processing technique that can promote a uniform etching result in low-power microwave plasma processing applications.

[0012] Problems, configurations, and effects other than those described above will become clear from the following description of embodiments for carrying out the present invention.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0014] In this specification, embodiments of the present invention are described with reference to the drawings. It should be noted that the embodiments described in this specification are not intended to limit the present invention described in the claims, and it should be understood that each of the elements described in the embodiments and their combinations are not strictly necessary for implementing aspects of the present invention.

[0015] In the following description and the associated drawings, various aspects are disclosed. Alternative aspects can be devised without departing from the scope of the present disclosure. In addition, well-known elements of the present disclosure are not described in detail or are omitted in order not to obscure the relevant details of the present disclosure.

[0016] The terms "exemplary" and / or "example" are used herein to mean "serving as an example, instance, or illustration." It should not necessarily be construed that any aspect described herein as "exemplary" and / or "example" is more preferred or beneficial than other aspects. Similarly, the expression "aspect of the present disclosure" does not require that all aspects of the present disclosure include the features, advantages, or characteristics being discussed in terms of operation.

[0017] Furthermore, for example, many aspects are described regarding the order of actions performed by elements of a computing device. It will be recognized that the various actions described herein can be performed by a specific circuit (e.g., an application specific integrated circuit (ASIC)), program instructions executed by one or more processors, or a combination of both. Additionally, the order of actions described herein can be embodied as a whole within any form of computer-readable storage medium that, when executed, stores a corresponding set of computer instructions that can cause a relevant processor to perform the functions described herein. Thus, the various aspects of the present disclosure may be embodied in many different forms, all of which are intended to be within the scope of the claimed subject matter.

[0018] In this specification, a detailed description of embodiments of the present disclosure is described with reference to the drawings.

[0019] Here, in the figure, a schematic configuration diagram of a longitudinal section of an ECR type microwave plasma processing apparatus according to an embodiment of the present disclosure is described with reference to FIG. 1.

[0020] FIG. 1 is a schematic configuration diagram of a longitudinal 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 the embodiment, each component such as the processing chamber 121, the substrate stage 114, and the wafer 115 of the plasma processing apparatus 1 can have an axisymmetric shape such as a cylinder, a column, or a disk.

[0021] In FIG. 1, the evacuation 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 upper plate 103 are arranged in the upper part inside 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 upper plate 103 is arranged on the shower plate 102, and a gap 106 for gas supply is provided between the quartz upper plate 103 and the quartz upper plate 103. The quartz upper plate 103 enables the transmission of electromagnetic waves from above and airtightly seals the upper part of the processing chamber 121.

[0022] The substrate stage 114 is arranged below the processing chamber 121 so as to face the quartz upper plate 103. The substrate stage 114 supports the wafer 115 (i.e., the sample) placed thereon.

[0023] The cavity resonator 104 is arranged on the quartz upper plate 103. The upper part of the cavity resonator 104 is open, and is connected to a waveguide 105 composed of a waveguide converter that couples a vertical waveguide extending in the vertical direction to a bent portion bent by 90 degrees in the electromagnetic wave direction. The waveguide 105 and the like operate as a transmitting waveguide for propagating electromagnetic waves, and at the end portion of the waveguide 105, a microwave power source 107 for plasma generation is connected via a regulator 108.

[0024] The microwave power supply 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 supply 107 can perform microwave oscillation at 2.45 GHz. The microwaves oscillated by the microwave power supply 107 propagate through the waveguide 105 and reach the inside of the processing chamber 121 via the cavity resonator 104, the quartz upper plate 103, and the shower plate 102. The magnetic field generating coils 110, 111, and 112 are arranged around the processing chamber 121. The magnetic field generating coils are composed of a plurality of coils and form a magnetic field inside the processing chamber 121. The high-frequency power oscillated from the microwave power supply 107 generates high-density plasma 120 inside the processing chamber 121 due to the interaction between the magnetic field generated by the magnetic field generating coils 110 to 112 and the ECR.

[0025] The microwave pulse unit 109 is connected to the microwave power supply 107. By the pulse-on signal from the microwave pulse unit 109, the microwave power supply 107 can pulse-modulate microwaves at a 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 causes the microwave power supply 107 to output a first microwave pulse having a first power and a first duty ratio in a first time period to generate plasma 120 uniformly distributed in the plasma processing chamber 121, and in a second time period following the first time period, can output a second microwave pulse having a second power smaller than the first power and a second duty ratio larger than the first duty ratio. The microwave power supply 107 can stop the output of the second microwave pulse over a third time period following the second time period.

[0026] In an embodiment, a plasma distribution sensor 125 configured to monitor the plasma density distribution of the plasma 120 can be disposed in the processing chamber 121. This plasma distribution sensor 125 can continuously monitor the plasma density distribution of the plasma 120 in the processing chamber 121. As described herein, the plasma density distribution measurement values collected by the plasma distribution sensor 125 can be used to determine when to stop the output of the second microwave pulse and the output of the wafer bias voltage in order to promote a uniform etching result. In an embodiment, the plasma distribution sensor 125 is 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 impregnated with the plasma 120, emission spectroscopy that analyzes the light emitted by the plasma 120 and uses a spectrometer to determine its composition, microwave interferometry that measures the plasma density by analyzing the interference pattern generated by microwaves passing through the plasma 120 using microwaves, an electrostatic probe configured to measure the plasma potential by measuring the voltage between the small electrode and the plasma 120, or the like.

[0027] The RF bias power supply 116 generates high-frequency power for ion attraction and supplies it to the susceptor 114. The matching box 117 is connected to the RF bias power supply 116 to match (align) with the RF bias. The matching box 117 functions to match the RF bias even when the plasma density is changed by microwave pulse oscillation and the plasma impedance rapidly fluctuates. The RF bias power supply 116 can be configured to apply a wafer bias voltage to the susceptor 114 in a second time period. The RF bias power supply 116 can stop the output of the wafer bias voltage over a third time period following the second time period.

[0028] 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 output of a first microwave pulse from the microwave power supply 107, a second microwave pulse from the microwave power supply 107, the wafer bias voltage output by the RF bias power supply 116 with respect to the substrate stage 114, the on and off timings of the microwave pulse section 109, the frequency and duty ratio of the microwave power supply 107, and the delay time of the microwave power supply 107. Further, the control unit may control the on and off timings of the pulses in the RF bias pulse section 118, the repetition frequency and duty ratio for turning the RF bias power supply 116 on and off, 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 such as gas flow rate, processing pressure, coil current, sample stage temperature, and etching time to promote desired etching performance.

[0029] Next, with reference to FIG. 2, an exemplary flow of the plasma processing method according to an embodiment of the present disclosure will be described.

[0030] FIG. 2 is a flowchart showing an exemplary flow of the plasma processing method 200 according to an embodiment of the present disclosure. The plasma processing method 200 is a process for performing plasma etching of a sample using a plasma processing apparatus such as the apparatus shown in FIG. 1. As described herein, the sample may include a wafer disposed on a substrate stage in the lower portion of the vacuum chamber of the plasma processing apparatus 1 shown in FIG. 1.

[0031] First, in step S210, the control unit 122 of the plasma processing apparatus 1 causes the microwave power source 107 to output a first microwave pulse having a first power and a first duty ratio in a first time period in order to generate plasma 120 that is densely and uniformly distributed in the plasma processing chamber 121 of the plasma processing apparatus 1. As an example, the first microwave pulse may have a first power of 1500 watts and a first duty ratio of 5%, but the present disclosure is not limited herein, and the first power and the first duty ratio can be adjusted according to the specifications of the etching application. Here, the first time period refers to the time window during which the first microwave pulse is output. In a specific embodiment, the first power and the first duty ratio can be set to values that can achieve a desired plasma density distribution as indicated by the simulation results. In this way, the first microwave pulse can be used to generate plasma 120 that is densely and uniformly distributed in the plasma processing chamber 121 of the plasma processing apparatus 1.

[0032] Next, in step S220, the control unit 122 of the plasma processing apparatus 1 causes the microwave power source 107 to output a second microwave pulse having a second power and a second duty ratio in a second time period following the first time period, and causes the RF bias power source 116 to apply a wafer bias voltage to the substrate stage 114 in the second time period. Here, the second power is smaller than the first power of the first microwave pulse, and the second duty ratio is larger than the first duty ratio of the first microwave pulse. For example, the second power may be 300 watts, and the second duty ratio may be 15%. However, as described above with respect to the first microwave pulse, the present disclosure is not limited herein, and the second power and the second duty ratio can be adjusted according to the specifications of the etching application or based on the simulation results.

[0033] As an example, referring to the case where a wafer having a height of 100 mm and a radius of 150 mm is used, the ratio of the second duty ratio of the second microwave pulse to the first duty ratio of the first microwave pulse can 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 are 1.48×10 per cubic meter 17 / 0.95×10 17 The ion density ratio of the first microwave pulse to the second microwave pulse of ions can be set to achieve. Note that an ion density ratio greater than this number may not be sufficient to achieve the desired ignition and plasma processing power for uniform plasma processing.

[0034] Note that it should be noted that the second microwave pulse and the wafer bias voltage are both applied in the second time period. For example, the second microwave pulse and the wafer bias voltage can be applied almost simultaneously with each other. In this way, efficient etching with respect to the sample can be promoted. Further, it should be noted that as the switching from the first microwave pulse to the second microwave pulse having a lower power, the plasma 120 starts to converge toward the center of the plasma processing chamber, and the plasma density distribution decreases. Accordingly, as described in this specification, aspects of the present disclosure relate to performing etching of a sample before the plasma density distribution becomes less than a predetermined plasma density distribution determination criterion in order to achieve a uniform etching result.

[0035] 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. The microwave pulse delay refers to the duration during which the output of a specific microwave pulse is delayed in a pulsed microwave plasma source. This microwave pulse delay may be set based on the output of another microwave pulse (e.g., the time interval between the output of a first microwave pulse and the output of a second microwave pulse), or the end of another microwave pulse (e.g., the time interval after the first microwave pulse ends before the second microwave pulse starts). Generally, the microwave pulse delay time can affect plasma characteristics such as plasma density, ion energy, and radical species concentration. The longer the delay time between pulses, the longer the period without microwave power may be as a result, which may lead to a low plasma density and a decrease in the etching or deposition rate. On the other hand, the shorter the delay time between pulses, the higher the plasma density, the higher the ion energy, and the increase in the etching or deposition rate may be as a result. However, the shorter the delay time, the more the ion impact and damage to the substrate or the deposited film may increase as a result. In an embodiment, the microwave pulse delay may be expressed as a ratio of the time of one processing cycle (e.g., the microwave pulse delay rate). This microwave pulse delay rate is the ratio of the delay time of the on-period of the microwave pulse to the total time of one cycle of the microwave modulation pulse.

[0036] Wafer bias delay is a parameter that refers to the duration during which the output of the wafer bias voltage is delayed in a pulsed microwave plasma source. This wafer bias delay may be set based on the output of another microwave pulse (e.g., the time interval between the output of the first microwave pulse and the output of the wafer bias voltage), or the end of another microwave pulse (e.g., the time interval after the first microwave pulse has ended and before the application of the wafer bias voltage begins). In some cases, during the wafer bias delay, the sample may be exposed to a DC bias voltage before plasma is generated. This bias voltage can affect the surface of the substrate by removing any oxide film layer and forming a clean and activated surface. This can improve the adhesion and quality of the deposited film and modify the interfacial chemistry of the substrate. However, if the wafer bias delay is too long, it may lead to excessive sputtering of the substrate, damaging the surface and resulting in 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, resulting in low film quality or adhesion. In an embodiment, the wafer bias delay may be expressed as a ratio of the time of one processing cycle (e.g., the wafer bias delay rate). This wafer bias delay rate is the ratio of the on-period delay time to one cycle of the wafer bias modulation pulse.

[0037] According to the investigation of the inventors of the present disclosure, 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 ratio (for example, 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 (for example, such that the wafer bias voltage is output simultaneously with or after the second microwave pulse), it has been found that etching results associated with high uniformity are achieved. This is because by starting the plasma processing using the second microwave pulse immediately after a uniform plasma is formed using the first pulse, etching can be performed at the point in time when the plasma density distribution has its most uniform state. As an example, when the first duty ratio is 30% and the second duty ratio is 50%, the second microwave pulse delay can be set to 30% (for example, equal to the first duty ratio), and the wafer bias delay can be set to 30% or more (for example, greater than or equal to the second microwave pulse).

[0038] Next, in step S230, during the second time period, while etching is being performed on the sample, the plasma distribution sensor 125 disposed in the plasma processing apparatus 1 continuously monitors the plasma density distribution of the plasma 120. For example, the plasma distribution sensor 125 can measure the plasma density distribution of the plasma 120 with respect to ions per cubic meter and compare the measured plasma density distribution value with a predetermined plasma density distribution determination criterion. Here, the plasma density distribution determination criterion is a benchmark, standard, or reference used to measure when the plasma density distribution has decreased below an acceptable threshold. In an embodiment, the plasma density distribution determination criterion can be set as the minimum plasma density distribution value at which satisfactory etching uniformity can be achieved.

[0039] As an example, referring to the case where a wafer having a height of 100 mm and a radius of 150 mm is used, the plasma density distribution determination criterion is 1.48×10 per cubic meter 17 / 0.95×10 17 It can be set to the ion density ratio of the first microwave pulse to the second microwave pulse of ions. This is because the higher the ion density ratio, the more insufficient the ion density becomes to achieve a uniform plasma process. As another example, the plasma density distribution determination criterion can be set to a value of "0.5×10^17 ions per cubic meter.

[0040] Next, in response to the determination that the plasma density distribution in step S240 does not reach the plasma density distribution determination criterion, the plasma processing method 200 may proceed to step S250. If the plasma density distribution reaches the plasma density distribution determination criterion, the plasma processing method 200 may return to step S230, and etching may continue until a desired etching result is obtained or until the plasma density distribution no longer reaches the plasma density distribution determination criterion.

[0041] Next, in step S250, the control unit 122 of the plasma processing apparatus 1 stops the output of the second microwave pulse and the wafer bias voltage over a third time period following the second time period to the microwave power supply 107 and the RF bias power supply 116. Here, the third time period corresponds to an off state. By stopping the output of the second microwave pulse and the wafer bias voltage, the plasma 120 returns to the gas and etching is no longer performed. Thus, by stopping the output of the second microwave pulse and the wafer bias voltage, when the plasma density distribution no longer reaches the desired plasma density distribution determination criterion, etching that results in a low uniformity can be avoided.

[0042] According to the plasma processing method 200 described with reference to FIG. 2, first, a high-power microwave pulse is output to generate a uniformly distributed plasma 120, and then, a low-power microwave pulse is output together with a wafer bias voltage to promote the etching process. In response to detecting that the plasma density distribution of the plasma 120 in the plasma processing chamber 121 has not reached a predetermined plasma density distribution determination criterion, by stopping the output of the low-power microwave pulse and the wafer bias voltage, an etching result related to high uniformity can be obtained.

[0043] Next, with reference to FIG. 3, the microwave power level setting and the bias power level setting according to the embodiment of the present disclosure will be described.

[0044] FIG. 3 is a diagram showing graphs of microwave power level setting and bias power level setting according to an embodiment of the present disclosure. As described in this specification, aspects of the present disclosure relate to controlling the power of microwaves and wafer bias during plasma processing to promote a highly uniform etching result. FIG. 3 shows a microwave power graph 310 and a wafer bias power graph 350 in one cycle of the plasma etching process.

[0045] As shown in the microwave power graph 310, first, during a 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 ratio. The first power and the first duty ratio are set to values that can generate a dense and 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 ratio of 5%. As shown in the wafer bias power graph 350, it can be seen that although the first microwave pulse 311 is being output during this first time period 301, no wafer bias is applied.

[0046] Next, during the second time period 302 following the first time period 301, the control unit 122 causes the microwave power supply to perform a discharge switching for switching from the first power to the second power, and outputs a second microwave pulse 312 having the second power and the second duty ratio. Here, the second power is smaller than the first power of the first microwave pulse, and the second duty ratio is larger than the first duty ratio of the first microwave pulse. For example, the second power may be 300 watts, and the second duty ratio may be 15%.

[0047] As an example, referring to the case where a wafer having a height of 100 mm and a radius of 150 mm is used, the ratio of the second duty ratio of the second microwave pulse to the first duty ratio of the first microwave pulse can 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 are 1.48×10 17 / 0.95×10 17 It can be set to achieve the ion density ratio of the first microwave pulse to the second microwave pulse of 1 ion per 0.95×10

[0048] With the switching from the first microwave pulse to the second microwave pulse having a lower power, the plasma 120 starts to converge toward the center of the plasma processing chamber 121, and the plasma density distribution decreases. In addition, in the second time period 302, simultaneously with the output of the second microwave pulse 312 by the microwave power supply 107, the RF bias power supply 116 applies a wafer bias voltage 352. The simultaneous application of the wafer bias voltage 352 and the second microwave pulse 312 promotes efficient etching of the sample. Thus, 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.

[0049] Next, in response to a determination that the plasma density distribution has not reached the plasma density distribution determination criterion, the control unit 122 may stop the output of the second microwave pulse 312 and the wafer bias voltage 352 to the microwave power supply 107 and the RF bias power supply 116 over a third time period 303 following 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, when the plasma density distribution fails to reach the desired plasma density distribution determination criterion, etching that results in low uniformity can be avoided.

[0050] Although the microwave power and the wafer bias power in a single cycle of the plasma etching process have been described with reference to FIG. 3, it should be noted that such cycles may be repeated a plurality of times until the desired etching result is obtained.

[0051] Next, with reference to FIGS. 4 and 5, examples of non-uniform and uniform plasma distributions will be described.

[0052] FIG. 4 is a diagram showing an example of a non-uniform plasma distribution 400. As described herein, according to conventional lower-power plasma etching techniques, the generated plasma distribution 400 has a relatively low density and does not spread homogeneously to the periphery of the processing chamber 121 or cover the entire diameter of the wafer 115. Etching performed with such a low-density and non-uniform plasma distribution 400 may lead to non-uniform etching results on the surface of the wafer 115.

[0053] FIG. 5 is a diagram showing an example of a uniform plasma distribution 500. As described in this specification, according to the plasma processing technology according to the present disclosure, a high-power microwave pulse is output to generate a uniform plasma distribution 500 that extends uniformly up to the enclosure 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 promote the etching process, and the output of the low-power microwave pulse and the wafer bias voltage is stopped in response to the detection that the plasma density distribution of the plasma in the plasma processing chamber 121 has reached a predetermined plasma density distribution determination criterion. 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.

[0054] Next, with reference to FIG. 6, an example of plasma processing parameters and corresponding plasma processing results according to an embodiment of the present disclosure will be described.

[0055] As described in this specification, the results of plasma processing may be affected by several parameters. For example, referring to the plasma processing according to the embodiment of the present disclosure, in order to promote a uniform etching result, it is desirable to adjust parameters such as microwave supply power, wafer bias duty frequency, wafer bias delay, wafer bias on-time, and wafer bias pulse width. Therefore, FIG. 6 shows a plasma processing table 600 including plasma processing parameters and corresponding plasma processing results according to an embodiment of the present disclosure.

[0056] As shown in FIG. 6, 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 trial where the microwave supply power is set to 1500 W at 5% duty for the first microwave pulse and 300 W at 15% duty for the second microwave pulse, and for a second trial where the microwave power is set to 300 W at 20% duty for the first microwave pulse and 1500 W at 20% duty for the second microwave pulse.

[0057] The set of plasma processing parameters 610 represents different parameters that can be controlled or changed to scan the characteristics and behavior of the plasma during plasma processing. As shown in FIG. 6, it may include microwave supply power 612, wafer bias duty frequency 614, wafer bias delay 616, wafer bias on-time 618, and wafer bias pulse width 620. However, while the plasma processing table 600 shows the set of plasma processing parameters 610 that are most suitable for obtaining uniform plasma results for the plasma processing technology according to the present disclosure, it should be noted that the present disclosure is not limited herein, and other plasma processing parameters such as gas pressure, gas flow rate, electrode configuration, and gas composition can also be appropriately adjusted.

[0058] The microwave supply power 612 is the amount of microwave energy applied to the plasma in the plasma processing chamber. Changing the microwave supply power 612 may affect the density and temperature of the plasma, which in turn may affect the etching rate, selectivity, and uniformity. The higher the supply power, the higher the plasma density and temperature, which may lead to a higher etching rate, but may also increase the possibility of damage to the substrate or the etched features. As described herein, aspects of the present disclosure relate to applying a first microwave pulse having a first power and a second microwave pulse having a second power, where the first power is greater than the second power. For example, as shown in FIG. 6, the first microwave pulse can have a first power of 1500 watts and the second microwave pulse can have a second power of 300 watts. That is, the first power can be five times the second power.

[0059] In addition, 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) to the total cycle time. In an embodiment, the duty cycle can be expressed as a percentage, and 100% represents continuous or constant application over the entire processing cycle of a particular parameter or condition. As described herein, aspects of the present disclosure relate to applying a first microwave pulse having a first duty cycle and a second microwave pulse having a second duty cycle, where the first duty cycle is greater than the second duty cycle. For example, as shown in FIG. 6, the first microwave pulse can have a first duty cycle of 5% and the second microwave pulse can have a second duty cycle of 15%. That is, the second duty cycle can be three times the first duty cycle.

[0060] The wafer bias duty frequency 614 refers to the frequency at which the wafer bias is switched on and off during the etching process. Changing the duty frequency can affect the ion energy and directionality, which can in turn affect the etching rate and selectivity. The higher the duty frequency, the higher the ion energy, which can lead to a higher etching rate, but can also lead to damage or roughness on the substrate surface. As an example, the wafer bias duty frequency for the first microwave pulse can be 100 Hz and the wafer bias duty frequency for the second microwave pulse can be 500 Hz.

[0061] The wafer bias delay 616 is the time delay between the start of a plasma processing cycle (e.g., the output of the first microwave pulse) and the application of the wafer bias voltage. Changing the wafer bias delay can affect surface activation and cleaning, which can in turn affect the adhesion and quality of the deposited film or etched features. The longer the wafer bias delay, the more surface activation can be improved, but it may also increase the likelihood of sputtering and damage to the substrate surface. As described herein, according to the investigations of the inventors of the present disclosure, 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 ratio (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 the second microwave pulse delay (e.g., such that the wafer bias voltage is output simultaneously with or after the second microwave pulse), has been found to achieve etching results associated with high uniformity. This is because etching can be performed at the point in time when the plasma density distribution has its most uniform state by starting the plasma processing using the second microwave pulse immediately after the formation using the first pulse.

[0062] The wafer bias on-time 618 refers to the duration for which the wafer bias voltage is applied during the etching process. Changing the wafer bias on-time can affect the ion energy and directionality, which can in turn affect the etching rate and selectivity. The longer the on-time, the higher the ion energy, which can lead to a higher etching rate, but it may also lead to damage or roughness on the substrate surface.

[0063] The wafer bias pulse width 620 refers to the duration of an individual pulse of the wafer bias voltage applied to the wafer. That is, the wafer bias on-time 618 refers to the total duration during which the wafer bias voltage is applied to the wafer, while the wafer bias pulse width 620 refers to the duration of an individual pulse of the wafer bias voltage applied to the wafer during each cycle. Changing the pulse width may affect the ion energy and directivity, which may in turn affect the etching rate and selectivity. The longer the pulse width, the higher the ion energy, which may lead to a higher etching rate but may also lead to damage or roughness on the substrate surface.

[0064] A set of plasma processing results 650 indicates different parameters that characterize the etching performance of a plasma etching process and may include, as shown in FIG. 6, a Poly-Si etching rate 652, a Poly-Si uniformity 654, a SiN etching rate 656, and a SiN uniformity 658. However, while the plasma processing table 600 shows a set of plasma processing results 650 that is most suitable for showing the uniformity of the etching results regarding the plasma processing technology according to the present disclosure, it should be noted that the present disclosure is not limited herein and other plasma processing results may also be monitored and measured.

[0065] The Poly-Si etching rate 652 refers to the rate at which polysilicon is removed from the surface of the substrate during the etching process. The etching rate can be affected by several factors including plasma density, gas composition, and substrate bias. Generally, a higher plasma density and a higher substrate bias result in a higher polysilicon etching rate. However, a high etching rate may also lead to over-etching or excessive removal of the material, which may negatively affect device performance.

[0066] The Poly-Si uniformity 654 refers to the homogeneity of the etching process across the surface of the polysilicon layer. Non-uniformity can result from variations, among other factors, particularly in plasma density, gas composition, or substrate bias. Non-uniformity can, as a result, lead to irregular device performance, a decrease in device yield rate, and even device failure. Therefore, achieving high uniformity is one goal in the polysilicon etching process.

[0067] The SiN etching rate 656 refers to the rate at which SiN (silicon nitride) is removed from the surface of the substrate during the etching process. The etching rate can be affected by several factors, including plasma density, gas composition, and substrate bias. Generally, higher plasma density and higher substrate bias result in a higher SiN etching rate. However, as with the etching of polysilicon, a high etching rate can also lead to over-etching or excessive removal of the material, which can negatively impact device performance.

[0068] The SiN uniformity 658 refers to the homogeneity of the etching process across the surface of the SiN layer. Non-uniformity can result from variations, among other factors, particularly in plasma density, gas composition, or substrate bias. Non-uniformity can, as a result, lead to irregular device performance, a decrease in device yield rate, and even device failure. Therefore, achieving high uniformity is one goal in the SiN etching process.

[0069] Referring to the set of plasma processing parameters 610 and the set of plasma processing results 650 included in the plasma processing table 600, for a given trial, the most desirable poly-Si uniformity 654 (16.6, 13.3) and SiN uniformity 658 (14.6, 17.3) are achieved by using a first microwave pulse having a power of 1500 watts and a duty ratio of 5%, a second microwave pulse having a power of 300 watts and a duty ratio of 15%, wafer bias duty 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 rate), and wafer bias pulse widths of 0.5 ms and 0.1 ms respectively. In other words, a first microwave pulse having five times the power of the second microwave pulse, one-third the duty ratio of the second microwave pulse, and a wafer bias delay equal to the first duty rate promoted a uniform etching result.

[0070] As shown by the plasma processing table 600, a first high-power microwave pulse is used to generate a dense and highly uniform plasma in the plasma processing chamber, and then, immediately after a uniform plasma is formed using the first pulse, a second low-power microwave pulse and an applied wafer bias are used to start plasma processing, so that etching can be performed when the plasma density distribution is in its most uniform state, leading to an etching result related to high uniformity.

[0071] As described herein, aspects of the present disclosure relate to first outputting a high-power microwave pulse to generate a uniformly distributed plasma, then outputting a low-power microwave pulse together with a wafer bias voltage to facilitate an etching process, and stopping the output of the low-power microwave pulse and the wafer bias voltage in response to detecting that the plasma density distribution of the plasma in the plasma processing chamber no longer reaches a predetermined plasma density distribution criterion.

[0072] To achieve a desired high-density and uniform plasma, a first microwave power and a first duty ratio are set, and to perform low-power plasma etching, a second microwave power and a second duty ratio are set, by which a high level of etching selectivity can be achieved while simultaneously reducing damage and promoting a highly uniform etching result.

[0073] In addition, a plasma distribution sensor is used to monitor the plasma density distribution of the plasma in the processing chamber, and in response to the detection that the plasma density distribution of the plasma in the plasma processing chamber detected by the plasma distribution sensor does not reach the plasma density distribution determination criterion, the output of the second microwave pulse and the wafer bias voltage is stopped, by which low-uniformity results caused by low-density etching can be avoided.

[0074] Furthermore, the microwave pulse delay of the second microwave pulse with respect to the output of the first microwave pulse is set to the same value (for example, 5%) as the first duty ratio of the first microwave pulse, and the wafer bias delay with respect to the output of the first microwave pulse is set to be greater than or equal to the microwave pulse delay, by which the second microwave pulse and the wafer bias voltage can be applied simultaneously with the termination of the first microwave pulse. As a result, it is possible to start plasma processing using the second microwave pulse immediately after a uniform plasma is formed using the first pulse, and etching can be performed when the plasma density distribution is in its most uniform state.

[0075] In this way, it is possible to provide a plasma processing technology that can promote a uniform etching result in the application of low-power microwave plasma processing.

[0076] As described in this specification, aspects of the present disclosure relate to the following aspects.

[0077] (Aspect 1) A plasma processing chamber, and A substrate stage disposed in the plasma processing chamber and configured to support a substrate; A microwave power source coupled to the plasma processing chamber and configured to generate a microwave signal; An RF bias power source coupled to the substrate stage and configured to generate an RF bias signal; A control unit configured to control the microwave power source and the RF bias power source; In a first time period, the control unit causes the microwave power source to output a first microwave pulse having a first power and a first duty ratio in order to generate plasma in the plasma processing chamber that reaches a plasma density distribution determination criterion. In a second time period following the first time period, the control unit causes the microwave power source to output a second microwave pulse having a second power smaller than the first power and a second duty ratio larger than the first duty ratio. In the second time period, the control unit causes the RF bias power source to apply a wafer bias voltage to the substrate stage. In a third time period following the second time period, the control unit stops outputting the second microwave pulse and the wafer bias voltage to the microwave power source and the RF bias power source. A plasma processing apparatus.

[0078] (Aspect 2) The plasma processing apparatus according to Aspect 1, wherein the output of the second microwave pulse is delayed with respect to the output of the first microwave pulse by a second microwave pulse delay equal to the first duty ratio.

[0079] (Aspect 3) The plasma processing apparatus according to Aspect 1 or 2, wherein the output of the wafer bias voltage is delayed with respect to the output of the first microwave pulse by a wafer bias delay greater than or equal to the second microwave pulse delay.

[0080] (Aspect 4) The plasma processing apparatus according to any one of aspects 1 to 3, further comprising a plasma distribution sensor configured to monitor a plasma density distribution of the plasma in the plasma processing chamber, wherein the control unit responds to a detection that the plasma density distribution of the plasma in the plasma processing chamber detected by the plasma distribution sensor does not reach the plasma density distribution determination criterion, and stops outputting the second microwave pulse and the wafer bias voltage to the microwave power supply and the RF bias power supply.

[0081] (Aspect 5) When the ion density ratio of the first microwave pulse to the second microwave pulse is greater than 1.48×10 17 ~0.95×10 17 ions per cubic meter, it is determined that the plasma density distribution of the plasma in the plasma processing chamber does not satisfy the plasma density distribution determination criterion. The plasma processing apparatus according to any one of aspects 1 to 4.

[0082] (Aspect 6) The plasma processing apparatus according to any one of aspects 1 to 5, wherein the second duty ratio is three times the first duty ratio.

[0083] (Aspect 7) The plasma processing apparatus according to any one of aspects 1 to 6, wherein the first power is five times the second power.

[0084] The present invention may also be a system, method, and / or computer program product. This computer program product may include a computer-readable storage medium having computer-readable program instructions for causing a processor to implement aspects of the present invention.

[0085] A computer-readable storage medium can be a tangible device that holds and stores instructions for use by an instruction execution device. The computer-readable storage medium can be, for example, but is 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 foregoing. A non-exhaustive list of more specific examples of computer-readable storage media includes portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disks (DVD), memory sticks, floppy disks, mechanically encoded devices such as punch cards or raised structures in grooves having instructions recorded thereon, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium should not be construed to be a primary signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., an optical pulse passing through an optical fiber cable), or an electrical signal transmitted by an electrical wire.

[0086] Aspects of the invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0087] The computer-readable program instructions described above may be provided to a processor of a general purpose computer, a special purpose computer, or other programmable data processing apparatus to create means for implementing the functions / operations specified in the blocks of the flowchart and / or block diagram when executed via the processor of the computer or other programmable data processing apparatus. These computer-readable program instructions may further be stored in a computer-readable storage medium that stores instructions for a product comprising a computer, a programmable data processing apparatus, and / or other devices that can be made to function in a particular manner so that the computer-readable storage medium stores instructions for implementing the functions / operations specified in the blocks of the flowchart and / or block diagram.

[0088] The computer-readable program instructions described above may be further loaded onto a computer, other programmable apparatus, or other device to cause a series of operational steps to be performed on the computer or other programmable apparatus to create a computer-implemented process for implementing the functions / operations specified in the blocks of the flowchart and / or block diagram when executed on the computer, other programmable apparatus, or other device.

[0089] The flowcharts and block diagrams in the drawings illustrate the architecture, functionality, and operation of possible embodiments of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagram may represent a module, segment, or portion of instructions that include one or more executable instructions for implementing a specialized logical function. In some alternative embodiments, the functions described in the blocks may occur in a different order than that depicted in the drawings. For example, two blocks shown in succession may, in fact, be executed substantially simultaneously, or the blocks may, in some cases, be executed in the reverse order depending on the related functionality. Also, it will be recognized that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by a system based on dedicated hardware that performs the specialized functions or operations, or combinations of dedicated hardware and computer instructions.

[0090] The foregoing is related to exemplary embodiments of the present invention, but other additional embodiments may be devised without departing from the basic scope of the present invention, which scope is determined by the claims set forth hereinafter. The descriptions of the various embodiments of the present disclosure are provided 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 skilled in the art without departing from the scope and spirit of the described embodiments. The terms used herein are chosen to describe embodiments for purposes of explaining the principles of the embodiments, to facilitate the practical application or technical improvement of technologies existing in the market, or to enable others having ordinary skill in the art to understand the embodiments disclosed herein.

[0091] The terms used in this specification are for the purpose of describing particular embodiments only and are not intended to limit the various embodiments. As used in this specification, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms as well. Terms such as "a set of", "a group of", "a bundle of", etc. are intended to include one or more. Further, as used in this specification, the terms "comprising" and / or "comprises" specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. In the above detailed description of exemplary embodiments of the various embodiments, reference has been made to the accompanying drawings (like numbers indicate like elements) that form a part thereof, and by way of example, particular exemplary embodiments have been shown, and the various embodiments are practicable. The above embodiments have been described in sufficient detail for those skilled in the art to practice the embodiments, but other embodiments may be used and logical, mechanical, electrical, and other changes may be made without departing from the scope of the various embodiments. In order to achieve a sufficient understanding of the various embodiments, numerous specific details have been set forth in the above description. However, the various embodiments may be practiced without those specific details. In other instances, well-known circuits, structures, and techniques have not been shown in detail so as not to obscure the embodiments.

Explanation of Reference Numerals

[0092] 1 Plasma processing apparatus 101 Vacuum chamber 102 Shower plate 103 Quartz upper plate 104 Cavity resonator 105 Waveguide 106 Gap 107 Microwave power source 108 Regulator 109 Microwave pulse section 110, 111, 112 Magnetic field generating coils 113 Retraction device 114 Substrate stage 115 Wafer 116 RF bias power supply 117 Matching box 118 RF bias pulse section 119 Gas supply device 120 High-density plasma 121 Processing chamber 122 Control unit 125 Plasma distribution sensor

Claims

1. A plasma processing chamber, a susceptor disposed in the plasma processing chamber and configured to support a substrate, a microwave power source coupled to the plasma processing chamber and configured to generate a microwave signal, an RF bias power source coupled to the susceptor and configured to generate an RF bias signal, and a control unit configured to control the microwave power source and the RF bias power source, wherein the control unit causes the microwave power source to output a first microwave pulse having a first power and a first duty ratio in a first time period to generate plasma in the plasma processing chamber that reaches a plasma density distribution determination criterion, causes the microwave power source to output a second microwave pulse having a second power smaller than the first power and a second duty ratio larger than the first duty ratio in a second time period following the first time period, causes the RF bias power source to apply a wafer bias voltage to the susceptor in the second time period, and causes the microwave power source and the RF bias power source to stop outputting the second microwave pulse and the wafer bias voltage over a third time period following the second time period, a plasma processing apparatus.

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

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

4. The plasma processing apparatus according to claim 1, further comprising a plasma distribution sensor configured to monitor a plasma density distribution of the plasma in the plasma processing chamber, wherein the control unit is configured to cause the microwave power source and the RF bias power source to stop outputting the second microwave pulse and the wafer bias voltage in response to detection by the plasma distribution sensor that the plasma density distribution of the plasma in the plasma processing chamber does not reach the plasma density distribution determination criterion.

5. The ion density ratio of the first microwave pulse to the second microwave pulse is 1.48×10 per cubic meter. １７ ~0.95 x 10 １７ 5. The plasma processing apparatus according to claim 4, wherein when the particle size is larger than the particle size, it is determined that the plasma density distribution of the plasma in the plasma processing chamber does not satisfy the plasma density distribution criterion.

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

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 apparatus, wherein the plasma processing apparatus includes a plasma processing chamber, a substrate stage disposed in the plasma processing chamber and configured to support a substrate, a microwave power source coupled to the plasma processing chamber and configured to generate a microwave signal, an RF bias power source coupled to the substrate stage and configured to generate an RF bias signal, a control unit configured to control the microwave power source and the RF bias power source, and a plasma distribution sensor configured to monitor a plasma density distribution of the plasma in the plasma processing chamber. The plasma processing method includes outputting, by the microwave power source, a first microwave pulse having a first power and a first duty ratio in a first time period to generate a plasma that reaches a plasma density distribution determination criterion in the plasma processing chamber; outputting, by the microwave power source, a second microwave pulse having a second power smaller than the first power and a second duty ratio larger than the first duty ratio in a second time period following the first time period; applying, by the RF bias power source, a wafer bias voltage to the substrate stage in the second time period; measuring, by the plasma distribution sensor, a plasma density distribution value of the plasma in the plasma processing chamber in the second time period; and stopping, in response to detection by the plasma distribution sensor that the plasma density distribution value of the plasma in the plasma processing chamber detected by the plasma distribution sensor does not reach the plasma density distribution determination criterion, outputting of the second microwave pulse and the wafer bias voltage over a third time period following the second time period. A plasma processing method including the above.

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