Plasma Processing Apparatus and Plasma Processing Method

Abstract

The plasma processing apparatus includes: a processing chamber for performing plasma processing on a specimen; a high-frequency power supply for supplying high-frequency power for generating plasma; a first high-frequency power supply for supplying first high-frequency power to a specimen stage on which the specimen is placed; a second high-frequency power supply for supplying second high-frequency power having a frequency higher than that of the first high-frequency power to the specimen stage; and a control device for controlling the first high-frequency power supply and the second high-frequency power supply so that the supply of the other high-frequency power is stopped during the supply of one of the high-frequency powers, and the frequencies of the first high-frequency power and the second high-frequency power are defined based on the peak half-value width of the ion energy distribution with respect to the frequency.

Description

Technical Field

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

[0002] In the manufacturing process of semiconductor devices, it is required to cope with the miniaturization and integration of the components included in the semiconductor device. For example, in integrated circuits and nanoelectromechanical systems, the nanostructuring of the structures is further promoted.

[0003] Generally, in the manufacturing process of semiconductor devices, photolithography technology is used to form fine patterns. In this technology, a pattern of a device structure is applied on a resist layer, and the substrate exposed through the pattern of the resist layer is selectively etched away. In subsequent processing steps, an integrated circuit can be formed as long as other materials are deposited in the etched area.

[0004] For example, in the manufacturing of MOSFET (Metal - Oxide - Semiconductor Field - Effect - Transistor) devices used in electronic devices and the like, plasma etching technology is used. In the etching process of a semiconductor substrate (hereinafter simply referred to as "substrate") using plasma etching, in order to improve the yield of the substrate, uniformity of the processing within the substrate surface is required, and as the miniaturization of the device progresses, the requirement for the perpendicularity of the etching shape increases. In order to make the etching shape uniformly perpendicular in the plane, it is important to control the ions incident from the plasma to the substrate.

[0005] As a method for controlling the ions incident from the plasma to the substrate, the following technique is disclosed in Patent Document 1: A plurality of bias application devices that attract ions from the plasma to the wafer are provided, and the energy and its distribution of the ions incident on the wafer are independently changed by controlling the bias power ratio (mixing ratio) of a plurality of frequencies.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008 - 244429

[0009] Patent Document 2: International Publication No. 2017 / 126184 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] The prior art described in the above-mentioned patent document 1 does not fully consider the controllability of ions for further miniaturization of components. That is, the high-frequency and low-frequency powers are overlapped (mixed) and the mixing ratio is changed to obtain a bias power for providing incident energy to the substrate to the ions. Therefore, the maximum potential difference (hereinafter referred to as "Vpp") of the voltage waveform of the overlapping synthetic high-frequency power applied to the sample stage must not exceed the hardware limit. Therefore, when the Vpp of each high-frequency power is used within a range smaller than the allowable maximum value, the respective maximum output cannot be exerted, and thus ion control may not be fully performed.

[0012] Furthermore, since the waveform of high-frequency power obtained by synthesizing different frequencies changes in a complex manner, impedance matching may become difficult. In addition, there is also a possibility that a problem of crosstalk may occur in which mutual electrical signals are mixed.

[0013] As a method for solving these problems, a method of switching bias power having a plurality of different frequencies applied to a sample stage is disclosed in Patent Document 2. In this method, by changing the switching time ratio, the problems that may occur in Patent Document 1 can be solved, and the energy and distribution of ions can be controlled by using different frequencies.

[0014] However, if the method of Patent Document 2 is used, although the in-plane uniformity of the etching rate of the blank wafer can be controlled, since the change in ion energy distribution caused by the frequency change is not taken into account, there is still a problem in controlling the in-plane uniformity of the etching shape. Figure 3 Explain the examples of the subject in detail. Figure 3 (b) shows the effect of applying only a single bias power on Figure 3 (a) is the result of etching the initial shape. Figure 3 (c) shows the result of etching using the condition that the distribution of the etching rate becomes flat in the method of Patent Document 2. In addition, here, etching is performed on a wafer in which a SiO2 film 24 is stacked on a Si substrate 23.

[0015] According to the results of etching with a single bias power, Figure 3 As shown in (b), the etching shape is vertical in both the center and the end of the wafer, but the shape depth is different between the center and the end of the wafer. In contrast, according to the method of Patent Document 2, the etching result is as follows: Figure 3 As shown in (c), the etching shape is different in the center of the wafer and the end of the wafer, but the shape depth is the same. Therefore, even when bias power of different frequencies is applied, there is a further problem in making the etching shape uniform within the wafer surface.

[0016] In order to solve the above problems, an object of the present invention is to provide a plasma processing apparatus and a plasma processing method capable of obtaining a desired etching shape within a wafer surface.

[0017] Means for Solving the Problems

[0018] One of the plasma processing apparatuses according to the present invention for solving the above problems is realized as follows. It is characterized by comprising: a processing chamber for performing plasma processing on a specimen; a high-frequency power supply for supplying high-frequency power for generating plasma; a first high-frequency power supply for supplying first high-frequency power to a specimen stage on which the specimen is placed; a second high-frequency power supply for supplying second high-frequency power having a frequency higher than that of the first high-frequency power to the specimen stage; and a control device for controlling the first high-frequency power supply and the second high-frequency power supply so that the supply of the other high-frequency power is stopped during the supply of one of the high-frequency powers, and the frequencies of the first high-frequency power and the second high-frequency power are defined according to the peak half-value width of the ion energy distribution with respect to the frequency.

[0019] One of the plasma processing methods according to the present invention is realized as follows. A plasma processing apparatus is used, which comprises: a processing chamber for performing plasma processing on a specimen; a high-frequency power supply for supplying high-frequency power for generating plasma; a first high-frequency power supply for supplying first high-frequency power to a specimen stage on which the specimen is placed; and a second high-frequency power supply for supplying second high-frequency power having a frequency higher than that of the first high-frequency power to the specimen stage. It is characterized by having the following steps: controlling the first high-frequency power supply and the second high-frequency power supply so that the supply of the other high-frequency power is stopped during the supply of one of the high-frequency powers; setting the pressure of the plasma processing to a pressure at which the mean free path of ions is longer than the sheath thickness on the specimen; and defining the frequencies of the first high-frequency power and the second high-frequency power according to the peak half-value width of the ion energy distribution with respect to the frequency.

[0020] Advantages of the Invention

[0021] According to the present invention, it is possible to provide a plasma processing apparatus and a plasma processing method capable of obtaining a desired etching shape within a wafer surface.

[0022] Problems, configurations, and effects other than the above become clear from the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic configuration diagram showing the plasma processing apparatus according to the present embodiment.

[0024] Figure 2 is a schematic structural diagram showing the plasma processing apparatus according to the present embodiment.

[0025] Figure 3 is a diagram showing the etching shape when etching a wafer using the prior art.

[0026] Figure 4 is a schematic diagram showing the basis for determining the range of the pressure conditions and the frequency conditions used in the embodiment of the present invention.

[0027] Figure 5 is a graph showing the relationship between the transit time of the ion sheath and the sheath voltage.

[0028] Figure 6 is Figure 4 a schematic diagram of the ion energy distribution function of the bias power within the range of the pressure conditions and the frequency conditions determined in

[0029] Figure 7 is a diagram showing Figure 2 the output waveforms of the high-frequency power source for plasma generation and the high-frequency power source for bias in the plasma processing apparatus of

[0030] Figure 8 is a diagram showing Figure 7 the etching rate at each output state when etching a wafer using the outputs of the high-frequency power source for plasma generation and the high-frequency power source for bias in the plasma processing apparatus of . The horizontal axis is the distance from the center of the wafer, and the vertical axis is the etching rate.

[0031] Figure 9 is a schematic diagram showing the plasma impedance in plasma etching.

[0032] Figure 10 is a diagram showing the etching shape when etching a wafer using the present embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] In the embodiments shown below, by utilizing the fact that the incident energy distribution of ions from the plasma to the wafer varies according to the frequency of the bias power, it is possible to further improve the controllability of ion incidence to the wafer, and to obtain in-plane uniformity of the etching process of the wafer, that is, in-plane uniformity of the etching rate and in-plane uniformity of the etching shape, corresponding to the miniaturized semiconductor device structure.

[0034] The bias voltage applied to the wafer is controlled independently of plasma generation, that is, independently of the control of the high-frequency power for plasma generation, and the high-frequency power applied to the sample stage for imparting energy to the ions incident on the wafer is controlled. Further, a plurality of bias power supplies having different frequencies are used to control the high-frequency power applied to the sample stage, and the supply of bias power at different frequencies is switched for each step.

[0035] By switching for each of these steps, a separate supply period of bias power at different frequencies is set, whereby the bias power supply at each frequency can be set to the maximum of the allowable value of the bias power supply 205 that can be applied to the sample stage during processing, further improving the controllability of ion incidence on the wafer. Hereinafter, embodiments of the present invention will be described.

[0036] Figure 1 It is a schematic structural diagram of the plasma processing apparatus according to the present embodiment. Figure 2 It is a schematic structural diagram of the plasma processing apparatus according to another embodiment. In Figure 1 、 Figure 2 ,the same reference numerals are given to the common structures. In the present embodiment, the vacuum container 101 constituting the processing chamber (chamber) is, for example, a cylindrical container made of a conductive material such as aluminum and is electrically grounded. The upper opening of the vacuum container 101 is sealed by a top plate 102 made of a material that can transmit electromagnetic waves, such as quartz. A vacuum exhaust device for decompressing and exhausting the inside to a given pressure is connected to the center of the lower part of the vacuum container 101. A waveguide 103 is provided above the top plate 102 so as to cover the top plate 102, and a high-frequency power supply for plasma generation (hereinafter referred to as "high-frequency power supply" or "plasma power supply 105") is connected via a matcher 104.

[0037] In this case, the plasma power supply 105 oscillates microwaves of 2.45 GHz. The oscillated microwaves propagate in the waveguide 103 and are introduced into the vacuum container 101 via the top plate 102. A solenoid coil (magnetic field generating device) 106 for forming a magnetic field in the vacuum container 101 is wound and installed outside the vacuum container 101. A shower plate 108 is provided above the lower part of the vacuum container 101 below the top plate 102, and a gas supply device 107 is connected between the top plate 102 and the shower plate 108 of the vacuum container 101.

[0038] Processing gas is supplied from the gas supply device 107 to the space between the top plate 102 and the shower plate 108, and the processing gas is supplied to the processing chamber formed in the vacuum container 101 via the shower plate 108. A sample stage 109 is provided in the vacuum container 101, and a wafer (sample) is carried in from a wafer carry-in port (not shown) and placed / held on the sample stage 109.

[0039] On the sample stage 109, there are provided a plurality of high-frequency power supplies for bias, specifically two high-frequency power supplies with different frequencies in this case, namely a first bias power supply with a frequency of 800 KHz (hereinafter referred to as "the first high-frequency power supply" or "the first bias power supply 113") and a second bias power supply with a frequency of 400 KHz (hereinafter referred to as "the second high-frequency power supply" or "the second bias power supply 114"). They are respectively connected in parallel via a filter 110 and first and second matchers 111, 112. The second high-frequency power supply can supply second high-frequency power with a frequency higher than that of the first high-frequency power in the first high-frequency power supply.

[0040] Here, in Figure 1 the plasma processing apparatus, after connecting the filter 110 with the first matcher 111 and the second matcher 112, output switching is performed under the control of the control device 115. In contrast, in Figure 2 the plasma processing apparatus, under the control of the control device 115, the connection between the filter 110 and the first matcher 111 or the second matcher 112 is switched via a switch.

[0041] The filter 110 in this case has the following functions: in the output of the first bias power supply 113, it does not allow the output from power supplies other than the first bias power supply 113, including power supplies (such as the power supply for the electrostatic chuck device for holding the wafer connected to the sample stage 109, the power supply for the heater for controlling the temperature of the wafer, etc.) whose illustration is omitted, to pass to the side of the first bias power supply 113 (for example, a high-pass filter, High Pass Filter); and in the output of the second bias power supply 114, it does not allow the output from power supplies other than the second bias power supply 114, including power supplies (such as the power supply for the electrostatic chuck device for holding the wafer connected to the sample stage 109, the power supply for the heater for controlling the temperature of the wafer, etc.) whose illustration is omitted, to pass to the side of the second bias power supply 114 (for example, a low-pass filter, Low Pass Filter). In addition, during the period when the high-frequency power of one of the first bias power supply 113 and the second bias power supply 114 is being supplied, the supply of the high-frequency power of the other is stopped. The plasma power supply 105, the first bias power supply 113, and the second bias power supply 114 are connected to the control device 115, and the output control of each power supply described below is performed by the control device 115.

[0042] In the plasma processing apparatus configured as described above, the processing gas supplied into the vacuum chamber 101 is plasmaized by the action of the electric field of the microwave introduced via the top plate 102 and the magnetic field formed by the solenoid coil 106 (for example, electron cyclotron resonance: Electron Cyclotron Resonance (ECR)), and plasma is formed in the space between the shower plate 108 and the sample stage 109.

[0043] In addition, high-frequency power with a frequency of 400 KHz is applied to the specimen stage 109 from the first bias power supply 113, or high-frequency power with a frequency of 800 KHz is applied from the second bias power supply 114. These high-frequency powers applied to the specimen stage 109 are controlled independently of the generation of plasma, and a bias voltage is generated to cause ions in the plasma to be incident on the wafer. The frequency of the high-frequency power applied to the specimen stage 109 is referred to as the bias frequency condition. In addition, the pressure in the chamber set by the vacuum pump 116 (pressure adjustment device) via the control device 115 is referred to as the pressure condition.

[0044] Refer to Figure 4 , and the differences in the motion states of ions under the pressure condition and the bias frequency condition (hereinafter referred to as the frequency condition) used in the chamber will be described. Figure 4 (a) of shows the motion state of ions when the frequency condition and the pressure condition determined in the present embodiment are satisfied. Furthermore, Figure 4 (b) of shows the motion state of ions when a frequency higher than the said frequency condition is selected. In addition, Figure 4 (c) of shows the motion state of ions when a pressure higher than the said pressure condition is selected. The said frequency condition and pressure condition are shown below.

[0045] Regarding the said frequency condition, it is determined as follows. Here, the boundary layer formed between the plasma and the wafer is called a sheath. The ion 201 passes through the sheath 202 by the force of the electric field generated by the bias power and finally reaches the wafer 203. However, if the cycle time of the positive and negative changes of the bias power is faster than the time for the ion to pass through the sheath, the time for the ion to stay in the sheath 202 becomes longer, and the deviation of the ion energy becomes larger. If the deviation of the ion energy becomes larger, the incident angle distribution of the ions becomes wider, so it is difficult to obtain a vertical etching shape. Therefore, in the present embodiment, a frequency condition having a cycle longer than the time for the ion 201 to pass through the sheath 202 is used. That is, the frequencies of the first high-frequency power and the second high-frequency power are preferably values specified according to the time for the ion to pass through the sheath, and more preferably values below the reciprocal of the time for the ion to pass through the sheath.

[0046] In addition, regarding the pressure condition in the chamber, it is determined as follows. The pressure condition used in the present embodiment is a value at which the mean free path of the ions 201 contained in the plasma exceeds the thickness of the sheath 202 existing directly above the wafer 203. By using this pressure condition, the influence caused by ion collisions in the sheath 202 can be ignored, and the deviation of ion energy can be suppressed.

[0047] The ion density of the plasma processing apparatus used in the present embodiment is 10 10 ~10 11 cm -3, the bias voltage is 100 to 400 V. Therefore, it is considered that the sheath thickness is about 0.4 mm to 4 mm. Thus, the pressure condition that can be used in this embodiment is 2.66 Pa or less, and the frequency condition is 3 MHz or less. The upper limit value of this frequency can be changed according to the gas type. Hereinafter, the reason will be described.

[0048] Figure 5 is a graph showing the relationship between the transit time of the ion sheath and the sheath voltage. As Figure 5 shown, the relationship between the transit time of the ion sheath and the sheath voltage varies according to the gas type used (e.g., Ar, Cl, He, H).

[0049] Here, if the sheath thickness is set to d, the sheath voltage is set to V, the transit time of the ion sheath is set to T i , the period of the bias power supply is set to T RF , the ion mass is set to m i , and the elementary charge is set to e, then the following Equation 1 and Equation 2 hold.

[0050] [Mathematical formula 1]

[0051] (Equation 1)

[0052] [Mathematical formula 2]

[0053] (Equation 2)

[0054] According to the required frequency condition, since T i <T RF / 2, in the case of using general gas types, the frequency of about 3 MHz becomes the upper limit. However, according to Figure 5 it can be seen that the upper limit of the frequency condition can be changed according to the gas type. In addition, Figure 5 shows an example of using one gas, but in the case of using a mixed gas, the graph changes according to its mixing ratio.

[0055] In order to satisfy the said frequency condition and the said pressure condition, in this embodiment, the frequency of the bias power is 400 KHz and 800 KHz, and the pressure of the chamber is 4.8 mTorr.

[0056] In Figure 6In the figure, the horizontal axis represents the energy of ions incident on the wafer, and the vertical axis represents the incident flux of ions with that energy towards the wafer. Here, the ion energy distributions at different bias power frequencies are compared and shown. It can be seen that the ion energy distributions 301 at 13.56 MHz and 302 at 400 KHz or 800 KHz respectively result in different peak ion energies. In addition, regarding the peak half-value widths (303, 304) of each, the ion energy distribution 301 is wider, and the deviation of the ion energy is large. Therefore, similar to the above high-pressure conditions, the incident angle distribution of ions becomes wide, and it is difficult to obtain a vertical etching shape.

[0057] (Etching evaluation)

[0058] Hereinafter, the etching evaluation conducted by the present inventor will be described. By switching the etching process of the first high-frequency power with a low frequency (400 KHz) and the second high-frequency power with a higher frequency (800 KHz) for output control as shown, the Figure 7 etching rate distribution shown is obtained. In addition, the etching process in this case is performed on the wafer having the film structure shown in Figure 8 (a) of Figure 3 , that is, a wafer in which a SiO2 film 24 is laminated on a Si substrate 23.

[0059] Regarding the etching conditions, a mixed gas of Cl2 and Ar is used as the processing gas, the total gas flow rate is set to 250 ml / min, the pressure is set to 4.8 mTorr, the output of the plasma power supply 105 is set to 700 W, and the outputs of the first bias power supply 113 and the second bias power supply 114 are set to 150 W respectively. The evaluation of the etching process is performed using the etching rate of the polysilicon film.

[0060] During the step time, the output ratio of the first bias power supply 113 and the second bias power supply 114 during etching is adjusted, and the adjustment is performed as shown in Figure 7 (a) - (c) of

[0061] Figure 8 (a) represents the etching rate distribution corresponding to the output control of Figure 7 (a) of Figure 7 . As shown in Figure 8 (a) of

[0062] Figure 8 (b) represents the etching rate distribution corresponding to the output control of Figure 7 (b) of Figure 7As shown in (b) thereof, when the low-frequency output and the high-frequency output are alternately output from the first and second bias power supplies for the same time, as Figure 8 shown in (b) thereof, the etching rate distribution becomes substantially uniform in the plane.

[0063] Figure 8 (c) of shows the etching rate distribution corresponding to the output control of Figure 7 (c). As Figure 7 shown in (c) thereof, when only the output from the second bias power supply having a high frequency is present, as Figure 8 shown in (c) thereof, the etching rate distribution becomes a high-on-the-outside distribution that is low at the wafer center and high at the periphery.

[0064] It can be seen that as the supply time ratio of the high-frequency power at a high frequency (800 KHz) gradually increases with respect to the supply time of the high-frequency power at a low frequency (400 KHz), the etching rate of the wafer peripheral portion increases. Therefore, the etching rate distribution in the wafer plane can be controlled.

[0065] In addition, as a reason for the increase in the etching rate of the wafer peripheral portion as the supply time ratio of the high-frequency power at a high frequency increases, in other words, as the supply time ratio of the high-frequency power at a low frequency decreases, the following is considered.

[0066] The plasma processing apparatus used in this embodiment is a plasma processing apparatus that utilizes the interaction between the electric field of microwaves and the magnetic field generated by a solenoid coil. In such a plasma processing apparatus, when a current flows between the sample stage 109 and the grounded vacuum vessel 101 via the plasma by the bias high-frequency power applied to the sample stage 109, electrons in the plasma cross the magnetic field formed in the vacuum vessel 101.

[0067] At this time, the magnetic field attempts to capture the electrons, which is expressed as the cross field impedance of the plasma. In Figure 9 , if the cross field impedance 207 from the central portion of the wafer 203 to the end portion of the wafer 203 is set as Z1, and the cross field impedance 208 from the end portion of the wafer 203 to the ground is set as Z2, then the cross field impedance (Z1 + Z2) observed from the central portion of the wafer 203 and the cross field impedance observed from the wafer end portion is only Z2. In addition, the sheath impedance 206 received from the sheath located directly above the wafer 203 is set as ZS. Since the sheath impedance ZS is the same in the plane of the wafer 203, the plasma impedance observed from the central portion of the wafer 203 is (ZS + Z1 + Z2), and the plasma impedance observed from the end portion of the wafer 203 is (ZS + Z2).

[0068] Here, the sheath impedance has an inverse relationship with the frequency of the high-frequency power. If the frequency increases, the sheath impedance decreases. Therefore, at high-frequency power with a high frequency, compared to the cross-magnetic-field impedance, the sheath impedance is small enough to be negligible. Thus, the plasma impedance at the central part of the wafer 203 can be approximated as (Z1 + Z2), and the plasma impedance at the end part of the wafer 203 is approximated as Z2. Therefore, compared with the central part of the wafer 203, the plasma impedance at the end part of the wafer 203 is lower. As a result, the ion energy from the plasma incident on the wafer 203 by applying a bias voltage increases at the end part of the wafer 203 compared to the central part of the wafer 203. Therefore, the etching rate at the end part of the wafer 203 is higher than that at the central part.

[0069] In contrast, at low-frequency high-frequency power, the sheath impedance increases, and the cross-magnetic-field impedance is negligible compared to the sheath impedance. Therefore, the plasma impedance at both the end part and the central part of the wafer 203 can be approximated as ZS. Thus, the difference in plasma impedance within the plane of the wafer 203 becomes smaller, and thus there is no difference in the ion incident energy from the plasma within the plane of the wafer 203.

[0070] According to the characteristics of the plasma processing apparatus used in this embodiment, the gas in the vacuum chamber 101 flows from the upper part to the lower part of the vacuum chamber 101 through the peripheral space of the specimen stage 109 and is exhausted. Therefore, the active species from the plasma supplied to the periphery of the wafer 203 are fewer than those at the central part of the wafer, and thus the etching rate around the wafer becomes lower, resulting in an etching rate distribution that is higher in the center. Therefore, this etching rate distribution that is higher in the center can be said to be a distribution based on the characteristics of the plasma processing apparatus of this embodiment.

[0071] As described above, according to this embodiment, by changing the ratio of the output time of the high-frequency power at a low frequency (400 KHz) to the high-frequency power at a high frequency (800 KHz), it is possible to adjust the etching rate distribution between a distribution that is higher in the center and a distribution that is higher towards the periphery. During this period, as shown in Figure 8 (b), by setting the conditions for the etching rate distribution to be approximately uniform, that is, the ratio of the output time of the high-frequency power at a low frequency and a high frequency, it is possible to achieve the uniformity of the etching rate within the plane of the wafer.

[0072] In addition, as shown in Figure 8 (b), the etching shape during the etching process under the conditions for making the etching rate uniform is shown in Figure 10 . Here, in the same manner as Figure 3 , the structure in which the SiO2 film 204 is formed on the mask 203 of the Si substrate was etched. Using the combination of the 400 KHz and 800 KHz high-frequency power used in this embodiment, as shown in Figure 8 (b), the etching process was performed under the conditions for making the etching rate uniform. As a result, asFigure 10 As shown, the etched shape becomes a vertical shape both in the central part and the end part of the wafer, and the shape depth is the same in the central part and the end part of the wafer.

[0073] In an example of etching treatment by the prior art (refer to Figure 3 (c) of Figure 6 ), there are differences in the etched shapes between the central part and the end part of the wafer. It is considered that the reason is that differences occur in the half-value width of the energy peak of the ion energy distribution due to the frequencies of two different bias powers. That is, as

[0074] shown, it is considered that if a combination is used in which the half-value width of the energy peak of the ion energy distribution generated by a low-frequency bias power (400 KHz) is different from the half-value width of the energy peak of the ion energy distribution generated by a high-frequency bias power (13.56 MHz), under the condition that the etching rate is made uniform by adjusting the time, the shape depth during etching becomes uniform at the central part and the end part of the wafer, but the etched shape is non-uniform.

[0075] In contrast, it is considered that if a combination of a low-frequency bias power (400 KHz) and a high-frequency bias power (800 KHz) used in the present embodiment is used, the half-value widths of the energy peaks of the ion energy distributions generated by the respective frequencies are equal. Therefore, under the condition that the etching rate is made uniform by adjusting the time, both the shape depth and the etched shape during etching become uniform at the central part and the end part of the wafer.

[0076] Furthermore, in the present embodiment, high-frequency powers of two different frequencies are supplied to the sample stage 109. However, when high-frequency power is supplied from one of the bias power supplies, the supply of high-frequency power from the other bias power supply is stopped. Therefore, current does not flow into the sample stage 109 from the other bias power supply. Thus, the generation of crosstalk can be prevented, and bias power can be stably supplied to the sample stage 109.

[0077] In addition, in the present embodiment, the pressure in the plasma treatment is set to 0.638 Pa. As a combination of bias power supplies having two different frequencies, a combination of a high-frequency power supply of 400 KHz and a high-frequency power supply of 800 KHz is used. However, as long as it is within the pressure condition and frequency condition, a combination of frequencies with a larger difference in sheath impedance can be selected. In other words, it is preferable that the frequency of the first high-frequency power and the frequency of the second high-frequency power are specified according to the impedance of the sheath on the specimen. For example, the frequencies are such that the difference in the impedance of the sheath at the frequency of the first high-frequency power and the impedance of the sheath at the frequency of the second high-frequency power is large. In addition, the switching between the high-frequency power of the lower frequency and the high-frequency power of the higher frequency can be performed first, either way.

[0078] As described above, according to the present embodiment, by changing the ratio of the output times of the first bias power supply and the second bias power supply to apply to the specimen stage, the etching rate distribution within the wafer surface can be controlled, and the etching rate uniformity within the wafer surface can be controlled. In addition, since the frequency is selected in consideration of the ion energy distribution, the distribution control of the etching shape within the wafer surface can also be performed.

[0079] In addition, in the above example, the combination of the pressure and the frequency of the bias power used is arbitrarily specified. However, since the sheath thickness is roughly estimated by the bias voltage, as long as the pressure is specified, the frequency condition of the bias power that can be used is determined. Therefore, if the frequency condition of the bias power that can be used is automatically shown by specifying the pressure, the control of ions becomes easier.

[0080] In addition, in the above embodiment, microwave ECR plasma is described as one example. However, the same effects as those of the present embodiment can also be obtained in plasma processing apparatuses using other plasma generation methods such as capacitively coupled plasma and inductively coupled plasma.

[0081] The above-described embodiment is an embodiment described in detail for easy understanding of the present invention, and is not limited to having all the structures described. In addition, a part of the structure of one embodiment can be replaced with the structure of another embodiment. In addition, the structure of another embodiment can be added to the structure of one embodiment. In addition, for a part of the structure of each embodiment, addition, deletion, and replacement of other structures can be performed.

[0082] Description of reference numerals

[0083] 101: Vacuum container, 102: Top plate, 103: Waveguide, 104: Matcher, 105: Plasma power supply, 106: Solenoid coil, 107: Gas supply device, 108: Shower plate, 109: Specimen stage, 110: Filter, 111: First matcher, 112: Second matcher, 113: First bias power supply, 114: Second bias power supply, 115: Control device, 116: Vacuum pump, 201: Ion, 202: Sheath, 203: Si substrate, 204: SiO2 film, 205: Bias power supply, 206: Sheath impedance, 207: Cross magnetic field impedance from electrode center to end, 208: Cross magnetic field impedance from electrode end to ground, 301: Ion energy distribution when the frequency of the bias power is 13.56 MHz, 302: Ion energy distribution when the frequency of the bias power is 400 KHz or 800 KHz, 303: Half-value width of the energy peak of the peak of the high energy side of the ion energy distribution when the frequency of the bias power is 13.56 MHz, 304: Half-value width of the energy peak of the peak of the high energy side of the ion energy distribution when the frequency of the bias power is 400 KHz or 800 KHz.

Claims

1. A plasma processing apparatus, characterized in that, Comprising: A processing chamber for performing plasma processing on a specimen; A high-frequency power supply for supplying high-frequency power for generating plasma; A first high-frequency power supply for supplying first high-frequency power to a specimen stage on which the specimen is placed; A second high-frequency power supply for supplying second high-frequency power having a frequency higher than that of the first high-frequency power to the specimen stage; And A control device for controlling the first high-frequency power supply and the second high-frequency power supply such that during the supply of one of the high-frequency powers, the supply of the other high-frequency power is stopped, The frequency of the first high-frequency power and the frequency of the second high-frequency power are defined according to the half-value width of the peak of the ion energy distribution with respect to the frequency.

2. The plasma processing apparatus according to claim 1, wherein The frequency of the second high-frequency power is a frequency at which the half-value width is substantially the same as the half-value width at the frequency of the first high-frequency power.

3. The plasma processing apparatus according to claim 2, wherein The frequency of the first high-frequency power and the frequency of the second high-frequency power are defined according to the impedance of the sheath on the specimen.

4. The plasma processing apparatus according to claim 3, wherein The frequency of the first high-frequency power and the frequency of the second high-frequency power are frequencies at which the difference between the impedance of the sheath at the frequency of the first high-frequency power and the impedance of the sheath at the frequency of the second high-frequency power becomes large.

5. The plasma processing apparatus according to claim 4, wherein The frequency of the first high-frequency power and the frequency of the second high-frequency power are values defined according to the time for ions to pass through the sheath.

6. The plasma processing apparatus according to claim 5, wherein The frequency of the first high-frequency power and the frequency of the second high-frequency power are values not exceeding the reciprocal of the time for ions to pass through the sheath.

7. The plasma processing apparatus according to claim 6, wherein The frequency of the second high-frequency power is 3 MHz or less.

8. A plasma treatment method, characterized in that, A plasma processing apparatus is used, which comprises: a processing chamber for performing plasma processing on a specimen; a high-frequency power supply for supplying high-frequency power for generating plasma; a first high-frequency power supply for supplying first high-frequency power to a specimen stage on which the specimen is placed; and a second high-frequency power supply for supplying second high-frequency power having a frequency higher than that of the first high-frequency power to the specimen stage, The plasma processing method has the following steps: Controlling the first high-frequency power supply and the second high-frequency power supply such that during the supply of one of the high-frequency powers, the supply of the other high-frequency power is stopped; Setting the pressure of the plasma processing to a pressure at which the mean free path of ions is longer than the thickness of the sheath on the specimen; And Defining the frequency of the first high-frequency power and the frequency of the second high-frequency power according to the half-value width of the peak of the ion energy distribution with respect to the frequency.

9. The plasma processing method according to claim 8, wherein The plasma processing method further has the following step: making the frequency of the second high-frequency power a frequency at which the half-value width is substantially the same as the half-value width at the frequency of the first high-frequency power.

10. The plasma treatment method according to claim 9, characterized in that: The plasma treatment method further has the following steps: making the frequencies of the first high-frequency power and the second high-frequency power be values below the reciprocal of the time for ions to pass through the sheath on the specimen.

11. The plasma treatment method according to claim 10, characterized in that: The plasma treatment method further has the following steps: making the pressure of the plasma treatment be 2.66 Pa or less.

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