JPH11340213A - Surface treatment method for sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To etch a multilayered film without omitting its base oxide film by etching the multilayered film in a flat surface without producing ruggedness on the etched surface by impressing a high-frequency bias voltage upon a sample stage and treating the multilayered film with plasma by periodically turning on and off the impressed high-frequency power. SOLUTION: In a plasma etching system, electromagnets 105 are arranged around a vacuum vessel 104 and a sample 107 is set up on a sample stage 108. In order to accelerate ions made incident to the sample 107, a radio- frequency(rf) bias power source 109 which is a high-frequency power source is connected to the sample stage 108 through a by-pass filter 111. The rf bias power impressed upon the sample 107 is periodically turned on and off. In other words, the etched surface is made smooth by periodically turning on and off the high-frequency voltage impressed upon the sample 107 at the time of etching a multilayered film composed of metallic films or metallic and polycrystalline silicon films.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for a semiconductor device, and more particularly to a surface treatment method for etching a semiconductor surface using plasma.

[0002]

2. Description of the Related Art Conventionally, as a means for treating the surface of a semiconductor element, an apparatus for etching a semiconductor element in plasma has been known. Here, a conventional technique will be described using an apparatus called an ECR (Electron Cyclotron Resonance) method as an example. In this method, plasma is generated by microwaves in a vacuum vessel to which a magnetic field is externally applied. Electrons move in a cyclotron due to the magnetic field, and a plasma can be generated efficiently by resonating this frequency with the frequency of the microwave. A high frequency voltage is applied to the sample to accelerate ions incident on the sample such as a semiconductor device. A halogen gas such as chlorine or fluorine is used as a gas to be plasma.

In such a conventional apparatus, the invention described in Japanese Patent Application Laid-Open No. 6-151360 (corresponding to US Pat. No. 5,352,324) has been known mainly for the purpose of improving the processing accuracy. Have been. According to the present invention, by selectively controlling the high-frequency voltage applied to the sample between on and off, the selectivity between silicon (Si), which is a substance to be etched, and the base oxide film can be increased, and the aspect ratio dependency can be reduced. . Also, JP-A-8-339989 (corresponding to US Pat. No. 5,614,060) states that
It is described that, by superimposing intermittent RF bias power short pulses in metal etching, the remaining etching can be reduced.

In Japanese Patent Application Laid-Open No. Sho 62-154734, a gas that causes deposition and etching is introduced, and a DC bias higher than a predetermined potential and a DC bias lower than a predetermined potential are alternately applied, thereby forming the inclined portion. A method of processing is described.

Japanese Patent Application Laid-Open No. 60-50923 (corresponding to US Pat. No. 4,579,623) discloses that the amount of etching gas introduced is periodically changed and the application time of a high-frequency voltage is changed. A method for improving surface treatment properties is described. Also, Japanese Patent Application Laid-Open No. 4-69415
No. (corresponding US Pat. No. 4,808,258) includes:
A method of modulating a high-frequency voltage applied to a sample to improve etching characteristics is described.

Further, US Pat. No. 4,585,516
According to the specification, in a three-electrode type etching apparatus, uniformity of an etching rate in a wafer surface is improved by modulating a high-frequency voltage of at least one of high-frequency power supplies connected to two of the electrodes. The method is described.

[0007]

With the recent trend toward higher speed and lower power consumption of semiconductor devices, large scale integrated circuits (LSIs) have been developed.
Conductor portions such as electrodes and wiring portions of an ed circuit) are required to have lower resistance. One of the solutions is
Conventionally, MOS (MetalOxide S)
There is a method in which a gate electrode of an element is formed of a metal such as tungsten. Since it is difficult to form a metal film directly on an oxide film with the current technology, a structure in which a polycrystalline silicon film is formed on an oxide film and a metal film is formed thereon is considered to be promising. Further, a barrier film such as titanium nitride is required between the polycrystalline silicon film and the metal film to suppress mutual diffusion. If there is no barrier film, the heating process after the film formation causes the polycrystalline silicon and the metal to be mixed by diffusion, thereby increasing the resistance value.

[0008] Etching of a film having a multilayer structure as described above causes problems that have not been encountered in the past. The problem results from the difference in the etching reaction between polycrystalline silicon and metal. For example, the sample temperature is set to a certain intermediate value because the optimum value of the temperature differs between metal and polycrystalline silicon. For this reason, the metal or the barrier film remains non-uniformly on the polycrystalline silicon, which causes a problem that unevenness occurs on the etched surface.

Further, with the recent increase in speed and power consumption of semiconductor devices, complementary metal oxide semiconductors (CMOS) have been developed.
The semiconductor has a dual gate structure in which polycrystalline silicon, which is the gate electrode on the pMOS side, is doped p-type and the nMOS side is doped n-type.

As described above, etching a film in which gate electrodes having different conductivities are mixed presents a problem which has not existed conventionally. For example, if the p-type gate and the n-type gate are separately etched by increasing the number of lithography steps, the manufacturing cost increases. Therefore, it is necessary to etch the p-type gate and the n-type gate simultaneously. However, when the p-type gate and the n-type gate are simultaneously etched, the underlying gate oxide film is exposed earlier on the n-side due to the high etching rate of the n-type polycrystalline silicon, and the n-side oxide film is thin or missing. .
In addition, side etching is easy to occur in the n-type.

Further, in recent semiconductor devices, higher precision of processing is required more than ever with the miniaturization. One of the problems is a problem of a mask for forming a fine pattern. is there. An organic resist is mainly used for the mask material. However, the resist usually has a thickness of about 1 μm. For this reason, the resist itself becomes a groove having a considerably high aspect, making processing of a narrow groove more difficult. If the resist is made thinner, there is a problem that the resist disappears before the processing of the base is completed. As a countermeasure, there is a method of using an inorganic material such as an oxide film called a hard mask as a mask material. Since the oxide film is more than five times as resistant as the resist, its thickness is reduced to one-fifth.
You can: As a result, the selectivity between the material to be etched and the mask is increased and improved compared to when the resist is used. However, in processing using a thin hard mask, it is a new task to further improve the selectivity between the underlying material as the material to be etched and the hard mask.

On the other hand, with the miniaturization of semiconductor elements, the processing dimensions of lines and spaces corresponding to wirings and electrodes are in the region of 1 μm or less, preferably 0.5 μm or less. In the processing of such fine patterns, the lines gradually become thicker,
The problem that the pattern cannot be processed to the design dimensions becomes significant. Further, in addition to the difference in the etching rate between the inside of the fine groove and the relatively wide portion, the difference in shape, that is, the so-called shape microloading becomes remarkable, which hinders the processing.

Further, the thickness of the gate oxide film of the MOS transistor described above is 6
nm or less. In such a device, the anisotropy and the selectivity of the base oxide film have a trade-off relationship, which makes processing more difficult.

Many of the above prior arts were invented in the era when the minimum processing size of the element was 1 μm or more, and it has become difficult to cope with the processing of finer elements with these techniques. In the processing of such a fine element, it is necessary to assemble under precise process conditions based on an analysis of the relationship between the physical quantity of the plasma and the etching characteristics, and many manufacturers are currently spending much labor here. The constructed process also enables the processing of new devices that are qualitatively different.

A first object of the present invention is to solve these problems. In the etching of a multilayer film composed of metal and polycrystalline silicon, the etching is performed on a flat surface without unevenness on the etching surface. It is another object of the present invention to provide a surface processing method capable of etching a multilayer film without removing an underlying oxide film.

A second object of the present invention is to solve these problems. In simultaneous etching in which gate electrodes having different conductivity are mixed, the difference in the processing shape can be minimized without removing the underlying gate oxide film. An object of the present invention is to provide a surface processing method capable of suppressing the number of times.

A third object of the present invention is to provide a surface treatment method capable of increasing the selectivity between a substance to be etched and a mask material in the surface treatment of a semiconductor or the like.

A fourth object of the present invention is to provide a surface treatment method and apparatus for a semiconductor element capable of processing an element having a processing size of 1 μm or less, preferably 0.5 μm or less in order to meet the demand for miniaturization of the semiconductor element. To provide.

[0019]

In order to achieve the above objects, the present invention provides a method for depositing a high-melting-point metal deposited on a substrate or a multilayer film sample comprising at least a high-melting-point metal and a semiconductor in a vacuum container. Plasma processing is performed by arranging a high-frequency bias voltage on the sample stage and periodically turning on and off high-frequency power applied to the sample stage while generating plasma in the vacuum vessel. It is characterized by doing.

Another feature of the present invention is that the ratio of the ON period to one cycle of turning on and off the high-frequency voltage is in the range of 5% to 60%.

Another feature of the present invention is that a plasma treatment is performed by periodically turning on and off a high-frequency power applied to a sample, on which at least polycrystalline silicon having different conductivity is mixed, deposited on a semiconductor substrate. Is to do.

Another feature of the present invention is that a sample in which a layer of a mask material not containing carbon as a main component is formed on a workpiece is placed on a sample table in a vacuum vessel, and plasma is supplied into the vacuum vessel. The plasma processing is performed by applying a high-frequency bias voltage to the sample stage and periodically turning on and off the high-frequency power applied to the sample stage.

In the present invention, in the processing of a fine pattern,
The high-frequency voltage applied to the sample is repeatedly turned on and off,
The voltage amplitude was set sufficiently high. In general, when the energy of ions incident on the wafer during etching is increased, the etching becomes dominant over the adhesion to the side wall, so that the line thickness is improved. However, when the ion energy is set to be high, the etching rate of the oxide film increases, which makes the underlying oxide film unsuitable for processing a gate electrode having a small thickness. Therefore, by reducing the number of high-energy ions by providing an off-period in the high-frequency voltage, a decrease in the selectivity was prevented.

Thus, a surface treatment method and apparatus for a semiconductor element capable of performing fine processing with a processing size of 1 μm or less, preferably 0.5 μm or less can be provided.

Further, according to the present invention, in etching a multilayer film composed of metal and polycrystalline silicon, a high-frequency voltage applied to a sample is periodically turned on and off, so that an etched surface is smoothed. As a result, the surface of the element can be processed without removing the underlying oxide film, and a high-speed device having a small gate resistance of a multilayer film composed of metal and polycrystalline silicon can be produced.

According to the present invention, a high-frequency voltage applied to a sample is periodically turned on and off during plasma processing of a sample having different conductivity, for example, etching of a film in which p-type and n-type are mixed. By increasing the ion energy in the ON state, it is possible to provide a surface processing method capable of minimizing a difference in processing shape without removing a gate oxide film as a base.

According to the present invention, in a surface treatment of a semiconductor or the like, for example, a material to be etched such as a wiring or a gate material of a semiconductor element such as TiN / Al / TiN or W / polySi, an oxide film or a nitride film is used. The selectivity with a mask material such as a film can be increased.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. First, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a plasma etching apparatus to which the present invention is applied. Microwaves are introduced into the vacuum chamber 104 from the magnetron 101 via the automatic matching unit 106, the waveguide 102, and the introduction window 103.
On the other hand, an etching gas such as halogen is introduced into the vacuum vessel 104 via the gas introduction means 100, and plasma of this gas is generated with the introduction of the microwave. The material of the introduction window 103 is a material that transmits microwaves (electromagnetic waves) such as quartz and ceramic.

An electromagnet 105 is provided around the vacuum vessel 104.
Is installed. The magnetic field strength of the electromagnet 105 is set so as to cause resonance with the frequency of the microwave. For example, if the frequency is 2.45 GHz, the magnetic field strength is 875 Gauss. At this magnetic field strength, the cyclotron motion of the electrons in the plasma resonates with the frequency of the electromagnetic wave, so that microwave energy is efficiently supplied to the plasma and a high-density plasma is generated. The frequency of the microwave is not limited to 2.45 GHz, but may be 100 Hz to 1 GHz. In this case, the magnetic field intensity changes according to the frequency.

The sample 107 is set on a sample stage 108. In order to accelerate ions incident on the sample, an rf (radio frequency) bias power supply 109 which is a high frequency power supply
Are connected to the sample stage 108 via a high-pass filter 111. An insulating film 110 such as a ceramic or polymer film is provided on the surface of the sample stage. Further, a DC power supply 112 is connected through a low-pass filter 113.
Is connected, and a voltage is applied to the sample stage 108, whereby the sample is held on the sample stage by electrostatic force.

FIG. 2 shows the gas supply inside the vacuum vessel 104 and the magnetron 10 during the etching process by the apparatus shown in FIG.
1, the operation of the rf bias power supply 109 is shown. Gas is supplied as shown in (a), the gas pressure is kept constant at the same time as the start of etching, and microwave power is also supplied continuously as shown in (b). On the other hand, as shown in (c), the rf bias applied to the sample is periodically turned on and off. By providing a period during which ions are accelerated by turning on / off the rf bias, a high-energy ion section and a low-energy ion section are generated during the surface treatment of the sample. Then, as shown in (d), in the low energy ion section, the etching does not proceed, but rather the deposition of the residual reaction product in the gas or plasma occurs.

Next, the relationship between the frequency of the rf bias, the on / off repetition frequency thereof, and the etching characteristics will be described. FIG. 3 shows the waveform of the rf bias, and (a) corresponds to the etching condition of the present embodiment, and is a waveform when the rf bias frequency is 100 KHz and the on / off frequency (modulation frequency) is 100 Hz. (B) is Japanese Patent Application Laid-Open No. 6-151360 (corresponding USP).
5, 352, 324),
This is a waveform when the rf bias frequency is 1 KHz and the on / off frequency (modulation frequency) is 1 Hz.

Hereinafter, specific examples of the present invention will be described.
This will be described in comparison with a conventional example.

Embodiment 1 First, an example of etching a polysilicon metal gate will be described.

FIG. 4 shows the change over time in the cross-sectional shape of a sample etched by the conventional method using the apparatus shown in FIG. FIG. 5 shows a temporal change in the cross-sectional shape of the sample processed under the etching conditions of the present embodiment.

As shown in FIGS. 4A and 5A, the sample in the initial state includes an oxide film 305, polycrystalline silicon 304, tungsten nitride 303, and tungsten 302 deposited on a silicon substrate 306. A mask 301 processed into a desired pattern is formed on the uppermost layer of the multilayer film.
The gas used for etching was 30 cc of chlorine and 15 cc of oxygen, a pressure of 0.2 Pa, and a microwave power of 5 cc.
00W, sample temperature 70 ° C.

The conventional example shown in FIG. 4 shows a cross section of a sample when etching is performed while a continuous high-frequency voltage (power 140 W) is applied to the sample.

FIG. 5 shows a cross section of a sample under the conditions of the present invention, that is, when high-frequency power is repeatedly applied on and off at a frequency of 1 kHz. In this example, a continuous power of 700 W was applied such that the ratio of the ON period to one cycle (hereinafter referred to as duty ratio) was 20%. That is, the net power is 20% of 700W
It becomes 140W.

In the case of the conventional method in which a high-frequency voltage is continuously applied, as shown in FIG. 4B, irregularities 307 are formed on the etched surface, so that even if the etching of the tungsten 302 or the tungsten nitride 303 is completed, In some parts, an etch residue 308 of tungsten or tungsten nitride occurs (FIGS. 4c, b). Since the etch rate of the polycrystalline silicon 304 is higher than that of tungsten or tungsten nitride, the remaining etch 308 serves as a mask, and the unevenness of the etched surface of the polycrystalline silicon 304 is further increased. Therefore, FIG.
As described above, even when the oxide film 305 is reached, a part 309 of the etch residue of the polycrystalline silicon 304 is left. If etching is further performed to remove the remaining etch, an oxide film loss 310 penetrating through the oxide film 305 occurs as shown in FIG. Since such a state results in a defective element, improvement is required.

The present invention is to solve such a problem. FIG. 5 shows an etching cross section when the method of the present invention, that is, high-frequency power is repeatedly applied on and off. The structure of FIG. 5A is the same as the structure of FIG. According to the method of the present invention, as shown in FIGS. 5B to 5D, the etched surface 401 of tungsten and the etched surface 402 of polycrystalline silicon 304 are smooth. In addition, finally, as shown in FIG. 5E, no etching remains and the etching surface 403 of the oxide film 305 can be etched flat.

Next, the cause of the above-mentioned result will be described. In tungsten etching, the etch rate is reduced by using only chlorine gas because the vapor pressure of tungsten chloride is low. Since a compound in which oxygen is added to tungsten chloride (chemical formula WxClyOz, where x, y, and z are natural numbers) has a high vapor pressure, the use of a mixed gas of chlorine and oxygen increases the tungsten etch rate. In plasma etching, the temperature of the surface on which ions are incident is locally increased to promote the etching reaction. Therefore, in order for etching to proceed uniformly on the surface, ions need to be incident while chlorine and oxygen are uniformly adsorbed on the tungsten surface. The etching of tungsten nitride has substantially the same mechanism as that of tungsten, and the etching speed is also substantially the same.

In order to uniformly adsorb a plurality of types of molecules, a pause period may be provided for etching by ions as shown in FIG. As a result, as shown in FIG. 6A, during the rest period, that is, during the OFF period of the high-frequency voltage applied to the sample, the chlorine 12 is uniformly applied to the surface of the tungsten 11.
And oxygen 13 are adsorbed. Thereafter, the high-frequency voltage is turned on to accelerate the ions 104 and make them incident on the surface (FIG. 6).
(b)). Then, the reaction product 105 evaporates uniformly from the surface of the tungsten 101, and the etching proceeds uniformly (FIG. 6C).

On the other hand, when a high frequency voltage is continuously applied,
Since accelerated ions are continuously incident on tungsten or tungsten nitride, the etching rate is increased in a portion where oxygen and chlorine are adsorbed, and the etch speed is decreased in a portion where adsorption is insufficient. Therefore, the etching speed becomes non-uniform in the plane, and irregularities are formed on the etched surface.

When the etching of the tungsten nitride is completed, the etching of the underlying polycrystalline silicon starts. However, with this gas, since the etching rate of the polycrystalline silicon is higher than the etching rate of the tungsten, there are portions where the tungsten etching remains and portions where the tungsten etching remains. The difference between the unevenness of
Etch residue occurs.

In addition to the above reasons, the high-frequency voltage is turned on.
When turned off, the frequency of incidence of accelerated ions is reduced, so that the etching rate is reduced. In order to obtain the same etching rate as that of the continuous bias, it is necessary to increase the energy of the ions. Increasing the ion energy also has the effect of smoothing the etched surface, so that a certain effect can be obtained even if a gas such as oxygen that promotes the etching of tungsten is not included.

The structure of the sample to be etched is shown in FIG.
The same effect is obtained even when there is no 03, that is, in the case of a single layer film of a high melting point metal such as tungsten 302.

Next, desirable etching conditions according to the present invention will be described. First, an appropriate amount of oxygen mixed with chlorine is 5% to 70%. As for the temperature of the sample, the higher the temperature, the higher the etching rate of tungsten. The on-off duty ratio of the voltage applied to the sample is preferably 5% to 60%. Below this, it is difficult to gain power and therefore the etch speed is reduced. Further, above this, the effect compared with the continuous bias becomes smaller. ON-OFF repetition frequency is 100H
The frequency is preferably not less than z and not more than 10 KHz.

For example, as described in Japanese Patent Application Laid-Open No. 63-174320, several Hz
At the following repetition frequency, irregularities corresponding to the frequency are generated on the side wall of the etching groove. If the frequency is too high, the configuration of the electric circuit becomes difficult. As for the high frequency voltage applied to the sample, it is effective to set the amplitude value of the voltage serving as a measure of ion energy to 500 V or more.

As a gas for etching tungsten or the like, there is a gas containing a fluorine atom such as SF6 or CF4. Even in this gas system, tungsten can be etched smoothly by controlling on / off of the high frequency voltage. Further, when oxygen is added to these gases, the effect is further enhanced because oxygen promotes the etching of tungsten. When a gas containing fluorine atoms is used, the etching rate becomes relatively high even when the sample temperature is low. However, since the etching of the sidewalls of the etching grooves in the polycrystalline silicon portion by fluorine progresses, the temperature of the sample is set at 20 ° C.
It is necessary to be below ° C.

The metal to be processed has been described by taking tungsten as an example, but other metals such as molybdenum, nickel, cobalt and titanium which can withstand high-temperature heat treatment can be used. Further, as a barrier film for preventing diffusion, there is a combination of nitrides of these metals. Even in the processing of these materials, the present invention is applied to control the high-frequency voltage on / off to set the ion energy high, and further, to add a gas such as oxygen that promotes the etching of the metal to achieve smoothness. An etched surface can be obtained.

The material of the mask used for processing these materials into a desired pattern may be an ordinary organic photoresist. However, since the carbon contained in the resist promotes the etching of the oxide film, the selectivity decreases. In contrast, an inorganic film such as silicon oxide or silicon nitride has a larger etching speed ratio of polycrystalline silicon to an underlying oxide film.

In a sample in which a high-melting metal film and a semiconductor film are laminated as in the sample of the present embodiment, it is effective to change the temperature of the sample at the time of the plasma processing according to the type of the film. For example, a high melting point metal film is processed at a high temperature, and a semiconductor film is processed at a low temperature or a normal temperature. This optimizes the reaction between the film to be etched and the etchant, improves the processing speed, and combines high-frequency power on / off control to achieve higher precision surface processing at a higher processing speed. can do.

[Embodiment 2] Next, in order to further enhance the effect of the above-described embodiment, an embodiment in which etching is performed in a plurality of steps will be described. This embodiment is a method of obtaining an optimum etching shape by changing the etching conditions at the point of time when the film type is switched, based on the emission intensity from the plasma during the etching or the etching time.

Taking the sample having the structure shown in FIG. 5 as an example, when the etching of the tungsten 302 and the tungsten nitride 303 is completed, the polycrystalline silicon 304 is replaced with the oxide film 30.
5 is switched to a condition that allows etching with high selectivity. In other words, the etching of the polycrystalline silicon 304 does not require as much ion energy as the etching of tungsten, so that the high-frequency voltage applied to the sample is reduced. In addition, since oxygen promotes the etching of tungsten but suppresses the etching of polycrystalline silicon, switching to a step with a small amount of added oxygen is performed. The timing at which the steps are switched may be based on monitoring the emission intensity of the tungsten atoms, measuring the time when etching of tungsten and tungsten nitride is completed in advance, and switching based on the time.

The switching of the steps is performed by using the polysilicon 3
At the time when the etching of 04 is completed, the condition may be switched to a condition that the selectivity with respect to the oxide film 305 is increased. For this purpose, there are methods such as lowering the high frequency power applied to the sample, increasing the amount of added oxygen, and adding HBr gas. The switching of the steps may be performed by monitoring changes in the light emission intensity of silicon.

Further, if the above two switchings are used simultaneously, more accurate etching can be performed. In this case, light of two different wavelengths, that is, light emission of tungsten and light emission of silicon, are simultaneously monitored, the end point of etching of each substance is monitored, and the steps are switched in three steps.

In order to suppress the unevenness of the etched surface,
This can also be achieved by making the etch rate of polycrystalline silicon sufficiently lower than the etch rate of tungsten and tungsten nitride. That is, even if the etching of the tungsten nitride is partially completed, if the etching is stopped in the polycrystalline silicon film, the unevenness of the metal surface can be reduced. Oxygen is
Since the function of suppressing the etching rate of polycrystalline silicon is also provided, the effect can be exerted by increasing the ratio of oxygen. Also in this case, by turning on and off the high-frequency voltage, oxygen is uniformly adsorbed on the polycrystalline silicon surface during the off period, so that the etched surface can be smoothed. In this method, since the etching rate of the polycrystalline silicon becomes extremely low, when the etching of the metal layer and the barrier layer is completed, the condition is switched to a condition where the polycrystalline silicon can be selectively etched with respect to the oxide film. Accurate etching can be achieved.

As described above, according to the present invention, in the etching of a multilayer film made of metal and polycrystalline silicon, the high-frequency voltage applied to the sample is periodically turned on and off to make the etched surface smooth. Thus, there is an effect that the element can be processed without the removal of the underlying oxide film.
This makes it possible to create a high-speed device having a small gate resistance of a multilayer film made of metal and polycrystalline silicon.

Embodiment 3 Next, an example in which the present invention is applied to dual gate etching will be described in comparison with a conventional method.

FIGS. 7A and 8A are initial cross-sectional views of a sample processed using the apparatus of FIG. An oxide film 305 and n-type polycrystalline silicon 3 are formed on a silicon substrate 306 of a sample.
02, a p-type polycrystalline silicon 303, and a mask 301 processed into a desired pattern on the uppermost layer are formed. The gas used for etching was 55 cc of chlorine and 4 cc of oxygen, the pressure was 0.4 Pa, and the microwave power was 400 W.

FIG. 7 shows a temporal change of an etching shape when a high-frequency voltage (power 35 W) is continuously applied, which is a conventional method. A difference 306 in etch depth occurs between the p-type and n-type due to the difference in etching rate. For this reason, as shown in FIG. 7C, the processing of the n-type polycrystalline silicon 302 is completed first. Since the p-type has an etching residue, if the etching is further continued, as shown in FIG.
At the completion of the processing of No. 3, oxide film omission 310 occurs on the n side. Also, side etch 312 occurs in n-type polycrystalline silicon. In this state, the element becomes defective, and therefore, an improvement is required.

On the other hand, FIG. 8 shows the change over time of the etching shape when the high frequency power according to the present invention is repeatedly applied on and off at a frequency of 1 kHz. Continuous 175 W power was applied so that the ratio of the ON period to one cycle (hereinafter referred to as duty ratio) was 20%. That is, the net power is 35 W at 20% of 175 W. As shown in FIGS. 8B to 8C, n-type and p-type polysilicon 302,
The etching of 303 proceeds at the same speed. When the oxide film began to be exposed as shown in FIG. 8C, the etching gas was changed to 100 cc of hydrogen bromide and 9 cc of oxygen, and the high frequency voltage was switched to continuous application. Hydrogen bromide is polycrystalline silicon 302,303
Since the processing speed ratio between the oxide film 305 and the oxide film 305 is large, finally, as shown in FIG. 8D, no etching remains and the oxide film etching surface 410 can be flattened.

The cause of the above result will be described.
In plasma etching, the temperature of the surface on which positively charged ions are incident is locally increased to promote the etching reaction. Since n-type polycrystalline silicon contains more electrons than p-type, even if the same ion energy is incident on polycrystalline silicon, a difference in ion energy occurs near the n-type and p-type polycrystalline silicon surfaces. When the ions are incident with high ion energy, the influence of the electrons contained in the polycrystalline silicon can be reduced and the difference in the etching reaction can be suppressed, but it becomes difficult to stop the etching in the base oxide film. In order to use high ion energy, a pause period may be provided for etching by ions as shown in FIG. Thus, as described in FIG. 6, the rest period, that is, the off-period of the high-frequency voltage applied to the sample during the high-frequency voltage applied to the sample, corresponds to the surface 11 of both the p-type and n-type polycrystalline silicon.
Adsorb chlorine 12 and oxygen 13 uniformly. Thereafter, when the high-frequency voltage is turned on to accelerate the high-energy ions 14 to be incident on the surface, the reaction products 15 are uniformly evaporated from the surface 11 of the polycrystalline silicon, and the etching proceeds uniformly.

Next, the etching conditions of this embodiment will be described. First, the amount of oxygen mixed with chlorine should be between 5% and 7%.
0% is an appropriate amount. The on-off duty ratio of the voltage applied to the sample is preferably 5% to 60%. Below this, it is difficult to gain power and therefore the etch speed is reduced. Further, above this, the effect compared with the continuous bias becomes smaller. On-off repetition frequency is 1
The frequency is preferably from 00 Hz to 10 KHz.

The material of the mask used for processing these materials into a desired pattern may be an ordinary organic photoresist. However, since the carbon contained in the resist promotes the etching of the oxide film and lowers the selectivity, An inorganic film such as silicon oxide or silicon nitride has a higher etch rate ratio of polycrystalline silicon to an underlying oxide film.

[Embodiment 4] FIG. 9 is a sectional view showing a time change of an etching shape of another sample processed by applying the present invention. The initial state of the sample is as shown in FIG.
A mask 301 processed into a desired pattern is formed on the uppermost layer by a multilayer film of an oxide film 305, an n-type polycrystalline silicon 302, a p-type polycrystalline silicon 303, a tungsten nitride 501, and a tungsten 502 deposited on a silicon substrate 306. ing. In this structure, tungsten, which is a metal, is used to reduce the resistance of the gate electrode, and tungsten nitride acts as a barrier layer for suppressing mutual diffusion between tungsten and polycrystalline silicon.

The tungsten and tungsten nitride films were etched by continuously applying a high-frequency voltage (power 140 W) with 38 cc of chlorine and 12 cc of oxygen, a pressure of 0.2 Pa, and a microwave power of 500 W. When the polycrystalline silicon films 302 and 303 started to be exposed as shown in FIG. 9B, the high-frequency voltage was switched to a 1 kHz frequency and a 40% duty ratio on / off application. Next, as shown in FIG.
When exposure began, the etching gas was changed from chlorine to 100 cc of hydrogen bromide and 9 cc of oxygen, and the high frequency voltage was switched to continuous application. Hydrogen bromide is polycrystalline silicon and oxide film 305
Since the processing speed ratio is large, finally, as shown in FIG. 9D, no etching remains and the oxide film etching surface 503 can be flattened.

Polycrystalline silicon can be processed in the same manner by using a combination of an intrinsic semiconductor (i-type) and n-type, and a combination of i-type and p-type, in addition to p-type and n-type. In addition, molybdenum, nickel, cobalt, and titanium are used for the metal layer, and nitride films of these metals are used for the barrier layer.

As described above, according to the present invention, p-type and n-type
In the etching of a film in which molds are mixed, the p-type and n-type gates can be etched at the same time without processing difference by periodically turning on / off the high-frequency voltage applied to the sample and increasing the ion energy when on. effective. This enables the creation of a CMOS device having a dual gate structure.

Embodiment 5 Next, the result of applying the present invention to metal etching of a metal such as aluminum will be described. As shown in FIG. 10, the sample structure is such that an oxide film (602) 300 nm, TiN (603) 100 nm, Al (6)
04) 400 nm and TiN (605) 75 nm are deposited, and the uppermost layer is provided with a resist mask (606) 1 μm. The line and space dimensions are 0.4 μm. The etching gas was a mixture of chlorine (80 sccm) and BCl3 (20 sccm) at a pressure of 1 Pa. The output of the microwave power supply 101 was 700 W, and the electrode temperature was 40 ° C. The frequency of the high-frequency voltage power supply 109 was 800 KHz, and the on / off repetition frequency was 2 kHz.

FIG. 10A shows a conventional continuous bias system in which the power is 70 W, and FIG. 10B shows an on / off bias system of the present invention in which the peak power is 350 W and the duty ratio is 2
The etching shape at 0% is shown. In this sample, the shape microloading is large, and the verticality of the side wall 607 facing a wide space at the time of continuous bias is particularly deteriorated, but it is suppressed by setting the on / off bias.

[Embodiment 6] Next, results of etching of aluminum used for wiring of a semiconductor element by a method of the present invention using a hard mask are shown in FIGS.
It is described in. The etching gas is Cl2 (80 scc)
m) + BCl 3 (20 sccm) and pressure of 1 Pa
And The output of the microwave power supply 11 was 700 W.
The output of the bias power supply 10 is 60 W and the frequency is 400 k
Hz and 800 KHz were tested. The ON / OFF repetition frequency was 2 KHz. FIG. 11 shows ON / OFF 1
ON ratio for the period (hereinafter referred to as duty ratio)
Of etching rate of Al and oxide film with respect to temperature, FIG.
Shows the relationship between the selectivity of Al and the oxide film. The duty ratio of 100% is a conventional continuous bias. When the duty ratio is reduced, the peak power is adjusted so that the product of the peak power and the duty ratio becomes 60 W.

When the bias frequency is 400 kHz, 800
When the on / off control is performed and the duty ratio is reduced at both kHz, the etching rate of the oxide film is reduced as shown in FIG. 11, and the selectivity of Al to the oxide film is increased as shown in FIG. That is, when an oxide film is used as the mask material and the bias is turned on / off, the selection ratio between the mask and Al can be increased. The effect becomes remarkable when the duty ratio is 50% or less.

As another embodiment of the present invention, on / off control is performed, and Cl2 (80 sccm) + BCl
CH4 (4%) + Ar 200 s for 3 (20 sccm)
When the pressure was increased to 2 Pa by adding ccm, the selectivity between Al and the oxide film was further increased by 20 to 50%. It is considered that a gas containing carbon, such as CH4, has a depositing property and deposits easily adhere to the oxide film during the bias-off period, so that the effect is further improved. In FIG. 13, under the condition that the deposition gas is added,
2 shows a cross-sectional shape obtained by etching a hard mask sample.

In the sample structure shown in FIG. 13, a TiN film 702 (80 nm) is formed under an oxide hard mask 701 (100 nm).
m), Al film 703 (500 nm), TiN film 704
(100 nm), an oxide film 705, and a Si substrate 706 in this order. The etching conditions are Cl2 (80 sccm) + BCl3 (20 scc) as a gas.
m), 200 sccm of CH4 (4%) + Ar was applied, the pressure was 2 Pa, and the microwave power was 800 W.

FIG. 13A shows the bias power of the system of the present invention, that is, the bias power of 250 W and the duty ratio of 20 W.
%, And FIG. 13B shows 50 W in the conventional continuous bias system. The etching time is determined by the emission waveform of the plasma, and 3 hours after the etching of the underlying TiN film 704 is completed.
0% over-etching. When etching is performed with an on-off bias, as shown in FIG.
10 nm of the hard mask 701 remained. On the other hand, when etching was performed with a continuous bias, as shown in FIG. 13B, the hard mask was completely etched and disappeared, and the TiN film 702 was etched. As described above, in metal etching using a hard mask,
By controlling the bias on / off, the selection ratio between the metal and the hard mask can be increased.

[Embodiment 7] Next, an example in which the present invention is applied to the gate processing of a semiconductor device using a hard mask will be described with reference to FIG. Since the gate processing is thinner than the metal processing, the selectivity with respect to the resist is not as large as that of the metal. However, the processing size is reduced, and conventional tungsten silicide (WSi) and poly Si
In the case of a multilayer film of W and polySi having a lower resistance instead of the multilayer film of above, even if a hard mask is used because of the low etching rate of W, the selection ratio between the mask and the base is still an issue.

FIG. 14 shows a W film 802 (100n) using a nitride film (Si3N4) as a hard mask 801 (200 nm).
m) / poly Si film 803 (100 nm) / SiO
The result of etching the two films 804 (4 nm) / Si substrate 805 is shown. Etching gas is chlorine (38sccm)
The pressure is 0.2 Pa with + oxygen (12 sccm). The microwave power is 500W. In this gas system, oxygen becomes a deposition gas. FIG. 14A shows an on-off bias with a peak power of 500 W and a duty ratio of 30%, and FIG. 14B shows a continuous bias of 150 W with a continuous bias.
It is.

The remaining thickness t of the mask after the completion of etching, which is determined by light emission, is equal to the on-off bias shown in FIG.
In contrast to t1 = 120 nm, in the case of the continuous bias shown in FIG. 14B, t2 = 80 nm, indicating that the present invention has a higher selectivity between the mask and the underlying multilayer film.

In this structure, a high melting point metal such as Mo or Cr is used instead of W. Also, metal and poly
A barrier layer such as a metal nitride may be provided between Si.

[Embodiment 8] Next, gas and other embodiments will be described. As a deposition gas in metal etching, a hydrocarbon gas such as methane, ethane, and propane is effective. The effect does not change even if used without diluting with Ar,
Dilution with Ar reduces explosiveness and increases safety.
Although the dilution ratio of CH4 with Ar is not limited to 4%, this gas has an advantage that it can be easily obtained. Further, CF4, CH2F2, CHF3, and C4F8 are included in the deposition gas containing carbon.
and so on. Further, a similar effect can be obtained by using a nitrogen gas or a gas containing nitrogen such as NH3.

As a deposition gas in the gate etching, there is a gas containing oxygen such as CO and CO 2 in addition to oxygen.

The halogen gas is chlorine, F2, HB
The same effect can be obtained by mixing these halogen gases containing r, HI or chlorine. Experimentally, the mixing ratio of the deposition gas is preferably 0.5% to 50%. If the mixing ratio is lower than 50%, there is no effect. If the mixing ratio is higher, the decrease in the metal etching rate is large.

The device mask may be a multilayer film of an oxide film and a nitride film or a multilayer film of a resist and a hard mask. As the hard mask, an inorganic substance not containing carbon as a main component, such as alumina, is used.

As described above, in the surface treatment method using plasma as in this embodiment, an oxide film and a nitride film are used as a mask material of a substance to be etched, and a bias power supply for accelerating ions in the plasma is repeatedly turned on and off. By controlling, even if a thin mask is used, the selectivity can be further improved.

Further, by mixing the deposition gas with the etching gas, the halogen gas has a function of promoting the etching, and the deposition gas has a function of inhibiting the etching. When an off period is provided for the bias power supply, only the function of the deposition gas becomes remarkable during the period when the bias power supply is off, that is, when the accelerating ions are not incident on the sample surface. And the selectivity increases.

[Embodiment 9] FIG. 15 shows another apparatus structure to which the present invention is applied. In this apparatus, plasma is generated by capacitive coupling of rf power. 2 in the vacuum vessel 901
The electrodes 902 and 905 are arranged in parallel. An rf power source 903 and a high frequency power source 906 are connected to the electrodes, respectively. The sample 904 is placed on an electrode 905 also serving as a sample stage. The gas is introduced into the container through the introduction tube 908 from a hole opened in the electrode 902 facing the sample. Plasma 907 is generated between the two electrodes.

Also in this apparatus, the selectivity between the mask and the material to be processed can be increased by processing the sample by the method of the present invention. The same effects can be obtained in the processing of various samples described in the above-described embodiments.

[Embodiment 10] FIG. 16 shows another apparatus structure to which the present invention is applied. In this device, plasma is generated by inductive coupling at a frequency of a so-called radio wave band (hereinafter referred to as rf) of several hundred kHz to several tens MHz. The vacuum container 913 is made of a material that transmits electromagnetic waves, such as alumina and quartz. An electromagnetic coil 912 for generating a plasma 920 is wound therearound. An rf power supply 914 is connected to the coil. In the vacuum vessel 911, there is a sample table 918, on which a sample 917 is placed, and a high frequency power supply 919 is connected. Vacuum container 91
Although 1 has an upper lid 915, this may be an integral type. Also in this apparatus, the selectivity between the mask and the material to be processed can be increased by the method of the present invention.

As described above, according to the present invention, TiN / Al
Wiring or gate material of a semiconductor element such as / TiN or W / poly Si can be etched with a high selectivity to a hard mask such as an oxide film or a nitride film. The same effects can be obtained in the processing of various samples described in the above-described embodiments.

In this embodiment, in the on / off control of the bias, the off period of the bias power supply 109 corresponds to the period shown in FIG.
Although the output is set to zero as shown in (c), the output need not always be zero. In other words, the period during which the accelerated ions are not incident on the sample surface is defined as the off period, and if the output is sufficiently smaller than that during the ON period, such that the ions are not incident on the sample surface to cause an etching action. , A bias voltage may be applied. Accordingly, turning off the on / off control includes a small output.

[0092]

As described above, according to the present invention, when etching a metal or a multilayer film made of metal and polycrystalline silicon, a high-frequency voltage applied to a sample is periodically turned on and off. It is possible to provide a surface processing method in which an etched surface is smoothed, etching is performed on a flat surface without unevenness on the etched surface, and a multilayer film can be etched without removing an underlying oxide film.

Further, it is possible to provide a surface processing method capable of minimizing a difference in processing shape without removing a base gate oxide film in simultaneous etching when gate electrodes having different conductivity are mixed.

Further, in the surface treatment of a semiconductor or the like,
A surface treatment method capable of increasing the selectivity between a substance to be etched and a mask material can be provided.

Further, it is possible to provide a surface treatment method and apparatus for a semiconductor element capable of processing an element having a processing size of 1 μm or less, preferably 0.5 μm or less in response to a demand for miniaturization of the semiconductor element.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a main part of a plasma etching apparatus suitable for carrying out the present invention.

FIG. 2 is a diagram showing operations of gas supply, a magnetron, and an rf bias power supply in a vacuum vessel during an etching process by the apparatus of FIG. 1;

FIG. 3 is an explanatory diagram of an rf bias waveform according to the present invention.

FIG. 4 is a cross-sectional view of each processing step of a semiconductor sample in which a polysilicon metal gate is etched by a conventional method.

FIG. 5 is a cross-sectional view of each process of processing a semiconductor sample in which a polysilicon metal gate is etched by a method according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating the operation and effect of the on / off bias method of the present invention.

FIG. 7 is a cross-sectional view of each processing step of a semiconductor sample in which a dual gate is etched by a conventional method.

FIG. 8 is a cross-sectional view of each processing step of a semiconductor sample in which a dual gate is etched by a method according to an embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a time change of an etching shape of another sample processed by applying the present invention.

FIG. 10 is a sample structure diagram showing a result of applying the present invention to metal etching.

FIG. 11 is a diagram showing the relationship between the duty ratio and the etching rate of Al and an oxide film when aluminum used for wiring of a semiconductor element is etched by the method of the present invention.

FIG. 12 is a diagram showing the relationship between the selectivity of Al and an oxide film when aluminum used for wiring of a semiconductor element is etched by the method of the present invention.

FIG. 13 is a diagram showing a cross-sectional shape obtained by etching a sample using a hard mask.

FIG. 14 is a diagram showing a cross-sectional shape of a semiconductor element after gate processing.

FIG. 15 is a diagram showing a structural example of another device to which the present invention is applied.

FIG. 16 is a diagram showing a structural example of another device to which the present invention is applied.

[Explanation of symbols]

100: gas introduction means, 101: magnetron, 102
... waveguide, 104 ... vacuum container, 105 ... electromagnet, 107
... sample, 108 ... sample stage, 109 ... rf bias power supply,
110: insulating film, 111: high-pass filter, 112
... DC power supply, 301 ... mask, 302 ... tungsten,
303: tungsten nitride, 304: polycrystalline silicon,
305: oxide film, 306: silicon substrate, 307: unevenness, 308, 309: remaining etch, 310: oxide film missing

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor, Tadafumi Umezawa 2326, Imaicho, Ome-shi, Tokyo Inside the Device Development Center, Hitachi, Ltd. Kasado Plant, Engineering Co., Ltd. (72) Inventor Tatsumi Mizutani 794, Higashi-Toyoi, Kazamatsu City, Yamaguchi Prefecture Inside Kasado Plant, Hitachi, Ltd. (72) Inventor Masayuki Kojima 5-2-1, Josuihonmachi, Kodaira-shi, Tokyo In-house Hitachi Semiconductor Co., Ltd. (72) Inventor Takashi Sato Larger section of Higashi-Toyoi, Kudamatsu City, Yamaguchi Prefecture 794 Hitachi Techno Engineering Co., Ltd. Kasado Office (72) Inventor Yasushi Goto Higashi Capital Kokubunji Higashikoigakubo chome 280 address Hitachi, Ltd. center within the Institute

Claims (33)

[Claims] A high-melting-point metal deposited on a substrate or a sample of a multilayer film comprising at least a high-melting-point metal and a semiconductor is placed on a sample stage in a vacuum vessel, and plasma is generated in the vacuum vessel. A high-frequency bias voltage is applied to the sample stage, and high-frequency power applied to the sample stage is periodically turned on and off to perform plasma processing. 2. A surface processing method according to claim 1, wherein said plasma is generated by a gas containing at least a gas containing a halogen atom and a gas having an action of accelerating a processing speed of a metal, and said plasma is used to generate said sample. A surface processing method characterized by performing a treatment. 3. The surface processing method according to claim 2, wherein the plasma is generated by a mixed gas of a gas containing at least chlorine atoms and a gas containing oxygen atoms, and the plasma is used to process the sample. Surface processing method. 4. The surface processing method according to claim 3, wherein the temperature of the sample to be processed is maintained at 50 ° C. or higher. 5. The surface processing method according to claim 1, wherein said plasma is generated by a mixed gas of a gas containing at least a fluorine atom and a gas containing an oxygen atom, and said sample is subjected to plasma processing by said plasma. Surface treatment method. 6. The surface processing method according to claim 5, wherein the temperature of the sample to be processed is maintained at 20 ° C. or less. 7. The surface processing method according to claim 1, wherein the multilayer film of the sample to be processed is formed by stacking at least a metal of a tungsten film and a semiconductor of a polycrystalline silicon film. Characteristic surface processing method. 8. The surface processing method according to claim 7, wherein a tungsten nitride or titanium nitride film is provided between the tungsten film and the polycrystalline silicon film. 9. The surface processing method according to claim 1, wherein a mask material not containing carbon as a main component is provided on the metal film. . 10. The surface processing method according to claim 1, wherein the processing step is divided into a plurality of steps, and the net power of the high-frequency power applied to the sample in at least the last step is reduced. A surface processing method, characterized in that: 11. The surface processing method according to claim 1, wherein a repetition frequency for turning on and off the high-frequency voltage is in a range of 100 Hz to 10 kHz. 12. The surface processing method according to claim 1, wherein an on-period in one cycle of turning on and off the high-frequency voltage is in a range of 5% to 60%. Surface treatment method. 13. A sample on which at least polycrystalline silicon having different conductivity mixed on a substrate is placed on a sample table in a vacuum vessel, plasma is generated in the vacuum vessel, and the sample table is placed on the sample table. Applying a high frequency bias voltage, periodically turning on the high frequency power applied to the sample stage,
A surface processing method characterized by turning off and performing a plasma treatment. 14. The surface processing method according to claim 13, wherein said plasma is generated by a gas containing at least a halogen atom, and said sample is processed by said plasma. 15. The surface processing method according to claim 14, wherein the plasma is generated by a mixed gas of a gas containing at least a chlorine atom and a gas containing an oxygen atom, and the plasma is used to process the sample. Surface processing method. 16. The surface processing method according to claim 13, wherein said polycrystalline silicon film has:
A surface processing method comprising providing a mask material containing no carbon as a main component. 17. The surface processing method according to claim 13, wherein the processing step is divided into a plurality of steps, and the processing speed ratio between the processing step and an underlying material for terminating the steps is completed. A high-frequency voltage is divided into an on period and an off period in at least one of the first half steps. 18. The surface processing method according to claim 17, wherein a hydrogen bromide gas is used in the latter half of the step in which the processing speed ratio with respect to the base material for terminating the processing is large. 19. The surface processing method according to claim 13, wherein a repetition frequency for turning on and off the high-frequency voltage is in a range of 100 Hz to 10 kHz. 20. The surface processing method according to claim 13, wherein an on-period in one cycle of turning on and off the high-frequency voltage is in a range of 5% to 60%. Characteristic surface processing method. 21. A sample in which a layer of a mask material not containing carbon as a main component is formed on a workpiece, placed on a sample table in a vacuum vessel, and plasma is generated in the vacuum vessel. Applying a high frequency bias voltage to the sample stage, periodically turning on the high frequency power applied to the sample stage,
A surface processing method characterized by turning off and performing a plasma treatment. 22. The surface treatment method according to claim 21, wherein the workpiece is a metal deposited on a semiconductor wafer.
A surface treatment method characterized in that a mask material of a semiconductor or an insulator is silicon nitride, silicon oxide or a multilayer film thereof. 23. The surface treatment method according to claim 21, wherein said plasma comprises a mixture of a halogen gas and a deposition gas. 24. The surface treatment method according to claim 23, wherein the halogen gas is a mixed gas of chlorine and BCl ₃ , and the deposition gas is a hydrocarbon such as methane, ethane, and propane. Surface treatment method. 25. The surface treatment method according to claim 23, wherein the halogen gas is a mixed gas of chlorine and BCl ₃ , and the deposition gas is a hydrocarbon such as methane, ethane, propane, or a rare gas such as argon. A surface treatment method characterized in that the gas is diluted with a gas. 26. The surface treatment method according to claim 23, wherein the deposition gas mixed with the halogen is a nitrogen gas or a gas containing a nitrogen atom. 27. A surface treatment method according to claim 23, wherein said halogen gas is chlorine, HBr or a mixed gas thereof, and said deposition gas is oxygen gas or a gas containing oxygen atoms. Surface treatment method. 28. The surface treatment method according to claim 23, wherein the halogen gas is a fluorine gas or a gas containing a fluorine atom. 29. The surface treatment method according to claim 21, wherein a frequency of a bias power supply applied to the sample is a high frequency of 200 KHz to 20 MHz. 30. The surface treatment method according to claim 21, wherein the bias power supply applied to the sample is intermittent, wherein the ratio of on to off in one cycle of bias on-off is determined. A surface treatment method characterized by being in the range of 5% to 60%. 31. The surface treatment method according to claim 21, wherein a mixing ratio of the deposition gas mixed with the halogen is in a range of 0.5% to 50%. Surface treatment method. 32. A surface processing method in which a plasma is generated in a vacuum vessel in which a sample is placed and a sample is etched by the plasma while applying a bias voltage to the sample. A surface treatment method characterized in that the gas used for the etching is controlled to be on and off, and a deposition gas is mixed in the gas used for the etching. 33. The surface treatment method according to claim 32, wherein a methane or oxygen deposition gas is mixed with the etching gas.