JPH08172081A - Plasma surface treater - Google Patents

Abstract

PURPOSE: To make it possible to obtain the surface treatment characteristics, which are impossible to obtaining by a conventional plasma surface treater, of a wafer by a method wherein a plasma surface treater is provided with a means, which changes the kind, composition and concentration of discharge gas one time only, a plurality of times or periodically in the middle of a surface treatment of the wafer. CONSTITUTION: The air in a vacuum chamber 6 is exhausted to a high vacuum state and a prescribed amount of discharge gas is fed in the chamber 6. For example, SF6 , N2 , He and H2 gases are respectively set at 5×10<-4> Torr, 5×10<-5> Torr, 5×10<-5> Torr and 2.5×10<-5> Torr at the partial pressure of the discharge gas in the camber 6. Then, microwave discharge from a microwave oscillator 1 is generated. An etching is proceeded by the physical and chemical reaction of active particles (F<+> ions and an F radical) generated during the discharge with the surface of an Si wafer. Here the flow rate of the SF6 gas in the middle of the etching is changed. This change in the flow rate of the gas is automatically made by a controller 18 and a needle valve 8a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment apparatus using plasma, and more particularly to a plasma etching apparatus and a plasma deposition (plasma CVD) apparatus used for manufacturing a semiconductor integrated circuit.

[0002]

2. Description of the Related Art A surface treatment apparatus using plasma is actively used industrially. This plasma surface treatment apparatus should have a vacuum chamber, a means for exhausting the vacuum chamber, a means for introducing a gas into the vacuum chamber, a means for generating plasma in the vacuum chamber (or a part thereof), and a surface treatment. It comprises means for holding the sample in the vacuum chamber. The characteristics of plasma surface treatment are:
It changes extremely depending on the type, composition, and concentration of (discharge gas). Depending on the purpose of the surface treatment, it may be necessary to change the type, composition, and concentration of the discharge gas for a certain period of time (periodically) during the treatment period to emphasize specific treatment characteristics. However, in the conventional apparatus, the gas introduction means does not have the function of changing the type, composition, and concentration of the gas, and only the processing with a certain characteristic can be performed throughout the processing period.

FIG. 1 and FIG. 2 show an example of the structure of a conventional plasma etching apparatus (plasma etching apparatus) (Semino Plasma Process Technology, edited by Takuo Sugano,
Sangyo Tosho Co., Ltd., 1980, pp101-164). FIG. 1 shows an apparatus using magnetic field microwave discharge, and FIG. 2 shows an apparatus using RF discharge. The means for generating a microwave with a magnetic field includes a microwave oscillator 1 (usually a magnetron), a microwave oscillator power supply 2, a waveguide 3, a discharge tube 4, an electromagnet 5, and a permanent magnet 12. Both the electromagnet 5 and the permanent magnet 12 are not necessarily required, and only one of them may be used. The means for generating the RF discharge is R
F power supply 15, condenser 16 and RF electrodes 13, 1
It is composed of 4. The lower RF electrode 14 is electrically insulated and held by an insulator 17. In FIG. 2, the RF electrode 1
Although 3 and 14 are installed in the vacuum chamber 6, the RF electrodes 13 and 14 may be installed outside the vacuum chamber in some cases.

[0004]

In order to apply the plasma etching apparatus to the semiconductor element manufacturing process, the following are important issues. (1) The etching speed is high. (2) The material to be etched 24 shown in FIG.
5 can be used to perform vertical etching (etching according to the mask) without undercut as shown in FIG. That is, the fine workability is good. In order to increase the etching rate, for example, when the material to be etched 24 is Si (or poly-Si), SF ₆ or F ₂ may be used as the discharge gas.
However, these discharge gases have large undercuts 26 as shown in FIG. 3B, and the above condition (2) is not satisfied. As described later, by periodically changing the composition of the discharge gas using the present invention, it becomes possible to simultaneously satisfy the above conditions (1) and (2).

The apparatus shown in FIGS. 1 and 2 can also be used as a plasma deposition apparatus (plasma CVD apparatus) by changing the type of discharge gas. For example, in Figure 1,
When a mixed gas of SiH ₄ and NH ₃ is used as a discharge gas in the apparatus of FIG. 2, a mixed film of Si and N (silicon nitride (Si—N) film) is formed on the sample surface and used as a protective film of a semiconductor element. You can However, a large amount (10% or more in atomic density ratio) of hydrogen is mixed in this silicon nitride film,
Inferior device characteristics (RB Fair et al .; IEEE, ED
−28, 83−94 (1981)). When a mixed gas of SiF ₄ and N ₂ is used as the discharge gas in the apparatus shown in FIG. 1, a silicon nitride film can be formed in the same manner as above. However, in this case, fluorine mixed into the film poses a problem. By periodically changing the composition of the discharge gas according to the present invention, it becomes possible to suppress the above-mentioned amount of hydrogen or fluorine mixed in to an extremely small amount.

Therefore, it is an object of the present invention to realize surface treatment characteristics which are not possible with the conventional plasma surface treatment apparatus described above.

[0007]

Means for Solving the Problems The above-mentioned object is a means for changing the type, composition, and concentration of discharge gas only once or a plurality of times or periodically in a plasma surface treatment apparatus during surface treatment. It is achieved by providing.

[0008]

[Function] Type of discharge gas for generating plasma,
Composition and concentration are parameters that can change the plasma surface treatment characteristics most effectively. Therefore, by changing the kind, composition, and concentration of the above-mentioned discharge gas during the surface treatment, it becomes possible to emphasize a specific surface treatment characteristic.

[0009]

Embodiments of the present invention will be described below. FIG. 4 is a structural example of a plasma etching apparatus according to the present invention.
Microwave discharge with magnetic field is used as plasma generation means, and Si (or poly -Si) is used as the material to be etched.
An example of is shown. The apparatus is the same as the apparatus shown in FIG. 1 except for gas supply means. Gas supply _{means, SF 6, N 2, He} , H 2 of 4 kinds of gas sources 9a, 9b, 9c, 9d, the gas flow rate adjusting needle valve 8a attached to the gas source, 8b, 8
c, 8d, and the gas pipe 7. However,
A feature of the present invention is that the gas supply amount of the SF ₆ needle valve 8a is electrically controlled by the controller 18. In this embodiment, the vacuum chamber 6 is first evacuated to a high vacuum (about 1 × 10 to ⁶ Torr), and then a predetermined amount of discharge gas is supplied. For example, SF ₆ is 5 × 10 to ⁴ Torr, N ₂ is 5 × 10 to ⁵ Torr, H
For example, e is 5 × 10 to ⁵ Torr and H ₂ is 2.5 × 10 to ⁵ Torr. However, the partial pressures wide (1 × 10 ~ ⁵ ~ ⁵
The effect of the present invention does not change even if it is changed to (× 10 to ³ Torr). Next, a magnetic field is formed in the discharge tube 4 by the electromagnet 5, and the microwave (frequency = 1 to 10 GHz, usually frequency = 2.4) from the microwave oscillator (magnetron) 1 is generated.
(5 GHz) is introduced into the discharge tube 4 to generate a magnetic field microwave discharge. Then, etching proceeds due to a physical / chemical reaction between active particles (for example, F ⁺ ions or F radicals) generated in the discharge and the Si surface. The feature of this embodiment is that the flow rate of SF ₆ gas during etching is changed as shown in FIG. This change in gas flow rate is automatically performed by the controller 18 and the needle valve 8a. The SF ₆ gas is supplied to the vacuum chamber at a gas flow rate of Q ₁ during τ ₁ and then Q during τ _2.
The gas flow rate is ₂ . The values of Q ₁ and Q ₂ are arbitrary, but as an example, Q ₁ is a gas flow rate required to give a partial pressure of 5 × 10 to ⁴ Torr (Q when using an ordinary exhaust system).
Can be ₁ = _1~10 SCC / min) a and Q ₂ = 0. The conditions for determining τ ₁ and τ ₂ will be described later, but as an example, τ ₁ = 25 sec and τ ₂ = 5 sec can be selected. By doing so, high-speed etching with SF ₆ gas (etching speed> 200 nm / min) is realized without undercut. It will be described below that such high-speed, vertical etching is possible for the first time by the present invention.

During the _first period of τ ₁ after the start of etching, a large amount of active particles (for example, F ⁺ ions and F radicals) are generated in the plasma and the etching proceeds. The sample 10 has a negative floating potential V (V = about −20 V) with respect to the plasma, and the F ⁺ ions are vertically incident on the sample surface.
Therefore, the etching by F ⁺ ions is perpendicular to the sample surface and no undercut occurs. On the other hand, since the F radical is electrically neutral, it isotropically enters the surface of the sample and causes an undercut. However, in etching with SF ₆ gas, the effect of F radicals is larger than the effect of F ⁺ ions, and the etching shape is as shown in FIG.
It becomes isotropic as shown in (a). That is, when the surface is etched by a depth d ₁ perpendicular to the surface during τ ₁ , an undercut 26 of about d ₁ also occurs in the lateral direction. Then SF
_{6 When the} gas supply is stopped, F ⁺ ions and F in the plasma
The radicals are not exhausted and are discharged only by N ₂ , He, and H ₂ . As shown in FIG. 6B, the Si surface (both horizontal and side surfaces) is nitrided by the N ⁺ ions and N radicals generated during this discharge (the silicon nitride film 2 is formed on the surface).
7 is formed). The supply of SF ₆ gas was stopped because a strong (dense) silicon nitride film cannot be formed when F ⁺ ions and F radicals are present and etching is in progress. He gas is mixed in
For the following reasons. That is, when the supply of SF ₆ gas is stopped, stable discharge cannot be maintained only by the partial pressure of N ₂ (5 × 10 to ⁵ Torr). This is because the discharge can be stabilized by increasing the discharge gas pressure (total pressure) by mixing chemically inert He. Therefore, He is Ne,
The same effect can be obtained by substituting another rare gas such as Ar, Kr, or Xe. Also, it is S that contains H ₂ gas.
This is to appropriately reduce the concentration of F radicals at the time of supplying F ₆ gas. Now, when SF ₆ gas is supplied again, F ⁺ ions and F radicals enter the surface of the sample. However, since the silicon nitride film 27 is hardly etched by only the F radicals, the side surface covered with the silicon nitride film 27 is not etched, but the vertical etching and the newly appearing side surface are etched. The size of the undercut at this time is also d ₁ . That is, it becomes as shown in FIG. By repeating this, etching having a sectional shape as shown in FIG. 6D is performed. If the intermittent supply of SF ₆ gas is repeated n times with τ ₀ = τ ₁ + τ ₂ as one cycle, the total etching time t _ε is

## EQU1 ## t _ε = nτ ₀ (1), and the vertical etching depth d _P and the horizontal etching amount (undercut amount) d _V are

[Formula 2] d _P = nd ₁ ………………… (2)

## EQU00003 ## d _V = d ₁ (3) For vertical etching, generally d _P / d _V >
I need 10

(4) n> 10 …………………… (4) is required. However, if SF ₆ gas has a low gas pressure and etching with a small amount of undercut is possible, the value of n may be small. Further, when the time required for stopping the supply of SF ₆ gas and exhausting the remaining F ⁺ ions and F radicals is τ _r

(5) τ ₂ >> τ _r …………………… (5) is required. τ _r is the residence time of gas molecules and atoms existing in the vacuum chamber, and the volume of the vacuum chamber is V
If (l) and the exhaust speed of the exhaust system is S (l / sec), then τ _r = V / S. In a normal device, V = about 20 l,
Since S = approximately 1000 l / sec, τ _r ≈0.02 sec
= 20 msec. Therefore, from equation (5)

[Equation 6] τ ₂ >> 20 msec …………………… (6) must be satisfied. Also, according to the experiment, the vertical etching depth during τ ₁ is 200 nm.
It needed to be: This is because if τ ₁ is made larger than this, the silicon nitride film on the sidewall once formed is etched and the undercut becomes large. That is, the final vertical etching speed is ε (nm / mi
n)

(7) τ ₁ <(200 / ε) × 60 …………………… (7) must be satisfied. For example, if ε = 200 nm / min, τ ₁ <60 sec is required. Further, since etching is not performed during τ ₂ , τ ₂ << τ ₁ is also practically necessary. Under the above conditions, in the above, τ ₁ = 25 sec, τ
Mentioned results ₂ = 5 sec, but τ ₁ = 5~60sec τ ₂ =
It was experimentally confirmed that the same effect (that is, etching with Si etching speed ε≈200 nm / min and almost no undercut) can be obtained even with (1/5 to 1/50) × τ _1. There is.

The embodiment shown in FIG. 4 describes an apparatus using a magnetic field microwave discharge, but the same effect can be obtained by applying the present invention to a plasma etching apparatus using an RF discharge. Further, in the embodiment of FIG. 4, SF ₆
+ N ₂ + He + has been described mixed gas of H _2, SF ₆
Gas containing F ₂ and other halogen elements instead of (for example, C _n F _m gas (CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F
₈ , C ₄ F ₁₀ etc.), NF ₃ gas, Cl ₂ gas, C _n Cl _m gas (CCl ₄ , C ₂ Cl ₆ etc.), C _n F _m Cl _k (n, m,
k; integers) _{gas, C n F m Cl k H} i (n, m, k, i; an integer) gas, BCl ₃ gas, even with a gas or the like) containing the other Br or I effects are the same. The same effect can be obtained by using O ₂ or a C—H-based compound gas instead of N ₂ and a gas containing one or more elements of N, O, and C (because of that, This is because the silicon oxide or SiC film obtained by (1) is not etched by F radicals like the above silicon nitride film). However, O
_The use of ₂ causes a problem that the photoresist used as the mask material is easily etched. Further, when the SF ₆ gas partial pressure is appropriate, the effect of the present invention is not changed even if H ₂ mixing is stopped. In addition, although the case where the substance to be etched is Si (or poly-Si) is shown in the present embodiment, the same effect is obtained even when the substance to be etched is Mo, W, Al or a silicide thereof. Further, in the embodiment of FIG. 4, the sample stage and the sample are located under the discharge tube, but they may be installed inside the discharge tube. By doing so, the F ⁺ ions and F radicals incident on the sample surface are increased and the etching rate can be increased.

FIG. 7 shows another embodiment of the present invention. Differences from the embodiment shown in FIG. 4 are as follows. (1) A means for applying an external voltage to the sample table 11 and the sample 10 by the power supply 15 is provided. The external voltage may be either direct current or alternating current, but when an electrically insulating thin film is present on the surface of the sample 10, the alternating voltage (high frequency voltage (RF voltage)) is charged on the surface of the insulating thin film. Is excellent to prevent. Experimentally, it is suitable that the frequency of the high frequency voltage is 100 to 1000 KHz and the amplitude is 0 to 200V. (2) Function to cool the sample table 11 (Sample table cooling mechanism 19)
Is provided. (3) N ₂ and He, H ₂ gas (in some cases, N ₂ and H
One of e and H ₂ ) is introduced into the vacuum chamber 6 through the inside of the sample table 11 and the gap between the sample table 11 and the sample 10. Sample 10 during etching due to the functions of (2) and (3) above
Can prevent the temperature rise. This is effective in preventing alteration of the photoresist used as a mask material. Also, above (1)
This function is effective in increasing the etching speed and reducing undercuts because it can accelerate the ions entering the sample. The external voltage (high frequency voltage) may be constantly applied during etching (during surface treatment). However, since the deterioration and consumption of the mask material is accelerated by the application of the high frequency voltage, the period during which the supply of SF ₆ gas is stopped (that is,
It is effective to prevent the deterioration and wear of the mask material by stopping the application of the high frequency voltage within the period of τ ₂ in FIG. The effects of this embodiment are as follows: (1) Even if the material to be etched is replaced with a material other than Si or poly-Si (Mo, W, Al and their silicides), (2) SF ₆ gas is replaced with another halogen element. Even if it is replaced with a gas containing (see the explanation column of the embodiment of FIG. 4),
Even if (3) He gas is replaced with other rare gas, or (4) H ₂ gas is removed, it is similarly effective. Further, the method of cooling the sample table and introducing the gas through the sample table is effective for all other plasma etching apparatuses and plasma surface treatment apparatus carrying the present invention. Further, the method of applying the radio frequency (RF) voltage is effective for the entire transportation of the plasma surface treatment apparatus using the present invention.

FIG. 8 shows still another embodiment of the present invention. A feature of the present embodiment is that not only the gas flow rate of SF ₆ gas but also the gas flow rate of N ₂ gas and the driving and stopping of the high frequency power supply 15 are controlled by electrical signals from the controller 18. Moreover, He gas and H ₂ gas are not used. FIG. 9A shows an example of control of the flow rates of SF ₆ and N ₂ gas and application of high-frequency voltage. τ ₁ , τ ₂ ,
The value described in the embodiment of FIG. 4 is suitable for τ ₀ . For example, τ ₁ = 27.5 sec and τ ₀ = 2.5 sec can be set. The gas flow rates Q ₁ , Q ₂ , Q ₁ ′ and Q ₂ ′ are free, but they can be, for example, Q ₁ = Q ₁ ′, Q ₂ = Q ₂ ′ = 0. The values of Q ₁ and Q ₁ ′ can be set such that the gas pressure in the vacuum chamber 6 is 5 × 10 ⁴ Torr, for example. Although the values of V ₁ and V ₂ are also free, they can be set to V ₁ = 100V and V ₂ = 0V, for example. The reason why the amplitude of the applied high frequency voltage is changed is the same as described in the embodiment of FIG. In this embodiment,
Unlike the case of the embodiment shown in FIG. 4, the following advantages are brought about by stopping the supply of SF ₆ gas and simultaneously increasing the supply amount of N ₂ gas. (1) Since the gas pressure in the vacuum chamber is always high enough to maintain discharge (generally 1 × 10 to ⁴ Torr or higher), the discharge auxiliary gas (such as He or the like) as in the embodiment of FIG. No introduction of noble gas) is required. (2) Since the partial pressure of N ₂ during the period of τ ₂ becomes high, a short τ
_A dense silicon nitride protective film can be formed in ₂ hours. According to the method of this embodiment, the etching rate of silicon is 250.
Etching without undercut was realized at nm / min. Of course, if the type of gas used is changed, the method of the present embodiment can be applied to etching other substances to be etched and other plasma surface treatments. In the method of the present embodiment, the timing of changing the supply amount of SF ₆ and N ₂ gas and the timing of changing the high frequency applied voltage are the same, but these timings may be shifted from each other (see FIG. 9 (b)). ). τ _a and τ _b represent the mutual phase shifts. For example, the time to apply high frequency voltage is τ ₁ 〃
Is smaller than τ ₁ and is a necessary minimum, so that the deterioration of the element characteristics due to the high frequency voltage application can be minimized.

FIG. 10 shows an embodiment in which the method described in the embodiment of FIG. 8 is applied to an etching apparatus using RF discharge.

FIG. 11 shows an orbiting plate 20 on the sample table.
An example is shown in which the present invention is applied to an apparatus for simultaneously etching a plurality of samples 10 by using. The surface of the sample is intermittently irradiated with plasma and etching progresses. A magnetic field microwave discharge is used as the plasma generating means. The high frequency voltage can be applied to the sample stage and the controller 18 controls the gas flow rate and the high frequency voltage, as in the embodiment of FIG. It should be noted that in the present embodiment, the revolution plate 2 is used in order to eliminate variations (errors) in etching progress among a plurality of samples.
This means that the rotation of 0 and the control of the gas flow rate and the high frequency voltage application must be performed in conjunction with each other. Therefore, as shown in the figure, it is desirable to operate the revolution plate drive mechanism 21 according to the electric signal from the controller 18 (or vice versa). Generally, when the revolution period of the revolution plate 20 (time required for one rotation) is τ _r , the period τ ₀ of the controller 18 shown in FIG. 9 is τ _r / τ ₀ ≈integer, or τ ₀ / τ _r ≈
It is desirable to have an integer relationship. This embodiment can also be applied to a plasma CVD apparatus by changing the gas type.

FIG. 12 shows an example in which the present invention is applied to an etching apparatus having an end point detection mechanism 22. As a plasma generation method, an example using a magnetic field microwave discharge is shown. In general, the end point detection is performed by capturing the change in the plasma state when the substance to be etched is exhausted. On the other hand, when the type, composition, and concentration of the supply gas are changed, the state of the plasma greatly changes. Therefore, it is necessary to link the timing of receiving the signal for detecting the end point from the plasma with the control of the gas flow rate and the high frequency voltage application. Therefore, in this embodiment, the end point detection mechanism 22 operates by receiving a signal from the controller 18. The method of the present embodiment can be applied to other plasma etching apparatuses and etching apparatuses using other discharge gases, as in the case of the embodiments of FIGS. 4 and 8.

As the cross-sectional shape of etching, not only a rectangle formed by vertical etching but also a trapezoid formed by slight undercut or an inverted trapezoid (effective for etching for isolation between elements and etching for removing overhang) may be desired. is there. Such a request can be realized by appropriately changing τ ₁ , τ ₂ , τ ₀ , Q ₁ , Q ₂ , Q ₁ ′, Q ₂ ′, V ₁ and V ₂ of FIG. 9 during the etching process. .

FIG. 13 shows an example in which the present invention is applied to a plasma CVD apparatus. A magnetic field microwave discharge is used as the plasma generating means. As an example, SiF ₄
And an N ₂ gas is used to form a silicon nitride film (Si—N film). Although the structure is the same as that of FIG. 8, the SF ₆ gas is replaced by the SiF ₄ gas. An example of adjusting the gas flow rate and controlling the high frequency voltage application is shown in FIG. The conditions of τ ₁ , τ ₂ , and τ ₀ will be described later, but for example, τ ₁ = 3 seconds, τ ₂ = 3 seconds, τ ₀ = τ ₁ + τ ₂ = 6 seconds can be set. Q ₁ , Q ₂ , Q ₁ ′, and Q ₂ ′ are also free, but for example, Q ₁ and Q ₁ ′ are SiF ₄ and N in the vacuum chamber.
₂ Gas pressure is 4 × 10 ~ ⁴ Torr and 8 × 10 ~ ^{4 respectively}
You can choose to be Torr. Also, Q ₂ =
It is appropriate that 0, Q ₂ ′ = ½Q ₁ ′. Also,
V ₁ and V ₂ are also free, but for example V ₁ = 100V, V ₂ =
50V is an example. By using this example,
It is possible to form a Si-N film containing less F element. The reason is as follows. That is, at the time of τ ₁ (SiF ₄
A Si-N film is formed on the surface of the sample by the discharge of + N ₂ ) gas, but at this time, the F element is mixed in the film. next,
When the supply of SiF ₄ gas is stopped and the supply amount of N ₂ gas is increased (the period of τ ₂ ), N radicals formed by N ₂ discharge are incident on the surface of the Si-N film and 2 (Si- F element is liberated and evaporated from the film by the reaction of F) + 2N → 2 (Si—N) + F ₂ ↑. By repeating this, a Si-N film containing less F element is formed. Similar to the embodiment of FIG. 4, τ ₂ is the vacuum chamber 6
It must be sufficiently longer than the residence time τ _r of the gas molecules and atoms inside. That is,

(8) τ ₂ >> τ _r ≈ 20 msec …………………… (8) is required. Further, according to the experiment, in order to sufficiently remove the F element during the period of τ ₂ , the film thickness formed during the period of τ ₁ needs to be 10 nm or less. That is, τ ₂ =
When the film is continuously formed with 0 sec, the film forming speed is D (n
m / min), τ ₁ is

It is necessary that τ ₁ <(10 / D) × 60 …………………… (9). Usually D ≈ 100 nm / min

[Equation 10] τ ₁ <6 sec …………………… (10) is required. The method similar to that of this embodiment can be applied to other plasma CVD apparatuses using RF discharge. Further, if the gas species is changed, it can be applied to a plasma CVD apparatus for films other than the Si-N film.

FIG. 15 shows an example of a method of controlling the gas flow rate by using an opening / closing valve, and is applicable to all the embodiments of the present invention described above. This embodiment is composed of a needle valve 8a, two on-off valves 23a and 23a 'for each gas type (for example, gas A), and a piping system connecting these valves. The opening / closing of the two opening / closing valves 23a and 23a 'is controlled by a signal from the controller 18. Gas emitted from the cylinders 9a and 9b is needle valve 8
It is adjusted by a and 8b so that a constant amount always flows. Gas can be introduced into the vacuum chamber by opening the open / close valve 23a and closing 23a '. Further, if the valve 23a is closed, the gas introduction to the vacuum chamber is stopped, but if it remains as it is, gas will accumulate between the valve 23a and the needle valve 8a. Since it will flow into the room, it will not be possible to control the inflow rate accurately. In order to prevent this, at the same time as closing the valve 23a, the valve 23a 'is opened to open the valve 23a.
The gas accumulated between the needle valve 8a and the needle valve 8a is exhausted. Next, to introduce gas into the vacuum chamber again,
The valve 23a 'may be closed and the valve 23a may be opened.
The feature of this method is that the flow rate control has better reproducibility and controllability than that of directly controlling the opening degree of the needle valve. The two open / close valves 23a and 23a 'can be replaced with one three-way valve. The gas species in FIG. 15 can be increased if necessary.

[0020]

According to the present invention, if the discharge gas species, composition and concentration of the plasma surface treatment apparatus are changed during the treatment,
It is possible to change the characteristics of the surface treatment in time series, and it becomes possible to emphasize specific treatment characteristics for a certain period. As a result, it becomes possible to realize the surface treatment characteristics that were impossible with the conventional apparatus.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a conventional plasma surface treatment apparatus.

FIG. 2 is a diagram showing another configuration example of a conventional plasma surface treatment apparatus.

FIG. 3 is an explanatory diagram of vertical etching and non-vertical etching.

FIG. 4 is a diagram showing a configuration of a plasma surface treatment apparatus according to an embodiment of the present invention.

5 is a diagram showing an example of controlling the SF ₆ gas flow rate in the apparatus of the embodiment shown in FIG.

6 is an explanatory view of the progress of etching by the apparatus of the embodiment shown in FIG.

FIG. 7 is a diagram showing the configuration of a plasma surface treatment apparatus according to another embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a plasma surface treatment apparatus according to still another embodiment of the present invention.

9 is a diagram showing a control example of gas flow rate and high frequency voltage application in the embodiment of FIG.

FIG. 10 is a diagram showing the configuration of a plasma surface treatment apparatus according to still another embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a plasma surface treatment apparatus according to still another embodiment of the present invention.

FIG. 12 is a diagram showing the configuration of a plasma surface treatment apparatus according to still another embodiment of the present invention.

FIG. 13 is a diagram showing a configuration of a plasma surface treatment apparatus according to still another embodiment of the present invention.

14 is a diagram showing an example of control of gas flow rate and high frequency voltage application in the embodiment of FIG.

FIG. 15 is a diagram showing another configuration example of the introduced gas flow rate control mechanism in the present invention.

[Explanation of symbols]

1 ... Microwave oscillator, 2 ... Microwave oscillator power supply, 3 ... Waveguide,
4 ... Discharge tube, 5 ... Electromagnet, 6
… Vacuum chamber, 7… Piping, 8…
Needle valve, 9 ... Gas source (gas cylinder),
10 ... Sample, 11 ... Sample stand, 1
2 ... Permanent magnet, 13 ... Upper RF electrode,
14 ... Lower RF electrode, 15 ... Radio frequency (RF) power supply,
16 ... Capacitor, 17 ... Insulator,
18 ... Controller, 19 ... Sample stage cooling mechanism, 20 ... Revolution plate (or revolving plate), 2
DESCRIPTION OF SYMBOLS 1 ... Revolution plate (auto revolution plate) drive mechanism, 22 ... End point detection mechanism, 23a, 23b ... Open / close valve, 23a ',
23b '... open / close valve, 24 ... material to be etched,
25 ... Mask, 26 ... Undercut,
27 ... Silicon nitride film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Sadayuki Okudaira 1-280, Higashi Koikeku, Kokubunji, Tokyo 1-280, Central Research Laboratory, Hitachi, Ltd. (72) Inventor, Shuji Okada 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Center

Claims (9)

[Claims] 1. A vacuum chamber, means for evacuating the vacuum chamber, means for introducing gas into the vacuum chamber, and means for generating plasma in the vacuum chamber, and surface treatment of a sample is performed by the generated plasma. In the plasma surface treatment apparatus, during the surface treatment of the sample, a mechanism for periodically changing the type, composition, pressure or partial pressure of the gas introduced into the vacuum chamber over a plurality of times is provided. Plasma surface treatment device. 2. A mechanism for periodically changing the type, composition, pressure or partial pressure of the introduced gas over a plurality of times is such that the type, composition, pressure or partial pressure of the introduced gas is automatically changed through a controller. The plasma surface treatment apparatus according to claim 1, wherein the plasma surface treatment apparatus is one that is periodically changed over time. 3. The mechanism for cyclically changing the type, composition, pressure or partial pressure of the introduced gas a plurality of times automatically adjusts the type, composition, pressure or partial pressure of the introduced gas according to a predetermined program. The plasma surface treatment apparatus according to claim 1, which has a function of periodically changing over a plurality of times. 4. The cycle of cyclically changing the type, composition, pressure or partial pressure of the introduced gas a plurality of times is longer than the residence time of the molecules or atoms of the introduced gas in the vacuum chamber. The plasma surface treatment apparatus according to claim 2 or 3. 5. A mechanism for cyclically changing the type, composition, pressure or partial pressure of the introduced gas a plurality of times, the progress of the surface treatment of the sample is measured, and the measurement result is fed back according to a program. The plasma surface treatment apparatus according to claim 1, wherein the type, composition, pressure or partial pressure of the introduced gas is changed. 6. A vacuum chamber, a means for exhausting the vacuum chamber, a means for introducing a gas into the vacuum chamber, a means for generating plasma in the vacuum chamber, and an external voltage applied to a sample to be surface-treated by the generated plasma. In the plasma surface treatment apparatus having a means for applying the, a mechanism for periodically changing the type, composition, pressure or partial pressure of the introduced gas a plurality of times is additionally provided during the surface treatment of the sample. Characteristic plasma surface treatment equipment. 7. The plasma surface treatment apparatus according to claim 6, wherein the external voltage applied to the sample by the external voltage applying means is a high frequency voltage. 8. The external voltage applying means has a function of changing the external voltage applied to the sample in accordance with changes in the type, composition, pressure or partial pressure of the introduced gas. The plasma surface treatment apparatus according to claim 6 or 7. 9. A vacuum chamber, means for exhausting the vacuum chamber, means for introducing gas into the vacuum chamber, and means for generating plasma in the vacuum chamber, and irradiating the generated plasma on the sample surface. In the plasma surface treatment apparatus for performing the surface treatment of the sample surface, means for periodically changing the type, composition, pressure or partial pressure of the introduced gas a plurality of times during the surface treatment of the sample, A plasma surface treatment apparatus, further comprising means for periodically changing the irradiation state of plasma on the sample surface according to changes in the type, composition, pressure or partial pressure of the introduced gas.