JPH0774116A - Plasma processing device - Google Patents

Abstract

PURPOSE:To improve the utilization efficiency of a generated plasma significantly and improve the quality of a processed film and, further, increase the processing speed. CONSTITUTION:The magnetic flux density on the microwave introducing side of a discharge tube 2 is larger than the magnetic flux density at the resonance generating position of the electron resonance caused by a magnetic field and a microwave 4. The flux density of the magnetic field is so distributed as to have a distribution having the resonance generating position of the electron cyclotron resonance on one of its curved surfaces and, further, the resonance generating position of the electron cyclotron resonance is positioned in a sample chamber 9 at least partially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and in particular, plasma processing suitable for performing thin film formation, etching, sputtering, plasma oxidation, etc. on a sample surface by utilizing plasma generated by microwave discharge. Regarding the device.

[0002]

2. Description of the Related Art Generally, a plasma processing apparatus using plasma generated by microwave discharge in a magnetic field has an electron cyclotron resonance generation position generated by the magnetic field and microwave in a discharge tube which is a part of discharge space. Further, the magnetic flux density distribution has a sharp decrease from the electron cyclotron resonance point toward the sample stage provided in the sample chamber.
Therefore, the plasma generated near the resonance point has a density of 1 to 1 while being transported from the discharge tube to the sample stage.
It decreased by two digits or more, and efficient plasma treatment could not be performed.

Although there is a conventional example in which the resonance position is arranged in the sample chamber, most of the microwaves are absorbed at the resonance position in the discharge tube due to the mirror magnetic field configuration having the resonance position in the discharge tube. , The amount of plasma generated at the resonance position in the sample chamber was restricted.

Even if plasma can be generated at the resonance position in the sample chamber, most of the plasma is directed toward the discharge tube because the magnetic field gradient in the vicinity thereof is directed from the sample chamber toward the discharge tube. The flow rate of the plasma returned to the sample stage decreases as a whole, and efficient plasma processing cannot be performed.

A description will be given below with reference to the drawings.

FIG. 4 is a preliminary paper P of the 31st Semiconductor Integrated Circuit Technology Symposium held on December 3 and 1986.
49-54 "CVD using ECS plasma" (hereinafter,
In the electron cyclotron in the magnetic field generated by the magnetic field coil 1, the microwave 4 is incident on the discharge tube 2 provided with the magnetic field coil 1 on the outside through the waveguide 3 from the incident window 5. When the motion and the microwave 4 resonate at the resonance position, the resonance electrons collide and ionize the plasma gas 6 to generate plasma.

Then, the sample 7 is connected to the discharge tube 2.
The generated plasma is pushed out in the direction of the sample chamber 9 provided with the sample table 8 holding the This is a device for plasma-treating the surface of the sample 7 by exciting or ionizing the material gas 10 newly introduced into the sample chamber 9 by the plasma.

FIG. 5 shows the magnetic flux density distribution from the microwave entrance window 5 to the sample stage 8 of FIG. 4, where the vertical axis is the axial direction with the boundary between the discharge tube 2 and the sample chamber 9 being 0. The distance and the horizontal axis are the magnetic flux density.

In the case of the conventional example A, the magnetic flux density which causes the electron cyclotron resonance corresponding to the frequency (2.45 GHz) of the incident microwave 4 is Be (875 Gauss),
In FIG. 5, this position is approximately 3 cm from the microwave entrance window 5 in the axial direction. Therefore, from the propagation characteristics of microwaves in the plasma and the conditions for resonance absorption of microwave energy, only the 3 cm region is effective for plasma generation, and the plasma generated in this 3 cm region is about 3 cm.
A force of a magnetic field gradient is applied for a distance of 5 cm, and the sample is transported in the direction of the sample stage 8 by ambipolar diffusion. At this time, since the transport distance is long and the magnetic field sharply decreases, the density of the plasma transported to the surface of the sample 7 is lower than the plasma density near the resonance position where the electron cyclotron resonance occurs. Tended to decrease.

FIG. 6 is a P6 of the 31st semiconductor integrated circuit technology symposium held on December 3 and 1986.
1 to 66 "a-Si: H by ECR plasma CVD method
FIG. 7 shows the magnetic flux density distribution of the “film” (hereinafter referred to as “conventional example B”). The difference from the conventional example A is that the magnetic flux density distribution is generally large.

Moreover, the position of the magnetic flux density corresponding to the resonance position is still inside the discharge tube 2, and the region having the magnetic flux density higher than that and effective for the resonance absorption of microwaves is at most 2 of the discharge tube 2. It is about / 3. Further, since the magnetic flux density is sharply decreased in the direction of the sample stage 8, the density of the plasma generated near the resonance position is the same as that in the conventional example A.
There was a tendency to decrease due to loss while diffusing to the surface of.

FIG. 8 shows Japanese Patent Laid-Open No. 59-3018 (hereinafter referred to as Conventional Example C), and FIG. 9 shows its magnetic flux density distribution.

The conventional example C shown in the figure has a mirror magnetic field configuration which is often used as a plasma confinement method for the purpose of increasing the plasma density, and assists in increasing the magnetic density near the surface of the sample 7 in the sample chamber 9. A permanent magnet 13 is provided.

In this conventional example C, the incident microwave 4
Is propagated through a magnetic flux density region (region (I) in FIG. 9) larger than the resonance position and is resonantly absorbed in the plasma in the vicinity of the first resonance position (a in FIG. 9). However, when the magnetic flux density region (region (II) in FIG. 9) smaller than the resonance position is further passed, it becomes difficult for the plasma to propagate, and even if it propagates, the second resonance position near the sample 7 The plasma generated in (b in FIG. 9) receives a force in the direction of the discharge tube due to the magnetic field gradient, and as a result, the sample 7
As compared with the plasma density in the vicinity of the first resonance position, the plasma density incident on was likely to decrease as in the conventional examples A and B.

As described above, in the above conventional method, no consideration was given to the position where the density of plasma generated by electron cyclotron resonance in a microwave and a magnetic field is reduced due to loss while being transported to the sample surface. .

[0016]

In the above-mentioned prior art, the relationship between the plasma density distribution and the magnetic flux density distribution in the direction from the discharge tube to the sample stage is not considered, and the electron is transported from the vicinity of the electron cyclotron resonance generation position to the sample surface. Since the density of plasma tends to decrease, there is a problem that the plasma utilization efficiency is low and a high-quality film cannot be obtained, and the processing speed is slow and efficient plasma processing cannot be performed.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a plasma processing apparatus capable of improving the processing film quality by significantly improving the utilization efficiency of generated plasma and increasing the processing speed.

[0018]

The above-mentioned object is to make the magnetic flux density on the microwave introduction side of the discharge tube larger than the magnetic flux density at the resonance generation position of electron cyclotron resonance by the magnetic field and the microwave so that the magnetic flux density of the magnetic field is A plasma processing apparatus having a distribution shape such that the resonance generation position of the electron cyclotron resonance is one curved surface, and the resonance generation position of the electron cyclotron resonance is at least partially located in the sample chamber; The magnetic flux density on the wave introduction side,
The magnetic flux density of the resonance generation position of the electron cyclotron resonance by the magnetic field and the microwave is made larger, and the magnetic flux density of the magnetic field has a distribution shape such that the resonance generation position of the electron cyclotron resonance becomes one curved surface, and the electron This is achieved by arranging the resonance generation position of the cyclotron resonance at least partly in the sample chamber and providing a plasma processing apparatus equipped with an auxiliary magnetic field generating means for generating a magnetic field weaker than the magnetic flux density of the magnetic field generated by the magnetic field generating means. It

[0019]

In general, a microwave propagating in plasma and causing electron cyclotron resonance is a right-handed circularly polarized wave, and this wave has a magnetic flux density smaller than that required for causing the electron cyclotron resonance. Inside,
It becomes a cutoff and cannot propagate.

Therefore, in the present invention, the magnetic flux density at the microwave incident end of the vacuum container is made larger than the magnetic flux density at the electron cyclotron resonance position, and the magnetic flux density of the magnetic field is such that the resonance generation position of the electron cyclotron resonance is a curved surface. By arranging the electron cyclotron resonance position at least partially inside the sample chamber, the region where high-density plasma is generated in the magnetic flux density region higher than the resonance magnetic flux density is formed in the vacuum container. Can be extended to the vicinity of the sample stage, and the distance that plasma is pushed out by the magnetic field gradient and transported to the sample stage can be reduced to zero.

As a result, the distance between the resonance position and the sample stage can be made sufficiently small with respect to the plasma density that sharply decreases on the magnetic flux density side smaller than the resonance magnetic flux density, so that high-density plasma is transported to the sample surface. It becomes possible.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the plasma processing apparatus of the present invention will be described below with reference to FIGS. 1, 2 and 3.

1 and 2 show an example in which the present invention is applied to a plasma processing apparatus which performs sample surface treatment (film formation) by magnetic field microwave discharge.

FIG. 1 shows a structure in which a microwave 4 is introduced through a waveguide 3 into a discharge tube 2 which forms a vacuum container having a magnetic field coil 1 on the outside, and the microwave 4 is introduced into the discharge tube 2. Plasma is generated by exciting or ionizing the gas 6 by electron cyclotron motion in the magnetic field generated by the magnetic field coil 1 and electron cyclotron resonance by the microwave 4.

Then, the plasma is generated by the gradient of the magnetic field generated in the magnetic field coil 1 in the direction of the sample chamber 9 forming the vacuum chamber having the sample stage 8 for holding the sample 7 to be processed, which is connected to the discharge tube 2. By pushing out and transporting the material gas 10 newly introduced to the front surface of the sample 7 in the sample chamber 9 to the surface of the sample 7 while being excited or ionized by the plasma flow, the plasma is transferred to the surface of the sample 7. This is a plasma processing apparatus for producing a thin film having a composition by use gas 6 and said material gas 10.

FIG. 2 shows the magnetic flux density distribution in the axial direction from the discharge tube 2 to the sample stage 8 of this embodiment, where the horizontal axis represents the axial distance and the vertical axis represents the magnetic flux density.

The present invention is characterized in that the distribution shape of and of FIG. 2 is adopted, and the curve of FIG.
2 shows a magnetic flux density distribution shape in the case where the electron cyclotron resonance generating magnetic field position is located at the boundary point of the sample chamber 9 and FIG. 2 shows an example of a known magnetic flux density distribution.

In FIG. 1, the microwave (2.45 GHz) 4 introduced into the discharge tube 2 by the waveguide 3 has a magnetic flux density (Be = 875 Gauss) is located near the sample table 8 in the sample chamber 9 (point a in FIG. 1),
The ionization and excitation by electron cyclotron resonance are activated as they propagate in the magnetic flux density region in the discharge tube 2 which is equal to or higher than the magnetic flux density corresponding to the resonance position and enter the sample chamber 9 and approach the resonance position, and the plasma is proportionally generated. The density also increases and the plasma generation probability reaches the maximum value at the resonance position. But,
When the microwave is going to propagate in the plasma having a magnetic flux density smaller than the resonance position-corresponding magnetic flux density (875 Gauss in this embodiment) beyond this region, the right-handed circularly polarized wave that causes the electron cyclotron resonance is generated. Due to the nature of the wave, it becomes a cutoff and cannot propagate, and the microwave that is not resonantly absorbed in the plasma is reflected at this resonant position.

Therefore, plasma is hardly generated in the low magnetic flux density region on the sample stage 8 side from the resonance position, and the plasma reaching the surface of the sample 7 follows the magnetic field gradually decreasing from the resonance position toward the sample stage 8. The plasma transported by the bipolar diffusion and the material gas 10 introduced in the vicinity of the resonance position become atoms and molecules ionized and excited by the plasma flow. Therefore, the sample stage 8 is moved from the resonance position.
The plasma density distribution in the direction shows a sharp decrease.

However, according to the present invention, the distance from the resonance position to the surface of the sample can be reduced to about 0. Therefore, the surface position of the sample 7 can be arranged before the plasma density sharply decreases. 7. The ion density that gives ion bombardment, which has an effect on the compactness at the time of film formation, can be appropriately selected without reducing the processing speed that is almost proportional to the electron density near the surface, and a thin film of good quality and high processing speed can be obtained. Can be generated. FIG. 3 shows the film formation rate when a thin film was formed on the sample surface according to this example, and was measured under the condition that the film composition was constant. The lower part of the horizontal axis of FIG. 3 shows the magnetic flux density distribution shape (to) shown in FIG.
The upper part of the horizontal axis shows the electron density on the surface of the sample corresponding thereto in arbitrary units (electron density ratio), and the vertical axis shows the film formation rate in arbitrary units (film formation rate ratio).

As is clear from this figure, the electron density increases when the resonance position is located in the sample chamber 9 (in FIG. 3) and closer to the surface of the sample 7, and as a result, It can be seen that the film formation rate is significantly increased.

10 and 11 show another embodiment of the present invention.

In FIG. 10, an auxiliary magnetic field generating means 21 for generating a magnetic field on the sample chamber 9 side is provided outside the sample chamber 9 as a means for positioning the electron cyclotron resonance generating magnetic field position in the sample chamber 9. FIG. 11 shows the magnetic flux density distribution in the axial direction of the embodiment of FIG. A broken line in FIG. 11 shows a magnetic flux density distribution curve by only the magnetic field coil 1 of FIG. 10, and a broken line in FIG. 11 shows a magnetic flux density distribution curve by only the auxiliary magnetic field generating means of FIG.

As a result, the curve in FIG. 11 is obtained by superimposing and, and the resonance generating magnetic field position is shown in FIG.
Inside, it is pulled out in the direction indicated by the arrow and is located in the sample chamber 9. In order to position the resonance generation position in the sample chamber 9 by the auxiliary magnetic field generation means 21, the magnetic flux density thereof may be about 50 gauss or more.

In this embodiment as described above, the magnetic field coil 1 can be made small, the same effect as that of the embodiment shown in FIGS. 1 to 3 can be obtained, and by adjusting the auxiliary magnetic field generating means 21,
The resonance generation position can be moved and adjusted without affecting the magnetic field distribution in the discharge tube 2 by the magnetic field coil 1, and the flow diameter, density, etc. of the plasma extracted by the auxiliary magnetic field generation means 21 can be adjusted. It has the effect of being controllable.

[0036]

According to the plasma processing apparatus of the present invention described above, the magnetic flux density on the microwave introduction side of the discharge tube is made larger than the magnetic flux density at the resonance generation position of electron cyclotron resonance due to the magnetic field and the microwave. The magnetic flux density of the magnetic field has a distribution shape such that the resonance generation position of the electron cyclotron resonance has one curved surface, and the resonance generation position of the electron cyclotron resonance is at least partly located in the sample chamber plasma processing apparatus, And the magnetic flux density on the microwave introduction side of the discharge tube is made larger than the magnetic flux density at the resonance generation position of electron cyclotron resonance due to the magnetic field and the microwave, and the magnetic flux density of the magnetic field is such that the resonance generation position of the electron cyclotron resonance is one curved surface. Has a distribution shape such that at least a part of the resonance generation position of the electron cyclotron resonance is present in the sample. Since the plasma processing apparatus is provided with the auxiliary magnetic field generating means for generating a magnetic field weaker than the magnetic flux density of the magnetic field generated by the magnetic field generating means, the distance between the high density plasma generating position and the sample surface Since high density plasma can be transported to the surface of the sample, plasma processing with good film quality and high processing speed can be performed, which is very effective for this type of plasma processing apparatus.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic field microwave discharge plasma processing apparatus showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an axial magnetic flux density distribution in the device of FIG.

FIG. 3 is a characteristic diagram showing a relationship between a film formation speed ratio, a magnetic flux density distribution shape, and an electron density ratio associated therewith when a film is formed by the apparatus of FIG.

FIG. 4 is a cross-sectional view showing a plasma processing apparatus of Conventional Example A.

5 is a characteristic diagram showing an axial magnetic flux density distribution in the device of FIG.

FIG. 6 is a cross-sectional view showing a plasma processing apparatus of Conventional Example B.

7 is a characteristic diagram showing an axial magnetic flux density distribution in the apparatus of FIG.

FIG. 8 is a cross-sectional view showing a plasma processing apparatus of Conventional Example C.

9 is a characteristic diagram showing an axial magnetic flux density distribution in the apparatus of FIG.

FIG. 10 is a sectional view showing another embodiment of the present invention.

11 is an axial magnetic flux density distribution diagram in the apparatus of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic field coil, 2 ... Discharge tube, 3 ... Waveguide, 4 ... Microwave, 5 ... Incident window, 6 ... Plasma gas, 7 ... Sample, 8
... Sample stand, 9 ... Sample chamber, 10 ... Material gas, 11a, 11b
… Cooling water, 12… vacuum exhaust.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C23F 4/00 G 8417-4K H01L 21/203 S 8122-4M 21/3065 21/31 (72) Inventor Tadashi Sonobe 3-1-1, Sachimachi, Hitachi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Atsushi Chiba 3-1-1, Sachimachi, Hitachi, Ibaraki Hitachi factory, Hitachi Ltd. (72) Inventor Naohiro Kadoma 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory, Inc. (72) Inventor Yasuhiro Mochizuki 4026 Kuji Town, Hitachi City, Ibaraki Hitachi Research Laboratory, Ltd. (72) Inventor Shigeru Takahashi 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Takuya Fukuda 4026 Kuji Town, Hitachi City, Hitachi City, Ibaraki Prefecture Factory Hitachi Research Laboratory

Claims (2)

[Claims] 1. A discharge tube which forms a part of a discharge space when a discharge gas is introduced, a magnetic field generating means which generates a magnetic field in the discharge space of the discharge tube, and a discharge space of the discharge tube. Means for introducing microwaves, connected to the discharge tube,
And, in a plasma processing apparatus provided with a sample chamber in which a sample table for holding a sample to be processed is arranged, the magnetic flux density of the microwave introduction side of the discharge tube, the electron cyclotron resonance of the magnetic field and the microwave Greater than the magnetic flux density at the resonance generation position, the magnetic flux density of the magnetic field,
A plasma processing apparatus having a distribution shape such that the resonance generation position of the electron cyclotron resonance has a curved surface, and the resonance generation position of the electron cyclotron resonance is at least partially located in the sample chamber. 2. A discharge tube into which a discharge gas is introduced and which forms a part of a discharge space, a magnetic field generating means for generating a magnetic field in the discharge space of the discharge tube, and a discharge space of the discharge tube. Means for introducing microwaves, connected to the discharge tube,
And, in a plasma processing apparatus provided with a sample chamber in which a sample table for holding a sample to be processed is arranged, the magnetic flux density of the microwave introduction side of the discharge tube, the electron cyclotron resonance of the magnetic field and the microwave Greater than the magnetic flux density at the resonance generation position, the magnetic flux density of the magnetic field,
The resonance generation position of the electron cyclotron resonance has a distribution shape such that it becomes one curved surface, and the resonance generation position of the electron cyclotron resonance is located at least partly in the sample chamber, and the magnetic field generated by the magnetic field generating means is A plasma processing apparatus comprising an auxiliary magnetic field generating means for generating a magnetic field weaker than a magnetic flux density.