JP2002313737A - Plasma treating equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide plasma treating equipment wherein treatment efficiency can be improved. SOLUTION: In this plasma treating equipment, a sheath width reducing member 10 which is a plate-shaped member having a plurality of penetrating holes is arranged between a cathode 2 and an a node 3. A distance between the sheath width reducing member 10 and the cathode 2 is smaller than the width of a cathode sheath in the state that the sheath width reducing member 10 is not arranged. A magnetron magnetic field generating means (magnet 20) and/or a cusp magnetic field generating means for confining the generated plasma are arranged in the vicinity of the cathode 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an apparatus for performing plasma processing such as plasma CVD and plasma etching.

[0002]

2. Description of the Related Art Si thin films and DLC (Diamond Like Carbo)
n) Plasma CVD is used to form a thin film. In addition, plasma etching is used to form a fine pattern required for manufacturing a semiconductor element or the like. Plasma CVD is a method of forming a film by converting a raw material gas into plasma and depositing ionized and dissociated species such as ions and radicals in the plasma on the surface of a substrate. On the other hand, plasma etching uses ionization and
This is a method of performing etching by causing a dissociated species to collide with an object to be processed.

As a plasma generation source used for plasma processing such as plasma CVD and plasma etching, for example, a capacitively-coupled high-frequency plasma source using a frequency of 13.56 MHz and Japanese Patent Application Laid-Open No. 64-65843 are disclosed. Some of them use electron cyclotron resonance (ECR). Among them, the capacitively-coupled high-frequency plasma source can perform large-area processing and stable discharge, and can be manufactured at a lower cost than an ECR plasma source.

The capacitively coupled high-frequency plasma processing apparatus generates plasma between a high-frequency electrode and a ground electrode, and applies a high-frequency voltage to the high-frequency electrode via a coupling capacitor. At this time, a deep negative bias is formed on average by the self-bias effect, so that the high-frequency electrode functions as a cathode. Then, a glow region is generated between the high-frequency electrode and the ground electrode. In this specification, the high-frequency electrode is called a cathode, and the ground electrode is called an anode.

FIG. 12 is a sectional view of a main part of a capacitively coupled plasma processing apparatus and a potential distribution in the processing apparatus. In the device shown in FIG. 12, a cathode 2 and an anode 3 are arranged to face each other, a high-frequency power supply 5 is connected to the cathode 2 via a coupling capacitor 4, and the anode 3 is grounded. When a high-frequency voltage is applied to the cathode 2, a glow region 6, which is a high-density plasma region, is generated between the two electrodes,
A cathode sheath is formed on the front surface of the cathode 2 (the surface facing the plasma), and an anode sheath is formed on the front surface of the anode 3 (the surface facing the plasma). Both the cathode sheath and the anode sheath are regions where light emission is weak.

[0006] A large potential difference appears in the cathode sheath, and ions in the plasma are accelerated by this potential difference and collide with the cathode 2 with a large energy, and secondary electrons (γ electrons) are emitted from the surface of the cathode 2 by the γ action. . Released γ
The electrons are accelerated by the potential gradient in the cathode sheath and enter the glow region 6 with a large energy, and ionize the gas molecules by the α action, so that the discharge is maintained. The darkness of the cathode sheath is caused by the γ emitted from the cathode 2.
This is because the gas molecules cannot be excited until the electrons are accelerated to the lowest excitation energy of the gas molecules.

On the other hand, in the vicinity of the anode 3, the electron current density to the anode 3 is usually smaller than the current density associated with the random particle flux, so that the anode potential becomes lower than the plasma potential in order to repel electrons by that much. Thus, an anode sheath having a potential gradient as shown is formed. However, when the area of the anode is small and the electron current density is equal to or higher than the current density associated with the random particle flux, the anode becomes higher than the plasma potential, and an electron sheath with partial ionization may be formed. In addition,
When the anode potential is lower than the plasma potential as in the example shown,
The anode sheath is an ion sheath.

[0008]

In such a plasma processing apparatus, the pressure of a neutral gas, such as a source gas or an etching gas, is reduced by collision between electron-neutral particles and ion-neutral particles in a cathode sheath. Is set to such an extent that frequent occurrence occurs, the ion collision energy applied to the cathode 2 is proportional to the electric field strength in the cathode sheath and inversely proportional to the neutral gas pressure. Since the neutral gas pressure can be arbitrarily set according to the purpose, it can be set to such a low pressure that collision between electrons and neutral particles and between ions and neutral particles does not substantially occur in the cathode sheath. . However, in that case, the efficiency of the plasma processing is significantly reduced. Therefore, the pressure is generally set to such a degree that the collision between the particles frequently occurs.

However, if the collision between the particles frequently occurs in the cathode sheath, ions and electrons are decelerated in the cathode sheath, so that the energy of the ions colliding with the cathode is reduced, and the energy of the ions in the glow region is reduced. The energy of the incident γ-electron becomes low. As a result, it becomes difficult to improve the plasma density, and it becomes difficult to increase the processing efficiency.

An object of the present invention is to provide a plasma processing apparatus capable of increasing processing efficiency.

[0011]

This and other objects are achieved by the present invention which is defined below as (1) to (9). (1) When a sheath width reducing member which is a plate-like body having a plurality of through holes is arranged between a cathode and an anode, and the distance from the cathode of the sheath width reducing member is not provided with the sheath width reducing member. A plasma processing apparatus having a magnetron magnetic field generating means and / or a cusp magnetic field generating means for confining generated plasma in the vicinity of the cathode, the width being smaller than the cathode sheath width. (2) The plasma processing apparatus according to the above (1), wherein the minor diameter of the through hole is 10 times or less the Debye length. (3) The above (1) or (2) having a bias voltage applying means for controlling a potential of the sheath width reducing member.
Plasma processing equipment. (4) The cathode has a magnetron magnetic field generating means, and at least the surface of the cathode facing the plasma has W, T
The plasma processing apparatus according to any one of the above (1) to (3), comprising a metal or an alloy containing at least one of a, Mo, Ti and Zr. (5) The plasma processing apparatus according to any one of (1) to (4), further comprising: a magnetron magnetic field generating unit, a high frequency power supply connected to the cathode, and a unit for reducing the cathode sheath voltage. (6) providing a high-frequency cutoff filter exhibiting high impedance at the frequency of the high-frequency power supply, and connecting one end of the high-frequency cutoff filter to the cathode in parallel with the high-frequency power supply;
The plasma processing apparatus according to the above (5), wherein the other end of the high-frequency cutoff filter is grounded to reduce the cathode sheath voltage. (7) Potential control means including a high-frequency cutoff filter exhibiting high impedance at the frequency of the high-frequency power supply and a resistor connected in series to the high-frequency cutoff filter is provided. The plasma processing apparatus according to the above (5), wherein the cathode sheath voltage is reduced by connecting the cathode sheath in parallel. (8) Potential control means including a high-frequency cutoff filter exhibiting high impedance at the frequency of the high-frequency power supply and a DC power supply connected in series to the high-frequency cutoff filter is provided. The plasma processing apparatus according to the above (5), wherein the cathode sheath voltage is reduced by connecting the cathode sheath in parallel. (9) The plasma processing apparatus according to any one of (1) to (8), wherein the cusp magnetic field generation means functions as the anode.

In the present invention, as shown in FIGS. 1 and 2, a sheath width reducing member 10 is provided in a region which was a cathode sheath in a conventional plasma processing apparatus as illustrated in FIG.
Place. The sheath width reducing member 10 is a plate-like body having a plurality of through holes 11, and by arranging this in the cathode sheath, the width of the cathode sheath can be reduced. As a result, the processing target 7 disposed on the plasma facing surface side of the anode 3 can be plasma-processed at high speed. Hereinafter, the operation and effect of the sheath width reducing member 10 will be described. The following description is for the case where the sheath width reducing member 10 is made of a conductive material.

By disposing the sheath width reducing member 10 in the cathode sheath and applying a DC bias voltage, the potential of the sheath width reducing member 10 is set to V _P shown in FIG. 12 (when the sheath width reducing member 10 is not provided). the plasma potential) equal to or, or, if you set higher than V _P, 1 and 2
Of, as shown respectively in potential distribution graph, region potential is greater than or equal to V _P is extended to the surface facing the cathode 2 of the sheath narrowing member 10, the width of the cathode sheath is reduced. The area became V _P over potential by placing a sheath narrowing member 10 is a glow region. That is, by providing the sheath width reducing member 10, the width of the cathode sheath is reduced and the glow region 6 is expanded.

Further, the direct voltage applied to the sheath width reducing member 10 is
The current bias voltage is V _PIf less than
Also, the width of the cathode sheath can be reduced. For example, as shown in FIG.
As shown in FIG.
The cathode sheath width should be reduced even if
Can be. In this case, in the cathode sheath shown in FIG.
The sheath reducing member 10 in a region where the potential is negative.
Place. As a result, the area of zero potential is
Since it is extended to the side facing the cathode 2 of the material 10, the cathode sheet
The width of the source is reduced. In this case, the sheath width reducing member
Because there is no need to actively control the potential of 10
It is possible to prevent the processing device from becoming complicated.

[0015] In the present invention, the electron-
This is effective when the neutral gas pressure is high enough to cause frequent collisions between neutral particles and ions-neutral particles. The case where the pressure is pressure, that is, the case where the mean free path between the particles is much larger than the cathode sheath width will be described. In this case, the electrons and ions are
Energy is not lost by collision with neutral particles in the cathode sheath. Therefore, the energy of the ion energy and the cathode sheath end of γ electrons emitted by the ion bombardment of the cathode entering the cathode (the boundary between the glow region), the plasma potential V _P and the cathode in the cathode sheath voltage (Fig. 1 (The difference from the potential V _C ). Therefore, the cathode sheath width is changed, even if thereby changing the potential gradient in the cathode sheath, the cathode sheath voltage (V _P -V _C)
If does not change, the energy of ions flowing into the cathode and the energy of γ electrons at the end of the cathode sheath do not change. Therefore, the plasma generation efficiency does not depend on the sheath width.

On the other hand, the present invention is directed to the case where the neutral gas pressure is relatively high and the mean free path between the particles in the cathode sheath is equal to or shorter than the cathode sheath width. In this case, ion and electron energy is lost due to collision with neutral particles in the cathode sheath. In this case, W _i: the energy of the ions flowing to the cathode, W _e: gamma electron energy at the cathode sheath end, lambda _in: Ion - mean free path between the neutral particles, lambda _en: Electronic - between neutral the mean free path of, <e>: the average electric field in the cathode sheath, q _e: charge of an electron, q _i: When you charge the amount of _{ions, W i = q i <e} > · λ in, W e = | q _e | <E> · λ _en . That is, in this case, unlike the case where no collision occurs during cathode sheath, W _i and W _e are, will vary in proportion to the electric field strength in the cathode sheath (<E>).

In this case, the sheath width reducing member 10
By providing, if reduced cathode sheath width without changing the cathode sheath voltage (V _P -V _C), the field strength (<E
>) Is W _i and W _e will increase both becomes larger. _Wi
Is increased, which means that the amount of emitted γ electrons increases, whereas, since the increase in W _e means the increase of energy in the cathode sheath emitted γ electrons, as a result,
A large amount of high-energy γ electrons enter the glow region 6. The neutralization of the neutral gas into a plasma proceeds with higher efficiency as the energy of the colliding electrons increases and as the number of the high-energy electrons increases. Therefore, by providing the sheath width reducing member 10, the high density plasma is generated. Becomes possible.

Further, a decrease in the cathode sheath width means an increase in the glow region 6. As the glow region 6 expands, the plasma density increases, and the increase in the plasma density causes an increase in ion flux into the cathode sheath. Therefore, the expansion of the glow region 6 also contributes to efficient plasma generation. Here, the reason why the plasma density increases as the glow region 6 expands will be described. First, as the glow region expands, the plasma generation further increases in response to the increase in the volume of the glow region. on the other hand,
Increasing the glow region means increasing the surface area of the glow region, thereby increasing losses at the glow region surface. However, the increase in loss due to the expansion of the glow region corresponds to the increase in the surface area of the glow region, and thus is one-dimensionally lower than the increase in plasma generation. As a result, it is considered that the plasma density is improved by increasing the plasma generation.

As described above, according to the present invention, high-density plasma can be generated, so that high-speed plasma processing can be performed on the processing target 7. That is, high-speed film formation in plasma CVD and high-speed etching in plasma etching are realized. Further, the present invention can easily cope with an increase in the area of the object 7 to be processed. When the processing area is increased, the area of the cathode 2 is increased. However, in the present invention, it is possible to process a large-area substrate at high speed only by enlarging the dimension of the sheath width reducing member 10 in accordance with the increase in the area of the cathode 2. It becomes possible.

In order to form a polycrystalline silicon film by plasma CVD, the substrate temperature must be relatively high. However, if the present invention is applied, the polycrystalline silicon film can be formed even when the substrate temperature is relatively low. A film is obtained. In the present invention, since the deceleration of the γ-electrons in the cathode sheath is small, high-speed γ-electrons enter the glow region, and as a result, the H ₂ gas is easily dissociated into atomic hydrogen. It is considered that silicon is easily generated.

Incidentally, even when the sheath width reducing member 10 is made of an insulating material, the width of the cathode sheath can be reduced. Most of the particles present in the cathode sheath are ions, and the number of electrons is small. When an insulating member is placed in such a cathode sheath, the surface of the insulating member is positively charged. Therefore, since the electric field intensity becomes the cathode sheath width is substantially reduced (<E>) increases, W _i and W _e are increased together.

In the present invention, a magnetron magnetic field generating means for generating a magnetron magnetic field is provided near the cathode, or a cusp magnetic field generating means for confining the generated plasma is provided, or both of them are provided.

The apparatus shown in FIGS. 1, 2 and 3 has a magnet 20 near the cathode 2 as a magnetron magnetic field generating means.
Is provided. In order to increase the processing speed in a plasma processing apparatus, it is effective to increase the plasma density. As a thin film forming means capable of increasing the plasma density, for example, a magnetron sputtering method is known. In the magnetron sputtering method, electrons draw a cycloidal trajectory in the vicinity of a target functioning as a cathode by the action of orthogonal electric and magnetic fields. As a result, the electrons repeatedly collide with the plasma gas, and a high-density plasma is generated. Therefore, the sputtering efficiency of the target is increased, and a high-speed film can be formed. The present inventors constructed a flat magnetron type electrode by arranging a magnet 20 on the back surface side (left side in the figure) of the cathode 2 in the plasma processing apparatus, and formed a thin film by the plasma CVD method using this. As a result, it was confirmed that the thin film formation speed was improved. In the present invention, by increasing the plasma density by using the magnetron magnetic field, it is possible to perform extremely efficient plasma processing in combination with the above-described improvement in processing efficiency by reducing the cathode sheath width.

However, in this case, the cathode 2 is sputtered as in the case of magnetron sputtering, and as a result, the cathode constituent material is mixed into the thin film formed on the processing target 7. Therefore, depending on the required level, the desired quality may not be obtained in some cases.

Therefore, in order to reduce the sputtering of the cathode 2 caused by the presence of the magnetron magnetic field, it is preferable that at least the surface of the cathode 2 facing the plasma is made of a material (W, Ta, etc.) which is hardly sputtered by ions. .

Also, by providing a means for reducing the cathode sheath voltage, it is possible to reduce the sputtering of the cathode 2. As shown in FIG. 1, the cathode sheath voltage V _S is a value obtained by subtracting the cathode potential V _C from the plasma potential V _P. Cathode 2 when used as a flat magnetron type electrode
Is easily sputtered because a large amount of ions generated in the high-density plasma are accelerated by the cathode sheath voltage V _S ,
This is because the light enters the cathode 2. Therefore, if reducing the cathode sheath voltage V _S, it can be reduced sputtering of the cathode 2 by the ion. As a result, the amount of the constituent material of the cathode 2 flying to the processing target 7 is reduced.

As described above, in the plasma processing apparatus, ions in the plasma are accelerated by the cathode sheath voltage V _S and collide with the cathode 2, and secondary electrons (γ electrons) are generated from the surface of the cathode 2 by the γ action. Release. The emitted γ-electrons are accelerated by the cathode sheath voltage V _S and enter the glow region 6 with a large energy and ionize gas molecules by the α action, so that the discharge is maintained. Therefore, when the cathode sheath voltage V _S is reduced, the amount of emitted γ electrons and the energy thereof are reduced, and as a result, the plasma processing speed is reduced. However, as a result of the experiments of the present inventors, the effect of improving the plasma density by using the magnetron-type electrode is not improved by the cathode sheath voltage V _S.
It was found to outweigh the negative effects of the decline. That is, by using the magnetron magnetic field, the film formation speed and the etching speed are remarkably improved.

In either case where the cathode 2 is made of a material which is not easily sputtered by ions, or where a means for reducing the plasma sheath voltage V _S is provided, the object to be processed 7 is placed on the object 7 during plasma CVD. It is possible to form a high-quality thin film with few impurities at a high speed, and at the time of plasma etching, it is possible to etch the object to be processed 7 at a high speed and to prevent the adhesion of impurities to a surface to be etched. Becomes In the present invention, the cathode 2 may be made of the above-described specific material, and a cathode sheath voltage V _S reducing means may be provided.

On the other hand, the apparatus shown in FIG. 8 is provided with a magnet 8 as cusp magnetic field generating means so as to surround the plasma. It is known that when plasma processing is performed, if plasma is confined in a predetermined space, processing efficiency is improved. For confinement of plasma, for example,
It is known that a cusp magnetic field can be used as described in JP-A-223997. In the present invention, by performing plasma confinement using a cusp magnetic field, it is possible to perform extremely high-efficiency plasma processing in combination with the above-described improvement in processing efficiency due to the reduction in the width of the cathode sheath.

In the present invention, a magnetron magnetic field and a cusp magnetic field may be used in combination. In this case, more efficient plasma processing can be performed.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 are cross-sectional views of main parts of a plasma processing apparatus according to the present invention, and FIG. 12 is a cross-sectional view of main parts of a conventional plasma processing apparatus. The plasma processing apparatus shown in each of FIGS. 1, 2 and 3 is provided with a sheath width reducing member 10 and a magnet 20 as a magnetron magnetic field generating means in the cathode sheath of the apparatus shown in FIG. Sheath width reducing member 1
By providing 0, the cathode sheath width is reduced. The cathode sheath is also called a cathode dark part, and exists in a sheath shape on the front surface of the cathode 2 (the surface facing the glow region 6). The presence of the cathode sheath can be confirmed with the naked eye. Therefore, it is easy to provide the sheath width reducing member 10 in the region that was the cathode sheath when not provided. Therefore, it is not necessary to numerically determine the cathode sheath width when implementing the present invention. However, usually, the cathode sheath width is

[0032]

(Equation 1)

The position where the sheath width reducing member 10 is arranged may be determined based on the above equation. In the above formula, [delta]: cathode sheath width, V _s: the cathode sheath voltage (V _P -V _C ≒ RF voltage), mu _i: ion mobility, C _s: ion sound speed, n _se: plasma density, e: Elementary charge, ε ₀ : dielectric constant in vacuum. The above equation is an equation representing a collision sheath in which collisions between electron-neutral particles and between ion-neutral particles frequently occur.

The sheath width reducing member 10 used in the present invention comprises:
It is a plate-like body having a plurality of through holes 11. FIG. 4 shows a configuration example of the sheath width reducing member. As shown in the figure, the shape of the through-hole may be circular or polygonal such as square or hexagonal. Specifically, a circular or polygonal through hole is formed in a plate-like body by punching as shown in FIG. 4 (A), and a plurality of linear bodies as shown in FIG. 4 (B) are arranged in parallel. 4C, a mesh formed by knitting a plurality of linear bodies in a lattice shape, and as shown in FIG. 4D, a plurality of short linear bodies are parallel to a long linear body. To form a dendritic body, and a plurality of such dendrites may be arranged, or a honeycomb-shaped formed body as shown in FIG. 4E may be used. All of these can increase the aperture ratio, and even in that case, sufficient mechanical strength can be obtained.

The constituent material of the sheath width reducing member 10 is not particularly limited. However, by using a conductive material, the potential control of the sheath width reducing member becomes easy. As the conductive material, a metal (including an alloy) is preferable. As metal,
For example, Al, Cr, Ni, W or an alloy containing at least one of these, for example, stainless steel is preferable. In addition,
The entire sheath width reducing member does not need to be made of a conductive material, and may have a structure in which a thin film of a conductive material is formed on the surface of an insulating base made of, for example, ceramics or glass. When the sheath width reducing member 10 is made of an insulating material, for example, ceramics or glass may be used. In the present invention, since the magnet for generating the magnetron magnetic field and / or the magnet for generating the cusp magnetic field are provided, the sheath width reducing member 10 needs to be made of a non-magnetic material.

The higher the aperture ratio of the sheath width reducing member 10, the higher the utilization efficiency of γ electrons. Therefore, it is preferable to increase the aperture ratio within a range that does not cause a significant decrease in mechanical strength. Specifically, the aperture ratio is preferably 60% or more, more preferably 80% or more. The upper limit of the aperture ratio at which sufficient mechanical strength can be ensured varies depending on the constituent material of the sheath width reducing member, the shape of the through hole, and the like, but is usually about 98%.

The minor diameter of the through hole 11 is preferably 10 times or less, more preferably 5 times or less the Debye length. If the short diameter of the through-hole 11 is too large, the electrostatic shielding becomes insufficient, so that the effect of reducing the cathode sheath width becomes insufficient. On the other hand, the smaller the shorter diameter of the through-hole 11, the more difficult it is to increase the aperture ratio. Note that the major axis of the through-hole is not particularly limited, as can be seen from the fact that, for example, a large number of linear bodies are arranged in parallel to form a striped sheath width reducing member.

In this specification, the minor axis of the through hole 11 is defined as
When the through-hole is circular, it has its diameter, when it is a regular polygon, it has its minimum diameter, and when it is a polygon such as a rectangle or an oval, it has its minor diameter. When a plurality of linear members are arranged in parallel to constitute a sheath width reducing member,
The minor axis is the distance between parallel linear bodies.

In the sheath width reducing member, all the through holes may have the same size, or through holes of different sizes may be mixed. For example, a configuration in which large and small through holes are mixed to increase the aperture ratio may be adopted.

In the present invention, the reduced width of the cathode sheath is substantially equal to the distance between the cathode 2 and the main surface of the sheath width reducing member 10 on the side facing the cathode 2. Therefore, as the sheath width reducing member 10 is brought closer to the cathode 2, the cathode sheath width can be reduced, and as a result, the plasma generation efficiency increases. However, the sheath width reducing member 10 made of a conductive material
If the distance between the capacitor and the cathode 2 is too short, the capacity of the capacitor formed by the two becomes large, and as a result, the loss increases. Therefore, the distance between the two is determined so that such a problem does not occur.

The thickness of the sheath width reducing member 10, that is, the dimension in the direction connecting the cathode 2 and the glow region 6 is not particularly limited. Since the glow region 6 is expanded to the main surface side of the sheath width reducing member 10 facing the anode 3, even if the sheath width reducing member 10 is made thinner, there is no problem in its function. on the other hand,
As the sheath width reducing member 10 is made thicker, the glow region 6 becomes larger.
Will be reduced in size. Therefore, the thickness of the sheath width reducing member 10 is set such that the main surface of the sheath width reducing member 10 on the glow region 6 side is closer to the cathode 2 than the cathode sheath end when the sheath width reducing member 10 is not provided. It is preferable to determine.

The DC bias voltage V _B applied to the sheath width reduction member 10 is preferably higher than the plasma potential V _P in FIG. If the V _B higher than V _P in FIG. 12, the cathode - the potential distribution between the anode becomes that shown in Figure 2. That is, since the sheath narrowing member functions as a maximum loss surface, will be the plasma potential V _P is determined by the DC bias voltage V _B, as a result, the type of the object, dimensions, the anode potential due to the structure, etc. Be less susceptible to change. Therefore, the plasma can be maintained in a stable state, and a high-quality CVD film can be stably formed.

If V _B is the same as V _P in FIG. 12, that is, if the potential distribution between the cathode and the anode is as shown in FIG. 1, V _P remains at V even if the anode potential fluctuates. _B is kept the same. Therefore, again, will be the plasma potential V _P is determined by the DC bias voltage V _B, as a result, the plasma state is hardly influenced by the change in the anode potential.

Next, the magnetron magnetic field generating means will be described. In the apparatus shown in FIGS. 1, 2 and 3, a magnet 20 is disposed on the back side (left side in the figure) of the cathode 2 as a magnetron magnetic field generating means. FIG. 9 shows the structure of the magnet 20. FIG. 9 shows the device shown in FIG.
FIG. 4 is a cross-sectional view when the cathode 2 side is viewed from the side. However, the cathode 2 has been removed, and the vacuum chamber 100 accommodating the main part of the apparatus is shown. As shown in FIG.
Numeral 0 is composed of a center magnet 20A and an annular outer peripheral magnet 20B surrounding the center magnet 20A, similarly to a normal magnetron sputtering apparatus. However, the center magnet 20A has an annular structure in order to introduce a processing gas such as a source gas into the vacuum chamber 100 from the center thereof.

The configuration of the magnetron magnetic field generating magnet 20 is not limited to the illustrated example, and its size and strength may be appropriately determined so that a magnetic field having a desired strength and shape can be formed in the plasma generation space.

As described above, when the magnetron magnetic field generating means is provided in the present invention, it is preferable that the cathode 2 is made of a material which is not easily sputtered by ions. Al is often used as a cathode constituent material in a normal plasma processing apparatus because of its good workability and low reactivity to NF ₃ used as a cleaning gas when cleaning the inside of the apparatus.
However, a cathode made of Al is relatively easily sputtered. On the other hand, in a preferred embodiment of the present invention, the cathode 2 is
It is made of a metal or an alloy containing at least one of W, Ta, Mo, Ti and Zr, and preferably, W, T
a, Mo, a metal or an alloy composed of at least one of Ti and Zr, more preferably W, Ta, M
It is composed of any of o, Ti and Zr. As a result, the amount of cathode sputtering can be significantly reduced.

When a material which is hard to be sputtered, such as W, is used, at least the surface of the cathode facing the plasma may be made of the above material. That is, the entire cathode may be made of these materials, or only the vicinity of the surface facing the plasma may be made of the above materials.
In the latter case, it is preferable that the material that is difficult to be sputtered exists over a thickness of 3 μm or more from the surface of the cathode facing the plasma.

Constituting the cathode 2 from the above-mentioned specific material is particularly effective when at least H ₂ is used as a raw material gas or an operating gas. Sputtering of the cathode when the gas containing H ₂ is turned into plasma is used. The amount is significantly reduced. The gas containing H ₂ is used, for example, when a thin film made of amorphous silicon is formed by a plasma CVD method.

As described above, the cathode sheath voltage V
_Also by reducing _S , the sputtering of the cathode 2 by ions can be reduced. As means for reducing the cathode sheath voltage, the following three embodiments are preferable.

In the first embodiment, a high-frequency cutoff filter having a high impedance at the frequency of the high-frequency power supply is provided, one end of the filter is connected to the cathode in parallel with the high-frequency power supply, and the other end of the filter is grounded. By
Reduce cathode sheath voltage.

FIG. 5A shows a cross-sectional view of a main part of the plasma processing apparatus according to the first embodiment and a potential distribution in the processing apparatus. The device shown in FIG. 5A is obtained by adding a cathode sheath voltage reducing means to the device shown in FIG. In this device, the cathode 2 has a magnet 20 disposed on the back surface side, and is a flat magnetron type electrode. Further, one end of a coil 21 is connected to the cathode 2 in parallel with the high-frequency power supply 5, and the other end of the coil 21 is grounded. Other configurations are the same as those of the conventional device shown in FIG. FIG.
In (A), the coil 21 is a high-frequency cutoff filter that exhibits high impedance at the frequency of the power generated by the high-frequency power supply 5 but does not substantially become a resistance to DC. Therefore, as shown in the potential distribution graph of FIG. 5A, the cathode potential V _C becomes substantially zero, and the cathode sheath voltage V _S becomes substantially equal to the plasma potential V _P. As a result, a large amount of ions in the high-density plasma hardly reach the cathode 2 and sputtering of the cathode 2 hardly occurs.

In FIG. 5A, the coil 21 is used as a high-frequency cutoff filter. However, a resonance circuit whose resonance frequency matches the frequency of the high-frequency power supply 5 can be used as the high-frequency cutoff filter.

In the processing apparatus shown in FIG.
Looking at the electrical configuration at the time of generating the zuma from the high-frequency power supply 5 side,
As shown in FIG.
Peedance Z_PAnd the impedance Z of the coil 21_CWhen
Are connected in parallel. Provided coil 21
In order to minimize the loss of input power due to
_PFor Z_CShould be relatively large, specifically, Z_C
/ Z_P≧ 10, Z_C/ Z_P≧ 20
More preferably, there is.

Next, the second embodiment will be described. Second
In the aspect, by providing a potential control means including the high-frequency cutoff filter and a resistor connected in series to the high-frequency cutoff filter, by connecting the potential control means to the cathode in parallel with the high-frequency power supply And reduce the cathode sheath voltage.

FIG. 6 shows a sectional view of a main part of a plasma processing apparatus according to the second embodiment and a potential distribution in the processing apparatus. This device has a configuration in which a variable resistor 22 is connected in series with a coil 21 in the processing device shown in FIG. The coil 21 and the variable resistor 22 constitute the potential control means. That is, one end of the potential control means is connected to the cathode 2 in parallel with the high frequency power supply 5, and the other end of the potential control means is grounded. In the configuration shown in FIG. 6, because the cathode 2 is grounded through a variable resistor 22, the cathode potential V _C is higher than in the conventional apparatus shown in FIG. 12. Therefore, conventional compared cathode sheath voltage V _S is low, the sputtering of the cathode is reduced. In FIG. 6, the variable resistor 2
2, there is a voltage drop due to the cathode potential V _C of FIG.
It is lower than the configuration shown in FIG. As a result, the amount of decrease in the cathode sheath voltage V _S can be reduced, so that a decrease in plasma density due to the decrease in V _S can be suppressed.

Next, a third embodiment will be described. Third
In the aspect, by providing a potential control means including the high-frequency cutoff filter and a DC power supply connected in series to the high-frequency cutoff filter, by connecting the potential control means to the cathode in parallel with the high-frequency power supply And reduce the cathode sheath voltage.

FIG. 7 shows a plasma processing apparatus according to the third embodiment.
The sectional view of the main part and the potential distribution in this processing device
Show. This apparatus is similar to the processing apparatus shown in FIG.
And a DC power supply 23 connected in series with the coil 21.
is there. The coil 21 and the DC power supply 23
Make up the steps. That is, one end of the potential control means
The other end of the potential control means is connected to the cathode 2 in parallel with the power supply 5.
Is grounded. In the configuration shown in FIG.
By the cathode potential V_CBy controlling the cathode
Voltage V_SLower. Therefore, compared to the conventional cathode cathode
Source voltage V_SAnd cathode spatter is reduced.
You. Also, as compared with FIG. _SHigher
V_SLow plasma density due to decrease
The bottom can be kept low.

In the second and third embodiments, the amount of decrease in the cathode sheath voltage V _S may be determined appropriately according to specific conditions during the plasma processing. That is, the ease with which the cathode is sputtered depends not only on the cathode sheath voltage V _S but also on the gas species and the cathode constituent material introduced into the processing apparatus. allowable amount, because it varies by treatment type and processed, in accordance with these various conditions may be controlled to decrease the cathode sheath voltage V _S.

As described above, in the present invention, the cathode 2 is set to W,
It consists of the specific materials such as Ta, and may be provided with a cathode sheath voltage V _S reducing means. In a second aspect and the third aspect of the, W, if constituting the cathode from the sputtered hard material such as Ta, it is possible to further reduce the amount of decrease in the cathode sheath voltage V _S without increasing the cathode sputtering amount, cathode It is possible to reduce the influence of the decrease in the sheath voltage V _{S on} the plasma processing speed.

Next, the cusp magnetic field generating means will be described. In the apparatus shown in FIG. 8, a magnet 8 is provided as a cusp magnetic field generating means so as to surround a plasma generation region including a glow region 6. The structure of this magnet 8 is shown in FIG.
Shown in FIG. 10 is a cross-sectional view of the apparatus shown in FIG. 1 when the cathode 2 side is viewed from the anode 3 side. However, only the end face is shown, and the display in the depth direction is omitted.
Further, a vacuum chamber 100 accommodating the main part of the apparatus is shown. In FIG. 10, eight magnets 8 are arranged at equal intervals near the inner peripheral side surface of the vacuum chamber 100 so as to be arranged in the circumferential direction. As shown in FIG. 10, the magnets 8 are arranged so that different poles are adjacent to each other. Since the plasma is confined by the magnets 8 arranged as described above, wall loss can be reduced, and the plasma processing efficiency is improved.

The configuration of the cusp magnetic field generating magnet 8 is not limited to the illustrated example. For example, the number of magnets 8 is preferably 4 to
It may be determined appropriately within the range of 256. The magnetic field strength in the vacuum chamber 100 may be set appropriately so that the plasma is sufficiently confined. Further, the magnet 8 for generating the cusp magnetic field may be provided outside the vacuum chamber 100. However,
As shown in FIG. 10, if the magnet 8 is provided in the vacuum chamber 100 and the magnet 8 functions as an anode, the influence of the anode 3 and the object 7 on plasma is reduced. It is possible to relatively freely select the position to be arranged.

In the plasma processing apparatus of the present invention, the configuration excluding the sheath width reducing member 10, the magnetron magnetic field generating means and the cusp magnetic field generating means is not particularly limited, and may be the same as the conventional plasma processing apparatus.

FIG. 11 shows a specific configuration example of the plasma processing apparatus of the present invention. FIG. 11 shows the main parts shown in FIG.
A vacuum chamber 100 accommodating the cathode 2, the anode 3, and the sheath width reducing member 10 is added.

An object 7 made of a long flexible film is held on the surface of the anode 3 in a wound state, and continuous plasma processing is possible.

The vacuum chamber 100 is provided with an exhaust path 101 and a source gas introduction path 102. Plasma CVD
Is performed, the gas in the vacuum chamber 100 is evacuated from an exhaust path 101 connected to an oil rotary pump, a turbo molecular pump, or the like (not shown) to make the inside of the chamber a high vacuum of about 10 ^-4 to 10 ^-5 Pa. Keep this up. Next, the source gas is introduced into the vacuum chamber 100 from the source gas introduction path 102. The supply of the source gas to the source gas introduction path 102 is adjusted by a mass flow controller (not shown). By providing a plurality of mass flow controllers, two or more types of gases can be mixed and used as a source gas.

The pressure in the vacuum chamber 100 during plasma CVD is preferably 700 Pa or less, more preferably 5 to 20 Pa.
0 Pa. If the pressure is too low, it becomes difficult to increase the plasma density, and the efficiency of the plasma processing is reduced. On the other hand, if the pressure is too high, the generation of higher-order radicals cannot be ignored and it is difficult to obtain a high-quality CVD film.

The pressure in the vacuum chamber 100 during the plasma etching is preferably 400 Pa or less, more preferably 5 to 5 Pa.
It is 200 Pa. If the pressure is too low, it becomes difficult to increase the plasma density, and the efficiency of the plasma processing is reduced. On the other hand, if the pressure is too high, the etching efficiency tends to decrease due to the generation of polyatomic molecules.

In addition, a heating means for heating the object 7 to be processed, for example, an electric heater or the like is provided in or near the anode 3 as needed.

Further, a DC bias voltage may be applied to the anode 3 as necessary. When a DC bias voltage is applied in a direction to lower the anode potential, ions are accelerated toward the object to be processed 7, which is particularly effective for improving the efficiency in plasma etching.

The present invention can be applied to the formation of various CVD films. For example, polycrystalline or single crystal diamond, Si,
_{SiC, BN, C, SiN x} , amorphous film made of SiO _x or the like, Si, SiC, polycrystalline film composed of c-BN and the like, Si, SiC, in any production, such as single crystal film composed of c-BN and the like The present invention can also be applied.

The source gas used in the plasma CVD is as follows:
What is necessary is just to select suitably similarly to the conventional according to the formation object,
There is no particular limitation.

[0072]

EXAMPLE No. 1 (Comparative) Using a device having the structure shown in FIG. 1 from which the magnet 20 for generating a magnetron magnetic field was removed, a 75 μm-thick polyethylene naphthalate film base was formed on a polyethylene naphthalate film substrate. A 0.7 μm thin film was formed by a plasma CVD method. Material gas and its flow _{rate, SiH 4: 50sccm, H 2} : was 500 sccm. Operating pressure, cathode 2 constituent material, cathode sheath voltage V
Table 1 shows _S and the plasma density.

In this apparatus, when the sheath width reducing member 10 is not provided, the cathode sheath width is about 20 mm. The sheath width reducing member 10 has a thickness of 1 mm made of Al and an aperture ratio of 70.
% Punching metal was used. The through-hole of this punching metal has a diameter of 0.2 mm (10 times the Debye length) and is arranged so as to be closest packed. The distance between the cathode 2 and the sheath width reducing member 10 was 5 mm. It was visually confirmed that the provision of the sheath width reducing member 10 reduced the cathode sheath width and increased the glow region.

Case No. 2 An amorphous silicon thin film was formed in the same manner as in Case No. 1 except that the apparatus having the structure shown in FIG. 1 was used.

Case No. 3 An amorphous silicon thin film was formed in the same manner as in Case No. 1, except that the apparatus having the structure shown in FIG. 8 was used.

Case No. 4 Case No. 1 except that an apparatus having a configuration in which a cusp magnetic field generating magnet 8 shown in FIG. 8 was added to the apparatus having the configuration shown in FIG. 1 was used.
In the same manner as described above, an amorphous silicon thin film was formed.

Case No. 5 An amorphous silicon thin film was formed in the same manner as in Case No. 2 except that a cathode 2 having a different material was used.

Case No. 6 An amorphous silicon thin film was formed in the same manner as in Case No. 1 except that the apparatus having the structure shown in FIG. 7 was used.

Evaluation For the thin films formed in each of the above cases, the amount of the cathode constituent material mixed was measured by SIMS. Table 1 shows the results.
In Table 1, “below the detection limit” means 10 ¹⁷ cm ^−3.
Means:

[0080]

[Table 1]

In Table 1, in cases No. 2 and No. 3 using the apparatus provided with the magnetron magnetic field generating magnet or the cusp magnetic field generating magnet, the plasma density is remarkably improved. Further, in case No. 4 using an apparatus provided with both of these magnets, the plasma density is further improved.

Case No. 2 in which a magnet for generating a magnetron magnetic field was provided and a cathode 2 made of Al was used.
In case No. 4 and cathode constituent elements were mixed in the thin film, case N using cathode 2 made of W was used.
In o.5, no contamination of cathode constituent elements was observed. Also,
Although using the cathode 2 composed of similarly Al a case No.2, Case No.6 reduced cathode sheath voltage V _S by using the apparatus shown in FIG. 7, the plasma density is slightly decreased, the cathode structure No element contamination is observed.

Even when the apparatus having the structure shown in FIG. 5 or FIG. 6 was used, it was possible to suppress the incorporation of the cathode constituent elements into the amorphous silicon thin film without greatly lowering the plasma density. The cathode 2 is made of Ta, M
The same was true for the case where it was composed of o, Ti or Zr.

[0084]

The plasma processing apparatus of the present invention has a sheath width reducing member and a magnet for generating a magnetron magnetic field and / or a magnet for generating a cusp magnetic field, thereby enabling high-speed plasma processing. That is, the plasma CV
High-speed film formation in D and high-speed etching in plasma etching are realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a plasma processing apparatus of the present invention and a graph showing a potential distribution between a cathode and an anode of the apparatus.

FIG. 2 is a sectional view showing a main part of the plasma processing apparatus of the present invention and a graph showing a potential distribution between a cathode and an anode of the apparatus.

FIG. 3 is a sectional view showing a main part of a plasma processing apparatus of the present invention and a graph showing a potential distribution between a cathode and an anode of the apparatus.

FIG. 4 is a plan view showing a configuration example of a sheath width reducing member.

FIG. 5A is a sectional view showing a main part of a plasma processing apparatus of the present invention and a graph showing a potential distribution between a cathode and an anode of the apparatus. FIG. 2B is a circuit diagram equivalently showing a discharge unit and a coil in the plasma processing apparatus shown in FIG.

FIG. 6 is a sectional view showing a main part of the plasma processing apparatus of the present invention and a graph showing a potential distribution between a cathode and an anode of the apparatus.

FIG. 7 is a sectional view showing a main part of a plasma processing apparatus of the present invention and a graph showing a potential distribution between a cathode and an anode of the apparatus.

FIG. 8 is a sectional view showing a main part of the plasma processing apparatus of the present invention.

FIG. 9 is a cross-sectional view illustrating a configuration of a magnet for generating a magnetron magnetic field provided in the plasma processing apparatus of the present invention.

FIG. 10 is a cross-sectional view illustrating a configuration of a cusp magnetic field generating magnet included in the plasma processing apparatus of the present invention.

FIG. 11 is a cross-sectional view showing a specific configuration example of the plasma processing apparatus of the present invention.

FIG. 12 is a sectional view showing a main part of a conventional plasma processing apparatus and a graph showing a potential distribution between a cathode and an anode of the apparatus.

[Explanation of symbols]

 2 Cathode 20 Magnet 20A Center magnet 20B Peripheral magnet 21 Coil 22 Variable resistor 23 DC power supply 3 Anode 4 Coupling capacitor 5 High frequency power supply 6 Glow area 7 Workpiece 8 Magnet 10 Sheath width reduction member 11 Through hole 100 Vacuum tank 101 Exhaust path 102 Source gas introduction path

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H05H 1/46 H01L 21/302 C (72) Inventor Shuichi Takamura 5860-11, Asagaga-cho, Asahigaoka-cho, Owariasahi-shi, Aichi Prefecture 11 (72) Inventor Yoshihiko Uesugi 1 Royal Royal Ark Tokugawacho 203, 2609 Tokugawacho, Higashi-ku, Nagoya-shi, Aichi (72) Inventor Tetsuyasu Ohno 5-105, Kakuyama, Nisshin-shi, Aichi F-term CA42 CA47 EB41 EC21 FC13 4K030 AA06 AA17 BA30 CA07 CA12 FA03 KA15 KA19 KA30 KA34 KA39 KA46 5F004 AA16 BA05 BA08 BA09 BB07 BB12 CA02 CA03 CA06 5F045 AA08 AB04 BB01 BB09 CA15 DP09 EB02 EH06 E16E16E08H

Claims (9)

[Claims] A sheath width reducing member, which is a plate-like body having a plurality of through holes, is disposed between a cathode and an anode, and the distance between the sheath width reducing member and the cathode is provided by a sheath width reducing member. A plasma processing apparatus having a magnet sheath magnetic field generating means and / or a cusp magnetic field generating means for confining generated plasma near the cathode, which is smaller than the width of the cathode sheath when there is no cathode sheath. 2. The plasma processing apparatus according to claim 1, wherein the minor diameter of the through hole is not more than 10 times the Debye length. 3. The apparatus according to claim 1, further comprising a bias voltage applying means for controlling an electric potential of said sheath width reducing member.
Plasma processing equipment. 4. A cathode having a magnetron magnetic field generating means, and at least a surface of the cathode facing the plasma,
The plasma processing apparatus according to any one of claims 1 to 3, comprising a metal or an alloy containing at least one of W, Ta, Mo, Ti and Zr. 5. The plasma processing apparatus according to claim 1, further comprising a magnetron magnetic field generating means, a high frequency power supply connected to the cathode, and means for reducing a cathode sheath voltage. 6. A high-frequency cutoff filter that exhibits a high impedance at the frequency of the high-frequency power supply, one end of the high-frequency cutoff filter is connected to a cathode in parallel with the high-frequency power supply, and the other end of the high-frequency cutoff filter is connected to a cathode. The plasma processing apparatus according to claim 5, wherein the grounding reduces the cathode sheath voltage. 7. A high-frequency cutoff filter having a high impedance at the frequency of the high-frequency power supply, and a potential control means including a resistor connected in series to the high-frequency cutoff filter, wherein the potential control means includes a high-frequency cutoff filter. 6. The plasma processing apparatus according to claim 5, wherein a cathode sheath voltage is reduced by connecting to a cathode in parallel with a power supply. 8. A high-frequency cutoff filter having a high impedance at the frequency of the high-frequency power supply, and a potential control means including a DC power supply connected in series to the high-frequency cutoff filter, wherein the potential control means is connected to the high-frequency cutoff filter. 6. The plasma processing apparatus according to claim 5, wherein a cathode sheath voltage is reduced by connecting to a cathode in parallel with a power supply. 9. The plasma processing apparatus according to claim 1, wherein said cusp magnetic field generating means functions as said anode.