JPH1064883A - Plasma equipment - Google Patents

Abstract

[PROBLEMS] To protect components of a vacuum chamber in which plasma is generated from the plasma. SOLUTION: A plasma apparatus 1 such as a reactive ion etching apparatus for generating a plasma 40 in a vacuum chamber 12 is provided.
At 0, the parts 36, 38 in the vacuum chamber to be protected from the plasma 40 are made of a material having a high dielectric constant and a high dielectric loss tangent, preferably a SiC ceramic. As a result, the potentials of the surfaces of the SiC ceramic portions 36 and 38 exposed to the plasma and the plasma potential are close to each other.
The amount of ions in the plasma 40 flowing toward 8 is reduced, and erosion is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a plasma apparatus utilizing plasma, such as a plasma etching apparatus and a plasma CVD apparatus.

[0002]

2. Description of the Related Art In recent years, a so-called dry process using plasma has become indispensable in the manufacture of semiconductor devices. For example, in the etching process, a reactive ion etching process in which a chemically active gas (hereinafter, referred to as “etchant gas”) is turned into a plasma state in a vacuum chamber, and generated ions and the like react with a silicon wafer to perform etching is widely used. Used.

[0003]

By the way, in a conventional etching apparatus utilizing plasma, the inner wall surface side of the vacuum chamber is generally made of quartz or alumina. Therefore, when plasma is generated, there is a problem that a part of active species such as ions collide with the inner wall surface of the vacuum chamber, causing erosion and generating oxygen gas. That is, if oxygen gas is mixed into the plasma, the photoresist on the silicon wafer is also etched, which may adversely affect the performance of the semiconductor device. This is an important problem to be solved in recent years for high integration and miniaturization of semiconductor devices.

In particular, when alumina is used for the wall surface of a vacuum chamber, not only is the alumina decomposed to emit oxygen gas, but also aluminum is released, which causes metal contamination of the semiconductor device.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is directed to a plasma apparatus such as a reactive ion etching apparatus that generates plasma in a vacuum chamber. Is made of a material having a high dielectric constant and a moderately large value of dielectric loss tangent, so that the potential of the surface of the portion exposed to the plasma and the plasma potential are close to each other, It is characterized in that almost no current due to the plasma potential flows.

With this configuration, the amount of ions in the plasma flowing toward the portion to be protected is reduced, and erosion is suppressed. As a material exhibiting such an action, a SiC ceramic having a relative dielectric constant of 20 or more and a specific resistance of 10 ⁵ Ω · cm or more is preferable.

The part to be protected from the plasma includes a liner disposed along the inner surface of a wall constituting the vacuum chamber, and an object to be processed (wafer) when the plasma apparatus is an etching apparatus. There is a focus ring or the like provided on the outer peripheral portion of the pedestal supporting the pedestal.

Further, the present invention provides a so-called inductively coupled plasma apparatus in which a coil is wound around a side wall constituting a vacuum chamber and plasma is generated in the vacuum chamber by applying high frequency power to the coil. The side wall is made of a material having a high dielectric constant and a large value of dielectric loss tangent, so that the potential of the side of the side wall exposed to plasma and the plasma potential are close to each other. . Also in this case, erosion due to ions in the plasma is suppressed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a parallel plate type reactive ion etching apparatus 10 to which the present invention is applied. The illustrated etching apparatus 10 includes a vacuum chamber 12 serving as an etching processing chamber, and the vacuum chamber 12 includes a side wall 1 having a cylindrical inner surface.
4, a bottom plate 16 arranged in a lower opening of the side wall 14, and an upper plate 18 arranged in an upper opening of the side wall 14. An anode electrode 20 is attached to the top plate 18 via an insulator 21, and a pedestal 22 as a cathode electrode is disposed on the bottom plate 16 so as to face the anode electrode 20 in parallel. I have. The pedestal 22 has a top surface on which a silicon wafer 24 as an object to be processed can be placed.

An electric lead 26 extends from the pedestal 22 and is grounded via a high frequency bias power supply 28 and a matching circuit 30 for controlling the impedance of the vacuum chamber 12 to a predetermined value. On the other hand, an electric lead 32 extends from the anode electrode 20 and is grounded. The side wall 14, the bottom plate 16 and the top plate 18 are made of a conductive material such as aluminum, and are also grounded via the electric leads 34.

Further, on the inner peripheral surface of the side wall 14, the upper surface of the bottom plate 16, and the lower surface of the upper plate 18, a liner 36 is provided over the entire surface for the purpose of protection and the like. For the same purpose, a focus ring 38 is attached to an outer peripheral portion of the upper surface of the pedestal 22 (more specifically, a portion outside the silicon wafer 24 when the silicon wafer 24 is placed at a predetermined position). ing.

The present invention is characterized in that the liner 36 and the focus ring 38 are made of SiC ceramic. In this case, the SiC ceramic has a high dielectric constant, preferably a dielectric constant of 20 or more,
In addition, a material having a large dielectric loss tangent (tan δ) in a high frequency region is used. Here, the dielectric loss tangent is
The tangent of the dielectric loss angle indicates the rate at which energy is lost as heat when an AC electric field is applied to the dielectric. Also, when the dielectric constant is large, when the dielectric loss tangent is too large, the current flows too much, so that the electric resistivity value is 10 ⁵ Ω ·
cm or more, preferably 10 ⁵ to 10 ⁸ Ω · cm.

In the above configuration, the vacuum chamber 12
When plasma is to be formed inside the vacuum chamber,
A vacuum system communicating with the inside is operated to reduce the pressure in the vacuum chamber 12 to a predetermined level. Thereafter, an etchant gas is introduced into the vacuum chamber 12 from an etchant gas supply source (not shown). And a high frequency bias power supply 2
When the high-frequency power is applied between the electrodes 20 and 22 by inputting 8, the discharge occurs in the etchant gas, and the plasma 40 is generated.

FIG. 2 shows the state of the etching apparatus 10 in FIG. 1 when the plasma 40 is generated in an electric equivalent circuit. As shown in FIG. 2, the plasma 40 in the vacuum chamber 12
It can be represented by a network in which a parallel circuit composed of 1 to C8 and the corresponding impedances R1 to R8 forms one unit. A space called a sheath is formed between the plasma 40 and the silicon wafer 24 on the pedestal 22, and this sheath is equivalent to the capacitor C9,
Therefore, the plasma 40 is connected to the pedestal 22 which is a cathode electrode via the capacitor C9. Further, since a space similar to the sheath is formed between the anode electrode 20 and the plasma 40, the plasma 40
10 is connected to the anode electrode 20.

The liner 36 is made of a high dielectric material called SiC ceramic, and the SiC ceramic has a moderately large dielectric loss tangent. Therefore, the liner 36 has capacitors C11 to C16 and impedances R9 to R14. And can be represented by a series circuit consisting of
Therefore, the side wall 14, the bottom plate 16 and the top plate 18 made of a conductive material are connected to the plasma 40 via the series impedances R9 to R14 and the capacitors C11 to C16. Similarly, in the case of the focus ring 38, the pedestal 22 is represented as being connected to the plasma 40 via the series impedances R15 and R16 and the capacitors C17 and C18.

Now, the liner 36 and the focus ring 3
8 is made of quartz or alumina as before, quartz or alumina has a small dielectric loss tangent,
When high-frequency power is applied, the impedances R9 to R16 in FIG. 2 are small enough to be almost ignored. In such a case, a potential difference is generated between the plasma 40 and the inner surfaces of the liner 36 and the focus ring 38 due to a difference in mobility between ions and electrons in the plasma. Due to this potential difference, some of the ions in the plasma 40 fly toward the liner 36 and the focus ring 38, causing erosion thereof.

On the other hand, the liner 36 and the focus ring 3
8 is a value of impedance R9 to R16 with respect to the plasma 40 when the dielectric loss tangent is larger than the insulator, and the resistance is slightly smaller than the insulator and made of a SiC ceramic having a high dielectric constant. Since the electric field applied to the electrodes is attenuated, the potentials on the surfaces of the liner 36 and the focus ring 38 become very close to the plasma potential. Therefore, the ions in the plasma 40 are directed to the silicon wafer 24 to be etched, and the collision with the liner 36 and the focus ring 38 is greatly reduced. Therefore, liner 3
6 and the focus ring 38 are suppressed, and even if the erosion occurs, the SiC
Oxygen gas is not generated from the ceramic and is vaporized at the same time as erosion, so that there is no fear of contaminating the silicon wafer 24.

Here, at room temperature, the specific resistance is about 10 ⁵ Ω ·
The relationship between the frequency of the applied AC power, the relative dielectric constant and the dielectric loss tangent for a cm SiC ceramic is shown in FIG.
Shown in In FIG. 3, the SiC ceramic was heated at 80 ° C. and 20 ° C.
And -20 ° C. are shown. From this figure, it can be seen that 1 which is normally used in the etching apparatus 10 is used.
At a high frequency power of 3.56 MHz, the relative permittivity is 20.
As described above, it can be seen that the dielectric loss tangent is 0.5 or more, which is sufficient for exhibiting the above-described effects.

The liner 36 and the focus ring 3
8 has a specific resistance of 10 ⁵ to 10 ^8.
Although it is described above that the resistance is preferably Ω · cm, the specific resistance is not limited to this value. During the etching process, a negative potential is applied to the side walls 14 and the like with respect to the plasma 40. However, if the specific resistance is low, current flows from the plasma 40 to the side walls 14 and the like in a short-circuit manner. The value of the specific resistance is a value for preventing such a flow of electricity, and can be appropriately changed according to a device design, a use mode, and the like.

Next, a second embodiment of the present invention will be described with reference to FIG. The apparatus shown in FIG. 4 is a so-called inductively coupled plasma (ICP) type reactive ion etching apparatus 50. This etching apparatus 50 is substantially the same as the parallel plate type etching apparatus 10 shown in FIG. 1 except that a coil 56 to which a matching circuit 52 and a high frequency power supply 54 are connected is arranged around a side wall 58 of the vacuum chamber 12. The configuration is substantially the same. Therefore, the same or corresponding parts as those of the etching apparatus 10 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the ICP type etching apparatus 50, when a high frequency is applied to the coil 56, the plasma 40 by inductive coupling is generated by the etchant gas introduced into the vacuum chamber 12. When a high-frequency bias is applied between the anode electrode 20 and the pedestal 22 as a cathode electrode by the high-frequency bias power supply 28,
The ions traveling downward are accelerated, and the silicon wafer 24 on the pedestal 22 is etched.

In such a structure, the side wall 58 of the vacuum chamber 12 is generally made of quartz or alumina, but the present invention is characterized in that the side wall 58 is made of SiC ceramic having the above characteristics.

FIG. 5 shows the etching apparatus 50 of FIG. 4 in a state where the plasma 40 is generated, in the form of an electric equivalent circuit. The etching apparatus 50 shown in FIG. It differs from the equivalent circuit of FIG. 2 in that it is connected to impedances R9 to R14 corresponding to the liner 36. Therefore, the operation and effect of the side wall 58 made of the SiC ceramic are substantially the same as those of the etching apparatus 10 of FIG.

Although the preferred embodiments of the present invention have been described in detail, it goes without saying that the present invention is not limited to the above embodiments. For example, the above embodiment relates to an etching apparatus, but the present invention can be applied to other types of plasma apparatuses that generate and use plasma.

The material constituting the liner or the like is not limited to SiC ceramic, and any material having at least a high dielectric constant and a large dielectric loss tangent is applicable to the present invention. Furthermore,
If the material has the property of not generating oxygen gas or vaporizing when erosion occurs,
More preferred.

[0027]

As described above, according to the present invention, the liner and the like in the vacuum chamber in which the plasma is generated are made of a material having a high dielectric constant, a high resistance and a large dielectric loss tangent. Can approach the plasma potential of the plasma generated using the insulator, so that ions in the plasma can be suppressed from going to the liner or the like. Thus, erosion of the liner or the like can be significantly reduced.

When SiC ceramic is used as the material, no oxygen gas is generated even if erosion occurs. In the etching process, when oxygen gas is mixed into the plasma, the selectivity of etching is reduced and the target to be processed is affected. Therefore, it is extremely important to prevent generation of oxygen gas. Furthermore, in the case of SiC ceramic, since it is vaporized at the same time as erosion, there is no fear of metal contamination. As described above, the use of the SiC ceramic will greatly contribute to high integration and miniaturization of semiconductor devices in the future.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a parallel plate type reactive ion etching apparatus to which the present invention is applied.

FIG. 2 is an electrical equivalent circuit diagram of the etching apparatus of FIG. 1 in a state where plasma is generated.

FIG. 3 is a graph showing a frequency dependence of a relative dielectric constant and a dielectric loss tangent of a SiC ceramic applied to the present invention.

FIG. 4 is a sectional view schematically showing an inductively coupled plasma type reactive ion etching apparatus to which the present invention is applied.

5 is an electrical equivalent circuit diagram of the etching apparatus of FIG. 4 in a state where plasma is generated.

[Explanation of symbols]

10, 50: etching apparatus, 12: vacuum chamber, 1
4, 58 side wall, 16 bottom plate, 18 top plate, 20 anode electrode, 22 pedestal, 24 silicon wafer, 28 high frequency bias power supply, 30 matching circuit, 36
... liner, 38 ... focus ring, 40 ... plasma,
52: matching circuit, 54: high frequency power supply, 56: coil.

Claims (6)

[Claims] In a plasma apparatus for generating plasma in a vacuum chamber, a portion in the vacuum chamber to be protected from the plasma is made of a material having a high resistance and a high dielectric constant and a moderately large dielectric tangent value. And a potential of the surface of the portion exposed to the plasma and a potential of the plasma are set to approximate values. 2. The plasma apparatus according to claim 1, wherein the material is a SiC ceramic having a relative dielectric constant of 20 or more and a specific resistance of 10 ⁵ Ω · cm or more. 3. The plasma apparatus according to claim 1, wherein the portion to be protected from the plasma is a liner disposed along an inner surface of a wall constituting the vacuum chamber. 4. The plasma apparatus is an etching apparatus, and the portion to be protected from the plasma is a focus ring provided on an outer peripheral portion of a pedestal for supporting an object to be processed. An apparatus according to any one of the preceding claims. 5. A plasma apparatus in which a coil is wound around a side wall constituting a vacuum chamber and high frequency power is applied to the coil to generate plasma in the vacuum chamber, wherein the side wall has a high dielectric constant. A plasma device comprising a material having a large dielectric loss tangent and a potential of a surface of the side wall exposed to the plasma being close to a plasma potential. 6. The plasma device according to claim 5, wherein the material is a SiC ceramic having a relative dielectric constant of 20 or more and a specific resistance of 10 ⁵ Ω · cm or more.