JPH11251093A - Electrodes for plasma generation - Google Patents

Abstract

(57) [Problem] To generate good plasma for a long period of time without corrosive even when exposed to plasma under a halogen-based corrosive gas and without adversely affecting particles such as semiconductor wafers. To be able to An electrically conductive substrate made of any one of silicon (Si), carbon (C), and silicon carbide (SiC) has an amorphous structure or an amorphous structure at least in a portion exposed to plasma under a halogen-based corrosive gas. A plasma-generating electrode 2 is formed by depositing a hard carbon film 4 of diamond-like carbon or diamond having a crystalline structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generating electrode provided in a plasma processing apparatus used in processes such as film formation, etching, cleaning, and ashing.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device manufacturing process, a plasma processing apparatus for converting a reactive gas into plasma and performing various plasma processes on a semiconductor wafer has been used. Such a reaction gas is not required to have a high temperature and can be processed at a relatively low temperature, so that it is widely used in various processing processes such as film formation, etching, cleaning, and ashing. As a plasma processing apparatus, a parallel plate type in which two plasma generating electrodes are arranged in parallel in a reaction processing chamber in which a semiconductor wafer is installed, and a plasma of a low-pressure gas is generated to perform plasma processing of the semiconductor wafer. There was one.

In this plasma processing apparatus,
Since a plasma generating electrode for generating plasma requires conductivity, some electrodes are formed of aluminum, graphite, glassy carbon, silicon, or the like.

[0004]

However, in this type of plasma processing apparatus, HBr, HCl,
Highly corrosive halogen-based corrosive gases such as Cl ₂ and SF ₆ are used, and when exposed to plasma under these gases, they are susceptible to corrosion and wear. In particular, on the surface of a plasma generating electrode having a high plasma density, Due to severe corrosive wear, the plasma generating electrode made of aluminum, graphite, glassy carbon, silicon, or the like has a problem that it cannot be used in a short time because it does not have sufficient plasma resistance. . Then, as the corrosion wear progresses, the wear powder adheres to the semiconductor wafer as particles, which adversely affects various processing accuracy.

In order to reduce the corrosive wear as much as possible, the surface roughness of the portion of the plasma generating electrode exposed to the plasma is set to a center line average roughness (Ra) of 8 to 0.0.
It has been proposed to have a smooth surface of 01 μm (see Japanese Patent Application Laid-Open No. 9-289195), but there is a limit due to the low plasma resistance of the material itself, and a plasma generating electrode with less corrosion and wear is desired. I was

[0006]

Accordingly, the present invention has been made in view of the above-mentioned problems, and has been developed in view of at least a halogen-based corrosive gas on a conductive substrate made of any of silicon (Si), carbon (C), and silicon carbide (SiC). In the part exposed to plasma at
A plasma generating electrode is formed by applying a hard carbon film having a Vickers hardness of 3000 kg / mm ² or more.

In the present invention, diamond-like carbon or diamond is preferable as the hard carbon film.

[0008]

FIG. 1 is a schematic view showing a state in which a plasma generating electrode of the present invention is used in a plasma processing apparatus, and 1 is a reaction processing chamber for accommodating a semiconductor wafer W. Plasma generating electrodes 2 and 7 for generating plasma are arranged opposite to each other in the upper and lower portions of the inside. A heater electrode 6a is provided on the lower plasma generating electrode 7.
Is embedded, and the ceramic heater 6 is heated while the semiconductor wafer W is mounted on the heat generating surface 6b of the ceramic heater 6, whereby the ceramic heater 6 generates heat.
The semiconductor wafer W is heated uniformly. Note that the ring body disposed on the peripheral portion of the semiconductor wafer W is a clamp ring 10 for holding the semiconductor wafer W.

Reference numeral 5 denotes an exhaust ring having an exhaust hole 5a provided in the reaction processing chamber 1. The upper surface of the exhaust ring 5 does not disturb the flow of the reaction gas introduced into the reaction processing chamber 1. Heating surface 6 of ceramic heater 6
It is arranged so as to be located on the same plane as b.

Further, a large number of minute through holes 3a penetrating the upper and lower surfaces are formed in the base 3 constituting the upper plasma generating electrode 2, and the reaction processing chamber 1 is formed through the through holes 3a. A reaction gas is supplied.

Then, using this plasma processing apparatus,
For example, to perform an etching process on the semiconductor wafer W,
The semiconductor wafer W is transferred into the reaction processing chamber 1 by a transfer device (not shown) and placed on the heating surface 6 b of the ceramic heater 6, and the periphery of the semiconductor wafer W is held by the clamp ring 4. Next, the air in the reaction processing chamber 1 is exhausted from the exhaust holes 5a, and a reaction gas containing a halogen-based corrosive gas whose flow rate has been adjusted through the through holes 3a of the plasma generating electrode 2 is supplied into the reaction processing chamber 1. Then, the internal pressure is set to, for example, about 1 to 2 Torr. Then, in this state, a high-frequency power of, for example, several hundred W is applied between the plasma generating electrodes 2 and 7 which are opposed to each other to turn the reaction gas into plasma, and radical ions collide with the semiconductor wafer W, so that the semiconductor wafer W The portion not covered with the resist film is etched.

By the way, the plasma generating members 2, 7
Requires conductivity, silicon (Si),
It is formed of conductive substrates 3 and 8 made of carbon (C) and silicon carbide (SiC), and the inner wall side of the plasma generating member 2 which is exposed to plasma under a halogen-based corrosive gas is 3000 kg / mm ² or more. The hard carbon film 4 having the Vickers hardness of 4 is applied. In the plasma processing apparatus shown in FIG. 1, the lower plasma generating member 7 is made of only the conductive substrate 8 because it is not exposed to plasma. May be adhered.

Here, the hard carbon film 4 means 1160 ± 40 cm ⁻¹ , 1340 ± 4 in the Raman spectrum.
0 cm ⁻¹ and 1500 ± 60 cm ⁻¹ , for example, 1340 ± 40 cm
^-1 and 1500 ± 60 cm ⁻¹ , with 1500 ±
Amorphous diamond-like carbon having a main peak of 60 cm ^-1 or 1160 ± 40 cm ^-1 or 134
0 ± 40 cm ^-1, and 1500 have respective peaks at ± 60cm ^-1, and 1340 diamond-like carbon crystalline structure having a ± 40 cm ^-1 to the main peak or 1340 diamond having a peak only ± 40 cm ^-1, Is mentioned.

Since these hard carbons 4 have strong interatomic bonding force and are dense, as shown in Table 1, their hardness is 3000 kg / mm ² or more in Vickers hardness and diamond-like carbon having a crystalline structure. Since diamond has a high hardness of 8000 kg / mm ² or more, even if it is exposed to plasma under a highly corrosive halogen-based corrosive gas, it does not significantly corrode and wear.

[0015]

[Table 1]

As a method for coating the conductive substrate 3 with the hard carbon 4, a known thin film forming means such as a CVD method, an ionization vapor deposition method and an ion beam method can be used. However, these hard carbons 4 are likely to be peeled off due to residual internal stress during film formation, but in the present invention, silicon (Si) or silicon carbide (SiC) whose thermal expansion coefficient is very similar to that of the conductive substrate 3 is used. Or the same kind of carbon (C), so that the hard carbon film 4 is peeled off even when used under heating conditions such as a CVD apparatus. There is no.

Therefore, the portion of the plasma generating member 2 exposed to the plasma is a hard carbon film 4 having excellent plasma resistance.
, It is possible to stably generate good plasma over a long period of time.

In order to obtain such an effect, the thickness t of the hard carbon film 4 needs to be 0.1 μm or more. However, when diamond-like carbon is used as the hard carbon film 4, its thickness width t is set to 2.0.
It is difficult to make it larger than μm in terms of manufacturing, and when diamond is used as the hard carbon film 4, its thickness width t
Is larger than 10.0 μm, it is easy to peel off.

Therefore, when diamond-like carbon is used as the hard carbon film 4, the thickness width t is 0.1 to
When diamond is used as the hard carbon film 4, its thickness t is 0.1 to 1 μm.
0.0 μm, preferably in the range of 1.0 to 10.0 μm.

The surface of the conductive substrate 3 on which the hard carbon film 4 is deposited has a center line average roughness (Ra) of 0.05-8.
The thickness is preferably set to 0 μm. This is because, if there are large irregularities on the surface of the conductive substrate 3, the plasma energy tends to concentrate on the edges of the convexities and the concaves and easily corrode and wear.
If the center line average roughness (Ra) is larger than 8.0 μm, the wear proceeds even if the hard carbon film 4 is adhered to the surface. .0
If the thickness is smaller than 5 μm, even if silicon (Si), silicon carbide (SiC), or carbon (C) having good adhesion to the hard carbon film 4 is used as the material of the conductive substrate 3, the conductive substrate 3 may be peeled off. .

As described above, in the present embodiment, the plasma generating electrode provided with the through-hole 3a for supplying the reaction gas into the reaction processing chamber 1 is shown as the plasma generating electrode exposed to the plasma. According to the present invention, the conductive substrate constituting the electrode for plasma generation is made of any one of silicon (Si), carbon (C), and silicon carbide (SiC). Any shape or structure may be used as long as a hard carbon film of 3000 kg / mm ² or more is applied to at least a portion exposed to plasma under a halogen-based corrosive gas.

(Example) Here, an electrode for plasma generation of the present invention was manufactured, and an experiment for examining its durability was performed.

As the plasma generation electrode, silicon (Si), carbon (C), silicon carbide (SiC)
And a hard carbon film of diamond-like carbon or diamond having an amorphous structure was coated on the surface thereof. In addition, when applying a hard carbon film of diamond-like carbon, using an ionization vapor deposition method,
C ₆ H ₆ is used as the reaction gas and the gas pressure is 2 ×
10 ^-2 to 10 ^-1 Pa, conductive substrate temperature 600 ° C, voltage applied to the conductive substrate 500 to 2000 V, anode voltage 50 to 200 V, current applied to the filament 15 to 30
When forming a film under the conditions of mA and coating the diamond hard carbon film, plasma CVD is used, CH ₄ and H ₂ Si (CH ₃ ) ₄ are used as reaction gases, and the pressure in the reaction processing chamber is 1. 3-67 Pa, conductive substrate temperature 650 ° C., high frequency output (frequency 2.45 GHz,
Films were formed with a thickness t of 0.8 μm under the conditions of a magnetic flux of 2.0 kGauss.

Then, these plasma generating electrodes are installed in the plasma processing apparatus shown in FIG.
While introducing a mixed gas of F ₄ and O ₂ , 13.56
Introducing a microwave of MHz and applying a magnetic field of 2.0 kGauss or more to generate plasma, and calculating the difference in weight between before the experiment and after exposure to the plasma for 3 hours as the amount of wear, the conventional plasma made of graphite It was determined as a relative value when the amount of wear of the generating electrode was set to 100.

The results are shown in Table 2.

[0026]

[Table 2]

As a result, as can be seen from Table 1, it is understood that the plasma generating electrode of the present invention can greatly improve the plasma resistance as compared with the conventional electrode.

[0028]

As described above, according to the present invention, a conductive substrate made of any of silicon (Si), carbon (C) and silicon carbide (SiC) is exposed to plasma under at least a halogen-based corrosive gas. A plasma-generating electrode was formed by applying a hard carbon film such as diamond-like carbon or diamond with an amorphous or crystalline structure to the exposed area, greatly improving plasma resistance. In addition, good plasma can be generated for a long period of time without adversely affecting particles or the like on a semiconductor wafer or the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state in which a plasma generating electrode of the present invention is used in a plasma processing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reaction processing chamber, 2 ... Upper plasma generation electrode, 3 ... Conductive base, 3a ... Through-hole, 4 ...
Hard carbon film, 5 ... exhaust ring, 5a ... exhaust hole,
6 ceramic heater, 6a heater electrode, 6
b: heating surface, 7: lower electrode for plasma generation,
8 ... conductive base, 10 ... clamp ring, W.
..Semiconductor wafers

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/3065 H01L 21/31 C 21/31 21/203 S // H01L 21/203 21/302 B

Claims (2)

[Claims] At least a portion of a conductive substrate made of one of silicon (Si), carbon (C) and silicon carbide (SiC) exposed to plasma under a halogen-based corrosive gas,
An electrode for plasma generation, comprising a hard carbon film having a Vickers hardness of 3000 kg / mm ² or more. 2. The plasma generating electrode according to claim 1, wherein said hard carbon film is one of diamond-like carbon and diamond.