JPH1126435A - Electrode for plasma etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode, whereby the faults of a silicon wafer is prevented in the case of its plasma etching processing and furthermore, its quality can be made uniform by reducing the variation of its etching speed accompanied by the consumption of the electrode. SOLUTION: In this electrode 6, gas-jetting holes 7 are provided in its thickness direction. Here, when the thickness of this electrode 6 is denoted by T, a hole diameter (D) of the gas-jetting hole 7 depth of which measured from the exposed surface side of the electrode 6 to a plasma is not smaller then 0.5 T, and not larger than 0.9 T, values are made different from a hole diameter (d) of the gas-jetting hole 7 of the residual thickness portion of the electrode 6 which is not smaller than 0.4 D, and not larger than 0.7 D in values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode used in a plasma etching apparatus used for processing a semiconductor wafer. More specifically, the present invention relates to a method for applying high frequency power to a reaction chamber and dispersing an etching gas in a shower. The present invention relates to an electrode to which the high-frequency power is applied in a parallel plate type plasma etching apparatus having an electrode having a gas blowing hole and an electrode on which a silicon wafer is placed so as to face the electrode.

[0002]

2. Description of the Related Art In order to form devices on a semiconductor wafer,
An etching process has been performed. In recent years, a plasma etching apparatus has been used as an apparatus for performing this etching. In the plasma etching apparatus, as shown in FIG. 1, an upper electrode 2 and a lower electrode 3 are provided in a vacuum vessel 1 at an interval, and a silicon wafer 4 is mounted on the lower electrode 3 as a material to be processed. It is location. The upper electrode 2 is composed of a back plate 5 and an electrode 6, each of which is provided with a gas blowing hole 7 for flowing an etching gas. A high frequency voltage is applied between the upper electrode 2 and the lower electrode 3 by the high frequency power supply 8 while flowing the etching gas toward the silicon wafer 4 through the gas blowing holes 7 to form plasma. The silicon wafer is etched by the plasma to form a device having a predetermined pattern.

With the recent high integration of semiconductor integrated circuits,
The shape of a silicon wafer after etching has been controlled with higher precision. Accordingly, it has been required that the fluctuation of the etching rate which affects the dimensional accuracy of the shape of the silicon wafer after etching is small. An amorphous carbon electrode widely used at present has a tendency that the etching rate increases with use time, and it is becoming difficult to achieve uniform quality. As a countermeasure, an electrode material is being changed from amorphous carbon to silicon single crystal, but the tendency that the etching rate increases with use time has not been reduced. Attempts have been made to reduce the variation in the etching rate by changing the diameter and number of the gas blowing holes, but none of them has been found to be effective in making the quality of the silicon wafer uniform.

[0004]

As a result of examining the relationship between the etching rate and the amount of electrode consumption, it has been found that the fluctuation of the etching rate has a correlation therebetween. That is, the thickness of the electrode becomes thinner with the passage of time due to the consumption by the plasma. For this reason, the pressure loss in the gas blowout hole of the electrode is reduced, and the flow speed of the etching gas blown out therefrom is increased, so that the etching rate is also increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to prevent a defect at the time of plasma etching of a silicon wafer by reducing fluctuations of an etching rate due to electrode consumption, and to further improve quality. The aim is to equalize.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a plasma etching electrode provided with a gas blowing hole in the thickness direction, where T is 0.5 T from the electrode surface on the side exposed to plasma when the thickness is T. Above, the hole diameter (D) of the gas blowing hole up to a depth of 0.9 T or less and the hole diameter (d) of the gas blowing hole in the remaining thickness portion are different. The present invention relates to an electrode for plasma etching having a gas blowing hole of 7D or less. In this way, by making the shape smaller at a specific ratio from the middle of the hole depth to the hole diameter of the electrode surface on the side exposed to the plasma, most of the pressure loss of the gas blowing hole is reduced in diameter. Since it can be provided in a part, even if the electrode is consumed by the plasma, the fluctuation of the pressure loss is small, and the fluctuation of the flow velocity of the etching gas flowing out from the gas blowing hole can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIGS. 2, 3 and 4. FIG. FIG. 2 is a sectional view showing the shape of a gas outlet of a conventional electrode, and FIG. 3 is a sectional view showing the shape of a gas outlet of an electrode according to the present invention. FIG. 4 is an enlarged sectional view of a portion of the hole in FIG. In the figure, when the thickness of the electrode is T and the diameter of the gas blowing hole on the side exposed to the plasma (electrode surface) is D, the depth from the electrode surface on the side exposed to the plasma is 0.5.
The diameter of the gas outlet hole from the depth of T to the depth of 0.9T or less is the same D. Then, processing is performed so that the hole diameter d of the gas blowing hole in the remaining thickness portion is 0.4D or more and 0.7D or less. Here, when the gas hole diameter d of the remaining thickness portion exceeds 0.7D, the etching gas blown out from the electrode back plate has almost all the pressure loss at the place where the hole diameter is reduced. Therefore, the desired effect cannot be obtained. If the diameter is less than 0.4D, the diameter becomes too small and processing becomes difficult.

Further, the reason why the hole depth for changing the diameter of the gas outlet hole is not less than 0.5T and not more than 0.9T is that, when the depth is less than 0.5T, fluctuations in pressure loss due to electrode consumption cannot be reduced. Therefore, the fluctuation of the etching rate cannot be reduced, and if it exceeds 0.9T, the pressure loss is small and the fluctuation due to electrode consumption cannot be reduced. The plasma etching electrode of the present invention only needs to have the gas outlet hole diameter in the above-described shape.
The content is preferably 0% or more, more preferably 70% or more, further preferably 90% or more, and most preferably 100%.

As an electrode material used in the plasma etching apparatus, amorphous carbon, silicon single crystal or silicon polycrystal (polysilicon), which has excellent plasma resistance and high purity, is preferable. As for the size and shape of the electrode, the outer diameter is 200 to 400 mm, and the thickness is 3 to 1.
A 0 mm disc is preferred. It is preferable to provide 8 to 24 mounting holes for mounting electrodes on the outer peripheral portion. Generally, a gas blowing hole for dispersing an etching gas in a shower shape is provided in an inner peripheral portion of the mounting hole.
The gas outlet hole varies depending on the etching conditions, but the hole diameter is 0.3 to 2.0 on the side exposed to the plasma.
mm is preferable, and the number of holes is preferably 100 to 2000. Hole processing can be performed by machining, electric discharge machining, ultrasonic machining, or the like.

[0010]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Plane orientation (100), conductivity type P type, resistivity 0.7
203 mm diameter from Ω-cm silicon single crystal ingot,
A disc having a thickness of 3 mm was prepared, and a diamond-coated drill having a shape within the range of the present invention under a machining condition of a rotation speed of 5000 rpm and a feed rate of 20 mm / min (D) was exposed to plasma. Were 1.0 mm in diameter, and the hole diameter (d) of the remaining thickness portion was as shown in Table 1, and gas blowing holes were formed at equal intervals of 3 mm. As a comparative example, an electrode having a gas outlet hole shape outside the range of the present invention was produced. The above silicon electrode was set in a plasma etching apparatus, and reaction gas: trifluoromethane (CHF ₃ ) 400 cc / min, tetrafluorocarbon (CF ₄ ) 60 cc / min, argon (A)
r) 300 cc / min, gas pressure in the reaction chamber: 0.
5 Torr, power frequency: 400 KHz, applied power: 600 W
Plasma etching of a silicon oxide film on a 6-inch wafer was performed under the conditions described above, and the change in etching rate was examined.
Table 1 shows the results. As shown in Table 1, the use of the plasma etching electrode of the present invention makes it possible to reduce the fluctuation of the etching rate.

[0011]

[Table 1]

Note 1) Change rate standard 10% or less 2) Formula for calculating change rate

(Equation 1)

[0013]

The characteristics of the plasma etching electrode according to the present invention are such that the fluctuation of the etching rate due to the use time can be reduced, and the plasma etching process with a good product yield can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic view of a parallel plate type plasma etching apparatus.

FIG. 2 is a sectional view showing an example of a conventional plasma etching electrode.

FIG. 3 is a sectional view showing an example of the electrode for plasma etching of the present invention.

FIG. 4 is an enlarged sectional view of a gas blowing hole of the electrode for plasma etching of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma etching apparatus 2 Upper electrode 3 Lower electrode 4 Silicon wafer 5 Back plate 6 Electrode 7 Gas blowout hole 8 High frequency power supply 9 Insulation ring 10 Shield ring 11 Plasma

Claims (1)

[Claims] In a plasma etching electrode provided with a gas blowing hole in a thickness direction, assuming that the thickness is T, a range from 0.5 T or more to 0.9 T or less from an electrode surface on a side exposed to plasma. Hole diameter (D) of the gas outlet hole up to the depth and the hole diameter (d) of the gas outlet hole of the remaining thickness portion
Unlike the above, an electrode for plasma etching having gas blowing holes in which d is 0.4D or more and 0.7D or less.