Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
1999-12-02
2001-05-29
Mills, Gregory (Department: 1763)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C438S715000, C216S071000, C156S345420
Reexamination Certificate
active
06239036
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and a method for plasma etching processing silicon substrates applied to semiconductor devices or the like.
RELATED ART
Plasma etching is a well-known method for treating silicon substrates applied to semiconductor devices or the like. According to this method, an object to be treated, for example, a silicon substrate is treated as follows. At first, the silicon substrate is placed in a treatment chamber, which is then evacuated. After evacuation, a gas for generating plasma is supplied in the chamber, then a high frequency voltage is applied to between electrodes disposed therein so as to generate plasma. As a result, ions and electrons are generated in the chamber and the substrate is treated by the etching action of those ions and electrons. Conventionally, those electrodes for discharging the plasma were disposed so as to be separated by approximately 30 to 80 mm from each other and the pressure in the treatment chamber was lowered up to about 1 to 10 Pa when in plasma etching.
However, such a conventional plasma etching has been confronted with the following problems. First of all, when plasma etching is performed in a high vacuum state as described above, the etching rate, which indicates a velocity for removing the surface of the object silicon substrate by etching becomes 0.1 &mgr;m/min or so. Therefore, if the surface must be removed more, the etching treatment takes a long time and further, since a high vacuum degree is required, the exhaust process for evacuation takes a long time for each treatment cycle. Along with such a low etching rate described above, those long time treatments result in further significant reduction of the efficiency in the entire substrate treatment.
Furthermore, because the conventional plasma etching requires such a high vacuum degree, the cost of the vacuum system facility also rises significantly. And furthermore, because the object substrate is placed in such a high vacuum state, it is impossible to employ a method of vacuum suction to hold the substrate. Instead, an expensive electrostatic suction method or a mechanical holding method had to be employed to hold the substrate. This was why it was very difficult to simplify the facility and reduce the cost of the facility. In addition, in case of the conventional plasma etching, it was difficult to generate the plasma in uniform between the electrodes. Thus, the etching effect was partially varied on the object substrate, which made stable etching difficult. Accordingly, in such the conventional plasma etching, there was a problem that it was difficult to process the etching for the substrate at a low cost, in uniform, and efficiently.
SUMMARY OF THE INVENTION
Under such circumstances, therefore, it is an object of the present invention to provide an apparatus and a method for plasma etching processing an object efficiently, in uniform, and at a low cost.
The plasma etching apparatus of the present invention, in which an object substrate to be treated is placed on one of parallel plate electrodes disposed oppositely to each other in a treatment chamber and the plasma etching treatment is conducted to the substrate, comprises gas supply means for supplying a mixed gas including oxygen and a fluorine gas in the treatment chamber, and the plasma discharge is conducted between the parallel plate electrodes on a condition that the product PL of the distance L[m] between the plate electrodes and the mixed gas pressure P[Pa] in the treatment chamber satisfies a range within 2.5[Pa·m] to 15[Pa·m].
The plasma etching apparatus of the present invention may also be used on a condition that the distance L between the plate electrodes is within 3[mm] to 7[mm].
Further, this plasma etching apparatus may be used on a condition that the volume ratio of the oxygen in the mixed gas is within 5% to 20%.
Furthermore, the plasma etching apparatus of the present invention may be provided with means for holding the object substrate to be treated by means of vacuum suction on one of the parallel plate electrodes and means for cooling the substrate.
The plasma etching method of the present invention, in which an object substrate to be treated is placed on one of parallel plate electrodes disposed oppositely to each other in a treatment chamber and the plasma etching treatment is conducted to the substrate, comprises the steps of supplying a mixed gas including oxygen and a fluorine gas, and conducting plasma discharge between the parallel plate electrodes on a condition for satisfying a value of a product P[Pa] of the distance L[m] between the parallel plate electrodes and the gas pressure P[Pa] in the treatment chamber within 2.5[Pa·m] to 15[Pa·m].
The plasma etching method of the present invention may also apply to the object substrate composed of silicon or silicon compound.
The plasma etching method of the present invention may also apply on a condition for satisfying a value of the distance L between the plate electrodes within 3[mm] to 7[mm].
The plasma etching method of the present invention may also apply on a condition for satisfying a volume ratio of the oxygen in the mixed gas within 5 to 20%.
The plasma etching method of the present invention may also apply on a condition for satisfying an etching speed of 10,000 Å (Angstroms)/min. or more for the object substrate.
The plasma etching method of the present invention may also comprise further steps of holding the object substrate by vacuum suction on one of the parallel plate electrodes and cooling the substrate by cooling means.
According to the present invention, therefore, the etching conditions can be set so that the product of the distance between the parallel plate electrodes and the pressure of the mixed gas in the treatment chamber takes a value within a predetermined range respectively for improving the etching efficiency. The plasma etching can thus be conducted at a lower cost and more efficiently.
REFERENCES:
patent: 5254213 (1993-10-01), Tamaki
patent: 5300460 (1994-04-01), Collins et al.
patent: 5399527 (1995-03-01), Tabara
patent: 5853602 (1998-12-01), Shoji
patent: 6030489 (2000-02-01), Hwang
Arita Kiyoshi
Haji Hiroshi
Goudreau George
Matsushita Electric - Industrial Co., Ltd.
Mills Gregory
Stevens Davis Miller & Mosher L.L.P.
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