Chemistry: analytical and immunological testing – Optical result – With reagent in absorbent or bibulous substrate
Reexamination Certificate
1998-11-09
2001-04-17
Nelms, David (Department: 2818)
Chemistry: analytical and immunological testing
Optical result
With reagent in absorbent or bibulous substrate
C438S689000
Reexamination Certificate
active
06218196
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an etching apparatus and method and, more specifically, to a plasma etching apparatus and method for performing etching by generating a plasma with pulse modulation. The invention also relates to a manufacturing method of a semiconductor using such an etching apparatus or method, as well as to a semiconductor device manufactured by that method.
2. Background Art
In recent years, as the degrees of integration of semiconductor devices etc. increase, their densities have increased at high speed by miniaturization of patterns. Particularly in the technical fields of DRAMs, ASICs, etc. where vertically processed shapes of a half micron or less are required, etching techniques capable of high-precision processing are needed. The dry etching technique is widely used as one of such means.
FIG. 14
shows the configuration of a conventional RF-biased etching apparatus. This is an example of most typical dry etching techniques using an RF bias. In
FIG. 14
, reference numeral
1
denotes a reaction container for maintaining a vacuum. The pressure in the reaction container
1
is controlled by an evacuation outlet
2
, a vacuum pressure indicator
3
, and a vacuum pressure setting valve
4
b
. Flow rate controllers
4
a
cause etching gases such as Cl
2
and BCl
3
to be introduced into the reaction container
1
through gas introduction inlets
5
while controlling their flow rates. A semiconductor substrate as a sample
6
to be etched is held by one of two opposed electrodes
7
that form a capacitor. The opposed electrodes
7
are connected to a matching box
10
for a plasma impedance control and a high-frequency power supply
8
. The high-frequency power supply
8
produces a sinusoidal voltage.
In this etching apparatus, negative charges are accumulated on the side of the sample-side one of the electrodes
7
that form a capacitor, because electrons supplied from a generated plasma are tens of times more than ions. Because of those capacitor charges, as shown in
FIG. 15
, a voltage that is shifted to the negative side appears on the semiconductor substrate as the sample
6
to be etched. Because of the presence of this negative voltage, positive ions as etching species are accelerated and strike the semiconductor substrate, to enable anisotropic etching. As disclosed in Japanese Unexamined Patent Publication Nos. 6-61182, 8-241885, 8-20880, etc., there have been invented dry etching methods that use a bias voltage having a pulse waveform.
In etching methods using a bias voltage having a pulse waveform, etching of a high selective ratio is possible and hence fine processing margins are increased. The term selective ratio as used above is defined by a ratio of the etching rate of a sample film to that of a photoresist for masking the sample film to be etched. However, since the rate of ion incidence on a sample film is low, the amount of reaction products that are produced from a photoresist and etching gases is small. Therefore, side wall protective films are thin in forming metal interconnections by etching the sample film. Accordingly, it is difficult to provide processed metal interconnections having good shapes due to side etching or roughening of side walls of interconnection.
Further, as disclosed in Japanese Unexamined Patent Publication No. 9-260359, there has been invented an etching method in which an etching gas of Cl
2
and a deposition-type gas of CHF
3
are used as well as a pulse waveform bias voltage is applied. However, this etching method possibly has problems that are fatal to an etched film from the viewpoint of recent etching techniques for fine processing. The problems are excess depositions of reactive products that are produced from CHF
3
and ions such as Cl
−
, etching residues, short-circuiting of wiring, and shape differences due to pattern density differences in a film to be etched.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems in the conventional art, and an object of the invention is therefore to provide an etching apparatus and method in which a high-frequency application voltage is pulse-modulated, and which uses, for instance, a Cl
2
gas and a BCl
3
gas as processing gases and, for instance, a CHF
3
gas as a deposition-type gas for assisting formation of side wall protective films, which enables etching of a large selective ratio to a photoresist, and which is free of influences of foreign substances due to deposition of reactive products as well as an RIE-lag (etching rate difference between sparse patterns and dense patterns in a film to be etched), and can thereby provide superior vertically etched shapes.
According to one aspect of the present invention, an etching apparatus comprises a processing container and a pair of electrodes provided in the processing container so as to be opposed to each other and to hold a sample to be etched. Also provided is a introducing means for introducing, into the processing container, etching processing gases in which main etching processing gases such as Cl
2
gas and a BCl
3
gas and a deposition type gas such as composed by at least two of C, H, F are included. Exhausting means is provided for exhausting the etching processing gases from the processing container. Voltage applying means is provided for applying a pulse-modulated high-frequency voltage between the pair of electrodes, to thereby generate a plasma between the pair of electrodes and to etch the sample by using the plasma.
In the voltage applying means, the pulse modulation frequency of the high-frequency voltage that is applied between the two electrodes may be set at a value in a range of 1 Hz to 50 kHz.
In the voltage applying means, the duty ratio of the pulse modulation of the high-frequency voltage that is applied between the two electrodes may be set at a value in a range of 20% to 75%.
In the voltage applying means, the pulse modulation may be performed so that the amplitude of the high-frequency voltage that is applied between the two electrodes has a first predetermined voltage that is 0 V or more in a discharge suspension period and a second predetermined voltage that is higher than the first predetermined voltage in a discharge period.
According to another aspect of the invention, in an etching method, etching processing gases are introducing into a processing container. In the etching processing gases, a deposition-type gas composed at least two of C, H, and F is added to main etching processing gases including a Cl
2
gas and a BCl
3
gas. A pulse-modulated high-frequency voltage is applied between two electrodes that are provided in the processing container so as to be opposed to each other and to hold a sample to be etched. A plasma is generated between the two electrodes, and the sample is etched by using the plasma.
The deposition-type gas may be one of a CHF
3
gas and a CF
4
gas.
The deposition-type gas may be added at a flow rate that is in a range of 1% to 45% of a flow rate of the Cl
2
gas.
The processing pressure of the etching may be set at a value in a range of 0.665 to 13.3 Pa (5 to 100 mTorr).
The pulse modulation may be performed in such a manner that the high-frequency voltage that is applied between the two electrodes are turned on and off at a modulation frequency in a range of 1 Hz to 50 kHz.
The pulse modulation may be performed in such a manner that the high-frequency voltage that is applied between the two electrodes are turned on and off with a duty ratio in a range of 20% to 75%.
The pulse modulation may be performed so that the amplitude of the high-frequency voltage that is applied between the two electrodes has a first predetermined voltage that is 0 V or more n a discharge suspension period and a second predetermined voltage that is higher than the first predetermined voltage in a discharge period.
According to a further aspect of the invention, there is provided a manufacturing method of a semiconductor method comprising the step of etching a metal layer on a semic
Hanazaki Minoru
Ikushima Takayuki
Ise Hirotoshi
Nishizaki Nobuhiro
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Nelms David
Nhu David
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