Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
1999-07-16
2001-03-20
Powell, William (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C216S057000, C438S690000, C438S720000, C438S734000, C438S742000
Reexamination Certificate
active
06204190
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing an electronic device. In more detail, the present invention relates to a method for producing an electronic device such as a semiconductor integrated circuit, a semiconductor device or a surface acoustic wave (SAW) device.
2. Description of the Related Art
Various electronic devices comprise patterned electrodes or metallizations on a substrate. For example, in the case of a surface acoustic wave device, an aluminum electrode is formed on a single crystal piezoelectric substrate by reactive ion etching (RIE). More specifically, as shown in
FIGS. 1A and 1B
, the surface of an electrode film
2
provided on a single crystal piezoelectric substrate
1
is covered with a photoresist
3
, and the electrode film
2
is selectively etched using a chlorine-based gas such as Cl
2
or BCl
3
and the patterned photoresist
3
as a mask. However, the electrode film
2
is not always completely removed and is sometimes left behind on the single crystal substrate
1
owing to heterogeneous distributions of the film thickness of the electrode film
2
or reactive ion etching rate on the surface of the single crystal substrate
1
as shown in
FIG. 1A. A
residue eliminating process called over-etching becomes therefore inevitable in order to completely remove the electrode film
2
without leaving any residues behind. An over-etching treatment by 5 to 50% excess of the overall etching time under the same etching condition is applied in the over-etching method, as shown in
FIG. 1B
, thereby slightly etching into the single crystal substrate
1
.
The portions where the electrode film
2
has been removed and the single crystal substrate
1
has been exposed are exposed to chlorine plasma during the over-etching time. Consequently, the single crystal substrate
1
is damaged forming damaged layers
4
as shown in
FIG. 2
, thereby deteriorating characteristics of the acoustic surface wave device.
It has been a common view that the cause of the substrate damage due to over-etching described above is a physical damage caused by impact of ions colliding with the substrate during the reactive ion etching. Accordingly, the substrate damage due to ion irradiation has been suppressed by the methods of: (1) reducing the ion irradiation energy; (2) improving homogeneity of the ion etching rate; and (3) detecting the etching terminal point with high precision. However, it was impossible to completely inhibit the damage of the substrate by the conventional methods, although it can be reduced.
SUMMARY OF THE INVENTION
The present invention is directed to a method that can solve the aforementioned problem and reduce the damage of the substrate by the reactive ion etching during production of an electronic device. The method for producing an electronic device, comprises the steps of: depositing a thin film on a single crystal substrate or single crystal film, or on a triaxial or uniaxial orientation film; etching the a portion of the thin film by a reactive ion etching so as to leave a remaining portion of the thin film behind; and removing the remaining thin film by a physical etching using an inert gas as the principal gas.
In the method, it is preferable to use a chlorine-based gas for the reactive ion etching, and that the physical etching is carried out by ion milling.
In addition, the thin film left behind after the reactive ion etching preferably has a film thickness in the range from about 0.5 nm through about 1000 nm and more preferably about 1-500 nm.
For the purpose of illustrating the invention, there is shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
REFERENCES:
patent: 4863557 (1989-09-01), Kokaku et al.
patent: 5411631 (1995-05-01), Hori et al.
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Powell William
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