Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
1999-12-01
2002-08-20
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C216S060000, C216S067000, C216S068000, C216S069000
Reexamination Certificate
active
06435196
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an impurity processing apparatus for doping impurities such as phosphorus, boron, or the like into a semiconductor substrate, etc., or a PSG (PhosphoSilicateGlass) film, a BSG (BoroSilicateGlass) film, or a BPSG (BoroPhosphoSilicateGlass) film, or a carbon film, etc. and to a method for cleaning the impurity processing apparatus.
2. Description of the Prior Art
In recent years, in manufacturing a semiconductor integrated circuit apparatus of superhigh integration, in the case where a p-type or n-type impurity region is formed in a semiconductor substrate, or in the case where an amorphous boron film or an amorphous carbon film is formed for use in absorption of neutron rays, the following methods have been used: an ion injecting method, a plasma doping method using a parallel plate type electrode, a method employing a wave guide for microwaves (&mgr; waves) causing ECR (Electron Cyclotron Resonance), or a plasma generating method using a power radiating antenna or the like for generating helicon-plasma, and a plasma CVD (Chemical Vapor Deposition) method using an impurity containing film-forming gas which is converted into a plasma (plasmanized).
FIG. 1
is a side view showing a plasma doping apparatus
101
according to the prior art.
This plasma doping apparatus
101
, as shown in
FIG. 1
, comprises a plasma process part
101
A for doping an impurity on a substrate
51
by a plasma gas; and a doping gas supply part
101
B having a doping gas source, and a parallel plate type electrode used as a plasma generating source for the plasma process part
101
A.
The plasma process part
101
A, as shown in
FIG. 1
, plasmanizes a doping gas and has a process chamber
1
which dopes the substrate
51
by use thereof and can decompress.
The process chamber
1
is connected to an exhaust apparatus
6
through an inducting/ exhausting piping
8
a.
An upper electrode
2
a
and lower electrode
2
b
opposing each other are provided in the process chamber
1
, and power is supplied from a power supply
5
, i.e., DC (a direct current), AC (an alternating current (frequency 50 Hz or 60 Hz)), LF (low frequency (frequency 100 to 800 kHz) or RF (radio frequency (frequency 1 to 25 MHz)) power, to these electrodes
2
a,
2
b,
and the doping gas is thereby plasmanized. The upper electrode
2
a,
the lower electrode
2
b
and the power supply
5
constitute the plasma generating means for plasmanizing the doping gas.
The upper electrode
2
a
serves as a dispersion member for the doping gas and is provided with a discharge port
3
for the doping gas. The discharge port
3
for the doping gas is connected to a doping gas supply part
101
B via piping
8
b.
The lower electrode
2
b
serves also as a holding base for the substrate
51
, and a heater
4
for heating the substrate
51
is provided under the lower electrode
2
b.
Gas bombs
7
for supplying the doping gas are installed in the doping gas supply part
101
B. The doping gas is supplied from these gas bombs
7
to the process chamber
1
of the plasma process part
101
A through pipings
8
c,
8
d,
8
b.
In this plasma doping apparatus, if used repeatedly for a long period of time, a decomposed product of a gas containing an element to be doped adheres to an inner wall of a partition surface of the chamber
1
and surfaces of the electrodes
2
a,
2
b
for generating a glow discharge, etc. Such circumstances also occur even in an ion implantation system or a plasma CVD apparatus.
If the insulating decomposed product accumulates on the surfaces of the electrodes
2
a,
2
b
for generating the glow discharge, charge-up occurs to destabilize the glow discharge. Furthermore, in an apparatus using the ECR, a glass surface of a window for introducing &mgr; waves into a plasma generating chamber is contaminated, and the decomposed product accumulates even on the inner wall of the plasma generating chamber thereby lowering plasma generating efficiency.
If such a state continues, the discharge becomes unstable and difficult to use. Furthermore, in the worst case, the discharge stops and cannot be used.
Additionally, when a weak p type or n type is doped, the decomposed product containing doping impurities which adhere to the inner wall of the chamber sputter and adhere to the semiconductor substrate, and it becomes difficult to perform lower concentration doping. Accordingly, in order to dope with excellent reproducibility, removal of the decomposed product adhered to the inner wall of the chamber is necessary.
Normally, the following methods are used for cleaning an interior of the chamber of such processing apparatus:
(i) a method glow-discharging for at least an hour in a gas such as argon or hydrogen. As a method for cleaning an inner wall of an ion source housing of an ion implantation system, a method for using hydrogen or an alkyl based substance is disclosed in Japanese Application Laid-Open No. 3-64462, for example.
(ii) a method in which, after a device is disassembled and each part is dipped in a mixture of, for example, a hydrogen peroxide solution and ammonia water, contaminants are manually shaved off by mechanical use of sandpaper or a wire brush, and after cleaning the apparatus, it is reassembled and used.
(iii) a method for cleaning the path of ion beams of the ion implantation system, a method for vaporizing a reaction product adhered to an inner wall, etc. by glow discharge of an oxygen containing gas such as O
2
, O
3
or the like, or a halogen fluoride gas such as CF
4
, C
2
F
6
, NF
3
or the like and cleaning is disclosed in Japanese Application Laid-Open No. 4-112441, for example. Furthermore, an example of use of a halogen fluoride gas such as ClF
3
or the like is disclosed in Japanese Application Laid-Open No. 8-162433.
However, there are the following drawbacks in a conventional method for cleaning an impurity processing apparatus: Namely, (i) in the method for glow-discharging in a gas such as argon or hydrogen, in the case of argon, an impurity layer adhered to a surface of a silicon substrate is removed, but upon a removal from the surface of the silicon substrate, these impurity atoms invade into the silicon substrate. Furthermore, the material forming the inner wall of the reaction apparatus is sputtered and adheres to the surface of the silicon substrate and invades the substrate, so that it may adversely affect its characteristics.
In the case of hydrogen, for example, when boron is present, a reaction product of boron and hydrogen is generated, and when the reaction chamber is opened to the outside air, diborane is released which is unfavorable for human health. Moreover, if a glow discharge continues for about an hour, a roughness occurs on a surface of the silicon substrate. Furthermore, if the adhered substance starts to be partially removed in the argon or hydrogen, the discharge concentrates on that part and a roughness occurs on the inner wall of the apparatus, the electrode surface and the surface of the silicon substrate. With the other gases, as an adhesive substance is scarcely removed in helium, it is not practical. (ii) the method for disassembling a apparatus and cleaning it chemically with chemicals, or mechanically by a wire brush, etc., takes much labor and time for a slight regulation or recovery of a vacuum after reassembly. Furthermore, a doping impurity element may adhere to a human body or be breathed in, so that this method is inconvenient for reasons of health. (iii) in the method for vaporizing a reaction product adhered to the inner wall, etc., by glow discharge of a halogen fluoride gas such as ClF
3
, CF
4
, C
2
F
6
or the like and cleaning, a decomposition product of Cl or F is generated and caution in handling these chemicals is necessary and a great expense is incurred for a public nuisance countermeasure for a rendering harmless this exhaust gas, etc. As the adhesive substance is scarcely removed in the other gases, for example oxygen, it is not practical.
SUMMARY OF THE INVENTION
It is an
Maeda Kazuo
Matsui Bunya
Ohira Kouichi
Satoh Noritada
Canon Sales Co., Inc.
Gulakowski Randy
Lorusso & Loud
Person Yolanda
LandOfFree
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