Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2002-08-20
2004-04-06
Ghyka, Alexandra (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S786000, C438S791000, C118S719000, C118S725000
Reexamination Certificate
active
06716772
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device manufacturing method and a semiconductor manufacturing apparatus, and more particularly, to a semiconductor device manufacturing method including a silicon nitride film manufacturing step using a thermal CVD (Chemical Vapor Deposition) method or a silicon oxynitride film manufacturing step using a thermal CVD method, and to a semiconductor manufacturing apparatus preferably used for the method.
2. Description of the Related Art
Conventionally, it is common that a silicon nitride film used in a semiconductor device is formed using mixed gas of SiH
2
Cl
2
(DCS, hereinafter) and NH
3
and that a silicon oxynitride film used in a semiconductor device is formed using mixed gas of DCS, NH
3
and N
2
O.
According to this method, however, it is necessary to form the silicon nitride film at a temperature as high as 700° C. to 800° C. and as a result, there is a problem that impurities are adversely diffused deeply into a shallow diffused layer and a semiconductor device element can not be formed small in size. Further, there is a problem that NH
4
Cl (ammonium chloride), which is a by-product of reaction, adheres to a discharge port, this NH
4
Cl generates rust on a metal surface, and metal contamination is generated on a semiconductor wafer.
SUMMARY OF THE INVENTION
To solve the problems, the present inventors examined forming a silicon nitride (Si
3
N
4
) film using NH
3
and SiH
2
(NH(C
4
H
9
))
2
(bis tertiary butyl amino silane: BTBAS, hereinafter) as raw gases and forming a silicon oxynitride (SiON) film using BTBAS, NH
3
and N
2
O as raw gases. As a result, the inventors have found that the silicon nitride film and the silicon oxynitride film can be formed at a low temperature of about 600° C. and NH
4
Cl, which is a cause of metal contamination, is not generated.
The present inventors, however, have found that when a silicon nitride film or a silicon oxynitride film is formed using BTBAS, uniformity in thickness of the formed film over the entire surface of the substrate is not sufficient.
FIG. 1
shows a structure of a furnace used when a silicon nitride film is formed using BTBAS and NH
3
as raw gases, and when a silicon oxynitride film is formed using BTBAS, NH
3
and N
2
O as raw gases.
A case in which the silicon nitride film is formed using BTBAS and NH
3
as raw gases will be explained as one example.
A quartz reaction tube (outer tube)
11
is located outside, and a cylindrical quartz inner tube
12
is disposed inside of the quartz reaction tube
11
. A quartz boat
14
is disposed inside of the quartz inner tube
12
. The quartz boat
14
supports a large number of semiconductor wafers
16
.
BTBAS and NH
3
are introduced into a furnace through quartz nozzles
21
and
18
, respectively. The gases are first introduced into the quartz inner tube
12
and flow from below upward. The gases are discharged out from the quartz inner tube
12
from above downward.
BTBAS and NH
3
decompose by heat during this process forming Si
3
N
4
on the semiconductor wafer
16
and a quartz surface.
FIG. 4A
shows a schematic transversal sectional view of the quartz inner tube
12
and its interior, and
FIG. 4B
is a schematic longitudinal sectional view thereof.
The present inventors first formed a silicon nitride film using BTBAS and NH
3
as raw gases having the same compositions as those used for other raw gases.
The plurality of semiconductor wafers
16
each having a diameter of 200 mm were stacked by boat columns
25
in the vertical direction in the quartz inner tube
12
having an inner diameter of 260 mm, and films were formed. A distance “b” between edges of the semiconductor wafers
16
and an inner wall of the quartz inner tube
12
was 30 mm. A distance “a” between the adjacent semiconductor wafers
16
was 6.35 mm.
As a result, a thickness of the Si
3
N
4
film was thin around a peripheral portion of the wafer, and the film at the central portion of the wafer was thin and reentrant in shape. When the silicon oxynitride film was formed using BTBAS, NH
3
and N
2
O as raw gases, the same result was obtained.
Thereupon, the present invention provides a semiconductor device manufacturing method and a semiconductor manufacturing apparatus in which when a silicon nitride film is formed using BTBAS and NH
3
as raw gases, and when a silicon oxynitride film is formed using BTBAS, NH
3
and N
2
O as raw gases, the uniformity in thickness of the formed film over the entire surface of the substrate can be enhanced.
The present inventors have considered that at the center portion of a semiconductor wafer
16
, because other semiconductor wafers
16
are located below and above the semiconductor wafer, space in the vicinity of the semiconductor wafer is small, but at the peripheral portion of the semiconductor wafer, a large space exists between the semiconductor wafer and the quartz inner tube
12
, and therefore, the film formed on the semiconductor wafer is thick at the peripheral portion of the semiconductor wafer and is thin and reentrant in shape at the central portion of the semiconductor wafer. Following the above-mentioned consideration, the present inventors have studied a relation of relative values between the distance “a” between the adjacent semiconductor wafers
16
and the distance “b” between the edge of the semiconductor wafer
16
and the quartz inner tube
12
, to distribution of a thickness of a film formed on the semiconductor wafer
16
over the entire surface of the wafer
16
, and as a result, the present inventors have reached the present invention.
According to a first aspect of the present invention, there is provided a semiconductor manufacturing apparatus which forms silicon nitride films on a plurality of substrates by thermal chemical vapor deposition, including:
a vertical reaction tube having an inner wall;
a substrate holder which is to hold the plurality of substrates in the vertical reaction tube with the plurality of substrates being vertically stacked, a distance “a” between adjacent substrates of the plurality of substrates and a distance “b” between edges of the plurality of substrates and the inner wall of the vertical reaction tube being maintained substantially equal to each other; and
gas supplies which supply bis tertiary butyl amino silane and NH
3
into the vertical reaction tube such that the bis tertiary butyl amino silane and the NH
3
flow vertically from one end of the plurality of substrates to an opposing end of the plurality of substrates and do not flow into the vertical reaction tube through the inner wall at a height between the one end and the opposing end of the plurality of substrates, to form the silicon nitride films on the plurality of substrates.
Preferably, a value of a ratio “b/a”, which is a ratio of the distance “b” between the edges of the plurality of substrates and the inner wall of the vertical reaction tube to the distance “a” between the adjacent substrates, is set to be in a range of 0.5 to 1.1.
According to a second aspect of the present invention, there is provided a semiconductor manufacturing apparatus which forms silicon oxynitride films on a plurality of substrates by thermal chemical vapor deposition, including:
a vertical reaction tube having an inner wall;
a substrate holder which is to hold the plurality of substrates in the vertical reaction tube with the plurality of substrates being vertically stacked, a distance a between adjacent substrates of the plurality of substrates and a distance “b” between edges of the plurality of substrates and the inner wall of the vertical reaction tube being maintained substantially equal to each other; and
gas supplies which supply bis tertiary butyl amino silane, NH
3
and N
2
O into the vertical reaction tube such that the bis tertiary butyl amino silane, the NH
3
and the N
2
O flow vertically from one end of the plurality of substrates to an opposing end of the plurality of substrates and do not flow into the vertical reaction tube through the inn
Maeda Kiyohiko
Mizuno Norikazu
Ghyka Alexandra
Hogan & Hartson LLP
Kokusai Electric Co. Ltd.
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