Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – Polycrystalline semiconductor
Reexamination Certificate
1998-09-03
2001-04-24
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Polycrystalline semiconductor
C438S239000, C438S255000, C438S398000, C438S488000, C438S396000, C257S309000
Reexamination Certificate
active
06221742
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for fabricating a polysilicon film for a semiconductor device.
2. Description of the Related Art
To manufacture a reliable semiconductor device:, one must keep the temperature of the apparatus uniform and minimize any contaminating particles.
Specifically, consider the case of forming a lower electrode with a hemispherical silicon grain (referred to as HSG-Si), in order to enlarge the electrostatic capacitance of a capacitor by increasing the area of the lower electrode. In this situation, it is critical to keep the temperature of the reaction chamber uniform and to keep the inside of the reaction chamber clean and free of contaminants.
Typically, to form the lower electrode with HSG-Si, a crystal growing step for forming crystal grains by migrating the amorphous silicon to the nucleus of crystalline silicon needs to be stable. Also, the speed of silicon surface migration for the growth of the crystal grain needs to be faster than the speed of the amorphous silicon crystallization in the lower amorphous silicon.
For the amorphous silicon to move toward the nucleus of the crystalline silicon, the amorphous silicon should have a free surface where the silicon atoms of the surface are not combined to any other atoms. When the surface is contaminated with other materials, the surface movement of the amorphous silicon atoms is impeded since the amorphous silicon atoms combine to the atoms of the other materials, thus making any further generation and growth of the nucleus impossible. Therefore, removing the surface contaminants on the wafer that is transferred to the reaction chamber, and keeping the inside of the chamber clean are important factors in semiconductor processing.
A general apparatus for fabricating the semiconductor device includes a cassette chamber in which a carrier having a wafer is loaded. The apparatus also contains a reaction chamber for performing a process, and a wafer cooling chamber after completing the process. A polyhedral transfer chamber having a robot arm is connected to the reaction chamber and cooling chambers for transferring the wafer to the respective chambers.
The structure of the reaction chamber is described as follows with reference to
FIG. 1. A
gate valve
31
that separates a wafer transfer chamber
10
and a reaction chamber
20
is disposed between the first side wall
30
of the reaction chamber and the wafer transfer chamber
10
. A gas vent opening
33
is formed on a second side wall
32
opposite to the first side wall
30
. A gas injection opening
35
is formed to pass through an upper wall
34
of the reaction chamber. Cooling jackets
40
and
42
are installed on the upper
34
and bottom
36
walls of the reaction chamber. A heating block
24
, having a heater
22
and a susceptor
26
for sustaining a wafer
28
on the heating block
24
, are installed inside the reaction chamber
20
. Also, a turbo pump
38
is connected to the second side wall
32
.
The operation of the apparatus of
FIG. 1
will now be described. First, the wafer is transferred to the reaction chamber
20
after being transferred from the cassette chamber (not shown) and the wafer transfer chamber
10
by the robot arm. The pressure of the cassette chamber at the beginning of the transfer is about 1 mtorr.
However, air at a pressure of about 1 mtoor, which contains polluting particles, is also transferred from the cassette chamber to the wafer transfer chamber when the wafer is transferred. Therefore, the wafer transfer chamber is contaminated with the polluting particles. As a result, the reaction chamber
20
connected to the wafer transfer chamber
10
is also contaminated with the polluting particles. The surface of the wafer is thus contaminated by these polluting particles, such as moisture and carbon compounds, during the process of raising the temperature of the wafer
28
in the reaction chamber
20
, thus reducing the reliability of the processing. Especially, in the case of forming the lower electrode with the HSG-Si, it is impossible to increase the surface area since the speed of the surface migration of the amorphous silicon is reduced by adsorption of contaminants to the amorphous silicon.
In the next steps, the surface of the wafer
28
is cleaned to remove an organic material or a native oxide film existing on the surface of the wafer prior to the processing in the reaction chamber
20
. Therefore, a certain amount of moisture exists on the surface of the wafer
28
which is loaded in the cassette chamber (not shown) and the moisture is not completely evaporated and removed in the cassette chamber under the pressure of lmtorr. Therefore, vapor is continuously generated when the wafer
28
is transferred from the wafer transfer chamber
10
to the reaction chamber
20
. Especially in a process for forming the HSG-Si, the speed of the surface migration of the amorphous silicon is reduced by the vapor which is continuously generated.
Typically, a cooling gas, such as argon or helium is injected into a cooling chamber (not shown) at a pressure of 1 to 100 torr. The cooling gas flows into the wafer transfer chamber
10
connected to the cooling chamber, and then flows into the reaction chamber
20
, thus acting as a contaminant. As before, the speed of the surface migration of the amorphous silicon is reduced since the surface of the wafer
28
is contaminated by the cooling gas.
As shown in
FIG. 1
, the reaction chamber includes the cooling jackets
40
and
42
for keeping the temperature uniform on the upper and bottom walls
34
and
36
thereof. However, the temperature of the gate valve
31
separating the transfer chamber
10
and the reaction chamber
20
, the first side wall
30
adjacent to the gate valve
31
and the second side wall
32
opposite to the first side wall
30
, are all approximately 50° C. or higher than the upper
34
and bottom
36
walls, since the above three portions have no cooling jackets. Thus, the surface contaminants existing on the chamber walls and the wafer may exude in a gas form from the gate valve
31
, the first side wall
30
, and the second side wall
32
. Especially in the case of the process for forming the HSG-Si, it is impossible to achieve the desired surface increase effect since the exuded gas is adsorbed to the surface of the silicon.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus for fabricating a semiconductor device and associated methods using such an apparatus, which substantially overcomes the limitations and disadvantages of the conventional art.
To achieve such advantages, the apparatus for fabricating the semiconductor device according to the present invention comprises a cassette chamber, a wafer transfer chamber, a reaction chamber and a wafer cooling chamber. First, second, third and fourth cooling jackets are installed on a first side wall adjacent to the wafer transfer chamber, a second side wall opposite to the first side Mall, an upper wall, and a bottom wall, respectively. A gate valve is disposed between the reaction chamber and the wafer transfer chamber to separate the reaction chamber from the wafer transfer chamber. The gate valve has a fifth cooling jacket thereon. A wafer cooling chamber is connected to a side portion of the wafer transfer chamber.
A polysilicon film is fabricated with the above apparatus by adjusting the pressure of the cassette chamber to be less than 0.05 mtorr. Alternatively, the pressures of the cooling chamber and the wafer transfer chamber may be controlled to be less than 1.0 &mgr;torr. A refrigerant, selected from the group consisting of cooling water, and mixture of the cooling water and ethylene glycol, is provided to the first through fifth cooling jackets of the above apparatus.
REFERENCES:
patent: 5658381 (1997-08-01), Thakur et al.
patent: 5721171 (1998-02-01), Ping et al.
patent: 5733809 (1998-03-01), Dennison et al.
patent: 5760434 (1998-06-01), Zahurak et al.
patent: 5837580 (1998-12-01), Thak
Kim Young-sun
Nam Seung-hee
Park Young-wook
Yoo Cha-young
Jones Volentine, L.L.C.
Keshavan Belur V
Samsung Electronics Co,. Ltd
Smith Matthew
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