Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of...
Reexamination Certificate
2004-03-22
2004-11-09
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
C257S009000
Reexamination Certificate
active
06815370
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chemical vapor deposition (CVD) apparatus and a method for forming a nitride layer using the same. More particularly, the present invention relates to a plasma enhanced chemical vapor deposition (PECVD) apparatus used for fabricating a semiconductor device and a method of forming a nitride layer using the same.
2. Description of the Related Art
There is a wide range of uses for a nitride layer in the field of semiconductor devices. One use of a nitride layer is as an etching mask in an etching process for forming metal patterns from an aluminum layer or a titanium layer, and as a protection layer for preventing a semiconductor device from being contaminated. Another use of a nitride layer is as an insulator when formed between conductive layers. Still another use of a nitride layer is as an etch-stopping layer to detect an end point in an etching process.
Typically, a nitride layer is formed by a method of PECVD, as disclosed in the prior art. The prior art discloses that a thin film is deposited by introducing a process gas and a carrier gas into a process chamber sustaining a temperature of about 350-450° C. and a pressure of about 1-10 Torr. Then, a high frequency voltage of about 50-200 W at a source radio frequency of 13.56 MHz is applied to the process chamber to create a plasma atmosphere therein.
The method disclosed in the prior art has an advantage that device operation characteristics are not deteriorated because the process is performed at low temperature of about 350-450° C. However, the method also has many disadvantages, such as high degree of hydrogen content, low film density, weak oxidation resistance and film lifting, which are caused by high thermal stress after the thin film undergoes subsequent heat treatment processes.
FIG. 1
shows a conventional plasma enhanced CVD apparatus. The conventional plasma enhanced CVD apparatus includes a cylinder-type process chamber that comprises an upper chamber
10
, a lower chamber
12
and an insulator
14
inserted between the upper chamber
10
and the lower chamber
12
.
The upper chamber
10
and the lower chamber
12
serve as an upper electrode and a lower electrode, respectively, so that an electric field may be generated therebetween.
An external end of a gas supply pipe
18
located outside the process chamber connected to a process gas supply source
20
, also located outside the process chamber, is externally inserted into the process chamber through a top portion of the upper chamber
10
. The other end, an internal end, of the gas supply pipe
18
located inside the process chamber is connected to a gas distributing plate
16
.
FIG. 2
depicts a perspective view of a gas distributor in accordance with the conventional PECVD apparatus.
As shown in
FIG. 2
, the gas distributing plate
16
is a circular disk and has a plurality of gas distributing nozzles
17
at a bottom surface thereof, for facilitating downward ejection of process gases from the nozzles
17
toward a bottom of the lower chamber
12
.
As shown in
FIG. 1
, the conventional plasma enhanced CVD apparatus further includes a rotating shaft
22
externally inserted into the process chamber through the bottom of the lower chamber
12
. An external end of the rotating shaft
22
is connected to a rotating driving source (not shown) for being rotated. The driving source is located outside the process chamber. A susceptor
24
formed of AIN is installed inside the process chamber and connected to an internal end of the rotating shaft
22
to support a wafer
26
. Further, The susceptor
24
has a heater (not shown) embedded therein to heat the wafer
26
placed thereon to a predetermined temperature and to control an internal temperature of the process chamber.
Further, a pumping pipe
32
is connected to the bottom of the lower chamber
12
to control an internal pressure of the process chamber and a vacuum pump
30
is connected to the pumping pipe
32
.
Still further, the lower chamber
12
is connected to a loadlock chamber
28
at side surface thereof, in which the wafer
26
is placed before being loaded to or after being unloaded from the susceptor
24
.
FIG. 3
illustrates a block diagram to explain operation of the conventional plasma enhanced CVD apparatus and a method of forming a nitride layer using the same.
First, a protective film such as an oxide layer having a dielectric constant of about 3.8-3.9 or a nitride layer having a dielectric constant of about 7.5 is coated on inner walls of the process chamber during a step S
2
. Ions in plasma tend to move toward the inner walls of the process chamber due to capacitance of the process chamber walls, so that an initial nitride layer formed at the beginning of a deposition process has low uniformity in thickness. The protective film on the inner walls of the process chamber serves to prevent the initial nitride layer from having a low uniformity in thickness.
The protective film formed of the oxide layer may be formed by supplying a process gas such as nitrogen oxide N
2
O or nitrogen monoxide NO and a carrier gas of nitrogen N
2
to the process chamber and creating a plasma atmosphere in the process chamber.
The protective film formed of the nitride layer may be formed by supplying process gases of silane and ammonia to the process chamber and then adjusting the internal temperature and pressure of the process chamber, and applying a high frequency power to the process chamber to create a plasma atmosphere therein.
Next, during a step S
4
, a sheet of wafers is loaded onto the susceptor
24
in the process chamber by a moving means such as a robot arm.
The process chamber maintains an internal pressure of about 0.5-0.7 mTorr after activation of the vacuum pump
30
, and an internal temperature of about 400° C. after activation of the heater embedded under the susceptor
24
. The heater also causes the temperature of the wafer
26
on the susceptor
24
to become about 400° C.
Next, the susceptor
24
is rotated at a predetermined speed by the rotating shaft
22
.
Next, during a step S
6
, ammonia and silane as process gases are supplied to the process chamber through the process gas supply pipe
18
and the gas distributing plate
16
, and electric power of about 500-1000 W is applied to the upper chamber
10
and the lower chamber
12
.
During the step S
6
, the process gases are converted to plasma due to an electric field induced by the electric power applied to the upper chamber
10
and the lower chamber
12
, so that a plasma atmosphere is created in the process chamber.
Next, during a step S
8
, ions in the plasma atmosphere are deposited on the wafer
26
, thereby forming a nitride layer on the wafer
26
after a predetermined time delay.
Next, during a step S
10
, the process gas supply and the electric power supply to the process chamber stop.
Next, during a step S
12
, the wafer
26
is unloaded from the susceptor
24
and shifted to the loadlock chamber
28
by the moving means of the robot arm.
Next, during a step S
14
, particles and process gases remaining in the process chamber are forced to be discharged by initiating a vacuum pump
30
and the inner part of the process chamber is cleaned by a cleaning gas of Argon.
Next, the steps S
2
-S
14
are repeated about 25 times, thereby forming a nitride layer on each of 25 wafers on a sheet.
Finally, after the 25 wafers are coated with the nitride layer, the inner part of the process chamber undergoes a plasma etching cleaning process in a step S
16
, so that the protective film coated on the inner walls and components in the process chamber, as well as byproducts, are removed. As a result, the process chamber is completely cleaned. The plasma etching cleaning process of the step
16
is performed by supplying a gas of nitrogen trifluoride NF
3
and a carrier gas of Ar to the process chamber and converting the same into plasma.
The conventional plasma enhanced CVD apparatus shown in
FIG. 1
has some drawbacks.
First, the plasma formed by
Ahn Byung-Ho
Han Jae-Jong
Kim Hwa-Sik
Kim Kyoung-Seok
Park Hong-Bae
Lee & Sterba, P.C.
Luk Olivia T.
Niebling John F.
Samsung Electronic Co. Ltd.
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