Method of preventing generation of particles in chamber

Details Method of preventing generation of particles in chamber Method of preventing generation of particles in chamber

2000-11-30

2004-04-06

Niebling, John (Department: 2812)

Semiconductor device manufacturing: process

Making device or circuit emissive of nonelectrical signal

Including integrally formed optical element

C438S758000, C438S905000, C438S158000

Reexamination Certificate

active

06716658

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a method of fabricating a liquid crystal display, and more particularly to a method of preventing a generation of contaminating particles in a chamber within a deposition device.
BACKGROUND OF THE INVENTION
Liquid crystal displays (LCD) have advantages such as small size, thinness, and low power consumption. Thus, LCDs have been used in notebook computers, office automation equipment, audio/video equipment, etc. In particular, active matrix LCDs, using thin film transistors (TFT) as switching devices, are suitable for displaying dynamic images.
The active matrix LCD displays a picture corresponding to a video signal, such as a television signal, on a picture element or pixel matrix having pixels arranged at intersections between gate lines and data lines. Each pixel includes a liquid crystal cell controlling an amount of light transmitted in accordance with a voltage level of a data signal from the data line. The TFT is installed at each intersection between the gate and data lines to switch data signals transmitted to the liquid crystal cell in response to scanning signals from the gate line.
FIG. 1
shows a TFT formed on a substrate
1
. A method of fabricating a conventional TFT is described below. First, a metal such as Al, Mo, Cr or their alloy, etc., is deposited and patterned by photolithography to form a gate electrode
20
and a gate line (not shown).
Then a gate insulating film
22
, made from an organic material such as SiN
x
or SiO
x
, is deposited on the substrate
1
and over the gate electrode
20
. A semiconductor layer
24
, made from an amorphous silicon (a-Si) layer, and an ohmic contact layer
26
, made from an a-Si doped with n+ ions, are subsequently deposited on the gate insulating film
22
.
Afterwards, a source electrode
28
and a drain electrode
30
, both made from a metal such as Mo or Cr, are formed on the ohmic contact layer
26
. The source electrode
28
is patterned integrally with the data line. Also a portion of the ohmic contact layer
26
exposed through an opening between the source electrode
28
the drain electrode
30
is removed by dry or wet etching.
A protective film
32
, made from SiN
x
or SiO
x
, is deposited to cover the TFT including over the source electrode
28
and the drain electrode
30
. Subsequently, a contact hole is formed on the protective film
32
to expose a portion of the drain electrode. Then a pixel electrode
34
, made from an indium tin oxide (ITO) is coated and is connected, via the contact hole, to the drain electrode
30
.
When fabricating the TFT, the gate electrode
20
, the gate line (not shown), the source electrode
28
, the data line (not shown), the drain electrode
30
, the pixel electrode
34
, as well as a color filter and a black matrix (both not shown) are formed and patterned using photoresists as masks in a light-exposure and development environment using a photo equipment.
It is difficult to bond the photoresist, which is made of an organic material, to the substrate which is made of almost entirely inorganic material. Thus, to improve the adhesive force between the photoresist and the substrate
1
, the surface of the substrate
1
is converted into an organic material using hexa methyl disiliane (HMDS) prior to formation of the photoresist. This process is described in conjunction with FIG.
2
.
First, as shown in
FIG. 2
, a substrate
1
is mounted into an adhesion chamber
2
of the photo equipment. Thereafter, a door of the adhesion chamber
2
(not shown) is closed to keep the interior of the chamber
2
airtight. Then, ejection valves
16
a
and
16
b
are opened and gases within the adhesion chamber
2
are evacuated through ejection lines
14
a
and
14
b
to decrease pressure within the adhesion chamber
2
.
Next, nitrogen N
2
is injected into an HMDS tank
4
to generate HMDS gas and supply valves
6
a
and
6
b
are opened to supply HMDS through supply lines
8
a
and
8
b
. The HMDS gas is injected into the adhesion chamber
2
in a bubble shape by a pressure difference between the interior of the HMDS tank
4
and the interior of the adhesion chamber
2
. Evacuation lines
10
a
and
10
b
are opened to continuously draw the HMDS gas into the adhesion chamber
2
by opening evacuation valves
12
a
and
12
b.
After a desired amount of time has elapsed, the supply valves
6
a
and
6
b
are closed. However, the evacuation valves
12
a
and
12
b
remain open to continuously draw the HMDS gas through the evacuation lines
10
a
and
10
b.
Then the pressure within the adhesion chamber
2
is equalized to atmospheric pressure by allowing air to enter the chamber. Finally, the door of the adhesion chamber
2
is opened and the substrate
1
is taken out.
However, the gas-exposure equipment as shown in
FIG. 2
has a problem in that moisture in the air also enters the adhesion chamber
2
when the air is allowed to enter. The moisture, within the adhesion chamber
2
, generates a white compound by combining with an ammonia component of the HMDS. This white compound converts into particles and contaminates the interior of the adhesion chamber
2
and the substrate
1
. The contamination particles on the substrate
1
leave a film residue upon patterning of the photoresist film and causes a short between the electrodes. The contamination also causes visible stains when displaying images.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method of preventing generation of particles in a chamber that is adapted to reduce the generation of particles.
In order to achieve these and other objects of the invention, a method of preventing generation of particles in a chamber according to the present invention includes the steps of mounting a substrate within a chamber of a photo equipment; decreasing a pressure within the chamber; injecting a surface treatment gas into the chamber; and evacuating the chamber while injecting a nitrogen gas into the chamber.


REFERENCES:
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patent: 5015330 (1991-05-01), Okumura et al.
patent: 5280012 (1994-01-01), Kirlin et al.
patent: 5501870 (1996-03-01), Shiraishi et al.
patent: 5728602 (1998-03-01), Bellows et al.
patent: 6043162 (2000-03-01), Shimizu et al.
patent: 6060397 (2000-05-01), Seamons et al.
patent: 6091056 (2000-07-01), Kannan et al.
patent: 6214751 (2001-04-01), Lee
patent: 6362115 (2002-03-01), Mandal
Academic Press Dictionary of Science and Technology, http://www.harcourt.com/dictionary/def/8/2/9/0/8290900.html, Purge definition.

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