Inverted hot plate cure module

Details Inverted hot plate cure module Inverted hot plate cure module

2000-02-10

2003-04-08

Edwards, Laura (Department: 1734)

Coating apparatus

With means to apply electrical and/or radiant energy to work...

Radiant heating

C118S059000, C118S066000, C118S069000, C118S050000, C118S724000, C118S725000, C118S500000, C165S080200, C165S080300, C165S080400

Reexamination Certificate

active

06544338

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the heat treatment of semiconductor wafers and more specifically to an apparatus for heat treating of layers formed over semiconductor wafers.
2. Description of the Related Art
Semiconductor devices are used extensively in today's marketplace. In order to meet the increased demand for devices employing semiconductor devices, techniques to fabricate semiconductor devices and apparatus used to fabricate semiconductor devices must increase in efficiency.
Semiconductor devices are formed from silicon wafers containing various circuitry defining the semiconductor device. During the formation of the circuitry on the silicon wafer, the wafers are subjected to various processes to enhance the quality of the layers formed over the wafers. As is well known, layers formed over wafers in the form of thin films must be cured in order to carry out thermolytic reactions and/or remove solvents. Typically, wafers are cured in curing modules. However, current cure modules suffer from non-uniform heating of wafers and thermal leakage within the module. These problems serve to increase the cure time of a wafer and the overall fabrication time for a semiconductor wafer.
FIG. 1
shows a cure module
10
in accordance with the prior art. The cure module
10
shown in
FIG. 1
includes a heating plate
12
and a cooling chamber
20
. A semiconductor wafer
11
is placed within a chamber
14
of the cure module
10
through a door
24
that is connected to an arm
24
a
. The semiconductor wafer
11
is set on lift pins
22
at lift points
22
a
in the cure module
10
as shown. During a heating operation, the wafer
11
is lowered onto heating plate standoffs
21
. The heating plate standoffs
21
are integrally formed with the heating plate
12
. After the wafer
11
is placed on the heating plate standoffs
21
, the wafer
11
will be held in place over the heating plate
12
with alignment pins
19
, as shown in FIG.
1
.
As can be seen from
FIG. 1
, the lift pins
22
, alignment pins
19
and heating plate standoffs
21
are in thermal contact with both the heating plate
12
and the wafer
11
. The lift pins
22
pass through the heating plate
12
and the alignment pins
19
and heating plate standoffs
21
are in thermal contact with the heating plate
12
. Thus, the temperature uniformity of the heating plate
12
will be reduced due to thermal losses from the lift pins
22
, alignment pins
19
and heating plate standoffs
21
.
The temperature losses in the hot plate due to the alignment pins
19
, the lift pins
22
and the heating plate standoffs
21
will cause thermal discontinuities in the wafer
11
as shown by the contact regions
13
in FIG.
1
. The thermal discontinuities at the contact regions
13
occur where the wafer is in thermal contact with the alignment pins
19
, heating plate standoffs
21
and the lift pins
22
. Thus, the non-contact regions
15
are at a lower temperature than the contact regions
13
. The thermal discontinuities and the resulting non-uniform heat treatment of the wafer
11
depicted by the non-contact regions
15
and the contact regions
13
will cause undesirable changes in the film properties on the surface of the wafer which may potentially affect the performance of a semiconductor device formed from the wafer.
After the wafer
11
is heated, the wafer
11
must be cooled so that organic components of the film will not oxidize on the surface of the wafer
11
after the wafer
11
is removed from the chamber
14
and exposed to air. The wafer
11
is cooled by first raising it on the lift pins
22
from the heating plate
12
towards a diffusion plate
18
. The diffusion plate
18
acts as a shower head for the cooling medium of the cure module
10
. The wafer
11
is commonly cooled with a water cooled (H
2
O) nitrogen gas (N
2
) flowing through the cooling chamber
20
. The nitrogen gas is dispensed through the diffusion plate
18
onto the wafer
11
. While the wafer
11
is being heated, heat will rise from the heating plate
12
to the diffusion plate
18
, increasing the surface temperature of the diffusion plate
18
. The increased temperature of the diffusion plate
18
raises the temperature of the nitrogen gas as it exits through the diffusion plate
18
. The higher temperature of the nitrogen gas increases the cooling time of the wafer
11
, thereby decreasing the overall efficiency of the curing process.
The diffusion plate
18
also affects the flow rate of the nitrogen gas into the cure module
10
. The diffusion plate
18
may contain particles (i.e., due to particle condensation from volatile organic material leaving the wafer surface during the bake process) which may become dislodged during the nitrogen cooling operation. Thus, in order to prevent the dislodging of particles, the nitrogen gas must be passed at a slower rate, thereby decreasing the cooling rate of the wafer
11
and the overall efficiency of the cure module
10
.
The seals
23
also make it difficult to maintain a low oxygen environment at high temperatures within the cure module and make vacuum baking impossible. A low oxygen environment is desirable to eliminate the possibility of film oxidation within the chamber
14
during the curing process. Further, during heating the seals
23
necessarily increase in temperature along with the lift pins
22
. As can be appreciated, when the seals
23
are constantly exposed to high temperatures, their sealing capabilities are decreased and their useable lifetime is reduced. Therefore, this increases the possibility of oxygen entering the chamber
14
while the wafer is being cured, along with the possibility of oxidation of the film on the wafer and the generation of particulates by the aging seals.
Wafers are loaded into the cure module
10
through a door mechanism
24
. The door mechanism
24
is pivoted into place against the cure module
10
with a door mechanism arm
24
a
. As the door mechanism arm
24
a
pivots the door mechanism
24
into place against the cure module
10
, both the door mechanism
24
and door mechanism arm
24
a
release particulates outside the chamber. These particulates may fall onto wafers as they are being moved into other processing chambers (not shown) and into the cure module
10
. These particulates are a possible cause of defects in a semiconductor device eventually formed with the wafer.
Lift pin through holes
25
also cause thermal discontinuities on the wafer
11
. The lift pin through holes
25
represent voids in the heating plate
12
, or areas where there is no source of heat emanating from the heating plate
12
. These voids cause uneven heating of the wafer
11
, which will result in thermal discontinuities.
In view of the foregoing, there is a need for a cure module which is configured to efficiently cure films formed over silicon wafers. There is also a need for modules that can cure formed films in a uniform manner and that avoid the introduction of thermal discontinuities that can affect the performance of the cured films, such as, spin-on glass (SOG), dielectrics including low-K dielectrics, and any other type of applied film.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing a curing module with an inverted hot plate. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a curing module for use in fabricating semiconductor wafers is disclosed. The cure module comprises a chamber having a bottom plate and a housing. The housing has a top surface and sidewalls that are configured to engage with the bottom plate. The top surface, sidewalls and the bottom plate define the chamber. The cure module also has a heating plate within the chamber and that is adjacent to the top surface of the housing.
In another embodiment, a method for making a

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