Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2001-02-28
2003-03-18
Paik, Sang (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C118S725000
Reexamination Certificate
active
06534751
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wafer heating apparatus to be employed for heating a semiconductor wafer homogeneously, and especially relates to a ceramic heater to be employed for a wafer heating apparatus.
The present invention relates to a method for the wafer heating apparatus and the ceramic heater for heating a wafer homogeneously.
2. Description of the Prior Art
A wafer heating apparatus has been used for, for example, heating a semiconductor wafer, forming a semiconductor thin film on a wafer to be used for a liquid crystal substrate or a circuit substrate, and forming a resist film on a wafer by drying and baking a resist liquid applied to the wafer.
The wafer heating apparatus has been used for, for example, heating a semiconductor wafer (hereafter simply referred as to a wafer) at the time of film formation treatment of a semiconductor thin film, etching and baking treatments for a resist film in the semiconductor device fabrication process.
A batch type apparatus for collectively carrying out film formation treatment for a plurality of wafers has conventionally been employed for semiconductor device fabrication apparatus. Recently, as wafers have been enlarged, e.g. into 8 to 12 inches in diameter, a technique, referred to as one-by-one treatment, has been employed in order to heighten the treatment precision. However, by the one-by-one treatment, the number of wafers to be treated for one time is decreased, so that the time taken to treat the wafers is required to be shortened. Consequently, it is required for a wafer supporting member to shorten the heating duration of a wafer, quickly perform attachment of the wafer thereto and detachment therefrom, and therefore improve the heating temperature precision as well.
As shown in
FIG. 14
, there has been employed a conventional wafer heating apparatus
31
including a heating plate
32
which is a metal plate made of aluminum or stainless steel and its upper face being used as a mounting surface
33
to mount a wafer thereon, a plurality of sheathed heaters
25
attached as heating element, to the lower face of the heating plate
32
, and a presser plate
24
for fixing the heaters
25
. Such a heating apparatus
31
is integrated with a container
27
containing the sheathed heaters
25
and lead wires
26
are connected to the sheathed heaters
25
.
Such a heating apparatus
31
has been employed for drying a liquid resist coated on a semiconductor wafer W by mounting on the mounting surface
33
and heating the semiconductor wafer W by the heaters
25
.
The heating plate
32
made of a metal has been formed rather thick to minimize deformation which would be made in repeatedly heating and cooling processes, and therefore the heating plate
32
has disadvantageously had high thermal capacity, and required considerably long time periods to heat and cool the heating plate effectively, resulting in low productivity.
There has been employed, as another wafer heating apparatus, as shown in
FIG. 15
, a ceramic heater
31
comprising a ceramic heating plate
32
in the form of a disk, which is made of alumina, silicon nitride, or aluminum nitride, and a heating element
35
buried within the heating plate
32
. In this example, the heating apparatus
31
utilizes the upper face of the heating plate
32
as a mounting surface
33
and further includes terminals
36
, for power supply, in the lower face, which terminals
36
are connected to the heating element
35
buried within the ceramic body. Although such a type heating apparatus has an advantage to be make a heating plate
32
thinner, it has been impossible to trim the heating resister for adjusting uniform desired resistance distribution because of the buried heating element. Consequently, this type of apparatuses have been not suitable to homogenize temperature distribution over the overall mounting surface
33
.
Further, as another heating apparatus
31
for drying a resist film on a semiconductor wafer, an apparatus
31
is disclosed, for example, in Japanese Patent Publication No. 11-2837729 in which this conventional wafer heating apparatus, as illustrated in
FIG. 11
, is composed of a supporting body
41
on a shallow container, a heating plate
32
of a nitride or carbide ceramic provided on the supporting body
41
, and a plate-like reflector
43
interposed immediate under the heating plate
32
over the bottom
41
a
of the supporting body
41
.
In
FIG. 12
, power supply terminals
37
are joined by soldering to terminal parts of heating element
35
for even heating and the power supply terminals
37
are inserted into the through holes
67
formed in the plate-like reflector
43
. Some holes
46
for leading out lead wires are formed in the outer circumference of the bottom part
41
a
. Lead wires
26
are inserted into the holes
46
to supply an electric current to the heating element and connected to the power supply terminals
37
.
The heating apparatus of
FIG. 12
is for drying a silicon wafer coated with a photosensitive resin at a high temperature (500° C. or higher) using the heating element in the heating plate
32
supported by dummy pins
47
in an opening
46
of the supporting body
41
.
The heating plate
32
with the heating element therein is designed to in the circular form and have approximately same diameter as that of the opening part
44
of the supporting body
41
. As illustrated in
FIG. 12
, the heating plate
32
is of multilayer structure, in which the heating element
35
are buried in between the respective ceramic layers. That is, the heating element
35
of this apparatus are not at all exposed to the outer surface of the heating plate
32
. The power supply terminals
37
relevant to electric power input to the heating element
35
are jointed to the heating element
35
by soldering.
The supporting body
41
is a aluminum made member having a bottom and has the opening part
44
with a circular cross-sectional on the upper side. Three holes
45
for inserting wafer-supporting pins therein are formed in the center area of the supporting body
41
. By raising and lowering the upper ends of the wafer-supporting pins while supporting a wafer W thereon, the wafer W can easily be transformed to and received from a transporting apparatus, respectively.
Japanese Patent Publication No. 11-40330 discloses a heater for drying a photosensitive resin formed on the wafer surface. The structure of the heater, as referred to
FIG. 13
, includes a heating plate
32
made of a ceramic and a heating element
35
formed on the lower surface of the heating plate
32
, wherein a metal sintered body
34
produced by sintering particles of one or more metal particles selected from gold (Au), silver (Ag), platinum (Pt), palladium (Pd), lead (Pb), tungsten (W), and nickel (Ni) is formed on the ceramic surface, and another metal coated layer
34
is provided on the metal sintered body
33
, the metal coated layer
34
being composed of one or more metals selected from Au, Ag, Pd, Pt, and Ni.
In the above case, power supply terminals
37
are fixed in the heating element
35
by soldering. A wafer W can be set spaced from the heating plate
32
by lift pins
39
.
An aluminum nitride-based ceramic and silicon carbide-based ceramic, having high thermal conductivity, are both suitable for the heating plate
32
of a semiconductor wafer heating apparatus required for carrying out homogeneously heating the wafer. Nevertheless, silicon carbide-based ceramics can more preferably be used for the heating plate
32
to be employed for the process of drying photosensitive resin films formed on wafers. That is because the aluminum nitride-based ceramic reacts to moisture in air at high temperature to generate ammonia gas which adversely affects the photosensitive resin. As a result, silicon carbide ceramics are more useful for heating plates
32
to be employed for process of drying of the photosensitive resin.
Although Silicon carbide is suitable for ceramic material composing a heating plate
32
Nakama Hidenori
Sakamoto Kouji
Tanaka Satoshi
Uchiyama Kyoji
Hogan & Hartson LLP
Kyocera Corporation
Paik Sang
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