Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2002-04-26
2004-06-22
Fuqua, Shawntina (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S465100, C219S466100, C219S467100, C219S543000, C219S544000, C219S546000, C219S548000, C118S724000, C118S725000, C118S728000
Reexamination Certificate
active
06753507
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wafer heating apparatus to be employed for heating mainly a wafer and a ceramic heater to be employed for the apparatus and for example to a wafer heating apparatus suitable for forming a semiconductor thin film on a semi conductor wafer, a liquid crystal substrate, a circuit board or the like and for forming a resist film by drying and baking a resist liquid applied to the water.
2. Prior Art
In semiconductor thin film formation treatment, etching treatment, resist film baking treatment and the like in semiconductor device fabrication process, a wafer heating apparatus is employed for heating a semiconductor wafer.
Conventionally, the wafer heating apparatus has been made to be a batch type apparatus for carrying out film formation treatment of a plurality of wafers. Along with the recent tendency to enlarge a wafer size from 8 to 12 inches, a sheet-fed manner for heating wafers one by one has been employed to increase the treatment precision.
In the sheet-fed manner, the number of wafers to be heated by one time treatment is lessened, so that wafer treatment time is required to be shortened. Accordingly, a wafer supporting member is required to be suitable for shortening the wafer heating duration and quickening the vacuum attachment, transportation, and vacuum detachment of wafers, and at the same time, the heating temperature precision of a heater is required to be improved.
As an example of such a wafer heating apparatus described above, Japanese Patent Publication No. 11-283729 discloses a wafer heating apparatus, as illustrated in
FIG. 12
, including main components of a support
31
, a heat homogenizing plate
22
, and a stainless steel plate
33
as a plate reflection body. The support
31
is a bottomed member made of aluminum and having an opening
34
with a circular cross-section shape in the upper side. In the center part of the support
31
, three pin insertion holes
35
are formed to insert wafer supporting pins (not illustrated in the figure) into. By moving the wafer supporting pins inserted into the pin insertion holes
35
up and down, a wafer W can be transported to and from a transferring apparatus. Also, a conductor terminal
27
is soldered to the terminal part of a heating element (not illustrated in the figure) and the conductor terminal
27
is inserted in a hole
57
formed in the stainless plate
33
. In the outer circumferential part of the bottom part
31
a
, some holes
36
for leading out lead wires are formed. Lead wires (illustrated in the figure) for supplying electric current to the heating element are inserted through the holes
36
and connected to the foregoing conductor terminal
27
.
Nitride ceramics or carbide ceramics may be used for the ceramic material forming the heat homogenizing plate
22
. The heating element is proposed to be resistor strips in a plurality of concentrically formed patterns, as illustrated in
FIG. 13
, to heat the heat homogenizing plate
22
by electricity application. A heating element
62
and electrodes
63
are formed in the heat homogenizing plate
22
and sensor installation holes
64
are also formed.
Heat Homosinizing
The heat homogenizing plate
22
of such a conventional wafer heating apparatus is required to precisely control the temperature distribution in the wafer W plane within a range of ±0.5° C. Therefore, Japanese Patent Application Laid-Open Publication No. 8-70007 proposes heating treatment of a substrate, as illustrated in
FIG. 14
, to be carried out while keeping a wafer W parallel to a heat homogenizing plate
22
made of aluminum and equipped with a heating means or a cooling means at a constant distance from the upper face of the heat homogenizing plate
22
by supporting the wafer W with spherical supporting pins
59
set in recessed parts
58
formed in the heat homogenizing plate
22
.
In such a manner, by holding the wafer W at a distance from the heat homogenizing plate
22
, even if warping or the evenness of the wafer W relative to the heat homogenizing plate
22
differs, the wafer is prevented from contact with the heat homogenizing plate and accordingly the unevenness of the temperature distribution in the wafer surface is suppressed. Further, such a structure is applied to a conventional heat homogenizing plate
22
, since the heat homogenizing plate
22
itself is thick, the temperature distribution caused in a heating element
25
can be moderated owing to the thickness of the heat homogenizing plate
22
. Even heating is thus made possible. However, the heat homogenizing plate
22
made of aluminum has a problem that it takes a long time to carry out heating and cooling to a set temperature and also it takes long to response to the altered set temperature due to a high thermal capacity.
In relation to that, along with requirement of fineness of semiconductor wiring, especially a photosensitive resist film is required to be heated in a widely varying temperature range. In order to shorten the heating treatment for every wafer, the thermal capacity of the heat homogenizing plate has to be small and the temperature has to be altered fast. Further, sensitive temperature control is also required from the time of setting the wafer on the heat homogenizing plate to the time of completing the heating treatment. As a heating element formed on a thin ceramic heat homogenizing plate
22
having a high toughness and a high thermal conductivity is proposed to carry out heating.
However, in such a wafer heating apparatus described above, if the thickness of the heat homogenizing plate is made thin, the temperature distribution generated by the heating element is not sufficiently moderated and the temperature of the wafer W takes a long time to become even.
Japanese Patent Application Laid-Open No. 6852 (2001) discloses a method for solving the thickness unevenness caused in the heating pattern printing direction by controlling the sheet receptivity of a heat generating unit to be less than 50 m&OHgr;/□ and making the strands of the patterned heat generating unit have curved parts. It is disclosed that the optimum range of the thickness of the heat generating unit is 1 to 50 &mgr;m and that of the width of the beat generating unit is 0.1 to 20 mm and as evaluation results by a thermoviewer, the temperature dispersion is reported to be improved to the degree of about 0.5° C.
However, the thermoviewer has an temperature measurement error depending on the uneven hue of the surface of an object to be measured and the ambient environments and therefore is impossible to carry out measurement as precisely as required temperature precision. Today, the temperature precision is required to be that measured in the state a wafer is actually mounted. For that, a temperature-measuring wafer, which is a silicon wafer in which sensors such as thermocouples, temperature-measuring resistors and the like are buried tends to be employed as a means for carrying out the measurement. When the heater disclosed in the foregoing Japanese Patent Application Laid-Open No. 6852 (2001) is subjected to measurement while such a temperature-measuring wafer is mounted on the apparatus, it is found difficult to satisfy the temperature dispersion within 0.5° C. Further, it is also found there exist points showing peculiar temperature values in the bent parts and gaps among patterns of the heating element formed for moderating the printing unevenness.
In the case of employing a conventional apparatus, even if heating is possible in a stable and saturated temperature state with even temperature distribution, when a wafer W cooled to a room temperature is mounted on a mounting face of the heating apparatus controlled to be at a prescribed temperature and heated, only the portions where the heat generation capacity is increased for even heating are sometimes heated quickly as compared with other portions to result in uneven temperature distribution during the transition time for heating. Further, only the portions where
Fure Hiroshi
Nagasaki Koichi
Uchiyama Kyoji
Fuqua Shawntina
Hogan & Hartson
Kyocera Corporation
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