Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2001-08-16
2002-08-20
Paschall, Mark (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S405000, C118S724000, C392S416000, C250S492200
Reexamination Certificate
active
06437290
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to heat treatment apparatuses and more particularly to a heat treatment apparatus which performs an anneal process or a chemical vapor deposition (CVD) process by heating an object to be processed, such as a single crystalline substrate or a glass substrate, with a lamp and a quartz window used for such a heat treatment apparatus. The present invention is suitable for a rapid thermal processing (RTP: Rapid Thermal Processing) used for manufacturing semiconductor devices, such as a memory or an integrated circuit (IC). The rapid thermal processing (RTP) includes rapid thermal annealing (RTA), rapid thermal cleaning (RTC), rapid thermal chemical vapor deposition (RTCVD), rapid thermal oxidization (RTO) and rapid thermal nitriding (RTN).
2. Description of Related Art
There is a single wafer heat treatment apparatus as one of semiconductor manufacturing apparatuses, which performs an annealing process or a CVD process by heating a semiconductor wafer (hereinafter simply referred to as a wafer) with a heat radiation lamp.
FIG. 1
shows an example of a conventional heat treatment apparatus. The heat treatment apparatus shown in
FIG. 1
comprises a process chamber
11
, a placement stage
12
on which a wafer W is placed and a heat radiation lamp
14
. The placement stage
12
having a ring-like shape is provided in the process chamber
11
, and is rotatable about the vertical axis thereof.
The heat radiation lamp
14
is arranged so as to opposite to the placement stage
12
with a light-transmitting window
13
formed of a quartz made flat plate. The placement stage
12
supports the peripheral edge of the wafer W from a lower part side. The wafer W is heated at a predetermined temperature while supplying a process gas from a side wall of one side of the process chamber
11
and exhausting from the side wall of another side. It should be noted that a rotation mechanism to rotate the placement stage
12
maintains airtightness of the process chamber
11
by using a magnetic coupling. The rotation mechanism is illustratively shown in FIG.
1
.
The placement stage
12
is formed of a material having a superior heat-resistance so that the placement stage
12
is not transformed at a processing temperature of about 1000° C. SiC (silicon carbide) is used as such a material.
In the above-mentioned heat treatment apparatus, both the placement stage
12
and the wafer W are heated with the heat radiation lamp
14
from an upper part side. When the placement stage
12
is formed by SiC, the temperature rise of the placement stage
12
is slower than that of the wafer W since the heat capacity of SiC is larger than Si (silicone) which forms the wafer W.
For this reason, at the time of heating the wafer W, the temperature of the placement stage
12
is lower than the temperature of the wafer W. Therefore, heat of the circumferential edge of the wafer W transmits to the placement stage
12
, and, thus, the temperature of the circumferential edge of the wafer W becomes lower than the temperature of the central part thereof. Consequently, a temperature distribution is generated in the surface of the wafer W.
On the other hand, heating of the wafer W at a temperature higher than about 800° C. generates a crystal defect referred to as a slip in the wafer W. The slip is easily generated as a temperature difference within the surface of the wafer W increases.
Therefore, in the conventional equipment, the wafer W cannot be heated at a high rate so that a delay in raising the temperature of the placement stage
12
does not become large, that is, the temperature difference within the surface of the wafer W is maintained small. This is one of causes that prevents improvement in a throughput. As for measures to solve the problem, it can be considered to increase an amount of heat radiation on the side of the periphery of the wafer W, such a method is difficult to realize since it is difficult to increase directivity of the heat radiation lamp
14
due to its construction.
Irradiation areas corresponding to a plurality of heat radiation lamps
14
are formed on the wafer W. A distance between the heat radiation lamp
14
and the wafer W cannot be made small from the point such as reservation of a conveyance area. For this reason, the directivity of each heat radiation lamp
14
is bad. Specifically, the directivity of a unit which is formed by combining a single heat radiation lamp and a reflector is bad. That is, a plurality of irradiation areas overlap with each other and the overlapping area between the irradiation areas is large since each above-mentioned irradiation domain spreads.
A plurality of probes of the radiation thermometer (not shown) is arranged at a plurality of positions, respectively, underneath the wafer W. The magnitude of heat dissipation from the wafer W differ from the position at which the probe of the radiation thermometer is arranged to position at which the probe is not arranged. Therefore, in order to heat the wafer W uniformly over the whole surface, it is necessary to adjust the illumination distribution by the light (radiation heat) from the lamp
14
on the wafer W. However, if the above-mentioned overlapping area between the irradiation areas is large, adjustment of an illumination distribution is difficult.
Additionally, in order to manufacture a semiconductor integrated circuit, various kinds of heat treatment, such as a film deposition process, an anneal process, an oxidization diffusion process, a sputtering process, an etching process and a nitriding processing may be repeatedly performed on a silicon wafer a plurality of times to silicone boards. Since yield rate and quality of semiconductor manufacturing processes can be improved, the RTP technology to rise and drop the temperature of the wafer (object to he processed) has attracted attention. A conventional RTP apparatus generally comprises: a single-wafer chamber (process chamber) for accommodating an object to be processed (for example, a semiconductor wafer, a glass substrate for photograph masks, a glass substrate for a liquid-crystal display or a substrate for optical discs); a reflector (reflective board) arranged at the opposite side of the object to be processed with respect to a quartz window arranged in the interior of the process chamber; and a heating lamp (for example, halogen lamp) arranged at an upper part or above the quartz window, and the lamp.
The reflector is made of aluminum, and gold plating is given to a reflective part thereof. A cooling mechanism such as a cooling pipe is provided so as to prevent temperature breakage of the reflector (for example, exfoliation of gold plating due to a high temperature). The cooling mechanism. is provided so as to prevent the reflector from being an obstacle of cooling the object to be processed at the time of cooling. The rapid temperature rising demanded for the RTP technology is dependent on the directivity of the optical irradiation to the object to be processed and the power density of the lamp.
FIG. 2
is an illustration showing an arrangement of a single end lamp and a reflector. As shown in
FIG. 2
, the directivity with respect to the object to be processed arranged underneath the single end lamp
15
having only one electrode part
16
and the energy efficiency of the lamp
15
is maximum when a degree of an angle a of inclination of the reflector
17
relative to the lamp
15
is set to 45 degrees.
The quartz window may be in the shape of a board, or can be in the form of tube which can accommodate the object to be processed. When maintaining a negative pressure environment in the process chamber by evacuating gasses in the process chamber by a vacuum pump, a thickness of the quartz window is set to, for example, about 30 to 40 mm so as to maintain the pressure difference between the internal pressure and the atmospheric pressure. The quartz window may be formed in a curved shape having a reduced thickness so as to prevent generation of a thermal stress
Li Yicheng
Sakuma Takeshi
Shao Shouqian
Shigeoka Takashi
Fuqua Shawntina
Paschall Mark
Pillsbury & Winthrop LLP
Tokyo Electron Limited
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