Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-03-22
2001-10-23
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S907000, C438S758000
Reexamination Certificate
active
06306764
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-077169, filed Mar. 23, 1999; and No. 2000-013531, filed Jan. 21, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a batch type heat-treating method of heat-treating a large number of target substrates, e.g., semiconductor wafers, at once as in a vertical furnace or a lateral furnace.
Generally, as a processing apparatus for performing heat treatment, e.g., film deposition, oxidation, diffusion, or the like for a large number of semiconductor wafers at once, a batch type heat-treating apparatus such as a lateral furnace or a vertical furnace is known.
FIG. 11
is a schematic view showing the arrangement of a general batch type heat-treating apparatus. This batch type heat-treating apparatus
2
has a double tube structured process vessel
8
comprising an inner tube
4
and outer tube
6
. A wafer boat
10
is accommodated in a process space S in the inner tube
4
from below. A large number of product wafers W, e.g., about 150 product wafers W, are placed on the wafer boat
10
in a full-loaded state at predetermined pitches, and are subjected to predetermined heat treatment, e.g., CVD (Chemical Vapor Deposition).
Various types of gases such as film deposition gases are introduced into the process vessel
8
from its lower portion, move upward in the process space S in the inner tube
4
while causing reaction, and are then turned downward and move downward through the space between the inner and outer tubes
4
and
6
, to be exhausted to the outside. A heater (not shown) divided into zones is disposed around the process vessel
8
. A process pressure is detected by a pressure sensor P
1
provided at an exhaust port
12
.
The process temperature, pressure, and gas flow rate employed when processing wafers fully loaded on the wafer boat
10
are obtained in accordance with the process purpose in advance. During the process, the process temperature, pressure, gas flow rate, and the like are controlled to match the process conditions. Generally, a plurality of side wafers (which do not become product wafers) for increasing the process reproducibility are placed at the upper and lower sides of the wafer boat
10
. Monitor wafers (which do not become product wafers) for confirming the process result lie scattered in the product wafers.
Recently, various types of semiconductor devices are required, and accordingly various types of wafer-heat treatments for small-lot are sometimes needed. For example, when, e.g., 150 wafers must be processed as product wafers, the wafer boat
10
is fully loaded. Sometimes a smaller number of wafers than that, e.g., 100, 50, or 25 wafers, must be heat-treated.
In these cases, if an empty region where no wafer is set is present in the wafer boat
10
, the wafer temperature and gas concentration may partially fall into disorder. Then, the wafer planar uniformity, surface-to-surface uniformity, and process rate of heat treatment change to decrease the heat-treating reproducibility, which is not preferable. In order to cope with this problem, the wafer boat
10
is fully loaded by using dummy wafers (which do not become product wafers) in number corresponding to the shortage, and heat treatment is performed with the ordinary process conditions for a wafer boat fully loaded with wafers. For example,
170
support grooves are formed in each support pillar
10
A of the wafer boat
10
which can process 150 product wafers in a full-loaded state. Thirteen side wafers and
7
monitor wafers can be set respectively by the support grooves.
After a plurality of times of process operation, the dummy wafers are cleaned and are repeatedly used. Finally, the dummy wafers are discarded. Accordingly, use of dummy wafers increases the running cost.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a batch type heat-treating method in which the running cost is reduced by decreasing the number of dummy substrates to be employed without degrading the quality of the process.
The present inventors have obtained findings that, even if target substrates, e.g., semiconductor wafers, are loaded in number smaller than that in a full-loaded state, the heat-treating reproducibility can be maintained at high level by appropriately elaborating the position to set the product wafers, the position to set the dummy wafers, the process temperature, and the like, and reached the present invention.
According to a first aspect of the present invention, there is provided a heat-treating method of accommodating, in a process vessel, a holder which holds a plurality of target substrates apart from each other, and subjecting the target substrates to heat treatment at once while flowing a process gas in the process vessel in a direction along which the target substrates are arranged, comprising:
setting the target substrates and dummy substrates to be stacked on an upstream side of a flow of the process gas, in the heat treatment, within main holding positions of the holder where the target substrates are to be set, the dummy substrates being set more downstream of the process gas than the target substrates, the target substrates and the dummy substrates being set in the holder in a total number smaller than a total number of the main holding positions corresponding to a maximum number of wafers that can be held by the holder, and thus the holder being in a partially loaded state; and
transferring into the process vessel the holder in the partially loaded state, and subjecting the target substrates to the heat treatment in the process vessel.
According to a second aspect of the present invention, there is provided a processing method in a vertical heat-treating apparatus for subjecting a plurality of target substrates having substantially the same size to heat treatment at once, wherein
the apparatus comprises
a hermetic process vessel for housing the target substrates,
a holder for holding the target substrates in the process vessel to be stacked with gaps thereamong, the holder having at least a (K+M+N)-number of main holding levels for respectively holding the target substrates (K, M, and N are integers of not less than 2),
a supply mechanism having a supply port which opens to the process vessel to supply a process gas into the process vessel,
a heating mechanism for heating an internal atmosphere in the process vessel, and
an exhaust mechanism having an exhaust port which opens to the process vessel to exhaust the process vessel, a process gas from the supply port to the exhaust port flowing in a direction along which the target substrates are arranged,
the method comprising:
setting a K-number of target substrates in the holder, the K-number of target substrates being set at a K-number of main holding levels, among the (K+M+N)-number of main holding levels, that are closest to the supply port in the heat treatment;
setting, in the holder, an M-number of dummy substrates having substantially the same size as that of the target substrates, the M-number of dummy substrates being set at an M-number of main holding levels, among a (M+N)-number of main holding levels at which the K-number of target substrates are not held, that are closest to the supply port in the heat treatment;
transferring into the process vessel the holder in a partially loaded state where a (K+M)-number of main holding levels hold the K-number of target substrates and the M-number of dummy substrates, and an N-number of main holding levels are empty; and
heating the holder in the partially loaded state in the process vessel and subjecting the K-number of target substrates to the heat treatment while flowing the process gas in the process vessel from the supply port toward the exhaust port.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious fro
Kato Hitoshi
Kikuchi Hiroyuki
Sano Takako
Yamamoto Yukio
Everhart Caridad
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokyo Electron Limited
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