Semiconductor device manufacturing: process – Radiation or energy treatment modifying properties of...
Reexamination Certificate
2003-03-12
2004-08-24
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Radiation or energy treatment modifying properties of...
C438S758000
Reexamination Certificate
active
06780795
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a heat treatment method and apparatus and, more particularly, to a heat treatment method and apparatus for applying a heat treatment to various substrates such as, for example, a semiconductor wafer or a glass substrate for liquid crystal displays.
2. Description of the Related Art
There are various types of heat treatment apparatuses for performing an annealing process, which is one of semiconductor manufacturing processes. For example, a heat treatment apparatus of a single-wafer type such as shown in
FIG. 1
is used as an apparatus used for, among annealing processes, a process for activating ions implanted in a polysilicon layer on a substrate surface. In
FIG. 1
, provided inside a heating furnace
1
is a reaction container
11
, which is made from quartz and forms a processing atmosphere therein. A substrate placement part
12
, which supports horizontally a semiconductor wafer (hereinafter referred to as a wafer) W as an object to be processed, is provided in the reaction container
11
. An opening part
13
is formed on one side of the reaction container
11
of the heating furnace
1
for carrying in and out the wafer W, and a purge-gas supply pipe
14
, which is connected to an interior of the reaction container
11
, is provided on another side by being extended through the side wall of the heating furnace
1
.
Additionally, heaters
15
(indicated by single-dashed chain lines) are provided to a ceiling part, a bottom part and side walls of the heating furnace
1
so as to surround the wafer W. A uniform-heating plate
16
is provided between the reaction container
11
and each of the heaters
15
. The uniform-heating plate
16
is formed of a material such as silicon carbide (SiC) having a large heat capacity so as to diffuse heat generated by the heaters
15
and uniformly heat the entire substrate. A thermocouple
17
is provided outside the uniform-heating plate
16
so as to detect a temperature in the vicinity of the heaters
15
. A value of a temperature detected by the thermocouple
17
is supplied to a control part
18
so as to adjust an amount of electric power supplied to the heaters
15
so that a surface temperature of the wafer W is maintained at a setting temperature. According to such a temperature control system, there is an advantage that a temperature control is easy.
However, in the heat treatment apparatus having the above-mentioned structure, when consecutively repeated operations are performed to carry wafers into the heating furnace
1
so as to process the wafers W and carry out the wafers W one after another, there is a problem in that the temperature inside the furnace at the time of processing the second sheet of wafers W becomes lower than the temperature at the time of processing the first sheet of wafers W. That is, although the cold wafer W carried into the reaction container
11
may reduce the temperature of the processing atmosphere inside the heating furnace
1
, the temperature of the uniform-heating plate
16
hardly decreases due to its large heat capacity. For this reason, there is a delay in the detection of the temperature inside the reaction container
11
by the thermocouple
17
, which is provided outside the uniform-heating plate
16
, which results in that the temperature of the processing atmosphere cannot return to the setting temperature. Moreover, similarly in a heat treatment apparatus that does not have the uniform-heating plate
16
, when a heat capacity of the reaction container is large, there is a delay in the detection of a temperature drop.
That is, the temperature inside the furnace cannot return to a predetermined process temperature since a response with respect to an external disturbance due to carry-in of wafers at an initial stage such as the time of carrying-in the first or second sheet of wafers. Moreover, since an increase in the wafer size has been progressed in recent years, the degree of cooling down inside the reaction container
11
becomes large at the time of carrying-in of the wafers. For the above-mentioned reasons, the temperature drop tends to be increased.
Specifically, in the example shown in
FIG. 6
(a process temperature of 600° C., a process time of 60 seconds, a carry-in and carry-out time of 120 seconds), the temperature of the processing atmosphere gradually decreases from the time of processing the first wafer to the time of processing the fifth wafer, and, thereafter, the temperature stays at a temperature lower than the process temperature by 25 degrees. The range of drop of the processing temperature seen from the process temperature tends to increase as a process time A
1
(time interval) per one sheet of wafers shown in the figure is reduced. If the time interval is shorter than that in the case of
FIG. 6
, and is set to, for example, 60 seconds, the range of temperature drop may become quite remarkable.
Moreover, there is a baking process being performed using a heating plate as measures for solving the problem due to the cold wafers at the time of heat-treating the wafers. When performing such a baking process, a heater provided in the heating plate is driven at a maximum power each time an individual wafer is placed on the heating plate, and, then, switched to an automatic temperature control state. It is known that a time period of driving the heater at the maximum power is set to a time period which is sufficient for supplying an amount of heat corresponding to an amount of heat generated by the heating plate and absorbed by the wafers. Japanese Laid-Open Patent Application No. 11-74187 discloses such a technique. Similar to a baking process for a resist film by a heating plate (hot plate), in a case where a supply of heat to wafers sensitively responds to an electric power supply to the heater, a heat treatment can be uniformly applied to each wafer. However, when a member having a large heat capacity such as a reaction container or a uniform-heating plate is interposed between the heater and the wafer, the process temperature after the process of the second sheet of wafers cannot be always equal to the process temperature at the time of processing the first sheet of wafers. Accordingly, a uniform process cannot be applied to each wafer.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful heat treatment method and apparatus in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a heat treatment method which can reduce a temperature drop when a plurality of objects to be processed are consecutively processed one after another so as to improve uniformity of process quality between the objects.
In order to achieve the above-mentioned objects, there is provided according to another aspect of the present invention a heat treatment method for continuously applying a heat treatment to a plurality of objects to be processed that are sequentially supplied to a reaction container, the heat treatment method using a heat treatment apparatus which heats the objects placed inside the reaction container by a heater provided outside the reaction container, the heat treatment method comprising the steps of: obtaining an offset temperature value which is a difference between a temperature of a processing atmosphere at a time immediately before a first one of the objects is carried into the reaction container and a temperature of the processing atmosphere at a time the temperature has become constant after the objects are subjected to a heat treatment process consecutively one after another; supplying an electric power to the heater so as to obtain a time period necessary for raising the temperature of the processing atmosphere to a temperature higher than a setting temperature for the heat treatment process by the offset temperature value; and supplying the electric power to the heater for only the time period obtained in the preceding step when the first one of the obje
Suzuki Fujio
Wakai Hideki
Lattin Christopher
Niebling John F.
Tokyo Electron Limited
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