Method of avoiding wall particle contamination in depositing...

Details Method of avoiding wall particle contamination in depositing... Method of avoiding wall particle contamination in depositing...

1998-11-24

2001-03-27

Lund, Jeffrie R. (Department: 1763)

Cleaning and liquid contact with solids

Processes

Including application of electrical radiant or wave energy...

C438S905000, C427S569000

Reexamination Certificate

active

06206012

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a Film Deposition apparatus and, more particularly, to a Film Deposition apparatus of a type utilizing the metal organic chemical vapor deposition (MOCVD) technique.
2. Description of the Prior Art
The Film Deposition apparatus of the kind referred to above, that is, the MOCVD-based Film Deposition apparatus is largely employed in the production of semiconductor lasers that can be utilized as a light source for an optical communication system and various information processing devices. With this MOCVD-based Film Deposition apparatus, a semiconductor film of a uniform thickness and a uniform composition can be formed substantially uniformly over a relatively large surface substrate by the thermal decomposition of gaseous materials which leads to crystal growth on the substrate.
The prior art MOCVD-based Film Deposition apparatus will now be discussed with particular reference to
FIGS. 5 and 6
. The prior art Film Deposition apparatus, generally identified by
30
, comprises a chamber-defining structure
2
c
having a reaction chamber defined therein, a gas introducing unit
3
and a preparatory chamber
10
. To form a semiconductor film on a semiconductor wafer within the MOCVD-based Film Deposition apparatus
30
, a wafer carrier having at least one semiconductor wafer mounted thereon is placed inside the preparatory chamber
10
which is subsequently evacuated to a substantial vacuum. A gate
9
is thereafter opened to load the wafer carrier
5
into the reaction chamber so as to rest on a substrate susceptor
4
within the reaction chamber.
After the placement of the wafer carrier
5
on the substrate susceptor
4
within the reaction chamber, the wafer on the wafer carrier
5
is heated to a predetermined temperature by means of a wafer heater
8
while the temperature thereof is monitored by a thermocouple
6
, and gaseous raw material is then introduced into the reaction chamber through the gas introducing unit
3
to effect a thermal decomposition of the raw material within the reaction chamber. By this thermal decomposition, the crystal growth is initiated to eventually form a semiconductor film on one surface of the wafer.
Specifically, when an InP film is desired to be on the semiconductor wafer, the wafer within the reaction chamber of the chamber-defining structure
2
c
is heated to a temperature generally within the range of 600 to 700° C. and a mixture of phosphine (PH
3
) and trimethyindium (TMI) ((CH
3
)
3
In) as the gaseous raw material is introduced into the reaction chamber.
At this time, by the effect of heat from the heater
8
, the wall of the chamber-defining structure
2
c
that defines the reaction chamber, as measured at an outer wall surface thereof by means of a thermocouple
13
, is also heated to a temperature of about 350° C. and, therefore, a wall film
11
resulting from the thermal decomposition of the gaseous raw material tends to be deposited on an inner wall surface of the chamber-defining structure
2
c.
After the formation of the desired semiconductor film on the wafer, the wafer heater
8
is deenergized to allow the temperature of the wafer to be lowered, followed by movement of the wafer carrier
5
from the reaction chamber into the preparatory chamber
10
, thereby completing a cycle of Film Deposition. Deenergization of the wafer heater
8
is accompanied by lowering of the temperature at the wall of the chamber-defining structure
2
c
and, at the time the wafer carrier
5
is unloaded from the reaction chamber, the temperature at the wall of the chamber-defining structure generally attains about 40° C.
By repeating the Film Deposition cycle described above a number of times, films can be successively formed on a plurality of semiconductor wafers.
The above discussed prior art Film Deposition apparatus has a problem. Specifically, successive formation of the films on the plural wafers accompanying cyclic energization and deenergization of the wafer heater
8
causes the wall of the chamber-defining structure
2
c
to experience a thermal hysteresis of from 40° C. to 350° C. and then from 350° C. down to 40° C. When the wall temperature of the chamber-defining structure
2
c
(the temperature measured at the outer wall surface of the chamber-defining structure
2
c
) is about 40° C., that is, when the wafer carrier
5
carrying the semiconductor wafer is to be loaded into or unloaded from the reaction chamber, the wall film sticking to the inner wall surface is prone to peel off under the influence of the difference in coefficients of thermal expansion of the wall film
11
and the material forming the chamber-defining structure
2
c.
The wall film peeling off from the inner wall surface of the chamber-defining structure
2
c
is generally in the form of particles which, when falling onto the wafer, will disturb the crystal growth, eventually resulting in a reduction in yield of the film-deposited wafers.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been devised to eliminate the above discussed problem substantially and is intended to provide an improved Film Deposition apparatus which makes use of means for reducing the obnoxious particles which tend to show up at the time the wafer is loaded into or unloaded from the work chamber in the chamber-defining structure.
In order to accomplish this object, the present invention provides a Film Deposition apparatus which includes a chamber-defining structure having a reaction chamber defined therein, a substrate heater accommodated within the reaction chamber for heating a substrate to form a film on one surface of the substrate, and a temperature control means operable when the substrate heater is deenergized, to retain a wall of the chamber-defining structure at a temperature equal to or higher than a predetermined temperature to avoid peel-off of wall film deposited on an inner wall surface of the chamber-defining structure.
The predetermined temperature referred to above is preferably 80° C. and, more preferably within the range of 80 to 300° C.
According to the present invention, by maintaining the wall of the chamber-defining structure at the specific temperature, that is, a temperature equal to or higher than the predetermined temperature, the particle count, that is, the number of particles of the wall film peeled off from the inner wall surface of the chamber-defining structure can advantageously be reduced. This in turn brings about an additional advantage in that the cleaning cycle of the chamber-defining structure to clean off the wall film sticking to the inner wall surface of the chamber-defining structure can be shortened.
Preferably, the temperature control means may be conveniently employed in the form of an electric wire heater externally mounted around the wall of the chamber-defining structure to thereby increase the workability of the apparatus.
If desired, the chamber-defining structure may be made of quartz and may include a fluid jacket formed in the wall of the chamber-defining structure. The fluid jacket contains a fluid medium having a boiling point higher than the predetermined temperature, and in this case, the temperature control means may comprise a fluid circulating means for circulating the fluid medium within the fluid jacket.
The fluid circulating means referred to above may include a fluid temperature control means for controlling the temperature of the homoiothermic fluid medium.
Where the chamber-defining structure is made of quartz, the temperature control means is preferably positioned so as to cover a portion of the wall of the chamber-defining structure that is encompassed by a space between a support member for supporting the substrate within the reaction chamber and a gas introducing unit fluid-coupled with the reaction chamber.
In any event, the present invention is effective not only to reduce the particle count, but also to increase the workability of the Film Deposition apparatus to thereby increase the yield of the film-d

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