Growing system for uniformly growing thin film over...

Details Growing system for uniformly growing thin film over... Growing system for uniformly growing thin film over...

1999-03-29

2001-01-09

Hiteshew, Felisa (Department: 1765)

Single-crystal, oriented-crystal, and epitaxy growth processes;

Apparatus

With means for treating single-crystal

C117S200000, C117S900000

Reexamination Certificate

active

06171396

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a semiconductor fabrication technology and, more particularly, to a growing system for growing a thin film over a semiconductor wafer and a process for fabricating a semiconductor device using the same.
DESCRIPTION OF THE RELATED ART
While a manufacturer is fabricating an integrated circuit on a semiconductor wafer, various kinds of material are sequentially grown on the semiconductor wafer, and the thin layers are patterned into inter-level insulating layers with contact holes and conductive strips for electric signals. One of the technical goals of the thin film growth is uniformity of thickness over the semiconductor wafer.
An atmospheric pressure chemical vapor deposition system is a typical example of the thin film growing apparatus. The atmospheric pressure chemical vapor deposition system has a reactor, and a reaction chamber is formed inside the reactor. A belt conveyer is provided in the reaction chamber, and semiconductor wafers are placed on the belt conveyer. A heater is provided under the belt conveyer, and heats the semiconductor wafers on the belt conveyer. While the semiconductor wafers are passing in the reaction chamber, a gas injection unit injects reactant gases to the semiconductor wafers. The reactant gases react with one another, and material is deposited on the semiconductor wafers.
FIG. 1
illustrates the prior art atmospheric pressure chemical vapor deposition system. A conveyer belt
1
is installed in a reaction chamber
2
, and semiconductor wafers
3
a
/
3
b
are placed on the conveyer belt
1
at intervals. A heater is provided under the conveyer belt
1
, and maintains the semiconductor wafers at a predetermined temperature. Though not shown in
FIG. 1
, a suitable driving mechanism is connected to the conveyer belt
1
, and moves the semiconductor wafers
3
a
/
3
b
in a direction indicated by arrow AR
1
. The conveyer belt
1
is unitary, and the entire surface of the conveyer belt
1
is moved at a constant speed. For this reason, the semiconductor wafers
3
a
/
3
b
are stationary on the conveyer belt
1
.
A gas injection unit
4
is provided over the conveyer belt
1
, and the semiconductor wafers
3
a
/
3
b
passes under the gas injection unit
4
. Reactant gases are injected from the gas injection unit
4
to the semiconductor wafers
3
a
/
3
b
, and the reaction product is grown on the entire surfaces of the semiconductor wafers
3
a
/
3
b.
However, the manufacturer encounters a problem in that the growth rate is not constant over the upper surface of the semiconductor wafer
3
a
/
3
b
. This is because of the fact that the temperature and the growing time are not strictly constant over the semiconductor wafer
3
a
/
3
b
. Although the manufacturer varies the gas injection area and the gas flow rate in the lateral direction of the conveyer belt
1
, the prior art atmospheric pressure chemical vapor deposition system can not achieve a uniform thin film over the semiconductor wafer
3
a
/
3
b.
Japanese Patent Publication of Unexamined Application No. 8-203835 discloses an atmospheric pressure chemical vapor deposition system. The prior art atmospheric pressure chemical vapor deposition system includes a conveyer belt straightforwardly moved along a guide and a reactant gas injecting unit provided over the conveyer belt for injecting reactant gases to semiconductor wafers conveyed by the conveyer belt. The semiconductor wafers are not directly put on the upper surface of the conveyer belt. Plural platens are placed on the conveyer belt, and each platen has turntables and motors for driving the turntables for rotation. The semiconductor wafers are respectively put on the turntables, and are also rotated on the conveyer belt. While the semiconductor wafers are passing through a growth region under the reactant gas injection unit, the motors rotate the turn tables and, accordingly, the semiconductor wafers put thereon, and thin films are grown on the surfaces of the semiconductor wafers, respectively.
The Japanese Patent Publication of Unexamined Application insists that the thin films are constant in thickness due to the rotation. However, the platen is a complicated mechanical unit including the motor and the turntable, and creates undesirable environment around the semiconductor wafers. First, the platens do not permit the heater under the conveyer belt to directly heat the semiconductor wafers. The heater heats the platens, and the platens propagate the heat to the semiconductor wafers. As a result, the temperature on the semiconductor wafers is different, and the chemical reaction is not stable over the semiconductor wafer. Moreover, the platens on the conveyer belt serve as an obstacle against the reactant gas flow. In order to make the growth rate constant, the reactant gas composition is to be stable throughout the reacting zone over the semiconductor wafer. For this reason, the conveyer belt is usually a net of suitable meshes, and the mesh conveyer belt permits the reactant gases to pass. In other words, the mesh conveyer belt makes the reactant gases fresh in the reacting zone. If the platens are placed on the conveyer belt, the reactant gases tend to stagnate in the reacting zone, and the reactant gas composition becomes unstable. Thus, the platens on the conveyer belt disturb the chemical reaction, and it is difficult to uniformly grow the thin films on the semiconductor wafers.
Moreover, the motors and the turntables are heated to a high temperature, and a heat-resistant motor and a turntable made of heat-resistant material are expensive. For this reason, the prior art atmospheric pressure chemical vapor deposition systems are not feasible.
Other related prior arts are disclosed in Japanese Utility Model Application No. 54-50227 and Japanese Patent Publication of Unexamined Application Nos. 57-151523, 3-123025 and 8-162416. Although the present inventor does not think the prior art technologies disclosed therein to be opposed against the present invention, the prior art technologies disclosed therein are described hereinbelow.
Japanese Utility Model Application No. 54-50227 discloses a conveying apparatus used for transferring semiconductor wafers to the next stage. The conveying apparatus disclosed in the Japanese Utility Model Application includes two rubber belts extending in parallel for conveying semiconductor wafers to the next treatment system, and the two rubber belts are independently driven at different speeds. As well known, a semiconductor wafer has a straight edge called as “orientation flat”. A detector monitors the semiconductor wafers on the two rubber belts to see whether the straight edge is oriented to a predetermined direction or not. If the straight edge is not oriented to the predetermined direction, the two rubber belts are moved at different speeds so as to rotate the semiconductor wafer until the predetermined direction. On the other hand, when the straight edge is oriented to the predetermined direction, the two rubber belts are moved at same speed, and the prior art conveying apparatus keeps the attitude of the semiconductor wafer on the two rubber belts.
The prior art conveying apparatus independently changes the moving speeds of the rubber belts, and the rubber belts moved at different speeds give rise to a rotation of the semiconductor wafer. However, the prior art conveying apparatus is available for a transfer from an apparatus to the next apparatus, and the relative moving speed between the rubber belts is changed for the attitude control. In other words, the Japanese Utility Model Application does not teach nor suggests a continuous rotation of all the semiconductor wafer in the reacting zone.
Japanese Patent Publication of Unexamined Application No. 57-151523 discloses a conveying apparatus for disk-shaped members. The prior art conveying apparatus disclosed in the Japanese Patent Publication of Unexamined Application also aims at attitude control for a disk-shaped member. The prior art conveying apparatus includes two straight-forwarded convey

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