Coating apparatus – Gas or vapor deposition
Patent
1996-10-07
2000-02-08
Breneman, Bruce
Coating apparatus
Gas or vapor deposition
118724, 118725, 118729, 427 72, 4272481, 422245, C23C 1646
Patent
active
060224126
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a system for the chemical-vapour deposition (CVD) of semiconductor material on substrates.
Specifically, it relates to an epitaxial reactor for the chemical vapour deposition (CVD) of materials on a substrate and, in particular, on silicon substrates used in the manufacture of semiconductor components such as chips for integrated circuits.
More particularly, the present invention relates to an epitaxial reactor consisting of a small-volume tubular reaction chamber of substantially rectangular cross-section with a cold wall with an external cooler which may be with a flow of liquid coolant. The chamber contains a rotary disc-shaped susceptor which can house more than one substrate and the reaction gases, which are admitted through one or more inlets, flow through the chamber with a flow parallel to the substrates. The susceptor is heated by low-frequency induction (from 3,000 to 20,000 Hz) by means of a substantially flat spiral inductor disposed outside the reaction chamber; the inductor may have electro-mechanical means for individually varying the distance of one or more turns from the susceptor in order to vary the electromagnetic flux linkage of one or more turns of the inductor with the susceptor or, alternatively, may have devices described further below, and the reaction chamber has means deposited on the external walls of the reaction chamber or in any case located externally, for controlling the reflection of the energy radiated by the susceptor, the means being fixed or being movable or orientable by means of electro-mechanical or pneumatic actuators and the external means also possibly being adjustable in order to control their reflection continuously from a minimum value to a maximum value.
The most popular epitaxial reactors are of the batch type, that is, they can process a plurality of substrates simultaneously.
Generally, there are two configurations which are most popular at industrial level, bearing in mind the type of container or reaction chamber and susceptor used: the configuration with a vertical cylinder and a frusto-pyramidal susceptor, or the like, known in the art as the "barrel" configuration and the configuration with a flat disc-shaped susceptor in a suitable chamber, known in the art as the "pancake" configuration.
The systems for heating the susceptors of the aforementioned reactors can also be divided into two types: lamp heating and medium- or high-frequency induction heating.
The barrel system has a frusto-pyramidal susceptor on which the wafers are disposed in substantially vertical positions, the susceptor rotating about its own axis to ensure uniform heating and gas-flow, and the flow of reaction gases being substantially parallel to the surfaces of the wafers to be processed.
The barrel system uses a reaction chamber with small volumes and good performance and may have lamp or induction heating system which, in any case, remains outside the reaction chamber. The limitation of this system is that it is difficult to deposit uniform layers on large-diameter wafers (from 150 mm upwards), particularly as the number of wafers housed on the susceptor increases. This is due to the fact that the container is cylindrical and the cross-section through which the gas flows over the wafer is not uniform, causing a difference in the speed of the gas along the cross-section and a consequent non-uniformity of the layer deposited.
In the conventional "pancake" system, the susceptor consists of a rotary disc on which the wafers are disposed horizontally. The pancake system is characterized by a substantially hemispherical reaction chamber of large volume which is disposed above the susceptor and in which the gas reaches the wafers vertically. This reactor permits the deposition of layers which have good uniformity even on large-diameter wafers but which suffer from worse electrical characteristics because of the large volume of the chamber which requires long clearing times, leading to greater risk of contamination. Moreover, heating by electromagnetic i
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Franco Preti
Vincenzo Ogliari
Vittorio Pozzetti
Breneman Bruce
LPE SPA
Torres Norca L.
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