Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2000-01-11
2001-05-08
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S724000, C118S728000, C156S345420
Reexamination Certificate
active
06228174
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a heat treatment system for heating disk-shaped workpieces such as semiconductor wafers, and in particular to a heat treatment system which is suitable for conducting various heat treatments for manufacturing semiconductor devices such as chemical vapor deposition (CVD), impurity diffusion, annealing, and epitaxial growth.
BACKGROUND OF THE INVENTION
Manufacture of semiconductor devices requires various heat treatment steps under controlled environments. Typically, a large number of semiconductor wafers carried by a wafer boat made of heat resistant material such as quartz glass is received in a processing chamber (such as a diffusion chamber and a reaction chamber) defined inside a pressure vessel typically made of heat resistant material such as quartz glass, and process gases are introduced into the processing chamber. A heating arrangement is placed around the processing chamber, and a desired process is conducted in the processing chamber with the semiconductor wafers heated to a desired temperature.
The heating arrangement for such a heat treatment system typically uses a coil-shaped electroresistive heater element, and the heater element is supported by spacers made of alumina or other refractory material. Additionally, insulating material typically consisting of ceramic fibers is filled in the gap defined between the exterior of the heating arrangement and the outer casing surrounding the processing chamber.
However, such a conventional heat treatment system using a electroresistive heater element has a relatively large heat capacity, and it is not possible to rapidly heat or cool the processing chamber. In other words, because of the time lag in heating or cooling the processing chamber, it is difficult to achieve an accurate and responsive temperature control. In particular, because the insulating material prevents rapid cooling, it is not possible to lower the temperature of the processing chamber as rapidly as desired. This is detrimental in reducing the turnaround time of the heat treatment system, and achieving a high quality heat treatment.
Also, according to a conventional heat treatment system using an electroresistive heater element, it is difficult to achieve an even temperature distribution in the processing chamber. This is particularly significant in view of the increasing demand for semiconductor wafers having large diameters. Handing such large semiconductor wafers requires a correspondingly large processing chamber, and an electroresistive heater element is often unable to heat the central part of the processing chamber as much as the peripheral part of the processing chamber.
Furthermore, an electroresistive heater element tends to produce particles during use, and this may seriously contaminate the clean room environment which is required for semiconductor manufacturing processes.
BRIEF SUMMARY OF THE INVENTION
In view of such problems of the prior art, a primary object of the present invention is to provide a heat treatment system which is capable of rapidly heating and cooling the processing chamber.
A second object of the present invention is to provide a heat treatment system which is capable of accurately and responsively controlling the temperature of the processing chamber.
A third object of the present invention is to provide a heat treatment system which has a short turnaround time, and is therefore economical to operate.
A fourth object of the present invention is to provide a heat treatment system which is compact in design and economical to build.
A fifth object of the present invention is to provide a heat treatment system which is relatively free from contamination.
According to the present invention, these and other objects can be accomplished by providing a heat treatment system for heating a disk-shaped workpiece, comprising: an outer casing; an inner shell received in the outer casing and defining an enclosed cylindrical processing chamber therein, the inner shell being made of radiation heat transmitting material and provided with an inlet and an outlet for admitting and removing processing gases into and out of the processing chamber; an enclosed heating chamber defined between the outer casing and the inner shell, the heating chamber being provided with a port for controlling an inner pressure thereof; and a plurality of ring-shaped heater elements disposed concentrically on an inner axial end surface of the outer casing, the heater elements being provided with individual power feed segments.
Because the enclosed heating chamber defined around the processing chamber can be either filled with gases or evacuated, it is possible to achieve a favorable heat insulation which contributes to a high heat efficiency. When the heating chamber is filled with gases or air, it is possible to achieve a controlled rapid cooling of the processing chamber, and this contributes to a short turnaround time of the heat treatment system.
In particular, when the heater elements consists of halogen infrared lamps, the heater elements can be controlled in a highly responsive manner. Because the heater elements can be individually controlled it is possible to control the heat distribution in the processing chamber at will, and can achieve either a uniform temperature distribution or a temperature gradient as desired. Preferably, the heater elements are received in corresponding ring-shaped grooves formed in the inner wall of the outer casing, each groove being provided with a reflective inner surface. Thus, the emitted heat radiation may be directed inward, and the requirement for insulating the outer casing is minimized so that the system can be designed in a both economical and compact manner.
According to a preferred embodiment suitable for treating a large number of semiconductor wafers at the same time, the inner shell comprises a cylindrical container coaxially received inside the outer casing so as to define the processing chamber inside the container and the heating chamber outside the container, and the outer casing comprises a cylindrical part and a pair of end plates, inner surfaces of the cylindrical part and the end plates being provided with the ring-shaped grooves for receiving the heater elements.
When the cylindrical part of the outer casing consists of at least two pieces which are joined by a plane passing through an axial center of the outer casing, the heater elements may be attached to the two casing halves in an alternating fashion so that the power feed segments which do not emit heat may be evenly distributed along the circumference of the casing, and a uniform heating result can be achieved. This arrangement also simplifies the assembling of the casing for the heat treatment system.
In such an arrangement using a cylindrical casing, the inner face of at least one of the end plates may directly face the processing chamber. This end plate is typically adapted to be detachable from the remaining part of the outer housing to permit charging and discharging of workpieces into and out of the processing chamber. If a cover plate made of radiation heat transmitting material is placed over the inner surface of the one end plate so as to define the heating chamber in the grooves of the one end plate, the interior of these grooves may define an auxiliary heating chamber which serves a similar purpose as the heating chamber defined in the cylindrical part of the casing. For the ease of evacuating or pressurizing the auxiliary heating chamber, the grooves may be communicated with each other via communication holes formed in walls separating the adjacent grooves.
According to an embodiment which is suitable for treating a single semiconductor wafer at a time, the outer casing consists of a pair of end plates having inner surfaces provided with ring-shaped grooves for receiving the heater elements, and a cover plate made of radiation heat transmitting material is placed over the inner surface of each of the end plates so as to define the processing chamber between the cover plates, and the heati
Hassanzadeh P.
Marshall & Melhorn LLC
Mills Gregory
LandOfFree
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