Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1998-09-09
2001-04-03
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C219S390000
Reexamination Certificate
active
06210484
ABSTRACT:
FIELD OF THE INVENTION
The present invention is generally directed to thermal processing chambers for heating semiconductor wafers using radiant energy. More particularly, the present invention is directed to improved heating lamp configurations for use in thermal processing chambers.
BACKGROUND OF THE INVENTION
A thermal processing chamber as used herein refers to a device that rapidly heats objects, such as semiconductor wafers. Such devices typically include a substrate holder for holding a semiconductor wafer and a source that emits light and heat energy for heating the wafer. During heat treatment, the semiconductor wafers are heated under controlled conditions according to a preset temperature regime. For monitoring the temperature of the semiconductor wafer during heat treatment, thermal processing chambers also typically include temperature sensing devices, such as pyrometers, that sense the radiation being emitted by the semiconductor wafer at a selected band of wavelengths. By sensing the thermal radiation being emitted by the wafer, the temperature of the wafer can be calculated with reasonable accuracy.
In alternative embodiments, instead of or in addition to using radiation sensing devices, thermal processing chambers can also contain thermocouples for monitoring the temperature of the wafers. Thermocouples measure the temperature of objects by direct contact.
Many semiconductor heating processes require a wafer to be heated to high temperatures so that various chemical and physical reactions can take place as the wafer is fabricated into a device. During rapid thermal processing, which is one type of processing, semiconductor wafers are typically heated by an array of lamps to temperatures, for instance, from about 400° C. to about 1,200° C., for times which are typically less than a few minutes. During these processes, one main goal is to heat the wafers as uniformly as possible.
Problems have been experienced in the past, however, in being able to maintain a constant temperature throughout the wafer and in being able to control the rate at which the wafer is heated. If the wafer is heated nonuniformly, various unwanted stresses can develop in the wafer. Not being able to heat the wafers uniformly also limits the ability to uniformly deposit films on the wafers, to uniformly etch the wafers, beside limiting the ability to perform various other chemical and physical processes on the wafers.
Temperature gradients can be created within the wafer due to various factors. For instance, due to the increased surface area to volume ratio, the edges of semiconductor wafers tend to have a cooling rate and a heating rate that are different than the center of the wafer. The energy absorption characteristics of wafers can also vary from location to location. Additionally, when gases are circulated in the chamber, the gases can create cooler areas on the wafer due to convection.
In the past, various lamp configurations have been proposed in order to overcome the above described deficiencies and improve the ability to heat wafers more uniformly and to control the temperature of the wafers at various locations. These systems, however, have become increasingly complex and expensive to produce. For instance, some systems can contain well over 100 lamps.
In view of the above, a need currently exists for an improved thermal processing chamber that is capable of uniformly heating semiconductor wafers. A need also exists for a thermal processing chamber containing an improved lamp heater configuration. Further, a need exists for an improved rapid thermal processing chamber for heating semiconductor wafers that is equipped with controls for varying the amount of energy that is applied to the wafer at different locations based upon the characteristics and properties of the wafer. Such controls are especially necessary due to the increasing demands that are being placed upon the preciseness at which the semiconductor wafers are heat treated and at which semiconductor devices are fabricated.
SUMMARY OF THE INVENTION
The present invention recognizes and addresses the foregoing disadvantages and others of prior art constructions and methods.
Accordingly, it is an object of the present invention to provide an improved thermal processing chamber for heat treating semiconductor wafers.
Another object of the present invention is to provide a thermal processing chamber having an improved lamp configuration for heating the wafers uniformly.
Still another object of the present invention is to provide a heating device for use in thermal processing chambers that contains a plurality of lamps which form overlapping heating zones on a wafer being heated.
Another object of the present invention is to provide a heating device for use in thermal processing chambers that contains at least one multi-lamp cone.
Still another object of the present invention is to provide a heating device for use in thermal processing chambers that contains a plurality of lamps surrounded by a conically-shaped reflector, wherein at least some of the lamps are tilted with respect to a semiconductor wafer being heated.
These and other objects of the present invention are achieved by providing an apparatus for heat treating semiconductor wafers. The apparatus includes a thermal processing chamber adapted to contain a semiconductor wafer. For instance, a substrate holder can be contained within the chamber upon which the wafer is held. A heating device is placed in communication with the thermal processing chamber which emits thermal light energy onto the wafer held on the substrate holder. The heating device can include an assembly of light energy sources which are positioned to preferentially heat different zones of the wafer.
During the heating process, either the semiconductor wafer is rotated or the light energy sources are rotated. In this manner, the light energy sources form radial heating zones on the wafer. In accordance with the present invention, the light energy sources are positioned so that most of the light energy sources are located at different radial locations with respect to one another. As such, many different radial heating zones are formed on the wafer which aid in heating the wafer uniformly and provide good temporal control during the heating cycle.
In accordance with the present invention, the heating device includes at least one heating cone having an axis that is perpendicular to a semiconductor wafer contained in the thermal processing chamber. The heating cone is designed to control the amount of electromagnetic energy being emitted by a group of lamps in a manner that more uniformly heats a semiconductor wafer. The heating cone includes a plurality of light energy sources positioned within a circular reflector. For instance, in one preferred embodiment, the circular reflector is conically-shaped such that the reflector gradually increases or decreases in diameter in a direction towards the semiconductor wafer.
In one embodiment, the light energy sources contained within the conically-shaped reflector are arranged in a circular configuration. In most applications, it is better not to place a light energy source directly in the center of the conically-shaped reflector. Typically, at least six light energy sources are placed within the reflector. The light energy sources can be substantially vertically oriented or tilted with respect to the axis of the heating cone. For example, in one embodiment, some of the lamps can be vertically oriented while some of the lamps can be tilted towards the axis. In particular, some of the lamps can be tilted up to about 20 degrees with respect to the axis, and particularly in an amount from about 6 degrees to about 12 degrees.
Besides light energy sources, the heating cone of the present invention can further include a reflective top that encloses the conically-shaped reflector. The reflective top can be flat or can be dome shaped or can be cone shaped. Preferably, both the reflective top and the conically-shaped reflector are made from highly reflective materials. F
Dority & Manning P.A.
Hassonzadeh P.
Mills Gregory
Steag RTP Systems, Inc.
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