Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1999-10-25
2001-06-26
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S390000, C118S724000, C392S416000, C362S296040
Reexamination Certificate
active
06252203
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to heating equipment and methods and more particularly to semiconductor wafer heating systems that use arc lamps for uniform surface heating in device fabrication.
2. Description of Related Art
There exists many prior art examples of processing equipment that use arc lamps to heat semiconductor wafers. For example, U.S. Pat. No. 5,446,825, issued Aug. 29, 1995, to Moslehi, et al., describes a high-performance multi-zone illuminator module (130) for directing light and heat onto a semiconductor wafer (60) in a device fabrication reactor to improve overall semiconductor wafer processing uniformity. A housing connected to the wafer processing reactor has a reflector mounted to the bottom side with a plurality of concentric circular zones (190, 192, 194 or 270, 262, 266, 264) for reflecting heat and light that include a plurality of circularly distributed lamp sockets (185). Within the lamp sockets (185) are point-source lamps (196) for directing light to the semiconductor wafer (60) surface. The point-source lamps (196) have reflectors (184 and 186 or 276 and 277) for directing light toward the wafer. The lamps within each circular zone provide a continuous and diffused light ring at the semiconductor wafer (60). The multiple circular lamp zones and the center zone can be controlled independently to allow real-time wafer temperature uniformity slip-free control for uniform device processing over a wide range of wafer temperatures.
U.S. Pat. 4,755,654, issued Jul. 5, 1988, to Crowley, et. al., describes a semiconductor wafer heating chamber that has an optical element between a light source and a wafer for redistributing the light from the light source. The optical element is constructed in such a manner as to produce the desired illumination (and thus heating) pattern on the semiconductor wafer from the light source. Preferably, the light source is a long-arc lamp mounted above a base plate of a heating chamber. A primary reflector is mounted above the long-arc lamp and is shaped to produce a substantially uniform light distribution on the base plate. A quartz window is mounted between the arc lamp and the base plate. The quartz window acts as a lens to redistribute the light from the lamp and the reflector on a wafer. The window can be constructed as a diffraction grating with a series of lines formed by etching into the window or depositing material on the window to produce a diffraction pattern which gives the desired illumination pattern on the wafer.
Interchangeable quartz windows are used to produce different illumination patterns which are appropriate for different size wafers and different types of heating processes.
U.S. Pat. No. 4,820,906 Apr. 11, 1989 Stultz, describes a long arc gas-discharge lamp for rapidly heating a semiconductor wafer. The spectral output of the lamp is specifically matched to the absorption characteristics of the particular semiconductor wafer being heated by choosing an appropriate gas or mixture of gases. The electrodes of the long arc lamp are separated by a distance greater than the largest dimension of the semiconductor wafer to insure that the entire wafer is illuminated at one time. In addition, the lamp has a high power density to raise the temperature of the semiconductor wafer to the required process temperature. Large diameter metal electrodes are used to conduct more heat from the ends of the lamp. The electrodes contain a low work function metal such as thorium oxide to increase the electron emission. The enclosing glass capillary has thin walls between the electrodes for improved heat dissipation. The glass capillary is cooled to carry the heat way from the lamp.
U.S. Pat. No. 4,630,182, issued Dec. 16, 1986, to Moroi, et. al., describes a system for generating a high-intensity light using a short arc lamp equipped with a cooling device capable of effectively cooling the arc lamp and the reflectors. The system comprises a high intensity lamp. A reflector is provided with a reflecting face that surrounds the lamp and further provided at an end with a window for transmitting the light from the reflecting face and at the other end with an aperture for passing a part of the lamp. A casing houses the reflector and the lamp and provides a ventilating hole to the exterior. An air guide connects the ventilating hole with an air path connecting the light transmitting window of the reflector with the aperture.
U.S. Pat. No. 5,446,824, issued Aug. 29, 1995, also to Moslehi, describes a chuck (82) for lamp-heated thermal and plasma semiconductor wafer (38) processing that comprises a surface (171) for absorbing heat and light from an illuminator module (84) that transforms the electrical energy into heat and light. Chuck (82) includes an absorbing surface (171) that absorbs heat and light and distributes the resultant thermal energy. From the absorbing surface, a contact surface (168) conducts the heat energy to semiconductor wafer (38) and uniformly heats the semiconductor wafer (38) over a large area with the distributed thermal energy. Chuck (82) not only provides significantly improved process temperature uniformity but also allows for the generation of RF plasma for plasma-enhanced fabrication processes as well as for in place chamber cleaning and etching. Additionally, chuck (82) provides at least two methods of determining semiconductor wafer temperature: a direct reading thermocouple (112) and association with the pyrometry sensor of illuminator module (84). The chuck (82) is thermally decoupled from the thermal mass of fabrication reactor (50) for purging optical quartz window (80) surface and semiconductor wafer (38) backside in order to prevent deposition on wafer backside and the quartz window.
U.S. Pat. No. 4,461,670, issued Jul. 24, 1984, to Celler, et. al., describes dielectrically isolated regions of a single crystal silicon that are subjected to a melting process. A substrate with single crystal silicon regions contacting non-single crystal silicon regions that overlie a dielectric material are treated. In particular, the entire region(s) of non-single crystal silicon is melted using primarily radiant energy. Cooling is then initiated and the molten silicon is converted into a region of single crystal material. Isolation is completed by removing the appropriate regions of single crystal silicon
SUMMARY OF THE INVENTION
An object of the present invention is to provide a lamp system for uniform heating of a target.
Another object of the present invention is to provide a method for using diffuse reflectors of relatively delicate materials in association with relatively hot arc lamps.
Briefly, a lamp system of the present invention with a spatially uniform high-intensity output is provided by water cooling a long-arc lamp inside a diffuse reflector of polytetrafluorethylene and titanium dioxide white pigment. The water is kept ultra-clean and pure by a one micron particulate filter, a de-ionizer, and an ultraviolet irradiation system that circulates and biologically sterilizes the coolant water at all times, even when the arc lamp is off.
An advantage of the present invention is that a lamp system is provided for operating at high lamp power levels with diffuse reflectors of polytetrafluorethylene.
Another advantage of the present invention is that a method is provided for constructing and operating a lamp system with a diffuse high intensity output over a large area.
Another advantage of the present invention is its ability to achieve higher temperatures and better temperature uniformity in the illuminated material over a larger area than before possible.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a functional block diagram of an arc lamp system embodiment of the present invention;
FIG. 2
is an axial cross-section of the arc lamp and diffuse reflector pair in the system of
FIG. 1
;
FIG. 3
is a transverse cross-section of the arc lamp and diffuse reflector pair taken along the line
3
—
3
in
FIG. 2
;
FIG. 4
is a computer model for a transve
Hackel Lloyd
Zapata Luis E.
Carnahan L. E.
Fuqua Shawntina T.
The Regents of the University of California
Thompson Alan H.
Walberg Teresa
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