Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1999-11-30
2001-10-16
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C118S724000, C118S050100, C392S416000, C219S405000
Reexamination Certificate
active
06303906
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to semiconductor manufacturing equipment and, more particularly, to an apparatus and method used for rapid thermal processing of a single semiconductor wafer.
2. Description of Related Art
In the semiconductor industry, to continue to make advancements in the development of semiconductor devices, especially semiconductor devices of decreased dimensions, new processing and manufacturing techniques have been developed. One such processing technique is know as Rapid Thermal Processing (RTP), which reduces the amount of time that a semiconductor device is exposed to high temperatures during processing. The RTP technique, typically includes irradiating the semiconductor device or wafer with sufficient power to quickly raise the temperature of the wafer and hold it at that temperature for a time long enough to successfully perform a fabrication process, but which avoids such problems as unwanted dopant diffusion that would otherwise occur at the high processing temperatures. Generally, RTP uses a light source and reflectors to heat the wafer. In a conventional rapid thermal processor a lamp is used as the light source because of its low thermal mass, which makes it easy to power up and down very quickly.
Unfortunately, conventional lamp-based RTP systems have considerable drawbacks with regard to uniform temperature distribution. Any single variation in the power output from the lamps can adversely affect the temperature distribution across the wafer. Because most lamp-based systems use lamps with filaments, the wafer is usually rotated to ensure that the temperature non-uniformity due to the filament array is not transferred to the wafer during exposure. The moving parts used to rotate the wafer, add to the cost and complexity of the system. Another particularly troublesome area for maintaining uniform temperature distribution is at the outer edges of the wafer. Most conventional RTP systems have no adequate means to adjust for this type of temperature non-uniformity. As a result, transient temperature fluctuations occur which may cause slip dislocations in the wafer at high temperatures (e.g. ~1000° C.).
Conventional lamp-based RTP systems have other drawbacks. For example, there are no adequate means for providing uniform power distribution and temperature uniformity during transient periods, such as when the lamps are powered on and off. Repeatability of performance is also usually a drawback of lamp-based systems, since each lamp tends to perform differently as it ages. Replacing lamps can also be costly and time consuming, especially when one considers that a given lamp system may have upwards of 180 lamps. The power requirement of the system may also be costly, since the lamps may have a peak power consumption of about 250 kWatts.
For the above reasons, what is needed is an apparatus and method for isothermally distributing a temperature across the surface of a semiconductor device during rapid thermal processing.
SUMMARY OF THE INVENTION
The present invention provides a heating apparatus and method for isothermally distributing a temperature across the surface of a semiconductor device or wafer during processing. The invention provides a potentially slip-free RTP process. In one embodiment, a chamber is provided defining a cavity, which is configured to receive a single semiconductor wafer. As described in greater detail below, a plurality of resistive heating elements are provided and advantageously arranged in the cavity. Preferably, the heating elements are disposed across the chamber and are aligned in close proximity to one another so as to provide an even heating temperature distribution. Advantageously, the resistive heating elements may be positioned above and below the wafer to provide dual-sided heating.
Preferably, in accordance with the present invention, the cavity is divided into heating zones. The resistive heating elements are each individually assigned to a zone and are independently controllable. By individually varying the amount of energy emanating from each resistive heating element, a substantially isothermal temperature distribution may be generated across each zone.
Unlike lamps in a lamp-based RTP system, the resistive heating elements do not require the use of reflectors to evenly distribute the thermal energy. Additionally, the resistive heating elements may be configured into various patterns (e.g. circular, zigzag, and cross-hatched patterns), which may be configured to provide an optimal temperature distribution and reduce the possibility of temperature fluctuations across the surface of the wafer. Advantageously, the heating elements may be covered with a heat diffusing material, which provides uniform temperature dissipation of the heat energy provided by the resistive heating elements.
The present invention overcomes the disadvantages of a lamp-based heating system since the system can provide a more uniform temperature distribution, for less power (e.g. about 5 kWatts) and reduced cost. Fortunately, in the present invention rapid thermal processing can be a potentially slip-free processing technique for a wide range of temperatures and time domains, particularly near the wafer edge.
No moving parts, such as lift pins or wafer spinners, are required within the cavity to load the wafer, nor are other complex and costly components required, such as reflectors, actuators, and complex power transformers and controllers. Since the invention does not require large lamps for heating nor moving parts, the size of the chamber, as well as the volume of the cavity, may be substantially reduced relative to other chambers. The reduced volume and size are of particular advantage for reasons that are made apparent below.
In one aspect of the present invention, an apparatus is provided for rapidly and uniformly heating a wafer during processing. The apparatus includes a process chamber, which defines a cavity configured to receive a wafer. The cavity further defines a plurality of heating zones. The apparatus also includes a plurality of resistive heating elements positioned proximate to the process chamber. Each of the plurality of resistive heating elements may be apportioned to one of the plurality of heating zones. A thermal energy output from each of the resistive heating elements may be capable of heating each of the zones to create a substantially isothermal environment throughout the cavity.
In another aspect of the present invention, a reactor is provided for rapidly and uniformly heating a semiconductor wafer. The reactor includes a chamber, which defines a cavity, which further defines a plurality of heating zones. A plurality of resistive heating elements may be positioned proximate to the chamber, and a portion of the heating elements may be apportioned to each one of the plurality of heating zones. The thermal energy output of each of the resistive heating elements heats the zones to provide a substantially isothermal temperature across each of the zones.
In yet another aspect of the invention, a method is provided for rapidly and uniformly heating a semiconductor wafer. The method includes apportioning a plurality of resistive heating to a heating zone; and creating a thermal output from each of the plurality of resistive heating elements to change the temperature of at least one of the heating zones in response to temperature fluctuations to provide a substantially isothermal environment over the surface of the semiconductor wafer.
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Fuqua Shawntina S.
Skjerven Morrill & MacPherson LLP
WaferMasters Inc.
Walberg Teresa
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