Patent Application
20060035477
The present invention relates to semiconductor manufacturing and, in particular, to rapid thermal processing.
Rapid thermal processing (RTP) has become widely used in various stages of semiconductor manufacturing. For example, rapid thermal processing is used for the chemical deposition of various films on semiconductor wafers. Rapid thermal processing has also been used in the annealing of ion or dopant implanted semiconductor wafers. Because the operating temperature in rapid thermal processing can be rapidly increased or decreased, the required processing time is short and the efficiency is high.
In many RTP applications the heat treatment often needs to be conducted under specific atmospheric conditions with a specific gas composition flowing through the processing chamber where the wafer is being treated.
Since there typically are some semiconductor device patterns on the surface of the front side of the semiconductor substrate, heat conduction is non-uniform if the patterns are facing the heat source. The non-uniformity results in variation of electrical characteristics. For example, the higher the local OD(active region) density is, the higher the non-salicide sheet resistance is.
As is well known in the art, it is critical that during the rapid thermal processing of a wafer, the entire surface of the wafer is heated uniformly. Non-uniformity in temperature distribution across the wafer surface can result in dislocations and distortion in the wafer. In conventional rapid thermal processing, however, it is often very difficult to achieve temperature uniformity across the wafer surface. As is apparent from
In addition, much effort has been focused on real-time control of the radiation energy emitted from individual lamps to achieve heat uniformity. In one method, an optical pyrometer is used with a wavelength of two to three micrometers (μm), to monitor temperatures at different points on the wafer backside surface. The monitored temperature parameters are then processed by a processor such as a computer to generate a new set of parameters. The power of the individual heating units is then adjusted based on the new parameters to compensate for the temperature differences at different points on the wafer surface to achieve temperature uniformity. In order to achieve temperature uniformity using this method, however, it is important that accurate temperature measurements are obtained by the pyrometer. In practice, the temperature measurements of the pyrometer are often distorted and inaccurate due to the interference from various factors during processing. Examples of such factors include wafer reflectivity, radiation from radiant lamps, radiant energy passing through around the wafer, radiant energy reflected back by the walls of the processing chamber, and heat energy generated by the chemical reaction during the deposition process.
An embodiment of a method for rapid thermal processing of a semiconductor substrate comprises directing the radiant heat energy from a heat source toward a backside surface of the semiconductor substrate. Moreover, a pyrometer can be placed at the front surface of the semiconductor substrate to measure the actual temperature thereof.
An embodiment of a system for rapid thermal processing of a semiconductor substrate comprises a heat source and a reflector. The heat source provides radiant heat energy for rapid thermal processing. The reflector reflects the radiant heat energy and redirects the reflected radiant heat energy to the backside surface of the semiconductor substrate. Furthermore, a pyrometer can be arranged at the front surface of the semiconductor substrate to measure the actual temperature thereof, without being affected by heat source temperature or radiant heat energy emitted from the heat source directly.
Another embodiment of a system for rapid thermal processing of a semiconductor substrate comprises a heat source and a susceptor. The heat source radiates heat energy for rapid thermal processing. The suspetor supports the semiconductor substrate such that the backside surface thereof faces the heat source. In addition, a pyrometer can be arranged at the front surface of the semiconductor substrate to measure the actual temperature thereof, without being affected by heat source temperature or radiant heat energy emitted from the heat source directly.
Another embodiment of provides a method and apparatus for rapid thermal processing. The radiant heat energy from the heat source is directed to the backside surface of the semiconductor substrate and the front surface of the semiconductor substrate is not exposed to the radiant heat energy. As a result, the patterns on the front surface of the semiconductor substrate do not influence heat flux uniformity. Moreover, since the heat source is not arranged at the front surface of the semiconductor substrate, a pyrometer can be placed thereat. An actual temperature of the front surface of the semiconductor substrate can thereby be measured for real-time control of the radiation energy emitted from individual lamps of the heat source to achieve heat uniformity.
Since heat conduction is pattern dependent, if the patterns on the front surface of a semiconductor substrate face a heat source, it is desirable to prevent the patterns from direct heat radiation produced by the heat source.
Methods and systems for rapid thermal processing are provided. In some embodiments of the present invention, radiant heat energy is directed to the backside surface of the semiconductor substrate and the front surface of the semiconductor substrate is not directly exposed to the radiant heat energy. As a result, the patterns on the front surface of the semiconductor substrate may not influence heat flux uniformity. Moreover, since the heat source is not arranged at the front surface of the semiconductor substrate, a pyrometer can be placed there. The actual temperature of the front surface of the semiconductor substrate can be measured and used for real-time control of the radiation energy emitted from individual lamps, for example, to improve heat uniformity.
An embodiment of a system for rapid thermal processing of a semiconductor substrate is depicted in
An embodiment of a system for rapid thermal processing of a semiconductor substrate is depicted in
The repeatability of rapid thermal processing is critical for mass production.
While the invention has been described by way of example and in terms of several embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications.
