Multizone bake/chill thermal cycling module

Details Multizone bake/chill thermal cycling module Multizone bake/chill thermal cycling module

1997-07-31

1998-09-08

Sollecito, John M.

Refrigeration

Using electrical or magnetic effect

Thermoelectric; e.g., peltier effect

62 33, 165206, 118724, 392416, 392418, F25B 2102

Patent

active

058028560

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION

This invention relates generally to devices and methods for providing integrated bake/chill thermal cycling. More particularly, it relates to multizone bake/chill modules for providing controlled thermal cycling of material substrates such as semiconductor wafers and flat panel displays.


BACKGROUND OF THE INVENTION

The photoresist processing stage of manufacturing a semiconductor wafer involves baking the wafer and subsequently chilling it. In order to produce high quality wafers suitable for present integrated circuit applications, the temperature of the wafer during this thermal cycling must be controlled to a high degree of precision in both time and space.
FIG. 1 shows the conventional method for baking and chilling semiconductor wafers. The bake and chill steps are performed by placing a substrate 20, usually a semiconductor wafer, on a hot plate 22 where it is baked at a temperature typically between 70.degree. and 250.degree. C. for a period of time typically between 45 s and 90 s. The wafer is then mechanically moved to a cold plate 24 where it is chilled to a temperature typically between 0.degree. and 30.degree. C.
This conventional method for baking and chilling semiconductor wafers has several disadvantages. First, the movement of the wafer through the air from the hot plate to the cold plate causes the wafer to experience uncontrolled and nonuniform temperature fluctuations. Second, uncontrolled temperature nonuniformities during the bake or chill steps may arise from convection currents or from warping of the substrate. Third, the time required to move the wafer between the plates prevents the realization of very short thermal transition times between the bake and chill steps. Fourth, the mechanical movement of the wafer between the plates may contaminate or otherwise damage the wafer.
U.S. Pat. No. 5,431,700 issued to Sloan on Jul. 11, 1995 discloses an apparatus which attempts to overcome some of these disadvantages. Rather than placing the hot plate beside the cold plate as shown in FIG. 1, the apparatus has a hot plate 26 placed upside down and directly above a cold plate 28, as shown in FIG. 2. Because a wafer 30 needs to move only a short distance from the cold plate directly upward to the hot plate, the apparatus of Sloan reduces the uncontrolled and nonuniform temperature fluctuations during the movement between the bake and chill steps. Nevertheless, because the wafer must be moved between separate bake and chill plates, it still experiences uncontrolled and nonuniform temperature fluctuations between the bake and chill steps. Moreover, the movement of the wafer may still contaminate or otherwise damage the wafer, and prevents the realization of short thermal transition times. Finally, Sloan does not teach any way to reduce temperature nonuniformities during the bake or chill steps.
It should be noted that, in addition to photoresist processing, semiconductor wafer manufacturing also includes other very different wafer heating processes. For example, rapid thermal processing (RTP) typically uses intense radiation to heat the wafer to temperatures over 700 OC to anneal and oxidize the wafer. As in photoresist processing, it is important in RTP to maintain wafer temperature uniformity.
Accordingly, various methods have been developed to control temperature uniformity in RTP, such as providing multiple radiant heating zones for differentially heating the wafer. Such methods are described in U.S. Pat. No. 5,418,885 issued to Hauser et al. on May 23, 1995 and U.S. Pat. No. 5,436,172 issued to Moslehi on Jul. 25, 1995. These methods, however, are not applicable to the problem of maintaining temperature uniformity in photoresist processing where the temperatures are several times lower, the heating is conductive rather than radiative, and the required use of both active cooling and heating involves wafer movement and its associated problems.


OBJECTS AND ADVANTAGES OF THE INVENTION

Accordingly, it is a primary object of the present invention to provide

REFERENCES:
patent: 5343012 (1994-08-01), Hardy et al.
patent: 5567267 (1996-10-01), Kazama et al.
patent: 5602756 (1997-02-01), Atwood et al.

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