1. Field of the Invention
The present invention relates to a substrate heating device, which heats a substrate such as a semiconductor wafer, a liquid crystal substrate or the like, and a manufacturing method for the same. More specifically, the present invention relates to a substrate heating device with a resistance heating element buried in a ceramic or metallic base plate, and a manufacturing method for the same.
2. Description of the Related Art
A heater with a resistance heating element buried in a ceramic or metallic base plate is widely used as a substrate heating device used for semiconductor manufacturing apparatus or the like. For example, a ceramic heater with a resistance heating element buried in a ceramic base plate made of high corrosion resistance ceramics; wherein the resistance heating element is not externally exposed. Therefore, a chemical vapor deposition (CVD) apparatus or a dry etching apparatus often using a corrosive gas may be used as the substrate heating device.
Furthermore, such a substrate heating device is often structured such that a tubular member is joined to the central undersurface of the ceramic base plate, and resistance heating element terminals and power supply members such as power supply rods connected thereto are housed in the tubular member so as to bring out the resistance heating element terminals without being exposed to a corrosive gas.
The ceramic heater used for semiconductor manufacturing apparatus is used over a wide range of temperatures from room temperature to a high temperature of 500° C. or greater depending on application thereof. Maintaining a uniform substrate temperature is desired for increasing yield of semiconductor products. Therefore, excellent temperature uniformity is desired for a surface on which the substrate is mounted of the substrate heating device, namely the substrate heating surface.
Meanwhile, with the ceramic heater equipped with a tubular member, which is joined to the ceramic base plate, since heat easily escapes from the tubular member through heat transfer, the temperature at the center of the substrate heating surface easily decreases to be lower than peripheral parts, in general.
Therefore, conventionally, adjustment of the helical pitch of the helical resistance heating element buried in the ceramic base plate, and adjustment of the shape and a position of the resistance heating element are performed for temperature uniformity in the substrate heating surface (Japanese Patent No. 2527836). Furthermore, adjustment of the shape and material of the tubular member is performed for temperature uniformity in the substrate heating surface.
However, conventionally, temperature uniformity evaluation of the substrate heating device is performed after the substrate heating device becomes possible to electrically connect and it is completed. Consequently, even if a certain degree of temperature uniformity is achieved with the above-mentioned conventional method of equalizing temperature, temperature variation due to slight differences in manufacturing conditions exists among production lots.
However, nowadays, the desired level of substrate temperature uniformity has risen; accordingly the level of substrate heating surface temperature uniformity has been rising. Correction of slight differences in temperature distribution based on the conventional design adjustments for resistance heating element or tubular member shape is not easy for achieving an extremely high level of temperature uniformity. Moreover, the temperature distribution in the substrate heating surface of the substrate heating device depends on working environment.