Abstract: An apparatus for controlling wafer temperature in a plasma etcher during a plasma-on state and a method for using such apparatus are disclosed. In the apparatus, an additional temperature sensor for sensing the wafer backside temperature and a second flow control valve of a mass flow controller are utilized such that the second flow control valve may be opened to increase the flow of cooling gas through the wafer backside when a temperature rise is detected by the temperature sensor. When the wafer temperature detected is too high, i.e., higher than 65° C., the second flow control valve is opened to increase the flow of helium cooling gas from a nominal rate of 13 sccm by at least 50%. When the temperature of the wafer detected is below 65° C., the flow of the helium cooling gas can be reduced by closing the second flow control valve.

Abstract: Herein is described a method for creating composite images from disparate sets of tomographic images. The images may be derived from CAT, MRI or PET systems. Initially, a "head" is created from one set of tomographic image slices. The head comprises a three dimensional stack of contours created from such slices. A "hat" is created from another set of tomographic image slices with the hat being described by a plurality of points with coordinate positions which define the three dimensional surface of stack of image slices. The hat is then superimposed over the head and subsequently, a determination is made by examination of side and top planar views of the hat and head, of a factor which defines the mean distance of the hat points from the head contours. The hat is subsequently adjusted relative to the head until the mean distance is found to be within minimum limits.