System and method for positioning a wafer coated with photoresist and for controlling the displacements of said wafer in a scanning electron apparatus

Claim 1

System for positioning a wafer coated with photoresist and for controlling the displacements of said wafer in a scanning electron beam apparatus such as a scanning electron microscope which has, within its evacuated enclosure and on the path of the electrons, a sample holder comprising a mobile carriage assembly comprising two carriages displaceable respectively in two predetermined directions, one of said directions being perpendicular to the other with micrometric positioning means and a wafer support, said support being placed on the carriage assembly so as to have at least two lateral surfaces approximately parallel to the displacement directions (X,Y) of said carriages of the assembly, characterized in that the wafer support (BS) is linked to the carriage assembly through fine adjustment actuators (CX, CY) placed between said lateral surfaces and a retaining member (23) of the carriage assembly, and in that interferometers are located within the evacuated enclosure (24), said interferometers having mobile and fixed mirrors, the mobile mirrors (AX,AY) being located on said lateral surfaces and the fixed mirrors (5FX1, FX2, FY) being located on a part of the microscope which is rigidly linked to a fixed point in the electron beam, said interferometers being coupled through a transparent window (27) with a set of apparatus (EX1, EX2, EY) capable of counting fringes and of sensing the direction of displacement of said fringes, the count manifested by said set increasing for fringes displacing in one direction and decreasing for fringes displacing in the opposite direction located outside the evacuated enclosure (24).