Electrostatic wafer chuck, and charged-particle-beam microlithography apparatus and methods comprising same

A charged-particle-beam (CPB) microlithography apparatus, comprising:

• an illumination-optical system situated and configured to direct an illumination charged particle beam to a pattern-defining reticle so as to illuminate a region of the pattern on the reticle;
• a projection-optical system situated and configured to direct an imaging beam, generated by passage of the illumination beam through the illuminated region of the reticle, from the reticle to a sensitive substrate;
• an electrostatic wafer chuck situated to hold the sensitive substrate as the sensitive substrate is being exposed with the pattern by the imaging beam, the wafer chuck comprising (a) a base plate including a first region and a second region, the first region including a central region and a peripheral segment region, and the second region including a general peripheral region that, in combination with the peripheral segment region, surrounds the central region;
• (b) an insulating layer overlying the base plate and defining a wafer-mounting surface of the chuck;
• and (c) first and second electrode sets situated between the base plate and insulating layer, the first electrode set being located in the first region so as to occupy the central region and peripheral segment region, and the second electrode set being located in the second region so as to occupy the general peripheral region;
• and
• a power supply connected to the first and second electrode sets, the power supply being configured, at start of energizing the chuck to electrostatically hold a substrate to the wafer-mounting surface, to electrically energize the first electrode set before energizing the second electrode set.

In a method for performing charged-particle-beam microlithography of a pattern, defined by a reticle, onto sensitive substrate, a method for holding the substrate, comprising:

• providing an electrostatic wafer chuck including (a) a base plate including a first region and a second region, the first region including a central region and a peripheral segment region, and the second region including a general peripheral region that, in combination with the peripheral segment region, surrounds the central region;
• (b) an insulating layer overlying the base plate and defining a wafer-mounting surface of the chuck;
• and (c) first and second electrode sets situated between the base plate and insulating layer, the first electrode set being located in the first region so as to occupy the central region and peripheral segment region, and the second electrode set being located in the second region so as to occupy the general peripheral region;
• and
• when initiating attachment of the substrate to the wafer chuck, energizing the first electrode set before energizing the second electrode set, then continuing to energize both electrode sets to hold the substrate on the wafer-mounting surface.