Phase shift mask, method of correcting the same and apparatus for carrying out the method

A phase shift mask comprising:

• a transparent substrate;
• and
• a phase shifter disposed on said transparent substrate, said phase shifter being formed into a predetermined pattern and acting to shift a phase of exposure light transmitted therethrough by a predetermined magnitude;
• wherein an etching stopper layer which is resistant to an etching to which said phase shifter is subjected and transparent for the exposure light is disposed between said phase shifter and said transparent substrate;
• and
• wherein said etching stopper layer has a thickness corresponding to a magnitude of an optical path for exposure light which is the same as that of the optical path for said exposure light in said phase shifter.

A defect-corrected phase shift mask comprising:

• a transparent substrate;
• and
• a phase shifter disposed on said transparent substrate, said phase shifter being formed into a predetermined pattern and acting to shift a phase of exposure light transmitted therethrough by a predetermined magnitude;
• wherein an etching stopper layer which is resistant to etching to which said phase shifter is subjected and transparent for the exposure light is disposed between said phase shifter and said transparent substrate, said etching stopper layer having a thickness corresponding to a negligible magnitude of an optical path for the exposure light as compared with the magnitude of the optical path for the exposure light in said phase shifter;
• wherein said mask has a hole extending from an upper surface of said phase shifter into said substrate through said etching stopper layer, a depth of the hole corresponding to a magnitude of an optical path of the phase shifter for the exposure light;
• and
• wherein said etching stopper layer is made of a material selected from a group consisting essentially of a metal oxide and a metal halide.

A method of correcting a defect of a phase shift mask, said phase shift mask having a phase shifter disposed on a transparent substrate and an etching stopper layer disposed between said phase shifter and said transparent substrate, said phase shifter being formed into a predetermined pattern and acting to shift a phase of exposure light transmitted therethrough, said etching stopper layer being resistant to an etching to which said phase shifter is subjected and transparent for the exposure light, said method comprising the steps of:

• etching a defective portion of said phase shifter having a lacking-type defect selectively with respect to said etching stopper layer along a whole thickness of said phase shifter;
• and
• perforating a portion of said etching stopper layer and said transparent substrate positioned under said etched defection portion by a depth which corresponds to a magnitude of an optical path of said phase shifter for exposure light;
• wherein said step of etching the defect of said phase shifter is a reactive etching which uses a charged particle beam and a reactive gas and, in said etching step, the bottom surface of a portion etched is flattened by utilizing a fact that said phase shifter is selectively etched.

A method of machining, with a focused ion beam, a phase shift mask having a phase shifter disposed on a transparent substrate, formed into a predetermined pattern and acting to shift a phase of exposure light transmitted therethrough and an etching stopper layer disposed between said phase shifter and said transparent substrate, which is resistant to an etching to which said phase shifter is subjected and transparent for the exposure light, comprising steps of:

• in order to correct a lacking type defect of said phase shifter, making a laser beam incident upon a surface of said mask which is being subjected to perforating with a focused ion beam;
• obtaining an interfered light by allowing a light beam reflected, by said surface to be perforated, of said incident laser beam and a reference laser beam obtained by reflecting said incident laser beam at a reference surface which is different from said surface to be perforated to interfere with each other;
• and
• monitoring a depth of perforation by detecting a change in said interfered light during perforating.

A phase shift mask comprising:

• a transparent substrate;
• and
• a phase shifter disposed on said transparent substrate, said phase shifter being formed into a predetermined pattern and acting to shift a phase of exposure light transmitted therethrough;
• wherein one of said transparent substrate and said phase shifter partially includes a portion the refraction index of which has been changed.