Alignment method for multi-level deep x-ray lithography utilizing alignment holes and posts

A method for aligning a mask having radiation blocking material formed thereon in a pattern with a first photoresist layer, comprising the steps of:

• (a) forming first alignment holes in the first photoresist layer;
• (b) placing alignment posts in the first alignment holes such that the alignment posts extend above a surface of the first photoresist layer;
• (c) placing spacer photoresist sheets over the alignment posts, each spacer sheet having a central aperture corresponding in geometry to the alignment posts, such that the alignment posts penetrate into the central apertures in the spacer sheets when the spacer sheets are placed over the alignment posts;
• (d) placing alignment posts in the central apertures of the spacer sheets such that the alignment posts extend above a surface of the spacer sheets;
• (e) attaching a mask photoresist layer to the mask;
• (f) forming mask alignment holes in the mask photoresist layer;
• and
• (g) assembling the mask onto the first photoresist layer by placing the mask alignment holes over the alignment posts extending from the spacer sheets such that the alignment posts penetrate into the mask alignment holes.

A method for fabricating aligned multi-layer microstructures, comprising the steps of:

• (a) exposing a first photoresist layer to radiation through a first mask having radiation blocking material formed thereon in a pattern defining a first layer microstructure pattern and a first alignment hole geometry, thereby making selected portions of the first photoresist layer corresponding to the first layer microstructure pattern and the first alignment hole geometry susceptible to removal by a developer;
• (b) developing the exposed first photoresist layer to form the first layer microstructure pattern and first alignment holes therein;
• (c) applying a second photoresist layer over the first photoresist layer such that the second photoresist layer does not cover the first alignment holes;
• (d) placing alignment posts in the first alignment holes, the alignment posts extending above a surface of the first photoresist layer;
• (e) attaching a mask photoresist layer to a second mask over an alignment structure area of the second mask, the second mask having radiation blocking material formed thereon in a pattern defining a mask alignment hole geometry in the alignment structure area and radiation blocking material formed thereon in a pattern defining a second layer microstructure pattern in a device area of the second mask;
• (f) exposing the mask photoresist layer to radiation through the second mask, thereby making a selected portion of the mask photoresist layer corresponding to the mask alignment hole geometry susceptible to removal by a developer;
• (g) developing the exposed mask photoresist layer to remove the selected portions therefrom to form mask alignment holes therein;
• (h) assembling the second mask onto the first photoresist layer by placing the mask alignment holes over the alignment posts such that the alignment posts penetrate into the mask alignment holes;
• (i) exposing the second photoresist layer to radiation through the second mask, thereby making selected portions of the second photoresist layer corresponding to the second layer microstructure pattern susceptible to removal by a developer;
• and
• (j) developing the second photoresist layer to form the second layer microstructure pattern therein.