A narrowly defined range of 
zinc silicate glass compositions is found to produce 
High Energy Beam Sensitive-glass (HEBS-glass) that possesses the essential properties of a true 
gray level mask which is necessary for the fabrication of general three dimensional microstructures with one optical 
exposure in a conventional photolithographic process. The essential properties are (1) A 
mask pattern or image is grainiless even when observed under 
optical microscope at 1000× or at higher magnifications. (2) The HEBS-glass is insensitive and / or 
inert to photons in the spectral ranges employed in photolithographic processes, and is also insensitive and / or 
inert to 
visible spectral range of light so that a HEBS-glass 
mask blank and a HEBS-glass mask are permanently stable under room lighting conditions. (3) The HEBS-glass is sufficiently sensitive to 
electron beam 
exposure, so that the cost of making a mask using an e-beam writer is affordable for at least certain applications. (4) The e-beam induced 
optical density is a unique function of, and is a very reproducible function of 
electron dosages for one or more combinations of the parameters of an e-beam writer. The parameters of e-beam writers include beam 
acceleration voltage, beam current, beam spot size, addressing 
grid size and number of retraces. A method of fabricating three-dimensional microstructures using HEBS-glass gray scale 
photomask for three dimensional profiling of 
photoresist and reproducing the 
photoresist replica in the substrate with the existing 
microfabrication methods normally used for the production of 
microelectronics is described.