An ultrahigh vacuum compatible planar corrugated millimeter mm‐waveguide structure (410‐μm‐deep) possessing bi‐fold symmetry and a precision beam aperture (800 μm) has been fabricated using silicon processing technology, modeled with numerical analysis software, geometrically characterized, and compared to a similar waveguide fabricated using deep x‐ray lithography (DXL) techniques. The waveguide was fabricated to operate at 60 GHz (λ=5 mm) with fields suitable for 2π/3 phase advance operation. Multichip alignment technology was used to provide a semiclosed conducting surface with aperture‐coupled periodic resonator cavities. A pair of Si/Pyrex composite metallized substrates patterned with corrugated geometries have been vertically stacked with 980‐μm‐diam Pyrex capillaries. Geometrical analysis of the muffin‐tin waveguide was divided into two classifications: substrate feature error and die‐to‐die orientation error. Both types of error were characterized with the following results: feature accuracy was maintained to 0.1%–1.0% tolerances in all directions (5 μm or less in most cases) and die‐to‐die aperture distance agreed to within ∼3% of theoretical calculation. Methods of improving these geometrical tolerances are suggested and critical issues are addressed. Electromagnetic testing of the mm waveguide has been investigated and a bead was fabricated for use in a bead‐pull perturbation measurement of acceleration properties. The concluding section compares deep‐etch silicon and DXL approaches for the fabrication of the ‘‘micro‐linac.’’ It is concluded that through further refinement of thermal and conductive properties that the silicon waveguide is a viable method of constructing a micro‐linac mm waveguide, requiring less fabrication complexity, processing time, and capital equipment investment than DXL.