Fine-grained polysilicon films with built-in tensile strain

Techniques in Residual Stress Measurement for MEMS and Their Applications

“…One of the most well-known residual stress characterization structures is the buckling type specimens such as fixed-fixed beams and the so-called Guckel's rings [121], [122]. These structures will buckle once the internal residual stresses exceeding their corresponding specific critical value.…”

Integrated MEMS: Opportunities & Challenges

“…There are many possible combinations of sacrificial and mechanical layers and a few examples are given in Table 5. It is important with deposited layers to have good stress control, preferably low tensile stress with little or no stress profile (Guckel, 1988, French 1996, Pakula, 2001. A further important issue when fabricating surface micromachined structures is the release while avoiding stiction.…”

Bulk-micromachined mass airflow sensor fabrication and testing methodology for an undergraduate microfabrication course.

“…In the top photo, tight cross members and deformed rings indicate large compressive residual strain. In the bottom photo, buckled center beams and deformed rings for critical geometries and larger reveal a high tensile strain field in the film [60].…”

“…As shown in Figure 47, residual tensile strain fields in a thin film layer can be measured by a series of rings with changing radii constrained to the substrate at two points on a diameter and spanned orthogonally by a clamped-clamped beam [45,56,59,60,61]. Once suspended from the substrate so that the structure is supported at the ends of two supporting members, a ring that is clamped rigidly only at two points along a diameter will contract significantly (as the thin film relaxes to relieve residual tensile stress) along a spanning beam diameter that is perpendicular to the support diameter, if the thin-film ring material is under tensile strain.…”

“…(Blank wafers) 60 Progressive depth cuts for round specimens, wi th alignment required for each pass.…”