Residual strain effects on large aspect ratio micro-diaphragms

Technical Report · Fri Sep 30 00:00:00 EDT 1988

DOI:https://doi.org/10.2172/5367418· OSTI ID:5367418

Hijab, R. S.; Muller, R. S. ^[1]

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1. California Univ., Berkeley, CA (USA)

Highly compliant, large aspect ratio diaphragms for use in low-pressure, capacitive-readout sensors, have been investigated. In such structures, unrelaxed strain in the diaphragms can radically alter mechanical behavior. Although strain can be reduced by thermal annealing, it usually reaches a remnant irreducible minimum. The purpose of this paper is to describe techniques that result in low-strain materials and that reduce the effects of residual strain in micro-diaphragms. Square polysilicon grilles and perforated diaphragms made from both single and double polysilicon layers and from single-crystal silicon, with aspect ratios (side/thickness) of up to 1000 and very low compressive strain ({approx}6 {times} 10{sup {minus}5}), have been fabricated. Strain reduction is achieved by combining thermal annealing with one of two mechanical design techniques. The first technique makes use of a series of cantilever beams to support the diaphragms. In a second procedure, corrugated surfaces in thinned membranes of single-crystal silicon are formed. The corrugations result from the use of boron doping and anisotropic silicon etching. In both of these techniques to produce low-strain diaphragms, an etched cavity is purposely formed in the substrate crystal below them. Only one-sided processing of wafers is employed, thus aiding reproducibility and providing ease of compatibility with an MOS process. A fast-etching sacrificial-support layer (phosphorus-doped CVD oxide) is used. 4 refs., 10 figs.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: DOE/DP
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5367418
• Report Number(s): UCRL-21253; ON: DE90003928
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
DIAPHRAGM
MINIATURIZATION
RESIDUAL STRESSES
MATERIALS TESTING
ANNEALING
BORON
COMPRESSION
CRYSTAL DOPING
DEFORMATION
DESIGN
ETCHING
FABRICATION
IMPLEMENTATION
MEASURING METHODS
MITIGATION
MOS TRANSISTORS
PERFORATION
PRESSURE EFFECTS
SILICON
STRAIN SOFTENING
STRUCTURE FACTORS
TEMPERATURE EFFECTS
BODY
ELEMENTS
HEAT TREATMENTS
MUSCLES
ORGANS
SEMICONDUCTOR DEVICES
SEMIMETALS
STRESSES
SURFACE FINISHING
TESTING
TRANSISTORS
420500* - Engineering- Materials Testing