The Effects of Processing Conditions on the Thermal Conductivity of Polycrystalline Silicon Films

2003 ◽  
Author(s):  
Samuel Graham ◽  
Brandon Olson ◽  
Channy Wong ◽  
Edward Piekos
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Thermal Management ◽  
Structural Properties ◽  
Polycrystalline Silicon ◽  
Thermal Dissipation ◽  
Processing Conditions ◽  
Mems Devices ◽  
Thermal Actuators ◽  
Polycrystalline Silicon Films

Polycrystalline silicon has been a primary material used in development of mocroelectrical mechanical systems due to its attractive structural properties and compatibility with CMOS processing. Among its many applications, polysilicon is currently being employed in MEMS devices that require thermal dissipation or thermal management to ensure functionality (thermal actuators, microengines, etc.). In these applications, heat conduction in polycrystalline silicon becomes a primary factor in the design, performance, and reliability of thermal MEMS.

Laser-Induced Damage of Polycrystalline Silicon Optically Powered MEMS Actuators

2005 ◽  
Author(s):  
Justin R. Serrano ◽  
Leslie M. Phinney ◽  
Carlton F. Brooks
Keyword(s):  
Polycrystalline Silicon ◽  
Continuous Wave ◽  
Continuous Wave Laser ◽  
Mems Devices ◽  
Optical Mems ◽  
Thermal Actuators ◽  
Incident Laser Power ◽  
Mems Actuators ◽  
Laser Induced Damage ◽  
Time Required

Optical MEMS devices are commonly interfaced with lasers for communication, switching, or imaging applications. Dissipation of the absorbed energy in such devices is often limited by dimensional constraints which may lead to overheating and damage of the component. Surface micromachined, optically powered thermal actuators fabricated from two 2.25 μm thick polycrystalline silicon layers were irradiated with 808 nm continuous wave laser light with a 100 μm diameter spot under increasing power levels to assess their resistance to laser-induced damage. Damage occurred immediately after laser irradiation at laser powers above 275 mW and 295 mW for 150 μm diameter circular and 194 μm by 150 μm oval targets, respectively. At laser powers below these thresholds, the exposure time required to damage the actuators increased linearly and steeply as the incident laser power decreased. Increasing the area of the connections between the two polycrystalline silicon layers of the actuator target decreases the extent of the laser damage. Additionally, an optical thermal actuator target with 15 μm × 15 μm posts withstood 326 mW for over 16 minutes without exhibiting damage to the surface.

Effect of Nanocavities on the Thermoelectric Properties of Polycrystalline Silicon

2011 ◽  
Vol 1329 ◽  
Author(s):  
Ekaterina Selezneva ◽  
Andrea Arcari ◽  
Gilles Pernot ◽  
Elisabetta Romano ◽  
Gianfranco Cerofolini ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Polycrystalline Silicon ◽  
Figure Of Merit ◽  
Annealing Temperature ◽  
Silicon Films ◽  
Negative Effect ◽  
Polycrystalline Silicon Films

ABSTRACTNanostructuring has opened new ways to increase the thermoelectric performance of a host of materials, mainly by decreasing their thermal conductivity κ while preserving the Seebeck coefficient S and electrical conductivity σ. The thermoelectric properties of degenerated polycrystalline silicon films with nanocavities (NCs) have been studied as a function of annealing temperature upon isochronous annealings in argon carried out every 50°C in the range 500 – 1000°C which were used to modify the shape of the NCs. We found that presence of the NCs had no negative effect on the electronic properties of the system. The measured values of S and σ were close to those previously reported for the blank polycrystalline silicon films with the same doping level. The thermal conductivity was also found to be close to the value measured on the blank sample, about half of the reported value in polycrystals. This led to a power factor of 15.2 mWm-1K-2 and a figure of merit of 0.18 at 300 K.

Lpcvd Polycrystalline Silicon Thin Films: The Evolution of Structure, Texture and Stress

1990 ◽  
Vol 202 ◽  
Author(s):  
P. Krulevitch ◽  
Tai D. Nguyen ◽  
G. C. Johnson ◽  
R. T. Howe ◽  
H. R. Wenk ◽  
...  
Keyword(s):  
Thin Films ◽  
Residual Stress ◽  
Compressive Stress ◽  
Polycrystalline Silicon ◽  
Amorphous State ◽  
Processing Conditions ◽  
Columnar Microstructure ◽  
Silicon Thin Films ◽  
Evolution Of Structure ◽  
Polycrystalline Silicon Films

ABSTRACTAn investigation of undoped LPCVD polycrystalline silicon films deposited at temperatures ranging from 605 to 700 C and silane pressures from 300 to 550 mTorr revealed large variations in stress with processing conditions and a correlation between stress and texture. TEM and HRTEM analysis show that morphology differences also exist. At lower temperatures (≈605 C) and higher pressures (≈400 mTorr), the films appear to deposit in an amorphous state and crystallize during the deposition to form microstructures characterized by equi-axed grains, tensile residual stress, and a texture with {110} and {11/} (/=2 or 3) components. Higher temperatures (between 620 and 650 C) produce films that nucleate at the Si02 interface, creating a {110} oriented columnar microstructure. At 700 C, the grains are still columnar, but the dominant texture is {100}. Films deposited at temperatures greater than 620 C exhibit compressive stress, and some contain regions of hexagonal silicon. This paper proposes possible causes of the varying stresses, textures, and microstructures in the films.

Effect of boron doping on the structural properties of polycrystalline silicon films grown at reduced pressures

1994 ◽  
Vol 76 (3) ◽  
pp. 1572-1577 ◽  
Author(s):  
Horng‐Chih Lin ◽  
Hsiao‐Yi Lin ◽  
Chun‐Yen Chang ◽  
Tz‐Gwei Jung ◽  
P. J. Wang ◽  
...  
Keyword(s):  
Structural Properties ◽  
Polycrystalline Silicon ◽  
Boron Doping ◽  
Silicon Films ◽  
Polycrystalline Silicon Films ◽  
Reduced Pressures

scholarly journals Effect of In-Plane Aspect Ratio of Graphene Filler on Anisotropic Heat Conduction in Paraffin/Graphene Composite

2021 ◽  
Author(s):  
Hiroki Matsubara ◽  
Taku Ohara
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Aspect Ratio ◽  
Thermal Management ◽  
Graphene Composite ◽  
Molecular Scale ◽  
Anisotropic Heat Conduction

Enhancement of polymer thermal conductivity by nanographene fillers and clarification of its molecular-scale mechanisms are of great concern in the development of advanced thermal management materials. In the present study,...

Cross-Plane Phonon Conduction in Polycrystalline Silicon Films

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Jungwan Cho ◽  
Daniel Francis ◽  
Pane C. Chao ◽  
Mehdi Asheghi ◽  
Kenneth E. Goodson
Keyword(s):  
Thermal Conductivity ◽  
Polycrystalline Silicon ◽  
Transport Theory ◽  
Phonon Scattering ◽  
Transport Model ◽  
Phonon Transport ◽  
Silicon Films ◽  
Theoretical Predictions ◽  
Crystalline Films ◽  
Polycrystalline Silicon Films

Silicon films of submicrometer thickness play a central role in many advanced technologies for computation and energy conversion. Numerous thermal conductivity data for silicon films are available in the literature, but they are mainly for the lateral, or in-plane, direction for both polycrystalline and single crystalline films. Here, we use time-domain thermoreflectance (TDTR), transmission electron microscopy, and semiclassical phonon transport theory to investigate thermal conduction normal to polycrystalline silicon (polysilicon) films of thickness 79, 176, and 630 nm on a diamond substrate. The data agree with theoretical predictions accounting for the coupled effects of phonon scattering on film boundaries and defects related to grain boundaries. Using the data and the phonon transport model, we extract the normal, or cross-plane thermal conductivity of the polysilicon (11.3 ± 3.5, 14.2 ± 3.5, and 25.6 ± 5.8 W m−1 K−1 for the 79, 176, and 630 nm films, respectively), as well as the thermal boundary resistance between polysilicon and diamond (6.5–8 m2 K GW−1) at room temperature. The nonuniformity in the extracted thermal conductivities is due to spatially varying distributions of imperfections in the direction normal to the film associated with nucleation and coalescence of grains and their subsequent columnar growth.

Sign in / Sign up

Export Citation Format

Share Document