Controlled anisotropic etching of polysilicon

World Abstracts on Mlcroelectronlcs and Rehablhty

Hot electron diffusion in fine line semiconductor devices. W T JONES, K HESS and G J IAFRATE Solid-St Electron_ 25(10), 1017 (1982) We present a simple formalism to include hot electron diffusion into device modeling programs_ The effectiveness of this method is dlustrated for a DMOS-structure and the permeable base transistor However, the formalism Is general and can be applied to any semiconductor device

The influence of hydrogen gas on the characteristics of amorphous silicon deposited by RF sputtering. J T LUE, O MEYER and J LOMBAARD Solid-St, Electron 25(10), 1011 (1982) The electrical and optical properties of a-Sl depend greatly on the fill gas and substrate temperature during RF sputterIng From the measured absorption coefficient, It was estimated that after the introduction of H 2 gas during sputtering the gap state density reduces from 3 2 x 10 I9 c m - ~ to 4 8 × 10 ~7 c m - a As a consequence the optical band gap was found to increase from 174 to 182eV The d c conductivity measurement shows three d~stlnct conducting mechanisms at different temperature regions The SI-H bonds m RF sputtered samples are perslstant to higher temperature treatment than the CVD prepared ones

Minority carrier diffusion length in LPE In~ Gal_~ P : N layers (x < 001) H HAEFNER, G OELGART,J KANIEWSKIand B MROZIEWlCZ Sohd-St Electron 25(10), 1023 (1982)_ Minority carrier diffusion length In,Ga~ _xP LPE layers has been measured using the electron beam method It has been found that this parameter significantly changes with the composmon of the alloy The measured relationship proves that minority carrier mobility in In~Gaj _~P alloys with low indium content strongly depends on the alloy composition It is suggested that alloy scattering may be responsible for this behavlour The effect of doping the In~Gal_~P LPE layers with nitrogen has also been investigated Results indicate that carrier mobility drops when the nitrogen concentration exceeds certain limits and this most probably can be ascribed to carrier scattering on the nitrogen centers

Non-homogeneous electrical transport through silicon-onsapphire thin films: evidence of the internal stress influence. JOHN-HYUN LEE, SORIN CRISTOLOVEANUand ALAINCHOVET Solid-St Electron 25 (9), 947 (1982) The non-homogeneous electrical parameters of carrier transport in slhcon on sapphire (SOS) films are investigated through galvanomagnetic experiments using "MOS-Hall" thin (0 65 ~,m) SOS devices wnh low n-type dopings (n o ~- 10 I5 to 1016cm -3) Capacitance-voltage (C V), Hall and magnetoresistance measurements are performed on the gate-controlled depleted or "'active" layers of the film Experimental results and theoretical calculations show that longitudinal magnetoresistance ILMR) measurements yield the accurate determmatlon of amsotropy and carrier drift mobility On the contrary, it is underhned that the (previous)characterization methods, exclusively based on C V or Hall experiments could produce inconsistent and misleading results m SOS This is partly due to the fact that the usual 6 valley conduction band model used for bulk silicon ~s no longer valid in thin SOS films, for which the high stress at Si-sapphlre interface requires the adoption of a 4 valley model throughout the film. this lmphes a high anlsotropy for carrier mobility and explains why. in SOS films, the Hall mobdlty is 40 ~o lower than the drift mobIhty, and the LMR is higher than the transverse magnetoresistance C-V, Hall and LMR measurements then give fully consistent results allowing one to describe the variation of the carrier scattering mechanisms across the film and to determine the exact profiles for carrier mobIhtles and concentration as well as for the amsotropy coefficient

Controlled anisotropic etching of polysilicon. STEVEN F, BERGERON and BERNARD F DUNCAN Sohd St Technol, 98 ~August 1982) The etchant system of C2FsCI and O2 in a

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radial-flow, parallel-plate reactor operated in the plasma mode is described It is demonstrated that the polyslhcon edge slope can be reproduclbly varied from nearly complete isotropic to almost vertical sidewalls with minimal etch bias or undercut The simultaneous optimization of etch rate and selectlvities to thermal oxide and photoreslst for a specified polysIhcon slope IS discussed

Average mobihties of carriers in subdoped silicon layers. Ju-YAN XU and Lt-Mo WANG Solid-St Electron 25 (10L 979 (1982) The average mobihtles of carriers in subdoped silicon layers as a function of surface as well as background concentrations are calculated using the universal formula for the average mobihties of carriers in nonhomogeneous doped layers along with Irvm's average conductivity curves The results are shown graphically

Effect of reactive sputter etching of SiO 2 on the properties of subsequently formed MOS systems. U NIGGEBRUGGEand P BALK Sohd-St Electron 25(9), 859 (1982) We investigated the effects of reactive sputter etching {RSE) of SIO 2 on the electrical properties of the SI SIO2 system using C H F 3 in a commercial apparatus SIMS and Auger spectrometry revealed contamination of RSE-exposed SI surfaces with carbon and heavy metals The generation of crystal defects during thermal reoxldation was observed to be closely related to the level of metal contamination C V C t and I I' measurements on subsequently formed MOS structures showed, that oxide charge, interface state and mobile ton densities are nearly unaffected by the RSE process However minority carrier hfetime m the SI substrate and isolation behavior of the oxide layer are strongly degraded, our results suggest, that both effects are mainly due to metallic impurities The use of inert cathode materials like quartz reduces metal contamination, but a non-negligible contribution from the grounded metal surfaces of the reactor remains Carrier lifetime and Insulating properties reach the values obtained on wet chemically etched samples only after extended times of plasma excitation in the apparatus This is attributed to a passlvation of the grounded surfaces by the formation of polymer films Taking advantage of this effect MOSFETs were fabricated by the use of RSE without deterioration of their electrical performance

Low frequency planar plasma etching of polycide structures in an SF 6 glow discharge. M E CuE and S H ROGERS Solid St Technol, 79 (August 1982) Polyclde films consisting of WSI~ over polysdlcon have been successfully etched in a hatchloaded planar plasma etching system This polycide technology is in pilot production, providing two micron interconnects with sheet resistances of 5 ohms/square Etch rates and selectwlties as a function of pressure, power, flow and gas composluon are presented The effects of film stoichiometry and phosphorus doping levels are discussed, as is etching residue formataon The origin and magnitude offlatband and threshold shifts are evaluated

Advances in contamination control of processing chemicals in VLSI. E M JULEFF, W J McLEOD, E A HULSE and S FAWCETT Solzd St Technol, 82 (September 1982) Recent results In particulate control of chemicals used in the manufacture of VLSI integrated circuits are presented and evaluated The status of particulate measurement and specification Is discussed and the inadequacies highlighted A system is proposed to relate particle counts to minimum critical device dimensions using the HIAC/ROYCO or equivalent in-hne measuring system as a standard

Single wafer plasma etching. 2. SiO 2 . etching mechanisms and characteristics. COREY MULLINS Sohd St Technol, 88 (August 1982) This is the second of a series of articles on Single Wafer Plasma Etching Advanced semiconductor pro-