摘要:

The use of a high density plasma to etch oxide side wall spacers was investigated. Process trends and the optimum process conditions required were determined. Oxide and polysilicon etch rates, uniformities, and the selectivity of oxide to polysilicon were all measured. The resulting etch chemistry had an oxide etch rate of 350 nm/min with a selectivity of oxide to polysilicon of 30:1.

ISSN:0734-211X    

DOI:10.1116/1.588782

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The characteristics of oxide and photoresist masked polysilicon trench etching has been studied by real‐time HeNe laser ellipsometry and quasiinsitux‐ray photoelectron spectroscopy (XPS). Poly‐Si films on SiO2‐covered Si (100) substrates were masked either with a 1‐μm‐thick photoresist or a 200‐nm‐thick oxide hard mask. The 200‐mm‐diam wafers were etched downstream in a helicon high density plasma source using a chlorine‐based gas chemistry. When using an oxide hard mask instead of a photoresist mask, the selectivity of polysilicon over oxide was improved by a factor greater than 3. A new approach to the surface characterization of semiconductor submicron structures by XPS is presented. Photoelectron signals originating from the gate oxide film and the underlying silicon substrate were measured in regular arrays of trenches. The ratio between the SiO2peak area of the gate oxide film and the Si 2ppeak area of the silicon substrate was correlated with the thickness of the SiO2film. The thickness determined was obtained by calibrating peak area ratios with oxide thickness measurements using spectroscopic ellipsometry. Consequently, the gate oxide thicknesses derived from the area ratios were calculated in patterned areas after etching of photoresist and oxide hard masked polysilicon features as a function of the aspect ratio of the features and mask coverage on the wafer. It was found that the gate oxide consumption is enhanced in high aspect ratio features masked with photoresist as well as in areas with high photoresist coverage; the carbon coverage on the gate oxide film was found to scale with the increased gate oxide etching in the small features. Similar effects were not observed with the oxide masked sample.

ISSN:0734-211X    

DOI:10.1116/1.588783

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Electron‐beam/ultraviolet (UV) exposure technology to produce undercut T‐shaped resist cavities with bottom openings as small as 0.15 μm is demonstrated with a novel bilayer resist system for AlInAs/InGaAs high electron mobility transistors operated at the millimeter‐wave band. We employed an image reversal resist (AZ5206E) for the top layer and a polydimethyl glutarimide (PMGI) for the bottom layer. The top layer is delineated by UV exposure and the bottom layer is delineated by electron‐beam direct writing. These resist layers are developed layer by layer in different content aqueous tetramethyl ammonium hydroxide solution. Resist profiles are extremely well controlled because exposure and development of both layers are completely independent. A reliable overhang structure for metal liftoff, with a 0.15 μm footprint, was obtained. Gate length variation of less than ±10% on a 3‐in.‐diam InP substrate was successfully accomplished. In addition, an interesting phenomenon was noted. The combination of these two resists leads to an electron‐beam sensitivity decrease of PMGI. This phenomenon is closely related to the change of molecular weight distribution in PMGI. The novel bilayer resist system also allows the further improvement of resolution. This would provide a practical means for electron‐beam lithography in the nanometer region.

ISSN:0734-211X    

DOI:10.1116/1.588784

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

At 193 nm, the Ag2Te/As2S3inorganic resist system exhibits many of the characteristics previously observed at longer wavelengths, namely, a contrast of the order of 10 and the edge effect, both of which contribute to the printing of narrow linewidths. We have observed 0.3 micron lines limited by the resolution capability of the optical system and not by the resist. Under pulsed excimer laser excitation, this system exhibits a threshold of the order of 3 mJ/cm2/pulse. The system does not exhibit reciprocity. While images were printed with two 17 ns pulses of 4 mJ/cm2/pulse, images could not be printed with a single pulse as large as 50 mJ/cm2/pulse. This behavior is not explained by our previously developed model.

ISSN:0734-211X    

DOI:10.1116/1.588785

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The neutral flux in the plasma etching of semiconductor wafers has been derived analytically for a simplified model for a circular cylindrical trench hole (circular via). The neutral molecules obey a Maxwellian distribution function and mutual collisions are neglected in the trench. Scattering of the neutrals with the sidewalls and trench bottom is ignored. The flux vector is given at each point on the etching profile surface. The flux vector reduces to the expression previously determined at the center of the trench. Etching profiles of the trench are displayed for neutral flux‐limited etch rates.

ISSN:0734-211X    

DOI:10.1116/1.588786

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

A seven‐layer process was developed to fabricate monolithic high‐speed logic circuits, requiring integration of Schottky diodes and resistors with interband resonant tunneling diodes (RTDs). With this process technology, we have demonstrated a functionally complete logic family based on RTDs with a maximum operating frequency in excess of 12 GHz and a minimum power dissipation on the order of 0.5 mW per gate.

ISSN:0734-211X    

DOI:10.1116/1.588787

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The use of an AlSiCu/TiN bilayer for the metallization of 1.0‐μm‐diam and 1.4‐μm‐deep straight wall contacts to 0.2‐μm‐deepn+andp+diffusions, results in an+/p−and ap+/ṇ− junction leakage lower than 10 pA even after nine heat treatments (60 min each) at 450 °C. However, there is a very important degradation of the contact chain resistance statistics at small contact size. On the other hand, the use of a Ti/TiN bilayer barrier under the AlSiCu/TiN interconnect maintains an+/p−and ap+/n−junction leakage lower than 20 pA and prevents the degradation of the contact chain resistance statistics after the nine heat treatments. It is finally demonstrated that a vent in nitrogen followed by a momentary air exposure of the Ti/TiN bilayer barrier results in larger contact resistance than a vent in nitrogen followed by a one hour long air exposure of the Ti/TiN bilayer barrier before the deposition of the AlSiCu/TiN interconnect.

ISSN:0734-211X    

DOI:10.1116/1.588788

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

We report the improved thermal stability of heavily C‐doped GaAs layers using atomic layer chemical beam epitaxy (ALCBE). The use of ALCBE improves the crystal quality and reduces hydrogen incorporation in the epilayers by about a factor of 2, resulting in enhanced electrical dopant activity as compared to conventional growth techniques. This process has been successfully applied to the fabrication of InGaP/GaAs heterojunction bipolar transistors (HBTs) with a highly C‐doped base grown by ALCBE and other layers grown by conventional CBE. Dc current gains up to 150, for a base doping layer of 3×1019cm−3, have been obtained. Moreover, the thermal stability of these devices is increased, as indicated by a post‐growth annealing (650°C, 60 min) which induces only a slight current gain degradation of about 20% at high collector currents, to be compared to a degradation of 60% for HBTs conventionally grown by CBE.

ISSN:0734-211X    

DOI:10.1116/1.588789

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Pd based and conventional TiPtAu contacts were realized on GaSb grown by molecular beam epitaxy. Forp‐type GaSb, an undoped sample with an acceptor background concentration of 6.6×1016cm−3and forn‐type GaSb tellurium‐doped samples with donor concentrations of 7.9×1017and 1.2×1018cm−3were used. Circular transmission line patterns were defined on the samples for determining the specific contact resistivity. Onn‐type GaSb, the metallizations consisted of palladium and one of the dopants germanium or sulphur. Rapid thermal annealing lead to values of 4×10−5Ω cm2. Onp‐type GaSb, nonalloyed TiPtAu and alloyed PdGePd contacts were deposited. Values as low as 5.6×10−6Ω cm2could be obtained. The interfaces of the TiPtAu, the PdGePd, and PdSPd contacts were studied by high resolution cross‐sectional transmission microscopy.

ISSN:0734-211X    

DOI:10.1116/1.588790

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The surface stoichiometry, surface morphology, and electrical conductivity of AlN, GaN, InN, InGaN, and InAlN were examined at rapid thermal annealing temperatures up to 1150 °C. The sheet resistance of the AlN dropped steadily with annealing, but the surface showed signs of roughening only above 1000 °C. Auger electron spectroscopy (AES) analysis showed little change in the surface stoichiometry even at 1150 °C. GaN root mean square (rms) surface roughness showed an overall improvement with annealing, but the surface became pitted at 1000 °C, at which point the sheet resistance also dropped by several orders of magnitude, and AES confirmed a loss of N from the surface. The InN surface had roughened considerably even at 650 °C, and scanning electron microscopy showed significant degradation. In contrast to the binary nitrides, the sheet resistance of InAlN was found to increase by ∼102from the as grown value (3.2×10−3Ω cm) after annealing at 800 °C and then remain constant up to 1000 °C, while that of InGaN increased by two orders of magnitude between 700 and 900 °C. The rms roughness increased above 800 and 700 °C, respectively, for InAlN and InGaN samples. In droplets began to form on the surface at 900 °C for InAlN and at 800 °C for InGaN, and then evaporate at 1000 °C, leaving pits. AES analysis showed a decrease in the N concentration in the top 500 Å of the sample for annealing ≥800 °C in both materials.

ISSN:0734-211X    

DOI:10.1116/1.588792

出版商:American Vacuum Society    

年代:1996

数据来源: AIP