摘要:

A selective wet chemical etching solution for removal of Al0.5In0.5P from GaAs based on HCl:H2O has been developed. Controllable etch rates from 600 Å min−1at 1HCl:30H2O to 6000 Å min−1at 1HCl:5H2O at 25 °C are obtained. The etch rate is thermally activated of the formR∝exp(−Ea/kT) whereEa=12.4 kCal mol−1, consistent with reaction‐limited etching. Dry etch rates of AlInP in PCl3/Ar, CCl2F2/Ar, or CH4/H2/Ar electron cyclotron resonance discharges are all<300 Å min−1for additional dc self‐biases of ≤250 V. Selectivities of ≳600:1 are obtained for etching GaAs over AlInP in CCl2F2/Ar discharges for dc biases ≤150 V. The etched surface morphologies are smooth, with small quantities of Cl‐containing residues remaining after PCl3/Ar exposure, and both Cl and F detectable after CCl2F2/Ar dry etching.

ISSN:1071-1023    

DOI:10.1116/1.586077

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Double pulse doped AlGaAs/InGaAs pseudomorphic high electron mobility transistors have been grown by molecular‐beam epitaxy on GaAs substrates. Hall mobilities in excess of 7100 cm2/V s at 300 K and 25 000 cm2/V s at 77 K are obtained with a sheet density of 3×1012cm−2. Photoluminescence measurements indicate that two electronic subbands are occupied, and the subband energies are determined. The doping pulses are resolved in secondary ion mass spectrometry measurements. Using a double recess process, transistors have been fabricated that have produced state of the art microwave performance. At 10 GHz a 1.2 mm device has simultaneously achieved a power added efficiency of 70%, output power of 0.97 W, and gain of 10 dB.

ISSN:1071-1023    

DOI:10.1116/1.586078

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Thin homoepitaxial films of gallium phosphide (GaP) have been grown by remote plasma enhanced chemical vapor deposition utilizinginsitugenerated phosphine precursors. The GaP forming reaction is kinetically controlled with an activation energy of 0.65 eV. The increase of the growth rate with increasing radio frequency (rf) power between 20 and 100 W is due to the combined effects of increasingly complete excitation and the spatial extension of the glow discharge toward the substrate, however, the saturation of the growth rate at even higher rf power indicates the saturation of the generation rate of phosphine precursors at this condition. Slight interdiffusion of P into Si and Si into GaP is indicated from GaP/Si heterostructures grown under similar conditions as the GaP homojunctions.

ISSN:1071-1023    

DOI:10.1116/1.586079

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

We present here the results of a study on the effect of substrate temperatureTson the electrical and physical characteristics of low temperature molecular‐beam epitaxy GaAs layers. Based on the x‐ray results, three temperature ranges have been defined forTs: 1) high range (Ts≥ 460 °C), 2) intermediate range (260 ≤Ts≤ 450 °C), and 3) low range (the amorphous range) (Ts≤ 250 °C). Hall measurements have been performed on the as‐grown samples and on samples annealed at 610 and 850 °C. Si implantation into these layers has also been investigated. From an electrical stand point, the most striking difference between the low range and the intermediate range is the fact that after annealing at 850 °C, the undoped layers grown below or at 250 °C have a low resistivity (net electron concentrations as high as 1.5×1018cm−3and mobilities as high as 920 cm2 V−1 s−1), while after anneal the undoped layers grown in the intermediate range have extremely high resistivity (about 8×105Ω cm).

ISSN:1071-1023    

DOI:10.1116/1.586080

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Low‐pressure chemical vapor deposition (LPCVD) of polycrystalline silicon in a cold‐wall, lamp‐heated, rapid‐thermal processor was investigated. Blanket polysilicon films were obtained by the pyrolysis of a 10% silane–argon gas mixture onto (100) Si wafers which were capped with a thermal SiO2layer. The depositions were performed at a total pressure ranging from 1 to 5 Torr and in a temperature range from 575 to 850 °C. It was found that the deposition of films was controlled by a surface limited reaction at temperatures below ∼780 °C, and an activation energy of 39±2 kcal/mol was measured for this reaction. Above 780 °C, a decrease in activation energy was observed. To meet the throughput requirement of single wafer processing, deposition temperatures higher than 700 °C are needed. In this temperature range, deposition rates exceed 1000 Å/min as compared to 20–300 Å/min in conventional LPCVD furnaces. The structural characteristics of the films were assessed by ultraviolet surface reflectance, Raman spectroscopy, and transmission electron microscopy. The transition temperature from amorphous silicon to polycrystalline silicon occurs at ∼600 °C. Processing windows, which result in smooth films with a root‐mean‐square roughness of less than 100 Å, are defined. Polysilicon films (∼2500 Å in thickness) have a columnarlike grain structure, and the grains span distances as little as ∼100 Å near the SiO2interface to ≥1000 Å as they approarch the upper surface. A correlation between average projected grain size and surface roughness is demonstrated. Oxygen levels were derived from secondary ion mass and Auger electron spectroscopic data. The oxygen content of the polysilicon films is estimated to be in the range of 3%–4%. We speculate that relatively high oxygen levels in the films may be responsible for smooth films at high temperatures. If this is true, it may be possible to obtain smooth polysilicon films at high deposition temperatures by adding measured amounts of oxygen to the gas stream.

ISSN:1071-1023    

DOI:10.1116/1.586082

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

A new annealing technique for silicidation using electron cyclotron resonance plasma is proposed, and the method is successfully used to apply self‐aligned silicide of molybdenum on a Si substrate. The technique enables the temperature to be rapidly increased above 500 °C independent of substrate materials and a high degree of controllability enables reliable, self‐aligned silicidation on Si.

ISSN:1071-1023    

DOI:10.1116/1.586083

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

This article describes a model that simulates etching profiles in reactive ion etching. In particular, models are developed to explain the significant lateral etch rate that is observed in many etch profiles. The total etch rate is considered to consist of two superimposed components: an ion‐assisted rate and a purely ‘‘chemical’’ etch rate, the latter rate being due to etching by radicals in the absence of ion bombardment. The transport of radicals to the evolving interface is studied for two different transport mechanisms: re‐emission from the surface and diffusion along the surface. For the case of transport by surface re‐emission, a reactive sticking coefficient is defined for the radicals, and a formulation is developed to simulate etching for any value (between zero and unity) that this sticking coefficient may assume. When the sticking coefficient approaches either zero or unity, the method of characteristics is shown to be useful for profile simulation. Transport of radicals by surface diffusion is also investigated, and it is shown that the important dimensionless parameter governing profile evolution is the Damkohler number. The two models are compared to experiments performed on the etching of silicon in a SF6plasma, and the surface re‐emission model is shown to accurately predict the development of etching profiles.

ISSN:1071-1023    

DOI:10.1116/1.586084

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

A new magnetron ion etching (MIE) process has been developed to etch 50 μm deep trenches into single crystal silicon. The optimized SF6/O2gas mixture results in a nearly vertical etch profile with a vertical to horizontal etch rate ratio of 9.4. Similar experiments were carried out on a Drytek reactive ion etching (RIE) system. Results indicate that although the sidewall angle, etch rate ratio, and etch rate of the RIE process for silicon is lower than that of the MIE process, the surfaces of the trench are smoother and more defect‐free due to better substrate cooling. The effects of the processing parameters on the silicon etch rate and anisotropy were explored in order to optimize both the MIE and RIE processes. Both processes were used to fabricate single crystal silicon doughnuts of dimensions 25–50 μm thick, 50 μm inner diameter, and 100–200 μm outer diameter.

ISSN:1071-1023    

DOI:10.1116/1.586085

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Hydrogen‐bombardment induced damage in single crystal silicon as a function of the substrate temperature, ion energy, and ion dose was studied usinginsituspectroscopic ellipsometry over the photon energy range 2.0–5.5 eV under high vacuum conditions. The incident hydrogen ion energies were 300 and 1000 eV, and the doses were 1015–1018ions/cm2.Insituspectroscopic ellipsometry results showed that the damage layer thicknesses for the samples bombarded at elevated temperatures are smaller than for samples bombarded at room temperature and subsequently annealed at the same elevated temperature. The diffusion coefficient for hydrogen in silicon of 6 × 10−15cm−2/s was obtained from theinsituspectroscopic ellipsometry data.

ISSN:1071-1023    

DOI:10.1116/1.586086

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Etching of photoresist in an O2plasma generated by an electron cyclotron resonance source (ECR) was investigated. The ECR source was a microwave multipolar reactor at 2.45 GHz, and the stage was connected to a rf power supply at 13.56 MHz. Effects of microwave power, rf power, ECR source to sample distance, and pressure on photoresist etch rate were characterized. It has been found that the photoresist etch rate increases with microwave and rf power, but decreases with source to sample distance. With microwave power at 1000 W and rf power at 300 W, smooth morphology and fast etch rate at 1.61 μm/min were obtained. Self‐induced dc bias voltage increases with rf power and source to sample distance, but decreases with microwave power. Etch rate uniformity better than 0.5% was obtained across 7.5 cm diam wafer even with a very close source to sample distance of 3 cm. Etch profile can be varied depending on the etch conditions. Vertical profile in polyimide has been obtained using a trilayer resist scheme.

ISSN:1071-1023    

DOI:10.1116/1.586087

出版商:American Vacuum Society    

年代:1992

数据来源: AIP