摘要:

An electron cyclotron resonance plasma etching system with the capability of additionally radio‐frequency biasing the substrate has been used to study the etching characteristics of InP, InAs, InSb, InGaAs, and AlInAs in CH4/H2‐based discharges. The etch rates of these materials increase linearly with rf power and retain smooth surface morphologies for microwave powers below 150 W. At higher microwave powers the surface becomes rough due to preferential removal of the group V species. The quality of Au Schottky diode contacts on InP degrades for high‐bias etching, but the addition of PCl3to the discharge retards this degradation by providing an overpressure of P. The room temperature photoluminescence intensity of InP is also preserved by this PCl3addition. We obtained highly anisotropic etching of all five semiconductors over the whole pressure range investigated (1–20 mTorr). Low‐bias (25–100 V) etching occurs with rates in the range 10–140 Å min−1, dependent on the particular semiconductor (InP is the fastest and AlInAs the slowest). Etch rates up to 500 Å min−1are obtained for high‐bias (≤1000 V) conditions. The use of CH3Cl in preference to CH4in order to increase the etch rate of InGaAs and AlInAs was investigated; this appears to have few advantages since the etch rates are comparable to those with CH4/H2. The degree of polymer deposition during CH4/H2/Ar etching on the type of mask used (photoresist, W, or SiO2) was also studied‐for short duration or low‐bias etches any of these masks perform adequately, but SiO2is a superior choice under all other conditions. Finally, the uniformity of etch depth for ECR plasma etching of 2 in. diam InP substrates was found to ±3.0% over the whole wafer and ±2.4% over a randomly chosen 1600×1600 μm2area.

ISSN:0734-211X    

DOI:10.1116/1.585445

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The plasma etching of InP using nontoxic, fluorocarbon free, N2and N2/O2mixtures has been demonstrated. The etch rates as a function of pressure, power, and O2content have been studied. Reactive sputtering appears to be the principal etching mechanism for both plasmas. These plasmas react with the InP substrate forming In2O3, InPO4and probably nitride and oxynitrides of indium. N+2and N+ions are the dominant sputtering species in the N2plasma, while addition of small quantities of O2(<2%) to the plasma appears to promote the formation of heavier ions like NO+and NO+2and easily sputterable NO compounds thereby dramatically increasing the etch rates. At higher O2contents (≥4%) strong surface oxidation and formation of compounds containing the NO2radical limit the sputtering rate. Both gas mixtures exhibit low etch rates but form very smooth surfaces.

ISSN:0734-211X    

DOI:10.1116/1.585446

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Results are presented on chemically assisted ion beam etching of InP and InSb using reactive flux of iodine vapours derived from elemental iodine and A+ion beam. The effect of iodine partial pressure has been studied on the etch rate at different ion beam current densities. The etch rate increases with increase in iodine partial pressure; but above 6×10−5Torr, the trend changes depending upon ion current density. The results are discussed in terms of etch mechanism. The scanning electron microscopy and transmission electron microscopy (TEM) results show that use of iodine flux overcomes the differential etching problem associated with inert ion beam etching of In containing compound semiconductors. The high‐resolution electron microscopy shows that no crystalline defects are introduced by the use of iodine. The technique has been successfully used for anisotropic etching of 1.5 μm test patterns using Dynachem OFPR‐800 postive resist and for preparation of TEM specimen.

ISSN:0734-211X    

DOI:10.1116/1.585447

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A dry etch fabrication technology for high‐speed AlInAs/InGaAs heterojunction bipolar transistors (HBTs) utilizing low‐damage electron cyclotron resonance (ECR) CH4/H2/Ar plasma etching is detailed. Small‐area (2×4 to 3×9 μm2) devices demonstrated current gains up to 160, unity gain cutoff frequency ( fT) of 57 GHz and a maximum oscillation frequency ( fmax) of 35 GHz. The dry etch process uses triple self‐alignment of the emitter and base metals and the base mesa, minimizing the base‐collector capacitance (CBC). These results represent the first report of a truly scalable process for In‐based HBTs and demonstrate the ability of ECR plasma etching to provide smooth, degradation‐free etching of III–V semiconductors.

ISSN:0734-211X    

DOI:10.1116/1.585448

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A mechanistic model for the plasma etching of GaAs is compared with experimentally determined kinetic reaction rates and thermodynamic data. The measurements were made on etching characteristics of radio frequency (rf) and electron cyclotron resonance (ECR) plasmas in alkane (CH4, C2H6, and C3H8), hydrogen and noble gas mixtures. The model examines the reaction mechanisms on the substrate surface in terms of sequential adsorption and fragmentation of the precursor alkane molecules and the subsequent desorption of volatile reaction products. Experimental results show GaAs etch rates in rf plasmas to be proportional to the initial alkane concentration, and the order of reaction increases with the number of constituent CHxgroups within the alkane precursor molecule. By using different noble gas admixtures it has been possible to determine their effect on etch rates with respect to pure hydrogen admixtures, where results show that etch rates scale with the substitution of He

ISSN:0734-211X    

DOI:10.1116/1.585449

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A low damage dry etch process has been developed for the gate recess of AlGaAs/GaAs heterostructure field effect transistor (HFET) with a selectivity of the etch rates greater than 750:1. The reactive ion etching induced damage has been compared to that reported from other etch processes in literature by the means of photoluminescence (PL) emission from multiple quantum well structures. Better resolution in amount and depth of created defects is obtained by PL measurements of undoped heterostructure layers. The temperature dependent Hall mobility μHand sheet carrier concentrationnsof a doped heterostructure layer which directly correspond to the HFET device properties are evaluated in the dark and under illumination. Values of 360.000 cm2/V s for μHand 8.6×1011cm−2fornsat 15 K after the etch process show that a residual damage can be neglected.

ISSN:0734-211X    

DOI:10.1116/1.585450

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The major species present in a fluorocarbon plasma environment were simulated and independently controlled using radical and ion beams in an ultrahigh‐vacuum apparatus. The beams used in this study were chosen to determine the importance of CFxradicals in a CF4plasma; the beams included F and CF2, with a beam of Ar+to simulate energetic ion bombardment. Both CF2and F enhance the etching yield of SiO2under energetic Ar+bombardment; however, the enhancement with F is twice that seen with CF2at similar fluxes. When CF2and F fluxes are used simultaneously, F dominates and the CF2flux has little effect on the overall etching yield. Combined with previous work on Si substrates, these results are consistent with qualitative theories for SiO2/Si selectivity in fluorocarbon plasmas. Possible elementary steps in the ion‐enhanced etching process are proposed and reduced to a two‐parameter model which represents the process as ion‐enhanced neutral adsorption followed by ion‐induced reaction to form volatile products.

ISSN:0734-211X    

DOI:10.1116/1.585451

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A radio‐frequency (rf) biased electron cyclotron resonance (ECR) plasma etching technology with efficient ion acceleration in high density and uniform ECR plasma for accurate Al–Si–Cu alloy film etching has been developed. Substrate is located at the ECR position (875 G position) and etching is carried out with 400 kHz rf bias power. This technology achieves high etching rate (more than 5000 Å/min), excellent uniformity (±5%), highly anisotropic and Cu residue‐free etching using only Cl2and Cl2/BCl3gas plasma at a low 100 °C substrate temperature. These characteristics are achieved by the combination of dense and uniform ECR plasma generation and efficient accelerated ion flux at the ECR position by using 400 kHz rf bias.

ISSN:0734-211X    

DOI:10.1116/1.585452

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Chemical vapor deposited (CVD) blanket tungsten has been studied at high pressure (80 Torr) in a single‐wafer cold wall reactor using response surface modeling methods. Deposition factors studied include temperature (430–490 °C), H2partial pressure (6–30 Torr), WF6partial pressure (1–2 Torr), and the gas inlet to wafer surface separation (200–600 mils). Quadratic models were generated for deposition rate, resistivity, sheet resistance uniformity, film stress, step coverage, reflectance, and WF6conversion. The models were examined for consistency with previously reported results for CVD tungsten films, and were used to construct contour plots that aided a deposition process optimization search for a plug application. Optimization requirements for step coverage and sheet resistanceRsuniformity resulted in significant constraints on the usable factor space, while requirements for deposition rate, resistivity, stress, WF6conversion, and reflectance were largely met throughout the original factor space. The resulting optimized factor space was found to be relatively large and offered additional opportunities for fine tuning of the process. Finally, data from replicated trials showed the high pressure CVD blanket tungsten process to be highly reproducible.

ISSN:0734-211X    

DOI:10.1116/1.585453

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The influence of Si concentration on the stress induced migration resistance and the electrical resistivity change from silicon precipitates of Al–Si–Cu and Al–Si–Cu/MoSi2interconnections was investigated. Electromigration of Al–Si–Cu/MoSi2was examined as a function of MoSi2thickness. A 1.5 wt. % Si concentration in aluminum alloy prevented grain growth and improved the stress induced migration resistance of the interconnections. However, this amount of Si addition caused resistance increases, because Si precipitates grew to the point that they were the same size as the interconnection linewidth. Layering of the Al–Si–Cu alloy containing 0.7 wt. % Si with MoSi2improved the stress induced migration resistance of aluminum interconnections and prevented the resistance increases. Furthermore, increasing MoSi2thickness improved electromigration resistance of layered interconnections. For MoSi2thickness of>30 nm, electromigration resistance was better than that of single layer Al–Si–Cu interconnections.

ISSN:0734-211X    

DOI:10.1116/1.585454

出版商:American Vacuum Society    

年代:1991

数据来源: AIP