摘要:

The interaction between hydrogen plasmas and a (001) surface of GaAs grown by molecular beam epitaxy is studied by photoemission using synchrotron radiation and reflection high energy electron diffraction (RHEED). Measurements of the As(3d) and Ga(3d) core levels show that the interaction is complex and bonding to both As and Ga occurs. It is seen from RHEED measurements that plasma exposures lead to an unreconstructed and partly disordered surface. Valence band studies by angle resolved photoemission show a prominent hydrogen induced feature in the heteropolar gap at an energy 7.7 eV below the valence band maximum.

ISSN:1071-1023    

DOI:10.1116/1.582861

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Experiments were conducted on two types of GaAs substrates according to the surface treatment which either resulted in oxidation of the substrate (chemical etching) or in nearly oxygen‐free interface (exposure of the substrate to a hydrogen/nitrogen mixture plasma). Owing to appropriate choices of the sequences of technological steps in the preparation of MIS samples, which include substrate treatment, deposition of the insulator (alumina obtained by reactive evaporation), and high temperature anneal (around 550 °C), it is given evidence of the great importance of the high temperature annealing step, solely responsible for the observed improvement in the electrical properties of the interface (as derived from capacitance and conductance measurements).

ISSN:1071-1023    

DOI:10.1116/1.582862

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

The reactive ion etching (RIE) of silicon nitride (Si3N4) films formed by low pressure chemical vapor deposition (LPCVD), has been investigated. Studies were done using plasmas of CHF3, CHF3+O2, and CHF3+CO2gases. Anisotropic profiles with vertical sidewalls and no undercut have been achieved with all three plasmas. The etch rate of the Si3N4films in a pure CHF3plasma was found to decrease as a function of time. This effect is explained via a mass transport limiting mechanism. Constant etch rates were observed with plasmas of CHF3+O2and CHF3+CO2. A selectivity of 10:1 for the etching of Si3N4to the underlying Si substrate has been achieved with a CHF3+CO2plasma.

ISSN:1071-1023    

DOI:10.1116/1.582863

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Conductive films are required to provide interconnection between contacts on the devices and between devices and outside world. Aluminum has been the most popular metal. Conducting polycrystalline silicon (polysilicon) film has been the conductor for gate and interconnection. PtSi has been used as a Schottky barrier contact and also simply as a contact for deep junctions. Refractory silicides are now used as gate and interconnection metallizations. Titanium/palladium/gold or titanium/platinum/gold beam lead technology was successful in providing high reliability connection to the outside world. Several similar schemes have been suggested or used in the integrated circuits. A considerable amount of work is carried out in adopting such a metallization scheme in integrated circuits. These include a study of metallurgical and chemical interactions between various materials and effect of such interactions on the properties of the materials and devices. In this paper a review of these studies will be presented.

ISSN:1071-1023    

DOI:10.1116/1.582864

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

A crucial criterion for utilizing silicide in MOS technologies is the ability to grow good thermal oxide. Silicides that are deposited or oxidized under nonoptimal conditions produce hazy or nonadherent oxides. The effects of three deposition parameters on subsequent oxide quality of planar magnetron cosputtered films were investigated. These variables are: (1) stoichiometry, (2) substrate bias, and (3) substrate rotation speed. The films were oxidized in steam at 920 °C for various time intervals. The appearances were determined visually. Oxide thicknesses were obtained. Substrate bias was observed to play a more critical role in oxide quality than the rotational speed. Changes in stoichiometry produced barely noticeable variations in oxide quality unless the films were too metal rich. Voids were not found to be an intrinsic characteristic of the oxide growth.

ISSN:1071-1023    

DOI:10.1116/1.582865

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

There presently exists the need to measure the postanneal thickness of silicide films deposited on Si. In addition, there exists the need to monitor the deposition parameters of silicide films, since variations in the deposition process may alter the film stoichiometry, density, and preanneal electrical resistivity. In this paper we describe results of efforts to satisfy these needs using a thermal‐wave Therma‐Probe 100.

ISSN:1071-1023    

DOI:10.1116/1.582866

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

For the purpose of searching information on the desired purity specification optimum of refractory metal/silicide materials to be used by the IC manufacturer, the views of a material supplier are presented. In particular, ‘‘high purity’’ does not necessarily mean high quality, because all impurities are not equal. Samples of materials representing currently achievable production technology have been collected and analyzed (principally by spark‐source mass‐spectrometry). Impurities are grouped into three categories, the known sensitive elements (alkalis and α emitters particularly uranium/thorium), the major impurities (mostly the 4th period transition elements) which define the overall purity, and other impurities in lesser concentrations with ill‐defined effects on material usefulness. The uranium content as a source of soft error is discussed in some detail. A specification for refractory metals/silicides for VLSI application is proposed for industry consideration.

ISSN:1071-1023    

DOI:10.1116/1.582867

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

The need to understand dopant redistribution in refractory metal silicides is important for reliable fabrication of polycide gates and other silicide‐containing structures in VLSI devices. This paper will review work on dopant redistribution in silicides with emphasis on polycide structures. Of particular concern is the high‐temperature sintering step required to form stable silicide and polycide structures. Results from conventional furnace sintering indicate that dopants can diffuse rapidly through certain silicides. The use of rapid thermal processing techniques to minimize dopant redistribution during the sintering step will also be reviewed. One conclusion is that our understanding of dopant redistribution in refractory metal silicides is limited and additional studies are required.

ISSN:1071-1023    

DOI:10.1116/1.582868

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Devices which use titanium polycide to replace polysilicon in a silicon‐gate process have been processed and evaluated. The circuit used was designed for standardN‐channel Si‐gate processing, and was a standard production part. Working devices were obtained and life tested. Electrical characteristics of polycide wafers were compared with electrical characteristics of devices made from the same mask set using polysilicon interconnects. The titanium polycide wafers successfully completed life testing (1000 h of dynamic life testing at 125 °C) showing no degradation.

ISSN:1071-1023    

DOI:10.1116/1.582870

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

The continuing trend toward smaller geometries and thinner junctions mandates that interconnect and gate materials have the lowest resistivity possible. Titanium silicide has the lowest resistivity of the refractory metal silicides and is, therefore, the prime candidate for advanced VLSI processing. This paper describes the CVD of titanium silicide in the ASM PECVD system. Reactor characteristics, deposition uniformities, and properties of the as‐deposited and annealed films are discussed. Film resistivity, after a 10 min anneal at 650 °C, is typically 15 to 20 μΩ cm. This result is obtained at a lower temperature (by about 100 °C) and lower resistivity (by about 25%) than is usually attainable with sputter‐deposited TiSix. Analysis using Rutherford backscattering spectrometry and Auger electron spectroscopy also indicates considerably better purity with these PECVD films. The step coverage of CVD TiSixis essentially conformal.

ISSN:1071-1023    

DOI:10.1116/1.582871

出版商:American Vacuum Society    

年代:1984

数据来源: AIP