摘要:

A new high vacuum system for laser induced chemical vapor deposition of tungsten on silicon is presented in this paper. In this apparatus, tungsten depositions have been performed in the 0.5–15 mbar pressure range at substrate temperatures up to 400 °C. The base pressure of the system is 10−8mbar after baking. Samples can be transferred via a sample loading system to maintain a low concentration of impurities. 193 nm UV photons are supplied by an ArF excimer laser (0–50 Hz, 160 mJ). A nitrogen window purge prevents tungsten deposition on the laser entrance and exit windows. Reaction product analysis can be performed with a quadrupole mass spectrometer which has been installed in a separate, differentially pumped, vacuum chamber close to the sample and the laser beam. Tungsten films have been analyzed with Rutherford backscattering spectrometry and scanning electron microscopy. Sheet resistivities less than twice the bulk value have been obtained with this setup.

ISSN:0734-211X    

DOI:10.1116/1.585794

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

During the past 20–25 years, the nondestructive surface acoustic wave (SAW) measurement technique has been developed and used to characterize the electrical properties of semiconductor materials and devices. Important semiconductor parameters such as carrier density, type and mobility, interface and fixed oxide charge densities, deep‐level cross section and activation energy, and excess carrier generation and recombination lifetimes are all determined using SAW. In the majority of these experiments, separate medium structure is used where SAW is generated at the surface of a piezoelectric substrate like LiNbO3. SAW in the piezoelectric materials is accompanied by a decaying electric field which interacts with the free carriers of a semiconductor placed nearby. The spatial resolution that is usually achieved in these measurements is on the order of the SAW wavelength or the extrinsic Debye length, whichever is shorter. Variety of semiconductors are characterized using SAW including: silicon, GaAs, AlxGa1−xAs, InAs, GaP, HgxCd1−xTe, CdTe, InP, CdS, and InAs. More recently, highTcceramic superconductors have also been studied. The most important aspect of the SAW technique is that it is nondestructive and it has very high sensitivity in studying high resistivity materials. Here, we present a review of the SAW technique discussing its application in quantitative characterization of semiconductor materials and devices.

ISSN:0734-211X    

DOI:10.1116/1.585796

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

To measure the logic state of passivated integrated circuits (ICs) using ane‐beam tester, we have devised voltage measurement and logic thresholding techniques to reduce the heavye‐beam dosage required in very long test sequences. These techniques make measurement stable by reducing both thee‐beam dosage and measurement time without compromising a reliability. It takes 30 s to measure logic states of a 16 K‐step‐length test sequence at a probe point. Measurement is estimated as stable up to 200 K steps for passivated ICs, sufficient for the practical failure analysis of complex logic ICs.

ISSN:0734-211X    

DOI:10.1116/1.585271

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Reactive ion etching of recessed gates for metal–semiconductor field effect transistors (MESFETs) and high electron mobility transistors (HEMTs) devices has been studied in SiCl4and SiCl4/SF6plasmas. The effects of etch parameters such as dc bias and overetch, on device characteristics were evaluated and compared with wet‐etched samples. Results indicate damage‐free etching of MESFETs in SiCl4plasma for dc bias values in the range of −100 to −300 V. The etched features did not exhibit any undercut, however, the etch profiles were generally sloped and more vertical etch profiles were obtained at higher dc bias conditions. The use of thin stop‐etch layers of Al0.26Ga0.74As inserted in the active epilayer of GaAs, in conjunction with selective etching of GaAs over AlGaAs in SiCl4/SF6mixtures resulted in significant improvement in etch uniformity as well as good device performance. The etch profiles became more vertical with increased overetching after etch stop on the AlGaAs layer. However, it was found that the value of drain‐source saturation currentIdssdecreased with increased overetching, as a result of the depletion of the active layer. Consequenty, devices with more than 200% overetch failed to operate in the depletion mode and could only operate in the enhancement mode. The SiCl4/SF6mixture was also utilized for etching of recessed gates for HEMT devices with an Al0.26Ga0.74As layer of 250 Å. These devices only operated in the enhancement mode and hold transconductancegmvalues similar to wet‐etched samples. The data indicate less damage with etching at lower dc bias conditions. Etching at a dc bias of −200 V with more than 200% overetch resulted a completely damaged device.

ISSN:0734-211X    

DOI:10.1116/1.585272

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We have developed a numerical model for the flux distribution in molecular beam epitaxy over stationary and rotating substrates. The existence of a temperature profile along the crucible and accumulation of material at the crucible orifice is taken into account. The influence of melt level tilt on the flux distribution is discussed in detail, and, in contrast to previous reports, is found to be small for the cases considered. Accurate thickness maps of GaAs wafers grown with two different types of effusion cells on stationary substrates were obtained using a scanning reflectance system. Excellent agreement of these experimental results with predictions of the model is demonstrated. We explain some of the deficiencies of the present arrangement and calculate the optimum system conditions for obtaining uniformity across a wafer to better than ±0.3%.

ISSN:0734-211X    

DOI:10.1116/1.585273

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A problem with molecular beam epitaxy growth of semiconductors is the presence of defects. Since most of them originate at the substrate/epitaxial interface, special attention must be given to the treatment of the surface before growth. It must be clean on an atomic scale. This study has found that a combination of ultraviolet–ozone treatment and chemical etching produces the lowest defect density in the grown layer.

ISSN:0734-211X    

DOI:10.1116/1.585274

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We have observed singularities in current–voltage data that indicate charge quantization in the accumulation layer of resonant tunneling diodes with thick spacer layers. The electrons are strongly localized between the artificial barrier formed by the lightly doped emitter spacer layer and the first metallurgical barrier. Tunneling occurs between these states and those confined to the quantum well. We presume this process to be the source of negative differential resistance in the single‐ and double‐well samples we have fabricated.

ISSN:0734-211X    

DOI:10.1116/1.585276

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The mechanism for the cause of stress in a sputter‐deposited tungsten (W) film has been clarified. The tensile stress of the film was calculated using the interatomic forces acting on the grain boundary. The average distance of the grain boundary gaps was determined from the measured film density assuming the film had homogeneous size rectangular grains. The calculated and measured stress values were in good agreement in the high working gas pressure region. The difference between these values in the low working gas pressure region has been able to be explained by the compressive stress due to the peening effect of Ar. The low stress in the high pressure region was obtained by large opened grain boundaries which produced low film density. A low film density causes a low x‐ray stopping power. The film deposited in the low pressure region is suitable as an x‐ray absorber because of its high film density.

ISSN:0734-211X    

DOI:10.1116/1.585277

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

An optimized gold direct current (dc) electroplating process from a cyanide bath was developed for the fabrication of x‐ray lithography masks. The stress behavior of 0.4–2 μm thick gold thin films dc electrodeposited from a neutral cyanide bath was studied as a function of their deposition parameters. Temperatures in the 40–70 °C range and current densities varying from 1 to 10 mA/cm2were used. Deposits with low total tensile stress (down to 10 MPa) were obtained. The influence of the plating base was addressed. A structuring process was developed, which enabled the fabrication of 0.65 μm thick gold patterns for x‐ray lithography masks. The minimum linewidth obtained was 70 nm in a single layer process and 0.2 or 0.3 μm period gratings in a single layer or trilayer stencil, respectively. The problem of thickness uniformity in the deposits was also studied.

ISSN:0734-211X    

DOI:10.1116/1.585278

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Focused ion beam induced deposition of platinum from a gas of (methylcyclopentadientyl) trimethyl platinum has been demonstrated and used for integrated circuit repair. Ga+ions in the range of 30–40 keV have been used and line widths down to 0.3 μm with resistivities as low as 70 μΩ cm have been observed. The deposition yield as a function of angle of incidence has been measured by scanning the ion beam across a 2.6 μm diameter pyrex rod. The conductors on an actual integrated circuit have been modified by milling and filling a via to connect two Al lines in a sandwiched configuration as well as by milling two vias through passivation and connecting two adjacent Al lines.

ISSN:0734-211X    

DOI:10.1116/1.585279

出版商:American Vacuum Society    

年代:1991

数据来源: AIP