摘要:

It has been demonstrated how material uniformity can be improved in a Gen II molecular beam epitaxy system by increasing the incidence angle between the Group III cells and the substrate. The theoretical basis for this behavior has been verified experimentally by studying reflectivity maps from wafers grown without continuous azimuthal rotation. The incidence angle is most easily increased by tilting the substrate holder upward in the machine. For single-heater evaporation cells with conventional 60 cc crucibles (7° taper) the practical substrate tilt limit is approximately 13°. At this point the radius within which the center-normalized uniformity is larger than 99% is about 29 mm for cells in the lowest position. Uniformity dramatically worsens beyond 30 mm due to shadowing. By examining the geometry of the growth chamber it was found that this angle is the initial point where the beam cones from the lowest sources no longer cover the entire wafer surface. The shadowing can be reduced by using crucibles with a larger taper. Using a crucible with a 8.5° taper and a substrate tilt angle of 13° we were able to change the uniformity distribution from having a negative to a positive curvature. The maximum deviation from the center value under these conditions was about 0.5%. The switch of sign of the curvature demonstrates that the tilt angle can be further optimized and near perfect uniformity be obtained.

ISSN:1071-1023    

DOI:10.1116/1.589375

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

We investigated an all-dry etching process of the development-free vapor photolithography (DFVP) with a 351 nm XeF excimer laser. After masked exposure,SiO2on a silicon wafer and under a microlithographically exposed photoaccelerator polymer film can be directly etched by a vapor containing a mixture of HF, water, andN2. Patterns with 0.4 μm resolution were obtained. In this article, effects of the etching temperature and time, exposure energy, and the concentration of 5-nitroacenaphthene in polymer on the resolution, as well as the mechanism of DFVP, are discussed.

ISSN:1071-1023    

DOI:10.1116/1.589376

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

We report on the fabrication of square arrays of submicron resist dots and holes using interference lithography—a relatively simple and inexpensive way of generating periodic structures over large areas. The arrays are formed by exposing a layer of resist to a two-beam interference pattern followed by a second exposure after rotating the sample by 90°. Arrays with periods of 0.67–3.2 μm were fabricated. The size of the structures is accurately controlled by varying the exposure dose. The exposure latitude for patterning arrays of dots is±16%for a±10%change in structure width when an optimum size-to-period ratio is chosen. Compared to dots, holes are patterned with a smaller process window. We show that arrays of dots with diameters as small as 0.20 μm, sidewall slopes of 88°, and aspect ratios as high as 3:1 can be produced. These structures are well suited for the production of field emission flat panel displays.

ISSN:1071-1023    

DOI:10.1116/1.589377

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

A newly developed electron cyclotron resonance plasma source coupled with divided microwaves was investigated for depositing SiC films as an x-ray mask membrane. Silicon carbide (SiC) films were deposited with high reliability and high repeatability using this source. The stress in SiC films has easily been controlled for a self-supported mask membrane by the addition of heat treatment. The SiC membrane has a very smooth surface (less than 1 nm ofRrms), and high stability against the x-ray irradiation, which enables highly accurate fine pattern replication with x-ray lithography.

ISSN:1071-1023    

DOI:10.1116/1.589378

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Technology for future integrated circuits will require advances in all facets of materials and processing. Low dielectric constant materials will require advances in electrical, thermal, and mechanical behavior before process integration can occur. The dielectric constant must be lower than that of amorphous silicon dioxide and possess the right properties for integration with future metallurgies such as copper. Several organic thermoset resins that were predicted to possess the necessary characteristics have been synthesized and studied. A thermoset copolymer of 1,3,5-tris(2-allyloxy-hexafluoro-2-propyl) benzene with polymethylhydrosiloxane oligomers was identified as a material worthy of further development. Thermal gravimetric analysis indicates relative stability up to 350 °C for short periods of time (30–60 min). The complex permittivity was measured up to 40 GHz and was found to be 2.40 with a loss tangent of 0.008. Compatibility with copper multilevel processing was determined by a secondary ion mass spectroscopy analysis. Copper ion migration did not occur. The processability of the dielectric resins was investigated to address the integration issues associated with the fabrication process.

ISSN:1071-1023    

DOI:10.1116/1.589379

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Polysiloxane thin films were proposed as low dielectric constant interlayer dielectrics for multilevel interconnection of ultralarge scale integration circuits. The films were prepared using oxygen-radical polymerization of siloxane oligomers. A variety of siloxane oligomers were thermally produced by the decomposition of polysiloxane bulk target usingCO2laser irradiation. Oxygen radicals generated by a remote microwaveO2plasma were injected into the vacuum chamber during film deposition. The films deposited with the oxygen radical injection were transformed from polysiloxane to carbon-deficient silicon oxide with increase of substrate temperature as confirmed by x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses. At aCO2laser power of 10 W, anO2pressure of 50 mTorr, a microwave power of 100 W, and a substrate temperature of 100 °C, the dielectric constant of the polysiloxane film was 2.0.

ISSN:1071-1023    

DOI:10.1116/1.589380

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

The electromigration behavior of hot-sputtered aluminum-copper (Al-Cu) vias is compared to that of chemical vapor deposition (CVD) tungsten (W) vias. Al(Cu) vias were prepared by one of two processes: (1) the via was filled and then defined by chemical mechanical polish (CMP) and (2) the via and top metal line were deposited in the same step (this is referred to as the “Sprint” process). During electromigration testing, the W via chains exhibited more uniform resistance changes with time than the CMP Al(Cu) via chains. This had a direct impact on the shape parameter of the log-normal lifetime distribution, whereσwas higher for the CMP Al(Cu) via chains. A closer examination of the failure distributions revealed the need to describe the CMP Al(Cu) via lifetimes by a three-parameter log-normal distribution as opposed to the conventional two-parameter log-normal distribution. Failure analysis of the CMP Al(Cu) samples indicated electromigration failures downstream from the via in the direction of the electron flow. Samples prepared by the Sprint process showed>5× electromigration lifetime improvement as compared to either the CVD W or CMP Al(Cu) via samples.

ISSN:1071-1023    

DOI:10.1116/1.589381

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Previous work on thermally induced arsenic deactivation in highly doped silicon has proven the generation of vacancies and suggests the formation of arsenic-vacancy clusters as the deactivation mechanism. Using positron annihilation spectroscopy in the two-detector coincidence geometry, we are able to show that the thermally generated vacancies are indeed surrounded by arsenic atoms.

ISSN:1071-1023    

DOI:10.1116/1.589382

出版商:American Vacuum Society    

年代:1997

数据来源: AIP