摘要:

A registration method using the two‐stage standard mark system is developed for high accuracy overlaying of patterns on a deformed wafer in an electron beam lithographic system used for direct wafer writing of 0.5 μm very large‐scale integrated (VLSI) patterns. Deflection distortions are corrected according to heightzof a pattern writing field on a wafer. In this paper, deflection distortion correction and overlay accuracies are examined experimentally. Main field (2.6×2.6 mm) distortions are corrected using the third‐order power function of the main field coordinates (X,Y). Correction coefficients related to shift, deflection gain, and deflection rotation are shown to be a linear function ofz, in spite of varying the beam focusing level withz. Each distortion expressed in terms up to the third‐order power of (X,Y) can be corrected with an accuracy within 0.02 μm. Overlay accuracies within 0.12 μm (3σ) are yielded when two‐layer test patterns are exposed on a wafer deformed about 75 μm in theZdirection.

ISSN:1071-1023    

DOI:10.1116/1.583595

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

The relation between beam properties and minimum linewidth for a rectangular electron beam for submicron lithography is obtained through experiments and electron scattering simulation. Patterns are exposed in a 0.5‐μm‐thick PMMA resist film on a silicon wafer. The result gives a guiding principle in designing an electron‐optical column of a rectangular electron‐beam exposure system. A minimum linewidth of 0.5 μm can be obtained using a beam with a beam edge width δ=0. 18 μm at a beam voltageVa=25 kV and 0.2‐μm minimum linewidth using a beam with δ=0.08 μm atVa=30 kV.

ISSN:1071-1023    

DOI:10.1116/1.583596

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

An electron beam pattern inspection system (EBIS) using digital image processing is presented. A pattern‐to‐data comparison method is used in this system to detect systematic, random and repeating defects of VLSI circuit patterns. The inspection data are generated from the design data, and transferred from a computer aided design (CAD) system via a computer network. In order to obtain the information of mask or wafer patterns, a low‐energy scanning electron microscope, which has the advantage of avoiding damage to the active devices and not charging the surface, is used. Frame memories are installed to store the inspection data and the actual pattern image. An extra image processor preprocesses the pattern image to obtain high signal‐to‐noise ratio and manipulates these images to extract defects. Two algorithms extracting the defects are studied. Spatial differentiation followed by a thresholding operation is a suitable procedure for the signal with drift.

ISSN:1071-1023    

DOI:10.1116/1.583597

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

A monodisperse negative Si‐containing photoresist (MAS) has been developed for use as the top imaging layer for a bilayer system. MAS is a formulation of poly(allyldimethylsilyl‐α‐methylstyrene) (PMA Si) and a bisazide. PMA Si was synthesized by anionic polymerization of the monomer withn‐butyl lithium in THF at −78 °C. The polymer has a high softening point (Ts=164–166 °C) and a narrow molecular weight distribution (Mw=41 400,Mw/Mn=1.05). Near‐UV‐exposure has been carried out using a Kasper 2001 P contact printer. TheDigof MAS (0.2 μm in thickness) is 4.5 mJ/cm2on a Si wafer and the γ value is over 2.0. The thickness reductions of MAS and MP‐1300 have been measured under various O2‐RIE conditions. The etching ratio of MP‐1300/MAS ranges from 3:1 to 10:1 depending on conditions and is decreased with an increase in rf power and with a decrease in chamber pressure. Under the optimized development and O2‐RIE condition, 0.75 μm line and space (L/S) patterns were accurately fabricated on the Si wafer having 0.5 μm high step. It is also noteworthy that 2.0 μm L/S patterns with a steep profile were obtained even in the MP‐1300 layer of 4.0 or 6.0 μm in thickness.

ISSN:1071-1023    

DOI:10.1116/1.583598

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Reactive ion stream etching has been developed for highly accurate etching with little bombardment induced damage by utilizing an electron cyclotron resonance (ECR) plasma. The ion energy during etching is controlled by utilizing the interaction between the ECR plasma and a divergent magnetic field, in a low energy range from 20 to 50 eV at low gas pressures of 10−2Pa. Highly accurate submicron patterns of polysilicon and molybdenum were obtained with high selectivities to SiO2, larger than 30, by using Cl2gas as the main etching gas.

ISSN:1071-1023    

DOI:10.1116/1.583599

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

High rate masked etching of III–V materials such as GaAs and InP is needed for device processing requirements, such as via formation and chip separation. We have investigated the use of magnetron enhanced reactive ion etching to etch GaAs using photoresist as a mask. This technique gives unmasked etch rates up to 7 μm/min in GaAs. With an adequate heat sink, a photoresist mask shows little degradation for etch rates up to 1.2 μm/min with an undercut less than about 0.5 μm. Mechanisms of these results and directions for future work are presented.

ISSN:1071-1023    

DOI:10.1116/1.583601

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Hydrogen doping of Ta films before thermal oxidation affects the dc leakage current in oxidized Ta films. Metal‐insulator‐semiconductor (MIS) capacitors of Al/Ta2O5 (40 nm thick)/Si‐substrate structures have been prepared for the electrical measurements. The Ta films were reactively sputtered onp‐type Si substrates in a mixture of Ar and H2gases suitable for hydrogen doping. The hydrogen doping was found to be effective in reducing the leakage current in the Ta2O5films to be less than 10−3times that of undoped films, especially after low temperature oxidation at 400 °C. Secondary ion mass spectrometry (SIMS) analysis showed that the incorporation in the Ta2O5films of Si from the substrate was decreased by the presence of hydrogen during sputtering. A possible explanation for the reduction of leakage current caused by hydrogen doping is that the prevention of Si entry into Ta2O5films reduces the density of oxygen vacancies induced by unsaturated SiOx(x<2). This is thought to suppress the Poole–Frenkel‐type conduction in the Ta2O5films.

ISSN:1071-1023    

DOI:10.1116/1.583602

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

A parallel beam reflection technique has been developed in our laboratory for measuring intrinsic residual stress for Si wafers thermally oxidized at temperatures of 600–1150 °C. A detailed description of this technique is provided, and stress values calculated for thermally grown SiO2films on Si are consistent with those reported in the literature. Low temperature thermal oxidations resulted in compressive intrinsic SiO2stresses greater than 4×109dyn/cm2.

ISSN:1071-1023    

DOI:10.1116/1.583603

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Pt films deposited by electron‐beam evaporation onto both heated and unheated Si substrates have been used to form PtSi by different annealing sequences and ambients. Pt films deposited on substrates at 350 °C show complete formation of PtSi. Subsequent annealing at 550 °C is needed to form the protective oxide desired for device processing, with little dependence on the annealing ambients used. Pt films deposited on unheated substrates, on the other hand, show a partial formation of Pt2Si. The formation of PtSi by further annealing of such films is clearly dependent on the annealing sequence and ambient used. A three‐temperature sequence at 200/300/550 °C in forming gas is shown to allow a complete reaction between Pt and Si, and to develop a surface protective oxide of excellent resistance against etching in aqua regia. PtSi films formed by single‐temperature annealing at 550 °C in various ambients, however, show incomplete reactions between Pt and Si, leaving unreacted Pt and traces of Pt2Si, and a surface passivating oxide of poor resistance against aqua regia. The results on such evaporated Pt films are therefore similar to those reported earlier for the sputtered Pt. Film structures and compositions, phases formed, and Schottky diodes using different processes are analyzed and compared with those using sputtered Pt.

ISSN:1071-1023    

DOI:10.1116/1.583559

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

A technique for enhancing the conductivity of polysilicon interconnects by self‐aligned layers of platinum has been developed. A sheet resistance of approximately 1 Ω/⧠ was achieved for an interconnect height of 270 nm. Very thin layers of platinum have also been used to provide self‐alignment of other metals such as nickel, titanium, and aluminum. Nickel and titanium required prolonged ultrasonic processing to achieve self‐alignment to the polysilicon, as their specific stiffness coefficients were less favorable than that of platinum. Aluminum self‐alignment was only achieved after overlaying with films of nickel and platinum, and subsequently removing the latter layers by dissolving the nickel in fuming nitric acid. Polysilicon interconnects enhanced with a layer of self‐aligned aluminum yielded a sheet resistance of 1.2 Ω/⧠ for a total interconnect height of 120 nm. Metal‐oxide semiconductor (MOS) transistors and ring oscillators manufactured with metal enhanced interconnects showed no degradation effects when compared to those manufactured by the standard MOS process. Therefore, the process offers the advantages of self‐aligned source and drain regions and high yields associated with polysilicon gate technology together with those of a highly conducting metal gate.

ISSN:1071-1023    

DOI:10.1116/1.583560

出版商:American Vacuum Society    

年代:1986

数据来源: AIP