Zone Melting Recrystallization Research Articles

Defect Control in Thick SOI-Films Produced by Zone Melting Recrystallization

Defect Control in Thick SOI-Films Produced by Zone Melting Recrystallization

Numerical Modeling of Energy-Beam Induced Localized Melting of Thin SI Films

ABSTRACTWe have developed a quantitative model, based on a two-dimensional finite difference enthalpy method, which accounts for the localized melting behavior of thin Si films on substrates. The model incorporates radiative and conductive heat flow components and takes account of the phase changes that occur during zone-melting recrystallization. Emphasis is placed on the effects resulting from the differences in reflectivity and emissivity between solid and liquid Si. The model provides quantitative information concerning the temperature profile of the Si film and the configuration of the solid-liquid interface. Results of the analysis indicate that there exist two distinct types of transition behavior: i) reflectivity-change dominated and ii) emissivity-change dominated. Partial melting and a nonplanar solid-liquid interface are characteristics of the reflectivity-change dominated behavior. The emissivity-change dominated behavior, on the other hand, can be characterized by explosive-like melting and a planar solid-liquid interface. The conditions and physical factors which give rise to these behaviors are discussed.

Study of dashed seed lines and capping layers for laser seeded zone melting recrystallization

This paper deals with the material quality of the SOI layers obtained through laser seeded ZMR. A numerical calculation and an experimental study have been performed to evaluate the merits of dashed seed lines and thick capping layers. As a result, defects are rejected at 100 μm from the seed, and the SOI layer thickness variations are reduced to ±200 Å.

SOI-Films by Zone Melting Recrystallization of Polycrystalline Silicon

SOI-Films by Zone Melting Recrystallization of Polycrystalline Silicon

Artificial epitaxy (graphoepitaxy) as an approach to the formation of SOI

A short review of the state-of-art for zone-melting recrystallization (ZMR) is given with emphasis on the versions of the process which allow the microstructure of SOI films to be controlled. In particular, a combination of ZMR with artificial epitaxy (graphoepitaxy) is considered as a fruitful approach for the preparation of such films with controllable configurations and/or reduced concentrations of defects.

Materials and devices toward three-dimensional integration

Abstract It has been shown that the apparent benefits of a two-layer stacked SOI system, i.e. packing density and speed improvements, are less than could be expected in the context of a VLSI requirement [1]. In this project the stacked SOI system has been identified as having major application in the realization of integrated, mixed technology systems. Zone-melting-recrystallization (ZMR) with lasers and electron beams have been used to produce device quality SOI material and a small test-bed circuit has been designed as a demonstration of the feasibility of this approach.

Time-resolved reflectivity techniques for dynamic studies of electron beam recrystallization of silicon-on-insulator films

A time-resolved reflectivity (TRR) technique has been developed for dynamic studies of swept beam heating of silicon-on-insulator (SOI) materials. The method exploits the temperature dependence of the reflectivity of SOI films to allow noncontact temperature measurement with high spatial and temporal resolution. This technique is of considerable practical importance for beam processing, since it allows the temperature distribution induced by a beam being scanned across a specimen to be determined. The temperature distribution produced by a line electron beam swept across a SOI specimen was experimentally measured and found to be consistent with a theoretical prediction. The TRR technique can also be used to study melting and will prove useful for characterizing zone melting recrystallization, where thermal modeling is often inadequate for the complex structures involved.

CW argon-laser-induced zone-melting recrystallization of thin silicon on oxide

Silicon on insulator (SOI) technologies offer significant possibilities for high-speed and high-density integrated circuit applications. Single-crystal silicon islands of 50 μm width and 165 μm length have been successfully obtained by a combination of seeding structures, a specially-shaped laser beam spot and locally altered capping layers. No grain boundaries and no sub-grain boundaries were observed in the island etched with Secco etchant. The recrystallized film had the same 〈100〉 crystal orientation as the silicon substrate. The layers were smooth on the surface. The silicon recrystallization obtained with a CW argon laser is described, and two types of seeding structures are compared. The mechanisms of the single-crystal seeding growth of these structures are discussed. p-Channel depletion MOSFET's with L=10 μm and w=40 μm were fabricated in the recrystallized film. The I D- V D characteristics of the devices were excellent. The surface hole mobility was calculated to be 170 cm 2/V·s, the same as for devices fabricated in bulk single crystal.

Role of impurities in zone melting recrystallization of 10 μm thick polycrystalline silicon films

Zone melting recrystallization (ZMR) of polycrystalline silicon on SiO2 can offer an interesting, i.e., cheaper, alternative to the dielectric isolation technology used for high-voltage integrated circuits or smart power devices. For that purpose crystalline Si layers of 10–15 μm thickness are needed. In this work a mercury-arc lamp stripheater was used to recrystallize 10 μm thick polycrystalline silicon films. In unseeded layers, grain boundaries and subgrain boundaries appeared. By applying seeding, single crystalline areas of at least 1 mm by 1 mm were obtained. In these layers stacking faults were revealed as being the major crystal defect. In ZMR oxygen, nitrogen, and carbon are the major impurities which are incorporated into the silicon either intentionally or unintentionally. Among these impurities, nitrogen and carbon are believed to play a crucial role in promoting the wetting of the insulator and cap layer by liquid silicon. In this paper the distribution and transport of oxygen and nitrogen during ZMR are studied. It is shown that nitrogen can cause dendritic growth and that oxygen is unlikely to do so.

Scanning electron microscopy study of seeded recrystallization of silicon-on-insulator layers with either polycrystalline or epitaxially deposited silicon in the seed windows

Silicon-on-insulator layers have been produced under conditions which are compatible with three-dimensional device integration. The layers were formed by zone melting recrystallization of two types of seeded silicon films in a dual electron beam system. High-resolution scanning electron microscopy was used to observe the starting materials and the stages of recrystallization from unseeded regrowth through seeded regrowth to under oxide melting. With the standard structure, which has an overall layer of polycrystalline silicon, good seeding requires melting into the bulk. However, when the silicon is deposited under conditions which give epitaxial growth in the seed windows, seeded recrystallization does not require melting in the substrate or even across the complete width of the window. A study of the silicon mass flow for the various stages is presented and the processing conditions for the minimum thickness variation of the silicon film are reported.

Cellular and dendritic morphologies on stationary and moving liquid-solid interfaces in zone-melting recrystallization

It is well known that when Si films are radiatively heated there exists a range of incident intensities for which liquid and solid regions coexist at near uniform temperature. Based on in situ microscopic observation of solidification interface morphologies, we argue that this phenomenon is responsible, at least in part, for the morphology of the liquid-solid interface in zone-melting recrystallization. We demonstrate this effect through stationary interface experiments. It is observed that even a stationary interface exposed to a gradient in radiation intensity develops interface morphologies similar to those of moving interfaces.

Electrical performances of devices made in SOI films obtained by lamp ZMR

Four-inch wafer lots have been processed in a conventional CMOS polysilicon gate process. The electrical parameters are used to study the influence of the problems related to the lamp zone-melting-recrystallization (ZMR) technique. Statistical results are available. The n-channel enhancement mode transistors of a 1.7-μm effective channel length exhibit a sharp threshold voltage distribution around 0.9 V with a standard deviation of 61 mV. The leakage current remains below a 0.1-pA/μm channel width for both p- and n-channel transistors. Two hundred forty-nine stage ring oscillators have been fabricated. They have a 0.5-ns propagation delay time for an effective channel length of 1.7 μm.

Zone-melting-recrystallization silicon-on-insulator technology

The author describes the zone-melting recrystallization (ZMR) technique and the crystallographic properties of silicon-on-insulator (SOI) films. He reviews the devices and circuits fabricated in these films, discusses their radiation hardness, and considers the prospects of the graphite-strip-heater technology for achieving commercialization.

Selective Epitaxial Growth Followed by in Situ Deposition of a- or Poly-Si for Seeded Soi.

AbstractSelective Epitaxial Growth (SEG) techniques find a growing number of applications in the field of Si IC's, such as, lateral isolation, vertical interconnects, seeded recrystallisation etc. In the present work, the use of Si SEG by CVD combined with in-situ deposition of a- or poly-Si for the improvement of SOI obtained by Zone Melting Recrystallisation (ZMR) or by Lateral Solid Phase Epitaxy (SPE) is described. The principle application for which the present work is intended is Three Dimentional (3D) Integration. One of the main constraints imposed on process is thermal compatibility with previously executed process steps. Hence the need to reduce the thermal budget for the Selective Epitaxial Growth as much as possible.

Improvement in crystalline quality of silicon on fused silica by zone melting recrystallization

AbstractIn the silicon‐on‐insulator (SOI) zonemelting crystallization method using a high‐frequency induction heating, an improvement has been examined for the crystalline quality of recrystallized silicon on a silica substrate. It is easy to obtain the (100) crystalline‐orientation by connecting island‐shaped areas with wide and short bridges (both made of polycrystal Si on a silica substrate). The (100) crystalline‐orientation can more easily be formed with a hexagon island area which has small angles to the bridge rather than a simple square. The reason can be explained by a thermal resistance during their recrystallization. When the bridge is wide and short so that its thermal resistance is small, there is an adequate thermal flow through it. This helps the recrystallization, otherwise it is supercooled. There was no subboundary in the side where the recrystallization occurred earlier, while subboundaries as crystalline defects were generally observed. This is considered to be due to the fact that the solid‐liquid boundary during the recrystallization has no significant micro irregularity. By utilizing this property, and by choosing appropriately the dimensions of the island and bridge, recrystallized Si with no subboundaries can be obtained.

Evaluation of Lamp Zone-Melting Recrystallization

AbstractThe intensity profiles of various kinds of topheaters are compared and discussed. Using the mercury-arc lamp heater experiments on polycrystalline silicon layers of thicknesses varying from 1 to 10 urn were performed. The 10 fiva layers were polished prior to recrystallization. After zone melting recrystallization they showed a strong (100) texture combined with an alignment of the [010] direction with the scan direction. By patterning 1 ¼m poly-silicon films into isolated narrow silicon stripes, the kinetic mechanism that is shown to be responsible for the alignment of the [010] direction along the scan direction could be inhibited. In this way other mechanisms that influence the orientation could be studied. Finally some electrical characteristics are presented.

Large Diameter Soi Wafers by Zone-Melting-Recrystallization

AbstractA pilot production Zone-melting Recrystallization system was designed and built with a capability to handle 25 wafer batches of 4“, 5“and 6“wafers. The design addresses several production requirements including high throughput, batch processing and automation. Measurements on product wafers indicate that material quality was not sacrificed to achieve production throughput levels. Exceptional structural quality and good electrical properties have been obtained on SOI wafers produced within this system. Specifically, defect densities as low as 5 X 104 /cm2 a level an order of magnitude lower than previously reported, have been achieved while the minority carrier lifetime of up to 30 microseconds, intrinsic dopant level < 2 X 1015 /cm3 and junction leakage below 1 X 1016 amperes/cm2 are either as good as or better than previously reported values. We believe that defect free ZMR material will become a reality.

Liquid-Solid Interface Morphologies and Defect Structures in Zone-Melting-Recrystallized Silicon-On-Insulator Films

AbstractIn-situ optical microscopy has been used to observe liquid-solid interface morphologies during zone-melting recrystallization of silicon-on-insulator films. These morphologies have been correlated with the defect morphologies of the recrystallized films. Stable cellular solidification fronts, which are obtained at low zone velocities if the radiation intensity gradient in the interfacial region is small, yield subboundary free films. We suggest that under these experimental conditions the interface morphology is primarily the result of radiative heating rather than constitutional supercooling.

ChemInform Abstract: Focused Lamp Zone Melting Recrystallization of Silicon on Insulating Substrates.

AbstractA new zone melting recrystallization (ZMR) technique for poly‐Si films on insulators has been developed using a pair of focused long tungsten lamps without keeping the entire wafer at the high temperature.

Focused Lamp Zone Melting Recrystallization of Silicon on Insulating Substrates

Zone melting recrystallization (ZMR) of silicon‐on‐insulator (SOI) has been performed by a pair of focused lamps. Distinction from conventional ZMR's is local instantaneous heating with focused beams on front and back surfaces of SOI wafers, instead of keeping the entire wafer uniformly at the high temperature. 0.4 μm thick poly‐Si films over 2 μm thick insulating layer on the Si substrate are recrystallized without an appreciable redistribution of arsenic atoms implanted,, 150 keV through 50 μm thick films on the Si substrate, which suggests that the focused lamp ZMR can be compatible with the three‐dimensional devices. The unseeded Si film recrystallization on grooved quartz wafers is crack‐free, large‐grained with (100) texture across several chips. For seeded samples, the lateral epitaxy takes place completely over the islands of in size without any subgrain boundaries, in which displacement of the island during ZMR can be avoided by connecting the island to each other with narrow bridges. Major remaining problems for SOI are the warpage of Si wafers and the subgrain boundaries.