U. Bussmann

Layer thickness calculations for silicon‐on‐insulator structures formed by oxygen implantation

A new computer program enables the evolution of oxygen distributions in separation by implanted oxygen (SIMOX) substrates to be simulated during implantation and also after high‐temperature annealing. The positions of the Si/SiO2 interfaces have been calculated for implantation energies of 150 and 200 keV. Theoretical results are in good agreement with experimental data over a wide range of fluences. It is found that the use of multiple implantation and annealing cycles, in comparison with a single implantation stage, shifts the buried oxide layer towards the surface.

Buried insulator formation by nitrogen implantation at elevated temperatures

Abstract Buried silicon nitride layers can be synthesized by high dose nitrogen implantation into silicon. To investigate temperature effects, 200 keV N + implantations into silicon were performed with doses of 0.35 to 1.05 × 10 18 N + cm −2 . A first set of samples was implanted at 500° C, using ion beam induced heating only. For the second set, a new sample holder provided constant background heating of the wafer maintaining it at a constant temperature of 670 ± 10° C by halogen lamp irradiation. Two hour anneals were carried out in flowing nitrogen at temperatures between 700 and 1200° C in 100° C steps. Rutherford backscattering measurements were performed in order to assess the quality of the silicon top layers. It is concluded that constant background heating leads to a major improvement of the crystalline quality for all implantation doses and for annealing temperatures up to 1100° C.

An investigation of Si0.5Ge0.5 alloy oxidation by high dose oxygen implantation

Abstract An attempt to implant a high dose (up to 1.8 × 1018 cm−2) O+ ions into a Si0.5Ge0.5 alloy grown by molecular beam epitaxy (MBE) was made in this work, and the oxidation of the alloy by the implantation before and after thermal treatment was studied using X-ray photoelectron spectroscopy (XPS). The changes of the composition distribution in the sample were observed from the XPS depth profiles. The chemical states of Si and Ge as well as the location of their oxides were obtained from the spectrum fitting. The results indicate that compared to the implantation made on single crystal Si or Ge, this alloy seems to have more in common with the bulk Si and the reason is attributed to the different reactivities between Si and Ge with oxygen and the different stabilities of their oxides. A possible way to improve the experiment to achieve the SIMOX (separation by implanted oxygen) structure in this material is also suggested.

Oxygen implantation through patterned masks: a method for forming insulated silicon device islands while maintaining a planar wafer surface

Abstract SIMOX (separation by implanted oxygen) is a recognized technology to produce silicon on insulator substrates. Laterally isolated device islands are formed by subsequent mesa etching or selective local oxidation of the silicon top layer. Alternatively, isolation can be achieved by using patterned masking layers in the implantation process, leading to continuous but nonplanar buried oxide layers. In order to ease device fabrication, it is desirable to achieve a planar wafer surface. Special test structures have been implanted with 200 keV oxygen to doses up to 2.4 × 10 18 O + cm −2 . The formation of TDI (total dielectric isolation) structures has been analyzed by Talystep and cross-sectional TEM. The successful formation of isolated islands in combination with a planar surface is demonstrated for an oxygen implantation through an oxide mask formed in a LOCOS process.

Silicon‐on‐insulator device islands formed by oxygen implantation through patterned masking layers

Separation by implanted oxygen is recognized as a versatile technology to produce silicon‐on‐insulator substrates. The lateral isolation of device islands is achieved by subsequent local oxidation or mesa etching of the silicon top layer. In an alternative approach, implantation is performed through patterned masking layers leading to a continuous but nonplanar buried oxide. Thereby, total dielectric isolation (vertical and lateral) of the device island is achieved in a single implantation stage. The masking structures used in this investigation are thermal oxides and polycrystalline silicon layers with window openings as well as patterned wafers formed by local oxidation of the bulk silicon wafers. Oxygen was implanted with energies of 100 and 200 keV to doses up to 2.2 × 1018 O+ cm−2. The resulting structures are studied by cross‐sectional scanning electron microscopy and transmission electron microscopy and the effects of mask material and implantation energy are discussed.

The effect of dose and temperature on the as-implanted microstructure of oxygen-implanted silicon

Abstract The effect of implantation temperature and oxygen dose on the structure of as-implanted separation by implantation of oxygen (SIMOX) wafers was studied by means of Rutherford backscattering spectrometry and ion channelling, secondary ion mass spectrometry and cross-sectional transmission electron microscopy. Silicon wafers were implanted with 400 keV 32 O 2 + ions at implantation temperatures varying from 200 °C to 700 °C, with oxygen doses from 5 × 10 16 O + cm −2 to 1.4 × 10 18 O + cm −2 . The formation of an amorphous phase in the buried layer, the crystallinity of the silicon overlayer and the corresponding layer thicknesses were monitored. A critical dose for the formation of an amorphous layer was established as a function of implantation temperature T i . The influence of T i on the microstructure was examined for a constant dose. The damage in the buried layer and the damage in the silicon overlayer relate to the implanted dose and the implantation temperature in a complex way.

Computer simulation of SIMOX and SIMNI formed by low-energy ion implantation

Abstract The computer program IRIS (Implantation of Reactive Ions into Silicon) has been modified and used to simulate low energy (

Behavior of high dose O+-implanted Si/Ge/Si structures

The synthesis of a buried oxide layer in multilayer Si/Ge/Si structures by the implantation of high doses of 200 keV O+ ions is studied by Rutherford backscattering analysis. The presence of Ge is found to have a minimal effect upon the mass transport of excess oxygen and interstitial silicon. Infrared transmission spectroscopy and x‐ray photoelectron spectroscopy confirm that the oxygen atoms bond preferentially to silicon forming silicon dioxide and SiOx, where x<2, with no evidence for Ge—O bonding.

Dynamic modelling of high dose oxygen profiles in SIMOX substrates

Abstract During the past decade SIMOX (separation by implanted oxygen) has emerged as one of the leading SOI (silicon-on-insulator) technologies. The implantation involves such high doses that sputtering, swelling and the diffusion of excess oxygen within the synthesized layer of SiO2 all contribute to a major oxygen redistribution. The computer program IRIS (implantation of reactive ions into silicon) has been developed to enable fast calculations of these oxygen profiles to be made over a wide range of implantation energies, doses and masking oxide layer thickness. In this paper the model is extended into two dimensions and calculations are performed to simulate high dose implantation through thick patterned masking layers. The resulting oxygen distributions near mask edges are discussed.

Dopant redistribution and activation in thin film SOI/SIMOX substrates

Experiments were performed to determine the transport properties, electrical activity, and redistribution of dopants implanted into SIMOX samples with different silicon layer thicknesses. High temperature annealed SIMOX samples with silicon film thicknesses of 2000 AA (SIMOX1) and 3000 AA (SIMOX2) were implanted with As/sup +/, Sb/sup +/, B/sup +/, and P/sup +/ ions. Activation of the dopant was achieved by annealing samples at either 950 degrees C or 1150 degrees C in flowing nitrogen gas in a resistivity heated furnace. Temperature dependence of the sheet resistance following As/sup +/ ion implantation into the same set of samples is presented. The main difference is seen above 800 degrees C when significant As diffusion occurs, which leads to uniform doping in the silicon layer and a value of sheet resistance which is temperature independent above 1000 degrees C.<<ETX>>