Separation By Implantation Of Oxygen Research Articles

Reactive Ion Etching of SOI (SIMOX and ZMR) Silicon in Nitrogen Containing CF 4 + O 2 and SF 6 + O 2 Plasmas

The effects of addition on the etch rate of bulk‐silicon and silicon‐on‐insulator (SOI) separation by implantation of oxygen (SIMOX) and zone melting recrystallization (ZMR) samples using and plasmas; as well as the damage assessment of the plasma are reported. In plasma, the additive reduces the etch rate of the masking oxide [chemical vapor deposited (CVD)] while significantly increasing the silicon etch rate and, thus, increasing the selectivity by 44–64%. In plasma, the silicon etch rate is increased due to the addition. However, the increase in selectivity is about 16–45%. The etch rate of SOI silicon especially in plasma is higher than that of bulk‐silicon samples. The higher etch rate of SOI samples appears related to the higher defect density of the SOI silicon. The damage assessment studied through Schottky diode and metal oxide semiconductor (MOS) capacitor samples indicates that plasma with additive introduces less damage as compared to without additive. Furthermore, postmetal annealing at 250°C for 15 min in ambient improves the characteristics of both Schottky diode and MOS capacitor devices. Thus the addition of improves the etch rate, and selectivity in some cases, and at the same time decreases the damage.

Manufacturing technology for 200mm SIMOX Wafers

Separation by IMplantation of Oxygen (SIMOX) has become the leading method for formation of high quality Silicon-On-Insulator (SOI) material. SIMOX material is currently being incorporated into technology designs for commercial ULSI CMOS applications. A critical issue for utilization of SIMOX for commercial applications is the availability of large diameter (>200mm) wafers in sufficient quantities. The need for large diameter wafers and the material quality requirements for ULSI CMOS applications present special issues for the design of implantation equipment used to fabricate the material. This paper discusses the design aspects of the Ibis 1000 implanter which allow the production of SIMOX wafers up to 300mm in diameter, and presents experimental results obtained using this machine.

Fabrication of ultrathin SOI by SIMOX water bonding (SWB)

Ultrathin silicon-on-insulator (SOI) layers of separation by implantation of oxygen (SIMOX) wafers have been transferred onto thermally oxidized silicon wafers by wafer bonding technology. Due to the technical availability and the complementary nature of SIMOX and wafer bonding approaches, SIMOX wafer bonding (SWB) solves some of the respective major difficulties faced by both SIMOX and wafer bonding for device quality ultrathin SOI mass production: the preparation of adequate buried oxide (including its interfaces) in SIMOX and the uniformly thinning one of the bonded wafers to less than 0.1 μm in wafer bonding. The effect of positive charges in the oxide on bondability of ultrathin SOI films and possible applications of SWB will also be outlined.

BaPbO 3-based thick film resistor : Yu-Hung Hsieh and Shen-Li Fu. IEEE Transactions on Components, Hybrids, and Manufacturing Technology15(3), 348 (1992)

Patterned silicon-on-insulator (SOI) materials have been fabricated by masked separation by implantation of oxygen (SIMOX) technique. The formed SOI structure was analyzed by cross-sectional transmission electron microscopy (XTEM). The patterned SOI materials prepared with low-dose and low-energy SIMOX technique exhibit high quality featured by defect free transition of SOI and bulk silicon region and high degree of surface planarity. Furthermore, the buried oxide (BOX) layer is of high integrity at such a low-dose ion implantation. The fabricated excellent quality patterned SOI materials will be the desirable substrates for system-on-a-chip (SOC) applications.

Microstructural analysis of nickel silicide formed by nickel/silicon-on-oxide annealing

Microstructures of crystalline nickel disilicide thin films formed on SIMOX (separation by implantation of oxygen) Si-on-oxide substrates were analyzed using electron microscopy. The samples were examined both in the top-down plane-view orientation and in cross section along a [110] direction. The nickel silicide films were formed through thermal reaction of metallic nickel deposited on the top Si layer of the SIMOX substrates. The results were compared with epitaxial NiSi2 layers grown on single crystal silicon substrates. Twin boundaries were observed at the silicide/oxide interface. The oxide layer acts as a diffusion barrier which prevents nickel from diffusing into the substrate resulting in uniform NiSi2 on a SiO2/Si substrate.

Defect generation sensitivity depth profile in buried SiO2 using Ar plasma exposure

The sensitivity to oxygen-vacancy defect (E′) generation of buried SiO2 (BOX) layers in separation by implantation of oxygen (SIMOX) structures is studied by electron spin resonance. The E′ generation tool used is exposure to a dc Ar glow discharge that produces E’s predominantly in a surface layer of ≊100 Å thick, reaching local volume densities at the surface up to 8×1019 cm−3. Reoxidation of the layers is observed to reduce this value close to that of regular dry thermal oxide (≥29 times lower). This glow discharge exposure, alternated with step-by-step etch back, allowed mapping of the defect generation sensitivity depth profile for the entire buried layer, revealing a fairly uniform sensitivity with a strong decline towards the BOX/substrate interface. The results provide evidence that the buried oxide contains excess Si, exceedingly so near the BOX/substrate interface.

A closed form analytic model for separation by implantation of oxygen oxide growth using a joined-Gaussian approximation

A closed form analytic solution to the growth characteristics of the separation by implantation of oxygen (SIMOX) buried oxide and silicon film, based on a two-sided Gaussian approximation to the oxygen implant profile in the SIMOX process, is presented. The model used includes the effects of substrate swelling and sputtering due to the implanted oxygen, as well as the effects of saturation of the oxygen density at the stoichiometric SiO2 level in the implanted region. The results of this investigation show that for typical SIMOX implant conditions currently used in high-current implanters, the total dose of oxygen required to first reach the saturation level is only slightly dependent on the swelling and sputtering effects associated with the oxygen implantation, and that the deviation of the location of the first saturation point from the commonly used implant range can be significantly affected by the implant profile. In addition, it is shown that a ‘‘natural parameter’’ GNsat, where G is the net growth of the substrate per implanted oxygen atom and Nsat is the saturation level of oxygen atoms in the buried oxide, can be used to characterize the magnitude of the effects of the implant parameters on the final SIMOX material. It is also shown that the parameter GNsat can be easily obtained from the slope of a Tox vs Tsi plot.

Ultrathin Low Energy Simox for Low Cost, High Density Applications

ABSTRACTSilicon-on-insulator (SOI) materials made by standard energy (150 to 200 keV) separation by implantation of oxygen (SIMOX) processes have shown great promise for meeting the needs of radiation-hard microelectronics. Since much smaller doses are required, low energy SIMOX (LES) reduces cost, improves radiation hardness, and increases the throughput of any ion implanter. The process can also produce high quality thin SIMOX structures that are of particular interest for fully depleted and submicron device structures. In this paper, we address the formation as well as the material and electrical characterization of LES wafers and compare them with standard SIMOX wafers.

Synthesis of Si1-xGex-on-Insulator by 74Ge+ Ion Implantation in a Simox Substrate

ABSTRACTA single crystalline Si1-xGex overlayer on insulator is realised by the implantation of germanium into a SIMOX (Separation by IMplantation of OXygen) substrate. Two SIMOX samples were implanted with 74Ge+ at elevated temperature (≈600°C), and subsequently annealed at different temperatures and anneal ambients. The microstructure, stoichiometry, and conductivity of the Si1-xGex over-layer were studied using transmission electron microscopy, Rutherford backscattering spectrometry/ion channelling and two-probe conductivity measurements. As a result of lattice reordering after final heat treatment, and despite high defect density observed in the XTEM microstructure, the measured conductivity of the over-layer is higher than of the starting SIMOX material. These results suggest a possibility of band-gap engineering by synthesis of Si1-xGex-on-insulator.

Distribution of Ge in O+ implanted silicon

We have studied 50 nm Si0.8Ge0.2 buried layers and 800 nm Si0.9Ge0.1 layers, grown by molecular beam epitaxy, which were implanted with 200 keV oxygen O+ ions to a dose of 1.8×1018/cm2. This implantation procedure is similar to that used in the formation of SIMOX (separation by implantation of oxygen), although it was not followed by the usual high temperature anneal. Because the initial implantation profile extends as far as 600 nm below the Si surface, the 50 nm Si0.8Ge0.2 layers were embedded in Si at depths of 600, 500, 400, and 300 nm from the Si surface. The effects of Ge incorporation could then be studied as a function of distance from the surface and position within the implantation profile. Using a scanning transmission electron microscope equipped with energy dispersive x-ray spectroscopy, we examined cross-sectional specimens for the distribution of the Ge in and around the implanted oxide layer. We found that the Ge tended to be excluded from the oxide in all the samples with the 50 nm buried layer. For the case where the oxide was implanted into the midst of an 800 nm layer, the Ge remained in the oxide.

Field dependent charge trapping effects in SIMOX and buried oxides at very high dose

SIMOX (separation by implantation of oxygen) devices have been irradiated at up to 100 Mrad under different positive and negative back-gate voltages. At low cumulated dose, hole trapping is controlled by external applied field. For higher doses up to 100 Mrad, the early positive net charge is compensated mainly by electron trapping. Nevertheless, at weak fields, no evidence of positive charge compensation is observed. Interface state buildup appears at very high dose (>10 Mrad) for the set of biases used, but influences slightly V/sub tb/ shift. The trapped hole recombination effect also occurs, but seems significant only for negative biases in the numerical approach. Furthermore, annealing data reveal a complex structure of traps that requires further investigations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Evidence for a deep electron trap and charge compensation in separation by implanted oxygen oxides

The authors present direct evidence for the creation of deep electron traps in SIMOX (separation by implantation of oxygen) buried oxides. In addition, they present combined electrical and electron spin resonance evidence which demonstrates that at least some positively charged paramagnetic E' centers are compensated by negatively charged centers. Finally, they present evidence which strongly suggests that a substantial fraction of the deep electron traps are coupled to E' centers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electron and hole trapping in irradiated SIMOX, ZMR and BESOI buried oxides

Shallow electron and deep hole trapping in the buried oxides of SIMOX (separation by implantation of oxygen), ZMR, and BESOI (bond and etchback silicon-on-insulator) material are examined. By irradiating the oxides with X-rays at cryogenic temperatures, 40-50 K, hole motion is frozen and electrons are trapped. The oxide charge is determined by C-V measurements. Following the cryogenic irradiation, the electrons are detrapped by field stressing (tunneling) or by annealing (thermal excitation). Hole trapping is examined by annealing after the trapped electrons are removed by field stressing. Substantial shallow electron and deep hole trapping distributed uniformly through the oxide is observed for all buried oxides that are processed above about 1100 degrees C. A comparison to thermal oxides grown at 850 degrees C and annealed at 1300 degrees C with and without a polysilicon capping layer shows that the top silicon layer significantly increases trap formation. These results indicate that the oxide defects responsible for the electron and hole trapping are produced by chemically reducing the oxide and producing defects such as Si-Si pairs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Time-dependent radiation-induced charge effects in wafer-bonded SOI buried oxides

Time-resolved capacitance-voltage (C(V/sub g/)) voltage shift measurements were performed on wafer-bonded and etched-back silicon-on-insulator (BESOI) buried oxide (BOX) capacitors following their exposure to pulsed irradiation. The results indicate that BESOI BOX, in some cases, more closely resembles thick thermal SiO/sub 2/ than SIMOX (separation by implantation of oxygen) BOX, and shows substantial hole transport and only moderate bulk hole trapping. However, unlike conventional thermal oxides, the BESOI BOX shows evidence of electron trapping in the oxide probably associated with the wafer bonding interface. High-temperature annealing reduces the electron trapping but enhances hole trapping at the Si-SiO/sub 2/ interfaces and possibly in the BOX bulk. The results indicate that location of the bonding surface and control of high-temperature annealing are important for producing radiation-hard BESOI.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Photoconduction measurements of the charge trapping and transport in bond-and-etch-back buried oxides

The charge trapping and transport characteristics of bond-and-etchback buried oxides (BESOI) were investigated using a photoconduction current technique and total dose capacitance-voltage shift measurements. Results are compared with results previously obtained on standard SIMOX (separation by implantation of oxygen) materials. The photocurrent experiment was also performed on thermally grown oxides with an oxide layer similar in thickness to the BESOI and SIMOX material used in this study. Measurements were performed on the thermal oxides as a method of calibration for both the experimental and analytical methods that are applied to the photoconduction current technique. Large normalized photoconduction currents and large postirradiation midgap voltage shifts in the BESOI material were measured. Taken together, these results indicate that most of the electrons and the holes move through the BESOI oxide and significant fractions of the holes are trapped at the interfaces. These radiation response characteristics are also typical of non-radiation-hardened thermal oxides, and this leads to the further conclusion that techniques used to successfully harden thermal oxides may also be successful when applied to BESOI material.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurements of film carrier lifetimes in silicon-on-insulator wafers by a contactless dual-beam optical modulation technique

A contactless dual-beam optical modulation (DBOM) technique has been applied to measure the film carrier lifetimes in the SIMOX (separation by implantation of oxygen) wafers with different oxygen implant doses, annealing temperatures, and film thicknesses. Film carrier lifetimes ranging from 0.23 to 0.72 μs were observed in these wafers. The DBOM method is based on the modulation of the transmission intensity of an infrared (IR) probe beam by a visible pump beam (hν≥Eg) via free-carrier absorption in the SIMOX wafer. A theoretical model is developed to deduce the excess carrier lifetimes in the SIMOX film by the DBOM technique. Mappings of the film carrier lifetimes in these SIMOX wafers were also carried out.

Trends in silicon-on-insulator technology

SOI technology has quickly evolved from the first laser recrystallization experiments of the early eighties to the recent fabrication of 256k SRAMs in thin-film material. Of the many different SOI materials which have been investigated, some have found successful applications, while others never really quite made it. For example, laser recrystallization has been used to produce incredible 3D integrated circuits in Japan, but the fabrication yield is close to zero. SIMOX (separation by implantation of oxygen), and BESOI (bonded and etched-back SOI), on the other hand, are quite successful, and are now used for the fabrication of integrated devices with good fabrication yield. This paper will quickly review the “history” of several major SOI materials and their field of application.

Effect of Thermal ramping rate on defect formation in oxygen-implanted silicon-on-insulator material

Integrated circuits on SIMOX (Separation by IMplantation of OXygen) have higher speed, radiation hardness, and higher temperature capability. Defects in the top Si layer inhibit bipolar applications and may affect CMOS(Complementary Metal-On-Semiconductor) device yield, operation and reliability. As-implanted SIMOX has many types of defects, including short stacking faults(SFs), multiply faulted defects(MFDs), and {113} defects. In annealed SIMOX, new defects form during the ramping cycle. The effect of thermal ramping rate on the development of new defects has received only limited study. In this work, the effects of rapid thermal annealing(RTA) and thermal ramp rate on defect density and structural change were studied.Two set of samples were prepared with different oxygen doses. First, one set of (100) Si wafers was implanted with a high dose of 1.8×l018cm−2 at 200 KeV at 620°C. A rapid thermal anneal(RTA) wafer was obtained from a lamp anneal for 1 minute at 1320°C using a ramp rate of 50°C/sec. A portion of this sample was then conventionally annealed in a tube furnace for 5 hours at 1320°C. Another set of (100) Si wafers was implanted with a low dose of 3×l015cm−2 at 25°C. Different samples were then annealed at 1250°C for 30 sec using three ramp rates of 50°C/sec, l°C/sec and 0.1°C/sec. Cross-sections of the samples were studied with conventional transmission electron microscopy (CTEM) at 200 KeV.

Measurements of substrate carrier lifetimes in silicon-on-insulator wafers by a contactless dual-beam optical modulation technique

A contactless dual-beam optical modulation (DBOM) technique has been applied to measure substrate carrier lifetimes in SIMOX (Separation by IMplantation of OXygen) wafers with different oxygen implant doses, annealing temperatures and film thicknesses. Substrate carrier lifetimes ranging from 5 to 20 μs were observed in these wafers. The DBOM method is based on the modulation of the transmission intensity of an infrared (IR) probe-beam by a visible pump-beam ( hν ⩾ E g) via free carrier absorption in the SIMOX wafer. A theoretical model is developed to deduce the excess carrier lifetimes in the SIMOX substrate by the DBOM technique. Mappings of the substrate carrier lifetimes in these SIMOX wafers were carried out, and the results are in good agreement with values determined by the surface photovoltage (SPV) method.

A model for analyzing the interface properties of a semiconductor-insulator-semiconductor structure. II. Transient capacitance technique

For pt.I see ibid., vol.39, no.7, p.1740-46 (1992). A bias-scan deep-level transient spectroscopy (DLTS) method for measuring interface states in a semiconductor-insulator-semiconductor (SIS) capacitor structure is described. Introducing a charge coupling factor between the film/oxide (F/O) and the substrate/oxide (S/O) interfaces made it possible to extract interface trap densities from the measured transient signals. This technique was used to determine the interface trap densities and capture cross sections at both the F/O and S/O interfaces of SIMOX (separation by implantation of oxygen) based SIS capacitors. >