J. Min

Formation of buried oxide in silicon using separation by plasma implantation of oxygen

Plasma immersion ion implantation (PIII) is used to fabricate buried oxide layers in silicon. This ‘‘separation by plasma implantation of oxygen’’ (SPIMOX) technique can achieve a nominal oxygen atom dose of 2×1017 cm−2 in implantation time of about 3 min. SPIMOX is thus presented as a practical high‐throughput process for manufacturing silicon‐on‐insulator. In the SPIMOX samples prepared, three distinct modes of buried oxide microstructure formation are identified and related to the as‐implanted oxygen profiles. A first‐order model based on oxygen transport and oxide precipitation explains the formation mechanisms of these three types of SPIMOX layers.

Ion-cut silicon-on-insulator fabrication with plasma immersion ion implantation

We report the implementation of ion-cut silicon-on-insulator (SOI) wafer fabrication technique with plasma immersion ion implantation (PIII). The hydrogen implantation rate, which is independent of the wafer size, is considerably higher than that of conventional implantation. The simple PIII reactor setup and its compatibility with cluster-tools offer other ion-cut process optimization opportunities. The feasibility of the PIII ion-cut process is demonstrated by successful fabrication of SOI structures. The hydrogen plasma can be optimized so that only one ion species is dominant. The feasibility of performing ion-cut using helium PIII is also demonstrated.

Separation by plasma implantation of oxygen (SPIMOX) operational phase space

Separation by plasma implantation of oxygen (SPIMOX) has been suggested as an economic alternative for separation by implantation of oxygen (SIMOX) to form the silicon-on-insulator (SOI) structure. The chief advantage of SPIMOX is the high throughput and low-cost implanter. The operation regime of implantation for SPIMOX, which uses dc plasma immersion ion implantation (PIII) for the oxygen implantation, has been studied in the phase space of implantation time and chamber pressure during implantation. The phase space is developed for a definite implantation voltage and dose which are dependent on the dimensions of the SOI structure to be fabricated. The effects of dose, implantation voltage, and fractional ionization on the phase space have been discussed. SPIMOX can achieve high throughputs for thin-SOI structure fabrications using high fractional ionization plasmas. The phase space developed for SPIMOX implantation ran also be used for other high-dose dc implantations with PIII which require a peaked implant profile below the surface.

Separation of plasma implantation of oxygen to form silicon on insulator

Separation by plasma implantation of oxygen (SPIMOX) is an economical method for silicon-on-insulator (SOI) wafer fabrication. This process employs the plasma immersion ion implantation (PIII) for the implantation of oxygen ions. The implantation rate, which is independent of the wafer size, is considerably higher than that of conventional implantation. The simpler implanter set-up is lower in cost and easier to maintain. The feasibility of SPIMOX has been demonstrated with successful fabrication of SOI structures implementing this process. The operational phase space on implantation condition, oxygen dose, and annealing requirement are identified. Secondary ion mass spectrometry analysis and cross-sectional transmission electron microscopy micrographs of the SPIMOX sample showed continuous buried oxide under single crystal overlayer with sharp silicon/oxide interfaces.

Buried oxide formation by plasma immersion ion implantation

Abstract Although separation by implantation of oxygen (SIMOX) is an attractive approach for fabricating silicon-on-insulator (SOI) materials for radiation-hardened electronic devices and high-speed CMOS circuits, the production cost is high. The novel technique of plasma immersion ion implantation (PIII) emulates the traditional beamline technique in many aspects. Some of the advantages are: no mass selection, no beam transport optics, large area implantation, high ion flux, short implantation time, and low costs. We used PIII and oxygen implantation (nominal dose: 5 × 10 17 atoms/cm 2 ) to form thin buried oxide layers in the sub-mtorr operating pressure regime. A 20–50 nm thick buried oxide layer with a Si overlayer thickness of 20–50 nm was fabricated in about 5 min. The implanted wafers were capped with a nitride layer and subsequently annealed for 6 h at 1300 °C in a nitrogen ambient to remove the damage. The resulting wafers were analyzed using a variety of techniques, including RBS and XTEM.

Nucleation mechanism of SPIMOX (separation by plasma implantation of oxygen)

Buried oxide layers in Si were fabricated using the SPIMOX (separation by plasma implantation of oxygen) technique. The implantation was carried out by applying a negative bias to a Si substrate wafer immersed in an oxygen plasma. An implantation time of 2–3 min was required to implant the oxygen at doses ranging from 1 × 1017 atoms cm−2−3 × 1017 atoms cm−2. At a lower ion dose (1 × 1017 atoms cm−2), buried oxide precipitates were observed. At a higher dose (3 × 1017 atoms cm−2), a continuous buried oxide layer could be obtained, as indicated by cross section transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS). By optimizing the concentration ratio of O+ and O2+ in the plasma and the implantation fluence, a double oxide layer (Si/oxide/Si/oxide/Si) structure could be produced in a single implantation step.

Combined impurity gettering effects of helium-induced cavities and oxygen precipitates created by plasma immersion ion implantation

Abstract Helium bubbles are formed in silicon by high dose implantation using the plasma immersion ion implantation technique. Thermal annealing of the implanted samples at a temperature above 700 °C causes the helium to diffuse out of silicon and form cavities which can be observed by cross-sectional transmission electron microscopy. The well-defined band of helium-induced cavities both with and without oxygen precipitates (formed by subsequent oxygen implantation and annealing) have been studied as gettering layers for copper and gold. Our secondary ion mass spectrometry and Rutherford backscattering spectrometry results demonstrate that the presence of oxygen does not increase significantly the gettering efficiency of these cavities. The combined cavity/oxygen gettering sites also remain stable up to 1200 °C

Synthesis of buried oxide by plasma implantation with oxygen and water plasma

Separation by plasma implantation of oxygen (SPIMOX) is a novel method for fabricating silicon-on-insulator (SOI) wafers. This method uses plasma immersion ion implantation (PIII) where the desired voltage of implant is applied to a wafer immersed in a plasma. SPIMOX is particularly suited for thin separation by implantation of oxygen (SIMOX) wafer fabrication. High implantation rates can be achieved in SPIMOX. A dose of nearly 10/sup 18/ cm/sup -2/ with an implant current density of 1 mA cm/sup -2/ can be achieved in 3 minutes of implantation time. The short implantation time and the simplicity of the implantation equipment makes it a potentially more economical method for fabricating SIMOX wafers. Moreover, the theoretical time for implantation remains constant in SPIMOX with increase in wafer size.

Gettering effects of helium cavities created by high dose plasma immersion ion implantation

Summary form only given, as follows. Helium bubbles are formed in silicon using high dose plasma immersion ion implantation (PIII). Thermal annealing of the implanted sample at temperature over 700/spl deg/C causes the helium bubbles to diffuse out of the silicon substrate. The cavities formed provide active sites for impurity gettering. The gettering of copper and gold impurities are characterized by secondary ion mass spectrometry and the results demonstrate that the cavities are effective sinks for copper and gold. The gettering process also remains stable up to 1200/spl deg/C. PIII is thus an excellent technique to create cavities for gettering sites, for example, on the backside of silicon wafers. The high-dose and immersion characteristics of PIII make it an ideal technique for future 300 mm and 400 mm silicon wafers.

Operational phase-space of separation by plasma implantation of oxygen (SPIMOX)

SPIMOX using plasma immersion ion implantation (PIII) has been proposed as a cost-effective method for fabricating silicon on insulator (SOI) wafers. PIII, compared to conventional implanters, allows for simpler and low maintenance-cost implanters. High throughput, independent of the wafer size can be achieved by the SPIMOX process. A phase-space of implantation time and implantation pressure is developed to determine the operational regions for SPIMOX implantation. SPIMOX process using high fractional ionization plasma for implantation is found to be particularly suited for thin SOI fabrication required for future low-power IC applications.