Separation By Plasma Implantation Of Oxygen Research Articles

Control of implantation area in direct-current plasma immersion ion implantation (DC-PIII)

In plasma immersion ion implantation (PIII) of planar samples such as silicon wafers in the PIII-ion-cut as well as separation by plasma implantation of oxygen (SPIMOX) processes, the only important ions are the ones arriving at the top surface. Ions implanted into the other surfaces are, in fact, undesirable as they reduce the efficiency of the power supply and plasma source and give rise to metallic contamination. We have demonstrated direct-current PIII (DC-PIII) by using a grounded grid to separate the vacuum chamber for planar sample implantation. The advantages include lower equipment cost, higher power and time efficiency, larger impact energy, and last but not least, smaller instrument footprint. In this paper, we investigate the control of the implantation area by adjusting the radius of the extraction hole, the distance between the conducting grid and the sample, and the radius of the wafer stage. Theoretical simulation is conducted using particle-in-cell and experiments are also carried out. Our results indicate that the implanted area increases with the radius of the extraction hole and wafer stage, but decreases with a larger distance between the grid and sample. The effects of the extraction hole radius G/sub r/ are the largest, followed by the placement of the sample to the conducting grid H. The wafer stage poses the least influence in this respect, but a proper wafer stage dimension improves the lateral implant dose and incident angle homogeneity. Our simulation and experimental results suggest optimal ratios of these parameters for each wafer size.

Two-dimensional sample temperature modeling in separation by plasma implantation of oxygen (SPIMOX) process

Plasma immersion ion implantation (PIII) offers high throughput and efficiency in the synthesis of silicon-on-insulator (SOI) materials. In the separation by plasma implantation of oxygen (SPIMOX) process, the spatial and time variation of the sample temperature must be known and well controlled to ensure uniform buried oxide and silicon overlying layer thicknesses over the entire silicon wafer. In this paper, we describe a two-dimensional model and derive the temperature distribution on the silicon wafer with respect to time and other process parameters. Our results show laterally nonuniform heating by the incoming ions and the local temperature is influenced more by the sample voltage and thermal irradiation coefficient of the target than the pulse duration and plasma density. The model provides a simple and quick means to determine whether external heating will be needed to maintain the sample temperature at 600/spl deg/C during the SPIMOX process.

Novel approaches for low cost fabrication of SOI

Two trials for low cost manufacture of silicon-on-insulator (SOI) wafers were implemented. Low dose separation by implantation of oxygen (SIMOX) procedure has been conducted on a beam-line ion implanter with mass analyzer. The energy dependence of the formed SOI structure was studied at varied implant dosages. The integrity of the buried oxide (BOX) layer was examined by transmission electron microscopy (TEM) and the threading dislocation in the top silicon layer was evaluated by Secco technique. The results indicated that not only the implanted oxygen dose but also the oxygen ion energy plays an important role in the formation of SOI structure with good crystallinity of top silicon, sharp Si/SiO2 interfaces and highly integrated BOX layer free of silicon inclusion. For separation by plasma implantation of oxygen (SPIMOX) approach, water plasma, rather than oxygen plasma, was employed to avoid oxygen spread in the implant depth profile. The SPIMOX process using water plasma was carried out on a beam-line ion implanter without mass selector to simulate the plasma implantation procedure. Cross-sectional TEM study revealed that uniform BOX layer was formed under single crystal silicon superficial layer with the present approach. The interfaces between silicon superficial layer, BOX layer and bulk silicon were smooth and sharp. An implant dose window has been identified for fabricating the desirable SOI structure.

Formation of silicon on insulator using separation by implantation of oxygen with water plasma

Separation by plasma implantation of oxygen (SPIMOX) was developed to fabricate silicon-on-insulator (SOI) wafers based on separation by implantation of oxygen technology, however, it suffers from the coexistence of O+ and O2+ ions in the oxygen plasma, which gives rise to nonuniformity of the formed buried oxide layer. In the present work, water plasma was used as a source of oxygen (H2O+, HO+, and O+) for achieving small spread in the oxygen implant depth profile. The feasibility of SPIMOX with water plasma to form SOI wafers was explored at an ion implanter without mass separator. Cross-sectional transmission electron microscopy revealed that a uniform buried oxide layer was formed under a single crystal silicon overlayer with the present process. The interfaces between the silicon overlayer, buried oxide layer, and bulk silicon were smooth and sharp. An implant dose window has been identified for producing a desirable SOI structure.

Instrumental and process considerations for the fabrication of silicon-on-insulators (SOI) structures by plasma immersion ion implantation

Plasma immersion ion implantation (PIII) has recently been shown to be a viable method to fabricate silicon-on-insulator (SOI) materials using either the SPIMOX (separation by plasma implantation of oxygen) or the ion cut/wafer bonding method. We have recently modified and characterized a new generation plasma immersion ion implanter for SOI fabrication, and this paper will discuss some of the instrumental and processing issues, including the plasma source, mean free path consideration, and dc sheath characteristics.

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.

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.

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.

Synthesis of Soi Materials Using Plasma Immersion Ion Implantation

AbstractAs the dimensions of integrated circuits shrink towards the deep sub-micromeLer regime, silicon-on-insulator is regarded to be more favorable than silicon substrates. The biggest drawback of SOI is cost which will become more critical for next generation 300-nm silicon wafers. Plasma immersion ion implantation (PIII) provides a viable alternative for the fabrication of SOI wafers as the processing time is very short and independent of wafer size. Pill is being employed to synthesize two types of SOI materials, SPIMOX (Separation by Plasma IMplantation of OXygen) and bonded SOL. In SPIMOX fabrication, both oxygen and water plasmas have been attempted and the results indicate that a discrete buried oxide layer can indeed be formed. In the case of wafer bonding, PIII is utilized for smart-cutting, a process in which implanted hydrogen or helium causes the bonded wafer to crack along the plane thereby making one side of the wafer recyclable. This article reviews the work done and current status of SOI fabrication by PIII.

Competitive Oxidation During Buried Oxide Formation Using Separation by Plasma Implantation of Oxygen (Spimox)

AbstractWe have recently demonstrated a new implantation technique called SPIMOX (separation by plasma implantation of oxygen) to synthesize silicon-on-insulator structures using plasma immersion ion implantation (PIII) process. the implantation is performed by applying a large negative bias to a Si wafer immersed in an oxygen plasma created by an ECR source. Since the technique has no mass analysis, coexistence of O+ and O2+ ions in oxygen plasma can cause a non-Gaussian profile of the as-implanted oxygen distribution. We observed that during post-implantation annealing, the ripening process of the oxide precipitates depends on depth and concentration of the oxygen peaks. IN addition, implanted oxygen can migrate towards the Si surface during annealing, preventing a continuous buried oxide layer formation. IN this paper, we report our observation on the effect of the implantation profile on the competitions between internal oxidation at different depths and between internal and surface oxidation processes. With an additional He implantation, we demonstrate that the nucleation of oxide precipitation can be enhanced.

Formation of Silicon on Insulator (Soi) With Separation by Plasma Implantation of Oxygen (Spimox)

AbstractBuried oxide layers in Si were fabricated using non-mass analyzed plasma immersion ion implantation (PHI). We call this process of making separation by implantation of oxygen (SIMOX) with implantation by PIII as separation by plasma implantation of oxygen (SPIMOX). The implantation was carried out by applying a large negative bias to a Si wafer immersed in an oxygen plasma and a nominal dose of 2 × 1017 cm”2 of oxygen was obtained in less than three minutes. Cross section transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS) were used to characterize the wafers. Three distinct modes of microstructure development were observed after post implantation annealing. With a low oxygen dose (< 1 × 1017 cm”2 ), isolated silicon dioxide precipitates did not grow large enough to form a continuous oxide layer. With a high oxygen dose ( > 3 × 1017 cm”2 ), however, a single buried oxide layer was observed. By optimizing the concentration ratio of 0+ and 02+ in the plasma and the implant dose, a double oxide layer (Si/oxide/Si/oxide/Si) structure, was produced in a single implantation step.