Oxygen Concentration In Silicon Research Articles

Ultrahigh sensitivity SIMS analysis of oxygen in silicon

We report on the detection of very low oxygen concentration in silicon by a secondary‐ion mass spectrometry (SIMS) method. Using a magnetic IMS 6F Cameca SIMS spectrometer and applying a very high primary Cs+ ion flux, prolonged presputtering, extensive vacuum chamber baking, titanium sublimation pump, and an LN trap, we have reached a detection limit of ~2 × 1015 O atoms/cm3 in chemical vapor deposition epitaxial Si films. This value appears to be at least 10 times lower than in any published or unpublished source known to the authors, including the reference sensitivities listed by the instrument manufacturer. Most likely, the key improvement that has allowed us to drive the detection limit to 1015 at/cm3 is the use of an ion pump in the analysis chamber. The working pressure in our analysis chamber is ~10−10 Thorr, ie, 1 decade lower than that the commercially equipped with a turbo pump. This paper demonstrates optimized analytical conditions for the oxygen measurements in Si, as a function of depth: (i) Very shallow profiles are practically impossible to measure accurately because of native oxide at the surface. (ii) Shallow‐to‐medium range profiles, up to ~20 μm, are the most amenable to SIMS measurements. (iii) Medium‐to‐deep (~20‐50 μm) range is required to follow interdiffusion and segregation in epitaxial layers when the oxygen‐free layer is grown on a CZ Si substrate. (iv) Extremely deep profiles, up to full thickness of the wafer, definitely necessitate beveling.

Process design and simulation for optimizing the oxygen concentration in Czochralski-grown single-crystal silicon

The highest-concentration impurity in a single-crystal silicon ingot is oxygen, which infiltrates the ingot during growth stage. This oxygen adversely affects the wafer is quality. This study was aimed at finding an optimal design for the Czochralski (Cz) process to enable high-quality and lowcost (by reducing power consumption) wafer production by controlling the oxygen concentration in the silicon ingots. In the Cz process, the characteristics of silicon ingots during crystallization are greatly influenced by the design and the configuration of the hot zone, and by crystallization rate. In order to identify process conditions for obtaining an optimal oxygen concentration of 11–13 ppma (required for industrial-grade ingots), designed two shield shapes for the hot zone. Furthermore, oxygen concentrations corresponding to these two shapes were compared by evaluating each shape at five different production speeds. In addition, simulations were performed to identify the optimal shield design for industrial applications.

Self‐consistent isotopic comparative method used to determine dependence of secondary‐ion yields on oxygen concentration in Si–O system up to 33 at%

AbstractWith the isotopic comparative method (ICM), we determined the ion yields of B+, O+, Si+, B−, O−, and Si− versus oxygen concentration in silicon under Ar+ bombardment. By multi‐energy implantation, we obtained samples containing a near‐uniform low concentration of 18O, which we then implanted with a high dose of 16O. The ICM allows us to determine the oxygen concentration profile as a function of substrate depth during analysis by secondary‐ion mass spectrometry, following which the ion yield is measured as a function of oxygen concentration from 0 to 33 at.%. The results show that, whatever the charge of secondary ions, all relative ion yields are enhanced with increasing of oxygen concentration. Very strong matrix effects due to oxygen are found for B+ (>100), whereas moderate or slight matrix effects are found for Si+ and O− (>10) and for Si−, B−, and O+ (<4). Whereas the relative ion yields of B+ and Si+ differ (as a function of oxygen concentration), the relative ion yields of B− and Si− are identical. The relative ionization probability versus oxygen concentration for Si+ agrees very well with the results of William's group. Copyright © 2012 John Wiley & Sons, Ltd.

A Fast and Easily Implemented Method for Interstitial Oxygen Concentration Mapping Through the Activation of Thermal Donors in Silicon.

Abstract In this paper a method is presented to accurately and readily measure the interstitial oxygen concentration in silicon. This method relies on the modification of the Si resistivity after the generation of some oxygen-based Thermal Donors. The method is made very accurate due to the strong dependence of the thermal donors formation rate on the interstitial oxygen concentration. The presented procedure is non destructive and only requires a resistivity measurement setup and a standard 450 °C air furnace. Very high spatial resolution mappings can be achieved using up-to-date resistivity measurement tools.

Effect of Combined Oxygenation and Gettering on Minority Carrier Lifetime in High-Resistivity FZ Silicon

High oxygen concentration in silicon increases the resistance of radiation detectors to high radiation doses. Unfortunately, high-resistivity float zone (FZ) silicon, needed for radiation detectors, has too low an oxygen content. The solution to this is silicon oxygenation. There are different ways of incorporating oxygen into silicon. The most accepted one is by high-temperature diffusion from a thick layer. In this paper, we investigate the impact of this silicon oxygenation technique as well as the application of different gettering techniques to improve the minority carrier lifetime of high-resistivity FZ silicon substrates for radiation detectors. The minority carrier lifetimes before and after surface etching have been measured on samples subjected to different oxygenation and gettering treatments by using a quasi steady-state photoconductance technique. A lifetime improvement efficiency factor is defined for each treatment process. The lifetime efficiency factors behave independently, so that the lifetime efficiency factors associated with different sequential combinations of treatments can be estimated by a multiplicative combination. Different gettering techniques that improve or degrade the minority carrier lifetime are analyzed, and the best options for silicon radiation detector fabrication are determined. Oxygenated silicon with a minority carrier lifetime close to 1 ms can be obtained. © 2004 The Electrochemical Society. All rights reserved.

Formation of electrically active centers in silicon irradiated with electrons and then annealed at temperatures of 400–700°C

The effect of irradiation with electrons on the formation of quenched-in donors in silicon is studied. It is found that n-and p-type regions are formed in the bulk of single-crystal silicon as a result of irradiation with electrons and subsequent annealing at a temperature of 450°C. The concentration of charge carriers in the regions of both types increases as the radiation dose and the annealing duration increase, which indicates that not only quenched-in donors but also quenched-in acceptors are formed. Nonuniformity in the distribution of the acceptor and donor centers correlates with fluctuations of the oxygen concentration in silicon.

The Marangoni convection and the oxygen concentration in Czochralski-grown silicon

Abstract The Marangoni convection on the silicon melt surface in Czochralski method was investigated. The results showed that Marangoni convection is related strongly to oxygen in silicon. Introducing a magnetic field by NdFeB permanent magnet into the melt, when B → → B → 0 ( B → 0 is the critical value), all the macro-convections were restrained in the melt and the Marangoni convection on the free surface emerges and becomes dominant. The oxygen concentration in silicon can be controlled freely by the Marangoni convection.

The impact of nitrogen on power diode characteristics

The impact of nitrogen in Czochralski (CZ) silicon on the characteristics of power diodes has been studied. The nitrogen doped CZ silicon (NCZ) grown in a nitrogen atmosphere was used for manufacturing diodes. For comparison, the common CZ silicon (ACZ) grown in an argon ambient with almost the same oxygen concentration and thermal history was also used. It was found that more oxygen precipitates and higher density of dislocations were generated in the diodes produced by NCZ silicon, especially with high oxygen concentration. The reverse breakdown voltages (Vr) and the times of reverse recovery (Trr) of the diodes produced by NCZ silicon with higher oxygen concentration were slightly lower. However, Vr and Trr of the diodes produced from NCZ silicon with lower oxygen concentration were almost the same as those from CZ silicon. It can be speculated that nitrogen decreases the Trr and Vr of diodes through the enhancement of the formation of oxygen precipitates and dislocations, if the oxygen concentration in silicon is high (>10 18 cm −3).

Influence of oxygen precipitation on the measure of interstitial oxygen concentration in silicon from the 1207 cm−1 infrared absorption band

The possible use of the absorption band at 1207 cm−1 for the measurement of the concentration of interstitial oxygen (Oi) in silicon samples subjected to a precipitation thermal treatment is discussed. The results of low temperature infrared absorption measurements show that the conversion factor for such evaluation of the residual Oi after precipitation is strongly influenced by the presence of oxide precipitates; a limit value for the concentration of precipitated oxygen is identified, above which the measure becomes unreliable.

Measurement of interstitial oxygen concentration in silicon below 1015 atoms/cm3

The absorption coefficient of silicon at 1118 cm−1 due to the multiphonon contribution related to the combination of two transverse optical and one transverse acoustical phonons is measured at the liquid He temperature. The precise knowledge of this contribution, usually hidden by the absorption band of the unavoidable oxygen impurities, permits the quantitative measurement of interstitial oxygen concentration down to 3×1014 atoms/cm3.

Heterogeneous Precipitation of Silicon Oxide in Silicon at Laser Induced Centres

The presence of oxygen precipitates in the region, where devices will be created, negatively affects the parameters of created structures1 and therefore, these regions must be free of precipitates. Using a heterogeneous mechanism of precipitation, it is possible to control the distribution of the precipitates in the crystal. Blums and Medvid’2 reported a generation of additional centres in silicon during the laser annealing without introduction of any additional impurity. One part of generated centres is stable up to 650–670° C, and their concentration rises with a rise in oxygen concentration in silicon. The aim of this work is an investigation of opportunity to use the above mentioned laser-induced centres as nuclei for silicon oxide (SiO2) precipitation.

A Numerical Study of the Effects of Electromagnetic Stirring on the Distributions of Temperature and Oxygen Concentration in Silicon Double‐Crucible Czochralski Processing

The effect of providing electromagnetic stirring of the melt contained in the double crucible in continuous Czochralski method was explored by a mathematical model. It was found that the surface temperature of the melt in the annular region was significantly increased by the stirring, which is quite beneficial for melting the solid feed material, and that the stirring could decrease the oxygen concentration at the crystal/melt interface. Moreover, a multiturned coils system in each phase current was found to be more efficient for driving the convection than the single‐turned coils system. The multiturned coils system showed that the temperature increase at the melt surface in the annular region became saturated when the current frequency was very high. Moreover, the oxygen concentration at the melt/crystal interface had a minimum value as the frequency was increased. Electromagnetic stirring may make very positive contributions to the performance of the continuous Czochralski system.

Influence of carbon and oxygen on phosphorus and aluminium co-gettering in silicon solar cells

The impact of carbon and oxygen on the performance of high efficiency photovoltaic devices is still poorly understood. As oxygen is one of the dominant impurities present in silicon, various applications require different levels of oxygen to improve the device performance. In this work, we have studied the effects of the oxygen concentration in silicon on the co-diffusion of phosphorus and aluminium by rapid and conventional processes. We will compare the effectiveness of the co-diffusion of PAl in a variety of silicon materials, as a function of temperature and duration of the thermal process in a classical and a rapid thermal furnace and examine the influence of carbon and oxygen on the gettering efficiency. In particular, we will show that the large enhancement of the minority carrier diffusion length (LD) due to this process can be related to the presence of oxygen and carbon, the influence of which during the thermal cycle is of importance.

放射率法によるSi中の酸素濃度測定

放射率法によるSi中の酸素濃度測定

Oxygen Transport Mechanism in Czochralski Silicon Melt: I . The Whole Bulk Melt

The mechanism of oxygen transport in the bulk silicon melt with and without crystal pulling were investigated experimentally and computationally. Crucible rotation rates were chosen as a parameter, and results suggest that rotation suppresses transport of oxygen from the crucible wall to the crystal growth interface, while calculations indicated the crucible bottom as the oxygen source when the crystal is pulled. The temperature distribution across the crucible bottom, possibly the impetus of the flow, was the most important term in control of the oxygen concentration in silicon single‐crystal growth.

Influence of Oxygen on Rapid Thermal Co-Diffusion of Phosphorus and Aluminium in Silicon

AbstractLocal motion, diffusion and interaction of impurities in solids are important aspects of semiconductor material and device processing. Rapid thermal processing (RTP) is extremely concerned and appears to offer significant advantages in these areas. As oxygen is one of the dominant impurities present in silicon, various applications require different level of oxygen to improve the device performance.In this work, we have taken the advantage of this feature to study the effects of the oxygen concentration in silicon on the rapid thermal co-diffusion of phosphorus and aluminium. In particular, we will show that the large enhancement of the minority carrier diffusion length (LD) due to this process can be related to the presence of oxygen and carbon which influences during the thermal cycle are of importance.

Features of measurement of the oxygen concentration in silicon at a temperature of 15 K

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Detection of oxygen concentration in silicon wafers using a tunable diode laser

Control of the oxygen concentration in silicon wafers is important for the fabrication of high quality integrated circuits. Techniques for the fast detection of oxygen would be desirable for production line quality control. The oxygen concentration in silicon has traditionally been measured by a Fourier transform infrared spectrometer (FTIS). Due to the slow response time (1-10 min), it is not suitable for wafer screening. In this report, we describe a diode laser spectroscopy technique for the fast (10 ms) detection of oxygen in production line silicon wafers. The results are in good agreement with those measured by the Fourier transform technique.

Method to Measure the Precipitated and Total Oxygen Concentration in Silicon

not Available.