Low Temperature Silicon Nitride Research Articles

Characteristics of low-temperature silicon nitride (SiN x:H) using electron cyclotron resonance plasma

Silicon nitride (SiN x :H) thin film deposited at 50°C using an electron cyclotron resonance plasma-enhanced chemical deposition (ECR PECVD) system has been explored. This 50°C silicon nitride deposited on a 150 mm diameter Si wafer shows an acceptable uniformity; ±0.9% of average index of refraction and ±6.5% of average thickness are maintained across 150 mm diameter of the Si wafer. As-deposited 50°C silicon nitrides have a leakage current density value of 2–3×10 −9 A/cm 2 at electric fields of 2 MV/cm and a breakdown electric field (i.e., field at a current density of 1×10 −6 A/cm 2) greater than 6 MV/cm. X-ray photoelectron spectroscopy (XPS) analysis displays that chemical bonding structure of this low-temperature ECR silicon nitride is very comparable to that of 250°C PECVD nitride. However, IR absorption data indicate that the low-temperature ECR nitride has more Si–H bonds and fewer N–H bonds than the high-temperature PECVD nitride. These ECR films manifest resistance to buffered oxide etchant (BOE) attack with the etch rates that are slower than 50% of a 250°C PECVD nitride. The lower concentration of N–H bonds may enable these low-temperature nitrides to resist BOE attack.

Low Temperature Silicon Nitride and Silicon Dioxide Film Processing by Inductively Coupled Plasma Chemical Vapor Deposition

High‐density plasma technology is becoming increasingly attractive for the deposition of dielectric films such as silicon nitride and silicon dioxide. In particular, inductively coupled plasma chemical vapor deposition (ICPCVD) offers a great advantage for low‐temperature processing over plasma‐enhanced chemical vapor deposition (PECVD) for a range of devices including compound semiconductors and magnetic heads. In this paper, the development of low temperature (<200°C) silicon nitride and silicon dioxide films utilizing ICP technology is discussed. The material properties of these films have been investigated as a function of ICP source power, radio‐frequency chuck power, chamber pressure, gas chemistry, and temperature. The ICPCVD films are compared to PECVD films in terms of wet etch rate, stress, and other film characteristics. Two different gas chemistries, and , were explored for the deposition of ICPCVD silicon nitride. The ICPCVD silicon dioxide films were prepared from . The wet etch rates of both silicon nitride and silicon dioxide films are significantly lower than films prepared by conventional PECVD. This implies that ICPCVD films prepared at these low temperatures are of higher quality. The advanced ICPCVD technology can also be used for efficient void‐free filling of high aspect ratio (3:1) sub‐micrometer trenches. © 2000 The Electrochemical Society. All rights reserved.

Development of Low Temperature Silicon Nitride and Silicon Dioxide Films by Inductively-Coupled Plasma Chemical Vapor Deposition

ABSTRACTHigh-density plasma technology is becoming increasingly attractive for the deposition of dielectric films such as silicon nitride and silicon dioxide. In particular, inductively-coupled plasma chemical vapor deposition (ICPCVD) offers a great advantage for low temperature processing over plasma-enhanced chemical vapor deposition (PECVD) for a range of devices including compound semiconductors. In this paper, the development of low temperature (&lt; 200°C) silicon nitride and silicon dioxide films utilizing ICP technology will be discussed. The material properties of these films have been investigated as a function of ICP source power, rf chuck power, chamber pressure, gas chemistry, and temperature. The ICPCVD films will be compared to PECVD films in terms of wet etch rate, stress, and other film characteristics. Two different gas chemistries, SiH4/N2/Ar and SiH4/NH3/He, were explored for the deposition of ICPCVD silicon nitride. The ICPCVD silicon dioxide films were prepared from SiH4/O2/Ar. The wet etch rates of both silicon nitride and silicon dioxide films are significantly lower than films prepared by conventional PECVD. This implies that ICPCVD films prepared at these low temperatures are of higher quality. The advanced ICPCVD technology can also be used for efficient void-free filling of high aspect ratio (3:1) sub-micron trenches.

Hydrogenated silicon nitride thin films deposited between 50 and 250 °C using nitrogen/silane mixtures with helium dilution

Silicon nitride thin films, deposited by plasma enhanced chemical vapor deposition at temperatures between 250 and 50 °C from SiH4, N2 and He, were characterized using transmission infrared spectroscopy, ellipsometry, wet etch rate, and current-voltage analysis. At 250 °C using SiH4/N2/He flow ratios of 1/150/75, films with refractive index=1.80 and H concentrations &amp;lt;20%, distributed equally in Si-H and N-H units were obtained. The concentration of hydrogen and its distribution in N-H and Si-H bonds are sensitive to process temperature, suggesting that thermally driven N incorporation reactions are important during growth. Inert gas dilution allows films to be formed at &amp;lt;100 °C, with bonded hydrogen configurations similar to films deposited at higher temperatures. Current versus voltage traces of as-deposited films show charge trapping, which can be reduced by extended low temperature anneals. These results show that chemical composition can be controlled in low temperature silicon nitride deposition. This processing approach may be useful for encapsulation or for barrier layer formation on low temperature organic electronic devices or flexible transparent plastic substrates.

Degradation of GaAs/AlGaAs Quantized Hall Resistors With Alloyed AuGe/Ni Contacts.

Careful testing over a period of 6 years of a number of GaAs/AlGaAs quantized Hall resistors (QHR) made with alloyed AuGe/Ni contacts, both with and without passivating silicon nitride coatings, has resulted in the identification of important mechanisms responsible for degradation in the performance of the devices as resistance standards. Covering the contacts with a film, such as a low-temperature silicon nitride, that is impervious to humidity and other contaminants in the atmosphere prevents the contacts from degrading. The devices coated with silicon nitride used in this study, however, showed the effects of a conducting path in parallel with the 2-dimensional electron gas (2-DEG) at temperatures above 1.1 K which interferes with their use as resistance standards. Several possible causes of this parallel conduction are evaluated. On the basis of this work, two methods are proposed for protecting QHR devices with alloyed AuGe/Ni contacts from degradation: the heterostructure can be left unpassivated, but the alloyed contacts can be completely covered with a very thick (> 3 μm) coating of gold; or the GaAs cap layer can be carefully etched away after alloying the contacts and prior to depositing a passivating silicon nitride coating over the entire sample. Of the two, the latter is more challenging to effect, but preferable because both the contacts and the heterostructure are protected from corrosion and oxidation.

Fully passivated AR coated InP/InGaAs MSM photodetectors

We report on a technique for antireflection (AR) coating and surface passivation of InP:Fe/InGaAs:Fe metal-semiconductor-metal (MSM) photodetectors using nonreactive radio frequency (RF) magnetron sputtered silicon nitride. Excessive leakage currents and photocurrent gain, major performance-limiting factors of unpassivated detectors, were strongly suppressed in this way. The influence of various chemical pretreatments including sulfide passivation applied to the InP:Fe surface prior to the low-temperature silicon nitride deposition in optimizing the passivating process is investigated. >

Low temperature silicon nitride deposition by direct photolysis using high power krypton flash lamps

Silicon nitride films have been deposited on InP using a photochemical process. A high power krypton flash lamp was used to produce the direct photolysis of conventional reactive gases with the highest deposition rates ever reported in UVCVD (93Å/min). Also, the high UV fluence allows a cold process and results in films with excellent structural and electrical properties.

A novel lift-off process using low-temperature PECVD silicon nitride for the fabrication of self-aligned gate GaAs MESFETs and InP MISFETs

A novel lift-off process for the fabrication of self-aligned gate GaAs MESFETs and InP MISFETs was developed using low-temperature plasma-enhanced chemical vapor deposition (PECVD) silicon nitride films. The gate areas of the GaAs MESFETs and InP MISFETs were defined by silicon nitride lift-off in a substitutional gate process so that the gate electrodes of the field effect transistors were automatically aligned with the source and drain areas. The lift-off of silicon nitride was made possible by characterizing PECVD silicon nitride at low temperatures and performing the silicon nitride deposition at 60°C which was lower than the soft bake temperature of normal photoresist.

Electron cyclotron resonance plasma chemical vapor deposition of large area uniform silicon nitride films

Electron cyclotron resonance plasma (f=2.45 GHz, microwave power P=200–800 W) generated in a radially uniform magnetic field (B=875–1000 G) was used to produce a large area (15–20 cm diam) uniform plasma stream at 20–30 cm from the source output. Low temperature (70–300 °C) silicon nitride films with a thickness of 800–3000 Å were deposited on 5–20 cm diameter wafers with deposition rates of 100–350 Å/min. Film thickness uniformity was ±1% for 7.6–10.0 cm diam wafers, ±3% for 15 cm diam wafers, and ±9% for 20.0 cm diam wafers. It was found that the film deposition rate Wg increased linearly with the silane flow rate, while Wg increased slower than power 1/2 with the nitrogen flow rate. The film refractive index was 1.9–2.0 at a silane/nitrogen flow rate ratio of 0.40–0.6. The effects of plasma density and its profile on the film growth rate and uniformity are discussed.

The preparation, characterization and application of plasma-enhanced chemically vapour deposited silicon nitride films deposited at low temperatures

Silicon nitride films are successfully deposited using plasma-enhanced chemical vapour deposition (PECVD) at the low substrate temperature range between room temperature and 300°C. The composition, deposition rate, etch rate, film uniformity and refractive index of the low temperature silicon nitride films are measured as functions of deposition substrate temperature (room temperature to 300°C), reactant gas ratio ( NH 3: SiH 4 ratio from 0.5 to 20), and r.f. power (30–230 W). The silicon nitride films deposited at room temperature are found to have low total stress. The low temperature PECVD silicon nitride films have been used successfully in a lift-off process for the fabrication of self-aligned gate GaAs metal-semiconductor field effect transistors MESFET and InP metal-insulator-semiconductor field effect transistors MISFET.

Silicon nitride formation from a silane–nitrogen electron cyclotron resonance plasma

Good quality, low temperature silicon nitride and oxynitride films were deposited downstream from an electron cyclotron resonance (ECR) plasma source using SiH4 and N2 gas mixtures. The Si/N ratio and H content in the deposited films were determined using Rutherford backscattering spectrometry and elastic recoil detection. The H concentration was minimum for films with compositions closest to that of stoichiometric Si3N4. The optimum conditions for producing a stoichiometric Si3N4 were a SiH4/N2 flow ratio between 0.1 and 0.2, and an electrically isolated sample far from the ECR source. Infrared absorption spectra showed that as the film composition changed from N rich to Si rich the dominant bonds associated with H changed from N–H to Si–H.

Photo-induced electrical defects in low-temperature photochemical vapor-deposited silicon nitride films

The electrical properties of the photochemical vapor-deposited silicon nitride/silicon interface are presented as a function of deposition temperature (70 to 200 °C). High values of interface state density Nss (about 3×1012 cm−2 eV−1), an equivalent charge at the interface Qss (about 5×1011 cm−2), and an important injection-type hysteresis of the capacitance voltage C-V curves are observed in the as-grown material. Most defects are found to be generated during the deposition process by the ultraviolet illumination used to activate the chemical reaction of the gases. Low-temperature (250 °C) and short-time (30 min) annealings eliminate part of the defects, resulting in lower values of Nss (about 1×1012 cm−2 eV−1), Qss (about 5×1010 cm−2), and reduced injection-type hysteresis.