摘要:

An extremely thin SiN film formed with electron cyclotron resonance (ECR) nitrogen plasma has been measured by x‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), ellipsometry, and electron spin resonance (ESR). The XPS and AES results show that the SiN layer is easily formed on a silicon surface by ECR nitrogen plasma, and it has a structure with high nitrogen content similar to Si3N4only near the surface of the film. The ellipsometry and ESR results reveal that the SiN film is very thin, 2.5–4.0 nm, and has spin density in the order of 1013cm−2, which is reduced drastically by exposing it to hydrogen plasma. The SiN film can be applied to the inexpensive dual‐polycide‐gate complementary metal–oxide–semiconductor process.

ISSN:1071-1023    

DOI:10.1116/1.588199

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We report the deposition of highly stable two‐layer TiO2/SiO2anti‐reflection (AR) coatings deposited using ion‐assisted deposition (IAD). We have measured the variation of refractive index with ion energy and beam current and found that this increases with the ion energy. This result, in conjunction with Auger electron spectroscopy measurements, implies that the IAD process densifies the deposited films without changing their stoichiometry. Wet etch rate measurements have confirmed that film porosity is correspondingly reduced. Anti‐reflection coatings have been deposited on InP substrates and reflectivities less than 0.1% have been obtained. The long‐term stability has been monitored over several hundred days and large improvements have been observed when IAD is used. We have also measured the changes in refractive index of single layer films immediately after deposition when the vacuum chamber is vented to atmosphere and no changes are evident in the IAD films. All the evidence implies that changes in non‐IAD anti‐reflection coatings are a result of a slow moisture ingression into the uppermost SiO2layer. We could not however simulate this by attempts to accelerate water ingression into non‐IAD AR coatings.

ISSN:1071-1023    

DOI:10.1116/1.588200

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A simple method for estimating charge buildup on gate oxide during plasma processing is proposed. This method is based on the observation that metal oxidation rate at the SiO2–metal interface is accelerated by the electric field formed by electrons diffused from the SiO2surface to the metal surface during plasma processing. The thickness of the metal oxide caused by electron‐induced charge buildup can be estimated by ellipsometry analysis. We applied the method to biased electron cyclotron resonance (ECR) plasma deposition of SiO2, compared the metal oxidation enhancement for biased ECR plasma deposition with that for exposing electron beams directly and also compared with the injected charge densityQinjfor gate–oxide breakdown during biased ECR plasma deposition evaluated by time‐dependent dielectrics breakdown measurements. In this way, we clarify that (i) the oxidation enhancement takes place at an electron‐beam exposure of over 10 C/cm2, and (ii) theQinjof over 10 C/cm2is closely related to gate–oxide breakdown. These results confirm that the metal–oxide thickness is strongly associated with the degradation in gate–oxide yield related to the injected electrons and that the charge buildup damage is caused by electrons diffused during biased ECR plasma deposition.

ISSN:1071-1023    

DOI:10.1116/1.588201

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The use of methane/hydrogen for reactive ion etching (RIE) of III–V compounds offers several advantages when compared to other chemistries. It shows a widespread use for etching of InP, GaAs, and related compounds for fabrication of optoelectronic devices, transistors, and mesoscopic systems. In the present work the etching of Al0.48In0.52As lattice matched to InP has been optimized by an experimental design technique by measuring the etch rate, the dc self‐bias, and the polymer formation as function of the following process parameters: total flow, methane content, pressure, and rf power. Results show that interactions between process parameters cannot be disregarded. The optimized process parameters are 90 sccm, 13.2% of CH4in H2, 60 mTorr, and 100 W. At this setup the process is diffusion limited, showing a maximum etch rate at 60 mTorr and strong sputtering action. Atomic force microscopy (AFM) shows that the trench quality is better compared to wet phosphoric based chemistry [2.07 nm root mean square (rms) versus 4.65 nm rms]. X‐ray photoelectron spectroscopy shows, when compared to a wet‐etched reference, a strong surface depletion of arsenic ([As]ref/[As]etch=15) and an increase in the aluminum and indium concentration ([Al]ref/[Al]etch=0.2; [In]ref/[In]etch=0.3). Before etching the surface consists mainly of indium oxide, aluminum oxide, pure As, and a small amount of arsenic oxide. After etching aluminum oxide is still present but the other oxides are being replaced by InAs compounds.

ISSN:1071-1023    

DOI:10.1116/1.588202

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A simple technique for cleaning a silicon surface after contact hole etching is proposed for obtaining stablep+silicon contact characteristics for very large scale integrated interconnections. The contaminated layer of the silicon contact surface after dry etching is first oxidized with electron cyclotron resonance (ECR) oxygen plasma and then the surface oxide is removed by wet etching with diluted HF. X‐ray photoemission spectroscopy and secondary‐ion‐mass spectroscopy analyses show that one of the main reasons for the instability of thep+silicon contact is fluorine contamination, which can be removed controllably by ECR oxygen plasma treatment followed by wet etching. This surface oxidation technique with ECR oxygen plasma is, therefore, an effective way to obtain stable and low‐resistancep+contact characteristics.

ISSN:1071-1023    

DOI:10.1116/1.588203

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Low‐temperature, defect‐free,insitucleaning of silicon prior to homoepitaxy is successfully developed by an electron cyclotron resonance hydrogen plasma treatment in an ultrahigh vacuum chamber. The plasma potential distribution was measured by a Langmuir probe method to understand the effect of the substrate dc bias during hydrogen plasma cleaning. It changes from downhill to uphill distribution as the dc bias changes from a negative to a positive value, which leads to a decrease in the ion number density arriving at the substrate and results in the complete suppression of the defect formation in the Si substrate.Insituhydrogen plasma cleaned Si wafer always resulted in higher quality epilayers than ones cleaned only by so‐called hydrogen passivation after the HF dip. We found that there is a critical dose of the hydrogen ions duringinsituplasma cleaning beyond which crystalline defects are observed in the Si substrate, subsequently leading to the poor crystallinity of the epilayers. The dose of the hydrogen ions during plasma cleaning can be effectively controlled by the substrate dc bias, the microwave power, the magnet current, and the cleaning time.

ISSN:1071-1023    

DOI:10.1116/1.588204

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The effect of CO and CO2addition to a CF4/O2plasma on the etching characteristics of a low‐pressure chemical vapor deposition tungsten film has been studied in a reactive ion etching reactor. Mass spectrometry and optical emission spectroscopy were used to monitor gas phase species at various compositions of etching gas. The main role of CO is scavenging F and O atoms, while that of CO2is increasing the concentration of the O atom. The addition of a small amount of CO (1 sccm) to a CF4/O2plasma enhances the etch rate of tungsten. With the addition of CO2, the etch rate of tungsten increases until the flow rate increases up to 5 sccm. The selectivity of W to SiO2by adding CO and CO2are 3.2 and 4.1, respectively. These values are relatively high when compared with the maximum selectivity of 2 in a CF4/O2gas system.

ISSN:1071-1023    

DOI:10.1116/1.588205

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Filling contact and vias holes with chemical vapor deposited (CVD) tungsten (W) eliminates the problems encountered with poor metal step coverage when using sputtered metals. Because of this advantage CVD W plugs have become widely used. The most common method of forming W plugs is to etchback a blanket layer of W leaving only the plugs intact. One major problem to overcome in this processing is the need for selectivity to the underlying barrier metal. This is especially true if the intent is to leave the barrier metal intact using it as the basis for the aluminum (Al) metallization. If this approach is taken, the effect of the W etchback process on the barrier metal and on any subsequent Al deposition is important. A blanket etchback process using a transformer coupled plasma (TCP) etcher was developed taking into account not only etch rate, selectivity, and plug loss, but also the effect of the structure of the barrier metal on the subsequent Al deposition. Surface damage of the underlying barrier metal during the W etch was examined by atomic force microscopy. The process flow used in our interconnect scheme leaves the barrier in place. Since the structure of the underlying barrier metal has been shown to affect the subsequent sputtered metal crystal structure [Hikoshietal., VLSI Multilevel Interconnection Conference, June 1993 (unpublished)], knowing how the structure of the titanium nitride (TiN) surface affects the Al deposition is important. The roughness of the TiN was studied as a function of the TCP coil power, wafer bias power, and gas flows. The parameters used to quantify the roughness of the surface were the areaRaand rms roughness and the fractal dimension of the surface. In addition, both the roughness of the deposited Al surface and the grain size of the Al were measured.

ISSN:1071-1023    

DOI:10.1116/1.588206

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The sidewall defects in high quality selective epitaxial growth (SEG) of silicon were characterized. Three different SEG diode structures were fabricated and the bulk and perimeter defects were characterized through electrical measurements and transmission electron microscopy (TEM). The structures investigated were SEG grown in a 1.2 μm thick wet‐etched field oxide, SEG grown in 1.2 μm thick reactive‐ion etched field oxide, and SEG grown in a 1.2 μm high and 0.3 μm wide sidewall oxide cavity. The thin sidewall oxide cavity SEG diode showed the best ideality factors and minimum saturation current densities for diodes intersecting the sidewall, indicating the least thermal stress generated at the SEG/oxide sidewall interface during the cool‐down period. Cross‐sectional TEM micrographs showed no defects in the bulk SEG or at the sidewall, indicating that the thermal stress in all the processes was not high enough to cause plastic deformation, dislocations, or stacking faults.

ISSN:1071-1023    

DOI:10.1116/1.588207

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The sidewall defects in selective epitaxial growth (SEG) of silicon were characterized and the nature of these defects was investigated. Electrical characterization of the sidewall defects was performed using diodes fabricated in structures using the SEG of silicon and chemical‐mechanical polishing. Diodes were fabricated with various perimeter to area ratios to extract the bulk and sidewall saturation current densities and ideality factors in as‐grown SEG diodes and reoxidized sidewall SEG diodes. Transmission electron microscopy was used to show that nitrogen annealing of the sample with the sidewall oxide removed exhibited a dramatic decrease in the sidewall defects as compared to the sample with the sidewall oxide present during the anneal. The generation of the defects was attributed to stress due to the mismatch in thermal expansion coefficients of oxide and silicon and a model describing the generation of these defects was formulated and described.

ISSN:1071-1023    

DOI:10.1116/1.588208

出版商:American Vacuum Society    

年代:1995

数据来源: AIP