摘要:

Bromine ion-beam-assisted etching produces smooth vertical sidewalls in GaAs wafers with substrate temperatures in the range of 20–200 °C and smooth vertical sidewalls in InP wafers with substrate temperatures in the range of 150–200 °C. Etch rates can be varied from several nm/min to 0.16 μm/min through the bromine flow rate,Ar+ion beam density and energy, and the substrate temperature. The etching rate ratios of bromine-only etching (noAr+ion beam) to argon ion-beam-assisted bromine etching to argon ion etching (no bromine) with an ion beam density of 40μA/cm2and ion beam energy of 500 V were measured to be 11.5:23:1 and 16:125:1 at a substrate temperature of 200 °C and 2:42:1 and 1:40:1 at a substrate temperature of 100 °C for GaAs and InP, respectively. Such rate enhancements were found to be typical with these materials. Bromine ion-beam-assisted etching also appears to have an advantage over chlorine ion-beam-assisted etching in that high anisotropy can be achieved with bromine in both the GaAs and the InP materials systems at substrate temperatures as high as 200 °C as compared to chlorine where the etching of GaAs is spontaneous and isotropic at temperatures above 150 °C.

ISSN:1071-1023    

DOI:10.1116/1.590060

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Reactive ion beam etching (RIBE) and chemically assisted ion beam etching (CAIBE) of InP at room temperature have been performed, using an inductively coupled plasma source. Two types of chemistries were used:N2/CH4/H2andAr/CH4/H2.The etch rate, surface roughness and anisotropy were investigated for different process parameters. In hydrocarbon chemistry polymer buildup is a commonly encountered problem and therefore efforts were also devoted to minimize the polymer growth. Comparing the two chemistries it was found that the Ar based processes always lead to rougher surfaces, while theN2based chemistry at low ion energies (<100 eV) results in very smooth surfaces for both types of ion beam processes. However, the CAIBE process not only provides smooth surfaces, but also generates much less polymers than its RIBE counterpart. CAIBE, usingN2/CH4/H2chemistry, is then identified as a promising candidate for fabrication of nanometer sized structures. In addition, the low polymer growth is also advantageous from an equipment service point of view.

ISSN:1071-1023    

DOI:10.1116/1.590061

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Optimization of etch depth and anisotropy ofIn0.53Ga0.47AsbyCH4/H2reactive ion etching is investigated using a central composite experimental design. Etching characteristics are examined by considering the general trends and main effects of pressure, flow rate, andCH4concentration factors on etch depth and sidewall profile responses. Predictive models are developed using regression analysis for etch depth and sidewall profile responses. These models can be used to predict with 95% confidence etch depth and sidewall profile within approximately 56 nm and 0.16 rad.

ISSN:1071-1023    

DOI:10.1116/1.590062

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We have examined minority-carrier recombination lifetimes of a silicon wafer’s backside after plasma processing. The decrease in lifetime reflects the degree ofSi-SiO2interface degradation caused by plasma-induced damage. We found that even if the silicon wafer’s backside is fully covered by the stage during plasma processing, there was a further decrease in the lifetime in a region about 20 mm from the wafer’s edge. We propose that when charges are ejected from the silicon wafer to the outside of the wafer, a portion of the charges flows via the interface betweenSiO2and the stage. To fully understand plasma-induced damage, in addition to examining the nature of the decrease in the lifetime of the wafer’s frontside, it is important to examine the nature of the decrease in the lifetime of the wafer’s backside in detail.

ISSN:1071-1023    

DOI:10.1116/1.590063

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Polished germanium Ge (100) was irradiated with 1.0–2.0 MeVSi+at different doses from4×1013to1×1014ions/cm2under different angles: 7°, 45°, and 60°. The radiation damage is studied by the Rutherford backscattering/channeling technique. The experimental damage distribution is extracted from the spectrum based on the procedure by Feldman et al. The experimental damage distributions are compared with the result from theTRIM(transport of ions in matter) code. The results show that (1) it is easier to amorphize Ge than Si, and the damage in Ge (100) induced by MeVSi+depends on the dose, energy, irradiation angle, and annealing temperature also; (2) the shape of damage profile in Ge (100) induced by 2.0 MeVSi+under 60° irradiation can be described well by theTRIMprediction, except the near-surface region where the experimental damage ratio is higher than that given by theTRIMprediction; (3) after 800 °C annealing, damaged Ge (100) trends to be recrystallized.

ISSN:1071-1023    

DOI:10.1116/1.590225

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

In polycrystalline silicon (polysilicon) etching for gate electrodes in high-performance complementary metal-oxide-semiconductor large scale integration fabrication, extremely high selectivity of polysilicon etching to the gate oxide is needed because the thickness of the gate oxide reduces. It is also important to overcome the well-known shape distortion problem, called “notching” or “local side etching,” where the gate side-wall is locally side-etched at the interface between the polysilicon and the gate oxide. We examine the origin of notching and the selectivity to the gate oxide in chlorine- and oxygen-based reactive ion etching of the phosphorous-doped polysilicon gate with anSiO2hard mask. It is found that the etching product returning to the surface plays an important role in both side-wall and gate-oxide protection, which determines the shape of the electrode and the selectivity. Based on our findings, we developed a novel step-etching method that provides high-performance gate electrode etching that is infinitely selective without notching. This method uses the addition of aSiCl4gas, which is equivalent to the etching product, as well as oxygen during overetching when the generation of etching product is reduced.

ISSN:1071-1023    

DOI:10.1116/1.590064

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The residence time effects onSiO2etching characteristics using inductively coupled plasma ofC4F8alone were first studied in the range from 6 to 300 ms. It was then found thatSiO2and Si etch rates were minimum at a residence time of 25 ms, at which theCF1+ion density and the fluorocarbon polymer deposition rate measured at 130 °C became maximum. From this good correspondence, theSiO2etching was considered to follow a reaction model where theCF1+ions might contribute to the polymer deposition, thus suppressing theSiO2etching, and where the dominantly observedCF3+ions could etchSiO2on the assumption of elevatedSiO2surface temperature due to the ion bombardment. Next, in the condition of short residence times (<25 ms), Ar was added toC4F8in order to allowAr+ions to remove the fluorocarbon polymer film that is responsible for the reduction of theSiO2etch rate. For a residence time of 10 ms theSiO2etch rate continuously increased with the Ar concentration up to a maximum etch rate of 0.4 μm/min for 90% Ar addition. Various plasma diagnostics demonstrated that the 90% Ar addition resulted in an increase of theCFx+(x=1–3),C+,andAr+ion densities, in contrast to a decrease of theCF3radical density. Metastable Ar atoms as well as highly elevated electron temperature are considered to be responsible for the increasing ion species. ConsequentlySiO2/Sicontact hole features with 0.18 μm opening and 2 μm depth were successfully fabricated employing the 90%Ar/C4F8mixture at a residence time of 10 ms. The He addition has also been investigated and showed similar changes in plasma characteristics to those observed for Ar addition, but the “etch stop” occurred. This probably resulted from the poor sputtering effect ofHe+ions due to their light mass.

ISSN:1071-1023    

DOI:10.1116/1.590007

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

High aspect ratioSiO2contacts are etched with aC4F8/CO/O2/Archemistry using a magnetically enhanced reactive ion etching (MERIE) plasma source with a good selectivity to the underlying silicon. X-ray photoelectron spectroscopy (XPS) studies allow chemical analysis of high aspect ratioSiO2contact holes. Using the charging effect, a complete separation of the XPS peaks originating from the resist mask and from the bottom of the contact holes is possible. XPS analyses show that the fluorination of the polymer on the bottom of the contact is low (F/C around 0.2) and independent of the aspect ratio of contact holes. Furthermore, XPS spectra also show that the full width at half maximum of theSi 2pdoublet measured at the bottom of contact holes strongly increases, showing that the highly energetic ion bombardment induced by the MERIE source lead to a severe amorphization of the silicon surface. Finally, comparisons between MERIE and high density plasma are discussed.

ISSN:1071-1023    

DOI:10.1116/1.590008

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The effects of process conditions and chamber geometry on the uniformity of Al etched byCl2were measured in a Lam TCP™ 9600 SE etch reactor. A computer simulation accurately predicted etch uniformity and aided in the explanation of uniformity trends. Parameters used in the experimental matrix included pressures between 6 and 24 mT, flow between 25 and 100 sccm, power supplied to the plasma between 0 and 350 W, and chamber heights ranging from 6 to 12 cm. The distinctive features of this study include the large number of input parameters studied in a commercial reactor and the accurate predictions obtained from a self-consistent simulation without free parameters. Reducing residence time in the experiments by adjusting chamber height or flow rate produces a more center-fast etch, as expected. The flow simulations were useful in corroborating intuitive arguments and in explaining anomalous results such as the effect of pressure on etch uniformity. More specifically, comparison of simulations and measurements demonstrated the quantitative connection between the Peclet number, the residence time, and the edge uniformity over a large range of process conditions. In addition to explaining general trends with residence time, Peclet number considerations also clarify the differing effects of pressure, flow rate, and chamber height change on uniformity. No attempt was made to impose plasma effects in the flow simulation because measurements of the neutral temperature and dissociation fraction were not available. Plasma power was observed experimentally to slightly improve uniformity without changing the average etch rate.

ISSN:1071-1023    

DOI:10.1116/1.590009

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

To explain the influence of the substrate temperatureTson the etching characteristics of tungsten in aSF6magnetoplasma, we have extended the surface diffusion model originally developed for the etching of the W–F system at constant (ambient) temperature. It allows us to understand our experimental observations which include the influence ofTson the anisotropy and the fact that the lateral (spontaneous) etch rate of W as a function of1/Tsdoes not follow an Arrhenius law. The model is valid as long as the pressure is sufficiently low(⩽0.5 mTorr)to neglect the influence of coadsorption and passivation effects, likely related to oxygen contamination of the gas phase coming from the fused silica discharge tube interacting with fluorine atoms. Consistency of the model is well demonstrated by observing that the lateral to vertical etch rate ratio as a function of1/Ts,under different plasma conditions, leads to a unique value of the activation energy(R=0.65 eV)for the associative desorption ofWF6,the volatile reaction product of tungsten with fluorine adatoms.

ISSN:1071-1023    

DOI:10.1116/1.590010

出版商:American Vacuum Society    

年代:1998

数据来源: AIP