摘要:

We have developed a pulse injection method of DNA oligomer aqueous solution onto Cu(111) surfaces as a new sample-preparation technique for scanning tunneling microscopy (STM) studies of biomolecules. The STM images revealed that the surface of Cu(111) retains its atomic flatness even after the injection of DNA-containing solution and that the deposition of intact DNA oligomers without aggregation is possible. The observed internal structure of deposited DNA suggests the promising possibility of sequencing DNA by means of STM. In order to examine the possibility of manipulation of DNA, translational positioning of DNA oligomer has been performed by a lateral pushing of the DNA with scanning tip.

ISSN:1071-1023    

DOI:10.1116/1.589299

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Scanning tunneling microscopy was used to characterize the developing surface morphology found during typical temperature programmed desorption experiments for halogen–GaAs. Surfaces exposed toBr2at 300 K were heated to temperatures between 450 and 675 K, followed by scanning at room temperature. This made it possible to relate the temperature-dependent gas phase etch product distribution to the surface structure and thereby examine atomic-level surface processes associated with the evolution of volatile products. We associate the desorption ofGaBr3around 500 K with the initiation of single-layer-deep terrace pits. Desorption of GaBr andAs2above 600 K accounts for the lateral enlargement of the pits.

ISSN:1071-1023    

DOI:10.1116/1.589300

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

A new precision cross-sectional transmission electron microscopy (XTEM) sample preparation method was developed and is reported here. The major advantage of this method over a conventional sample prepared using a focused ion beam (FIB) microsection is that the sample sectioned with a FIB can be extracted directly from the matrix and transferred to a carbon supporting grid for TEM examination. With this technique, a XTEM sample can be prepared, totally eliminating the requirement for mechanical polishing. Samples can be made easily and quickly, thus enhancing both productivity and turnaround time.

ISSN:1071-1023    

DOI:10.1116/1.589301

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Using scanning probe microscopy, we have modified a silicon surface and measured its current–voltage(I–V)characteristics. In the modified area, both an increase in film thickness and a decrease in current caused by field-induced oxidation (FIO) have been observed. TheI–Vcharacteristics of the FIO film shows a good fit to a Fowler–Nordheim (FN) tunneling current model. The barrier height determined by a FN plot shows a good agreement with that of conventional metal–oxide–semiconductor structure with thermal thick silicon oxide.

ISSN:1071-1023    

DOI:10.1116/1.589302

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Current–voltage characteristics of process-damagedp-njunction diodes are investigated for the purpose of damage evaluation. In this technique, damage is assessed by examining its effect on the diode characteristics of the peripheral portion of Zn-diffusedp-njunctions. The depth information for the current–voltage measurements is obtained by wet etching. This technique is applied to determine the extent of damage caused by Ar bombardment during Ar-ion beam etching and film deposition of sputteredSiO2.The forward-bias current–voltage characteristics are found to be more effective for damage-depth evaluation than the reverse-bias ones. The depth of the damaged layer is determined from the behavior of the ideality factor(n)of the forward-bias current–voltage characteristics. This technique was used to probe a damaged layer to a depth of up to 350 nm in Ar-ion beam etching, which is much deeper than the 60 nm that is typically evaluated by the current–voltage characteristics of Schottky diodes. This thickness is equivalent to that evaluated by the photoluminescence intensity and cathodoluminescence properties of multiquantum well structures. In addition, the damage depth profile can be represented quantitatively by considering then≃2recombination current deduced from the diameter dependence of the diode current–voltage characteristics. Three damaged regions with different recombination current densities are revealed in both Ar-ion beam etching and film deposition of sputteredSiO2.

ISSN:1071-1023    

DOI:10.1116/1.589303

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Deep level transient spectroscopy was used to detect the presence of deep levels correlated to the defects induced in the Si substrate by aCHF3/Ardry etch of a 550 Å gate oxide as a function of the rf power. Several energy levels were observed; some of them were due to the processing before the dry etching. Three traps produced by the dry etching, with Arrhenius plot activation energies, respectively,Ena1=350 meV,Ena2=220 meV,andEna3=100 meV,and capture cross sections around10−20 cm2were detected. The correlation with the surface recombination velocity variations and the F and C diffusion in the Si substrate was investigated.

ISSN:1071-1023    

DOI:10.1116/1.589304

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

High aspect ratio sub-half-micron contacts were etched inSiO2using a high densityC2F6plasma generated by an inductively coupled, low pressure reactor. Process development studies have shown that high aspect ratio contact holes can be open in thick dielectric layers with a good selectivity to the underlying silicon. Minimization of reactive ion etching lag is obtained by using high bias power conditions, which on the other hand induce a degradation of the photoresist, described as a graphitization of the resist. The degradation induces considerable roughness at the edges of the resist structures which leads to the creation of striations in the silicon dioxide as the pattern transfer in theSiO2proceeds. X-ray photoelectron spectroscopy (XPS) studies have allowed analysis of high aspect ratioSiO2contact holes. Using appropriate flood gun conditions, a complete separation of the XPS peaks originating from the resist mask and from the fluorocarbon polymer deposited on the bottom of the contact holes is possible. The XPS analyses show, in particular, that the fluorination of the polymers on the bottom of the contact holes strongly increases with the aspect ratio of the contact hole, and that the fluorination of the polymers deposited on the contact hole sidewalls is even greater.

ISSN:1071-1023    

DOI:10.1116/1.589305

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

A novel highly anisotropic room-temperature process for silicon etching, using mixtures ofSF6andCHF3gases is presented. The etch rate, selectivity, dc bias voltage and anisotropy as a function of the reactive ion etching conditions (mixture composition, pressure and rf power) are discussed. Excellent anisotropy combined with clean, damage-free surfaces and etching uniformity and reproducibility have been achieved. It was thus possible to fabricate free standing silicon wires with diameter less than 50 nm and with aspect ratios up to 50:1. Optical emission spectroscopy,ex situx-ray photoelectron spectroscopy and atomic force microscopy were employed as plasma gas phase and surface diagnostics.

ISSN:1071-1023    

DOI:10.1116/1.589306

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

We modified a polycide gate etching chamber of an Applied Materials Precision 5000 platform to accept a commercially available Prototech 150-mm-diam helical resonator plasma source to extend the utility of this proven manufacturing platform to 0.25 μm technology and beyond. We successfully demonstrated the use of the helical resonator on the Precision 5000 platform to etchWSix/α-Sigate stacks using a multistep process. At low pressures (<10 mTorr), the helical resonator etches polysilicon andWSixmore uniformly than a standard Precision 5000 MERIE chamber. In addition, theWSix-to-α-Si selectivity for theWSixetching step is also higher with the high-density source.

ISSN:1071-1023    

DOI:10.1116/1.589307

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Etch rates in excess of 1.5 μm/min for InP and InSb, 1.2 μm/min for GaAs and 0.7 μm/min for GaSb at room temperature were obtained in electron cyclotron resonance IC1/Ar plasmas at low additional rf power (150 W). There was little dependence of etch rate on microwave power over the range 400–1000 W for InP, and selectivities of 6–10 over mask materials such asSiO2,SiNx,and W were typical. Smooth surface morphologies were obtained over a wide range of plasma parameters for GaAs and GaSb, while preferential loss of P led to rough morphologies for InP at high rf powers. IC1-based plasmas appear to be promising universal etchants for Ga- and In-based III–V semiconductors.

ISSN:1071-1023    

DOI:10.1116/1.589308

出版商:American Vacuum Society    

年代:1997

数据来源: AIP