• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.472-472
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• 2011

The capacitive coupled plasma (CCP) has been extensively used in the semiconductor industry because it has not only good uniformity, but also low electron temperature. But CCP source has some problems, such as difficulty in varying the ion bombardment energy separately, low plasma density, and high processing pressure, etc. In this reason, dual frequency CCP has been investigated with a separate substrate biasing to control the plasma parameters and to obtain high etch rate with high etch selectivity. Especially, in this study, we studied on the etching of $SiO_2$ by using the pulse-time modulation in the dual-frequency CCP source composed of 60 MHz/ 2 MHz rf power. By using the combination of high /low rf powers, the differences in the gas dissociation, plasma density, and etch characteristics were investigated. Also, as the size of the semiconductor device is decreased to nano-scale, the etching of contact hole which has nano-scale higher aspect ratio is required. For the nano-scale contact hole etching by using continuous plasma, several etch problems such as bowing, sidewall taper, twist, mask faceting, erosion, distortions etc. occurs. To resolve these problems, etching in low process pressure, more sidewall passivation by using fluorocarbon-based plasma with high carbon ratio, low temperature processing, charge effect breaking, power modulation are needed. Therefore, in this study, to resolve these problems, we used the pulse-time modulated dual-frequency CCP system. Pulse plasma is generated by periodical turning the RF power On and Off state. We measured the etch rate, etch selectivity and etch profile by using a step profilometer and SEM. Also the X-ray photoelectron spectroscopic analysis on the surfaces etched by different duty ratio conditions correlate with the results above.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.417-420
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• 2004

The electrical effects of dry-etch on n-type GaN by an inductively coupled $Cl_2/CH_4/H_2/Ar$ plasma were investigated as a function of ion energy, by means of ohmic and Schottky metallization method. The specific contact resistivity(${\rho}_c$) of ohmic contact was decreased, while the leakage current in Schottky diode was increased with increasing ion energy due to the preferential sputtering of nitrogen. At a higher rf power, an additional effect of damage was found on the etched sample, which was sensitive to the dopant concentration in terms of the ${\rho}_c$ of ohmic contact. This was attributed to the effects such as the formation of deep acceptor as well as the electron-enriched surface layer within the depletion layer. Furthermore, thermal annealing process enhanced the ohmic and Schottky property of heavily damaged surface.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.8
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• pp.438-444
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• 2000

We report the effects of etch process parameters on the ohmic contact formation in the plasma etching of GaN. Planar inductively coupled plasma system with $CH_4/H_2/Ar$gas chemistry has been used as etch reactor. The contact resistance and the specific contact resistance have been investigated using transfer length method as a function of RF bias power and %Ar gas concentration in total flow rate. AES(Auger electron spectroscopy) analysis revealed that the etched GaN has nonstoichiometric Ga rich surface and was contaminated by carbon and oxygen. Especially large amount of carbon was detected at the sample etched for high bias power (or voltage) condition, where severe degradation of contact resistance was occurred. We achieved the low ohmic contact of $2.4{\times}10^{-3} {\Omega}cm^2$ specific contact resistance at the input power 400 W, RF bias power 150 W, and working pressure 10mTorr with 10 sccm $CH_4$, 15 sccm H2, 5 sccm Ar gas composition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.5
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• pp.353-360
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• 2012

As semiconductor device technology continuously shrinks, low-open area etch process prevails in front-end etch process, such as contact etch as well as one cylindrical storage (OCS) etch. To eliminate over loaded wafer processing test, it is commonly performed to emply diced small coupons at stage of initiative process development. In nominal etch condition, etch responses of whole wafer test and coupon test may be regarded to provide similar results; however, optical emission spectroscopy (OES) which is frequently utilize to monitor etch chemistry inside the chamber cannot be regarded as the same, especially etch mask is not the same material with wafer chuck. In this experiment, we compared OES data acquired from two cases of etch experiments; one with coupon etch tests mounted on photoresist coated wafer and the other with coupons only on the chuck. We observed different behaviors of OES data from the two sets of experiment, and the analytical results showed that careful investigation should be taken place in OES study, especially in coupon size etch.

• Journal of Magnetics
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• v.15 no.3
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• pp.132-137
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• 2010

Plasma etching of $SiO_2$ contact holes was statistically analyzed by a fractional factorial experimental design. The analysis revealed the dependence of the etch rate and DC self-bias voltage on the input factors of the magnetically enhanced reactive ion etching reactor, including gas pressure, magnetic field, and the gas flow rates of $CHF_3$, $CF_4$, and Ar. Empirical models of the DC self-bias voltage and etch rate were obtained. The DC self-bias voltage was found to be determined mainly by the operating pressure and the magnetic field, and the etch rate was related mainly to the pressure and the flow rates of Ar and $CHF_3$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.57-63
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• 2008

In this paper, the dependence of MOSFET performance on the channel stress is characterized in depth. The tensile and compressive stresses are applied to CMOSFET using a nitride film which is used for the contact etch stop layer (CESL). Drain current of NMOS and PMOS is increased by inducing tensile and compressive stress, respectively, due to the increased mobility as well known. In case of NMOS with tensile stress, both decrease of the back scattering ratio ($\tau_{sat}$) and increase of the thermal injection velocity ($V_{inj}$) contribute the increase of mobility. It is also shown that the decrease of the $\tau_{sat}$ is due to the decrease of the mean free path ($\lambda_O$). On the other hand, the mobility improvement of PMOS with compressive stress is analyzed to be only due to the so increased $V_{inj}$ because the back scattering ratio is increased by the compressive stress. Therefore it was confirmed that the device performance has a strong dependency on the channel back scattering of the inversion layer and thermal injection velocity at the source side and NMOS and PMOS have different dependency on them.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.774-779
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• 1995

Process optimization experiments based on the Taguchi method were performed in order to set up the optimal process conditions for the contact oxide etching process module which was built in order to be attached to the cluster system of multi-processing purpose. In order to compare with Taguchi method, the contact oxide etching process carried out with different process parameters(CHF$_{3}$/CF$_{4}$ gas flow rate, chamber pressure, RF power and magnetic field intensity). Optimal etching characteristics were evaluated in terms of etch rate, selectivity, uniformity and etched profile. In this paper, as a final analysis of experimental results the optimal etching characteristics were obtained at the process conditions of CHF3/CF4 gas flow rate = 72/8 sccm, chamber pressure = 50 mTorr, RF power = 500 watts, and magnetic field intensity = 90 gauss.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.284-284
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• 2011

Recently, the increasing degree of device integration in the fabrication of Si semiconductor devices, etching processes of nano-scale materials and high aspect-ratio (HAR) structures become more important. Due to this reason, etch selectivity control during etching of HAR contact holes and trenches is very important. In this study, The etch selectivity and etch rate of TEOS oxide layer using ACL (amorphous carbon layer) mask are investigated various process parameters in CH2F2/C4F8/O2/Ar plasma during etching TEOS oxide layer using ArF/BARC/SiOx/ACL multilevel resist (MLR) structures. The deformation and etch characteristics of TEOS oxide layer using ACL hard mask was investigated in a dual-frequency superimposed capacitively coupled plasma (DFS-CCP) etcher by different fHF/ fLF combinations by varying the CH2F2/ C4F8 gas flow ratio plasmas. The etch characteristics were measured by on scanning electron microscopy (SEM) And X-ray photoelectron spectroscopy (XPS) analyses and Fourier transform infrared spectroscopy (FT-IR). A process window for very high selective etching of TEOS oxide using ACL mask could be determined by controlling the process parameters and in turn degree of polymerization. Mechanisms for high etch selectivity will discussed in detail.

• Korean Journal of Materials Research
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• v.9 no.5
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• pp.496-502
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• 1999

In this study, n-GaN samples were etched using planar inductively coupled $Cl_2$/$H_2$plasmas and the effects of plasma conditions on the etch properties, surface composition, and ohmic contact formation were investigated as a function of gas combination. As the addition of hydrogen to the $Cl_2$plasma increased to 100%, GaN etch rates decreased due to the reduction of chlorine radical density. Even though the variation of the surface composition is limited under $50\AA$, the surface composition was also changed from Ga-rich to N-rich with the increased addition of hydrogen to $Cl_2$. Etch products by the reaction between Ga in GaN and Cl in $Cl_2$ plasma were investigated using OES analysis during the GaN etching. The value of specific resistivity of the contact formed on the n-GaN etched using 100% $Cl_2$plasma was 3.1$\times$10\ulcorner$\Omega$$\textrm{cm}^2$, and which was lower than that formed on the non-etched n-GaN. However, the resistively was increased with the increased hydrogen percent in $Cl_2$/$H_2$.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.11
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• pp.902-909
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• 1991

A reproducible selective dry etch process of GaAs/AlGaAs Heterostructures for High Electron Mobility Transistor(HEMT) Device fabrication is developed. Using RIE mode with $CCl_{2}F_{2}$ as the basic process gas, the observed etch selectivity of GaAs layer with respect to GaAs/$Al_{0.3}Ga_{0.7}$As is about 610:1. Severe polymer deposition problem, parialy generated from the use of $CCl_{2}F_{2}$ gas only, has been significantly reduced by adding a small amount of He gas or by $O_{2}$ plasma ashing after etch process. In order to obtain an optimized etch process for HEMT device fabrication, we com pared the properties of the wet etched Schottky contact with those of the dry etched one, and set dry etch condition to approach the characteristics of Schottky diode on wet etched surface. By applying the optimized etch process, the fabricated HEMT devices have the maximum transconductance $g_{mext}$ of 224 mS/mm, and have relatively uniform distribution across the 2inch wafer in the value of 200$\pm$20mS/mm.