• Journal of the Korean Vacuum Society
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• v.6 no.3
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• pp.267-274
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• 1997

Silicon shallow trenches applied to the STI (Shallow Trench Isolation) of integrated circuits were etched using inductively coupled $Cl_2$ and HBr/$Cl_2$ plasmas and the effects of process parameters on the etch profiles of silicon trenches and the physical damages on the trench sidewall and bottom were investigated. The increase of inductive power and bias voltage in $Cl_2$ and HBr/$Cl_2$ plasmas increased polysilicon etch rates in general, but reduced the etch selectivities over nitride. In case of $Cl_2$ plasma, low inductive power and high bias voltage showed an anisotropic trench etch profile, and also the addition of oxygen or nitrogen to chlorine increased the etch anisotropy. The use of pure HBr showed a positively angled etch profile and the addition of $Cl_2$ to HBr improved the etch profile more anisotropically. HRTEM study showed physical defects formed on the silicon trench surfaces etched in $Cl_2/N_2$ or HBr/ $Cl_2$ plasmas.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.599-602
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• 2003

A new technique is presented to construct predictive models of plasma etch processes. This was accomplished by combining a backpropagation neural network (BPNN) and a random generator (RC). The RG played a critical role to control neuron gradients in the hidden layer, The predictive model constructed in this way is referred to as a randomized BPNN (RG-BPNN). The proposed scheme was evaluated with a set of experimental plasma etch process data. The etch process was characterized by a 2$^3$ full factorial experiment. The etch responses modeled are 4, including aluminum (Al) etch rate, profile angle, Al selectivity, and do bias. Additional test data were prepared to evaluate model appropriateness. The performance of RC-BPNN was evaluated as a function of the number of hidden neurons and the range of gradient. for given range and hidden neurons, 100 sets of random neuron gradients were generated and among them one best set was selected for evaluation. Compared to the conventional BPNN, the proposed RC-BPNN demonstrated about 50％ improvements in all comparisons. This illustrates that the RG-BPNN of multi-valued gradients is an effective way to considerably improve the predictive ability of current BPNN of single-valued gradient.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.10
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• pp.844-850
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• 2002

Linearly graded profiles on the field area oxide are frequently used in power integrated circuits to reduce the surface electric field when power devices are operated in forward or reverse blocking modes. It is shown here that tapered windows can be made using the difference of etch rates between the bottom and the top layer of TEOS film. Annealed TEOS films are etched at a lower rate than the TEOS film without annealing Process. The fast etching layer results in window walls having slopes in the range of 25$^{\circ}$∼ 80$^{\circ}$ with respect to the wafer surface. Taper etching technique by annealing the TEOS film applies to high voltage LDMOS, which is compatible with CMOS process, due to the minimum changes in both of design rules and thermal budget.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.46.5-46
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• 2002

As device dimension shrinks down to sub 100nm, it is increasingly important to monitor plasma states. Plasma etching is a key means to fine patterning of thin films. Many parameters are involved in etching and each parameter has different impact on process performances, including etch rate and profile. The uniformity of etch responses should be maintained high to improve device yield and throughput. The uniformity can be measured on any etch response. The most difficulty arises when attempting to characterize etched profile. Conventionally, the profile has been estimated by measuring the slope or angle of etched pattern. One critical drawback in this measurement is that this is unable to cap...

• ETRI Journal
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• v.36 no.4
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• pp.617-624
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• 2014

Through-silicon via (TSV) technology provides much of the benefits seen in advanced packaging, such as three-dimensional integrated circuits and 3D packaging, with shorter interconnection paths for homo- and heterogeneous device integration. In TSV, a destructive cross-sectional analysis of an image from a scanning electron microscope is the most frequently used method for quality control purposes. We propose a quantitative evaluation method for TSV etch profiles whereby we consider sidewall angle, curvature profile, undercut, and scallop. A weighted sum of the four evaluated parameters, nominally total score (TS), is suggested for the numerical evaluation of an individual TSV profile. Uniformity, defined by the ratio of the standard deviation and average of the parameters that comprise TS, is suggested for the evaluation of wafer-to-wafer variation in volume manufacturing.

• Transactions on Electrical and Electronic Materials
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• v.18 no.4
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• pp.199-202
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• 2017

Silicon carbide (SiC) is being spotlighted as a next-generation power semiconductor material owing to the characteristic limitations of the existing silicon materials. SiC has a wider band gap, higher breakdown voltage, higher thermal conductivity, and higher saturation electron mobility than those of Si. When using this material to implement Schottky barrier diode (SBD) devices, SBD-state operation loss and switching loss can be greatly reduced as compared to that of traditional Si. However, actual SiC SBDs exhibit a lower dielectric breakdown voltage than the theoretical breakdown voltage that causes the electric field concentration, a phenomenon that occurs on the edge of the contact surface as in conventional power semiconductor devices. Therefore in order to obtain a high breakdown voltage, it is necessary to distribute the electric field concentration using the edge termination structure. In this paper, we designed an edge termination structure using a field plate structure through oxide etch angle control, and optimized the structure to obtain a high breakdown voltage. We designed the edge termination structure for a 650 V breakdown voltage using Sentaurus Workbench provided by IDEC. We conducted field plate experiments. under the following conditions: $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $75^{\circ}$. The experimental results indicated that the oxide etch angle was $45^{\circ}$ when the breakdown voltage characteristics of the SiC SBD were optimized and a breakdown voltage of 681 V was obtained.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1399-1401
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• 2009

In this article, we reported the results of etching polymonochloro-para-xylylene (parylene-C) thin films using inductively coupled plasma and $CF_4/O_2$ gas mixture. The $CF_4$ gas fraction increased up to the approximately 16 %, the polymer etch rate increased in the range of 277 - 373 nm/min. It confirmed that the etch rate of the parylene-C mainly depended on the O radical density in the plasma. Using a contact angle measurement, the contact angle increased with increasing the $CF_4$ fraction. Moreover, the contact angle was highly related a $CF_x$ functional group on parylene films.

• Korean Journal of Materials Research
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• v.16 no.1
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• pp.63-67
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• 2006

The characteristics of the wet-etching of ZnO thin films were investigated using hydrochloric and phosphoric acid solutions as etchants. The etch rate of ZnO films, using highly diluted hydrochloric acid solutions at a concentration of 0.25% in deionized water, was determined to be about 120 nm/min, and linearly increased with increasing the acid concentration, resulting in $1.17{\mu}m/min$ when a 2% HCl solution was used. The surface of ZnO etched by an HCl solution, observed by scanning electron microscopy, showed a rough morphology with a high density of hexagonal pyramids or cones with sidewall angles of about ${\sim}45^{\circ}C$. Moreover, the sidewall angles of the masked area were similar to those of the pyramids on the surface. In comparison, the surface of ZnO etched by a phosphoric acid had a smooth surface morphology. The origin of this difference is from the very initial stage of etching, indicating that the etch-mechanism is different for each solution. Furthermore, when $H_3PO_4$ was added to the HCl aqueous solution, the morphology of the etched surface was greatly enhanced and the sidewall angle was also increased to about $65^{\circ}C$.

• Restorative Dentistry and Endodontics
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• v.7 no.1
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• pp.131-138
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• 1981

The purpose of this study was to evaluate the marginal leakage of composite resin. Preparing 144 class V cavities on freshly extracted noncarious teeth, composite resins were prepared and inserted by one dentist according to the manufacturer's instructions. The experiments were performed in two different groups; In group I; Class V cavities with $90^{\circ}$ cavosurface angle, In group II; Class V cavities with $135^{\circ}$ cavosurface angle. And each group was divided 2 subgroups; In control group; composite resin restoraions without acid etch technique. In experimental group; composite resin restorations with acid etch technique. All specimens were immersed in 0.05% crystal violet solution. Before examination, the restored teeth were subjected to thermal stress. The specimens were sectioned occlusogingivally through the center of the restorations with a diamond disk. The sections were examined under a reflected light microscope at 1 day, 7 days and 30 days after immersing the specimens in dye solution. The results were as follows; 1. Control group of group I and group II showed marginal leakage. 2. The degree of marginal leakage in experimental group was greater reduced than control group. 3. In control group, the degree of marginal leakage in group I was greater than group II. 4. In experimental group, there is not statistical differences of the degree of marginal leakage between group I & group II.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.7
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• pp.50-57
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• 1989

Tapered etching of polysilicon films has been achieved by implanting phosphorus ions into the polysilicon film and using plasma etch in either $CF_4-O_2\;or\;SF_6$. A two-step plasma etching method is also proposed to control the taper angle of the etched edge without changing the implantion conditions. The taper angle is determined by the ratio of the etch rate of the undamaged region to that of the damaged top region of the polysilicon layer. The ratio is found to be dependent on the implantion dose, the implantion energy and the anisotropy of etching. The minimum angle in our experiments is about $10^{\circ}$. When the two-step etching method is employed, the taper angles can be controlled from the minimum angle up to about $55^{\circ}$.