• Journal of IKEEE
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• v.19 no.4
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• pp.541-547
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• 2015

In current semiconductor manufacturing, as the feature size of integrated circuit (IC) devices continuously shrinks, detecting endpoint in plasma etching process is more difficult than before. For endpoint detection, various kinds of sensors are installed in semiconductor manufacturing equipments, and sensor data are gathered with predefined sampling rate. Generally, detecting endpoint is performed using OES data of by-product. In this study, OES data of both by-product and etchant gas are used to improve reliability of endpoint detection. For the OES data pre-processing, a combination of Signal to Noise Ratio (SNR) and Principal Component Analysis (PCA),are used. Polynomial Regression and Expanded Hidden Markov model (eHMM) technique are applied to pre-processed OES data to detect endpoint.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11b
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• pp.300-315
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• 2005

Recently plasma surface-cleaning or surface-etching techniques have been focused in the respect of decontamination of spent or used nuclear parts and equipment. In this study decontamination rate of metallic cobalt surface was experimentally investigated via its surface etching rate with a $CF_4-O_2$ mixed gas plasma and metallic surface wastes of cobalt oxides were simulated and decontaminated with $NF_3$ - Ar mixed gas plasma. Experimental results revealed that a mixed etchant gas with about $80{\%}\;CF_4-20{\%}\;O_2$ gives the highest reaction rate of cobalt disk and the rate reaches with a negative 300 DC bias voltage up to $0.43\;{\mu}m$/min at $380^{\circ}C$ and $20{\%}\;NF_3-80\%$ Ar mixed gas gives $0.2\;{\mu}m$/min of reaction rate of cobalt oxide film.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.460-460
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• 2012

반도체 Device가 Shrink 함에 따라 Pattern Size가 작아지게 되고, 이로 인해 Photo Resist 물질 자체만으로는 원하는 Patterning 물질들을 Plasma Etching 하기가 어려워지고 있다. 이로 인해 Photoresist를 대체할 Hard Mask 개념이 도입되었으며, 이 Hardmask Layer 중 Amorphous Carbon Layer 가 가장 널리 사용되고 지고 있다. 이 Amorphous Carbon 계열의 Hardmask를 Etching 하기 위해서 기본적으로 O2 Plasma가 사용되는데, 이 O2 Plasma 내의 Oxygen Species들이 가지는 등 방성 Diffusion 특성으로 인해, 원하고자 하는 미세 Pattern의 Vertical Profile을 얻는데 많은 어려움이 있어왔다. 이를 Control 하기 인해 O2 Plasma Parameter들의 변화 및 Source/Bias Power 등의 변수가 연구되어 왔으며, 이와 다른 접근으로, N2 및 CO, CO2, SO2 등의 여러 Additive Gas 들의 첨가를 통해 미세 Pattern의 Profile을 개선하고, Plasma Etching 특성을 개선하는 연구가 같이 진행되어져 왔다. 본 논문에서 VLSI Device의 Masking Layer로 사용되는, Carbon 계 유기 층의 Plasma 식각 특성에 대한 연구를 진행하였다. Plasma Etchant로 사용되는 O2 Plasma에 새로운 첨가제 가스인 카르보닐 황화물 (COS) Gas를 추가하였을 시 나타나는 Plasma 내의 변화를 Plasma Parameter 및 IR 및 XPS, OES 분석을 통하여 규명하고, 이로 인한 Etch Rate 및 Plasma Potential에 대해 비교 분석하였다. COS Gas를 정량적으로 추가할 시, Plasma의 변화 및 이로 인해 얻어지는 Pattern에서의 Etchant Species들의 변화를 통해 Profile의 변화를 Mechanism 적으로 규명할 수 있었으며, 이로 인해 기존의 O2 Plasma를 통해 얻어진 Vertical Profile 대비, COS Additive Gas를 추가하였을 경우, Pattern Profile 변화가 개선됨을 최종적으로 확인 할 수 있었다.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.6
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• pp.113-120
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• 2007

Chemical vapor deposition (CVD) is one of the various synthesis methods that have been employed for carbon nanotube (CNT) growth. In particular, Ren et al reported that large areas of vertically aligned multi-wall carbon nanotubes could be grown using a direct current (dc) PECVD system. The synthesis of CNT requires a metal catalyst layer, etchant gas, and a carbon source. In this work, the substrates consists of Si wafers with Ni-deposited film. Ammonia $NH_3$) and acetylene ($C_2H_2$) were used as the etchant gases and carbon source, respectively. Pretreated conditions had an influence on vertical growth and density of CNTs. And patterned growth of CNTs could be achieved by lithographical defining the Ni catalyst prior to growth. The length of single CNT was increased as niclel dot size increased, but the growth rate was reduced when nickel dot size was more than 200 nm due to the synthesis of several CNTs on single Ni dot. The morphology of the carbon nanotubes by TEM showed that vertical CNTs were multi-wall and tip-type growth mode structure in which a Ni cap was at the end of the CNT.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1183-1185
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• 1993

The plasma polymerized thin film of MMA+Sty was prepared using a capacitively coupled gas-flow-type reactor. This thin films were also delincated by the electron-beam apparatus with an acceleration voltage 30KV, and the pattern in the resist was developed with the gas-flow-type reactor using an argon as an etchant. The effect of discharge power on groth rate and etching rate of the thin film were studied. The molacular structure of the resist was investigated by ESCA and FT-IR.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.10
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• pp.1406-1418
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• 2002

The direct simulation Monte Carlo(DSMC) method is employed to calculate the etch rate on Al wafer. The etchant is assumed to be Cl$_2$. The etching process of an Al wafer in a helicon plasma etcher is examined by simulating molecular collisions of reactant and product. The flow field inside a plasma etch reactor is also simulated by the DSMC method fur a chlorine feed gas flow. The surface reaction on the Al wafer is simply modelled by one-step reaction: 3C1$_2$+2Allongrightarrow1 2AIC1$_3$. The gas flow inside the reactor is compared for six different nozzle locations. It is found that the flow field inside the reactor is affected by the nozzle locations. The Cl$_2$ number density on the wafer decreases as the nozzle location moves toward the side of the reactor. Also, the present numerical results show that the nozzle location 1, which is at the top of the reactor chamber, produces a higher etch rate.

• Korean Journal of Metals and Materials
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• v.48 no.11
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• pp.1028-1034
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• 2010

In the development of 3D package, through silicon via (TSV) formation technology by using deep reactive ion etching (DRIE) is one of the key processes. We performed the Bosch process, which consists of sequentially alternating the etch and passivation steps using $SF_6$ with $O_2$ and $C_4F_8$ plasma, respectively. We investigated the effect of changing variables on vias: the gas flow time, the ratio of $O_2$ gas, source and bias power, and process time. Each parameter plays a critical role in obtaining a specified via profile. Analysis of via profiles shows that the gas flow time is the most critical process parameter. A high source power accelerated more etchant species fluorine ions toward the silicon wafer and improved their directionality. With $O_2$ gas addition, there is an optimized condition to form the desired vertical interconnection. Overall, the etching rate decreased when the process time was longer.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.32-42
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• 2004

Recently, plasma surface-cleaning or surface-etching techniques have been focused in respect of the decontamination of spent or used nuclear parts and equipment. In this study the removal rate of metallic cobalt surface is experimentally investigated via its surface etching rate with a $CF_4-o_2$mixed gas plasma. Experimental results reveal that a mixed etchant gas with about 80% $CF_4$-20% $O_2$ (molar) gives the highest reaction rate and the rate reaches 0.06 ${\mu}m$/min at $380^{\circ}C$ and ion-assisted etching dramatically enhances the surface reaction rate. With a negative 300 V DC bias voltage applied to the substrate, the surface reaction initiation temperature lowers and the rate increases about 20 times at $350^{\circ}C$ and up to 0.43 ${\mu}m$/min at $380^{\circ}C$, respectively. Surface morphology analysis confirms the etching rate measurements. Auger spectrum analysis clearly shows the adsorption of fluorine atoms on the reacted surface. From the current experimental findings and the results discussed in previous studies, mechanistic understanding of the surface reaction, fluorination and/or fluoro-carbonylation reaction, is provided.

• Korean Chemical Engineering Research
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• v.44 no.5
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• pp.483-488
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• 2006

Etching process of PMMA (Polymethyl Methacrylate) on glass surface was investigated by dry etching technique using remote plasma. To determine the etching characteristics, the remote plasma etching was conducted for various process parameters such as plasma power, reaction gas and distance from plasma generation. As the distance from the plasma generation was increased, the etch rate of PMMA was linearly decreased by radical density in plasma. PMMA has removed by reactive radicals in the plasma. The etch rate increased with plasma power because of more reactive radicals. The etch rate and surface roughness of PMMA increased with $O_2$ concentration in the etchant.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.58-62
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• 2003

Silicon carbide (SiC) was etched in a $NF_3/CH_4$ inductively coupled plasma. The etch process was modeled by using a neural network called generalized regression neural network (GRNN). For modeling, the process was characterized by a $2^4$ full factorial experiment with one center point. To test model appropriateness, additional test data of 16 experiments were conducted. Particularly, the GRNN predictive capability was drastically improved by a genetic algorithm (GA). This was demonstrated by an improvement of more than 80% compared to a conventionally obtained model. Predicted model behaviors were highly consistent with actual measurements. From the optimized model, several plots were generated to examine etch rate variation under various plasma conditions. Unlike the typical behavior, the etch rate variation was quite different depending on the bias power Under lower bias powers, the source power effect was strongly dependent on induced dc bias. The etch rate was strongly correated to the do bias induced by the gas ratio. Particularly, the etch rate variation with the bias power at different gas ratio seemed to be limited by the etchant supply.