• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.160-160
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• 2008

In practical etching process, etch ant is sprayed on the metal-deposited panel through nozzles collectively connected to the manifold and that panel is usually composed of many PCB(printed circuit board)'s. The etching uniformity, the difference between individual PCB's on the same panel, has become one of most important features of etching process. In this paper, the prediction of nozzle trajectory has been performed by the combination of algebraic formula and numerical simulation. With the pre-determined geometrical factors of nozzle distribution, the trajectories of individual nozzles were predicted with the change of process operational factors such as panel speed, nozzle swing frequency and so on. As results, two dimensional distribution of impulsive force of etchant spray which could be considered as a key factor determining the etching performance have been successfully obtained. Though only qualitative prediction of etching uniformity have been predicted by the process developed in this study, the expansion to the quantitative prediction of etching uniformity is expected to be apparent by this study.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.136.2-136.2
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• 2015

반도체 제조는 chip의 성능 향상 및 단가 하락을 위해 지속적으로 pattern size가 nano size로 감소해 왔고, capacitor 용량은 증가해 왔다. 이러한 현상은 contact hole의 aspect ratio를 지속적으로 증가시킨바, 그에 따라 최적의 HARC (high aspect ratio contact)을 확보하는 적합한 dry etch process가 필수적이다. 그러나 HARC dry etch process는 많은 critical plasma properties 에 의존하는 매우 복잡한 공정이다. 따라서, critical plasma properties를 적절히 조절하여 higher aspect ratio, higher etch selectivity, tighter critical dimension control, lower P2ID과 같은 plasma characteristics을 확보하는 것이 요구된다. 현재 critical plasma properties를 제어하기 위해 다양한 plasma etching 방법이 연구 되어왔다. 이 중 plasma를 낮은 kHz의 frequency에서 on/off 하는 pulsed plasma etching technique은 nanoscale semiconductor material의 etch 특성을 효과적으로 향상 시킬 수 있다. 따라서 본 실험에서는 dual-frequency capacitive coupled plasma (DF-CCP)을 사용하여 plasma operation 동안 duty ratio와 pulse frequency와 같은 pulse parameters를 적용하여 plasma의 특성을 각각 제어함으로써 etch selectivity와 uniformity를 향상 시키고자 하였다. Selective SiO2 contact etching을 위해 top electrode에는 60 MHz pulsed RF source power를, bottom electrode에는 2MHz pulse plasma를 인가하여 synchronously pulsed dual-frequency capacitive coupled plasma (DF-CCP)에서의 plasma 특성과 dual pulsed plasma의 sync. pulsing duty ratio의 영향에 따른 etching 특성 등을 연구 진행하였다. 또한 emissive probe를 통해 전자온도, OES를 통한 radical 분석으로 critical Plasma properties를 분석하였고 SEM을 통한 etch 특성분석과 XPS를 통한 표면분석도 함께 진행하였다. 그 결과 60%의 source duty percentage와 50%의 bias duty percentage에서 가장 향상된 etch 특성을 얻을 수 있었다.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.1033-1036
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• 2003

In this paper, Si anisotropic etching characteristics of tetramethylammonium hydroxide (TMAH)/ ammonium persulfate (AP) solutions were investigated to realize the optimum structure of a diaphragm for the piezoresistive pressure sensor application. Due to its low toxicity and its high compatibility with the CMOS processing, TMAH was used as Si anisotropic etchants. The variations of Si etch rate on the etching temperature, TMAH concentration, and etching time were obtained. With increasing the etching temperature and decreasing TMAH concentrations, the Si etch rate is increased while a significant non-uniformity exists on the etched surface because of formation of hillocks on the <100> surface. With the addition of AP to TMAH solution, the Si etch rate is increased and an improvement in flatness on the etching front is observed. The Si etch rate is also maximized with increasing the number of addition of AP to TMAH solution per one hour. The Si square diaphragms of 20${\mu}{\textrm}{m}$ thickness and 100~400${\mu}{\textrm}{m}$ one-side length were fabricated successfully by applying optimum Si etching conditions of TMAH/AP solutions.

• Journal of the Semiconductor & Display Technology
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• v.2 no.4
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• pp.19-22
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• 2003

In this paper, Si anisotropic etching characteristics of tetramethylammonium hydroxide (TMAH)/ammonium persulfate (AP) solutions were investigated to realize the optimum structure of a diaphragm for the piezoresistive pressure sensor application. Due to its low toxicity and its high compatibility with the CMOS processing, TMAH was used as Si anisotropic etchants. The variations of Si etch rate on the etching temperature, TMAH concentration, and etching time were obtained. With increasing the etching temperature and decreasing TMAH concentrations, the Si etch rate is increased while a significant non-uniformity exists on the etched surface because of formation of hillocks on the <100> surface. With the addition of AP to TMAH solution, the Si etch rate is increased and an improvement in flatness on the etching front is observed. The Si etch rate is also maximized with increasing the number of addition of AP to TMAH solution per one hour. The Si square diaphragms of 20$\mu\textrm{m}$ thickness and 100-400 $\mu\textrm{m}$ one-side length were fabricated successfully by adding AP of (5/6)g to 800 ml TMAH solution every 10 minutes.

• Journal of Sensor Science and Technology
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• v.24 no.1
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• pp.10-14
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• 2015

This paper reports the results of a study on the optimization of the etching profile, which is an important factor in deep-reactive-ion etching (DRIE), i.e., dry etching. Dry etching is the key processing step necessary for the development of the Internet of Things (IoT) and various microelectromechanical sensors (MEMS). Large-area etching (open area > 20%) under a high-frequency (HF) condition with nonoptimized processing parameters results in damage to the etched sidewall. Therefore, in this study, optimization was performed under a low-frequency (LF) condition. The HF method, which is typically used for through-silicon via (TSV) technology, applies a high etch rate and cannot be easily adapted to processes sensitive to sidewall damage. The optimal etching profile was determined by controlling various parameters for the DRIE of a large Si wafer area (open area > 20%). The optimal processing condition was derived after establishing the correlations of etch rate, uniformity, and sidewall damage on a 6-in Si wafer to the parameters of coil power, run pressure, platen power for passivation etching, and $SF_6$ gas flow rate. The processing-parameter-dependent results of the experiments performed for optimization of the etching profile in terms of etch rate, uniformity, and sidewall damage in the case of large Si area etching can be summarized as follows. When LF is applied, the platen power, coil power, and $SF_6$ should be low, whereas the run pressure has little effect on the etching performance. Under the optimal LF condition of 380 Hz, the platen power, coil power, and $SF_6$ were set at 115W, 3500W, and 700 sccm, respectively. In addition, the aforementioned standard recipe was applied as follows: run pressure of 4 Pa, $C_4F_8$ content of 400 sccm, and a gas exchange interval of $SF_6/C_4F_8=2s/3s$.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.1
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• pp.33-40
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• 1992

Several etching phenomena were observed and analyzed in diaphragm process performed on 4-inch (100) Si wafers for sensor application. In case of deep etching to above 300$\mu$m depth, the etch-defects appeared at etched surface could be classified into three categories such as hillocks, reaction products, and white residues. It was known that the hillock had a pyramidal shape or trapizoidal hexahedron structure depending on the density and size of the reaction products. The IR spectra showed that the white residue, which was due to the local over-saturation of Si dissolved in solution, was mostly Si-N-O compounds mixed with a small amount of H and C etc. Also, the difference in both the existence of etch-defects and etch rate distribution over a whole wafer was investigated when the etched surfaces were downward, upward horizontally and erective in etching solutions. The obtained data were analyzed through flow pattern in the etching bath. As the results, the downward and erective postures were favorable in the etch rate uniformity and the etch-defect removal, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1269-1271
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• 2008

We find some array mura are caused by S/D bridge or channel open in 4 mask process. The gray tone PR thickness non-uniformity is the main reason of these defects. By the adjustment of exposure and dry etch parameters, S/D bridge and channel open ratio drops by 10.87%.

• 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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• 2012.08a
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• pp.319-320
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• 2012

Large aperture optical modulator called optical shutter is a key component to realize time-of-flight (TOF) based three dimensional (3D) imaging systems [1-2]. The transmission type electro-absorption modulator (EAM) is a prime candidate for 3D imaging systems due to its advantages such as small size, high modulation performance [3], and ease of forming two dimensional (2D) array over large area [4]. In order to use the EAM for 3D imaging systems, it is crucial to remove GaAs substrate over large area so as to obtain high uniformity modulation performance at 850 nm. In this study, we propose and experimentally demonstrate techniques for backside etching of GaAs substrate over a large area having high uniformity. Various methods such as lapping and polishing, dry etching for anisotropic etching, and wet etching ([20%] C6H8O7 : H2O2 = 5:1) for high selectivity backside etching [5] are employed. A high transmittance of 80% over the large aperture area ($5{\times}5mm^2$) can be obtained with good uniformity through optimized backside etching method. These results reveal that the proposed methods for backside etching can etch the substrate over a large area with high uniformity, and the EAM fabricated by using backside etching method is an excellent candidate as optical shutter for 3D imaging systems.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.201-204
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• 2002

A large area inductively coupled plasma which is applicable to LCD processing is built with a modified single loop RF antenna. Combination of parallel and series paths of RF current through the antenna induces local enhancement of plasma density, which in turn provides uniform plasma density near the substrate. The plasma density distribution is measured and compared with that of the conventional single loop antenna. Aisotropic etching of photoresist is performed, and it is found that etch uniformity is improved by 3％ from 15% of the conventional etcher over 350$\times$300mm glass substrates. Photoresist etching rate and uniformity can be further improved by applying a periodic weak axial magnetic fieid.