• 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 $SF_6/C_4F_8=2s/3s$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.361-365
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• 2003

Planar Inductively Coupled Plasma (PICP) etching of InGaP was performed in $BCl_3,\;BCl_3/Ar\;and\;BCl_3/Ne$ plasmas as a function of ICP source power ($0\;{\sim}\;500\;W$), RIE chuck power ($0\;{\sim}\;150\;W$), chamber pressure ($5\;{\sim}\;15\;mTorr$) and gas composition of $BCl_3/Ar\;and\;BCl_3/Ne$. Total gas flow was fixed at 20 sccm (standard cubic centimeter per minute). Increase of ICP source power and RIE chuck power raised etch rate of InGaP, while that of chamber pressure reduced etch rate. We also found that some addition of Ar and Ne in $BCl_3$ plasma improved etch rate of InGaP. InGaP etch rate was varied from $1580\;{\AA}/min$ with pure $BC_3\;to\;2800\;{\AA}/min$ and $4700\;{\AA}/min$ with 25 % Ar and Ne addition, respectively. Other process conditions were fixed at 300 W ICP source power, 100 W RIE chuck power and 7.5 mTorr chamber pressure. SEM (scanning electron microscopy) and AFM (atomic force microscopy) data showed vertical side wall and smooth surface of InGaP at the same condition. Proper addition of noble gases Ar and Ne (less than about 50 %) in $BCl_3$ inductively coupled plasma have resulted in not only increase of etch rate but also minimum preferential loss and smooth surface morphology by ion-assisted effect.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.448-448
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• 2010

Magnetic random access memory (MRAM) has made a prominent progress in memory performance and has brought a bright prospect for the next generation nonvolatile memory technologies due to its excellent advantages. Dry etching process of magnetic thin films is one of the important issues for the magnetic devices such as magnetic tunneling junctions (MTJs) based MRAM. CoFeB is a well-known soft ferromagnetic material, of particular interest for magnetic tunnel junctions (MTJs) and other devices based on tunneling magneto-resistance (TMR), such as spin-transfer-torque MRAM. One particular example is the CoFeB - MgO - CoFeB system, which has already been integrated in MRAM. In all of these applications, knowledge of control over the etching properties of CoFeB is crucial. Recently, transferring the pattern by using milling is a commonly used, although the redeposition of back-sputtered etch products on the sidewalls and the low etch rate of this method are main disadvantages. So the other method which has reported about much higher etch rates of >$50{\AA}/s$ for magnetic multi-layer structures using $Cl_2$/Ar plasmas is proposed. However, the chlorinated etch residues on the sidewalls of the etched features tend to severely corrode the magnetic material. Besides avoiding corrosion, during etching facets format the sidewalls of the mask due to physical sputtering of the mask material. Therefore, in this work, magnetic material such as CoFeB was etched in an ICP etching system using the gases which can be expected to form volatile metallo-organic compounds. As the gases, carbon monoxide (CO) and ammonia ($NH_3$) were used as etching gases to form carbonyl volatiles, and the etched features of CoFeB thin films under by Ta masking material were observed with electron microscopy to confirm etched resolution. And the etch conditions such as bias power, gas combination flow, process pressure, and source power were varied to find out and control the properties of magnetic layer during the process.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.78-79
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• 2007

In this study, chemical dry characteristics of silicon nitride layers were investigated in the $F_2/N_2/Ar$ remote plasma. A toroidal-type remote plasma source was used for the generation of remote plasmas. The effects of additive $N_2$ gas on the etch rates of various silicon nitride layers deposited using different deposition techniques and precursors were investigated by varying the various process parameters, such as the $F_2$ flow rate, the addition $N_2$ flow rate and the substrate temperature. The etch rates of the various silicon nitride layers at the room temperature were initially increased and then decreased with the $N_2$ flow increased, which indicates an existence of the maximum etch rates. The etch rates of the silicon oxide layers were also significantly increased with the substrate temperature increased. In the present experiments the $F_2$ gas flow, addition $N_2$ flow rate and the substrate temperature were found to be the critical parameters in determining the etch rate of the silicon nitride layers

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.775-778
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• 2003

We studied InP etching in high density planar inductively coupled $BCl_3$and $BCl_3$/Ar plasmas(PICP). The investigated process parameters were PICP source power, RIE chuck power, chamber pressure and $BCl_3$/Ar gas composition. It was found that increase of PICP source power and RIE chuck power increased etch rate of InP, while that of chamber pressure decreased etch rate. Etched InP surface was clean and smooth (RMS roughness <2 nm) with a moderate etch rate (300-500 $\AA$/min) after the planar $BCl_3$/Ar ICP etching. It may make it possible to open a new regime of InP etching with $CH_4$$H_2$-free plasma chemistry. Some amount of Ar addition (<50%) also improved etch rates of InP, while too much Ar addition reduced etch rates of InP.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.391-392
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• 2012

In these days, the desire for the precise and tiny displays in mobile application has been increased strongly. Currently, laser displays ranging from large-size laser TV to mobile projectors, are commercially available or due to appear on the market [1]. In order to achieve a mobile projectors, the semiconductor laser diodes should be used as a laser source due to their size and weight. In this presentation, the continuous etch characteristics of Pd and AlGaN/GaN superlattice for the fabrication of blue laser diodes were investigated by using inductively coupled $CHF_3$ and $Cl_2$ -based plasma. The GaN laser diode samples were grown on the sapphire (0001) substrate using a metal organic chemical vapor deposition system. A Si-doped GaN layer was grown on the substrate, followed by growth of LD structures, including the active layers of InGaN/GaN quantum well and barriers layer, as shown in other literature [2], and the palladium was used as a p-type ohmic contact metal. The etch rate of AlGaN/GaN superlattice (2.5/2.5 nm for 100 periods) and n-GaN by using $Cl_2$ (90%)/Ar (10%) and $Cl_2$ (50%)/$CHF_3$ (50%) plasma chemistry, respectively. While when the $Cl_2$/Ar plasma were used, the etch rate of AlGaN/GaN superlattice shows a similar etch rate as that of n-GaN, the $Cl_2/CHF_3$ plasma shows decreased etch rate, compared with that of $Cl_2$/Ar plasma, especially for AlGaN/GaN superlattice. Furthermore, it was also found that the Pd which is deposited on top of the superlattice couldn't be etched with $Cl_2$/Ar plasma. It was indicating that the etching step should be separated into 2 steps for the Pd etching and the superlattice etching, respectively. The etched surface of stacked Pd/superlattice as a result of 2-step etching process including Pd etching ($Cl_2/CHF_3$) and SLs ($Cl_2$/Ar) etching, respectively. EDX results shows that the etched surface is a GaN waveguide free from the Al, indicating the SLs were fully removed by etching. Furthermore, the optical and electrical properties will be also investigated in this presentation. In summary, Pd/AlGaN/GaN SLs were successfully etched exploiting noble 2-step etching processes.

• Journal of the Korean institute of surface engineering
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• v.34 no.5
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• pp.516-521
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• 2001

Dry etching of Si wafer and $SiO_2$ layers was performed using He/Cl$_2$ mixture plasma by diode-type reactive ion etcher (RIE) system. For Si etching, the Cl molecules react with the Si molecules on the surface and become chemically stable, indicating that the reactants need energetic ion bombardment. During the ion assisted desorption, energetic ions would damage the photoresist (PR) and produce the bad etch Si-profile. Moreover, we have examined the characteristics of the Cl-Si reaction system, and developed the new fabrication procedures with a $Cl_2$/He mixture for Si and $SiO_2$-etching. The developed novel fabrication procedure allows the RIE to be unexpensive and useful a Si deep etching system. Since the etch rate was proved to increase linearly with fHe and the selectivity of Si to $SiO_2$ etch rate was observed to be inversely proportional to fHe.

• Journal of the Korean institute of surface engineering
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• v.42 no.6
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• pp.256-259
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• 2009

The wafer surface temperature is an important parameter in the etching process which influences the reaction probabilities of incident species, the vapor pressure of etch products, and the re-deposition of reaction products on feature surfaces. In this study, we investigated all of the effects of substrate temperature on the etch rate of $ZrO_2$ thin film and selectivity of $ZrO_2$ thin film over $SiO_2$ thin film in inductively coupled plasma as functions of $Cl_2$ addition in $BCl_3$/Ar plasma, RF power and dc-bias voltage based on the substrate temperature in range of $10^{\circ}C$ to $80^{\circ}C$. The elements on the surface were analyzed by x-ray photoelectron spectroscopy (XPS).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.12
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• pp.1051-1056
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• 2008

In this study, the investigations of the TiN etching characteristics were carried out with addition of $Cl_2$ gas in an inductively coupled $BCl_3$-base plasma system. Dry etching of the TiN was studied by varying the etching parameters including $Cl_2$ gas addition ratio, RF power, DC-bias voltage and pressure. The etch rate of TiN thin film was maximum when the $Cl_2$ gas addition flow was 2 sccm with fixed other conditions. As the RF power DC-bias voltage were increased, the etch rate of TiN thin film showed increasing tendency. $BCl_3/Cl_2$/Ar plasmas were characterized by optical emission spectroscopy (OES) analysis. The chemical reaction on the surface of the etched TiN films was investigated with X-ray photoelectron spectroscopy (XPS).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05b
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• pp.84-87
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• 2001

In this study, $CeO_2$ thin films were etched with a $CF_4/Ar$ gas combination in inductively coupled plasma (ICP), The maximum etch rate of $CeO_2$ thin films is $270{\AA}/min$under $CF_4/(CF_4+Ar)$ of 0.2, 600 W/-200 V, 15 mTorr, and $25^{\circ}C$. The selectivities of $CeO_2$ to PR and SBT are 0.21, 0.25. respectively. The surface reaction of the etched $CeO_2$ thin films was investigated with x-ray photoelectron spectroscopy (XPS). There is a chemical reaction between Ce and F, Compounds such as $Ce-F_x$ are remains on the surface of $CeO_2$ thin films. Those products can be removed by Ar ion bombardment effect, The results of secondary ion mass spectrometer (SIMS) were equal to these of XPS. Scanning electron microscopy (SEM) was used to examine etched profiles of $Ce-F_x$ thin films. The etch profile of over-etched $CeO_2$ films with the $0.5 {\mu}m$ line was approximately $65^{\circ}$.