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Summary Vitiligo-like depigmentation in patients with malignant melanoma is a poorly understood phenomenon. We report a patient who presented with a 4-month history of vitiligo-like depigmentation of the face, trunk and limbs. Physical examination revealed an enlarged left inguinal lymph node. A needle biopsy taken from the lymph nodes revealed metastatic malignant melanoma. One small nodule on the left sole was found subsequently. Despite the absence of junctional activity, it was considered to be a primary tumour with regression of the epidermal lesion. The patient died from sepsis, the main complication of immunosuppressive therapy, without evidence of distant metastasis. We report this case to highlight the importance of careful physical examination of patients with skin hypomelanoses. We also propose that, due to the favourable prognosis in patients with malignant melanomas and vitiligo-like depigmentation, the treatment plan may be more conservative to minimize the adverse effects of chemotherapy.

An electron cyclotron resonance source has been used to generate a Cl 2 plasma and etch Si trenches >100 μm deep. High microwave power was used to achieve Si etch rates of 1.09 μm/min for trench openings >500 μm. With pressure ranging from 2 to 30 mTorr, etching at higher pressures, up to 20 mTorr, increased the anisotropy of the etch, due to sidewall passivation. In addition, Si etch rates were faster at high pressures, increasing from 0.47 to 0.78 μm/min as the pressure was increased from 2 to 30 mTorr. Features with aspect ratios >30 have been fabricated using 1200 W microwave power and 50 W radio-frequency power at 20 mTorr with 20 sccm of Cl 2 flow. Under these conditions,the self-induced dc bias at the stage was 50 V, and a selectivity >250 over an evaporated Ni mask was achieved. This allowed the use of an evaporated Ni mask for trench depths >50 μm. Electroplated Ni could be used as an etch mask, and the selectivity of Si over Ni was 75. Also, the addition of SF 6 increased the etch rate to as high as 1.89 μm/min for trench openings >500 μm, while keeping the vertical profile and smooth surface. The Si etch rate was found to depend on the aspect ratio and an etch rate reduction of 18% was seen in the Cl 2 plasma for 1.5 μm wide trench openings relative to the etch rate of a 50 μm wide trench opening. The etch rate also increased as the etch time increased. For a 30 min etch in the Cl 2 plasma, an etch rate of 0.79 μm/min was measured; however, for a 2 h etch, an etch rate of 1.00 μm/min was measured.

Si has been etched with an electron cyclotron resonance source in a Cl2 plasma to fabricate microsensors with high‐aspect‐ratio structures. Resonating elements in Si with an aspect ratio of 20 were generated. For these high‐aspect‐ratio sensing elements, the etch rate and profile strongly depend on feature size and etch depth. When the spacing between elements was increased from 2 to 50 μm, the Si etch depth varied from 21.5 to 24.6 μm for a 156 min etch. Typical etch conditions were 100 W microwave power, 100 W rf power, at 3 mTorr and 8 cm source distance. The Si etch rate decreased linearly from 156 to 119 nm/min as the trench aspect ratio varied from 2 to 34. The etch rate also decreased from 151 to 124 nm/min in 2‐μm‐wide trenches and from 163 to 141 nm/min in 10‐μm‐wide trenches as the pressure was increased from 3 to 30 mTorr. Etch profile was vertical at 3 mTorr and it became undercut at pressures ≥10 mTorr. Larger undercut widths were found for trenches with narrower spacings. As microwave power ...

Etching of high‐aspect‐ratio Si structures for microsensors was carried out in a Cl2 plasma generated by a multipolar electron cyclotron resonance (ECR) source. Si etch rate is found to increase with microwave and rf power, and it is the highest at 1 mTorr over the range of 0.5–50 mTorr. Optical emission spectroscopy (OES) and mass spectrometry (MS) were used to monitor the etch process to provide precise control for the sensor fabrication. The Si emission intensity at 288.1 nm and the mass spectrometric signal for 63SiCl+ follow the Si etch rate directly. The selectivity of etch masks decreases at higher rf power and Ni has higher selectivity than SiO2. Si etch rate is reduced for structures with smaller linewidth, but this microloading effect decreases at lower pressure. For the etch conditions used, the Si etch rate remains almost constant when flow rate is changed, but the optical emission and mass spectrometric signals of the etch products are found to decrease with increasing flow. Endpoint detectio...

A multipolar electron cyclotron resonance (ECR) plasma source was characterized by Langmuir probe measurements and the charged particle energy and density are related to photoresist etch rate. Ion density was found to increase with microwave power but decrease with source distance, and is independent of rf power and flow rate. Among the different gases investigated, Ar plasma was found to have higher ion density compared to O2, N2, and Cl2 discharge. Ion density peaked at 5 mTorr for Ar and 2 mTorr for O2 plasma. For a N2 plasma, the maximum ion density was found to occur at 10 mTorr at 3 cm and 2 mTorr at 23 cm below the ECR source. Electron temperature is ∼3 eV for pressure ranging from 1 to 5 mTorr but decreases to 2 eV at 20 mTorr. Photoresist etch rate follows the same trend as ion density. It increases with microwave power and decreases with source distance. On the other hand, photoresist etch rate increases with rf power and flow rate, even though the ion density remains constant. This suggests tha...

Dry development of silylated resist has been studied using an O 2 plasma generated by a multipolar electron cyclotron resonance source. Etch rate, uniformity, selectivity, and profile were investigated as a function of process parameters including microwave power, RF power, flow rate, sample area, pressure, temperature, and gas addition. It was found that etch rate increases as microwave and/or RF power increase. Vertical etch profile was obtained by using low pressure (3m Torr) and 50 W RF power

Features as fine as 4 μm with high aspect ratio were produced from ceria‐zirconia ceramic using a thick plasma‐etched polyimide layer as a micromold.

In this work, Langmuir probe measurements were used to characterize a multipolar electron cyclotron resonance (ECR) plasma source. This system has many controllable parameters including microwave power, rf power, gas, pressure, flow rate, and source distance. Both double and triple Langmuir probes were used for the plasma characterization. The results from the Langmuir probe measurements were correlated to the etch characteristics of photoresist. Ion density and photoresist etch rate were found to increase with microwave power but decrease with source distance. However, rf power does not have significant influence on ion density although the photoresist etch rate increases substantially with if power. Ion density first increases then decreases at higher pressure. Maximum ion density occurs at lower pressure for larger distance below the ECR source. Ion density uniformity for an O2 plasma is ±2% across a 16 cm diameter region at 23 cm below the source. For photoresist etched at 10 cm source distance, etch rate uniformity is ±2% for a 15 cm diameter wafer. The results from the Langmuir probe measurements indicate that photoresist etching is enhanced by ion density and ion energy.

Optical interferometry has been applied to determine the displacement of p++ Si beams. Clamped-clamped Si beams and cantilevered beams were fabricated with short and long B diffusion processes and characterized. Measurements of beam bending for released Si structures with length varying from 50 to 1000 μm, width varying from 5 to 15 μm, and thickness varying from 6 to 37 μm were obtained. By taking advantage of an etch-diffusion process, thicker beams can be fabricated which have less bending due to stress gradients. A 6.0-μm-thick cantilevered beam had a deflection of 11.2 μm due to stress gradients, while a 36.7-μm-thick beam had a deflection of only 0.3 μm. Beams fabricated using a dissolved wafer process with a 12 h B diffusion were found to bend the same amount as those fabricated with a 4 h diffusion. This indicates that bending in doped Si beams not only depends on the gradients in the B concentrations, it could also be related to the distribution of dislocations. Using the deep-etch shallow-diffus...

Etching of InP using an electron cyclotron resonance source in a Cl2/Ar plasma has been investigated for the fabrication of microcavity laser structures. Fast, smooth, and reproducible etching was achieved with etch rates of 2.14 μm/min. It was found that the etch profile depended on the Cl2 concentration in the Cl2/Ar plasma. Vertical etch profile was obtained for Cl2 concentration ⩽15%. Hard-baked photoresist and Ni have been used as etch masks. Typical etch rate of hard-baked photoresist was 0.10 μm/min and etch selectivity between InP and photoresist was 21. Typical etch rate of Ni was 13 nm/min with a selectivity of 165. The etched InP surface was smoother for samples with photoresist mask. For samples with Ni mask, the etched surface became rougher when narrower or deeper trenches were etched. With optimized etch conditions, high aspect ratio microstructures in InP that were 0.75 μm wide and 10.7 μm tall were fabricated with nearly vertical profile and smooth etched surface using photoresist mask. S...

This article discusses etching and boron diffusion in Si for the purpose of fabricating micromachined devices with high aspect ratio features. The etch rate of Si under various doping conditions in a Cl2 plasma generated by an electron cyclotron resonance (ECR) source was measured. It was found that lightly boron and phosphorus doped Si were etched at rates of 0.17 μm/min, whereas heavily boron doped Si had a similar etch rate of 0.16 μm/min. Si doped with high phosphorus concentrations had a faster etch rate of 0.31 μm/min. These etch rates were measured for Si etched at 100 W microwave power, 100 W rf power, 3 mTorr, with 20 sccm of Cl2 flow, and an ECR source to sample distance of 8 cm. The difference between the p++ and n++Si etch rates was more significant when etched at higher microwave power, higher rf power, or higher temperature. The depth of a heavily doped boron diffusion layer was measured for different feature sizes, trench openings, and aspect ratios. The diffusion layer thickness was found ...

High aspect ratio etching of polyimide in an O2 plasma generated by an electron cyclotron resonance (ECR) source was investigated. The dependence of etch rate, profile, and selectivity on microwave power, rf power, pressure, etch time, and gas composition were characterized. Etch rate was found to increase with microwave and rf power. Etch anisotropy increases with rf power but decreases with pressure and etch time. With 750 W microwave power, 300 W rf power, and 0.5 mTorr pressure, the polyimide etch rate was 0.91 μm/min and the anisotropy was 0.92. Etch selectivity between polyimide and the Ti mask was 3150:1 at 50 W and 536:1 at 300 W rf power. Compared to reactive ion etching, etching using an ECR source provides etch rate that is typically 10× faster and etch selectivity that is 4–6× higher. High aspect ratio (≳15:1) structures in polyimide that were 50 μm deep and 3 μm wide have been obtained using an O2 plasma generated by an ECR source.

Micromachined Si vertical structures were sputter coated with Au onto sidewalls as reflective mirrors. These vertical micromirrors were integrated with comb drives as optical switching arrays. The micromirrors were first etched in a Cl2 plasma generated by an electron cyclotron resonance source, followed by a short B diffusion and a wet etch with ethylenediamine pyrocatechol to reduce sidewall roughness and to separate the mirrors from the substrate. The sputter-deposited Au films have nearly uniform thickness along the sidewalls of the micromirrors. There was only a 6% thickness variation from the top to the bottom of the mirror sidewalls. Reducing the sputtering pressure from 30 to 4 mTorr improved the coating uniformity for high aspect ratio, closely spaced mirrors. For 30-μm-tall micromirrors with 6 μm spacing, the Au thickness close to the bottom of the sidewalls decreased by 52% compared to the top of the sidewalls when sputtered at 4 mTorr. The roughness along the micromirror sidewalls was found to...

Nanometer‐scale Si structures have been fabricated by anodic oxidation with an atomic force microscope (AFM) and dry etching using an electron cyclotron resonance (ECR) source. The AFM is used to anodically oxidize a thin surface layer on a H‐passivated (100) Si surface. This oxide is used as a mask for etching in a Cl2 plasma generated by the ECR source. An etch selectivity ≳20 was obtained by adding 20% O2 to the Cl2 plasma. The AFM‐defined mask withstands a 70 nm deep etch, and linewidths∼10 nm have been obtained with a 30 nm etch depth.