• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.456-456
• /
• 2010

CMOS 소자가 서브마이크론($0.1\;{\mu}m$) 이하로 스케일다운 되면서 단채널 효과(short channel effect), 게이트 산화막(gate oxide)의 누설전류(leakage current)의 증가와 높은 직렬저항(series resistance) 등의 문제가 발생한다. CMOS 소자의 구동전류(drive current)를 높이고, 단채널 효과를 줄이기 위한 가장 효율적인 방법은 소스 및 드레인의 얕은 접합(shallow junction) 형성과 직렬 저항을 줄이는 것이다. 플라즈마 도핑 방법은 플라즈마 밀도 컨트롤, 주입 바이어스 전압 조절 등을 통해 저 에너지 이온주입법보다 기판 손상 및 표면 결함의 생성을 억제하면서 고농도로 얕은 접합을 형성할 수 있다. 그리고 얕은 접합을 형성하기 위해 주입된 불순물의 활성화와 확산을 위해 후속 열처리 공정은 높은 온도에서 짧은 시간 열처리하여 불순물 물질의 활성화를 높여주면서 열처리로 인한 접합 깊이를 얕게 해야 한다. 그러나 접합의 깊이가 줄어듦에 따라서 소스 및 드레인의 표면 저항(sheet resistance)과 접촉저항(contact resistance)이 급격하게 증가하는 문제점이 있다. 이러한 표면저항과 접촉저항을 줄이기 위한 방안으로 실리사이드 박막(silicide thin film)을 형성하는 방법이 사용되고 있다. 본 논문에서는 (100) p-type 웨이퍼 He(90 %) 가스로 희석된 $PH_3$(10 %) 가스를 사용하여 플라즈마 도핑을 실시하였다. 10 mTorr의 압력에서 200 W RF 파워를 인가하여 플라즈마를 생성하였고 도핑은 바이어스 전압 -1 kV에서 60 초 동안 실시하였다. 얕은 접합을 형성하기 위한 불순물의 활성화는 ArF(193 nm) excimer laser를 통해 $460\;mJ/cm^2$의 에니지로 열처리를 실시하였다. 그리고 낮은 접촉비저항과 표면저항을 얻기 위해 metal sputter를 통해 TiN/Ti를 $800/400\;{\AA}$ 증착하고 metal RTP를 사용하여 실리사이드 형성 온도를 $650{\sim}800^{\circ}C$까지 60 초 동안 열처리를 실시하여 $TiSi_2$ 박막을 형성하였다. 그리고 $TiSi_2$의 두께를 측정하기 위해 TEM(Transmission Electron Microscopy)을 측정하였다. 화학적 결합상태를 분석하기 위해 XPS(X-ray photoelectronic)와 XRD(X-ray diffraction)를 측정하였다. 접촉비저항, 접촉저항과 표면저항을 분석하기 위해 TLM(Transfer Length Method) 패턴을 제작하여 I-V 특성을 측정하였다. TEM 측정결과 $TiSi_2$의 두께는 약 $580{\AA}$ 정도이고 morphology는 안정적이고 실리사이드 집괴 현상은 발견되지 않았다. XPS와 XRD 분석결과 실리사이드 형성 온도가 $700^{\circ}C$에서 C54 형태의 $TiSi_2$ 박막이 형성되었고 가장 낮은 접촉비저항과 접촉저항 값을 가진다.

• Korean Journal of Materials Research
• /
• v.19 no.1
• /
• pp.28-32
• /
• 2009

Silicon carbide (SiC) is a promising material for power device applications due to its wide band gap (3.26 eV for 4H-SiC), high critical electric field and excellent thermal conductivity. The Schottky barrier diode is the representative high-power device that is currently available commercially. A field plate edge-terminated 4H-SiC was fabricated using a lift-off process for opening the Schottky contacts. In this case, Ni/Ti dual-metal contacts were unintentionally formed at the edge of the Schottky contacts and resulted in the degradation of the electrical properties of the diodes. The breakdown voltage and Schottky barrier height (SBH, ${\Phi}_B$) was 107 V and 0.67 eV, respectively. To form homogeneous single-metal Ni/4H-SiC Schottky contacts, a deposition and etching method was employed, and the electrical properties of the diodes were improved. The modified SBDs showed enhanced electrical properties, as witnessed by a breakdown voltage of 635 V, a Schottky barrier height of ${\Phi}_B$=1.48 eV, an ideality factor of n=1.04 (close to one), a forward voltage drop of $V_F$=1.6 V, a specific on resistance of $R_{on}=2.1m{\Omega}-cm^2$ and a power loss of $P_L=79.6Wcm^{-2}$.

• Korean Journal of Head & Neck Oncology
• /
• v.19 no.1
• /
• pp.58-62
• /
• 2003

Purpose: To evaluate the efficacy of positron emission tomography with 2-[F-18] fluoro-2-deoxy-D-glucose in discrimination of response in the nasopharyngeal carcinoma patients who treated with radiotherapy. Methods and Materials: Twenty-four patients who underwent FDG-PET scan before and after radiotherapy for no disseminated head and neck carcinoma at the Asan Medical Center between August 2001 and September 2002 were evaluate by prospective analysis. First FDG-PET scan performed before radiotherapy within 1 month, and second FDG-PET scan performed 1 month after radiotherapy. FDG-PET images were analyzed by standard uptake value (SUV). Follow-up period was more than 6 months. Results: The pretreatment SUV was 3.4-14.0 (median: 6.0) and posttreatment SUV was ground level-7.7 (median: 2.0). The overall sensitivity and specicity of FDG-PET to evaluate residual tumors in the nasopharyngeal carcinoma patients were 94% and 94%. Conclusion: FDG-PET is effective in evaluation of radiation response in the nasopharyngeal carcinoma. We think that the timing of one month after finished radiotherapy FDG-PET scan was not too fast to evaluation of radiation response.

• The Journal of the Korean bone and joint tumor society
• /
• v.20 no.1
• /
• pp.14-21
• /
• 2014

Purpose: To analyze the clinical features and treatment outcome of Langerhans' cell histocytosis. Materials and Methods: From August 1996 to June 2013, 28 patients who histologically proven with LCH were analyzed of medical records, radiography, pathologic character retrospectively. Results: A total of 28 cases of LCH including 22 child has been reported. Onset age was 0.6 to 51 years old, occurred in the average age was 14.8 years. Follow-up period was 6 months to 134 months average was 44.6 months. The M:F ratio was 2.5:1. The initial symptoms was pain in 18 cases, 5 cases of pathologic fracture, 3 case of palpable mass, 1 case of discovered by accident in radiography, 1 case of torticollis. In radiological examination osteolysis was seen all cases, 7 cases showed a periosteal reaction, 1 case showed soft tissue extension. Clinical type of all cases were eosinophilic granuloma. 25 cases were classified as unifocal disease and 3 cases were multifocal single systemic diseases. In all cases, incisional biopsy was performed. After histologic confirmed, 14 cases was treated with curettage or surgical excision of the lesion and the other 14 cases were followed up without treatment. There is no death during follow up period. 11 cases has no radiological improvement after 3-6 months observation, intralesional steroid injection was performed. Conclusion: Patients with LCH who has rapid systemic onset is very rare, so if you meet the young children who suspected LCH, you shoulder avoid the examination which cause excessive radiation exposure to the young patient. In order to confirm the diagnosis of disease, biopsy is needed. Close observation after confirmed by histological method will bring the satisfactory results. But the patients who had pathologic fracture or wide bone destruction already may need curettage and bone grafting to lesion or internal fixation. The lesion which has no radiological improvement after 3-6 months observation or appear with pain interferes daily life may need local steroid injection as a good treatment.

• Childhood Kidney Diseases
• /
• v.8 no.1
• /
• pp.43-50
• /
• 2004

Background : Steroid-induced osteoporosis(SIO) is one of the serious complications of long-term steroid therapy, especially in growing children. Recently bisphosphonates have been used to treat or prevent SIO in adult, which is rare in children with glomerular diseases. We studied the effect of pamidronate on SIO using dual energy X-ray absorptiometry and biochemical markers of bone turnover. Methods : Forty four children receiving moderate-to-high doses of steroids were enrolled. They had no history of bone, liver, or endocrine disease. Patients were stratified by their baseline bone mineral density(BMD) findings. All patients received corticosteroids for 3 month and oral calcium supplementation(500 mg/day) daily. Among them, 28 patients were treated with placebo and 16 were treated with pamidronate(125 mg) for 3 months. Blood chemistry and bone mineral density(BMD) were measured at baseline, and 3months. In addition, parathyroid hormone(PTH), serum osteocalcin, and urinary dipyridinoline levels were evaluated. Results : In overall population, the mean lumbar spine BMD decreased from $0.754{\pm}0.211(g/cm^2)$ to $0.728{\pm}0.208(g/cm^2)$ in the placebo group(P<0.05) and increased from $0.652{\pm}0.194(g/cm^2)$ to $0.658{\pm}0.226(g/cm^2)$ in the pamidronate group(P>0.05). Conclusion : Pamidronate appears to be effective in preventing SIO in children with glomerular diseases requiring long-term steroids therapy. Further careful observation and follow-up might be needed for children receiving bisphosphonates such as pamidronate.

• Economic and Environmental Geology
• /
• v.35 no.1
• /
• pp.25-41
• /
• 2002

In order to investigate the hydrogeochemical characteristics and contamination of dissolved major ions and heavy metals in the Tancheon River, river water and sediment samples were collected at 18 locations, along a distance of 69 km, between Yongin-si in Kyunggi-do and Samsung-dong in Seoul on October in 2000 and April in 2001. After appropriate sample preparation, waters were analyzed for the dissolved constituents and sediments. The pH values of river waters were in the range of 7.0 to 9.3 and could be plotted in the area of surface environment. The level of $Ca^{2+}$, , CI-, sol-, N0$_{3}$ and HC0$_{3}$ in the Tancheon River were higher than those in world average river water. Most of dissolved constituents in the river waters increased toward downstream from upstream. In particular, high concentrations of Zn2+, Na$_{+}$, CI$^{-}$, SO$_{4}^{2-}$ and N03- were found near densely residential areas and the Sungnam waste water treatment plant. The relative ion enrichment was caused by the inflow of local domestic and industrial sewages. Also, Ca2+ and HC03- concentrations were enriched in the middle of the Tancheon River due to the dissolution of cements. This indicates that the apartment complexes were built on a large scale in the upriver since these ten years and large amounts of construction materials such as cements were flowed into the Tancheon River. Concentrations of heavy metals (Mn, Cd, Cu, Pb, Zn) in sediments from the Tancheon River exceeded the lower limit of tolerence level in bottom sediment established by the Ontario Ministry of the Environment (OME) of Canada. In particular, these metals were highly elevated in sediment (TSM-12) collected from near the Sungnam waste water treatment plant. Heavy metals were higher enriched in sediments collected from dry period rather than wet period.

• Investigative Magnetic Resonance Imaging
• /
• v.17 no.3
• /
• pp.232-238
• /
• 2013

Purpose : We investigated the possible added value of magnetic resonance imaging (MR) in staging of malignant pleural mesothelioma (MPM) compared to computed tomography (CT). Materials and Methods: We retrospectively enrolled 20 patients (M;F = 14:6; mean age, 53.5 yrs) who diagnosed as MPM by histology and underwent CT and MR at initial evaluation from Jan 1997 to Dec 2012. Two radiologists performed clinical staging by using CT alone or MR alone in consensus. In patients underwent surgery (n = 13), we evaluated the diagnostic accuracy of CT and MR in terms of staging compared to surgical staging. In all patients, we compared clinical staging of CT only and CT with MR. Results: The diagnostic accuracy for T staging of CT only was 23.1% (3/13) and that of combined CT and MR was 38.5% (5/13), respectively. Among 13 patients underwent surgery, surgical stage was higher than combined CT and MR stage in 5 patients, but lower in 3 patients. CT only and combined CT and MR agreed in 85.0% (17/ 20). In cases of disagree (15.0%, 3/20), combined CT and MR showed higher stage than CT only. Conclusion: Combined CT and MR increases the diagnostic accuracy in staging of MPM compared to CT only and is important in determining the appropriate treatment in patients being considered for surgery.

• Journal of the Korean Society of Radiology
• /
• v.83 no.1
• /
• pp.102-111
• /
• 2022

Purpose To evaluate the correlation between Lee's grades and surgical intervention for central lumbar spinal stenosis (CLSS) and to assess whether this grading system can be used as a decision-making tool for the surgical treatment of this condition. Materials and Methods This retrospective study included 290 patients (M:F = 156:134; mean age, 46 ± 16 years). Radiologists assessed the presence and grade of CLSS at the stenosis point according to Lee's grading system, in which CLSS is classified into four grades according to the shape of the cauda equina. Correlation coefficients (r_s) between Lee's grades and the operation were calculated with Spearman rank correlation. Results Among the operated patients, grade 2 was the most commonly assigned grade (50%-58%), grade 3 was less common (35%), and grade 0 was the least common (2%-3%). Among the non-operated patients, grade 1 was the most common (63%-65%), grade 0 was less common (15%-16%), and grade 3 was the least common (8%). The distribution of grades differed between the operated and non-operated groups (p < 0.001). Less than 25% of patients who underwent surgery were assigned grades 0 and 1, and more than 88% were assigned grades 2 and 3. A moderate correlation was found between the grade and surgical intervention (r_s = 0.632 and r_s = 0.583). Conclusion Lee's grade was moderately correlated with surgical intervention. Lee's grading system can be a decision-making tool for the surgical treatment of CLSS.

• Journal of Korean Academy of Nursing
• /
• v.25 no.4
• /
• pp.653-667
• /
• 1995

Post - operative wound infections have been a serious problem in nursing care in the operating room and appear to be strongly related to the infection occurring during the performance of operation. The purpose of this study is to identify patterns in duration of surgical hand scrub (SHS), to evaluate the method of SHS and to examine the rate of glove perforation. Subjects for this study include 244 doctors and 169 nurses working in the operative theatre of a hospital in Seoul area. Test samples and related data were collected from this medical facility between April 1, through 15, and July 1, through 5, 1995 by the author and a staff member working in the operating room. For the study, data on the SHS of doctors and nurses were obtained at the time of operation and multiple batches of surgical gloves worn by the operating doctors were collected after each operation. The duration of SHS was measured with a stop watch and the method of SHS was evaluated according to Scoring Hand Scrub Criteria (SHS Criteria) and expressed as SHS scores. For the analysis of the data, t-test was used to compare the differences in the duration and the SHS scores of doctors and nurses, and Pearson's correlation coefficient was used to examine the relationship between the SHS duration and the SHS scores. The results of the study are summarized as follows. 1) The mean time spent in each SHS was 167 seconds in nurses, and 127 seconds in doctors. The data comparing nurses and doctors indicated that there were significant differences in Our ation of SH S between these two groups (t=5.58, p=.000). 2) The mean time spent in the first SHS was 145 seconds and that in the End SHS, 135 seconds, and there was not a significant difference in the duration of the SHS between doctors and nurses (t=1.44, P=.156). 3) The mean time spent in the SHS by OS (Orthopaedic surgery) doctors was 162 seconds, 150 seconds by NS(Neurologic surgery), 121 seconds by GS(General surgery), 94 seconds by OPH(Opthalmology) and DS(Dental surgery), 82 seconds by URO(Urology), 78 seconds by PS(Plastic surgery) and 40 seconds by ENT(Ear, Nose & Throat) These also showed a significant difference in the duration of the SHS among the medical specialities (t=4.8, P=.0001). 4) The average SHS score of the nurses was 15.2, while that of doctors was 13.1. The statistical analysis showed that t-value was 3.66, p was. 000. This indicates that the nurses actually clean their hands more thoroughly than the doctors do. 5) The average SHS score of NS doctors was 15.5, 15.3 for doctors for OPH,14.3 for OS,12.7 for GS, 12.0 for DS, 11.7 for URO, 10.1 for PS, 7.5 for ENT. Comparison of the average SHS scores from 8 specialties showed that there was a significant differences in the patterns of the SHS (F=5.08, P=.000) among medical specialties. 6) It appears that the operating personnel scrub the palms and dorsum of their hand relatively well, however, less thorough the nails and fingers. 7) The more the operating personnel spend their time in hand scrubbing, the more correctly they clean their hands(r=.6427, P<.001). 8) The overall frequencies of perforation in all post-operative gloves tested was 38 out of 389 gloves (10.3%). The perforation rate for PS was 13%, 12.1% for GS,8.8% for 05, and 3.3% for NS.

• Tuberculosis and Respiratory Diseases
• /
• v.53 no.3
• /
• pp.309-318
• /
• 2002

Background : Usual interstitial pneumonia (UIP) is a fatal progressive fibrotic disorder of the lung with unknown etiology and characterized by a poor response to conventional immunosuppressive therapy. The histologic hallmark of UIP is parchy distribution of subpleural fibrosis and fibroblastic foci(FBF) with interposed normal appearing lung. Because FBF is a collection of actively proliferating myofibroblasts, it can be a marker of activity and prognosis of UIP. However, there were contradictory reports about the correlation between the degree of FBF and survival. Therefore we performed this study to investigate the value of FBF as prognostic marker of UIP. Methods : This was a retrospective study on the 46 patients(M:F=33:13, mean age:$59{\pm}12$ years) with UIP diagnosed by the surgical lung biopsy at the Asan Medical Center, Seoul, Korea between 1990 and 2000 and had follow-up of more than a year. All the biopsy specimens were reevaluated and diagnosed as UIP according to the ATS/ERS classification. Semiquantitative grading of FBF(absent, 0; mild 1; moderate 2; marked 3) by the experienced pathologists who did not know the clinical findings were compared to the clinical data and the follow up course. Results : Thirteen patients(28.2%) died of UIP progression during the study period. The median survival time of all the subjects was 26 months after the biopsy. At the univariate analysis, FVC, $D_Lco$, smoking history and the grade of FBF were significantly related to the survial. The survival was longer in subjects with lesser degrees of FBF, higher DLco, higher FVC and history of smoking. However the multivariate analysis with Cox regression test showed the extent of FBF was the only independent prognostic marker of UIP. Conclusion : These data suggested that the extent of FBF on the surgical lung biopsy can be used as a prognostic marker of UIP.