적외선 카메라-레이저 공통광학계의 레이저빔 열 영향성 분석

김성재 한국광학회 2017 한국광학회지 Vol.28 No.4

An infrared camera and laser common-path optical system is applied to DIRCM (directional infrared countermeasures), toincrease boresighting accuracy and decrease weight. Thermal effects of a laser beam in a common-path optical system are analyzedand evaluated, to predict any degradation in image quality. A laser beam with high energy density is absorbed by and heats theoptical components, and then the surface temperature of the optical components increases. The heated optical components of thecommon-path optical system decrease system transmittance, which can degrade image quality. For analysis, the assumed simulationcondition is that the laser is incident for 10 seconds on the mirror (aluminum, silica glass, silicon) and lens (sapphire, zincselenide, silicon, germanium) materials, and the surface temperature distribution of each material is calculated. The wavelengthof the laser beam is 4 μm and its output power is 3 W. According to the results of the calculations, the surface temperatureof silica glass for the mirror material and sapphire for the lens material is higher than for other materials; the main reason forthe temperature increase is the absorption coefficient and thermal conductivity of the material. Consequently, materials for theoptical components with high thermal conductivity and low absorption coefficient can reduce the image-quality degradation dueto laser-beam thermal effects in an infrared camera and laser common-path optical system.

Theoretical calculation of high thermal conductivity in heat path connected system

문수민,최시영 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

High thermal conductivity composite has attracted much attention because recent trends for the electronic devices have been higher integration. To make these composite, people have mixed metal, ceramic powders with polymer for achieving both high thermal conductivity (k) and excellent processibility. However, the resulting k could be relatively low because the polymer located between the powders has low k. Here, we assume that bridging particles with high k are added to the polymer and the bridging particles create a direct heat path between the powders. In this case, k of composite could be largely improved. Because heat can escape from the composite well through the bridging particles even though the polymer is still present between the powders. In this research, we set the model which predicted k of composite as a function of k of bridging particles / the powders. Moreover, we calculate enhanced k of heat path connected system compared to k of powder dispersed system.

규소 나노필름의 포논 자유행정거리 분포

김태훈(Taehoon Kim),설재훈(Jae Hun Seol) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

Fourier’s law can not be applied when phonon mean free path is longer than system’s characteristic length. In this regime, ballistic transport occur and thus thermal transport is suppressed. Therefore, phonon mean free path is a key engineering factor in nanostructuring. Although the knowledge of phonon mean free path is critical, there is not indisputable results in most materials. In this work, thermal resistance of silicon nanofilm with nano-constriction was measured by AC heating thermal bridge method. By tailoring the size of nano-constriction, we can obtain effective thermal conductivity in phonon ballistic transport regime. To make it more clear, We will compare experimental results to Monte Carlo simulation. From these experimental and simulation results, phonon mean free path spectra can be extracted in an analytical way.

A Low-jitter Ring-DCO-Based Digital PLL Using P/I-Gain Co-Optimization and Optimally Spaced TDC for Flicker-Noise Reduction

황찬웅,박한기,이용선,성태호,최재혁 한국과학기술원 반도체설계교육센터 2023 IDEC Journal of Integrated Circuits and Systems Vol.9 No.4

This work presents a low-jitter ring-oscillator-based digital PLL (RO-DPLL). To achieve low jitter, the proposed RO-DPLL used calibration techniques to optimize the gain of the Proportional-path (P-path) and Integral-path (I-path) in the digital-loop-filter (DLF) simultaneously. Since the effect of flicker noise increases as the frequency increases, the frequency drift of the RO-DPLL becomes more severe in the operation of the RO-DPLL. Thus, it is critical to calibrate the gain of the I-path to an optimal value because I-path of DLF compensates for the frequency error of the PLL. Moreover, the optimally-spaced time-to-digital-converter (OS-TDC) with the threshold calibrator provides sufficient information, supporting the efficient operation of the calibrators. Due to the use of the P/I-path co-optimization (PICO) and OS-TDC with calibrator, the proposed RO-DPLL achieved the rms jitter of 343 fs and the reference spur of –65dBc. And, its FoMjitter,N was –258.5 dBc, comparable to the state-of-the-art RO-based analog PLLs.

실리콘 지지와 뜬 그래핀 나노메쉬 내 포논 산란 특성의 정량적 연구

진재식(Jae Sik Jin) 대한기계학회 2019 大韓機械學會論文集B Vol.43 No.3

본 연구는 포논(phonon) 평균자유행로(mean free path, MFP) 스펙트럼(spectrum) 분포 별 열전도 기여도를 이용하여, 실리콘(Si) 기질로 지지된 그래핀 나노메쉬(Si-GNM) 내 포논 산란 특성을 살폈다. 그래핀 나노메쉬(GNM) 내 포논 MFP에 대한 현상학적 접근(phenomenological approach)을 이용하여, Si-GNM와 뜬(suspended) GNM(Sus-GNM) 내 복잡한 포논 산란(scattering) 정도(n)를 표현할 수 있는 간단한 함수를 도입하고, 기존 연구에서 제시하지 못한 다공도(porosity, Ø) 증가에 따라 Si-GNM이 Sus-GNM 경우 보다 열전도율 억제 효과가 작아짐을 정량적으로 설명했다. 즉, 1.52%≤ Ø ≤ 9% 범위에서 Ø 가 커지면서 nsup/nsus=2.81에서 2.37로 감소함을 보였다. 본 연구 방법은 향후 GNM 기반 시스템에 대한 열 관리 및 열 제어 연구에 활용될 수 있다. In this study, the phonon scattering of a graphene nanomesh (Si-GNM) supported by a silicon substrate was investigated using the spectral thermal conductivity contribution of the phonon mean free path (MFP) at room temperature. Using the phenomenological approach to phonon MFPs in a GNM, we can express the complex scattering degree (n) in Si-GNM and suspended GNM (Sus-GNM) by proposing a simple form as a function of the hole spacing, phonon MFP, and porosity, showing a lower thermal conduction suppression effect than that of Sus-GNM as the porosity (Ø) increases, which has not been presented in previous studies. It was shown that the relative value of nsup/nsus is changed from 2.81 to 2.37 within the range of 1.52%≤Ø≤ 9%. This method can be applied to future thermal management and thermal control studies for GNM-based systems.

Nano-Scale CMOSFET에서 Contact Etch Stop Layer의 Mechanical Film Stress에 대한 소자특성 분석

나민기(Min-Ki Na),한인식(In-Shik Han),최원호(Won-Ho Choi),권혁민(Hyuk-Min Kwon),지희환(Hee-Hwan Ji),박성형(Sung-Hyung Park),이가원(Ga-Won Lee),이희덕(Hi-Deok Lee) 대한전자공학회 2008 電子工學會論文誌-SD (Semiconductor and devices) Vol.45 No.4

본 논문에서는 Contact Etch Stop Layer (CESL)인 nitride film의 mechanical stress에 의해 인가되는 channel stress가 소자특성에 미치는 영향에 대해 분석하였다. 잘 알려진 바와 같이 NMOS는 tensile stress와 PMOS에서는 compressive stress가 인가되었을 경우 drain current가 증가하였으며 그 원인을 체계적으로 분석하였다. NMOS의 경우 tensile stress가 인가됨으로써 back scattering ratio (rsat)의 감소와 thermal injection velocity (Vinj)의 증가로 인해 mobility가 개선됨을 확인하였다. 또한 rsat 의 감소는 온도에 따른 mobility의 감소율이 작고, 그에 따른 mean free path ( λO)의 감소율이 작기 때문인 것으로 확인되었다. 한편 PMOS의 compressive stress 경우에는 tensile stress에 비해 온도에 따른 mobility의 감소율이 크기 때문에 channel back scattering 현상은 심해지지만 source에서의 Vinj가 큰 폭으로 증가함으로써 mobility가 개선됨을 확인 할 수 있었다. 따라서 CES-Layer에 의해 인가된 channel stress에 따른 소자 특성의 변화는 inversion layer에서의 channel back scattering 현상과 source에서의 thermal injection velocity에 매우 의존함을 알 수 있다. In this paper, the dependence of MOSFET performance on the channel stress is characterized in depth. The tensile and compressive stresses are applied to CMOSFET using a nitride film which is used for the contact etch stop layer (CESL). Drain current of NMOS and PMOS is increased by inducing tensile and compressive stress, respectively, due to the increased mobility as well known. In case of NMOS with tensile stress, both decrease of the back scattering ratio (rsat) and increase of the thermal injection velocity (Vinj) contribute the increase of mobility. It is also shown that the decrease of the rsat is due to the decrease of the mean free path (λ?). On the other hand, the mobility improvement of PMOS with compressive stress is analyzed to be only due to the so increased Vinj because the back scattering ratio is increased by the compressive stress. Therefore it was confirmed that the device performance has a strong dependency on the channel back scattering of the inversion layer and thermal injection velocity at the source side and NMOS and PMOS have different dependency on them.

온도 영향을 고려한 실리콘 내 포논 열전달 특성에 대한 실험 기반 연구

진재식 대한기계학회 2021 大韓機械學會論文集B Vol.45 No.6

The heat transfer characteristics for each phonon mode, which plays a key role in various thermal engineering applications, were examined with varying temperatures. By employing the results of existing experimental data on the ability of heat transfer by each phonon mode based on the phonon mean free path, its spectral distributions in silicon were discussed under the conditions of 100K, 300K, and 500K. As temperature increased, the contribution of the LA phonon mode to the thermal conductivity increased, and at a temperature of 100K, a critical frequency existed owing to the relative influence between the phonon-phonon scattering and impurity–phonon scattering processes. It was also shown that at a temperature of 500K the heat transfer contribution of the phonon mode of about 8.1 THz or more was decreased owing to the increase in high-order phonon scattering such as a four-phonon scattering process. 포논 전달 특성을 활용한 공학적 응용에 핵심적인 역할을 하는 포논 모드별 열전달 특성을 온도 변화에 대해 살펴봤다. 기존 실험적 연구 결과 기반에 수치적 연구 결과를 적용하여, 온도 100K, 300K, 500K 조건에서 실리콘 내 포논 전달의 주파수 스펙트럼 특성에 대해 논했다. 온도가 상승하면서 LA 포논 모드의 열전도 기여도가 증가했으며, 온도 100K에서는 포논-포논 산란과 불순물-포논 산란 과정의 상대적 크기 변화의 영향으로 임계 주파수가 존재함을 보였고, 온도 500K에서는 4-포논-포논 산란 과정으로 인한 포논 산란의 증가로 약 8.1 THz 이상의 포논 모드의 열전달 기여도가 작아짐을 보였다.

CAE 기법을 이용한 정보저장시스템의 Fanless 열설계

류호철 ( Ho Chul Ryu ),단병주 ( Byung Ju Dan ),최인호 ( In Ho Choi ),김진용 ( Jin Yong Kim ) 정보저장시스템학회 2005 추계학술대회논문집 Vol.2005 No.-

This study suggested fanless thelmal design using CAE technique for the information storage system under the serious themlal problem. At first, main heat 11o\v was controlled by CAE based fanless heat sink design not to influence sensitive optical pick -up sensor. Then, vent parametric studies found a thermal solution about highly concentrated case top heat due to fan less. These CAE results were verified by experimental methods. As a consequence of ne\vly designed thermal path, thermal specification of optical pick-up sensor was satisfied and fan less thenmll design for the information storage system was achieved.

포논 기체 운동론을 이용한 실리콘 내 포논 평균자유행로 스펙트럼 열전도율 기여도 예측

진재식(Jae Sik Jin) 대한기계학회 2017 大韓機械學會論文集B Vol.41 No.5

본 연구는 해석적 접근이 용이한 실리콘 내 포논 평균자유행로(mean free path, MFP) 스펙트럼(spectrum) 열전도 특성 예측 모델을 제시했다. 해석이 용이한 포논 기체 운동론(kinetic theory)을 적용하기 위해, 나노구조물의 현상학적 접근으로 열전도에 관여하는 포논 모드(mode)들만 추출하고, 300 K의 실리콘에 대한 포논의 분산관계(dispersion relations) 및 분극(polarization) 효과가 고려된 포논의 주파수 변화에 따른 비열(specific heat)과 군속도(group velocity) 및 MFP 정보를 사용했다. 300 K의 실리콘 내 포논의 MFP 스펙트럼 열전도율 기여를 계산하고, 기존 실험결과 및 제1원리 기법 결과와 비교하여, 본 방법의 타당함을 보였다. 본 연구를 통해, 나노구조물 열전달 해석모델 개발 및 나노재료 열전달 특성 조정(tailoring) 전략 설계에 필요한 포논 MFP 스펙트럼 열전도 특성 정보를 해석이 용이한 방법으로 구할 수 있는 방법을 제공했다. Knowing the mean free paths (MFPs) of thermal phonons is an essential step in performing heat transfer analysis for nanomaterials, and in determining the optimum design for tailoring the heat transfer characteristics of nanomaterials. In this study, we present a method that can be used to calculate accurately the phonon MFP spectra of nanostructures based on simple phonon kinetic theory. Here, the kinetic theory may be employed by extracting only the diffusive-transport part of the phonon spectrum (i.e., the MFPs are less than a thermal length). By considering phonon dispersion and polarization effects, the phonon MFP distributions of silicon at room temperature are calculated from phonon transport properties and the spectral MFP. Our results are validated by comparison with those of the first principle and MFP spectroscopy data.

포논 평균자유행로 분포를 이용한 실리콘 포노닉 나노 구조에서의 포논 전달 예측 모델

진재식(Jae Sik Jin) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.3

본 연구는 포논(phonon) 평균자유행로(mean free path, MFP) 스펙트럼(spectrum) 분포 별 열전도 기여도를 이용하여, 실리콘(Si)-포노닉 결정체(phononic crystals, PnC) 내 포논 전달 해석 모델을 제시했다. Si-PnC 내 포논 MFP에 대한 현상학적 접근(phenomenological approach)을 이용하여, Si-PnC 내 복잡한 홀(hole)-포논 산란(scattering) 정도를 표현할 수 있는 간단한 인자를 도입하고, 기존 연구에서 제시한 다양한 실험 조건 및 결과를 활용하여 모델을 완성했다. 이렇게 개발된 모델을 기존의 다른 조건의 Si-PnC 열전도율 측정 결과들에 적용하여, 본 연구에서 제시된 모델의 타당함을 보였고, 모델 개발 과정에서 사용된 홀(hole)-홀 간격의 범위를 벗어나는 경우에 대한 맞춤 매개 변수(fitting parameter) 값을 추가로 구하여, 본 모델의 결과가 기존의 Monte Carlo 기법의 수치적 결과 보다 예측 정확도가 높음을 확인했다. 본 연구결과는 향후 열전모듈 효율 향상 및 반도체 시스템의 열 관리 및 열 제어 연구에 활용될 수 있다. Using data from phonon mean-free path (MFP) spectrum distributions of silicon (Si), a model for estimating the thermal conductivity (K) of Si-phononic crystals (PnC) was developed. Based on the phenomenological approach regarding phonon MFP in a Si-PnC, simple fitting parameters were introduced to express the complex hole-phonon scattering mechanisms. By using previous experimental conditions and measured results, the fitting parameters were determined. The present model was applied to other existing measurement conditions for measuring K in Si-PnC, from which the justification for the method developed here was identified. Additional parametric values for conditions beyond those used in the developed hole-hole intervals were obtained, and we can confirm that the accuracy is higher than the accuracy of the numerical result obtained by the existing Monte Carlo technique. This study can be used in future for thermal management and the thermal control of semiconductor systems.