Rapid thermal chemical vapor deposition of germanium on silicon and silicon dioxide and new applications of ge in ULSI technologies

In this study, low pressure chemical vapor deposition of pure germanium on silicon and silicon dioxide has been considered for new applications in future ultra large scale integration (ULSI) technologies. Germanium depositions were performed in a lamp heated cold-wall rapid thermal processor using thermal decomposition of GeH₄. It is shown that Ge deposition on Si can be characterized by two different regions: a) at temperatures below approximately 450° C, the deposition is controlled by the rate of surface reactions resulting in an activation energy of 41.7 kcal/mole. b) Above this temperature, mass transport effects become dominant. The deposition rate at the transition temperature is approximately 800 Å/min. It is shown that Ge deposition on SiO₂ does not occur, even at temperatures as high as 600° C, resulting in a highly selective deposition process. Selectivity, combined with low deposition temperature makes the process very attractive for a number of applications. In this work, it is shown for the first time that selective Ge deposition can be used to eliminate silicon consumption below the gate level during the silicidation of the shallow source and drain junctions of deep submicron MOSFETs. In addition, a new in situ technique has been developed which allows polycrystalline germanium (poly-Ge) deposition on SiO₂. In this work poly-Ge has been considered as a low temperature alternative to polycrystalline silicon (poly-Si) in the formation of gate electrodes in single-wafer manufacturing where low-thermal budget processes are most desirable.     

FRGPP管芯的研制

在普通玻璃钝化管芯工艺基础上研制出了快速恢复玻璃钝化管芯。重点分析快速恢复玻璃钝化 ( FRGPP)二极管管芯制造过程中扩散工艺的调整、玻璃粉的选择以及 LPCVD工艺的必要性     

Neural Network Structures for Optimal Control of LPCVD Reactors

In this paper, a new approach of LPCVD reactor modelling and control is presented, based on the use of neural networks. We first present the development of a hybrid networks model of the reactor. The objective is to provide a simulation model which can be used to compute online the film thickness on each wafer. In the second section, the thermal control of a LPCVD reactor is studied. The objective is to develop a multivariable controller to control a space- and time-varying temperature profile inside the reactor. A neural network is designed using a methodology based on process inverse dynamics modelling. Good control results have been obtained when tracking space-time temperature profiles inside the LPCVD reactor pilot plant. Finally, global software is elaborated to achieve film thickness control in an experimental LPCVD reactor pilot plant, in order to get a defined and uniform deposition thickness on the wafers all along the reactor. Experimental results are presented which confirm the efficiency of the optimal control strategy.     

无掩模硅图形衬底上3C-SiC的异质外延生长

采用低压化学气相沉积方法在无掩模的硅图形衬底上异质外延生长3C-SiC.硅图形衬底采用光刻和ICP刻蚀得到.图形由平行长条状沟槽和台面组成,其中沟槽宽度为1～10μm不同间隔,沟槽之间距离为1～10μm不同间隔.对于在不同的沟槽和台面尺寸区域3C-SiC的生长进行了详细研究.采用扫描电镜分别观察了不同区域的生长形貌,分析了图形衬底结构上SiC的生长行为.其中合并生长形成的空气隙结构可以释放由Si和SiC晶格失配引起的应力,从而可以用来解决SiC生长中的晶片翘曲问题,进行厚膜生长.XRD结果表明此无掩模硅图形衬底上得到3C-SiC(111)取向生长.     

SiH_2Cl_2-NH_3-N_2体系LPCVD氮化硅薄膜生长工艺

以自行研制的LPCVD设备所进行的工艺试验为基础,简要介绍了Si3N4薄膜的制备方法和LPCVD法制备的Si3N4薄膜的特性以及低压化学气相淀积(LPCVD)氮化硅的工艺。通过调节淀积温度、工艺气体流量、工艺压力及片距等工艺参数,最终使批量生产的氮化硅薄膜在均匀性、应力、耐腐蚀等方面均达到了使用要求。     

利用ISSG退火改善隧穿氧化层的厚度均匀性

利用ISSG低压退火法来取代传统的氧气退火法,对沉积后的隧穿氧化薄膜进行退火处理.由于其独特的可控补偿氧化生长机制,最终在晶圆表面形成了厚度均匀的氧化层,薄膜质量也有了较大改善.这一结果为低压化学汽相沉积得到的隧穿氧化薄膜的平坦化提供了新思路.     

Polycrystalline ZnO: B grown by LPCVD as TCO for thin film silicon solar cells

Conductive zinc oxide (ZnO) grown by low pressure chemical vapor deposition (LPCVD) technique possesses a rough surface that induces an efficient light scattering in thin film silicon (TF Si) solar cells, which makes this TCO an ideal candidate for contacting such devices. IMT-EPFL has developed an in-house LPCVD process for the deposition of nanotextured boron doped ZnO films used as rough TCO for TF Si solar cells. This paper is a general review and synthesis of the study of the electrical, optical and structural properties of the ZnO:B that has been performed at IMT-EPFL.The influence of the free carrier absorption and the grain size on the electrical and optical properties of LPCVD ZnO:B is discussed. Transport mechanisms at grain boundaries are studied. It is seen that high doping of the ZnO grains facilitates the tunnelling of the electrons through potential barriers that are located at the grain boundaries. Therefore, even if these potential barriers increase after an exposition of the film to a humid atmosphere, the heavily doped LPCVD ZnO:B layers show a remarkable stable conductivity. However, the introduction of diborane in the CVD reaction induces also a degradation of the intra-grain mobility and increases over-proportionally the optical absorption of the ZnO:B films. Hence, the necessity to finely tune the doping level of LPCVD ZnO:B films is highlighted. Finally, the next challenges to push further the optimization of LPCVD ZnO:B films for thin film silicon solar cells are discussed, as well as some remarkable record cell results achieved with LPCVD ZnO:B as front electrode.     

3C-SiC/Si异质结二极管的高温特性

研究了低压化学气相淀积方法制备的n- 3C- Si C/p- Si(10 0 )异质结二极管(HJD)在30 0～4 80 K高温下的电流密度-电压(J- V)特性.室温下HJD的正反向整流比(通常定义为±1V外加偏压下)最高可达1.8×10 4 ,在4 80 K时仍存在较小整流特性,整流比减小至3.1.在30 0 K温度下反向击穿电压最高可达2 2 0 V .电容-电压特性表明该Si C/Si异质结为突变结,内建电势Vbi为0 .75 V.采用了一个含多个参数的方程式对不同温度下异质结二极管的正向J-V实验曲线进行了很好的拟和与说明,并讨论了电流输运机制.该异质结构可用于制备高质量异质结器件,如宽带隙发射极Si C/Si HBT     

SiH_4-NH_3-N_2体系LPCVD氮化硅薄膜的生长动力学

以硅烷和氨气分别作为低压化学气相沉积(LPCVD)氮化硅(SiNx)薄膜的硅源和氮源,以高纯氮气为载气,在热壁型管式反应炉中,借助椭圆偏振仪和原子力显微镜,系统考察了工作压力、反应温度、气体原料组成等因素对SiNx薄膜沉积速率和表面形貌的影响。结果表明:SiNx薄膜的生长速率随着工作压力的增大单调增加,随着原料气中氨气与硅烷的流量之比的增大单调减小。随着反应温度的升高,沉积速率逐渐增加,在840℃附近达到最大,随后迅速降低。在适当的工艺条件下,制备的SiNx薄膜均匀、平整。较低的薄膜沉积速率有助于提高薄膜的均匀性,降低薄膜的表面粗糙度。     

PSG膜中含磷量对晶体管放大倍数的影响

本文研究了以低压化学气相淀积方法生长 磷的一中ＰＮＰ管放大倍数的影响。给出了民实验数据，得到一个为适用于集成电路中横向ＰＮＰ管钝化膜的最佳工艺数据，在这种工艺条件下，得到ＰＳＧ膜中含磷量为４Ｗｔ．％。