Thomas E. Zirkle

Fabrication and modeling of gigahertz photodetectors in heteroepitaxial Ge-on-Si using a graded buffer layer deposited by low energy plasma enhanced CVD

Photodetectors were fabricated in a heteroepitaxial Ge-on-Si deposited by low energy plasma enhanced CVD. Dark current density of 4.6 nA//spl mu/m, 49 % quantum efficiency, and a -3 dB bandwidth of 3.5 GHz were measured at 1.3 /spl mu/m wavelength and -3 V bias. Numerical simulations predict device modifications can achieve 10 Gbps (/spl cong/ 7 GHz) bandwidth.

Introduction to Plasma Enhanced Chemical Vapor Deposition

Chemical vapor deposition (CVD) is a process in which gaseous species react on solid substrates to form solid, nonvolatile films. The energy needed to activate the chemical reactions can be provided in several different forms; e.g., thermal, photon, or plasma. When a plasma or (to be more accurate) a glow discharge is used to provide at least some of the energy needed in a CVD process the process is called plasma enhanced CVD (PECVD). This Chapter begins with a brief, ‘big picture’ view of PECVD processes and applications relevant to semiconductor device manufacturing. More details can be found in several texts which cover this topic more extensively [1–4].

Sequential deposition of SiO2 and poly‐Si in isolation trenches

Low pressure chemical vapor deposition (LPCVD) of SiO2 from tetraethoxysilane followed by LPCVD of polycrystalline silicon (poly‐Si) from silane is used to refill isolation trenches. Two important characteristics of the refilled trenches which can adversely affect subsequent processing are the position of the void in the poly‐Si and the depth of the groove along the top of the trench. We use evolve, a physically based, low pressure deposition simulator, to study the effects of trench width and the details of the trench profile before refill on void position and groove depth. Simulated SiO2 and poly‐Si profiles in trenches with aspect ratios which range from near 4 to 20 are in good agreement with experimental profiles. In particular, evolve’s predictions of (1) the void position as a function of the position of the edge of the nitride film on the wafer’s surface, and (2) the depth of the groove as a function of the trench aspect ratio agree well with available experimental information. The reaction rate expressions used in evolve were developed in independent experiments. We do not adjust any parameters, and our simulations are entirely physically based.Low pressure chemical vapor deposition (LPCVD) of SiO2 from tetraethoxysilane followed by LPCVD of polycrystalline silicon (poly‐Si) from silane is used to refill isolation trenches. Two important characteristics of the refilled trenches which can adversely affect subsequent processing are the position of the void in the poly‐Si and the depth of the groove along the top of the trench. We use evolve, a physically based, low pressure deposition simulator, to study the effects of trench width and the details of the trench profile before refill on void position and groove depth. Simulated SiO2 and poly‐Si profiles in trenches with aspect ratios which range from near 4 to 20 are in good agreement with experimental profiles. In particular, evolve’s predictions of (1) the void position as a function of the position of the edge of the nitride film on the wafer’s surface, and (2) the depth of the groove as a function of the trench aspect ratio agree well with available experimental information. The reaction rate e...