A Direct Approach for Evaluating the Thermal Condition of a Silicon Substrate under Infrared Rays and Specular Reflectors

Abstract

Rapid thermal processing (RTP) using radiative heat transfer has advanced after the early studies 1,2 and is currently a very popular technology. It is widely used for many applications in semiconductor manufacturing processes including chemical vapor deposition (CVD) on silicon substrates. Although a new modification of RTP has been developed 3 and RTP has been extended for various materials including gallium arsenide, 4 major problems in the current RTP system or process still exist, such as thermal budget, 5 temperature reproducibility and uniformity 6 which lead to nonuniform film thickness, slip lines, and warpage of the silicon substrate. [7][8][9][10] The reproducibility and the uniformity of the substrate temperature are affected by parameters 6 such as (i) sensing and control of substrate temperature, (ii) process chamber (substrate properties, film properties, dimensions, shape, wall material properties, gas flow dynamics, etc.), and (iii) heat source (size, shape, location, type, reflector set). For (i), temperature measurement systems have been developed by many researchers. 11-18 For (ii) and (iii), transport phenomena including gas flow dynamics and film formation rate in the RTP system have been intensively studied 8,19-25 using numerical calculations, in which the substrate temperature and its uniformity were assumed as the boundary conditions.For further improvement of these numerical calculation models and for obtaining a flat temperature profile by optimizing the radiation of heat from the heat source, a model based on the physics of the RTP system is required. 26 In particular, the numerical model for evaluating the infrared radiation heat should be applicable to the complicated three-dimensional geometry of a RTP system. For this purpose, many researchers have studied models for evaluating the temperatures of the silicon substrates in the furnaces for oxidation and diffusion by accounting for the diffusive reflectors, infrared radiation heat, and the reflections between the walls of the furnace and the substrates. 7,9,12,[27][28][29][30][31][32] However, very few models which take into account the three-dimensional configuration of the RTP system using reflectors, tungsten/halogen filament lamps, and a silicon substrate have been discussed, 26 because of the difficulty in accounting for the view factor under the complicated reflections of the rays in the RTP system. 7 Although an image source of the lamp has been used to account for the rays reflected at the surface of the specular reflector near the real source of the lamp, the image construction is not practical in three-dimensional systems. 7 Additionally, the effect of the second or later reflections at the polished surface of the silicon substrate has not been evaluated, since the rays after the reflections at the surface of the silicon substrate have been unfortunately assumed to show only a negligible effect because of the small reflectivity. 32 Therefore, a model which is able to account for these factors should be developed.For evalu...

Simulation of infrared rapid surface heating for injection molding

“…The silicon substrate is insulated by quartz pillars and the temperature of silicon substrate can be raised from 300 K to 1300 K in 10 s. Some researchers have studied the temperature control of the RTPCVD system [8,9]. Habuka et al [10,11] have used a direct approach using the three-dimensional ray-tracing simulation (DARTS model) to evaluate the thermal condition in a RTP system. The system is composed of tungsten/ halogen filament lamps, specular reflectors and the silicon substrate.…”

Nonempirical Design of Rapid Thermal Processing System

“…For the analysis and the optimization of the entire heat transport from the radiation heat source to the substrate in the RTP system, many researchers have studied the theoretical calculation models. 7,9,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] The next step is providing the technology to design the RTP system.…”

“…To achieve these objectives, the theoretical model should take into account the extremely complicated paths of the rays from the lamps to the silicon wafer surface in the threedimensional geometry of the reflectors, the lamps and the silicon wafer in the RTP system. This is the reason why the direct approach model using ray trace simulation (DARTS) has been developed [33][34][35] as an extension of the ray tracing method, [27][28][29][30][31][32] for achieving item (iii). In relation to item (i), the DARTS model successfully showed the temperature trend induced by the specular reflectors, such as the reflector tube 33) and the cylindrical reflectors.…”

Reflector Influence on Rapid Heating of Minimal Manufacturing Chemical Vapor Deposition Reactor

“…6 For obtaining a uniform epitaxial film thickness profile by the quick process, the thermal conditions should be further improved. In addition to the most important issue, such as the infrared ray reflection design, [9][10][11] the heat transport through the reactor parts set around the wafer may be important, particularly about the lamp heating apparatus. The CVD reactor for the large wafer has a large infrared light heater consisting of thick and wide reflector plates.…”

“…The CVD reactor for the large wafer has a large infrared light heater consisting of thick and wide reflector plates. 9,10 While the reflector effectively reflects and concentrates the infrared rays from the halogen lamps to the wafer surface, the reflector surface simultaneously absorbs the heat from the lamps and is heated to a high temperature. The heat absorbed by the reflector is slowly transported to the wafer via various reactor parts and the gas phase.…”