Modeling of three-dimensional effects on temperature uniformity in rapid thermal processing of eight inch wafers

Otsuka

Mayusumi

et al. 1999

J. Electrochem. Soc.

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...

Section: Resultsmentioning

confidence: 83%

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

Otsuka

Mayusumi

et al. 1999

J. Electrochem. Soc.

“…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.…”

Section: Introductionmentioning

confidence: 99%

Nonempirical Design of Rapid Thermal Processing System

Suzuki

Sakurai

et al. 2001

Jpn. J. Appl. Phys.

In order to develop a nonempirical technology to design a rapid thermal processing (RTP) system, a direct approach model using the ray tracing simulation (DARTS) is applied for designing the small RTP system composed of tungsten/halogen filament lamps, specular reflectors and a silicon wafer. The temperature profiles on the silicon wafer surface are theoretically predicted and experimentally evaluated using the two RTP systems. The quantitative agreement of the theoretically predicted and experimentally evaluated temperature profiles on the silicon surface suggests that the nonempirical design of the RTP system is possible using the DARTS model. The reflection-resolved analysis based on this model is considered to provide information on the entire path of the rays from the lamps to the silicon wafer surface and on the heat loss caused by the reflectors in the RTP system.

“…The circular-shaped tungsten/halogen filament lamp with a radius of 100 mm is located above the silicon substrate, with a diam of 300 mm. On the outside edge of the silicon substrate, this calculation model uses a ring plate 20,40,41 having a large absorptivity, such as the guard ring made of carbon or silicon carbide used in industry for avoiding any slip defect of the silicon substrate.Beneath the reflector base plate having a specular surface, cylindrical reflectors having specular internal and external surfaces, R-1 through R-11, with radii of 10,30, 50, 70, 90, 110, 130, 150, 170, 190, and 210 mm are arranged. In this study, the height of the cylindrical reflectors is 20, 40, 60, and 80 mm.…”

mentioning

confidence: 99%

Design of a Rapid Thermal Processing System Using a Reflection-Resolved Ray Tracing Method

Maruyama

Suzuki

2001

J. Electrochem. Soc.

The thermal condition of a silicon substrate in a rapid thermal processing system using circular infrared lamps and specular reflectors is systematically studied based on the direct approach model using a ray trace simulation with resolving the number of reflections, for the first time, in order to clarify the mechanism that the thermal condition for the silicon substrate is not sensitive to the distance between the circular infrared lamp and the reflector base plate forming the region behind the circular infrared lamp. Since total reflection from the specular reflectors behind the circular infrared lamp causes no energy loss on their surface, the intensity of the ray emitted from the infrared lamp toward the reflector base plate can be maintained and transported to the silicon substrate surface, even if the distance between the circular infrared lamp and the reflector base plate influences the path of the rays which are approaching the silicon substrate. Therefore, it is concluded that the thermal condition of the silicon substrate can be robust to the geometry of the specular reflectors behind the circular infrared lamp.Temperature of materials is a key parameter for controlling any chemical process, chemical kinetics, product quality, and productivity. For obtaining both a reasonable throughput and quality, rapid thermal processing ͑RTP͒ 1-18 is widely used in semiconductor device manufacturing processes. Further improvement in the RTP system for various aspects, 15 such as uniformity, reproducibility, and the ramp rate of the substrate temperature, requires advanced and appropriate theoretical calculation models 19,20 which can optimize the entire heat radiation from the heat source accounting for entirely and exactly the complicated three-dimensional geometry of the RTP system. Since the rays from tungsten/halogen filament lamps to a mirror-polished silicon substrate surface surrounded by reflectors have extremely complicated paths, the usual theoretical models 16,17,19,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] are insufficient to describe the RTP system. Therefore, the direct approach model using ray trace simulation ͑DARTS͒ 36-38 has been developed and evaluated as an extension of the ray tracing method. 19,[31][32][33][34][35] The DARTS model has, experimentally, been shown to be valid 36 and capable of evaluating in detail the temperature and its profile in the RTP system. [36][37][38] The RTP system using an arrangement of circular infrared lamps 39 with various diameters is expected as an industrial application due to its high flexibility in adjusting the temperature profile in the radial direction of the silicon substrate. Our previous studies 37,38 showed that the thermal condition of the silicon substrate was very sensitive to the distance between the circular infrared lamp and the silicon substrate surface. However, we simultaneously showed that the distance between the circular infrared lamp and the reflector base plate forming the region behind the circular infrared lamp was in...