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ABEDRABBO,1 F.M. TONG 1 N.M. RAVINDRA,1 J. GELPEY,2 MARCUS,2 and A.T. FIORY:
A study on the techniques to yield wafer emissivity independent temperature measurements in rapid thermal processing has been presented. This study focuses on the Steag-AST Electronik approach to enhance wafer emissivity by using the Hotliner . The Hotliner comprises of a heavily doped p-Si substrate sandwiched with Si3NJSiO2 from both sides. Experimental measurements on the optical properties of the Hotliner using a spectral emissometer operating in the wavelength range of 1-20 Fm are presented here. Results of the simulation of the experimental data using the MIT/SEMATECH Multi-Rad model are discussed.
Key words: Emissivity, Hotliner, pyrometer, Si
INTRODUCTION
As we approach the 21st century, it appears that single wafer and cluster-based tools will be the manufacturing approach adopted by the silicon device industry. This trend is coupled with the miniaturization of devices. These factors necessitate a rigid, reliable, and reproducible process control and have thus led to novel processes like rapid thermal processing (RTP). For RTP, pyrometers are the instruments of choice for in-situ temperature measurements. Pyrometers measure the amount of radiation emitted, usually, from the backside of a wafer. The ratio of the wafer emitted radiation to that of a blackbody under the same conditions oftemperature, wavelength, angle of incidence, and direction of polarization is referred to as emissivity. Emissivity of silicon is a complicated function of both temperature and wavelength."'2 It is also a function of surface roughness.3' This emissivity is referred to as intrinsic emissivity.5 The emission that the pyrometer detects, however, is a function of layers on top of the substrate, the surroundings, and chamber components. This is referred to as effective emissivity. In this paper, a materials based approach that leads to emissivity independent temperature measurements is described. This approach is compared with other similar methodologies that are being developed in the silicon industry.
EXPERIMENTAL DETAILS
In this study, a spectral emissometer operating in the wavelength range of 1-20 gm and capable of the simultaneous measurement of reflection, transmission, and emission of samples under investigation has been utilized. The methodology deployed by this novel tool has been described in detail in previous papers.6 7 The schematic of the spectral emissometer is presented in Fig. 1. This...