Backside Roughness Research Articles

Irradiation effect on optical properties and structure of sapphire single crystal

Sapphire single crystal for optical window material was irradiated by rays and particles when served in the space environment, thus, the optical properties and structure would be changed even the window lost its effectiveness. The change of the surface roughness and transmittance caused by electron, proton and integrated currents was discussed through the ground simulation experiment. The AFM test indicated that the space particle irradiation led to roughness decreased with dose effect and energy effect, meanwhile, the integrated current caused the maximum effect and the electron minimum; different range between electron and proton caused the distinguishing effect on roughness of back side. According to the UV-Vis-VIR and FTIR testing result, the particle irradiation gave rise to decrease of transmittance accompanied by dose effect and energy effect, especially in ultraviolet band, different kinds of particle caused different effect in each band.

Influence of temperature and backside roughness on the emissivity of Si wafers during rapid thermal processing

The influence of temperature and roughness on the backside emissivity of Si wafers was studied. In situ measurements were done in two commercial rapid thermal processing systems. An experimental setup was built for in situ emissivity measurements of wafers with a polished or nonpolished backside. The emissivity of double-side polished wafers was measured for temperatures ranging from 300 to 700 °C and at wavelengths of 1.7 and 3.4 μm. It was found that the absorption coefficient α of lightly doped silicon is described by the equation α=4.15×10−5λ1.51T2.95 exp(−7000/T) cm−1, for wavelengths λ ranging from 1.5 to 5 μm and temperatures T ranging from 673 to 973 K (λ in μm, T in K). The backside emissivity of Si wafers with different roughnesses was measured. At temperatures above 600–700 °C the wafers are opaque and the emissivity is only slightly dependent on backside roughness. At lower temperatures the wafers are partially transparent and the emissivity is strongly dependent on the backside roughness of the wafer due to light trapping in the bulk of the wafer. For the latter case a new model was developed to simulate the emissivity of wafers with a rough backside at low temperatures.

Non-intrusive mapping of subsurface defects in semiconductors

We have adapted differential interference contrast Nomarski microscopy in the transmission configuration to the problem of mapping subsurface defects in semiconductors. We have demonstrated the ability to rapidly measure the depth of the precipitate-free-zone in silicon with a reproducibility of ±1 μm in whole Si wafers up to 200 nm in diameter, having an extrinsic doping concentration up to 7×1019 cm−3 and a nominal, as received, back side roughness. Because our subsurface defect profiler is completely non-destructive, product wafers can be inspected at various stages of processing and immediately returned to the production line.

In-situ emissivity and temperature measurement during rapid thermal processing (RTP)

ABSTRACTA prototype RTP system has been developed which allows for in-situ emissivity and temperature measurements. The wafer emissivity is measured by using an optical detector at a wavelength of 2.4 μm and by modulation of the lamp power. This method permits accurate temperature determination in the range from 400 to 1200°C, independent of wafer backside roughness, backside layers, and transmit tance. The feasibility of the temperature measurement technique is demonstrated by using wafers with built-in thermocouples and highly As-doped wafers with different backside roughnesses or layers. The emissivity variations during processing can also be used to study thin film reactions in-situ. This is demonstrated for Co silicidation using probing wavelengths varying from 0.6 to 3.2 μm.

Modelling of rapid thermal processing

Abstract An overview is given of modelling issues in rapid thermal processing. Firstly, the influence of surface and bulk properties on wafer emissivity is discussed. Secondly, the influence of back-side layers, wafer transparency and back-side roughness on temperature measurement is discussed. Thirdly, several causes of temperature non-uniformity are mentioned.