In-Line Characterization of Heterojunction Bipolar Transistor Base Layers by High-Resolution X-Ray Diffraction

Abstract

The suitability of high-resolution X-ray diffraction (HRXRD) as an in-line measurement tool for the characterization of heterojunction bipolar transistor SiGe base layers and Si cap layers was investigated. We showed that despite of polycrystalline Si on the mask material of patterned wafers, HRXRD measurements performed on an array of small windows yield results which are comparable to those that were obtained on a window which is larger than the size of the source beam, regarding the thickness and the Ge content of the SiGe layers. The possibility to extract layer parameters for active device windows of different sizes was therefore demonstrated. The suitability of HRXRD for in-line measurement of the Si cap thickness was also assessed and the sensitivity of this technique for determining the substitutional boron concentration in SiGe was studied. The detection limit in the monitoring of the active dopant concentration was about 2.7 x 10^19 cm-3.

B and Ga Co-Doped Si1−xGex for p-Type Source/Drain Contacts

“…The magnitude of the recorded shift can be used to estimate the concentration of substitutional boron [B] sub . 31 For a certain boron molar fraction (y), the relaxed lattice parameter for Si 1−x−y Ge x B y is given by: 32 a a x y a x y b x x 3.806 1 1 4…”

(Invited) Highly Doped Si1-XGex Epitaxy in View of S/D Applications

“…The peak position is at slightly lower (absolute) angles, than expected for the given Ge concentrations. This is due to the substitutional boron in the layers causing a partial stress release in the pseudomorphic Si1-xGex (17,18). For thicker Si1-xGex:B layers, misfits are formed at the wafer surface when the critical thickness exceeds tc (Fig.…”

“…Boron is the most used p-type dopant for Si and Si1-xGex and it has been extensively explored (9,10,11). Because of its smaller ionic radius compared to Si and Ge, when placed in a substitutional position in the lattice, B is responsible for a partial stress release in pseudomorphic Si1-xGex layers on Si substrate (17,18). Thanks to this effect and to lowtemperature deposition processes with high growth rates, it is possible to achieve active B concentrations as high as 110 21 atoms/cm -3 in strained Si1-xGex (11).…”