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Selective Epitaxial Growth with Full Control of Pattern Dependency Behavior for pMOSFET Structures
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
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2009 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 156, no 3, H169-H171 p.Article in journal (Refereed) Published
Abstract [en]

This study presents a way to design chips to obtain uniform selective epitaxial growth of SiGe layers in p-type metal-oxide-semiconductor field-effect transistor (pMOSFET) structures. The pattern dependency behavior of the growth has been controlled over different sizes of transistors. It is shown that the exposed Si coverage of the chip is the main parameter in order to maintain control of the layer profile. This has been explained by the gas depletion theory of the growth species in the stationary boundary layer over the water. Control of the SiGe layer profile has been obtained over a wide range of device sizes by optimized process parameters in combination with a wafer pattern design consisting of dummy features causing uniform gas depletion over the chips of the wafer.

Place, publisher, year, edition, pages
2009. Vol. 156, no 3, H169-H171 p.
Keyword [en]
URN: urn:nbn:se:kth:diva-18398DOI: 10.1149/1.3049842ISI: 000265837900055ScopusID: 2-s2.0-59349106630OAI: diva2:336445
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-04-05Bibliographically approved
In thesis
1. Application of SiGe(C) in high performance MOSFETs and infrared detectors
Open this publication in new window or tab >>Application of SiGe(C) in high performance MOSFETs and infrared detectors
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Epitaxially grown SiGe(C) materials have a great importance for many device applications. In these applications, (strained or relaxed) SiGe(C) layers are grown either selectively on the active areas, or on the entire wafer. Epitaxy is a sensitive step in the device processing and choosing an appropriate thermal budget is crucial to avoid the dopant out–diffusion and strain relaxation. Strain is important for bandgap engineering in (SiGe/Si) heterostructures, and to increase the mobility of the carriers. An example for the latter application is implementing SiGe as the biaxially strained channel layer or in recessed source/drain (S/D) of pMOSFETs. For this case, SiGe is grown selectively in recessed S/D regions where the Si channel region experiences uniaxial strain.The main focus of this Ph.D. thesis is on developing the first empirical model for selective epitaxial growth of SiGe using SiH2Cl2, GeH4 and HCl precursors in a reduced pressure chemical vapor deposition (RPCVD) reactor. The model describes the growth kinetics and considers the contribution of each gas precursor in the gas–phase and surface reactions. In this way, the growth rate and Ge content of the SiGe layers grown on the patterned substrates can be calculated. The gas flow and temperature distribution were simulated in the CVD reactor and the results were exerted as input parameters for the diffusion of gas molecules through gas boundaries. Fick‟s law and the Langmuir isotherm theory (in non–equilibrium case) have been applied to estimate the real flow of impinging molecules. For a patterned substrate, the interactions between the chips were calculated using an established interaction theory. Overall, a good agreement between this model and the experimental data has been presented. This work provides, for the first time, a guideline for chip manufacturers who are implementing SiGe layers in the devices.The other focus of this thesis is to implement SiGe layers or dots as a thermistor material to detect infrared radiation. The result provides a fundamental understanding of noise sources and thermal response of SiGe/Si multilayer structures. Temperature coefficient of resistance (TCR) and noise voltage have been measured for different detector prototypes in terms of pixel size and multilayer designs. The performance of such structures was studied and optimized as a function of quantum well and Si barrier thickness (or dot size), number of periods in the SiGe/Si stack, Ge content and contact resistance. Both electrical and thermal responses of such detectors were sensitive to the quality of the epitaxial layers which was evaluated by the interfacial roughness and strain amount. The strain in SiGe material was carefully controlled in the meta–stable region by implementingivcarbon in multi quantum wells (MQWs) of SiGe(C)/Si(C). A state of the art thermistor material with TCR of 4.5 %/K for 100×100 μm2 pixel area and low noise constant (K1/f) value of 4.4×10-15 is presented. The outstanding performance of these devices is due to Ni silicide contacts, smooth interfaces, and high quality of multi quantum wells (MQWs) containing high Ge content.The novel idea of generating local strain using Ge multi quantum dots structures has also been studied. Ge dots were deposited at different growth temperatures in order to tune the intermixing of Si into Ge. The structures demonstrated a noise constant of 2×10-9 and TCR of 3.44%/K for pixel area of 70×70 μm2. These structures displayed an improvement in the TCR value compared to quantum well structures; however, strain relaxation and unevenness of the multi layer structures caused low signal–to–noise ratio. In this thesis, the physical importance of different design parameters of IR detectors has been quantified by using a statistical analysis. The factorial method has been applied to evaluate design parameters for IR detection improvements. Among design parameters, increasing the Ge content of SiGe quantum wells has the most significant effect on the measured TCR value.

Place, publisher, year, edition, pages
Stockholm: Royal Institute of Technology, 2011. xxi, 95 p.
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2011:02
Silicon Germanium Carbon (SiGeC), Reduced Pressure Chemical Vapor Deposition (RPCVD), Epitaxy, Pattern Dependency, MOSFET, Mobility, bolometer, Quantum Well, Infrared (IR) Detection, Ni Silicide, High Resolution X-ray Diffraction (HRXRD), High Resolution Scanning Electron Microscopy (HRSEM)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-32049 (URN)KTH/ICT-MAP/AVH-2011:02-SE (ISRN)
Public defence
2011-04-29, Sal / Room C2, Electrum, Isafjordsgatan 22, Kista, 13:00 (English)
QC 20110405Available from: 2011-04-05 Created: 2011-04-04 Last updated: 2011-04-13Bibliographically approved

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