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Application of SiGe(C) in high performance MOSFETs and infrared detectors
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
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.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2011:02
Keyword [en]
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
Identifiers
URN: urn:nbn:se:kth:diva-32049ISRN: KTH/ICT-MAP/AVH-2011:02-SEOAI: oai:DiVA.org:kth-32049DiVA: diva2:408188
Public defence
2011-04-29, Sal / Room C2, Electrum, Isafjordsgatan 22, Kista, 13:00 (English)
Opponent
Supervisors
Note
QC 20110405Available from: 2011-04-05 Created: 2011-04-04 Last updated: 2011-04-13Bibliographically approved
List of papers
1. Selective Epitaxial Growth with Full Control of Pattern Dependency Behavior for pMOSFET Structures
Open this publication in new window or tab >>Selective Epitaxial Growth with Full Control of Pattern Dependency Behavior for pMOSFET Structures
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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.

Keyword
sige
Identifiers
urn:nbn:se:kth:diva-18398 (URN)10.1149/1.3049842 (DOI)000265837900055 ()2-s2.0-59349106630 (ScopusID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-04-05Bibliographically approved
2. Comprehensive Evaluation and Study of Pattern Dependency Behavior in Selective Epitaxial Growth of B-Doped SiGe Layers
Open this publication in new window or tab >>Comprehensive Evaluation and Study of Pattern Dependency Behavior in Selective Epitaxial Growth of B-Doped SiGe Layers
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2009 (English)In: IEEE transactions on nanotechnology, ISSN 1536-125X, E-ISSN 1941-0085, Vol. 8, no 3, 291-297 p.Article in journal (Refereed) Published
Abstract [en]

The influence of chip layout and architecture on the pattern dependency of selective epitaxy of B-doped SiGe layers has been studied. The variations of Ge-, B-content, and growth rate have been investigated locally within a wafer and globally from wafer to wafer. The results are described by the gas depletion theory. Methods to control the variation of layer profile are suggested.

Keyword
Loading effect, pattern dependency, selective epitaxy, SiGe, chemical-vapor-deposition, parameters
Identifiers
urn:nbn:se:kth:diva-18435 (URN)10.1109/tnano.2008.2009219 (DOI)000266162900004 ()2-s2.0-67249161740 (ScopusID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-04-05Bibliographically approved
3. New method to calibrate the pattern dependency of selective epitaxy of SiGe layers
Open this publication in new window or tab >>New method to calibrate the pattern dependency of selective epitaxy of SiGe layers
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2009 (English)In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 53, no 8, 858-861 p.Article in journal (Refereed) Published
Abstract [en]

Selective epitaxial growth (SEG) of Si1-xGex layers on patterned substrates containing isolated, grouped and global chips has been investigated. The interaction between chips on a wafer was studied, and the results are explained by kinetic gas theory for CVD techniques. A test pattern was designed with a series of grouped chips to calibrate the pattern dependency of SEG (both growth rate and Ge content). The amount of exposed Si coverage on chips in the test pattern ranged between 0.05 and 37%. The layer profile of the calibration pattern was compared to profiles on wafers having a global chip design. A model was developed to estimate the Ge content on substrates with a global design.

Keyword
SiGe, Selective epitaxy, CVD, Gas kinetic modeling, Composition, Pattern dependency
Identifiers
urn:nbn:se:kth:diva-18643 (URN)10.1016/j.sse.2009.04.018 (DOI)000268505600009 ()2-s2.0-67649224118 (ScopusID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-04-05Bibliographically approved
4. Selective Growth of B- and C-Doped SiGe Layers in Unprocessed and Recessed Si Openings for p-type Metal-Oxide-Semiconductor Field-Effect Transistors Application
Open this publication in new window or tab >>Selective Growth of B- and C-Doped SiGe Layers in Unprocessed and Recessed Si Openings for p-type Metal-Oxide-Semiconductor Field-Effect Transistors Application
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2010 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 157, no 6, H633-H637 p.Article in journal (Refereed) Published
Abstract [en]

This work presents the pattern dependency of the selective epitaxial growth of boron- and carbon-doped SiGe layers in recessed and unprocessed openings. The layer profile is dependent on deposition time, chip layout, and growth parameters. Carbon and boron doping compensates for the strain in SiGe layers, and when both dopants are introduced, the strain reduction is additive. The incorporation of boron and carbon in the SiGe matrix is a competitive action. The concentration of carbon decreases, whereas the boron amount increases in SiGe layers with higher Ge content. In recessed openings, the Ge content is independent of the recess depth. The strain amount in the grown layers is graded vertically, which is due to the thickness of the epilayer exceeding the critical thickness.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-30645 (URN)10.1149/1.3363736 (DOI)000277260200078 ()2-s2.0-77958565024 (ScopusID)
Note
QC 20110302Available from: 2011-03-02 Created: 2011-03-02 Last updated: 2011-04-05Bibliographically approved
5. Kinetic Model of SiGe Selective Epitaxial Growth Using RPCVD Technique
Open this publication in new window or tab >>Kinetic Model of SiGe Selective Epitaxial Growth Using RPCVD Technique
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2011 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 158, no 4, H457-H464 p.Article in journal (Refereed) Published
Abstract [en]

Recently, selective epitaxial growth (SEG) of B-doped SiGe layers has been used in recessed source/drain (S/D) of pMOSFETs. The uniaxial induced strain enhances the carrier mobility in the channel. In this work, a detailed model for SEG of SiGe has been developed to predict the growth rate and Ge content of layers in dichlorosilane(DCS)-based epitaxy using a reduced-pressure CVD reactor. The model considers each gas precursor contributions from the gas-phase and the surface. The gas flow and temperature distribution were simulated in the CVD reactor and the results were exerted as input parameters for Maxwell energy distribution. The diffusion of molecules from the gas boundaries was calculated by Fick's law and Langmuir isotherm theory (in non-equilibrium case) was applied to analyze the surface. The pattern dependency of the selective growth was also modeled through an interaction theory between different subdivisions of the chips. Overall, a good agreement between the kinetic model and the experimental data were obtained.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-30646 (URN)10.1149/1.3548113 (DOI)000287972300063 ()2-s2.0-79955126180 (ScopusID)
Note
QC 20110302Available from: 2011-03-02 Created: 2011-03-02 Last updated: 2011-04-05Bibliographically approved
6. Improvement of infrared detection using Ge quantum dots multilayer structure
Open this publication in new window or tab >>Improvement of infrared detection using Ge quantum dots multilayer structure
2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 21, 213516- p.Article in journal (Refereed) Published
Abstract [en]

Monocrystalline SiGe/Si multiquantum dot and well structures have been manufactured/compared as thermistor materials for infrared detection. The performance of the devices (both the thermal and electrical) has been very sensitive to the quality of the epitaxial layers which is evaluated by the interfacial roughness and strain amount. This study demonstrates that the devices containing quantum dots have higher thermal coefficient resistance 3.4%/K with a noise constant (K-1/f) value of 2x10(-9).

Keyword
Ge-Si alloys, infrared detectors, interface roughness, internal stresses, noise, semiconductor epitaxial layers, semiconductor quantum dots, semiconductor quantum wells, thermal resistance, thermistors
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-27556 (URN)10.1063/1.3441120 (DOI)000278183200092 ()2-s2.0-77956232780 (ScopusID)
Note
QC 20101216Available from: 2010-12-16 Created: 2010-12-13 Last updated: 2011-04-05Bibliographically approved
7. Carbon-doped single-crystalline SiGe/Si thermistor with high temperature coefficient of resistance and low noise level.
Open this publication in new window or tab >>Carbon-doped single-crystalline SiGe/Si thermistor with high temperature coefficient of resistance and low noise level.
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2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 22, 223507- p.Article in journal (Refereed) Published
Abstract [en]

SiGe (C)/Si(C) multiquantum wells have been studied as a thermistor material for future bolometers. A thermistor material for uncooled Si-based thermal detectors with thermal coefficient of resistance of 4.5%/K for 100 x 100 mu m(2) pixel sizes and low noise constant (K-1/f) value of 4.4 x 10(-15) is presented. The outstanding performance of the devices is due to Ni-silicide contacts, smooth interfaces, and high quality multiquantum wells containing high Ge content.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-27961 (URN)10.1063/1.3524211 (DOI)000284965000089 ()2-s2.0-78650659237 (ScopusID)
Note
QC 20110104Available from: 2011-01-04 Created: 2011-01-03 Last updated: 2011-04-05Bibliographically approved
8. The performance improvement evaluation for SiGe-based IR detectors
Open this publication in new window or tab >>The performance improvement evaluation for SiGe-based IR detectors
2011 (English)In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 62, no 1, 72-76 p.Article in journal (Refereed) Published
Abstract [en]

During recent years, single crystalline (Sc) SiGe has been recognized as a new low cost thermistor material for IR detection. In this study the effect of Ge content, pixel size and the Ni silicide on the performance of SiGe/Si thermistor material have been presented. The noise level was decreased for more than one order of magnitude when the Ni silicide layer was integrated below the metal contacts. The silicidation slightly improved TCR values for the detectors (+0.22%/K). However, increasing the Ge content had the most significant effect on the TCR. A statistical analysis was applied to evaluate the effect of each parameter. Using the factorial method, it was realized that decreasing the pixel size would enhance the TCR value.

Keyword
IR detector, Bolometer, SiGe, Epitaxy
National Category
Computer and Information Science
Identifiers
urn:nbn:se:kth:diva-30648 (URN)10.1016/j.sse.2011.01.010 (DOI)000292444000012 ()2-s2.0-79957957447 (ScopusID)
Available from: 2011-03-03 Created: 2011-03-02 Last updated: 2011-08-03Bibliographically approved

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