high k dielectrics

HighHigh--K Dielectric Materials K Dielectric Materials In MicroelectronicsIn Microelectronics

NAME: Neha TomarNAME: Neha Tomar

IIT GUWAHATIIIT GUWAHATI

OUTLINEOUTLINEINTRODUCTIONINTRODUCTIONMOOREMOORE’’S LAW AND TRANSISTOR SCALINGS LAW AND TRANSISTOR SCALINGWHY HIGHWHY HIGH--K DIELECTRICS?K DIELECTRICS?

APPLICATIONS IN MICROELECTRONICS APPLICATIONS IN MICROELECTRONICS HIGHHIGH--K DIELECTRICS IN DRAMS K DIELECTRICS IN DRAMS HIGHHIGH--K GATE DIELECTRICSK GATE DIELECTRICS

SUMMARYSUMMARY

HIGHHIGH--K DIELECTRICS IN MICROELECTRONICSK DIELECTRICS IN MICROELECTRONICS

INTRODUCTIONINTRODUCTIONMOOREMOORE’’S LAWS LAW


A prediction made by Mr. Gordon Moorethat the number of transistors on a chip double every two years.


INTRODUCTION

•Transistor physical

gate length will reach

~15nm before

end of this decade, and ~10nm early next decade

HIGHHIGH--K DIELECTRICS IN MICROELECTONICSK DIELECTRICS IN MICROELECTONICS

PROBLEM AS TRANSISTOR IS MADESMALLER.

INTRODUCTION

Gate dielectric ,Silicon dioxide are only a few atomic layers thick now.

Leakage current increases, as thickness decreases.

A New dielectric material is needed to reduce leakage current.


INTRODUCTION

Thicker class of material known as “High-K” is likely to replace Silicon oxide.

K stands for dielectric constant, a measure of how much charge a material can hold.

WHAT ARE HIGH-K MATERIALS?


INTRODUCTIONHIGH-K MATERIAL BENEFITS

Sio2Sio2 HighHigh--k k CapacitanceCapacitance 1*1* 1.6*1.6*LeakageLeakage 1*1* < 0.01*< 0.01*


TRANSISTORA simple switch Current flows source to drain when a certain Voltage is applied on The gate, otherwiseDoesn’t flow.

HIGH-K GATE STACKS

Schematic of important regionsOf field effect transistor gate stack

APPLICATIONS IN MICROELECTRONICS


Scaling limits for current Gate DielectricsSilicon dioxide is current gate dielectrics

So, Continual scaling.will require high-K

material for dielectric layer.

Sio2 thickness can’t be decreased less than 1-1.5nm, becauseleakage currentincreases

HIGH-K GATE STACKSAPPLICATIONS IN MICROELECTRONICS


ALTERNATIVE HIGH-K GATE DIELECTRICS

Metal oxides of ZrO2, HfO2, Y2O3 and Al2O3

HighHigh--KKmaterialmaterial

Dielectric Dielectric constantconstant

LeakageLeakageCurrent Current reductionreduction

Thermal Thermal stabilitystabilityTmax Tmax ‘‘cc

ZrO2ZrO2 ~23~23 *10*1044--101055 ~900~900HfO2HfO2 ~20~20 *10*1044--101055 ~950~950Y2O3Y2O3 ~15~15 *10*1044--101055 Silicate Silicate

formation formation Al2O3Al2O3 ~10~10 *10*1022--101033 ~1000~1000

HIGH-K GATE STACKSAPPLICATIONS IN MICROELECTRONICS


Pseudo binary materials(HfO2)x (SiO2)1-x and (ZrO2)x(SiO2)1-x

ALTERNATIVE HIGH-K GATE DIELECTRICS

Silicate-Si interfaceis chemically similarto the SiO2-Si Interface.

Low defect densities

HIGH-K GATE STACKS

Hf-silicate between Si layer




KEY GUIDELINES FOR SELECTING AN ALTERNATIVE GATE DIELECTRIC

Interface qualityPermittivity and band gapThermodynamic stabilityCompatibility with the current or expected materialsto be used in processing for CMOS devicesReliability

HIGH-K GATE STACKS



HIGH-K GATE STACKS

PROCESS ISSUES THAT AFFECT DEVICE

Pre-deposition treatmentsHF last,O3 etc.

Pre/post-depositionannealingO2 and N2 annealing etc.

High-k depositionALD,CVD etc.

Gate electrodemetal gates, poly-silicongates etc.



HIGH-K GATE STACKS

GATE ELECTRODE

Problems arise due to interaction with the Poly-Si gate

Phonon Scattering –electrons slow down

Threshold voltage pinning-Due to defects that arise at the gate-dielectric/gate electrode

PROBLEMS WHEN SiO2 IS REPLACED WITH HIGH-K

APPLICATIONS IN MICROELECTRONICSHIGH-K DIELECTRICS IN DRAMS


GATE ELECTRODE

SOLUTION-METAL GATE



STATE-OF-THE-ART TRANSISTOR

HIGH-K GATE STACKS

Other technologies are also emerging for low-powerand high-performance logic. For exampleNanoelectronic devices, SOI, double gateand tri-gate etc.

Metal gate and high-K dielectric transistor offerthe promise toward CMOS Technology nodes.


APPLICATIONS IN MICROELECTRONICSHIGH-K DIELECTRICS FOR DRAMS

WHAT IS DRAM?

DRAM is a type of random access memory that stores each bit of data in a separate capacitor.



The continuous “shrinking technology” up to Gbit density exposes many challenges.

Sio2 can not be made thinner any more.

Alternative dielectric having a substantially higher permittivity is needed for further high density DRAMs.



HIGH-K DIELECTRICS FOR DRAMSALTERNATIVE HIGH-K DIELECTRICS FOR DRAMS

Among this, BST film is the most promising capacitor material in future DRAM applications.



HIGH-K DIELECTRICS FOR DRAMS

Cross-section TEMImage of a stacked-capacitorStructure with a BST dielectricPt electrode and a TaSiN barrier layer.Minimum feature size=0.2umDielectric thickness=27 nm

BST capacitor structure with the stacked barrier scheme.




Factors that influence BST thin film properties

Processing methodsFilm compositionCrystalline structureMicrostructure Surface morphologyFilm thickness

HIGH-K DIELECTRICS FOR DRAMSAPPLICATIONS IN MICROELECTRONICS


Process Integration

Main Points

BST deposition techniques

Electrode material & Barriers



Process IntegrationBST deposition techniques

Main techniques

MOCVD

rf-sputtering



Process Integration

ELECTRODE MATERIAL

Noble metalsExp-Pt, Ru etc

•Low leakage current

Conducting Oxides

Exp-Iro2 etc•High leakage

current



Process Integration

Various integration schemes for BST capacitor




Reliability

Time to breakdown Ba0.47Sr0.53TiO3Deposited on various electrodes

Time to breakdown Ba0.47Sr0.53TiO3 at various OMR

TDDB for various DRAM dielectrics

Last but not least



High-k dielectrics (BST film ) has become the dielectricmaterial of choice for cell capacitor of the dynamicrandom access memory devices (DRAMs) having gigabitdensities

To continue “shrinking technology” , BST thin films willbe a productive field of research and development.


SUMMARY

To continue Moore’s law for next decades,New materials are needed.

High-k dielectrics may ultimately lead to vaster and enable applications.

Industry is seeking for new materials and technologies that can replace SiO2 and scaling remains continue.


References1. H.R. Huff , A. Hou, C. Lim, Y. Kim, J. Barnett, G. Bersuker, G.A Brown, C.D.

Young,P.M. Zeitzoff, J. Gutt, P. Lysaght, M.I. Gardner, R.W. Murto” High-k gate stacks for planar, scaled CMOS integrated circuits”(2003).

2. Cheol Seong Hwang” (Ba,Sr)TiO3 thin films for ultra large scale dynamic random access memory. A review on the process integration”.(1998)

3. S. Ezhilvalavan, Tseung-Yuen Tseng” Progress in the developments of (Ba,Sr)TiO3 (BST) thin films for Gigabit era DRAMs”(2000).

4. G. D. Wilk, R. M. Wallaceb, J. M. Anthony” High- kgate dielectrics: Current status and materials properties considerations”(2001).

5. Ofer Sneh*, Robert B.Clark-Phelps, Ana R.Londer gan, Jereld Winkler, Thomas E.Seidel” Thin film atomic layer deposition equipment for semiconductor processing”(2002).

6. E.P. Gusev , E. Cartier , D.A. Buchanan , M. Gribelyuk , M. Copel ,a H. Okorn-Schmidt , C. D’Emic” Ultrathin high-K metal oxides on silicon:

processing, characterization and integration issues”(2001).

References


7. D. E. Kotecki,J. D. Baniecki,H. Shen ,R. B. Laibowitz,K. L. Saenger ,J. J. Lian,T. M Shaw ,S. D. Athavale,C. Cabral, Jr.,P. R. Duncombe ,M. Gutsche ,G. Kunkel ,Y.-J. Park,Y.-Y. Wang,R. Wise “(Ba,Sr)TiO3 dielectrics for future stacked capacitor DRAM”(1999).

8.Intel’s High Gate k/Metal Gate Announcement November 4th, 2003.

9.Wilman Tsai and Robert Chau” Integration of Metal gate-High k Dielectrics to Extend Transistor Scaling”(2004).

high k dielectrics

Documents

microelectronicsk dielectrics

microelectonicsk dielectrics

gate stacksapplications

dielectric materials

drams highhigh

microelectronics highhigh

introductiongate dielectric

dielectric layer