High-K Dielectric Materials In Microelectronics

High-K Dielectric Materials In Microelectronics NAME: Neha Tomar IIT GUWAHATI

OUTLINE INTRODUCTION MOORE’S LAW AND TRANSISTOR SCALING WHY HIGH-K DIELECTRICS?

APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS IN DRAMS HIGH-K GATE DIELECTRICS

SUMMARY

HIGH-K DIELECTRICS IN MICROELECTRONICS

INTRODUCTION MOORE’S LAW A prediction made by Mr. Gordon Moore that 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


INTRODUCTION PROBLEM AS TRANSISTOR IS MADE SMALLER. 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.

HIGH-K DIELECTRICS IN MICROELECTONICS

INTRODUCTION WHAT ARE HIGH-K MATERIALS? 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.


INTRODUCTION HIGH-K MATERIAL BENEFITS

Sio2 Capacitance 1* Leakage 1*

High-k 1.6* < 0.01*


APPLICATIONS IN MICROELECTRONICS HIGH-K GATE STACKS TRANSISTOR A simple switch Current flows source to drain when a certain Voltage is applied on The gate, otherwise Doesn’t flow.

Schematic of important regions Of field effect transistor gate stack


APPLICATIONS IN MICROELECTRONICS HIGH-K GATE STACKS Scaling limits for current Gate Dielectrics Silicon dioxide is current gate dielectrics

Sio2 thickness can’t be decreased less than 1-1.5nm, because leakage current increases So, Continual scaling. will require high-K material for dielectric layer.


APPLICATIONS IN MICROELECTRONICS HIGH-K GATE STACKS ALTERNATIVE HIGH-K GATE DIELECTRICS Metal oxides of ZrO2, HfO2, Y2O3 and Al2O3

High-K Dielectric Leakage material constant Current reduction ZrO2 ~23 *104-105 HfO2 ~20 *104-105 Y2O3 ~15 *104-105 Al2O3

~10

*102-103

Thermal stability Tmax ‘c ~900 ~950 Silicate formation ~1000


APPLICATIONS IN MICROELECTRONICS HIGH-K GATE STACKS ALTERNATIVE HIGH-K GATE DIELECTRICS Pseudo binary materials (HfO2)x (SiO2)1-x and (ZrO2)x(SiO2)1-x Silicate-Si

interface is chemically similar to the SiO2-Si Interface. Low

defect densities

Hf-silicate between Si layer


APPLICATIONS IN MICROELECTRONICS HIGH-K GATE STACKS ALTERNATIVE HIGH-K GATE DIELECTRICS Pseudo binary materials (HfO2)x (SiO2)1-x and (ZrO2)x(SiO2)1-x Silicate-Si

interface is chemically similar to the SiO2-Si Interface. Low

defect densities

Hf-silicate between Si layer


APPLICATIONS IN MICROELECTRONICS HIGH-K GATE STACKS KEY GUIDELINES FOR SELECTING AN ALTERNATIVE GATE DIELECTRIC Interface quality Permittivity and band gap Thermodynamic stability Compatibility with the current or expected materials to be used in processing for CMOS devices Reliability


APPLICATIONS IN MICROELECTRONICS HIGH-K GATE STACKS PROCESS ISSUES THAT AFFECT DEVICE Pre-deposition treatments HF last,O3 etc. Pre/post-deposition annealing O2 and N2 annealing etc. High-k deposition ALD,CVD etc. Gate electrode metal gates, poly-silicon gates etc.


APPLICATIONS IN MICROELECTRONICS HIGH-K GATE STACKS GATE ELECTRODE PROBLEMS WHEN SiO2 IS REPLACED WITH HIGH-K 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


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS IN DRAMS GATE ELECTRODE SOLUTION-METAL GATE


APPLICATIONS IN MICROELECTRONICS HIGH-K GATE STACKS STATE-OF-THE-ART TRANSISTOR Metal gate and high-K dielectric transistor offer the promise toward CMOS Technology nodes.

Other technologies are also emerging for low-power and high-performance logic. For example Nanoelectronic devices, SOI, double gate and tri-gate etc.


APPLICATIONS IN MICROELECTRONICS HIGH-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.


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS 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.


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS ALTERNATIVE HIGH-K DIELECTRICS FOR DRAMS

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


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS BST capacitor structure with the stacked barrier scheme. Cross-section TEM Image of a stacked-capacitor Structure with a BST dielectric Pt electrode and a TaSiN barrier layer. Minimum feature size=0.2um Dielectric thickness=27 nm


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS Factors that influence BST thin film properties Processing methods Film composition Crystalline structure Microstructure Surface morphology Film thickness


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS Process Integration Main Points BST deposition techniques Electrode material & Barriers


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS Process Integration BST deposition techniques Main techniques

MOCVD rf-sputtering


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS Process Integration

ELECTRODE MATERIAL

Noble metals Exp-Pt, Ru etc •Low leakage current

Conducting Oxides Exp-Iro2 etc •High leakage current


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS Process Integration Various integration schemes for BST capacitor


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS Last but not least

Reliability

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

Time to breakdown Ba0.47Sr0.53TiO3 Deposited on various electrodes TDDB for various DRAM dielectrics


APPLICATIONS IN MICROELECTRONICS HIGH-K DIELECTRICS FOR DRAMS High-k dielectrics (BST film ) has become the dielectric material of choice for cell capacitor of the dynamic random access memory devices (DRAMs) having gigabit densities To continue “shrinking technology” , BST thin films will be 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.


References 1. 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 Dielectric Materials In Microelectronics

Recommend Documents