IC Industry Award Winner Materials Enabling Award
Abs-Sr™ and Star-Ti™: Precursors for STO Deposition
STRONTIUM TITANIUM OXIDE (STO) is poised to make a next higher k material entry for DRAM capacitor applications. Air Liquide took this challenge to develop much awaited precursor chemistry for the semi-industry. Commercially available precursors faced tough process requirement constraints, such as high Aspect Ratio ALD deposition, with wider process window to match with Ti precursor. This prompted the initiation of Strontium and Titanium precursor development project at Air Liquide R&D. Strontium precursor was designed to
overcome high melting point, dimers or mononuclear compounds with adducts, thermal stability and volatility. AL solution for these issues is the Absolute-Sr precursor, which has a low melting point, good volatility and excellent thermal stability resulting from its ligand system. Ligand selection was very critical, so that it would provide enough steric bulk to prevent any dimers, result in increased surface reactivity and would favor high temperature deposition process – all of which are key requirements for deposition in conjunction with the Ti precursor. Standard titanium precursors derived
from alkylamido or beta-diketonate were proven unsatisfactory from both precursor physical property standpoint as well as for ALD deposition processes. For example, while the alkylamido precursors are highly volatile, they show low thermal stability,
narrow process window for ALD and higher carbon impurities in post deposited films. Our approach to this problem is to propose a heteroleptic ligand system, possessing unique set of two different classes of ligands to provide high volatility, enhanced thermal stability and higher surface reactivity. The result was the development of Air Liquide’s Star-Ti precursor.
Several academic partners, industrial
research consortiums, and industrial partners have already tested this precursor combination for STO deposition, and their results demonstrate high quality conformal STO layers, even in high aspect ratio trenches. In addition, in-situ crystallization has also been achieved.
Complimentary to this development is
Air Liquide’s award winning ruthenium precursor - ToRuS. This precursor can be used to deposit a very critical Ru layer on which STO can be epitaxially grown to initiate and achieve in-situ crystallization that provides higher k material form.
Using a combination of Absolute-Sr and
Star-Ti precursors, customers can deposit high quality STO films at the same process temperature to yield high throughput, manufacturable process. Both precursors allow for sufficient tunability in film stoichiometry, providing customers the flexibility to control and achieve desired Sr:Ti ratio in deposited films.
15
www.euroasiasemiconductor.com Issue IV 2010
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32