System for depositing a layered film
View Patent ↗The present invention relates to an electrically conductive film stack for semiconductors and methods and apparatus for providing same. A film stack comprising a first layer of a platinum-rhodium alloy deposited by metal organic chemical vapor deposition (MOCVD) in the presence of a reducer, such as hydrogen (H 2 ) gas, and a second layer of the platinum-rhodium alloy deposited in the presence of an oxidizing gas, such as ozone (O 3 ), provides an electrical conductor that is also a relatively good barrier to oxygen. The platinum-rhodium film stack can be used as an electrode or capacitor plate for a capacitor with a high-k dielectric material. The electrode formed with alternating reducing and oxidizing agents produces a rough surface texture, which enhances the memory cell capacitance.
1. A system for depositing a layered film on a substrate substantially in accordance with a metal organic chemical vapor deposition (MOCVD) process, the system comprising:
a chamber adapted to house the substrate and to maintain a controlled environment that includes maintaining a substrate temperature to within 200 degrees to 550 degrees Celsius during deposition, the chamber further adapted to maintain a low pressure in the chamber;
an inlet system adapted to introduce reactant gases and organometallic precursors in gas vapor phase to the chamber; and
an alternating system comprising mass flow controllers under software control, wherein the software is programmed to maintain the flow of the organometallic precursors in gas vapor phase while selecting among reactant gases to alternate between a reducing reactant gas and an oxidizing reactant gas.
2. The system as defined in claim 1 , wherein the organometallic precursors are introduced by a plurality of vaporizers coupled to the chamber, wherein a first vaporizer is adapted to heat and to flow a platinum source and a second vaporizer is adapted to heat and to flow a rhodium source.
3. The system as defined in claim 1 , wherein the chamber is further adapted to maintain the low pressure within the range of 0.1 Torr and 100 Torr.
4. The system as defined in claim 1 , wherein the reducing reactant gas comprises at least one of hydrogen (H 2 ) and ammonia (NH 3 ).
5. The system as defined in claim 1 , wherein the oxidizing reactant gas comprises at least one of oxygen (O 2 ), ozone (O 3 ), nitrous oxide (N 2 O), hydrogen peroxide (H 2 O 2 ), steam (H 2 O), and nitric oxide (NO).
6. The system as defined in claim 1 , wherein the organometallic precursors comprise Pt(acac) 2 and Rh(CO) 2 (acac).
7. The system as defined in claim 6 wherein the inlet system is further adapted to introduce the organometallic precursors such that a deposited platinum-rhodium alloy film comprises from about 5% to about 50% rhodium as measured by atomic ratio.
8. The system as defined in claim 6 , wherein the inlet system is further adapted to introduce the organometallic precursors such that a deposited platinum-rhodium alloy film comprises from about 10% to about 40% rhodium as measured by atomic ratio.
9. The system as defined in claim 6 , wherein the inlet system is further adapted to introduce the organometallic precursors such that a deposited platinum-rhodium alloy film comprises from about 30% rhodium as measured by atomic ratio.