Issue 10, February 2008
Precursor Chemistries for Depositing Ancillary Dielectric Films
The fabrication of transistors for logic and memory devices continues to grow ever more complex as dimensions shrink and performance requirements increase. Silicon oxide and silicon nitride films are employed for sidewall spacers, but the film requirements are undergoing changes. In addition to uses as a mask material for controlling ion implantation profiles, these films are also employed to strain the gate structure for enhancing device performance. Within memory manufacturing, dielectrics are finding new uses as sacrificial films to assist in patterning, as protection for other films, etching stops and diffusion barriers. These applications cannot all be addressed by just one composition of oxide or nitride; there are emerging needs for oxide and nitride-based films with variable dielectric constants, with varying wet/dry etching rates and/or with stress that is either compressive or tensile.
Air Products New Product Offering
To address these needs, Air Products is introducing the AP-LTO™ (low temperature oxide) and AP-LTN™ (low temperature nitride) series of chemical precursors for use in depositing modified silicon oxide and nitride films by Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Atomic Layer Deposition (PE-ALD), Atomic Layer Deposition (ALD), and Plasma Enhanced Chemical Vapor Deposition (PE-CVD). These products can be tailored to meet the film requirements for IC fabrication processes. For a silicon nitride film with a dielectric constant lower than 7.0 and a wet etching rate commensurate with a dense silicon nitride, Air Products’ AP-LTN 500 series has offerings that can tune the dielectric constant to values less than 6.0, and etch at or below the rate typically measured for dense silicon nitride films. Other products in this series are specifically targeted for ALD-based applications to deposit high quality silicon oxide and silicon nitride films.
Application Information
LPCVD, PE-ALD, and ALD are utilized in the front end of line fabrication process for depositing many types of dielectric films. AP-LTN and AP-LTO chemical precursors are designed to be compatible with all of these types of deposition processes. Within the sidewall spacer film stack there is a trend toward using silicon oxide and silicon nitride films that diverge from the typical properties for these materials. Lowering the dielectric constant of silicon nitride without compromising the wet etching rate for the material is being addressed with our AP-LTN 530 product line. Depending on the process need, this product can be formulated to deliver the required performance properties. For silicon oxide applications, our AP-LTO 530 precursor is designed to modify the film composition and lower the wet etching rate.
Deposition of low hydrogen containing silicon oxide and nitride films is being addressed with our LTO-510 and LTN-510 precursors. These products enable the deposition of low hydrogen content dielectric films by either thermal or plasma enhanced processes. In addition to applications in integrated circuit manufacturing, Air Products sees potential for this product to be utilized for lower temperature PE-CVD based processes for depositing silicon nitride at temperatures well below 400°C for use in the fabrication of displays.
For further information on our LTO/LTN product offering, please listen to our podcast or contact our AP-LTO/LTN product development manager, Dr. Bing Han. |
