Manufacturers can not achieve superconformal (bottom-up) filling of high aspect ratio features by a modified chemical vapor deposition method. The CVD precursor flux is augmented by a small flux of a growth suppressor, which slows deposition near the upper surface of the substrate while permitting growth at normal rates deep in a trench or via.
Details
As circuit densities increase, the width of their gap structures decrease, making uniform deposition of semiconductor materials more difficult and more expensive. In order to keep-up with the demand for increasing miniaturization, transistor manufacturers have developed several novel alternatives to physical layer deposition. Among the most successful of these alternatives is Atomic Layer Deposition (ALD), a technique that essentially builds thin-film depositions one atom-layer at a time. Atomic layer deposition, however, is slow and must be repeatedly exposed to alternating reactive gasses. Electrochemical Deposition (ECD) has also been used as a solution in increasing circuit densities, but ECD is limited to certain materials and requires an additional "wet processing" step. Superconformal CVD avoids these obstacles through super heating elemental hydrogen or nitrogen, changing the gas into its atomic, or plasmatic, state. During the chemical deposition process, a plasma beam that is directed at the substrate suppresses the chemical reaction along the surface of the etched wafer, preventing undesirable material accumulation around the cusp of the wafer's trenches.
Applications
For use in the development of micro- and nano-scale semiconductor devices, Superconformal CVD gives producers of microchips, MEMS, and various other microelectronic devices greater control over their manufacturing process. All current methods of CVD: Superconformal CVD has been demonstrated to be successful for the deposition of several different types of materials. The technique should be widely applicable for the superconformal deposition of essentially any material, although additional development work may be required to identify the best combination of suppressor gas and growth gas.
Benefits
The semiconductor device industry strives to develop manufacturing techniques to meet increasingly stringent design rules. By offering a gas-phase method for achieving superconformal, bottom-up filling of features with high aspect-ratios, this technology solves a long-standing manufacturing obstacle.
- Eliminates Pinch-off: Pinch-off occurs when unwanted film deposition near the opening of a trench or via accumulates to the point that the gap closes. Pinch-off creates voids within a trench or via, resulting in reduced device performance. These problems have proven difficult to overcome; alternative manufacturing methods - atomic layer deposition (ALD) and electrochemical deposition (ECD) - require several extra steps.
- Fast and inexpensive: Our Superconformal Chemical Vapor Deposition method is fast and inexpensive and does not require extra chemical washing or polishing steps. The process is compatible with existing microelectronic manufacturing methods.
- Clean deposition: Atomic hydrogen often serves as an effective suppressor gas, and a significant advantage of its use is that impurities are not introduced that could compromise device performance. The metastable nature of the atomic hydrogen ensures that it rapidly recombines on and desorbs from the surface as molecular hydrogen gas.
- High Aspect Ratio Processes: With our improved method, pinch-off is reduced or eliminated, often achieving complete filling even for aspect ratios as high as 50:1.