Flowfill-Process as a New Concept for Inter-Metal-Dielectrics

Various process sequences are established for depositing inter-metal-dielectrics (IMD). The most common insulating stack between metal layers is SOG/etch-back. The sequence is as follows: silane-oxide deposition - spin-on-glass application - etch-back of SOG - another silane-oxide deposition. This process flow has several drawbacks. It is time consuming, takes a lot of equipment, and has high COO due to the complexity of process steps. As an alternative, we investigated Flowfill. Flowfill is a new self-planarizing process for depositing silane oxide layers. The chemistry is very simple. It is a reaction of silane and hydrogen peroxide, leading to a liquid intermediate. The gas phase reaction produces vaporized glass which condenses as a liquid on substrates cooled to approximately zero degrees Celsius. This liquid state is the main reason for reaching good gap fill and excellent planarity. After polymerization, the resulting silica film contains a lot of water. This problem is solved by a heat treatment. In the Flowfill sequence, the insulating block of layers between the metal lines is done in one system and in one go, thus saving a lot of physical process time. (Author)