Enhancement of Adhesion Properties of Sio₂ Film by Gas Atmosphere Pre-Soak and Low Deposition Rate Initial Layer in PECVD Process

Silicon dioxide (SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>) films, especially those deposited by plasma-enhanced chemical vapor deposition (PECVD), are commonly used as dielectric layer layers in semiconductor devices and, at the same time, as effective bonding layers between other functional layers, such as silicon nitride, titanium nitride, and so on. When the interlayer stress is not balanced, or the condition of wafer bevel is complex after multi etching and scrubbing processes, the interface of films may flake off from each other due to insufficient adhesion. The formed large peeling defects might affect the subsequent processes and the capability of devices. Therefore, increasing the adhesion of the SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> layer is important for the reduction of such defects. In this study, adding a gas atmosphere preheating step and an initial step with low deposition rate, can effectively enhance the adhesion of the SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> films in the PECVD process. Nano-scratch experiments show that the mechanical properties of SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> films deposited with the pretreatment step are significantly improved from those deposited without the pretreatment step. The change in properties depends on the preheating time and the deposition rate of the initial step. Experiments on structured wafers show that the number of peeling defects is significantly reduced for the pretreated samples in both the center and edge regions. It is hypothesized that the gas preheating step was effective in making the wafer surface more uniformly heated, which is of benefit to the formation the chemical bonding between reactive precursors and wafer surface, as well as, the consistency of the growth rate of initial island.