Deposition of thin films on a substrate surface is an important process in a variety of industries including semiconductor processing, diffusion barrier coatings and dielectrics for magnetic read/write heads. In the semiconductor industry, in particular, miniaturization requires atomic level control of thin film deposition to produce conformal coatings on high aspect structures. One method for deposition of thin films with atomic layer control and conformal deposition is atomic layer deposition (ALD), which employs sequential, self-limiting surface reactions to form layers of precise thickness controlled at the Ångstrom or monolayer level. Most ALD processes are based on binary reaction sequences which deposit a binary compound film. Each of the two surface reactions occurs sequentially and because they are self-limiting a thin film can be deposited with atomic level control. Because the surface reactions are sequential, the two gas phase reactants are not in contact and possible gas phase reactions that may form and deposit particles are limited. The self-limiting nature of the surface reactions also allows the reaction to be driven to completion during every reaction cycle, resulting in films that are continuous and pinhole-free.
Atomic layer deposition may be used to form features in the manufacturing process of circuit devices such as semiconductors. A thin film is grown layer by layer by exposing a surface of the substrate disposed in a process chamber to alternating pulses of reactants or chemical precursors, each of which undergoes a reaction, generally providing controlled film thickness. Each reactant pulse provides an additional atomic layer to previously deposited layers. The film growth cycle generally consists of two pulses, each pulse being separated by a purge. The process chamber can be purged with an inert gas to remove the reactant or precursor material. When second reactant or precursor material is pulsed into the reactor, the second reactant or precursor material reacts with the precursor material on the wafer surface. The reactor is purged again with an inert gas. In an ALD manufacturing process, the thickness of the deposited film is controlled by the number of cycles.
Atomic layer deposition may also be referred to as cyclical deposition, referring to the sequential introduction of two or more reactive compounds to deposit a layer of material on a substrate surface. The two or more reactive compounds are alternatively introduced into a reaction zone or process region of a processing chamber. The reactive compounds may be in a state of gas, plasma, vapor, fluid or other state of matter useful for a vapor deposition process. Usually, each reactive compound is separated by a time delay to allow each compound to adhere, adsorb, absorb and/or react on the substrate surface. In typical ALD processes, a first precursor or compound A is pulsed into the reaction zone followed by a first time delay. Next, a second precursor or compound B is pulsed into the reaction zone followed by a second delay. Compound A and compound B react to form a deposited material. During each time delay, a purge gas is introduced into the processing chamber to purge the reaction zone or otherwise remove any residual reactive compound or by-products from the reaction zone. Alternatively, the purge gas may flow continuously throughout the deposition process so that only the purge gas flows during the time delay between pulses of reactive compounds. The reactive compounds are alternatively pulsed until a desired film thickness of the deposited material is formed on the substrate surface. In either scenario, the ALD process of pulsing compound A, purge gas, pulsing compound B and purge gas is a cycle.
Silicon carbide (SixCyHz) and similar films are promising materials for a variety of applications. For example, in semiconductor devices some compositions of SixCyHz functions at high temperature, high voltage and high frequency without degradation. Excellent mechanical, chemical, and electrical capabilities also make silicon carbide an attractive material in microelectromechanical systems (MEMS). Silicon carbide is considered an attractive material for EUV and soft X-ray optics, passivation layers in solar cells.
In addition to ALD, a variety of other techniques are used for deposition of silicon carbide thin films, including traditional chemical vapor deposition (CVD) and plasma enhanced CVD (PECVD). Improvements in existing processes as well as new deposition processes are desired. The present invention provides thin film deposition processes which may be conducted at relatively low temperatures with good conformality and deposition rates, low stress and high etch rate selectivity.