1. Field of the Invention
The present invention relates to a method of manufacturing a dielectric film in a capacitor. In particular, the present invention relates to a method of manufacturing a dielectric film having a crystallization preventing layer between two metal-oxide layers by way of an atomic deposition layer process. The inventive method provides a dielectric film exhibiting excellent electrical properties, while achieving cost-effective throughput.
2. Description of the Related Art
In general, capacitors may have a structure of Metal-Insulator-Metal (MIM) to improve their electrical properties. Among such capacitors, the structure of Tin/HfO2/Tin, as compared, for example, to the structure of Ru/TaO2/Ru, may exhibit low leakage current and high capacitance. As such, capacitors having the structure of Tin/HfO2/Tin may have an advantage of being applied to semiconductor memory devices with a design rule of 100 nm or less. However, the Tin/HfO2/Tin capacitors may have a relatively high leakage current during their back-end processing as a result of the HfO2 layer crystallization.
Typically, crystallization of the HfO2 layer during the back-end processing of the capacitors may be prevented by interposing an Al2O3 layer between two HfO2 layers as a crystallization preventing layer to form a dielectric film of the structure HfO2/Al2O3/HfO2. The relatively high crystallization temperature of the Al2O3 layer may increase the effective crystallization temperature of the overall dielectric film, thereby reducing leakage current during back-end processing even at high processing temperatures.
A dielectric film composed of HfO2/Al2O3/HfO2 may be formed by an Atomic Layer Deposition (ALD) process to provide a uniform layer deposition on a surface of a lower electrode of a capacitor. Such uniform step coverage and thickness of a dielectric film on the electrode may require increased deposition time of precursor materials; a factor which may result in overall increased processing time of the dielectric film and reduced throughput of the process.
An attempt has been made to increase the throughput of the ALD process, while maintaining good product quality, by employing a batch-type manufacturing process, i.e., depositing films on more than one wafer at a time. However, when the deposition time of the required precursor materials is increased, the resulting overall throughput in such a process is almost indistinguishable over an ALD processing of a single wafer. On the other hand, when the deposition time of the precursor materials is decreased, the precursor materials are not properly applied to the lower electrode of the capacitor, thereby reducing the step coverage of the film and providing inferior wafer thickness and film uniformity, consequently producing an electrically defective capacitor.
Accordingly, there exists a need for a method of manufacturing a dielectric film by an ALD process that produces high quality dielectric films, having excellent step coverage and electrical properties, while providing cost-effective throughput.