Low-temperature plasma power hydrogen plasma cleans the surface of silicon substrate in situ:
Silicon surface cleaning technology consists of two parts: ex-situ surface cleaning before the substrate is installed in the deposition system and in-situ cleaning in the deposition system before epitaxy. Alkaline and acid hydrogen peroxide cleaning solutions that have been widely used at present can remove most of the metal ions and carbon-containing groups contaminated on the surface of silicon wafers, and form a thin oxide layer with almost no carbon. This thin oxide layer It plays a very important role. It minimizes the contamination of the silicon surface by the carbon-containing groups in the atmosphere and the system.
The effectiveness of this oxide layer in reducing carbon contamination on the surface of silicon wafers has been widely proven. In order to form a controllable and stable protective oxide film, ultraviolet ozone cleaning (UVOC) technology has been developed. Therefore, the problem of in-situ cleaning is how to effectively remove this oxide layer. The technology of using low-temperature plasma power hydrogen plasma to clean the silicon wafer before epitaxy in situ is considered to be a very promising low-temperature cleaning technology.
Hydrogen plasma can effectively remove silicon dioxide on the surface of silicon wafers. Experiments have found that a perfect low-temperature plasma power hydrogen plasma cleaning process is a multi-parameter problem. To obtain a complete clean surface of the crystal lattice, the substrate temperature, plasma energy, annealing temperature and annealing time used in the experiment will all affect the results. Influence.

The extended resistance test can indirectly reflect the degree of damage to the substrate surface. The expansion resistance test for lattice damage of the surface layer of a silicon wafer is very effective. The damaged and distorted lattice will increase the expansion resistance value, and its value will have a considerable range of distribution. The greater the plasma energy output at a certain substrate temperature, the faster the removal of silicon dioxide, but at the same time the more serious the lattice damage caused to the silicon surface; insufficient processing time, the silicon surface oxide layer cannot be completely removed. In the case of a certain plasma energy output power, there is a very good processing time range.

Under the action of low-temperature plasma power and high-frequency electric field, low-pressure hydrogen gas can produce stable self-sustained discharge. The glow discharge produced is a quasi-neutral plasma containing a large number of electrons and ions. When hydrogen molecules are ionized, many possibilities occur. During the collision process, the reaction generates many active groups, which can react with silicon and contaminants on the surface of the substrate. Especially for the contamination of oxygen and carbon, which has a great influence on the integrity of the epitaxial layer, active hydrogen atoms or hydrogen ions can react with them to generate volatile products and be removed.
The surface of the silicon sample in the plasma not only chemically reacts with active hydrogen atoms and hydrogen ions, but also produces a physical effect of sputtering due to the bombardment of charged particles. Both of these effects are effective for removing contamination on the silicon surface. In the process of epitaxial growth such as three-dimensional structure, since there is no damage layer caused by polishing, the low-temperature plasma power hydrogen plasma cleaning can be used directly to fully play its role. Low-temperature plasma power hydrogen plasma cleaning the surface of silicon wafers has the advantages of low processing temperature and short time. It is a promising in-situ cleaning method for silicon substrates for low-temperature epitaxy.