Plasmonic Plasma Process for Reduced Energy Costs of Ultra-Thin Silicon Oxide Films

In order to achieve the carbon dioxide emission reduction target in the first half of the 21st century, it is indispensable to reform various thermal processes in the manufacturing industry including the semiconductor industry.<br/>Taking the process of forming a silicon oxide film used in an integrated circuit as an example, a high-quality film can be realized by raising the temperature of the substrate to around 900 celsius.<br/>Here, the energy consumption for heat generation cannot be ignored as well as the time cost for raising and lowering the temperature.<br/>If the silicon oxide film formation process can be replaced with a low-temperature and short-time process, emission reduction and high throughput can be realized at the same time.<br/>We have developed a new process that realizes non-thermal oxidation by introducing the hot electron supply effect of gold nanoparticles plasmon into the low temperature formation process of ultrathin silicon oxide film by oxygen plasma. The chemical state and electrical characteristics of the insulating film were evaluated.<br/>The loading of gold nanoparticles on a commercially available silicon wafer used gold deposition in an ultra-high vacuum chamber.<br/>According to the non-contact AFM measurement, gold nanoparticles having an average particle size of 6 nm were formed on the substrate surface at high density by vapor deposition with an average film thickness of 0.4 nm at room temperature.<br/>After the sample was introduced into the high vacuum chamber, it was oxidized for 10 minutes with pure oxygen inductively coupled plasma at a gas pressure of 10 Pa via a metal mesh electrode.<br/>Regarding the sample temperature during processing, there is no heating process other than plasma-derived ions, electrons, and light irradiation.<br/>In the chemical analysis by XPS after the treatment, a peak of Si-O bond was observed in the Si 2p spectrum, and the chemical shift seen from the Si-Si bond (99.6 eV) was 3.5 eV.<br/>As a result of measuring the electrical characteristics by the mercury probe method, the equivalent oxide film thickness of the film was 2 nm, and the leakage current density at this time was 6×10^-3 A/cm², showing the insulation characteristics equivalent to those of the thermal oxide film.<br/>Conventionally, the plasma process is not suitable for forming an insulating film due to ionic impact and residual charge.<br/>This time, by exciting gold nanoparticle plasmons with light derived from plasma and supplying hot electrons that induce surface chemical reactions, a short-time low-temperature energy-saving process was realized, which brought about a breakthrough in insulating film formation. Details such as the light wavelength selection effect of plasmon excitation will be presented at the time of presentation.