Selective and rapid heating method for polycrystallization of amorphous Si using microwave plasma irradiation

我们开发了一种利用微波等离子体辐照对具有高电导率和/或高介电常数的半导体薄膜进行选择性快速加热的新技术。为了将该技术应用于非晶硅的结晶，由于非晶硅既不具有高导电性也不具有高介电常数，因此将Ni、Pt和PtPd等金属选择性地沉积在非晶层上。本文将表明，等离子体辐照的升温速率和可达到的最高温度取决于大气的气体种类、气体压力和金属种类。采用分子束沉积法在石英衬底上沉积了100 nm的非晶硅膜，并在非晶膜上选择性地形成了Ni层。然后，将样品放入真空室，用频率为2.45GH_z，输出功率为1kW的微波等离子体在一定的气体气氛中辐照。等离子体辐照后，样品的整个Si区颜色由红色变为黄色，表明非晶膜转变为结晶膜。横断面STEM观察表明，样品在等离子体辐照下多晶化。在辐照过程中，Ni膜部分区域蒸发，表明Ni的温度至少升高到1000℃。等离子体辐照后，距镍层边缘1mm处的Si区温度立即升高。温度取决于压力，在150P_a左右可达到900℃的最高温度。Si区域的最高温度是氦、氮和氩以及氢压力的函数。除氢外，所有压力区的最高温度均在400℃，与气体种类无关，这表明与氢有关的自由基和原子等不稳定的激发态物质也参与了加热过程。少

We have developed a new technique which enables the selective and rapid heating of semiconductor films with the high conductivity and/or high dielectric constant by using microwave plasma irradiation. In order to apply the technique to crystallization of amorphous Si, a metal such as Ni, Pt and PtPd is deposited selectively on amorphous layers, since amorphous Si has neither high conductivity nor high dielectric constant. It will be shown in this present that the temperature ramping rate and attainable highest temperature by plasma irradiation depend on gas species of the atmosphere, gas pressure and metal species.A 100 nm amorphous silicon film was deposited on a quartz substrate by molecular beam deposition method, and a Ni layer was selectively formed on the amorphous film. Then, the sample was put in a vacuum chamber and irradiated in some gas atmosphere by microwave plasma with the frequency of 2.45GH_z and the output electric power of 1kW.The color of the entire Si region of the … More sample was changed from red to yellow by plasma irradiation, which means that the amorphous film changes to crystalline one. The cross-sectional STEM observation shows that the sample is poly-crystallized by plasma irradiation. During irradiation, some region of Ni film evaporated, which implies that the temperature of Ni increased up to at least 1000℃.The temperature of the Si region, which is 1 mm apart from the edge of the nickel layer, increases immediately after the plasma irradiation in the hydrogen ambient. The temperature depends on the pressure, and the highest temperature of 900℃ is achieved at about 150P_a.The highest temperatures of the Si regions are obtained as functions of the pressures of helium, nitrogen and argon in addition to hydrogen. The highest temperatures are at most 400℃ in all pressure regions independently of gas species except hydrogen, which suggests that the unstable and excited hydrogen-related species such as radicals and atoms also participate in the heating process. Less