The etching process can be physical and/or chemical, wet or dry, and isotropic or anisotropic. All these etch process variations can be used during solar cell processing. Figure 1: Etching processes divided according to their physical, chemical, or combined (physical and chemical) nature.
1. INTRODUCTION Although in semiconductor industry plasma etching has been a well established technology for more than 15 years it is not widely used in solar cell production. Only edge isolation is performed by plasma etching using barrel type reactors in some fabrication lines.
Plasma etching processes for saw damage and phosphorous glass removal are developed reaching high etch rates and high selectivities fulfilling the requirements for high throughput fabrication in solar cell production lines.
The etch rate of alkaline etch solutions are generally lower than at he etch rates of acidic etching solutions. Consequently, alkaline etch processes are often performed at high temperatures (70-80 °C). Alkaline etching is typically anisotropic with an etch rate of 1-2 µm/min for low concentration (1-5% v/v) alkaline solutions.
high etch rate. There are two other types of etch technologies, ion-enhanced energy driven (also known as reactive ion-etching) and ion-enhanced inhibitor. The first combines the properties of physical and chemical etching by using a chemically reactive plasma. Common applications are edge isolation and surface texturing.
Consequently, alkaline etch processes are often performed at high temperatures (70-80 °C). Alkaline etching is typically anisotropic with an etch rate of 1-2 µm/min for low concentration (1-5% v/v) alkaline solutions. This type of etching is used to texture monocrystalline silicon.