**2.3 Photolithography process**

The photo-mask patterns were designed by CAD. Photolithography is a process of using light to transfer a geometric pattern from a photo-mask to a photo-resist on a 430BA SS substrate. The steps involved in the photolithographic process are metal cleaning, barrier layer formation, photo-resist application, soft baking, mask alignment, exposure and development, and hard-baking. After the photolithographic process, the 430BA SS substrate is etched by aqua regia (HNO3 : HCl=1 : 3). There are two types of photo-mask patterns: one, different diameters but with the same interval, and two, the same diameters but with a different interval. They are both designed to study light trapping for the application of thin film solar cells. Finally, silver coating technique by e-beam evaporation was used to improve the TR and DR rates of the 430BA SS substrate.

Enhanced Diffuse Reflection of Light by

Fig. 5. The experimental flow charts of etching process.

Fig. 6. The total reflection and diffuse reflection measured by integrating Sphere.

of thin-films solar cells.

Using a Periodically Textured Stainless Steel Substrate 43

Integrating Sphere is used for diffuse reflectance measurements. Reflectance measurements include total and diffuse reflectance at an incident angle of 8 degrees. Specular reflectance can be calculated from the total and diffuse reflectance measurements. The TR and DR rate of a textured substrate are important indexes when increasing the light trapping efficiency
