Methods and devices for ultra smooth substrate for use in thin film solar cell manufacturing

A substrate smoothening method comprising:

• providing a metal substrate with a front surface having substantially flat surface portions and protruded surface portions;
• rough finishing the metal substrate to have an Ra in the range of about 0.2 to about 0.5 microns;
• removing the some of the protruded surface portions by etching the some of the protruded surface portions to form exposed substrate sections of the metal substrate, wherein the metal substrate has a hardness that prevents smoothening to a desired finish;
• flowing a second material into depressed surface portions of the substrate to build up a new top surface having a roughness of about 0.05 microns or smoother;
• depositing a contact layer on the second material.