Nano tech : Photolithography Process

Photolithography Process

Cleaning Process 

Photolithography is a patterning process in which a photosensitive polymer is selectively exposed to light through a mask, leaving a latent image in the polymer that can then be selectively dissolved to provide patterned access to an underlying substrate.

 In photolithography process clean the substrate or wafer is important. There create a lot of circumstance e.g. unwanted material or process can't occur and so on. Etching is the process of selectively removing material by chemically, physically or electrolytic system. There are three ways to clean the substrate.

Chemical clean :

In the photolithography process, firstly substrate immerse in chemical solution so that reactive and chemical element can be removed. There have some ways to clean the substrate using chemical are given below :

 Piranha mixture 

   In this process the solution of mixture is 3:1 to 7:1. It means 3 part of  Sulfuric Acid, H₂SO₄ & 1 part of Hydrogen Peroxide, H₂O₂. It removes organics & metals from the substrate. 

 Standard cleaning 1: SC1

In this process, the solution of the mixture is Ammonium Hydroxide, NH₄OH; Hydrogen Peroxide, H₂O₂ & H₂O. It removes organics & particles from surface.

Standard cleaning 2: SC2

The solution of the mixture is Hydrochloric Acid, HCl; Hydrogen Peroxide, H₂O₂ & H₂O. It removes metallic residues from the surface.

 HF or BOE: 

Hydrofluoric Acid or Buffer oxide etching is the solution of Hydrofluoric Acid, HF; Buffer & H₂O. It removes native oxide, SiO₂ .

 Rinse clean :

 In this process, the substrate immerse in water to clean the chemical component.

 Dry :

In this process, the substrate removes water from it's surface.