Asher / Ashing

Semiconductor equipment : asher n : a machine used to remove resist from substrates. [SEMATECH] 

Semiconductor process :  ashing  n : the operation of removing resist 
from a substrate by oxidation; a reaction of resist with oxygen to remove the resist from the 
substrate.
 [SEMATECH] 

A Lecture on Ashing for the Non-Professional-By PSK Tech Inc 

1. A summary of Semiconductors.

A semiconductor is a material that falls somewhere between a conductor and a non-conductor.
Though it cannot transfer electricity or light, when heat, light, or impurities are added,
electricity can be transferred and this amount can even be controlled. Semiconductor
 manufacturing is seperated into three phases: Fabrication, Assembly, and Testing. 
A wafer, a raw material, is then subjected to these phases, After repeatedly applying 
steps such as diffusion, photolithography, etching, and thin-filming to incorporate the 
use of a wafer, we have a new, processed wafer. 

2. Ashing(Photoresistant Strip)

During the semiconductor manufacturing process, we take a mask which contains the desired wafer pattern,
 and let light pass through it. Next, we make the pattern photoresistant, calling the process 
"photolithography." We call "ashing" (Photoresistant Strip:PR Strip) the process which removes the 
photoresistant used in photolithography. Ashing has a close relation to the photoresistant process.
 Ashing can be devided into dry ashing and wet ashing. In the wet ashing process, a dilution of
 sulferic acid and hydrogen peroxide is used to removing the photoresistant, while dry ashing uses 
the exhaust from oxygen plasma, or ozone. 


2.1. Plasma Ashing.
Oxygen plasma ashing is well-known to remove photoresistant through CO2 exhaust formed during a 
chemical reaction when O2 plasma impurities meet radical oxygen and the photoresistant. 

2.2. Ozone Ashing.
In Ozone ashing, a single method is primarily used since the wafer needs to be heated to a 
temperature of 250 degrees celcius. Since Ozone reacting temperature cannot usually supply 
a useful ashing rate, N2, and N2 mixtures are added as catalysts to increase the ashing
 rate when ozone hits an O2 particle and O2 atom. 

3. Ashing Equipment Classification.
* Ozone Asher.   
* Plasma Asher. -Batch-mode (1)Counter-axial Electrode Asher.
(2)Co-axial Electrode Asher  
 -Single mode (1)RF Down Flow Asher.
(2)”Ķi-Wave Plasma Asher.
(3)High-density Plasma Asher  

semiconductor equipment : asher : manufacturer