반도체 공정 #8 Deposition - ALD (Atomic Layer Deposition)

ALD(Atomic Layer Deposition)

 

원자층을 번갈아가며 한층씩 증착하는 구조.

반응 기체들이 자기 제한적 반응을 진행한다. (Self-limiting reaction) = 반응물과 표면에서만 반응이 일어나고 반응물 간의 반응은 일어나지 않는다.

화학 흡착(Chemisorption), 표면 반응(Surface Reaction), 부산물 탈착(by-product Desobtion)의 반응을 기본으로 한다.

 

ALD - Self limiting Reaction

 

ALD Process

 

1. Put gas A in to the chamber - Reaction - purge gas A

 

2. Put gas B in to the chamber - Reaction - purge gas B

 

Each process is independent!!

Purge: After reaction gas & W/F to thin film process,

remove remain gas

 

 

 

ALD 장점.

 

1. Good Step Coverage: Because of Self - limiting Reaction (Good for high aspect ratio)

 

2. Possible to low temperture process: Don't need to outdoor energy to make by-product.

 

3. Utility to adjust thick: ALD process is one layer depo so, possible to very thin thick deposition.

 

4. Good film quality & process margin: The reason of the Self-limiting proess, impurity is good (low particle)

and low possibility to make void (Good film quality)

 

ALD 단점.

 

1. Hard for supply precusor: it doesn't contain precusor process so, only can use good react precusor

(also, need to supply enough amount of precusor)

 

2. if react gas and precusor put together in to the chamber, it will lost characteristic of ALD

 

3. Low velocity process: Long time process (Bad for large scale material)

 

ALD 적용분야

 

1. Gate dielecttric

2. Capacitor (DRAM)

3. Gate spacer - Use possible to low temperature ALD blocking to ion diffusion 

4. Metal depo: Metal barrier, 

 

 

Compare to three depo: PVD, CVD, ALD

 

 

DEPO 끗!!! 이제 metalization으로 들어가봐야지~~~~