전해 이온화를 이용한 CMP (EI-CMP) 에서의 재료제거 효율 향상에 관한 연구 = A Study on Improvement of Material Removal Efficiency in Electrolytically Ionized CMP (EI-CMP)

국문 초록 (Abstract)

환경오염에 관한 국제적인 관심이 높아지면서 여러 환경 규제가 생기
면서 기존의 산업 구조를 압박하고 있다. 반도체 산업에서도 반도체 공
정에서 발생하는 폐액을 비롯해 여러 환경에 영향을 미치는 요인으로 인
해서 규제를 받고 있다. 이런 규제 속에서 4차 산업을 비롯해 여러 산업
에서 반도체에 대한 수요가 급증하며 공급에 차질이 발생하고 있다. 이
를 해결하고자 친환경적 반도체 공정에 대한 여러 연구가 진행되고 있
다. 연마입자를 포함하지 않은 슬러리를 사용한 CMP, Abrasive-free C
MP는 친환경적 반도체 공정 중 하나로 거론되고 있다. 환경오염에 큰
요인으로 거론되는 연마입자를 포함하지 않아 환경오염에 대한 부담은
감소하였지만, 낮은 연마효율로 인해 가공 시간의 증가와 그로 인해 발
생하는 폐액의 양이 증가하는 문제점을 가지고 있다. 본 연구에서는 Abr
asive-free CMP의 낮은 연마효율을 개선하고자 슬러리의 전해 이온화
방식을 접목하여 CMP의 화학적 연마의 효율을 증가시키고자 한다.
본 연구에서는 구리 웨이퍼와 사파이어 웨이퍼를 사용하여 CMP를 진
행하였다. 구리 CMP에서는 Abrasive-free CMP 방식으로 실험을 진행
하였고, 사파이어 CMP에서는 기존의 CMP 방식에서 슬러리의 연마입자
함량을 줄이고 과산화수소(H2O2)와 이산화 타이타늄(TiO2)을 추가하여
실험을 진행하였다. 구리 CMP에서 사용된 Abrasive-free 슬러리는 산화
제인 과산화수소(H2O2)와 착화제인 구연산(Citric Acid) 그리고 부식억제
제인 벤조트리아졸(BTA)로 구성된 초순수(DI-Water) 기반으로 제조하
였다. 구리 CMP 실험에서는 산화제와 착화제의 함량을 조절하거나 슬
러리의 전해 이온화를 위한 AC 전압을 조절하여 구리 웨이퍼의 두께를
통한 재료제거율(MRR)을 비교하였다. 사파이어 CMP에서는 기존의 CM
P 방식과 슬러리의 전해 이온화 방식, 슬러리에 용존산소(DO)를 증가시
켜 슬러리의 전해 이온화 방식 그리고 앞선 방식에서 연마패드와 슬러리
에 자외선(UV) 조사를 추가한 방식을 통해 서로의 CMP 방식에서 얻은
사파이어 웨이퍼 무게를 비교하여 얻은 재료제거율(MRR)을 비교하였다.
실험결과, 구리 CMP에서 산화제의 함량이 증가한 경우와 착화제의 함
량이 증가한 경우 그리고 슬러리의 전해 이온화를 위한 AC 전압이 증가
한 경우 구리 웨이퍼의 재료제거율(MRR)이 증가하는 경향을 보였다. 이
는 구리 웨이퍼 표면의 부식의 증가로 인한 화학적 연마의 효율이 증가
한 것으로 판단된다. 사파이어 CMP에서 기존의 방식에서 슬러리의 전해
이온화는 기존의 방식과 재료제거율(MRR)의 차이가 미미하였다. 슬러리
의 전해 이온화 방식에서 슬러리 탱크에 산소를 투입하여 용존산소(DO)
를 증가한 경우는 슬러리의 전해 이온화 방식보다 재료제거율(MRR)이
증가하는 경향을 보이나, 슬러리 탱크 내에 산소가 공기 중으로 비산하여
용존산소(DO) 조절의 어려움이라는 문제점이 발생하였다. 앞선 방식에서
슬러리의 구성요소에 이산화 타이타늄(TiO2)을 추가한 후, 슬러리와 연마
패드에 자외선(UV)을 조사한 방식에서는 기존의 사파이어 CMP 방식의
재료제거율(MRR)보다 약 29.9 (%) 증가한 경향을 보였다. 이는 슬러리의
전해 이온화와 슬러리의 용존산소(DO) 증가 그리고 광촉매인 이산화 타
이타늄(TiO2)을 활용한 자외선 조사로 사파이어 웨이퍼 표면의 부식이
활성화되어 화학적 연마의 효율이 증가한 것으로 판단된다. 이를 통해 기
계적 연마의 어려움이 있는 구리 웨이퍼와 사파이어 웨이퍼의 친환경적
CMP의 연마효율 개선을 기대할 수 있을 거로 판단된다.

다국어 초록 (Multilingual Abstract)

As international interest in environmental pollution is growing,
various environmental regulations have been put in place, putting
pressure on the existing industrial structure. The semiconductor
industry is also being regulated due to factors affecting the
environment, including waste liquid generated from the semiconductor
process. Under these regulations, the demand for semiconductors in
various industries including the 4th industry is rapidly increasing,
causing supply disruptions. In order to solve this problem, various
studies on eco-friendly semiconductor processes are being conducted.
CMP using a slurry that does not contain abrasive particles and
abrasive-free CMP are being discussed as one of the eco-friendly
semiconductor processes. The burden on environmental pollution is
reduced because it does not contain abrasive particles, which are
mentioned as a major factor in environmental pollution. In this study,
to improve the low polishing efficiency of abrasive-free CMP, the
electrolytic ionization method of the slurry is applied to increase the
chemical polishing efficiency of CMP.
In this study, CMP was performed using copper wafers and
sapphire wafers. In copper CMP, an abrasive-free CMP method was
used, and in sapphire CMP, the abrasive grain content was reduced
and hydrogen peroxide (H2O2) and titanium dioxide (TiO2) were added
in the conventional CMP method. The abrasive-free slurry used in
copper CMP was prepared based on DI-Water consisting of hydrogen
peroxide (H2O2) as an oxidizing agent, Citric Acid as a complexing
agent, and benzotriazole (BTA) as a corrosion inhibitor. In the copper
CMP experiment, the material removal rate (MRR) through the
thickness of the copper wafer was compared by controlling the
content of the oxidizing agent and the complexing agent or by
adjusting the AC voltage for electrolytic ionization of the slurry. In
sapphire CMP, each other through the conventional CMP method, the
electrolytic ionization method of the slurry, the electrolytic ionization
method of the slurry by increasing dissolved oxygen (DO) in the
slurry, and the method adding ultraviolet (UV) irradiation to the
polishing pad and the slurry in the previous method. The material
removal rate (MRR) obtained by comparing the thickness of the
sapphire wafer obtained by the CMP method of
As a result of the experiment, the material removal rate (MRR) of
copper wafers tended to increase when the content of the oxidizing
agent increased in copper CMP, when the content of the complexing
agent increased, and when the AC voltage for electrolytic ionization
of the slurry increased. It is considered that the efficiency of chemical
polishing is increased due to the increase in corrosion of the copper
wafer surface. In sapphire CMP, the difference in material removal
rate (MRR) from the conventional method for electrolytic ionization of
the slurry in the conventional method was insignificant. In the case
of increasing the dissolved oxygen (DO) by adding oxygen to the
slurry tank in the electrolytic ionization method of the slurry, the
material removal rate (MRR) tends to increase compared to the
electrolytic ionization method of the slurry. There was a problem of
difficulty in controlling oxygen (DO). In the method in which titanium
dioxide (TiO2) was added to the components of the slurry in the
previous method and then ultraviolet (UV) was irradiated to the
slurry and the polishing pad, the material removal rate (MRR) of the
conventional sapphire CMP method increased by about 29.9 (%)
showed It is considered that the electrolytic ionization of the slurry,
increase in dissolved oxygen (DO) in the slurry, and ultraviolet
irradiation using titanium dioxide (TiO2), a photocatalyst, activate the
corrosion of the sapphire wafer surface, thereby increasing the
efficiency of chemical polishing. This is expected to improve the
polishing efficiency of environmentally friendly CMP of copper wafers
and sapphire wafers, which are difficult to mechanically polish.

목차 (Table of Contents)

• Ⅰ. 서 론············································································································· 1
• 1.1 연구의 배경······························································································· 1
• 1.2 연구의 목적······························································································· 6
• 1.3 논문의 구성····························································································· 10
• Ⅱ. 실험 조건·································································································· 11
• 2.1 실험 장치의 구성··················································································· 11
• 2.2 전기화학적 분석 ····················································································· 20
• 2.3 CMP 실험 조건····················································································· 23
• 2.4 측정 조건 ································································································· 26
• Ⅲ. 실험 결과 및 고찰················································································· 32
• 3.1 구리 EAF-CMP 적용 연구································································· 32
• 3.1.1 전기화학 분석················································································ 32
• 3.1.2 재료제거 특성················································································ 37
• 3.1.2.1 전압의 영향 ········································································· 37
• 3.1.2.2 과산화수소의 영향 ····························································· 40
• 3.1.2.3 구연산의 영향····································································· 43
• 3.2 사파이어 EI-CMP 적용 및 재료제거율 향상 연구······················· 46
• 3.2.1 사파이어 EI-CMP 적용 연구···················································· 46
• 3.2.2 사파이어 EI-CMP에서 재료제거율 향상 연구······················ 48
• 3.2.2.1 용존산소를 이용한 방법 ··················································· 48
• 3.2.2.2 용존산소와 UV를 이용한 방법······································ 50
• Ⅳ. 결론············································································································· 56
• Reference ········································································································ 59
• Abstract ·········································································································· 65