Mathematical modeling based on contact mechanism due to elastic and plastic deformation of pad asperities during CMP

HyunJinKim,신소민,Dasol Lee,정해도 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1

Technologies in semiconductor industry have been developed into a threedimensional multilayer wiring for high integration of devices. Chemical mechanical planarization (CMP) process is one of the key technologies for achieving multilayer wiring, which enables global planarization. In addition, highly integrated devices can be realized by increasing the depth of focus in the photolithography process. However, in the inter-layer dielectric (ILD) CMP of the transistor, the uppermost oxide layer has the step due to the arrangement of the devices. The ideal material removal mechanism is to gradually remove materials from the top of the step height which allows for global planarization. However, in the CMP of the patterned wafers, simultaneous polishing of the upper and lower layers occurs when the step height reaches a certain height. This means that the polishing is strongly dependent on the structural characteristics of the pattern. Especially, the difference in the material removal rate depending on the pattern density acts as a constraint in terms of device layout. Therefore, it is essential to develop an accurate prediction model of material removal rate as a function of pattern density, size and arrangement. This study aims to define the mathematical planarization model according to contact mode between a polishing pad and patterned wafer. Considering that the real contact area between the actual polishing pad and the wafer is about 1 %, the mathematical model is derived based on the microscopic deformation of the pad asperities, not the macroscopic deformation of the bulk pad. Finally, we describe the verification between the theoretical material removal rate model and step height reduction and the actual CMP results. The root mean square error of the upper layer material rate, the lower material removal rate, and the step height reduction were 24.59 nm/min, 22.03 nm/min and 22.6 nm, respectively. Compared with the previous studies, the new model of this study improved the error by up to 50.9 %.

Highly Selective Polishing Rate Between a Tungsten Film and a Silicon-Dioxide Film by Using a Malic-Acid Selectivity Agent in Tungsten-Film Chemical-Mechanical Planarization

Seo Eun-Bin,Park Jea-Gun,Bae Jae-Young,Park Jin-Hyung 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.12

For achieving a highly selective polishing rate between a tungsten (W) film and a silicon-dioxide (SiO2) film in W chemical-mechanical planarization (CMP), we designed W-film CMP slurry by mixing a small-molecule having two carboxylic functional groups (i.e., malic acid) as a selectivity agent. The selectivity was principally controlled by the malic acid concentration: it rapidly increased with increasing malic acid concentration in the W-film CMP slurry, and a W-film polishing rate:SiO2-film polishing rate of >100:1 was achieved. We found that the selectivity was mainly determined by the chemical properties, such as the corrosion and the chemical reaction between the films and malic acid rather than by the mechanical property, i.e., the electrostatic force between the ZrO2 abrasive and the films.

pH level 및 slurry 입도가 langasite wafer의 chemical mechanical planarization에 미치는 영향

조현,Cho Hyun 한국결정성장학회 2005 韓國結晶成長學會誌 Vol.15 No.1

Effects of pH level and slurry particle size on material removal rate and planarization of langasite single crystal wafer have been examined. Higher material removal rate was obtained with lower pH level slurries while the planarization was found to be determined by average particle size of colloidal silica slurries. Slurries containing 0.045 ㎛ amorphous silica particles showed the best polishing effect without any scratches on the surface. Effective particle number has a strong effect on the surface planarization and the removal rate, so that the lower effective particle numbers produced low removal rate but the better planarization results. Langasite 단결정 wafer의 chemical mechanical planarization 공정에서 pH level 및 slurry 입도가 가공속도 및 평탄화도에 미치는 영향을 조사하였다. 낮은 pH level 조건하에서 더 높은 가공속도 값이 얻어진 반면에 평탄화도는 colloidal silica slurry의 평균입경에 의해 좌우됨을 확인하였다. 0.045 ㎛의 비정질 silica 입자를 함유한 슬러리를 사용하였을 때 표면에 잔류 scratch 형성이 없이 가장 좋은 가공성을 확보할 수 있었다. 가공속도와 평탄화도는 effective particle number에 대한 강한 의존성을 나타내었으며, effective particle number가 낮은 조건하에서 가공속도는 더 낮은 분포를 나타내었으나 평탄화도는 더 우수한 경향성을 확인하였다.

Experimental and Numerical Analysis of A Novel Ceria Based Abrasive Slurry for Interlayer Dielectric Chemical Mechanical Planarization

Yun Zhuang,Leonard Borucki,Ara Philipossian,Eric Dien,Mohamed Ennahali,George Michel,Bernard Laborie,Yun Zhuang,Manish Keswani,Daniel Rosales-Yeomans,Hyosang Lee,Ara Philipossian 한국전기전자재료학회 2007 Transactions on Electrical and Electronic Material Vol.8 No.2

In this study, a novel slurry containing ceria as the abrasive particles was analyzed in terms of its frictional, thermal and kinetic attributes for interlayer dielectric (ILD) CMP application. The novel slurry was used to polish 200-mm blanket ILD wafers on an IC1000TM K-groove pad with in-situ conditioning. Polishing pressures ranged from 1 to 5 PSI and the sliding velocity ranged from 0.5 to 1.5 m/s. Shear force and pad temperature were measured in real time during the polishing process. The frictional analysis indicated that boundary lubrication was the dominant tribological mechanism. The measured average pad leading edge temperature increased from 26.4 to 38.4 °C with the increase in polishing power. The ILD removal rate also increased with the polishing power, ranging from 400 to 4000 A/min. The ILD removal rate deviated from Prestonian behavior at the highest p´V polishing condition and exhibited a strong correlation with the measured average pad leading edge temperature. A modified two-step Langmuir-Hinshelwood kinetic model was used to simulate the ILD removal rate. In this model, transient flash heating temperature is assumed to dominate the chemical reaction temperature. The model successfully captured the variable removal rate behavior at the highest p´V polishing condition and indicates that the polishing process was mechanical limited in the low p´V polishing region and became chemically and mechanically balanced with increasing polishing power.

패드 마모 균일성 향상을 위한 CMP 컨디셔닝 시스템설계 변수 연구

박병훈,박범영,전언찬,이현섭 한국트라이볼로지학회 2022 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.38 No.1

Chemical-mechanical polishing (CMP) process is a semiconductor process that planarizes a wafer surface using mechanical friction between a polishing pad and a substrate surface during a specific chemical reaction. During the CMP process, polishing pad conditioning is applied to prevent the rapid degradation of the polishing quality caused by polishing pad glazing through repeated material removal processes. However, during the conditioning process, uneven wear on the polishing pad is inevitable because the disk on which diamond particles are electrodeposited is used. Therefore, the abrasion of the polishing pad should be considered not only for the variables during the conditioning process but also when designing the CMP conditioning system. In this study, three design variables of the conditioning system were analyzed, and the effect on the pad wear profile during conditioning was investigated. The three design variables considered in this study were the length of the conditioner arm, diameter of the conditioner disk, and distance between centers. The Taguchi method was used for the experimental design. The effect of the three design variables on pad wear and uniformity was assessed, and new variables used in conditioning system design were proposed.

앙상블 모델을 통한 화학적 기계연마 기술 연마율 예측

전병주(Byungjoo Jeon),하종문(Jong Moon Ha),이준민(Junmin Lee),박찬희(Chanhee Park),김수지(Su Jii Kim),윤병동(Byeng Dong Youn) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

Chemical-Mechanical planarization (CMP) is a process to flatten a surface of a substrate with combination of chemical and mechanical effect. For a successful CMP process, various operating parameters (e.g. rotating speed and pressure) of CMP should be optimized. However, relationship between the operating parameters and the performance of the CMP process has not been fully identified. To address this challenge, this paper introduces a model that estimates the removal rate of Chemical-Mechanical planarization (CMP) process which is known to represent performance of the CMP machine using various time-series operating parameters. First, 135 features were extracted from the time-series variables for physical representation of the polishing process. Second, Gaussian process (i.e. Kriging) and regression tree were employed to estimate the removal rate of the CMP process. To avoid the overfitting problems, various feature selection schemes were used to define candidates for the best feature subsets. Finally, ensemble regression model was developed to integrate the regression models with the feature subsets.

Chemical mechanical planarization mechanism of epitaxially grown Ge-film for sequential integrating 3D-structured transistor cells

Bae Jae-Young,Han Man-Hyup,Shim Tae-Hun,Park Jea-Gun 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.12

Recently, three-dimensional (3D) integration technology has been actively pursued as an alternative solution to overcome the signifcant issues such as the increase in resistance capacitance (RC) delay and power consumption in fabricating twodimensional complementary metal oxide semiconductor feld emission transistor of less than 10 nm node. To integrate the 3D structure of a transistor cell, a high Ge-flm polishing rate is required to polish the facet crystalline Ge while fabricating the Ge channel or germanium on insulator (GOI) substrate through recrystallization and epitaxial growth processes in the sequential 3D integration technology. The analysis of the chemical composition of the Ge surface and Ge-flm CMP in the neutral and alkaline regions from pH 7 to 11 using a slurry containing colloidal silica abrasive and H2O2 revealed that the formation of oxidation layer (GeO and GeO2) in the polished Ge-flm surface linearly increased when the pH of the slurry was between 7 and 10 and slightly decreased when it was higher than 10. These results indicate that the main CMP mechanism is based on the formation of GeO and GeO2 owing to the oxidation reaction between dissolved oxygen and the Ge-flm surface in the neutral and alkaline pH regions, rather than the dissolution mechanism associated with the Ge-flm CMP mechanism. Signifcantly, a very high Ge-flm polishing rate of 623.9 nm/min was achieved at a pH of 10, at which maximum number of layers of GeO and GeO2 were formed on the Ge-flm surface.

CeO₂ 슬러리에서 Glycine의 흡착이 질화규소 박막의 연마특성에 미치는 영향

김태은,임건자,이종호,김주선,이해원,임대순 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.1

수용액 내에서 질화물 박막의 산화저항성 흡착 피막의 형성을 확인하기 위하여 Si$_3$N$_4$분말 표면의 glycine 흡착 거동을 조사하였다. 염기성분위기에서 glycine은 Si$_3$N$_4$ 분말 표면에 포화 흡착되었으며 이러한 흡착거동은 Si$_3$N$_4$ 박막의 경우에도 동일하게 일어날 것으로 예상되었다. Glycine을 첨가한 CeO$_2$ 슬러리를 제조하고 PH에 따른 Si$_3$N$_4$와 SiO$_2$ 박막의 연마시험을 수행하여 연마율은 감소하고 선택비는 증가하는 것을 확인하였다. 실험에서 얻은 최대 선택비는 pH=12에서 35 이상이었다. 이는 염기성 분위기에서 glycine이 해리하여 막 표면에 화학흡착하고 산화와 용해를 억제함으로써 연마율을 낮추고 선택비 향상에 기여하였기 때문으로 판단된다. 아미노산 계열의 첨가제를 CeO$_2$계 CMP용 슬러리에 적용하는 경우 산화물/질화물 박막의 선택비를 향상시키는데 효과적임을 확인하였다. Adsorption of glycine on$Si_3N_4$powder surface has been investigated, which is supposed to enhance the formation of passive layer inhibiting oxidation in aqueous solution. In the basic solution, multinuclear surface complexing between Si and dissociated ligands was responsible for the saturated adsorption of glycine. In addition, $CeO_2$-based CMP slurry containing glycine was manufactured and then applied to planarize$SiO_2$and$Si_3N_4$thin film. Owing to the passivation by glycine, the removal rates, Rh, were decreased, however, the selectivities, RE(SiO$_2$)/RR($Si_3N_4$), increased and showed maximum at pH=12. The suppressed oxidation and dissolution by adsorbate were correlated with the dissociation behavior of glycine at different pH and subsequent chemical adsorption.

Self-stopping slurry for planarizing extremely high surface film topography in nanoscale semiconductor devices

Son Young-Hye,Park Jea-Gun,Choo Byoung-Kwon,Kang Seung-bae 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.1

In this study, a novel chemical–mechanical planarization (CMP) slurry that can perform self-stop polishing was designed. The essential aspects for self-stop polishing are precise design of a nonionic polymer type, molecular weight, and molecular concentration of a self-stopping chemical agent. A good example is polyvinylpyrrolidone (PVP) with a molecular weight of 1300 k and molecular concentration of 0.3 wt%. In this chemical design, the adsorption of a polymer hindrance layer on the surface film topography during CMP can become sufficient under self-stop conditions such as a specific polishing time (e.g., 4 min). The self-stop polishing mechanism is associated with the presence of a relative local pressure difference on the surface film topography. The proper adsorption of the polymer hindrance layer on the surface topography can achieve a uniform relative local pressure distribution globally, and the film polishing rate can achieve adequate planarization of the surface film topography.

CMP 컨디셔너의 다이아몬드 입자 모양이 연마 패드 표면 형상 제어에 미치는 영향

이동환,이기훈,정선호,김형재,조한철,정해도 한국트라이볼로지학회 2019 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.35 No.6

Conditioning is a process involving pad surface scraping by a moving metallic disk that is electrodeposited with diamond abrasives. It is an indispensable process in chemical-mechanical planarization, which regulates the pad roughness by removing the surface residues. Additionally, conditioning maintains the material removal rates and increases the pad lifetime. As the conditioning continues, the pad profile becomes unevenly to be deformed, which causes poor polishing quality. Simulation calculates the density at which the diamond abrasives on the conditioner scratch the unit area on the pad. It can predict the profile deformation through the control of conditioner dwell time. Previously, this effect of the diamond shape on conditioning has been investigated with regard to microscopic areas, such as surface roughness, rather than global pad-profile deformation. In this study, the effect of diamond shape on the pad profile is evaluated by comparing the simulated and experimental conditioning using two conditioners: a) random-shaped abrasive conditioner (RSC) and b) uniform-shaped abrasive conditioner (USC). Consequently, it is confirmed that the USC is incapable of controlling the pad profile, which is consistent with the simulation results.