Tae-Young Kwon

Effect of Sodium Periodate in Alumina-Based Slurry on Ru CMP for Metal–Insulator–Metal Capacitor

In this study, a ruthenium (Ru) chemical mechanical planarization (CMP) slurry was developed and characterized to fabricate Ru bottom electrodes in capacitor structures. Sodium periodate (NaIO 4 ) was chosen as both the oxidant and etchant due to its strong oxidizing power. The effect of NaIO 4 on Ru etching and polishing behaviors was investigated as a function of its concentration and polishing condition. The largest removal rate of 70 nm/min was obtained in a slurry of 0.1 M NaIO 4 and 2 wt % alumina particles at pH 9 and a polishing pressure of 4 psi. Planarization and isolation of each capacitor was successfully performed with the developed Ru slurry.

Investigation of Source-Based Scratch Formation During Oxide Chemical Mechanical Planarization

The formation of scratches on silicon dioxide surfaces during chemical mechanical planarization in the semiconductor manufacturing process is a significant concern, as it adversely affects yield and reliability. In this study, scratch formation during CMP processing of the oxide surface was examined. The shapes of the resulting scratches were classified into three types: chatter mark type, line type, and rolling type. Chatter mark types were further subdivided into line chatter, broken chatter, and group chatter based on the shape. The effect of three different scratch sources (viz., pad debris, dried particles, and diamond particles) on scratch formation was comprehensively investigated. Chatter-mark-type scratches are predominant in the presence of agglomerated particles and pad debris. Group chatter marks are caused by the addition of pad debris. Unique scratch formation was observed on the wafer with different scratch sources. In particular, multiple-line-type scratches were observed in the presence of diamond particles.

Effect of Alkaline pH on Polishing and Etching of Single and Polycrystalline Silicon

In this paper, the polishing and etching behavior of single and polycrystalline silicon were studied. Prior to chemical mechanical polishing (CMP) process, the surfaces were treated with dilute hydrofluoric acid (DHF) to remove native oxides. The surface analysis shows that the poly contains trace amount of oxygen even after DHF treatment. The static and dynamic etch rates, and removal rates were measured as a function of slurry pH. The single silicon showed a higher static etch rate than the poly. After static etch rate measurements, poly showed higher surface roughness and more hydrophilic which indicates that the surface of poly is different from single crystal silicon. The friction force between pad and substrate and pad temperature was also measured as a function of pH during polishing in order to get more understanding of polishing process. At all the pH values being investigated, poly showed lower dynamic and removal rates, higher friction force and higher temperature. This indicates that the removal of poly in CMP is predominantly by mechanical actions. Also, these results, suggest a mechanism in which the oxygen present in the poly grain boundaries strongly influences the etching and removal mechanism.

Effect of Silicon Dioxide Hardness on Scratches in Interlevel Dielectric Chemical–Mechanical Polishing

In the silicon dioxide chemical–mechanical polishing (CMP) process, one of the most challenging issues is the formation of defects such as scratches. In this study, scratch formation behavior and CMP performance were evaluated on high-density plasma oxide (HDP), plasma-enhanced tetraethylorthosilicate (PETEOS), and borophosphosilicate glass (BPSG) wafers. To evaluate the number of scratches after the CMP process, contaminated abrasive particles were removed using an optimized post-CMP cleaning process consisting of scrubber cleaning and dilute SC1 megasonic cleaning. The oxide wafers were then treated with dilute hydrogen fluoride (HF) in order to improve the visibility of the generated scratches. The number and shape of the scratches were investigated as a function of oxide film hardness. The results show that a decrease in film hardness correlates with an increase in the number of scratches. Three different types of scratches (chatter marks, line, and rolling) were observed on the oxide surfaces. The dominant scratch shape on all three oxide films was chatter mark–type scratches. This could be attributed to the stick–slip phenomenon. However, the overall fraction of chatter marks compared to other types of scratches (especially line scratches) was proportional to the film hardness. It was also found that scratch depth was strongly influenced by the polishing pressure during CMP. The results clearly show that the mechanical pro- perties of the surface play a critical role in scratch generation.

Hybrid Cleaning Technology for Enhanced Post-Cu/Low-Dielectric Constant Chemical Mechanical Planarization Cleaning Performance

During chemical mechanical planarization (CMP), a copper/low-k surface is often contaminated by abrasive particles, organic materials and other additives. These contaminants need to be removed in the subsequent cleaning process with minimum material loss. In this study, a dilute amine-based alkaline cleaning solution is used along with physical force in the form of megasonic energy to remove particles and organic contaminants. Tetramethylammonium hydroxide (TMAH) and monoethanolamine (MEA) are used as an organic base and complexing agent, respectively, in the proposed solution. Ethanolamine acts as a corrosion inhibitor in the solution. Organic residue removal was confirmed through contact angle measurements and X-ray photoelectron spectroscopy analysis. Electrochemical studies showed that the proposed solution increases protection against corrosion, and that the hybrid cleaning technology resulted in higher particle removal efficiency from both the copper and low-k surfaces.

Effects of Additives in KOH Based Electrolytes on Cu ECMP

The purpose of this study was to characterize KOH based electrolytes and effects of additives on electro-chemical mechanical planarization. The electrochemical mechanical polisher was made to measure the potentiodynamic curve and removal rate of Cu. The potentiodynamic curves were measured in static and dynamic states in investigated electrolytes using a potentiostat. Cu disk of 2 inch was used as a working electrode and Pt electroplated platen was used as a counter electrode. KOH was used as the electrolyte. H 2 O 2 and citric acid were used as additives for the ECMP of Cu. In static and dynamic potentiodynamic measurements, the corrosion potential decreased and corrosion current increased as a function of KOH concentration. In dynamic state, different potentiodynamic curve was obtained when compared to the static state. The current density did not decrease in passivation region by mechanical polishing effect. The static etch and removal rate were measured as function of KOH concentration and applied voltage. In ECMP system, polishing was performed at 30 rpm and 1 psi. The removal rate was about 60 nm/min at 0.3 V when 5 wt% KOH was used. Also, the effect of additive was investigated in KOH based electrolyte on removal rates. As a result, The removal rate was increased to 350 nm/min when 5wt% KOH, 5vol% H 2 O 2 , 0.3 M citric acid were used.

The Effect of Electrolytes on Polshing Behavior in Cu ECMP

The purpose of this study is to characterize various electrolytes on electrochemical mechanical planarization (ECMP). The ECMP system was modified from conventional CMP system to measure the potentiodynamic curve and removal rate of Cu. The potentiodynamic curves were measured in static and dynamic states in investigated electrolytes using a potentiostat for the evaluation of the polishing behavior on ECMP. KOH (alkaline) and NaNO (salt) were selected as electrolytes which have high conductivity. In static and dynamic states, the corrosion potential decreased and the corrosion current increased as a function of the electrolyte concentration. But, the electrochemical reaction was prevented by mechanical polishing effect in the dynamic state. The static etch and removal rate were measured as functions of concentration and applied voltage. When NaNO was used, the dissolution was much faster than that of KOH. It was concluded that the removal rate was strongly depended on electrochemical dissolution. The removal rate increased up to 350 nm/min in NaNO based electrolyte.