Copper Chemical Mechanical Planarization Slurry Research Articles

Effect of Complexing Agent Choices on Dishing Control Level and the Shelf Life in Copper CMP Slurry

There has been lot of work going on reducing dishing without benzotriazole (BTA) because it can lead to organic debris and other defects during the chemical mechanical planarization (CMP) although being an effective dissolution inhibitor on dishing elimination. Slurry destabilization problems also have to be closely monitored because it can cause surface defects and changes in the material removal due to particle agglomeration and the chemical degradation. In this study, FA/O chelating agent, a unique alkaline organic macromolecule, yielded a lower dishing level under the condition of no BTA compared with glycine, which allows for a substantial reduction in the use of BTA. The dissolution rate, polish rate and changes in the in-situ open circuit potential (OCP) were performed to elucidate the planarization mechanism and how the use of carcinogenic BTA can be reduced. It was also observed that the FA/O based slurry had a shelf life of no more than 7 days and the root cause was the oxidation reduction reaction between FA/O chelating agent and H2O2 rather than the self-decomposition of the hydrogen peroxide.

Material Removal Mechanism during Copper Chemical Mechanical Planarization Based on Nano-Scale Material Behavior

Comparison of the experimentally measured electrochemical corrosion rate and the physical material removal rate (MRR) revealed that during copper chemical mechanical planarization (CMP) most of the copper was removed mechanically by interaction with sliding abrasive particles. The mechanism for mechanical removal of copper was explained by considering literature values of the properties of copper at the nano-scale. Although the force applied on the copper by abrasive particles may be insufficient to initiate plastic deformation, friction between moving abrasive particles and copper reduces the maximum Hertz pressure required for plasticity. Crystallographic defects and a copper surface roughened by repetitive abrasions and chemical attack further lower the local threshold for plastic deformation, leading to selective plastic deformation of copper at weakened regions. The plastically deformed copper is then removed by a mechanism similar to cutting, releasing free debris that is subsequently dissolved by the oxidizer and/or complexing agent in the CMP slurry. Hardness values obtained from AFM tip scratching experiments on chemically treated copper predicted the MRR behavior during CMP well. In contrast, hardness values obtained by nanoindentation, where the applied force and the tip diameter were much larger than those during AFM tip scratching, yielded poor predictions of the MRR.

Synergetic effect of chelating agent and nonionic surfactant for benzotriazole removal on post Cu-CMP cleaning**Project supported by the Natural Science Foundation of Hebei Province, China (No. F2015202267) and the Scientific Innovation Grant for Excellent Young Scientists of Hebei University of Technology (No. 2015007).

The cleaning of copper interconnects after chemical mechanical planarization (CMP) process is a critical step in integrated circuits (ICs) fabrication. Benzotriazole (BTA), which is used as corrosion inhibitor in the copper CMP slurry, is the primary source for the formation of organic contaminants. The presence of BTA can degrade the electrical properties and reliability of ICs which needs to be removed by using an effective cleaning solution. In this paper, an alkaline cleaning solution was proposed. The alkaline cleaning solution studied in this work consists of a chelating agent and a nonionic surfactant. The removal of BTA was characterized by contact angle measurements and potentiodynamic polarization studies. The cleaning properties of the proposed cleaning solution on a 300 mm copper patterned wafer were also quantified, total defect counts after cleaning was studied, scanning electron microscopy (SEM) review was used to identify types of BTA to confirm the ability of cleaning solution for BTA removal. All the results reveal that the chelating agent can effectively remove the BTA residual, nonionic surfactant can further improve the performance.

Synergic effect of chelating agent and oxidant on chemical mechanical planarization

Chemically dominant alkaline slurry, which is free of BTA (benzotriazole) and other inhibitors, was investigated. The synergic effect of the chelating agent and oxidant on the chemical mechanical planarization (CMP) was taken into consideration. Copper CMP slurry is mainly composed of an oxidizer, nonionic surfactant, chelating agent and abrasive particles. The effect of different synergic ratios of oxidant with chelating agent on the polishing removal rate, static etch rate and planarization were detected. The planarization results reveal that with the increase of oxidant concentration, the dishing value firstly diminished and then increased again. When the synergic ratios is 3, the dishing increases the least. A theoretical model combined with chemical-mechanical kinetics process was proposed in the investigation, which can explain this phenomenon. Based on the theoretical model, the effect of synergic ratios of oxidant with chelating agent on velocity D-value (convex removal rate minus recessed removal rate) was analyzed. The results illustrate that when the synergic ratio is between 2.5–3.5, the velocity D-value is relatively higher, thereby good planarization can be achieved in this interval. This investigation provides a new guide to analyze and study copper line corrosion in the recessed region during copper clearing polishing.

Potassium sorbate as an inhibitor in copper chemical mechanical planarization slurry. Part I. Elucidating slurry chemistry

The integration of an advanced inhibitor, potassium sorbate (K[CH 3(CH) 4CO 2]), in a copper CMP slurry based on hydrogen peroxide and glycine is reported. The first part of the study discusses the slurry chemistry by qualitatively describing the processes involved and proposes a mechanism for a hydrogen peroxide–glycine based slurry having sorbate anion as an inhibitor. For this purpose, the specific role of each chemical constituent in the slurry was elucidated at a fundamental level by electrochemical studies, X-ray photon spectroscopy (XPS) and contact angle measurements, all linked to the CMP performance on blanket wafers. Once the polishing mechanism was resolved the influence of the inhibitor was evaluated by CMP processing of patterned wafers.

Mechanical effect of colloidal silica in copper chemical mechanical planarization

The mechanical effect of colloidal silica concentration in copper chemical mechanical planarization (CMP) is considered in this paper by using friction force monitoring system. The copper peak was detected in the result of the energy-dispersive X-ray (EDX) spectra of the polishing residues. The addition of colloidal silica into copper CMP slurry increased both the material removal rate and the friction force. During CMP, as the concentration of the colloidal silica was increased, the temperature generated by the friction force also increased. To understand effect of abrasive concentration on the material removal and friction force, we considered the material removal and the friction energy for a single abrasive. The surface of the polished copper film was measured by X-ray photoelectron spectroscopy (XPS). All the material removal rates as a function of friction energy after polishing with various concentrations of colloidal silica had a non-linear characteristic.

The Effect of Hydrogen Peroxide on Frictional and Thermal Behaviors in a Citric Acid-Based Copper Chemical Mechanical Planarization Slurry

The effect of H2O2 on the frictional and thermal behaviors of a citric acid-based slurry was characterized during Cu polishing. As the H2O2 concentration increased, the static and dynamic etching rates gradually decreased. The removal rate of Cu initially increased and reached the maximum value at a slurry concentration of 5 vol % H2O2 after which the removal rate gradually decreased with further increases in H2O2 due to the formation of a thick Cu oxide layer. The frictional force gradually decreased with increased H2O2 concentration. The friction force was high in spite of the low removal rate in the 1 vol % H2O2 slurry. The pad temperature changed as a function of H2O2 concentration in a manner similar to at that of the friction force. The higher pad temperature resulted in higher static etching and corrosion rates of Cu during polishing.

Chemical Mechanical Planarization Method for Thick Copper Films of Micro-Electro-Mechanical Systems and Integrated Circuits

Modern industries require more accurate and high power-efficient micro-electro-mechanical systems (MEMS) and integrated circuits (ICs). Because the structure of MEMS and ICs becomes complicated, chemical mechanical planarization (CMP) has been introduced to fabricate highly integrated electro-mechanical structures. This study aims to reduce dishing and erosion using a negative photoresist (PR) as a protective layer in CMP for thick copper. After bulk copper CMP, soft-landing was carried out using an acidic copper CMP slurry. Method I was the CMP of a thick copper pattern without a negative PR, and method II was a new concept for the CMP method which removed the copper and negative PR to reduce the amount of copper dishing and erosion. In comparison with method I, method II reduced the dishing and erosion by about 46 and 60%, respectively.

Mechanical effect of process condition and abrasive concentration on material removal rate profile in copper chemical mechanical planarization

Recently, many researchers have studied the material removal mechanism of copper chemical mechanical planarization (CMP). On the basis of their previous works, we studied the mechanical effect of copper (Cu) CMP on the material removal rate profile. Copper CMP was performed using citric acid (C 6H 8O 7), hydrogen peroxide (H 2O 2), colloidal silica, and benzotriazole (BTA, C 6H 4N 3H) as a complexing agent, an oxidizer, an abrasive, and a corrosion inhibitor, respectively. In this paper, the abrasives and process condition are main mechanical factors of CMP. The colloidal silica, used as an abrasive in copper CMP slurry containing 0.01 M citric acid and 3 vol% hydrogen peroxide, controlled the wafer edge profile by abrading the wafer edge. The polishing pressure did not contribute to the material removal rate (MRR) profile, but did to the MRR. As the rotational velocity of the polishing head and table increased, the deviation of MRR profile became smaller. The results of this paper showed that the abrasive concentration was the key factor which controlled the wafer edge profile, and also the rotational velocity was the key factor which controlled wafer center profile of MRR.

Influence of slurry components on uniformity in copper chemical mechanical planarization

Many researchers studying copper chemical mechanical planarization (CMP) have been focused on mechanisms of copper removal using various chemicals. On the basis of these previous works, we studied the effect of slurry components on uniformity. Chemical mechanical planarization of copper was performed using citric acid (C 6H 8O 7), hydrogen peroxide (H 2O 2), colloidal silica, and benzotriazole (BTA, C 6H 4N 3H) as a complexing agent, an oxidizer, an abrasive, and a corrosion inhibitor, respectively. As citric acid was added to copper CMP slurry (pH 4) containing 3 vol% hydrogen peroxide and 3 wt% colloidal silica, the material removal (MRR) at the wafer center was higher than its edge. Hydrogen peroxide could not induce a remarkable change in the profile of MRR. Colloidal silica, used as an abrasive in copper CMP slurry containing 0.01 M of citric acid and 3 vol% of hydrogen peroxide, controlled the profile of MRR by abrading the wafer edge. BTA as a corrosion inhibitor decreased the MRR and seems to control the material removal around the wafer center. All the results of in this study showed that the MRR profile of copper CMP could be controlled by the contents of slurry components.

The Effects of Copper CMP Slurry Chemistry on the Colloidal Behavior of Alumina Abrasives

The effects of common slurry additives on the colloidal behavior of alumina suspensions used for copper chemical mechanical planarization (CMP) were investigated. The alumina suspensions were characterized by zeta potential and agglomerate size distribution measurements with various chemical additives. To simulate the slurry during copper CMP, the effect of the addition of diameter copper particles was studied. The presence of copper caused a decrease in agglomeration for pH values less than 6.5 and an increase in agglomeration ranging from for pH values greater than 7 in aqueous solutions. Addition of glycine caused the formation of a soluble Cu-glycine complex that decreased agglomeration at pH values less than 4. The addition of did not affect the effective alumina agglomerate size without copper, but with copper in the solution the majority of the alumina agglomerated to for all pH values. However, increasing concentration to decreased the agglomerate size by . The pH of the slurry had the largest effect on the zeta potential and agglomerate size distributions.

Effects of CMP Slurry Chemistry on the Zeta Potential of Alumina Abrasives

The colloidal behavior of alumina in typical copper chemical mechanical planarization (CMP) solutions was investigated through the measurement of zeta potential and particle cluster size distribution. The effects of various common additives on zeta potential for alumina slurries used in copper CMP were studied. Addition of to glycine stabilized the zeta potential for alumina for a large pH range. Although slurry pH has the largest effect on zeta potential and particle cluster size distribution, sodium dodecyl sulfate caused alumina to maintain a small aggregate size while ethylenediaminetetraacetic acid caused alumina to agglomerate over the entire pH range investigated.

Semi-abrasive free slurry with acid colloidal silica for copper chemical mechanical planarization

New semi-abrasive free slurry for copper chemical mechanical planarization (CMP) was investigated through the addition of below 0.5 wt% acid colloidal silica, hydrogen peroxide and other additives. The additives as stabilizers for hydrogen peroxide as well as accelerators in tantalum nitride CMP were also evaluated. This semi-abrasive free slurry provides good hydrogen peroxide stability, excellent colloidal silica dispersion ability and easiness of post-CMP cleaning. The extent of enhancement in tantalum nitride CMP was verified through an electrochemical test. This approach may be useful for the application of single and first step copper CMP slurry with one package system.

구리 CMP 적용을 위한 산성 콜로이드 실리카를 포함한 준무연마제 슬러리 연구

The primary aim of this study is to investigate new semi-abrasive free slurry including acid colloidal silica and hydrogen peroxide for copper chemical-mechanical planarization (CMP). In general, slurry for copper CMP consists of colloidal silica as an abrasive, organic acid as a complex-forming agent, hydrogen peroxide as an oxidizing agent, a film forming agent, a pH control agent and several additives. We developed new semi-abrasive free slurry (SAFS) including below 0.5％ acid colloidal silica. We evaluated additives as stabilizers for hydrogen peroxide as well as accelerators in tantalum nitride CMP process. We also estimated dispersion stability and Zeta potential of the acid colloidal silica with additives. The extent of enhancement in tantalum nitride CMP was verified through anelectrochemical test. This approach may be useful for the application of single and first step copper CMP slurry with one package system.

Effects of phosphoric acid stabilizer on copper and tantalum nitride CMP

The effects of phosphoric acid addition on slurry for chemical–mechanical planarization (CMP) of copper and tantalum nitride were investigated. It is generally known that the slurry for copper CMP consists of alumina or colloidal silica as an abrasive, organic acid as a complexing agent, an oxidizing agent, a film forming agent, a pH control agent and additives. Hydrogen peroxide (H 2O 2) is one of the materials that are commonly used as an oxidizing agent in copper CMP. However, hydrogen peroxide needs some stabilizers to prevent decomposition. We evaluated phosphoric acid (H 3PO 4) as an accelerator of the tantalum nitride CMP as well as process a stabilizer of the hydrogen peroxide. We also estimated dispersion stability and zeta potential of the abrasive slurry with the contents of phosphoric acid. An acceleration of the tantalum nitride CMP was verified through the electrochemical test. This approach may be useful for the development of the second step copper CMP slurry or in general stabilization of hydrogen peroxide in abrasive slurry.

Effect of Organic Acids in Copper Chemical Mechanical Planarization Slurry on Slurry Stability and Particle Contamination on Copper Surfaces

The purpose of this study was to investigate the effect of organic acids in alumina-based slurry on the stability of slurry particles and particle contamination on a wafer surface after Cu Chemical Mechanical Planarization (CMP). The electrokinetic behavior of alumina particles in the presence and absence of organic acids was studied. When organic acids were added to slurries, the charge reversal of zeta potential was measured on alumina particles in acidic pH ranges. The stability of alumina particles was seen to be dependent on the type of organic acid added to the slurry. An unstable suspension of particles was observed when oxalic and succinic acids were added to the slurry. The presence of citric acid led to a stable suspension of alumina particles in the slurry. The sedimentation rate of particles was calculated to be the slowest in the citric-acid-added slurry. No increase of particle size was measured in the slurry containing citric acid. A rapid increase of mean particle size was found when oxalic and succinic acids were added to the slurry. The addition of citric acid in the slurry effectively prevented a slurry particle contamination from the Cu surface after Cu CMP.