Polishing pad conditioning is essential for achieving stable chemical mechanical polishing (CMP). While diamond disk conditioners (DDCs) are often applied, flexible fiber conditioners (FFCs) have been proposed as a new conditioning tool. FFCs are intended for roughening the pad surface appropriately by bundling fine wire fibers. Our previous study demonstrated the fine conditioning characteristics of FFCs for a hard urethane foam pad. In this study, the conditioning characteristics of an FFC are compared with those of a DDC. First, we evaluate the conditioning performance of an FFC using SUS fibers on a soft urethane foam pad. The result indicates that on a soft pad, the SUS-FFC can restore the pad surface asperities more finely, as confirmed via the stabilized number of contact points based on contact image and luminance value distribution analyses. Subsequently, for a metal-contamination-free FFC process intended for semiconductor CMP, we develop an FFC fabricated using polyether ether ketone (PEEK) and verify its performance via the CMP test of a silicon oxide film. It is shown that the hard pad can be conditioned using the developed PEEK-FFC; this implies that a stable removal rate can be realized immediately after pad break-in conditioning.

An original eddy current sensor by making use of skin effect of copper film was developed for end point prediction in CMP (Chemical Mechanical Planarization). The main operation principle is based on detecting a local maximum point of eddy current due to skin effect in the course of film thickness reduction by CMP. This paper focuses on the verification of the operation principle. The verification evaluation using ferrite sheet supported that magnetic field passing through to a copper film is indispensable to operate the end point detection. From the result of both copper film process and tungsten film process, it was apparent that the resonant frequency profile depends on the skin depth of film material. The equivalent circuit model including the plane inductor and copper film indicates that a real part of an impedance of a plane inductor is proportion to the square of mutual inductance corresponding to eddy current induced. The simulation result of the real part of impedance of the plane inductor was a good agreement with actual resonant frequency profile. It was clarified that the operation principle of the end point detection is based on eddy current generation due to skin effect.

In the Chemical Mechanical Planarization system, the removal profile improvement was attempted by subtly correcting the pressure distribution by means of scraping the underlay assist pad surface made of an elastic solid. As a result of pressure distribution correction, the non-uniformity of the pressure integration was improved from 3% to 0.9%, which results in an improvement from 3.9% to 1.9% in the non-uniformity of the removal rate. Fine adjustment of pressure distribution is the most crucial factor to correct removal profile finely. In addition, the fine adjustment of pressure distribution must be maintained reproducibly to secure stable removal profile. In this study, it was demonstrated that the developed system is a robust polishing system to keep stable pressure distribution without influence on shearing force of polishing. The polishing mechanism is based on the following three features: (1) maintaining a datum plane with a wafer chuck, (2) pressure distribution control using the constitution of the original pad, and (3) a machine configuration that maintains the wafer level in parallel with the pad level.

An original polishing mechanism with a triple layer pad was developed as a surface conformable polishing mechanism in CMP (Chemical Mechanical Planarization). According to the polishing mechanism, removal profile can be controlled by base plate curvature through an assist pad made of elastic material. A pad system supported by an envelope plane composed of five wafers contributes to make a wafer level paralleled to a pad level relatively during polishing. As the result, a static pressure distribution can be transferred precisely to a dynamic polishing profile regardless of strong shearing force by polishing. In order to verify the polishing removal controllability, an original pressure distribution analysis was developed by an actual pressure distribution measurement around an entire pad surface. The analyzed pressure distribution profile was in good agreement with the actual polishing profile. From the result that the static pressure profile can be transferred to the polishing profile precisely, it was verified that the polishing mechanism is reasonable for surface conformable polishing system in CMP.

Chemical mechanical polishing/ planarization (CMP) is a key technology for fabricating high-efficient semiconductor devices, and the CMP characteristics (removal rate and accuracy, etc.) is depended on the various consumables represented by slurry, polishing pad and dresser used in the CMP process. Currently, in the pad, there are many studies that have pointed the evaluation methodology and the correlation between the pad surface asperity and the CMP characteristics. On the other hand, the dresser is one of the most important consumables because the dresser can control the pad surface asperity, and the diamond grains electrodeposited dresser (diamond dresser) is frequently used. One drawback point of the diamond dresser is that the dressing performance declines owing to the deterioration of the diamond grains. Previously, we have developed a novel flexible fiber dresser that would ensure high performance and longer life of tools, and we have reported the fundamental characteristics by the flexible fiber dresser compared with that of the diamond dresser. In this paper, we will show the results of tool life evaluation of the flexible fiber dresser using a contact image analysis method. As a result, the flexible fiber dresser can be continuously used over 35 hours. Furthermore, the result of having examined the stability of the removal rate of a silicon wafer is reported. Therefore, we found that the flexible fiber dresser is one of the most effective dressing methods for the polishing pad.

An original end point detection system was developed by making use of the skin effect in chemical mechanical polishing (CMP). The developed system utilizes a critical change in the eddy current due to the skin effect. The critical change is caused by the following two phases in the polishing process. The first phase is that the eddy current increases when the magnetic flux begins to penetrate the copper film as the film thickness reduces to less than 'skin depth'. The next phase is that the eddy current fades out due to substantial elimination of the copper film by further polishing. Consequently, a prominent local maximum point of the eddy current emerges at the turning point between the two phases, which can be detected sensitively before the copper film is eliminated. It was demonstrated that the developed system gains a high sensitivity by making use of a critical change in the eddy current due to the skin effect without exposing the semiconductor device excessively to an intense magnetic flux. © 2011 The Japan Society of Applied Physics.

As a surface reference conditioner, original flexible fiber conditioner was developed to realize uniform pad conditioning in CMP (Chemical Mechanical Polishing). The developed conditioner is composed of a lot of bundles of fine metal fibers to contact pad surface independently. Constant conditioning force can be applied to pad surface with fiber edges regardless of long range of height variation of pad surface. In fact, the developed conditioner made pad surface to be roughened with conforming to a protruding area of 50um on pad surface. Furthermore, an original evaluation on conditioning uniformity was demonstrated quantitatively by making use of relationship between in-depth color variation and pad conditioning depth using dyed pad. As the result, the developed pad conditioning was more uniform entirely across a pad than traditional disk type conditioner. The performance resulted in both contraction of pad break-in process and improvement of removal rate uniformity within wafer in the course of pad break-in process.

Surface conformable polishing mechanism, which means a uniform removal mechanism conforming to wafer thickness variation, was developed for chemical mechanical polishing. The polishing mechanism provides both global uniform removal regardless of wafer curvature and local planarization to protruding parts on a patterned surface. The improved triple-layer pad contributes to the uniform removal profile on the wafer surface with a long range of height variation. Selective polish function to planarize protruding parts was separated from the uniform polish function to conform to the surface height variation. The two opposite functions could be controlled by stiffness of a deflection film in a surface layer pad. Moreover, the wafer was held with the back-side surface flattened to exclude wafer curvature influence. Consequently, the developed polishing mechanism overcame the traditional problem on the wafer curvature, which has not been solved. Uniform polish with nonuniformity within the wafer of 1.25% was demonstrated using the wafer with a thickness variation of 3 μm. In addition, local planarization was achieved in pattern features from 5 microns to 500 microns. © 2009 The Electrochemical Society.

In order to evaluate pad surface condition to stabilize removal rate in oxide-CMP(Chemical Mechanical Polishing), chemical modification on pad surface was evaluated under no conditioning process as an opposite phase. As the result, the pad surface was hydrolyzed in accordance with no conditioning process proceeding. Silanol groups contained in slurry or generated by oxide polish combined with polarized molecules in poly-urethane material of the pad by a hydrogen bond. The pad surface stacked silica component with the silanol groups leads to removal rate drop due to inhibition of chemical reaction to polish oxide film. The pad treatment by means of the following Si substrate polish contributed to removal rate recovery of oxide film. The behavior suggested that not only geometrical factor of pad surface such as asperity or roughness but also chemical factor of pad surface such as hydrophilicity or hybrid formation has an influence on keeping removal rate. The removal rate recovery of oxide film after Si substrate polish was attributed to silanol groups elimination on pad surface which was caused by condensation between silanol groups on pad surface and hydroxyl groups on Si surface.

The novel conditioner was developed for uniform conditioning across a pad. The conditioner is composed by bendable fibers. Therefore, each abrasive conforms independently to the pad surface, differently from the traditional conditioner of plate type. The removal rate using the developed conditioner is equal to that using the traditional conditioner. However, the cut rate of pad using the developed one is tenth part of the cut rate using traditional one. Therefore, it was demonstrated that the developed conditioner realized more efficient conditioning. In addition, in order to evaluate the conditioning non-uniformity effectively, novel uniformity evaluation method was developed. The principle uses color variation by abrading the pad dyed on the surface. As the result, the conditioning non-uniformity was 8.3% with the developed conditioner, compared with 23.8% with the traditional conditioner.

The various pad surface treatments were evaluated to clarify dominant factors on a pad surface to get removal rate on CMP(Chemical Mechanical Polishing). On evaluating the dominant surface' factors, pad surface recovery without grinding removal of pad surface was tried using a no-conditioning pad. After eliminating the by-products involved in the pad surface, recovery ratio on removal rate became 31% at most, which indicated that the by-products clogging in the pad surface was not a dominant factor to inhibit removal rate. Not grinding the surface but scraping the surface was valid for effective surface recovery to get removal rate. In this study, a noble pad conditioner was proposed from their results. The developed conditioner, which is the scraping brush conditioner, makes use of deflective deformation in order to apply constant contact force against height variation of pad surface. Consequently, it was demonstrated that the developed conditioner was applicable on surface reference conditioning on CMP without the stick-slip motion that occurs on the traditional conditioner.

Pad conditioning is one of significant subjects to keep constant polishing rate and polishing uniformity for CMP(Chemical Mechanical Polishing). To achieve constant pad conditioning, the following three factors are indispensable: (1) Formation of stable contact condition between pad and conditioner, (2) Real time pad condition, (3) Conditioning uniformity within the whole area of the pad. In order to meet their factors, pad conditioner with abrasives on retainer surface, which was termed 'conditioning retainer', has been developed to realize stable polishing performance for CMP. The conditioning retainer carrying out simultaneously both pad conditioning and wafer polishing has a great deal of stiffness enough to keep horizontal contact to the pad against continuous friction resistance during pad conditioning. In addition, surface of the double layer pad conforms to surface of the conditioning retainer, so that contact configuration between conditioning retainer and pad has been kept to be constant. For uniform pad conditioning, the shoulder slope shape was formed on the assist pad to compensate the excessive wearing on the pad edge. The shape relieving polishing pressure at the pad edge corresponds to retainer trajectory density on the pad. The measure resulted in uniform pad wearing and the continuous uniform polishing profile.

Fundamental investigation for pad conditioning was studied on CMP (Chemical Mechanical Polishing). In particular, pad surface roughness was focused on various pad surface conditions. Pad conditioning under wet condition makes pad surface roughness finer than pad conditioning under dry condition. The pad surface with fine roughness contributes to rapid pad break-in and removal rate stabilization. In this study, various factors of pad conditioning were verified to clarify the difference of pad conditioning between under wet condition and dry condition. One of major differences of pad conditioning under dry condition against wet condition was the magnitude of friction force between pad and conditioner, which generates stick-slip motion of pad conditioner on a pad. The other was removal efficiency of pad fragment to be scraped away on conditioning pad. Pad fragments disturbs a stable contact between pad and conditioner. Consequently, it will be possible to realize pad pre-conditioning without pasting pad on a platen by taking appropriate measures against the two.

Anovel polishing pad system and machine were designed and developed to perform a uniform removal rate for a whole wafer surface in CMP (Chemical Mechanical Polishing) planarization process. The pad materials which are composed of hard and soft two layers, and the dimensions were designed based on the calculation of polishing pressure distribution by FEM. The CMP machine developed has good and original features of the followings: Five wafers which axe checked on high precision and rigid stages are simultaneously polished rotating with planetary motion The wafers surface to be polished are set with up and the pad surface is determined by the five wafers envelope. The hand pad which practices the wafer surface polishing do not attached on platen, but are stretched from the periphery of the platen. Using this CMP system, the polishing pressure distribution was measured and calculated for whole wafer area in static state. Then the wafers on which have oxide film were actually polished and the removal rate distribution of die wafers were measured The actual surface profile corresponds well to the measured and calculated pressure profile. It is found that the removal rate distribution of a wafer is controllable from the center-fast to center-slow by using the base-plate which has different radius under the pad system.

Electro-CMP(Electro-Chemical Mechanical Polishing) was studied to reduce surface damage on copper and low-K dielectric for copper damascene process. It is indispensable to understand both copper surface oxidation and copper removal mechanism for accurate removal rate control. This study deals with the observation results of the polished copper surface by XPS (X-ray Photoelectron Spectroscopy) and AES(Auger Electron Spectroscopy). In particular, copper samples are measured immediately after polishing to estimate surface oxidation precisely. In addition, the depth profile of oxygen penetration into copper surface was evaluated to measure copper oxide layer thickness. As a result, the surface dipped in slurry for 30 min was oxidized 20A in depth. The formation of CuO on copper surface in Electro-CMP was less than that of conventional CMP. The oxygen penetration in Electro-CMP was loA in depth, less than 15A in conventional CMP.

This study presents a new approach to edge profile control during air back carrier Chemical Mechanical Polishing (CMP). Control of wafer edge profile proves to be difficult as different factors are reported to influence polishing characteristics. To evaluate a CMP on the wafer's edge it needs to look at polish characteristics of leading and trailing edges separately. To understand polish performance on both leading and trailing edges, and their impact on resulting wafer's edge profile a non-rotating carrier experiment had been conducted [4]. Based on the results of the non-rotating carrier experiment a novel retaining ring design has been proposed. In the course of this study CMP of the wafer's edge evaluation for a novel retaining ring has been performed on blanket PETEOS 200mm wafers for different retaining pressures. Edge profile evaluation provided a proof for the Pad Wave Hypothesis and helped to significantly enhance the CMP performance by increasing process stability and achieving wider process window for retaining ring pressure.

Air Float Carrier is developed to achieve uniform polishing with continuous air supply during polishing wafer. The carrier has a thin support film inside retainer ring. Retainer pressure enables the support film to push the wafer edge down to the pad locally to control edge-polishing profile. Using this air float carrier, we try to evaluate relationship between pressure profile measured under static condition and actual edge-polishing profile at various retainer extensions and various retainer pressures. As a result of this comparison, it has become evident that the calculated pressure profile corresponds to the actual edge-polishing profile virtually and retainer pressure has a great influence on the actual edge-polishing profile.

次世代CMP(Chemical Mechanical Polishing)装置に対応する研磨方式として、線接触ポリッシング装置の開発を進めている。線接触ポリッシング方法では、連続的な線接触状態の重ね合わせにより研磨が進行し、ウェハに対するドラムの揺動条件を設定することで研磨形状を制御することが可能になる。通常の面接触研磨装置と比べ、研磨部へのスラリー搬送性やウェハーパッド接触状態制御の点で、研磨各部位における研磨状態を精度良く設定することが可能となり、極めて均一な研磨加工が実現できるものと期待されている。本研究では、この線接触ポリッシング方式に対し、厳密な揺動評価の前段階としてウェハに対する各ドラム定在位置における研磨形状に関し、理論形状と実際の研磨形状との比較を行った。その結果、ドラムのウェハに対する接触状態を考慮して得た理論形状は実際に得られた研磨形状とほぼ一致し、均一な線接触状態の下で適正な揺動条件を選択することで、均一研磨実現への可能性を見い出した。