Pad Conditioner Research Articles

Effects of CMP Pad Conditioner Properties and Performance on Polishing Pad, Process and Wafer Removal Rate

The focus of this work is CMP pad conditioners and the impact of diamond shape, size, density and protrusion on pad cut rate, pad surface roughness and wafer removal rate. Conditioner properties such as diamond shape, density and protrusion were found to directly impact the pad cut rate and wafer removal rate. Conditioners with high variation in diamond protrusion and uneven diamond shapes exhibited high drop in pad cut rate and wafer removal rate over the test period. Conditioners with high and very aggressive diamonds led to uneven pad conditioning creating step like features on the pad. Diamonds show wearing off sharp edges and chipping of edges due to mechanical forces exerted on them during conditioning. Also diamonds on some of the tested conditioners were found to be missing or sheared off during conditioning due to the mechanical stress and weak bonding process.

Diamond Pad Conditioners with Oriented Polycrystalline Diamond Cubes

Sintered polycrystalline diamond cubicles were oriented to make CMP pad conditioners. The dressing experiments demonstrated the capability of fast pad cutting and efficient removal of glazed layer that is formed by polishing wafers with slurry on dressed pad.

Effects of CMP Pad Conditioner Properties and Performance on Polishing Pad, Process and Wafer Removal Rate

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Experimental Analysis of Pad Wear Response Effect on Removal Rate Variations in Tungsten Chemical Mechanical Polishing

We investigated the effects of the pad surface response during polishing and conditioning on the removal rate variation in a tungsten chemical mechanical polishing (CMP) process. We examined the coefficient of friction (COF) to identify the tribology of the pad conditioning. The variation in the removal rate was dependent on the COF during conditioning. We also evaluated the effects of diamond edge degradation of the pad conditioner disk on its cutting ability from the viewpoint of mechanical wear. The results showed that the decline in pad wear rate was caused by a decrease in the cutting ability as the diamond sharp edges rounded off, while the diamond contact area with the pad surface depended little on the diamond abrasive degradation. Furthermore, we demonstrated the usefulness of measuring the height ratio of the asperity called “top surface area (TSA) ratio” as an appropriate topographical parameter to study the dependence of COF during conditioning on the decay of the removal rate. We present a clear correlation between the pad wear rate degradation and the TSA ratio after CMP to elucidate an increase in the conditioning COF related to truncation of the asperity tip by wear and plastic deformation.

PCD dresser for dressing CMP polyurethane pads

This paper investigating a revolutionary design of pad conditioners is based on carving a structure out of sintered polycrystalline diamond (PCD) matrix. The PCD dresser is manufactured by wire electro discharge machining to form cutting pyramids of a specific size with a designed shape. The dressing characteristics of pad surface textures are studied by comparison with conventional diamond pad conditioner. Experimental results indicate that the PCD dresser can dress asperities of the pad more uniformly than the conventional diamond dresser due to PCD dresser having identically shaped tip and the same height diamond. In addition, the cutting rate of PCD dresser for IC1000 pad not only is reduced by about 30% and also it can dress pad more effectively than conventional diamond dresser.

Real-time Control System for Improved CMP Pad Profiles

AbstractChemical mechanical planarization (CMP) pads require conditioning to maintain the surfaces yielding optimal performance. However, conditioning not only regenerates the pad surface but also wears away the pad material and slurry transport grooves. Non-optimized conditioning may result in non-uniform pad profiles, limiting the productive lifetimes of pads. A new approach to conditioning uses closed-loop control (CLC) of conditioning sweep to enable uniform groove depth removal across the pad, throughout pad life. A sensor integrated into the conditioning arm enables the pad stack thickness to be monitored in situ and in real time. Feedback from the thickness sensor is used to modify pad conditioner dwell times across the pad surface, correcting for drifts in the pad profile that may arise as the pad and disk age. Pad profile CLC enables uniform reduction in groove depth with continued conditioning, providing longer consumables lifetimes and reduced operating costs.

Design, Characteristics and Performance of Diamond Pad Conditioners

AbstractA wide range of diamond pad conditioner (disk) designs have been characterized and key performance metrics have been collected. Relationships between design characteristics including diamond size and shape, spatial density, and tip height distribution and polishing pad wear rates and pad surface textures have been established for a variety of pads.Estimation of the depth-of-penetration of working diamonds, from used disk analyses, allows meaningful topographic assessments of alternative conditioner designs and predictions of relative performance. An example of an improved conditioner that illustrates this design methodology is given.Conditioner aggressiveness and its decay in various slurries have been measured to assess disk lifetime in Chemical Mechanical Planarization (CMP) processes environments. Key factors affecting disk lifetime are discussed and an improved-lifetime conditioner for use in aggressive slurries will be reviewed.

Investigation of the Wear of the Pad Conditioner in Chemical Mechanical Polishing Process

The pad surface will become grazed because of the accumulated debris in the chemical mechanical polishing (CMP) process. It results in the reduction of the wafer removal rate, and a pad conditioner or diamond disk must be frequently employed to refresh the pad surface. The wear behavior of a diamond with respect to its location, original relative protruded height and protruded shape on a diamond disk was investigated in this thesis. It was found from experimental data that the diamonds which were located outside, originally protruded more highly and with crest lines oriented upward wore faster. Accordingly, four suggestions were proposed to obtain the uniform diamond wear. They are: lowering the protruded heights of the outside diamonds, replacing the current flat substrate by a curved surface substrate, changing the diamond distribution on the disk from the current uniform one to a higher concentration around outside diameter, and orienting the diamonds such that the flats are protruded upward for the outside diamonds and the crest lines are projected upward for the inside diamonds. Experiment had verified that the pad conditioner with center-protruded substrate led to a stable and higher dressing rate.

Analysis of Fixed Abrasive Pads with a Nano-Sized Diamond for Silicon Wafer Polishing

Current polishing pads cannot polish a workpiece without using slurry with free abrasive. The new slurry is required to be continually poured into the working area, so more than half of the slurry may be lost from the table without contacting the wafer surface; this leads to economic and environmental problems. In the current work, the fixed abrasive pad was used, where nano-sized diamond abrasives were embedded in the polishing pad; distilled water, rather than slurry, was used. The effect of various fixed abrasive pad designs on polishing characteristics during silicon wafer polishing was investigated. Moreover, the primary function of fixed abrasive was to remove the rough parts of silicon wafer as they were being polished. Consequently, it needed to disperse the nano-sized abrasives into the pad material with high hardness value; this way, working abrasives are not pressed into the pad material. Furthermore, with the use of a pad conditioner, the interior working abrasives were exposed to the pad surface. As a result, the best outcome of using the fixed abrasive pad with a nano-sized diamond was a surface roughness of Ra 0.47 nm.

Dressing Behaviors of PCD Conditioners on CMP Polishing Pads

Diamond pad conditioner or dresser can determine the efficiency of chemical mechanical polishing (CMP) processes and the quality of polished wafers. Conventional diamond pad conditioners are made by adhering discrete diamond grits on a flat substrate. The size distribution of diamond grits coupled with the deformation of the substrate often make the tips of diamond grits lying at different heights. Instead of attaching individual diamond grits to a metal substrate, a revolutionary design of pad conditioners is based on carving a structure out of sintered polycrystalline diamond (PCD) matrix. The PCD dresser is manufactured by wire electro discharge machining to form cutting pyramids of a specific size with a designed shape. The dressing characteristics of pad surface textures are studied by comparison with conventional diamond pad conditioner. Experimental results indicate that the PCD dresser can dress asperities of the pad more uniformly than the conventional diamond dresser due to PCD dresser having identically shaped tip and the same height diamond. In addition the cutting rate of PCD dresser for IC1000 pad not only is reduced by about 30% but also it can dress pad more effectively than conventional diamond dresser.

Novel diamond conditioner dressing characteristics of CMP polishing pad

A diamond pad conditioner or dresser is required to regenerate the asperity structure of a pad used in chemical mechanical polishing (CMP). A conventional diamond dresser (CDD) is made by attaching discrete diamond grits to the flat surface of a substrate. Although the CDD has regularly distributed diamond grits, the tips of diamond grits are not leveled to the same height. Additionally, diamond grits have different shapes and orientations. A newly designed diamond conditioner, called the advanced diamond dresser (ADD), is made by sculpting a sintered polycrystalline diamond substrate to form identically shaped tips with diamond pieces of equal height, rather than by attaching individual diamond grits to a metal substrate. The dressing characteristics of pad surface textures are compared with those of a CDD. Experimental results reveal that the ADD can create asperities of the pad more uniformly than the CDD. Not only the dressing rate of the ADD is reduced by about 30% but also the stable pad surface texture is formed more quickly than the dressing can be performed using the CDD, extending pad life. The polishing rate of the ADD exceeds that of the CDD. The polishing rate varies with the polishing time, which is less for ADD than for CDD.

The Design Features of Ultimate Diamond Disks (UDD): W CMP with In-Situ Dressing of Metal Free Diamond Disks

All pad conditioners used for CMP today are made by attaching discrete diamond grits on a flat substrate. Polycrystalline diamond (PCD) was wire-EDM cut to form blades with different designs of cutting tips. These blades were assembled to form the so-called ultimate diamond disk (UDD). The pad asperities formed with UDD were compared with conventional diamond disks. It was confirmed that UDD dressed pad asperities were more uniform than that for polishing IC wafers today. The UDD dressed pads were also used to polish tungsten (W) IC layer deposited on 300 mm wafers. As the surface of PCD contains only merged diamond grains that are corrosion immune, UDD was dressing in-situ, by immersing in the acid slurry. The wafer uniformity so polished was comparable to that of ex-situ CMP pad dressing with metallized diamond disks. The in-situ dressing can boost the CMP throughput by deglazing the pad in real time while the wafer is being polished. After 15 hours, the wafer profiles for this in-situ dressing were sustained without decay.

Polycrystalline Diamond (PCD) Shaving Dresser: The Ultimate Diamond Disk (UDD) for CMP Pad Conditioning

All conventional pad conditioners dress the CMP pad with discrete diamond grits of random orientation. With the advent of polycrystalline diamond (PCD) dressers, the pad conditioning can be performed with an unprecedented regularity. The result is a total elimination of "killer asperities" that may scratch the soft copper layer or porous dielectric layer. Moreover, the PCD dressers may be constructed to form a blade shaver so pad disruption during conditioning can be minimized. As a result, the original pad polymers can be preserved for polishing wafers. This ultimate diamond disk (UDD) has transformed stick slipping pad destruction to smooth shaving pad construction. UDD is particularly suitable for dressing CMP pads for polishing 22 nm interconnects, in particularly, with the anticipated debut of 450 mm pancake wafers scheduled for 2012.

A Matching Game for CMP Pads and Conditioners

The relationship between a pad and a conditioner may be the most critical among all "consumables" in a CMP process. The effect of a pad conditioner on pad can be both short-term (instant) and long-term (stability). This paper compares the instantaneous effect of different conditioners on removal rate of oxide, tungsten, and copper CMP. The impact of conditioners in removal profile in copper polishing and rate stability (long-term) in oxide polishing are also presented. The pad wear rate by conditioners of different aggressiveness on Epic® D100 vs. conventional hard pad is compared and the benefits and risks of adopting a more aggressive conditioning on Epic® D100 pad vs. a less aggressive conditioning on conventional pad is discussed.

PCD pad conditioners for low pressure chemical mechanical planarisation of semiconductors

Instead of attaching individual diamond grits to a metal substrate, Advanced Diamond Disk (ADD) are manufactured by Electro Discharge Machining (EDM) of sintered Polycrystalline Diamond (PCD) to form cutting pyramids of a designed shape. This is not possible with single crystal diamond grits that possess obtuse solid angles for dressing plastic pads. The test data confirmed that ADD can dress pad more effectively than conventional pad conditioners with discrete diamond grits. Moreover, the service lives of ADD and pad can both be lengthened due to the much milder dressing action. These unique features of ADD can reduce significantly the Cost of Consumable (CoC) of Chemical Mechanical Planarisation (CMP) for the manufacture of advanced semiconductors.

Study on Reduction of Micro-Scratch in Oxide CMP for Multi-Level Interconnection

Chemical-mechanical polishing (CMP) has been widely accepted for the planarization of multi-layer structures in semiconductor manufacturing. Micro-scratch is the typical defect made during the CMP process, which are produced mainly because of agglomeration of slurry. Defects like micro-scratch lead to severe circuit failure, and affects yield. In this study, we described approaches to a production-worthy CMP process to prevent impact of micro-scratches on product wafer and lead to yield improvement. We have studied the effects of slurry filtration, pad cut rate of pad conditioner disks, and pad grooving design of the hard pads. By optimizing the consumables and polishing conditions, the hard pad-pad process showed 80% improvement in defectivity compared to the stack-type pad process.

The In-Situ Dressing of CMP Pad Conditioners with Novel Coating Protection

Kinik Company pioneered diamond pad conditioners protected by DLC barrier (DiaShield® Coating) back in 1999 (Sung & Lin, US Patent 6,368,198) and there has been no follower since then. Kinik's offered two varieties of DiaShield® Coatings: ultrahard tetrahedral amorphous carbon and superhard hydrogenated DLC. Kink also evaluated Cermet Composite Coating (CCC or C3, patent pending). C3 is unique that the coating composition grades from a metallic (e.g. stainless steel) under layer to a ceramic (e.g. Al2O3 or SiC) exterior. The metallic under layer can form metallurgical bond with metallic matrix on the diamond pad conditioner. The ceramic exterior is both wear and corrosion resistant. The gradational design of C3 coating will assure its strong adherence to the substrate because there is no weak boundary between coating and substrate. By dipping diamond pad conditioners of various designs in acidic solution (e.g. copper cleaning solution) for extended periods of time (e.g. 50 hours) the chemical inertness of various matrix materials are determined with the decreasing ranking as: hydrogenated DLC > C3 coating > tetrahedral amorphous carbon > sintered nichrome > brazed alloy > electroplated nickel.

Diamond Tools with Diamond Grits Set in a Predetermined Pattern

Although diamond tools have been used for over a century, the diamond grits distribution in the matrix is not uniform. This is because the large and light diamond grits tend to segregate from the small and heavy metal powder during the mixing process, hence diamond distribution in the diamond tools is intrinsically heterogeneous. As a result, the cutting performance of the diamond tools cannot be optimized. In 1997, Dr. James Chien-Min Sung applied two historical patents that can allow the design of diamond distribution according to a predetermined pattern. As the result, the life of diamond tools may be doubled; and the cutting speed, may also be twice as high. The three-dimensional saw segments with arrayed diamond grits were made back in 1999 with the improved performance as predicted. The Sung invention can allow the diamond tools industry to make ideal saw segment that has variable diamond size and diamond separation at different regions. Conventional diamond saws contain diamond grits that are distributed randomly in a metal matrix, as a result, their cutting speeds are slow and their sawing lives are short. In 1997, Dr. James C. Sung applied new patents that revealed revolutionary technology for making diamond tools with diamond grits set in a predetermined pattern. The diamond placement design was first appeared in a series of DiaGrid® products, such as wire saws and grinding wheels. In 1999, DiaGrid® pad conditioners was introduced and it has since become the world's standard for dressing pads, particularly those used for chemical mechanical planarization of semiconductor devices. In 2005, Shinhan adapted the idea and produced saw segments with diamond grits set in a predetermined pattern, their results confirmed that the sawing speed and the life were significantly improved over conventional designs.

Amorphous Diamond Dresser for CMP Fixed Abrasives Pad

The primary consumables in chemical mechanical polishing (CMP) are the polishing pad and slurry. The polishing pad significantly influences the stability of the polishing process and the cost of consumables (CoC). Usually a diamond pad conditioner is used to scrap off the polishing debris from the pad top. Recently, an alternative planarization process can be achieved by polishing with a "fixed abrasive pad" (FAP). In order to dress bumps on FAP, this paper use an amorphous diamond, a diamond-like carbon deposited by cathode arc system as the dresser for FAP. The amorphous diamond can produce a surface relief that ranges from a few nanometers to about 200 nanometers. With the addition of this dressing step on a rotary platform, FAP can renew its polishing surface 10 to 100 times before the bumps are used up. The pad cost for polishing can be reduced by at least ten folds and make FAP more desirable than slurry pad for silicon wafer manufacturer due to its intrinsic capabilities to produce flatter wafers with high polishing rate.

Advanced Pad Conditioner Design for Oxide/Metal CMP

Advanced CMP conditioner design requires investigations of key conditioner manufacturing parameters and their effects on pad surface and then wafer performance. In the present investigation, diamond shape, concentration, distribution, and other key manufacturing parameters are considered to improve CMP process stability and conditioner life. Self avoiding random distribution () of diamond abrasives has been developed and both numerical simulation and experimental results show very stable and reliable polishing performance.