Diamond Conditioner Research Articles

Investigating the Impact of Pad Groove Depth Reduction on Process Variation in Oxide Chemical Mechanical Polishing

Abstract The groove depth of a polishing pad diminishes due to continuous wear from the diamond conditioner. Over the course of approximately 20 hours of use, this reduction in groove depth enhances slurry flow across both the pad grooves and surface. A fluid simulation analysis indicates that the new slurry mass fraction at 0.51 seconds increases from 72.34% for an 850 µm groove depth to 100.00% for a 250 µm depth. Consequently, polishing performance metrics including removal rate, within-wafer nonuniformity (WIWNU), and added defects exhibit variations commensurate with groove depth alterations. To explore the influence of process parameters on these polishing performance metrics, oxide film polishing experiments were conducted using pads with initial groove depths of 250, 500, 750, and 850 µm. The effects of process parameters, including pad cut rate, retainer ring pressure, and slurry flow rate on polishing were separately examined across different groove depth pads. Generally, shallow groove pads display improved removal rates but worse WIWNU. Additionally, the maximum surface temperature of the pads was recorded, serving as an indirect indicator of individual parameter effects. The findings have implications for advanced process control, guiding the optimization of polishing protocol in consideration of pad lifetime.

CMP Pad Conditioning Using the High-Pressure Micro-Jet Method.

In this study, in order to improve and restore the performance of the polishing pads and reduce the cost of chemical mechanical polishing, three types of material polishing pads, namely, polyurethane, damping cloth, and non-woven fabric, were selected for the experiment. Accordingly, each polishing pad was set up with diamond conditioner and high-pressure micro-jet (HPMJ) conditioning control experiments. Subsequently, the fluctuation ranges of the material removal rate on the three polishing pads were 2.73-3.75 μm/h, 1.38-1.99 μm/h, and 2.36-4.32 μm/h, respectively under the HPMJ conditioning method, while the fluctuation ranges of the material removal rate on the three polishing pads were 1.80-4.14 μm/h, 1.02-2.09 μm/h, and 1.78-5.88 μm/h under the diamond conditioning method. Comparing the polishing pad morphologies under SEM, we observed that the surface of the polishing pad after HPMJ conditioning was relatively clean, and the hole structure was not blocked. Contrastingly, there remained numerous abrasive particles on the surface after the conventional diamond conditioning and the hole structure was blocked. Thus, the HPMJ conditioning technology is better than the traditional diamond conditioning technology. Subsequently, the polishing pad after HPMJ conditioning has a longer service life and a more stable material removal rate than that after traditional diamond conditioning.

Kinematic Prediction and Experimental Demonstration of Conditioning Process for Controlling the Profile Shape of a Chemical Mechanical Polishing Pad

The uniformity of the wafer in a chemical mechanical polishing (CMP) process is vital to the ultra-fine and high integration of semiconductor structures. In particular, the uniformity of the polishing pad corresponding to the tool directly affects the polishing uniformity and wafer shape. In this study, the profile shape of a CMP pad was predicted through a kinematic simulation based on the trajectory density of the diamond abrasives of the diamond conditioner disc. The kinematic prediction was found to be in good agreement with the experimentally measured pad profile shape. Based on this, the shape error of the pad could be maintained within 10 μm even after performing the pad conditioning process for more than 2 h, through the overhang of the conditioner.

Analysis on Pad Surface Roughness of Diamond Conditioning Process for CMP

Chemical Mechanical Polishing/Planarization (CMP) is the key process of the wafer and thin film planarization process for semiconductor manufacturing. In the CMP process, the pad can restore its surface topography and efficiency by diamond conditioner or named as diamond conditioning process. The pad surface roughness is essential to the removal rate in the CMP process because it can represent the contact level of the polishing pad and wafer. This study has developed a simulation program based on precise diamond-grits conditioning routes and numbers of cross points. By studying the OP (overlap cutting points) distribution in a specific area on the pad which is generated by CL (cutting locus), the trend of roughness parameters is discovered. The simulation and experimental model can be effective to observe pores deformation and predict pad surface topography. The results show the pad roughness would become steady over a certain OP number, and the OP can be precisely calculated and compared to the actual pad surface. The final results of the break-in and pad conditioning process can be estimated or further optimized. The other high-density and customized diamond-grits arrangement of conditioner can be designed according to the study in future work.

Prediction of Pad Wear Depending on Structural Factors of Diamond Conditioner

The conditioning process with diamond conditioners is an important role in maintaining chemical mechanical polishing (CMP) performance constant. The conditioning process maintains the surface roughness of the pad and uniformity of the pad wear, resulting in stable material removal rate (MRR) and low within wafer non-uniformity (WIWNU). The pad uniformity is greatly changed by the mechanical action in the conditioning process, and the action is controlled by three mechanical movements; pad / conditioner rotation, conditioner arm sweep. From these three motions, the pad wear profile can be obtained by accumulating the number of points in the pad mesh containing the coordinates of the diamonds moving at a specific time or distance by the movement of the diamond grit as shown in Fig. 1. In addition, we tried to confirm the pad profile and wear amount depending on the structural properties of the conditioner, applying the diamond characteristics of the conditioner which directly causes the wear. The structural factors of conditioner that affect conditioning are pattern, pitch, size, number and shape of diamond. These factors were formulated and applied in simulation. Then, pad wear amount was calculated from the indentation depth according to the diamond characteristics, and pad profile by wear rather than profile by line density was proposed. The pad wear amount of simulation results according to the number of diamonds are shown in Fig. 2. Finally, pad wear can be predictable according to various equipment or process conditions and it is also possible to analyze the effect of the conditioner on pad wear through this research. This work is achieved by approaching the process of conditioning in CMP from the topologic aspects and the program is developed through it. The kinematic motion of individual diamonds is modelized and simulated with structural properties of the conditioner to see how these affects the pad wear and profile. Figure 1

Improvement and application of pad conditioning accuracy in chemical mechanical polishing

Chemical mechanical polishing (CMP) is the key application process in the fabrication of large optical flats to achieve global planarity and smooth surface. The large-diameter pad is a significant part and plays a vital role in CMP. To improve the polishing quality and efficiency, high-profile accuracy of the pad, conditioned by a diamond conditioner, is necessary. However, the conventional conditioning method (CCM) has been unable to satisfy the machining requirements for optical flats, and it is a challenge to improve the conditioning accuracy of the large-diameter polyurethane pad. In this study, we propose an advanced conditioning method (ACM) using the idea of subaperture conditioning, which reduces the size of the conditioner and adds the traverse movement to control the removal of different regions. Based on the conditioning density distribution model, the effect of conditioner diameter and process parameters on the pad planarity is investigated. The conditioning accuracy of the pad and polishing quality of the optical flats obtained with ACM are compared with those of a CCM. Experimental results showed that ACM can create the surface shape of the pad more uniformly than CCM. Furthermore, the polishing accuracy of the large optical flats of ACM exceeds that of CCM.

Diamond structure-dependent pad and wafer polishing performance during chemical mechanical polishing

A diamond conditioner is one of the essential components in the maintenance of surface roughness of a pad during chemical mechanical polishing (CMP). In this paper, four different types of diamond conditioner were evaluated for the pad wear rate (PWR) and the material removal rate (MRR) during the pad conditioning and the wafer polishing ex situ. The experiment results revealed that the pad conditioning is strongly dependent on the diamond orientation as compared to grit size and pitch. It is observed that the PWR for “C type” conditioners is about 0.3 mm/h which is higher than that of “N type” diamond conditioner. The COF of “N type” diamond conditioner has the lowest value of ~0.56. The MRR using pad treated by “N type” diamond conditioner is approximately 3500 A/min, which is about 1.6 times higher than that of C1-type diamond conditioner which has same diamond grit size and pitch.

Method for accelerated diamond fracture characterization in chemical mechanical planarization

An accelerated method for diamond fracture characterization in chemical mechanical planarization processes was developed and several practice examples were described showing that the accelerated fracture test was appropriate for differentiating among typical diamond conditioner disks. First, the top ten aggressive diamonds for each of the three conditioner disks tested were identified and imaged using scanning electron microscopy (SEM). Next, the three disks were subjected to a 30-min accelerated fracture test against an aluminum plate on an Araca APD-800 polisher. SEM images were taken again on the same ten most aggressive diamonds. Even though the accelerated fracture test was designed to be analogous to conventional pad conditioning, significant changes to the diamonds could be seen only after 30min of conditioning. Image analysis demonstrated that diamond fracture occurred in all three cases, but to very different extents.

Development and Analysis of Double-Faced Radial and Cluster-Arranged CMP Diamond Disk

In semiconductor manufacturing, diamond disks are indispensable for dressing chemical mechanical polishing (CMP) pads. Recently, 450 mm (18 inch) diameter wafers have been used to improve output and reduce wafer production cost. To polish 450 mm diameter wafers, the diameter of polishing pads must be increased to 1050 mm. In particular, because diamond disks are limited to 100 mm diameters, a much greater number of working crystals will be required for dressing a 1050 mm diameter pad. Consequently, new diamond disks must be developed. In this study, novel arrangements are made using a braze in diamond patterns, which are radial with a cluster arrangement of 3-4 grits per cluster. Furthermore, a double-faced combined diamond disk is developed. The polishing pad surface was characterized, and the effect of different diamond conditioners on wafer removal rate was studied. This research aims to develop a more suitable diamond disk for dressing 1050 mm diameter polishing pads.

Investigation of Dressing Characteristics of Single Crystal Diamond in CMP

Diamond conditioners, or dressers, are commonly used to dress polishing pads that are applied to the chemical mechanical polishing of silicon wafers for integrated circuits. Although the diamond conditioner has regular distribution diamond grits, they differ in shape and can be oriented differently because the shape of diamond grits is generally cubo-octahedral. Therefore, the dressing behaviors on the polishing pad are unpredictable. In this work, the fundamental characteristics of dressing are investigated by a single crystal diamond with various shapes (each resulting in point-cutting, line-cutting, and face-cutting), a rake angle of-50°, and cutting faces in the (100) and (111) planes. For the purpose of analysis, plowing ratio is defined as the sum of the areas of the two side ridges divided by the groove area. This ratio can be used to evaluate the contribution of plowing and cutting actions from the dressing. Experimental results reveal that a groove with ridges on both side walls is formed as the diamond is moved over the pad. The profile of the scratch correlates with the shape of the diamond. In summary, cutting dominates when point-cutting is responsible for the dressing. On the contrary, plowing plays a major role with respect to line-cutting. The cutting action tends to dominate when the dressing is completed by face-cutting a (111) plane. Alternatively, the wear tends to be dominated by the plowing action if the dressing is conducted via face-cutting a (100) plane.

The impact of diamond conditioners on scratch formation during chemical mechanical planarization (CMP) of silicon dioxide

The effects of pad surface roughness and debris induced by various types of diamond conditioners during the chemical mechanical planarization (CMP) process and their scratch forming behaviors were evaluated. Five types of conditioners having different grade numbers and densities were used to condition the polyurethane pads. When conditioned using low-density and sharp diamond conditioners, the roughness and wear rate of the pads were found to be higher with higher removal rates. The scratch generation behavior showed a similar trend to that of the removal rate. Additionally, the scratch formation was evaluated through the in-situ/ex-situ pad conditioning. Based on in-situ/ex-situ pad conditioning experiments, it was found that ex-situ pad conditioning process resulted in lower removal rate with lesser number of scratches.

Improvement of Surface Figure in the Polyurethane Pad Continuous Polishing Process

Primary factors determining surface figure of optics, including the velocity and pressure distributions, have been analyzed and improving methods provided accordingly for the pad continuous polishing (CP). With a septum on the exterior of the workpiece pre-pressing the pad, the inevitable depression on the edge of the workpiece incurred by the elastic response of the pad has been relieved obviously. By introducing the driving wheel system, the rotation speed of the septum & workpiece can be regulated and adjusted to that of the lap/pad, which produces a uniform velocity distribution on the polishing surface. Diamond conditioners with ring & disk patterns are employed to planarize the annular polyurethane pad and hence uniformise the pressure distribution on the workpiece/pad interface. Polishing experiments (Fused silica flat, 320 mm in diameter x 30 mm thick) conducted on the typical CP machine have demonstrated advantages of these methods.

Modification of Diamond Conditioner with V-SAM Coatings for Corrosion Prevention During Metal CMP

Modification of Diamond Conditioner with V-SAM Coatings for Corrosion Prevention During Metal CMP

Mid-Spatial Frequency Error (PSD-2) of optics induced during CCOS and full-aperture polishing

Mid-Spatial Frequency (MSF) Wavefront Error of optics divided into the PSD-1 and PSD-2 ranges plays an important role in the performance of high power laser systems. The present work focuses on the PSD-2 range in terms of short ripples which haven’t been well studied in the literature. Characteristics and origins of these short ripples were detailed, whereafter small tool computer controlled polishing (CCP) and conventional full aperture polishing experiments were conducted on fused silica. It is revealed that PSD2 error is independent of the main process parameters including lap rotating rate and polishing pressure in continuous polishing and tool path pitch and crossfeed velocity in small tool CCP processes. Whereas the type of polishing lap has a decisive effect on PSD2 error of the optics. The pitch lap shows superiority in restraint of short ripples over polyurethane pad. By introducing diamond conditioner for dressing polyurethane pad, the PSD2 error has been greatly decreased.

光学元件中高频PSD2误差的实验研究

Mid-spatial frequency wavefront error of optics is characterized with the power spectrum density (PSD) specification, and is divided into two parts: PSD1 (wavelength 2.5-33 mm) and PSD2 (wavelength 0.12-2.5 mm). Rather than the PSD1 error which has been researched in the literature, the present work focuses on the PSD2 range. Potential factors affecting PSD2 error are firstly analyzed. Polishing experiments reveal that computer controlled small-tool polishing process does not worsen PSD2 error compared to the full-aperture process, while the lap has a decisive effect. The optics polished by pitch laps shows a fair PSD2 error of 0.7 nm (RMS), which is much lower than the specified 1.1 nm. The polyurethane pad commonly results in a much higher PSD2 error of more than 1.5 nm (RMS). For this problem, we adopt diamond conditioner to dress the pad and decrease pad surface roughness. The validation of restraining PSD2 error by diamond dressing has been confirmed.

Fabrication of diamond conditioners by using a micro patterning and electroforming approach

Micro patterning and nickel electroforming, which are commonly used in MEMS process to fabricate microstructures or micro components, were employed in this study for the fabrication of diamond conditioners. The thickness of the JSR THB-151N resist on the stainless steel substrate can reach up to [email protected], which is sufficient for forming a mask. The diamond grits which were embedded in the nickel deposit formed microcolumns array on the substrate with the guidance of the resist mold. By using this technique, the population density of the working diamond grits in the diamond conditioner can be increased. Moreover, an extra strike nickel plating was performed to functionalize the surface of the nickel deposit for increasing the polarization of the nickel deposit which can eliminate the edge effect in the enhancement electroplating process. This fabrication process developed herein can produce diamond conditioners with improved uniformity in both distribution and protrusion control of micro column diamond cutting tips. In addition, the developed diamond conditioners exhibit an increase in material removal rate (MRR) by some 15%, while, at the same time, maintain a relatively low worn rate as compared to the commercially available conditioners.

CMP Defects; Their Detection and Analysis on Root Causes

Particles and scratches are most wanted defects to be minimized in CMP processes. The root causes for them are mostly consumables related such as pad, slurry and diamond conditioning. The evaluation of additives in slurry is neglected in terms of their defect generation on wafer. The adhesion force can be measured between particle and wafer surface in given chemistry to select the additive which causes least particle contamination in both slurry and cleaning solutions. Also, the scratch detection and analysis are very time consuming and require advanced methodology even in wafer production facility. The lab scale scratch detection method was developed to study the effect of slurry and conditioning on wafer during CMP. In this presentation, we report the utilization of particle adhesion force on CMP process development and the detection of scratches on oxide wafer. The effect of slurry, pad and diamond conditioner on scratch formation was investigated with their classification

Organic diamond disk versus brazed diamond disk for dressing a chemical–mechanical polishing pad

Diamond pad conditioners can be used to determine the efficiency of chemical–mechanical polishing (CMP) processes and the quality of polished wafers. Conventional diamond conditioners such as brazed diamond disks (BDDs) consist of braze-bonded diamond grits. Although conventional diamond conditioners consist of regularly distributed diamond grits, the grit tips are not leveled to the same height. In this research, we evaluated diamond conditioners manufactured using polymer-bonded diamond grits for use in CMP; these conditioners are known as organic diamond disks (ODDs). ODDs are fabricated by reverse casting the substrate. Instead of using a flat substrate as the backing for attaching diamond grits, the substrate is prepared after the diamond grits are leveled on the surface of a mold. The ODD and the BDD were fabricated as circular dressing disks and used in the CMP of dielectric oxide films. Diamond leveling (height distribution of the diamond grits) for the BDD is found to be greater than 50μm. The diamond tips of the ODD are leveled to less than 15μm. The results show that the ODD-dressed pads produce fewer defects in wafers than the BDD-dressed ones. Although the pad dressing rate is lower for the ODD, the wafer removal rate for the ODD is higher than that for the BDD. Hence, the use of ODDs for the mass production of semiconductors can increase not only the lifespan of both the disks and the pads but also the throughput of wafers produced during CMP. Finally, the ODD is processed at room temperature to prevent thermal degradation of its diamond grits.

Hydrophobic Modification of Diamond Conditioner for Prevention of Particle Adhesion During Oxide CMP

Conditioning with a diamond conditioner is a routine practice in the chemical mechanical planarization process to maintain removal rate and uniformity. Electroplated Ni conditioner surfaces can be easily contaminated by polishing residues from the slurry, pad, and by-products during conditioning. In this study, a hydrophobic film was coated onto a Ni conditioner by vapor phase self assembled monolayer (V-SAM) deposition to prevent contamination. The film was deposited in a vacuum chamber at 0.5 Torr and 100°C using a fluorocarbon (FC) precursor. The modification of the Ni surfaces increased the contact angle from 50 to 105°. The adhesion force between the Ni surface and silica particles was approximately 100 nN in a solution of pH 11.2. The precursor coated Ni resulted in a five times lower adhesion force than the uncoated Ni conditioner. The coated conditioner did not attract any slurry residues on its surface, even after conditioning for 20 h with a fumed silica oxide slurry.

Diamond Conditioner Microwear Effect on Pad Surface Height Distribution in Tungsten Chemical Mechanical Polishing

In this study, the surface topographies of chemical mechanical polishing (CMP) pad samples for varying levels of diamond microwear of a conditioner have been measured using a confocal microscope and an X-ray computer tomography (CT) scanner. The experimental results showed that the increase in the pad debris on the pad surface reduced the pad height ratio of the asperity called the “top surface area (TSA) ratio”. In addition, the overall removal rate in tungsten CMP was more dependent on the TSA ratio after polishing than on that after conditioning because the pad surface condition became worse with deformed asperities and micropores due to the insufficient conditioning.