Pad roughness variation and its effect on material removal profile in ceria-based CMP slurry

Park, Boumyoung; Lee, Hyunseop; Park, Ki Hyun; Kim, Hyoungjae; Jeong, Haedo

doi:10.1016/j.jmatprotec.2007.10.033

Cited by 37 publications

(20 citation statements)

References 14 publications

(13 reference statements)

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“…The influences of pad wear and changes in pad properties during polishing have been previously investigated. Park et al 18 showed that the wafer (or workpiece) also contributes to non-uniform pad roughness and thickness of a polyurethane foam pad. can occur.…”

Section: Introductionmentioning

confidence: 99%

“…The influences of pad wear and changes in pad properties during polishing have been previously investigated. [15][16][17][18] Here the workpiece and/or conditioner (typically a fixed diamond abrasive to treat the pad for CMP or a sacrificial workpiece used during pad optical polishing) is loaded against the pad surface and, as a result, spatial and temporal changes in the pad properties (thickness profile, roughness, slurry charging level, etc.) can occur.…”

Section: Introductionmentioning

confidence: 99%

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Convergent Pad Polishing of Amorphous Silica

Suratwala

Steele

Feit

et al. 2012

Int J of Appl Glass Sci

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A new method of optical polishing termed “Convergent Polishing” is demonstrated where a workpiece, regardless of its initial surface figure, will converge to the lap shape in a single iteration. This method of polishing is accomplished by identifying the phenomena that contribute to non‐uniform spatial material removal, and mitigating the non‐uniformity for each phenomenon (except for the workpiece‐lap mismatch due to the workpiece surface shape). The surface mismatch at the interface between the workpiece and lap causes a spatial and time varying pressure differential which decreases with removal, thus allowing the workpiece to converge to the shape of the lap. In this study, fused (amorphous) silica workpieces are polished using ceria slurry on various polyurethane pads. Polishing parameters were systematically controlled to prevent various sources of non‐uniform material removal which include: (i) moment force, (ii) viscoelastic lap relaxation, (iii) kinematics, (iv) pad wear, and (v) workpiece bending. The last two are described herein. With these mitigations, removal uniformity has been demonstrated to within 1.0 μm over the surface after 83 μm of material removal corresponding to a within workpiece non‐uniformity (WIWNU) of <1.2%. Also, convergence has been demonstrated down to 0.18 ± 0.04 μm peak‐to‐valley flatness on 100 mm‐sized workpieces.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Convergent Pad Polishing of Amorphous Silica

Suratwala

Steele

Feit

et al. 2012

Int J of Appl Glass Sci

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“…Normally, the surface roughness tends to diminish throughout the polishing process because conditioning ability of the disk is reduced along with the polishing process. In the silica based slurry, oxide removal rate and roughness of pad in Rpk profile have negative relationship [4]. In W CMP, the removal rate is also influenced by temperature and slurry concentrations.…”

Section: Introductionmentioning

confidence: 98%

A novel pad conditioner and pad roughness effects on tungsten CMP

Lim

Kim

Jang

et al. 2014

Proceedings of International Conference on Planarization/CMP Technology 2014

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In the BEOL (back end of line) process, tungsten (W) chemical mechanical planarization (CMP) has been commonly used to form contacts. As size of the metal line is shrunk, metal CMP will directly impacts resistance and reliability characteristic of final product. As examples, W contact recess and seam (or void) defects make resistance problems and block failure.In the W CMP Process, W is oxidized by etchant, and then removed by abrasives. Progressively, this process is cycled again until all bulk W is removed. Hydrogen peroxide (H 2 O 2 ) and silica nanoparticles are commonly used as etchant and abrasive, respectively, to remove the material.To overcome W contact recess issue, we recently have used less selective slurry for W bulk and oxide films. To maintain such selectivity between these films during CMP, however, control of pad roughness evolution throughout the pad lifetime is the most important. Thus, proper selection of pad conditioner is demanded.Chemical etchant is essential to remove W but it also impacts on diamond grits on the pad conditioner in the manner if accelerating wear of the grits. As the pad roughness is diminishing by the wear of the grits, wear resistance of diamond is a key factor to keep desired W to oxide selectivity throughout the pad lifetime. In this experimental study, we used low selective slurry to decrease W recess and evaluated two different types of pad conditioners for keeping the process time variation as stable as possible throughout the pad lifetime. The conditioners have novel design of diamond grit pattern. Pad cut rate (PCR) of the each conditioner was evaluated as well. It was shown that minimum threshold PCR is exist to maintain the pad roughness to reduce process time variation. Finally, it is suggested that moderate surface roughness is required to form contact between pad and wafer to maintain moderate process time.

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“…9 Thus, the polishing pad needs to be maintained in an effective form by appropriate conditioning. 4,10 In particular, stabilization of the pad surface is very important for achieving a high removal rate. Therefore, during serial batch polishing tests, it is important to monitor polishing-induced changes in the pad surface texture so that the duration of polishing the pad surface can be modified in order to achieve the desired surface texture.…”

mentioning

confidence: 99%

“…4 Therefore, it is extremely important to develop methods for the quantitative evaluation of the actual contact conditions between the wafer and the polishing pad and to examine the effects of these conditions on the CMP characteristics.…”

mentioning

confidence: 99%

Relationships between Contact Image Analysis Results for Pad Surface Texture and Removal Rate in CMP

Uneda

Maeda

Ishikawa

et al. 2011

J. Electrochem. Soc.

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In chemical mechanical polishing (CMP) process, the removal rate is affected by the actual contact conditions between the wafer and the polishing pad. Further, the free abrasives in the slurry attack the wafer at the regions of actual contact. The polishing pad is one of the most important consumable materials in CMP since the pad surface texture changes during wafer polishing and substantially influences the actual contact conditions. Therefore, methods for quantitative evaluation of the pad surface texture have been proposed by various research institutes. We have developed a novel method for the quantitative evaluation of the polishing pad surface texture; this method is based on contact image analysis using an image rotation prism. We have proposed the use of four effective evaluation parameters: the number of contact points, the contact ratio, the maximum value of the minimum spacing of the contact points, and the half-width of the peak of the spatial fast Fourier transform (FFT) of a contact image. We determine the changes in the polishing pad surface texture on the basis of the proposed evaluation parameters in serial batch polishing tests. In particular, we focus on the relationships between the proposed evaluation parameters and the removal rate, which changes with an increase in the number of batch polishing tests. The evaluation parameters are linearly correlated with the removal rate. Hence, the removal rate is improved not only with an increase of the number of contact points and the contact ratio but also with a decrease in the size of the cohesion regions and the spacing between the contact points.Progress in science and technology depends substantially on innovations in the semiconductor industry. For example, silicon wafers used for semiconductor device fabrication should have highly flat surfaces, and because of the continuous downsizing of such devices, 1 nanometer-scale planarization becomes important. Therefore, there is an increasing demand for chemical mechanical polishing (CMP) techniques.Recently, it was found that the material removal rate in wafer polishing is affected by the actual contact conditions between the wafer and the polishing pad. 2, 3 The actual contact conditions affect both the mix effects of chemical mechanical factors of the slurry and the viscoelastic deformation of the pad. Additionally, the free abrasives in the slurry attack the wafer at the regions of actual contact. 3 Therefore, it is important to identify the optimum contact conditions under which the slurry can effectively act on the wafer and the removal rate can be improved.The polishing pad is one of the most important consumable materials used in CMP since its surface texture has a substantial influence on the actual contact conditions. 4 Therefore, it is extremely important to develop methods for the quantitative evaluation of the actual contact conditions between the wafer and the polishing pad and to examine the effects of these conditions on the CMP characteristics.With this background, we have developed ...

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Pad roughness variation and its effect on material removal profile in ceria-based CMP slurry

Cited by 37 publications

References 14 publications

Convergent Pad Polishing of Amorphous Silica

Convergent Pad Polishing of Amorphous Silica

A novel pad conditioner and pad roughness effects on tungsten CMP

Relationships between Contact Image Analysis Results for Pad Surface Texture and Removal Rate in CMP

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