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Effects of HEC Concentration on Silicon Polishing
摘要： Hydroxyethyl cellulose (HEC) is believed to effectively reduce haze level in silicon final polishing. We find that the removal rate(RR) and roughness of the polishing are very sensitive to the concentration of HEC, which can be divided into two concentration ranges. Its machanism is not only absorption occurence on silicon surface but also related to HEC colloid properties. Evidence has shown that HEC covers on the surface of silica sol, and there are three forms of coverage depending on the concentration, which have different effects on the interface between silicon and abrasive during polishing. Combined with steric hindrance, a possible polishing model is discussed based on the existence of HEC which is verifed by coeffiecient of friction force(CoF) according to HEC concentration. The results not only provide guidance for effective silicon polishing, but also imply that colloidal properties of additives with surface activity should be considered in other polishing systems.
关键词： Silicon wafer,Hydroxyethyl cellulose(HEC),Chemical-mechanical polishing(CMP)
更新于2025-09-10 09:29:36
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Materials Science and Technology of Optical Fabrication || Material Removal Rate
摘要： This chapter covers the last of the four major characteristics of optical fabrication, material removal rate (see Figure 1.6). As discussed in Chapter 1, the macroscopic material removal rate is governed by the Preston equation (Equation (1.3)), where removal rate largely scales linearly with applied pressure and relative velocity, and all the process and material parameters are lumped into the Preston coefficient kp. The Preston equation can be applied to both grinding (which is discussed in Section 5.1) and polishing (Section 5.2). The parameters that govern material removal rate and resulting surface roughness are intimately connected. Hence, the principles of the ensemble Hertzian multi-gap (EHMG) and island distribution gap (IDG) models, as discussed in Chapter 4, can be largely applied when discussing polishing material removal rate.
关键词： optical fabrication,IDG model,material removal rate,Preston equation,grinding,polishing,EHMG model
更新于2025-09-10 09:29:36
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Effect of chemical action on the chemical mechanical polishing of β-Ga2O3(100) substrate
摘要： Chemical mechanical polishing (CMP) is an essential processing step to realize ultra-precision machining of the fragile material Ga2O3 crystal and obtain ultra-smooth and undamaged crystal surface. The chemical auxiliary polishing mechanism of Ga2O3 in the CMP process was studied considering that the chemical action directly affects the CMP result. First, H3PO4 and NaOH were used to regulate the pH of slurry. This slurry was then applied to the CMP experiment of Ga2O3, and the corrosion test of Ga2O3 was implemented in H3PO4 and NaOH solutions. Second, the influence of the slurry with different acids or bases on the polishing result was analyzed. Finally, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the influence of the corrosive action on the chemical structure of the crystal surface. Results showed that the slurry prepared by H3PO4 was more suitable for the CMP of Ga2O3 than that prepared by NaOH. The polishing efficiency was enhanced by approximately 20% and the surface quality was improved, with surface roughness of 0.21 nm. This study provides a reference for preparing the slurry of Ga2O3.
关键词： Etching,Gallium oxide,Chemical mechanical polishing
更新于2025-09-10 09:29:36
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Improvement of the surface shape error of the pitch lap to a deterministic continuous polishing process
摘要： Continuous polishing using pitch lap is a key process in ?nishing large ?at optical elements. The ?gure of the optics is primarily dependent on the surface shape of the pitch lap. In this study, a novel method is proposed to determine the lap shape error by rotating the lap while the measurement point is moved radially using a precision slide mechanism. The systematic measuring error including the slide straightness error and slide perpendicularity error with respect to the lap rotary axis is divided into 1) the straightness and absolute horizontality error of the slide and 2) the absolute verticality error of the lap rotary axis. It is proposed that the former can be determined using a displacement sensor to measure water surface while moving along the slide, while the latter can be determined by an electric gradienter placed on the rotating lap. Furthermore, a small heating tool is proposed for correcting the local surface shape error of the pitch lap considering its viscoelastic property, and thus obtaining a favorable shape on the entire surface by controlling the dwell time of the small tool. Our experiments validated that the surface shape error of the pitch lap can be corrected by the method signi?cantly, and that the optic ?gure is signi?cantly promoted.
关键词： Determination and correction,Lap surface shape,Continuous polishing
更新于2025-09-09 09:28:46
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Materials Science and Technology of Optical Fabrication || Novel Process and Characterization Techniques
摘要： There are many conventional optical-fabrication process and characterization techniques, and they are well documented in the literature [1, 2]. These include the following: ? Interferometry techniques and test plating to measure surface ?gure, wedge, and parallelism ? Needle pro?lometry, white-light interferometry, and atomic force microscopy (AFM) to measure surface roughness ? Optical, confocal, and dark-?eld microscopy and visual inspection to measure surface quality ? Baume density ?oats, pH sensors, and particle-size analyzers to characterize polishing slurries ? Hardness testers to characterize lap materials, particularly pitch In this chapter, some novel techniques (and perhaps obscure techniques) that provide additional insight into the optical-fabrication process are described. Chapters 2–5 focused on the phenomena that govern the basic properties of a workpiece during and after optical fabrication, namely surface ?gure, surface quality, surface roughness, and material removal rate. The novel process and characterization techniques explored in this chapter are described for an optical-fabrication engineer or an optician who might wish to use them.
关键词： optical-fabrication,AFM,interferometry,characterization techniques,polishing slurries
更新于2025-09-09 09:28:46
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Materials Science and Technology of Optical Fabrication || Surface Figure
摘要： As described in Section 1.2, one of the major characteristics of the final optic is the surface figure, or long-range surface shape of the workpiece. Achieving the desired surface figure is a primary objective in fabricating an optic, because surface figure influences the wavefront modification of the incoming light, both in transmission and reflection. At the most basic level, the final surface figure of the workpiece is simply determined by its initial surface shape and the amount of material removed from each point on the workpiece surface, discounting residual stress changes. Hence, to quantitatively (i.e. deterministically) determine surface figure evolution in a given finishing process, one must understand all the phenomena that contribute to the material removal rate at each point and as a function of time. A useful approach to describe and organize these phenomena is to expand the traditional material removal rate Preston equation (Equation (1.3)). Preston’s equation may be described in a more general form as follows: [1]
关键词： material removal rate,Preston equation,surface figure,optical fabrication,polishing
更新于2025-09-09 09:28:46
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Materials Science and Technology of Optical Fabrication || Surface Quality
摘要： The terms “surface quality” and “subsurface mechanical damage” (SSD) are often loosely used. Here we define surface quality as a measure of the level of perfection a workpiece surface exhibits after finishing and cleaning. A perfect surface is defined as a surface free of mechanical, structural, and chemical modification relative to bulk. Note surface quality does not include surface roughness, which is treated separately in Chapter 4. In practice, there is no such thing as a perfect surface, because a variety of microscopic and molecular surface modifications may occur on or just below the surface of the workpiece. As illustrated in Figure 3.1, surface modifications include the following: ? Subsurface mechanical interactions (SSD), which may lead to fracturing, plastic flow, or densification at the surface. ? Foreign particles or residue that may be deposited on the surface as particles land or precipitate during drying. ? Chemical and structural interactions that may result from changes in surface molecular moieties or by altering the near-subsurface (Beilby) layer. These factors affecting surface quality may vary significantly in scale length, from tens of μm to Angstrom level.
关键词： etching,Beilby layer,subsurface mechanical damage,SSD,polishing,grinding,surface quality
更新于2025-09-09 09:28:46
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Ammonium Persulfate and Potassium Oleate Containing Silica Dispersions for Chemical Mechanical Polishing for Cobalt Interconnect Applications
摘要： We investigated the suitability of ammonium persulfate (APS) and potassium oleate (PO) containing silica dispersions for polishing Co interconnects based on removal and dissolution rates, corrosion, post-polish surface quality, and post-polish particle contamination. A slurry consisting of 3 wt% silica, 1 wt% APS and 0.2 mM PO produced a removal rate of ～465 nm/min at pH 9, along with removal rate selectivity of >100:1 between Co and TiN. The same composition but without abrasives reduced the (cid:2)Ecorr between Co and TiN to ～ 7 mV and Igc to ～0.04 μAcm?2, indicating minimal galvanic corrosion. Addition of PO led to no measurable dissolution of the Co ?lms. Surface analysis showed very good post-polish surface quality and minimal contamination with silica particles. These and results obtained with similar H2O2 containing slurries suggest that the APS and PO-based silica slurry is more suitable for the Co bulk CMP process. The roles of persulfates ions, pH, and PO on the removal process and passivation behavior of Co are discussed and a removal mechanism is proposed.
关键词： potassium oleate,Ammonium persulfate,cobalt interconnect applications,chemical mechanical polishing,silica dispersions
更新于2025-09-04 15:30:14
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Materials Science and Technology of Optical Fabrication || Surface Roughness
摘要： Because it influences optical-scatter losses and downstream laser modulation [1], the surface roughness of an optical-glass component is an important parameter for many optical systems (including lasers and telescopes). During optical polishing, a number of interactions between the workpiece, polishing slurry, and pad may influence the resulting workpiece roughness at different spatial scale lengths. The phenomena affecting large spatial scale length (>1 mm) on the workpiece (i.e. surface figure) are described in Chapter 2 (see Figure 2.1). By contrast, in this chapter, the phenomena and process parameters affecting short spatial scale lengths (<1 mm) (i.e., surface roughness from AFM2 scale roughness to μ-roughness) are described (see Figure 1.8). Fine-scale roughness, typically measured by atomic force microscopy (AFM), is referred to as AFM1 (≤5 μm) and AFM2 roughness (≤50 μm), as represented on the right of the plot. Roughness at this scale is influenced by parameters such as the single-particle removal function, Beilby layer properties, slurry particle size distribution (PSD), pad topography, pad mechanical properties, and slurry particle redeposition. The next higher spatial scale length (the micrometer to millimeter range, known as micro- or μ-roughness), is usually measured by white-light interferometry (Figure 1.8). μ-Roughness is affected not only by the smaller spatial-scale length phenomena given above, but also by factors governing slurry-interface interactions, such as the spatial distribution of slurry particles present at the interface. These parameters and phenomena are listed Figure 4.1, consisting of a schematic of the workpiece–lap interface at the spatial scale length of interest that influences the final polished surface roughness. Figure 4.1 provides a valuable outline for this chapter.
关键词： Optical Polishing,Slurry PSD,Pad Topography,AFM,μ-Roughness,Surface Roughness
更新于2025-09-04 15:30:14