{"id":2604,"date":"2026-08-06T13:44:42","date_gmt":"2026-08-06T05:44:42","guid":{"rendered":"https:\/\/jeez-semicon.com\/?p=2604"},"modified":"2026-08-06T13:44:42","modified_gmt":"2026-08-06T05:44:42","slug":"colloidal-silica-for-sapphire-and-glass-polishing-cmp-beyond-the-silicon-wafer","status":"publish","type":"post","link":"https:\/\/jeez-semicon.com\/es\/blog\/colloidal-silica-for-sapphire-and-glass-polishing-cmp-beyond-the-silicon-wafer\/","title":{"rendered":"Colloidal Silica for Sapphire and Glass Polishing: CMP Beyond the Silicon Wafer"},"content":{"rendered":"<style>\n@import url('https:\/\/fonts.googleapis.com\/css2?family=Sora:wght@400;500;600;700&family=IBM+Plex+Sans:ital,wght@0,400;0,500;0,600;1,400&display=swap');\n.jcs-wrap *{box-sizing:border-box}.jcs-wrap{font-family:'IBM Plex Sans',system-ui,sans-serif;font-size:16px;line-height:1.8;color:#1a1a2e;max-width:920px;margin:0 auto}\n.jcs-wrap 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2.1rem;border-radius:6px;text-decoration:none}\n.jcs-cta-btn:hover{opacity:.9;color:#0b1840;text-decoration:none}\n.jcs-hr{border:none;border-top:1px solid #e2e8f0;margin:2.25rem 0}\n.jcs-footnote{font-size:.82rem;color:#64748b;line-height:1.65;margin-top:1.75rem}\n.jcs-footnote strong{color:#475569}\n@media(max-width:600px){.jcs-hero{padding:1.75rem 1.4rem}.jcs-cta{padding:1.75rem 1.4rem}.jcs-wrap h2{font-size:1.15rem}}\n<\/style>\n\n<article class=\"jcs-wrap\">\n<div class=\"jcs-hero\">\n  <span class=\"jcs-hero-tag\">Application Guide \u00b7 Cluster C-07<\/span>\n  <p>A technical guide to applying colloidal silica CMP slurry beyond silicon\u2014covering the tribochemical polishing mechanism for sapphire (Al\u2082O\u2083), process parameter optimization for LED and power device substrates, display glass final polishing, precision optical components, and hard disk drive substrates.<\/p>\n  <div class=\"jcs-hero-meta\">\n    <span class=\"jcs-meta-pill\">\ud83d\udcc5 <b>August 2026<\/b><\/span>\n    <span class=\"jcs-meta-pill\">\u23f1 <b>~12 min read<\/b><\/span>\n    <span class=\"jcs-meta-pill\">\u270d <b>JEEZ Technical Team<\/b><\/span>\n  <\/div>\n<\/div>\n<span class=\"jcs-updated\">Published by Jizhi Electronic Technology Co., Ltd. (JEEZ) \u00b7 August 2026<\/span>\n\n<nav class=\"jcs-toc\" aria-label=\"\u00cdndice\">\n  <p class=\"jcs-toc-label\">\u00cdndice<\/p>\n  <ol>\n    <li><a href=\"#beyond-silicon\">Colloidal Silica Beyond the Silicon Wafer<\/a><\/li>\n    <li><a href=\"#sapphire-properties\">Sapphire: Material Properties and CMP Challenges<\/a><\/li>\n    <li><a href=\"#al2o3-mechanism\">Tribochemical Mechanism for Al\u2082O\u2083 Removal<\/a><\/li>\n    <li><a href=\"#sapphire-process\">Process Parameters for Sapphire CMP<\/a><\/li>\n    <li><a href=\"#sapphire-targets\">Surface Quality Targets: LED vs Power Device Substrates<\/a><\/li>\n    <li><a href=\"#display-glass\">Display Glass Polishing<\/a><\/li>\n    <li><a href=\"#optical-glass\">Optical Glass and Precision Optics<\/a><\/li>\n    <li><a href=\"#hdd\">Hard Disk Drive Substrate Polishing<\/a><\/li>\n    <li><a href=\"#jeez-cs100\">JEEZ CS-100 for Non-Silicon Applications<\/a><\/li>\n    <li><a href=\"#faq\">Preguntas frecuentes<\/a><\/li>\n  <\/ol>\n<\/nav>\n\n<p>The semiconductor industry is colloidal silica&#8217;s largest and most technologically demanding market, but it is far from its only application. The same properties that make colloidal silica ideal for silicon and oxide CMP\u2014nanometer-scale particle uniformity, tribochemical surface reactivity, chemical tunability, and process flexibility\u2014also make it the preferred abrasive for precision polishing of sapphire substrates for LED and power electronics, large-format display glass panels, precision optical components, and hard disk drive substrates.<\/p>\n\n<p>In each of these applications, colloidal silica achieves surface quality results that conventional abrasives cannot match, through a fundamentally similar tribochemical mechanism adapted to the specific surface chemistry of each substrate material. This guide covers the science and practice of each major non-silicon application.<\/p>\n\n<section id=\"beyond-silicon\">\n  <h2>1. Colloidal Silica Beyond the Silicon Wafer<\/h2>\n  <p>The versatility of colloidal silica as a precision polishing abrasive stems from a single material property: the surface silanol groups (Si-OH) on every colloidal SiO\u2082 particle can form transient chemical bonds not only with SiO\u2082 surfaces but also with the hydrated surfaces of other oxide materials\u2014Al\u2082O\u2083, SiO\u2082 glass, aluminosilicate glass\u2014enabling the same tribochemical removal mechanism to function across a wide range of substrate chemistries.<\/p>\n  <p>The mechanism in all cases is analogous to silicon dioxide CMP: alkaline slurry chemistry attacks the substrate surface to form a softer, hydrated surface layer; the colloidal silica abrasive forms transient bonds with the hydrated layer; relative motion between abrasive and substrate shears surface fragments away; the cycle repeats. What changes between applications is the specific chemistry required to hydrate each substrate, the particle size and pressure parameters needed to optimize MRR vs. surface quality for each material&#8217;s hardness and roughness specification, and the pH window dictated by each substrate&#8217;s chemical stability.<\/p>\n<\/section>\n\n<section id=\"sapphire-properties\">\n  <h2>2. Sapphire: Material Properties and CMP Challenges<\/h2>\n  <p>Single-crystal sapphire (corundum, \u03b1-Al\u2082O\u2083) is the dominant substrate material for GaN-based blue and UV LED devices, and is increasingly used for GaN-on-sapphire power transistors (GaN HEMT), micro-LED display backlights, and RF filter substrates. Its dominance is due to excellent thermal stability, transparency to UV and visible light, close lattice match to GaN (a-plane mismatch of only 13.8%), and relatively low cost at 2\u20134 inch wafer sizes.<\/p>\n  <p>However, sapphire&#8217;s material properties make it one of the most challenging substrates to polish to semiconductor-grade surface quality:<\/p>\n  <ul>\n    <li><strong>Dureza extrema<\/strong>: Mohs hardness 9.0 (quartz = 7.0; silicon = 6.5\u20137.0; diamond = 10). Only diamond and boron nitride are harder than sapphire among commercially relevant materials.<\/li>\n    <li><strong>High fracture toughness<\/strong>: K\u2081c \u2248 2.0 MPa\u00b7m^0.5, meaning sapphire resists crack propagation and requires high contact stresses to mechanically damage the surface\u2014but once damaged (by too-aggressive abrasive or too-high pressure), the sub-surface damage layer extends micrometers deep.<\/li>\n    <li><strong>Crystal anisotropy<\/strong>: Sapphire&#8217;s hexagonal crystal structure means polishing rates and surface reactivity differ between crystal orientations (c-plane vs. r-plane vs. a-plane), complicating process optimization for multi-orientation wafer batches.<\/li>\n    <li><strong>Chemical inertness<\/strong>: Al\u2082O\u2083 is resistant to most acids and bases at room temperature, requiring specifically engineered alkaline chemistry to achieve meaningful chemical removal rates.<\/li>\n  <\/ul>\n<\/section>\n\n<section id=\"al2o3-mechanism\">\n  <h2>3. Tribochemical Mechanism for Al\u2082O\u2083 Removal<\/h2>\n  <p>The tribochemical removal mechanism for sapphire with alkaline colloidal silica is analogous to, but chemically distinct from, the mechanism for SiO\u2082:<\/p>\n  <ol>\n    <li><strong>Surface hydration<\/strong>: At pH 10\u201312, hydroxide ions (OH\u207b) attack Al-O bonds at the sapphire surface, forming aluminum hydroxide species (Al(OH)\u2084\u207b in solution, Al(OH)\u2083 or AlOOH as a surface layer). This hydration layer has significantly lower hardness and yield strength than the underlying crystalline Al\u2082O\u2083.<\/li>\n    <li><strong>Abrasive-surface interaction<\/strong>: Silanol groups on the colloidal SiO\u2082 abrasive form hydrogen bonds and\u2014under contact pressure\u2014condensation bonds (Si-O-Al) with the aluminum hydroxide surface species. The Si-O-Al bond provides the chemical adhesion needed for efficient load transfer.<\/li>\n    <li><strong>Mechanical shear<\/strong>: Relative motion between the pad and the sapphire wafer shears the bonded aluminum hydroxide fragment from the surface, exposing fresh Al\u2082O\u2083 for the next hydration cycle.<\/li>\n    <li><strong>Transport<\/strong>: The removed Al(OH)\u2083 fragment dissolves in the alkaline slurry (forming Al(OH)\u2084\u207b) and is carried away from the polishing interface by slurry flow.<\/li>\n  <\/ol>\n  <div class=\"jcs-note\">\n    <p><strong>Higher pH accelerates sapphire removal\u2014but within limits:<\/strong> Increasing pH from 10 to 12 can double or triple the sapphire MRR by accelerating both surface hydration and Al dissolution. However, above pH 12, the slurry becomes corrosive to some tool components (seals, delivery lines) and the pH adjustment chemicals (KOH, NaOH) introduce metallic contamination risk. Most production processes optimize at pH 10.0\u201311.5.<\/p>\n  <\/div>\n<\/section>\n\n<section id=\"sapphire-process\">\n  <h2>4. Process Parameters for Sapphire CMP<\/h2>\n  <p>Sapphire CMP process parameters differ significantly from silicon CMP due to sapphire&#8217;s much greater hardness and the different tribochemical mechanism:<\/p>\n  <div class=\"jcs-table-wrap\">\n    <table>\n      <thead><tr><th>Par\u00e1metro<\/th><th>Silicon Final Polish<\/th><th>Sapphire Final Polish<\/th><th>Why Different<\/th><\/tr><\/thead>\n      <tbody>\n        <tr><td>Down-force (pressure)<\/td><td>0.5\u20131.5 psi<\/td><td>2\u20135 psi<\/td><td>Sapphire&#8217;s hardness (Mohs 9) requires higher stress to initiate tribochemical contact<\/td><\/tr>\n        <tr><td>Table speed<\/td><td>30\u201380 rpm<\/td><td>60\u2013120 rpm<\/td><td>Higher velocity compensates for lower chemical removal rate per contact<\/td><\/tr>\n        <tr><td>Pad type<\/td><td>Soft (Suba, Politex)<\/td><td>Semi-hard to hard (IC1000 or Politex depending on step)<\/td><td>Hard pad needed for efficient load transfer on stiff sapphire surface<\/td><\/tr>\n        <tr><td>Abrasive D50<\/td><td>20\u201335 nm<\/td><td>50\u2013100 nm<\/td><td>Larger particles needed for acceptable MRR on harder substrate<\/td><\/tr>\n        <tr><td>pH<\/td><td>10.5\u201312.0<\/td><td>10.0\u201311.5<\/td><td>Alkaline chemistry targets Al-O bonds; above 12, tool compatibility issues<\/td><\/tr>\n        <tr><td>Typical MRR<\/td><td>100\u2013400 \u00c5\/min<\/td><td>50\u2013250 \u00c5\/min<\/td><td>Lower due to sapphire&#8217;s extreme hardness despite higher pressure\/velocity<\/td><\/tr>\n        <tr><td>Polish time<\/td><td>120\u2013600 s<\/td><td>600\u20133,600 s<\/td><td>Lower MRR requires substantially longer polishing for epi-ready finish<\/td><\/tr>\n      <\/tbody>\n    <\/table>\n  <\/div>\n  <p>The most important practical consideration is <strong>multi-step process design<\/strong>. Sapphire wafer manufacturing typically involves: (1) slicing from boule and rough grinding (diamond wheel) to remove bulk material; (2) mechanical lapping with Al\u2082O\u2083 or SiC abrasive to achieve flatness and remove deep grinding damage; (3) rough CMP with coarser colloidal silica or ceria slurry to remove lapping damage; (4) final CMP with fine colloidal silica (D50 = 50\u201380 nm) at pH 10\u201311.5 to achieve the epi-ready surface specification. The step sequence is analogous to silicon wafer polishing but with longer times at each step due to the lower MRR on sapphire.<\/p>\n<\/section>\n\n<section id=\"sapphire-targets\">\n  <h2>5. Surface Quality Targets: LED vs Power Device Substrates<\/h2>\n  <p>Surface quality requirements for sapphire substrates differ by end device application:<\/p>\n  <div class=\"jcs-box\">\n    <div class=\"jcs-box-label\">Sapphire Substrate Surface Quality Targets by Application<\/div>\n    <ul>\n      <li><strong>LED (GaN blue\/UV epitaxy)<\/strong>: Surface roughness &lt;0.3 nm RMS over 5\u00d75 \u00b5m\u00b2 AFM scan; pit density &lt;1,000 cm\u207b\u00b2; subsurface damage depth &lt;5 nm; no visible scratches at 100\u00d7 DIC microscopy<\/li>\n      <li><strong>Power GaN (HEMT, Schottky)<\/strong>: Surface roughness &lt;0.2 nm RMS; pit density &lt;500 cm\u207b\u00b2; surface metal contamination &lt;1\u00d710\u00b9\u2070 atoms\/cm\u00b2 for Fe, Cu; atomically smooth step-terrace structure preferred for AlGaN\/GaN buffer growth<\/li>\n      <li><strong>UV-C LEDs (AlGaN on sapphire)<\/strong>: Roughness &lt;0.1 nm RMS; highest specification due to AlN nucleation sensitivity to surface steps and pits; typical process uses D50 = 50\u201370 nm colloidal silica at pH 10.5\u201311.0<\/li>\n      <li><strong>Micro-LED and display<\/strong>: Roughness &lt;0.5 nm RMS; LPD &lt;100 at &gt;0.1 \u00b5m; lower spec than power device but high wafer-level uniformity (WIWNU \u22645%) is critical for multi-die display applications<\/li>\n    <\/ul>\n  <\/div>\n  <div class=\"jcs-link-box\">\n    <span class=\"jcs-link-box-icon\">\u2192<\/span>\n    <span>For guidance on qualifying colloidal silica slurry suppliers for specialty non-silicon substrates including sapphire: <a href=\"https:\/\/jeez-semicon.com\/es\/blog\/Colloidal-Silica-Slurry-Suppliers-How-to-Evaluate-Quality-Consistency-and-Technical-Support\/\" target=\"_blank\" rel=\"noopener noreferrer\">Colloidal Silica Slurry Suppliers: How to Evaluate Quality, Consistency, and Technical Support<\/a><\/span>\n  <\/div>\n<\/section>\n\n<section id=\"display-glass\">\n  <h2>6. Display Glass Polishing<\/h2>\n  <p>Large-format display glass\u2014borosilicate glass for LCD panels, aluminosilicate glass for OLED substrates, and ultra-thin glass for foldable display covers\u2014is polished with colloidal silica to achieve the surface quality required for pixel-level uniformity and optical clarity. As of August 2026, Gen 10.5 LCD panels (2,940 \u00d7 3,370 mm substrate size) are in volume production at several Asian display manufacturers, all using colloidal silica-based CMP in the final glass polishing step.<\/p>\n  <h3>6.1 Polishing Requirements<\/h3>\n  <p>Display glass polishing requirements include: surface roughness &lt;0.5 nm RMS (visible light scattering from roughness above this threshold degrades display contrast ratio); zero sub-surface crack damage (cracks propagate under thermal cycling and cause panel delamination); and strict particle count on the glass surface after polishing (particles cause pixel-level defects in the TFT or OLED layer deposited on the glass).<\/p>\n  <h3>6.2 Slurry Formulation for Glass<\/h3>\n  <p>Display glass polishing uses colloidal silica in the 80\u2013150 nm D50 range at pH 7\u201310\u2014lower pH than for silicon CMP because borosilicate glass surface chemistry is active at near-neutral pH, and aggressive alkaline conditions can leach boron from the glass surface, altering the surface composition. Solids content is typically 10\u201320 wt% at the point of use. The tribochemical mechanism is essentially identical to SiO\u2082 CMP on silicon wafers: OH\u207b ions hydrolyze Si-O-Si bonds in the glass surface, creating a soft gel layer that the colloidal silica abrasive removes by shear.<\/p>\n  <div class=\"jcs-link-box\">\n    <span class=\"jcs-link-box-icon\">\u2192<\/span>\n    <span>The oxide CMP process principles that apply to silicon device manufacturing also govern display glass polishing\u2014for the underlying science: <a href=\"https:\/\/jeez-semicon.com\/es\/blog\/Colloidal-Silica-Slurry-for-Oxide-CMP-Optimizing-STI-and-ILD-Planarization\/\" target=\"_blank\" rel=\"noopener noreferrer\">Colloidal Silica Slurry for Oxide CMP: Optimizing STI and ILD Planarization<\/a><\/span>\n  <\/div>\n<\/section>\n\n<section id=\"optical-glass\">\n  <h2>7. Optical Glass and Precision Optics<\/h2>\n  <p>Precision optical manufacturing\u2014telescope mirrors, laser optics, semiconductor photomask substrates, and reticle glass blanks\u2014was historically one of the first industries to adopt colloidal silica as a precision polishing abrasive, predating its widespread use in semiconductor CMP by several decades. The extreme surface form accuracy requirements (\u03bb\/100 surface figure error for laser cavity mirrors) and sub-0.1 nm RMS roughness specifications for laser optics represent the highest precision demands for any colloidal silica polishing application.<\/p>\n  <p>Key process features for precision optical polishing:<\/p>\n  <ul>\n    <li><strong>Very fine abrasive<\/strong>: D50 = 20\u201350 nm for final figuring polish on optical-grade fused silica or borosilicate glass<\/li>\n    <li><strong>Ultra-low solids content<\/strong>: 2\u201310 wt% working concentration minimizes surface roughness contribution from abrasive-pad-substrate contact dynamics<\/li>\n    <li><strong>pH 8\u201310<\/strong>: Moderate alkalinity to activate surface hydration without glass composition degradation<\/li>\n    <li><strong>Very long polish times<\/strong>: Hours to days for large telescope mirror blanks (&gt;1 m diameter); this demands exceptional slurry stability (see Section 7 in our stability guide)<\/li>\n    <li><strong>Computer-Controlled Optical Surfacing (CCOS)<\/strong>: Colloidal silica is the standard slurry for magnetorheological finishing (MRF) and ion beam figuring support polishing steps in precision optics manufacturing<\/li>\n  <\/ul>\n  <p>For photomask substrates (synthetic fused silica blanks for EUV and DUV lithography), colloidal silica is used in the final CMP step to achieve &lt;0.05 nm RMS roughness and \u22640.1 nm peak-to-valley over any 1 mm\u00b2 area\u2014among the tightest surface quality specifications in any industrial polishing application.<\/p>\n<\/section>\n\n<section id=\"hdd\">\n  <h2>8. Hard Disk Drive Substrate Polishing<\/h2>\n  <p>Hard disk drives (HDD) use aluminum or glass platters (substrates) that must be polished to extreme flatness and smoothness to enable reliable sub-5 nm head-disk spacing in modern perpendicular magnetic recording drives. The surface roughness requirement (&lt;0.10 nm RMS) is comparable to silicon wafer final polish, while flatness requirements (total thickness variation &lt;2 \u00b5m) are tighter than for standard optical flats.<\/p>\n  <p>Colloidal silica is used in the final polishing steps for both aluminum (NiP-coated Al alloy) and glass HDD substrates. For aluminum substrates, the slurry must include aluminum corrosion inhibitors (such as benzotriazole or phosphate-based inhibitors) to protect the NiP-coated surface from chemical attack at alkaline pH while still enabling tribochemical removal. For glass substrates, standard alkaline colloidal silica at pH 8\u201310 achieves the required roughness with no corrosion inhibitor needed.<\/p>\n<\/section>\n\n<section id=\"jeez-cs100\">\n  <h2>9. JEEZ CS-100 for Non-Silicon Applications<\/h2>\n  <p>The JEEZ CS-100 Series (D50 = 90\u2013110 nm, pH 10.0\u201311.5) is the recommended starting point for sapphire CMP, display glass final polish, and HDD glass substrate polishing. Its particle size and pH range are optimized for the higher-pressure, moderate-roughness-target applications that characterize these non-silicon substrates. For ultra-high-quality optical glass or UV-C sapphire applications requiring roughness below 0.2 nm RMS, the JEEZ CS-60 Series (D50 = 55\u201370 nm) provides a better roughness-throughput balance.<\/p>\n  <p>JEEZ provides application-specific formulation recommendations and process integration support for all non-silicon substrate polishing applications. For the complete colloidal silica technical reference: <a href=\"https:\/\/jeez-semicon.com\/es\/blog\/Colloidal-Silica-Slurry-The-Complete-Guide-to-CMP-Applications-Properties-and-Selection\/\" target=\"_blank\" rel=\"noopener noreferrer\">Colloidal Silica Slurry: The Complete Guide to CMP Applications, Properties, and Selection<\/a>.<\/p>\n<\/section>\n\n<section id=\"faq\">\n  <h2>10. Frequently Asked Questions<\/h2>\n  <div class=\"jcs-faq-item\">\n    <div class=\"jcs-faq-q\">Why is colloidal silica effective for polishing sapphire even though SiO\u2082 is softer than Al\u2082O\u2083?<\/div>\n    <div class=\"jcs-faq-a\"><p>The effectiveness of colloidal silica on sapphire is not due to the abrasive being harder than the substrate\u2014it isn&#8217;t. Instead, it works through the same tribochemical mechanism as silicon CMP: alkaline slurry chemistry (pH 10\u201312) attacks the sapphire surface to form a thin, softer aluminum hydroxide (Al(OH)\u2083 or AlOOH) hydration layer with significantly lower hardness than the underlying crystalline Al\u2082O\u2083. The colloidal silica abrasive removes this hydrated layer rather than the hard bulk sapphire. This chemical-assistance mechanism enables effective material removal at much lower contact stresses than purely mechanical abrasion of crystalline Al\u2082O\u2083 would require.<\/p><\/div>\n  <\/div>\n  <div class=\"jcs-faq-item\">\n    <div class=\"jcs-faq-q\">What particle size should I use for sapphire CMP to achieve epi-ready quality for GaN growth?<\/div>\n    <div class=\"jcs-faq-a\"><p>For the final CMP step targeting GaN epi-ready quality (&lt;0.3 nm RMS, &lt;1,000 pit\/cm\u00b2), use D50 = 50\u201380 nm colloidal silica at pH 10.0\u201311.0 and process pressure of 2\u20134 psi. For UV-C AlGaN applications requiring tighter roughness (&lt;0.15 nm RMS), use D50 = 50\u201365 nm with lower pressure (1.5\u20133 psi) and longer polish time. The rough CMP step before final polish typically uses D50 = 80\u2013150 nm or a mixed ceria\/colloidal silica formulation to achieve acceptable throughput on the harder substrate.<\/p><\/div>\n  <\/div>\n  <div class=\"jcs-faq-item\">\n    <div class=\"jcs-faq-q\">Can I use the same colloidal silica slurry for both silicon and sapphire polishing?<\/div>\n    <div class=\"jcs-faq-a\"><p>The same colloidal silica grade (same D50, same pH) can in principle be used on both substrates, but the process parameters (pressure, velocity, pad type, polish time) must be re-optimized for each substrate. Silicon final polish uses D50 = 20\u201335 nm at low pressure (0.5\u20131.5 psi) on soft pads; sapphire CMP uses D50 = 50\u2013100 nm at higher pressure (2\u20135 psi) on semi-hard pads. Using the fine silicon polish slurry (D50 = 25 nm) on sapphire will produce unacceptably low MRR and very long polish times. Dedicated slurry grades optimized for each substrate are the preferred approach in production.<\/p><\/div>\n  <\/div>\n  <div class=\"jcs-faq-item\">\n    <div class=\"jcs-faq-q\">What pH should I use for display glass polishing with colloidal silica?<\/div>\n    <div class=\"jcs-faq-a\"><p>For borosilicate display glass (LCD-grade), use pH 7\u20139. Aggressive alkaline conditions (pH &gt;10) can leach boron and alkali metal ions from the glass surface, altering the surface composition and potentially causing haze or corrosion defects. For aluminosilicate glass (OLED\/foldable displays, which have higher Al\u2082O\u2083 content and greater alkali resistance), pH 9\u201310.5 is acceptable and provides higher MRR. The pH optimum for any specific glass composition should be verified experimentally, as glass surface reactivity depends strongly on composition.<\/p><\/div>\n  <\/div>\n<\/section>\n\n<div class=\"jcs-cta\">\n  <h2>JEEZ Colloidal Silica for Sapphire, Glass, and Specialty Substrates<\/h2>\n  <p>Our CS-60 and CS-100 series are used in sapphire CMP, display glass final polish, and optical component polishing worldwide. Contact our application engineering team to discuss your substrate specification and process requirements.<\/p>\n  <a href=\"https:\/\/jeez-semicon.com\/es\/contact\/\" class=\"jcs-cta-btn\" target=\"_blank\" rel=\"noopener noreferrer\">Request Application Guidance \u2192<\/a>\n<\/div>\n\n<hr class=\"jcs-hr\">\n<p class=\"jcs-footnote\">Published by <strong>Jizhi Electronic Technology Co., Ltd. (JEEZ)<\/strong> \u00b7 August 2026. For process-specific advice, <a href=\"https:\/\/jeez-semicon.com\/es\/contact\/\" target=\"_blank\" rel=\"noopener noreferrer\">contact our application engineering team<\/a>.<\/p>\n<\/article>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"Why is colloidal silica effective for polishing sapphire even though SiO2 is softer than Al2O3?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Colloidal silica works on sapphire through tribochemical action: alkaline slurry (pH 10\u201312) creates a softer aluminum hydroxide hydration layer on the sapphire surface, which the colloidal silica abrasive then removes mechanically. The hard bulk Al2O3 is never directly abraded\u2014only the soft hydrated surface layer is removed, enabling effective polishing at much lower contact stresses than purely mechanical abrasion would require.\"}},{\"@type\":\"Question\",\"name\":\"What particle size should I use for sapphire CMP to achieve epi-ready quality for GaN growth?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"For GaN epi-ready quality (less than 0.3 nm RMS, less than 1000 pit\/cm2), use D50 = 50\u201380 nm at pH 10.0\u201311.0 and 2\u20134 psi. For UV-C AlGaN requiring less than 0.15 nm RMS, use D50 = 50\u201365 nm at lower pressure and longer time. Rough CMP before final polish typically uses D50 = 80\u2013150 nm for acceptable throughput.\"}},{\"@type\":\"Question\",\"name\":\"Can I use the same colloidal silica slurry for both silicon and sapphire polishing?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Technically possible but not recommended for production. 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The pH optimum depends on glass composition and should be verified experimentally, as reactivity varies with Al2O3 and alkali content.\"}}]}\n<\/script>","protected":false},"excerpt":{"rendered":"<p>Application Guide \u00b7 Cluster C-07 A technical guide to applying colloidal silica CMP slurry beyond silicon\u2014covering the tribochemical polishing mechanism for sapphire (Al\u2082O\u2083), process parameter optimization for LED and power  &#8230;<\/p>","protected":false},"author":1,"featured_media":2607,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[9,59],"tags":[],"class_list":["post-2604","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","category-industry"],"acf":[],"_links":{"self":[{"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/posts\/2604","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/comments?post=2604"}],"version-history":[{"count":2,"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/posts\/2604\/revisions"}],"predecessor-version":[{"id":2606,"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/posts\/2604\/revisions\/2606"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/media\/2607"}],"wp:attachment":[{"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/media?parent=2604"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/categories?post=2604"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jeez-semicon.com\/es\/wp-json\/wp\/v2\/tags?post=2604"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}