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Background Statement for SEMI Draft Document 5723New Standard: Specification for Single Crystal Sapphire Intended for Use for Manufacturing HB-LED Wafers

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Background Statement

Single crystal sapphire is used as a substrate material for manufacturing HB-LED wafers. Despite the importance of single crystal sapphire, however, there currently is no industry-consensus standard in the LED industry for single crystal sapphire. Such a standard would improve communication between users and suppliers, reduce costs, and increase productivity, so it is critical for the LED industry to come to consensus in the near future.

Review and Adjudication Information

Task Force Review Committee AdjudicationGroup: Single Crystal Sapphire Task Force HB-LED China TC ChapterDate: TBD April 22nd , 2016Time &Timezone: TBD 9AM — 4PM, Beijing timeLocation: TBD Xuzhou Hotel (Tentatively)City, State/Country: China Xuzhou, Jiangsu, ChinaLeader(s): Lena Qi(GHTOT)

Xuejun Zhang(AURORA)Yong Ji (GHTOT),XinHong Yang (AURORA)

Standards Staff: Kris Shen(SEMI China) Kris Shen(SEMI China)

Meeting date and time are subject to change, and additional TF review sessions may be scheduled if necessary. Contact the task force leaders or Standards staff for confirmation. Check www.semi.org/standards for the latest schedule.

If you have any questions, please contact the Single Crystal Sapphire Task Force.

Lena Qi (GHTOT)Tel: +86 18785035580E-mail: [email protected] contact SEMI Staff, Kris Shen at [email protected]

https://mail.ldksolar.com/owa/redir.aspx?C=06a0695f5f4241b18e1235c2a71656cb&URL=mailto%[email protected]

http://www.semi.org/standards

DRAFTDocument Number:

Date: 5/9/23

SEMI Draft Document 5723New Standard: Specification for Single Crystal Sapphire Intended for Use for Manufacturing HB-LED Wafers1 PurposeThe purpose of this standard is to standardize the specification of single crystal sapphire intended for use in manufacturing HB-LED wafers.

2 Scope 2.1 This specification includes the physical and chemical properties of single crystal sapphire, and the defects of sapphire.

2.2 The physical and chemical properties include the component, structure, lattice constant, hardness, density, thermal expansivity, thermal conductivity, specific heat, reflectivity, refractive index, light transmission, dielectric constant, and full width at half maximum.

2.3 The defects include bubbles, cloud, grain boundary, inclusion, color, micro crack, and EPD.

NOTICE: SEMI Standards and Safety Guidelines do not purport to address all safety issues associated with their use. It is the responsibility of the users of the documents to establish appropriate safety and health practices, and determine the applicability of regulatory or other limitations prior to use.

3 Limitations3.1 None

4 Referenced Standards and Documents 4.1 ASTM Standards1

4.1.1 ASTM C693-93(2013) — Standard Test Method for Density of Glass by Buoyancy

4.1.2 ASTME384 — Standard Test Method for Knoop and Vickers Hardness of Materials

4.1.3 ASTMD696 — Standard Test Method for Coefficient of Linear Thermal Expansion of Plastics Between −30°C and 30°C with a Vitreous Silica Dilatometer

4.1.4 ASTMC202 — Standard Test Method for Thermal Conductivity of Refractory Brick

4.1.5 ASTM E2716-09 — Standard Test Method for Determining Specific Heat Capacity by Sinusoidal Modulated Temperature Differential Scanning Calorimetry

4.1.6 ASTMD1082 — Standard Test Method for Dissipation Factor and Permittivity (Dielectric Constant) of Mica

4.1.7 ASTM F43-99 — Standard Test Method for Resistivity of Semiconductor Materials

4.1.8 ASTM F1252-10 — Standard Test Method for Measuring Optical Reflectivity of Transparent Materials

4.1.9 ASTMC1648 — Standard Guide for Choosing a Method for Determining the Index of Refraction and Dispersion of Glass

4.1.10 ASTM F1316 – 90 — Standard Test Method for Measuring the Transmissivity of Transparent Parts

4.1.11 SEMI Standards

4.1.12 SEMI M36-0699 — Test Method for Measuring Etch Pit Density in Low Dislocation Density Gallium Arsenide Wafers

1American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, USA; Telephone: 610.832.9585, Fax: 610.832.9555, http://www.astm.org

This is a Draft Document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted Standard or Safety Guideline. Permission is granted to reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other reproduction and/or distribution without the prior written consent of SEMI is prohibited.

Page 1 Doc. jn l SEMI

Semiconductor Equipment and Materials International3081 Zanker RoadSan Jose, CA 95134-2127Phone: 408.943.6900, Fax: 408.943.7943

http://www.astm.org/


Date: 5/9/23

4.2 ISO Standards2

4.2.1 ISO 10110-3:1996 — Optics and optical instruments - Preparation of drawings for optical elements and Systems - Part 3: Material imperfections -Bubbles and inclusions

4.3 Other Documents

4.3.1 Sapphire Material, Manufacturing, Applications, Elena R. Dobrovinskaya, Leonid A. Lytvynov, Valerian Pishchik

NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.

5 Terminology5.1 Abbreviations and Acronyms

5.1.1 a,b,c — crystal lattice constants

5.1.2 FWHM — full width at half maximum

5.1.3 EPD — etch pit density

5.1.4 Cp — specific heat

5.1.5 N — refraction index

5.1.6 T% — light transmission

5.1.7 R — reflection index

5.1.8 Λ — thermal conductivity

5.1.9 GB — grain boundary

5.2 Definitions

5.2.1 bubble — a crystal defect that exists in single crystal sapphire, and includes gaseous and vacuum pores. These defects can be observed by projecting bright light through the material and may appear as spherical, pear-shaped, dumb-bell shaped, fiber-shaped, and hexagonal disk-like structures that scatter light.

5.2.2 inclusion — a crystal defect that results from the capture of foreign solid particles in the crystallization growth front (interface) or in the phase segregation during the crystal anneal or cooling stage. These defects can be observed by projecting bright light though the material and appear as irregular shaped light scatterers.5.2.3 grain boundary — a crystal defect, which is the interface between grains or crystallites of the same phase in monocrystal or polycrystal material. These two grains differ in mutual orientations.

5.2.4 cloud — dense micro bubbles that appear as cloudiness or fog when the material is illuminated with bright light.

5.2.5 color — crystal defects, which may or may not be eliminated, that cause a selective absorption of light caused by impurity elements or crystal internal defects, and the crystal presents a different color.

6 Requirements6.1 Physical and chemical properties

6.1.1 Crystal structure and morphology — the ditrigonal-scalenohedral class of the trinomial symmetry D3d

6 −R 3C (L3 3 L2 3 PC )[4.3.1 .

1) Mirror-turn axis of the sixth order (ternary inversion axis)

2) Three axes of the second order normal to ternary inversion axis

2 International Organization for Standardization, ISO Central Secretariat, 1 rue de Varembé, Case postale 56, CH-1211 Geneva 20, Switzerland; Telephone: 41.22.749.01.11, Fax: 41.22.733.34.30, http://www.iso.ch




http://www.iso.ch/


Date: 5/9/23

3) Three symmetry planes normal to the axes of the second order and intercrossing along the axis of the highest order

4) Symmetry center

(1) Aluminum ions (2) Octahedral hollows

6.1.2 Lattice parameters — a = 4.7592 A, b = 4.7592 A,c = 12.9915 A at 295.65K. [4.3.1 ]

6.1.3 Density — Density of single crystal sapphire should be 3.97~3.99 g/cm3 according to the test method specified in §4.1.1.[4.3.1 ]

6.1.4 Hardness — Mohs’ hardness should be 9 ~10. Vickers-hardness of single crystal sapphire should be⊥C-axis 1800~2500 HV,∥C-axis 1800-2300 HV according to the method specified in §4.1.2 .

6.1.5 Linear expansion coefficient — The linear expansion coefficient of single crystal sapphire depends on temperature and orientation, according to the method specified in §4.1.3, the linear expansion coefficient of single crystal sapphire should be followed in Table 1.[4.3.1 ]

Table 1 Temperature and Orientation Dependence of the Linear Expansion Coefficient of Single Crystal Sapphire

Orientation Temperature(K) Linear Expansion Coefficient(K-1)

⊥C-axis293~323

5.6×10−6

∥C-axis 6.6 ×10−6

⊥C-axis1273

(7.9 8.3)× 10−6

∥C-axis (8.8 9.0)×10−6

6.1.6 Thermal conductivity coefficient — The thermal conductivity coefficient of single crystal sapphire depends on temperature and orientation. According to the method specified in §4.1.4, the thermal conductivity coefficient of single crystal sapphire should be as shown in Table 2.[4.3.1 ]





Date: 5/9/23

Table 2 Temperature and Orientation Dependence of the Thermal Conductivity Coefficient of Single Crystal Sapphire

Orientation Temperature(K)Thermal Conductivity

Coefficient(W /(m. K ))

⊥C-axis298

30.3

∥C-axis 32.5

6.1.7 Specific heat — The specific heat of single crystal sapphire depends on temperature. According to the method specified in §4.1.5 at 298K, the specific heat of single crystal sapphire should be as shown in Table 3.[4.3.1 ]

Table 3 Temperature Dependences of Specific Heat of Single Crystal Sapphire

T(K) cp(J/kg/K) T(K) cp(J/kg/K) T(K) cp(J/kg/K)5 0.2 115 200 237 7709 0.5 130 275 247 778

18.3 2.37 145 350 260 80026.7 4.96 156 425 272 81536.8 9.84 165 475 276 82046.6 20.87 175 540 278 82556.6 39.41 185 600 284 83065.1 50.85 195 684 286 84073.8 65.82 205 690 290 84588 100 216 725 295 850100 145 226 745 298 842

6.1.8 Dielectric constant — The dielectric constant of single crystal sapphire depends on temperature and orientation. According to the method specified in §4.1.6. At 298K, in 103~109 Hz interval, the dielectric constant of single crystal sapphire should be about 9.3 perpendicular to the C-axis, and 11.5 in parallel to the C-axis [4.3.1 ]. The value of the dielectric constant increases with temperature irrespective of the crystallographic orientation (Figure 1).[4.3.1 ]

Figure 1





Date: 5/9/23

Temperature Dependences of the Dielectric Constant in the Directions Parallel and Perpendicular to the C Axis

6.1.9 Resistivity — The resistivity of single crystal sapphire depends on temperature and orientation. According to the method specified in §4.1.7, the resistivity of single crystal sapphire should be as shown in Table 4.[4.3.1 ]

Table 4 Temperature and Orientation Dependence of the Resistivity of Single Crystal Sapphire

Orientation Temperature(K) Resistivity(Ω.m)

⊥C-axis293

5.0 ×1018

∥C-axis (1.3 2.9)×1019

Any orientation 773 ¿1012

Any orientation 1273 ¿109

6.1.10 Reflectivity coefficient (n) — Reflectivity coefficient depends on wavelength and the state of the surface. According to the method specified in §4.1.8, the reflectivity coefficient of single crystal sapphire should be as shown in Figure 2.

Figure 2

Dependence of Reflection Coefficient on Wavelength

6.1.11 Refractive index — Refractive index depends on wavelength. According to the method specified in §4.1.9, the refractive index of single crystal sapphire should be as shown in Figure 3.[4.3.1 ]





Date: 5/9/23

Figure 3

Dependence of Refractive Index on Wavelength

6.1.12 Light transmission — Light transmission depends on the wavelength and the test sample surface quality. Therefore, transmissivity of sapphire wafers shall be measured under the following conditions:

1) Thickness of test part 0.5 mm, Parallelism of surfaces <30″.

2) Surface finish — polished, roughness <0.3 nm.

3) Incident angle – 0º±1º.Following the method specified in §4.1.10, the light transmission of single crystal sapphire should be similar to Figure 4. For HB-LED wafers, the light transmission should be >60% at 250~400 nm wavelength, and more than 85% at 400~900 nm wavelength.

Figure 4

Dependence of Transmission on Wavelength[4.3.1 ]

6.1.13 FWHM — The full width at half maximum (FWHM) of sapphire for HB-LED wafers shall be no more than 15″. According to the X-RD test method, the X-Ray Diffraction FWHM chart should be shown as in Figure 5.





Date: 5/9/23

Figure 5

X-Ray Diffraction FWHM Chart Example

6.2 Defects

6.2.1 Purity — Al2O3 purity of single crystal sapphire intended for use for manufacturing HB-LED wafers must be great than 99.996%. Table 5 gives the maximum impurities allowed for specific elements. Purity is to be tested using the GDMS (Glow Discharge Mass Spectrometry) test method.

Table 5 Chemical Impurities Unit:ppm

6.2.2 EPD — EPD for single crystal sapphire for HB-LED wafers must be less than 1000 pcs/cm² according to the method specified in §4.1.11.

Figure 6

EPD Sample

6.2.3 Bubble/inclusion — It is impractical to avoid bubbles and inclusions in the process of sapphire crystal growth. Sapphire for HB-LED wafers grade 4 levels per diameter of bubble and inclusion, according to the method specified in §4.1.12, take a maximum length as diameter for noncircular bubble and inclusion. Bubble and inclusion of single crystal sapphire grade should be as shown in Table 6.




Na Si Fe Mg Ni Ti Cr Mn Ca Cu,Mo,W

<8 <4 <2 <1 <1 <1 <2 <1 <2 <3


Date: 5/9/23

Figure 7.1 Bubble in Ingot - Figure 7.2 Bubble in Double Polished Wafer

6.2.4 Grain boundary (GB) — It is impractical to avoid grain boundary in the process of sapphire crystal growth. The grain boundary includes low angle grain boundary and large angle grain boundary, twin crystal, polycrystalline, and crystal lattice distortion. Due to the same test method and similar map, single crystal sapphire for manufacturing HB-LED wafers are graded into 4 levels. Grain boundaries are observed and graded according to the OHT (Optical Homogeneity Technique) test method. GB of single crystal sapphire grade should be as shown in Table 7.




Table 6 Bubble and Inclusion of Single Crystal Sapphire

Grade Defect Specification Detection Tool

1 The maximum bubble or inclusion is smaller than 5 µm, located not closer than 10 mm.

High intensity lamp, ~8000 LUX

2 The maximum bubble or inclusion is smaller than10 µm, located not closer than 10 mm.


3 The maximum bubble or inclusion is smaller than 20 µm, located not closer than 10 mm


4 The maximum bubble or inclusion is smaller than 20 µm, located not closer than 2mm


Table 7 GB of Single Crystal Sapphire Grade

Grade Defect Specification Reference Figure Detection Tool

1 Free of GB Figure 8.1, Figure 8.2, Figure 8.3

Polarization light1000~3000 LUX

2 No obvious GB, slight deformation circle and Maltese cross

Figure 8.4, Figure 8.5, Figure 8.6


3 No more than one sharp GB, the length less than 8 mm at each diameter 2 inch ingot, or moderate deformation circle and Maltese cross



4 Total obvious GB length more than 8 mm, or serious deformation circle and Maltese cross




Date: 5/9/23

Figure 8.1 GB Grade1 OHT Image Figure8.2 GB Grade1 OHT Image Figure 8.3 GB Grade1 OHT Image

Figure 8.4 GB Grade2 OHT Image Figure 8.5 GB Grade2 OHT Image Figure 8.6 GB Grade2 OHT Image

Figure 8.7 GB Grade3 OHT Image Figure8.8 GB Grade3 OHT Image Figure8.9 GB Grade3 OHT Image





Date: 5/9/23

Figure 8.10 GB Grade4 OHT Image Figure8.11 GB Grade4 OHT Image Figure 8.12 GB Grade4 OHT Image

6.2.5 Cloud — Perfect sapphire crystal is colorless, and transparent. However, large quantities of micro bubbles that are densely packed will appear as cloudiness in the crystal. Single crystal sapphire for HB-LED wafers does not allow any cloud defects visible to the naked eye, with same detection tool and condition for bubbles.

Figure 9.1 Cloud in Ingot Figure 9.2 Cloud in Double Polished Wafer

6.2.6 Color — Color can be introduced to the crystal by micro impurities or elements captured in the lattice structure during growth or by the absence of oxygen. These phenomena can cause the sapphire to appear yellow, pink or others color. Sapphire with color is suitable for HB-LED production if the color is removed during the production process (typically during the annealing process). Single crystal sapphire for HB-LED does not allow other colors if the color cannot be removed.

6.2.7 Crack — Single crystal sapphire for HB-LED does not allow any crack defects visible to the naked eye.

NOTICE: Semiconductor Equipment and Materials International (SEMI) makes no warranties or representations as to the suitability of the Standards and Safety Guidelines set forth herein for any particular application. The determination of the suitability of the Standard or Safety Guideline is solely the responsibility of the user. Users are cautioned to refer to manufacturer’s instructions, product labels, product data sheets, and other relevant literature, respecting any materials or equipment mentioned herein. Standards and Safety Guidelines are subject to change without notice.

By publication of this Standard or Safety Guideline, SEMI takes no position respecting the validity of any patent rights or copyrights asserted in connection with any items mentioned in this Standard or Safety Guideline. Users of this Standard or Safety Guideline are expressly advised that determination of any such patent rights or copyrights, and the risk of infringement of such rights are entirely their own responsibility.


