< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral

1. Sapphire Crystal Growth Process Introduction

2. Actual Drilling

3. D

4. Sapphire Crystal Growth Process SOP (temporary version)

< Ingot Growth Dept.> / < Paul Liu> Internal use only

1. Sapphire Crystal Growth Procedure

Pre-process Preparation Heating Seeding

Growing Detachment Anneal & Cooling

Training Report @ Mineral

1. Raw material preparation2. Machine & hot zone preparation3. Seed fix preparation

1. Seeding 2. Constriction formation3. Shouldering

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Prepare raw material

•Verneuil stones scrap•Compacted powder (density over 3.3 g/cm^3)

Purity 99.998% (4N8)1. Mineral suggest to use 4N8 at least for yield concern. 2. Use 4N5 cold be easy to enhance bubble and dislocation.3. Difficult to distinguish 4N5 and 4N8Check purity under UV lamp (Hg)Size: 20-60 mmLayer by layer dense loading

Training Report @ Mineral _ Pre-process Preparation

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Pre-process Preparation

Prepare machine and hot zone

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Pre-process Preparation

Prepare CrucibleCurrently Mineral choose W to be the material of crucible. The reason is as the following.

1. Use W to the crucible material will has less ion perception. 2. More ion perception will enhance impurity more, and will easy cause cool island.3. The cost of W is much less than Ir.4. After changing the material crucible from W/Mo to W, now cool island is much less happen.

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Pre-process Preparation

Preparation of the seed and fixing it to the seed holder1. Seed size is 12mm × 12mm × 120 mm

2. Attach the seed to the cut on the seed holder and put the marks by pencil on the three corners of the seed on the opposite to each cut of the seed holder.

3. Fix the seed on the seed holder with the wire WRe-20.

4. Insert the seed holder into the collet

5. Insert the chuck jaws, molybdenum (Mo) ring and molybdenum spacer into the collet.

Old type seed holder

Seed

Seed holderSeed holder

New type seed holder

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Heating

Pumping out the grower Vacuum value reach 2 × 10-2 Pa, start to heat up crucible. Heat up the grower 1. If vacuum value is higher than 3 × 10-2 Pa, stop heat up crucible. Wait vacuum value reach 2 × 10-2 Pa, then re-start to heat up crucible. 2. When all raw material melt in the crucible, hold the melt within two hours.

5 cm

melt

Due to hot zone design, the temperature of melted sapphire will be getting higher from surface to bottom. And the temperature of side wall also will be higher than center.

Dens

ity o

f mel

t

Temperature ( )℃2050 2200

3.05

2.75

Avg. ρ = 2.88 g/ cm3

Average density of melted sapphire is about 2.88 g/cm3

Δ ～ 150 ℃

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Seeding

Hot area

Cold area

Convection lineTop View

Side View

1. The converged point of convection line is the area with lower temperature. And this area is also the best area for seeding. 2. If the melted sapphire temperature is too high, convection line will become more disorder. It is hard to do seeding. 3. Higher temperature of melted sapphire can make bubble in melted sapphire flush out more, but the convection line also will become more disorder.4. Best seeding is to put seed in the converged point and overall higher temperature is better.

Seed

Convection line

Island

Over heatedNormal

2 cm

Melted Sapphire Introduction

seeding

Perfect condition

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Seeding

Formation Constrictions (Neck Growth)

Constriction Purpose Heat removal from grown ingot – to provide ingot temperature lower then crucible walls Decreasing dislocations density Decrease inner stress Symmetrical growth

constriction

Best constriction formation speed is to grow 2 mm (Horizontal direction) in 30 mins. Best constriction formation can make less dislocation and reduce internal Stress, and finally make a good quality crystal.

If convection flow speed is too fast or convection line is Instable (shift), constriction could become crooked shape (like left picture). It will easily cause crystal broken.

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Seeding

Shouldering Introduction

Seed

Crystal

1. After finishing constriction formation, start shoulder growth.2. Shouldering growth speed: Horizontal direction : 20 mm/10 hr Vertical direction : 3 mm/10 hr conical direction : 15 mm/10hr3. Pulling rate is about 0.3 ~ 0.7mm

2 mm/hr

0.3 mm/hr

1.5 mm/hr

16 cm

shouldering

Pulling rate : 0.3 ~ 0.7mm

< Ingot Growth Dept.> / < Paul Liu> Internal use only

1. Almost no growth @ vertical direction2. cause high internal stress. 3. High possibility to cause crystal broken shown as the below picture.

Training Report @ Mineral _ Seeding

Shouldering Shape Introduction

Growth of Horizontal direction too fast Standard Shouldering Growth

2 mm/hr0.3 mm/hr

16 cm

Pulling rate is ~ 0.3-0.4 mm/hourPulling rate is ~ 0.6-0.7mm/hour

Pulling rate higher will make crystal grow more fast @ vertical direction, and make different shouldering shape.

crack

crack

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Seeding

Shouldering Shape Introduction

Stick issue

When shouldering process is close to end (usually crystal grow to 5 kg), it is easy to find stick issue fromcrystal to sidewall.

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Seeding

Seeding Trouble Shooting IntroductionCondition: During seeding (constriction) process, one island happen. How to fix this issue? (shown as the following)

Island moving Island moving cause stick1. Convection flow

2. Surface energy

If stick happen, they will result in 2 seed. One is original seed , the other is island .This island seed will grow along the island. This crystal so called parasitism crystal.

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Growth/Detachment

In general when “F “ reach 23 kg, crystal start to touch the bottom of Crucible. If touch the bottom of crucible, need to increase the pulling rate to 0.5 ~ 0.6 mm/hr

The judgment indication for Crystal Growth Complete:1. Voltage (major)2. Weight (reference)When weight sensor up to 35~37 kg, need to check voltage reach forecast value or not. If yes, start to detachment. If no, need wait for the forecastValue. How to create the forecast value?1) Create the base value Put some solid sapphire in the bottom of crucible and seed in the top of crucible. Then increase the voltage to melt sapphire, including seed and solid sapphire, and record the voltage value when sapphire melt. We should get 2 voltage value. One is for solid sapphire, and another is for seed. (example seed melted voltage is 9.35, bottom sapphire is 8.35)2) Fine tune forecast value base on previous run First run need to base on base value to decide when we can execute detachment. And for the following run, need to fine tune the forecast value, like run-to-run control.

16 cm

20 cm100 mm

F

6cm

Solid sapphire

seed

8.35 V

9.35 V

Growth / Detachment Introduction

< Ingot Growth Dept.> / < Paul Liu> Internal use only

Training Report @ Mineral _ Growth/Detachment

Growth / Detachment Introduction