Development of High Density

Optical Storage Media

高密度光儲存媒體之發展

何永鈞

國立中興大學材料工程學系

2002. 04. 26

Outline

Development History of Optical Storage

Media

Classification for Optical Storage Media

Principles of Optical Storage Technology

High Density Optical Storage Media

Conclusions

Development History of Optical Storage Disc

1981 1983 1985 1987 1989 19911993 1995 1997 1999 2001 2003

CD-DA

CD-RO M

CD-RW

Photo CD

Video CD

CD-R

CD-MO

CD-I

DVD-RAM 2..6GB

DVD ROM & Video

DVD–RAM/R/RW 4.7GB

DVD Audio

DVR 22.5GB

DVD+R /RW 4.7GB

Classification for Optical Storage Disc

Read-Only ：CD-DA、CD-ROM、VCD、

DVD-Video、DVD-ROM、DVD-Audio

Recordable：CD-R、DVD-R

Rewritable：CD-RW、DVD-RAM、DVD-

RW、DVD+RW、DVR

Read-Only Disc Structure

Mastering→ Replication→ metallization→

Lacquering ( bonding )→ Printing

Recordable Disc Structure

Mastering→ Replication→ Dye coating→metallization→ Lacquering→ Printing

Recordable Disc Structure

Mastering→ Replication→ Dye coating→metallization→ Bonding→ Printing

Mastering→ Replication→ ZnS-SiO2/AgInTeSb/ZnS-SiO2/Al-Ti Sputtering → Lacquering→ Printing

Rewritable Disc Structure

Rewritable Disc Structure

Pick-up Head

Optical Path of Pick-up Head

Read for Read-Only Disc

00000100010000000100000000010000

Land Pit Land Pit Land

Read for Read-Only Disc

Read and Record for Recordable Disc

After RecordedBefore Recorded

Write strategy

Write、Erase and Read for Rewritable Disc

Initialized Active Layer Written Bit

Temp.

Tm

Tg

Write Read Erase

Time

Multi-Media Applications

1997 2000 2005 2010 2015

4.7 GB 15GB 36GB 100GB 1TB

VideoROM2 hrs

VideoRAM2 hrs

HDTV4 hrs

3-DVideo

Interactive3-D Video

Capacity

Transfer Rate

Seek Time

20 MB/s 50-100 MB/s 100-250 MB/s 1 GB/s

30 ms 10-20 ms 5-10 ms 1-2 ms

How to Increase Recording Density？

Spot Size Reduction

Volumetric Storage

Data Format

Disc Fabrication

High DensityOptical

Storage Media

Multi-layer

Photo-induced

HolographicECC

Multi-level

Modulation

Short λ High NA Near-Field Super Resolution

High-tech mastering L/G and Deep Groove

How to Increase Recording Density？

Reduce Laser Spot Size

Short Wavelength（λ=400nm）、High Numerical Aperture （NA=0.8）

Solid Immersion Lens (SLI) : To Increase Numerical Aperture

Super-RENS

Increase Coding Efficiency ：Multi-level Coding

Multiple-layer Structure ：Multi-layer Recording

Volumetric Recording ：Holographic Optical Recording

DVR ( λ = 400 nm ＆ NA = 0.85 )

Blue Laser

High NA double-Lens

Assemble

0.1mm Hard Cover Layer

Single layer capacity 22.5GB

DVR ( λ = 400 nm ＆ NA = 0.85 )

Solid Immersion Lens

Excess theoretical NA limit

“1”

Air Gap ：10 ∼ 100 nm

Near Field Recording

Laser spot size ＜ 100 nm

Single layer capacity 100Gdisc

f

NA=0.55~0.8

n1=1.45~1.9 h < λ

會聚透鏡

半球型SIL

SUPER-RENS

Optical Super-Resolution

Near Field Structure

Can read pit length < 60 nm

Single layer capacity 200GB

SUPER-RENS

Diffraction-Limit

Spot size ∼0.6 λ/NA

SUPER-RENS

0 50 100 150 2000

100

200

300

400

500

600

700

Tim e(ns)

Tem

pera

ture

(C)

Tx

Tm

recording layer

mask layer

front partrear part

read

out s

igna

l

mask layerrecording layer middle dielectric layer

SUPER-RENS

Requirements for mask layer

Fast Response

High sensitivity

Large transmittance change

High stability

SUPER-RENS

Transmitted Type Scattering Type

Multi-level

Multi-level is to improve the coding efficiency of

recording bits to increase recording density

PPM ：Pit Position ModulationPWM ：Pit Width Modulation

Multi-level Pulse Depth Modulation

Multi-Level Rewritable

Matsushita - Mark Radial Width Modula

Multiple-level Reflection Modulation

Terabyte Optical Storage

3D Storage3D3D StorageStorage

Multi-function／Volumeric optical disks Holographic Memory

Fluorescent Multilayer Disc （FMD）

US Constellation 3D

(C3D) Company

06/2000：40GB

Analogue Video Disc

10/2000： 50GB Digital

Video Disc

Future > 100GB

Fluorescent Multilayer Disc （FMD）

Fluorescent Multilayer Disc （FMD）

Advantages

Every layer is transparent. There is no reflective

interface between layers.

The exciting radiation energy can be achieved by

absorption of 1% incident light.

The exciting fluorescent signals won’t be absorbed by

other fluorescent materials.

Fluorescent Multilayer Disc （FMD）

With larger tolerance for the imperfection of storage

media as well as disc drive.

Compatible with the existing CD and DVD systems.

Read and write can be performed simultaneously. Data

transfer rate is much higher than that of single layer

disc.

Fluorescent Multilayer Disc （FMD）

Fluorescent Multilayer Disc （FMD）

螢光材料的選擇

必須與基版的材料相容，亦即可被塗佈於基版上且在多層的

製造程序中自始至終必須維持它的特性而不變質。

螢光材料的吸收波長最好是與市售低價格、穩定度高的半導

體雷射波長相同，例如紅光雷射系統650nm。

所放射出的螢光波長最好比入射雷射光高50nm左右，如此較

易分離入射和信號光源。

此材料應該有高的螢光轉換效率。

Fluorescent Multilayer Disc （FMD）

此材料的折射率（Refraction Index）應該要稍大於聚碳酸

樹酯的折射率。

此材料在合理的時間範圍內應該維持穩定不能變質，當其暴

露於周遭的光線（Ambient Light）或讀取光源不能產生劣

化。

若應用於旋轉的碟片系統而非卡片式的系統，尚須具備快速

的反應時間（1 nsec）及訊號強度在高飽和水平（Saturated

Level；1mW/cm2）。

Holographic Optical Recording

原理：

經由物體反射的物光與參考光

因重疊而干涉，在全像底片上

以光柵的形式將訊號記錄下

來。記錄媒體讀取時，需要與

記錄相同的參考光，藉由物光

的還原來讀取訊號。

全像片

物光

物體

參考光

全像片

實像

參考光

原物光再生

直接穿透光

Holographic Optical Recording

Holographic Optical Recording

Holographic Optical Recording

High data transfer rate Rewritable Disc

Requirements for phase change materials

High Photo-sensitivity

Large optical contrast between crystalline and

amorphous phases

High thermal stability

High structural stability

Fast re-crystallization rate

How to increase re-crystallization rate ?

Optimum recording layer

thickness

thickness ~ 30 nm

t (nucleation) ~ 17 ns

CET ~ 38 ns

Crystallization acceleration layer

SiC or GeN

t (nucleation) ~ 14 ns

CET ~ 27 ns

GeSbTe + O2

How to increase re-crystallization rate ?

How to increase re-crystallization rate ?

7800.50

6580.60

6580.85

4000.85

AgInSbTe

Ge2Sb2Te5

0.0 0.4 0.8 1.2 1.6 2.0Reciprocal Spot Diameter ( µm-1 )

Max

imum

Use

r Dat

a R

ate

( Mbi

t/s)

0

10

20

30

40

50

60

70

80

Fast Growth Materials

0 10 20 30 40 50 60 70 80 90 100100

90

80

7060

5040

30

0

10

20

90

100

80

70

60

50

40

3020

10

0Te (at%) Sb (at%)

Ge (at%)

Conclusions

“ Higher recording density “、” Larger

capacity “ and “ Faster data transfer rate “

is the trend in the development of optical

storage medium !!

Thank you !!