ELECTRONIC MATERIALS

Soochow University

2009

In Profile - Huang

• More than 30 years: electrochemistry research

• and surface chemistry (Sep. 1975)

• Near 30 years: WA

• Near 30 years: AESF

• More than 20 years (from July 1986): CSIS

• And others

Contents

• Introduction• Wire & Cable• Semiconductor• Capacitor• PCB• MEMS• Battery• CD-R• EMI/RFI• ITO• Electrowetting, LCD &LED

Introduction

Electronic Materials

Basic structures of solids a. electron orbitals b. energy bonds c. crystal structures: bcc, fcc…. d. crystal solids: bcc, -Fe V Cr Mo W fcc, -Fe Al Ni Cu Ag Pt Au hcp, -Ti Zn Zr metal oxides or nitrides…: ceramics

e. polycrystalline & noncrystalline solid polycrystalline: for example PVD amorphous solids: the atoms or ions are arranged randomly, hence there are dangling bonds (incomplete energy bonds) and voids. In general, stable only up to a certain temp. polymers: partially crystalline and partially amorphous f. phase diagrams

g. Techniques for crystal growth & thin-film deposition: Czochralski growth of semiconductorh. crystal imperfections: defect and impurityi. diffusion in solids: depends on the size difference between the impurity and the host atoms (or ions) via vacancy or interstitial

Wire and Cable

Wire & Cable

• WA: The Wire Association International• Ag: 1.49 -cm at 20oC• Cu: 1.72 -cm, OFHC 0.008%O2

• Cu alloy: TS (tensile strength) 1.2-1.4%Cd, 200% TS, 85-90% <10% Sn, P & Si, 3-400% TS, 40-50% 2-2.5% Be, Ag• Al: 99.3% purity 45% TS, 62% , 30% density Au:

Rod quality

Wire breaks

Wire drawing

Drawing force

Lubricants

Optical fiber

• Core: fused mixtures of metal oxide

3 – 80 μ

• Cladding material: low n

20 – 50 μ

Total reflection at the cladding-core material.

Optical fiber

Semiconductor90, 65, 55, 45 nm

semiconductor

• 1. physics

classification of materials:

insulator

metal

semiconductor: electron and hole

conduction, the resistivity of silicon

depends upon the number of acceptor or

donor atoms added and the temperature

2. Wafer preparation

a. sand: silicon dioxide containing less than 1 % impurities.

b. react with carbon: SiO2 + C → Si(99% purity) + CO2

c. react with hydrogen chloride: Si + 3HCl → SiHCl3 + H2

d. decomposed using electric current: SiHCl3 + H2 → Si(ultrapure polycrystalline) + 3H

Cle. Silicon crystal growth: Czochralski method

CZ method

• Si at 1415oC in a rotating quartz crucible

→Add the desired impurities

→An arm with a piece of seed crystal with the Si

→Ar is used to prevent contamination of the molten Si

→The seed crystal is slowly withdraw from the molten Si

CZ拉晶法• CZ拉晶法：

CZ (Czochralski) 法進行單結晶矽之生產；此方法目前被工業界廣泛地使用於大尺寸單結晶之製造。此法先將原子排列不規則之多結晶矽原料在高溫下熔化 (Meltdown) ，再以單結晶之晶種 (Seed) 慢慢浸入矽熔湯中，經過晶頸生長 (Neck Growth) 、晶冠生長 (Crown Growth) 、晶身生長(Body Growth) 、尾部生長 (Tail Growth) 等製程，即可得到與晶種相同之排列整齊之晶格、原子，成為製造矽晶圓所需要之單結晶材料。

wafer

• Orientation: XRD provides the orientation

• sawing: thin slices (wafer)

• Polishing: one side is mirror-like finish

3. Epitaxial deposition

• Is the deposition of a single crystal layer on a substrate (same composition). Etchant (HCl gas) is used to create nucleation site for epitaxial deposition

Method of epitaxial deposition: sputtering, evaporation: low rate vapor growth: deposited from SiCl4 and SiH4 (bett

er from hydrogen reduction SiCl4(g) + H2(g) = Si + HCl(g) or pyrolysis of SiH4(g) = Si + H2(g)

4. Oxidation

• The ability to grow a chemically stable protective layer of SiO2 on Si, makes Si the most widely used semiconductor.

• This protective layer is growth in atmospheres containing either oxygen or water vapor (faster) at temp. in the range of 900 – 1300oC.

5. Impurity introduction: by diffusion

• A. predeposition: heat semiconductor to a temp. and an excess of the desired dopant is made available at the surface of the wafer. The dopant will enter the crystal lattice. Solid solubility. Ion implanation: take ions of a desired dopant, accelerates them using an electric field.

• B. drive-in: is performed in a high temp. diffusion furnace.

6. Photomasking

• For the successful transfer of an image to the surface of a wafer: generate a mask and transfer to the wafer through use of a photoresist (光阻 ).

• The circuit be fabricated by sequentially transferring images the wafer while performing steps such as CVD, epitaxy, predeposition, and drive-in, or metallization between successive image transfers.

• Light-hardened resist is negative resist, while light-softened resist is positive resist.

Basic photoresis flowchart

• Surface preparation – application of resist – soft bake (low temp. cure to dry resist, expose, develop (dissolve the unpolymerized resist)) – visual inspection – hard bake (higher temp. cure to completely dry and polymerize) – etch – strip resist – visual inspection

7. Chemical vapor deposition

• The formation of a stable compound on a heated substrate by the thermal reaction or decomposition of gaseous cpds.

• SiH4 + heat = Si (polycrystalline)+ H2

• SiH4 + O2 = SiO2 + H2

• SiH4 + NH3 = Si3N4 (a dense dielectric used to passivate circuits) + H2

8. Metallization

• After the devices in the silicon substrate have been fabricated, they must be connected together to perform circuit functions.

• Vacuum deposition of Al by sputtering

• Copper deposition

STM, 15 x 15 nm2

MEMS

Microelectromechanical systems

nm?

電 鑄

Electroforming

Since 1858

Cyclic voltammetric stripping analysis, CVS

CVS

• Potentiostat and three-electrode:

• A platinum wire auxiliary

• A saturated calomel electrode (SCE)

• A rotating platinum disc of area 0.071 cm2.

The disc was rotated at 2500 rpm and swept continuously at 10 mV/sec between -0.150 and 1.850 V vs. SCE in solution.

Relative rate parameter, Ar/As

• The area under the stripping peak (Ar) corresponds to the charge required to oxidize the deposit completely and is proportional to the average deposition rate of copper, whereas As is the strippping peak for the static electrode without any additive.

印刷線路版

PCB

Image transfer

etching

lamination

Copper through hole plating

Solder plating

電容 , capacitor, condenser

• Ta

• MOS capacitor, fig. 55

• Ceramic

• Al/oxide

• Paper

• mica

Energy density

Wh/kg

Work density

Kw/kg

Li battery 100 - 125 < 0.2

Ni-H battery 50 - 60 < 0.2

Acidic lead

battery

30 - 40 < 0.2

capacitor 0.17 50

V = E, Q ∞ V, C = Q/V

• F, farad• μF• μμF = pF = 10-12F

values:

PbLaZrTiO3 1000

TiO2 50

Ta2O5 25

Al2O3 9

Solid tantalum capacitors

• Capacitor that use a metal oxide film having a valve effect as a dielectric are known as electrolytic capacitors. Because their dielectric film is extremely thin, electrolytic capacitors are the smallest of all capacitors in terms of volume per unit capacitance.

Ta capacitor

• Dielectric strength:

breakdown voltage =

working voltage

glass: 90 kV/mm

mica: 200 kV/mm

Ag paste, cathode

graphite

MnO2

Ta2O5

Ta, anode +

Sintered Ta Powder

Tantalum oxide is formed by electrochemical technique on tantalum as the metal electrode, which serves as the dielectric. On the top of the tantalum

oxide a manganese dioxide layer is formed as electrolyte. Solid electrolyte

capacitor. To make sure that this manganese dioxide is electrically

connected, a graphite layer is provided to create a metal layer that serves as a

cathode.

Sintered Ta, 2 – 10 μm

Ta powder is compressed under high pressure around a Ta wire to form a pellet. This is subsequently

vacuum sintered at high temperature (typically 1500 –

2000oC). This structure is of high mechanical strength and density, but is also high porous giving a

large internal surface area.

Construction of solid Ta capacitors

Neocapacitor (conducting polymer tantalum capacitor)

High conductivity 20 S/cm, high temp. for thermal decomposition

200 – 300oC

CD 等光碟族

CD 族• Glass master: 玻璃基版• Metalizing: 電鑄• Stamper: 壓模• Injection molding, optical polycarbonate, sputtering• Lacquering: 塗漆層• Printing: 印刷

CD 族• CD-ROM

• CD-R

• CR-RW

• DVD-ROM

• DVD-R

• DVD-RW

• DVD-RAM

針孔

EMI/RFI Shielding

• Electromagnetic interference:

conducted emission

radiated emission

EMI

Indium tin oxide, ITO

• High conductivity (about 104 -1cm-1) from the creation of a conducting carrier-oxygen

vacancy with the addition of dopant Sn to the matrix In2O3.

• High transparency (85 – 90%)

The crystallite size of ITO powder

• Could be calculated from the line broadening of the (222) diffraction line according to the Scherrer equation:

D = 0.9λ / cos where D is the crystallite size (in angstroms), λthe wav

elength of Cu K1 radiation, and the corrected half-widt

h of the diffraction peak.

ITO powder

=0.456o

• D= 18 nm

Electrowetting

• Electrowetting: a voltage is used to modify the wetting properties of a solid material

• Without a voltage: the requirement of spreading is s > sl + l

• With a voltage:

cosΘv = cosΘo + V2/2 wo d

Surface tension, dyne/cm

• Water, 72.6

• Fluoro-polymer, 8-15

• Hydrocarbon-polymer, 18-30

• Molten glass, 200-400

• Molten metal, 350-1800

• Detergent solutions, 24-40

Battery

• History

• Li battery

• Polymer electrolyte

• Thermal battery

Construction for Polymer electrolyte

• Al foil• Anode: C (LixCn = Li+ + e + Cn)• Anode material• Polymer (gel polymer, monomer and electr

olyte)• Cathode material• Cathode: Li, Co oxides• Al foil

Thermal battery

Thermal battery

• The conductivity of eutectic point of LiCl-KCl is 2.1 (Ωcm)-1, while aqueous NaCl is only 0.2.

• Plus: more than 10 years less than 1 sec high charge rate reliability maintenance

Thermal battery

• Two main types: Li and Ca systems

Li/LiCl-KCl/FeS2

Ca/LiCl-KCl/CaCrO4

(when 61% LiCl, then m.p. is 352oC)

Reactions:

Li + FeS2 = Li2Fe2S5 + FeS

Ca + CaCrO4 = CaCl2 + Cr2O42CaO

Thermal battery

• Thermal source: paper and sheet

a. Thermal paper: 1-10 μm powder of Zr and BaCrO4

burning rate is 10-15 cm/sec thermal content is 1675 j/gb. Thermal sheet: KClO4 and Fe powder excess iron powder is a conductor thermal content is 920 -1420 j/g

LCD, liquid crystal display

判別液晶種類(homeotropic 組織 =全部液晶分子垂直排列於玻璃上 )

Pixel, picture element

• Vertical polarizing filter film

• ITO, transparent electrode

• Twisted nematic LC

• ITO, transparent electrode

• Horizontal polarizing filter film

具有光學異方向性的物質第四態

Plasma display pane

cost

• 70%:

1. 背光模組 37%

2. 彩色濾光片 27%

3. 偏光板 15%

4. 驅動 IC 8%

5. 玻璃基板 7%

物理蒸鍍法直接獲取金屬精密圖案

• Image: dry film or photoresist

• Metal pattern: sputtering

• Stripping of dry film or photoresist

sputtering

•      濺鍍的基本原理是將加速了的離子轟擊固體表面，離子在和固體表面的原子交換動量之後，就會從固體表面濺出原子，此現象為濺射 (Sputtering) 。濺射是真空鍍膜方法之一。通常陰極 (cathode) 上裝載的是靶材 (target) ，而陽極 (anode) 上裝載的則是待鍍物 (試片基板或碟片 )。為使於濺鍍氣體 (sputtering gas) 中電漿 (plasma) 能夠點燃，將陰極加到數百伏特電壓。陰極所加的電壓相對於陽極而言是負的，因而游離的氬正離子被加速往陰極表面飛去。當氬正離子與靶材表面發生碰撞時，靶材表面原子被撞擊出而飛向置於陽極的基板並鍍在基板表面。 

target

Sputtering target• Pure Metal Sputtering Targets

Aluminum/Al, Silver/Ag, Gold/Au, Lanthanum/La, Cerium/Ce, Cobalt/Co,Carbon/C, Chromium/Cr, Copper/Cu, Dysprosium/Dy, Erbium/Er, Europium/Eu, Gadolinium/Gd, Holmium/Ho, Hafnium/Hf , Indium/In, Iridium/Ir, Lutetium/Lu, Magnesium/Mg,Molybdenum/Mo, Niobium/Nb, Neodymium/Nd, Nickel/Ni, Praseodymium/Pr, Palladium/Pd, Platinum/Pt, Rhenium/Re, Ruthenium/Ru, Rhodium/Rh, Scandium/Sc, Silicon/Si, Samarium/Sm , Tantalum/Ta, Terbium/Tb, Titanium/Ti, Thulium/Tm, Vanadium/V, Tungsten/W, Ytterbium/Yb, Yttrium/Y, Zirconium/Zr

• Alloy Sputtering TargetsRare earth TbDyFe alloy, Al-Ag, Al-Si, Ag-Pt, Ag-Cu, Ce-Gd, Cu-Ce ,Ce-Sm ,Co-Zr , Co-Cr , Co-Ni , Co-Pd , Co-Fe , Cr-V , Cr-B , Cr-Cu , Dy-Fe , Gd-Fe , In-Sn , Ir-Rh , Ir-Pd , Ni-Fe , Ni-Ti , Ni-V , Ni-Cr , Mn-Ir , Mn-Fe ,Mn-Ni , Tb-Fe , Ti-Al, W-Si , Zr-Ti, Zr-Ni , Zr-Nb , Zr-Al , Zr-Cu , Zr-Y , Zr-Hf , Ga-As , Gd-Fe-Co , Nd-Dy-Fe-Co , Tb-Fe-Co , Co-Ni-Cr , Al-Si-Cu , Tb-Gd-Fe-Co

• Compound targets/ Ceramic Sputtering Targets: TiO2, CaO, SiO, Ta2O5, La2O3, CeO2, Pr6O11, Nd2O3, Sm2O3 ,Eu2O3, Gd2O3, Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3, Sc2O3, Y2O3, CeF3, NdF3, YF3, LaF3, YbF3, MgF2, Nb2O5, ZnS, In2O3, ITO targets, Al2O3 ， CaF2 ， GaP ， LaAlO3, LiNbO3, LiTaO3, MgO, MgF2, SrTiO3, SiO2 , YSZ , HoBCO ， ITO, MgO, SiC, SmBCO, SiO2 ， YBCO, ZnO, ZrO2

直接獲取金屬精密圖案的物理蒸鍍室

鈔票上的細條紋0.05mm 寬 (508 lpi)

鋁金屬圖案的精密度•例 1      (F6 液體溶劑於 PC塑膠板上的 110 倍圖 )    其 A線條寬為 0.064 mm ，有每英吋 397 線 (lpi) 的精密度，而 B線條更細至 0.027 mm ，即有每英吋 940 線 (lpi) 的高精密度。 

•例 2      (IPA 液體溶劑於 ABS 塑膠板的 50倍之圖 )     其 A線條寬為 0.08 mm ，有每英吋 318 線 (lpi) 的精密度，而 B線條更細至 0.027mm 以下，意即有每英吋 1270 線 (lpi) 以上的高精密度。

F6 液體於 PC 塑膠板上的圖案之放大 110 倍照片

液體溶劑 (a,b) 在底材上的接觸角。

PC 塑膠片於真空鍍鋁後的塗有 F-3 溶劑處之3D 掃瞄功能表面形貌量測儀的量測圖。

LED, light-emitting diode

• A chip of semiconducting material doped with impurities to create p-n junction. Charge-carriers (i.e. electrons and holes) flow into the junction from electrodes with different voltage. When an electron recombines with a hole, it falls into a lower energy level and releases energy in the form of a photon.

LED, light-emitting diode

• Light source The efficiency of a standard W-filament light bulb is only 5%, so 95%

is lost as heat.

The fluorescent tube is 15 – 25%.

In Tailand, lighting accounts for 40% of all electricity consumption.

A US Department of Energy report states that if 50% of the lighting in the USA were replaced by white GaN-based LEDs, 41 GW of electricity would be saved (41 power stateions). – Greenhouse

• Indium gallium nitride/gallium nitride, (InGaN/GaN), stay cool, very little heat

LED, light-emitting diode

• Blue LEDs are based on one or more InGaN layers sandwiched between thicker layers of GaN.

• By varying the relative InN-GaN fraction in the InGaN, the light emission can be varied from violet to amber.

• White light LEDs are fabricated by coating the surface of blue LEDs with a yellow phosphor. Coating?

• Non-radiative recombination: dislocation?

LEDs

• Low energy consumption

• Long life

trafic lights are replaced every 6 months

while LEDs can last 10 years

• Low maintenance

White LEDs

• Home and office lighting: high efficiency, 30%: 60% in lab and for the future is 80%.

• High quality

• Long life:100,000 hr, but packaging?

• Low cost: white LEDs are more expensive than filament light bulbs and fluorescent tubes