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電漿技術於清潔製程之應用電漿技術於清潔製程之應用

梁國超 博士gtliang@creating-nanotech.com馗鼎奈米科技股份有限公司

中華民國九十三年七月十三、十四日

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大大 綱綱

電漿為一熱力學非平衡狀態, 電漿中分佈了多種形態的高能量粒子, 利用電漿, 可以將適當的氣體分子如O2,H2,CF4,N2等分解成離子,電子,自由基等高反應性的粒子,這些高反應性的物質,在室溫即可與待清潔物表面油污反應,並形成穩定的氣體分子。電漿清潔所需的能源少,產生的污染物極少,是一個相當環保、節能的製程。課程內容如下

電漿基本特性

電漿中的化學反應

電漿清潔的應用

電漿清潔裝置

大氣電漿

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Gas reaction

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Plasma reaction

E

N

E

Ea

A+B

C+D

∆H

中性物質

EACT

電子離子

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Introduction to Plasma Principles

(Kinetic Energy) gained＝ F．d＝q．ε．λ

＝q．(V/de)．λ

λ：mean free path de：electrode distance

ε：electric field V：electrode voltage

Electron with small volume has large free path than other species in plasma

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Electron and ion temperatures

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Elastic and Inelastic Collision

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Elastic and Inelastic Collision

•千萬不要加速特大的particles•若要增加別的分子的內能，最好加速小的particle•動能的傳遞要靠加速相同質量的particle

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Inelastic collision

Excitatione-+Ar Ar*+e-RelaxationAr* Ar+ hνIonizatione-+Ar 2e-+Ar+hν+Ar Ar*+e-, Recombinatione-+Ar++M Ar+Me-+Ar+ Ar+ hνDissociatione-+O2 e-+2Oe-+CF4 e-+CF3+F (dissociation)e-+CF4 2e-+CF3++F (dissociative ionization)

Electron Attachmente-+SF6 SF6-e-+SF6 SF5-+FIon-neutral collision & Neutral-neutral collisionA+A+ A++AB++C B+C+Metastable collisionAr*+G G++Ar+e-

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Plasma ions (positive and /or negative), electron and neutrals.Net total charge is neutral.The degree of ionization is typically only 10-4.In the absence of electric filed, the charge in plasma move around as free particles, similar to conduction electrons in solids.

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Introduction to plasma principles

Plasma Cleaning Principles

Two cleaning mechanisms:Chemical reactions by free radicalsPhysical sputtering by high energy ions

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Introduction to plasma principles

Chemical reactions by free radicals

• e- + H 2 2H•• e- + O 2 2O• O•+ O2 O 3

Highly reactive free radicals generated in plasma may react with the hydrocarbon contaminants or surface oxide.

Both H• and O• can react with grease or oil on surface to form volatile hydrocarbons.

• H• (g) + CnH2n+2(s) CH4(g)• O• (g) + CnH2n+2(s) CO(g) + CHxOy (g) + H2O (g)

O• is more reactive than H•. But O• may also react with surface metal to form oxide, deteriorating the material properties. And, H• can also reduce metal oxide back to metal.

• H• + MeO Me + H2O• O• + Me MeO

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Introduction to plasma principles

Chemical reactions by free radicalsAdvantages:

Stable gas products are formed. There is no redeposition problem. High etching selectivity can be obtained.Disadvantages:

Higher concentration of H2 or O2 is required to ensure an appropriate etching rate. H2 safety or O2 strong oxidation ability needs to be monitored. Operation:

The effect of chemical reactions is increased as the pressure increases.

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Introduction to plasma principles

Physical sputtering by high energy ions

Ions generated in plasma can be accelerated toward the substrate to physically bombard away the atoms of contaminants. The physical sputtering rate increases as the plasma density, acceleration voltage or the mass of bombardment atoms increases. Physical sputtering is also enhanced by lowering the pressure to increase the ion energy.Therefore, a high cathode bias will enhance the sputtering rate . H+ or H2+ will have little physical sputtering effect. Ar+ will have strong sputtering effect.

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Introduction to plasma principles

Physical sputtering by high energy ions

Advantages:Highly efficient cleaning effect can be achieved. Gas

consumption rate can be very low. Disadvantages:

Non - selective etching by physical sputtering may induce over – etching problems. The products sputtered out may be highly unstable and tend to deposit again downstream, inducing the redeposition problem.Operation:

The effect of physical sputtering is increased as the pressure decreases or as the cathode bias and Ar concentration increase.

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Plasma Cleaning Principles

Physical sputter and/or Chemical etching can be chosen

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Plasma Cleaning Theory

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電漿清潔的應用

IC封裝前、wire bond前印刷電路板貼合、印刷、電鍍或sputter前IC 去除殘餘光阻液晶面板趨動IC封裝前光學塑膠鍍膜印刷前

光學或特殊薄膜塗佈前

其他表面清潔及改質(增加附著性)

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Plasma Cleaning for Improving Wire Bonding

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電漿清潔裝置

依照電漿產生的方式可分為：

微波電漿

ICP電漿RF電漿DC 電漿

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微波電漿清潔器

2.45GHzElectrode-freeDown stream plasmaNon UniformLow pressure high density

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ICP 電漿清潔器

13.56MHzElectrode-freeUniformLow pressure

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高周波電漿清潔器

13.56MHzElectrodeUniformHigh pressure

Hollow cathode

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大氣電漿

Low pressure plasma (cold plasma)：non-equilibrium system

Te＞＞Ti＞＞TnHigh pressure plasma (thermal plasma):pseudo-equilibrium system

Te=Ti=Tn

High Pressure：

TAr＋＝TArAr*＋Ar→ 2 Ar (hot)

e–＋Ar＋＋Ar→2 Ar (hot)

510 −≈i

e

mm 510∝P

11010 55 ≈×−

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大氣電漿之放電特性

負電阻Arcing

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大氣電漿

(Kinetic Energy) gained ＝q．(V/de)．λ

In atmospheric pressure, λis small V沒有真空設備操作成本便宜連續製程電漿密度高,處理速度快均勻性差

V

Plasma jet (spot type)DBD CoronaGliding ArcPlasma torch (thermal plasma)

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Palsma jet

Spot type Small areaHigh efficiencyWithout ozoneLow electro static chargeNo ArcingApplication: for small area or scanningfor large issue

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DBD

Large areaLow efficiencyOzoneNo Arcing

以絕緣物包覆電極，通以高頻高壓電位，產生之週期性絲狀放電。

優點：在高濃度惰性氣體下可得到較均勻之輝光放電。

缺點：氣體昂貴。

應用：可作為UV燈管

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Corona Discharge

利用尖端局部高電場引發氣體崩潰產生之電漿。

優點：溫度低、省能源。

缺點：處理量小、arcing。

Spot type

Line type優點：溫度低、省能源、處理量大

缺點： arcing 。

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Gliding Discharge

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Plasma Torch

大量電流加熱氣體產生之高溫電漿。

優點：設備簡單，解離率高，處理量大。

缺點：能源損耗大、能源效率低、電極壽命短、溫度太高。

電漿技術於清潔製程之應用大 綱Gas reactionPlasma reactionIntroduction to Plasma PrinciplesElectron and ion temperaturesElastic and Inelastic CollisionElastic and Inelastic CollisionInelastic collisionPlasmaPlasma Cleaning PrinciplesChemical reactions by free radicalsChemical reactions by free radicalsPhysical sputtering by high energy ionsPhysical sputtering by high energy ionsPlasma Cleaning PrinciplesPlasma Cleaning Theory電漿清潔的應用Plasma Cleaning for Improving Wire Bonding電漿清潔裝置微波電漿清潔器ICP 電漿清潔器高周波電漿清潔器大氣電漿Palsma jetDBDCorona DischargeGliding DischargePlasma Torch