半导体制造技术导论（第二版）萧宏 第7章 等离子体工艺

7.3等离子体系统7.4等离子体工艺7.5本章小结2023-05-271第7章等离子体工艺本章主要内容7.1等离子体基本概念7.2等离子体参数7.1等离子体基本概念2本节主要内容何为等离子体等离子体的用途等离子体的产生何为等离子体—定义3What

Is

Plasma？(什么是等离子体)

A

plasma(等离子体)is

a

ionized

gas(离化的气体)

with

equal

numbers

of

positive

and

negative

charges

A

more

precise

definition(更准确的定义):a

plasmais

a

quasi-neutral

gas(准中性的气体)of

charged(带电的)and

neutral(中性的)particles

which

exhibitscollective

behavior(集体行为).何为等离子体—成分4A

plasma(等离子体)consists

of

neutral(中性的)

atoms(原子)or

molecules(分子),negative

charges(electrons)and

positive

charges(ions)Quasi-neutral(准中性):ni

≈

neIonization

rate(离化率):ne/(ne

+nn)IonizationRate(离化率)

Ionization

rate(离化率)is

mainly

determined(决定)

electron

energy

in

plasma(等离子体)5Plasma

processing

chambers(等离子体工艺反应室),thionization

rate(离化率)is

less

than

0.001%.

Plasma

etching

chambers(等离子体刻蚀反应室),theionization

rate(离化率)is

about

0.01%.

High

density

plasma(e.g.,ICP感应耦合等离子体,ECR电子回旋共振),the

ionization

rate

is

about

1%~

5%.何为等离子体—离化率等离子体的用途6Applications

of

Plasma(等离子体用途)CVD(化学气相淀积)Etch(刻蚀)PVD(物理气相淀积)Ion

Implantation(离子注入)Photoresist

strip(剥离光刻胶)

Process

chamber

dry

clean(工艺反应室干式清洗)Collision(碰撞)Ionization(离化)Excitation-Relaxation(激发—松弛)Dissociation(分解)……7等离子体的产生—碰撞Ionization(离化)

Electron

collides(碰撞)with

neutral(中性的)atom(原子)or

molecule(分子)Knock

out(击出)one

of

orbital

electron(轨道电子)等离子体的产生—离化8Ionization(离化)等离子体的产生—离化(自由电子)9(轨道电子)(自由电子)(原子核)(原子核)Excitation-Relaxation(激发—松弛)

Different

atoms(原子)or

molecules(分子)havedifference

frequencies(频率),that

is

why

differengases

have

different

glow(发光)colors.

The

change

of

the

glow(发光)colors

is

used

foretch

and

chamber

clean

process

endpoint(终结点).等离子体的产生—激发松弛10(原子核)11(原子核)(碰撞电子)Excitation

Collision(激发碰撞)(碰撞电子)(基态电子)(激发态电子)等离子体的产生—激发松弛12(基态)Relaxation(松弛)(普朗克常数)(激发态)可见光UV等离子体的产生—激发松弛等离子体的产生—分解Dissociation(分解)

Electron

collides(碰撞)with

a

molecule(分子),itcan

break

the

chemical

bond(化学键)and

generatefree

radicals(自由基):Increasing

chemical

reaction

rate(化学反应速率)Very

important

for

both

etch

and

CVD13等离子体的产生—分解(分子)14Dissociation(分解)(自由基)Plasma

Etch(等离子体刻蚀)

CF4

is

used

in

plasma(等离子体)to

generate(产生)

fluorine

free

radical(F自由基)for

oxide

etch(刻蚀)等离子体的产生—分解15Plasma

Enhanced

CVD(等离子体增强CVD)PECVD

with

SiH4

and

N2O(笑气)PECVD

can

achieve(获得)high

deposition

rate(淀积速率)at

relatively(相对)lower

temperature.等离子体的产生—分解16等离子体的产生—分解177.3等离子体系统7.4等离子体工艺7.5本章小结2023-05-2718第7章等离子体工艺本章主要内容7.1等离子体基本概念7.2等离子体参数7.2等离子体参数19本节主要内容平均自由程热速度磁场中的带电粒子玻尔兹曼分布平均自由程Mean

Free

Path

(MFP)

The

average

distance(平均距离)a

particle(粒子)cantravel

before

colliding(碰撞)with

another

particlen

is

the

density

of

the

particle(粒子浓度)

s

is

the

collision

cross-section

of

the

particle(粒截面)20平均自由程Exercise

分子直径为4Å，密度为5×1016

cm-3，请计算分子的平均自由程。MFP

=

1/[1.414×5×1016

×p(2×10-8)2]

=

0.011

cm2122平均自由程MFP

Illustration(MFP介绍)高压情形低压情形Question(问题)

Q:Why

does

one

need

a

vacuum

chamber(真空反应室)to

generate(产生)a

stable(稳定的)plasma?

A:在标准大气压下(760

Torr),电子的平均自由程很短，因此电子很难获得足够的能量离化气

体分子。而当电场很强时，等离子体将形成弧

光放电，而不是稳定的辉光放电。23平均自由程热速度Electron(电子)is

much

lighter(更轻)than

ion(离子

Electric

forces(电场力)on

electrons

and

ions(离子the

sameElectron

has

much

higher

acceleration(加速度)24Movement

of

Charged

Particle(带电粒子)RF(射频)electric

field(电场)varies(变化)quickl25electrons

are

accelerated(加速)very

quickly

whileions(离子)react(反应)slowly.

Ions(离子)have

more

collisions(碰撞)due

to

theirlarger

cross-section(横截面)that

further(进一步)

slowing

them

down(降低它们的速度)Electrons

move(移动)much

faster

than

ions(离子)

in

plasma(等离子体)热速度热速度Thermal

Velocity(热速度)Electron

thermal

velocity(电子热速度)*

k:波尔兹曼常数RF

plasma(射频等离子体),kTe

is

about

2

eV*

mph,

miles

per

hour;

1

mph

=

4.4704

cm/s26Magnetic

Force

and

Gyro-motion(磁场力和螺旋运动)Magnetic

force(磁场力)on

a

charged

particle(带电粒

Magnetic

force(磁场力)is

always

perpendicular(垂直the

particle

velocity(粒子速度)

Charged

particle(带电粒子)will

spiral

around(螺旋围the

magnetic

field

line(磁力线),Gyro-motion(螺旋运磁场中的带电粒子27Gyro-motion(螺旋运动)磁场中的带电粒子28参数电子氩离子热速度v

(cm/s)5.93×1073.46×104螺旋转动半径r

(cm)at

B

=100

G=0.01

T0.0341.44Gyrofrequency(螺旋转动频率)磁场中的带电粒子Gyro

radius(螺旋转动半径)29玻尔兹曼分布307.3等离子体系统7.4等离子体工艺7.5本章小结2023-05-2731第7章等离子体工艺本章主要内容7.1等离子体基本概念7.2等离子体参数7.3等离子体系统32本节主要内容离子轰击直流偏压离子轰击33Ion

Bombardment(离子轰击)

Electrons

reach(到达)electrodes(电极)andchamber

wall(反应室墙壁)first

Electrodes(电极)charged

negatively(带负电),

repel(排斥)electrons

and

attract

ions(吸引离子).

The

sheath

potential(鞘层电势)accelerates(加速)itowards

the

electrode(电极)and

causes(引起)ionbombardment(离子轰击)Very

important

for

sputtering(溅射),etch

and

PECVD34离子轰击Sheath

Potential(鞘层电势)(暗区)(鞘层电势)(体内等离子体)(鞘层区)Applications

of

Ion

bombardment(离子轰击的应用)Help

control

film

stress(膜应力)in

PECVD

processesHelp

to

achieve(获得)anisotropic(各向异性)etch

prArgon

sputtering(氩离子溅射)35离子轰击直流偏压36Plasma

Potential

&

DC

Bias(等离子体电势和直流偏压)DC

biases

and

RF

powers(直流偏压和射频功率)(等离子体电势)37Lower

RF

powerSmaller

DC

biasHigher

RF

powerLarger

DC

bias直流偏压38直流偏压(暗区或鞘层区)DC

Bias

of

CVD

Chamber

Plasma(CVD反应室等离子体的直流偏压)(地)(射频热电极)DC

Bias

of

Etch

Chamber

Plasma(刻蚀反应室等离子体的直流偏压)直流偏压39DC

Bias

of

Etch

Chamber

Plasma(刻蚀反应室等离子体的直流偏压)直流偏压407.3等离子体系统7.4等离子体工艺7.5本章小结2023-05-2741第7章等离子体工艺本章主要内容7.1等离子体基本概念7.2等离子体参数7.4等离子工艺42本节主要内容等离子体工艺的优点PECVD与等离子体刻蚀遥控等离子体工艺高密度等离子体工艺等离子体工艺的优点43Plasma

processes(等离子体工艺):PECVD(等离子体增强化学气相淀积)CVD

chamber

dry

clean(CVD反应室干法清洗)Plasma

Etch(等离子体刻蚀)PVD(物理汽相淀积)Ion

implantation(离子注入)Benefits

of

Using

Plasma

For

CVD

Process(CVD工艺使用等离子体的优点)

High

deposition

rate(淀积速率)at

relatively(相对

lower

temperatureIndependent

film

stress

control(控制薄膜应力)Chamber

dry

clean(反应室干法清洗)44等离子体工艺的优点—CVDComparison(比较)of

PECVD

and

LPCVD等离子体工艺的优点—CVD4546Gap

Fill(间隙填充)

by

HDP-CVD等离子体工艺的优点—CVD0.25

mm,深宽比=4:147Benefits

of

Using

Plasma

For

Etch

Process(刻蚀工艺使用等离子体的优点)High

etch

rate(刻蚀速率)Anisotropic(各向异性)etch

profile(形状)Optical

endpoint(光学终点监测)Less

chemical(化学制品)usage

and

disposal(处理)等离子体工艺的优点—刻蚀Benefits

of

Using

Plasma

For

PVD

Process(物理汽相淀积使用等离子体的优点)Argon

sputtering(氩离子溅射)Higher

film

quality(膜质量)—Less

impurity(杂质)and

higher

conductivityBetter

uniformity(均匀性)Better

process

control(工艺控制)Higher

process

integration(工艺兼容)capabilityEasier

to

deposit

metal

alloy

films(合金薄膜)48等离子体工艺的优点—PVD49PECVD与等离子体刻蚀PECVD

and

Plasma

Etch

Chambers(PECVD和等离子体刻蚀反应室)CVD:Adding

materials(添加材料)on

wafer

surfaceFree

radicals(自由基)Some

bombardment(轰击)for

stress(应力)controlEtch:Removing(去除)materials

from

wafer

surfaceFree

radicals(自由基)Heavy

bombardment(轰击)Prefer

low

pressure(低压),better

directionalityof

ions50PECVD与等离子体刻蚀Schematic

of

a

PECVD

ChamberElectrodes(电极)have

about

the

same

area(相同面积The

ion

bombardment(轰击)energy

is

about

10

to

20

eV51PECVD与等离子体刻蚀Schematic

of

an

Etch

Chamber(工艺气体)(磁场线圈)(真空泵抽走副产物)(氦气冷却晶圆背面)Plasma

Etch

ChambersIon

bombardment

energy(离子轰击能量)on

wafer

(RF

hot

electrode):

200

to

1000

eVon

lid(盖子)(ground

electrode):10

to

20

eV.Ion

bombardment(离子轰击)Physically

dislodge(物理移除)break

chemical

bonds(打破化学键)Heat

generation(热产生)Need

to

protect

masking

PR(掩膜光刻胶)Helium(氦气)backside

cooling

required52PECVD与等离子体刻蚀Plasma

Etch

ChambersEtch

prefer

lower

pressure(低压)longer

MFP(平均自由程)more

ion

energy(能量)and

less

scattering(散射)Low

pressure,less

ionization

collision(碰撞)hard

to

generate

and

sustain

plasma

Magnets(磁体)are

used

to

force(促使)electron

sp(电子自旋)and

travel

longer

distance

to

increasecollisions(碰撞)53PECVD与等离子体刻蚀遥控等离子体工艺—Plasma

Clean(等离子体清洗)54Remote

Plasma

Processes(遥控等离子体工艺Need

free

radicals(自由基)Enhance

chemical

reactions(增强化学反应)Don’t

want

ion

bombardment(离子轰击)Avoid

plasma-induced

damage(损伤)Remote

plasma

systems(遥控等离子体系统)Photoresist

Strip(剥离光刻胶)Plasma

Etch(等离子体刻蚀)55遥控等离子体工艺—剥离光刻胶(有光刻胶的晶圆)(加热平板)Photoresist

Strip

Process(剥离光刻胶工(微波)(远端等离子反应室)Remote

Plasma

Etch(遥控等离子体刻蚀)Isotropic

etch

processes(各项同性刻蚀工艺):LOCOS

or

STI

nitride

strip(剥离氮化物)wineglass

contact

hole

etch(酒杯状接触孔刻蚀)Part

of

efforts

to

replace(取代)wet

process(湿法工56遥控等离子体工艺—等离子体刻蚀遥控等离子体工艺—等离子体清洗Remote

Plasma

Clean(遥控等离子体清洗)(微波)(远端等离子反应室)57(加热平板)Remote

Plasma

CVD

(RPCVD)Epitaxial(外延)Si,GeDielectric(介质):SiO2,SiON,and

Si3N4High-k

dielectrics:

HfO2,

TiO2,

and

Ta2O5PMD(金属淀积前介质)barrier

nitrideLPCVD:budget

limitations(热预算限制)PECVD:plasma

induced

damage(损伤)58遥控等离子体工艺—等离子体CVDHigh-density

Plasma(高密度等离子体)

Etch

and

CVD

desire(需要)high-density

plasma

atlow

pressure(低压下高密度等离子体)

Lower

pressure(低压),less

ion

scattering(散射),

enhances(增强)etch

profile(刻蚀轮廓)controlHigher

density,more

ions

and

free

radicals(自由基)Enhance

chemical

reaction(化学反应)Increase

ion

bombardment(离子轰击)CVD

processes,dep/etch/dep

enhance

gap

fill(填空隙59高密度等离子体工艺Limitation

of

Parallel

Plate

Pla