Upload File

fe-sem basicatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...hitachi sem’s magnification...

  • Home
  • Documents
  • FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of
32
FE-SEM BASIC

Upload: others

Post on 18-Mar-2021

7 views

Category:

Documents


0 download

Report

TRANSCRIPT

Page 1: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

FE-SEM BASIC

Page 2: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Image

Specimen

Obj Lens

Optical source

Opt

Screen Image Image

Specimen

Specimen

Obj Lens

Electric source

Condenser Lens

SE Detector

C R T

T E M S E M

Scanning

Difference among OM, TEM and SEM

Electric source

Page 3: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Condenser Lens

Deflection Coil

Object Lens

Specimen

Chamber

Vacuum Pump

SE Detector

Amplifier

Deflection Amplifier

Electron Beam

Deflection

Coil

Monitor

1st Anode

2nd Anode

FE Tip

Vacuum Pump

Specimen

Electron Gun

SE

Configuration of a scanning electron microscope

Page 4: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

SEM

Scanning Electron Beam of CRT

CRT

DS

Scanning(X)

Scanning(Y)

Magnification :( M)=DS / DD

Specimen

Scanning Electron Beam of SEM

Scanning(X)

Scanning(Y)

Magnifying mechanism in the SEM

DD

Page 5: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Hitachi SEM’s Magnification is base on the size of 4x5 inch film.

（Otherwise CD-SEM is base on the size of Monitor’s Window)

4×5 inch Film

DD

Deflection Coil

DS

Sample

（M）= DS / DD

Magnifying mechanism in the SEM

Page 6: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Specimen Interactions

Electron scatting area

Secondary Electron

（surface features）

Primary Electron Beam (～30kV)

試料

Characteristic X-Ray

（Composition)

Backscattered

Electron

（Topography・Composition ）

Cathodeluminescence

(chemical composition )

Specimen absorption

current

Auger electron

（composition of surface layer）

<10nm (the depth of SE

generation)

Page 7: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

d

Primary Electron Beam (～30kV)

Auger electron Secondary Electron

BSE

Characteristic

X-Ray

continuous x-ray

Cathode luminescence

Electron Scatting inside of specimen

Page 8: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

－

－

－

－

Backscattered

Electron

(internal information) Secondary Electron

(Surface features)

Sample(Metal)

Vacuum

Characteristics of SE and BSE

（How to produce）

Page 9: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

100 10,000 1

Energy of Electron (eV)

Qu

an

tity

o

f

Ele

ctr

on

s

(Incident beam energy : 10,000eV)

Secondary Electrons

Backscattered

Electrons

Energy spectrum of the electrons emitted

from a specimen

Page 10: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Electron Scatting inside of specimen

Vacc= 1kV Vacc= 15kV

1μm

Zoom out

20 nm

1μm

20 nm

Specimen:Carbon

Page 11: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Vacc=20kV Vacc=1.0kV

Specimen：16MDRAM Capacitor

Magnification：x50k

一

一

一

一

一

一

一

電子ビーム照射部位からの二次電子放出(低加速電圧の場合)

電子ビーム照射部位からの二次電子放出電子ビーム照射部位からの二次電子放出((低加速電圧の場合低加速電圧の場合))

一

Z(10nm)

２次電子発生領域

２次電子(SE1)(試料表面情報)

２次電子(SE2､3)内部情報はなし

最表面の情報を忠実に再現

一

一

一

一

一

一

一一

Z(10nm)

２次電子発生領域

２次電子(SE1)(試料表面情報)

電子ビーム照射部位からの二次電子放出(高加速電圧の場合)

電子ビーム照射部位からの二次電子放出電子ビーム照射部位からの二次電子放出((高加速電圧の場合高加速電圧の場合))

２次電子

一

一

一

一

一

一

一

一

一

一

一

２次電子(SE2､3)(内部情報含む)

表面情報と内部情報が混在

試料

Image at different Vacc

Page 12: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Electron beam

Second Electron

Specimen

Scanning

θ

Emitted SE amount vary depending on

topography

composition

Potential difference

Electron incident angle and emitted SE amount

Page 13: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

SE signal

intensity

Upper section

appears darker

for a large

sphere.

Small particles

often appear

abnormally

bright. Edges appear

abnormally bright.

(Edge effect)

＞10μm

Scanning beam

Internal

compositional

information

SE : Secondary electrons only come out of topmost shallow layer

(approx.10nm).

BSE

Review of SEM basic

(Secondary Electron excitation volume)

Sample surface

profile

MonteCalro simulation

Comparison of scattering region of incident electrons (Sample : Si)

Vacc : 10kV Vacc : 1kV

Scanning beam

Page 14: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Sample surface

profile

HA-BSE intensity

compositional/channeling

information

＞10μm

1μm

MonteCalro simulation

Comparison of scattering region of incident electrons (Sample : Si)

Vacc : 10kV Vacc : 1kV

Scanning beam HA-BSE

Compositional information

LA-BSE Compositional information

+ topographical information

BSE Internal compositional information

Intensity vary depending on

accelerating voltage.

LA-BSE intensity

compositional/channeling

information

+ topographical information

BSE : Emission depth depends on

accelerating voltage.

Sample : Ni-Al alloy

Review of SEM basic

(BackScattered Electron excitation volume)

Scanning beam

Page 15: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Resolution of SEM

放大

放大

For example: Digital Camera

Page 16: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Resolution of SEM = the minimum recognizable distance between

two particles

unrecognizable recognizable

Resolution of SEM

Page 17: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Wehnelt

Filament

a2

b2 M2=b2/a2

a1

b1 M1=b1/a1

a3

b3

M3=b3/a3

Cross Over Point (d0)

Anode

Electron Beam

Aperture

Specimen

1st Condenser Lens

2nd Condenser Lens

Aperture

Objective Lens

Spot Size (d)

d=d0・M1・ M2・M3

The lens system of a scanning electron microscope

Page 18: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

specimen

Vacc

Mag.

Resolution

: Pt particles

: 30kV

: 800kX

: 0.4nm

S-5500

Specimen

Vacc

Mag.

Resolution

: Pt particles

: 15kV

: 220kX

: 1.0nm

S-4800

100nm

Base on

4x5 inch

film

Resolution of SEM

Page 19: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Tungsten SEM

Vacc

V Bias Tungsten SEM Tip Vacc

Vext

Flashing Power

FE SEM Tip

1st Anode

2nd Anode

FE SEM

750μm

Page 20: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

ΔV= ～2eV ΔV=～0.2eV Tungsten SEM Tip FE Tip

Energy spread is better

Page 21: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Comparison

Tungsten LaB6 Schottky Cold FE

Electron Size 30μ 10μ 20nm 5nm

Luminance（A/cm3･sr) 106 107 108 109

Energy spread（ｅＶ） 2 1.5 0.5~1 0.2~0.5

Cathode Temperature 2500 1800 1700~ room

Vacuum (Pa) 10-4 10-5 10-6 10-7

Life Time of Tip（ｈｒ） 50 100 5000 More than 1 year

Range of

use

Low Vaccum

Surface structure observation

WDX/EDX analysis

CL/EBSD analysis

Stable Ip of long time running

High resolution

Low accelerated Voltage

Observation

WDX/EDX analysis

CL/EBSD analysis

Stable Ip of long time running

CD-SEM（On line SEM）

Ultra high resolution

Ultra low accelerated

Voltage Observation

EDX analysis

Signal selection

STEM

Series S-2000 S-3000 S-4300SE/N

CD-SEM

S-4000

S-5000

Resolution

&Max Mag

(for example)

3.0nm/x300k 1.5nm/x500k 0.4nm/x2000k

Page 22: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Object lens type

Primary Beam SE detector

specimen

Primary Beam

Lens

spcimen

SE detector Primary Beam

SE detector

Lens

specimen

Out Lens In Lens Semi-in Lens

Accelerated Voltage(kV)

Out Lens

Semi-in Lens

In lens

S-4300SE S-5200/S-5500 S-4700/S-4800

Re

so

lutio

n (n

m)

Page 23: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Specimen

Object

Lens

+V

+10kV

|FE|=|FB|

FB

電流 I

力

磁界 B

E×B

B FE

FB

E

e

FE

FB

Upper Detector

ExB

Page 24: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Specimen

Upper Detector

Object

Lens

+V

E×B

+10kV

電流 I

力 FB

磁界 B

B FE

FB

E

e

e

FE

FB

ExB

Page 25: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Multi signal detection

SE/BSE signal

Primary Beam

Specimen

Super ExB SED1

BF-STEM APT

(option)

S-4800 signal detected system

SE

BSE

・Surface information

・High resolution

・easy to charge up

・energy :10 -100eV

ＳＥ

・composition information

・not easy to charge up

・less edge effect

・energy: depend on Vacc

ＢＳＥ

SE or SE+BSE-L

Super ExB

SED2

BF-STEM Detector

(option)

Obj lens

Page 26: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Al / W

Wire

SE

BSE

ExB

SE

BSE

ExB

Lens

Specimen

Primary Beam Upper

Detector

SE Mode BSE Mode

Lens

Specimen

Upper

Detector Primary Beam

Page 27: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

2μm

SE Mode SE+BSE-L Mode

SE/BSE-L

TFT(Thin Film Transistor) Vacc：2kV Mag：×12K

FIB, no coated

Glass

S-4800

Page 28: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

SE Mode SE+BSE-L Mode

500nm Glass

SE/BSE-L

TFT(Thin Film Transistor) Vacc：2kV Mag：×12K

FIB, no coated

S-4800

Page 29: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Vacuum System

离子泵（Ion Pump)

机械泵（Rotary Pump）

（干泵 Dry pump）

油扩散泵（Diffusion Pump)

分子泵（Turbo Molecular

pump)

Vacuum（Ｐａ） Point Hi-SEM FE-SEM

～１０－１

１０－５～１０－８Ｐａ

・可以从大气压开始抽 ・有挥发油(RP) ・ 无挥发油(干泵)

使用 使用

使用

使用

１０－３～１０－６

・价格底・耐用

・震动少

・有挥发油

・需要前期抽真空装置

・无油干净的真空 ・与DP相比,比较贵 ・需要做一定的减震措施 ・需要前期抽真空装置

～１０－１０Ｐａ

・可以达到超高真空

・无震动

・需要前期抽真空装置 使用

使用

使用

Page 30: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

ｶﾞｽ分子

ﾌﾗｯｼﾝｸﾞ前

FEﾁｯﾌﾟ ｶﾞｽ分子

ﾌﾗｯｼﾝｸﾞ前

FEﾁｯﾌﾟ

　 ﾌﾗｯｼﾝｸﾞ　 ﾌﾗｯｼﾝｸﾞ

吸着、吸蔵されたｶﾞｽ分子が完全に除去されている吸着、吸蔵されたｶﾞｽ分子が完全に除去されている吸着、吸蔵されたｶﾞｽ分子が完全に除去されている

The function of Flashing is to reflash the surface of FE tip

Flashing

Flashing

FE Tip Gas

Before Flashing

Remove gas from FE tip

Page 31: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

Ie

Time After Flashing

15 min

10%

Flashing

FE Tip FE Tip FE Tip

Flashing necessary

Stable period：4~8hr

Page 32: FE-SEM BASICatc.hitwh.edu.cn/_upload/article/files/1b/0d/27d661264f...Hitachi SEM’s Magnification is base on the size of 4x5 inch film. （Otherwise CD-SEM is base on the size of

END


is Full Moon Hikes at Borderland State Park · 2019-02-16 · been musing about SEM’s “little data.” Those of you who attended this past November’s SEM Annual Meeting or read

heritageit.edu · B.TECH / MCA TILL DATE ANY OTHER FINANCIAL ASSISTANCE APPLIED FOR / GRANTED Sem I Sem 11 Sem I Sem 11 Sem 111 Sem IV Sem 111 Sem IV Sem V Sem VI Sem V Sem VI Sem

GENERAL REQUIREMENTS. MathGen ChemPhysicsPhysioSocial Science EnglishPublic Speaking USC1 sem2 sem + lab1 sem + lab1 sem UOP1 sem*2 sem + lab1 sem *1

SEM study of surface structures of the spathe in ... · & Rajan, M. Sivadasan s.n. 17.4.1985, Base of Athirapally Waterfalls, Trichur District, India. 2n= 72. 60) from the base of

Guía de growth marketing aplicado a las búsquedas …...cómo una base sólida de SEM, un canal adecuado y las herramientas inteligentes de SEM pueden transformar su estrategia de

Anna University Syllabus BioMedical Engineering 3rd Sem,5th Sem ,7thth Sem Syllabus -

Conseil en data stratégie - Mémorandum...Sem. 1 Sem. 2 Sem. 3 Sem. 4 Sem. 5 Sem. 6 Sem. 7 Sem. 8 Sem. 9 Sem. 10 Sem. 11 Sem. 12 Sem. 13 Sem. 14 Sem. 15 Sem. 16 Sem. 17 Sem. 18 Sem

Bank Notice Odd sem 12th June, 2019.pdf · Sem ECE (B) 5th Sem Civil 3rd Sem ME(A) 3rd Sem IT Sem IT 5th Sem Sem ME(A) 5th Sem DEE(Diploma) 5th Sem Entitled students are advised to

Annexure- Department of Computer Science and Engineering ...nith.ac.in/wp-content/uploads/2016/10/Syllabus.pdf · Semester Sem-I Sem-II Sem-III Sem-IV Sem-V Sem-VI Sem-VII Sem-VIII

Synthèse Echelle du Vivant, Méthodes d’Observation & Ultrastructure de la Cellule Eucaryote 5-ième Générale / Transition Sciences de Base (3P/Sem.) Biologie

INDIAN INSTITUTE OF TECHNOLOGY KANPUR Dean of …iitk.ac.in/dosa/dsarareg_ug_without_categ_21_12_12-1.pdfSSBB 1 Sem Fee Sem Fee Sem Fee Sem Fee Sem Fee Sem Fee Sem Fee Sem Fee 9775

UNIVERSITY OF MUMBAI FEBRUARY 6, 2018 OFFICE ...nktdegreecollege.org/MCOM SEM II CHOICE BASE NOV 17...UNIVERSITY OF MUMBAI FEBRUARY 6, 2018 OFFICE REGISTER FOR THE M.Com.(SEM-II)(CHOICE

Documento de Base do Planeamento do de... · Documento de Base do Planeamento do ... Tendência de crescimento da população em idade de frequência dos ... Total Sem Nível Pré-escolar

Diploma IInd Sem SEM II

Message from the Principal - Rockingham Senior High Schoolrockingham.wa.edu.au/wp-content/uploads/2016/03/Annual_Report_… · 2012 2013 2014 Sem 1 Sem 2 Sem 1 Sem 2 Sem 1 Sem 2 A

Scanned by CamScanner › download › › New Doc 2020-06... · 2020-06-01 · Total Eight Sem. 1st Sem. 2nd Sem. 3rd Sem. 4th Sem. 5th Sem. 6th Sem. 7th Sem. 8th Sem. Session 2019

heritageit.edu · B.TECH TILL DATE ANY OTHER FINANCIAL ASSISTANCE APPLIED FOR / GRANTED Sem I Sem Il Sem I Sem Il Sem 111 Sem IV Sem 111 Sem IV Sem V Sem VI Sem V Sem VI Sem Vll Sem

SEM 1 SEM 4 SEM 2 SEM 3 SEM 6

Bayes Factors - Mathematics & Statisticsmath.bu.edu/people/sray/talk/bic.pdf · 2006. 8. 17. · Bayes Factor in SEM Bayes factor in SEM Model Fit in SEM’s SEM Hypothesis testing

final inside page 2014 Y 65 series-oneup ENDMILL CARBIDE 200 Y65.pdf · yf4-sem 2010 yf4-sem 2015 yf4-sem 2020 yf4-sem 2025 yf4-sem 2030 yf4-sem 2040 yf6-sem 2030 yf6-sem 2040 yf6-sem

Acid Base Disorders 5th Sem

3rd sem and 4th sem ece

Maharshi Dayanand Universitymdu.ac.in › UpFiles › UpPdfFiles › 2019 › Jun › press note... · 10th Sem 2 Sem. 4th Sem. & 6th Sem. 5 sem & sem Re-appear only Re-appear only

B (Sem –I & Sem.-IV )

Field-Emission SEM (FESEM) - MTEC · PDF fileField-Emission SEM (FESEM) Sometime called • Field Emission Gun SEM (FEG-SEM ) • High resolution SEM • Low-Voltage SEM Hitachi S8020

A New Scanning Electron Microscope Lakeview has just received a $77,000 grant to purchase a new Scanning Electron Microscope (SEM for short). SEM’s are

Sushi, Cappuccino andBassem Youssef · Sushi, Cappuccino andBassem Youssef ... Modeled after The Daily Show with Jon Stewart, ... sem’s content, writing and performance

„Many faces of the bicycle” - Home - CESIE“Many faces of the bicycle” (MFOT) is a second EVS project planned by SEM in trilogy which will promote 3 SEM’s main sports activities:

FLUID, ELECTROLYTES & ACID-BASE BALANCE 2 SEM C3T

Cryo-SEM & Cryo-FIB/SEM Preparation - EMSDIASUM...Cryo-SEM & Cryo-FIB/SEM Preparation TECHNIQUES & APPLICATIONS featuring the PP3010 Cryo-SEM/Cryo-FIB/SEM Preparation System EMS_CryoSEM

Sem-1 Sem-2 Sem-3 Sem-4

Sem-1 Sem-2 Sem-3 Sem-4 - University of Calcutta · 2018-06-06 · Sem ‐1 Sem‐2 Sem ... Engineering and ... Microbes in Sustainable Agriculture and Development B3. Instrumentation

Syllabus Sem 1 Sem 2

Conventional SEM (C)SEM Environmental SEM ESEM material em paper… · Conventional SEM "(C)SEM" Environmental SEM "ESEM" 3 4 Increasing chamber pressure. 5 temperature just above

Redes de Computadoresnfonseca/arquivos/cap1-2017.pdfRedes de Acesso sem Fio (wireless) rede de acesso compartilhado sem fio conecta o sistema final ao roteador via estação base (ponto