Victor Bellido-González,

Sarah Powell,

Benoit Daniel,

John Counsell,

Dermot Monaghan

Gencoa - Dermot Monaghan

Using a standard Penning Gauge as a powerful means of

monitoring and feedback control

Structure of the presentation

• Plasma Spectroscopy• In-situ & Ex-situ Monitoring

• Feedback Control

• Penning Gauge and PEM

• Examples of spectra and uses• Examples of plasma instabilities / drifts

• Feedback modes from Penning Gauge

• Conclusions

Plasma or Optical Emission Monitoring (PEM)

Optic fibre

monitoring

Optical Emission Spectroscopy - The Plasma Spectrum

Magnetron Sputtering Ti/Ar

0

500

1000

1500

350 450 550 650 750 850

Wavelength, nm

Pla

sma

em

issi

on

, a

.u.

Process Control by Optical Emission Spectroscopy

450 550 650

• Select a high intensity peak

• Can be done by filter, monochromator or CCD array

• Use the change in peak intensity as the feedback control for the reactive gas

• Select a high intensity peak

• Can be done by filter, monochromator or CCD array

• Use the change in peak intensity as the feedback control for the reactive gas

• PEM provides valuable process information for feedback control or condition monitoring

• PEM provides valuable process information for feedback control or condition monitoring

Reactive gas input alters intensity due to target poisoning

500 550

PEM picks up the changes in the plasma environment

PACVD - DLC deposition

0

1000

2000

3000

4000

325 375 425

Wavelength, nm

Pla

sma

Em

issi

on

, a

.u.

IPA-01

IPA-03

IPA-04

IPA-06

DIRECT mode:

More REACTIVE GAS ≡ More signale.g. DLC- PACVD process

Control of the reactive gas input in a INVERSE mode

Magnetron Sputtering - TiOx deposition

0

200

400

600

800

1000

1200

400 450 500 550 600

Wavelength, nm

Pla

sma

Em

issi

on

, a

.u.

O2= 0

O2= 14

O2= 18

O2= 22

INVERSE mode:

More REACTIVE GAS ≡ Less signale.g. Ti sputtering (Ar + O2)

In-situ plasma monitoring - conventional

Examples of Reactive Sputtering

Reactive gas input

Exhaust

Substrate

Target

Control

Part. Press.

Transp.,σ,nVoltage, Freq.Plasma emmission

Ideal Controller Handles ALL I/O’s

Inputs

• PEM

•Metal line / multiple

lines

• Gas line

• Argon line

• Plasma spectrum

• Target voltage

• Gas partial pressure

Inputs

• PEM

•Metal line / multiple

lines

• Gas line

• Argon line

• Plasma spectrum

• Target voltage

• Gas partial pressure

Outputs (Actuator)

• Reactive Gas Flow

• Target Voltage

• Target Power Output

• Gas partial pressure (Ar /

throttle valve)

Outputs (Actuator)

• Reactive Gas Flow

• Target Voltage

• Target Power Output

• Gas partial pressure (Ar /

throttle valve)

Controller

• Why is Multi-function important?

• Some processes are hard to control and drifts / fluctuations can

occur

• Why is Multi-function important?

• Some processes are hard to control and drifts / fluctuations can

occur

Stepped control by PEM at 520nm

St.St. Control at different % of PEM

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700

Time, s

Sig

na

ls, (%

, a

.u.)

%PEM-Control setpoint

%O2 MFC

%Target Voltage

50%

90%

70%

50%

30%

20% 10%5%

50%

• The controller can control at any value of PEM The controller can control at any value of PEM The controller can control at any value of PEM The controller can control at any value of PEM setpointsetpointsetpointsetpoint (520nm(520nm(520nm(520nm----

Cr peak). Different Cr peak). Different Cr peak). Different Cr peak). Different setpointssetpointssetpointssetpoints correspond to different target status.correspond to different target status.correspond to different target status.correspond to different target status.

Ex-situ monitoring – inside a Penning Gauge

• A plasma is generated inside a Penning type pressure gauge.

• The ionisation in the gas creates a current between the anode and cathode which represents the pressure.

• The information from the plasma spectrum can be extracted.

• A plasma is generated inside a Penning type pressure gauge.

• The ionisation in the gas creates a current between the anode and cathode which represents the pressure.

• The information from the plasma spectrum can be extracted.

Pro / Cons of In/Ex situ PEM

In-Situ Pro’s

• High intensity plasma signal

• Represents the process

environment – displays all

species

• Faster response from process

• Allows local zone control

• Measures all species

In-Situ Con’s

• Subject to drifts and

disturbances as process

environment changes

• Requires a process plasma

In-Situ Pro’s

• High intensity plasma signal

• Represents the process

environment – displays all

species

• Faster response from process

• Allows local zone control

• Measures all species

In-Situ Con’s

• Subject to drifts and

disturbances as process

environment changes

• Requires a process plasma

Ex-Situ Pro’s

• Less subject to drifts and

substrate disturbances

• Process can be off – remote

plasma generation

• Measures the excess gas

• Optics don’t coat or heat-up

and are outside the vacuum

Ex-Situ Con’s

• Plasma intensity lower

• Reaction time slower

• Generally no local zone control

• Only for gases

Ex-Situ Pro’s

• Less subject to drifts and

substrate disturbances

• Process can be off – remote

plasma generation

• Measures the excess gas

• Optics don’t coat or heat-up

and are outside the vacuum

Ex-Situ Con’s

• Plasma intensity lower

• Reaction time slower

• Generally no local zone control

• Only for gases

What other things can PEM Achieve?

• Diagnose the system condition

• Predict a suitable process start condition

• Eliminate long term drift – condition monitoring • Rate measurement

• Intelligent plasma pre-treatment

• Improve uniformity of deposition or pre-treatment

– zone control• Leak detection

• Preventative maintenance

-200

0

200

400

600

800

1000

1200

200 300 400 500 600 700 800

Wavelength (nm)

Inte

ns

ity

Measured Intensity - plasma and gauge on

Measured Intensity - dark - process plasma off - gauge on -Hydrogen peak from moisture

Full optical spectrum from penning gauge

50% O2 8.5E-04 Torr

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800 900 1000

Wavelength (nm)

Ine

ns

ity

O2 peak

Full optical spectrum from penning gauge with O2 in chamber

30% N2 2.4E-03 Torr

0

200

400

600

800

1000

1200

1400

1600

1800

0 100 200 300 400 500 600 700 800 900 1000

Wavelength (nm)

Inte

ns

ity

N2 peak

Full optical spectrum from penning gauge with N2 in chamber

Examples of water monitoring

TiOx Penning gauge sensor control using Gencoa Speedflo

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 50 100 150 200 250 300

Time (s)

Ga

s f

ee

db

ac

k (

sc

cm

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Ta

rge

t / S

en

so

r (v

)

Gas Feedback (SCCM)

Target voltage (V)

Sensor (V)

Set point (V)

Variable setpoint feedback control from O2 signal in Gauge

Penning gauge sensor control for TiN

-10

0

10

20

30

40

50

60

70

80

90

0 50 100 150 200 250 300 350 400 450

Time (s)

Ga

s fe

ed

ba

ck

(s

cc

m)

0

0.5

1

1.5

2

2.5

3

3.5

Ta

rge

t / S

en

so

r (V

)

Gas Feedback (SCCM)

Sensor (V)

Set point (V)

Target Voltage (V)

Variable setpoint feedback control from N2 signal in Gauge

TiN penning sensor with Speedflo feedback control - substrate rotation on/off

0

2

4

6

8

10

12

14

0 50 100 150 200 250

Time, s

MF

C, T

i (5

00

nm

) a

nd

Ta

rge

t V

sig

na

ls

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

Se

tpo

int

an

d C

on

tro

l s

ign

als

Ch2 Ti 500 nm fromprocess chamber -monitor only notcontrol

Ch4 Target V signal -monitoring only oftarget voltage assubstrate movementvaries

MFC1 - change inreactive gas inputfrom Speedflo tomaintain control

Ch1 Penning N2670nm as feedbackcontrol signal

setpoint Ch1 - theintensity / gas signalto control around

Rotation on

Rotation off

Intensity in Gauge - Setpoint

& Control not disturbed

samples moved

closer to plasma

samples moved

away from plasma

In chamber plasma disturbance as a result of substrate movement & position

MFC1

Ch4

Ch2

Ch1

Setpoint

Other considerations in long term stability -Plasma drifts

Anode at 149mm width - earthed

Anode at 147mm width - floating

Anode at 147mm width - earthed

• The plasma changes shown

simulate drifting conditions that

can happen as the anode or

chamber is covered in oxide:

Disappearing anode + web

damage + outgassing!!!

Monitoring - increased productivity

• Things can change with time on a short and / or long

term basis and in different ways and for different reasons depending upon the material system and operating parameters. Monitoring can help.

• A summary of possible advantages:

• Increase rates with feedback control

• Detect faults by monitoring – water, leaks, outgassing

• Set plasma pre-treatment parameters to the environment

• Predict drift into unsuitable process regimes

• Optimise uniformity of deposition of plasma treatment

• Predicting maintenance intervals

• Things can change with time on a short and / or long

term basis and in different ways and for different reasons depending upon the material system and operating parameters. Monitoring can help.

• A summary of possible advantages:

• Increase rates with feedback control

• Detect faults by monitoring – water, leaks, outgassing

• Set plasma pre-treatment parameters to the environment

• Predict drift into unsuitable process regimes

• Optimise uniformity of deposition of plasma treatment

• Predicting maintenance intervals

Where to monitor – In/Ex-Situ?

• Both have their advantages and disadvantages and the optimum solution is probably to combine both.

• In-Situ is better for zonal control (large area) and where drifts and

local plasma disturbances are less likely to occur.

• Ex-Situ in principle is better for reactive gas control as it measures

the excess. Also can sense the chamber environment before any

process has begun.

• There are now a very powerful array of sensors that can be fed into

a controller and combined to optimise short and long-term

performance.

• This intelligent monitoring can then be use to control any number of

outputs simultaneously – MFC (gas or argon), source power (thermal

or sputtering), pumping.

• Both have their advantages and disadvantages and the optimum solution is probably to combine both.

• In-Situ is better for zonal control (large area) and where drifts and

local plasma disturbances are less likely to occur.

• Ex-Situ in principle is better for reactive gas control as it measures

the excess. Also can sense the chamber environment before any

process has begun.

• There are now a very powerful array of sensors that can be fed into

a controller and combined to optimise short and long-term

performance.

• This intelligent monitoring can then be use to control any number of

outputs simultaneously – MFC (gas or argon), source power (thermal

or sputtering), pumping.

The controller needs to very flexible

• To be able to provide the required short term and

long term control the use of multiple inputs and outputs are highly desirable.

• The software then needs to be able to easily combine the

configurations of the different inputs and outputs and allow the most

appropriate combination to be used.

• In addition the integration of the input signal to ‘smooth’ out

some short-term process shifts should be possible

• To be able to provide the required short term and

long term control the use of multiple inputs and outputs are highly desirable.

• The software then needs to be able to easily combine the

configurations of the different inputs and outputs and allow the most

appropriate combination to be used.

• In addition the integration of the input signal to ‘smooth’ out

some short-term process shifts should be possible

Conclusions

• Process monitoring and feedback control can improve

process yields and reduce product variations.

• Plasma emission monitoring provides an excellent tool

to diagnose the process environment.

• By choosing or combining In-situ with Ex-situ

monitoring a more robust solution is possible.

• Process monitoring and feedback control can improve

process yields and reduce product variations.

• Plasma emission monitoring provides an excellent tool

to diagnose the process environment.

• By choosing or combining In-situ with Ex-situ

monitoring a more robust solution is possible.