Submillimeter spectroscopic diagnostics in a semiconductor processing plasma

surprisesameSemiconductor

Nov 1, 2013 (3 years and 10 months ago)

225 views

Submillimeter spectroscopic
diagnostics in a semiconductor
processing plasma

Yaser H. Helal
, Christopher F. Neese, Jennifer A. Holt,
Frank C. De Lucia

Department of Physics

The Ohio State University

Paul R. Ewing, Phillip J. Stout, Michael D. Armacost

Applied Materials

Sunnyvale,
CA

June
19,
2013

Outline


Semiconductor processing


Spectroscopy


The plasma


Spectroscopic measurements

Semiconductor Chip

http://www.mikeseeman.com/index.php?id=engineering/research

Semiconductor Processing

http://www.atp.nist.gov/eao/gcr03
-
844/append
-
a.htm


Cleaning


Deposition


Lithography


Etching

Spectroscopy


The plasma is transparent to and unaltered
by mm/smm radiation, background and
clutter free



10
-
100 mtorr pressure is ideal for high
sensitivity and specificity



Species of interest must have a dipole
moment



Long wavelength is diffraction limited,
restraining spatial resolution



Combinations of argon, oxygen,
and octofluorocyclobutane (C
4
F
8
)
gases are flowed through a
vacuum chamber.



Plasma is initiated through an
induction coil by an rf generator
typically with 100 W power.



The plasmas generated contain many ions, radicals,
and molecules, most notably: CF
2
, CO, COF
2
, and
CF*.


The Plasma

What are the variables?


Flow rates for Ar, O
2
, and C
4
F
8
.



Power delivered to plasma



Pressure

What can be measured?


Abundances of plasma products which have
dipole moments



Temperature

Oxygen Flow

18.5 mtorr

22.3 mtorr

24 mtorr

29 mtorr

42 mtorr

O
2
: variable

C
4
F
8
: 20 sccm

Ar: 12 sccm

100
W



185.9885


194.114132




230.538



206.8505

(GHz)

Relative Intensity

(arbitrary zero)

(frequency snippets)

Ar : 30 sccm

C
4
F
8
: variable


O
2
: 0 sccm

100 W



CF
2

Spectra vs. C
4
F
8

Flow

307.7252275 GHz

Scaled Fractional Absorbance

Optical Emission Spectroscopy

Ar : 10 sccm

C
4
F
8
: 10 sccm


O
2
: 10 sccm

20.1 mtorr

100 W


Industry standard instrument


Can see atoms


Cannot measure densities

Ar : 10 sccm

C
4
F
8
: 10 sccm


O
2
: 10 sccm

20.1 mtorr

100 W

CO

COF
2

CF
2

Calculated Densities:

CO: 1.65 x 10
13

cm
-
3

CF
2
: 1.23 x 10
13

cm
-
3

COF
2
: 1.73 x 10
13

cm
-
3

Densities

Scaled Fractional Absorbance



345.7959899



307.7252275


311.7487602

(GHz)

(frequency snippets)







CF
2

D
ensity vs. C
4
F
8

Flow

CO, CF
2
, COF
2

Densities vs.
O
2

Flow

C
4
F
8
: 13 sccm

O
2
: 13 sccm

Ar: 13 sccm

150 W (18 W reflected)

13.1 mtorr

Reference Line

COF
2

as a thermometer for
rotational temperature

(frequency snippets)

Scaled Fractional Absorbance

Boltzmann Plot

Slope


1
𝑇

𝑇
=
336
.
9

K

Temperature vs. Power

Summary


SMM absorption spectroscopy can be used as an
in situ

probe of the conditions of semiconductor
processing plasmas



Density measurements can be made to further
study the behavior of plasma production



Rotational temperature measurement
demonstrated



Advantages of SMM spectroscopy over industry
standard optical emission spectrometer have
been demonstrated