Particle Counter KS-41 for
photoresist measurement
1. Problems of counting particles in photoresist
2. KS-41 Specifications
3. Adjustment and calibration method
4. Actual measurement example
Principle of the Light scattering particle counter
Interaction between Light and Particle
Reflection
Diffraction
Incident Light
(wave length=λ,
Intensity=I0 )
Absorption
Refraction
φ
Refractive index
of media=m0
Particle
(diameter=D,
refractive index=m1)
1-1
Scattering
(Intensity=Iφ )
Reyleigh scattering pattern
Direction of electrolytic vibration
Irradiating light
Direction of magnetic
vibration
1-2
Light scattering intensity
pattern
The structure of sensor for
Airborne particle counter
Inlet
Scattering light
reflection mirror
Scattering light
collection lenses
Photodiode
Beam forming
lenses
Outlet
Light source
1-4
Pulse signal from PSL particle
Pulse height
Pulse height
Pulse number
(frequency)
Time
1-5
Cumulative
累積分布
distribution
Particle Count
(standardization)
粒 子 数 （規 格 化 ）
1
0.8
Frequency
頻度分布
distribution
0.6
Calibration
校正
電圧
voltage
0.4
0.2
13
14
15
16
パルス
電圧
Pulse
voltage
1-6
17
18
Problems of measuring particles in photoresist
・Scattering of irradiating light in resist becomes noise.
・Refractive index of the resist (approx. 1.4 to 1.6) affects the
precision of particle diameter determination.
・Sample flow rate changes according to its viscosity.
polymer molecule,
polymer, etc
1.6
1.5
1.33
Sample Flow cell
Irradiating light
Photo detector
Particle
Particle
Particle detector
Scattering by polymer in photoresist (Top view)
Photo Diode
Flow cell
Sample
Laser beam
Lens
Aperture
Collection light spot diameter depending on refractive index
(Top View)
Photo Diode
Laser beam
Flow cell
Lens
Sample
Aperture
Laser
Spot diameter in DI-water
Spot diameter in resist
Noise increase due to photoresist
measurement
Scattered light pulses of particles
0.15μm
0.1μm
0.1μm
0.15μm
Noise
Noise
Voltage
Voltage
Scattered light pulses of particles
Time
Time
Scattered light of photo-resist and
wall of flow-cell (DC voltage)
Signal output of photo-detector
Signal output of photo-detector
KS-41 Specifications
Outline
• KS-41 is a sensor for measuring particles in photoresist.
• By connecting the unit to the controller (KE-40 or KE-40A), power
supply, measurement control and data output are carried out.
• As the unit does not incorporate flow control circuit, the additional
flow rate controller should be prepared.
Specifications
Optional system:
Light source:
90°sideway light scattering method
Laser diode
(wave length 830nm, rated output 200 mW)
Light detector:
PIN type photodiodes
Materials of component parts exposed to sample fluid
Fused silica, PFA
KS-41 Specifications
Measurement size ranges:
0.15µm, 0.2µm, 0.3µm, 0. 5µm
Counting efficiency:
50±10%
(measuring PSL particles in the range of 0.3µm,
using count of 0.2µm and above for comparison with
reference unit)
Sample fluid rate:
10mL/min
Maximum particle concentration:
12,000 particles/mL
(coincidence loss 5% for 0.15 µm particles)
Ambient conditions for operation:
15 to 30ºC, 0 to 85% RH (no condensation)
Allowable sample fluid pressure
300 kPa or less (gauge pressure)
Particle detector system for photoresist measurement
Scattered light
( from fringe of the flow cell)
Photo Diode
(Side View)
Aperture
×1 Lenses
Flow Cell
Scattered light
(from center of flow cell)
KL-26 Optical System
Laser Beam
(Vertical to paper)
Scattered light
( from fringe of the flow cell)
10ch Photo Diode
L Shape Flow Cell
×8 Lenses
KS-41 Optical System
Scattered light
(from center of flow cell)
L Shape Flow Cell
10ch Photo Diode
Photoresist measurement using sensor
calibrated with PSL particles and DI-water
Scattered light
( from fringe of the flow cell)
L Shape Flow Cell
10ch Photo Diode
×8 Lenses
Laser Beam
(Vertical to paper)
Proto-KS-41 Optical System
Scattered light
(from center of flow cell).
Scattered light
( from fringe of the flow cell)
10ch Photo Diode
L Shape Flow Cell
×8 Lenses
KS-41 Optical System
Scattered light
(from center of flow cell)
Standard PSL particles
in DI-water
Adjustment：
Calibration：
Standard PSL particles
in photoresist
Using a solution of glycerin (refractive
index of 1.4) and PSL particles.
With PSL particles (refractive index 1.6)
in pure water
KS-41
Sensor construction drawing
Collection lenses
Photodiode
Laser diode
Scattering light
collection lens
Beam forming lenses
Noise increase when measuring photoresist
Noise
64.5mv
KL-24 DI-water
Noise
113.5mv
KS-41 DI-water
Noise
538.6mv
Noise increase
rate
8.4 times
KL-24 Photoresist
Noise increase
Noise
rate
197mv
1.7 times
KS-41 Photoresist
Example of particle counts in photoresist ( I )
Noise(mV) 0.15<
I-line positive
582
1052
Excimer A
243
740
235
620
Excimer B
339
236
Excimer C
415
256
Excimer D
494
584
Excimer E
0.2<
97
368
295
91
116
289
0.22<
74
278
195
65
79
213
0.25<
41
173
83
33
45
118
0.3<
28
107
54
21
35
77
(Number /10mL)
Example of particle counts in photoresist ( II )
KL-20A
C. E.
0.15≦
0.20≦
0.3≦
0.5≦
1.0≦
KS-41
875
512
150
72
22
1128
483
112
12
45%
31%
64%
Resist A
0.15≦
0.20≦
0.3≦
0.5≦
1.0≦
KS-41
1209
67
10
4
1
KL-20A
C.E.
116
34
8
1
58%
29%
50%
Solvent
Resist B
0.15≦
0.20≦
0.3≦
0.5≦
1.0≦
KS-41
574
76
22
9
4
KL-20A
C.E.
142
56
16
3
54%
39%
56%
Resist C
0.15≦
0.20≦
0.3≦
0.5≦
1.0≦
KS-41
845
322
102
42
12
KL-20A
C.E.
814
243
50
6
40%
42%
84%
(Number /10mL)
Particle measurement in DI water
KS-41
KL-20A
80
43
22
15
97
55
20
Unit: particle/10mL
Counting
efficiency
44.3%
40.0%
75.0%
PSL particle measurement in Ethyllactate (particle size: 0.321 µm)
First time
KS-41
5657
4337
619
278
KL-20A
9575
2140
519
Second time
Counting
efficiency
45.3%
28.9%
53.6%
KS-41
5832
4392
629
296
KL-20A
9682
2140
546
Counting
efficiency
45.4%
29.4%
54.2%
Reference: KS-41 (Counting efficiency 58%, measuring in the range of
0.2 µm, using count of 0.309 µm for comparison with reference unit)
Viscous resistance of Particle counters
Flow Rate(ml/min)
1000
KS-28(1×1mm)
KL-22(0.5mmφ)
KL-26(0.3×0.7mm)
KL-20A(0.5×0.5mm)
100
10
1
10
100
Viscosity(cp)
1000
•When sample input pressure is 3 kg/cm2, flow rate limitations which depend on
viscosity of sample are measured.
•Absolute values depend on measurement error of sample viscosity and
surface exposed to sample fluid.
•The difference of the flow path shape varies the maximum flow rate widely.
Measurement of babble and solid particles
1.0E+06
KL-26
Relative Intensity
1.0E+04
1.0E+02
Bubble
PSL
1.0E+00
Media:H2O
1.0E-02
0.1
1
10
Diameter(μm）
Light scattering intensity is almost the same with PSL particles
and bubbles in water.
Particle measurement example in APM cleaning tank
80
75
100
70
65
10
60
0.2μm
0.5μm
temp
Temperature (℃)
Particle Numbers(N/10mL)
1000
55
1
50
0
10
20
30
TIME
40
50
•Particle counts which vary depending on the APM temperature are
regarded as bubble counts.
•Particle counts are not affected by the temperature 60℃ and below.