1. Surfscan SP1TBI Operations and Overview Course KLA-Tencor
660 Alder Drive
Milpitas, CA 95035
The Surfscan SP1TBI is the newest in a series of Surfscan tools. It’s optics and capabilities are the next generation for the Surfscan 6000.
Surfscan inspection systems are used for in-line detection of Yield Limiting Defects. Laser scattering technology and the registration of bright field information light provides sub-micron defect detection capability.
The Surfscan family of instruments can be used to inspect the vast majority of unpatterned wafer materials (depending on the Surfscan model), for example, bare silicon, oxides, nitrides, epitaxial silicon, poly silicon, metals, and CMP.
The Surfscan systems offer variable throughput measurement capability.
Typical applications include qualification of wafer materials and deposition system performance, and contamination monitoring of wafers during yield limiting process steps such as metal and cmp.
The types of surface defects detected include pits, particles, scratches, area defects, mounds, and dimples.

2. Surfscan 6XY0
The Surfscan SP1TBI is the newest in a series of Surfscan tools. It’s optics and capabilities are the next generation for the Surfscan 6000 family.

3. Unpatterned Surfscan Product Mix
6220
488nm, 30mW Ar laser
0.09µm sensitivity*
smooth surfaces
surface quality
6420
488nm, 30mW Ar laser
0.10µm sensitivity
rough surfaces
varying film thickness
6100
633n m, 5mW HeNe laser
0.15µm sensitivity
smooth surfaces
surface quality
*All sensitivities refer to latex spheres on well-polished bare silicon

4. How does the Surfscan work?
Illuminates wafer with scanning laser
Uses normal incidence for 62X0 (SP1)
Grazing-angle incidence for 64X0 (SP1TBI)
Collects scattered light from particles
Sizes and counts particles
Accepts or rejects and then sorts wafers
Displays information and writes information to file

5. Dark field and bright field basic definitions
Dark field detection: refers to the collection and registration of scattered radiation.
Bright field detection: refers to operations performed on the reflected light.
The SP1 collects data from the dark field and bright field channels. The Surfscan 6200 collects data from only the dark field channel.

6. Inspection System Beam Dump Light Source Scattered Light Specular Beam
Regardless of whether the system is a normal incidence system or an oblique incidence system, the goal is to collect light scattered from defects and to ignore the specular beam. The specular beam is the part of the incident beam that is reflected in a mirror like fashion (angle of incidence = angle of reflection). The specular beam contains no useful information for this type of defect detection technology. If it were collected it would destroy the signal to noise ratio required to detect particles.
Incident Beam
Substrate

7. Raster Scanning the Wafer
Wafer Motion
85mm
Raster Motion

8. LPDs & Haze Particles are High Amplitude & High Frequency
Haze is Low Amplitude & Low Frequency

9. Dark Field (Normal)

10. Fundamentals of Light Scattering
Light from laser illuminates particles on wafer and surrounding surface
Particles and surface scatter light simultaneously
Maximize detection of particle scatter and minimize detection of surface scatter

11. SP1TBI Optics & measurement principle
Static Optics :
Moving Sample
The Surfscan SP1 includes Stationary Beam Technology (SBTTM) which provides a short beam path (of about 3 feet) with highly optimized illumination optics reducing the optical background to a few ppb and preserves the Gaussian beam profile. The Surfscan 6200 includes an oscillating scanning mirror and a much longer beam path (about 17 feet) which adds to the background noise of the system.

12. Scanning principles The wafer is transferred underneath the beam
in a spiral motion
The above allows for the following:
-Edge exclusions < 1mm (from bevel) without sensitivity degradation
-No edge artifacts since the PMT is not exposed to excessive light from the edges
-Edge detection with below wafer sensor for wafer orientation and position
-High throughput due to maximized time the laser spot is on the surface

13. Dark Field vs. Bright Field
(Scattered Light vs. Reflected Light)
Incident Light
Scattered Light
(Dark Field)
Defect
Scattered Light
(Dark Field)
Detector A
(Dark Field)
Reflected Light
(Bright Field)
The instrument contains a laser that operates at 30 mW power with a wavelength of 488nm. This laser illuminates the wafer surface producing scattered and reflected light. The intensity of the scattered light depends on the particle defect size encountered while the intensity of the reflected light depends on the surface defects.
Detector B

14. Two Dark Field detection channels increase sensitivity and dynamic range
The SP1 has two dark field detection channels: dark field wide collects scattered light from 25o to 70o and dark field narrow collects scattered light from 5o to 20o. The two channels allow for maximize data collection (avoid saturating the PMT), giving exceptional surface quality measurement with resolution better than 0.1ppb.

15. SP1 Dark-field optics optimized for detection uniformity
fy µm-1
2.3
SP1
6220
1.0
-2.0
-1.0
1.0
2.0
fx µm-1
Some of the advantages of the Surfscan SP1 over the Surfscan 6220 can be realized by comparing the differences in the range of detection of the two tools.
-1.0
-2.3

16. Surface scattering (haze) limits ability to detect particles on unpatterned wafers.
Position in mm
Photo-
electrons
from PMT
photocathode
Particle signal
Threshold level
Noise
Background (100 photoelectrons)

17. Rotational collection symmetry is insensitive to defect orientation
Amplitude
Amplitude
Signal response WITH rotational symmetry
-Rotational collection symmetry ensures defect capture regardless of scattering direction, so that defect orientation and defect location are independent.
-Scratches and other extended defects are easily detected
time
time
Amplitude
Amplitude
Signal response WITHOUT rotational symmetry
time

18. Light Scattering Inspection Process
Detector
Point Defect
Collector
Surface Information
Dark Field / Bright Field
Scan
The SP1 translates and rotates the wafer under the illumination spot, thus ensuring that data is collected from all areas on the wafer surface. Because defects and irregularities on and in the wafer surface affect the scattering power of the surface, variations in the intensity of the scattered light can be correlated with surface features. The system processes the scattered-light data to produce data, called scan data, that identifies the size and location of surface features.
Defect Display
Surface Data Display

19. LPDs & Areas scatter light into different polar angles
narrow
collector
wide
collector
small PSL sphere
Scattering Intensity
large PSL sphere
Point defects LPDs: Surface defects that are significantly smaller than the laser spot size and can include pits or particles (ppm or um LSE).
Areas: Surface defects that scatter light at an intensity that exceeds the saturation threshold of the collection optics (um LSE).
Haze: Light scattered from defects that are distributed over areas larger than the laser spot size (ppm).
Si Surface 20 40 60 80
Scattering Polar Angle [degree]

20. Different defect types scatter light into different polar angles ...
… allowing distinction of defect types
(particle)
(crystal defect)

21. Distinction of Defects with multiple DF-Collectors

22. Dark Field (Oblique)

23. TBI Optics Layout Dark Field Wide PMT Narrow PMT Ellipsoidal Collector
Oblique
Incidence
Beam
Normal
Wafer
Lens
Beam Position
CCD
Deflection
Wedge
ND, polarizers
Apertures

24. Scattering Cross-Section
LSE diameter and geometric diameter are not the same.
All of these particles have LSE diameters of 100 nm on a Surfscan 6200. Si
3.88
72 nm Cu i
72 nm Al i
75 nm
Si3N4
2.04
90 nm
PSL
1.60*
100 nm
SiO2
1.47
105 nm
Index
LSE
*bulk refractive
index at 488 nm
All of these spheres have an LSE diameter of 100 nm on a Surfscan However, only the PSL sphere has a geometric diameter of 100 nm.
The biggest contributor to the change in diameter is the refractive index. For this picture, I have listed the bulk refractive index of the material. For dielectrics, you can see that the higher the index, the smaller the geometric diameter. Or in other words, the higher the index, the stronger a sphere of a particular size scatters.
The metals, Cu and Al, have a little different story. For these materials I have listed the complex refractive index, and you can see that the metals have a strong imaginary component. This absorptive contribution to light scattering dominates in the calculation of scattering cross-section.
You’ll notice that almost all of the materials scatter stronger than latex with the notable exception of oxide. This means that when we specify the Surfscan as having a minimum detectable particle size of 100 nm, it can really see a 72 nm particle of silicon.
LSE : Laboratory scale enclosure

25. PSL Full deposition Spot deposition
PSL Wafer Standards are used to calibrate the size response curves of Scanning Surface Inspection Systems (SSIS) manufactured by KLA-Tencor, Topcon, ADE and Hitachi.  PSL Wafer Standards are also used to evaluate how well the SSIS performs a uniform surface scan across the wafer.

27. 최근 관련 기사
KLA-Tencor사는 자사의 결함검출 툴인 Surfscan SP1 제품군에 결함의 검출, 분석과 공정 감시 기능을 추가했다.
Monitor eXpert(MX 4.0)라는 명칭의 소프트웨어 옵션 모음은 이 툴이 추가적인 비용을 들이지 않고도 단일 주사로 공정 감시 정보와 벤치마크 결함 검출 기능을 제공할 수 있게 한다.
웨이퍼와 IC 제조자는 Surfscan SP1에 MX 4.0을 사용하면 표면 거칠기, 낮은 k 유전체의 유공률 수준, 방식제와 박막 두께의 균일화, 화학 기계 연마(CMP) 패드의 상태조절과 연마 균일성, 구리의 전자화학식 증착(ECD)을 하는 동안 용액의 화학적 성분 변경을 비롯하여 동시에 다양한 경과 특성에 대한 결함을 검출하고 필수적인 통찰력을 확보할 수 있다.
MX 4.0의 웨이퍼 탁도 감시 기능은 정상 조작 창의 바깥으로 벗어나기 시작하는 공정에 대해 조기에 검출 경보를 제공한다. 이 소프트웨어의 업그레이드 판에는 검사를 하는 동안 비정상적인 탁도 패턴을 찾아내고 사용자가 공정 기술자를 위해 이것들을 이전에는 탐색 및 관측이 불가능하던 결함으로 판별할 수 있게 하는 새로운 탁도 분석 기능도 포함되어 있다.