Case Studies of All-Surface Inspection in a - Sematech

Case Studies of All-Surface 

Inspection in a 3DI-TSV R&D 

Environment 

Rolf Shervey 

Sr. Applications Engineer 

Rudolph Technologies, Inc.

Equipment in Albany 

Explorer Inspection Cluster 

•AXi 935 for top surface 

•E30 for wafer edge-bevel 

•B30 for wafer backside 

•Installed in 1st half of 2008

All Surface Inspection – Case Studies 

Defect inspection (pre- and post-bond) 

• Defects at bond interface can break wafers 

• Edge bevel chips/slip can create cleave lines during 

bonding 

AXi 935 All-Surface System is used to inspect top, bottom, 

and edge bevel: 

• Identify defects that will break wafers & impact yield 

• pre-bonder 

• post-bonder 

• before wafer thinning (grinding) 

3

FRONT-SIDE INSPECTION

Misaligned via pattern in BF inspection 

Images 

courtesy of 

SEMATECH 

AXi inspection of metal via- 

patterned wafers found 

misalignment of via 

pattern. 

5


Missing vias 

• Following M1 oxide deposition, 

missing vias in the alignment 

marks used for lithography were 

observed 

• Subsequent inspection revealed 

multiple missing vias 

• Used the Rudolph Axi935 all- 

surface inspection tool to gather 

statistics. 

• Missing vias are ~10X more 

probable on square vias than on 

round or octagonal vias 

• Suggests that stress plays a role 

• One single missing VSPM via 

(1/395,472) was observed on 2 

wafers subjected to 150°C anneal 

Slide courtesy Larry Smith - SEMATECH 

0% 1% 2% 3% 4% 5% 6% 

only after CMP 0% 1% 2% 3% 4% 5% 6% 

6 

½ of a VSPM alignment mark 

Image and inspection data from Rudolph AXi 

Missing 46EBL052SJA3; Via Defect 

46EBL052SJA3; 

defect% Density 

defect% 

4x4 (8x8) TSV arrays, 

4,5,6 µm diameter; square, octagonal, and round 

8x8_5um_P25um_round 












4x4_4um_P8um_oct 






4x4_4um_P8um_square 





4x4_6um_P12um_square


Slide courtesy Larry Smith - SEMATECH 

Missing via – failure analysis 

• Top ~3 microns of copper missing in the TSV 

• Stress related – Copper anneal modified 

• AXi 935 useful to detect, quantify, and inspect TSV defects 

Missing via 

7 

Delamination?

EDGE-BEVEL INSPECTION

E30 System Overview 

Edge Top 

Camera 

• Darkfield and Brightfield inspection and metrology 

• Multiple EBR line metrology in zones 1-4 

• Brightfield color image defect capture driven by darkfield sensitivity 

• Advanced defect binning based on defect attributes 

• Color, intensity, size, area, location, contrast strength, illumination type 

• Bin specific defects can be further classified by an Edge ADC engine 

• High throughput capable up to 100WPH 

9 

Edge Normal 

Camera

Wafer Edge Zones and Defects of Interest 

6mm 

~ 

~ 

Zone 1 

Pattern side 

Top Edge 

~ 

Wafer Edge Exclusion (WEE) 

~ 

Zone 1 Typical Inspection Criteria 

Zones Multi-film 2, 3 & 4 EBR Typical / EEW Inspection Zone Metrology5 

Criteria 

EBR centricity with 0.1 mm resolution 

Backside Rinse EBR Bottom metrology of Wafer 

Supported in zones 2 - 4 

Coating Problems, Chips, Cracks, Mechanical 

Zone Blisters, Residues, Coating Problems 

Damage 5 Typical Inspection Criteria 

Particles, Visual defects > 5µm 

Resolution Mechanical > 4umDamage, 

Stains 

Delamination, Peeling, Particles 

Blisters, > 3µm 

Delamination, Peeling, Particles 

> 2µm 

> 1µm 

Distance from Apex with 0.1 mm resolution 

Up to 3600 measurement points possible 

Bevel Transition 

10 

Wafer Bevel 

~ 2-4mm 

(profile shape 

dependent) 

Zone 2 

Top Bevel 

Zone 3 

Apex 

Zone 4 

Bottom Bevel


Bonded wafer pair re-entry to CMOS fab 

• SEMI M1.15 defines wafer diameter, thickness, notch, bevel edge 

(100s of parameters…) 

• Bonded, thinned, and edge-trimmed wafers challenge SEMI M1.15 

• Other SEMI standards affected 

• SEMI E47.1 (FOUP) 

• SEMI M31 (FOSB) 

• SEMI E15.1 – Load ports 

• SEMI M1 – Notch 

• SEMI T7 – Wafer identification 

• Potential issues: 

• Pre-aligner 

• Wafer indexer/mapper 

• Double stack, cross-slot errors 

• Edge bevel scattering 

• Carrier damage to BWP 

Slide courtesy Andy Rudack - SEMATECH 

11

Bonded Wafer Pair Metrology & Defect 

Inspection 

SEMATECH Phase I‐ 

Bonded Wafer Pair 

Mechanical Testing: 

Edge inspection on E30 

successfully completed 

May 29, 2009. 

12

Thinned Top Wafer (via wafer) 

Edge-Top (ET) inspection 

of edge trimmed via 

wafer. 

E30 proven to detect 

critical defects in sub- 

contracted edge trim 

process. 

Scallop marks 

(chips) detected in 

the trim line 

Bottom wafer (handle 

wafer) 

has grind tracks from 

saw 

13 

(top 

wafer)

Application software for edge trim monitoring – adapted 

from EBR metrology 

Edge Top 

Camera 

wafer 

open space 

Acquire individual brightfield 

Edge Top images around full 

circumference 

Stitch and compress the Edge 

Top images into a single 

composite image 

Find the EBR lines 

• Rudolph’s existing EBR metrology software for the edge can 

be adapted to monitor edge trim process. 

14

TSV METROLOGY 

DEVELOPMENT 

PARALLEL EXPERIMENTS AT RUDOLPH’S 

DEVELOPMENT FACILITIES

Optical inspection – Defects of Interest 

Cover Glass Bottom Defect 

Cover Glass 

Silicon Via Depth Silicon Thickness 

Via Bottom Defect 

Via Wall Defect 

Cover Glass Top Defect 

Via Bottom Diameter 

Via Top Diameter 

16 

Cover Glass Thickness

Via Wall and Bottom Defect Inspection 

Defect Images – 10X Via Bottom 

17

Via Top and Bottom Diameter Measurement 

Results – Via Too Small and Via Too Large 

• Vias reported as Too Small due to defects in the 

vias 

• Vias reported as Too Large are actually larger than 

the limits 

18

NEAR-INFRARED (NIR) 

INSPECTION EXPERIMENTS* 

ON RUDOLPH AXI PLATFORM 

*NOTE: EXPERIMENTS ONLY, NO COMMERCIAL PLANS AT THIS 

TIME. 

Experiments conducted in conjunction with 

SEMATECH 3DIC Group

NIR Prototype Optics 

• Bonded wafer pair interface 

• Must image through top wafer, up to 

775 micron thick (opaque in visible) 

• Silicon is transparent in NIR/SWIR 

• Prototype NIR optics were 

installed on SEMATECH AXi 935 

system 

20 

NIR SWIR 

1000 1700

Configurations – Design of Experiments 

1. Nominal: Existing CMOS camera / strobe lamp 

A. Current camera 

B. Available, current design, high-intensity xenon-tungsten stroboscopic 

illumination. Broadband light: 400nm – 1300nm+ 

2. Existing CMOS camera / halogen source 

A. Current camera (same as 1, A.) 

B. Constant-on illumination source: requires start/stop vs. continuous 

motion inspection. Throughput hit. 

3. IR camera / halogen 

A. NIR-specific camera (InGaAs, InSb or similar IR FPA). High cost. 

B. (Same as 2, B.) 

4. IR camera / strobe lamp 

A. (same as 3, A.) 

B. This would have the advantage of strobe-based, continuous motion 

inspection. 

21

Slide courtesy of SEMATECH 

22 

This is what 

we might 

expect to see 

in NIR with a 

misalignment.

#1: CMOS Camera / Xe Strobe Light Source 

5X Raw image through 775um Si 

Advantages 

1. Current camera & available 

stroboscopic light source. Could be 

used for high-speed inspection. 

2. Hardware costs are lower. 

Disadvantages 

1. Dark image / low photon quantity. 

2. Extra image processing used to 

boost signal has a possible 

throughput impact & technical 

challenges. 

23

#2: CMOS Camera / Halogen (DC) Light Source 


Advantages 

1. Current camera. 

2. Hardware costs are still lower than IR 

camera. 

3. Image processing may not be 

required. 

Disadvantages 

1. Start/stop inspection only, because 

light source is “constant on”. 

2. Some integration costs to develop & 

qualify new light source. 

24

#3: IR Camera / Halogen Source 


Advantages 

1. Best quantity of light. 

2. Good overall image quality. 


required. 

Disadvantages 

1. Pixel scale is 3.6x CMOS camera. 

(0.5um @ 20X on CMOS = 1.8um on 

IR camera) 

2. High cost camera. 

3. Some integration costs to develop & 

qualify new light source. 

25

#4: IR Camera / 4400 strobe 

Not able to acquire 

images in this 

configuration because 

of camera timing 

configuration. 

Needs further 

development before 

experiments can be 

performed. 

Theoretical Advantages 

1. Good quantity of light – middle 

ground. 

2. Retain high-speed, stroboscopic & 

continuous motion capabilities. 


required. 

Theoretical Disadvantages 

1. Pixel scale is 3.6x CMOS camera. 

(0.5um @ 20X on CMOS = 1.8um on 

IR camera) 

2. High cost camera. 

26

Results 

What the camera “sees” processed image 

27 

Wafer 

bonding 

defects of 

interest 

(DOI) shown 

should be 

captured by 

standard 

inspection 

algorithm.

Conclusions & Future Work on NIR 

• This kind of metrology is currently being done by 

destructive cross-section SEMs, or by manual IR 

microscope review. 

• Would it be interesting to have in-line and production 

worthy automated metrology capability to measure for 

overlay alignment and process-specific adder defects so 

that improvements can be driven into the bonding and 

related processes, and potential yield killers caught 

earlier in this very deep TSV manufacturing process? 

• What is the required Cost-of-Ownership for this tool? 

28

Summary 

1. The AXi 935 All-Surface Inspection platform has 

demonstrated capability for bonded wafer pair metrology, 

including bonded, thinned, and edge trimmed wafers 

2. The Rudolph AXi 935 + E30/B30 All-Surface Inspection 

System has proven to be a useful tool for supporting 3D 

interconnect and TSV research. 

3. Rudolph gained important insights into 3DIC/TSV 

manufacturing market needs and benefited from the 

unique environment & working relationship with 

SEMATECH during the conduct of these experiments. 

29

Acknowledgements 

SEMATECH 3D Team 

Tawfeeq Alzaben 

Sitaram Arkalgud 

Raymond Caramto 

Jose Colon 

John Hudnall 

Gary Knodler 

Jerry Mase 

Steve Olson 

Jamal Qureshi 

Andrew C. Rudack 

Pratibha Singh 

Larry Smith 

Susan Smith 

Travis Smith 

Chris Taylor 

Weng-Hong Teh 

Bryan Thomas 

30

Rudolph’s Total Solution for 3DIC/TSV Manufacturing 

Process 

Inspection / 

Metrology 

Specific criteria 

Solution 

Via Etch or Drill 

Via depth, Via 

CD, sidewall 

defect 

NSX 320 

With laser 

sensor (>20u) 

High‐res 3D 

(

Rudolph Technologies Confidential 

Thank You! 

32 

32

Case Studies of All-Surface Inspection in a - Sematech

Create successful ePaper yourself

Delete template?

Save as template?