MEMS solutions - Hilpert

SEMICONDUCTOR & OPTICAL

METROLOGY SOLUTION

Summary Related Products FOGALE Technologies and applications Conclusion

MEMS solutions


METROLOGY SOLUTION


SUMMARY

Technologies and application:

1) 3D surface profiling solutions

2) MEMS in motion analysis

3) High A/R Via and trench process control

4) Membrane inspection, thickness, TTV and shape

5) 3D and Wafer Level Packaging process control

6) Bonded wafers metrology

7) Overlay and registration

Conclusion

METROLOGY and INSPECTION FOR MEMS and 3D MEMS MANUFACTURING


METROLOGY SOLUTION


1) 3D Surface Profiling: Full Field White Light Interferometer

filter, for get red light with the

halogen lamp

CCD camera

filter

Illumination

Beam splitter

Piezo

Sample to measure

Light source

Objective

Interferometer

Select the magnification

Data information

Measurement done all over the field of view of the microscope: Z-scan only


METROLOGY SOLUTION



How does it work?


METROLOGY SOLUTION



Objective

Step height, 3D metrology and Roughness

Z-scan

A

B

h

For step height > 500 nm z-scanning

Accuracy: 1 to 10nm

For step height < 500 nm Phase shifting

Accuracy: 0.1nm

Example: Pilar height measurement


METROLOGY SOLUTION



Film Thickness measurement and buried surface 3D profiling

ng x d

film (ng)

Substrat

d

Sample

650 µm

~4 µm

Objective

A

Example: 3D Profile through 120µm Thick layer

Surface Buried layer


METROLOGY SOLUTION



Some Results

PZT Membrane Copper RDL

Top and bottom CD of a line

3D measurement of interconnect metal layer Micro accelerometer


METROLOGY SOLUTION


• Mirau

– Medium Magnification

– Central obscuration

– Limited numerical aperture

• Michelson

– Low magnification, large field of view

– Beamsplitter limits working distance

– No central obscuration

– Low numerical aperture

• Linnik

– Large numerical aperture, large magnification

– Beamsplitter does no limit working distance

– Expensive, matched objectives

Interferometer Objective : Advantages/Disadvantages



METROLOGY SOLUTION


1) 3D Surface Profiling: Confocal Chromatic technology

Spectrometer

Light source

Control unit

Probe

Object surface Measurement range

Optical fiber

FPGA Calculator

Single point method: no z-scan required due to multi confocal points

x,y scan only


METROLOGY SOLUTION



Low cost solution for high speed surface profiling:

Step height

Full scanning across the entire wafer diameter

Bump height and co-planarity

Capability to measure surface shape at the same time.

Accuracy down to 10nm depending on sensor measurement range

Speed: Up to 2KHz

Example:

Trench depth and profile across a wafer diameter and substrate flatness: 10000 data points obtained in 30 seconds


METROLOGY SOLUTION



Trench dimensional measurement with high Numerical aperture CC sensor

SEM


METROLOGY SOLUTION


1) 3D Surface Profiling: Comparison between Confocal Chromatic and WLI

Technology: White Light Interferometer Confocal Chromatic

+ No high accuracy x,y stage required even for nm roughness measurement Sub nm accuracy Through transparent or semi transparent layer 3D surface profiling Thin film thickness

High speed 1D profile scanning. No z scan required. Low cost solution. Easy to integrate in Multi sensor tool. High angular acceptance

- Stitching required for large area scanning. Low angular acceptance. Cost

Low throughput for area scaning

Main application Local 3D profile 3D profiling. MEMS in Motion metrology.

Large area 3D profiling. Trench (up to 5:1 A/R) profile scanning across an entire wafer diameter.


METROLOGY SOLUTION


2) MEMS in motion metrology

M(O)EMS

In Plane / Out of Plane dynamic measurement

Resonnance frequency Resonnance modes Quality factor Reliability

Mechanical Properties

Response time

Signal Analysis

Couplage des vibrations

Comportement global

Cushion Life time

Environmental factor (T°C, P, Vacuum) Reliability

Needs : fréquencies=100Hz to , Amplitude <1nm to µm level


METROLOGY SOLUTION



CCD

Camera

Sample

Objective

Reference

mirror

Beam

splitterStroboscopic

Light source

Beam splitter

Mirau

Interferometric

Objective

Tube

lens

Image

processing

Interferogram

analysis

In-plane

motion

Out-of-plane

motion

CCD

Camera

Sample

Objective

Reference

mirror

Beam

splitterStroboscopic

Light source

Beam splitter

Mirau

Interferometric

Objective

Tube

lens

Image

processing

Interferogram

analysis

In-plane

motion

Out-of-plane

motion

Fringes


METROLOGY SOLUTION



Stroboscopic illumination

-T: Pulse width

Intensity

- N : cycles per exposure

(Typ. N > 1000)

- t0 : Pulse delay

Temps

Temps

Pu

lse

L

igh

tin

g

T

t0

T td

f

Mode 31 of a membrane (FFT measurement, f=226.5 kHz)

t0 t0+60° t0+120° t0+180°


METROLOGY SOLUTION



Thermally actuated silicone membrane (courtesy Barcelone University)

Phase shifting stroboscopic interferometry

Test device with out of plane actuation

Test device with in plane electrostatic actuation

Electrostatic actuation study


METROLOGY SOLUTION



Environmental parameters study:

VACUUM BOX & MIRAU INTERFEROMETRIC OBJECTIVES

Stroboscopic interferometric microscopy combined with vacuum box

is the perfect tool for MEMS testing, mechanical measurements

(quality factor, rising/falling time), and MEMS behaviour testing

(reliability) under temperature.

> Device characterization under controlled environmental contitions:

> Vacuum

> Gaz partial pressure

> Temperature

User-customizable I/O ports

Easy sample handling (PLCC 68 pin or user configurable)

Membrane deflection: Pressure chamber.

> Fogale developped specific glass-compensated, long-working

distance, interferometric objectives for 3D mode shape

measurement across the vacuum box glass plate:

> MEMS BOX (Vacuum, WLP Hermiticity)

> Probe applications

> Measurement across glass / transparent film


METROLOGY SOLUTION


2) Environmental Chamber

Environmental parameters study:

VACUUM BOX & MIRAU INTERFEROMETRIC OBJECTIVES

Stroboscopic interferometric microscopy combined with vacuum box

is the perfect tool for MEMS testing, mechanical measurements

(quality factor, rising/falling time), and MEMS behaviour testing

(reliability) under temperature.

> Device characterization under controlled environmental contitions:

> Vacuum

> Gaz partial pressure

> Temperature

User-customizable I/O ports

Easy sample handling (PLCC 68 pin or user configurable)

Membrane deflection: Pressure chamber.

> Fogale developped specific glass-compensated, long-working

distance, interferometric objectives for 3D mode shape

measurement across the vacuum box glass plate:

> MEMS BOX

> Probe applications

> Measurement across glass / transparent film


METROLOGY SOLUTION


3) High A/R Via and Trench process control

Absolute height measurements with a single beam larger than pattern:

Single point IR interferometrer: Fiber based interferometer

Core of the system: low coherence interferometer based on optical fibers and using an infrared broadband source:

The light source: Super luminescent diode (SLD)

A spatial filter retains only the information of phase difference between the two groups of waves

The system combines microscopy and metrology for spot positioning and pattern rec.

Internal reference

mirror

Interferometer

R1

R2

Fiber


METROLOGY SOLUTION



200mm wafer: TSV

TSV diameter : 3 to 5 µm

TSV Depth: 25 to 35 µm

300mm wafer: TSV

TSV diameter : 2 to 5 µm

TSV Depth: 40 to 50 µm

Used platform: IMEC 65nm node CMOS

TSV: After first metallization

VIA # DEEPROBE SEM (average)

1 33.77 µm 34.35µm

2 34.13µm 34.35µm

3 34.54 µm 34.35µm

4 34.04 µm 34.35µm

5 33.93µm 34.35µm

Mean 34.082 µm 34.35µm

1.Accuracy: Cross referencing, correlating DeeProbe measurements with Via depth measurements resulting from X-SEM, and FIB inspections. spec: < 0.5µm

2. Reproducibility: Reproducibility of the measurements when identical structures are measured multiple times with some intermittent delay Spec: < 0.5 µm and etch uniformity study.

Repeatability : 0.08 µm @ 3sigma

2 3 4 5

6 7 8 9

1

3.Linearity: Measurement of etched wafer with variable depth Measurement across 300 mm wafer diameter

Note: SEM measurement accuracy is estimated in the 0.1 to 0.5 µm range

Via depth

50 µm

45 µm

40 µm

35 µm

30 µm

25µm

20 µm

15 µm

10 µm Die #

Qualified by IMEC in 2010


METROLOGY SOLUTION



Die #

µm

16 etching runs: “M” shape of depth across wafer diameter

SEM measurement on one 300 mm wafer

Edge Center

• Measure every die (37) over the west-east axis • XSEM verification of 6 dies


METROLOGY SOLUTION


4) Membrane inspection, thickness and TTV

Combination of Microscopy and IR interferometry in the same optical path (unique!) •Materials: Si, GaAs, SiC, InP, GaN, Sapphire, Glass and all materials transparent to IR wavelenght •IR spot size: from 4 µm to 100 µm. •Minimum distance between measurement points: down to 0.01 µm

IR view of a membrane and measurement point positioning

Membrane: bulk micromachining

2D view of membrane thickness mapping

Over etch through oxide (pinholes) Scratches Particles Geometrical defect

Inspection and metrology performed at the same time


METROLOGY SOLUTION



Infra-Red Microscopy and metrology for MEMS above ICs Wafer Level packaging inspection: The IR microscopy allows to get the image of the pattern below the Silicon cap. The user can position the metrology spot on a defined pattern and detect any defects Material thickness and Air gap dimensions can be obtained in one pass WLP: Membrane Thickness and shape by IR Inspection (fringes) or air gap thickness mapping

Cap thickness

Air gap

Si Air Si Air

Post bonding inspection and metrology

Si Air gap

IR interferometric signal: detection of all interfaces


METROLOGY SOLUTION



Wafer Level Packaging: IR Inspection and metrology after bonding


METROLOGY SOLUTION


Courtesy of ST micro & LETI


3D Stack: Post Interconnect bonding process control: Combination of IR interferometry and IR microscopy

IR microscopy and Moiré interferometry:

Defect detection at the Die interface

Die Alignment

Defect detection Alignment

Interface Thickness Metrology


METROLOGY SOLUTION


6) BONDED WAFERS: Thickness and inspection

Wafer Bonding: Thickness and TTV of individual wafer of a stack

IR microscopy combined with IR interferometry allowed to detect voids at the interfaces and to measure all layers

Bow/Warp measured at the same time than TTV

Layer Bow (um) Warp (um) Average

Thickness (um)

TTV (um)

All -328.706 375.119 1509.816 13.865

Si 779.947 <1um

Glue + Glass 729.869 14.858

Full wafer surface inspection Courtesy of Nanda Tec

Bow/ warp Glue + Glass TTV

Bonding deffects


METROLOGY SOLUTION


7) OVERLAY AND REGISTRATION

In plane

Out of plane

Others: Out of field of view Registration

Within field of view Registration

Example: Front to back registration of back side trench versus front µfluidic device (3 cm)

x1 x2

Dual side microscopy with automatic alignment

High accuracy (0.1 µm) displacement stage

Repeatability (3 s) < 0.5 µm

Front objective

Back objective


METROLOGY SOLUTION


Conclusion

Several non contact optical technologies are available for MEMS and 3D

process control solution.

MEMS manufacturers need flexible and multiple metrology solutions.

Inspection and Metrology embedded on the samed platform seems to fit with

new required process control solutions.

Multiple sensors approach is the key.


METROLOGY SOLUTION


Thanks For your attention

www.fogale-semicon.com

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MEMS solutions - Hilpert