Sub-Micron Lithography with the Sub-Micron Lithography with the - - PowerPoint PPT Presentation

Quate Group, Stanford University

Sub-Micron Lithography with the Sub-Micron Lithography with the Atomic Force Microscope Atomic Force Microscope

• S. C. Minne, J. D. Adams, S. R.
• S. C. Minne, J. D. Adams, S. R. Manalis

Manalis, K. Wilder, T. , K. Wilder, T. Soh Soh, E. Chow and C. F. , E. Chow and C. F. Quate Quate

• E. L.
• E. L. Ginzton

Ginzton Laboratory, Stanford University, Stanford, CA 94305 Laboratory, Stanford University, Stanford, CA 94305

Quate Group, Stanford University

CD Control Requirements CD Control Requirements

I I The 1997 SIA Roadmap for Semiconductors predicts strict CD

The 1997 SIA Roadmap for Semiconductors predicts strict CD tolerances as tolerances as linewidths linewidths shrink: shrink: 2001 150 nm ± 12 nm 2003 130 nm ± 10 nm 2006 100 nm ± 7 nm 2009 70 nm ± 5 nm 2012 50 nm ± 4 nm I This trend presents a variety of challenges: Year Feature Size 3σ CD Tolerance

• resolution
• uniformity (along features and

across fields & wafers)

• repeatability (process latitude)
• pattern transfer capabilities

(selective, anisotropic etches)

• pattern placement (overlay

registration)

• throughput

Quate Group, Stanford University

Atomic Force Microscope Atomic Force Microscope

X Y Z Actuator Sample (A - B) Display Feedback Control Actuator Driver Laser A B

Optical Lever Detection

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Throughput Requirements Throughput Requirements

I I Goals

Goals

– – 200 mm wafer 200 mm wafer – – 10 1013

13 50nm pixels per wafer

50nm pixels per wafer – – 10 wafers per hour 10 wafers per hour I I Required Capabilities

Required Capabilities

– – 10 mm/s scan speed 10 mm/s scan speed – – 5 probes per mm 5 probes per mm2

2

I I Achievements

Achievements

– – 10 mm/s scan speed (optical lever) 10 mm/s scan speed (optical lever) – – 32 tips in parallel ( 32 tips in parallel (piezoresistor piezoresistor) ) – – 5 probes per linear mm (PR + 5 probes per linear mm (PR + ZnO ZnO) ) – – 4 mm 4 mm2

2 image (

image (piezoresistor piezoresistor) ) – – Arbitrary pixels up to 100 Arbitrary pixels up to 100 MBytes MBytes for Sub-Micron Lithography with the Atomic Force Microscope

Quate Group, Stanford University

Array of 50 Cantilevers with Array of 50 Cantilevers with Integrated Sensors & Actuators Integrated Sensors & Actuators

ZnO Ground Bus Piezoresistor Ground Bus Piezoresistive Sensor Output ZnO Actuator Input Lithography Write Input Piezoresistor ZnO Actuator Individual Cantilever’s. . .

Quate Group, Stanford University

High Speed Atomic Force Microscopy High Speed Atomic Force Microscopy

0.1 1 10 0.1 1 10 100 Drive Frequency (kHz) piezo tube ZnO Amplitude (arb)

Quate Group, Stanford University

2 mm x 2mm Parallel AFM Image 2 mm x 2mm Parallel AFM Image

2 mm 200 um 10 tips in parallel at 1mm/s. No feedback.

Quate Group, Stanford University

32 Images over 6.4 mm 32 Images over 6.4 mm

1 9 17 25 8 16 24 32 Automated Data Acquisition, Constant Height 200 um

Quate Group, Stanford University

Throughput Requirements Throughput Requirements

I I Goals

Goals

– – 200 mm wafer 200 mm wafer – – 10 1013

13 50nm pixels per wafer

50nm pixels per wafer – – 10 wafers per hour 10 wafers per hour I I Required Capabilities

Required Capabilities

– – 10 mm/s scan speed 10 mm/s scan speed – – 5 probes per mm 5 probes per mm2

2

I I Achievements

Achievements

– – 10 mm/s scan speed (optical lever) 10 mm/s scan speed (optical lever) – – 32 tips in parallel ( 32 tips in parallel (piezoresistor piezoresistor) ) – – 5 probes per linear mm (PR + 5 probes per linear mm (PR + ZnO ZnO) ) – – 4 mm 4 mm2

2 image (

image (piezoresistor piezoresistor) ) – – Arbitrary pixels up to 100 Arbitrary pixels up to 100 MBytes MBytes for Sub-Micron Lithography with the Atomic Force Microscope

Quate Group, Stanford University

Uniform High Aspect Ratio Tall Tips for Uniform High Aspect Ratio Tall Tips for Large Arrays Large Arrays

I I Uniform tips allow for

Uniform tips allow for larger arrays larger arrays

I I Tall tips facilitate 2-D

Tall tips facilitate 2-D imaging imaging

I I High aspect ratio tips for

High aspect ratio tips for demanding applications demanding applications

Quate Group, Stanford University

Through-Wafer Metal Through-Wafer Metal Interconnection Interconnection

L L Goal

Goal

Through-wafer Electrical Through-wafer Electrical Interconnection for 2 Dimensional Interconnection for 2 Dimensional Array Addressing. Array Addressing. L L Processing Techniques

Processing Techniques

G G

Through-wafer anisotropic RIE etching Through-wafer anisotropic RIE etching

• f 30um
• f 30um vias
• vias. (AR > 18:1)

. (AR > 18:1)

G G

Oxide Insulation. Oxide Insulation.

G G

CVD CVD Metalization Metalization. .

G G

Metal Patterning using Metal Patterning using electro electro-

• deposited

deposited Photoresist Photoresist. .

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Isolation and Isolation and Metallization Metallization of Deep Trenches

• f Deep Trenches

Cross Sectional SEM Micrograph Top Side Middle of Wafer

Quate Group, Stanford University

SAL601 Exposure and Etch SAL601 Exposure and Etch

430 nm 600 nm SAL601 Resist Etched Silicon

e-

65 nm SAL601

Expose with EBL or SPL: Develop in MF-322: Etch in high density plasma (HBr + O2):

silicon

Quate Group, Stanford University

Scanning Probe Lithography (SPL) Scanning Probe Lithography (SPL)

cantilever tip z piezo tube signal [v]

detector laser

deflection sensor xyz scanner current amplifier bias

CURRENT FEEDBACK FORCE FEEDBACK

I F

stage sample resist

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EBL Proximity Effects EBL Proximity Effects

I I Patterns printed with EBL in

Patterns printed with EBL in SAL601 with a 40 SAL601 with a 40 nm nm pixel spacing pixel spacing and etched into and etched into Si Si

– – Isolated single pass line is 120 Isolated single pass line is 120 nm nm wide wide – – 4-pixel-wide feature has width greater 4-pixel-wide feature has width greater than four times the width of the single than four times the width of the single pass line pass line – – Lines on 500 Lines on 500 nm nm pitch are resolved but pitch are resolved but are wider than isolated lines are wider than isolated lines – – No lines on 200 No lines on 200 nm nm pitch are resolved pitch are resolved

7.5 µm Pixel Width: 1 2 3 4 500 nm pitch 200 nm pitch

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SPL Linearity SPL Linearity

300 nm

40 nm

Pixels: 1

2 3 4 5 6 Exposure Dose=20 nC/cm

37 nm 239 nm

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SPL SPL Linewidth Linewidth Control Control

1 µm Linewidth=65 nm 1 µm

150 nm

1 µm

600 nm 430 nm

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SPL Resolution & Transfer SPL Resolution & Transfer

120 nm 200 nm

10:1 Aspect Ratio 10:1 Aspect Ratio

Linewidth Linewidth=26 =26 nm nm PMMA Exposure, PMMA Exposure, Lift-Off, & Etch Lift-Off, & Etch

6:1 Aspect Ratio 6:1 Aspect Ratio

Linewidth Linewidth=50 =50 nm nm SAL601 Exposure SAL601 Exposure & Etch & Etch

Quate Group, Stanford University

Non-Contact AFM Lithography Non-Contact AFM Lithography

cantilever tip piezo tube actuator resist silicon stage trans-impedance amplifier bias differential amplifier error signal DSP setpoint current measured current ADC

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Developed Resist Features Developed Resist Features

I I

AFM image of SAL601 AFM image of SAL601 resist patterns exposed resist patterns exposed in the non-contact AFM in the non-contact AFM mode mode

I I

Image taken in the Image taken in the tapping AFM mode with tapping AFM mode with the same cantilever the same cantilever used for patterning used for patterning

I I

Resist features are 65 Resist features are 65 nm nm tall and about 30 tall and about 30 nm nm wide wide

Quate Group, Stanford University

Etched Lines Patterned by Etched Lines Patterned by Non-Contact AFM Lithography Non-Contact AFM Lithography

I I

Features are 28 Features are 28 nm nm wide near the center of the lines and 32 wide near the center of the lines and 32 nm nm wide near the ends wide near the ends

I I

Lines were etched 320 Lines were etched 320 nm nm deep into the silicon, giving an deep into the silicon, giving an aspect ratio of about 10:1 aspect ratio of about 10:1