Vapor Phase Thiol Self-Assembled Monolayers for DoD ASD

Sebastiaan J. F. Herregods, Tinne Delande, Mattia Pasquali, Zsolt Tokei, Herbert Struyf, Silvia Armini

2

OUTLINE

▪ Introduction

▪ HfNx ALD

▪ UDT on blanket substrates

▪ UDT on Patterned substrates

▪ Summary

3

MOTIVATION

Downscaling makes top-down fabrication by litho more challenging

Bottom-up approach by Area-Selective Deposition (ASD)

Block film growth by SAM passivation

Dielectric on Dielectric (DoD) enabled by Thiol SAM passivation

RS-H + M(n)0 → RS-M+M(n-1)

0 + ½ H2

Application:

Self-Aligned Vias

Selective Anchoring group

Hydrocarbon chain

10 nm

4

SAVANNAH S300

Veeco/Ultratech Savannah G2 S300

Cross flow reactor

300 mm

Integrated in a glovebox (EHS)

Quarts Crystal Microbalance (QCM)

2 SAMs kits (Thiol)

Metal Organic Precursor lines

H2O precursor line (Metal Oxides)

NH3 precursor line (Nitrides)

ATOMIC LAYER DEPOSITION (ALD) TOOL EQUIPPED WITH SAM-KITS

Ultratech’s Savannah with

opened cross flow reactor

opened cross flow reactor

Savannah S300 integrated in a glovebox

Pballast

Preactor

5

SAM DEPOSITION

Quality of vapor deposited SAMs is strongly dependent on:

precursor dosage

duration of the exposure.

Typical Pressure profile during SAM deposition

precursor dosage duration of the exposure

6

OUTLINE

▪ Introduction

▪ HfNx ALD

▪ UDT on blanket substrates

▪ UDT on Patterned substrates

▪ Summary

7

HAFNIUM NITRIDE ALD

▪ Process

▪ Tdeposition = 120 °C

▪ 0,025 s NH3 pulse

▪ 0,300 s TDMAHf pulse (at 75 °C)

▪ 10 s 20 sccm N2 purge

▪ Spectroscopic Ellipsometry

▪ Linear growth: GPCHfNx on SiO2 = 0.22 nm

▪ n = 2.0

▪ Thickness gradient (Inlet/West < Center < Outlet/East)

▪ Good run to run reproducibility

▪ Similar results for Tdeposition = 150 °C

100 cycles ALD HfNx 120ºC

TEM image of 100 Cycles HfNx at 120 °C

21.4 nm

▪ k value = 6,4 ± 0.6 (Pt dots)

▪ XPS:

▪ Hf:N ratio ~ 1:4

▪ signal present indicating not all the ligands reacted

▪ Top layer oxidized (Hf:N:O ratio ~ 3:1:6)

8

OUTLINE

▪ Introduction

▪ HfNx ALD

▪ UDT on blanket substrates

▪ UDT on Patterned substrates

▪ Summary

9

UDT DEPOSITION ON CU BLANKETS

▪ Pretreatment

▪ Asis

▪ 15 minutes forming gas at 250 °C

▪ Process

▪ n-undecanethiol (UDT) at 80 °C

▪ 300 mTorr UDT build up (Tprecursor = 65 °C)

▪ 4 UDT pulses with each 600 s exposure (uniform WCA)

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UDT DEPOSITION ON CU BLANKETS

▪ UDT layer

▪ HfNx ALD blocking at 120 °C

> 100 nm HfNx

▪ UDT on Cu after CMP

▪ Thicker & more hydrophobic

▪ HfNx ALD blocking until at least 500 cycles (> 100 nm HfNx)

▪ UDT on Cu after forming gas pretreatment

▪ reduced blocking behaviour: 50 cycles HfNx blocked(~ 11 nm HfNx on SiO2), but not 100 cycles of HfNx

▪ Blocking up to 100 cycles observed at higher precursor T/dose (not shown, by SE)

Asis (after CMP) 15’ forming gas (FG) @ 250 °C

WCA [°] 106 ± 2 103 ± 2

Thickness by SE [nm] 8 ± 1.8 3.1 ± 1.2

Selectivity S = 𝜃𝐺 − 𝜃𝑁𝐺

𝜃𝐺+ 𝜃𝑁𝐺

𝜃 = surface coverage (RBS)

G = growth area

NG = non-growth area

G. Parsons, J. Vac. Sci. Technol.

A, Vol. 37, No. 2, 020911-1

11

OUTLINE

▪ Introduction

▪ HfNx ALD

▪ UDT on blanket substrates

▪ UDT on Patterned substrates

▪ Summary

UDT REMOVAL

800 W H2-plasma

DOD ASD ENABLED BY THIOL PASSIVATION

12

UDT only

SiO2

UDT

Cu

UDT + 50 HfNX

tHfNx_on_SiO2blanket = 11 nm

SiO2

UDT

Cu

HfNx

UDT + 25 HfNX

tHfNx_on_SiO2blanket = 5.5 nm

SiO2

UDT

Cu

HfNx

UDT + 100 HfNX

tHfNx_on_SiO2blanket = 22 nm

SiO2 Cu

HfNx

8 – 9 nm

tHfNx ~ tUDT

~ 20 nm

~ 6-7 nm

AFM STEP analysis – 160 nm CD, 500 nm Pitch

Increasing topography with ALD cycles

Topography in line with ALD target

→As expected for AS-ALD

UDT multilayer formation on Cu

HfNx

UDT thickness decreasing with ALD cycles

Step Height ~ 14 nm

3 nm Cu recess

→ 11nm HfNx on SiO2

HIGH LER

Incre

asing

HfN

xcycle

s

Confirmed on patterned

undesired passivation at the edge of the SiO2 growth surface → high LER

CD dependence: more substantial at lower CD (for constant PD)

Increasing Passivated edge

DOD ASD ENABLED BY THIOL PASSIVATION

13

ASD OBSERVATIONS

160 nm CD, 400 nm Pitch 80 nm CD, 200 nm Pitch

HfNx on SiO2

Cu

40 nm CD, 100 nm Pitch

No ASDASD

Temperature dependence: more substantial at 150°C

150 °C ASD

160 nm CD, 500 nm Pitch

120 °C ASD

~ 10 % ~ 30 %

14

UDT EXCESS: REMOVAL PRIOR TO ALD

UDT on Cu

Heigth ~ 10 nm

Width ~ 200 nm

High LER

UDT on Cu

Heigth ~ 7 – 8 nm

Width ~ 160 nm

UDT

DOD ASD ENABLED BY THIOL PASSIVATION

UDT (no treatment)

UDT

Post SAM treatment leads to UDT width decrease: match with measured CD

Post SAM treatment leads to drastic decrease in LER

AFM, 160 nm CD, 500 nm PitchAFM, 160 nm CD, 500 nm Pitch

UDT + Post SAM treatment

5’ forming gas treatment at 200 °C

15

UDT EXCESS: REMOVAL PRIOR TO ALD

DOD ASD ENABLED BY THIOL PASSIVATION

UDT (no treatment) + ALD UDT + Post SAM treatment + ALD

Treatment leads to significant decrease of undesired passivation on SiO2 growth surface

Treatment leads to drastic decrease in LER after ALD

Similar effect at 80 nm CD, but no ASD at 40 nm CD

AFM, 160 nm CD, 500 nm PitchAFM, 160 nm CD, 500 nm PitchTDSEM, 160 nm CD, 500 nm PitchTDSEM, 160 nm CD, 500 nm Pitch

16

UDT EXCESS: REACTION WITH SURFACE DURING ALD

DOD ASD ENABLED BY THIOL PASSIVATION

Pulsing UDT during half cycles leads to no HfNx ALD growth on SiO2 blanket

SiO2

SiO2

Purge

Purge

HfNx ALD

UDT

UDT

UDT thickness decreases during HfNx ALD

→ In situ passivation at edge of SiO2 growth surface?

17

OUTLINE

▪ Introduction

▪ HfNx ALD

▪ UDT on blanket substrates

▪ UDT on Patterned substrates

▪ Summary

18

SUMMARY

DOD ASD ENABLED BY THIOL PASSIVATION

UDT multilayer formation on copper oxide

ASD achieved on 160 & 80 nm CD, not on 40 nm CD

Post SAM treatment

UDT confinement by forming gas

drastic LER decrease

match original CD and passivated area

In-situ UDT release during half cycle may lead to undesired passivation on

intermediates of HfNx ALD

CONFIDENTIAL – INTERNAL USE