Atomic Level Precision Materials Engineering

Peter Loewenhardt, Terry S Lee, Jun-Chieh Wang , Leonid Dorf, Shahid Rauf, Amulya Athyde

Applied Materials

Mobility’s Implications for Semiconductor Equipment

2

THEN NOW

Litho-enabled 2D transistor Materials-enabled 3D transistor

Litho-enabled 2D NAND Materials-enabled 3D NAND

Conventional processes Selective material processes

Bulk dominates Interface engineering increasingly critical

Standalone tool Integrated processes on same tool

3

Performance improvement is not about scaling… At 28 nm, 90% of the performance gains come from materials and device architecture innovation

SOURCE: ARM, IBM, IC INSIGHTS

Era of Precision Materials Engineering

4

NEW MATERIALS will be the driver of technology migrations in advanced nodes

2X INCREASE IN NEW MATERIALS

5

Mobility and Connectivity Drive Performance Gains

Increasing Functionality Driving the Biggest Semiconductor Inflections in Decades

Speech Recognition Gesture Sensor Mobile Payment Ultra Power

Saving Mode

Video Chat Finger Print ID Facial Recognition

Wireless Charging

45nm 32 / 28nm 20nm 14nm High-k Metal

Gate n-MOS Epi FinFET

0.3 | 6 GB 0.8 | 13 GB 1.5 | 21 GB 2.2 | 23 GB *

FEATURES

AND

FUNCTIONS

INFLECTIONS

2010 – 2011 2012 – 2013 2014 2015F

Sources: Gartner * Average Mobile DRAM and NAND Content Per Unit of Premium Smartphone

3D Inflections Driving ALD Market Growth

3D FinFET Tighter thickness/conformality control Decreasing thermal budgets

3D NAND Higher aspect ratios Vertical, electrical grade films

3D Inflections Driving new Materials High-Performance ALD required

ATOMIC LAYER DEPOSITION (ALD)

ALD Has Become an Industry Norm However many Practical Challenges:

•Thermal budget (getting lower and lower . . .)

•Increased quality of films

•Monolayer engineering for high performance

•Incompatible chemistries

•Stringent and ever tightening low defect requirements

•Productivity: maximize output

–Minimize non-process time (reduce heat-up/cool down, etc.)

–Increase cycle time (reduce purges, etc.)

–Increase MWBC to >10,000 wafers

8

ALD Practical Challenges and Improvements

•Time separated ALD challenges:

–Added time for purge & pump-down

–Potential interaction between precursors

•Spatially separated ALD challenges:

–Chemistry precursor separation

9

Conventional ALD Olympia ALD

Wafer travels continuously Spatially separated chemistries Chemistry-free zones isolate

individual chemistries

Precursor Precursor

Wafer is stationary Alternating chemistries Purge separates chemistries

Primary technology used today

A B A B

A B

Applied’s Focus is on Spatially Separated ALD OlympiaTM ALD

0

1

2

3

4

5

Al2O340Å

TiO2200Å

SiO2250Å

TiN50Å

550°C SiN250Å

450°C SiN300Å

Nor

mal

ized

Thro

ughp

ut

Time Separated

Olympia

Single Wafer Furnace Olympia

Purge Time

Medium Common

precursor volume

Extremely Long Common precursor

volume

Short Precursor specific volume

MWBC Low

Deposition everywhere

Medium Deposition everywhere

Batch

High Contained deposition

Applied’s Focus is on Spatially Separated ALD OlympiaTM ALD

Applied’s Focus is on Spatially Separated ALD OlympiaTM ALD

Concept

Wafer travels continuously Spatially separated chemistries Chemistry-free zones isolate

individual chemistries

Precursor

A B

A B High-quality, low-temperature films

for ≤10nm

Modularity for materials engineering of future ALD films

Unique chemical confinement to minimize defects

High-productivity platform

Proven differentiation - DTOR at multiple customer sites

Proof

External Use

Treatment X

Modular Design for Atomic-Level Engineering

Precursor Precursor

20nm

Silicon Oxide

20nm

Silicon Nitride

20nm

Titanium Oxide

100nm

Aluminum Oxide

20nm

Titanium Nitride

Versatility Broadens Spectrum of Achievable ALD Materials

without Compromising Productivity

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A B Thermal

B P A

Plasma Enhanced

ALD Mode Process Sequence

Atomic-Layer

Treatment X B A

Conventional ALD

Olympia ALD

Source: Applied Materials, Inc.

External Use

Olympia Solution Industry Challenge

Spatially Separated Sequence Preserves Films

Film

Qua

lity

Conventional ALD

Olympia ALD

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B P A

X B A

Unique ALD Sequence Preserves Film Quality at Low Temperatures

Impurities Jeopardize Quality

High-Quality Film

14nm 10nm

20nm

7nm

External Use

Precursor Precursor Treatment X Precursor Treatment X

Modular Adaptability for Next-Generation Materials

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Post-Treated X B A

Pre-Treated X B A

Multi-Chemical

C B A

Multi-Chemical

/Treatments

C B A X

Olympia ALD Modes

Opens the Way to Widest Spectrum of

Achievable Next-Generation Films

Selective Deposition

Advanced Patterning Films

Low-Temperature Films

Lower-k Films

Nano-Laminates Higher-k Films

Spatially Separated (Olympia) ALD

ATOMIC LAYER REMOVAL

Parameters Governing Isotropic Removal Etch Governing Equation:

: rate parameters for spontaneous chemical etching : neutral, and ion flux

: physical and ion enhanced etching yield : the fraction of surface sites occupied by the reactant species

a E k , 0 + Γ Γ ,

IE p Y Y ,

Θ

: neutral, and ion flux IE p Y Y ,

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Parameters Governing Isotropic Removal Etch Governing Equation:

Pure Chemical Neutrals, Radicals

Parameters Governing Isotropic Removal Etch Governing Equation:

Physical Etch

Plasma Density (type of reactor)

Voltage (Bias)

If Bias = 0, Then Etch Rate is determined by the sheath voltage

Kinetic energy of electrons in plasma

To avoid underlayer damage, lower Te as much as possible

Atomic Layer Etching (ALE)

ALE allows for control of critical dimension to Å level, especially on ultra-sensitive materials.

In ALE, etching proceeds monolayer by monolayer in a cyclic, self limiting process. ► Passivation: Top monolayer is passivated by chemical precursors. ► Passivation makes top layer more easily etched compared to sub-layers. ► Purge: Remove the remaining chemical reactants. ► Etching: Passivated surface is exposed to ion bombardment with energy

below the sputtering threshold. ► The etch process stops once the topmost layer of the passivated crystal

was removed (self limiting).

Sputtering Yield of Si – Cl+ Bombardment

The density distribution within the simulation cell after 400 successive 5 and 85 eV Cl+ impacts on an initially defect-free silicon lattice.

Damage on Si surface increase with impact energy. Ultra-thin chlorinated layer produced by low energy ions and/or radicals is critical to ALE.

Sputtering Yield of Si

Successively bombardment: Crystalline Si surface bombarded successively by 400 ions (O).

Parallel bombardment: Crystalline Si surface bombarded by 1 ion, 400 samples (O).

Qualitatively good agreement with experimental and simulation results.

Si Etch Using Cl and Cl+ Ions – Cl+ Bombardment

We use the chlorinated surface generated using 5 eV Cl+ ions (400 ion impacts) and bombard it with 105 eV Cl+ ions (1000 ion impacts).

A deep crack/roughness is developed at the surface, and Cl is distributed inhomogeneously.

Si is continuously etched with Y ≈ 0.3

Thicker damage caused by high energy Cl+.

For more on this model please see paper: Molecular Dynamics Simulations of Low Damage Atomic Layer Etching. J-C. Wang, S. Rauf, J. Kenney, L. Dorf, and K. Collins, Applied Materials, Inc ALE 2015 Workshop, Portland, Oregon USA

Si Etch Using Cl and Ar+ Ions – Ar+ Bombardment

We use the chlorinated surface generated using 5 eV Cl+ ions (400 ion impacts) and bombard it with 50 eV Ar+ ions (1000 ion impacts).

Ar+ energy below sputtering threshold.

Cl removal rate is significantly reduced after 500 Ar+ impacts due to lower Cl density on surface. Etch stops.

Damage layer is thin.

Electron Beam-Generated Plasma Etch Tool Motivation: need for ultra-low ion energies

Atomic layer precision requires accurate control of ion energy during plasma processing

Damage caused by conventional plasma technologies (capacitive or inductively coupled plasmas) is becoming marginal for critical applications

Electron Beam-Generated Plasma Etch Tool

Electron beams’ energy targeted for ionization: reduces the overall ‘Maxwellian’ Te Also allows for tailoring of species dissociation

Ar/N2, e-Jet source power = 3 kW

Very low Te (and therefore low Plasma Potential) plasmas can be generated and sustained

Electron Beam-Generated Plasma Etch Tool

Si ALE in chlorine at different ion energies

Ei = 46.2 eV τsat ~ 25 s

Ei = 28.7 eV τsat ~ 60 s

Markers = data with repeats Curves = tanh fit

P = 5 mT Saturation is limited by Ar-only etch rate of ~ 1 A/min

As Bias Phase Duration is increased the etch depth per cycle saturates

Signifies passivation layer is being removed each cycle, resulting in layer-by-layer etching. For more on this chamber please see paper: Low Damage Etch Chamber for Atomic Precision Etching L. Dorf, S. Rauf, A. Agarwal, G. Monroy, K. Ramaswamy, Applied Materials ALE 2015 Workshop, Portland, Oregon USA

Atomic Level Precision Materials Engineering

•Each technology node is aggressively exploring new materials many of which require atomic layer deposition and removal control

•Technologies exist and are being developed that are making ALD/ALE possible in a production environment