Low Temperature (LT) Thermal ALD Silicon Dioxide … Tempreature (LT) Thermal ALD Silicon...printed...
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Low Temperature (LT) Thermal ALD Silicon Dioxide Using Ozone Process Huazhi Li*, Jayasri Narayanamoorthy, Neal Sullivan, Dmitry Gorelikov Arradiance Inc., Sudbury, MA USA *[email protected] Atomic Layer Deposition (ALD) is a powerful nanofabrication technique capable of depositing highly-conformal coatings for a variety of applications. ALD is based on a modified chemical vapor deposition (CVD) process, in which the overall chemical reaction is split into two sequential, self-limiting, half reactions. This allows for sub-nanometer precision in material thickness, which can be controlled with a resolution of ~1 Angstrom. Due to the self-limiting nature of the surface chemical reactions, ALD processes enable excellent uniformity when coating high aspect ratios (above 2000:1), allowing for 3-dimensional engineering of complex nanostructured architectures. The atomically-precise tuning of surfaces and interfaces afforded by this process create numerous opportunities in the fields of semiconductor devices and memory, energy conversion and storage, MEMS/NEMS, catalysis, and other emerging areas. ALD SiO 2 is a very important material in microelectronics. The increasing interest in three- dimensional 3D transistor structures e.g., nanowire or FinFETs requires ultrathin SiO 2 as gate insulator, diffusion barrier, or sacrificial layer covering 3D nanostructures homogeneously during processing. The coating of thermally fragile substrates such as double patterning over photoresist surface by ALD SiO 2 require low process temperatures. In recent years, various Si precursors have been tested in combination with O 3 or H 2 O as the oxidants. These processes include the use of pyridine and TMA (Gordon et al) as catalysts. And Because of the nature of these precursors, ALD processes are hard to practice at lower temperature (<100 ̊C ). In addition, a thermal ALD process for low-temperature SiO 2 was reported which was free of catalysts or corrosive by-products (D. Hiller et al). In this respect, the use of precursors with amino ligands has also shown promising results, in particular when combined with H 2 O 2 , O 3 , or O 2 plasma as the oxidant and the process based on these precursors can go down to really low temperature . Here Arradiance demonstrates an efficient low temperature ALD SiO 2 process based on ozone and aminosilane precursor with GEMStar ALD tool . Data presented here is for process temperatures ranging from 80⁰C to 200⁰C. Our low temperature SiO 2 process has also been successfully used in photoresist double patterning as shown here. Low Temperature ALD Overview Experimental Method: GEMStar and Ozone system Characterization of LT ALD SiO 2 Films Double Patterning Application Using LT ALD SiO 2 Process Summary Arradiance has developed a LT ALD SiO 2 process on GEMStar which showed: 1. Conformal and uniform coating over photoresist substrate; 2. Excellent uniformity (< 1%) demonstrated for SiO 2 films; 3. Low temperature SiO 2 deposition, using ozone as oxidant, exhibited linear growth at 80 ̊C ; 4. Full integration of ozone source with GEMStar user interface software allows for fully automated processing. References •D.R. Beaulieu et al "Plastic microchannel plates with nano-engineered films", IWORID 2009 conference, Nucl. Instr. Meth. A 633, pp. S59-S61 (2011) •P. de Rouffignac et al “ALD of Insulators and Conductors in Novel MEMS Devices", (Invited), 10th AVS-ALD 2010, Seoul, Korea •D. Hiller et al.“Low temperature silicon dioxide by thermal atomic layer deposition: Investigation of material properties”, J. of App. Phys. 107, 2010 •N. Sullivan, et al. "Novel microchannel plate device fabricated with atomic layer deposition", 9th AVS-ALD, Monterey CA, July 19-22, 2009. •R. G. Gordon “Rapid vapor deposition of highly conformal silica nanolaminates”, Science, 298, 402, 2002. •H. Li, et al "High Surface area /High Aspect Ratio ALD process optimization using Anodic Aluminum Oxide" 13th AVS-ALD, 2013. GEMStar-8 system is designed for extreme surface area, high aspect ratio structures: Multi-channel precursor delivery system isolates & distributes precursors combined with a tapered exhaust to provide exceptional nanofilm uniformity. Metrology Interface for QCM, ellipsometry , FTIR, OES and room for up to six high capacity precursor cylinders (up to 4 heated) with 2 additional independent gas lines, maximizes system productivity. The hot wall design allows stacks of multi-wafers or samples to improve the through- put and reduce the cost per device. Arradiance specifies a durable ozone system (~10% ozone concentration) as an option for LT ALD. The ozone system is engineered into one of the gas ports of GEMStar with the majority of the output of ozone going to the ozone destruct. We use N 2 buffered O 2 to generate higher concentration of ozone. This system shows advantage of reducing ALD oxide cycle time at low temperature. Most of the organometallic precursors can be obtained through pre-loaded Arradiance bottles by Strem. LT SiO 2 ALD process temperature typically range between 80 to 200 ̊C. Characterization of LT ALD SiO 2 Films The linear growth shows the typical ALD behavior of SiO 2 process at 80 ̊C. And the growth rate saturates at 0.27 A/cy. The growth rate increases with temperature which is consistent with the previous report. This is due to the increased reactivity of aminosilane towards ozone at higher temperature. Ozone system Photoresist image hp100nmL/S 131.7n m 101.6nm 100nm Photoresist image hp200nmL/S Saturation studies show that the growth saturates at 1200 ms dosing of aminosilane precursor. In subsequent runs a 1200 ms dose of Si precursor was used. 100nm 100nm 12.28nm 131.7nm 101.6nm ALD-SiO2 thickness After Arradiance ALD process 100nm After Arradiance ALD process Typical LT ALD SiO 2 conditions on photoresist include deposition temperature of 80 ̊C, ozone (0.2s) and aminosilane (1.2s) as reactant gas and source temperature at 50 ̊C. In conclusion: the LT ALD SiO 2 process developed on GEMStar successfully provided a very conformal (>95%) and uniform SiO 2 patterning layer with controllable thickness (13 nm) on photoresist material. The post etching films showed conformal coatings as well (not shown here). 61.838Å 62.270Å 61.989Å 61.810Å 61.003Å Uniformity of LT SiO 2 film by ozone over 8”: 0.76% (1σ) Reactants: SAM24 and O 3 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 50 100 150 200 250 Growth Rate (Å/cy) Temperature (̊C) y = 0.2667x + 1.3101 0 20 40 60 80 100 120 140 0 100 200 300 400 500 Thickness (Å) Cycles 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0 500 1000 1500 2000 Growth rate (Å/cy) Pulse time (ms) 12.35nm
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Low Temperature (LT) Thermal ALD Silicon Dioxide
Using Ozone Process
Huazhi Li*, Jayasri Narayanamoorthy, Neal Sullivan, Dmitry Gorelikov
Arradiance Inc., Sudbury, MA USA *[email protected]
Atomic Layer Deposition (ALD) is a powerful nanofabrication technique capable of
depositing highly-conformal coatings for a variety of applications. ALD is based on a modified
chemical vapor deposition (CVD) process, in which the overall chemical reaction is split into two
sequential, self-limiting, half reactions. This allows for sub-nanometer precision in material
thickness, which can be controlled with a resolution of ~1 Angstrom. Due to the self-limiting
nature of the surface chemical reactions, ALD processes enable excellent uniformity when coating
high aspect ratios (above 2000:1), allowing for 3-dimensional engineering of complex
nanostructured architectures. The atomically-precise tuning of surfaces and interfaces afforded by
this process create numerous opportunities in the fields of semiconductor devices and memory,
energy conversion and storage, MEMS/NEMS, catalysis, and other emerging areas.
ALD SiO2 is a very important material in microelectronics. The increasing interest in three-
dimensional 3D transistor structures e.g., nanowire or FinFETs requires ultrathin SiO2 as gate
insulator, diffusion barrier, or sacrificial layer covering 3D nanostructures homogeneously during
processing. The coating of thermally fragile substrates such as double patterning over photoresist
surface by ALD SiO2 require low process temperatures.
In recent years, various Si precursors have been tested in combination with O3 or H2O as the
oxidants. These processes include the use of pyridine and TMA (Gordon et al) as catalysts. And
Because of the nature of these precursors, ALD processes are hard to practice at lower temperature
(<100 ̊C ). In addition, a thermal ALD process for low-temperature SiO2 was reported which was
free of catalysts or corrosive by-products (D. Hiller et al). In this respect, the use of precursors with
amino ligands has also shown promising results, in particular when combined with H2O2, O3, or O2
plasma as the oxidant and the process based on these precursors can go down to really low
temperature . Here Arradiance demonstrates an efficient low temperature ALD SiO2 process based
on ozone and aminosilane precursor with GEMStar ALD tool. Data presented here is for process
temperatures ranging from 80⁰C to 200⁰C. Our low temperature SiO2 process has also been
successfully used in photoresist double patterning as shown here.
Low Temperature ALD Overview
Experimental Method: GEMStar and Ozone system
Characterization of LT ALD SiO2 Films
Double Patterning Application Using LT ALD SiO2 Process
Summary
Arradiance has developed a LT ALD SiO2 process on GEMStar which showed:
1. Conformal and uniform coating over photoresist substrate;
2. Excellent uniformity (< 1%) demonstrated for SiO2 films;
3. Low temperature SiO2 deposition, using ozone as oxidant, exhibited linear growth at 80 ̊C ;
4. Full integration of ozone source with GEMStar user interface software allows for fully
automated processing.
References
•D.R. Beaulieu et al "Plastic microchannel plates with nano-engineered films", IWORID 2009 conference, Nucl. Instr. Meth. A 633, pp. S59-S61 (2011)
•P. de Rouffignac et al “ALD of Insulators and Conductors in Novel MEMS Devices", (Invited), 10th AVS-ALD 2010, Seoul, Korea
•D. Hiller et al.“Low temperature silicon dioxide by thermal atomic layer deposition: Investigation of material properties”, J. of App. Phys. 107, 2010
•N. Sullivan, et al. "Novel microchannel plate device fabricated with atomic layer deposition", 9th AVS-ALD, Monterey CA, July 19-22, 2009.
•R. G. Gordon “Rapid vapor deposition of highly conformal silica nanolaminates”, Science, 298, 402, 2002.
•H. Li, et al "High Surface area /High Aspect Ratio ALD process optimization using Anodic Aluminum Oxide" 13th AVS-ALD, 2013.
GEMStar-8 system is designed for extreme surface area, high aspect ratio structures: Multi-channel
precursor delivery system isolates & distributes precursors combined with a tapered exhaust to
provide exceptional nanofilm uniformity.
Metrology Interface for QCM, ellipsometry , FTIR, OES and room for up to six high capacity
precursor cylinders (up to 4 heated) with 2 additional independent gas lines, maximizes system
productivity. The hot wall design allows stacks of multi-wafers or samples to improve the through-
put and reduce the cost per device.
Arradiance specifies a durable ozone system (~10% ozone concentration) as an option for LT ALD.
The ozone system is engineered into one of the gas ports of GEMStar with the majority of the
output of ozone going to the ozone destruct. We use N2 buffered O2 to generate higher
concentration of ozone. This system shows advantage of reducing ALD oxide cycle time at low
temperature.
Most of the organometallic precursors can be obtained through pre-loaded Arradiance bottles by
Strem.
LT SiO2 ALD process temperature typically range between 80 to 200 ̊C.
Characterization of LT ALD SiO2 Films
The linear growth shows the typical ALD
behavior of SiO2 process at 80 ̊C. And the
growth rate saturates at 0.27 A/cy.
The growth rate increases with
temperature which is consistent with
the previous report. This is due to the
increased reactivity of aminosilane
towards ozone at higher temperature.
Ozone system
Photoresist image hp100nmL/S
131.7n
m 101.6nm 100nm
Photoresist image hp200nmL/S
Saturation studies show that the growth
saturates at 1200 ms dosing of
aminosilane precursor. In subsequent runs
a 1200 ms dose of Si precursor was used.
100nm
100nm 12.28nm 131.7nm 101.6nm
ALD-SiO2 thickness
After Arradiance ALD process
100nm
After Arradiance ALD process
Typical LT ALD SiO2 conditions on photoresist include deposition
temperature of 80 ̊C, ozone (0.2s) and aminosilane (1.2s) as reactant gas
and source temperature at 50 ̊C. In conclusion: the LT ALD SiO2 process
developed on GEMStar successfully provided a very conformal (>95%) and
uniform SiO2 patterning layer with controllable thickness (13 nm) on
photoresist material. The post etching films showed conformal coatings as
well (not shown here).
61.838Å
62.270Å 61.989Å
61.810Å
61.003Å
Uniformity of LT SiO2 film by ozone over
8”: 0.76% (1σ)
Reactants: SAM24 and O3
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 50 100 150 200 250
Gro
wth
Ra
te (
Å/c
y)
Temperature (̊C)
y = 0.2667x + 1.3101
0
20
40
60
80
100
120
140
0 100 200 300 400 500
Th
ick
nes
s (Å
)
Cycles
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0 500 1000 1500 2000
Gro
wth
ra
te (
Å/c
y)
Pulse time (ms)
12.35nm
