Difference between revisions of "Deposition"

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[[{{PAGENAME}}]] is any process that grows, coats, or otherwise transfers a material onto the substrate.  
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[[{{PAGENAME}}]] or Growth refers to the controlled synthesis, growth, or transfer of materials as thin films on a substrate. A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness.  Based on the growth dynamics which prevail during the deposition, the resulting material can be amorphous, polycrystalline, or crystalline. Deposition techniques that result in crystalline material are often referred to as epitaxial growth.
  
 
==Technologies==
 
==Technologies==
Typical technologies include atomic layer deposition (ALD), chemical vapor deposition (CVD), electrodeposition/ electroplating or electrochemical deposition (ECD), and physical vapor deposition (PVD).
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Typical technologies include atomic layer deposition (ALD), chemical vapor deposition (CVD), electrodeposition/ electroplating or electrochemical deposition (ECD), physical vapor deposition (PVD), and molecular beam epitaxy (MBE).   Selection of deposition technique depends on material deposited, desired film characteristics, and substrate temperature tolerance:
  
===Atomic layer deposition (ALD)===
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{| class="wikitable sortable"
[https://en.wikipedia.org/wiki/Atomic_layer_deposition Atomic Layer Deposition (ALD)] at the LNF is performed on the Oxford OpAL ALD system that currently offers three films Alumina/Aluminum Oxide ([[Al2O3|Al<sub>2</sub>O<sub>3</sub>]]), Hafnia/Hafnium Oxide ([[HfO2|HfO<sub>2</sub>]]), and Zinc Oxide ([[ZnO|ZnO]]).
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! style="font-weight: bold;" |Deposition Method
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! style="font-weight: bold;" |Materials
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! style="font-weight: bold;" |Deposition Rate
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! style="font-weight: bold;" |Substrate Temperature
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! style="font-weight: bold;" |Conformality / Sidewall Coverage
 +
! style="font-weight: bold;" |Film Density
 +
! style="font-weight: bold;" |Impurity Levels
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! style="font-weight: bold;" |Uniformity
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! style="font-weight: bold;" |Grain Size
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! style="font-weight: bold;" |Primarily Used for:
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|-
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|[[Evaporation]]
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|Metals and Dielectrics
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|1{{ndash}}15{{nbsp}}Å/sec
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|10{{ndash}}100ºC from dep.  300ºC with heater
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|Poor{{ndash}}None
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|Poor
 +
|Low
 +
|Poor
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|10{{ndash}}100{{nbsp}}nm
 +
|Thicker blanket metal films.  Low substrate temp. Directionality means it works well with lift-off patterning
 +
|-
 +
|[[Sputter deposition]]
 +
|Metals and dielectrics
 +
|0.1{{ndash}}10{{nbsp}}Å/sec
 +
|50{{ndash}}300ºC
 +
|OK
 +
|Good
 +
|Low
 +
|Good
 +
|5{{ndash}}20{{nbsp}}nm
 +
|More conformal metal and dielectric thin film deposition.  Better than evaporation for maintaining stoichiometry of compounds
 +
|-
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|[[Parylene deposition|CVD Parylene Deposition]]
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|Parylene
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|25{{ndash}}50{{nbsp}}Å/sec
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|20ºC
 +
|Good
 +
|Good
 +
|Very Low
 +
|Good
 +
|unknown
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|Thick (0.8{{ndash}}75{{nbsp}}μm) encapsulation and insulation; Biocompatible
 +
|-
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|[[Plasma enhanced chemical vapor deposition|Plasma Enhanced]]
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[[Plasma enhanced chemical vapor deposition|CVD (PECVD)]]
 +
|Mainly Dielectrics
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|5{{ndash}}200{{nbsp}}Å/sec
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|200{{ndash}}400ºC
 +
|OK
 +
|Good
 +
|Very Low
 +
|Good
 +
|10{{ndash}}100{{nbsp}}nm
 +
|Lower temp oxide/nitride deposition
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|-
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|[[Low pressure chemical vapor deposition|Low Pressure CVD (LPCVD)]]
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|Mainly Dielectrics
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|10{{ndash}}100{{nbsp}}Å/sec
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|600{{ndash}}1200ºC
 +
|Very Good
 +
|Very Good
 +
|Very Low
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|Very Good
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|1{{ndash}}10{{nbsp}}nm
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|Better quality oxide/nitride dep where substrate can handle higher temp
 +
|-
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|[[Thermal oxidation]]
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|Oxide on Silicon
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|0.1{{ndash}}100{{nbsp}}Å/sec
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|900{{ndash}}1200ºC
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|Very Good
 +
|Very Good
 +
|Very Low
 +
|Very Good
 +
|1{{ndash}}10{{nbsp}}nm
 +
|Best quality oxide when substrate can handle higher temp and slower deposition rate
 +
|-
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|[[Electroplating|ECD/Plating]]
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|Conductive Materials
 +
|Depends on process
 +
|0{{ndash}}100ºC
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|Very Good
 +
|Good
 +
|Depends on process
 +
|Depends on process
 +
|Depends on Process
 +
|Thicker films deposition with good conformality
 +
|-
 +
|[[Atomic layer deposition|Atomic Layer Deposition (ALD)]]
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|Metals, metal oxides and nitrides
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|0.1{{ndash}}3{{nbsp}}Å/cycle.  
 +
5{{ndash}}200{{nbsp}}sec cycle
 +
|50{{ndash}}300ºC
 +
|Very Good
 +
|Good
 +
|Low
 +
|Very good
 +
|10{{ndash}}100{{nbsp}}nm
 +
|Very thin, very conformal films such as gate dieletrics, barriers, encapsulation
 +
|}
  
 
===Chemical vapor deposition (CVD)===
 
===Chemical vapor deposition (CVD)===
Chemical vapor deposition (CVD) consists of the substrate being exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit. There are many methods for enhancing the chemical reaction rates of the precursors. The LNF has fourteen [[Low pressure chemical vapor deposition| Low Pressure CVD (LPCVD)]] furnace tubes and five [[Plasma Enhanced Chemical Vapor Deposition| Plasma Enhanced CVD (PECVD)]] chambers. 
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{{main|Chemical vapor deposition}}
  
===Electrodeposition/ Electroplating/ Electrochemical deposition (ECD)===
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In [[chemical vapor deposition]] (CVD), a substrate is typically heated and exposed to one or more gaseous precursors, which decompose and react on the substrate surface to produce the desired thin-film material. CVD can be used to grow high quality and uniform thin films of various materials (mostly insulating or semiconducting).
[https://en.wikipedia.org/wiki/Electroplating Electrodeposition]
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 +
CVD can be subdivided into classifications based on pressure requirements (atmospheric (APCVD), low-pressure (LPCVD), and ultra-high vacuum (UHCVD)). LPCVD is used in the LNF to deposit silicon dioxide, silicon nitride, and doped and undoped polysilicon. It can also be classified based on the mechanism used to decompose the source gas: plasma-enhanced CVD (PECVD) breaks apart gas molecules by application of ionizing voltage, whereas LPCVD and APCVD use elevated temperatures to cause the source gas to decompose.  PECVD is used in the LNF to deposit silicon dioxide, silicon nitride, and amorphous silicon (a-Si:H). Catalytic CVD refers to CVD where the surface reaction is facilitated by the presence of a catalyst material on the substrate, or where the substrate itself is a catalyst for the growth reaction.  [[Carbon nanotubes and graphene]] can be grown by catalytic CVD.  Another type of CVD is metalorganic CVD, which uses organometallic gas precursors to grow III-V and II-VI compound semiconductors such as InP, GaN, AlGaAs, etc. Other example of CVD is the deposition of Parylene, in this case the solid Parylene dimer is evaporated and separated into the monomer by heat and deposited in uniform, pin hole free thin films.
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<!--The LNF has fourteen [[Low pressure chemical vapor deposition| Low Pressure CVD (LPCVD)]] furnace tubes for growing doped and undoped polysilicon, silicon dioxide, and silicon nitride.  It has five [[Plasma enhanced chemical vapor deposition| Plasma Enhanced CVD (PECVD)]] chambers.-->
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===Electroplating===
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{{main|Electroplating}}
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Electroplating (electrodeposition, electrochemical deposition (ECD), plating) is the technique recommended when metal layers of more than a micron of thickness are needed.  It is only available on conductive substrates and for conductive films. It is also the technique of choice when there is no line of sight with the surface to be deposited, for example, the filling of vias in semiconductor processing. The principle is simple: positive ions are attracted to the negative electrode (anode which is the sample in the case of metal deposition), and negative ions travel towards the cathode or positive electrode. ECD is an electrochemical cell, which consists of a cathode, anode, and electrolyte that contains the ion to be deposited. Electrodeposition does not require a vacuum environment and can be done in batch processes, thus making it relatively inexpensive. It creates a thick, durable film whose surface finish can be tailored depending on the requirements.
  
 
===Physical vapor deposition (PVD)===
 
===Physical vapor deposition (PVD)===
[[PVD|Physical vapor deposition (PVD)]] describes a variety of vacuum deposition methods used to deposit thin films by the condensation of a vaporized form of the desired film material onto various substrates.
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{{main|Physical vapor deposition}}
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[[PVD|Physical vapor deposition (PVD)]] Physical vapor deposition (PVD) is a type of deposition where source materials are transformed into a vapor or plasma using a physical process (typically heating or bombardment.) The vapor then moves towards a substrate, usually in a vacuum or inert gas environment, where it condenses on the substrate surface.
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===Thermal Oxidation===
 +
{{main|Thermal oxidation}}
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Thermal oxidation is used to grow very high-quality silicon dioxide on silicon. By exposing silicon to oxygen at very high temperatures (~1000 C), the silicon and oxygen react and form silicon dioxide. Thermal oxidation is typically used to grow silicon dioxide for MOS transistor gates.
  
 
==Figures of merit==
 
==Figures of merit==
  
 
===Deposition rate===
 
===Deposition rate===
The amount of material deposited in units of time, typically expressed in angstroms per second or minute.
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The deposition rate, usually expressed in Å/sec, is measured at the substrate using various methods depending on the type of film deposited. It is in measured real-time in the evaporators and after run completion for other techniques.
 +
===Film Composition===
 +
Also known as stoichiometry and usually expressed in units of atomic % or weight %. The film composition affects film behavior, optical constants, stress, etch rates, and other physical properties like melting point, vapor pressure, etc.
 +
===Refractive index===
 +
It defines the optical properties of a given material for a specific frequency or wavelength of light. Also known as the index of refraction, or n. The refractive index of a film can be measured using [[Ellipsometry]] and also gives clues as to the density, dielectric constant, and stoichiometry of the film <ref name="handbook">Handbook of Thin Film Deposition: Processes and Technologies</ref>.
  
===Refractive index===
+
===Conformality or Step Coverage===
Defines optical properties of a given material for a specific frequency or wavelength of light. Also known as index of refraction n.
+
Step coverage is the measure of how much coating is on the bottom/sidewall of a feature vs. how much coating is on the top/field areas. It is highly dependent on the geometry of the features and the type of deposition chosen. ALD, TEOS, HTO, and thermal oxide are very conformal. LTO, PECVD, sputtering, and evaporation are much less conformal.
  
 
===Film Stress===
 
===Film Stress===
The elastic mismatch between the thin film deposited and the substrate that results in a change in substrate curvature. Residual stress is typically defined by a unit of measurement (MPa) across a given area.
+
It is the elastic mismatch between the thin film deposited and the substrate that results in a change in substrate curvature. Residual stress is typically defined by a unit of measurement (MPa) across a given area.
  
 
===Thermal budget===
 
===Thermal budget===
 +
It is defined as the amount of thermal energy that is transferred to the substrate. The thermal budget is determined by temperature, time-at-temperature and heat transfer to the substrate.  Higher-temperature (and higher-kinetic-energy) methods of deposition tend to have better step coverage/conformality, lower defects, better optical properties and may have lower stress.  However, lower temperatures methods may be needed to account for temperature limitations of the substrate, previously deposited layers and patterning/sacrificial layers.
 +
 +
==References==
 +
<!-- You can define a reference in the text using <ref name="NAME">[link.to.reference text to display]</ref> and it will add a footnote and then put the reference here.-->
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<references />
  
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==Further reading==
  
===Segregation===
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*[http://lnf-wiki.eecs.umich.edu/wiki/User_Resources#LNF_Tech_Talks_.28technology_seminar_series.29 LNF Tech Talk for Deposition is Coming Soon!]
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*Other stuff, e.g. technology workshop slides
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*External links (can be in another section below, if appropriate)
  
[[Category:Etching| ]]
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<!-- Do not add anything below this point besides categories. -->
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[[Category:Deposition| ]]
 
[[Category:Technology]]
 
[[Category:Technology]]

Latest revision as of 08:05, 1 May 2020

Deposition or Growth refers to the controlled synthesis, growth, or transfer of materials as thin films on a substrate. A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. Based on the growth dynamics which prevail during the deposition, the resulting material can be amorphous, polycrystalline, or crystalline. Deposition techniques that result in crystalline material are often referred to as epitaxial growth.

Technologies

Typical technologies include atomic layer deposition (ALD), chemical vapor deposition (CVD), electrodeposition/ electroplating or electrochemical deposition (ECD), physical vapor deposition (PVD), and molecular beam epitaxy (MBE). Selection of deposition technique depends on material deposited, desired film characteristics, and substrate temperature tolerance:

Deposition Method Materials Deposition Rate Substrate Temperature Conformality / Sidewall Coverage Film Density Impurity Levels Uniformity Grain Size Primarily Used for:
Evaporation Metals and Dielectrics 1–15 Å/sec 10–100ºC from dep. 300ºC with heater Poor–None Poor Low Poor 10–100 nm Thicker blanket metal films. Low substrate temp. Directionality means it works well with lift-off patterning
Sputter deposition Metals and dielectrics 0.1–10 Å/sec 50–300ºC OK Good Low Good 5–20 nm More conformal metal and dielectric thin film deposition. Better than evaporation for maintaining stoichiometry of compounds
CVD Parylene Deposition Parylene 25–50 Å/sec 20ºC Good Good Very Low Good unknown Thick (0.8–75 μm) encapsulation and insulation; Biocompatible
Plasma Enhanced

CVD (PECVD)

Mainly Dielectrics 5–200 Å/sec 200–400ºC OK Good Very Low Good 10–100 nm Lower temp oxide/nitride deposition
Low Pressure CVD (LPCVD) Mainly Dielectrics 10–100 Å/sec 600–1200ºC Very Good Very Good Very Low Very Good 1–10 nm Better quality oxide/nitride dep where substrate can handle higher temp
Thermal oxidation Oxide on Silicon 0.1–100 Å/sec 900–1200ºC Very Good Very Good Very Low Very Good 1–10 nm Best quality oxide when substrate can handle higher temp and slower deposition rate
ECD/Plating Conductive Materials Depends on process 0–100ºC Very Good Good Depends on process Depends on process Depends on Process Thicker films deposition with good conformality
Atomic Layer Deposition (ALD) Metals, metal oxides and nitrides 0.1–3 Å/cycle.

5–200 sec cycle

50–300ºC Very Good Good Low Very good 10–100 nm Very thin, very conformal films such as gate dieletrics, barriers, encapsulation

Chemical vapor deposition (CVD)

In chemical vapor deposition (CVD), a substrate is typically heated and exposed to one or more gaseous precursors, which decompose and react on the substrate surface to produce the desired thin-film material. CVD can be used to grow high quality and uniform thin films of various materials (mostly insulating or semiconducting).

CVD can be subdivided into classifications based on pressure requirements (atmospheric (APCVD), low-pressure (LPCVD), and ultra-high vacuum (UHCVD)). LPCVD is used in the LNF to deposit silicon dioxide, silicon nitride, and doped and undoped polysilicon. It can also be classified based on the mechanism used to decompose the source gas: plasma-enhanced CVD (PECVD) breaks apart gas molecules by application of ionizing voltage, whereas LPCVD and APCVD use elevated temperatures to cause the source gas to decompose. PECVD is used in the LNF to deposit silicon dioxide, silicon nitride, and amorphous silicon (a-Si:H). Catalytic CVD refers to CVD where the surface reaction is facilitated by the presence of a catalyst material on the substrate, or where the substrate itself is a catalyst for the growth reaction. Carbon nanotubes and graphene can be grown by catalytic CVD. Another type of CVD is metalorganic CVD, which uses organometallic gas precursors to grow III-V and II-VI compound semiconductors such as InP, GaN, AlGaAs, etc. Other example of CVD is the deposition of Parylene, in this case the solid Parylene dimer is evaporated and separated into the monomer by heat and deposited in uniform, pin hole free thin films.

Electroplating

Main article: Electroplating

Electroplating (electrodeposition, electrochemical deposition (ECD), plating) is the technique recommended when metal layers of more than a micron of thickness are needed. It is only available on conductive substrates and for conductive films. It is also the technique of choice when there is no line of sight with the surface to be deposited, for example, the filling of vias in semiconductor processing. The principle is simple: positive ions are attracted to the negative electrode (anode which is the sample in the case of metal deposition), and negative ions travel towards the cathode or positive electrode. ECD is an electrochemical cell, which consists of a cathode, anode, and electrolyte that contains the ion to be deposited. Electrodeposition does not require a vacuum environment and can be done in batch processes, thus making it relatively inexpensive. It creates a thick, durable film whose surface finish can be tailored depending on the requirements.

Physical vapor deposition (PVD)

Physical vapor deposition (PVD) Physical vapor deposition (PVD) is a type of deposition where source materials are transformed into a vapor or plasma using a physical process (typically heating or bombardment.) The vapor then moves towards a substrate, usually in a vacuum or inert gas environment, where it condenses on the substrate surface.

Thermal Oxidation

Main article: Thermal oxidation

Thermal oxidation is used to grow very high-quality silicon dioxide on silicon. By exposing silicon to oxygen at very high temperatures (~1000 C), the silicon and oxygen react and form silicon dioxide. Thermal oxidation is typically used to grow silicon dioxide for MOS transistor gates.

Figures of merit

Deposition rate

The deposition rate, usually expressed in Å/sec, is measured at the substrate using various methods depending on the type of film deposited. It is in measured real-time in the evaporators and after run completion for other techniques.

Film Composition

Also known as stoichiometry and usually expressed in units of atomic % or weight %. The film composition affects film behavior, optical constants, stress, etch rates, and other physical properties like melting point, vapor pressure, etc.

Refractive index

It defines the optical properties of a given material for a specific frequency or wavelength of light. Also known as the index of refraction, or n. The refractive index of a film can be measured using Ellipsometry and also gives clues as to the density, dielectric constant, and stoichiometry of the film [1].

Conformality or Step Coverage

Step coverage is the measure of how much coating is on the bottom/sidewall of a feature vs. how much coating is on the top/field areas. It is highly dependent on the geometry of the features and the type of deposition chosen. ALD, TEOS, HTO, and thermal oxide are very conformal. LTO, PECVD, sputtering, and evaporation are much less conformal.

Film Stress

It is the elastic mismatch between the thin film deposited and the substrate that results in a change in substrate curvature. Residual stress is typically defined by a unit of measurement (MPa) across a given area.

Thermal budget

It is defined as the amount of thermal energy that is transferred to the substrate. The thermal budget is determined by temperature, time-at-temperature and heat transfer to the substrate. Higher-temperature (and higher-kinetic-energy) methods of deposition tend to have better step coverage/conformality, lower defects, better optical properties and may have lower stress. However, lower temperatures methods may be needed to account for temperature limitations of the substrate, previously deposited layers and patterning/sacrificial layers.

References

  1. Handbook of Thin Film Deposition: Processes and Technologies

Further reading