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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 which that result in crystalline material are often referred to as epitaxial growth.
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:
{| class="wikitable sortable"
! style="font-weight: bold;" | Deposition Method! style="font-weight: bold;" | Materials! style="font-weight: bold;" | Deposition Rate! style="font-weight: bold;" | Substrate Temperature! style="font-weight: bold;" | Conformality / Sidewall Coverage! style="font-weight: bold;" | Film Density! style="font-weight: bold;" | Impurity Levels! style="font-weight: bold;" | Uniformity! style="font-weight: bold;" | Grain Size! style="font-weight: bold;" | Primarily Used for:
| [[Evaporation]]| Metals and Dielectrics| 1{{ndash}}15{{nbsp}}Å/sec| 10{{ndash}}100ºC from dep. 300ºC with heater| Poor{{ndash}}None| Poor| Low| Poor| 10{{ndash}}100{{nbsp}}nm| Thicker blanket metal films. Low substrate temp. Works well with liftoff 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
| [[Parylene deposition| CVD Parylene Deposition]]| Parylene| 25{{ndash}}50{{nbsp}}Å/sec| 20ºC| Good| Good| Very Low| Good| unknown| Thick (0.8{{ndash}}75{{nbsp}}μm) encapsulation and insulation; Biocompatible
| [[Plasma enhanced chemical vapor deposition| Plasma Enhanced ]] [[Plasma enhanced chemical vapor deposition|CVD (PECVD)]]| Mainly Dielectrics| 5{{ndash}}200{{nbsp}}Å/sec| 200{{ndash}}400ºC| OK| Good| Very Low| Good| 10{{ndash}}100{{nbsp}}nm| Lower temp oxide/nitride deposition
| [[Low pressure chemical vapor deposition| Low Pressure CVD (LPCVD)]]| Mainly Dielectrics| 10{{ndash}}100{{nbsp}}Å/sec| 600{{ndash}}1200ºC| Very Good| Very Good| Very Low| Very Good| 1{{ndash}}10{{nbsp}}nm| Better quality oxide/nitride dep where substrate can handle higher temp
| [[Thermal oxidation]]| Oxide on Silicon| 0.1{{ndash}}100{{nbsp}}Å/sec| 900{{ndash}}1200ºC| 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
| [[Electroplating|ECD/Plating]]| Conductive Materials| Depends on process| 0{{ndash}}100ºC| 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)]]| Metals, metal oxides and nitrides| 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
{{main|Chemical vapor deposition}}
{{missing information|Parylene deposition}}
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, materials).
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.
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)===
===Thermal Oxidation===
{{main|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===
Deposition 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. Usually and usually expressed in units of atomic % or weight %. Film The film composition affects film behavior, optical constants, stress, etch rates, and other physical properties like melting point, vapor pressure, etc.
===Refractive index===
Defines 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>.
===Conformality or Step Coverage===
===Film Stress===
The 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===
Defined It is defined as the amount of thermal energy that is transfered 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 will 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.
==Further reading==
*[ LNF Tech Talk for Deposition is Coming Soon!]
* Other stuff, e.g. technology workshop slides* External links (can be in another section below, if appropriate)
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[[Category:Deposition| ]]
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