Difference between revisions of "Reactive ion etching"

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Reactive Ion Etching (RIE) is a high resolution mechanism for etching materials. Samples are first masked by one of many patterning processes. They are then placed into a vacuum chamber. Gases are introduced into the chamber and then activated by Rf or microwave power to create a plasma. This plasma consists of a wide variety of reactive species, ions, and electrons. A negative DC bias is induced at the substrate by the free electrons. This bias accelerates ions in the plasma perpendicular to the sample surface. This provides a directional physical motivating force to the etch. Generally some form of passivating component is incorporated such that the etch proceeds only where energetic ions strike the surface. A well tuned etch can be very [[Isotropy|anisotropic]] compared to [[:Category:Wet Bench|wet etches]] which are typically isotropic.
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{{Infobox technology
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|image = Rieoperation.svg
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|technology = Plasma etching
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|names = RIE
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|equipment = [[:Category:RIE equipment|List of RIE equipment]]
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}}
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Reactive ion etching (RIE) is a high resolution mechanism for [[etching]] materials using [[Plasma etching|reactive gas discharges]]. It is a highly controllable process that can process a wide variety of materials, including [[semiconductors]], [[dielectrics]] and some [[Reactive metals|metals]]. One major advantage to RIE over other forms of etching is that the process can be designed to be highly [[Isotropy|anisotropic]], allowing for much finer resolution and higher aspect ratios.  For a detailed overview of RIE, please review the [https://drive.google.com/file/d/0B76AgohVTgqdamFiaE1mRk9mVmM/view?usp=sharing&resourcekey=0-yGk7A8kAmb0kQArcKPNlTQ technology workshop].
  
RIE is a key enabling semiconductor technology allowing IC processes to continue to approach the range of a few nanometers. This same technology may be used as a machining process for nano and micro scale devices. As such, RIE is also key enabling technology for MEMS and nanofabrication.
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{{TOC|limit=2|clear=left}}
  
==Technology Overview/Workshop Presentation==
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==Equipment==
* [https://docs.google.com/a/lnf.umich.edu/file/d/0B76AgohVTgqdamFiaE1mRk9mVmM/preview RIE Workshop January 16th, 2015]
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Below is a general description of the RIE equipment at the LNF.  For a complete list, please see [[:Category:RIE equipment|list of RIE equipment]].
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<onlyinclude>
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===P5000 RIE===
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{{main|P5000 RIE}}
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The P5000 is a 3 chamber tool designed for production etching. Chambers A and B are configured for SiO<sub>2</sub> and Si<sub>3</sub>N<sub>4</sub> etching, where as chamber C is configured for [[polysilicon]] and amorphous silicon etching.  Chambers B and C are restricted to [[CMOS clean]] devices where as chamber A is open to [[semi-clean]] devices.
  
==Plasma Generation==
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===STS APS DGRIE===
===Capacitively Coupled Plasma===
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{{main|STS Glass Etcher}}
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The glass etcher excels at deep etching of [[Fused silica|fused silica]] but it also has a nearly vertical [[silicon dioxide|SiO<sub>2</sub>]] etch.  It's capable of very high bias powers enabling it to process difficult to etch materials.
  
===Inductively Coupled Plasma===
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===LAM 9400 SE===
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{{main|LAM 9400}}
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The LAM 9400 SE is an [[ICP]] etcher configured with a wide range of gas chemistries.  It is mainly used to etch [[polysilicon]] but can also etch [[silicon dioxide|SiO<sub>2</sub>]], [[silicon nitride|Si<sub>3</sub>N<sub>4</sub>]], [[compound semiconductors]], some [[Reactive metals|metals]], and [[polymers|organic]] materials.
  
===Downstream Plasma===
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===Oxford Plasmalab System 100===
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{{main|Oxford Plasmalab System 100}}
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The oxford is another ICP etcher that also has a [[cryogenic etching|cryogenic]] chuck.  By cooling the sample down to -150°C nearly vertical etches are possible in certain materials.
  
==Deep Reactive Ion Etching==
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===Plasmatherm 790===
{{Main|:Category:DRIE|}}
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{{main|Plasmatherm 790}}
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The Plasmatherm is configured with a variety of gases so that it can etch a wide array of materials.  Most recipes tend to have slow etch rates on the order of 200 Å/min which is ideal for very thin films.  The tool also has few material restrictions to allow it to process as many things as possible.</onlyinclude>
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==Deep reactive ion etching==
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{{main|Deep reactive ion etching}}
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Deep reactive ion etching (DRIE), while often referring specifically to the [[Wikipedia:Bosch process|Bosch process]], generally is any RIE used to etch high aspect ratio (> 10:1) features.  This may be simply a longer, well controlled RIE etch, or may use a specific process such as [[cryogenic etching]] or the [[Wikipedia:Bosch process|Bosch process]].  For all DRIE equipment at the LNF, please refer to the [[:Category:DRIE equipment|list of DRIE equipment]].
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{{:Deep reactive ion etching}}
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==Method of operation==
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Samples are first masked by one of many patterning processes.  They are then placed into a vacuum chamber.  Gases are introduced into the chamber and then activated by RF or microwave power to create a plasma consisting of a wide variety of reactive species, ions, and electrons.  The reactive species are chosen for their ability to react chemically with the material being etched.  A negative DC bias is induced at the substrate by the free electrons which accelerates the ions towards the sample surface. The energy imparted by these ions reaching the surface greatly enhances the effectiveness of the chemical reaction and provides directionality to the etch.  Generally some form of [[Etch passivation|passivating]] component is incorporated such that the etch proceeds only where energetic ions strike the surface.
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==Parameters==
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Many of the same parameters used in [[Plasma etching#Parameters|plasma etching]] apply to RIE, including pressure, gas composition, and generator power.  Of particular importance is the [[plasma generation]] method (commonly a parallel plate or ICP configuration), as they have different advantages depending on the material being etched.
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===DC bias===
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A critical parameter specific to RIE is the DC bias applied to the sample, which directly affects the physicality of the etch.  Many materials (e.g. [[silicon dioxide|SiO<sub>2</sub>]]) require high activation energy to react with the gases in the reactor.  Other materials ([[silicon]], in particular) may be etched using a passivating component which must be removed on the surface being etched.  Still other materials have little to no reactivity and must be physically removed from the surface.
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In most reactors, DC bias is not controlled directly, but will depend on the conductance of the plasma and the power applied to the sample.
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<!--
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==Materials==
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RIE can be used to etch a wide variety of materials, including dielectrics, semiconductors, polymers, and some metals.  For information on etching specific materials, please review the sections below.
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===Dielectric etching===
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{{main|Dielectric plasma etching}}
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not sure if I like where this is going... <I have to agree, I think you should save this for tool pages>
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-->
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==Complete tool list==
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<categorytree mode="pages">RIE equipment</categorytree>
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==See also==
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*[[Plasma etching]]
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*[[Plasma processing]]
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<!--
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==Notes==
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<footnotes>
  
 
==References==
 
==References==
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<reflist />
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-->
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==Further reading==
  
{{quote|text=Reactive-ion etching (RIE) is an etching technology used in microfabrication. It uses chemically reactive plasma to remove material deposited on wafers. The plasma is generated under low pressure (vacuum) by an electromagnetic field. High-energy ions from the plasma attack the wafer surface and react with it.|source=[[wikipedia:Reactive-ion_etching|Wikipedia]]}}
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*[http://lnf-wiki.eecs.umich.edu/wiki/User_Resources#LNF_Tech_Talks_.28technology_seminar_series.29 LNF Tech Talk for RIE]
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*[https://docs.google.com/document/d/1L5g-WyoX10ZDYI9IKdeGb32dLsOeVUgFD01yvKdj544/edit Etching nano features with SF<sub>6</sub>ːO<sub>2</sub> plasma]
  
[[Category:Equipment]]
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[[Category:RIE| ]]

Latest revision as of 12:36, 26 October 2021

Reactive ion etching
Rieoperation.svg
Technology Details
Other Names RIE
Technology Plasma etching
Equipment List of RIE equipment

Reactive ion etching (RIE) is a high resolution mechanism for etching materials using reactive gas discharges. It is a highly controllable process that can process a wide variety of materials, including semiconductors, dielectrics and some metals. One major advantage to RIE over other forms of etching is that the process can be designed to be highly anisotropic, allowing for much finer resolution and higher aspect ratios. For a detailed overview of RIE, please review the technology workshop.

Equipment

Below is a general description of the RIE equipment at the LNF. For a complete list, please see list of RIE equipment.

P5000 RIE

Main article: P5000 RIE

The P5000 is a 3 chamber tool designed for production etching. Chambers A and B are configured for SiO2 and Si3N4 etching, where as chamber C is configured for polysilicon and amorphous silicon etching. Chambers B and C are restricted to CMOS clean devices where as chamber A is open to semi-clean devices.

STS APS DGRIE

Main article: STS Glass Etcher

The glass etcher excels at deep etching of fused silica but it also has a nearly vertical SiO2 etch. It's capable of very high bias powers enabling it to process difficult to etch materials.

LAM 9400 SE

Main article: LAM 9400

The LAM 9400 SE is an ICP etcher configured with a wide range of gas chemistries. It is mainly used to etch polysilicon but can also etch SiO2, Si3N4, compound semiconductors, some metals, and organic materials.

Oxford Plasmalab System 100

The oxford is another ICP etcher that also has a cryogenic chuck. By cooling the sample down to -150°C nearly vertical etches are possible in certain materials.

Plasmatherm 790

Main article: Plasmatherm 790

The Plasmatherm is configured with a variety of gases so that it can etch a wide array of materials. Most recipes tend to have slow etch rates on the order of 200 Å/min which is ideal for very thin films. The tool also has few material restrictions to allow it to process as many things as possible.

Deep reactive ion etching

Deep reactive ion etching (DRIE), while often referring specifically to the Bosch process, generally is any RIE used to etch high aspect ratio (> 10:1) features. This may be simply a longer, well controlled RIE etch, or may use a specific process such as cryogenic etching or the Bosch process. For all DRIE equipment at the LNF, please refer to the list of DRIE equipment.

STS Pegasus

Main articles: STS Pegasus 4 and STS Pegasus 6

The STS Pegasus is a tool that utilizes the Bosch process for high aspect ratio etching of silicon. It uses SF6 for the etch step and C4F8 for passivation. It can achieve etch rates of up to 20 μm/min and aspect ratios up to 50:1.

STS Glass Etcher

Main article: STS Glass Etcher

The STS Glass Etcher is a DGRIE tool for high aspect ratio etching of silicon dioxide, glass, and fused silica.

Oxford ICP

The Oxford Plasmalab is an ICP RIE system capable of cryogenic etching. While not configured to etch silicon, it can etch compound semiconductors and perform a cryogenic etch of polymers.

Method of operation

Samples are first masked by one of many patterning processes. They are then placed into a vacuum chamber. Gases are introduced into the chamber and then activated by RF or microwave power to create a plasma consisting of a wide variety of reactive species, ions, and electrons. The reactive species are chosen for their ability to react chemically with the material being etched. A negative DC bias is induced at the substrate by the free electrons which accelerates the ions towards the sample surface. The energy imparted by these ions reaching the surface greatly enhances the effectiveness of the chemical reaction and provides directionality to the etch. Generally some form of passivating component is incorporated such that the etch proceeds only where energetic ions strike the surface.

Parameters

Many of the same parameters used in plasma etching apply to RIE, including pressure, gas composition, and generator power. Of particular importance is the plasma generation method (commonly a parallel plate or ICP configuration), as they have different advantages depending on the material being etched.

DC bias

A critical parameter specific to RIE is the DC bias applied to the sample, which directly affects the physicality of the etch. Many materials (e.g. SiO2) require high activation energy to react with the gases in the reactor. Other materials (silicon, in particular) may be etched using a passivating component which must be removed on the surface being etched. Still other materials have little to no reactivity and must be physically removed from the surface.

In most reactors, DC bias is not controlled directly, but will depend on the conductance of the plasma and the power applied to the sample.


Complete tool list

See also

Further reading