Difference between revisions of "Substrate bonding"

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[[{{Packaging/Mechanical}}]] is...  
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[[{{PAGENAME}}]] refers to attaching two or more substrates of material such as glass or silicon, to each other by means of various chemical and physical effects. Substrate bonding is mainly used in MEMS, where sensor components are encapsulated in the application. The most common types of bonding are adhesive, anodic, eutectic, fusion, glass frit, direct wafer or fusion bonding, and metallic diffusion.
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==Equipment==
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===SB-6E Bonder===
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{{main|SB-6E Bonder}}
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The SB-6E is primary used for 100mm wafer bonding (no polymers), although it can be configured for 150mm for special circumstances.  
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===EVG 520IS Bonder===
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{{main|EVG 520IS}}
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The EVG 520IS allows bonding (no polymers) on pieces up to 6" wafers.
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===EVG 510 Bonder===
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{{main|EVG 510}}
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The EVG 510 allows polymer bonding on pieces up to 6" wafers
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Substrate bonding refers to attaching two or more substrates of material such as glass or silicon, to each other by means of various chemical and physical effects. Substrate bonding is mainly used in MEMS, where sensor components are encapsulated in the application.  The most common types of bonding are adhesive, anodic, eutectic, fusion, glass frit, direct wafer or fusion bonding, and metallic diffusion.
 
  
 
==Technologies==
 
==Technologies==
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{| class="wikitable"
 
{| class="wikitable"
 
! style="font-weight: bold;" | Bonding method
 
! style="font-weight: bold;" | Bonding method
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! style="font-weight: bold;" | Substrate types
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! style="font-weight: bold;" | Bond materials
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! style="font-weight: bold;" | materials used
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! style="font-weight: bold;" | Temperature range
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! style="font-weight: bold;" | common temperature ranges
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! style="font-weight: bold;" | Pressure range
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! style="font-weight: bold;" | pressure ranges
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! style="font-weight: bold;" | Bond Surface Roughness
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! style="font-weight: bold;" | flatness requirements
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! style="font-weight: bold;" | Hermetic seal
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! style="font-weight: bold;" | hermetic seal
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! style="font-weight: bold;" | Relative bond strength
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! style="font-weight: bold;" | relative bond strength
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! style="font-weight: bold;" | Tool
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! style="font-weight: bold;" | best tool to use
 
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! style="font-weight: bold;" | Primarily Used for:
 
 
|-
 
|-
 
| Adhesive bonding
 
| Adhesive bonding
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| almost any
 
 
| variety of materials including polymers, adhesives, epoxies, dry films, BCB, polyimides, and UV curable compounds
 
| variety of materials including polymers, adhesives, epoxies, dry films, BCB, polyimides, and UV curable compounds
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| 10-100ºC
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| <400ºC
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| Highly directional - no sidewall coverage
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| Low
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| Poor
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|  
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| High
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| Adhesive will reflow to fill voids.
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| Poor
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|  
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| 10-100nm
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| EVG 510, FCB
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| Liftoff metal deposition especially e-beam resists
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|  
 
|-
 
|-
 
| Anodic  
 
| Anodic  
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| Si, ionic glass
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| Si, ionic glass (pyrex)
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| 1-15 Å/sec
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| 180-450ºC
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| 10-100ºC
 
−
| Highly directional - no sidewall coverage
 
−
| Poor
 
 
| Low
 
| Low
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| Poor
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| R<sub>a</sub><1um roughness
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| 10-100nm
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|  
−
| Liftoff or thicker metal deposition
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| Yes
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| SB-6E or EVG 520IS
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|  
 
|-
 
|-
 
| Eutectic  
 
| Eutectic  
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| Si, glass(with adhesion layer)
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| Materials to form eutectic compound
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| 0.1-10 Å/sec
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| 150-400°C
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| 50-300ºC
 
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| Some sidewall coverage
 
−
| Good
 
 
| Low
 
| Low
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| Good
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| Eutectic metal will reflow to fill voids and incorporate particles up to melt thickness.
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| ~10nm
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|
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| More conformal metal and dielectric thin film deposition.  Compounds that do not evaporate while keeping stoichiomettry
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|
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|EVG 520IS or SB-6E
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|  
 
|-
 
|-
 
| Fusion (direct wafer)
 
| Fusion (direct wafer)
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| Si, SiO2
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|Si, silica, quartz, quartz glass, other glasses, compound semiconductors, oxide materials.
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| 5-200Å/sec
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|25-1100°C (prebond in bonder, annealing in separate tool)
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| 200-400ºC
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| Low
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| Some sidewall coverage
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|R<sub>a</sub><40Å
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| Good
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|  
−
| Very Low
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|  
−
| Good
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| EVG 520IS or SB-6E
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| 10-100nm
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|  
−
| Lower temp oxide/nitride deposition
 
 
|-
 
|-
 
| Glass frit
 
| Glass frit
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| Si, SiO2, Si2N4, Al, Ti, Glass
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|  
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| 10-100 Å/sec
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|  
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| 600-1200ºC
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| High
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| Isotropic - good sidewall coverage
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|Can tolerate high surface roughness.
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| Very Good
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|
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| Very Low
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|
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| Very Good
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| EVG 520IS or SB-6E
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| 1-10nm
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|
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| Better quality oxide/nitride dep where substrate can handle higher temp
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|-
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|Thermal Compression
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|
 +
|
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| High
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|  
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|  
 +
|  
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| EVG 520IS
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|  
 
|-
 
|-
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| Metallic diffusion
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|Transient Liquid Phase
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| materials with similar CTE's
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|  
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| Depends on process
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|  
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| 0-100ºC
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| Low
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| Isotropic - good sidewall coverage
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|  
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| Good
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|  
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| Depends on process
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|  
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| Depends on process
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| EVG 520IS or SB-6E
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| Depends on Process
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|  
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| Thicker films deposition with good conformality
 
 
|-
 
|-
 
|}
 
|}
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===Anodic bonding===
 
===Anodic bonding===
 
{{main|Anodic bonding}}
 
{{main|Anodic bonding}}
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This type of bonding involves encapsulating components on a silicon wafer by means of ionic glass.  When ionic glass is heated, it becomes increasingly less insulating.  When a high voltage is applied, current is able to flow which causes the migration of the ions in the glass.
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This type of bonding involves encapsulating components on a silicon wafer by means of ionic glass.  When ionic glass is heated, it becomes increasingly less insulating.  When a high voltage is applied, current is able to flow which causes the migration of the ions in the glass.  The resistance of the ionic glass dramatically decreases with increased temperatures, thus successful bonding can occur through a range of temperatures and voltages depending on your device tolerances.  Altering the surface energy of the substrate materials through plasma activation can also provide some process lattitude depending on your stress, temperature, and voltage tolerances.
  
 
Bond is hermetically sealed and displays good resistance to thermal and chemical effects
 
Bond is hermetically sealed and displays good resistance to thermal and chemical effects
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In order to control reflow of the eutectic material, eutectic bonding requires precise dosing of the bonding force and even temperature distribution.
 
In order to control reflow of the eutectic material, eutectic bonding requires precise dosing of the bonding force and even temperature distribution.
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*High mechanical strength
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*High resistance to thermal and chemical effects
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    High mechanical strength
 
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    High resistance to thermal and chemical effects
 
  
 
===Fusion (direct wafer) bonding===
 
===Fusion (direct wafer) bonding===
 
{{main|Fusion bonding}}
 
{{main|Fusion bonding}}
 
Fusion bonding refers to spontaneous adhesion of two planar substrates. The process involves rinsing the polished discs and rendering them largely hydrophilic, then placing them in contact and tempering them at high temperatures. Plasma pretreatment allows the substrates to be bonded at room temperature.
 
Fusion bonding refers to spontaneous adhesion of two planar substrates. The process involves rinsing the polished discs and rendering them largely hydrophilic, then placing them in contact and tempering them at high temperatures. Plasma pretreatment allows the substrates to be bonded at room temperature.
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*Less process time required
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*Low temperatures protect sensitive components
  
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    Less process time required
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===Glass Frit bonding===
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    Low temperatures protect sensitive components
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{{main|Glass Frit bonding}}
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===Glass frit bonding===
 
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{{main|Glass frit bonding}}
 
 
This process involves screen-printing glass frits onto the bonding surfaces. This results in structures that are subsequently heated and fused when the two substrate surfaces are placed in contact. On cooling, a mechanically stable bond results.  
 
This process involves screen-printing glass frits onto the bonding surfaces. This results in structures that are subsequently heated and fused when the two substrate surfaces are placed in contact. On cooling, a mechanically stable bond results.  
  
 
Low production costs
 
Low production costs
  
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===Technology 6===
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===Thermal Compression bonding===
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{{main|Metallic diffusion bonding}}
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{{main|Thermal Compression bonding}}
 
Metal diffusion bonding is based on Cu-Cu, Al-Al, Au-Au and other metallic bonds. In addition, the use of metal diffusion allows two wafers to be bonded both mechanically and electrically in a single step. The technique is required for bonding in 3D applications such as 3D stacking.  
 
Metal diffusion bonding is based on Cu-Cu, Al-Al, Au-Au and other metallic bonds. In addition, the use of metal diffusion allows two wafers to be bonded both mechanically and electrically in a single step. The technique is required for bonding in 3D applications such as 3D stacking.  
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*Highest level of impermeability among all common bonding processes
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    Highest level of impermeability among all common bonding processes
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*High alignment precision following bonding
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    High alignment precision following bonding
 
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==Figures of Merit==
 
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What is important to look for in the technology? Etch/dep rate? Resolution?
 
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===FOM 1===
 
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Subheadings are optional.
 
  
 
==Applications==
 
==Applications==
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How is this technology used in nanofabrication and what types of devices/research areas is it useful in?
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{{expand section}}
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*End of process packaging
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==Equipment==
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*Hermetic Sealing
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<!-- This section may be dropped if the group is very broad -->
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*Bonding Sensor and IC chips
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Specific equipment for each technology can be found on its page above.  Additionally, below is a list of all metrology equipment in the LNF:
 
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<categorytree mode=pages>{{PAGENAME}} equipment</categorytree>
 
  
 
==See also==
 
==See also==
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<references />
 
<references />
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Madou, Marc J (2012), Fundamentals of Microfabrication and Nanotechnology, Volume III
  
 
==Further reading==
 
==Further reading==
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* Other stuff, e.g. technology workshop slides
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*[[User_Resources#LNF_Tech_Talks_.28technology_seminar_series.29 | LNF Tech Talk for Wafer bonding]]
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* External links (can be in another section below, if appropriate)
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*[https://drive.google.com/file/d/0B3k-qgz56T_4S0tKV2FmUFY3VkE/view?usp=sharing&resourcekey=0--x01H8LfpZ-j0D60Gpwp8w Handbook of Wafer Bonding]
  
 
<!-- Do not add anything below this point besides categories. -->
 
<!-- Do not add anything below this point besides categories. -->
 
[[Category:{{PAGENAME}}| ]]
 
[[Category:{{PAGENAME}}| ]]
 
[[Category:Technology]]
 
[[Category:Technology]]

Latest revision as of 14:46, 12 November 2021

Substrate bonding refers to attaching two or more substrates of material such as glass or silicon, to each other by means of various chemical and physical effects. Substrate bonding is mainly used in MEMS, where sensor components are encapsulated in the application. The most common types of bonding are adhesive, anodic, eutectic, fusion, glass frit, direct wafer or fusion bonding, and metallic diffusion.

Equipment

SB-6E Bonder

Main article: SB-6E Bonder

The SB-6E is primary used for 100mm wafer bonding (no polymers), although it can be configured for 150mm for special circumstances.

EVG 520IS Bonder

Main article: EVG 520IS

The EVG 520IS allows bonding (no polymers) on pieces up to 6" wafers.

EVG 510 Bonder

Main article: EVG 510

The EVG 510 allows polymer bonding on pieces up to 6" wafers



Technologies

There are 7 primary methods which define substrate bonding technology. These have been mentioned above and are described in detail below.

Bonding method Bond materials Temperature range Pressure range Bond Surface Roughness Hermetic seal Relative bond strength Tool
Adhesive bonding variety of materials including polymers, adhesives, epoxies, dry films, BCB, polyimides, and UV curable compounds <400ºC Low Adhesive will reflow to fill voids. EVG 510, FCB
Anodic Si, ionic glass (pyrex) 180-450ºC Low Ra<1um roughness Yes SB-6E or EVG 520IS
Eutectic Materials to form eutectic compound 150-400°C Low Eutectic metal will reflow to fill voids and incorporate particles up to melt thickness. EVG 520IS or SB-6E
Fusion (direct wafer) Si, silica, quartz, quartz glass, other glasses, compound semiconductors, oxide materials. 25-1100°C (prebond in bonder, annealing in separate tool) Low Ra<40Å EVG 520IS or SB-6E
Glass frit High Can tolerate high surface roughness. EVG 520IS or SB-6E
Thermal Compression High EVG 520IS
Transient Liquid Phase Low EVG 520IS or SB-6E

Adhesive bonding

Main article: Adhesive bonding

Uses a layer of polymer or adhesive, including epoxies, dry films, BCB, polyimides, and UV curable compounds between the substrates to bond the substrates together. This introduces a foreign material between your substrates, but there is a wide variety of materials that can make this method desirable for it's extremely wide range of temperature and control.

Relatively low temperatures help protect sensitive components

Anodic bonding

Main article: Anodic bonding

This type of bonding involves encapsulating components on a silicon wafer by means of ionic glass. When ionic glass is heated, it becomes increasingly less insulating. When a high voltage is applied, current is able to flow which causes the migration of the ions in the glass. The resistance of the ionic glass dramatically decreases with increased temperatures, thus successful bonding can occur through a range of temperatures and voltages depending on your device tolerances. Altering the surface energy of the substrate materials through plasma activation can also provide some process lattitude depending on your stress, temperature, and voltage tolerances.

Bond is hermetically sealed and displays good resistance to thermal and chemical effects Very reliable bond, probably the most forgiving with substrate flatness

Eutectic bonding

Main article: Eutectic bonding

Eutectic wafer bonding takes advantage of the special properties of eutectic metals. Similar to soldering alloys, such metals melt already at low temperatures. This property allows planar surfaces to be achieved.

In order to control reflow of the eutectic material, eutectic bonding requires precise dosing of the bonding force and even temperature distribution.

  • High mechanical strength
  • High resistance to thermal and chemical effects

Fusion (direct wafer) bonding

Main article: Fusion bonding

Fusion bonding refers to spontaneous adhesion of two planar substrates. The process involves rinsing the polished discs and rendering them largely hydrophilic, then placing them in contact and tempering them at high temperatures. Plasma pretreatment allows the substrates to be bonded at room temperature.

  • Less process time required
  • Low temperatures protect sensitive components

Glass Frit bonding

Main article: Glass Frit bonding

This process involves screen-printing glass frits onto the bonding surfaces. This results in structures that are subsequently heated and fused when the two substrate surfaces are placed in contact. On cooling, a mechanically stable bond results.

Low production costs

Thermal Compression bonding

Main article: Thermal Compression bonding

Metal diffusion bonding is based on Cu-Cu, Al-Al, Au-Au and other metallic bonds. In addition, the use of metal diffusion allows two wafers to be bonded both mechanically and electrically in a single step. The technique is required for bonding in 3D applications such as 3D stacking.

  • Highest level of impermeability among all common bonding processes
  • High alignment precision following bonding

Applications

  • End of process packaging
  • Hermetic Sealing
  • Bonding Sensor and IC chips

See also

Other related wiki pages

References

Madou, Marc J (2012), Fundamentals of Microfabrication and Nanotechnology, Volume III

Further reading

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