CAIBE (Oxford Ion Mill): Difference between revisions
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|picture= |
|picture=CAIBE.jpg |
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|type = Dry Etch |
|type = Dry Etch |
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|super= |
|super= Bill Millerski |
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|super2= Lee Sawyer |
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|phone= 805-893-3918x210 |
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|location=Bay |
|location=Bay 2 |
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|description = CAIBE (Chemically Assisted Ion Beam Etcher) |
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|email=lingg@ece.ucsb.edu |
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|manufacturer = Oxford Instruments |
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|description = RIE #3 Fluorine-Based System MRC 51 |
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|model = Ionfab 300 Plus |
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|manufacturer = Materials Research Corporation (MRC) |
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|materials = |
|materials = Various |
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|toolid= |
|toolid=58 |
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}} |
}} |
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==About== |
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This is an Oxford Instruments PlasmaLab 300 IBE/RIBE/CAIBE system used for ion beam etching of a variety of materials including metals, oxides, semiconductors. Ion beam etching (IBE) allows control of sidewall etch profiles by tilting and rotating the sample during the etch. Reactive chemistry ("Chemically Assisted Ion Beam Etching", CAIBE) can be used, when appropriate, to enhance the etch rate of materials, such as oxides, polymers, and semiconductors. |
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This is a Materials Research Corporation RIE-51 parallel plate, 13.56 MHz system used for etching with fluorine-containing gases (CF<sub>4</sub>, SF<sub>6</sub>, and CHF<sub>3</sub>). The system is used primarily for etching of Si, SiO<sub>2</sub>, and Si<sub>3</sub>N<sub>4</sub> films. Metals such as tungsten may also be etched. Tool features include: six inch diameter water cooled cathode/substrate platform, pyrex cylinder for plasma confinement and gas flow control, adjustable cathode-anode spacing, fixed DC bias or RF power control and a HeNe laser etch monitor with chart recorder. It is turbo pumped and has no loadlock. |
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This system is used to physically ion beam etch noble and inert metals with Ar ion milling, and to etch other materials that react with chlorine, fluorine, or oxygen using a reactive ion beam. The ion beam is generated in a 15cm diameter 3-grid ion source manufactured by Oxford. The Ion beam voltage & current control the etch rate. Beam voltage (related to ion energy) affects the sputter yield (atoms etched per incident ion) and Ion beam current controls the flux of ions (number of ions in the beam). Etch rate should be roughly linear with beam current. Neutralizing electrons are generated by a plasma bridge neutralizer (PBN) so that samples are not charged by ions during the etch. Samples can be cooled to 5°C or heated to 300°C for etching. He back-side cooling is used to transfer heat from(to) the sample to(from) the cooled(heated) platen. |
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CF<sub>4</sub>/O<sub>2</sub> and SF<sub>6</sub>/O<sub>2</sub> will etch Si, SiO<sub>2</sub> and Si<sub>3</sub>N<sub>4</sub> readily since free fluorine is readily liberated in the plasma. The oxygen (up to 40%) initially enhances the fluorine concentration resulting in a higher etch rate. The oxygen also minimizes polymer formation in CF<sub>4</sub>/O<sub>2</sub>. Too much Oxygen will compete for fluorine available, suppressing the etch rate. Argon can be added to increase the physical component of etching. The highest etch rates are achieved with SF<sub>6</sub> due to the ease of liberating fluorine compared with CF<sub>4</sub>. The relative etch rate decreases as one goes from Si to Si<sub>3</sub>N<sub>4</sub> to SiO<sub>2</sub>. CF4/H<sub>2</sub> and CHF3 can be used to selectivity etch SiO<sub>2</sub> over Si and resist due to increased polymer formation from the presence of hydrogen. This polymer layer is thicker on Si and resist than on SiO<sub>2</sub>. The trade-off is selectivity versus sidewall profile as the polymer will result in a tapered wall profile. Also, the polymer can be difficult to remove after etching. |
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===Cluster Configuration=== |
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The etches have good selectivity to many metals and semiconductors such as Ni, Al, Cr, Ti, GaAs, InP, and GaN. The system generally produces anisotropic etch profiles unless one goes into a purely chemical fluorine etch mode with higher pressure SF<sub>6</sub> processes. The system also has a strong loading effect so that larger substrates and open areas will require more feed gas and higher pressure to compensate. As a result, individual processes need to be characterized. |
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The Ion Mill system is clustered with 2 Oxford ALD systems, allowing the process flexibility of etching followed by ALD passivation or metalization without breaking vacuum. |
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*Chamber #1: [[Atomic Layer Deposition (Oxford FlexAL)|ALD Metal Films only]] |
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*Chamber #2: [[CAIBE (Oxford Ion Mill)|CAIBE Oxford Ion Mill]] (this page) |
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*Chamber #3: [[Atomic Layer Deposition (Oxford FlexAL)|ALD Dielectrics Films only]] |
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*13.56 Mhz excitation frequency |
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*Manual gas control |
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*Automatic pressure control |
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*Manual RF tuning network |
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*Timer circuit for stopping the plasma |
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*HeNe laser monitoring for etch stop |
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*Sample size limited to approximately 4 inches |
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*Masking materials include: Ni, photoresist (limited to low bias/power), Cr, Al |
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*Cl<sub>2</sub> available in CAIBE mode (Cl2 not entering ion gun) through a gas ring. |
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*RIBE (reactive gas entering ion gun during RF discharge) mode for all reactive gases |
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*15cm ion-gun with PBN neutralizer |
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*Angled etch control from 0 degrees (normal incidence) to 75 degrees. |
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*Sample Rotated or fixed at controlled position for etching. |
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*Vb from 50V to over 1000V |
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*Ib up to 500mA |
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*He-backside cooling |
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*Substrate temperature 5C to 300C |
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*Sample sizes: |
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**6" wafer (no carrier needed) |
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**4" wafer mount with backside Helium cooling ports |
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**2" wafer mount with backside Helium cooling ports |
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**35mm square pieces or smaller, mount with backside Helium cooling ports |
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*Clustered through vacuum chambers with ALD systems. |
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*Masking material depends on material being etched and etch gas used |
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==Recipes== |
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*[[media:RIE 3 Operationing instructions.pdf|Operating Instructions]] |
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Recipes can be found on the [https://wiki.nanotech.ucsb.edu/w/index.php?title=Other_Dry_Etching_Recipes#CAIBE_.28Oxford_Ion_Mill.29 '''CAIBE Recipes Page''']. |
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*[https://wiki.nanotech.ucsb.edu/w/images/4/40/Oxford_Cluster_Tool_Operating_Instructions_Rev_B.pdf Cluster Operating Instructions] - same instructions as ALD, except for the '''following difference''': |
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**''Make sure to securely attach your samples to the platens with clips, since the holder will be angled and rotated!'' ''6-inch wafers can be loaded as-is.'' |
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*[https://wiki.nanofab.ucsb.edu/w/images/4/4d/Oxford_Ion_Mill_SOP.pdf Ion Mill SOP] |
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*[//wiki.nanotech.ucsb.edu/wiki/images/7/75/Ion_Beam_Etch_Overview_rev1.pdf Additional Documentation] |
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Latest revision as of 16:47, 21 December 2023
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About
This is an Oxford Instruments PlasmaLab 300 IBE/RIBE/CAIBE system used for ion beam etching of a variety of materials including metals, oxides, semiconductors. Ion beam etching (IBE) allows control of sidewall etch profiles by tilting and rotating the sample during the etch. Reactive chemistry ("Chemically Assisted Ion Beam Etching", CAIBE) can be used, when appropriate, to enhance the etch rate of materials, such as oxides, polymers, and semiconductors.
This system is used to physically ion beam etch noble and inert metals with Ar ion milling, and to etch other materials that react with chlorine, fluorine, or oxygen using a reactive ion beam. The ion beam is generated in a 15cm diameter 3-grid ion source manufactured by Oxford. The Ion beam voltage & current control the etch rate. Beam voltage (related to ion energy) affects the sputter yield (atoms etched per incident ion) and Ion beam current controls the flux of ions (number of ions in the beam). Etch rate should be roughly linear with beam current. Neutralizing electrons are generated by a plasma bridge neutralizer (PBN) so that samples are not charged by ions during the etch. Samples can be cooled to 5°C or heated to 300°C for etching. He back-side cooling is used to transfer heat from(to) the sample to(from) the cooled(heated) platen.
Cluster Configuration
The Ion Mill system is clustered with 2 Oxford ALD systems, allowing the process flexibility of etching followed by ALD passivation or metalization without breaking vacuum.
- Chamber #1: ALD Metal Films only
- Chamber #2: CAIBE Oxford Ion Mill (this page)
- Chamber #3: ALD Dielectrics Films only
Detailed Specifications
- Etch gases include: CF4, Cl2, Ar, O2
- Cl2 available in CAIBE mode (Cl2 not entering ion gun) through a gas ring.
- RIBE (reactive gas entering ion gun during RF discharge) mode for all reactive gases
- Low 1 E -7 Torr ultimate chamber pressure, etch pressure ~1 E-4 Torr
- 15cm ion-gun with PBN neutralizer
- Angled etch control from 0 degrees (normal incidence) to 75 degrees.
- Sample Rotated or fixed at controlled position for etching.
- Vb from 50V to over 1000V
- Ib up to 500mA
- He-backside cooling
- Substrate temperature 5C to 300C
- Sample sizes:
- 6" wafer (no carrier needed)
- 4" wafer mount with backside Helium cooling ports
- 2" wafer mount with backside Helium cooling ports
- 35mm square pieces or smaller, mount with backside Helium cooling ports
- Clustered through vacuum chambers with ALD systems.
- Masking material depends on material being etched and etch gas used
Recipes
Recipes can be found on the CAIBE Recipes Page.
Procedures & Documentation
- Cluster Operating Instructions - same instructions as ALD, except for the following difference:
- Make sure to securely attach your samples to the platens with clips, since the holder will be angled and rotated! 6-inch wafers can be loaded as-is.