Specific Process Knowledge/Etch/IBE⁄IBSD Ionfab 300/IBE process trends: Difference between revisions
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'''Feedback to this page''': '''[mailto:labadviser@ | '''Feedback to this page''': '''[mailto:labadviser@nanolab.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.nanolab.dtu.dk/index.php/Specific_Process_Knowledge/Etch/IBE⁄IBSD_Ionfab_300/IBE_process_trends click here]''' | ||
=Some general process trends= | =Some general process trends= | ||
This page is supposed to gather some general process trends and good | This page is supposed to gather some general process trends and good advice for designing IBE recipes. So far these trends has been developed etching Si with resist as masking material and by etching some multilayered films. The work has been done by ''Kristian Hagsted Rasmussen @ nanolab before 2012'' | ||
==Etch rate== | ==Etch rate== | ||
| Line 18: | Line 18: | ||
|Beam current * Beam voltage | |Beam current * Beam voltage | ||
|- | |- | ||
|not significantly | |not significantly affected by | ||
|Stage angle | |Stage angle | ||
|- | |- | ||
|not significantly | |not significantly affected by | ||
|Accelerator voltage | |Accelerator voltage | ||
|- | |- | ||
| Line 41: | Line 41: | ||
|Accelerator voltage * Stage angle | |Accelerator voltage * Stage angle | ||
|- | |- | ||
|not significantly | |not significantly affected by | ||
|Beam voltage | |Beam voltage | ||
|- | |- | ||
| Line 48: | Line 48: | ||
==Rotation speed== | ==Rotation speed== | ||
The rotation is activated to get a good uniformity over the wafer. The minimum number of rotations to get a good uniformity is 100 rotations for the whole etch. the maximum rotation speed is | The rotation is activated to get a good uniformity over the wafer. The minimum number of rotations to get a good uniformity is 100 rotations for the whole etch. the maximum rotation speed is 20 rpm. That means that an etch shorter that 5 min cannot obtain a very good uniformity. | ||
{| border="2" cellspacing="2" cellpadding="3" | {| border="2" cellspacing="2" cellpadding="3" | ||
!Etch Length [min] | !Etch Length [min] | ||
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|- | |- | ||
|} | |} | ||
<br clear="all" /> | |||
=General tips for finding etching parameters (given by Oxford Instruments)= | =General tips for finding etching parameters (given by Oxford Instruments [https://plasma.oxinst.com/products/ion-beam/ionfab], used with permission)= | ||
One thing to remember is that the etch rate varies linearly with beam current while it varies exponentially with beam voltage. | One thing to remember is that the etch rate varies linearly with beam current while it varies exponentially with beam voltage. | ||
*Beam voltage – depends on application, 200-800eV. | *Beam voltage – depends on application, 200-800eV. | ||
*Always have neutraliser current 20% extra of the beam current value. | *Always have neutraliser current 20% extra of the beam current value. | ||
*Accelerator voltage between 100V –500V, adjust to get Ia < 10% Ib ('''it helps protect electronics and power supplies'''). | *Accelerator voltage between 100V –500V, adjust to get Ia (beam accelerator current) < 10% Ib (bean current) ('''it helps protect electronics and power supplies'''). | ||
*The real beam current is effectively the beam current minus accelerator current. | *The real beam current is effectively the beam current minus accelerator current. | ||
*Varying Ar flow for source gas as well as beam current will have an effect on the accelerator current. | *Varying Ar flow for source gas as well as beam current will have an effect on the accelerator current. | ||
| Line 95: | Line 96: | ||
*A guide to optimize etch uniformity is as follows: | *A guide to optimize etch uniformity is as follows: | ||
#Set beam energy —a rough guide is, the higher the energy the rougher the surface as seen on an SEM. | #Set beam energy —a rough guide is, the higher the energy the rougher the surface as seen on an SEM. 500 eV is considered medium energy.<br> | ||
#Then starting with beam current of 300mA increase the value until you reach the value where the PR is getting burnt.<br> | #Then starting with beam current of 300mA increase the value until you reach the value where the PR is getting burnt.<br> | ||
#Adjust beam current to give optimum etch rate without overheating the sample.< | #Adjust beam current to give optimum etch rate without overheating the sample.<br> | ||
#Adjust Accelerator voltage to get uniformity. Note that as this will change beam divergence, the sample temperature will change. | #Adjust Accelerator voltage to get uniformity. Note that as this will change beam divergence, the sample temperature will change. | ||
*Sample temperature is important because:<br> | *Sample temperature is important because:<br> | ||
#Need to keep any resist cool<br> | #Need to keep any resist cool<br> | ||
#Temperature can affect chemical processes | #Temperature can affect chemical processes. | ||
Latest revision as of 13:00, 24 March 2023
Feedback to this page: click here
Some general process trends
This page is supposed to gather some general process trends and good advice for designing IBE recipes. So far these trends has been developed etching Si with resist as masking material and by etching some multilayered films. The work has been done by Kristian Hagsted Rasmussen @ nanolab before 2012
Etch rate
| Etch rate | Parameters |
|---|---|
| increases with | Beam current |
| increases with | Beam voltage |
| increases with | Beam current * Beam voltage |
| not significantly affected by | Stage angle |
| not significantly affected by | Accelerator voltage |
Etch profile
| Etch profile (goal 90dg) | Parameters |
|---|---|
| improves with | Low stage angle (optimum around 5-10 dg) |
| is effected by | Beam current (low I(B)(400mA) better than high I(B)(600mA)) |
| is effected by | Accelerator voltage * Stage angle |
| not significantly affected by | Beam voltage |
Rotation speed
The rotation is activated to get a good uniformity over the wafer. The minimum number of rotations to get a good uniformity is 100 rotations for the whole etch. the maximum rotation speed is 20 rpm. That means that an etch shorter that 5 min cannot obtain a very good uniformity.
| Etch Length [min] | 5 | 6 | 7 | 8 | 9 | 10 | 15 | 20 | 25 | 34 | 50 | 100 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Minimum rotation speed [rpm] | 20 | 17 | 15 | 13 | 12 | 10 | 7 | 5 | 4 | 3 | 2 | 1 |
General tips for finding etching parameters (given by Oxford Instruments [1], used with permission)
One thing to remember is that the etch rate varies linearly with beam current while it varies exponentially with beam voltage.
- Beam voltage – depends on application, 200-800eV.
- Always have neutraliser current 20% extra of the beam current value.
- Accelerator voltage between 100V –500V, adjust to get Ia (beam accelerator current) < 10% Ib (bean current) (it helps protect electronics and power supplies).
- The real beam current is effectively the beam current minus accelerator current.
- Varying Ar flow for source gas as well as beam current will have an effect on the accelerator current.
- Arm Tilt affects:
- Etch uniformity—the steeper the angle, the better the uniformity. However the etch rate reduces.
- Wall angle profile (Argon IBE) theoretical ideal is 11 degrees from vertical. Actual value depends on the design of the grids, i.e. beam divergence etc.
Typical arm angle is 0-12 degrees. The sample is usually rotated to cater for any non-uniformity in the beam profile.
- A guide to optimize etch uniformity is as follows:
- Set beam energy —a rough guide is, the higher the energy the rougher the surface as seen on an SEM. 500 eV is considered medium energy.
- Then starting with beam current of 300mA increase the value until you reach the value where the PR is getting burnt.
- Adjust beam current to give optimum etch rate without overheating the sample.
- Adjust Accelerator voltage to get uniformity. Note that as this will change beam divergence, the sample temperature will change.
- Sample temperature is important because:
- Need to keep any resist cool
- Temperature can affect chemical processes.