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--- ebpg_raith-100 [2018/06/07 06:51] – [Preparing and loading substrate] scholma
+++ ebpg_raith-100 [2025/07/29 10:30] (current) – wigbout
@@ Line 1: / Line 1: @@
-==== Preparing and loading substrate ====
+====== Raith 100 E-beam Lithography (EBL) ======
-  * spincoat your resist of choice, see [[resist_and_e-beam_recipes|resist recipes]]
-    * if sample is non-conducting: spincoat (multiple) layers of conductive polymer (e.g. PEDOT or Electra92)
+===== Introduction =====
-  * check the sample under the optical microscope. Look for clean spots where you can write your pattern. Write down the coordinates of the good spots in your logbook (global coordinate system)
+The Raith 100 is a direct-write machine used for maskless lithography.
-  * vent system
+A 30 keV electron beam is emitted from a field-emitter, and is focused through electromagnetic lenses.
-  * mount the substrate on the sample holder as close as possible to the faraday cup.
+Using a deflection system the beam can be moved in the xy-plane.
-  * make a scratch in the lower left corner of your substrate, about 1mm in length, start on your sample and scratch outwards.
+Lithography is crucial for the [[https://en.wikipedia.org/wiki/Planar_process|planar process]] (i.e. fabrication of devices), since it is one of the few techniques((along with, e.g. FIB and (F)EBID)) that allows //local// changes, whereas deposition and etching typically is a //global// step.
-  * clean sample and kinematic mount by blowing N2
-  * mount the sample holder in the system, the sample holder is fixed with ceramic parts, be careful
+If you would like to use this system, contact [[wigbout@physics.leidenuniv.nl|Luc Wigbout]].
-  * pump down
+**The Raith 100 EBL system is located in the Cleanroom. Before you can use this system, you should have had a [[Cleanroom Safety Training]].**
+----
+===== Preparing and loading substrate =====
+  - Spincoat your resist of choice, see [[resist_and_e-beam_recipes|resist recipes]]
+    * If sample is non-conducting: spincoat (multiple) layers of conductive polymer (e.g. PEDOT or Electra92).
+  - Check the sample under the optical microscope. Look for clean spots where you can write your pattern. Write down the coordinates of the good spots (Global Coordinate System (CS))
+  - Vent system.
+  - Mount the substrate on the sample holder as close as possible to the faraday cup.
+  - Make a scratch in the lower left corner of your substrate, about 1 mm in length, start on your sample and scratch outwards.
+  - Clean sample and kinematic mount by blowing N2.
+  - Mount the sample holder in the system, be careful; the sample holder is fixed with ceramic parts
+  - Pump down.
 ----
-==== Ebeam steps ====
+===== E-beam lithography steps =====
-Try to follow these 8 global steps to get a nice working routine.
+Try to follow these 8 steps to develop a nice working routine.
   - [[EBPG_RAITH-100#PREPARATIONS|Preparations]]
@@ Line 20: / Line 37: @@
   - [[EBPG_RAITH-100#FOCUS|Focus]]
   - [[EBPG_RAITH-100#Writefield Alignment|Writefield Alignment]]
-    *when doing overlay: 3-point Alignment in Local CS, following WF Alignment)
+    * When doing overlay: first 3-point alignment in Local CS then follow with WF alignment)
   - [[EBPG_RAITH-100#BEAM CURRENT|Beam current]]
   - [[EBPG_RAITH-100#EXPOSURE PARAMETERS|Exposure parameters]]
@@ Line 26: / Line 43: @@
   - [[EBPG_RAITH-100#SCAN|Scan]]
-=== 1. Preparations===
+==== 1. Preparations ====
 Making sure everything behaves normally before really starting.
@@ Line 51: / Line 68: @@
 ^ PC ^ Typical beam current ^
-|1|8 nA|
+|1|10 nA|
 |2| |
 |3| |
 |4| |
-|5| |
+|5|1.3 nA |
-|6| |
+|6|0.8 nA |
 |7| |
 |8| 0.3 nA|
@@ Line 67: / Line 84: @@
-=== 2. Origin ==
+==== 2. Origin ===
 Define the origin of the global coordinate system on your sample. Typically this is the lower left corner.
@@ Line 79: / Line 96: @@
   * do an origin correction (1st tab), click adjust.
-=== 3. Focus ===
+==== 3. Focus ====
 Focusing will determine the resolution of your patterning. Do this well.
@@ Line 91: / Line 108: @@
-=== 4. Writefield Alignment ===
+==== 4. Writefield Alignment ====
-**when doing overlay: 3-POINT ALIGNMENT in local CS, following WF ALIGNMENT**\\
+**when doing an overlay: first perform a 3-POINT ALIGNMENT in local CS and then perform a WF ALIGNMENT**\\
 With a writefield alignment the beam coordinate system is aligned with the stage coordinate system. Without a proper writefield alignment you will get stitch errors at writefield boundaries.
@@ Line 102: / Line 119: @@
   * repeat the alignment procedure until the parameters are in the correct range. After the large scan area, you can use the Automatic writefield with Images procedure/100 µm WF, 1 µm marks
-=== 5. Beam current ===
+==== 5. Beam current ====
 The beam current is used to calculate the exposure time to reach the exposure dose of your resist.
@@ Line 108: / Line 125: @@
-=== 6. Exposure parameters ===
+==== 6. Exposure parameters ====
 Based on the measured beam current and the sensitivity of your resist you can now calculate the exposure parameters.
@@ Line 121: / Line 138: @@
   * Always click ‘calc’ next to dwell time last and make sure the beam speed is not too high
-=== 7. Position list ===
+==== 7. Position list ====
 In the position list you decide what and where to pattern. You can choose the order of patterning and add all sorts of automation scripts.
@@ Line 132: / Line 149: @@
   * save your positionlist, especially when doing a proces with multiple steps
-=== 8. Scan ===
+===== 8. Scan =====
   * check if you didn't forget anything
   * You can calculate the time it will take to pattern your device. Patterning parameters/drop down/times.
-  * Click on scan all from the  to start!
+  * Click on scan all in the 'filter' menu to start!
 ----
-==== Unloading your sample ====
+===== Unloading your sample =====
   * e-line/3rd tab/exchange position and GO
@@ Line 149: / Line 166: @@
   * pump down and check vacuum before you leave
-==== Developing ====
+===== Developing =====
 Each resist typically has a dedicated developer. PMMA type resist can in general be developed by MIBK or a MIBK/IPA solution. See [[resist_and_e-beam_recipes|resist recipes]] for the specific developing process for a specific resist.
-==== Lift off ====
+===== Lift off =====
 As for developing, a resist typically has a dedicated remover. Most resists can be removed -lifted off- with aceton. See [[resist_and_e-beam_recipes|resist recipes]] for the specific lift off process for a specific resist.
@@ Line 159: / Line 176: @@
 ----
-==== Overlays ====
+===== Overlays =====
-=== 3-point alignment ===
+==== 3-point alignment ====
   * Make sure all previous flags are cleared by unchecking the checkboxes next to the blue flags. (Do not use the blue flags, they have different meaning!)
@@ Line 187: / Line 204: @@
   * Now you have coupled the design coordinates (local coordinates) to the stage coordinates
-=== WF alignment on markers ===
+==== WF alignment on markers ====
   * After stage alignment, comes e-beam alignment.
@@ Line 201: / Line 218: @@
 ----
-==== Tips and tricks ====
+===== Tips and tricks =====
-=== AUTO HEAT ===
+==== AUTO HEAT ====
 Move the stage to a empty part of the waferholder. Turn on the beam and make sure focus is good.
 Press 'AUTO' next to 'HEAT' in VegaTC.
 The system will find the optimal saturation point for heating of the filament and will perform an auto gun alignment. Check if the gun tilt and gun shift values are between -20% and 20%. If the values are 0% this means the procedure failed. To high values need be adjusted with a mechanical alignment of the filament, find a technician to do this for you.
-=== Switching PC ===
+==== Switching PC ====
 Often it is necessary to switch to a lower PC to write large structures. PC-1 has a 700nm spot size, compared to a 70nm spot size for PC-10. FIXME Writing large structures >1µm, can be done with a high PC, but will require long patterning times.\\
 Since the spot size of PC1 is large, the resolution to do a proper writefield alignment is low. For this reason the PC is changed after the writefield alignment is performed at PC-10, but before the beam current is measured. Switching between PC generally introduces a small shift in the pattern. When you take into account this error during the design of your pattern you can easily correct for the shift without going through the trouble of a proper writefield alignment for a low PC.
@@ Line 214: / Line 231: @@
 ----
-==== Keyboard shortcuts ====
+===== Keyboard shortcuts =====
-=== E-line ===
+==== E-line ====
 CTRL-right click on the wafermap will move the stage to the position. This is used when you want to navigate close to the origin and when doing 3-point alignment.\\
@@ Line 225: / Line 242: @@
 T – opens the toolbox.
-=== Vega-TC ===
+==== Vega-TC ====
 Double click to create a reduced area in the SEM image. When reduced area is active you can change the size of the area using the right mouse button.
+===== Common problems =====
+==== Failed WF alignment ====
+A failed WF alignment typically happens when a particle isn't anymore in the field of view (FoV) of the WF alignment procedure. This indicates the parameters have drifted from the optimal settings after a -few- bad WF alignments. A bad WF aligment can be due to: bad focus, WF alignment at low PCs (low resolution), particle not centred, etc...\\
+In the second tab 'writefield' control, open 'writefield manager', reset the WF alignment. Choose a WF alignment with large FoV (> 10µm). After this rough WF alignment reset the shift values in the writefield manager. Then perform the WF alignment you need till you're happy with the correction values in Raith Protocol Tool.
+===== Extra reading =====
+{{ :fundamentals_of_electron_beam_exposure_and_development.pdf|}}
+===== New manual (WIP) =====
+==== The electron beam and writing fields ====
+The Raith-100 e-beam lithography machine can be used to pattern nanoscale structures using an electron beam. The system is, in essence, an scanning electron microscope (SEM) with additional features such as a pattern generator that can write the desired patterns.
+The e-beam is generated by thermionic emission from a hot cathode emitter at an energy of 30 keV, after which it is formed by the Wehnelt cylinder and several lenses (a.o. the stigmator and objective lens). Within the lens-column, there is also a deflector housed, which can change the incident angle of the electron beams. The amount of power necessary the deflect the 30 keV e-beam, increases with the beam angle. Thus, deflections at larger angles need bigger amplification. In the Raith-100, the large amplifiers tend to be noisy, so when writing, we will keep to the smaller amplification, so that the maximum angle corresponds to a field of view of 400x400 um.
+The system can still be used as a SEM, were the electron beam is scanned across an area. The scanning movement is ‘locked-in’ with a detector such that an image can be created. The area that is imaged, is the field of view (FOV) at that specific magnification, e.g., at 575x mag., the FOV is 400x400 um and at 2300x mag., the FOV is 100x100 um.
+When writing, we typically use 100x100 um as the area of our writing fields (WF). Thus, the WF is the area onto which can be written by purely changing the deflection of the beam.
+Since most patterns tend to be a bit larger than 100x100 um, we have to come up with creative solutions as not to write a noisy pattern. One way of overcoming this issue, is by stitching several WF's in two dimensions. This can be done by moving the sample with high accuracy.
+==== WF alignment ====
+The sample is put onto a sample holder which can be mounted inside the Raith-100 onto a stage with sapphire ball spacers to ensure that it is held in place with extreme accuracy. Furthermore, the sample stage can be moved in X and Y directions. The movement is measured with a laser-interferometer.
+:!: __Be aware that when you mount the sample, the stage should be in the exchange position. Otherwise the mirrors of the interferometer could be exposed to the outer environment (and potentially get dusty).__
+By moving the stage 100 um along the X or Y axis, one could switch to another part on the sample. In order to make sure that all the WF’s are aligned--connect properly--a WF-alignment procedure has to be done. This procedure makes sure that all the writing fields are correctly stitched to each other.
+WF alignment with images is done using an automated function, which does the following. After you searched for a particle or clear feature with a size of about 5 um, the procedure takes an image.