Specific Process Knowledge/Back-end processing/Laser Micromachining Tool/Laser Micromachining Tool acceptance test
Unless anything else is stated, everything on this page, text and pictures are made by DTU Nanolab.
These are results from the acceptance test of the machine in March 2012
Silicon straight line dice through
A single line is cut into the sample. The line may be realized by multiple passes, the line should be parallel with the flat of the test sample and must go all the way through the wafer. Time and quality of dice (chipping, cracking) will be evaluated.
Sample material : Silicon wafer 4" <100>, single side polished, thickness = 525µm
Acceptance criteria : Instances of chipping beyond 0.2 mm from kerf: <2
Laser setting :
- IPG 1064nm, f= 255mm Objective. As of March 2020 the IPG laser is no longer available, and is replaced by the TB laser \ rkch
Results : Final kerf width = 212um. No chipping or cracking beyond that.
Time for cut: 38sec for 40 mm line.
The test is accepted
Silicon two directions line dice through
Multiple lines are cut through the wafer. Line-to-line separation of lines parallel to the flat is, 20 mm (5 lines in parallel with flat), the first line parallel with the flat should lie 10 mm from the flat, line to line separation perpendicular to the flat must be 15 mm (7 lines) the first line perpendicular to the flat should be located 5 mm from the edge. Time and quality of dice (chipping, cracking) will be evaluated
Sample material : Silicon wafer 4" <100>, single side polished, thickness = 525µm
Acceptance criteria : Instances of chipping beyond 0.2 mm from kerf: <2
Laser setting :
- IPG 1064nm, f= 255mm Objective. As of March 2020 the IPG laser is no longer available, and is replaced by the TB laser \ rkch
Results :
- Final kerf width = ~200um.
- Time for cut: 14 min
The test is accepted
Silica on silicon curved line dice through
Five curved lines are cut into the sample. Two of the curved lines are only cut through the silica top layer (“LQO”) of 10 µm ± 1 µm and two of the curved lines are cut through the top silica and the silicon bulk (“LQO” and “LSA”). The final line is cut through both silica layers and the bulk silicon (“LQO” + “LSA” + “LQB”). The total length of each line is less than 150 mm. Two wavelengths have been used, one for the silica (355nm) and the other one for the silicon (1064nm). The sample got an ultrasonic bath after processing.
Sample material : Silicon wafer 4" <100>, single side polished, thickness = 525µm, with a 10 µm ± 1 µm coating of thermally grown oxide on both sides.
Acceptance criteria :
- Instances of chipping beyond 0.2 mm from kerf: <2
| Samples | Process time allowed (the processing time may deviate ± 25%) | Process time measured | Kerf widths |
| 1. Only SiO2 cut (1 line) | 85,28 sec | 34 sec | ~260µm |
| 2. Only SiO2 cut (1 line) | 85,28 sec | 34 sec | ~260µm |
| 3. SiO2 +Si cut (1 line) | 85.28 s + 305.66 s = 390.94 sec | 34 sec + 154 sec = 188 sec | SiO2: ~290um Si: ~200um |
| 4. SiO2 +Si cut (1 line) | 85.28 s + 305.66 s = 390.94 sec | 34 sec + 154 sec = 188 sec | SiO2: ~290um Si: ~200um |
| 5. SiO2 +Si cut through | 85.28 s + 611.32 s = 696.60 sec | 34 sec + 253 sec = 287 sec | 1st SiO2: ~310um Si: 220um |
Laser settings :
- Fuego 355nm, f= 255mm Objectives
- Fuego 1064nm, f= 255mm Objectives
Results :
Sample broke after cleaning in Ultrasonic bath at cut #5. Chipping < 200um.
Test is accepted
Quartz dicing straight lines
A single line is cut into the sample through centre and entire sample. The line may be realized by multiple passes, the line should be parallel with the flat of the test sample and should go all the way through the wafer.
Sample material : Quartz wafer 4" double side polished, thickness = 500 µm
Acceptance criteria :
| Parameter | Acceptance criteria | Process value measured |
| Time for writting line | <320 sec | 78 sec |
| Instances of chipping beyond 0.2 mm from kerf | < 2 | 0 (<30 µm) |
| Instances of cracking within 5 mm from edge | 0 | 0 |
Laser settings :
- Fuego 1064nm, f= 103mm Objective
- Power : 72%
Results :
- Short line on the top of the quartz wafer, not cutting the edges. The wafer broke during the cutting.
- Entire line cut through centre and entire sample
Test is accepted
Silicon hole drilling
Structures with 4 by 4 holes (5 mm spacing) are cut. The set of 16 holes should have a top diameter of 0.2 mm. The hole dimensions have been measured with a calibrated microscope.
Sample material : Silicon wafer 4" <100>, single side polished, thickness = 525µm
Acceptance criteria :
| Parameter | Acceptance criteria | Process value measured |
| Time per hole (200 µm) | <35 sec | 10 sec |
| Instances of chipping beyond 0.2 mm from kerf | < 2 | 0 |
| Number of through holes in set (0,2mm top diameter holes) | 16 | 16 |
| Average hole diameter on top of wafer for set 2 (0,2mm nominally top diameter) | 0.195 mm to 0.205 mm | 195 um |
| Average hole diameter on bottom of wafer for set 2 (0,03 mm nominally top diameter) | 0.025 mm to 0.035 mm | 150 um |
Laser settings :
- Fuego 1064nm, f= 103mm Objective
Results :
Test is accepted
Borosilicate glass hole drilling
Structures with 4 by 4 holes (5 mm spacing) are cut. The set of 16 holes should have a top diameter of 0.2 mm. The hole dimensions have been measured with a calibrated microscope.
Sample material : Silicon wafer 4" <100>, single side polished, thickness = 525µm
Acceptance criteria :
| Parameter | Acceptance criteria | Process value measured |
| Time per hole (200 µm) | < 45 sec | 44,75 sec |
| Instances of chipping beyond 0.2 mm from kerf | < 2 | 0 (front) |
| Number of through holes in set (0,2mm top diameter holes) | 16 | 16 |
| Average hole diameter on top of wafer for set 2 (0,2mm nominally top diameter) | 0.195 mm to 0.205 mm | 199 um |
| Average hole diameter on bottom of wafer for set 2 (0,03 mm nominally top diameter) | 0.025 mm to 0.035 mm | 107 um |
Laser settings :
- Fuego 355nm, f= 103mm Objective
Results :
Test is accepted
Stainless steel - thick sample - drilling hole
Array (10x10) of holes with a diameter of 0.1 mm and a pitch of 0.5 mm
Sample material : Stainless steel foil with a thickness of 0.5 mm
Acceptance criteria :
| Parameter | Acceptance criteria | Process value measured |
| Time per hole | max 40 sec/hole | 9,6 sec |
| Instances of chipping beyond 0.2 mm from kerf | < 2 | 0 |
| Number of through holes in set (0,1mm top diameter holes) | 10x10 | 10x10 |
| Average hole diameter on top of foil (0,1mm nominally top diameter) | 0.09 mm to 0.11 mm | 100 um |
| Average hole diameter on bottom of foil | Because no helical drilling head is used, an exact estimation of the average hole diameter on the bottom of the foil cannot be made |
Laser settings :
- Fuego 1064nm, f= 103mm Objective
Results :
Test is accepted
Stainless steel - drilling small holes
Array (50x50) of holes with a diameter of 0.035 mm and a pitch of 0.05 mm
Sample material : Stainless steel foil with a thickness of 0.08 mm
Acceptance criteria :
| Parameter | Acceptance criteria | Process value measured |
| Time per hole | min 10 holes/ min | 71.5 holes/ min |
| Instances of chipping beyond 0.2 mm from kerf | < 2 | 0 |
| Number of through holes in set (0,1mm top diameter holes) | 50 x 50 | 50 x 50 |
| Average hole diameter on top of foil (0.035 mm nominally top diameter) | 0.035 mm ± 0.005 | 32 um |
| Average hole diameter on the bottom of foil (0.01 mm nominally bottom diameter) | 0.01 mm ± 0.005 | 16 um |
Laser settings :
- Fuego 1064nm, f= 103mm Objective
Results :
| Radius set in VBscript | Radius measured | |
| 0,0025mm | ~25µm | |
| 0,004mm | ~24µm | |
| 0,005mm | ~28µm | |
| 0,006mm | ~29µm | |
| 0,01mm | ~32µm |
Test is accepted
Nickel - cutting curves
A single closed non- circular line with a path length of 270 mm is cut through the shim
Sample material : Nickel shim 180 mm diameter, 300 µm thickness
Acceptance criteria :
| Parameter | Acceptance criteria | Process value measured |
| Time for writing line | max 7 min | 6:30 min |
| Instances of chipping beyond 0.2 mm from kerf | < 2 | 0 |
| Line width | < 500 µm | 165 um |
| Average hole diameter on top of foil (0.035 mm nominally top diameter) | 0.035 mm ± 0.005 | 32 um |
Laser settings :
- Fuego 1064nm, f= 255mm Objective
Results :
Test is accepted
Nickel - micromachining
Machines 4-sided pyramidal recesses in nickel to a depth of 100 µm and a pyramid side width 0f 200 µm
Sample material : Nickel shim 85 mm diameter, 300 µm thickness
Acceptance criteria :
| Parameter | Acceptance criteria | Process value measured |
| Time for writing recess | max 2 min | 17 sec |
| Center depth of recess (nominally 100 µm) | 80 µm to 120 µm | 95 um |
| Side width (nominally 200 µm) | 180 µm to 220 µm | 206 um |
Laser settings :
- Fuego 355nm, f= 103mm Objective
Results :
Test is accepted