Etching a Micro-Trench with a Maximum Aspect Ratio of 60 on Silica Glass by Laser-Induced Backside Wet Etching (LIBWE)

Abstract

We have successfully fabricated a deep micro-trench about 7 µm wide and 420 µm deep on silica glass with a maximum aspect ratio of 60 by laser induced backside wet etching (LIBWE) via KrF laser ablation of a saturated pyrene/acetone solution. The processing time for the microetching was as short as 5 min at a repetition rate of 80 Hz and a fluence of F = 1.0 J·cm-2·pulse-1. The etch rate was calculated to be approximately 17 nm·pulse-1. The LIBWE method is shown to be very useful for surface microstructuring of silica glass with high aspect ratio and high throughput.

Surface Micro-Structuring of Silica Glass by Laser-induced Backside Wet Etching

“…14) It is possible to fabricate a deep micro-trench about 7 μm wide and 420 μm deep on silica glass with a maximum aspect ratio of 60 by LIBWE with a KrF laser and saturated pyrene/acetone solution (0.4 mol dm -3 ). 23,26) Because the projection lens has a limited depth of focus, the silica plate was moved further from the projection lens after irradiation of every 1000 pulses in order to adjust the position of the interface between the silica plate and the solution to the imaging area of the projection lens.…”

Fabrication of deep microtrenches with inclined parts by laser-induced backside wet etching

“…One surprinsing result of the LIBWE would be deep trench fabrication with high aspect ratio up to 60 [5]. Indirect process using liquid enables us to fabricate such deep trenches [6].…”

Surface microstructures of silica glass by laser-induced backside wet etching

“…Micro-fabrications of various transparent materials, such as silica glass [9,[12][13][14][15][16][18][19][20][21][22][23][24][25][26][27]29,30,34,35], quartz [10,25,28,[31][32][33], glasses (Pyrex, etc.) [26], calcium fluoride [12,25,32], magnesium fluoride [25], barium fluoride [32], fluorocarbon resin [11], and sapphire [17,25,32,36], have been reported.…”

“…[26], calcium fluoride [12,25,32], magnesium fluoride [25], barium fluoride [32], fluorocarbon resin [11], and sapphire [17,25,32,36], have been reported. Furthermore, various dye solutions, such as pyrene/acetone [9,10,12,13,17,18,19,[24][25][26][27][31][32][33], pyrene/tetrahydrofuran (THF) [11,33], pyrene/ tetrachloroethylene [25,26,28,29], pyrene/cyclohexane [25], pyrene/toluene [26][27][28][29][30], pyranine/water [14], naphthalenesulfonic acid/water [15,20,22], naphthalene/methyl methacrylate [34,35], phenolphthalein/N-methyl-2-pyrrolidone [36], and pure toluene [16,21,22,23], have been used in c...…”

“…The depth of the etch increases linearly with the number of laser shots. Typical etch rates of the material were 0.1-40 nm pulse -1 , depending on irradiation conditions such as laser wavelength, laser fluence, and dye concentrations.Micro-fabrications of various transparent materials, such as silica glass [9,[12][13][14][15][16][18][19][20][21][22][23][24][25][26][27]29,30,34,35], quartz [10,25,28,[31][32][33], glasses (Pyrex, etc.) …”