Deep etched DBR gratings in InP for photonic integratedcircuitsCitation for published version (APA):Docter, B., Geluk, E. J., Sander - Jochem, M. J. H., Karouta, F., & Smit, M. K. (2007). Deep etched DBR gratingsin InP for photonic integrated circuits. In Proceedings of the 2007 IEEE 19th International Conference on IndiumPhosphide & Related Materials (IPRM 2007) 14-18 May 2007, Matsue, Japan (pp. 226-228). Institute ofElectrical and Electronics Engineers. https://doi.org/10.1109/ICIPRM.2007.381164

DOI:10.1109/ICIPRM.2007.381164

Document status and date:Published: 01/01/2007

Document Version:Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers)

Please check the document version of this publication:

• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publication

General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.

• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.

If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverne

Take down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.

Download date: 12. Aug. 2020

2007 International Conference on Indium Phosphide and Related Materials 16:00-1 8:00Conference Proceedings PB5 (Poster)19th IPRM 14 - 18, May 2007 Matsue, JapanDEEP ETCHED DBR GRATINGS IN InP FOR PHOTONIC INTEGRATED

CIRCUITS

B. Docter, E.J. Geluk, M.J.H. Sander-Jochem, F. Karouta and M.K. Smit

COBRA Inter-University Research Institute on Communication TechnologyEindhoven University of Technology

Faculty of Electrical Engineering, Opto-Electronic Devices GroupP.O.Box 513, 5600 MB Eindhoven, The Netherlands

Email: b.docter tue.nl

AbstractA novel fabrication process was developed to realize high quality SiO, masks for Cl2 based ICP etching of InP.First order DBR mirrors, 3 [tm deep, were realized that can be used in photonic circuits. The process can beused in combination with conventional optical lithography, reducing production cost.

I. Introduction 120 nm 388nm

Deep etched distributed Bragg reflector (DBR) gratings areII II

very prom ising devices for InP/InG aA sP-based photonic..............................................................................................rd er eep etch ed

ra tin can ie re fle tiv ity re th ith in p-In................................................................................................................................................................P....

ed rc is iss ableo y, fi ee tc

etching..................

grtnGaAs ahiverel ctvcontact ha 9% wthn layer,..........which.........is.....necessary..............to.....integrate...p nm..............PMMA........layer.........is.....patterned..............using...... 20... kV...e-beam..lithography................

process..................

makes the DBR grating an ideal buetchingbprocess,buthresults fro th almnm lf-f

1-4244-0875-X/07/$20.OO ©2007 IEEE. 226~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~....................................

Authorized licensed use limited to: Eindhoven University of Technology. Downloaded on April 01,2010 at 08:46:40 EDT from IEEE Xplore. Restrictions apply.

E-beam E-beamnexposure exposure ZEP

PMMA Al 4- CrxQo

InP lnP~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~....................................................................................................InGaAsP lnGaAsP~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.....................................................................................................

20kVe-beampatternwriting70nmaluminumdeposition~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.............................................................................................................

.........................selectivity is.aboutI1:17. ..................removing.........................the...........Cr.........mask,................. the........

Fig 3. urn................deep.....DBR.....gratings...........in....In.......pattern.........is.....then......transferred..............into.......the.......n.....by....the ......same........CP..

...................................p ss...

.....................................................A..SEM...image....of...the...resulting......structure.......is..shown.....in..fig...5..prcs..It.is.expcted.thatby.using.otical.litography.fo.the.The.aveguide.hs.very.smoth sidewals and th.roughneswaveguides this roughness will be reduced drastically........................................ that.. was.................InaAP .....................present............in.....the......aluminum.............lift-offP process............is.....not......visible...........

gives better results than a lift-off process to define our metal Another problem with this e-beamVesystemaisrnwritingICPthatCrwiitC1uses

gratin epattern wastr wreitte uin a70 kVlUiLn de-ba.p feowihcasaseuwntdrflcinsadlossdevelopment of the ZEP resist, the Cr layer was etched in an To overcome both the proximity effect problem andthe~~~~~~~~~~~~~................................. ........ ...ICP system usingaC12:02 chemistry. This is a process that is stitching errors, we developed a process that combinese-beam~~~~~~~~~................................ ...........................alsousedinphoto-maskfabricationandisknowntoetchCr lithography with conventional optical lithographytofabricate~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~............................................................................................................and CrO~~~~~~~~~~~~~~~~~~~~ layers at about the same etch speed [4]. high quality deep etched DBR gratings.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~................................................................................. ...... ... ............TheCrlayerthenservesasanetchingmaskforthe~~ ~ ~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~................................................................................................opening of the SiO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~, layer in CHF3 RIB process. The~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.................................................................................. ...............

Authorized licensed use limited to: Eindhoven University of Technology. Downloaded on April 01,2010 at 08:46:40 EDT from IEEE Xplore. Restrictions apply.

VI. EBL - optical lithography combinationAoro . ...........~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~...............top view of the process flow for the combined e-beam-

and optical lithography process is given in fig. 6. First a 400nm SiO, mask is deposited by PECVD followed by a 50 nm e-beam evaporated Cr layer. The grating patterns are definedtogether with some alignment markers in a 320 nm thick ZEPlayer by 30 kV e-beam writing (fig. 6a). This pattern is thentransferred into the Cr layer by C12:02 ICP etching.

Next the waveguides are defined in HPR5O4 opticalphotoresist, using the e-beam written alignment markers (fig. Fig. 6a. EBL pattern6b). This pattern is then also etched into the Cr layer by thesecond C12:02 etch step (fig. 6c). Note that with this type ofgratings, the alignment of the optical mask is not very critical,since the grating pattern can be much wider than thewaveguide. Also, the written pattern resembles much more a

effect correction algorithm works much better.The rest of the processing iS the same as mentioned in the_

previous section. The resulting structure is shown in figure 7.

VII. Conlcusion Fg6:Wvgieptenaindt B atrWe presented a novel fabrication method for high quality, Fi.6.WvgdeptrnagedoEBpten

The use of a thin chromium layer also enables us to use acombination of e-beam lithography and optical lithography.This does not only decrease writing time, it also avoids

Furthermore the technology is fully compatible with otherprocessing steps and therefore enables the use of deep etched Fig. 6c: Final chrome maskDBR gratings as building blocks in future advanced photonic

[1] K.J. Kasunic, "Design Equations for the Reflectivity ofDeep-Etch Distributed Bragg Reflector Gratings", J. ofLightwave Techn., Vol. 18, N. 3, 2000t ....................................

Grting Dsributed Bragg Rfblectlors" Jpn.aJ. Appl_

multi-wavelength ~ ~ ~~~~~~iglase on InP" IEE Phot.oTechn Lett., 4Hwdwvguds

228Authorized licensed use limited to: Eindhoven University of Technology. Downloaded on April 01,2010 at 08:46:40 EDT from IEEE Xplore. Restrictions apply.