Development of a Oxygen Sensor for Marine ... - DTU Nanotech

More documents

Recommendations

Info

44 CHAPTER 5. FABRICATION Thermometer), Ag (Reference Electrode), and Au (Contacts) are deposited. Why these 3? As discussed previously Pt and Ag have been used almost exclusively for Clark Sensors, and referenced as the best suited metals from a dissolved oxygen sensor[37]. Where as Au gold provides an excellent surface for bonding to wirebond, as well as being able resist some exposure to saltwater. Figure 5.7: Illustration of the wafer with the three metals added. Figure 5.8: Alignment marks after the metals are added. From left to right, ignoring the first one, it is Pt(brown), Ag(light brown), Au(red). Each metal have double alignment marks, two boxes and a crisscross pattern. This is mainly to have a little extra safety when aligning the masks, so that there is always another alignment mark to check with. Pt will be put on first for two reasons; It is the metal with the smallest structure, and hence the metal where the lithography step is most sensitive, and therefore where it is most like to go wrong. Also since the Au-Contacts and the Pt-Thermometer crosses, having the PT buried beneath the Au will ensure an unbroken line (Especially as the Au, 3000 ˚A, layer is over 10 times as thick as the Pt, 200 ˚A, layer). A minor problem however is that a lot of metals have poor adhesion to many forms of Silicon (including Silicide), hence a titanium layer is added
5.2. BACK-END PROCESSING 45 under each to improve adhesion. The 3 metals are added and patterned with 3 double rounds (First Ti, then the actual metal) of metalization and then lift-off. 5.2 Back-end Processing Once the cleanroom processes are done, there is still a few steps that have to be completed. These steps involves chemicals usually not found in a cleanroom, and the chip have to soak in them for a while, therefore they are done outside the cleanroom, also there is no real contamination danger for the electronics part of the wafer at this point. 5.2.1 Packaging First the chip have to be packaged, this is done in three steps. The Flexprint and then Chip is glued to the middle layer of the PMMA. The Flexprint is attached first as to avoid getting glue onto the chip, however should it occur, the glue used (Super Attakgel) can be removed using ethanol, provided it is only a thin layer of glue. Figure 5.9: Flex print and Chip glued to the PMMA. Once the glue have dried (for 1-2 hours to be sure that it is completely dry), the flex print and the Au-contacts have to be connected. This can be done with either wirebonding, which will be the first choice, or by using a
Page 1 and 2:
Development of a Oxygen Sensor for
Page 3: Abstract This thesis described the
Page 7 and 8: Contents 1 Introduction 1 1.1 Disso
Page 9 and 10: CONTENTS vii B Fabrication Process
Page 11 and 12: Chapter 1 Introduction Roughly 70 %
Page 13 and 14: 1.1. DISSOLVED OXYGEN LEVEL 3 K = a
Page 15 and 16: 1.2. THESIS OUTLINE 5 In Chapter 8
Page 17 and 18: Chapter 2 Optodes and ISFET There a
Page 19 and 20: 2.2. ISFET (ION SELECTIVE FIELD EFF
Page 21 and 22: 2.3. SUMMARY 11 of oxygen molecules
Page 23 and 24: Chapter 3 Theory of the Clark Senso
Page 25 and 26: 3.1. CHEMISTRY OF THE CLARK SENSOR
Page 33 and 34: 3.2. THE POTENTIOSTAT 23 Reference
Page 35 and 36: 3.2. THE POTENTIOSTAT 25 Working El
Page 37 and 38: Chapter 4 System Design The sensor
Page 39 and 40: 4.2. ACTUAL DESIGN 29 seen on figur
Page 41 and 42: 4.2. ACTUAL DESIGN 31 The third des
Page 43 and 44: 4.3. TEMPERATURE SENSOR 33 Figure 4
Page 45 and 46: 4.3. TEMPERATURE SENSOR 35 a Pt300,
Page 47 and 48: 4.4. PACKAGING 37 Figure 4.11: Clos
Page 49 and 50: 4.4. PACKAGING 39 90 mm 15 mm 6 mm
Page 51 and 52: Chapter 5 Fabrication The fabricati
Page 53: 5.1. PROCESSING 43 Figure 5.4: Alig
Page 57 and 58: 5.2. BACK-END PROCESSING 47 5.2.2 A
Page 59 and 60: Chapter 6 Problems and Solutions In
Page 61 and 62: 6.1. WIREBONDING 51 make a line bet
Page 63 and 64: 6.2. THE FLEX PRINT 53 The reason b
Page 65 and 66: 6.3. THE ’O’-RING 55 Figure 6.8
Page 67 and 68: Chapter 7 Evaluation of Results and
Page 69 and 70: 7.2. TEMPERATURE SENSOR 59 Figure 7
Page 71 and 72: 7.4. SUMMARY 61 Figure 7.5: Polarog
Page 73 and 74: Chapter 8 Conclusion The primary go
Page 75 and 76: Bibliography [1] http://earthobserv
Page 77 and 78: BIBLIOGRAPHY 67 [26] W.E. Morf. The
Page 79 and 80: Appendix A Silicide Recipe The foll
Page 81 and 82: Appendix B Fabrication Process 71
Page 84 and 85: 74 APPENDIX B. FABRICATION PROCESS
Page 86: 76 APPENDIX C. PROCESS SEQUENCE
show all

Development of a Oxygen Sensor for Marine ... - DTU Nanotech

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?