Micro/Nanofabrication and Instrumentation Laboratory EECE 403. Dr. Lukas Chrostowski

Transcription

1 Micro/Nanofabrication and Instrumentation Laboratory EECE 403 Dr. Lukas Chrostowski 1

2 Design cycle Design & Modelling Mask Layout Fabrication (outside) today: electrical testing. Final Test Fabrication (UBC) Midprocess test 2

3 Today Problem with metal Optical & Electronic Testing Lab?? Re-do Lithography & Metal evaporation Testing 3

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9 Metal Problem discussion What are the possible sources of the problem? Photoresist left over under-developed non-uniform thickness under-exposed over-baked too hot too long expired photoresist Cr on SiN? thermal coefficient of expansion adhesion What are the solutions? under-exposed: expose longer non-uniform thickness: particles/cleanliness, scratches: over-expose, new resist? 9

10 Hypothesis Samples we ALL under-exposed some variations Solution: expose longer Control: re-do the same conditions another with even less Experiment: dummy samples with SiN + patterns; one SiN without resist 5 sampled with different exposure, developed All evaporated, lift-off 10

11 Under-development Figure 1. Photoresist pattern errors after exposure with cross pattern. a) Underexposed or underdeveloped. b) Overexposed or overdeveloped. c) Underdeveloped. d) Overdeveloped. 11

12 Photoresist exposure Resist materials are often characterized by curves of fractional thickness remaining after development (normalized) versus log10 (dose). Early resists had a contrast (gamma) of about one, so that a tenfold change in dose was needed to achieve a relief image of areas of full thickness and zero thickness. R. Fabian Pease, and Stephen Y. Chou, Proceedings of the IEEE Vol. 96, No. 2, February

13 Metal Adhesion to SiN? The Adhesion of Evaporated Metal Films on Glass Benjamin, P.; Weaver, C. Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Volume 261, Issue 1307, pp , May 1961 The adhesion of films of a large number of metals deposited by vacuum techniques on to a glass surface have been examined. It has been found that the affinity of the metal for oxygen plays an important role in determining the adhesion and the results appear to confirm the theory that the formation of an intermediate oxide layer at the metal/glass interface is necessary for good adhesion. There has been some doubt as to how this intermediate oxide layer is formed and the present investigation has shown that the nature and pressure of the residual atmosphere during deposition determines the extent of the formation of the oxide layer during deposition and therefore the initial adhesion of the films. However, variations in adhesion with time have been observed with films of a number of metals and it would appear that if the formation of the oxide layer is not complete during deposition then diffusion of gas to the metal/glass interface can continue the formation of the oxide layer after deposition thus accounting for the variation in adhesion with time. Since the film structure would determine the rate and extent of the diffusion of gas to the interface, it can be an important factor affecting the adhesion. Electron-microscope examination of a number of the films has been made and confirms the importance of the film structure. Furthermore, certain anomalies such as the poor adhesion of films of the low melting point metals and aluminium can be explained on the basis of film structure. 13

14 Improved lift-off Want to create overhangs of photoresist to aid the metal lift-off Chlorobenzene dip: I will do that to ensure an undercut in the AZP4110 Photoresist, followed by a slight overdevelopment, in an effort to ensure a PR-free surface at the bottom of your metal trace areas. Mask Undercut in the liftoff layer 6.d 6.a Substrate Exposed photoresist Development Substrate Deposition of film Photoresist Liftoff film 6.c Substrate 6.d Final structure Substrate fy.chalmers.se/~yurgens/fka196/.../photolithography.pdf 14

15 Keithley 2602 Source-Measure system Overview: Figure 1: Keithley Source Meter Precision power supply and meter source: either as current or voltage source. measure: voltage, current, power, resistance 15

16 Keithley 2602 Source-Measure system Maximum current, voltage: Max power: e.g., 20V x 1 A = 20W +10A +5A +3A +1.5A +1A 0A 1A 1.5A DC Pulse 3A 5A 10A 40V 35V 20V 6V 0V +6V +20V +35V +40V Models 2601B, 2602B, and 2604B I-V capability VOLTAGE SOURCE SPECIFICATIONS VOLTAGE PROGRAMMING ACCURACY 1 Range Programming Resolution Accuracy (1 Year) 23 C ±5 C ±(% rdg. + volts) Typical Noise (peak-peak) 0.1Hz 10Hz 100 mv 5 µv 0.02% µv 20 µv 1 V 50 µv 0.02% µv 50 µv 6 V 50 µv 0.02% mv 100 µv 40 V 500 µv 0.02% + 12 mv 500 µv CURRENT SOURCE SPECIFICATIONS CURRENT PROGRAMMING ACCURACY Range Programming Resolution Accuracy (1 Year) 23 C ±5 C ±(% rdg. + amps) Typical Noise (peak-peak) 0.1Hz 10Hz 100 na 2 pa 0.06% pa 5 pa 1 µa 20 pa 0.03% pa 25 pa 10 µa 200 pa 0.03% + 5 na 60 pa 100 µa 2 na 0.03% + 60 na 3 na 1 ma 20 na 0.03% na 6 na 10 ma 200 na 0.03% + 6 µa 200 na 100 ma 2 µa 0.03% + 30 µa 600 na 1 A 5 20 µa 0.05% ma 70 µa 3 A 5 20 µa 0.06% + 4 ma 150 µa 10 A 5, µa 0.5 % + 40 ma (typical) 16

17 Probes Signatone S-725 Two probes XYZ adjustment Manual 17

18 Measurements to be done Collect optical spectra for different electrical powers record Voltage, current, power, optical spectrum Find lambda / Power Calibrate for contact probe resistance measure two probes on a single pad, subtract this from the above measurements. 18