Periodic Reporting for period 3 - MICROPRINCE (Pilot line for micro-transfer-printing of functional components on wafer level)
Reporting period: 2019-04-01 to 2020-09-30
Moreover, in cooperation with the project partners TU Dresden a first μTP design aid tool was developed to relieve the co-design of source and target chips. Additionally, the new processes and materials were characterized and their reliability performance was tested in cooperation with the project partner IMWS. Concerning the transfer-printing of GaAs-based sensing elements in WP2, sensor ICs (target) and GaAs source chiplets with SiN tethers were prepared. Based on these materials, release and printing experiments (on BCB) were performed at XMF indicating issues with the chiplet warpage and, therefore, reduce print yields. Nevertheless, characterized samples indicated that GaAs transfer-printed Hall elements provide increased signal to noise ratio (SNR) of a factor of five, compared to chips with Silicon Hall plates. The main objectives of WP3 were process developments for the printing of filters on optical sensors. To achieve this goal, source wafers carrying HER filter were fabricated at the project partner OBJ. By further processing at ISIT (tether formation and release etch) these wafers were prepared for the transfer-printing. These print-ready filter devices were finally heterogeneously integrated at XMF. Optical measurements of the integrated sensors (Responsivity and dark current) indicated a full functionality of the HER sensors.The objectives of WP4 (printing silicon photonics for data transmission) cannot be achieved in the MICROPRINCE project since HUAWEI stepped out of the project early in the 2nd project year. Concerning WP 5, a new LED driver IC for transfer-printed RGB μLEDs was developed. Additionally, special GaN based blue and green LEDs for μTP were designed and fabricated in cooperation with the project partner TYN. These LEDs were afterwards directly printed on the driver IC in the XMF MEMS clean room. After metallization and packaging, the integrated µLEDs were tested indicating a promising performance. The main objective for WP6 has been the heterogeneous integration of active components in silicon photonic circuits. Therefore, InP and GaAs photodiodes (PDs) have been fabricated and revealed promising performance with respect to bandwidth (3dB of ~50 nm), dark current (as low as 200nA) and responsivity (0.85 A/W). Moreover these PDs have been packaged on Si photonic circuits and functional integrated spectrometers were build. Accordingly, the main goal of the MICROPRINCE project of building a pilot line for heterogeneous integration and showing its applicability for different material classes and target applications by the generation of demonstrator devices has been achieved.
• Completion of the installation of a Pilot line for micro-transfer-printing (Silane supply, Coater/Developer, μTP tool & curing oven).
• Design and production of μTP test vehicles for the development of required baseline processes.
• Based on these test vehicles several process sequences have been developed including:
1) SiN deposition, stress optimization and patterning for the tether formation,
2) the release etch of Si-based coupons with KOH,
3) the release etch of GaAs and InP chiplets by HCl and FeCl3,
4) the adhesive (BCB) deposition, annealing and curing process,
5) the µTP process itself including the metrology of printed devices,
6) the adhesive patterning and the RDL formation to contact these coupons
7) the final passivation of the 3D-integrated stack.
• Process sequences for a stamp master wafer fabrication were developed.
• Process characterization, reliability evaluations and FEM simulations of the printing process were performed by XMF and the project partner FhG IMWS Halle.
• Creation of a first generation of design aid tool by TU Dresden.
• GaAs source wafers with SiN based tether structures were developed.
• GaAs sensors with transfer-printed Hall elements were characterized and demonstrated an improved SNR about roughly a factor of five.
• HER sensors based on printed filters were build and characterized. The test results demonstrate a full functionality of the filters/ sensors without major influences of the integration process on the PD performance.
• A new generation of LED driver IC was designed, fabricated and demonstrated. Furthermore, the driver IC was completely characterized and qualified according to automotive standards.
• Printable GaN blue and green LEDs were designed and fabricated by Tyndal and integrated by XMF.
• The functionality of the “integrated LED” driver package was shown and general characterization procedures were started.
• InP and GaAs PDs for Si-photonic based spectrometers were fabricated at imec and revealed a promising performance.
• The developed III/V- diodes were printed, wired and tested and, thereby, the functionality of the integrated spectrometers was proven.