1. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 1/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Simulation of new P-type strip detectors with trench to enhance the charge multiplication effect in the n- type electrodes G. Pellegrini G. Pellegrini, J. P. Balbuena, C. Fleta, P. Fernández-Martínez, D. Quirion, S. Hidalgo, D. Flores, M. Lozano Centro Nacional de Microelectrónica (IMB-CNM-CSIC) G. Casse, D. Forshaw Liverpool University Work partially supported by RD50 collaboration

2. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 2/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Introduction Project: fabricate a p-type strip detector with small gain  Similar signal before and after irradiation Multiplication occurs at low bias voltage Gain should be limited between 2 and 10: - Avoid Crosstalk - Avoid exceeding the dynamic range of readout electronics Capacitance should not increase significantly - Higher capacitance  Higher noise

3. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 3/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Technological proposals I.Trench filled with doped polysilicon along the centre of the strip pitch −A N + contact is created into the silicon bulk that modifies the electric field in the collection region  multiplication 285µm 80µm n+ p- p+ 32µm 5µm 20µm 8µm p-stop Poly trench

4. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 4/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Technological proposals II.P-type diffusion along the centre of the strip pitch −Under reverse bias conditions, a high electric field region is created at the N + – P junction  multiplication p- p+ 285µm 32µm 80µm 20µm 8µm n+ 5µm p-stop P-type diffusion

5. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 5/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Simulation Model  Irradiation trap model: Acceptor;E= E c + 0.46 eV;η=0.9; σ e = 5 x 10 -15 ;σ h = 5 x 10 -14 Acceptor;E= E c + 0.42 eV;η=1.613; σ e = 2 x 10 -15 ;σ h = 2 x 10 -14 Acceptor;E= E c + 0.10 eV;η=100; σ e = 2 x 10 -15 ;σ h = 2.5 x 10 -15 Donor;E= E v - 0.36 eV;η=0.9; σ e = 2.5 x 10 -14 ;σ h = 2.5 x 10 -15  Impact Ionization Model: Universty of Bolonia Sentaurus ISE-TCAD

6. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 6/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Simulation of the Electric Field Strip Detector Poly Trench P diffusion High Electric Field region driven deep in the bulk High Electric Field peak at the centre of the strip

7. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 7/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona High Electric Field peak at the junction Simulation of the Electric Field High Electric Field region driven deep in the bulk Curves at 500 V No Irradiated Irradiated. Φ eq = 1 x 10 16

8. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 8/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Simulation of the Capacitance p- p+ n+ C Bulk C InterStrip Once Fully Depleted, the bulk capacitance is the same for all the structures Increment related with the depletion of the P diffusion We need experimental results to extract any conclusion

9. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 9/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Variation over the basic proposals I.P – type diffusion, implanted through a trench filled with oxide, along the centre of the strip pitch −N + / P-type diffusion junction creates a high electric field region  multiplication n+ p- p+ 285µm 32µm 80µm 5µm 20µm 8µm p-stop Oxide trench P-type diffusion

10. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 10/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Variation over the basic proposals II.Large P-Type covering all the strip width −N + / P-type diffusion junction creates a high electric field region  multiplication p- p+ 285µm 32µm 80µm 20µm 8µm n+ 30µm p-stop P-type diffusion

11. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 11/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Variation over the basic proposals DRAWBACK: If N + and P diffusions are performed with the same mask, a premature breakdown is expected due to the curvature of the junction N + diffusion should overlap P diffusion  One extra level of Mask  Optimisation of the overlap size It should work after irradiation p- p+ n+ Premature Cylindrical Breakdown

12. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 12/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Status of the Work: Fabrication The fabrication run includes: Conventional Strip Detectors Poly Trench structures with different trench depths: − 5 µm − 10 µm − 50 µm Structures with small P layer along the center of the strip Devices with large P layer along the center of the strip Oxide filled trench structures with a P layer implanted through the trench: − 5 µm − 10 µm − 50 µm Fabrication: step 50 out of 80. Doping trenches.

13. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 13/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Status of the Work: PAD Diodes We have fabricated PAD diodes with a P layer diffused under the N + diffusion −N + / P-type diffusion junction creates a high electric field region  multiplication 385 m N+N+ P High Electric Field region leading to multiplication 5000 µm First Measurements: Gain ~2

14. Simulation of new P-Type strip detectors 17th RD50 Workshop, CERN, Geneva 14/15 Centro Nacional de MicroelectrónicaInstituto de Microelectrónica de Barcelona Conclusions and Applications 1.We have shown several new designs to enhance the multiplication process. 2.If detector will work many tests must be done: uniformity, stability, reproducibility etc..... 3.A PAD detector with small gain has been fabricated following some of the procedures described in this work. 4.A run containing the discussed designs is being fabricated for subsequent characterisation. 5.Test uniformity with test beam or laser with Alibava Applications: - Radiation Hard Detectors - Tracking Detectors - Charge multiplication permits the fabrication of thinner detectors