1. A NEUTRON IRRADIATION DEVICE FOR THE TESTING OF MICROELECTRONIC COMPONENETS TO BE USED IN THE RADIATION ENVIRONMENT OF HIGH-ENERGY PARTICLE ACCELERATORS AT DESY B. Mukherjee 1, D. Makowski 2, A. Kalicki 3, D. Rybka 3, M. Grecki 2, S. Simrock 1 1 Deutsches Elektronen Synchrotron, Hamburg, Germany 2 Department of Microelectronics and Computer Science, TUL, Poland 3 Institute of Electronic Systems, WUT, Poland 12 th International MIXDES Conference, 22-25 June 2005, Krakow, Poland

2. INTRODUCTION A significant number of microelectronic instrumentation and control devices vital to the operation of the VUV-Free Electron Laser (FEL) of DESY will be located in the close vicinity of the 1.2 GeV super- conducting electron linac driving the FEL. During the linac operation the microelectronic components will be subjected to parasitic radiation field, primarily made of brems- strahlung and photoneutrons. The radiation exposure will trigger Soft-Error (Single Event Upset) as well as Permanent Damage in the electronic circuitry. We have developed a variable energy neutron irradiation device for the radiation effect testing of microelectronic components. The device is based on a 241 Am-Be( , n) source placed at the centre of a water filled jar acting as neutron moderator. The neutron energy variation is accomplished by varying the jar diameter.

3. RADIATION EFFECTS IN MICROELECTRONICS

4. THE NEUTRON IRRADIATION DEVICE Legend B: Thermal Neutron Shield (Borated Polyethylene) D: Device under Test (DUT) H: Table J1, J2: Jars (16 and 33 cm radius respectively) P: Stand S: 241 Am-Be Neutron source T: Tripod (Source holder) Photograph of the neutron Irradiation device showing diverse types of DUT under irradiation.

5. CHARACTERISTICS OF THE NEUTRON RADIATION FIELD The Reference Neutron Spectra (a) Un-moderated, En (av) = 5.2 MeV (b) Moderated (6.9 cm H 2 O), En (av) = 4.1 MeV (c) Moderated (15.9 cm H 2 O), En (av) = 3.2 MeV The areas under the histogram (a), (b) and (c) are normalised to unity. Legend Tmod = Moderator (H2O) Thickness SDD = Source to Detector Distance Hnm = Measured Neutron Dose Equiv. Hnc = Calculated Neutron Dose Equiv Hgm = Measured Gamma Dose Equiv. * With thermal neutron shield

6. VERIFICATION OF THE REFERENCE RADIATION FIELD Neutron Detector The Neutron Dose Equivalent at various moderator thicknesses was verified by Superheated Bubble Dosimeters (Gamma Insensitive) Gamma Detector The background Gamma Dose at various moderator thicknesses was verified by a PIN Diode based miniature Electronic Dosimeter (Neutron Insensitive)

7. TESTING OF MICROELCTRONIC COMPONENTS We have irradiated the following items (1) Commercially available SRAM chips of 256, 512, 1024 and 2048 kB memory density (s. Table below) memory density (s. Table below) (2) Two miniature CCD Cameras Irradiation Parameters (1) Un-moderated neutrons (2) Neutrons moderated with 6.9 cm H2O layer (3) Moderated neutrons (as above),Shielded (3.5 mm Bor-Poly) Irradiation device Specifications of the SRAM (Static Random Access Memory) Chips used in this Investigation.

8. TEST RESULTS Number of SEU in 512 kB SRAM Chips induced by neutrons for three exposure modes. Neutron induced SEU in CCD Cameras for two exposure modes. Results showing the neutron irradiation effects in SRAM chips of four different memory densities.

9. SUMMARY AND CONCLUSION We have demonstrated the construction and operation principles of a simple variable energy neutron irradiation device based on an isotopic neutron source. The primary neutrons from the 241 Am-Be ( , n) source with an energy of 5.2 MeV was moderated with 6.9 (Jar 1) and 15 (Jar 2) cm thick water layers to obtain the neutron radiation field of 4.1 and 3.2 MeV average energy respectively. The system consists of a 241 Am-Be ( , n) source located at the centre of an assembly of concentric polyethylene jars of 8.0 and 16.5 cm radius respectively. The neutron dose equivalents at different configurations (Moderator layer thickness) and the corresponding gamma background doses were estimated with Superheated bubble dosimeter and PIN diode dosimeter respectively. A cylindrical thermal neutron shield made of 3.5 mm thick borated polyethylene sheet was used to attenuate the thermal neutron component of the irradiation field. A radiation hardness of various microelectronic devices like, SRAM and FPGA chips as well as CCD cameras have been tested using the above device prior to their installation in the high-energy accelerator environment at DESY. THANK YOU FOR YOUR ATTENTION (bhaskar.mukherjee@desy.de)