Semiconductor Detectors for Particle Physics

1. Semiconductor Detectorsfor Particle Physics Troisieme Cycle – Lecture 1

2. Outline • Background • Objectives of lecture course • Contents • Part 1/4 Troisieme Cycle – Lecture 1

3. TECHNOLOGY PHYSICS INDUSTRY Troisieme Cycle – Lecture 1

4. HEP Experiments • ATLAS • CDF • LHCb Troisieme Cycle – Lecture 1

5. Focus of Activities • High Precision Tracking Troisieme Cycle – Lecture 1

6. Facilities • Liverpool Semiconductor Detector Centre • Electronic and Mechanical Design and Integration • Sensor Simulation • Workshop Troisieme Cycle – Lecture 1

7. LSDC Troisieme Cycle – Lecture 1

8. ATLAS Troisieme Cycle – Lecture 1

9. CDF Layer 00 Troisieme Cycle – Lecture 1

10. LHCb VELO Troisieme Cycle – Lecture 1

11. CCDs • LCFI • CCD Troisieme Cycle – Lecture 1

12. Active Pixels • Future • integration of pixels and electronics • low mass • low cost Troisieme Cycle – Lecture 1

13. Basic concepts of semiconductors Simple Devices Fabrication Techniques Particle Physics Experiments Sensors Assembly and Testing Advanced Techniques Future Developments Objectives Troisieme Cycle – Lecture 1

14. Level… • Basic semiconductor physics • Not a course on Solid State • A little Particle Physics • Concepts • Detectors Troisieme Cycle – Lecture 1

15. Notes for Course • Written notes on web http://www.ph.liv.ac.uk/~tjvb/teaching Troisieme Cycle – Lecture 1

16. Text Books • Sze – Semiconductor Detectors • Taur & Ning – Modern VLSI devices • Nicollian & Brews – MOS Physics and Technology • Early chapters/lectures have drawn heavily on these sources…. Troisieme Cycle – Lecture 1

17. Course Structure • Part 1: Basic Semiconductors • Part 2: Particle Physics and technology • Part 3: Future technology and advanced topics Troisieme Cycle – Lecture 1

18. BASICS 1.1Properties of Materials 1.2Energy Bands 1.3Carrier Concentration 1.4Transitions CARRIER PROPERTIES 2.1Transport Phenomena 2.2Carrier Diffusion 2.3Generation/Recombination. 2.4Continuity Equation 2.5High Field Effects 2.6Summary of Properties of Si P-N JUNCTION 3.1Thermal Equilibrium 3.2Depletion Region 3.3Junction Capacitance 3.4Current-Voltage Properties 3.5Breakdown 3.6Bipolar Transistor Action JUNCTIONS 4.1Metal Semiconductor Junction 4.2JFET 4.3MOS diode 4.4MOSFET WAFER PROCESSING 5.2Wafer Properties 5.3Ion Implantation and Diffusion 5.4Lithography and Etching 5.5Polysilicon 5.6Dielectric Layers 5.7Metallization SIMULATION 6.1Simple models 6.2Commercial Packages 6.3Typical Uses in Particle Physics 6.4Limitations Basic Semiconductors Lecture 2 Lecture 1 Troisieme Cycle – Lecture 1

19. HEP EXPERIMENTS 7.1Accelerators 7.2Interactions 7.3Detectors and Technologies PHOTONIC DEVICES 8.1Photons 8.2Photoemitters 8.3Photodetectors STRIP DETECTORS 9.1Simple Sensors 9.2DC Coupled Strip Devices 9.3AC Coupled Strip Devices 9.4Strip Bias Techniques 9.5Spatial Resolution 9.6Edge Effects 9.7Bulk and Implants PIXEL DETECTORS 10.1Pads, Strips and Pixels 10.2Pixel Detectors 10.3Bonding CHARGE COUPLED DEVICES 9.8Readout 11.1CCD 11.2High Speed Readout APPLICATIONS 12.1SLAC 12.2Fermilab 12.3CERN Devices in Particle Physics Lecture 2/3 Lecture 3 Troisieme Cycle – Lecture 1

20. RADIATION TOLERANCE 13.1Effects of Radiation 13.2Strip Detectors 13.3Pixels Detectors 13.4CCDs 3D PROCESSING 14.1Edge Processing 14.23D detectors 14.3Laser Cutting DRIFT DETECTORS 15.1Solid State Drift 15.2Applications CMOS 16.1Technology 16.2Active Pixel Sensors Advanced Techniques Lecture 4 Troisieme Cycle – Lecture 1

21. Basics • Properties of Materials • Energy Bands • Carrier Concentration • Transitions Troisieme Cycle – Lecture 1

22. Conductivities of insulators, semiconductors and conductors Properties of Materials • Conductivity Troisieme Cycle – Lecture 1

23. Silicon • By far the most important semiconductor for detector development is silicon. • The discovery of silicon (L. silex: silicis, flint) - silicium in French - is generally credited to Berzelius 1824. • He prepared amorphous silicon heating potassium with silicon tetrafluorided and purified the product by removing the fluosilicates by repeated washings. • Deville in 1854 first prepared crystalline silicon, the second allotropic form of the element. Troisieme Cycle – Lecture 1

24. Silicon cont’d • Silicon is present in the sun and stars • principal component of a class of meteorites known as aerolites. It is also a component of tektites, a natural glass of uncertain origin. • Silicon makes up 25.7% of the earth's crust, • by weight, and is the second most abundant element, being exceeded only by oxygen. • Silicon is not found free in nature, but occurs chiefly as the oxide and as silicates. • Sand, quartz, rock crystal, amethyst, agate, flint, jasper, and opal are some of the forms in which the oxide appears. Granite, hornblende, asbestos, feldspar, clay, mica, etc. are but a few of the numerous silicate minerals. Troisieme Cycle – Lecture 1

25. Silicon cont’d • Silicon is one of man's most useful elements. In the form of sand and clay it is used to make concrete and brick; • it is a useful refractory material for high-temperature work, and in the form of silicates it is used in making enamels, pottery, etc. • Silica, as sand, is a principal ingredient of glass, • one of the most inexpensive of materials with excellent mechanical, optical, thermal, and electrical properties. Troisieme Cycle – Lecture 1

26. No silicon life forms… • At least not life as we know it… Troisieme Cycle – Lecture 1

27. Periodic Table Table 2 Part of the periodic table containing silicon Troisieme Cycle – Lecture 1

28. Silicon Properties • Atomic Number14 • Melting Point 1687 K • Atomic Symbol Si • Boiling Point 3538 K • Atomic Weight 28.0855 • Density2.3296 g/cm3 • Electronic Configuration(Ne)(3s)2(3p)2 • Ionization Potential8.1eV Troisieme Cycle – Lecture 1

29. Crystal Structure Troisieme Cycle – Lecture 1

30. bcc Troisieme Cycle – Lecture 1

31. Diamond Structure Troisieme Cycle – Lecture 1

32. Diamond Structure Troisieme Cycle – Lecture 1

33. Packing Ratio • For silicon this ratio is about 0.3 which may be compared with the value for a closely packed (classical) system which occupies over 0.7. (see Problem 1.1 and 1.2) Troisieme Cycle – Lecture 1

34. Miller Indices Troisieme Cycle – Lecture 1

35. Si (111) Troisieme Cycle – Lecture 1

36. Valence Bonds • The silicon crystal is bound together via valence bonds. • Silicon is tetravalent and is able to share its outer four electrons with each of its four neighbours. • Each identical electron cannot thus be uniquely associated with a particular atom. The force of attraction between the atoms can only be calculated using complex quantum chemistry techniques and involves a detailed knowledge, or prediction, of the electron wavefunctions in the solid. Troisieme Cycle – Lecture 1

37. Valence Bonds • Positive ion cores should be kept apart to minimize the Coulomb energy • Valence electrons should also be kept apart • Valence electrons should stay close to positive ions to maximize attraction Troisieme Cycle – Lecture 1

38. Si Bonds • For covalent crystals e.g. Silicon or carbon the bond is very strong • The other important feature of the covalent bond is that it is strongly directional. • It is this that gives rise to the tehahedral diamond structure we have already discussed and hence why the packing ratio, and hence density, of the diamond lattice is so low. • A curiosity associated with the Si diamond structure is that electrons localized within a “bond” have the tendency to be spin aligned. Troisieme Cycle – Lecture 1

39. Energy Bands • Free electron Troisieme Cycle – Lecture 1

40. Energy Bands • Bloch Theorem in 1D Troisieme Cycle – Lecture 1

41. Perturbation Theory • Solution allowed if Now if G is sufficiently large compared to 1/L then both V11 and V22 are zero as they integrate of a rapidly oscillating function. By the same token V12 is only non zero if G=2k. At this value V12=VG. Troisieme Cycle – Lecture 1

42. Perturbation Theory • Solution. Bandgap is natural Troisieme Cycle – Lecture 1

43. Effective Mass Troisieme Cycle – Lecture 1

44. Effective Mass • For an electron at the top of a band, the effective mass is negative • the electron decelerating as the field is applied and the electron exchanges momentum with the lattice. • At the bottom of the band the electron behaves much as a free particle having an E-k relation almost the same as that in free space. Troisieme Cycle – Lecture 1

45. Holes • The peculiar behaviour of an electron close to the top of an energy band is usefully understood in terms of the behaviour of vacant states, or holes. In a full energy band containing n electrons with no net current flow • If the mth is missing there will, instantaneously, be a net current equal to • i.e. the net current is the same as that due to a particle with the same velocity as the missing electron but carrying opposite charge. • Thus for a system containing a missing electron close the top of the band, • behaviour of the system may be considered to that of a positive particle moving with an effective mass which is positive. Troisieme Cycle – Lecture 1

46. Band Structure Si Conduction Band Valence band Troisieme Cycle – Lecture 1

47. E-k Surface Troisieme Cycle – Lecture 1

48. Density of States Troisieme Cycle – Lecture 1

49. Metals, insulators and Semiconductors Troisieme Cycle – Lecture 1

50. Materials • For an insulator the first energy band is completely filled. • In order for an electron to move within the crystal when an electric field is applied energy must be supplied (from thermal excitation) to drive an electron across the forbidden region into the conduction band. If the band gap is sufficiently large, compared to thermal energies, i.e several eV, the transition rarely takes place and the material is an insulator. • If the energy gap is not too large (1.1eV in Si) then thermal excitations will leave some electrons in the conduction band at all time. • As the temperature is increased(decreased) the conductivity will increase(decrease). This is the classic behaviour of a semiconductor. Troisieme Cycle – Lecture 1