12004 MAPLD/138Bytkin Reduction of the Thermo stable Radiation Defects Probability Formation in Si and SiGe as a Physical Basis of the Bipolar npn Transistors Radiation Hardness Increase at the Application of the Radiation & Thermal Processing (RTP- technology). S.V. Bytkin Ukraine, Zaporozhye,

22004 MAPLD/138Bytkin I.Introduction In the previous report the author proposed the combination of the level of the Si doping by isovalent impurity (Ge), level of the preliminary irradiation of bipolar transistors and temperature of their isothermal annealing for the achievement of the maximal radiation hardness. Actually, experimentally was found technological factor combination, providing theoretically full radiation hardness: h 21E (   )/h 21E (0)=1. Results,which are in the next slide, are to be explained.

32004 MAPLD/138Bytkin Y= h 21E (   )/h 21E (0)) N Ge =0 N Ge =1,2x10 19 cm -3 Technological annealing temperature,  C N Ge =1,2x10 20 cm -3 TID of the technological  - irradiation, cm -2

42004 MAPLD/138Bytkin Purpose of the work: -explanation of the various character of npn transistor beta-current gain change after  - irradiation for the transistors, subjected to various dozes of a preliminary technological  -irradiation and isothermal annealing and manufactured on SiGe with different Ge content; -description of the main RTP steps;

52004 MAPLD/138Bytkin II. CHOICE OF THE TECHNOLOGICAL  - IRRADIATION TID. The basic purpose of a preliminary technological irradiation of npn transistor is decrease of the radiation defects formation probability, P iV (probability of the vacancy capture by various impurities) in a material, on which the device was made. Formation of the defects at manufacturing of the device will decrease probability of their formation at the subsequent work of the device in real conditions of its application.

62004 MAPLD/138Bytkin For the definition of P iV were used the empirical equations, describing accumulation of the radiation defects. Quantity of the defects was measured by DLTS method. Obtained results were expressed by formulas using STATISTICA 5.0, for example:

72004 MAPLD/138Bytkin Samples, used for the measurements and obtained results: For the measurements was used CZ n- Si and n- SiGe (5x10 19 cm -3 ), 35 Ohm x cm test p + n diodes (boron diffusion, depth of p + n junction  5 microns),concentration of oxygen in the initial wafer 7x10 17 cm -3, carbon 2x10 16 cm -3. Main difference between Si and SiGe from the technologist’s point of view : the increased values of complexes C i -O i -V-V (K – centers) speed formation in SiGe during technological irradiation:

82004 MAPLD/138Bytkin

92004 MAPLD/138Bytkin For calculation of P iV numerical values in Si and SiGe use of the received empirical equations and the account of reduction of concentration of oxygen and carbon during an irradiation are necessary. For example:

MAPLD/138Bytkin

MAPLD/138Bytkin Probability of the K-center creation in Si, SiGe

MAPLD/138Bytkin Practical point of view: received result specifies necessity of application of a long technological irradiation by  -particles,  10 6 s. For  =6,4x10 6 cm -2 s -1,    5х10 12 cm -2. Initial values of npn transistor beta- current gain should be not less than 200, and their value after an irradiation makes 2…10.

MAPLD/138Bytkin II. CHOICE OF THE TEMPERATURE AND DURATION OF THE TECHNOLOGICAL ISOTHERMAL ANNEALING. From the point of view of RTP application, technological  -irradiation creates in the recombination area "mix", consisting of the thermo stable and not thermo stable radiation defects. Consequently, the temperature of the annealing must be not less than 350  С. It must provide preservation of low P iV of the main radiation defects (E V +0.35eV) at guaranteed stability of npn transistor beta-current gain in all range of working temperatures.

MAPLD/138Bytkin The curve, describing the recovery of the  -irradiated transistors during annealing is the following:

MAPLD/138Bytkin Practical point of view: -npn IC transistors after technological irradiation are to be annealed at the temperature not less than 350  С. -duration of the annealing must be determined experimentally for every type of the transistor, but in every case it has to provide stabilization of the beta-current gain.

MAPLD/138Bytkin III. PROVIDING OF THE INVERSE B ETA-CURRENT GAIN OF THE OVERLAY TRANSISTOR LOW VALUE DURING OF THE TECHNOLOGICAL ISOTHERMAL ANNEALING. Primary goal at realization of the high- temperature annealing is restoration of amplification properties of the output transistor at preservation low, achieved as a result of an irradiation, values of the inverse beta-current gain of the TTL overlay transistor. Low Ge concentration allows separate recovery of different TTL transistors and produce well-behaved IC (low values of the input current).

MAPLD/138Bytkin Regression equation looks like: q=3,294-2,218x N Ge -1,329x ,17x N Ge. For N Ge  1x10 19 cm -3 and  =50 min, q=2.5, where

MAPLD/138Bytkin RESUME. 1. Physical basis of bipolar npn transistors radiation hardness increase at RTP application is decrease of the basic recombination centers probability formation at realization of technological irradiation. Main level (E V +0.35eV) is thermo stable. Distinction in probability of K-center formation in Si and SiGe explains previously received results. 2. Long (about 60 min. for the SiGe npn transistors and 150min. for Si devices) annealing at 350  С as a part of RTP allows excluding presence in an active transistor base practically all radiation defects which bake out at work in actual conditions will result in instability of the IC performance. 3. Manufacturing of the bipolar devices on SiGe with N Ge  1x10 13 cm -3 allows to speed up RTP realization and to make the integrated microcircuits appropriate to standards due to the separation of the annealing of the inverse beta-current gain of the TTL overlay transistor and of the output transistor.