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).

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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, bytkin_at_zp.ukrtel.net

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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 h21E(??)/h21E(0)1.
  Results,which are in the next slide, are to be
  explained.

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Y h21E(??)/h21E(0))
NGe0
NGe1,2x1019cm-3
Technological annealing temperature, ?C
TID of the technological ?- irradiation, cm-2
NGe1,2x1020cm-3
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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

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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, PiV (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.

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For the definition of PiV 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
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Samples, used for the measurements and obtained
results

• For the measurements was used CZ n- Si and
  n-SiGe (5x1019 cm-3), 35 Ohm x cm test pn diodes
  (boron diffusion, depth of pn junction ?5
  microns),concentration of oxygen in the initial
  wafer 7x1017 cm-3, carbon 2x1016 cm-3.
• Main difference between Si and SiGe from the
  technologists point of view the increased
  values of complexes Ci-Oi-V-V (K centers) speed
  formation in SiGe during technological
  irradiation

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• For calculation of PiV 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

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Probability of the K-center creation in Si, SiGe
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Practical point of view

• received result specifies necessity of
  application of a long technological irradiation
  by ?-particles, ? 106s. For ?6,4x106 cm-2s-1,
  ???5?1012cm-2.
• Initial values of npn transistor beta-current
  gain should be not less than 200, and their value
  after an irradiation makes 210.

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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??. It must
  provide preservation of low PiV of the main
  radiation defects (EV0.35eV) at guaranteed
  stability of npn transistor beta-current gain in
  all range of working temperatures.

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The curve, describing the recovery of the
?-irradiated transistors during annealing is the
following
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Practical point of view

• -npn IC transistors after technological
  irradiation are to be annealed at the temperature
  not less than 350??.
• -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.

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III. PROVIDING OF THE INVERSE BETA-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).

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Regression equation looks like
q3,294-2,218x10-20NGe-1,329x10-21,17x10-22NGe.
For NGe?1x1019cm-3 and ?50 min, q2.5, where
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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
  (EV0.35eV) 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?? 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 NGe?1x1013cm-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.