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WO2001004610A2 - Procede et appareil de mesure sensible de la duree de vie des porteurs minoritaires dans des materiaux semi-conducteurs - Google Patents

Procede et appareil de mesure sensible de la duree de vie des porteurs minoritaires dans des materiaux semi-conducteurs Download PDF

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Publication number
WO2001004610A2
WO2001004610A2 PCT/HU2000/000077 HU0000077W WO0104610A2 WO 2001004610 A2 WO2001004610 A2 WO 2001004610A2 HU 0000077 W HU0000077 W HU 0000077W WO 0104610 A2 WO0104610 A2 WO 0104610A2
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WIPO (PCT)
Prior art keywords
output
semiconductor
microwave
input
light source
Prior art date
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Ceased
Application number
PCT/HU2000/000077
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English (en)
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WO2001004610A3 (fr
Inventor
Tibor Pavelka
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Semilab Felvezeto Fizikai Laboratorium Rt
Original Assignee
Semilab Felvezeto Fizikai Laboratorium Rt
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Publication of WO2001004610A2 publication Critical patent/WO2001004610A2/fr
Publication of WO2001004610A3 publication Critical patent/WO2001004610A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/28—Testing of electronic circuits, e.g. by signal tracer
    • G01R31/302—Contactless testing
    • G01R31/308—Contactless testing using non-ionising electromagnetic radiation, e.g. optical radiation
    • G01R31/311—Contactless testing using non-ionising electromagnetic radiation, e.g. optical radiation of integrated circuits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/26—Testing of individual semiconductor devices
    • G01R31/2648—Characterising semiconductor materials

Definitions

  • the lifetime of minority carriers is a characteristic parameter for the purity of semiconductor materials or devices, since it is very sensitive even for small amounts of impurities Defects or impurities present below concentrations even of 10 10 /cm 3 can be detected by methods measuring the lifetime of minority carriers These measuring techniques became fundamental in the development of semiconductor technologies or technological apparatuses Several methods are known for studying the recombination lifetime of minority carriers One of the basic methods is based on microwave reflection The present invention can be considered a development of the method using microwave, thus in what follows, only this method will be described
  • the concentration of charge carriers shows dependence on time, this is reflected also in the intensity variation of the reflected microwave
  • the intensity of the reflected microwave signal is directly proportional to the change of the conductivity or of the charge earner concentration Due to this, the time course of microwave intensity sensed by the detector reflects accurately the change in charge carrier concentration
  • the lifetime of minority carriers can be determined
  • the recombined transient detected is characteristic only for the illuminated area.
  • microwave is reflected from a larger part of the specimen than this. This can be described in other words shortly so that only a small part of the microwave carries information on the recombination process.
  • reflections are also detected to a significant extent from unexcited parts of the sample and the surrounding, which have no value from the viewpoint of the aim of the measurement. Due to this, the signal to noise ratio is significantly worse than ideal.
  • the most favourable arrangement from the point of view of sensitivity would be, if the microwave reflection were restricted to the excited volume of the sample.
  • epitaxial wafers These wafers are not homogeneous.
  • a highly doped support i.e. one of low conductivity (about 5-20 m ⁇ cm) the thickness of which is about 500-700 ⁇ m
  • an extraordinarily thin layer 1 -20 ⁇ m m with a resistivity of typically 10 ⁇ cm (the so-called epi-layer) is to be found.
  • the properties among others, also lifetime of the epi-layer are important parameters.
  • the microwave suffers partial reflection in the epi-layer, thus, in principle, it may be suitable for studying the epi-layer.
  • the signal due to the extraordinarily small layer thickness, the signal generally remains below the noise level.
  • Another difficulty is that the process takes place in the immediate neighbourhood of a support layer with very high conductivity. Thus, in case of a typical epitaxial semiconductor wafer, this traditional measurement usually cannot be applied.
  • the aim of our method is to eliminate this draw-back and to increase thereby to a significant extent the sensitivity of lifetime measurements based on microwave reflection while keeping the resolution high ( 1 mm).
  • the present invention relates to a method for measuring the recombination lifetime of minority carriers in semiconductors so that the semiconductor is illuminated by pulses from a suitably chosen light source (they should have an energy higher than the forbidden band of the semiconductor), and the variation owing to illumination in microwave reflection caused by the minority carriers in the semiconductor material is detected as a function of time in such a way that the microwave conductor is directly contacted with the sample.
  • the essence of the present invention is that the microwave is led on a coaxial cable to the immediate neighbourhood of the sample, and the microwave is coupled in direct contact to the material.
  • microwave reflection occurs from a relatively smaller field as compared to contact-free methods.
  • the volume sensed by microwave reflection can be restricted to the surrounding of the illuminated spot of 1 mm.
  • the invention also relates to the arrangement for carrying out the method according to the present invention, which apparatus comprises a tunable, adjustable microwave signal generator, the output of which is connected to the first gate of a circulator, to the second gate of the circulator a microwave conductor (typically a coaxial cable) is connected, which is in direct contact with the material to be tested, whereas the third gate of the circulator is connected to a signal processing device, and the semiconductor is coupled to a suitably chosen laser light source
  • the essence of the arrangement consists of the fact that due to a direct contact between the microwave system and the specimen, the microwave is concentrated to the neighbourhood of the volume to be tested, thus the signal/noise ratio is significantly better than in traditional arrangements
  • the frequency of the signal generator can be varied (in a range of about 500 MHz, around the base frequency of 10,3 GHz), whereby the system can be tuned so that the reflection on the specimen is the highest possible
  • the frequency of the signal generator can be varied (in a range of about 500 MHz, around the base frequency of 10,3 GHz), whereby the system can be tuned so that the reflection on the specimen is the highest possible
  • the apparatus shown is suitable for measuring the recombination lifetime of minority carriers in semiconductor material 6 as a specimen, as the time constant of the change in resistivity caused by charge carriers generated by a laser beam
  • the arrangement comprises microwave signal generator 2 tunable by varactor 1 , the oscillation frequency of which can be changed so that it is coupled to varactor 1 through a control connection
  • the microwave signal generator 2 is preferably a known Gunn oscillator, its frequency range being between 102 and 1045 GHz, and its output power about 50-100 mW
  • other types of microwave signal generators 2 can also be used
  • the output of microwave signal generator 2 is connected to the input of isolator 3, the output of which is connected to the first gate of circulator 4 via a coaxial cable
  • the second gate of circulator 4 is led to a contact needle also via a coaxial cable, whereas the third gate of circulator 4 is connected via a coaxial connector to detector 8, which is, in this case, a peak-value rectifier Contact needle 5 leads the microwave field to semiconductor material 6
  • pulse generator 12 is connected to the output of central signal processing unit 13 controlling the timing of the system, e.g. to a computer-controlled signal processor.
  • central signal processing unit 13 controlling the timing of the system, e.g. to a computer-controlled signal processor.
  • inputs of varactor 1 and laser light source 7 are also connected.
  • Detector 8 is connected through amplifier 9 to the input of sample and hold circuit 10, which separates and filters the D.C. component and low frequency noise from the signal measured, thus at its output, a zero level adjusting signal appears.
  • the output of sample and hold circuit 10 is fed back to the input of amplifier 9.
  • the output of amplifier 9 is connected to the input of a known type of transient recorder 11 , it means that a signal having the restored null-level is coupled from the output of amplifier 9 to the transient recorder 11 , which stores the transient signal in a form transformed into a digital signal.
  • the control and timing input of transient recorder 11 is also connected to the output of pulse generator 12, as well as the control and timing input of sample and hold circuit 10. Signal processing is performed by central signal processing unit 13, which also controls varactor 1 , laser beam source 7 and pulse generator 12.
  • the method according to the invention and the functioning of the apparatus performing this method is the following:
  • the measurement consists essentially in measuring the resistivity change of semiconductor material 6 caused by minority carriers generated by the laser light, and determining the time constant of resistivity change.
  • Detector 8 is in this case a broad band peak-value rectifier.
  • the output signal of detector 8 is amplified by amplifier 9 and then led to sample and hold circuit 10, which filters the D.C. component and the low frequency (typically below 100 Hz) noise present in the signal.
  • Transient recorder 11 transforms the signals arriving to its input into digital signals, and stores them in its memory. The stored signals are then evaluated by central signal processing unit 13. The measurement consists thus essentially in a highly accurate measuring of the time course of resistivity change caused by charge carriers generated by the laser beam.
  • Contact needle 5 used leads the microwave directly into the specimen, thus only insignificant reflection originates from the surrounding.
  • Laser light source 7 ensuring optical excitation can easily be located and focussed.
  • contact needle 5 is the extension of the central core of a coaxial wave-guide, which extension is short enough (shorter than a quarter of the wavelength) to irradiate the microwave into free space only to a small extent, thus it leads the major part of the microwave signal into semiconductor material 6.
  • the electric potential at the output of detector 8 changes, proportionally with the conductivity of semiconductor material 6.
  • the time constant of the attenuation of the signal form at the output of detector 8 to a base level is proportional to the recombination lifetime of minority carriers, which base level corresponds to the energy of the unmodulated constant or steady state reflected microwave energy, if there is no excitation from laser light source 7.
  • microwave is carried into semiconductor material 6 via a direct contact, instead of irradiation into free space.
  • higher sensitivity can be achieved as compared to traditional arrangements.
  • the present method due to its increased sensitivity, is suitable for detecting signals also from thin epitaxial layers.
  • the recombination process taking place at the surface may disturb the measurement, thus surface recombination is expedient to be suppressed.
  • the surface is either passivated chemically, or covered by a thermal oxide-layer which is then charged.
  • Both methods are suitable for minimising the effect of surface recombination on the measurement, and thus we can measure the characteristic lifetime in the thin layer. Due to increased sensitivity, materials can also be tested in which, under traditional conditions, the signal level is very low or even if it does not exceed the noise level.
  • Typical examples for this are materials of small conductivity, characteristically materials of specific resistivities smaller than 0.5 ' ⁇ .cm.
  • Another case important from the point of view of technology is, when a thin layer (the so-called epitaxial layer) is supported on supports of very low resistivity (typically of m ⁇ cm).
  • the measurement can be carried out not only in case of high excitation, i.e. when large number of excess charge carriers are generated, but can also be performed at low levels of excess carriers.
  • the significance of measurements with low excitations is that these results can be modelled by calculations, and compared with results from different measurements (surface phototension).
  • lifetime measuring in dependence of excitation level leads also to getting acquainted with the characteristic properties of dominant impurities. For this, small signal data are also indispensable.
  • the contact needle is in direct mechanical contact with the specimen, which takes over the vibrations of the sample, thus no relative dislocation occurs.
  • the vibrations of the surrounding have no significant effect on the measurement.
  • the air gap between the specimen and the antenna can change due to vibrations, thus the signal to be measured may become noisy.
  • the measuring needle is very small (its diameter is smaller than 1 mm), thus it covers only a small field out of the surrounding of the specimen. Accordingly, the excitation of the specimen, e.g. its illumination by' light pulses can easily be carried out.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Toxicology (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Computer Hardware Design (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
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  • Testing Or Measuring Of Semiconductors Or The Like (AREA)

Abstract

L'invention concerne un procédé et un dispositif de mesure de la durée de vie de recombinaison des porteurs minoritaires dans des semi-conducteurs. D'après ce procédé, le semi-conducteur est éclairé par des impulsions provenant d'une source lumineuse, et la liaison temporelle du changement dans la réflexion de micro-ondes, provoquée par les porteurs minoritaires, générée dans le semi-conducteur par la lumière, est détectée de manière à ce que le guide de micro-ondes soit directement en contact avec le semi-conducteur. Ainsi, la réflexion de micro-ondes se produit à partir d'une très petite partie du volume, si on la compare aux procédés sans contact. Le dispositif comprend un générateur de micro-ondes (2) réglable par un varactor (1), la sortie du générateur (2) étant connectée à l'entrée d'un isolateur (3), la sortie de celui-ci étant connectée à la première grille d'un circulateur (4), la seconde grille de ce dernier est connectée à une patte de contact (5), également par un câble coaxial, tandis que la troisième grille du circulateur (4) est dirigée vers un détecteur (8) par une connexion coaxiale. La patte de contact (5) met le champ micro-ondes en contact direct avec le semi-conducteur (6), qui est l'impédance fermant le chemin micro-ondes. Le semi-conducteur (6) est optiquement excité par une source de lumière laser (7), qui est connectée à l'une des sorties d'un générateur d'impulsions (12), l'entrée de celui-ci étant connectée à la sortie d'une unité centrale de traitement de signaux (13). Les entrées du varactor (1) et de la source de lumière laser (7) sont également connectées à cette sortie de l'unité centrale susmentionnée. Le détecteur (8) est connecté à l'entrée d'un circuit d'échantillonnage et de stockage (10) via un amplificateur (9), qui sépare le bruit à basse fréquence. La sortie du circuit d'échantillonnage et de stockage (10) est connectée à l'entrée de l'amplificateur (9). La sortie de l'amplificateur (9) est connectée à un enregistreur transitoire connu (11). L'entrée de commande et de synchronisation de l'enregistreur transitoire connu (11) est connectée à la sortie du générateur d'impulsions (12). A cette sortie, est également connectée l'entrée de synchronisation du circuit d'échantillonnage et de stockage (10). Le traitement du signal est réalisé par l'unité centrale de traitement de signaux (13) qui commande également le varactor (1), la source de lumière laser (7) et le générateur d'impulsions (12).
PCT/HU2000/000077 1999-07-12 2000-07-12 Procede et appareil de mesure sensible de la duree de vie des porteurs minoritaires dans des materiaux semi-conducteurs Ceased WO2001004610A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
HUP99/02355 1999-07-12
HU9902355A HUP9902355A2 (hu) 1999-07-12 1999-07-12 Nagy érzékenységű eljárás és berendezés kisebbségi töltéshordozók élettartamának mérésére félvezető anyagokban

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WO2001004610A2 true WO2001004610A2 (fr) 2001-01-18
WO2001004610A3 WO2001004610A3 (fr) 2001-08-09

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2318218C1 (ru) * 2006-04-21 2008-02-27 Закрытое Акционерное Общество "ТЕЛЕКОМ-СТВ" Устройство для измерения времени жизни неосновных носителей заряда в полупроводниках
TWI718251B (zh) 2016-03-28 2021-02-11 日商迪思科股份有限公司 裝置晶圓之評估方法
CN113834783A (zh) * 2021-09-18 2021-12-24 王红珍 一种检测半导体电子器件的装置及方法
CN113834784A (zh) * 2021-09-18 2021-12-24 王红珍 一种检测宽禁带半导体电子器件的装置

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111624158B (zh) * 2020-06-10 2022-12-13 苏州科技大学 一种在线激光脉冲超快动力学检测设备及其应用方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5236817B2 (fr) * 1973-07-27 1977-09-19
DE3407850A1 (de) * 1984-02-29 1985-09-05 Hahn-Meitner-Institut für Kernforschung Berlin GmbH, 1000 Berlin Mikrowellen-messverfahren und -messapparatur zur kontaktlosen und zerstoerungsfreien untersuchung photoempfindlicher materialien
US5406214A (en) * 1990-12-17 1995-04-11 Semilab Felvezeto Fizikai Lab, Rt Method and apparatus for measuring minority carrier lifetime in semiconductor materials

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2318218C1 (ru) * 2006-04-21 2008-02-27 Закрытое Акционерное Общество "ТЕЛЕКОМ-СТВ" Устройство для измерения времени жизни неосновных носителей заряда в полупроводниках
TWI718251B (zh) 2016-03-28 2021-02-11 日商迪思科股份有限公司 裝置晶圓之評估方法
CN113834783A (zh) * 2021-09-18 2021-12-24 王红珍 一种检测半导体电子器件的装置及方法
CN113834784A (zh) * 2021-09-18 2021-12-24 王红珍 一种检测宽禁带半导体电子器件的装置

Also Published As

Publication number Publication date
HUP9902355A2 (hu) 2001-07-30
WO2001004610A3 (fr) 2001-08-09
HU9902355D0 (en) 1999-09-28

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