FR2799049A1 - Process for preventing boron diffusion in silicon by ionic carbon implantation - Google Patents

Process for preventing boron diffusion in silicon by ionic carbon implantation Download PDF

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Publication number
FR2799049A1
FR2799049A1 FR9912115A FR9912115A FR2799049A1 FR 2799049 A1 FR2799049 A1 FR 2799049A1 FR 9912115 A FR9912115 A FR 9912115A FR 9912115 A FR9912115 A FR 9912115A FR 2799049 A1 FR2799049 A1 FR 2799049A1
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layer
characterized
region
boron
method according
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French (fr)
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Jorge Luis Regolini
Pascal Ribot
Christine Morin
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France Telecom SA
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France Telecom SA
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L29/00Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof; Multistep manufacturing processes therefor
    • H01L29/66Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/66007Multistep manufacturing processes
    • H01L29/66075Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
    • H01L29/66227Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
    • H01L29/66234Bipolar junction transistors [BJT]
    • H01L29/66242Heterojunction transistors [HBT]
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/26Bombardment with radiation
    • H01L21/263Bombardment with radiation with high-energy radiation
    • H01L21/265Bombardment with radiation with high-energy radiation producing ion implantation
    • H01L21/26506Bombardment with radiation with high-energy radiation producing ion implantation in group IV semiconductors

Abstract

The invention relates to a method for manufacturing a memory point of the type comprising a control gate and a floating gate comprising the following steps: delimiting at the surface of a semiconductor substrate (1), by field isolation zones (2), an active region; forming a first gate insulator (3) on the surface of the substrate; depositing and etching a first conductive layer (4); depositing a second grid insulator (5); and depositing a second conductive layer (6). The first conductive layer has a thickness (h) not negligible in front of its width (W) and is engraved so as to round its corners (10).

Description

Process for preventing the diffusion of boron in silicon by ion implantation of carbon The invention relates to a method for preventing the diffusion of boron in silicon (Si) by ion implantation of carbon, and more particularly when producing a heterojunction bipolar transistor (TBH) of the silicon-germanium (SiGe) die. . However, the method according to the invention can also be applied during the production of other semiconductor components such as the MOS transistor (Metal Oxide Semiconductor) in order to solve the problem of short channel effects for example.

The semiconductor component embodiment comprises many complex steps resulting in a stack of layers of different nature. The differentiation of these layers is done by doping. Doping involves either introducing impurities (doping ions) into a semiconductor material using ion implantation thermal diffusion techniques, or growing a new layer over the semiconductor material using of the epitaxial technique. Doping is called positive doping or negative doping depending on the nature of the doping ions used and the nature of the semiconductor material.

In principle, a heterojunction bipolar transistor of the SilSiGe die has three layers of semiconductor material. By way of example, the three layers may be a first negatively doped Si layer, a second SiGe layer positively doped with boron and made on the first layer, and a third negatively doped Si layer made on a part of the second layer. The first layer is the collector, the second layer is the base and the third layer is the transmitter of TBH. The TBH is remarkable in the sense that the Si-SiGe junction (base-collector and base-emitter) is a heterojunction because the two semiconductor materials Si and SiGe are not of the same nature.

The factors making it possible to considerably improve the TBH technical characteristics are, inter alia, the obtaining of so-called steep fine heterojunctions, that is to say, for example, making it possible, for example, to pass abruptly from uniform positive doping to uniform negative doping, and a very small base thickness. A reduced base guarantees a short transit time of the electrons between the emitter and the collector, thus a maximum operating frequency of the high TBH.

As previously described, the base of a TBH of the Si / SiGe die is generally doped with boron. However, boron tends to readily diffuse to adjacent layers thus expanding the base, which significantly degrades TBH's technical characteristics.

The mechanism of boron diffusion is a complex mechanism in which the doping ions (boron) progress by exchange with positively charged vacancies. In general, dopant diffusion in semiconductors is a function of concentration and temperature. The thermal balance in the production lines of a semiconductor component comprising at least one boron-doped region must therefore be low. But different steps such as oxidation or ion implantation, generally performed during the manufacture of a semiconductor component, can accelerate the diffusion of dopants.

Methods for preventing the diffusion of boron in the case of manufacture of TBH are known. One method is to incorporate carbon into substitutional sites during the manufacture of the TBH base using the so-called physical vapor deposition (PVD) epitaxy technique or the so-called chemical deposition technique. vapor phase (CVD). This method is very complex to implement because it requires, for example in the case of a PVD-evaporation technique, to have a source of material to be deposited at high temperature and placed in a vacuum reactor. Epitaxial growth requires effective control of temperature so that the atoms of the material to be deposited once transformed into vapor by evaporation have sufficient mobility to migrate and ensure steady growth on a crystal. Thus the growth of the base with at the same time the incorporation of carbon requires the addition of an additional source of carbon in the reactor, which leads to complications of maintenance, flow measurement and reactor contamination.

In addition, dopant activation annealing steps at about 1025 C for several seconds generally performed as a result of the techniques described above, are not carried out completely so as not to promote diffusion. The characteristics of the semiconductor component produced are not then optimum.

An object of the invention is to provide a method for preventing boron diffusion which overcomes the above disadvantages.

In particular, the object of the present invention is to provide a method for preventing boron diffusion during the manufacture of a semiconductor component such as one which does not preclude complete completion of all activation annealing steps.

Those skilled in the art will readily understand that the present invention can be advantageously applied to any manufacturing die other than TBH Si / SiGe in order to prevent the diffusion of boron.

The above objects are achieved according to the invention by a method for preventing the boron present as a dopant in a predetermined region of a semiconductor component from diffusing into at least one region adjacent to the predetermined region during manufacture of the component, which comprises introduction by ion implantation into the predetermined region of a dose of carbon between 0.1 and 117o atomic.

In contrast to the state of the prior art in which carbon is incorporated in situ during the epitaxial formation of the region to be protected, according to the invention, the ion implantation technique which has numerous advantages such as cost price linked to the speed of the technique making it possible to produce a large number of components; an "ionic" purity because it is possible to work under vacuum and to sort ions by electronic methods so as to obtain a very pure mono-energetic beam of the doping atom; the possibility of selective implantation by masking; and the fairly precise control of the dose of implanted dopant ions as well as their depth of penetration.

Preferably, the implantation energy is such that the maximum of the implanted carbon ion distribution is the predetermined region.

According to a preferred embodiment of the invention, the semiconductor component is a heterojunction bipolar transistor (TBH).

Advantageously, the carbon is implanted after the formation of the collector and the base of the bipolar heterojunction transistor (TBH). And in this case, the predetermined region is the base of the TBH and the adjacent region is the TBH collector.

The incorporation of the carbon after the formation of the collector and the base differs advantageously from the method used according to the state of the prior art because it makes it possible to use the ion implantation technique.

The invention also relates to a method for manufacturing a heterojunction bipolar transistor comprising the following steps: a) the formation on a silicon substrate, by epitaxy and in situ doping, of a thin layer of SiGe alloy heavily doped with boron; b) ion implantation of phosphorus with first and second implantation energy, the second implantation energy being lower than the first, so as to form in the substrate a first region strongly doped with phosphorus separated from the thin layer of SiGe alloy by a second region weakly doped with phosphorus.

According to the invention, after step b) is introduced by ion implantation a carbon dose of between 0.1 and 1 atomic% in the thin SiGe alloy layer.

Other advantages and features of the invention will appear on examining the detailed description of an embodiment and the appended drawings which represent respectively - FIG. 1; a schematic sectional view of a heterojunction bipolar transistor (TBH); - Figures 2a, 2b and 2c, schematic sectional views of the main steps of manufacturing a heterojunction bipolar transistor (TBH) incorporating the carbon implantation method according to the invention; FIG. 3, curves of the concentration of boron as a function of the depth in the base for heterojunction bipolar transistors subjected to anti-diffusion treatments of the prior art (D2, D3) and according to the invention (D4) , after heat treatment, and for a bipolar heterojunction transistor whose base has been doped by low temperature epitaxy <B> (D1.), </ B> and which has not undergone any heat treatment.

Although the description will be made for a bipolar heterojunction transistor (TBH) in particular having an SiGe alloy base, it can be applied to any other suitable semiconductor device.

FIG. 1 diagrammatically shows a bipolar transistor with conventionally structured heterojunction. It consists of a stack of layers of Si and SiGe. This transistor more specifically comprises a first strongly negatively doped (N +) Si layer 1 on which a second slightly negatively doped (N-) Si layer 2 is made. Then, a highly positively doped (P +) SiGe layer 3, using boron atoms for example, covers an upper part of the layer 2 of Si (N-). Finally, two layers of Si are produced on an upper part of the SiGe layer 3, a first slightly negatively doped (N-) Si layer 4 adjacent to the SiGe layer 3 and a second strongly doped Si layer 5 ( N +) adjacent to the Si layer 4.

The three central layers 2, 3 and 4 constitute the heart of the TBH. SiGe layer 3 is the basis of TBH. She must be fine. A metal contact 8 is disposed on the upper part of the layer 3 left free. The metallic contact 8 is in the form of a ring around the upper layers 4 and 5 of Si. The layer 3 of SiGe doped with boron also contains carbon atoms that have been incorporated according to the invention to prevent diffusion. boron. Generally, the manufacture of a TBH is done by producing successive layers in the upward vertical direction (from layer 1 to layer 5).

The layer 4 of Si (N-) is the emitter of the TBH. It is surmounted by the layer 5 of heavily doped Si (N +). The layer 5 makes it possible to form a good bond between the layer 4 and a metal contact 7 disposed on the layer 5.

The layer 2 of Si (N-) is the collector of the TBH. As for the transmitter, it is made on a layer 1 of heavily doped Si (N +) serving as a link with a metal contact 6.

Figures 2a to 2c illustrate the steps of incorporation of carbon during the manufacture of a TBH according to the invention.

FIG. 2a shows a Si layer 9 on which a layer 10 of highly positively doped (P +) SiGe has been deposited by boron atoms. SiGe layer 10 is the basis of TBH. This base is made by epitaxy of SiGe and is doped with boron either in situ or after ion implantation.

 As can be seen in FIG. 2b, doping of the Si layer 9 is then carried out so as to form the TBH collector. To do this, a first ion implantation 11 of phosphorus atoms (P) having an energy of 400 keV (kiloelectron-volt) is performed to obtain a first layer 9a of strongly negatively doped (N +) placed at low level. in the layer 9 of Si. The layer 9a plays the same role as the layer 1 in FIG. 1. Then, a second ion implantation 11 of phosphorus atoms (P) having an energy of 100 keV is performed to obtain a second layer 9b of weakly negatively doped Si (N-). Since the energy of the ions of the second ion implantation (100 keV) is less than that (400 keV) of the ions of the first ion implantation, these ions of the second ion implantation penetrate less into the layer 9 of Si. The layer 9b becomes Thus, the layer 9b plays the same role as the layer 2 in FIG. 1. The energies 100 keV and 400 keV are determined in such a way that the phosphorus ions cross the layer 9a in the layer 9 of Si. layer 10 of SiGe (the base) and penetrate the layer 9 of Si.

As can be seen in FIG. 2c, carbon (C) is then incorporated into the SiGe layer 10 (the base) by an ion implantation 12. The energy of the carbon ions is 35 keV, which enables them to penetrate the base and have a distribution whose top is substantially in the middle of the base. The implanted carbon dose of between 0.1 and <I> 1 </ I> atomic yo at the maximum of the distribution.

Ion implantation is a technique of accelerating ions, which penetrate a target material by losing their energy by successive collisions with electrons and atoms of the target material. It is then necessary for the material to undergo an annealing at a very high temperature in order to reconstitute the partially destroyed crystal lattice by the arrival of the external ions and at the same time activate the dopants. Thus, once implanted carbon ions in base by the method of the invention, the element consisting of the layers 9 and 10, can undergo annealing at very high temperature without the boron diffuses into the layer 9b Si adjacent.

The subsequent steps for producing the emitting part of the TBH can then be carried out by carrying out completely the necessary annealing steps without the boron diffusing, whereas in the state of the prior art the annealing steps were shortened, for example at 20 seconds instead of the 30 seconds normally required. FIG. 3 is a graph that groups together four diffusion profile curves obtained by the secondary ion mass spectroscopy (SIMS) method. The SIMS method consists of mass and depth analysis of ions torn from the surface of a sample by an energetic ion beam. The four curves correspond respectively to four samples that have undergone different operations. Initially, the four samples are identical to the element of Figure 2a, a layer of SiGe strongly positively doped with boron is formed by low temperature epitaxy and doping in situ on an undoped Si layer.

The first curve D 1 is a SIMS profile of the boron concentration corresponding to a first of the samples as obtained previously (control).

The second curve D2 is a SIMS profile of boron concentration corresponding to a second of the preceding samples which has been annealed at 1025 C for 30 seconds. The widening of the curve D2 with respect to the control curve D1 shows that the boron diffuses towards the inside of the substrate (increasing depths) as well as toward the outer surface.

The curve D3 is a SIMS profile corresponding to a third of the preceding samples which first underwent an ion implantation of phosphorus atoms for the doping of the collector (to form the layers 9a and 9b of FIG. 2b) and then a heat treatment. identical to that suffered by the second sample, that is to say an annealing at 1025 C for 30 seconds. The widening of the curve D3 with respect to the curve D2 shows that the diffusion of boron is even more important.

Finally, the curve D4 is a SIMS profile corresponding to the fourth of the preceding samples which has been subjected to the same treatment as the third sample, but in addition between the doping step of the collector and the annealing step at 1025 C during 30 seconds, an ion implantation of carbon according to the invention with an energy of 35 keV. The implanted carbon dose is 1015 atoms / cm 2. It can be seen that the curve D4 is substantially superimposed on the control curve <B> D1, </ B>, demonstrating that in this case the boron has practically not diffused.

The present invention therefore makes it possible to produce a heterojunction bipolar transistor comprising a narrow base in order to guarantee real technical characteristics such as the maximum operating frequency, close to theoretical characteristics.

 The set of technical characteristics can be significantly improved since the heat treatments necessary for the activation of the dopants can perform completely without causing any boron diffusion.

Claims (8)

  1. A method for preventing the boron present as a dopant in a predetermined region (10) of a semiconductor component from diffusing into at least one other adjacent region (9b, 2, 4) at the predetermined region during manufacture of the component, characterized in that it comprises introduction by ion implantation (12) into the predetermined region of a carbon dose of between 0.1 and 1 70 atomic.
  2. 2. Method according to the preceding claim, characterized in that said predetermined region is the base (3) of a heterojunction bipolar transistor.
  3. 3. Method according to claim 2, characterized in that said base consists of a thin layer of SiGe alloy.
  4. 4. Method according to any one of claims 1 to 3, characterized in that said adjacent region is the collector (2) of a heterojunction bipolar transistor.
  5. 5. Method according to claim 4, characterized in that the collector is silicon.
  6. 6. A method of manufacturing a heterojunction bipolar transistor comprising the following steps a) the formation on a silicon substrate (9), by epitaxy and in situ doping, of a thin layer (10) of strongly doped SiGe alloy with boron; b) the ion implantation (11) of phosphorus with a first and a second implantation energy, the second implantation energy being lower than the first, so as to form in the substrate a first region (9a) strongly doped with phosphorus separated from the thin layer of SiGe alloy by a second region (9b) weakly doped with phosphorus; characterized in that after step b) is introduced by ion implantation (12) a carbon dose of between 0.1 and 117o atomic in the thin SiGe alloy layer.
  7. 7. Method according to claim 6, characterized in that the thin layer (3) of SiGe alloy is the base of the transistor.
  8. 8. A method according to claim 6 or 7, characterized in that the region (2) of the substrate weakly doped with phosphorus constitutes the collector of the transistor.
FR9912115A 1999-09-29 1999-09-29 Process for preventing boron diffusion in silicon by ionic carbon implantation Withdrawn FR2799049A1 (en)

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PCT/FR2000/002686 WO2001024249A1 (en) 1999-09-29 2000-09-28 Method for preventing diffusion of boron in silicon by ion implantation of carbon

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002101810A1 (en) * 2001-06-11 2002-12-19 International Business Machines C implants for improved sige bipolar transistors yield

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RU2629659C1 (en) * 2016-11-22 2017-08-30 Федеральное государственное бюджетное образовательное учреждение высшего образования "Кабардино-Балкарский государственный университет им. Х.М. Бербекова" (КБГУ) Method of manufacturing semiconductor appliance

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US5708281A (en) * 1989-03-29 1998-01-13 Canon Kabushiki Kaisha Semiconductor device and photoelectric conversion apparatus using the same
WO1998026457A1 (en) * 1996-12-09 1998-06-18 Institut für Halbleiterphysik Frankfurt (Oder) GmbH Silicon-germanium hetero-bipolar transistor, and method for making its various epitactiv layers
US5959333A (en) * 1997-05-30 1999-09-28 Advanced Micro Devices, Inc. Reduction of dopant diffusion by the co-implantation of impurities into the transistor gate conductor

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
US5708281A (en) * 1989-03-29 1998-01-13 Canon Kabushiki Kaisha Semiconductor device and photoelectric conversion apparatus using the same
WO1998026457A1 (en) * 1996-12-09 1998-06-18 Institut für Halbleiterphysik Frankfurt (Oder) GmbH Silicon-germanium hetero-bipolar transistor, and method for making its various epitactiv layers
US5959333A (en) * 1997-05-30 1999-09-28 Advanced Micro Devices, Inc. Reduction of dopant diffusion by the co-implantation of impurities into the transistor gate conductor

Non-Patent Citations (2)

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Title
LANZEROTTI L D ET AL: "SI/SI1-X-YGEXCY/SI HETEROJUNCTION BIPOLAR TRANSISTORS", IEEE ELECTRON DEVICE LETTERS,US,IEEE INC. NEW YORK, vol. 17, no. 7, 1 July 1996 (1996-07-01), pages 334 - 337, XP000595110, ISSN: 0741-3106 *
LANZEROTTI L D ET AL: "Suppression of boron outdiffusion in SiGe HBTs by carbon incorporation", INTERNATIONAL ELECTRON DEVICES MEETING. TECHNICAL DIGEST (CAT. NO.96CH35961), INTERNATIONAL ELECTRON DEVICES MEETING. TECHNICAL DIGEST, SAN FRANCISCO, CA, USA, 8-11 DEC. 1996, 1996, New York, NY, USA, IEEE, USA, pages 249 - 252, XP000753756, ISBN: 0-7803-3393-4 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002101810A1 (en) * 2001-06-11 2002-12-19 International Business Machines C implants for improved sige bipolar transistors yield
EP2091076A2 (en) 2001-06-11 2009-08-19 International Business Machines Corporation C implants for improved SiGe bipolar yield
EP2091076A3 (en) * 2001-06-11 2009-09-16 International Business Machines Corporation C implants for improved SiGe bipolar yield

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