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GB2185851A - Method of fabricating an mos transistor - Google Patents

Method of fabricating an mos transistor Download PDF

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Publication number
GB2185851A
GB2185851A GB08601830A GB8601830A GB2185851A GB 2185851 A GB2185851 A GB 2185851A GB 08601830 A GB08601830 A GB 08601830A GB 8601830 A GB8601830 A GB 8601830A GB 2185851 A GB2185851 A GB 2185851A
Authority
GB
United Kingdom
Prior art keywords
layer
amorphous
insulating layer
polycrystalline
seed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB08601830A
Other versions
GB8601830D0 (en
Inventor
Raymond Edward Oakley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
GE Healthcare UK Ltd
Plessey Co Ltd
Original Assignee
GE Healthcare UK Ltd
Plessey Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by GE Healthcare UK Ltd, Plessey Co Ltd filed Critical GE Healthcare UK Ltd
Priority to GB08601830A priority Critical patent/GB2185851A/en
Publication of GB8601830D0 publication Critical patent/GB8601830D0/en
Priority to EP87900849A priority patent/EP0258285A1/en
Priority to PCT/GB1987/000030 priority patent/WO1987004563A1/en
Priority to JP62500890A priority patent/JPS63502544A/en
Publication of GB2185851A publication Critical patent/GB2185851A/en
Withdrawn legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10DINORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D30/00Field-effect transistors [FET]
    • H10D30/01Manufacture or treatment
    • H10D30/021Manufacture or treatment of FETs having insulated gates [IGFET]
    • H10D30/027Manufacture or treatment of FETs having insulated gates [IGFET] of lateral single-gate IGFETs
    • H10D30/0278Manufacture or treatment of FETs having insulated gates [IGFET] of lateral single-gate IGFETs forming single crystalline channels on wafers after forming insulating device isolations
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10DINORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D62/00Semiconductor bodies, or regions thereof, of devices having potential barriers
    • H10D62/10Shapes, relative sizes or dispositions of the regions of the semiconductor bodies; Shapes of the semiconductor bodies
    • H10D62/113Isolations within a component, i.e. internal isolations
    • H10D62/115Dielectric isolations, e.g. air gaps
    • H10D62/116Dielectric isolations, e.g. air gaps adjoining the input or output regions of field-effect devices, e.g. adjoining source or drain regions
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10DINORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D62/00Semiconductor bodies, or regions thereof, of devices having potential barriers
    • H10D62/40Crystalline structures

Landscapes

  • Recrystallisation Techniques (AREA)
  • Thin Film Transistor (AREA)

Abstract

A metal oxide silicon (MOS) transistor comprises a semiconductor substrate (2), an insulating layer (1) on the substrate, and a seed window (3) in the insulating layer (1), which seed window (3) communicates with the semiconductor substrate. The MOS transistor also comprises a re-crystallised amorphous or polycrystalline semiconductor layer (4) which overlies the insulating layer (1) at least in the region of the seed window and contacts the semiconductor substrate (2). A source is formed in the re-crystallised amorphous or polycrystalline semiconductor layer (4) upon the insulating layer (1) on one side of the seed window (3), and a drain is formed in the re-crystallised amorphous or polycrystalline semiconductor layer (4) upon the other side of the seed window (3), and a gate electrode comprising a dielectric layer (9) and a conducting or semiconducting layer (10) is formed between the source and the drain.

Description

SPECIFICATION Methods for fabricating transistors and MOS transistors fabricated by such methods This invention relates to methods for fabricating transistors, and to metal oxide silicon (MOS) transistors fabricated by such methods.
A A conventional type of transistor structure comprises a positively doped bulk silicon structure which includes source and drain regions in the form of diffused N conductivity type regions spaced apart in a silicon substrate. A gate electrode is formed over. the silicon substrate between the source and drain regions. This structure has the disadvantage that undesirable capacitances exist between the source and drain regions and the substrate.
Another conventional type of transistor structure, in this case a silicon on saphire (SOS) transistor, comprises a silicon layer having spaced apart source and drain regions on an insulating layer of saphire. Such a transistor attempts to reduce undesirable capacitances by putting the insulating layer under the device but this isolates the active channel region resulting in the device taking up an undefined potential which can modify the transistor action. Although this can be avoided by including a substrate contact on the top surface of the device, such a contact necesitates that the device takes up more space.
A A further conventional type of transistor which is subject to the same disadvantages as the SOS transistor is a silicon on insulator (S0l) transistor. Such a device comprises an insulating layer formed on a silicon substrate.
A A further silicon layer which includes source and drain regions is formed on the insulating layer.
A conventional method of fabricating the silicon on insulator (SOI) transistor structures comprises forming an insulating layer on a silicon substrate and etching seed windows in the insulating layer. A layer of polysilicon is then formed over the insulating layer and over the seed window. The polysilicon is then recrystallised (solid phase epitaxy) by way of a recrystallisation process, such as the one described in H.W. Lam IEDM Technical Digest 1980 paper 22.1. Source and drain regions are then formed in the recrystallised polysilicon layer by, for example, an implant doping process and a gate is formed between the source and the drain. In this structure, the gate overlies the insulating layer.
Such methods have the disadvantage that the seed window serves no further purpose after the recrystallisation process and so forms wasted space in the integrated circuit.
Further, it is difficult to recrystallise the polysilicon over large areas, particularly in areas distant from the seed window, which imposes restrictions on circuit layout and design.
The present invention is directed to a method for fabricating transistors which alleviates the aforementioned disadvantages, and MOS transistors fabricated by such methods, which transistors have relatively low capacitances associated therewith.
According to the present invention there is provided a metal oxide silicon (MOS) transistor comprising a semiconductor substrate, an insulating layer on the semiconductor substrate, a seed window in the insulating layer which seed window communicates with the semiconductor substrate, and a recrystallised amorphous or polycrystalline semiconductor layer overlying the insulating layer at least in the region of the seed window and contacting the semiconductor substrate, a source formed in the recrystallised amorphous or polycrystalline semiconductor layer upon the insulating layer on one side of the seed window, a drain formed in the recrystallised amorphous or polycrystalline semiconductor layer upon the other side of the seed window, and a gate between the source and the drain, the gate overlying the seed window.
The source and the drain may be diffused N type regions formed in the part of the recrystallised amorphous or polycrystalline layer which overlies the insulator.
According to the present invention there is also provided a method for fabricating a metal oxide silicon (MOS) transistor, the method comprising: forming an insulating layer having one or more seed windows on a semiconductor substrate; depositing an amorphous or polycrystalline semiconductor layer on the insulating layer and on the seed window(s); recrystallising the amorphous or polycrystalline semiconductor layer at least in the region of the seed window(s); isolating the recrystallised amorphous or polycrystalline semiconductor layer in the region of the seed window from the remaining amorphous or polycrystalline semiconductor layer; and forming a source on one side of the seed window over the insulating layer, a drain on another side of the seed window over the insulating layer, and a gate between the source and the drain, the gate being located over the seed window.
The step of forming the insulating layer having one or more seed windows may comprise forming the insulating layer on the semiconductor substrate and then etching holes, corresponding to the seed window(s), through the insulating layer.
Alternatively, recesses may be formed in the semiconductor substrate and the insulating layer may be formed in the recesses, the seed window(s) and the insulating layer thereby having a substantially flat surface. The isolation of the recrystallised amorphous or polycrystalline semiconductor layer in the seed window region(s) may be effected by etching away the non-recrystallised and/or recrystal lised amorphous or polycrystalline semiconductor layer in the field region or by converting the non-recrystallised and/or recrystallised amorphous or polycrystalline semiconductor layer in the field region to an insulator.
The drain and the source may be formed doping the polycrystalline layer during deposition of the polycrystalline layer, by implanting or furnace doping of the polycrystalline layer after deposition.
The step of recrystallising the amorphous or polycrystalline layer may be by solid phase epitaxy or by direct epitaxy. In direct epitaxy, the amorphous polycrystalline layer recrystallises in the region of the seed window as the layer is deposited over the insulating layer and the seed window.
Embodiments of the present invention are advantageous in that they enable the fabrication of a novel MOS transistor structure having relatively low capacitances associated therewith. In addition, they provide for the elimination of the need to waste space due to adandonment of seed window regions by incorporating the seed window regions into the MOS transistor structures. This saving of space can lead to increased packing density.
The invention will now be further described, by way of example with reference to the accompanying drawings, in which: Figures la to le show fabrication stages for a MOS transistor structure embodying the present invention; and Figures 2a to 2e show fabrication stages of an alternative MOS transistor structure embodying the present invention.
In Fig. 1a an insulating layer, for example, silicon dioxide is formed on a single crystal semiconductor substrate 2 such as silicon. A hole is etched through the insulating layer 1 to form a seed window 3; although only one seed window 3 is shown, a plurality of seed windows may be formed. A layer of amorphous or polycrystalline semiconductor, such as polysilicon 4, is then deposited over the insulating layer 1 and in the seed window 3 as illustrated in Fig. 1 b.
At least some of the polysilicon 4 in the region of the seed window 3 spontaneously becomes recrystallised using the substrate as a seed (direct epitaxy, that is, gas phase epitaxial deposition). However, the polysilicon 4 may be subjected to, for example, furnace treatment to cause solid phase epitaxy which grows single crystal silicon regions in the polysilicon around the seed window 3 using the substrate as a seed. The single crystal silicon region so formed is illustrated in Fig. 1c by reference numeral 5. Alternatively, the recrystallisation may be induced by laser treatments, electron beam treatments or quartz halogen lamps.
The seed window 3 is to correspond to an active region of a gate of a metal oxide silicon (MOS) transistor to be formed in the seed window 3 region. The next stage in the method of fabrication of the MOS transistor is to etch away field regions 6 of the MOS transistor, the resulting structure being illustrated in Fig. 1d. Alternatively, the field region 6 may be formed by converting the polysilicon layer in these regions into an insulator by oxidation. Source and drain regions 7 and 8 are formed in the regions of the polysilicon layer which overlie the insulating layer 1, for example, by furnace doping or implant. In the arrangement illustrated in Fig. 1e, the source region 7 and the drain region 8 are formed on opposite sides of the seed window 3 and may be of N or P conductivity type.A gate electrode, comprising a dielectric layer 9 and a conducting or semiconducting layer 10 is formed over the seed window 3 as shown in Fig. 1 e. The gate electrode may be formed before the source and drain regions 7 and 8 are formed.
An MOS transistor, formed in the above described way, such as the one illustrated in Fig.
1e, is advantageous in that the benefits of silicon on insulator (SOI) technology (i.e. low capacitances) may be achieved for MOS transistors while using a simple fabrication process.
The relatively low capacitance achievable in MOS transistors using the above described fabrication method exist since the fabrication method enables the MOS transistor to be formed in islands of good quality silicon which are connected to the substrate in the gate region, but have their source and drain regions over the initially formed oxide layer. Additionally, the transistors fabricated in this way may have low field capacitance because the field oxide may be made up of the oxidised polysilicon plus the original oxide.
An alternative series of fabrication stages for an MOS transistor structure is shown in Figs. 2a to 2e. In this case, the insulating layer 1 is formed in recesses which have been etched in the single crystal semiconductor substrate 2, which results in the seed window 3 and the insulating layer 1 having a substantially flat surface (Fig. 2a). The polysilicon 4 is then formed on the surface of the insulating layer 1 and the seed window 3 as shown in Fig. 2b. Recrystallisation of the polysilicon 4 in the region of the seed window 3 then takes place in a similar way to that described with reference to Fig. 1c to form a single crystal silicon region 5.
Source and drain regions 7 and 8 are then formed in a similar manner to that described earlier and the structure is then isolated, in this case, by converting the field regions to oxide 11 (Fig. 2d). Source and drain electrodes S, D are connected to the respective source and drain regions 7, 8 and a gate electrode G is formed over the seed window 3 (Fig. 2e) in a similar manner to that described with reference to Fig. 1e.
The methods for fabricating transistors, and the MOS transistors described above are intended to be examples and it is envisaged that variations may be adopted without departing from the scope of the present invention. For example, the step of recrystallisation by solid phase epitaxy may be combined with the isolation step which involves oxidation of the field regions.

Claims (4)

1. A method for fabricating a metal oxide silicon (MOS) transistor, the method comprising: forming on insulating layer having one or more seed windows on a semiconductor substrate; depositing an amorphous or polycrystalline semiconductor layer on the insulating layer and on the one or more seed windows; recrystallising the amorphous or polycrystalline semiconductor layer at least in the region of the seed windows; isolating the recrystallised amorphous or polycrystalline semiconductor layer in the region of the seed window from the remaining amorphous or polycrystalline semiconductor layer; and forming a source on one side of the seed window over the insulating layer; a drain on another side of the seed window over the insulating layer, and a gate between the source and the drain, the gate being located over the seed window.
2. A method of fabricating a metal oxide silicon (MOS) transistor as claimed in claim 1 wherein the step of forming the insulating layer having one or more seed windows comprises forming the insulating layer on the semiconductor substrate and then etching holes, corresponding to the seed windows through the insulating layer.
3. A method of fabricating a metal oxide silicon (MOS) transistor as claimed in claim 1 wherein recesses are formed in the semiconductor substrate and the insulating layer, the seed windows and the insulating layer thereby having a substantially flat surface.
4. A method of. fabricating a metal oxide silicon (MOS) transistor as claimed in claim 1 wherein isolation of the recrystallised amorphous or polycrystalline semiconductor layer in the seed window regions is achieved by etching away the non-crystallised and/or recrystallised amorphous or polycrystalline semiconductor layer in the field region or by converting the non-recrystallised and/or recrystallised amorphous or polycrystalline semiconductor layer in the field regions to an insulator.
4. A method of fabricating a metal oxide silicon (MOS) transistor wherein isolation of the recrystallised amorphous or polycrystalline semiconductor layer in the seed window regions is achieved by etching away the noncrystallised and/or recrystallised amorphous or polycrystalline semiconductor layer in the field region or by converting the non-recrystallised and/or recrystallised amorphous or polycrystalline semiconductor layer in the field regions to an insulator.
5. A method of fabricating a metal oxide silicon (MOS) transistor as claimed in any preceding claim wherein the drain is formed by doping the polycrystalline layer during deposition of the polycrystalline layer, by implanting or furnace doping of the polycrystalline layer after deposition.
6. A method of fabricating a metal oxide silicon (MOS) transistor as claimed in any preceding claim wherein the the source is formed by doping the polycrystalline layer during deposition of the polycrystalline layer, by implanting or furnace doping the polycrystalline layer after deposition.
7. A method of fabricating a metal oxide silicon (MOS) transistor as claimed in any preceding claim wherein the step of recrystallising the amorphous or polycrystalline layer is by solid phase epitaxy or direct epitaxy.
8. A method of fabricating a metal oxide silicon (MOS) transistor substantially as hereinbefore described with reference to the accompanying drawings.
9. A metal oxide silicon (MOS) transistor comprising a semiconductor substrate, an insulating layer on the semiconductor substrate, a seed window in the insulating layer which seed window communicates with the semiconductor substrate, and a recrystallised amorphous or polycrystalline semiconductor layer overlying the insulating layer at least in the region of the seed window and contacting the semiconductor substrate, a source formed in the recrystallised amorphous or polycrystalline semiconductor layer upon the insulating layer on one side of the seed window, a drain formed in the recrystallised amorphous or polycrystalline semiconductor layer upon the other side of the seed window and a gate between the source and the drain, the gate overlying the seed window.
10. A metal oxide silicon (MOS) transistor as claimed in claim 9 wherein the source and the drain are diffused N-type regions formed in the part of the recrystallised amorphous or polycrystalline layer which overlies the insulator.
11. A metal oxide silicon (MOS) transistor substantially as hereinbefore described with reference to the accompanying drawings.
CLAIMS Amendments to the claims have been filed, and have the following effect: Claim 4 above has been textually amended.
New or textually amended claims have been filed as follows:
GB08601830A 1986-01-25 1986-01-25 Method of fabricating an mos transistor Withdrawn GB2185851A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
GB08601830A GB2185851A (en) 1986-01-25 1986-01-25 Method of fabricating an mos transistor
EP87900849A EP0258285A1 (en) 1986-01-25 1987-01-19 Methods for fabricating transistors and mos transistors fabricated by such methods
PCT/GB1987/000030 WO1987004563A1 (en) 1986-01-25 1987-01-19 Methods for fabricating transistors and mos transistors fabricated by such methods
JP62500890A JPS63502544A (en) 1986-01-25 1987-01-19 Transistor manufacturing method and MOS transistor manufactured by the same method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08601830A GB2185851A (en) 1986-01-25 1986-01-25 Method of fabricating an mos transistor

Publications (2)

Publication Number Publication Date
GB8601830D0 GB8601830D0 (en) 1986-02-26
GB2185851A true GB2185851A (en) 1987-07-29

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ID=10591944

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08601830A Withdrawn GB2185851A (en) 1986-01-25 1986-01-25 Method of fabricating an mos transistor

Country Status (4)

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EP (1) EP0258285A1 (en)
JP (1) JPS63502544A (en)
GB (1) GB2185851A (en)
WO (1) WO1987004563A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1274134A3 (en) * 2001-07-04 2006-11-02 Matsushita Electric Industrial Co., Ltd. MOS transistor and its fabrication method
EP4297099A1 (en) * 2022-06-24 2023-12-27 NXP USA, Inc. Transistor with current terminal regions and channel region in layer over dielectric

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4863877A (en) * 1987-11-13 1989-09-05 Kopin Corporation Ion implantation and annealing of compound semiconductor layers
US5021119A (en) * 1987-11-13 1991-06-04 Kopin Corporation Zone-melting recrystallization process
US5453153A (en) * 1987-11-13 1995-09-26 Kopin Corporation Zone-melting recrystallization process

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3764413A (en) * 1970-11-25 1973-10-09 Nippon Electric Co Method of producing insulated gate field effect transistors
GB1457800A (en) * 1973-02-24 1976-12-08 Hitachi Ltd Mis Semiconductor devices
GB1604786A (en) * 1977-06-03 1981-12-16 Fujitsu Ltd Semiconductor device and process for producing the same
US4476475A (en) * 1982-11-19 1984-10-09 Northern Telecom Limited Stacked MOS transistor
US4514895A (en) * 1983-04-20 1985-05-07 Mitsubishi Denki Kabushiki Kaisha Method of forming field-effect transistors using selectively beam-crystallized polysilicon channel regions

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4269631A (en) * 1980-01-14 1981-05-26 International Business Machines Corporation Selective epitaxy method using laser annealing for making filamentary transistors
JPS5861622A (en) * 1981-10-09 1983-04-12 Hitachi Ltd Manufacture of single crystal thin film
EP0077737A3 (en) * 1981-10-19 1984-11-07 FAIRCHILD CAMERA & INSTRUMENT CORPORATION Low capacitance field effect transistor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3764413A (en) * 1970-11-25 1973-10-09 Nippon Electric Co Method of producing insulated gate field effect transistors
GB1457800A (en) * 1973-02-24 1976-12-08 Hitachi Ltd Mis Semiconductor devices
GB1604786A (en) * 1977-06-03 1981-12-16 Fujitsu Ltd Semiconductor device and process for producing the same
US4476475A (en) * 1982-11-19 1984-10-09 Northern Telecom Limited Stacked MOS transistor
US4514895A (en) * 1983-04-20 1985-05-07 Mitsubishi Denki Kabushiki Kaisha Method of forming field-effect transistors using selectively beam-crystallized polysilicon channel regions

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1274134A3 (en) * 2001-07-04 2006-11-02 Matsushita Electric Industrial Co., Ltd. MOS transistor and its fabrication method
EP4297099A1 (en) * 2022-06-24 2023-12-27 NXP USA, Inc. Transistor with current terminal regions and channel region in layer over dielectric
US20230420546A1 (en) * 2022-06-24 2023-12-28 Nxp Usa, Inc. Transistor with current terminal regions and channel region in layer over dielectric

Also Published As

Publication number Publication date
JPS63502544A (en) 1988-09-22
EP0258285A1 (en) 1988-03-09
WO1987004563A1 (en) 1987-07-30
GB8601830D0 (en) 1986-02-26

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