US20090309131A1 - Igbt transistor with protection against parasitic component activation and manufacturing process thereof - Google Patents
Igbt transistor with protection against parasitic component activation and manufacturing process thereof Download PDFInfo
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- US20090309131A1 US20090309131A1 US12/300,136 US30013606A US2009309131A1 US 20090309131 A1 US20090309131 A1 US 20090309131A1 US 30013606 A US30013606 A US 30013606A US 2009309131 A1 US2009309131 A1 US 2009309131A1
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- 230000003071 parasitic effect Effects 0.000 title description 6
- 230000004913 activation Effects 0.000 title description 4
- 238000001994 activation Methods 0.000 title description 4
- 210000000746 body region Anatomy 0.000 claims abstract description 56
- 239000007943 implant Substances 0.000 claims abstract description 27
- 238000000034 method Methods 0.000 claims description 21
- 230000008569 process Effects 0.000 claims description 21
- 238000002513 implantation Methods 0.000 claims description 19
- 239000002019 doping agent Substances 0.000 claims description 14
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- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 2
- 229920005591 polysilicon Polymers 0.000 claims description 2
- 230000003213 activating effect Effects 0.000 claims 1
- 238000000151 deposition Methods 0.000 claims 1
- 238000010438 heat treatment Methods 0.000 claims 1
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
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- 229910052814 silicon oxide Inorganic materials 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor 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
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep 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
- H01L29/66234—Bipolar junction transistors [BJT]
- H01L29/66325—Bipolar junction transistors [BJT] controlled by field-effect, e.g. insulated gate bipolar transistors [IGBT]
- H01L29/66333—Vertical insulated gate bipolar transistors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor 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
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/10—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions with semiconductor regions connected to an electrode not carrying current to be rectified, amplified or switched and such electrode being part of a semiconductor device which comprises three or more electrodes
- H01L29/1095—Body region, i.e. base region, of DMOS transistors or IGBTs
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor 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
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep 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
- H01L29/66234—Bipolar junction transistors [BJT]
- H01L29/66325—Bipolar junction transistors [BJT] controlled by field-effect, e.g. insulated gate bipolar transistors [IGBT]
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor 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
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/70—Bipolar devices
- H01L29/72—Transistor-type devices, i.e. able to continuously respond to applied control signals
- H01L29/739—Transistor-type devices, i.e. able to continuously respond to applied control signals controlled by field-effect, e.g. bipolar static induction transistors [BSIT]
- H01L29/7393—Insulated gate bipolar mode transistors, i.e. IGBT; IGT; COMFET
- H01L29/7395—Vertical transistors, e.g. vertical IGBT
Definitions
- the present invention relates to an IGBT transistor with protection against activation of parasitic components and to a manufacturing process thereof.
- FIG. 1 shows the structure of a conventional IGBT transistor, designated by the reference number 1 .
- the IGBT transistor 1 comprises a drift region 2 of an N ⁇ -type, a body region 3 , of a P ⁇ -type.
- the body region 3 houses two symmetrical source regions 5 , of an N + -type.
- the body region 3 and the source regions 5 are aligned to a surface 2 a of the drift region 2 and are contacted by an emitter line 7 .
- Gate regions 8 are arranged on the surface 2 a, at sides of and partly overlying the body region 3 , and are separated from the underlying structures by gate-oxide regions 9 . More precisely, the gate regions 8 are each aligned to a respective one of the source regions 5 , and portions of the body region 3 immediately underlying the gate regions 8 define channel regions 10 . The gate regions 8 are directly connected to one another and are provided with a gate terminal (not shown).
- the IGBT transistor 1 further comprises a collector region 12 , of a P + -type, separated from the drift region 2 by a transition region 13 , of an N + -type. Finally, a collector contact 15 coats the collector region 13 throughout its extension.
- the body region 3 , the drift region 2 , and the collector region 13 define a PNP transistor 17 , controlled by an NMOS transistor 18 formed by the source regions 5 , the body region 3 (in particular, the channel regions 10 ) and the drift region 2 .
- a further parasitic NPN transistor 19 is present, formed by the source regions 5 , the body region 3 (outside the channel regions 10 ) and, once again, the drift region 2 .
- the PNP transistor 17 , the MOS transistor 18 and the NPN transistor 19 form a thyristor 20 .
- the current of the IGBT transistor 1 is substantially determined by a conduction current I D (of holes, in this case) of the PNP transistor 17 and by a control current I C (of electrons), which flows through the NMOS transistor 18 .
- the NPN transistor 19 should be normally off.
- the body region 3 has a low doping level and hence a relatively high internal resistance R I . Consequently, the conduction current ID may cause a voltage drop between the source regions 5 and the body region 3 (which form the emitter and the base, respectively, of the NPN transistor 19 ) such as to turn the NPN transistor 19 on.
- the thyristor 20 is activated, and the current flows directly towards the emitter line 7 , independently of the MOS transistor 18 , and hence can no longer be controlled by means of the gate terminal 11 .
- activation of the transistor 20 limits the maximum current of the IGBT transistor 1 , especially at high temperatures.
- the treatment concerns that portion of the body region 3 where mainly the conduction current ID is present.
- the dopant species is introduced through the openings between the gate regions 8 and diffuses towards the drift region 2 .
- the diffusion is substantially isotropic and hence can easily alter doping of the channel region 10 , in effect increasing the threshold voltage of the MOS transistor 18 .
- the phenomenon hence limits the depth that the diffusion can reach and, consequently, also the benefit that can be achieved.
- a shallow implantation self-aligned to the gate regions 20 is performed and is followed by a diffusion for a short time. In this way, doping of the channel regions 10 and the value of the threshold voltage of the MOS transistor 18 are preserved, but it is possible to obtain only a modest reduction in the resistance of the body region 3 .
- the present invention provides an IGBT transistor and a manufacturing process thereof which will overcome at least some of the limitations described.
- an IGBT transistor comprising a drift region, at least one body region housed in said drift region and having a first type of conductivity, and a conduction region crossing said body region in a direction perpendicular to a surface of said drift region and having said first type of conductivity and a lower resistance than said body region, characterized in that said conduction region comprises a plurality of implant regions arranged at respective depths from said surface of said drift region and a process for manufacturing an IGBT transistor comprising the steps of providing, in a semiconductor wafer, a drift region forming, in said drift region, at least one body region having a first type of conductivity, and forming a conduction region crossing said body region in a direction perpendicular to a surface of said drift region and having said first type of conductivity and a resistance lower than that of said body region, characterized in that said step of forming said conduction region comprises carrying out a plurality of implantations of dopant species in said body region at respective depths from said surface of said surface of said
- FIG. 1 is a cross-sectional view through a known IGBT transistor
- FIGS. 2 and 3 are cross-sectional views through a semiconductor wafer, in successive steps of a process of fabrication according to the present invention
- FIG. 4 is a top plan view of the wafer of FIG. 3 , at a different scale
- FIGS. 5-12 show the same view as that of FIGS. 2 and 3 , in successive fabrication steps;
- FIG. 13 is a top plan view of the wafer of FIG. 12 , at a different scale.
- FIG. 14 is a cross-sectional view through an IGBT transistor according to the present invention.
- number 100 designates a semiconductor wafer comprising a substrate 101 , which in the embodiment described herein has a P + -type conductivity.
- a transition region 102 of an N + -type
- a drift region 103 of an N ⁇ -type, are made in succession starting from the substrate 101 .
- the drift region 103 has a doping level of approximately 10 14 atoms/cm 3 .
- a gate-oxide layer 105 having a thickness of some hundreds of nanometres, is formed on the free surface 103 a of the drift region 103 , by means of a thermal oxidation of short duration.
- a conductive polysilicon layer 107 is deposited on the wafer 100 .
- a resist layer is deposited and delineated so as to form a first mask 108 having first windows 109 , in the form of strips that extend perpendicular to the plane of the drawing.
- the conductive layer 107 and the gate-oxide layer 105 are etched and removed through the first windows 109 of the first mask 108 so as to expose the drift region 103 .
- residual portions of the conductive layer 107 define gate regions 107 a, spaced apart by openings 110 and separated from the drift region 103 by gate-oxide regions 105 a.
- the gate regions 107 a are connected to one another through a continuous portion 107 b, as shown in FIG. 4 (here the first mask 108 is not illustrated).
- a P-type dopant species is introduced into the drift region 103 through the openings 110 and made to diffuse by means of a thermal process.
- body regions 112 are formed, of a P ⁇ -type, which extend laterally on the outside of respective windows 110 and reach a pre-set depth.
- Portions of the body region immediately underlying the respective gate-oxide regions 105 a define channel regions 113 (represented with a dashed line in FIG. 5 ).
- the first mask 108 is removed, and in its place a second mask 114 is provided, as shown in FIG. 6 .
- the second mask 114 On each body region 112 , the second mask 114 has two second windows 115 , which extend in a direction perpendicular to the plane of the drawing.
- the second windows 115 leave respective strips exposed and are aligned to respective gate regions 107 a, which delimit the body region 112 .
- an N + -type implantation is carried out using the second mask 114 .
- source regions 117 of an N + -type are formed, having, for example, a level of doping of 10 20 atoms/cm 3 .
- each body region 112 two source regions 117 are made, aligned to respective gate regions 110 .
- the channel regions 113 are defined between the source regions 117 and the drift region 103 , immediately underneath the gate-oxide regions 105 a.
- a third mask 118 is defined, having third windows 120 that expose at the centre strips of respective body regions 112 , but coat at least in part the source regions 117 . Also the windows 120 extend in a direction perpendicular to the plane of the drawing.
- the third mask 118 is then configured so as to leave a margin of distance L between the exposed part of the body region 112 and the gate regions 107 a.
- a surface implantation of a P + -type is first carried out so as to create a surface implant region 121 of a P + -type, having approximately the same doping level as the source regions 117 (approximately 10 20 atoms/cm 3 ), but opposite conductivity. Furthermore, the energy of the implantation is such that the peak of the doping density of the surface implant region 121 is found slightly underneath the source regions 117 .
- a plurality of P-type deep implantations are then carried out, once again using the third mask 118 .
- Each implantation is performed at an higher energy than the previous one; hence the dopant species implanted penetrate to a greater depth in the body regions 112 , thus forming a conduction region 124 that defines a continuous, high-conductivity path throughout the body region 112 , in a direction perpendicular to the surface 103 a of the drift region 103 .
- a first buried implant region 123 a is provided, underneath the surface implant region 121 and contiguous thereto (at a depth D 1 ).
- the second and third deep implantations ( FIGS. 9 and 10 ) give rise to a second deep implant region 123 b and to a third deep implant region 123 c, respectively, at increasing depths D 2 , D 3 from the surface 103 a of the drift region 103 , as shown in FIGS. 9 and 10 .
- the fourth implantation is carried out at the maximum energy as compared to the previous ones and forms a fourth deep implant region 123 d at a depth D 4 , contiguous to the drift region 103 .
- the buried implant regions 123 a - 123 d are arranged at increasing depths, are contiguous to one another and moreover have an intermediate doping level between the body region 112 and the surface implant region 121 (for example, approximately 10 19 atoms/cm 3 ). Consequently, the conduction region 124 , comprising the buried implant regions 123 a - 123 d and the surface implant region 121 , defines a continuous conductive path through the body region 112 in a direction perpendicular to the surface 103 a of the drift region 103 .
- the conduction region 124 has a resistance smaller than the body region 112 .
- the third mask 118 is removed, and an ultra-rapid thermal process is carried out, for example bringing the wafer 100 to a temperature of between 1000° C. and 1150° C. for 10-30 s.
- the dopant species introduced into the wafer 100 are electrically activated, but do not have enough time to diffuse and consequently remain where they are.
- a dielectric layer 125 for example, a silicon-oxide layer, is then deposited and selectively etched in order to define insulating regions, which incorporate the gate regions 107 a and leave the body regions 112 and portions of the source regions 117 exposed.
- the dielectric layer 125 is opened also on top of the gate regions 107 a in areas which are to form emitter electrical contacts.
- a metal layer is deposited and delineated by a photolithographic process in order to provide an emitter line 126 , which extends within the openings 110 and electrically connects the body regions 112 and the source regions 117 to one another.
- a gate line 127 is defined, connected to the gate regions 107 a ( FIG. 13 ).
- the substrate 101 is thinned to a pre-determined thickness and coated with a metal layer forming a collector electrode 128 .
- the wafer 100 is divided up into dice, each of which comprises a respective IGBT transistor 130 having the structure illustrated in FIG. 14 .
- the process described advantageously enables provision of an IGBT transistor in which latch-up of the intrinsic parasitic thyristor requires a particularly high current density.
- the highly conductive paths traversing entirely the body regions 112 enable drawing high currents without causing any significant voltage drops between the body regions 112 themselves and the source regions 117 housed therein.
- doping of the channel regions 113 is preserved.
- the deep implantations are, in fact, carried out maintaining a margin of distance from the respective gate regions 107 , which delimit the channel regions 113 .
- the dopant species introduced into the body regions are subjected to inevitable phenomena of scattering associated to the implantation, and hence the surface implant region 121 and deep implant regions 123 a - 123 b can be slightly misaligned with respect to the third mask 118 .
- the margin of distance is sufficient to prevent the dopant species from reaching the channel regions 113 , thus maintaining the doping substantially unaltered. Consequently, also the threshold voltage can be controlled easily.
- the conductive path through the body regions 112 can be obtained by an arbitrary number of implantations.
- the deep implants could be obtained starting from the deepest, then decreasing the implantation energy, or even in any other arbitrary order.
Abstract
An IGBT transistor includes a drift region, at least one body region housed in the drift region and having a first type of conductivity, and a conduction region, which crosses the body region in a direction perpendicular to a surface of the drift region and has the first type of conductivity and a lower resistance than the body region. The conduction region includes a plurality of implant region, arranged at respective depths from the surface of the drift region.
Description
- This application claims the priority benefit of International patent application number PCT/IT2006/000350 filed on 11 May 2006, entitled “IGBT Transistor With Protection Against Parasitic Component Activation And Manufacturing Process Thereof,” which is hereby incorporated by reference to the maximum extent allowable by law.
- The present invention relates to an IGBT transistor with protection against activation of parasitic components and to a manufacturing process thereof.
- As is known, in IGBT transistors the maximum current in the conduction state is limited by the presence of an intrinsic parasitic thyristor. For greater clarity, reference may be made to
FIG. 1 , which shows the structure of a conventional IGBT transistor, designated by thereference number 1. TheIGBT transistor 1 comprises adrift region 2 of an N−-type, abody region 3, of a P−-type. In turn thebody region 3 houses twosymmetrical source regions 5, of an N+-type. Thebody region 3 and thesource regions 5 are aligned to asurface 2 a of thedrift region 2 and are contacted by anemitter line 7.Gate regions 8 are arranged on thesurface 2 a, at sides of and partly overlying thebody region 3, and are separated from the underlying structures by gate-oxide regions 9. More precisely, thegate regions 8 are each aligned to a respective one of thesource regions 5, and portions of thebody region 3 immediately underlying thegate regions 8 definechannel regions 10. Thegate regions 8 are directly connected to one another and are provided with a gate terminal (not shown). TheIGBT transistor 1 further comprises acollector region 12, of a P+-type, separated from thedrift region 2 by atransition region 13, of an N+-type. Finally, a collector contact 15 coats thecollector region 13 throughout its extension. - From an electrical standpoint, the
body region 3, thedrift region 2, and thecollector region 13 define aPNP transistor 17, controlled by anNMOS transistor 18 formed by thesource regions 5, the body region 3 (in particular, the channel regions 10) and thedrift region 2. In addition, a furtherparasitic NPN transistor 19 is present, formed by thesource regions 5, the body region 3 (outside the channel regions 10) and, once again, thedrift region 2. In practice, thePNP transistor 17, theMOS transistor 18 and theNPN transistor 19 form athyristor 20. In use, the current of theIGBT transistor 1 is substantially determined by a conduction current ID (of holes, in this case) of thePNP transistor 17 and by a control current IC (of electrons), which flows through theNMOS transistor 18. TheNPN transistor 19 should be normally off. Thebody region 3, however, has a low doping level and hence a relatively high internal resistance RI. Consequently, the conduction current ID may cause a voltage drop between thesource regions 5 and the body region 3 (which form the emitter and the base, respectively, of the NPN transistor 19) such as to turn theNPN transistor 19 on. In this case, thethyristor 20 is activated, and the current flows directly towards theemitter line 7, independently of theMOS transistor 18, and hence can no longer be controlled by means of the gate terminal 11. In addition, activation of thetransistor 20 limits the maximum current of theIGBT transistor 1, especially at high temperatures. - In order to overcome this problem, it has been proposed to reduce the resistance of the
body region 3 by means of deep diffusion of a dopant species. In particular, the treatment concerns that portion of thebody region 3 where mainly the conduction current ID is present. The dopant species is introduced through the openings between thegate regions 8 and diffuses towards thedrift region 2. However, the diffusion is substantially isotropic and hence can easily alter doping of thechannel region 10, in effect increasing the threshold voltage of theMOS transistor 18. The phenomenon hence limits the depth that the diffusion can reach and, consequently, also the benefit that can be achieved. - According to an alternative solution, a shallow implantation self-aligned to the
gate regions 20 is performed and is followed by a diffusion for a short time. In this way, doping of thechannel regions 10 and the value of the threshold voltage of theMOS transistor 18 are preserved, but it is possible to obtain only a modest reduction in the resistance of thebody region 3. - According to one embodiment, the present invention provides an IGBT transistor and a manufacturing process thereof which will overcome at least some of the limitations described.
- According to one embodiment, there is provided an IGBT transistor comprising a drift region, at least one body region housed in said drift region and having a first type of conductivity, and a conduction region crossing said body region in a direction perpendicular to a surface of said drift region and having said first type of conductivity and a lower resistance than said body region, characterized in that said conduction region comprises a plurality of implant regions arranged at respective depths from said surface of said drift region and a process for manufacturing an IGBT transistor comprising the steps of providing, in a semiconductor wafer, a drift region forming, in said drift region, at least one body region having a first type of conductivity, and forming a conduction region crossing said body region in a direction perpendicular to a surface of said drift region and having said first type of conductivity and a resistance lower than that of said body region, characterized in that said step of forming said conduction region comprises carrying out a plurality of implantations of dopant species in said body region at respective depths from said surface of said drift region.
- For a better understanding of the invention, an embodiment thereof will now be described, purely by way of non-limiting example, with reference to the attached drawings, wherein:
-
FIG. 1 is a cross-sectional view through a known IGBT transistor; -
FIGS. 2 and 3 are cross-sectional views through a semiconductor wafer, in successive steps of a process of fabrication according to the present invention; -
FIG. 4 is a top plan view of the wafer ofFIG. 3 , at a different scale; -
FIGS. 5-12 show the same view as that ofFIGS. 2 and 3 , in successive fabrication steps; -
FIG. 13 is a top plan view of the wafer ofFIG. 12 , at a different scale; and -
FIG. 14 is a cross-sectional view through an IGBT transistor according to the present invention. - With reference to
FIG. 2 ,number 100 designates a semiconductor wafer comprising asubstrate 101, which in the embodiment described herein has a P+-type conductivity. By an epitaxial growth, atransition region 102, of an N+-type, and adrift region 103, of an N−-type, are made in succession starting from thesubstrate 101. For example, thedrift region 103 has a doping level of approximately 1014 atoms/cm3. Then, a gate-oxide layer 105, having a thickness of some hundreds of nanometres, is formed on thefree surface 103 a of thedrift region 103, by means of a thermal oxidation of short duration. Then, aconductive polysilicon layer 107 is deposited on thewafer 100. - As is shown in
FIG. 3 , a resist layer is deposited and delineated so as to form afirst mask 108 havingfirst windows 109, in the form of strips that extend perpendicular to the plane of the drawing. Theconductive layer 107 and the gate-oxide layer 105 are etched and removed through thefirst windows 109 of thefirst mask 108 so as to expose thedrift region 103. After etching, residual portions of theconductive layer 107 definegate regions 107 a, spaced apart byopenings 110 and separated from thedrift region 103 by gate-oxide regions 105 a. In addition, thegate regions 107 a are connected to one another through acontinuous portion 107 b, as shown inFIG. 4 (here thefirst mask 108 is not illustrated). - Next (
FIG. 5 ), a P-type dopant species is introduced into thedrift region 103 through theopenings 110 and made to diffuse by means of a thermal process. Given that the dopant species diffuses in a substantially isotropic way,body regions 112 are formed, of a P−-type, which extend laterally on the outside ofrespective windows 110 and reach a pre-set depth. Portions of the body region immediately underlying the respective gate-oxide regions 105 a define channel regions 113 (represented with a dashed line inFIG. 5 ). - The
first mask 108 is removed, and in its place asecond mask 114 is provided, as shown inFIG. 6 . On eachbody region 112, thesecond mask 114 has twosecond windows 115, which extend in a direction perpendicular to the plane of the drawing. Thesecond windows 115 leave respective strips exposed and are aligned torespective gate regions 107 a, which delimit thebody region 112. - Then, an N+-type implantation is carried out using the
second mask 114. In this step, through thesecond windows 115 of thesecond mask 115,source regions 117 of an N+-type are formed, having, for example, a level of doping of 1020 atoms/cm3. In eachbody region 112 twosource regions 117 are made, aligned torespective gate regions 110. Thechannel regions 113 are defined between thesource regions 117 and thedrift region 103, immediately underneath the gate-oxide regions 105 a. - With reference to
FIG. 7 , after removal of thesecond mask 114, athird mask 118 is defined, havingthird windows 120 that expose at the centre strips ofrespective body regions 112, but coat at least in part thesource regions 117. Also thewindows 120 extend in a direction perpendicular to the plane of the drawing. Thethird mask 118 is then configured so as to leave a margin of distance L between the exposed part of thebody region 112 and thegate regions 107 a. - Using the
third mask 118, a surface implantation of a P+-type is first carried out so as to create asurface implant region 121 of a P+-type, having approximately the same doping level as the source regions 117 (approximately 1020 atoms/cm3), but opposite conductivity. Furthermore, the energy of the implantation is such that the peak of the doping density of thesurface implant region 121 is found slightly underneath thesource regions 117. - As shown in
FIGS. 8-11 , a plurality of P-type deep implantations (four in the embodiment described herein) are then carried out, once again using thethird mask 118. Each implantation is performed at an higher energy than the previous one; hence the dopant species implanted penetrate to a greater depth in thebody regions 112, thus forming aconduction region 124 that defines a continuous, high-conductivity path throughout thebody region 112, in a direction perpendicular to thesurface 103 a of thedrift region 103. - In detail (
FIG. 8 ), following upon the first deep implantation, a first buriedimplant region 123 a is provided, underneath thesurface implant region 121 and contiguous thereto (at a depth D1). The second and third deep implantations (FIGS. 9 and 10 ) give rise to a seconddeep implant region 123 b and to a thirddeep implant region 123 c, respectively, at increasing depths D2, D3 from thesurface 103 a of thedrift region 103, as shown inFIGS. 9 and 10 . Finally (FIG. 11 ), the fourth implantation is carried out at the maximum energy as compared to the previous ones and forms a fourthdeep implant region 123 d at a depth D4, contiguous to thedrift region 103. - The buried implant regions 123 a-123 d are arranged at increasing depths, are contiguous to one another and moreover have an intermediate doping level between the
body region 112 and the surface implant region 121 (for example, approximately 1019 atoms/cm3). Consequently, theconduction region 124, comprising the buried implant regions 123 a-123 d and thesurface implant region 121, defines a continuous conductive path through thebody region 112 in a direction perpendicular to thesurface 103 a of thedrift region 103. Theconduction region 124 has a resistance smaller than thebody region 112. - At the end of the sequence of implantations, the
third mask 118 is removed, and an ultra-rapid thermal process is carried out, for example bringing thewafer 100 to a temperature of between 1000° C. and 1150° C. for 10-30 s. During the ultra-rapid thermal process, the dopant species introduced into thewafer 100 are electrically activated, but do not have enough time to diffuse and consequently remain where they are. - With reference to
FIG. 12 , adielectric layer 125, for example, a silicon-oxide layer, is then deposited and selectively etched in order to define insulating regions, which incorporate thegate regions 107 a and leave thebody regions 112 and portions of thesource regions 117 exposed. In addition, in a way known and not shown, thedielectric layer 125 is opened also on top of thegate regions 107 a in areas which are to form emitter electrical contacts. - Then, a metal layer is deposited and delineated by a photolithographic process in order to provide an
emitter line 126, which extends within theopenings 110 and electrically connects thebody regions 112 and thesource regions 117 to one another. In addition, also agate line 127 is defined, connected to thegate regions 107 a (FIG. 13 ). - Finally (
FIG. 14 ), thesubstrate 101 is thinned to a pre-determined thickness and coated with a metal layer forming acollector electrode 128. Thewafer 100 is divided up into dice, each of which comprises arespective IGBT transistor 130 having the structure illustrated inFIG. 14 . - The process described advantageously enables provision of an IGBT transistor in which latch-up of the intrinsic parasitic thyristor requires a particularly high current density. In fact, the highly conductive paths traversing entirely the
body regions 112 enable drawing high currents without causing any significant voltage drops between thebody regions 112 themselves and thesource regions 117 housed therein. - In addition, doping of the
channel regions 113 is preserved. The deep implantations are, in fact, carried out maintaining a margin of distance from therespective gate regions 107, which delimit thechannel regions 113. The dopant species introduced into the body regions are subjected to inevitable phenomena of scattering associated to the implantation, and hence thesurface implant region 121 and deep implant regions 123 a-123 b can be slightly misaligned with respect to thethird mask 118. However, the margin of distance is sufficient to prevent the dopant species from reaching thechannel regions 113, thus maintaining the doping substantially unaltered. Consequently, also the threshold voltage can be controlled easily. - Finally, it is evident that modifications and variations can be made to the IGBT transistor and to the manufacturing process described herein, without departing from the scope of the present invention, as defined in the annexed claims.
- In particular, the conductive path through the
body regions 112 can be obtained by an arbitrary number of implantations. In addition, the deep implants could be obtained starting from the deepest, then decreasing the implantation energy, or even in any other arbitrary order. - Having thus described at least one illustrative embodiment of the invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention is limited only as defined in the following claims and the equivalents thereto.
Claims (20)
1. An IGBT transistor comprising:
a drift region;
at least one body region housed in said drift region and having a first type of conductivity; and
a conduction region, crossing said body region in a direction perpendicular to a surface of said drift region and having said first type of conductivity and a lower resistance than said body region;
wherein said conduction region comprises a plurality of implant regions, arranged at respective depths from said surface of said drift region.
2. The transistor according to claim 1 , wherein said implant regions comprise a surface implant region and a plurality of buried implant regions contiguous to one another.
3. The transistor according to claim 2 , wherein one of said deep implant regions is contiguous to said drift region.
4. The transistor according to claim 2 , wherein said conduction region has a higher doping level than said body region.
5. The transistor according to claim 4 , wherein said deep implant regions have an intermediate doping level between said body region and said surface implant region.
6. The transistor according to claim 1 , wherein said drift region has a second type of conductivity, opposite to said first type of conductivity.
7. The transistor according to claim 6 , comprising at least one source region housed in said body region and having said second type of conductivity.
8. The transistor according to claim 7 , comprising gate regions arranged on said drift region and defining an opening above said conduction region.
9. The transistor according to claim 8 , wherein said conduction region is arranged centrally with respect to said opening.
10. The transistor according to claim 8 , wherein said body region extends around said opening and is separated from said gate regions by gate-oxide regions and wherein portions of said body region immediately underlying said gate-oxide regions define channel regions.
11. A process for manufacturing an IGBT transistor, comprising the steps of:
providing, in a semiconductor wafer, a drift region;
forming, in said drift region, at least one body region having a first type of conductivity; and
forming a conduction region, crossing said body region in a direction perpendicular to a surface of said drift region and having said first type of conductivity and a resistance lower than that of said body region;
wherein said step of forming said conduction region comprises:
carrying out a plurality of implantations of dopant species in said body regions at respective depths from said surface of said drift region.
12. The process according to claim 11 , wherein said step of carrying out a plurality of implantations comprises carrying out a surface implantation for forming a surface implant region and a plurality of deep implantations for providing respective deep implant regions.
13. The process according to claim 12 , wherein said conduction region has a higher doping level than said body region.
14. The process according to claim 13 , wherein said deep implant regions have an intermediate doping level between said body region and that of said surface implant region.
15. The process according to claim 11 , wherein said drift region has a second type of conductivity, opposite to said first type of conductivity.
16. The process according to claim 11 , comprising the step of subjecting said semiconductor wafer to a thermal process for electrically activating the implanted dopant species, wherein said thermal process has a duration such as to prevent diffusion of the implanted dopant species.
17. The process according to claim 16 , wherein a duration of said thermal process is between 10 s and 30 s.
18. The process according to claim 16 , wherein said thermal process comprises heating said wafer up to a temperature of between 1000° C. and 1150° C.
19. The process according to claim 16 , comprising the steps of:
forming a gate-oxide layer on said drift region;
depositing a conductive polysilicon layer on said gate-oxide layer; and
shaping said conductive layer and said gate-oxide layer for forming gate regions, separated from said drift region by respective gate-oxide regions and defining openings above said drift region.
20. The process according to claim 19 , wherein said step of forming said body region comprises:
introducing dopant species into said drift region through said openings; and
diffusing the dopant species introduced.
Applications Claiming Priority (1)
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PCT/IT2006/000350 WO2007132483A1 (en) | 2006-05-11 | 2006-05-11 | Igbt transistor with protection against parasitic component activation and manufacturing process thereof |
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PCT/IT2006/000350 A-371-Of-International WO2007132483A1 (en) | 2006-05-11 | 2006-05-11 | Igbt transistor with protection against parasitic component activation and manufacturing process thereof |
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US13/211,650 Continuation US20120001224A1 (en) | 2006-05-11 | 2011-08-17 | Igbt transistor with protection against parasitic component activation and manufacturing process thereof |
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US20090309131A1 true US20090309131A1 (en) | 2009-12-17 |
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US12/300,136 Abandoned US20090309131A1 (en) | 2006-05-11 | 2006-05-11 | Igbt transistor with protection against parasitic component activation and manufacturing process thereof |
US13/211,650 Abandoned US20120001224A1 (en) | 2006-05-11 | 2011-08-17 | Igbt transistor with protection against parasitic component activation and manufacturing process thereof |
US14/162,200 Expired - Fee Related US9240457B2 (en) | 2006-05-11 | 2014-01-23 | IGBT transistor with protection against parasitic component activation and manufacturing process thereof |
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US13/211,650 Abandoned US20120001224A1 (en) | 2006-05-11 | 2011-08-17 | Igbt transistor with protection against parasitic component activation and manufacturing process thereof |
US14/162,200 Expired - Fee Related US9240457B2 (en) | 2006-05-11 | 2014-01-23 | IGBT transistor with protection against parasitic component activation and manufacturing process thereof |
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US (3) | US20090309131A1 (en) |
WO (1) | WO2007132483A1 (en) |
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US8823084B2 (en) * | 2012-12-31 | 2014-09-02 | Infineon Technologies Austria Ag | Semiconductor device with charge compensation structure arrangement for optimized on-state resistance and switching losses |
US9147763B2 (en) | 2013-09-23 | 2015-09-29 | Infineon Technologies Austria Ag | Charge-compensation semiconductor device |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4809047A (en) * | 1983-09-06 | 1989-02-28 | General Electric Company | Insulated-gate semiconductor device with improved base-to-source electrode short and method of fabricating said short |
US5034336A (en) * | 1988-03-03 | 1991-07-23 | Fuji Electric Co., Ltd. | Method of producing insulated gate bipolar tranistor |
US5397905A (en) * | 1993-02-16 | 1995-03-14 | Fuji Electric Co., Ltd. | Power semiconductor device having an insulated gate field effect transistor and a bipolar transistor |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
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JPH04152536A (en) * | 1990-10-16 | 1992-05-26 | Fuji Electric Co Ltd | Manufacture of mis semiconductor device |
US5701023A (en) * | 1994-08-03 | 1997-12-23 | National Semiconductor Corporation | Insulated gate semiconductor device typically having subsurface-peaked portion of body region for improved ruggedness |
-
2006
- 2006-05-11 US US12/300,136 patent/US20090309131A1/en not_active Abandoned
- 2006-05-11 WO PCT/IT2006/000350 patent/WO2007132483A1/en active Application Filing
-
2011
- 2011-08-17 US US13/211,650 patent/US20120001224A1/en not_active Abandoned
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2014
- 2014-01-23 US US14/162,200 patent/US9240457B2/en not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4809047A (en) * | 1983-09-06 | 1989-02-28 | General Electric Company | Insulated-gate semiconductor device with improved base-to-source electrode short and method of fabricating said short |
US5034336A (en) * | 1988-03-03 | 1991-07-23 | Fuji Electric Co., Ltd. | Method of producing insulated gate bipolar tranistor |
US5397905A (en) * | 1993-02-16 | 1995-03-14 | Fuji Electric Co., Ltd. | Power semiconductor device having an insulated gate field effect transistor and a bipolar transistor |
Also Published As
Publication number | Publication date |
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US9240457B2 (en) | 2016-01-19 |
US20140134807A1 (en) | 2014-05-15 |
US20120001224A1 (en) | 2012-01-05 |
WO2007132483A1 (en) | 2007-11-22 |
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