GB2179496A - A method of controlling a distribution of carrier lifetimes within a semiconductor material - Google Patents
A method of controlling a distribution of carrier lifetimes within a semiconductor material Download PDFInfo
- Publication number
- GB2179496A GB2179496A GB08521223A GB8521223A GB2179496A GB 2179496 A GB2179496 A GB 2179496A GB 08521223 A GB08521223 A GB 08521223A GB 8521223 A GB8521223 A GB 8521223A GB 2179496 A GB2179496 A GB 2179496A
- Authority
- GB
- United Kingdom
- Prior art keywords
- distribution
- damage sites
- carrier lifetimes
- damage
- semiconductor material
- 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.)
- Granted
Links
- 239000000463 material Substances 0.000 title claims abstract description 50
- 238000009826 distribution Methods 0.000 title claims abstract description 21
- 239000004065 semiconductor Substances 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 title claims description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 9
- 238000010894 electron beam technology Methods 0.000 claims abstract description 8
- 238000009827 uniform distribution Methods 0.000 abstract description 6
- 239000002800 charge carrier Substances 0.000 abstract description 3
- 239000013078 crystal Substances 0.000 description 5
- 238000005215 recombination Methods 0.000 description 3
- 230000006798 recombination Effects 0.000 description 3
- 238000000137 annealing Methods 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/324—Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- High Energy & Nuclear Physics (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Thyristors (AREA)
Abstract
The lifetime of charge carriers within a semiconductor material 1 depends on the density of damage sites in the material 1. Damage sites 4 may be introduced into the material 1 by electron beam irradiation to produce a uniform distribution. By selectively heating part of the material such that one face 5 of the material 1 is hotter than the opposite face 6 the distribution density of damage sites 4 may be modified and hence the carrier lifetime distribution in the material changed. <IMAGE>
Description
SPECIFICATION
A method of controlling a distribution of carrier lifetimes within a semiconductor material
This invention relates to a method of controlling a distribution of carrier lifetimes within a semiconductor material having damage sites distributed throughout a volume thereof.
Semiconductor materials include carriers of charge which may be either electrons which carry negative charge or holes which carry positive charge. The lifetimes of these carriers depend on a number of factors and it is often desired to modify them to improve the characteristics of a semiconductor device. The carrier lifetime within a semiconductor material is the average time for which a charge carrier exists. It may be desired to have a relatively short lifetime, in order to speed up the turn off of a device, or to have a relatively long lifetime in order to reduce the forward voltage drop across a device.
One way in which carrier lifetimes may be reduced is by creating damage sites within the semiconductor material. A damage site is an imperfection in the crystal lattice in the semiconductor material. For example, a damage site is formed when an atom is moved from its low energy position in a crystal. Damage sites affect the carrier lifetime because they act as recombination centres, that is, they tend to trap one type of carrier and thus lead to a greater likelihood of recombination. Thus a greater concentration of damage sites tends to reduce the carrier lifetime.
One way in which damage sites are introduced into a semiconductor material in order to reduce carrier lifetimes within the material, is to use electron beam irradiation. The material is exposed to a high energy electron beam having energies of the order of 2 to 10 MeV. The electrons have a relatively small mass compared to the atoms in the crystal lattice and as they pass through the material, suffer numerous collisions with the atoms, losing a little energy at each collision. This tends to give a fairly uniform distribution of damage sites throughout the material. However, it may be desirable in a semiconductor device to have a carrier lifetime which varies throughout the device depending on the characteristics required of the device.The amount of damage produced can be reduced by annealing the device at temperatures of about 2500 to 400 C, the extent of removal of the damage being determined by the temperature and duration of the annealing process. However, this serves only to uniformly modify the distribution throughout the material.
Another method of creating damage sites within a semiconductive material is to use proton or neutron beam irradiation. Such heavier particles tend to only suffer one or two collisions at the end of their path in the material.
Thus by controlling the energy of the beam a desired amount of damage at a desired level may be obtained. However, this technique requires expensive equipment.
The present invention seeks to provide a simple and inexpensive way of modifying carrier lifetimes within a semiconductor material.
According to this invention, a method of controlling a distribution of carrier lifetimes within a semiconductor material having damage sites distributed throughout a volume thereof, includes the step of selectively heating part of the material thereby reducing the distribution density of damage sites at that part. By selectively heating part of the material enough energy is supplied at the damage sites at that part of the material to return atoms of the crystal to their low energy locations.
Hence a chosen profile of carrier lifetimes within the material may be obtained.
Preferably, before the part is heated, the distribution of damage sites is substantially uniform throughout the volume and advantageously damage sites are introduced into the material by electron beam irradiation. By employing an initially uniform distribution of damage sites it may be easier to select the correct amount of heating at various parts throughout the material to achieve an acceptable distribution of carrier lifetimes within the material.
Preferably a temperature gradient is established across the material thereby producing a corresponding gradient in the density of the damaged sites. This is easy to achieve and results in carrier lifetimes near one surface of the material being longer than those near the other. However, different distributions of carrier lifetime may be obtained by heating only a small part of one surface, or a number of parts along the surface, or by establishing two temperature gradients from either side of the material.
According to a feature of the invention a semiconductor device includes a distribution of carrier lifetimes, modified by a method in accordance with the invention.
According to another feature of the invention, apparatus for modified minority carrier lifetimes in a semiconductor material comprises means for selectively reducing a distribution density of damage sites in the material by heating part of the material.
The invention is now further described by way of example with reference to the accompanying drawings, in which:
Figure la illustrates schematically the introduction of damage sites in a semiconductor material;
Figure 1b illustrates a method and apparatus in accordance with the invention; and
Figure 2 illustrates schematically part of a thyristor in accordance with the invention.
With reference to Fig. la, a piece of semi conductor material 1 is subjected to a high energy electron beam, the direction of which is illustrated by the arrow 2. The electron beam produces a substantially uniform distribution of damage sites illustrated schematically at 4 in that part of the material which is exposed to the beam.
Referring to Fig. 1 b, a temperature gradient is then applied across the material 1 from one of its surfaces 5 to the facing surface 6. The surface 5 is maintained at a temperature of about 4000C by a heating element 7 and the opposite face 6 is maintained at a temperature of about 2500C by a cooling element 8. This temperature gradient is maintained for about an hour and has the effect of reducing the density of damage sites 4 at the hotter surface than at the other such that a gradient of density distribution of damage sites 4 is produced throughout the material. Energy must be applied to remove a damage site to enable the displaced lattice atom to move to its position of lowest energy within the crystal lattice.
Thus by modifying the density distribution of damage sites the distribution of carrier lifetimes is also modified, there being a gradient from the relatively longer lifetimes at the surface 5 to the shorter lifetimes at the surface 6. This difference may be of the order of 20%.
With reference to Fig. 2, a thyristor includes a cathode electrode 9 and an anode electrode 10 between which in normal operation a current flows. To obtain conduction initially a current is applied to a gate electrode 11 and flows through a p base region 12 to the cathode 9. This current flow causes a junction J3 between an n emitter region 13 and the p base region 12 to become forward biased and electrons are injected into the p base region 12 from the n emmitter region 13. These electrons are then accelerated across a depletion layer associated with a junction J2 between the p base region 12 and an n base region 14. Electron diffusion occurs through the n base region 14 to another junction J1 between that region 14 and another p type region 15. The presence of these diffused electrons causes hole injection from the P type anode 15, and conduction occurs through the device.It is desirable that the lifetime of the charge carriers near the anode region is relatively long, since then the resistance in this part of the device is reduced.
However it is also desirable that the carrier lifetime in the region of the blocking junction
J2 and the n base region 14 be relatively short so that when reverse bias is applied across the device to switch it off there is relatively rapid recombination with a correspondingly short turn off time.
Initially, a high energy electron beam is used to irradiate the thyristor and hence cause relatively uniform distribution of damage sites throughout the material. Thus there is also a uniform distribution of carrier lifetimes throughout the material. The thyristor is then subjected to a temperature gradient as described above with reference to Fig. 1 b, with the anode region being at a higher temperature than the cathode region. The process may be repeated with the cathode region to give a temperature gradient in the other direction, thus reducing the carrier lifetime in the region of the blocking junction J2 and n base region 14 and more of the damage sites may be removed from the anode region and a longer carrier lifetime is established in this region than in the cathode region. Thus a more rapid turn off is achieved with little cost in associated voltage drop across the device.
Of course other devices, such as diodes, may also benefit by employing the present invention.
Claims (8)
1. A method of controlling a distribution of carrier lifetimes within a semiconductor material having damage sites distributed throughout a volume thereof, including the step of selectively heating part of the material thereby reducing the distribution density of damage sites at that part.
2. A method as claimed in claim 1 and wherein, before the part is heated, the distribution of damage sites is substantially uniform throughout the volume.
3. A method as claimed in claim 1 or 2, and including the step of introducing damage sites into the material by electron beam irradiation.
4. A method as claimed in claim 1, 2 or 3 and wherein a temperature gradient is established across the material thereby producing a corresponding gradient in the density of damage sites.
5. A semiconductor device including a distribution of carrier lifetimes modified by a method as claimed in any preceding claims.
6. Apparatus for modifying carrier lifetimes in a semiconductor material comprising means for seictively reducing a distribution density of damage sites in the material by heating part of the material.
7. A method substantially as described with reference to Figs. 1a and 1b of the accompanying Drawings.
8. A thyristor substantially as illustrated in and described with reference to Fig. 2 of the accompanying Drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8521223A GB2179496B (en) | 1985-08-23 | 1985-08-23 | A method of controlling a distribution of carrier lifetimes within a semiconductor material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8521223A GB2179496B (en) | 1985-08-23 | 1985-08-23 | A method of controlling a distribution of carrier lifetimes within a semiconductor material |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8521223D0 GB8521223D0 (en) | 1985-10-02 |
| GB2179496A true GB2179496A (en) | 1987-03-04 |
| GB2179496B GB2179496B (en) | 1989-08-09 |
Family
ID=10584265
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8521223A Expired GB2179496B (en) | 1985-08-23 | 1985-08-23 | A method of controlling a distribution of carrier lifetimes within a semiconductor material |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2179496B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0432612A2 (en) * | 1989-12-09 | 1991-06-19 | eupec Europäische Gesellschaft für Leistungshalbleiter mbH & Co. KG | Process for profiling the charge carriers life-time in a semiconductor |
| EP0767500A2 (en) * | 1995-10-03 | 1997-04-09 | Hitachi, Ltd. | Power semiconductor device with lattice defects |
| DE102007026387B4 (en) * | 2006-10-03 | 2012-12-13 | Mitsubishi Electric Corp. | Method for producing a semiconductor device |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0028934A1 (en) * | 1979-11-12 | 1981-05-20 | Fujitsu Limited | A method of manufacturing a semiconductor device |
| EP0036157A1 (en) * | 1980-03-14 | 1981-09-23 | Rockwell International Corporation | Low temperature annealing of semiconductor devices |
-
1985
- 1985-08-23 GB GB8521223A patent/GB2179496B/en not_active Expired
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0028934A1 (en) * | 1979-11-12 | 1981-05-20 | Fujitsu Limited | A method of manufacturing a semiconductor device |
| EP0036157A1 (en) * | 1980-03-14 | 1981-09-23 | Rockwell International Corporation | Low temperature annealing of semiconductor devices |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0432612A2 (en) * | 1989-12-09 | 1991-06-19 | eupec Europäische Gesellschaft für Leistungshalbleiter mbH & Co. KG | Process for profiling the charge carriers life-time in a semiconductor |
| EP0432612A3 (en) * | 1989-12-09 | 1994-07-20 | eupec Europäische Gesellschaft für Leistungshalbleiter mbH & Co. KG | Process for profiling the charge carriers life-time in a semiconductor |
| EP0767500A2 (en) * | 1995-10-03 | 1997-04-09 | Hitachi, Ltd. | Power semiconductor device with lattice defects |
| EP0767500A3 (en) * | 1995-10-03 | 1999-07-28 | Hitachi, Ltd. | Power semiconductor device with lattice defects |
| DE102007026387B4 (en) * | 2006-10-03 | 2012-12-13 | Mitsubishi Electric Corp. | Method for producing a semiconductor device |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8521223D0 (en) | 1985-10-02 |
| GB2179496B (en) | 1989-08-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR940002916B1 (en) | Manufacturing method of semiconductor device and device thereby | |
| US3881964A (en) | Annealing to control gate sensitivity of gated semiconductor devices | |
| CA1160359A (en) | Reducing the reverse recovery charge of thyristors by nuclear irradiation | |
| US2816847A (en) | Method of fabricating semiconductor signal translating devices | |
| US4259683A (en) | High switching speed P-N junction devices with recombination means centrally located in high resistivity layer | |
| JPH09121052A (en) | Semiconductor device and fabrication thereof | |
| US4004950A (en) | Method for improving the doping of a semiconductor material | |
| US4281336A (en) | Thyristor element with short turn-off time and method for producing such element | |
| US6100575A (en) | Semiconductor switching device having different carrier lifetimes between a first portion serving as a main current path and the remaining portion of the device | |
| JP3968129B2 (en) | High speed power diode | |
| JPH07226405A (en) | Manufacture of semiconductor device | |
| JPH05102161A (en) | Manufacture of semiconductor device, and the semiconductor device | |
| US3990091A (en) | Low forward voltage drop thyristor | |
| US3877997A (en) | Selective irradiation for fast switching thyristor with low forward voltage drop | |
| GB2179496A (en) | A method of controlling a distribution of carrier lifetimes within a semiconductor material | |
| US3840887A (en) | Selective irradiation of gated semiconductor devices to control gate sensitivity | |
| US3881963A (en) | Irradiation for fast switching thyristors | |
| US4076555A (en) | Irradiation for rapid turn-off reverse blocking diode thyristor | |
| US4043837A (en) | Low forward voltage drop thyristor | |
| US3532910A (en) | Increasing the power output of certain diodes | |
| US4075037A (en) | Tailoring of recovery charge in power diodes and thyristors by irradiation | |
| JPH01162368A (en) | Semiconductor device | |
| US5144402A (en) | Semiconductor switching device and method of controlling a carrier life time in a semiconductor switching device | |
| EP0032386A2 (en) | A method for tailoring forward voltage drop (VTM) switching time (tq) and reverse-recovery charge (Qrr) in a power thyristor using nuclear particle and electron irradiation | |
| KR950001170B1 (en) | Manufacturing methdo of switching device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920823 |