GB2023857A - Photoresist structure, particularly suitable for photolithographically depositing parallel metal strips on to a base substrate, and the method for forming it - Google Patents
Photoresist structure, particularly suitable for photolithographically depositing parallel metal strips on to a base substrate, and the method for forming it Download PDFInfo
- Publication number
- GB2023857A GB2023857A GB7909598A GB7909598A GB2023857A GB 2023857 A GB2023857 A GB 2023857A GB 7909598 A GB7909598 A GB 7909598A GB 7909598 A GB7909598 A GB 7909598A GB 2023857 A GB2023857 A GB 2023857A
- Authority
- GB
- United Kingdom
- Prior art keywords
- photoresist
- metal strips
- base substrate
- photoresist structure
- forming
- 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
- 229920002120 photoresistant polymer Polymers 0.000 title claims abstract description 48
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 32
- 239000002184 metal Substances 0.000 title claims abstract description 32
- 239000000758 substrate Substances 0.000 title claims abstract description 16
- 238000000034 method Methods 0.000 title claims description 26
- 238000000151 deposition Methods 0.000 title claims description 4
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims abstract description 11
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000002635 aromatic organic solvent Substances 0.000 claims abstract description 8
- MVPPADPHJFYWMZ-UHFFFAOYSA-N chlorobenzene Chemical compound ClC1=CC=CC=C1 MVPPADPHJFYWMZ-UHFFFAOYSA-N 0.000 claims abstract description 7
- MVPPADPHJFYWMZ-IDEBNGHGSA-N chlorobenzene Chemical group Cl[13C]1=[13CH][13CH]=[13CH][13CH]=[13CH]1 MVPPADPHJFYWMZ-IDEBNGHGSA-N 0.000 claims 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims 1
- 125000003944 tolyl group Chemical group 0.000 claims 1
- 239000002904 solvent Substances 0.000 abstract description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 8
- 239000004411 aluminium Substances 0.000 description 8
- 229910052782 aluminium Inorganic materials 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 5
- 230000003287 optical effect Effects 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 4
- 230000005669 field effect Effects 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 2
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 230000000873 masking effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000001465 metallisation Methods 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 238000004377 microelectronic Methods 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical group [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 235000011007 phosphoric acid Nutrition 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000007738 vacuum evaporation Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a 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
- H01L29/66409—Unipolar field-effect transistors
- H01L29/66848—Unipolar field-effect transistors with a Schottky gate, i.e. MESFET
- H01L29/66856—Unipolar field-effect transistors with a Schottky gate, i.e. MESFET with an active layer made of a group 13/15 material
- H01L29/66863—Lateral single gate transistors
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/26—Processing photosensitive materials; Apparatus therefor
- G03F7/38—Treatment before imagewise removal, e.g. prebaking
-
- 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
- H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
- H01L21/0271—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers
- H01L21/0272—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers for lift-off processes
-
- 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
- H01L21/28—Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/268
- H01L21/283—Deposition of conductive or insulating materials for electrodes conducting electric current
- H01L21/285—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation
- H01L21/28506—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers
- H01L21/28575—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising AIIIBV compounds
- H01L21/28587—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising AIIIBV compounds characterised by the sectional shape, e.g. T, inverted T
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a 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
- H01L29/66409—Unipolar field-effect transistors
- H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
- H01L29/66568—Lateral single gate silicon transistors
- H01L29/66575—Lateral single gate silicon transistors where the source and drain or source and drain extensions are self-aligned to the sides of the gate
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Computer Hardware Design (AREA)
- Ceramic Engineering (AREA)
- Liquid Deposition Of Substances Of Which Semiconductor Devices Are Composed (AREA)
- Electrodes Of Semiconductors (AREA)
- Photosensitive Polymer And Photoresist Processing (AREA)
Abstract
The photoresist structure includes at least one residual sector 16 of T- shaped section on a substrate 11 and is formed by immersing a layer of photoresist in a bath of aromatic organic solvent after imagewise exposure and before a final stage of time controlled development. Exemplified solvents are toluene, chlorobenzene and benzene. The invention is said to allow a reduction in the spacings of the metal strips compared with the spacings on the mask through which imagewise exposure takes place. <IMAGE>
Description
SPECIFICATION
Photoresist structure, particularly suitable for photolithographically depositing parallel metal strips on to a base substrate, and the method for forming it
This invention relates to a new photoresist structure, which is particularly suitable for photolithographically depositing parallel metal strips on to a base substrate, and the method for forming it.
The use of photoresist (photoresistive material) is known and usual in photolithographic methods of various kinds, in particular for optical and microelectronic applications in which parallel metal strips are deposited on to a base substrate.
When parallel strips of a single metal are to be obtained, as in the case of optical reticules, a photoresist layer is applied to the base substrate, and a number of parallel areas equal to the number of metal strips to be deposited on to the substrate are then removed from this layer by masking, photographic exposure and development. The metal is then successively deposited on to the substrate through said removed areas, and the metal deposited on the residual photoresist sectors is finally removed together with the photoresist itself by known methods such as the so-called lift-off (dissolving with a solvent).
However, if said metal strips are to alternate with others of a different metal, as in the case of electronic components such as geometrically planar
Schottky diodes and field effect transistors (MES
FET), the photoresist layer is no longer applied directly to the base substrate, but on to an interposed layer of said different metal, which is then chemically attacked and removed in the zones corresponding to the removed areas of the photoresist.
In both cases there are limits to the dimensions and spacing of the strips, which depend on the masks and the relative equipment used, and can only be reduced at the expense of considerable structural complications and cost increase. In addition there are alignment problems in the case of strips of different metal.
The object of the present invention is to provide a residual photoresist structure (i.e. after removing parallel areas), which enables the dimensions and spacing of the metal strips to be considerably reduced for the same mask and equipment used.
This object is attained according to the invention by a photoresist structure, comprising at least one residual sector of T-shaped section.
Again according to the invention, said photoresist structure is obtained by a method comprising immersing a layer of photoresist in a bath of aromatic organic solvent after an initial photomasking stage and before a final stage of time controlled development.
In this respect, it has been found experimentally that when a photoresist subjected to photomasking and then immersed in a bath of aromatic organic solvent (such as toluene, chlorobenzene or benzene) is developed, the photoresist becomes shaped in the form of residual sectors having a T section, the transverse dimensions of which reduce as the development time increases. By suitably controlling the developing time in addition to the exposure and immersion time, it has been found possible to give the photoresist the required transverse dimensions, in particular making them fall much below those which would otherwise be determined by the masking used (for example 0.7 microns for the vertical arm and 1.2 micronsforthe horizontal arm against a width of 3 microns of the relative line on the mask).
This makes it possible to obtain much narrower metal strips, below the T sectors of the photoresist, and much smaller spacing between metal strips deposited on adjacent empty spaces of said photoresist.
The photoresist according to the invention can have many uses. In particular, it has already proved of considerable use in optics and microelectronics for constructing the following structures:
1. Reticules of metal strips having a width down to 0.5 microns spaced apart by a distance equal to their width, in the form of a parallel periodic structure and deposited on insulating substrates.
These structures can be used for optical reticules and surface wave filters.
2. Structures constituted by a strip of metal A (for example aluminium) having a width down to 0.5 microns deposited on a semiconductor material (for example gallium arsenide) and separated on both sides from areas metallised with metals B which are different from the first, by distances down to 0.5 microns. These structures are used to construct electronic components such as geometrically planar
Schottky diodes, and the field effect transistors known as MESFET.
3. MOS (mMOS (metal-insulant-semiconductor) struc- tures, characterized by a metal strip of width down to 0.5 microns deposited on a thin layer of insulant (for example silicon oxide), which in its turn is deposited on silicon. In the zone lying below the strip of metal (for example aluminium), the silicon is of type p, whereas outside this there is a surface zone of opposite doping (type n+). This structure is typical of n-channel MOS transistors. An analogous structure can be obtained for p-channel MOS transistors.
The main advantages deriving from the use of the photoresist according to the invention for constructing the aforesaid structures by a photolithographic method are as follows:
a) It possesses self-alignment characteristics, and therefore enables the strip of metal A to be automatically set between the two areas of metal B without the need for optical, mechanical or electronic alignment, when producing structures for electronic components such as that described under the previous point 2.
b) It enables thin sizes to be obtained, both with regard to the width of the metal strips of the structures described under the preceding points 1,2 and 3, and with regard to the interspaces between the different metals of the structure described under point 2.
c) Especially thin geometrical arrangements are not necessary. For example, lines having a width of 3 microns on the photolithographic mask enable dimensions to be obtained of the order of 0.5 microns.
d) An exact reduction by a factor of 2 in the pitch of the reticule under point 1 ) relative to the pitch of the original mask.
e) The method used for its formation is a high efficiency, highly reproducible method, which does not required the use of highly qualified specialist personnel.
Characteristics and advantages of the present invention will be more apparent by reference to the accompanying drawings, given by way of example only, and in which:
Figures 1 to 3 show successive operational stages in the method for forming a photoresist according to the invention;
Figure 4 shows graphs illustrating the variation in the dimensions of the photoresist according to the invention, as a function of the development time.
Figures 5to 7 show successive operational stages in a method for producing reticules in the form of parallel metal strips which uses a photoresist according to the present invention.
Figures 8 to 11 show successive operational stages in a method for producing an electronic component such as a planar Schottky diode or MESFET transistor, using a photoresist according to the present invention;
Figures 12to 15show successive operational stages in a method for producing a MOS structure, using a photoresist in accordance with the present invention.
As shown in Figures 1 to 3, the method according to the invention generally comprises the application, on to a base substrate 11, of a photoresist layer 12 (Figure 1) which is then exposed through a photolithographic mask 13 (Figure 2) which establishes different physical conditions for the protected and unprotected zones 14 and 15 respectively, of the photoresist. This latter is then immersed into a toluene bath (or alternatively chlorobenzene, benzene or another aromatic organic solvent) for a time which depends on the thickness of the photoresist layer (3 to 10 minutes for a thickness of about 1 micron).This determines a further physical difference between the zones 14 and 15 of the photoresist, presumably by increasing the resistance of the protected zone 14 to development, to an extent greater in the portion closest to the solvent attack front than in the portion farthest therefrom. At this point, by controlling the development time it is possible to obtain a residual T-shaped sector 16 of dimensions which are variable, butwhich in all cases are less than the original dimensions of the protected zone 14 (Figure 3).Figure 4, in which the development time (measured in minutes) is represented by the abscissa and the dimensions of the residual sector 16 (measured in microns) are represented by the ordinate, shows the variation curves (a, b) of the width of the horizontal branch 17 and vertical branch 18 respectively, of the residual sector 16 for an immersion time of 7 minutes. As shown in
Figure 4, from an original dimension of 3 microns, depending on the scoring of the mask 13, it is possible to descend to a width of 0.7 and 1.2 microns for the two branches 18 and 17 respectively of the residual sector 16 of the photoresist.
The described photoresist, with a residual sector or sectors 16 in the form of a T of controllable width, and its method of formation, have numerous uses, generally in photolithographic methods for forming parallel metal strip structures.
Figures 5 to 7 show for example the various stages in an optical reticule production process using a photoresist structure according to the invention. In this process, an appropriate numberofTsectors 16 are formed on a substrate 21 by the method already described. By inclined evaporation (arrows 22 and 23) of the desired metal 24, the condition shown in
Figure 6 is reached, and finally the photoresist and overlying metallisation are removed by known methods, for example by dissolving with a solvent (lift-off). There thus remains on the substrate 21 a set of parallel metal stripe 24, their distance apart being considerably reduced by utilising the T shape of the photoresist.
Figures 8 to 11 show the various stages in a process for producing an electronic component such as a planar Schottky diode or a field effect transistor (MESFET), in which a photoresist with a central
T-shaped residual sector 16 and lateral residual sectors 31 is formed by the method according to the invention on an aluminium layer 32 having a thickness of the order of 1 micron, applied by vacuum evaporation on to a GaAs substrate 33, on which an active semiconductor layer 33 has been previously disposed (Figures 8 and 9). The aluminium 32 is removed from the empty spaces of the photoresist, using a chemical solvent which does not attack the underlying semiconductor layer 34 (80% H3PO4 at 50 C), and metal strips 35 (Ni-AuGe) are evaporated in its place (and on the photoresist) (Figure 10), to form the ohmic contacts.The T structure of the central sector 16 of the photoresist ensures that the central aluminium strip 32 below said central sector is aligned with the two lateral strips of different metal 35. The photoresist and the overlying metallisation are then removed by known methods, for example by dissolving with a solvent (lift-off). The lateral aluminium residues outside the active areas are finally removed, to give the fluid device of Figure 11.
Finally, Figures 12 to 15 show the various operational stages of a process which uses the photoresist structure and the method according to the invention for producing a silicon MOS structure. More precisely, starting from the structure shown diagrammatically in Figure 12, with a p substrate 41, n+ areas 42 and a layer of silicon oxide 43, obtainable by a normal MOS manufacturing process, an aluminium layer 44 is deposited, on which a photoresist structure comprising a central Tsector 16 and lateral sectors 45 is formed by the method according to the invention (Figure 13). At this point, the aluminium is removed from the zones corresponding to the apertures of the photoresist (Figure 14), and doping donors are implanted to form a n+ layer 46 in the zones not masked by the aluminium strips 44, after which the photoresist is removed to give the finished device of Figure 15.
Claims (5)
1. A photoresist structure, particularly suitable for photolithographically depositing parallel metal strips on to a base substrate, comprising at least one residual sector of T-shaped section.
2. A method for forming the photoresist structure as claimed in Claim 1, comprising immersing a layer of photoresist in a bath of aromatic organic solvent after an initial photomasking stage and before a final stage of time controlled development.
3. A method as claimed in Claim 2, wherein said aromatic organic solvent is toluene.
4. A method as claimed in Claim 2, wherein said aromatic organic solvent is chlorobenzene.
5. A method as claimed in Claim 2, wherein said aromatic organic solvent is benzene.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT24955/78A IT1096042B (en) | 1978-06-26 | 1978-06-26 | STRUCTURE OF PHOTORESIST PARTICULARLY SUITABLE FOR THE PHOTOLITHOGRAPHIC DEPOSITION OF PARALLEL METAL STRIPS ON A BASIC SUBSTRATE AND PROCEDURE FOR ITS REALIZATION |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2023857A true GB2023857A (en) | 1980-01-03 |
| GB2023857B GB2023857B (en) | 1982-09-15 |
Family
ID=11215250
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7909598A Expired GB2023857B (en) | 1978-06-26 | 1979-03-19 | Photoresist structure particularly suitable for photolithohraphically depositing parallel metal strips on to a base substrate and the method for forming it |
Country Status (4)
| Country | Link |
|---|---|
| DE (1) | DE2911976A1 (en) |
| FR (1) | FR2432727A1 (en) |
| GB (1) | GB2023857B (en) |
| IT (1) | IT1096042B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3138761A1 (en) * | 1981-09-29 | 1983-04-14 | Siemens AG, 1000 Berlin und 8000 München | Method for producing overlap-weighted interdigital structures |
| EP0152164A2 (en) * | 1984-01-06 | 1985-08-21 | International Standard Electric Corporation | Provision of a sub-half-micron-size recess in a semiconductor substrate |
| US4568411A (en) * | 1983-11-22 | 1986-02-04 | British Telecommunications Plc | Metal/semiconductor deposition |
| FR2636471A1 (en) * | 1988-09-14 | 1990-03-16 | Mitsubishi Electric Corp | METHOD FOR MANUFACTURING A GRID ELECTRODE FOR A FIELD EFFECT TRANSISTOR |
| US7189751B2 (en) | 2001-06-25 | 2007-03-13 | Nippon Soda Co., Ltd. | Oxa(thia)zolidine compounds, process for preparation thereof and anti-inflammatory agents |
-
1978
- 1978-06-26 IT IT24955/78A patent/IT1096042B/en active
-
1979
- 1979-03-19 GB GB7909598A patent/GB2023857B/en not_active Expired
- 1979-03-27 DE DE19792911976 patent/DE2911976A1/en not_active Withdrawn
- 1979-03-28 FR FR7907763A patent/FR2432727A1/en not_active Withdrawn
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3138761A1 (en) * | 1981-09-29 | 1983-04-14 | Siemens AG, 1000 Berlin und 8000 München | Method for producing overlap-weighted interdigital structures |
| US4568411A (en) * | 1983-11-22 | 1986-02-04 | British Telecommunications Plc | Metal/semiconductor deposition |
| EP0152164A2 (en) * | 1984-01-06 | 1985-08-21 | International Standard Electric Corporation | Provision of a sub-half-micron-size recess in a semiconductor substrate |
| EP0152164A3 (en) * | 1984-01-06 | 1988-06-08 | International Standard Electric Corporation | Provision of a sub-half-micron-size recess in a semiconductor substrate |
| FR2636471A1 (en) * | 1988-09-14 | 1990-03-16 | Mitsubishi Electric Corp | METHOD FOR MANUFACTURING A GRID ELECTRODE FOR A FIELD EFFECT TRANSISTOR |
| US7189751B2 (en) | 2001-06-25 | 2007-03-13 | Nippon Soda Co., Ltd. | Oxa(thia)zolidine compounds, process for preparation thereof and anti-inflammatory agents |
Also Published As
| Publication number | Publication date |
|---|---|
| IT1096042B (en) | 1985-08-17 |
| DE2911976A1 (en) | 1980-01-17 |
| IT7824955A0 (en) | 1978-06-26 |
| GB2023857B (en) | 1982-09-15 |
| FR2432727A1 (en) | 1980-02-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |