WO2003014829A1 - Mask and method for producing a mask - Google Patents
Mask and method for producing a mask Download PDFInfo
- Publication number
- WO2003014829A1 WO2003014829A1 PCT/EP2002/007824 EP0207824W WO03014829A1 WO 2003014829 A1 WO2003014829 A1 WO 2003014829A1 EP 0207824 W EP0207824 W EP 0207824W WO 03014829 A1 WO03014829 A1 WO 03014829A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- mask
- membrane
- silicon body
- thin layer
- monocrystalline silicon
- Prior art date
Links
Classifications
-
- 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
- G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
- G03F1/20—Masks or mask blanks for imaging by charged particle beam [CPB] radiation, e.g. by electron beam; Preparation thereof
Definitions
- the present invention relates to a mask, in particular for use in electron projection lithography, with a monocrystalline silicon body, in the surface of which depressions corresponding to a pattern to be imaged are arranged, which have inner surfaces, and with a membrane.
- the present invention further relates to a method for producing masks.
- an electron beam is used to image structures that are predetermined by a mask onto the surface of a wafer.
- the first type is the so-called stencil mask, in which the electron beam can act directly on the wafer surface through openings in the mask or is scattered in the areas to be shadowed by the mask through a membrane consisting of monocrystalline silicon.
- the second type of mask for electron projection lithography the membrane mask with a closed membrane, has a continuous thin membrane through which the electron beam must pass in order to be able to act on the wafer surface.
- the shading takes place here by scattering segments arranged on the thin membrane, which usually consist of an element with a high atomic number or a connection with such an element in order to achieve a sufficiently large scattering of the electrons even with a small segment thickness.
- the object of the invention is to provide an improved mask for electron projection lithography and an inexpensive and flexible manufacturing method.
- the mask according to the invention is very easy to produce and represents a flexible concept for mask production, since its construction enables the mask to be designed as a stencil mask or also as a membrane mask with a closed membrane in only one further different production step. To obtain a stencil mask from the membrane mask with the membrane closed, simply remove the membrane.
- Another advantage over known membrane masks with a closed membrane is that the proposed mask does not require an etch stop layer between scattering segments and the closed membrane. This eliminates the problem of undesirable scattering of the electron beam through the etch stop layer. There is also no risk of distortion of the mask structures, which can be attributed to different tensile stresses in the etching stop layer and the membrane.
- a preferred embodiment of the mask according to the invention is characterized in that the membrane consists of silicon nitride, which is particularly easy to handle and has been used in semiconductor production for decades.
- the silicon nitride is preferably applied to the mask in a so-called "low pressure chemical vapor deposition" (LPCVD) process.
- LPCVD low pressure chemical vapor deposition
- a very advantageous feature of this embodiment is the possibility of being able to adjust the tensile stress of the membrane consisting of silicon nitride in a wide range from approximately 50 MPa to approximately IgPa. This enables an optimal adaptation to the tensile stress of the monocrystalline silicon body to avoid mask distortion. This also increases the life of the mask.
- Another variant of the mask according to the invention has on its underside a thin layer of a material with an element with a low atomic number or a connection with such an element, which absorbs or scatters only a small proportion of the electron radiation.
- an electrically conductive layer prevents electrostatic charging of the mask due to the irradiation with electrons, on the other hand there is good heat dissipation.
- a material that can be easily applied to the mask in order to keep the mechanical stress on the mask to a minimum during application is very particularly advantageous for forming the thin layer.
- the monocrystalline silicon body is designed such that sections of the silicon body can be used as a support device for the mask.
- the masks made of approx. 400 ⁇ m to 750 ⁇ m thick wafers are attached to a support frame made of heat-resistant glass that is several millimeters thick. The fastening process places a great mechanical load on the masks.
- the above-mentioned further development of the mask according to the invention virtually has an integrated support frame. This is achieved by using a relatively thick, monocrystalline silicon body, the inner region of which is reduced by means of etching to the thickness of a conventional wafer that can be used to manufacture a membrane mask. This leaves sections of great thickness in the outer region of the wafer which can be used as a carrying device. It is no longer necessary to attach the mask to a more stable structure with the associated mechanical stress.
- the thin layer has a mechanical stability which is approximately the mechanical stability of the membrane corresponds, and that the membrane is selectively removable from the monocrystalline silicon body and the thin layer.
- the thin layer proposed in this embodiment additionally takes on the stabilizing function of the membrane, as a result of which the membrane can be dispensed with.
- a method for producing a mask in particular for use in electron projection lithography, is presented with a monocrystalline silicon body of thickness d, recesses corresponding to a pattern to be imaged being etched in the surface thereof, have the inner surfaces, a membrane being applied to the surface and the inner surfaces in such a way that a closed surface is formed, and openings being etched into the monocrystalline silicon body, so that radiation incident in the openings in the region of the depressions through the membrane and the Depressions can emerge from the mask again.
- An embodiment of the method according to the invention is particularly advantageous and provides that the monocrystalline silicon body has a thickness d2 that is a multiple of the thickness d of a conventional membrane mask, that part of the monocrystalline silicon body of thickness d2 is removed using a rapid wet etching process, so that Sections of the thickness d2 and sections of the thickness d remain, and that the sections of the thickness d2 can be used as a support device for the mask.
- the use of an inexpensive wet etching method is very advantageous in order to remove the comparatively large amount of material from the inner regions of the monocrystalline silicon body, which should contain the mask structures, and must accordingly be made thin.
- the wet etching process can be done in Wet etching reactors can be run for many substrates simultaneously. As soon as the thickness of the monocrystalline silicon body has fallen below a certain limit in this area, a more precise and at the same time slower etching process is selected in order to develop the mask structures.
- the proposed method is therefore suitable for providing a unit consisting of a monocrystalline silicon body, consisting of a mask and a support device for the mask, which at the same time ensures high economy of the mask structures and a high level of economy through process steps which can be carried out quickly.
- a further embodiment of the method according to the invention provides that an electrically conductive and / or thermally conductive thin layer of an element / elements with a low atomic number is applied to the underside of the mask.
- Another embodiment of the method according to the invention provides for the membrane to be selectively removed from the monocrystalline silicon body and the thin layer after the thin layer has been applied. If the thin layer has sufficient mechanical stability, it can also take on the stabilizing effect of the membrane, so that the membrane can be removed again.
- FIG. 1 shows a cross section through a first embodiment of a mask according to the invention
- FIG. 2a shows a first part of the mask shown in cross section from FIG. 1 on an enlarged scale
- FIG. 2b shows a second part of the mask shown in cross section from FIG. 1 on an enlarged scale
- FIG. 3 shows a cross section of a second embodiment of the mask according to the invention
- Fig. 5 shows a cross section through a third embodiment of a mask according to the invention.
- FIG. 1 A first embodiment of a mask according to the invention for electron projection lithography is shown in cross section in FIG. In the description of this first embodiment, reference is also made to FIGS. 2a and 2b, which each show an enlarged section of the mask from FIG.
- the mask consists of a monocrystalline silicon body 10 of thickness d, which has depressions 14 which interrupt the surface 11 of the mask.
- the depressions 14 have inner surfaces 15.
- the surface 11 of the monocrystalline silicon body 10 is, like the inner surfaces 15 of the depressions 14, with a membrane 20 covered.
- the membrane 20 forms a closed surface on the upper side of the monocrystalline silicon body 10.
- FIG. 2a A first part of the mask from FIG. 1 is shown enlarged in FIG. 2a. This is a part of the mask that has no depression 14.
- a second part of the mask, shown in FIG. 2b, has two depressions 14, the inner surfaces 15 of which are also shown.
- the membrane 20 is not shown in Figures 2a and 2b for reasons of clarity.
- this embodiment of the mask is also referred to as a "corrugated continuous membrane” (CCM) mask.
- CCM corrugated continuous membrane
- the mask In electron projection lithography, the mask is placed between an electron beam generator and a wafer to be written.
- the thin layer 13 is designed to be electrically conductive.
- a good thermal conductivity of the thin layer 13 is also advantageous to prevent local overheating of the mask and thus avoid thermal deformations.
- the thin layer 13 and the membrane 20 are made of materials with elements with a low atomic number, so that the electron beam can penetrate the mask in the region of the depressions 14 and can hit a radiation-sensitive layer of the wafer.
- the thin layer 13 is preferably made of conductive amorphous carbon and is approximately 10 nm thick.
- the electron beam strikes a part of the monocrystalline silicon body 10 between the depressions 14, the electrons are scattered in the silicon, are directed onto the edge of an aperture stop located in the imaging beam path, and no longer hit the wafer in a focused beam, which is why none "Exposure" of the wafer takes place.
- the position of the depressions 14 in the mask must be selected accordingly.
- the depressions 14 are typically approximately 1 ⁇ m to 2 ⁇ m deep, while the thickness d of the mask is approximately between 200 ⁇ m to 750 ⁇ m.
- the monocrystalline silicon body 10 of the mask is obtained from a conventional wafer.
- the mask has the lowest mechanical stability in the region of the depressions 14. A stabilizing effect results from support walls 12. These typically form a grid of 1mm x 1mm.
- the mechanical stability of the mask is particularly advantageously increased by the membrane 20, which, in contrast to the support walls 12, enables a uniform distribution of occurring forces.
- the membrane 20 preferably consists of an approximately 20 nm to about 50nm thick silicon nitride layer. Silicon nitride can be gently applied to the mask in a so-called "low pressure chemical vapor deposition" (LPCVD) process.
- LPCVD low pressure chemical vapor deposition
- the tensile stress of the membrane 20 can be set within a very wide range, so that an adaptation to the tensile stress of adjacent layers is possible.
- FIG. 3 shows a further embodiment of the mask according to the invention in cross section.
- the monocrystalline silicon body 10 has a thickness d2 which is a multiple of the thickness d of the silicon body 10 of the first embodiment. Openings 9 can also be seen, which are separated from one another by supporting walls 12.
- Sections 30 of the monocrystalline silicon body 10 are located on the lateral edges of the mask and, because of their large thickness d2, are suitable as a support device for the entire mask in the range from approximately 0.5 mm to approximately 4 mm. As a result, no subsequent attachment of the sensitive mask to a separate support is required.
- the area of the monocrystalline silicon body 10 located between the outer sections 30 is removed in a method step of the method according to the invention by a chemical wet etching method.
- the wet etching process has the advantage that many substrates can be etched simultaneously in inexpensive wet etching reactors.
- the depressions 14 are, for example, with a So-called “reactive ion etching” (RIE) process etched into the surface 11 of the monocrystalline silicon body 10.
- RIE reactive ion etching
- the membrane 20 made of silicon nitride is applied to both the surface 11 and the inner surfaces 15 of the depressions 14 in an LPCVD process.
- the openings 9 must be etched using an etching mask 28.
- the area of the rear side, which is to be retained as the support wall 12, is also to be provided with the etching mask 28.
- a combination of two etching processes is used, which is described in more detail in the German patent DE 197 10 798 Cl.
- an RIE process is carried out and then a KOH wet etching process is carried out to ensure that the support wall 12 and the further lateral boundaries of the openings 9 are exactly perpendicular to the surface 11 of the mask.
- the membrane 20 and a boron doping introduced into the top of the monocrystalline silicon body 10 act as a protective layer for the top of the mask.
- a stencil mask can be produced by a single further method step by removing the membrane 20 again.
- a thin layer 13 can also be applied to the back of the mask, the function of which has already been explained.
- This variant of the procedure provides a so-called “corrugated continuous membrane” (CCM) mask.
- CCM corrugated continuous membrane
- the membrane 20 can be removed again in a further method step after the application of the thin layer 13.
- a corresponding mask is shown in FIG. 5.
- the membrane 20 In order not to damage the mask when removing the membrane 20, the membrane 20 must be removed selectively against the monocrystalline silicon body 10 and the thin layer 13.
- the mechanical stability of the thin layer 13 must correspond approximately to the mechanical stability of the membrane 20.
- the thin layer 13 can consist, for example, of diamond-like doped carbon and must have a corresponding tensile stress in comparison with neighboring layers.
- the thickness d3 of the thin layer 13 is approximately between 30 nm and 60 nm.
- the invention also specifies a universal production process for EPL masks which enables more stable masks, the formation of two frequently used mask types (stencil masks and membrane masks) by means of only one type-specific process step and more economical processes.
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Electron Beam Exposure (AREA)
- Preparing Plates And Mask In Photomechanical Process (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10293574T DE10293574D2 (en) | 2001-08-02 | 2002-07-13 | Mask and mask manufacturing process |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10137834.3 | 2001-08-02 | ||
DE2001137834 DE10137834A1 (en) | 2001-08-02 | 2001-08-02 | Mask comprises a monocrystalline silicon body having recesses corresponding to a pattern to be formed in its surface, and a membrane covering the surface of the silicon body and the inner surfaces of the recesses to form a closed surface |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2003014829A1 true WO2003014829A1 (en) | 2003-02-20 |
Family
ID=7694090
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2002/007824 WO2003014829A1 (en) | 2001-08-02 | 2002-07-13 | Mask and method for producing a mask |
Country Status (2)
Country | Link |
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DE (2) | DE10137834A1 (en) |
WO (1) | WO2003014829A1 (en) |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4393127A (en) * | 1980-09-19 | 1983-07-12 | International Business Machines Corporation | Structure with a silicon body having through openings |
US5334845A (en) * | 1989-03-24 | 1994-08-02 | Hitachi Limited | Charged beam exposure method and apparatus as well as aperture stop and production method thereof |
US5759722A (en) * | 1995-01-13 | 1998-06-02 | Nec Corporation | Electron beam aperture structure and method for fabricating the same |
US5972794A (en) * | 1997-03-18 | 1999-10-26 | Nikon Corporation | Silicon stencil mask manufacturing method |
EP1065566A2 (en) * | 1999-06-30 | 2001-01-03 | Hoya Corporation | Electron beam drawing mask blank, electron beam drawing mask, and method of manufacturing the same |
-
2001
- 2001-08-02 DE DE2001137834 patent/DE10137834A1/en not_active Withdrawn
-
2002
- 2002-07-13 DE DE10293574T patent/DE10293574D2/en not_active Expired - Fee Related
- 2002-07-13 WO PCT/EP2002/007824 patent/WO2003014829A1/en not_active Application Discontinuation
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4393127A (en) * | 1980-09-19 | 1983-07-12 | International Business Machines Corporation | Structure with a silicon body having through openings |
US5334845A (en) * | 1989-03-24 | 1994-08-02 | Hitachi Limited | Charged beam exposure method and apparatus as well as aperture stop and production method thereof |
US5759722A (en) * | 1995-01-13 | 1998-06-02 | Nec Corporation | Electron beam aperture structure and method for fabricating the same |
US5972794A (en) * | 1997-03-18 | 1999-10-26 | Nikon Corporation | Silicon stencil mask manufacturing method |
EP1065566A2 (en) * | 1999-06-30 | 2001-01-03 | Hoya Corporation | Electron beam drawing mask blank, electron beam drawing mask, and method of manufacturing the same |
Non-Patent Citations (1)
Title |
---|
NAKAYAMA Y.: "Electron-beam cell projection lithography: A new high-throughput electron-beam direct-writing technology using a specially tailored Si aperture", J. VAC. SCI. TECHNOL. B 8, no. 6, 1990, pages 1836 - 1840, XP002220121 * |
Also Published As
Publication number | Publication date |
---|---|
DE10293574D2 (en) | 2004-08-05 |
DE10137834A1 (en) | 2003-02-13 |
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