• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A reflection mask for projecting a structure onto a semiconductor wafer contains a carrier material, a layer stack for reflecting obliquely incident light and formed of an alternating sequence of reflective layers disposed on a front side of the carrier material, and a light-absorbing layer. In the light-absorbing layer at least one opening is formed as the structure to be projected and which is disposed on the alternating layer stack. An electrically conductive layer is buried within the carrier material near a surface of a rear side of the carrier material. The buried electrically conductive layer is produced by ion implantation preferably in a whole-area manner on the rear side of the mask. The depth and the depth extent of the layer are controlled by the ion energy and also the dose.
    公开号:NL1024900A1
    申请号:NL1024900
    申请日:2003-11-28
    公开日:2004-06-02
    发明作者:Frank-Michael Kamm
    申请人:Infineon Technologies Ag；
    IPC主号:
    专利说明:

    Reflection mask for the projection of a structure on a semiconductor wafer as well as a method for manufacturing the same.
    The invention relates to a reflection mask for the projection of a structure on a semiconductor wafer and a method for the manufacture thereof. The invention relates in particular to a reflection mask which can be attached to a substrate holder energized with an electrostatic potential, so that a process can be exerted on the structures formed on a front side of the reflection mask.
    For projecting structures onto substrates such as semiconductor wafers or flat panels, light with a wavelength is used, which is increasingly reduced to improve the solution. Currently used wavelengths are at 193 nm and 248 nm.
    The structures to be formed on the substrate are usually projected onto the substrate by a mask in a photosensitive layer. For the light with the wavelengths currently used, so-called transmission masks are used, with structures formed as openings in a light-absorbing layer on a transparent support material. With the progressive reduction of the wavelengths, the hitherto transparent support material, for example quartz, becomes less than 157 nm impervious to light, so that so-called reflection masks must be used from now on. These comprise a carrier material which is formed by a so-called LTEM material (Low Thermal Expansion Material) on the basis of the extreme radiation conditions of the short-wavelength light. This has a very low thermal expansion coefficient and is therefore particularly applicable for achieving high positional accuracy in the various processes.
    So-called multilayer, i.e., layered stacks with alternating series of thin reflection layers, are usually formed on the carrier material. The alternating series of layers comprises, for example, alternately molvbdenum and silicon layers. The reflection of incident light is based on the principle of distributed Bragg reflection. The period of the multiple layers (multilayer) is thereby adapted to the exposure wavelengths. The thickness of the individual layers in the layered stack is a few nanometers.
    In a manner similar to the transmission masks, structures to be imaged on the substrate through a projection are determined by light-absorbing layers applied to the reflective layered stack.
    Because of the structure widths which can only be achieved on the substrate, which are still very small, the requirements in particular also increase with regard to the smoothness of the upper surfaces of the reflection masks. The reason for this is that in the case of an unevenness representing a vertical deviation, the light beam incidently inclined to reach the reflection leads to a horizontal displacement of a relevant structure in the image plane.
    In order to prevent the formation of such irregularities, in particular by bending during the execution of a process, such as the projection of structures on a substrate, it is therefore necessary to attach an entire surface of the back of ensure the support material of the reflection mask on a substrate holder. Such substrate holders (chucks) have a high degree of smoothness, so that the corresponding bending is considerably reduced.
    The adhesion could be effected by means of a vacuum-generating suction device. However, with the illumination wavelengths envisaged, in particular the extremely ultraviolet wavelength range (10-15 nm) and with electron beam writers, the illumination devices must operate in the vacuum. That is why the use of a substrate holder which works according to the electrostatic attraction principle is provided. Such a type of substrate holder requires a conductive layer which has hitherto been provided on the reverse side of the insulating support material of the reflection mask as a counter electrode for the electric field built up by the substrate holder. The substrate holder is thereby energized with an electrostatic potential.
    Until now, metallic or otherwise conductive layers were applied to the reverse side of the carrier material, i.e., the side opposite the front coated with the reflective and the absorbent layer, by sputtering or other separation method.
    A particular problem here is the adhesion of the metallic or other conductive layers to the carrier material while exercising the suction or attachment forces by the substrate holder. As a result of contact or friction, particles released from the rear are thereby released, which can have a contaminating effect in follow-up processes. The generation of particles is particularly intensive when differently hard or rigid materials are used for the metallic or otherwise conductive layer as well as for the upper surface of the substrate holder. As a material for the substrate holder, a Low Thermal Expansion Material (LTEM) similar to the carrier material of the reflection mask is usually used.
    The object of the present invention is to provide a mask and a method for the manufacture thereof, with which the quality of the exposure process of substrates such as semiconductor wafers or flat panels is considerably improved. In particular, an object of the present invention is to reduce the particle contamination during and after the attachment of reflection masks to a substrate holder in an exposure process.
    The object is achieved by a reflection mask for projecting a structure onto a semiconductor wafer, comprising: a support material, a layered stack for reflecting obliquely incident light, comprising an alternating series of reflective layers formed on a front side of the support material a light-absorbing layer, in which at least one aperture is formed as the structure to be projected and which is disposed on the alternating layered stack, an electrically conductive layer buried within the support material near an upper surface of a rear side of the support material.
    The object is furthermore achieved by a method for manufacturing a reflection mask from a mask base form, wherein the mask base form has an electrically insulating carrier material, a front side and a rear side, comprising the steps of: preparing a mask base form comprising the carrier material, a layered stack for the reflection of obliquely incident light, comprising an alternating series of reflective layers formed on a front side of the support material and a light-absorbing layer applied to the alternating layered stack, implanting ions into the support material on the rear side of the mask base shape to form a buried, electrically conductive layer in the support material, forming openings as structures in the light-absorbing layer on the front to form the reflection mask.
    Further advantageous embodiments are described in the dependent claims.
    An electrically conductive layer is, for example, formed by means of ion implantation as a buried layer in the buried layer as a precursor substrate without further action of electrically insulating support material of a reflection mask or its mask base shape. The doping of the carrier material causes, according to the adjusting profile of the concentration of dopant atoms or molecules, a counter-electrode lying near the upper surface of the rear side for an electric field arranged from outside.
    The field applied from outside is provided, for example, by a substrate holder energized with an electrostatic potential. The electric field built up by the substrate holder causes such a redistribution of charge carriers within the electrically conductive layer that attraction between the electrode deformed by the substrate holder and the counter-electrode in the buried layer is achieved. Due to the attraction, the mask base shape or the reflection mask adheres to the substrate holder.
    The application of a further layer, which is substantially different from the carrier material, chemically does not occur on the rear side. The composition of the carrier material remains substantially unchanged. Only a relatively small uptake of foreign atoms takes place. Because the electrically conductive layer is buried, in particular the material composition on the upper surface of the carrier material on the rear side of the reflection mask remains substantially unchanged.
    Ideally, the carrier material of the reflection mask corresponds to the material contained in the substrate holder, so that in the case of contact between mask and holder, only a very small particle transfer takes place. The materials have the same rigidity, with which the generation of particles at the rear is advantageously reduced. A further advantage is that no thin rear coating with metal layers is present, which can adhere to the upper surface of the substrate holder due to the strong attraction forces.
    A further advantage is that a roughening of the upper surface of the rear side of the carrier material takes place as a result of the implantation, so that adhesion of the rear side is reduced by friction at rest. This behavior is particularly favorable for the removal of the mask from the substrate holder. Otherwise, particularly flat and smooth upper surfaces of the mask and substrate holder would stick to each other due to so-called bonding effects.
    The present invention does not exclude that a concentration of dopant atoms is also present on the upper surface of the rear side of the carrier material. An important feature is that the carrier material is substantially retained on the upper surface of the rear of the mask. However, the deeper burial of the electrically conductive layer offers special advantages, because the already quantitatively small proportion of dopant atoms on the upper surface of the rear is further reduced. As a result, for example, reactions with gas atoms in further processes to be carried out can be reduced.
    The present invention also includes the formation of buried, electrically conductive layers by analogous processes to form doped support material, for example, a top surface treatment of the back with a temporary interlayer and subsequent diffusion into the support material. In a further step, the upper surface can again be freed from the temporary intermediate layer. By means of further processes, it is no doubt possible to reduce the upper surface concentration of dopant atoms again, so that a buried, electrically conductive layer is created.
    Substances that can be used for implantation are all materials that can be used, for example, for the doping of semiconductor material, with which an electrical conductivity is produced. And in particular these are gallium, aluminum, molecular hydrogen, boron, arsenic. Iron, gold, copper, etc. are also conceivable.
    The invention will now be explained in more detail with reference to an exemplary embodiment and with the aid of a drawing. Therein: figure 1 shows a profile of a reflection mask with an electrically conductive layer according to the prior art, figure 2 shows a profile of a reflection mask with an electrically conductive layer which is clad at the rear according to an exemplary embodiment of the present invention .
    For a better understanding of the problems with attaching (chucking) reflection masks according to the prior art, Figure 1 shows a simplified cross-sectional view of an EUV reflection mask known to the person skilled in the art. The abbreviation EUV is used for the extreme ultraviolet wavelength range and here means an interval for example 10 nm to 15 nm. The invention is particularly advantageously applicable in this wavelength range, as shown below.
    The EUV reflection mask 1 comprises a carrier material 10, which is formed from LTEM material, for example the Zerodur product from Schott or the ULE product from Coming.
    A front side 7 and a rear side 8 are fixed for manufacturing such an EUV reflection mask. A layered stack 20 of an alternating series of thin layers of molybdenum and silicon is formed on the front side 7. A buffer layer 21 is deposited on the layered stack, which serves to protect the layered stack 20 in an absorbent layer 22 provided on the buffer layer in an etching process for forming structures 40.
    A metallic layer 4 is provided on the upper surface 80 on the rear side 8 of the carrier material 10. As shown on the right in Figure 1, it serves as a counter electrode for an electric field 51 arranged by a substrate holder 50 as the first electrode.
    On the left in figure 1 it is shown how parts 101 can break out of the metallic layer 4 when the substrate holder 50 is made into contact and remain as contaminating particle deposits 102.
    An exemplary embodiment of the invention is shown in Figure 2. On the backside 8 of the carrier material 10 of an EUV reflection mask 1, a buried, electrically conductive layer 5 is provided within the carrier material 10 at a depth 70. The depth 70 is considerably smaller than the thickness of the carrier material 10, so that the buried layer is located near the upper surface 81 of the carrier material 10 on the rear side thereof.
    The buried, electrically conductive layer 5 shown in Figure 2 is achieved by means of an ion implantation of, for example, gallium ions.
    It is clear that, albeit with low probability, gallium ions are distributed over a large depth range of the support material. The dotted surface shown in Fig. 2 again shows only a depth region in the carrier material 10, where the profile variation of the concentration of dopant atoms, i.e. gallium ions, has a maximum. The depth region, which is only shown schematically, for example, reflects that region in which the concentration is still within an order of magnitude of the maximum dopant concentration.
    It is important that a layer-shaped portion which has become sufficiently conductive due to dopants is present in the further insulated carrier material, so that a charge carrier concentration can be achieved under the influence of an external electric field. For this purpose, in the exemplary embodiment, the dopant concentration of the upper surface 81 in the direction of greater depths on the rear side 8 increases, reaches a maximum value and then decreases to even greater depths in the carrier material 10.
    In the depth region, where the maximum value is reached, a conductive layer with an effective thickness is created by the implantation. For gallium ions energized with 30 keV the depth of the dopant concentration follows a depth of 250 run, for boron ions energized with 30 keV a depth of 2 µm, for phosphorus ions energized with 30 keV a depth of 480 nm. For boron ions implanted with only 10 keV, a depth of 560 nm results. Effective thicknesses of the electrically conductive layers are usually an order of magnitude of 10 run, in which particularly narrow distributions can be achieved with a phosphor implantation. Typical dopant concentrations are of an order of magnitude of 1018 atoms per cubic centimeter.
    In an exemplary manufacturing method, the ion implantation can be advantageously controlled so that the electrically conductive buried layer has the desired depth (absolute) and depth dimension. The corresponding dopant profile is set by the ion energy as well as the dose for the ion beam. The depth dimension is selected such that an effective charge separation through the field can be achieved. The absolute depth is limited by a maximum distance to the substrate holder or the upper surface thereof, so that the electric field is just still sufficient to allow an attraction which presses the reflection mask against the substrate holder and is therefore stronger than bending stresses.
    It is clear to the person skilled in the art that the present invention can also be applied in other fields in which substrates with an insulating material carrier material must be adhered from a substrate holder. The corresponding embodiments are included in the present invention. These can be transmission masks, semiconductor wafers, flat panels, compact disks, etc., and other flat disk-shaped objects.
    权利要求:
    Claims (11)
    [1]
    A reflection mask (1) for projecting a structure (40) onto a semiconductor wafer, comprising: a carrier material, a layered stack (21) for reflecting obliquely incident light, comprising an alternating array of reflective layers, which are on a front side (7) is formed from the carrier material (10), a light-absorbing layer (22), in which at least one opening is formed as the structure (40) to be projected and which is buried on the alternating layered stack, an electrically conductive layer (5) , which is arranged within the carrier material near an upper surface (81) of a rear side (8) of the carrier material (10).
    [2]
    Reflection mask according to claim 1, characterized in that the buried, electrically conductive layer (5) comprises a concentration of dopant atoms arranged within the carrier material (10).
    [3]
    Reflection mask according to one of claims 1 or 2, characterized in that the carrier material (10) comprises at least one material from the group of low-thermal expansion materials (LTEM).
    [4]
    Reflection mask according to one of the preceding claims, characterized in that the buried, electrically conductive layer (5) comprises at least one element from the group comprising gallium, aluminum, molecular hydrogen, boron, arsenic, phosphorus.
    [5]
    Reflection mask according to and of the preceding claims, characterized in that the buried, electrically conductive layer (5) is formed over the entire surface near the upper surface on the rear side of the carrier material.
    [6]
    A method for manufacturing a reflection mask (1) from a mask base shape, the mask base shape having an electrically insulating support material (10) a front side (7) and a rear side (8), comprising the steps of: providing a mask base shape comprising the support material (10), a layered stack for the reflection of obliquely incident light, comprising an alternating series of reflective layers formed on a front side (7) of the carrier material (10), and a light-absorbing layer which is deposited on the alternating layered stack is provided, doping the support material (10) with ions on the backside (8) of the mask base form to form a buried, electrically conductive layer (5) in the support material (10), forming openings as structures (40) in the light-absorbing layer (22) on the front to form the reflection mask (1).
    [7]
    Method according to claim 6, characterized in that the doping step is carried out by means of an ion beam implantation.
    [8]
    A method according to claim 6, characterized in that the doping step is carried out by applying a further layer comprising the ions and subsequently diffusing the ions into the carrier material (10).
    [9]
    Method according to one of claims 6 to 8, characterized in that the doping is carried out over the entire surface on the rear side of the carrier material (10).
    [10]
    Use of the reflection mask (1) according to one of the preceding claims for attaching the reflection mask (1) to a substrate holder (50), which is designed to be energized with an electrostatic potential.
    [11]
    The use according to claim 10, characterized in that a substrate holder (50) is selected, which comprises a material which substantially corresponds to the carrier material (10) of the reflection mask (1). 11 Removal scifles 1 EUV reflection mask 4 buried metallic or otherwise electrically conductive layer 5, electrically conductive layer 7 front of the mask with structures 8 rear of the mask for contacting the substrate holder 10 carrier material, mask substrate, LTEM material 20 layered stack, multilayer 21 buffer layer 22 light-absorbing layer, absorbent layer 40 structures, openings in absorbent layer 50 substrate holder 51 electric field, generated by potential at substrate holder 70 depth of buried layer 80 upper surface on the back of the carrier material, state of the art 81 upper surface on the back of the carrier material parts of the metallic layer 102 broken away according to the invention, contaminated particles
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    同族专利:
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    US20040106051A1|2004-06-03|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20030179354A1|1996-03-22|2003-09-25|Nikon Corporation|Mask-holding apparatus for a light exposure apparatus and related scanning-exposure method|
    ES2223122T3|1997-02-28|2005-02-16|Commonwealth Scientific And Industrial Research Organisation|MOISTURE DETECTION.|
    US6180291B1|1999-01-22|2001-01-30|International Business Machines Corporation|Static resistant reticle|
    EP1190276A2|1999-06-07|2002-03-27|The Regents of the University of California|Coatings on reflective mask substrates|
    JP2002299228A|2001-04-03|2002-10-11|Nikon Corp|Reticle, aligner using the same and exposure method|JP4099589B2|2004-02-20|2008-06-11|ソニー株式会社|Mask pattern correction method, exposure mask and mask manufacturing method|
    JP2006267595A|2005-03-24|2006-10-05|Toshiba Corp|Mask blank and its manufacturing method and using method, and mask and its manufacturing method and using method|
    JP2006324268A|2005-05-17|2006-11-30|Dainippon Printing Co Ltd|Mask blanks for euv exposure, its manufacturing method and mask for euv exposure|
    EP1962326B1|2005-12-12|2012-06-06|Asahi Glass Company, Limited|Reflection-type mask blank for euv lithography, and substrate with electrically conductive film for the mask blank|
    US7678511B2|2006-01-12|2010-03-16|Asahi Glass Company, Limited|Reflective-type mask blank for EUV lithography|
    法律状态:
    2004-08-02| AD1A| A request for search or an international type search has been filed|
    2008-02-01| RD2N| Patents in respect of which a decision has been taken or a report has been made (novelty report)|Effective date: 20071213 |
    优先权:
    申请号 | 申请日 | 专利标题
    DE10255605|2002-11-28|
    DE10255605A|DE10255605B4|2002-11-28|2002-11-28|Reflection mask for the projection of a structure onto a semiconductor wafer and method for its production|
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