KR100787701B1 - Method, device and computer readable recording medium for lithography - Google Patents

Abstract

A method of forming a lithographic beam 2 with a groove 6 of material exposed to a predetermined degree on a surface 4 of a substantially flat substrate 3 which rotates about an axis 5 by exposure is lithographic. The beam 2 and the axis 5 are controlled relative to each other during the rotation of the substrate 3 about the axis such that a portion of the groove 6 is exposed to the lithographic beam 2 one or more times and the groove 6 ) Is formed as a sum of the one or more exposures. In addition, one apparatus according to the method and a computer readable recording medium having instructions for controlling the apparatus according to the method are described.

Description

Method, apparatus and computer readable recording medium for lithography {METHOD, DEVICE AND COMPUTER READABLE RECORDING MEDIUM FOR LITHOGRAPHY}

The present invention relates to a method, apparatus and computer readable recording medium for forming a groove of a material exposed to a predetermined degree in a surface layer of a substrate which is essentially flat and rotatable by exposure of a lithographic beam.

When manufacturing rotatable memory media, such as optical, magnetic, magneto-optical or holographic memory media, it is necessary to form grooves on the surface with great precision. The groove may have a width on the order of 1-100 nanometers.

Known methods for this purpose are called lithography, in which the substrate is exposed to lithographic beams which are particle beams such as ion beams or electron beams. The beam can be very small in cross section. When the lithographic beam is directed onto the substrate surface, an exposure point is formed, the area of the exposure point essentially corresponding to the cross section of the lithographic.

This type of lithography can be used, for example, to form an embossed pattern for stamps for imprint lithography described in more detail in WO 01 / 42858A1 and WO 01/69317, incorporated herein by reference.

This technology is excellent in the manufacture of new generation hard disks, and the surface of the disks is provided with a high storage capacity structure. In order to increase the storage capacity, it is desirable to reduce the size of the regions to be magnetized. However, there is a limitation as to whether the storage of data in one region can cause regions to be reduced before being affected by neighboring regions up to the extent of changing data in the neighboring region.

One way to mimic this is to predefine the magnetization regions of each layer, which regions are separated. For example, the magnetization regions may have a concentric ring form called "grooves" after they are distributed on the surface of the rotatable disk.

When manufacturing embossed patterns for imprint lithography of a substrate to obtain the grooves, it is desirable to provide a stamp of the same format as the intended product, wherein the stamp has a plurality of concentric grooves, where each groove is as possible Have small radial deformations.

Problems associated with the manufacture of such concentric grooves are caused by mechanical slack and play in the apparatus used, and tolerances in grooves made by lithographic beams that are themselves uncontrollable and difficult to manipulate. Include variations. This problem occurs especially with very small structures made with great precision on relatively large surfaces. To produce the structures, particle beams such as electron or ion beams are preferably used, for example in the case of optical wavelengths or X-ray wavelengths, since electromagnetic radiation cannot generally be focused to the same small sizes.

U. S. Patent No. 5,621, 216 discloses a method of manipulating position errors at a spot boundary when manufacturing X-ray masks for E-beam lithography. This is done by electron beam resist that is partially exposed during multiple exposures, so that an average exposure is achieved. However, the technique proposed in US Pat. No. 5,621,216 is only suitable for exposure of small surfaces since the electron beam can only be controlled in very small areas.

Thus, there is a need for a method of forming concentric grooves in the surface layer by lithographic beams, by which the influences exerted by the mechanical slack or action of this type are reduced.

It is therefore an object of the present invention to provide a method, apparatus and computer readable recording medium by lithography in which the above problems are eliminated in whole or in part.

This object is achieved in whole or in part by a method according to claim 1, a computer readable recording medium according to claim 18 and an apparatus according to claim 19. Embodiments of the invention are apparent from the dependent claims and the following detailed description.

In accordance with a first aspect of the present invention, a method is provided for exposing a lithographic beam to a groove of a material that is exposed to a predetermined degree in a surface layer of an essentially flat substrate that rotates about an axis. The method is characterized in that during the rotation of the substrate about an axis the lithographic beam and the axis are controlled in relation to each other such that a portion of the groove is exposed to the lithographic beam one or more times, wherein the groove is subjected to the one or more exposures. It is formed as a sum.

The preset groove exposure degree is sufficient for the surface layer to be further processed by developing the surface layer when in the form of a resist.

Essentially flat means that the substrate is flat enough to be exposed to lithographic processing by the lithographic beam. In the case of a focused beam, the flatness and beam field depth of the substrate are adapted to each other.

By the sum of the one or more exposures essentially corresponding to the preset exposure degree, the sensitivity to mechanical slack or action is reduced because each exposure contributes to an arbitrary range in the final groove. Thus, the effect that the polarization of the individual exposures provide to the final groove is reduced.

According to the method, the lithographic beam and the axis can be held at essentially constant distances from each other while the substrate is rotated several times around the axis to form a circular groove concentric with the axis. The lithographic beam and axis are then controlled in relation to each other to form a plurality of grooves concentric with the axis, each groove being exposed to the predetermined exposure degree essentially regardless of the radial distance of the groove to the axis. Thus, multiple grooves with the same degree of exposure can be provided. This can happen in a variety of ways.

According to a first variant, the number of exposures on which the groove is affected may be a function of the radial distance of the group with respect to the axis. The advantage of this is that it is easy to vary the rotation speed when exposure occurs. According to a second variant, the intensity of the lithographic beam can be controlled as a function of groove radius distance to the axis. This results in more precise exposure but requires lithographic beam intensity to be controlled. According to a third variant, the angular velocity at which the substrate is rotated is a function of the radial distance of the groove to the axis. This leads to more precise exposure and is useful if the intensity of the lithographic beam cannot be controlled.

In addition, the groove is continuously exposed to the lithographic beam to form a continuous groove of the exposure material, or to form a groove constituting a portion of the plurality of exposed materials that are wholly or partially separated in the tangent direction. Can be exposed intermittently.

As another variant, the lithographic beam and the substrate can be controlled in relation to each other to form essentially spiral grooves at varying radial distances from the axis. Also in this case the lithographic beam and the substrate can be controlled with each other as described above to form a plurality of grooves or groove portions with essentially the same degree of exposure.

According to a second aspect of the present invention, a computer readable recording medium is provided with instructions for controlling an apparatus for forming a groove of a material that is exposed to a predetermined degree in a surface layer of an essentially flat substrate on which the lithographic beam rotates about an axis during execution. Include. The instructions of the computer readable recording medium are characterized in that during rotation of the substrate about an axis, the lithographic beam and the axes are controlled in relation to each other to ensure that a portion of the groove is exposed to the lithographic beam one or more times. Is formed as the sum of the one or more exposures.

The computer readable recording medium may be a storage medium suitable for the above purpose and for storing software and / or control instructions for controlling the lithographic apparatus to execute the method according to the present invention during execution. Examples of such storage media are diskettes, CD-ROMs, DVD ROMs, hard disks, and the like. It is also contemplated to distribute the instructions over a computer network such as the Internet.

According to a third aspect of the invention, an apparatus for lithography comprises a radiation source for generating a lithographic beam, rotation means for supporting an essentially flat substrate that can rotate on said rotation means, a lithographic beam in relation to each other, and Positioning means for moving the substrate, and control means for controlling the lithographic beam, the rotation means and the positioning means. The apparatus is characterized in that during the rotation of the substrate on the rotating means the control means controls the lithographic beam and the rotating means relative to each other such that a portion of the groove is exposed to the lithographic beam one or more times. It is formed as the sum of one or more exposures.

In the device according to the invention, the rotating source can be a specific source, preferably an ion source or an electron source. Alternatively, electromagnetic sources such as X-ray sources or light sources may be used although radiation from these types of sources may not be accurately focused, such as particle radiation. Light source means, for example, a point light source that is reproduced on the surface layer or a laser in which light is focused on the surface layer. However, it is not up to the resolution made possible by the particle sources which are mainly applied in the present invention.

The rotating means may be a device in which the substrate is arranged to rotate about the axis of rotation with sufficient accuracy and sufficient speed. The positioning means may be an apparatus for moving the lithographic beam relative to the substrate. For example, the radiation source or substrate may be displaced or the beam may be controlled in a conventional manner, for example by deflection. The control means can be a positioning means and optionally a prior art numerical control system for generating signals to the rotating means and / or the radiation source.

It goes without saying that the various features described above can be combined in the same embodiment.

Embodiments of the present invention are described in more detail by non-limiting embodiments and reference is made to the accompanying drawings.

1 is a schematic perspective view of a first system in which the present invention may be practiced.

2 is a more detailed schematic plan view of a substrate obtainable in accordance with the present invention.

3 is a schematic plan view of a first variant of the substrate according to the invention;

4 is a schematic plan view of a second variant of the substrate according to the invention;

5 is a schematic plan view of a third modification of the substrate according to the present invention;

6 is a schematic plan view of a fourth modification of the substrate according to the present invention;

7 is a schematic cross-sectional view of an apparatus for lithography in which the invention is practiced.

1 shows a system for forming essentially circular grooves in a surface layer of a rotatable medium, such as an optical or magnetic memory medium, or a template / stamp for forming the memory medium. In the system shown in FIG. 1, essentially flat substrates 3 are arranged rotatably about an axis 5. The surface layer 4 arranged on the substrate 3 may be sufficiently flat to be lithographically processed by the lithographic beam 2 to form the groove 6 on the layer 4. The lithographic beam 2 is emitted from the radiation source 1 and can be an electron beam or an ion beam. Other types of specific beams suitable for lithography are also contemplated. Alternatively, an electromagnetic radiation source, for example an X ray source or a light source, can be used although radiation from these types of sources cannot be precisely focused like particle radiation. Light source means a point light source regenerated on a surface layer or a laser in which light is focused on the surface layer. The surface layer 4 may be made of a material suitable for lithography, such as positive or negative resist. It is recognized that the substrate 3 may be provided with a plurality of full or partial overlapping surface layers, one of which has properties influenced by the lithographic beam 2. Thus, assuming that the outer layers pass through the lithographic and are absorbed by a layer that can be affected by the beam, the affected layer is not the only outermost surface layer that can be treated according to the method. Typically the lithographic beam 2 is directed towards the surface layer of the substrate with only a small spot, the cross section essentially corresponding to the cross section of the lithographic beam 2.

The radiation source 1 and the substrate 3 are arranged such that the lithographic beams incident on the surface layer 4 of the substrate can be displaced in at least one direction across the surface layer 4 of the substrate. This is caused, for example, by the displacement of the radiation source or the substrate such that the lithographic beam incident on the surface layer 4 is moved along the radius on the rotating substrate 3. The displacement of the lithographic beam can occur in a suitable prior art manner, for example by physical movement of the radiation source 1, physical displacement of the substrate 3, or a combination thereof. The substrate 3 can be suspended on the shaft 5 by means of a rotating bearing suitable for a pose, such as a high precision rotating bearing (not shown), and can be provided with a driving mechanism (not shown).

The system of FIG. 1 functions in such a way that the surface layer 4 of the substrate is exposed to the lithographic beam 2 in one spot while the substrate is rotated about the axis 5. If the lithographic beam 2 is held at a distance from the center of rotation, a groove 6 of exposure material concentric with the axis of rotation will be formed in the surface layer 4 of the substrate.

In lithography, the surface layer 4 must be exposed to a predetermined degree so that the pattern can be developed. The development is carried out by dissolving the exposed or non-exposed portions of the surface layer depending on whether the surface layer consists of a positive resist or a negative resist. Then some form of post treatment may be performed, such as depositing or etching additional layers. Optionally, deposition is performed prior to development, forming hollow structures. A predetermined degree of exposure causes the desired post treatment of the surface layer 4 to occur according to the invention.

As described above, the groove 6 is formed by a surface layer 4 in which the desired groove is repeatedly exposed to the lithographic beam 2, each exposure being at a predetermined degree of exposure necessary during the formation of the desired groove. It provides a smaller degree of exposure. In the embodiment shown in FIG. 1, this repeated exposure can be performed by the substrate 3 which is rotated several times about the axis 5 while the lithographic beam 2 is held at a constant distance from the center of rotation. have. Thus, for example, the impact exerted by any slack or action associated with mechanical suspension and rotation mechanisms (not shown) is reduced.

For example, instead of one exposure, it is possible to choose ten exposures, ie to rotate the substrate ten times, and the lithographic beam 2 is held in a fixed position. If the exposure of the preset degree is Q, it is possible to expose the region 10 at an exposure degree of Q / 10. Thus, the deflection of each exposure will only contribute 10% to the total deflection while the “average area” of the exposure will obtain an essentially complete exposure corresponding to a preset degree of exposure. According to a further embodiment, 100 exposures at the exposure (Q / 100) degree are selected, wherein the deflection of each exposure contributes 1% to the total deflection. It is recognized that other exposure times can be selected and that the intensity of the lithographic beam can vary within the exposure sequence.

Several control strategies will be described in order to obtain the same degree of exposure in the outer grooves on the rotatable substrate 3 as in the inner grooves.

According to the first control strategy, the number of exposures on which the groove is affected may be a function of the radius of the groove.

According to a second control strategy, the intensity of the lithographic beam can be controlled to be a function of the radius of the groove.

According to a third control strategy, the angular velocity at which the lithographic beam and the surface layer are controlled relative to each other can be a function of the radial distance of the groove with respect to the axis 5.

These three control strategies can be combined to achieve optimal control for the respective applications.

2 is a more detailed schematic plan view of a substrate obtainable in accordance with the present invention. 2 shows a groove 6 of exposure material formed by moving the beam 2 relative to the substrate 3 in three cases, such that three grooves 10, 11 and 12 of the lithographically exposed material are formed. Shows. Obviously, each of the three grooves 10, 11 and 12 deviates from the desired groove 13. This departure can be the result of the action of a rotating bearing or interference of the lithographic beam generated by ambient static, magnetic or electric fields. As shown in FIG. 2, the contribution from the departure of each exposure is smaller than if only one exposure is made, and thus the groove 6 is obtained in the form of the sum of three grooves 10, 11 and 12, The sum better approximates the desired groove 13.

3 is a schematic plan view of a first variant of the substrate according to the invention. In this variant, a plurality of continuous grooves 6 concentric with the axis of rotation of the substrate 3 are formed in the substrate surface layer 4 according to one of the methods described above.

4 is a schematic plan view of a second modification of the substrate according to the present invention. In this variant, a number of discontinuous grooves 6 concentric with the axis of rotation of the substrate 3 are formed in the surface layer 4 of the substrate according to one of the methods described above. The grooves 6 consist of parts of a plurality of exposed materials which are wholly or partly separated in the tangent direction. These discontinuous grooves can be formed by intermittently exposing, that is, the lithographic beam 2 is directed to the surface layer in the form of pulses. This may be provided by a constant lithographic beam passing through the radiation valve or a real lithographic beam that is pulsed.

5 is a schematic plan view of a third variant of the substrate according to the invention. In this variant, helical continuous grooves 6 are formed in the surface layer 4 of the substrate according to one of the methods described above. Such a helical groove may be formed by the surface layer 4 of the substrate which is repeatedly exposed to the lithographic beam while the lithographic beam is displaced radially with respect to the substrate 3 as shown in FIG. 1. Alternatively, the groove may be formed by deflection as shown in FIG. It will be appreciated that multiple helical grooves may be formed on the surface layer of the substrate.

6 is a schematic plan view of a fourth modification of the substrate according to the invention. In this variant, a helical discontinuous groove 6 is formed in the surface layer 4 of the substrate according to one of the methods described above. These grooves consist of parts of a plurality of exposure materials that are wholly or partially separated in the tangent direction.

7 is a schematic cross-sectional view of a lithographic apparatus that may be implemented of the present invention.

The apparatus comprises a preferred type of radiation source 1, for example a particle radiation source such as an ion source or an electron source, and components provided for forming a lithographic beam 2 suitable for this purpose. Alternatively, an electromagnetic radiation source, such as an X-ray source or a light source, can be used even if radiation from these types of sources cannot be accurately focused like particle radiation. Light source means, for example, a point light source regenerated on a surface layer or a laser in which light is focused on the surface layer.

In addition, the apparatus has means 5 for rotatably supporting the substrate 3 with the surface layer 4 which is to be exposed to the lithographic beam 2. The rotating means 5 are arranged to allow the substrate 3 to be rotated with minimal slack or action and at a well controlled speed. According to one embodiment, the rotating means has a rotatable body in which the substrate is arranged and optionally secured during processing. The rotating means 5 may be provided with a lubricant bearing suitable for this purpose and a drive mechanism for driving the rotation of the rotating means 5.

In addition, the apparatus comprises positioning means 7 for positioning the radiation source 1 with respect to the substrate 3. The positioning means 7 can be configured in various ways. For example, as shown in FIG. 7, the positioning means may comprise a carriage 7 which can be displaced along the radius of the substrate, wherein the radiation source 1 is arranged fixedly and the substrate 3. ) Is disposed relative to the radiation source. Alternatively the radiation source may be displaceable or rotatable and the rotating means 5 for supporting the substrate may be arranged fixedly. As another alternative, the lithographic beam can be deflected by a suitable field, such as a magnetic or electric field (not shown). The combination of other forms of positioning means described above is also feasible.

In addition, the apparatus comprises control means 14 which can be a control unit suitable for this purpose. For example, a microcomputer (not shown) connected to suitable control loops (not shown) can be used to control one or more rotation sources 1, rotation means 5 and positioning means 7.

The control means may be provided with instructions for controlling the apparatus according to the method described above.

The method of the present invention can be executed by a computer readable recording medium for controlling the lithographic apparatus. The computer readable recording medium may include instructions in which a lithographic apparatus is controlled in accordance with one of the methods.

Claims (21)

As a method for forming a groove (6) of material exposed to a predetermined degree in a surface layer (4) of a substantially flat substrate (3) rotating about an axis (5) by exposure to a lithographic beam (2), The lithographic beam 2 and the axis 5 are controlled relative to each other while the substrate 4 is rotated about an axis such that a portion of the groove 6 is exposed to the lithographic beam 2 at least once, and the Grooves (6) are formed as a sum of said one or more exposures. 2. The method of claim 1, wherein the sum of the one or more exposures substantially corresponds to the exposure of the preset degree. The lithographic beam 2 and the axis 5 are substantially free from each other while the substrate 4 is rotated several times about the axis to form a circular groove concentric with the axis. Groove formation method, characterized in that maintained at a constant distance. 4. The lithographic beam (2) and the axis (5) are controlled in relation to each other to form a plurality of grooves concentric with the axis (5), and each groove (6) 5) A method of forming a groove, characterized in that it is exposed substantially to said predetermined exposure degree irrespective of the radial distance of the groove (6) with respect to 5). Method according to claim 4, characterized in that the number of times the groove (6) is exposed is a function of the radial distance of the groove (6) to the axis (5). 5. Method according to claim 4, characterized in that the intensity of the lithographic packet (2) is controlled to be a function of the radial distance of the groove (6) with respect to the axis (5). Method according to claim 4, characterized in that the angular velocity at which the substrate (3) is rotated is a function of the radial distance of the groove (6) with respect to the axis (5). 3. The lithographic beam 2 and the substrate according to claim 1, wherein the lithographic beam 2 and the substrate are controlled in relation to each other to form substantially helical grooves 6 at varying radial distances from the axis 5. How to form grooves. 9. The groove according to claim 8, wherein the groove is formed as a plurality of groove portions (8), each groove portion (8) being substantially in advance regardless of the radial distance of the groove portion (8) with respect to the axis (5). A groove forming method characterized by being exposed to a set degree. 10. A method according to claim 9, wherein the number of times the groove portion (8) is exposed is a function of the distance of the radius of the groove portion (8) with respect to the axis (5). 10. The method according to claim 9, wherein the intensity of the lithographic beam (2) is controlled to be a function of the radial distance of the groove portion (8) with respect to the axis (5). 10. A method according to claim 9, wherein the angular velocity at which the substrate is rotated is a function of the radial distance of the groove portion (8) with respect to the axis (5). 4. A method according to claim 3, wherein the groove (6) is continuously exposed to the lithographic beam to form a continuous groove of the exposed material. 3. The groove (6) according to claim 1 or 2, wherein the groove (6) is intermittently exposed to the lithographic beam to form a groove consisting of a plurality of portions (9) of exposed material which are wholly or partially separated in the tangent direction. Groove formation method, characterized in that. Method according to one of the preceding claims, characterized in that the substrate (3) is rotated about an axis of rotation (5) perpendicular to the surface layer (4). Method according to one of the preceding claims, characterized in that the lithographic beam (2) is a particle beam such as an ion beam or an electron beam. Method according to one of the preceding claims, characterized in that the lithographic beam (2) is an electromagnetic beam. Controls the apparatus for forming a groove 6 of material which is exposed to a preset degree in the surface layer 4 of the substantially flat substrate 3 as the lithographic beam 2 rotates about the axis 5 during execution. A computer readable recording medium comprising instructions, comprising: The lithographic beam 2 and the axis 5 are controlled relative to each other while the substrate is rotated about an axis such that a portion of the groove 6 is exposed to the lithographic beam 2 one or more times and the groove ( 6) is formed as the sum of the one or more exposures. The radiation source 1 for generating the lithographic beam 2, the rotating means 5 for supporting the rotatable substantially flat substrate 3, the lithographic beam 2 and the substrate 3 are mutually A lithographic apparatus comprising a positioning means (7) for moving relative to and a control means (14) for controlling the lithographic beam (2), the rotating means and the positioning means (7), The control means 14 control the lithographic beam 2 and the rotation means 5 relative to each other while the substrate 4 is rotating on the rotation means 5 so that a portion of the groove 6 is lithographic. A lithographic apparatus exposed to the beam (2) at least once and the groove (6) is formed as a sum of the at least one exposure. A lithographic apparatus according to claim 19, wherein the radiation source (1) is a particle source such as an ion source or an electron source. A lithographic apparatus according to claim 19, wherein the radiation source (1) is an electromagnetic radiation source.

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