SE522183C2 - Groove forming method for memory media manufacturing, involves controlling lithographic beam and rotating axis of substrate relative to each other such that groove is subjected to more than one exposure of beam - Google Patents

Abstract

The method involves exposing a lithographic beam (2) to a predetermined degree in a surface layer (4) of a flat substrate (3) rotating about an axis (5) to form a groove (6). The lithographic beam and the axis are controlled relative to each other such that the groove is subjected to more than one exposure of the lithographic beam. The groove is formed as a sum of more than one exposure of the lithographic beam. Independent claims are also included for the following: (a) a device for lithography (b) a computer program product with instructions to control device for lithography.

Description

lO 15 20 25 30 35 522 183 I n ~ u. nu u I - o o. .- 2 storing data in an area changes data in an adjacent area.

One way to deal with this is to define in advance magnetizable areas in each of the layers, which areas are separated. For example, such magnetizable areas may take the form of a number of concentric rings, hereinafter referred to as "grooves", which are distributed over the surface of a rotatable disk.

When making relief patterns for printing lithography of substrates which are to obtain such grooves, it is desirable to be able to produce a stamp in the same format as the intended product, and which has a large number of concentric grooves, each groove having such small radial variations as possible.

A problem in connection with the creation of such concentric grooves is tolerance variations in the groove created by the lithography beam, which are caused by inherently uncontrollable and difficult-to-handle mechanical play or play in the equipment used. This problem arises especially in connection with the creation of very small structures with high precision over a relatively large area. To create such structures, particle beams such as electron or ion beams are preferably used, since electromagnetic radiation, for example at optical wavelengths or X-ray wavelengths, cannot normally be focused to equally small dimensions.

US 5,621,216 shows a way of handling position errors at point boundaries in connection with the manufacture of X-ray masks for electron beam lithography. This is done by partially exposing the electron beam resistance during a plurality of exposures, whereby an average exposure is obtained. However, the technique proposed in US 5,621,216 is only suitable for exposure of small areas, since the electron beam can only be controlled over a very small area.

Thus, there is a need for a method of using a lithographic beam to achieve concentration n 15 un 25 un 35 u. v a.. 1 1 - ".." ¿H 'Q n u ... ß - v a. . . , 'O n n. n. v un; va. .., _ _ "I ~ -ø n apa...:, _ __ _ _ _ z -. ... ano.. Von _“ ~ ~ va ... .. .- I l in I !! 3 tric grooves in a surface layer, by which method the effect of mechanical play or play of the above-mentioned type is reduced.

SUMMARY OF THE INVENTION An object of the present invention is thus to provide a method, an apparatus and a computer program product for lithography, whereby the above-mentioned problems are completely or partially eliminated.

This object is achieved in whole or in part by means of a method according to appended claim 1, a computer program product according to claim 18 and a device according to claim 19.

Embodiments of the invention appear from the appended dependent claims and from the following description.

According to a first aspect of the present invention, there is provided a method of forming, by exposure to a lithographic beam, a trace of material exposed to a predetermined degree in a surface layer on a substantially planar, axis-rotatable substrate. The method is characterized in that the lithographic beam and the shaft, while the substrate is rotated or rotated about the axis, are controlled relative to each other so that a part of the groove is exposed to more than one exposure to the lithographic beam, the groove being formed as a sum of more than an exposure.

The predetermined degree to which the groove is exposed is sufficient to enable later treatment of the surface layer by, for example, developing the surface layer when it is a resist.

By substantially flat is meant that the substrate is sufficiently flat to be able to be subjected to lithographic treatment with the lithographic beam. In the case of a focused beam, the flatness of the substrate and the depth of field of the beam are adapted to each other.

Because the sum of said more than one exposures substantially corresponds to said predetermined degree of exposure, the sensitivity to mechanical play or play decreases, in that each exposure only to some extent contributes to the final track. This reduces the impact that a deviation of an individual exposure has on the final trace 10 l5 20 25 30 35 522 185 gg.

According to the method, the lithographic beam and the shaft can be kept at a substantially constant distance from each other while the substrate is rotated several times around the shaft, to form a circular and with the shaft concentric groove. The lithographic beam and the shaft can then be guided relative to each other to form a plurality of tracks concentric with the shaft, each track being exposed to substantially said predetermined degree of exposure, regardless of the radial distance of the track to the shaft. Thus, a number of traces with the same degree of exposure can be achieved. This can be done in a number of different ways.

According to a first variant, the number of exposures the groove is exposed to may be a function of the radial distance of the rafter to the shaft. One advantage of this is that it is easy to vary the number of turns that exposure occurs.

According to a second variant, the intensity of the lithographic beam can be controlled so that it is a function of the radial distance of the track to the axis. This provides a more accurate exposure, but requires that the intensity of the lithographic beam can be controlled.

According to a third variant, an angular velocity at which the substrate is rotated can be a function of the radial distance of the groove to the axis. This provides a more accurate exposure and is useful if the intensity of the lithographic beam cannot be controlled.

Furthermore, the track may be subjected to continuous exposure to the lithographic beam, to form a continuous track of exposed material, or to intermittent exposure to the lithographic beam, to form a track consisting of a plurality of parts wholly or partly separated in the direction of the tangent. of exposed material.

As yet another alternative, the lithographic beam and the substrate may be guided relative to each other to form a substantially helical groove, with varying radial distances to the axis. Even in this case, lithography- 'Åš .L = í å,. d fl jiï: c c c lO 15 20 25 30 35. -. The beam and the substrate are controlled relative to each other in accordance with what has been described above in order to provide a plurality of grooves or grooves with substantially the same degree of exposure.

According to a second aspect of the invention, a computer program product controls, comprises a device comprising, when executed in which a lithographic beam forms a trace of material to a predetermined degree exposed in a surface layer on a substantially planar, about an axis rotatable or rotatable substrate . The instructions of the computer program product are characterized in that they ensure that the lithography beam and the shaft, while the substrate is rotated or rotated about the shaft, are controlled relative to each other so that a part of the groove is exposed to more than one exposure to the lithography beam. more than one exposure.

The computer program product may be a memory medium suitable for the purpose on which software and / or control instructions for controlling the lithography device are stored and which, when executed, performs the method according to the invention. Examples of such storage media are floppy disks, CD-ROMs, DVD-ROMs, hard disks, etc. It is also conceivable that the instructions are distributed over a computer network, such as the Internet.

According to a third aspect of the invention, a lithography device comprises a radiation source for generating a lithographic beam, rotating means for supporting a substantially flat, rotatable or rotatable substrate about said rotating means, positioning means for moving the lithographic beam and the substrate relative to each other and control means said lithographic beam, rotating means, and positioning means. The device is characterized in that said guide means, while the substrate is rotated around the rotating means, controls the lithographic beam and the rotating means relative to each other so that a part of the groove is exposed to more than one exposure to the lithographic beam, the groove being formed as a sum of said more than one exposure. ... see 10 15 20 25 30 35 522 183 6 In the device according to the invention, said radiation source may be a particle source, preferably an ion source or an electron source. Alternatively, an electromagnetic radiation source, such as an X-ray source or a light source, may be used, although the radiation from this type of source may not normally be as well focused as particulate radiation. By light source is meant, for example, a point-shaped light source which is imaged on the surface layer or a laser whose light is focused on the surface layer. However, it is only at the resolution made possible by particle sources that the invention has its main application.

The rotating member can be a device on which the substrate is arranged so that it can be rotated or rotated about an axis of rotation with sufficient precision and speed.

The positioning means may be a device for moving the lithographic beam relative to the substrate.

For example, the beam source or substrate can be displaced, or the beam can be controlled in a known manner by, for example, deflection. The control means can for instance be a previously known numerical control system for generating signals to the positioning means and possibly also to the rotating means and / or the beam source.

Of course, the various features described above are also combinable in the same embodiment.

Brief Description of the Drawings Embodiments of the invention will now be described in more detail by way of non-limiting example, with reference to the accompanying drawings.

Fig. 1 is a schematic perspective view of a first system with which the present invention can be implemented.

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

Fig. 3 is a schematic top view of a first variant of a substrate in accordance with the present invention. Fig. 4 is a schematic top view of a second variant of a substrate in accordance with the present invention.

Fig. 5 is a schematic top view of a third variant of a substrate in accordance with the present invention.

Fig. 6 is a schematic top view of a fourth variant of a substrate in accordance with the present invention.

Fig. 7 is a schematic cross-sectional view of a lithography apparatus with which the present invention may be implemented.

Description of embodiments of the invention With reference to Fig. 1, a system for forming substantially circular grooves in a surface layer of a rotatable medium, such as for example an optical or magnetic memory medium, or a template / stamp for manufacturing such memory media, is shown. In the system shown in Fig. 1, a substantially flat substrate 3 is rotatably or rotatably arranged on a shaft 5. A surface layer 4 arranged on the substrate 3 can be substantially flat, ie sufficiently flat to be able to be subjected to lithographic treatment by means of a lithographic beam 2. , in order to form a groove 6 on the layer 3. The lithographic beam 2 may come from a radiation source 1, and be an electron beam or ion beam. Other types of particle beams suitable for lithography are also conceivable. Alternatively, an electromagnetic radiation source, such as an X-ray source or a light source, may be used, although the radiation from this type of source may not normally be as well focused as particulate radiation. By light source is meant, for example, a point light source which is imaged on the surface layer or a laser whose light is focused on the surface layer. The surface layer 4 may be of any material suitable for lithography, such as a positive or negative resist. It is also understood that the substrate 3 may be provided with a plurality of completely or partially overlapping surface layers, some of these having such properties that it is affected by the lithography beam 2.

Thus, it is not only the outermost surface layer that can be treated according to the process, given that the surface,: sno. o, .sgø: av o oc: o nano oana- 10 15 20 25 30 35 522 183 a | . ~ o: »n. . ..

I n. 8 layers let the lithographic beam through so that it can be absorbed by the layer that is impressionable. Typically, the lithographic beam 2 impinges on the surface layer of the substrate at only a small point, the cross section of which substantially corresponds to the cross section of the lithographic beam 2.

The radiation source 1 and the substrate 3 are arranged so that the lithographic beam incident on the surface layer 4 can be displaced in at least one direction over the surface layer 4 of the substrate. This can be done, for example, by displacing the radiation source or substrate the rotatable substrate 3. The displacement of the lithographic beams can take place in a suitably known manner, for example by physically displacing the radiation source 1, by physically displacing the substrate 3, or by a combination of these. The substrate 3 can be suspended on the shaft 5 by means of a rotary bearing suitable for the purpose, for example a rotary bearing (not shown) with high precision, and be provided with a drive mechanism (not shown).

The system in Fig. 1 works so that the surface layer 4 of the substrate is exposed at one point to the lithographic beam 2 while the substrate is rotated about the axis 5. If the lithographic beam 2 is kept at a constant distance from the center of rotation, a groove 6 of exposed material concentric with the rotation axis to be formed in the surface layer 4 of the substrate.

In lithography, the surface layer 4 needs to be exposed to a predetermined degree in order to be able to develop the pattern. Development is done by dissolving the exposed or unexposed parts of the surface layer depending on whether the surface layer consists of a positive or negative resist. Thereafter, some type of finishing, such as, for example, deposition of additional layers or etching, can be performed. Deposition may be performed prior to development, to provide hollow structures. The predetermined degree of exposure according to the invention is 10 ~ 25 20 25 30 35 - - ~. nu 1. 522 183 - - -. . - -. -. ø p. 9 such that the desired finishing of the surface layer 4 can take place.

As described above, the groove 6 is provided by repeatedly exposing the surface layer 4 where the groove is desired to the lithographic beam 2, each exposure giving a degree of exposure which is less than the predetermined degree of exposure necessary for the formation of the desired groove. This repeated exposure in the embodiment shown in Fig. 1 can be achieved by rotating the substrate 3 a number of turns around the axis 5 while keeping the lithography beam 2 at a constant distance from the center of rotation. Thus, for example, the effect of any play or play associated with the mechanical suspension and rotation mechanism (not shown) can be reduced.

As an example, one can choose to instead of one exposure, perform 10 exposures, i.e. rotate the substrate 10 times while keeping the lithography beam 2 at a fixed position. If the predetermined exposure rate is Q, then you can choose to expose the area 10 times with an exposure rate that is Q / 10. As a result, each exposure deviation will only contribute 10% to the total deviation, while the “average range” of the exposures will receive essentially complete exposure corresponding to the predetermined degree of exposure. According to another example, 100 exposures with an exposure degree Q / 100 are selected, where each exposure deviation contributes 1% to the total deviation. It will be appreciated that other numbers of exposures may be selected and that the intensity of the lithographic beam may be varied within an exposure sequence.

In order to obtain the same degree of exposure at the outer grooves on a rotatable substrate 3 as at the inner grooves, some control strategies will now be described.

According to an initial control strategy, the number of exposures to the track can be a function of the track's radius. uucø »non 10 15 20 25 30 35 522 183 -. - - - u. 10 According to a second control strategy, the intensity of the lithographic beam can be controlled so that it is a function of the radius of the track.

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

These three control strategies can be combined to achieve optimal control for each application.

Fig. 2 is a more detailed schematic top view of a substrate obtainable in accordance with the present invention. Specifically, Fig. 2 shows a groove 6 of exposed material, which is formed by moving the lithographic beam 2 in three turns relative to the substrate 3, so that three grooves 10, 11 and 12 of exposed material are formed. As can be seen, each of the three grooves 10, 11 and 12 deviates from the desired groove 13. This deviation may be due to, for example, play in the rotary bearing or disturbances of the lithographic beam due to ambient static electricity, magnetic fields or electric field.

However, as shown in Fig. 2, the contribution from each deviation deviation is smaller than if only one exposure had been performed, so that a track 6 is obtained in the form of a sum of the three tracks 10, 11 and 12, which sum better approximates the desired track 13. .

Fig. 3 is a schematic top view of a first variant of a substrate in accordance with the present invention.

According to this variant, a plurality of concentric and continuous grooves 6 with the axis of rotation of the substrate 3 have been formed in the surface layer 4 of the substrate, in accordance with one of the methods described above.

Fig. 4 is a schematic top view of a second variant of a substrate in accordance with the present invention.

According to this variant, a plurality of concentric and non-continuous grooves 6 with the axis of rotation of the substrate 3 have been formed in the surface layer 4 of the substrate, in accordance with any of the methods described above. These tracks 6 consist of 10 15 20 25 30 35 522 183. . -; ~ .u ll a plurality of exposed material completely or partially separated in the direction of the tangent. These non-continuous tracks can be formed by being exposed intermittently, ie by causing lithographic beam 2 to be incident on the surface layer in the form of pulses. This can be achieved by pulsing the lithographic beam itself or by passing a constant lithographic beam through a radiation valve.

Fig. 5 is a schematic top view of a third variant of a substrate in accordance with the present invention.

According to this variant, a helical, continuous groove 6 has been formed in the surface layer 4 of the substrate, in accordance with one of the methods described above. This helical groove can be formed by repeatedly exposing the surface layer 4 of the substrate to the lithographic beam while the lithographic beam is displaced radially relative to the substrate 3, as shown in Fig. 1.

Alternatively, the groove may be formed by deflection, as shown in Fig. 4. It will be appreciated that a plurality of helical grooves may be formed on the surface layer of the substrate.

Fig. 6 is a schematic top view of a fourth variant of a substrate in accordance with the present invention.

According to this variant, a helical, non-continuous groove 6 has been formed in the surface layer 4 of the substrate, in accordance with one of the methods described above. These grooves consist of a plurality of parts of exposed material completely or partially separated in the direction of the tangent.

Fig. 7 is a schematic cross-sectional view of a lithography apparatus with which the present invention may be implemented.

The device comprises a radiation source 1, of the desired type, for example a particle radiation source such as an ion source or an electron source and components necessary therewith to form a lithographic beam 2 suitable for the purpose.

Alternatively, an electromagnetic radiation source, for example an X-ray source or a light source, may be used, although the radiation from this type of source normally cannot vol 10 15 20 25 30 35 ... H. . _. 1; _ - _ _ - _ - - .. ... ...... .. .z H - .. _ ... ...... . . ... 22.2. "'0 o a nu w, _ _ _' I '' ~ I ~. U ..,.

- - ~. Q n. 12 focuses as well as particle radiation. By light source is meant, for example, a point-shaped light source which is imaged on the surface layer or a laser whose light is focused on the surface layer.

Furthermore, the device has means 5 for rotatably or rotatably supporting a substrate 3 with a surface layer 4 which is intended to be exposed to the lithographic beam 2. This rotating means 5 must be arranged so that it can with minimal play or play and with well controllable speed causing the substrate 3 to rotate. According to one embodiment, the rotating member has a rotatable body on which the substrate is arranged and possibly attached during the treatment. The rotating member 5 may be provided with a rolling bearing suitable for the purpose and provided with a drive mechanism for driving the rotation of the rotating member 5.

Furthermore, the device comprises a positioning means 7 for positioning the radiation source 1 relative to the substrate 3. This positioning means 7 can be designed in a number of different ways. For example, as shown in Fig. 7, it may comprise a carriage 7 displaceable along a radius of the substrate, the radiation source 1 being fixedly arranged and the substrate 3 being displaced relative to the radiation source. Alternatively, the radiation source can be displaceable or rotatable and the rotating member 5 supporting the substrate 5 be fixedly arranged. As a further alternative, the lithographic beam may be deflectable by means of a suitable field, such as a magnetic field or electric field (not shown). Combinations of the above-mentioned different types of positioning means are also possible.

Furthermore, the device comprises control means 14, which may be a control unit suitable for the purpose. For example, a microcomputer (not shown) connected to suitable control circuits (not shown) may be used to control one or more of the radiation source 1, the rotating means 5 and the positioning means 7c; n no oo o v n. a u u; anno II u oc: nano lO 5 2 2 1 8 3 ¿f :: ¿g; _ = -. »- - .u 13 The control means may be provided with instructions which control the device in accordance with the procedure described above.

The method according to the present invention can also be implemented by means of a computer program product for controlling a lithography device. Such a computer program product may contain instructions by which the lithography device is controlled in accordance with any of the above procedures.

Claims (20)

10 15 20 25 30 35. . s n q. . - | . o. »». - 1 522 183 »r PATENTKRAV A method for forming, by exposure to a lithographic beam (2), a groove (6) of material exposed to a predetermined degree in a surface layer (4) on a substantially flat surface, (5) (3), known from that the lithography beam (2) and the shaft (5), while the substrate (3) is rotated about the axis, are guided relative to a shaft rotatable substrate known to each other so that a part of the groove (6) is exposed to more than one exposure to the lithography beam (2), wherein the groove (6) is formed as a sum of said more than one exposure, which sum substantially corresponds to said predetermined degree of exposure. Method according to claim 1, characterized in that the lithographic beam (2) and the shaft (5) are kept at a substantially constant distance from each other while the substrate (3) is rotated several times around the shaft, to form a circular and with shaft concentric groove. A method according to claim 1, characterized in by (2) (5) each other to form a plurality with the shaft (5) that the lithographic beam and the shaft are guided relative to concentric grooves, each groove (6) being exposed to substantially said predetermined degree of exposure, regardless of the radial distance of the groove (6) to the axis (5). Method according to claim 1, characterized in that the number of exposures to which the groove (6) is exposed is a function of the radial distance of the groove (6) to the axis (5). Method according to claim 1, characterized in that the intensity of the lithographic beam (2) is controlled so that it is a function of the radial distance of the groove (6) to the axis (5). Method according to claim 1, characterized in that an angular velocity with which the substrate (3) is rotated is a function of the groove (6) (5). radial distances to the axis 10 15 20 25 30 35. - »-. Q a - ø - .. 522 183 / s ~ 7. A method according to claim 1, characterized in that the lithography beam (2) and the substrate are guided relative to each other to form a substantially helical groove (6) with varying radial distance to the axis (5). A method according to claim 7, characterized in that the groove is formed as a plurality of groove portions (8), each groove portion (8) being exposed to substantially said predetermined degree of exposure, regardless of the radial distance of the groove portion (8) to the shaft (5). 9. A method according to claim 8, characterized in that the number of exposures to which the groove portion (8) is exposed is a function of the radial distance of the groove portion (8) to the shaft (5). 10. As the method of the lithographic beam according to claim 8 or 9, characterized (2) this is a function of the radial distance intensity of the track portion (8) is controlled so that to the axis (5). 11. ll. Method according to one of Claims 8 to 10, characterized in that an angular velocity with which the substrate (3) is rotated is a function of the radial distance of the groove portion to the axis (5). (8) A method according to any one of the preceding claims, characterized in that the groove (6) is subjected to continuous to form a continuous groove of exposed material. exposure to the lithographic beam (2), A mark according to any one of the preceding claims 1 - 11, k (6) exposure to the lithographic beam, for forming a groove is subjected to intermittent consisting of a plurality of parts (9) of exposed material completely or partially separated in the direction of the tangent . A method according to any one of the preceding claims, characterized in that (3) perpendicular axis of rotation is characterized in that the substrate (4) is rotated about one towards said surface layer (5). 10 15 20 25 30 35 -. ø - u. -. -. n. a. . . . n u e »u. 522 183/6 Method according to one of the preceding claims, characterized in that the lithography beam (2) is a particle beam, preferably an ion beam or an electron beam. 16. It is known that the lithographic beam (2) is an electromagnetic beam. Method according to any one of claims 1-14, characterized by e A computer program product comprising instructions which, upon execution, control a device in which a lithography beam (2) forms a groove (6) of material to a predetermined degree in a surface layer (4) of a substantially (5) (3) , characterized in that the lithographic beam (2) and the shaft (5), the substrate (3) being so that a part of the groove (6) is exposed to more than one plane, a substrate rotatable about an axis can be rotated about the axis, is controlled relative to exposure to the lithographic beam (2), the groove (6) being formed as a sum of said more than one exposure, which sum substantially corresponds to said predetermined degree of exposure. A lithography device, the device comprising a radiation source (1) for generating a lithographic ray (2), rotating means (5) for supporting a substantially flat substrate (3) rotatable about said rotating means, positioning means (7) for movement of the lithography beam (2) and the substrate (3) relative to each other and control means (14) for controlling said lithography beam (2), rotating means (5), characterized in that (14), while the substrate (3) (5) ), (2) and the rotating means (5) relative to each other so that a part of the groove (6) and positioning means (7), said guide means are rotated about the rotating means guiding the lithographic beam is exposed to more than one exposure to the lithographic beam (2), the groove (6 ) is formed as a sum of said more than one exposure, which sum substantially corresponds to said predetermined degree of exposure. n. n. n n n n »n nn n n .nn n n n. nn n n n n n n n n n n n n n n n n n n n n n n n n n. a a n n n u n n a n .nn n n. . n nn- nun n n n n n n n n n n. n n n n n n n n nn n n. n n n n n n n n .__ n n n u n. .n n, nn. - n n. n n nn n «I? Lithographic apparatus according to claim 18, characterized in that said radiation source (1) is a particle source, preferably an ion source or an electron source. 5 A lithography apparatus according to claim 19, characterized in that said radiation source (1} is an electromagnetic radiation source.