DE2704441A1 - DEVICE AND METHOD FOR IRRADIATING A WORKPIECE SURFACE - Google Patents

Description

BLUMBACH. WESER. BERGEN · KRAMER ZWIRNER · HIRSCH · BREHM

PATENT LAWYERS IN MUNICH AND WIESBADEN ^ ■ * ·

5 "

Patenlconsull RadedcestraOe 43 8000 Munich 60 Telephone (089) 883603/883604 Telex 05-212313 Telegrams Patentconsult Patentconsult Sonnenberger Straße 43 6200 Wiesbaden Telelon (06121) 562943/561998 Telex 04-186237 Telegrams Palenlconsull

Western Electric Company

Incorporated
New York, NY 10007, USA Collier, RJ 14-1

Device and method for irradiating a workpiece surface

The invention relates to a device and a method for irradiation a workpiece surface having first means for scanning a beam sequentially through a plurality of address positions leads across the area.

In US Pat. No. 3,900,737, an electron beam exposure system (EBES = Electron Beam Exposure System) is used to generate very fine, high quality masks for integrated circuits. With the help of this system, samples can also be directly applied to varnish-coated Semiconductor wafers are exposed. In this system, a continuous passage through the mask or the semiconductor wafer combined with a periodic deflection of the electron beam in the manner of a raster scan.

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Munich: R. Kramer Dipl.-Ing. ■ W. Weser Dipl.-Phys. Dr. rer. nal. · P. Hirsch Dipl.-Ing. · H. P. Brehm Dipl.-Chem. Or. Phil. nat. Wiesbaden: P.C. Blumbach Dipl.-Ing. · P.Bergen Dipl.-Ing. D'.jur. . G. Zwirner Dipl.-Ing. Dipl.-W.-Ing.

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The method according to the system described above requires that an electron beam emitted from a cathode to a spot smaller than a micrometer on an electron-sensitive one Cover layer is focused. In practice, the diameter of the spot also corresponds to the address dimension of the system. In a special practical embodiment of EBES, the electron beam is on a spot of 0.5 micrometers (μηα) in diameter focused on the cover layer and switched on and off during its raster-like scanning movement over an area of the layer. Each scan line of the raster is one address dimension wide and 256 address dimensions long. One such System fulfills important requirements for devices of medium resolution (line widths of about 2 pm with a resolution of 0.5 / im), shows but not the extreme limits of the possibilities of EBES.

Numerous modifications to EBES are possible to adapt to the increasing demand for components with even smaller structures. For example, if you want to write structures with minimum dimensions of 1 / im at a resolution of 0.25 μπι, namely under Use of those described in the aforementioned U.S. patent

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EBES scanning so you can spot an electron beam with a Use a diameter of 0.25 m. However, this has the disadvantage that the time required to expose a given area increases, in the example by a factor of 4. For many applications of practical importance, this disadvantage is unacceptable.

The invention aims to provide an irradiation device and method to create, in which the explained disadvantage does not occur or occurs only to a lesser extent.

To achieve the object, the invention is based on a device of the type mentioned and is characterized by a second device which, depending on a control signal, the expansion of the Beam changed at the address positions when guiding the beam.

It can be provided according to a further development of the invention, that the first device guides the beam in a grid pattern over the surface and that the second device depends on the extent of the beam changed by the control signal perpendicular to the scanning direction.

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In addition, there is the possibility that, in a further development of the invention, the second device has a device which gives the beam a predetermined cross-sectional area, and also a pinhole which is arranged so that it lets through that part of the beam with the predetermined cross-sectional area which the hole of the Diaphragm covers, and means for deflecting the beam with the predetermined cross-sectional area for changing its orientation with respect to the pinhole in dependence on the control signal in order to change the extent of the beam.

There is also the possibility that the device which gives the beam the predetermined cross-sectional area has a pinhole, and that a device is provided to illuminate the pinhole evenly with the beam in the region of its recess. In addition, a device can be provided for bundling the beam passed through the first-mentioned aperture and for focusing on the workpiece surface. The deflection device can be designed in such a way that the beam can be deflected in two directions at right angles to one another as a function of the control signal.

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A further development of the invention is characterized by a device for blanking the beam as a function of a control signal in order to prevent it from hitting the workpiece surface.

In addition, the deflector can adjust the beam depending on the Deflect the control signal to such an extent that the beam with its cross-sectional area no longer touches the first-mentioned pinhole in the area of its recess covered, so that it is prevented that the beam strikes the workpiece surface.

The invention also provides a method for solving the problem Irradiation of a workpiece surface before, in which a beam while sequentially passing through a plurality of address positions scanned over a Area is guided and which is characterized in that the expansion of the beam at the address positions while guiding the beam is selective will be changed. It can be provided according to a further development of the invention that the beam is guided in a grid-like manner over the surface that the extent of the beam changed at right angles to the scanning direction and that the beam is modulated in its intensity during scanning.

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The invention is described in more detail below with reference to the drawings will. Show it:

Fig. 1 is a schematic representation of an electrical

nenstrahlsäule to achieve a raster scan with variable spot size

Figures 2 and 3 show the geometrical dimensions of two

Openings that can be used in the device of Figure 1;

4 to 11 superimposed representations of the openings according to

Figs. 2 and 3, the result of the deflection of the image of the opening according to Fig. 2 with reference to represent the opening of Figure 3;

Fig. 12 shows a portion of a pattern made with the aid of

the column according to FIG. 1 when equipped with the openings according to FIGS. 2 and 3 have been written is;

13 and 14 the geometrical dimensions of two wide

Ren openings that can be used in the device of Figure 1;

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Fig. 15 shows part of a special pattern associated with

of the device according to FIG. 1 when equipped with the openings according to FIGS. 13 and 14 has been.

In Fig. 1 is a device for controllable movement of an electron beam spot of variable size at each specified position on the surface of an electron beam cover layer 10 on a substrate 12. The substrate 12 is fastened on a table 16 of known type which can be moved in the x and y directions.

There are numerous positive and negative electron beam masking materials known that can be used for the layer 10. By selectively guiding the electron beam spot over the surface of the cover layer 10 in a very precise and fast manner there is the possibility of producing masks for integrated circuits or directly on a coated one Writing silicon wafers to make extremely small, accurate and inexpensive integrated circuits. Suitable covering materials for use for layer 10 are, for example, in a two-part article by L. F. Thompson "Design of Polymer Resists for

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Electron Lithography "in Solid State Technology, July 1974, pp 27-30 and August 1974, pages 41-4G.

The device according to FIG. 1 can be composed of two main components to be understood as consisting. The one main component is an electron beam column, which is to be described in more detail below and is characterized by possibilities for very precise and quick distraction as well Blanking similar to that described in U.S. Patent 3,801,792 Pillar. In addition, however, the column shown has the possibility of scanning with an electron beam spot of variable size.

The other major component of the apparatus of FIG. 1 comprises the Control arrangement 14. This can, for example, from that in US Pat 3. 900.737 described type. The control assembly 14 provides electrical signals to the column to facilitate scanning and blanking to control the electron beam systematically. In addition, supplies the assembly 14 control signals to the x-y table 16 to scan the workpiece surface 10 during the electron beam scanning operation in the manner described in the latter US patent.

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The column according to FIG. 1 has an electron source 22 (for example a tungsten wire), a grid 24 and an accelerating anode 26 in the form of a cylindrical metal cap with a central opening in their flat floor area. The metal cap is kept at ground potential. In this case the source 22 is on a relative basis high negative potential (for example 10 kV below ground potential).

The initial trajectories of the electrons supplied by the source 22 are in of the drawing represented by dashed lines. In the vicinity of the opening in the anode 26, these trajectories run through an intersection or source projection point 28 which, for example, has a diameter of 35 µm has. Then the electron beam paths diverge and converge alternately when the electrons are along the longitudinal axis Move 30 in the direction of the workpiece surface 10. The successive Crossing points or image points 28 are represented in FIG. 1 by points 32, 34, 36 and 38 on axis 30.

The column in Fig. 1 optionally has coils 40, with the help of which the electron trajectories emanating from source point 28 exactly with reference

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can be centered on the longitudinal axis 30. Then the Electron beam directed onto a plate or aperture 42 which has a precisely shaped opening 44. The beam is designed so that it evenly illuminates the full extent of the opening or recess 44 in the aperture plate 42 and immediately behind the aperture plate 42 appears with a cross-sectional area that exactly matches the shape of the opening 44 corresponds.

A plan view of a geometric shape of the opening 44 in the pinhole 42 is shown in FIG. For example, the perforated diaphragm 42 consists of a Molypdän disc, in which the opening 44 is highly precise Way is made, for example with the aid of known milling processes using lasers.

The dashed lines within opening 44 in FIG. 2 are for purposes only the following explanation. In reality the opening is a single continuous opening with straight edges going through the solid straight lines indicated v.'erden. For explanation, the opening 44 can be made up of six square sections Ml to M6 can be viewed as composed, each by one or more

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solid straight lines and one or more dashed straight lines Lines are defined. Each of the squares Ml to M6 can have an edge length of 100 μm. If the pinhole according to FIG. 2 in the Column according to Fig. 1 is attached, the longitudinal axis 30 of the column is perpendicular to the aperture and passes through the center of the square M3 in Fig. 2.

As indicated above, the cross section of the through the aperture 42 leading electron beam determined by the geometry of the opening 44. The beam then passes through an electromagnetic lens 46 of a conventional type (for example a toroidal coil with pole pieces made of iron), which images the opening 44 onto a second masking plate or aperture plate 48. The pinhole 48 contains a precisely shaped opening 52. The aperture plate 48 is arranged, for example, in the electromagnetic lens 49 and is in one piece trained with this. The lens 49 is not provided to the cross-sectional shape of the electron beam immediately behind the pinhole 48 to enlarge or bundle. Rather, the lens 49 is used in combination with the immediately following lens, which will be described later to maximize the transfer of electrons through the column. Forms together with the next lens

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the lens 49 crosses the point of intersection 28 to the center of a beam limiting opening 59 from.

A predetermined rest orientation of the image of the opening 44 on the Orifice plate 48 is secured by alignment coils 51 in the column.

The position of the image of the illuminated opening 44 of the perforated diaphragm 48 is selectively controlled at high speed during the time the electron beam is scanned across the workpiece surface 10 is performed. This is done with baffles 50, for example are arranged as shown in Fig. 1 so that they deflect the beam in the x and / or y direction. Appropriate the deflectors 50 consist of two pairs of electrostatic deflector plates arranged at right angles to one another. Instead of Electrostatic deflection plates, electromagnetic deflection coils can be used, but this usually results in some reduction the deflection speed and accuracy. Regardless of whether electrostatic or electromagnetic deflection is used, the deflectors 50 can also be used to make a

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Alignment of the image of the opening 44 on the second pinhole to reach. This is done by applying a centering direct current signal to the deflectors 50. In this case, of course, the separate alignment coils 51 can be omitted.

Before further describing the components of the electron beam column in Fig. 1 it should be useful to explain the aperture plate 48 in more detail and to illustrate the influence that a movement of the image the opening 44 on the aperture 48 has. A top view of a specific embodiment of a perforated diaphragm 48 for use in the column according to FIG. 1 is shown in FIG. The opening 52 in the aperture 48 can, for example, have the shape shown in FIG. 3 with dimensions of 100 × 300 μm and be produced with a laser. Of the Central point 54 in FIG. 3 indicates the position of the longitudinal axis 30 in FIG. 1 when the screen 48 is attached in the column according to FIG. 1.

In the rest state, the opening 44 of the pinhole 42 is through the lens 46 mapped onto the center of the aperture 48. As an example, assume that the image projected onto the plate 48 through the lens 46 in its dimensions exactly with the dimensions of the opening 44

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agrees. (If desired, the lens 46 can of course also be designed in such a way that a projection of the opening 44 deviating from the ratio 1: 1 is achieved. In other cases of practical interest, the lens 46 can be omitted at all). With the aid of the coils 51, the projected image is aligned precisely centrally on the diaphragm 48, as shown in FIG. 4.

From Fig. 4 it appears that only the portions M2, M3 and M6 of the imaged aperture 44 are transmitted through the rectangular opening 52 of the hole faceplate 48. Accordingly, for the orientation shown, the electron beam has a cross section directly behind the perforated diaphragm 48 which corresponds exactly to the geometric configuration of the opening 52. In the case shown as an example, in which the opening 52 has a width of 100 μm and a height of 300 μm, the cross section of the electron beam immediately behind the perforated diaphragm 48 shows the same dimensions.

The cross-sectional area is then de & through the perforated diaphragm 48 transmitted electron beam is reduced. This is done with the help of three electromagnetic lenses 54, 56, 58 of the usual type.

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These lenses can be designed in such a way that an overall reduction or concentration of the electron beam by a factor of 400 results. More precisely, the lenses are selected in such a way that they reduce the above-mentioned cross-sectional area of the beam transmitted through the perforated diaphragm 48 and project a reduced image onto the workpiece surface 10. For a total reduction of 400 and for the case chosen as an example, in which the beam immediately behind the aperture plate 48 has a cross section of 100 × 300 μπα, the electron beam spot imaged on the surface 10 represents a rectangle with a width of 0.25 in the resting state , Um and a height of 0.75 μια .

The other components in the column according to FIG. 1 are of the usual type ν 1, for example, can be identical to the corresponding parts in US Pat. No. 3,801. 792 be the column described. These components include the beam limiting pinhole 59, electrostatic beam blanking plates 60 and 62, an aperture limiting plate 64, and electromagnetic deflection coils 65-68.

When the beam blanking plates 60 and 62 in Fig. 1 are energized, so the beam traveling along the axis 30 is deflected so that the

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impinges on an unopened portion of the plate 64. In this way, the electron beam is blocked for predetermined time intervals and does not appear on the surface 10. When the Beam is not blocked, it is selectively deflected by the coils 65 68 so that it is at any desired position of a specified Area of the workpiece surface 10 on Uitt. Other areas of the surface 10 can be irradiated by moving the workpiece, for example with the aid of one described in US Pat. No. 3,900,737, computer-controlled micromanipulator.

As stated above, the rectangular electron beam spot, the with a central image of the opening 44 on the perforated diaphragm 48, controlled by the electron beam column in Fig. 1 so that it impinges on a specific location of the workpiece surface 10 or not.

A reduced representation of the rectangular area composed of the segments M2, M3 and M6 (FIG. 4) is shown in FIG and provided with the reference number 70. To simplify the description, the rectangular electron beam spot 70 which hits the workpiece surface 10 in Fig. 12, into three square sections M2 ', M3'

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and Μ6 '. These segments correspond to sections M2, M3 and M6 in FIG. 4. For the particular embodiment assumed above, in which the total reduction is 400, each has the segments M2 ', M3' and M6 'have an edge length of 0.25

The scanning of the through the electron beam column in FIG generated beam is in Fig. 12 in the direction from right to left in the direction -x along the center line 72 is shown. As an example, assume that there are 512 equally spaced address positions lie along scan centerline 72. The location of the The first of these address positions are indicated in FIG. 12 by the arrows AP1 to AP9. At each address position, the electron beam becomes blanked or not blanked during linear scanning in the manner described above. In addition, the Cross-section of the beam impinging on the workpiece surface 10 at each address position selectively controlled.

When the electron spot of variable size is deflected along a line of the scanning field, the spot is caused by the beam blanking plates 60 and 62 with a frequency of, for example, 10MHz in his

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Modulated intensity. This modulation frequency corresponds to an exposure time for a single address of 100 ns adapted to the sensitivity of the available electron beam masking materials is.

At the end of each scanning line, the electron beam is quickly returned to the starting position in order to begin the next scanning line. In the example shown in FIG. 12, such a return or such a return brings the beam above the address position AP1 onto a new scanning center line 74, which lies parallel to and by 0.75 μια above the line 72. In this way, successive lines of a region of the workpiece surface are selectively irradiated in the manner of a grid. This raster-like scanning (without the variable spot size) is described in detail in US Pat. No. 3,900,737.

The geometric shape of the electron beam spot on surface 10 is changed during the scanning at high speed as a function of control signals sent by the device 14 (FIG. 1) the deflectors 50 are applied. For example

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by applying the correct deflection voltages to the deflectors 50 the image of the opening 44 on the perforated diaphragm 48 in the x and / or y direction be moved. The result of such a process is shown in the group of figures described below.

5 shows the case in which the projected image of the opening 44 has been deflected by the deflection device 50 by 100 μm in the + y direction and by 100 μm in the -x direction. This relative displacement has the effect that only the irradiated segment M4 of the image is transmitted through the opening 52 in the pinhole 48. A reduced image (M4 ') of the segment M4 then arrives on the workpiece surface 10. This image with a size of 0.25 o.25 Jim is shown in FIG. 1 ° sr _: the address position AP2.

In the operating mode explained as an example, the deflection device 50 in Fig. 1 applied deflection voltages (if necessary) while the electron beam is approximately midway between adjacent address positions. The generation of the new deflection voltages is carried out at high speed. For the Example assumed above with an exposure time of 100 ns

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for each individual address the deflection voltages needed to achieve a specified spot size are required, generated by the control device 14 in, for example, about 10 ns or faster.

The geometric overlay shown in FIG. 5 is for example generated by changing the deflection voltages at the deflection device 50, while the electron beam is approximately in the middle between the address positions AP1 and AP2 (Fig. 12). In practice, changes range from about 5 to 10 volts to the electrostatic Deflection plates applied deflection voltage in order to achieve a change from the rest position according to FIG. 4 to the deflected position according to FIG. 5. Such voltage changes can be achieved in about 5 to 10 ns with the help of extremely fast amplifiers.

Fig. 6 shows the case that the image of the opening 44 by the deflector 50 has been deflected by 100 μπα in the + y direction. The illuminated sections M3 and M6 of the image are then transmitted through the opening 52 in the perforated diaphragm 48. Again will a reduced image (M3 ', M6') of the segments M3 and M6 is projected onto the workpiece surface 10. This reduced image with the

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Dimensions 0.25 χ 0.5 μηι is in Fig. 12 at the address position AP3 shown.

Figures 7 to 10 show further geometric overlays that can be reached. The reduced electron steel spots that correspond to the superimpositions shown in FIGS. 7 to 10, are shown in Figure 12 at address positions AP4 through AP7. Any such overlay is thereby made in the manner described above achieves that the deflection device 50 μηι the image of the opening 44 by 100 deflects in the x and / or y direction.

As explained above, the blanking of the electron beam in the Column according to FIG. 1 with the help of the plates 60, 62 and the blanking lock plate 64 achieved. Alternatively, blanking can be achieved by that the projected image of the opening 44 is deflected by the deflecting device 50 with respect to the opening 52 in the perforated diaphragm 48 becomes that no portion of the projected image covers the opening 52. This case shown in Fig. 11 makes it necessary to that the deflector 50 the image by 200; im in the direction -x distracts. (Of course, a deflection of 200 / im in that direction would be

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+ χ are also sufficient). In some cases of practical interest such a deflection can be achieved by the deflection device 50 sufficiently quickly for this alternative blanking technique to appear expedient allow. Then, of course, the components 60, 62 and 64 in the column according to FIG. 1 can be omitted.

As already said above, the special design of the openings in the perforated diaphragms 42 and 48 according to FIGS. 2 and 3 only given as an example. It turns out that a variety of other trainings for Achieving the selective overlay can be chosen. Two such other geometrical shapes for the openings are shown in Figs. 13 and 14 shown. The perforated diaphragm 80 with its opening 82 (FIG. 13) can be the perforated diaphragm 42 in the column according to FIG. 1 and the perforated diaphragm 84 with the opening 86 (FIG. 14) replace the aperture plate 48. As an example, it is assumed that each of the segments M7 to M14 of the opening 82 according to FIG. 13 has an edge length of 100 μm and for the rectangular opening 86 according to FIG. 14 a width of 100 μm and assumed a height of 400 pm.

By deflecting the projected image of opening 82 in FIG. 13 with

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With respect to opening 86 in FIG. 14, there is the possibility of a plurality of electron spot sizes on the surface 10. This in turn allows high-resolution patterns to be produced at high speed the surface 10 can be blasted.

In Fig. 15 there is shown part of an angle pattern using of openings 82 and 86 has been made. Lines 90 and 92 represent the actual, ideal boundaries of the on surface 10 The grid of horizontal and vertical lines 0.25 µm apart shown is not actual present on surface 10, but only given for ease of understanding. Lines 94 and 96 are scan centerlines, which correspond to lines 72 and 74 in FIG.

Assume that the scanning of surface 10 in Figure 15 is from right to left, first along the center line 94 and then along the line 96. Those squares of the grid that were captured by the electron beam during the raster-like scanning of the Areas with variable spot size are irradiated are shown shaded. Each shaded square has a painted symbol

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to indicate which reduced part of the illuminated Opening 82 actually strikes the surface 10. The rectangular patches of variable height shown in Fig. 15 at the respective address positions are by deflecting the image of the opening 82 by 100 μπι in the x and / or y direction achieved.

As stated above, an embodiment for an electron beam exposure system can have an address length of 0.25 μm and a spot size that varies, for example, between a square with an edge length of 0.25 μm to a rectangle of 0.25 μm χ 1 Jim can be. With such a system, for a given writing spot exposure time, areas can be exposed at a speed which is approximately four times greater than that which can be achieved with a known raster scan with a spot of fixed size and a diameter of 0.25 µm. In other words, a system equipped with the variable spot size raster scanning described herein can write patterns with a resolution of 0.25 microns at the same speed as a conventional exposure system that produces patterns with a resolution of 0.5 µm.

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Those skilled in the art can create additional arrangements. For example Although the change in the extent of an electron beam spot in the direction perpendicular to the scanning direction has been emphasized in the explanation, but the spot size or position in the scanning direction can also be changed. In addition to electron beams, the invention can also be used with other beams (for example light beams, X-rays and ion beams).

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Claims (10)

BLUMBACH. WESER BERGEN KRAMER ZWIRNER HIRSCH - BREHM PATENT LAWYERS IN MUNICH AND WIESBADEN * ■ 'U 4 4 4 1 Patentconsult Radedcestraße 43 8000 Munich 60 Telephone (089) 833603/883604 Telex 05-212313 Telegrams Patentconsuli Patentconsult Sonnenberger Straße 43 6200 Wiesbaden Telephone (06121) 56294J7561998 Telex 04-186237 Telegrams Patentconsul! PATENT CLAIMS [1. Device for irradiating a workpiece surface with a first Means which scans a beam over the surface while sequentially traversing a plurality of address positions, marked by a second device (42, 48, 50) which is dependent on a control signal (from 14) the expansion of the beam at the address positions (on 10) is changed when the beam is guided. 2. Device according to claim 1,
characterized, that the first device (65 to 68) the beam raster-like over the Surface leads and that the second device determines the extent of the beam as a function of the control signal at right angles to the scanning direction changes. 709832/0701 Munich: R. Kramer Dipl.-Ing. · W. Weser Dipl.-Phys. Dr. rer. nal. · P. Hirsch Dipl.-Ing. . H. P. Brehm Dipl.-Chem. Dr. phil. nal. Wiesbaden: P. G. Blumbach Dipl.-Ing. · P. Bergen Dipl.-Ing. Or. Jur. · G. Zwirner Dipl.-Ing. Dipl -W.-Ing. ORIGINAL INSPECTED 3. Device according to claim 1 or 2,
characterized, in that the second means comprises means (42) for giving the jet a predetermined cross-sectional area, further a pinhole (48) which is arranged so as to cover that part of the beam with the predetermined cross-sectional area passes, which covers the hole of the diaphragm (48), and a device (50), which the beam with the predetermined cross-sectional area to change its orientation with respect to the pinhole in dependence on the control signal nblenken to the To change the extent of the beam. 4. Apparatus according to claim 3,
characterized, that the device which gives the beam the predetermined cross-sectional area comprises a pinhole (42), and that a device (22, 24, 26) is provided in order to illuminate the aperture plate (42) uniformly with the beam in the region of its recess (44). 5. Apparatus according to claim 3 or 4,
marked by ι η 9832/0701 ³ 27UU41 -Bi- means (54, 56, 58) for bundling the through the former Orifice plate (48) allows the beam to pass through and for focusing on the workpiece surface. 6. Apparatus according to claim 3, 4 or 5,
characterized, that the deflector (50) is designed so that the beam is dependent can be deflected by the control signal in two mutually perpendicular directions (x, y). 7. Device according to one of the preceding claims, characterized by means (60, 62, 64) for blanking the beam as a function of a control signal in order to ensure that it strikes the workpiece surface to prevent. 8. Device according to one of claims 3, 4, 5 or 6, characterized, that the deflection device (50) deflects the beam as a function of the control signal so far that the beam with its cross-sectional 7 09832/0701 270444 surface the first-mentioned perforated diaphragm (48) in the area of its recess no longer covered and thus prevents the beam from striking the workpiece surface. 9. A method for irradiating a workpiece surface, in which a beam while sequentially passing through a plurality of address positions is scanned over a surface, characterized in that that the extent of the beam at the address positions is selectively changed as the beam is guided. 10. The method according to claim 9, characterized, that the beam is guided over the surface like a grid, that the extent of the beam changes at right angles to the scanning direction and that the beam is modulated in its intensity during scanning. 709832/0701