EP0738572A1 - Method for orienting monocrystals for cutting in a cutting machine and device for performing the method - Google Patents

Abstract

The method involves aligning a monocrystal (2) on a positioning unit (1) situated outside the cutting machine. Two parallel cylindrical supports (8) rotate on a frame (5). An angle measuring element (10) determines a first angle of rotation. A rotary plate (12) can turn relative to the frame, and has its main plane parallel to the cylindrical supports. The monocrystal is fixed in a predetermined position on a support (3). The positioning unit is then inserted into the machine in a definite geometrical situation and fixed in place. The predetermined alignment of the monocrystal is obtained by placing it on the positioning unit. One of the monocrystal geometrical axes (x) is located within the corresponding reference plane of the cutting machine. The angles used are determined mathematically.

Description

The present invention relates to a method for orienting single crystals for cutting in a cutting machine according to a predetermined cutting plane.

Monocrystals generally for optical or semiconductor uses require that they be cut according to very precise orientations relative to the axes of the crystal lattice. In addition, their manufacture does not allow perfect control of the orientation of the axes of the crystal lattice relative to the geometric axes. It is therefore necessary for correct cutting to correct on the one hand the manufacturing error and on the other hand, take into account the angles formed between the cutting plane and the crystalline plane chosen or imposed by the subsequent uses or processes. Since the cutting is done from a geometric single crystal, it will have to be positioned and maintained in space so that the movement of the cutting system is parallel to the desired cutting plane. There are an infinite number of possible positions, however there are only four which in addition places the single crystal in a plane perpendicular to the cutting plane of the machine. The positioning of the single crystals according to one of these four positions therefore makes it possible to cut not only in the desired orientation but also to minimize the cutting time, thus improving the productivity of the cutting device.

Single crystal orientation devices are already known and used in the semiconductor industry on internal diameter chainsaws or on wire saws. Positioning is done using an adjustable table y '' ', z' '' mounted directly on the machine. The adjustment is made after optical or X-ray measurement. The correction is then introduced according to y '' ', z' ''. This way of practicing has the disadvantage on the one hand of having a position of the single crystal inclined with respect to the advance of the cutting element, which is very unfavorable in the case of a wire saw or the web of wires must be parallel to the geometric single crystal, and on the other hand not to minimize the cutting length, which is then unfavorable for saws with internal diameter by reducing their productivity. In addition, this way of practicing requires adjusting the machine table before each cut very precisely and in an often dirty industrial environment therefore not conducive to this type of operation. Machine set-up time also contributes to lower productivity.

The present invention aims to remedy the aforementioned drawbacks and to allow precise adjustment of the positioning of the single crystal in a clean environment and to increase the productivity of cutting.

The invention is characterized for this purpose by the characteristics appearing in the independent claims and is characterized by the fact that the single crystal is oriented by means of a positioning device outside the cutting machine in a predetermined orientation relative to a cutting support, which the single crystal is fixed in accordance with said predetermined orientation on the cutting support, the positioning of which in the machine cutting is geometrically defined with respect to the cutting plane of the machine, and that the cutting support is available after fixing the single crystal in the cutting machine according to said geometrically defined positioning to obtain said predetermined orientation of the single crystal in the machine cutting.

By these characteristics, it is possible to obtain precise positioning and orientation of the single crystal in a suitable measurement environment, without it being necessary to make any positioning adjustment on the cutting machine. The downtime of the latter can therefore be considerably reduced so as to increase productivity.

In a preferred embodiment, the invention is characterized in that said predetermined orientation is obtained by placing the single crystal on the positioning device so that one of its geometric axes of the geometric shape of the single crystal is included in a reference plane corresponding to the working plane of the cutting machine perpendicular to the cutting plane, by rotating the single crystal by a first predetermined angle around said geometric axis to bring the normal to the cutting plane of the single crystal in said reference plane , and by performing a relative rotation between the cutting support and the single crystal of a second predetermined angle about an axis perpendicular to said reference plane so that the normal to the cutting plane is oriented in a reference direction corresponding to the normal in the cutting plane of the machine, said geometric axis and the normal to the cutting plane of the single crystal being included in the reference plane.

The disadvantage of having an inclined position of the single crystal relative to the direction of advance of the cutting elements of the machine is thus remedied in a precise and easy manner, which is particularly unfavorable in wire saws. The main geometrical axis of the single crystal can thus be oriented perfectly parallel to the work surface or to the ply of wires, an optimal cutting is therefore obtained while minimizing the cutting length.

Favorably, the method is characterized in that the orientation of the cutting plane of the single crystal is defined relative to the crystal lattice, in that the orientation of the crystal lattice is measured in relation to the geometric shape of the single crystal, and in what the first and second angles of rotation are calculated taking into account the orientation of the cutting plane with respect to the crystal lattice and with respect to the geometric shape of the single crystal.

By these characteristics, great positioning accuracy and considerable assembly speed are obtained.

The method according to the invention is particularly advantageously applicable to the use of a single crystal of which the geometric shape is substantially circular cylindrical, said geometric axis corresponding to the main axis of the single crystal and by placing the single crystal on two parallel rotating cylinders of the positioning device, the axes of the two cylinders being parallel to said reference plane.

The invention also applies to a device for implementing the method which is characterized in that it comprises a positioning device intended to orient the single crystal out of the cutting machine in accordance with a predetermined orientation relative to a cutting support on which the single crystal is intended to be fixed and whose placement in the cutting machine is geometrically defined and whose main axes are parallel to the axes of the cutting machine.

This device for implementing the method is advantageously characterized in that it comprises first means for supporting the single crystal in an orientation such that one of the geometric axes of the geometric shape of the single crystal is included in a corresponding reference plane to the working plane of the cutting machine and to perform a rotation of the single crystal by a first predetermined angle about said geometric axis to bring the normal to the cutting plane of the single crystal in said reference plane and second means for carrying out a relative rotation between the cutting support and the single crystal of a second predetermined angle around an axis perpendicular to said reference plane so that the normal to the cutting plane is oriented along a reference direction corresponding to the normal to the cutting plane of the machine, and by the fact that it comprises third means for effecting a relative translational movement between the single crystal and the cutting support intended to bring the cutting support closer and the single crystal in order to fix the latter on the cutting support, in said predetermined orientation.

By these characteristics, we obtain a fast, precise positioning adapted to cutting machines allowing an exact cutting in a minimum time. In addition, the cutting precision will be independent of the machine used or of the operator in the case of production lines.

A favorable embodiment is characterized in that the first means comprise two parallel cylindrical supports rotatably mounted on a chassis of the positioning device and arranged so as to support the single crystal and a first angular measurement member capable of determining the first predetermined angle of rotation, by the fact that the second means comprise a rotary plate rotatably mounted with respect to said chassis and the main plane of which is parallel to the axes of said cylindrical supports, this rotary plate being arranged so as to maintain the support of cutting in a geometrically defined position, a second angular measuring member being provided for determining said second predetermined angle of rotation, by the fact that the third means comprise a translation mechanism allowing the cutting support to be brought closer to the single crystal and by the fact that the cutting support is shaped so that its positioning in the cutting machine is effected according to a geometric position corresponding to the geometric position defined on said rotary table so that the reference plane and the reference direction correspond to the work plan and normal to the cutting plane of the machine.

These characteristics allow a particularly simple and inexpensive construction of the positioning device, while ensuring high cutting precision.

Other advantages emerge from the characteristics expressed in the dependent claims and from the description setting out the invention below in more detail with the aid of drawings which diagrammatically represent an embodiment by way of example.

Figure 1 illustrates in perspective an example of a single crystal with its geometric and crystallographic axes and the chosen cutting plane.

FIGS. 2A and 2B illustrate in two orthogonal views the position of the single crystal obtained by a known and commonly used method.

Figures 3A and 3B show in two orthogonal views the position of the single crystal obtained in accordance with the present invention.

FIG. 4 represents a vector diagram of the various reference systems used.

FIGS. 5A, 5B, 5C illustrate the positions occupied by the single crystal following the orientation method according to the invention.

Figure 6 is a perspective view of an embodiment of the device for the implementation of the method.

In general, the invention gives the possibility of installing pre-oriented single crystals on the cutting machine, the cutting plane of which is oriented parallel to the cutting plane of the machine and rotated along a perpendicular axis (normal to the cutting plane), so as to minimize the cutting length. This determination will be made mathematically from the measurements carried out to determine the error of the geometric single crystal with respect to the crystal lattice by including the requirements of the subsequent process in relation to the crystal axes. The mounting of the single crystal on its support can then be done using a positioning device which allows the exact measurement of the angles of rotation of the geometric single crystal, and to mount it as is on a cutting support which is a part with indexing belonging to the cutting machine. The single crystal can be clamped or preferably glued to the support, support which once transferred to the cutting machine will present a perfectly preoriented single crystal ready to be sawed without subsequent adjustment. In addition, the cutting precision will be independent of the machine used or of the operator in the case of production lines.

The positioning device will be in the form of a table or a frame with a rotary table having its axis of rotation z '''vertical on which is posed the support of the single crystal on which it will be fixed later. This support has an indexing system identical to that of the cutting machine. The single crystal support is an interface piece between the positioning device and the cutting machine. It will therefore have the same position on the positioning device and on the cutting machine. Above the rotary table but fixed relative to the table is a mechanism for holding the single crystal and rotating it along its horizontal axis x. This system is composed in the case of cylindrical single crystals of two cylinders on which the single crystal rests. The single crystal can then rotate along its x axis. The movement of the plate and the rotation of the single crystal x allow it to be positioned in any orientation. The value of the two angles of rotation will be determined by the requirements of the finished product and calculated mathematically. Once the two rotations have been carried out, a mechanism brings the support into contact with the single crystal itself while retaining their relative position. This can be done either by raising the turntable or by lowering the single crystal. Once brought into contact, the single crystal will be clamped or glued in position. The single crystal support can then be transferred to the cutting machine. The single crystal is then oriented, ready to be cut. The angles of rotation along x and z '''are measured by integrated electronic devices such as encoders or mechanical by verniers for example.

FIG. 1 represents an example of a single crystal to be cut 2 which has a cylindrical geometric shape with geometric axes x, y, z, the x axis being the main axis. The axes x ', y', z 'of the crystal lattice of this single crystal are not parallel to the geometric axes. The angles a and f between the axes y ', y and z', z are determined by optical or X-ray measurement and generally define the manufacturing error of the single crystal. Figure 1 also shows the chosen or imposed cutting plane 16 of the single crystal with its axes y '' and Z '' inclined by the angular values p and t relative to the axes y ', z' of the crystal lattice and the normal x '' on the cutting plane. The angular values p and t are generally defined according to the needs of the subsequent use of the cut single crystal. It is understood that these angles p and t may for example be equal to zero in the case where it is desired to obtain silicon wafers cut parallel to the plane (100).

FIGS. 2A and 2B show in lateral and plan view, the position of the single crystal 2 obtained by the known method and commonly used before the present invention by performing an orientation of the single crystal by rotation around the geometric axes y and z. The single crystal 2 is then not parallel to the plane of the ply of wires 17 in the case of the use of a wire saw as a cutting means. The machine plane x ''',y''' of the cutting machine is not parallel to the geometrical axis x of the single crystal 1. The direction of advance along z '''of the ply of wires 17 n 'is not perpendicular to the single crystal, which is detrimental to the quality of the cut.

Figures 3A and 3B illustrate the orientation of the single crystal obtained by the method according to the present invention by performing an orientation of the single crystal by rotation around the geometric axes x and z '' '. The ply of wires 17 of the saw used as a cutting machine is located in the plane x '' 'y' '' and the geometric axis x of the single crystal is parallel to this plane x '' ', y' ''. The single crystal is therefore in an optimal position relative to the cutting means, so as to obtain a very precise cutting.

The vector diagram of the various reference systems used for positioning is shown in FIG. 4 and includes the reference system x, y, z linked to the geometric shape of the single crystal, the reference system x ', y', z 'linked to the crystal lattice of the single crystal, the reference frame x '', y '', z '' corresponding to the cutting plane of the single crystal and the reference frame x '' ', y' '', z '' 'used for the positioning device and the cutting machine.

The cutting plane corresponds to the y '', z '' plane and its normal corresponds to the x '' direction. The misalignment of the geometric shape of the single crystal 2 with the crystal lattice is determined by the angles a and f, corresponding to the angles y'y and z'z. The angles p and t corresponding to the angles y''y 'and z''z' determine the orientation of the chosen cutting planes with respect to the reference frame of the crystal lattice. The normal x '' to the cutting plane y''z '' defines a vector x '' (x, y, z) which makes an angle g with the geometric axis x and the projection of the vector X '' (x, y, z) on the y-plane, z makes an angle d with y.

The angle d therefore corresponds to the angle of rotation around the geometric axis x to bring the normal x '' to the cutting plane y '', z '' in a reference plane corresponding to the work plane x '' ', y' '' of the machine.

The angle g corresponds to the angle of rotation around the vertical axis z '' 'so that the normal x' 'to the cutting plane is oriented in a reference direction corresponding to the normal x' '' to the plane cutting y '' 'z' '' of the machine to make the desired cutting plane coincide with the cutting plane of the cutting machine.

avec M(a,f) matrice de rotation pour les angles a,f et $$\text{X'' = M(t,p)X'}$$

avec M(t,p) matrice de rotation pour les angles p,t.The angles d and g can be calculated and the mathematical solution will appear in the following form: $$\text{X '= M (a, f) X}$$

with M (a, f) rotation matrix for angles a, f and $$\text{X '' = M (t, p) X '}$$

with M (t, p) rotation matrix for the angles p, t.

We deduce that the two angles d and g that we will make with the geometric single crystal according to x and z '''will be obtained by the components X''x, X''y, X''z of X''( x, y, z) in the coordinate system x ''',y''', z '''whereX''is the vector normal to the plane y'',Z''in the machine reference system. $$\begin{array}{c}\begin{array}{c}\text{d = arctang (X''z / X''y)}\\ \text{g = arctang ((sqrt (X''y ** 2 + X''z ** 2)) / X''x)}\end{array}\end{array}$$

The positioning process for obtaining the optimal orientation shown in FIGS. 3A and 3B is described more precisely with reference to FIGS. 5A, 5B and 5C illustrating three successive positions. In FIG. 5A, the single crystal is placed on the positioning device and its geometric axes x, y, z are aligned with the axes x ''',y''', z '''of the alignment device and the cutting machine.

One then performs a rotation around the geometric axis x '' 'or x of the angular value d to bring the vector X' 'in the plane x' '', y '' '(Figure 5B). A rotation of an angle g of the geometric single crystal along the z axis '' 'brings the vector X' 'into a collinear position with the x axis' '' (Figure 5C). After these two rotations, the geometric single crystal x, y, z is oriented parallel to the plane x '' ', y' '' with an angle g relative to the normal X '' 'to the cutting plane corresponding to the requirements of the process used later. The resulting sawing will have the angles t and p relative to the crystallographic axes y 'and z'. It is understood that the second rotation may also be carried out by rotating the cutting support by an angle -g, the single crystal remaining stationary as is done in the embodiment illustrated in FIG. 6.

The latter is constituted by a positioning device 1 which makes it possible to orient the single crystal 2 out of a cutting machine in accordance with a predetermined orientation with respect to a cutting support which is in the form of a support 3 on which the single crystal will be fixed after proper orientation. The positioning device 1 for this purpose comprises a table or a frame 5 with an upper part 6 and a lower part 7.

The single crystal 2 is carried by two support cylinders 8 mounted rotating on the upper part 6 with their main axis oriented parallel to the x axis. An angular measuring member, in the form of an encoder 10 makes it possible to measure the angle of rotation d of the single crystal around the x axis.

A rotary plate 12 is mounted to rotate along the axis z '' 'on the lower part 7 of the chassis. An angular measurement system integrated in the rotary plate 12 makes it possible to measure the angle of rotation g around the axis z '' '. The support 3 is maintained in a precise predetermined orientation on the rotary plate 12.

The turntable 12 is also slidably mounted in the direction z '''on the lower part 7 of the chassis in order to be able to bring the support 3 closer to the single crystal 2 by means of a lifting mechanism 14 to fix the single crystal 2 to the support 3. After fixing, the support 3 and the single crystal 2 can be placed in the cutting machine according to a predetermined geometric position so that the reference plane x ''' _s , y''' _s of the support 3 corresponds to the plane x ''',y''' of the cutting machine and so that the perpendicular x '''to the cutting plane of the machine is parallel to the reference direction x''' _s of the support.

Thus the method and the device described allow the positioning of a single crystal on a support outside the cutting machine so that the single crystal, once mounted with its support on a cutting machine, is cut with a given orientation of the axes crystalline with respect to the saw plane. In addition, the position of a cylindrical single crystal is such that the generators thereof are placed parallel to the ply of wires 17 in the case of a wire saw or parallel to the direction of movement defining the thickness of the slices if it is a cut with cam. For this, the orientation of the crystal lattice is measured with respect to the geometric shape of the single crystal optically or by means of X-rays. The positioning device or the cutting support can advantageously be arranged for this purpose so that they can be mounted on a generator X-rays so that the positioning of the single crystal can be carried out and controlled simultaneously. The orientation of the cutting plane y '', z '' with respect to the crystal lattice x ', y,' z 'being imposed by the subsequent application, the values of the two angles of rotation of the single crystal d along the x axis and g along the z axis''' of the positioning device are determined mathematically. Once the two rotations carried out according to the calculated values, the single crystal will be in the position sought for the cutting machine, namely perpendicular to the cutting advance having in addition its cutting plane parallel to that of the machine. The positioning device will allow the single crystal to be fixed either by clamping or by gluing on a pre-indexed support relative to the cutting machine. In addition, the orientation given by the method minimizes in the case of cylindrical single crystals the sawing length. The cutting machine therefore does not require any adjustment device to ensure cutting according to the angular specifications required after the transfer of the single crystal onto its cutting support and of the latter into the cutting machine. The wire table of a wire saw remains parallel to the geometrical single crystal throughout the cutting while ensuring an adequate orientation of the slices thus produced. Likewise, the saw blade of a blade machine remains perpendicular to the single crystal.

It is understood that the embodiment described above has no limiting character and that it can receive any desirable modifications inside the frame as defined by claim 1. In particular, the two angles of rotation around x and z axes' '' could be replaced by angles taken and calculated with respect to other geometric and crystallographic reference frames, but which lead to the same result as the normal to the cutting plane of the single crystal is oriented in a reference direction corresponding to the normal to the cutting plane of the machine and that a predetermined geometric axis of the single crystal and the normal to the cutting plane are included in a reference plane corresponding to the working plane of the machine. Similarly, the cutting plane can be determined by other angles than p and t relative to the crystal lattice and the shift of the crystal lattice relative to the geometric shape of the single crystal can be indicated by other angles measured than a and f.

The two support cylinders 8 could be replaced by other means for supporting the single crystal and for performing a rotation of the single crystal such as for example a single support in or on which the single crystal is temporarily fixed and which is mounted to rotate on the table or the chassis. This rotation support could be arranged at one or two opposite ends of the single crystal. The relative rotation between the single crystal and the cutting support around the axis z '''could also be obtained by rotating the single crystal with respect to the cutting support which would remain stationary on the table or the chassis of the positioning device. The rotary table would then be replaced by a rotary member along z '''and carrying the temporary support of the single crystal.

The angular measurement members could be electronic, optical or mechanical.

The approximation or bringing into contact of the single crystal and the cutting support could be carried out from the bottom or from the top and by moving either the cutting support or the single crystal.

The rotations around the two horizontal and vertical axes x, z '' 'could be inverted over time by first performing the rotation around the z axis' '' and then the rotation around the horizontal x axis.

The method and the device could also be used for the oriented cutting of single crystals of any other geometric shape or of any material other than a single crystal, such as polycrystalline assemblies with predetermined crystal orientation, crystals with simple or polysynthetic rings, aggregates. oriented crystallines, alloys, oriented crystalline substances contained in an amorphous substance, for example polarizing materials.

Claims (11)

Method for orienting single crystals (2) for cutting in a cutting machine (17) according to a predetermined cutting plane (y '', z ''), characterized in that the single crystal is oriented (2) by means of a positioning device (1) outside the cutting machine in a predetermined orientation relative to a cutting support (3), that the single crystal (2) is fixed in accordance with said predetermined orientation on the cutting support (3), the positioning of which in the cutting machine (17) is geometrically defined with respect to the cutting plane (y '' ', z' '') of the machine, and that the cutting support (3) after fixing the single crystal in the cutting machine (17) according to said geometrically defined positioning to obtain said predetermined orientation of the single crystal (2) in the cutting machine. Method according to claim 1, characterized in that the said predetermined orientation is obtained by placing the single crystal (2) on the positioning device (1) so that one of its geometric axes (x) of the geometric shape (x, y, z) of the single crystal is included in a reference plane corresponding to the working plane (x ''',y''') of the cutting machine (17) perpendicular to the cutting plane (y ''',z'''), by rotating the single crystal by a first predetermined angle (d) around said geometric axis (x) to bring the normal (x '') to the cutting plane (y '', z '') of the single crystal in said reference plane, and by performing a relative rotation between the cutting support (3) and the single crystal by a second angle predetermined (g) around an axis (z ''') perpendicular to said reference plane so that the normal (x'') to the cutting plane (y'',z'') is oriented in a reference direction corresponding to the normal to the cutting plane (y ''',z''') of the machine, said geometric axis (x) and the normal (x '') to the cutting plane of the single crystal (2) being included in said reference plane. Method according to claim 2, characterized in that the first and second angles of rotation (d, g) are determined mathematically. Method according to claim 3, characterized in that the orientation of the cutting plane (y '', z '') of the single crystal relative to the crystal lattice (x ', y', z ') is defined, in that 'we measure the orientation of the crystal lattice (x', y ', z') relative to the geometric shape (x, y, z) of the single crystal, and in that we calculate the first and second angles of rotation ( d, g) taking into account the orientation of the cutting plane (y '', z '') with respect to the crystal lattice (x ', y', z ') and with respect to the geometric shape (x, y , z) of the single crystal. Method according to claim 4, characterized in that the orientation of the crystal lattice (x ', y', z ') by relation to the geometric shape (x, y, z) is determined optically or by means of X-rays. Method according to one of claims 2 to 5, characterized in that a single crystal (2) is used whose geometric shape is substantially circular cylindrical, said geometric axis (x) corresponding to the main axis of the single crystal and in that 'the single crystal is placed on two parallel rotating cylinders (8) of the positioning device (1), the axes of the two cylinders (8) being parallel to said reference plane. Device for implementing the method according to one of the preceding claims, characterized in that it comprises a positioning device (1) intended to orient the single crystal (2) out of the cutting machine in accordance with a predetermined orientation relative to a cutting support (3) on which the single crystal is intended to be fixed and whose placement in the cutting machine is geometrically defined and whose main axes (X ''' _s , Y''' _s ) are parallel to the axes (x ''',y''') of the cutting machine. Device according to claim 7, characterized in that it comprises first means (8) for supporting the single crystal (2) in an orientation such that one of the geometric axes (x) of the geometric shape (x, y, z ) of the single crystal is included in a reference plane corresponding to the work plane (x ''',y''') of the cutting and for performing a rotation of the single crystal (2) by a first predetermined angle (d) around said geometric axis (x) to bring the normal (x '') to the cutting plane (y '', x '') of the single crystal in said reference plane and second means (12) for carrying out a relative rotation between the cutting support (3) and the single crystal (2) by a second predetermined angle (g) about an axis (z ''') perpendicular to said reference plane so that the normal (x'') to the cutting plane (y', z ') is oriented in a reference direction corresponding to the normal to the cutting plane (y''', z ''') of the machine. Device according to claim 8, characterized in that it comprises third means (14) for effecting a relative translational movement between the single crystal (2) and the cutting support (3) intended to bring the cutting support (3 ) and the single crystal (2) in order to fix the latter on the cutting support, in said predetermined orientation. Device according to claim 9, characterized in that the first means comprise two parallel cylindrical supports (8) rotatably mounted on a frame (5) of the positioning device (1) and arranged to support the single crystal (2) , and a first angular measurement member (10) capable of determining the first predetermined angle of rotation (d), by the fact that the second means comprise a rotary plate (12) mounted so as to rotate relative to said chassis (5) and the main plane of which is parallel to the axes of said cylindrical supports (8), this rotary plate (12) being arranged so as to maintain the cutting support (3) in a geometrically defined position, a second measuring member being provided to determine said second predetermined angle of rotation (g), by the fact that the third means comprise a translation mechanism (14) allowing the cutting support (3) and the single crystal (2) to be brought together and thereby that the cutting support (3) is shaped so that its positioning in the cutting machine takes place in a geometric position corresponding to the geometric position defined on said rotary table so that the reference plane and the reference direction correspond at the work plan (x ''',y''') and at normal (x ''') at the cutting plane of the machine. Device according to one of Claims 7 to 10, characterized in that the cutting support (3) or the positioning device (1) are arranged so that they can be mounted on an X-ray generator.

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