CS253199B1 - Apparatus for implanting rotationally symmetrical surfaces and cavities - Google Patents

Abstract

The device for implantation of rotationally symmetric surfaces and cavities consists of a diagnostic ion beam unit, behind which are located electrostatic vertical and horizontal ion beam deflectors. The ion beam is focused on the substrate, which is placed in a clamping element, connected via a gear member for changing the angle of the rotation axis with the drive unit.

Description

The invention relates to a device for implanting rotationally symmetrical surfaces and cavities, used in particular in micrometallurgy, for example for surface refinement of materials.

Ion implantation methods have so far been used in applications on planar semiconductor surfaces. However, new development trends are directed towards metallurgy, where issues of surface refinement of any shape are addressed by nitriding and sputtering with other ions such as carbon, titanium, tungsten, and the like.

Classical methods of metal refinement mainly consist of applications of the technological process of thermodiffusion, in which alloying substances penetrate beneath the surface of the processed material. The disadvantage of the thermodiffusion process is the significant consumption of alloying elements, which are often very expensive, and the process also involves the difficult-to-control penetration of undesirable or harmful impurities.

The above-mentioned shortcomings are eliminated by the device for implanting rotationally symmetric surfaces and cavities according to the invention, the essence of which lies in the fact that electrostatic vertical and horizontal ion beam deflectors are placed in the vacuum chamber behind the diagnostic ion beam unit for homogeneous substrate coverage.

A drive unit is mounted outside the vacuum chamber, the output of which is connected via a gear member for changing the angle of the rotation axis in the range from 0 to ± 90°, located inside the vacuum chamber with a substrate clamping element.

The advantages of the device are that practically all elements of the periodic table can be used for alloying and, in addition, molecular complexes of heavy metals that are not achievable in common practice can be synthesized in the plasma of the ion source.

Furthermore, a significant effect is achieved only on narrowly defined parts of the material, which can be advantageously applied in industrial applications, for example for modifying cutting surfaces of machining tools, etc. By introducing programmed movement, it is possible to implant bodies of complex shapes under the surface to depths that are not accessible for thermal processing methods.

The device according to the invention is schematically illustrated in the accompanying drawing, where Fig. 1 shows an application for implanting the outer surface and Fig. 2 shows an application for implanting the cavity of a cylindrical substrate.

At the inlet of the vacuum chamber, a diagnostic unit 11 of the ion beam and an electrostatic horizontal and vertical deflector 2 of the ion beam for homogeneous coverage of the substrate _3 are located one behind the other. Outside the vacuum chamber, on the insulating flange j!, a drive unit £ is mounted, which is connected by its output to a transmission member 5; for changing the angle of the rotation axis, which is located inside the vacuum chamber, as well as a clamping element 2 of the substrate 2 connected at its output.

The ion beam diagnostic unit 11 at the input of the device according to the invention is composed of a horizontal and a vertical probe, which serves to precisely investigate the configuration of the track of the incident ion beam.

The ion beam diagnostic unit 11 can be supplemented with an imaging system of an optically transparent plate coated with a luminophore layer. Using probes, the geometry of the trace can be adjusted with an accuracy of a few tenths of a mm.

The electrostatic horizontal deflector JI of the ion beam for homogeneous coverage of the substrate 2 also performs the selection of neutral components, the origin of which is given by charge exchange processes in interactions with molecules of the residual vacuum.

High precision of the implantation homogeneity is based on a combination of mechanical and electrostatic scanning. The individual parts of the mechanical scanning device are mounted on an insulating flange 2 in the target space of the vacuum chamber, where the substrate 2 is located.

Outside the insulating flange 2 3® is located the drive unit 4^ which is connected by means of a vacuum-tight passage to other elements placed inside the vacuum chamber. The key element here is the gear member 2 for changing the angle of the rotation axis, which can change this angle in the range from 0 to - 90°.

The insulating flange 8 is protected from the impact of the scattered primary part of the beam and from the secondary products of implantation by an electrically conductive plate, which is provided with an outlet from the vacuum chamber and allows continuous control of internal processes by measuring the current.

The adjustment of the device consists primarily in the selection of the doping ion beam at the output of the mass separator. Using the ion beam diagnostic unit 11, the operating mode of the ion source and the extraction system are sensitively adjusted so that the intensity of the desired mass spectrum line is as intense as possible and at the same time meets the basic requirements of ion-optical parameters, as demonstrated by the sharpness of the current rise to a clearly defined maximum.

The electrostatic horizontal deflector JL of the ion beam for homogeneous coverage of the substrate 2 is set so that the output axis of the beam follows the precisely defined position of the target, i.e. the substrate 2. If the set homogeneity of the beam track is within the tolerances of a fixed requirement, implantation of the surface of the cylindrical substrates 2 can be carried out ^using exclusively a mechanical scan.

If the axial length of the substrate 2 exceeds the vertical dimension of the beam track, or if the homogeneity of the track is insufficient, it is necessary to introduce an electrostatic scan using an electrostatic vertical ion beam deflector 2 for homogeneous coverage of the substrate 2.

If implantation of the faces of cylindrical substrates 3 is required at the same time, the angle of inclination of the rotation axis can be changed in the following operation and the implantation can be completed after the necessary exposure time has elapsed exclusively using the electrostatic vertical deflector 2_ of the ion beam for homogeneous coverage of the substrate 2*

Implantation of cavities can be performed in an analogous manner, with the difference that much higher requirements are placed on the basic geometry. For precise adjustment of the angle of inclination of the axis of rotation, it is advantageous to use a tracing laser beam that simulates the actual geometry of the inlet.

Since the implantation takes place at an inclined angle, it is necessary to choose an adequate energy of the doping ions. The basic relationship for the total run-out R _tot can be written in the form

2/3 2/3 1/2

0.6 (2 ₁ + Z ₂ ) (1^ + M ₂ ) M ₂ E where / 2 ₂ ^and ' —2 j ^{are the atomic} numbers and masses of the incident ions and atoms of the substrate 2. The depth of the doping atoms below the surface of the substrate 2 is proportional to the energy of the incident ion beam. The constant 0.6 used is chosen so that the calculated value of R _tot is given in mg/cm for the energy expressed in keV.

For the inclined surface of the substrate 2 P ^from the angle alpha, the expression specifying the effective component of the penetration E holds

E = E sin alpha s where E^ is the energy of the primary beam of incident ions in keV and alpha is the angle of inclination of the rotation axis. The actual run-up depth R _p in the direction parallel to the energy vector under consideration is represented by the projection of the total path length R _tot using the relation

The validity of this simplified expression is limited to ·

The device according to the invention was tested on a Scandinavian-type mass separator as a basic means of pilot production of coaxial nuclear radiation detectors.

11+ 2

A beam of ions B with an intensity of about 3 yuA/cm and an energy of 20 keV was shot into a sufficient depth of a cylindrical substrate 3 made of pure germanium.

The vertical dimension of the beam footprint completely covered the height of the cylinder and homogeneous dose application -14 2

5.10 at/cm was performed exclusively using a mechanical scan, with substrate A rotating in a perpendicular direction to the shot at a selected speed.

The front surfaces of the substrate A, ⁱⁿ this case the coaxial detector, were implanted after tilting the axis of rotation in the direction of the incoming ion beam using an electrostatic horizontal ion beam deflector A for homogeneous coverage of the substrate 3_.

The perpendicular firing condition is not critical and further operation can be simplified by a reduced tilt, where the rotation axis intersects the horizontal beam axis. Implantation was then performed after appropriate energy correction with respect to the size of the rotation axis angle.

When implanting the surface of the concave cavity of substrate A, it ^is possible to implement the requirement of subsequent implantation of the bottom and the front ring simultaneously. In the first step of the operation, it was necessary to deflect the bundle of filaments using the electrostatic vertical deflector 2 of the ion beam for homogeneous coverage of the substrate 3 so that it followed the point of intersection of the swing axis of the transmission member 5 for changing the angle of the rotation axis. After performing the correction of the rotation axis of substrate A, the implantation was carried out exclusively by applying the electrostatic horizontal deflector 1 of the ion beam for homogeneous coverage of the substrate A.

Claims (1)

SUBJECT OF THE INVENTION Device for implantation of rotationally symmetrical surfaces and cavities, formed by a vacuum chamber, at the inlet of which is mounted an ion beam diagnostic unit, characterized in that an electrostatic horizontal and vertical beam deflector (1, 2) are placed behind the ion beam diagnostic unit (11). an ions for homogeneous coating of the substrate (3), wherein a drive unit (4) is mounted outside the vacuum chamber, the output of which is connected via a transmission member (5) to change the rotation axis angle between 0 and - 90 ° with a clamping element (7) of the substrate (3).