Energy filter element for ion implantation system used in wafer manufacturing

Abstract

To provide an energy filter element for an ion implantation system used in wafer manufacturing.SOLUTION: The present invention relates to an implantation device, an injection system, and a method. The implantation device includes a filter frame and a filter held by the filter frame, and the filter is designed to be irradiated with ion beam.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an implanter with an energy filter (implant filter) for ion implantation and for use therein, and to a method of implantation. [Background technology]

[0002] By ion implantation, the creation of doping or defect profiles in any desired material, such as for example semiconductor materials (silicon, silicon carbide, gallium nitride) or optical materials (LiNbO3), can be achieved with a predefined depth profile ranging from a few nanometers to a few hundred micrometers in depth. In particular, it is desirable to create depth profiles characterized by a wider depth distribution of doping or defect concentration peaks than can be obtained by monoenergetic ion bombardment, or to create doping or defect depth profiles that cannot be created by one or a few simple monoenergetic implants. [Brief description of the drawings]

[0003] [Figure 1] The basic principle of energy filtering is illustrated in Figure 1. The energy of a monoenergetic ion beam is modified upon passage through a microstructured energy filter element as a function of the point of incidence. The resulting energy distribution of the ions results in a modification of the depth profile of the implanted material in the substrate body. [Diagram 2] Figure 2 shows on the left side a wafer wheel on which the substrate to be implanted is fixed in position. During processing / implantation the wheel rotates at an angle of 90°. The ion beam, shown in green, thus "writes" concentric circles onto the wheel. To irradiate the entire wafer surface, the wheel is moved vertically during processing. On the right side, Figure 2 shows an energy filter attached in the area of ​​the beam aperture. [Diagram 3]Figure 3 shows schematic diagrams of various doping profiles (dopant concentration as a function of depth into the substrate) for energy filter microstructures of different configurations (in each case shown in side and top views). (a) A triangular prism shaped structure produces a rectangular doping profile. (b) A smaller triangular prism shaped structure produces a doping profile with a shallow depth distribution. (c) A trapezoidal prism shaped structure produces a rectangular doping profile with a peak at the beginning of the profile. (d) A pyramid shaped structure produces a triangular doping profile, increasing in height with increasing depth into the substrate. [Figure 4] FIG. 4 shows a cross-sectional view of a filter frame for holding an energy filter chip. [Diagram 5] FIG. 5 shows a filter frame for holding an energy filter element with a locking element and a top view of an attached energy filter. [Figure 6] FIG. 6 shows a typical installation of a frame for holding an energy filter element in the beam path of an ion implanter. In this example, the filter holder is placed on one side of the chamber wall. In this example, this side is the inside of the chamber wall, i.e., the side that faces the wafer (not shown) during implantation. The frame with the filter chip inserted is pressed into the filter holder and then covers the opening in the chamber wall through which the ion beam passes during implantation. [Figure 7] FIG. 7 shows a partial frame (left side of the figure) and a complete frame (right side of the figure), each of which may be made of the same material (eg, monolithic) as the energy filter and / or another material. [Figure 8] FIG. 8 illustrates the use of one or more bars for mounting of a filter frame surrounding a filter or any other passive scattering element. [Figure 9] FIG. 9 illustrates the use of single or multiple suspension elements for mounting of a filter frame surrounding a filter or any other scattering element. [Figure 10]FIG. 10 illustrates the use of a magnetic field for the attachment of a filter frame surrounding a filter or any other scattering element. [Figure 11] Figure 11 shows a simple realization of a multi-filter. Three differently shaped filter elements are combined in a filter holding frame to form a complete energy filter. The ion beam passes uniformly across the individual filter elements. In this example (left), the dopant depth profile shown on the right is generated. This profile contains three depth profiles numbered 1, 2, and 3. Each of these sub-profiles originates from one of the three sub-filters shown on the left, i.e. the correspondingly numbered sub-filter. [Figure 12] Figure 12 shows a detailed view of the multi-filter concept. On the left, three filter elements are shown as an example. Four elements are numbered and written. For a given ion species and primary energy, a dopant depth profile is obtained from each filter element. The weighting, i.e. the resulting concentration, can be adjusted by varying the surface dimensions of the individual filter elements. In this example, we assume that the filter and the substrate have the same energy-dependent stopping power. However, this is usually not the case. [Figure 13] FIG. 13 shows the sum profile that is obtained when all of the filter elements described in FIG. 12 are mounted together as a complete filter with appropriate weighting and uniformly exposed to an ion beam of appropriate primary energy. [Figure 14] 14 shows an exemplary arrangement of individual filter elements within a multi-filter, where the individual elements F1, F2, F3, etc. are shown cut at an angle and attached directly to one another. [Figure 15] Figure 15 shows the arrangement of the filter installed in the ion implantation system. The cooling lines, supplied with coolant by an external cooling device, are built into the filter holder that holds the filter frame. The cooling lines can also be located on the surface of the filter holder (not shown). [Figure 16]Figure 16 shows an energy filter with a large surface area that is only partially irradiated per unit of time. The non-irradiated areas can therefore be cooled by radiative cooling. This embodiment can also be configured as a multi-filter, as mentioned above, i.e. as a filter that includes several different filter elements. In the illustrated example, the frame with the filter vibrates in a direction perpendicular to the direction of the ion beam. The area of ​​the filter covered by the ion beam is smaller than the total surface area of ​​the filter, so that only a part of the filter is exposed to the beam per unit of time. This part changes continuously due to the oscillatory motion. [Figure 17] Figure 17 shows another configuration of an energy filter arrangement rotating around a central axis. Again, the illumination per unit time is partial, so that non-illuminated elements can be cooled. This embodiment can also be configured as a multi-filter. [Figure 18] Figure 18 shows a schematic of "peak shifting". By implanting ions into the energy filter with the help of trapezoidal prism shaped structures, a rectangular profile can be generated in the substrate. The first peak is embedded in the energy filter. This implantation profile has the advantageous property of starting immediately at the surface of the substrate, which is crucial for the application of energy filters. [Figure 19] Figure 19 shows how ions are implanted into a PMMA substrate by an energy filter during static implantation. The ions destroy the molecular structure of the PMMA. A subsequent development process reveals the energy distribution of the ions. Areas of high energy deposition are dissolved away. Areas with low or no energy deposition by the ions are not dissolved by the developer. [Figure 20] FIG. 20 shows a monitoring system for identifying filters and monitoring compliance with filter specifications (maximum temperature, maximum accumulated ion dose). [Figure 21]Figure 21 shows the collimator structure mounted on a filter holder. The aspect ratio determines the maximum angle α. If the available distance to the implanted substrate is not large enough, the collimator can consist of several collimator units with smaller openings arranged side by side. This can be arranged, for example, in a honeycomb pattern. [Figure 22] Figure 22 shows a collimator structure built directly on the filter. The aspect ratio determines the maximum angle α. Here, the filter is placed in the ion beam in a back-to-front configuration. If properly designed, the collimator has a beneficial mechanical stabilizing effect on the filter and improves radiative cooling as a result of the increased surface area of ​​the filter tip. [Figure 23] Figure 23 shows a collimator structure built directly on the filter. The aspect ratio determines the maximum angle α. In this example, the filter is placed in a front-to-back configuration in the ion beam. [Figure 24] Figure 24 shows a collimator structure built directly on the filter. The collimator structure can have a lamella, strip, tubular or honeycomb structure depending on the filter layout and the required maximum angular distribution. [Diagram 25] Figure 25 shows a collimator structure built directly on the target substrate. The collimator structure can have a lamella, strip, tube or honeycomb structure depending on the layout of the substrate structure and the required maximum angular distribution. [Figure 26] FIG. 26 shows the doping profiles obtained with the same filter using different collimator configurations. [Figure 27] FIG. 27 shows the doping profiles obtained with the multi-filter by implantation with and without the collimator structure. [Figure 28]Figure 28 shows diagrammatically the "inside out" of a filter. (A) The filter is used in the normal orientation, which means that the microstructures face away from the beam. (B) The filter can be inverted, which means that the microstructures face towards the beam. This has a beneficial effect on the sputtering effect in the filter. [Figure 29] Figure 29 shows a schematic of the "tilting" of a filter. If the energy filter is made of anisotropic materials, there may be channeling effects. This can be prevented by tilting the energy filter. [Diagram 30] FIG. 30 shows schematics of various doping profiles (dopant concentration as a function of depth into the substrate) for energy filter microstructures of various shapes (in each case shown in side and top views). (A) A triangular prism shaped structure produces a rectangular doping profile. (B) A smaller triangular prism shaped structure produces a doping profile with a shallow depth distribution. (C) A trapezoidal prism shaped structure produces a rectangular doping profile with a peak at the beginning of the profile. (D) A pyramidal structure produces a triangular doping profile, which rises with increasing depth into the substrate. [Diagram 31] Figure 31 shows various target profile shapes for the same primary ion and the same primary energy based on different target materials, in each case the filter material is silicon. [Diagram 32] Figure 32 shows the variation of stopping power as a function of energy [4] (SRIM simulation). [Diagram 33] Figure 33 shows the starting materials for a simple multi-layer filter. Filter materials with appropriate stopping power are placed on top of each other in sequence by an appropriate deposition method. [Diagram 34] FIG. 34 shows how, with appropriate configuration of layered stacks of materials with different stopping powers, complex dopant depth profiles can be realized even with simple filter shapes (here strip-shaped triangles). [Diagram 35]Figure 35 shows the general principle of constructing an energy filter from materials 1-6, where each of the individual filter structures has a different geometric shape. [Diagram 36] Figure 36 shows the equilibrium charge state of an ion (black line: Thomas-Fermi estimate; blue line: Monte Carlo simulation; red line: experimental result) as a function of the ion's kinetic energy as it passes through a thin film. Ion: sulfur; film: carbon

[27] . [Figure 37] Figure 37 shows the heating of an energy filter due to ion bombardment. There are 6 MeV C ions in the energy filter, which is not transparent under these conditions [2]. [Figure 38] FIG. 38 shows an embodiment of a filter arrangement in which the filter is held in a filter frame at a defined (positive) potential relative to the filter holder for the purpose of suppressing secondary electrons. [Figure 39] Figure 39 shows the work functions of several elements.

[25] Materials Science-Poland, Vol. 24, No. 4, 2006 [Diagram 40] Figure 40 shows an arrangement for energy filter implantation, where complete illumination of a stationary substrate is achieved by an ion deflection system in front of the filter and by choosing an appropriate distance between the filter and the substrate (typically in the range of a few cm to a few m). [Diagram 41] Figure 41 shows an arrangement for energy filter implantation, where a filter surface larger than the surface of the substrate is used to achieve complete illumination of the substrate. The diameter of the illuminated filter area is larger than the diameter of the substrate. [Diagram 42] FIG. 42 shows a filter with only a portion of it active and with mechanical scanning in one direction. [Diagram 43] Figure 43 shows the modification of the doping profile in the substrate by a sacrificial layer in the case of a masked and energy filtered implant. In the example shown, the start of the implant profile has been shifted into the sacrificial layer. This principle can be used similarly for unmasked and energy filtered ion implants. [Diagram 44] Figure 44 shows the lateral modification of the doping profile in the substrate by a sacrificial layer for unmasked and energy filtered ion implantation. This principle can be used similarly for masked and energy filtered implantation. [Diagram 45] Figure 45 shows the coupling of the filters with the substrate with a vertical movement in the y direction. Due to the rotation of the wafer wheel, the wafer is guided in the x direction behind the substrate. The ion beam (not shown) is expanded, for example in the x direction, and scans over the surface of the multi-filter as a result of the vertical vibration of the implantation chamber. This surface consists of active filter areas and inactive holder areas. The arrangement shown in (A) is an unfavorable arrangement. Consider a filter surface illuminated at y1 and y2, where at y1 three filters are illuminated and at y2 no filters are illuminated. As a result, a laterally inhomogeneous stripe pattern is obtained on the wafer. The arrangement shown in (B) is a possible example of a better arrangement. Two filters are illuminated at y1 and y2. This is true for all y. As a result, a laterally homogeneous doping is achieved over the entire surface of the wafer. [Diagram 46] FIG. 46 shows a wafer wheel having an array of irradiated wafers and a monitoring structure positioned between the wafers. [Figure 47] FIG. 47 shows a surveillance mask with an example of an arrangement of various mask structures Ma1 to Ma10 that are transparent or partially transparent to the ion beam. [Figure 48] FIG. 48 shows a cross section of the monitoring mask and monitoring material. [Figure 49] FIG. 49 shows an example of a concentration depth profile produced using an energy filter. [Figure 50] FIG. 50 shows an example of a mask structure for monitoring the depth dependent dose distribution. [Figure 51] FIG. 51 illustrates monitoring of the injection process by a monitoring structure. [Figure 52] FIG. 52 illustrates monitoring of the injection process by a monitoring structure. [Figure 53]FIG. 53 shows the monitoring of maximum projected range. [Figure 54] FIG. 54 shows the mask structure. [Figure 55] FIG. 55 shows another example of a mask structure. [Figure 56] FIG. 56 shows another example of a mask structure. [Figure 57] FIG. 57 shows a mask structure for monitoring asymmetric angular distribution. [Figure 58] FIG. 58 shows various configurations of mask structures for detecting ion angular distribution in various directions. [Figure 59] Figure 59 shows a neat fit of the transition between two implantation profiles A and B, such that the resulting overall concentration profile results in a desired profile, e.g., a homogenous profile. This can be particularly beneficial in the case of a layer system consisting of two layers, as in the figure shown here (although this does not have to be the case).

[0004] This is proposed to be achieved through the following process: (1) doping the underlayer (implant B); (2) growing an upper layer; and (3) doping the top layer;

[0005] There are limited possibilities for the configuration of the high-energy tail of implant A. However, the low-energy tail of implant B can be influenced in particular by the introduction of sacrificial layers as described in "15: Modifying the doping profile in the substrate by sacrificial layers."

[0006] This is proposed to be achieved through the following process: (1) growing a sacrificial layer; (2) doping the underlayer (implant B); (3) removing the sacrificial layer; (4) growing an upper layer; (5) doping the top layer; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Detailed Description Figure 1 shows a method known from [7] for generating a depth profile. In this case, an ion beam is implanted into a substrate by a structured energy filter in an ion implantation system for wafer processing. The implantation method and the dopant or defect distribution in the wafer after processing are shown. In particular, it is shown how the energy of a monoenergetic ion beam is modified when passing through a microstructured energy filter component depending on its point of incidence. The resulting energy distribution of the ions leads to a modification of the depth profile of the implanted material in the substrate body. This depth profile is also shown in Figure 1 and is rectangular in the example shown here.

[0008] Figure 2 shows a system for ion implantation. The system includes an implantation chamber in which several wafers can be placed on a wafer wheel. The wafer wheel rotates during implantation so that the individual wafers repeatedly pass through a beam aperture in which an energy filter is located, allowing the ion beam to reach the implantation chamber and impinge on the wafer. The wafer wheel, on which the substrate to be implanted is mounted, is shown on the left side of Figure 2. During processing / implantation, the wheel rotates at an angle of 90°. Thus, the ions of the ion beam, shown in green, "write" concentric circles on the wheel. To irradiate the entire surface of the wafer, the wheel is moved vertically during processing. An energy filter attached to the beam aperture is shown on the right side of Figure 2.

[0009] FIG. 3 shows several layouts or three-dimensional structures of filters as examples to illustrate the principle of how a number of different dopant depth profiles can be generated by appropriate selection of filters. The individual filter profiles shown in FIG. 3 can be combined with each other to obtain additional filter profiles and therefore additional dopant depth profiles. A cross-sectional view of the energy filter (at the left edge of the drawing) is shown in each case, as well as a top view of the energy filter and a curve showing the variation of the achieved dopant concentration versus wafer depth (as a function of depth). The "depth" of the wafer is the direction perpendicular to the surface of the wafer where the ions are implanted. As shown in FIG. 3, (a) a triangular prism-shaped structure results in a rectangular dopant profile. (b) a smaller triangular prism-shaped structure produces a rectangular dopant profile with a smaller depth than in (a) (thus the depth of the profile can be adjusted by selecting the size of the structure). (c) a trapezoidal prism-shaped structure produces a rectangular doping profile with a peak at the beginning of the profile. (d) a pyramidal structure produces a triangular doping profile whose height increases as the depth in the substrate increases.

[0010] For many reasons, the energy filters (implant filters) or energy filter elements known so far are not adapted to achieve a high throughput, i.e. many wafers per hour. In particular, it is desirable to have a high wafer throughput per hour, easy handling, easy manufacturing, and realization of the desired profile shape. Static or movably mounted filters, manufactured monolithically, i.e. from a solid block of material, and individually mounted in the ion beam, are known from the literature [2], [3], [4], [5], [6], [7], [8], [9],

[10] . In contrast to silicon, the shape of the doped regions of SiC wafers generally cannot be modified by out-diffusion of the dopant profile [2], [4], [5], [6]. The reason for this is the very small diffusion constants (even at high temperatures) of common dopants such as Al, B, N, and P. These diffusion constants are several orders of magnitude smaller than the comparable values ​​for silicon, for example. For this reason, it has not been possible up to now to economically realize doped regions with a particularly high aspect ratio, ie a small ratio between base surface area and depth.

[0011] Dopant depth profiles of semiconductor wafers can be produced by in-situ doping during epitaxial deposition or by (masked) monoenergetic ion implantation. In the case of in-situ doping, a high level of imprecision can occur. Even in the case of homogeneous dopant profiles, the nature of the process means that significant deviations from ideal doping are expected on the wafer, i.e. from the middle to the edge. In the case of gradient depth profiles, this imprecision also extends to the vertical direction of the doped region, since the local dopant concentration now depends on a large number of process parameters, such as, for example, temperature, local dopant gas concentration, topology, Prandtl boundary layer thickness, growth rate, etc. The use of monoenergetic ion beams means that many separate implants must be performed to obtain a dopant profile with acceptable vertical waviness. This approach can only be adjusted to a certain extent and very quickly becomes economically unfeasible.

[0012] Examples of the invention relate to the configuration of an energy filter element for an ion implantation system, which makes it possible to meet the requirements for the use of the energy filter element in the industrial production of semiconductor components, in particular components based on SiC semiconductor material. The production conditions for the use of the energy filter element are defined, for example, by the following aspects:

[0013] 1. Technical ease of filter replacement In a production environment, i.e., a factory, production also occurs at the ion implanter, most often by trained, non-technical industrial workers ("operators").

[0014] Energy filters are very fragile microstructured membranes that are difficult to handle without destroying them. To make this filter technology economical to use, it should be ensured that after a short period of training even a non-specialist (i.e., a non-technical person) can replace the filter like a worn tool, or exchange the filter for another one in the injection system.

[0015] 2.Any vertical profile shape Novel semiconductor components such as superjunction components or optimized diode structures require non-uniform doping curves. However, simple energy filters described in [1-6] produce only constant profiles. Complex filter structures such as those described in Rub [8] are technically very sophisticated and difficult to realize according to state of the art manufacturing methods. The goal is to realize complex vertical profile shapes by using uncomplicated, i.e. easy to manufacture, filter structures.

[0016] 3. High-throughput cooling system combined with filter movement The production conditions are, for example, typically about 2×10 ions per hour on an ion implanter (typical terminal voltage of a tandem accelerator >1 MV to 6 MV). 13 cm -2This means that more than 20-30 wafers with a diameter of 6 inches should be produced with a fluence per wafer of 10 ... 2 The filter (typical surface area is 1-2 cm 2 ) above the filter. This leads to the filter getting hot. The problem is to cool the filter by suitable means.

[0017] 4. Simple and low-cost fabrication of filter structures to obtain homogeneous and uniform depth profiles The filter structure can be produced by anisotropic wet-chemical etching. In its simplest form, the filter structure consists of appropriately dimensioned long triangular lamellae (for example, 6 μm high, 8.4 μm apart, several millimeters long) arranged periodically on a membrane as thin as possible. The production of triangular lamellae with sharp points is costly, since the wet-chemical anisotropic etching must be precisely adjusted. The production of lamellae with sharp points, i.e. non-trapezoidal, is costly, since the etching rate and the etching time must be precisely adjusted to each other to obtain a pointed lamellae. In practice, this results in a rather large number of process control operations during etching. As a result of the non-uniform processing expected during etching on a chip with hundreds of lamellae (etching rates of wet-chemical processes are never perfectly reproducible and never homogeneous over larger areas), it leads to yield losses, i.e. poorly structured filter elements. The goal is to realize a simple and low-cost method for the production of energy filters.

[0018] 5. High lateral uniformity of the produced dopant or defect regions The energy filters for ion implantation described in the previously cited documents [2], [3], [4], [5], [6], [7], [8], [9],

[10] have an internal three-dimensional structure that results in differences in the distances that ions travel when passing through the filter. These differences in travel distances result in a modification of the kinetic energy of the transmitted ions, depending on the stopping power of the filter material. Thus, a monoenergetic ion beam is transformed into a beam consisting of ions with different kinetic energies. The energy distribution is determined by the shape and material of the filter; i.e., the filter structure is transferred to the substrate by ion lithography.

[0019] 6. Monitoring the "end of life" of energy filters Due to the nuclear interaction of the ion beam with the filter material and the heat load, the typical lifetime of the filter is the result of each ion implantation process using the energy filter in particular. For an energy filter in silicon with a support layer of about 2 μm thickness, a regular protruding structure of the order of 8 μm, and an implantation process with 12 MeV nitrogen with a current of about 0.1 pμA, the maximum production volume is about 100 wafers (6 inches).

[0020] For the safety of the machine operators and the filter manufacturers, it is necessary to monitor the total number of wafers processed on a particular filter.

[0021] 7. Limiting the angular distribution of transmitted ions For the production of masked dopant regions, i.e. regions with limited lateral dimensions, especially in the case of high aspect ratios, the angular spectrum of transmitted ions must be limited to avoid implanting ions below the masking layer.

[0022] 8. Minimization of filter wear caused by sputtering effects

[0023] 9. Avoidance of channeling effect (lattice induced effect) by arranging filters for ion beam

[0024] 10. Achieving complex dopant depth profiles with simple filter shapes

[0025] 11. Electronic suppression during use of filters It is known that during the transmission of ions through a solid, the charge of the ions comes into equilibrium: electrons of the primary beam are either emitted to or accepted by the solid. That is, the transmitted ions have, on average, a higher or lower charge state after passing through the filter, depending on the characteristics of the filter material and the primary energy

[26] . This can lead to a positive or negative charging of the filter.

[0026] At the same time, secondary electrons of high kinetic energy can be generated by ion bombardment of the front or rear surface of the filter.

[0027] At the high current densities required for industrial production, energy filters heat up (see Figure 6.5.24). Due to thermionic emission (Richardson-Dushman method), hot electrons are generated as a function of the temperature and the work function of the filter material.

[0028] The distance in an ion accelerator (in high vacuum) between the filter and the substrate is usually no more than a few centimetres: the diffusion of hot electrons (from thermionic emission) and the action of fast electrons (from ion bombardment) will modify the measurement of the ion current at the substrate, for example by a Faraday cup placed there.

[0029] 12. Alternative manufacturing methods by injection molding, casting, or sintering In documents [2]-

[15] microtechnical methods for the manufacture of energy filters are proposed. In particular, the use of lithographic methods in combination with wet or dry chemical etching for the manufacture of filters is described. For the manufacture of filters, anisotropic wet chemical etching methods with alkaline etchants (for example KOH or TMAH) in silicon are preferred.

[0030] In the case of filters manufactured by the last-mentioned method, the functional filter layer is manufactured from monocrystalline silicon, and it must therefore always be assumed that channeling effects, when bombarded with energetic ions, will in principle affect the effective energy losses in the filter layer in a manner that is difficult to control.

[0031] 13. Arrangement for irradiating stationary substrates Irradiation devices should be used that allow to irradiate stationary materials under energy filtering with high lateral homogeneity over the entire surface of the substrate. Reason: The end stations of irradiation systems often do not have the full mechanical ability to scan the entire wafer (wafer wheel) with a point-like or nearly point-like beam spot. On the contrary, many systems have, for example, an electrostatically expanded beam (= stripe in x direction) that scans the wafer electrostatically (in y direction). In some cases, partially mechanical scanners are used, i.e. the beam is expanded in x direction and the wafer is moved (slowly) mechanically in y direction.

[0032] 14. Arrangement to take advantage of large filter surface Irradiation equipment must be used that allows to irradiate stationary or moving substrates under energy filtering with high lateral homogeneity over the entire surface of the substrate and to do so over a larger filter surface, thereby reducing the effects of thermal and degradation effects of the filter.

[0033] 15. Modifying the doping profile in the substrate using sacrificial layers Energy filters are tools for manipulating the doping profile in a substrate. Under certain conditions, it is desirable to manipulate the doping profile produced in the substrate after the energy filter, i.e. at a location downstream of the energy filter. In particular, it is desirable to "push" the near-surface beginning of the doping profile out of the substrate. This can be particularly advantageous when, for various reasons (in particular, loss of ions due to scattering), the beginning of the dopant profile in the substrate cannot be precisely adjusted by the filter. Such manipulation of the doping profile after the energy filter can be achieved by implantation into a sacrificial layer on the substrate.

[0034] 16. Lateral modification of doping profile in substrate by sacrificial layer In certain applications, it is desirable for the doping profile in the substrate to exhibit lateral variations. In particular, variations in implantation depth of a homogeneous doping profile can be advantageously used for edge termination of semiconductor components. Such lateral tuning of the doping profile can be achieved by providing a sacrificial layer having a lateral thickness variation on the substrate.

[0035] 17. Accommodating profile transitions between several injection profiles In certain applications, it is desirable to join two or more profiles together at a certain depth along a "seam" since otherwise there would be insulation between the layers. This problem arises especially in layer systems that contain a "tail" of gradually tapering concentration at the bottom of an upper doping profile or at the top of a lower doping profile.

[0036] 18. Special arrangement of the multi-filter concept for coupled vibration motion If the multi-filter is mounted in a part of the movable substrate chamber that can move linearly back and forth in front of the beam (e.g. in the vertical scanning direction in the case of a rotating wafer disk), the multi-filter is easily moved relative to the beam by simply moving the substrate chamber. By using a magnetic or static scanning device that scans in one direction in front of the filter, very large multi-filter surfaces can be used, for example equal to the product of the vertical oscillation distance and the horizontal scanning distance. The movements of the wafer and the filter are coupled in this arrangement, which can cause problems with the lateral homogeneity of the doping. Due to the rotation of the wafer wheel, the ion beam "writes" a line on the wafer. As a result of the above arrangement, for example the position of a horizontal illumination line on the wafer is coupled to a certain vertical position on the multi-filter. Gaps between the individual filter elements result, for example, inhomogeneously doped lines on the wafer. The arrangement of the filter components in the multi-filter must therefore be chosen in such a way that lateral homogeneity is ensured despite the coupling of the linear movements of the filter and the substrate.

[0037] Examples of energy filters, implanters, or implanter parts that meet the aforementioned manufacturing conditions are described below. It should be noted that the methods and concepts described below can be combined with each other in any desired manner, but each of them can also be applied individually on their own.

[0038] Point 1: Technical ease of filter replacement It has been proposed to provide a frame for the filter in question, hereafter referred to as a "filter tip", which facilitates handling of the implantation filter. As shown in Figures 4-6, this frame can be configured for use in a suitably sized pre-installed frame holder on the ion implantation system. The frame protects the energy filter, facilitates handling, handles electrical and heat dissipation, and / or electrical insulation (see Figure 36). The frame can be provided by the filter element manufacturer in a dust-free environment with the filter tip and can be supplied to the ion implantation system in dust-free packaging.

[0039] 4 and 5 show examples of geometric and mechanical configurations of the filter frame. The filter held thereby can have any desired surface structure selected according to the desired doping profile to be obtained therewith. The filter holder and / or the filter frame can be provided with a coating that prevents material from being abraded from the filter frame and filter holder.

[0040] The filter frame and the filter holder can be made of metal, preferably high grade steel or the like. During the ion implantation process, sputtering effects in the local environment of the energy filter caused by scattered ions are expected, i.e. material at and near the surface of the frame and the filter is expected to be carried away. Metal contamination on the substrate wafer can be an undesirable consequence. The coating prevents such contamination, and the coating consists of a non-contaminating material. What materials are non-contaminating depends on the properties of the target substrate used. Examples of suitable materials include silicon or silicon carbide.

[0041] FIG. 4 shows a cross-sectional view of a filter frame for holding an energy filter chip. The energy filter chip, also shown in FIG. 4, can be attached to the frame in various ways, such as the use of adhesives or mechanical springs. FIG. 5 shows a top view of a filter frame for holding an energy filter element, also shown in FIG. 5. The filter frame includes a locking element that allows the frame to be opened and closed to allow replacement of the filter. FIG. 6 shows an example of an installation of a frame for holding an energy filter element in the beam path of an ion implanter. Shown in the upper part of FIG. 6 is a cross-section through the chamber wall and a filter holder placed therein. In this example, the filter holder is placed on the inner surface of the chamber wall, i.e., on the side facing the wafer (not shown) during the implantation process. Also shown in FIG. 6 is a schematic of the ion beam passing through an opening in the chamber wall and a filter placed in front of the opening during the implantation process. The frame with the filter chip inserted in the filter holder covers the opening in the chamber wall through which the ion beam passes during the implantation process. This is shown in the lower part of FIG. 6, where a front view of the chamber wall with the filter holder attached is shown.

[0042] The frame can be made of the same material as the filter. In this case, the frame can be manufactured monolithically together with the filter and can therefore be called a "monolithic frame". As mentioned above, the frame can also be made of a material different from the material of the filter, such as metal. In this case, the filter can be inserted into the frame. According to another example, the frame comprises a monolithic frame and at least one additional frame of a material different from the material of the filter attached to the monolithic frame. This additional frame is, for example, a metal frame.

[0043] As described and illustrated above and as shown on the right side of FIG. 7, the frame can completely surround the filter. According to additional examples, the frame does not border all (four) sides (edges) of the filter, but rather only borders three, two (opposite sides) or only one of the edges of the filter. The term "frame" should therefore be understood in the context of this description as a volumetric frame that completely surrounds the filter on all sides (edges) and also as a partial frame that extends only around some edges of the filter. Examples of such partial frames are also shown in FIG. 7. Thus, FIG. 7 shows various partial frames (left side of the figure) and complete frames (right side of the figure). Each of these frames can be made of the same material as the energy filter (e.g. monolithic) or a different material.

[0044] The energy filter or any other scattering element can be mounted in the beam path of the implanter in various ways by its frame, which can be realized according to one of the above-mentioned embodiments. The above-mentioned insertion of the frame into the filter holder is only one of several possibilities. Further possibilities are described below.

[0045] According to an example shown in Fig. 8, the frame can be attached to the chamber wall by means of at least one bar. In this case, at least one bar serves as a filter holder. Shown in Fig. 8 are examples of attachment with only one bar, two bars and three bars. It is clear that more than two bars can also be provided.

[0046] According to another example shown in Fig. 9, the frame can also be attached to the chamber wall by suspension brackets or suspension elements. These suspension elements can be, for example, flexible and can be attached between the frame and the chamber wall so that the frame is held firmly in place. The suspension elements act as filter holders in this example. Fig. 9 shows examples of mounting with only one suspension element, two suspension elements and three suspension elements. Of course, more than two suspension elements can also be provided.

[0047] According to another example shown in Fig. 10, the frame with the filter is held by magnets in a floating (non-contact) manner. For this purpose, magnets are attached to the front and rear sides of the frame and to the chamber wall, in each case such that the magnets on the chamber wall or the magnets on the holder attached to the chamber wall face the magnets on the frame, and the opposing poles of the opposing magnets are of opposite polarity. As a result of the magnetic forces, the frame floats between the magnets attached to the chamber wall and the magnets attached to the holder. The magnets on the frame of the filter can be realized, for example, by thermal evaporation or any other layer formation method.

[0048] Point 2. Any vertical profile shape In principle, the geometric configuration of an energy filter for an ion implantation system can make it possible to realize any desired doping profile in the semiconductor material. For complex profiles, this means that it is necessary to generate geometrically demanding three-dimensional etched structures of different sizes and sometimes different heights, such as pyramids, pits with defined wall slopes, inverted pyramids, etc., on the same filter chip.

[0049] It is proposed to approximate any desired profile using rectangular profile shapes, such as those that can be generated by simple triangular structures (multiple filters). Under certain conditions, it is also possible to use non-triangular structures (e.g. pyramids) as basic elements of the approximation.

[0050] That is, it is proposed to decompose the desired doping profile into, for example, box profiles and to generate a triangular filter structure for each box profile. The individual filter chips are then mounted, for example in a frame as shown in Fig. 6.5.1, in such a way that their area weighting corresponds to the dopant concentration appropriate for the box profile element in question, see Fig. 6.5.4.

[0051] The decomposition of the dopant depth profile is not limited to the triangular structures shown here. On the contrary, it can include additional structures, including in the most general case slopes, or convex or concave rising flanks. The flanks do not necessarily have to rise monotonically, but can also include valleys and depressions. Binary structures with 90° flank angles are also contemplated.

[0052] In one example, the filter elements are cut at an angle and placed directly adjacent to each other. The angled cut has the advantage that no adhesive bond between the filters is required to block the ions at the filter edges. Furthermore, in this way it is possible to make optimal use of the illuminated surface. For the same total filter dimensions and a given ion current, this has the effect of increasing the wafer throughput.

[0053] Figure 11 shows a simple implementation of a multi-filter. In this example, three differently shaped filter elements are combined in the frame of a filter holder to form a complete energy filter. In the upper left of Figure 11, a cross-sectional view of a filter holder with three filter elements is shown, and in the lower left of Figure 11, a top view of a filter holder with three filter elements is shown. On the right side of Figure 11, the filter profile obtained with the combined filter is shown. When this filter is used as an implantation filter, the ion beam passes uniformly through all of the individual filter elements, thus producing the dopant depth profile shown on the right side of Figure 11. This profile contains three depth profiles, numbered 1, 2, and 3. Each of these depth profiles results from one of the three sub-filters shown on the left, i.e., the sub-filters identified by the same number.

[0054] FIG. 12 shows, by way of example, how three different filter elements function when combined into a multi-filter. The figure shows a cross-section of each of the individual filter elements, example dimensions of these filter elements, and a doping profile as can be obtained with the individual filter elements. In FIG. 12, by way of example, only dimensions are shown for a fourth filter element (not shown). The weighting, i.e. the resulting concentration or doping profile, can be adjusted by varying the dimensions of the surface area of ​​the individual filter elements. In this example, it is assumed, although this does not necessarily have to be the case, that the filter and the substrate have the same energy-dependent stopping power. FIG. 13 shows an example of a doping profile obtained when the four filter elements described on the basis of FIG. 12 are combined into a multi-filter and used for embedding. This summation profile results from the addition of the weighted filter elements over the surface in question. In this figure, it is assumed that the filter elements described on the basis of FIG. 12 are assembled with the appropriate weighting to form a complete filter and are uniformly exposed to an ion beam of the appropriate primary energy, so that the summation profile shown is obtained.

[0055] In the example described on the basis of Fig. 11, the individual filter elements of the multi-filter are separated from one another by webs of the frame. According to another example shown in Fig. 14, the individual filter elements can also be directly adjacent to one another. Fig. 14 shows a cross-sectional view of a multi-filter with several adjacent filter elements F1, F2, F3. The multi-filter is inserted into a filter frame. The individual filter elements F1, F2, F3 are cut obliquely in this example and are arranged directly adjacent to one another.

[0056] Point 3. High-throughput cooling system combined with filter movement A high wafer throughput for a given target doping can only be achieved with a high ion current. Since about 20% to about 99% of the primary energy of the ion beam is deposited on the filter membrane, i.e., the part of the implant filter through which the beam passes, the use of cooling methods has been proposed as a way to prevent excessive increase in the temperature of the filter even at high ion currents.

[0057] This type of cooling can be achieved, for example, by using one or more of the following measures a. to c. described below.

[0058] a. Coolant flow in the filter holder The heated filter chips are thereby cooled by heat dissipation. Figure 15 shows an example of such a cooled filter holder. In particular, shown is a cross section through a filter holder mounted on the chamber wall of an ion implanter. In this example, coolant lines are integrated into the filter holder which houses the filter frame. Liquid coolant is supplied to these coolant lines by an external cooling device (not shown). Alternatively or additionally, the coolant lines can be located on the surface of the filter holder (not shown).

[0059] b. Filter or ion beam movement In the case of using a rotating wafer wheel loaded with, for example, 10-15 wafers, it has been proposed that the filter or filter holder be configured to oscillate in a rotational or linear motion. Alternatively, the ion beam can be moved electrostatically over the filter while the filter remains stationary.

[0060] In these variants, the filter is only partially irradiated per unit of time by the ion beam. As a result, the parts of the filter that are not irradiated at a particular instant are cooled by radiative cooling. It is therefore possible to achieve a higher average current density for a given filter under continuous use conditions. Examples of how this can be achieved are shown in Figures 16 and 17.

[0061] Figure 16 shows an energy filter with a relatively large surface area that is only partially irradiated per unit of time. The non-irradiated areas can therefore be cooled by radiative cooling. This embodiment can also be configured as a multi-filter as described above, i.e. a filter that includes several different filter elements. In the example shown, the frame with the filter vibrates in a direction perpendicular to the direction of the ion beam, which is shown diagrammatically. The area of ​​the filter covered by the ion beam is smaller than the total area of ​​the filter, so that only a portion of the filter is irradiated per unit of time. This portion changes continuously as a result of the oscillatory motion.

[0062] FIG. 17 shows an example of a filter arrangement with several filter elements supported by a rotating filter holder. Each of the individual filter elements can be constructed in the same way, but can also have a different structure to obtain a multi-filter. As shown in FIG. 17, the individual filter elements traverse a circular path around the axis of rotation (central axis) of the holder as it rotates. In this example too, only partial irradiation per unit time occurs; i.e., not all filter elements are irradiated at the same time, so that the non-irradiated filter elements can cool down.

[0063] Point 4. Simplified filter design The manufacture of filter elements having protruding structures with precise heights and perfect sharp points is demanding from a processing technology standpoint and correspondingly expensive.

[0064] For simple doping curves (e.g. homogeneous doping) starting from the surface of the substrate and requiring only simple protruding structures, a simplified design and, associated therewith, a simplified manufacturing process are proposed here.

[0065] It is proposed that the microstructured membrane of the filter (e.g., protruding structure) is configured to have flats on the protrusions instead of sharp points, and that the thickness of the support layer of the membrane is dimensioned so that the low energy dopant peaks that are formed are pushed into the support layer of the filter and are therefore not embedded in the substrate. An example of this type of filter is shown in FIG. 18. Shown are a cross section (left side of the figure), a top view (center), and an example of a doping profile obtained by using the illustrated filter. As shown, a rectangular profile can be created in the substrate by implanting ions into the energy filter using a trapezoidal prism shaped structure. The first peak is embedded in the energy filter, i.e. there is no peak of the dopant profile in the substrate. This implantation profile has the advantageous property of starting immediately at the surface of the substrate, which can be crucial for the application of energy filters.

[0066] As can be seen from the cross section of the filter in Fig. 18, this filter structure contains flats instead of sharp points. The individual structural elements are therefore trapezoidal in cross section. This significantly simplifies the process technology required for the realization of the filter. It is known that triangular structures can be produced in silicon, for example by wet chemical etching with KOH or TMAH. For this purpose, the tips of the triangles must be masked lithographically. When manufacturing complete chips, this leads to the problem that the etching may penetrate under the lacquer or hard mask structure. Without the idea proposed here, this problem could only be solved by a perfect (and therefore complex and costly) processing. The idea proposed here greatly simplifies the manufacture of the filter structure. The same applies to modern plasma-assisted etching methods such as RIBE (Reactive Ion Beam Etching) or CAIBE (Chemically Assisted Ion Beam Etching).

[0067] Point 5. High lateral uniformity of the produced dopant or defect regions The lateral uniformity aspect can be important in static implant situations: when a rotating wafer disk (wafer wheel) is used with, for example, 11 wafers and a fixed ion beam, the uniformity is determined by the rotational and translational motion of the wafer disk relative to the ion beam.

[0068] Filter-substrate distance: the angular distribution of transmitted ions is energy dependent. In particular, if the filter and ion energy are adjusted relative to each other so that very low energy ions (nuclear stopped states) leave the filter, there will be a wide angular distribution, since large angle scattering events will occur. If the filter and ion energy are adjusted relative to each other so that only high energy ions (electron states only, dE / dxelectron>dE / dxnuclear) leave the filter, the angular distribution will be very narrow.

[0069] The minimum distance is characterized by the fact that the structure of the filter is not transferred to the substrate, i.e. for a given distribution of scattering angles of the transmitted ions, these ions pass a lateral distance at least comparable to the period of the lattice constant of the ion filter.

[0070] The maximum distance is determined by the loss of scattered ions that can still be tolerated by the application for a given distribution of scattering angles, especially at the edge of the semiconductor wafer.

[0071] Figure 19 shows the results of an experiment in which ions were injected through an energy filter during static injection into a PMMA (polymethyl acrylate) substrate. The ions destroy the molecular structure of the PMMA, so the subsequent development process reveals the energy distribution of the ions by dissolving areas of high energy deposition. Areas with low or no energy deposition by the ions are not dissolved by the developer.

[0072] The idea proposed here is to produce high lateral doping uniformity by accurately selecting the filter-to-substrate distance for both dynamic and static implantation configurations.

[0073] Point 6. Monitoring the "end of life" of energy filters Due to nuclear interactions and significant temperature changes (typically heating of the filter up to several hundred degrees Celsius), the energy filters degrade as a function of the accumulated implanted ion dose.

[0074] The chemical composition, density and shape of the filter are changed such that when a critical ion dose is reached, its effect on the realized target profile is no longer negligible. The critical ion dose depends on the filter material used, the implanted ion species, energy, shape and the allowable variation range (=specification) of the target profile.

[0075] Thus, for each filter implantation process with a given energy, ion species, profile, etc., specifications can be defined, including the maximum temperature during implantation and the maximum allowed cumulative ion dose. According to an example, it is provided that the use of the energy filters is monitored so that the filters cannot be used outside the specified tolerances, even when not monitored by a technician. For this purpose, it is proposed that each filter is detected based on an electronically readable signature as soon as it is inserted into the filter holder on the implantation device, and this signature is read, for example, by a control computer. The signature is stored for this purpose in an electronically readable memory arranged on the filter. A database stores, for example, the signatures of filters that can be used in a certain implantation device, as well as the process (ion species, energy) to which the filter is applied, as well as characteristics such as what cumulative dose and what maximum temperature is allowed to be reached. By reading the signature and comparing it with the information in the database, the control computer can determine whether the filter is suitable for the planned implantation process.

[0076] FIG. 20 shows a monitoring system for identifying filters and monitoring compliance with filter specifications (maximum temperature, maximum accumulated ion dose). Once the filter is identified by built-in sensors (charge integrator and temperature sensor), for example the accumulated dose and temperature of the filter are continuously measured. The implantation process is terminated when one of the specified parameters is reached or exceeded, i.e. when the filter becomes too hot or the maximum allowable dose has been implanted through the filter. That is, when a certain value no longer meets the specification, a signal is sent to the control computer, which terminates the implantation process.

[0077] Point 7. Limiting the angular distribution of transmitted ions In applications requiring blank areas on the target substrate, a masking material can be applied to the target substrate.

[0078] To avoid lateral "blurring" of structures due to an excessively wide ion distribution caused by the filter, it has been proposed to collimate the ion beam transmitted by the filter. Collimation can be achieved by strip-like, tubular, lattice-like or hexagonal structures with high aspect ratios, which are placed after the energy filter in the transmitted beam. The aspect ratio of these structures defines the maximum angle allowed.

[0079] Various examples are shown in Figs. 21 to 25. Fig. 21 shows a cross-section through the chamber wall of the implantation device in the region of the beam opening, a filter holder with a filter inserted and fixed to the chamber wall, and a collimator, which in this example is mounted on the side of the filter holder facing away from the chamber wall. The aspect ratio of the collimator, determined by the length and width of the collimator, determines the maximum angle α with respect to the length of the collimator. At this maximum angle α, the ion beam can be directed to the collimator and pass through it. Segments of the ion beam emitted at relatively large angles hit the wall of the collimator and do not pass through it. If the available distance between the filter and the substrate into which the ions are implanted is not sufficient for the desired aspect ratio, the collimator can also consist of several collimator units with smaller openings arranged adjacent to each other. They can be arranged, for example, in a honeycomb pattern.

[0080] Alternatively, the collimator structure can be placed directly on the filter element. This type of element can be manufactured as a monolith or by microbonding methods. Figure 22 shows two examples of collimator structures placed directly on the filter. This type of collimator structure placed directly on the filter can mechanically stabilize the filter and also has a cooling effect, since the collimator structure can act as a cooling body with a surface area larger than that of the filter. Here, the maximum angle α is also defined by the aspect ratio of the individual collimator structures placed on the filter, each of which includes a length and a width. The collimator structures can be attached to the filter by bonding, for example by using adhesives, or by some similar method.

[0081] In the example shown in Fig. 22, the collimator structures are arranged on the structured side of the filter, i.e. where the filter has ridges and recesses. In this example, the structures are trapezoidal. Fig. 23 shows a variation of the arrangement of Fig. 22. In this example, the collimator surface is arranged on the unstructured side of the filter. In both cases, the collimator structures are arranged downstream from the filter with respect to the direction of the ion beam (indicated by the arrows in Figs. 21 and 22), so that the ion beam passes through the collimator structures only after it has passed through the filter.

[0082] FIG. 24 shows a top view of a collimator structure according to various examples. In the illustrated examples, this collimator structure is arranged on a filter having a lamella-like structure when viewed from above. The individual "filter lamellae" can be, for example, triangular or trapezoidal in cross section, as already explained above. However, the lamella-like structure of the filter is only an example. Other types of filter structures as mentioned above can also be used. On the left and in the center, FIG. 24 shows an example in which the collimator structure is arranged in strips. That is, it includes a number of parallel strips that extend over the entire width of the filter. Each pair of adjacent strips forms a collimator, the width of which is determined by the distance between the adjacent strips. The length of the collimator is determined by the height of the individual strips. The "height" of the strip is the dimension in the direction perpendicular to the plane of the drawing. The strips of the collimator structure can be perpendicular to the lamellae of the filter, as shown on the left side of FIG. 24, or parallel to the lamellae, as shown in the center. On the right side of FIG. 24, an example is shown in which the collimator structure appears as a grid in a top view, resulting in the formation of a number of collimators whose geometry is determined by the geometry of the grid. In the illustrated example, the individual collimators are rectangular, in particular square, in top view, so that the collimators are in the form of rectangular tubes. However, this is only one example. The grid can also be realised so that the individual collimators are circular, elliptical or hexagonal (honeycomb) in plan view, or have any other desired polygonal shape.

[0083] Collimation by hard mask on target substrate In the case of masked implantation, instead of or in addition to the collimator on the filter, it is possible to apply a masking to the target wafer to act as a collimator structure. A condition for this masking is that the stopping power of the masking must at least correspond to the average range of the transmitted ion beam in the target substrate material. The aspect ratio of the masking can be adapted accordingly so that the required limit on the angular distribution is also achieved by the masking. Figure 25 shows an example of this type of collimator structure, placed directly on the target substrate. This collimator structure can have any of the geometric shapes previously described and can therefore be, for example, lamella-like, strip-like, tubular or honeycomb-like, depending on the layout of the substrate structure and the required maximum angular distribution. The aspect ratio of this collimator structure is the ratio of the height (h in Figure 25) to the width (b in Figure 25) of the blank area of ​​the mask on the substrate forming the collimator structure.

[0084] It has been found that the collimator structure affects not only the lateral scattering but also the depth profile. This is illustrated in Figure 26, which shows the doping profiles of three different implantation methods, each performed with the same filter but with different collimator structures. In this example, each filter has a lamellar-like structure with a trapezoidal cross section. However, this is only one example. On the left side of the figure, an implantation method is shown in which the implantation is performed without a collimator structure. The implantation profile thus obtained starts at the surface of the substrate.

[0085] In the center and right of FIG. 26, implantation methods are shown in which the implantation is performed with a collimator structure, the aspect ratio of the collimator structure in the case of the right example is higher than in the case of the center example. As can be seen, the doping profile obtained by these implantation methods does not start at the surface of the substrate, but rather at a certain distance from it, the higher the aspect ratio, the further the doping profile is from the surface and the flatter the rise. The explanation for this is that the dopant profile in the near-surface region of the substrate is caused by ions that stop more strongly at the filter and therefore have a lower energy. Such low-energy ions are scattered more strongly by the filter than high-energy ions, which have a wider angular distribution than high-energy ions. Thus, the number of low-energy ions that can pass through the collimator structure is smaller than the number of high-energy ions, and the larger the aspect ratio of the collimator structure, the more pronounced the effect is, and the smaller the maximum allowable angle at which ions can still pass through the collimator structure becomes.

[0086] In order to be able to produce an almost homogeneous doping profile starting from the surface despite the collimator structure, the filter can be designed so that low energy ions are "favored". That is, more low energy ions pass through the filter than more energetic ions. An example of this type of filter is shown in FIG. 27. In this example, the filter has different filter regions, each with a maximum and a minimum thickness. The maximum thickness is the same in all three regions, but the minimum thickness is different. This is achieved in an embodiment in that the filter has, in each of the individual regions, a trapezoidal structure arranged on a base with a different height or thickness, and thus the height of the trapezoidal structure is different. In the first section, the base is the thinnest and the trapezoidal structure is the tallest, so that in this section the distance CD1 between adjacent structures is the largest. In the third section, the base has the largest thickness and the trapezoidal structure is the lowest, so that in this section the distance CD3 between adjacent structures is the smallest. In the second section, the thickness of the base is between the thickness of the first section and the thickness of the third section. Correspondingly, the height of the trapezoidal structures in this section is between the height of the first section and the height of the third section, and the distance CD2 between adjacent structures in this section is between the distance CD1 of the first section and the distance CD3 of the third section. The individual sections can be of the same size in terms of their surface area, but can also be of different sizes. It is also clear that three or more sections can be provided with different minimum filter thicknesses.

[0087] FIG. 27 shows on the left the implantation profile obtained by implantation with the filter just described, when the implantation is carried out without a collimator structure. This implantation profile starts at the surface, but the doping concentration decreases in a step-like manner with increasing depth. In this figure, CD1 indicates the area of ​​the doping profile due to the first section of the filter, CD2 indicates the area of ​​the doping profile due to the second section of the filter, and CD3 indicates the area of ​​the doping profile due to the third section of the filter. It can be seen based on the doping profile that the greater the minimum thickness of the base of the relevant section, the less deeply the ions passing through the filter area in question penetrate into the substrate, i.e. the lower their energy. The doping profile also shows that ions of low energy pass through this filter more than ions of high energy. Since, as mentioned above, low energy ions are scattered more strongly than high energy ions and therefore less low energy ions pass through the collimator structure than high energy ions, an almost homogeneous doping profile starting from the surface is obtained by using such a filter in combination with a collimator structure. This is shown on the right side of FIG. 27, where a method of implantation using the described filter and collimator structure is shown. Although the collimator structure in this example is disposed on the substrate, it may also be disposed on the filter.

[0088] Point 8. Reducing filter wear caused by sputtering effect Implantation arrangement of the filter relative to the substrate: in one case the projections face the substrate, in other cases the projections point away from the substrate (→ sputtering, scattering during impact). During the implantation methods described above and below, the filter can in each case be used so that its microstructure faces the substrate, i.e. away from the ion beam, as shown in FIG. 28(a). Alternatively, the filter can be rotated so that its microstructure faces away from the substrate, i.e. towards the ion beam, as shown in FIG. 28(b). The latter can have a beneficial effect on the sputtering effect.

[0089] Point 9. Avoiding channeling by arranging filters for the ion beam Tilt of filter and / or substrate As long as the filter and / or substrate are made of crystalline materials, undesirable channeling effects can occur; i.e., ions can achieve increased coverage along certain crystallographic directions. The magnitude and acceptance angle of the effect are functions of temperature and energy. The implantation angle and the crystallographic surface orientation of the starting material used for the filter and substrate play an important role. In general, channeling effects cannot be reliably reproduced across a wafer, since the above-mentioned parameters can differ from wafer to wafer and from one implantation system to another.

[0090] Therefore, channeling must be avoided. By tilting the filter and the substrate, channeling can be prevented. Channeling in the filter or the substrate can have very different effects on the depth profile of the implanted dopant, especially if the filter and the substrate are made of different materials.

[0091] 29 shows a schematic representation of a filter tilted with respect to the substrate during the implantation process such that the base surface of the filter forms an angle with the surface of the substrate that is greater than zero. This angle is, for example, greater than 3°, greater than 5°, or greater than 10° and less than 30°. In this way it is possible to prevent or reduce channeling effects, particularly when the energy filter is made of anisotropic material.

[0092] Point 10. Realization of complex dopant depth profiles with simple filter shapes As mentioned above, more complex dopant depth profiles can be realized by adapting the geometric design of the filter elements. For simplicity of the following discussion, scattering effects of all types are ignored.

[0093] If the stopping power of the ions (dE / dx) is the same in both the filter and the substrate material, a situation can occur as illustrated in FIG. 30. FIG. 30 shows schematic diagrams of various doping profiles (dopant concentration as a function of depth in the substrate) of different designs of energy filters, each of which is shown in side and top views. As shown, (a) the triangular prism-shaped structure produces a rectangular doping profile; (b) the smaller triangular prism-shaped structure produces a doping profile with less depth distribution than the larger triangular prism-shaped structure shown in (a); (c) the trapezoidal structure produces a rectangular doping profile with a peak at the beginning of the profile; and (d) the pyramidal structure produces a triangular doping profile whose height increases as the depth in the substrate increases.

[0094] If the energy filter is constructed of heterogeneous materials, for example with silicon as the substrate material doped with boron, then a change in the dopant depth profile in the substrate is obtained according to the change in density and dE / dx of the filter as a function of the actual kinetic ion energy. A completely homogeneous, i.e. constant, change in doping in depth is only achieved if the same material is used for both the filter and the substrate. This is illustrated in FIG. 31, where doping profiles are shown in various substrate materials (target materials) obtained by the same implantation process, i.e. with the same primary ions and the same primary energy. In each case the filter material was silicon. The doping profiles are different as a result of the different substrate materials.

[0095] Figure 32 shows the variation of the stopping power as a function of energy for various substrate materials on which the diagram in Figure 31 is based [4] (SRIM simulations).

[0096] For a given surface geometry, it has been proposed to accommodate the energy-dependent variation of the stopping power, for example by designing the filter as a multi-layer system.

[0097] It is proposed that the variation of stopping power as a function of ion energy (i.e. as a function of vertical position on the filter projection for a given ion species and primary energy) is modeled by the incidence position on the filter (or more precisely, the actual path of the ion through the filter and substrate) so that the total loss of kinetic energy is obtained globally (i.e. from the ion's incidence on the filter to its end on the irradiated substrate). Thus, the energy loss in the filter is no longer determined solely by the irradiated length of filter material, but by the position-dependent variation of the stopping power.

[0098] Thus, with appropriate modeling and fixed geometry, it is possible to generate doping curves that, for example, rise or fall in depth. The stopping power is therefore a function of lateral position. Examples of such filters are shown in Figures 33 to 35. The lateral position in each of these figures is indicated by "y".

[0099] FIG. 33 shows a multi-layer starting material for a multi-layer filter. In this example, the starting material comprises four different layers, designated 1-4. However, the use of four layers is only an example. It is also possible to use less than four layers or more than four layers. The individual layers may differ not only in the material used, but also in their thickness. It is also possible that two layers comprise the same material and are separated by two or more layers of different materials. The individual layers may be deposited or produced sequentially on top of each other by suitable deposition methods.

[0100] With the appropriate configuration of layered stacks of materials with different stopping powers, complex dopant depth profiles can be realized even with simple filter shapes. Figure 34 shows a cross section of a filter realized on the basis of the starting material produced in Figure 33 and including, in the illustrated example, a base and triangular structures arranged on the base. These triangular structures may be in the form of strips, i.e. extending in a direction perpendicular to the plane of the drawing, or may be part of a pyramidal structure.

[0101] As shown in Figure 35, the filter may be realized in such a way that several structures are arranged next to each other in the lateral direction (y-direction), these structures comprising different geometries and / or different layered stacks, i.e. layered stacks having different structures with respect to the individual layers and / or the sequence of materials of the individual layers. For example, six different materials are used in the illustrated filter, these layers being indicated with 1 to 6.

[0102] For example, silicon, silicon compounds or metals are suitable as materials for the individual layers, although the choice is not limited to such materials. Silicon compounds include, for example, silicon carbide (SiC), silicon dioxide (SiO2), silicon nitride (SiN), etc. Suitable metals include, for example, copper, gold, platinum, nickel and aluminum. According to one example, at least one layer of silicon compounds is grown on the silicon layer, and a metal layer is deposited from the vapor phase on the at least one layer of silicon compounds. The metal layer can also be evaporated directly onto the silicon layer. There is also the possibility of producing various metal layers on top of each other by evaporation, in order to obtain a filter with different layers.

[0103] Point 11. Electronic restraints It is known that during the transmission of ions through a solid, the electrons of the primary beam either remain in the solid or are absorbed by the ions, i.e., depending on the properties of the filter material and the primary energy, the transmitted ions have, on average, a higher or lower charge state after passing through the filter

[26] . Electrons are either emitted or absorbed by the filter.

[0104] Figure 36 shows the equilibrium charge state of the ions as a function of the ion's kinetic energy for irradiation of a thin film (black line: Thomas-Fermi estimate, blue line: Monte Carlo simulation, red line: experimental result). Ion: sulfur. Film: carbon

[27] .

[0105] As a result of ion bombardment, secondary electrons with high kinetic energy can be generated simultaneously on both the front and back sides of the filter. At the high current densities required for industrial production, the energy filter heats up. As a result of thermionic emission (Richardson-Dushman method), thermal electrons are generated as a function of the temperature and the work function of the filter material. This is shown in Figure 37, which shows the heating of an energy filter by ion bombardment. The curve shown is based on an experiment in which a filter was bombarded with 6 MeV high-energy carbon (C) ions. The filter in this case was an opaque energy filter [2].

[0106] The distance in an ion accelerator (in high vacuum) between the filter and the substrate is typically no more than a few centimeters, so that measurements of the ion current at the substrate, for example by a Faraday cup mounted there, are modified by the diffusion of hot electrons (from thermionic emission) and by the action of fast electrons (from ion bombardment).

[0107] As mentioned above, from the point of view of the filter, there are both processes that generate electrons (stripping of primary ions) and processes that release electrons. Therefore, the potential of an implemented electrically isolated filter is not well defined. On the contrary, it changes during the implantation process as a function of the ion current, vacuum conditions, temperature, etc. A net negative charge promotes the release of electrons, while a net positive charge tends to inhibit the release of electrons. Various methods of preventing such charging are described below.

[0108] (a) Energy filter element at a prescribed (positive) potential It is proposed that the energy filter be designed and mounted in such a way that the filter is always at a defined potential during ion bombardment. Figure 38 shows a cross section of a filter arrangement in which this is ensured. In this filter arrangement, the filter in the filter frame is held at a defined (positive) potential with respect to the filter holder in order to suppress secondary electrons. The filter frame is connected to a voltage source and is electrically isolated from the filter holder and the implanter chamber wall.

[0109] The potential of the filter holder can be adjusted, for example in such a way that a constant potential relative to the potential of the substrate to be implanted or to ground potential is maintained during implantation, independent of the charge balance resulting from the implantation process. For this purpose, a controlled supply of positive or negative charges by a current source can be provided.

[0110] The potential maintained can in particular be chosen such that, for example, the emission of electrons from the filter is completely suppressed, so that only the (positive) charges of the transmitted ion current are measured in a Faraday cup next to or on the substrate. Typical values ​​of such (positive) potentials are in the range of a few tens of volts to a few thousand volts.

[0111] If the energy filter is very high ohmic due to its material composition, it is proposed that the filter be equipped on one or both sides with a thin highly conductive layer with a thickness ranging from a few nanometers to a few tens of nanometers. The stopping power of this layer must be incorporated into the overall balance of stopping power when the filter is designed. Care must be taken to ensure that the applied layer (even if applied on the side facing away from the substrate) does not in principle cause any harmful contamination of the implanted substrate material. For the processing of SiC substrates, this layer can consist of carbon, for example.

[0112] (b) The energy filter is coated with a high work function material.

[0113] To reduce the strong thermionic emission, it is proposed that the energy filter be coated on one or both sides with a material having a high electron work function to prevent thermionic emission as much as possible at a given temperature. The work functions of some elements are shown in Figure 39

[25] , Materials Science Poland, Vol. 24, No. 4, 2006. In particular, materials with a work function greater than 3.5 eV, greater than 4 eV or greater than 4.5 eV are suitable.

[0114] The stopping power of this layer must be included in the overall balance of stopping power calculated when designing the filter. Care must be taken to ensure that the applied layer (even if applied on a face away from the substrate) does not in principle cause any harmful contamination of the implanted substrate material.

[0115] Point 12. Alternative manufacturing methods using injection molding, casting or sintering Implant filters can be manufactured by microtechnical methods such as lithography combined with wet chemical etching or dry chemical etching. In particular, anisotropic wet chemical etching with alkaline etchants (e.g. KOH or TMAH) is used for filter manufacturing from silicon. In this type of filter, the functional filter layer consists of monocrystalline silicon. Therefore, during bombardment by energetic ions, channeling effects can affect the effective energy loss of the filter layer in a way that is difficult to control. An example of how such effects can be avoided is described below.

[0116] (a) In one example, it is provided that for manufacturing by typical microtechnological processes, wet chemical anisotropic etching, which requires monocrystalline materials, is replaced by dry chemical etching, which means that polycrystalline or amorphous starting materials are used for the filter membrane. Due to its material structure, the resulting filter shows improved properties in terms of channeling.

[0117] (b) In another example, it is provided that the filter is manufactured not by a sequence of typical microtechnological processes, but rather by imprinting, injection molding, casting or sintering. The core idea is to carry out the above-mentioned processes in such a way that the mold or die insert determines the final shape of the energy filter membrane. The selected filter material is processed in a manner familiar to the method in question: a given casting mold, die insert, stamping, etc. gives it the required shape in soft form (for imprinting), liquid form (for injection molding and casting) or granular form (for sintering).

[0118] One advantage of the use of the above-mentioned methods is that single-crystalline filter membranes are typically not obtained and therefore channeling is suppressed. Another advantage is that the range of available filter membrane materials is very large. For example, the use of filter membranes of sintered SiC for the production of homogeneous doping profiles in SiC substrates is particularly advantageous.

[0119] Another advantage is that by using the above-mentioned molding method the manufacturing costs of a large number of filter elements can be significantly reduced compared to the manufacturing costs by microtechnology.

[0120] Point 13. Irradiation of stationary substrates As shown by way of example in Fig. 40, a homogeneous and energy-filtered irradiation of a stationary substrate is achieved by "wobbling" the ion beam in front of the filter (=controlled deflection), by placing the filter between a wobbling unit (=ion beam deflection system) and the stationary substrate, and by choosing the correct deflection angle and the correct distance d between the filter and the substrate (typically a few cm to a few m). Fig. 40 shows an arrangement for implantation into a substrate through an energy filter. This arrangement includes a deflection device of the ion beam placed in front of the filter. The deflection of the ion beam that can be achieved by this deflection device is adjusted with the distance between the filter and the substrate (typically in the range of a few cm to a few m) so that for implantation the substrate can be fully irradiated, i.e. its entire surface can be irradiated.

[0121] Point 14: Arrangement for utilizing a large filter surface area (a) Configuration where the entire filter surface is active Figure 41 shows an arrangement for energy filter implantation (i.e. implantation by energy filter), in which the beam area is expanded by suitable means and the illuminated filter surface area is larger than the substrate surface area. As a result, the substrate can be completely illuminated and large filter surfaces can be used. The diameter of the illuminated filter area is larger than the diameter of the substrate. The substrate can be either static or movable. This arrangement allows to use a large filter surface (=reduced filter degradation effects and thermal effects) and ensures illumination of the entire surface of the substrate. The use of this type of arrangement is particularly advantageous when the required filter structures are "large". To dope high-voltage Si-IGBTs or Si power diodes with protons, a penetration depth of more than 100 μm is required. For this application, filter structures with a "protrusion height" of >100 μm must therefore be provided. Such filter structures can be manufactured very easily with sufficient mechanical stability, even for large substrates (e.g. 6 or 8 inch).

[0122] In the arrangement described here, a certain minimum distance should be maintained between the substrate and the filter to ensure sufficient lateral homogenization of the implanted ions as a result of scattering effects.

[0123] (b) An arrangement in which part of the filter surface is inactive The same configuration is used as described initially in section 14(a). Arrangement for energy filter implantation, where the beam area is enlarged by suitable means so that the illuminated filter surface is larger than the substrate surface. Nevertheless, the entire filter surface is not active here. On the contrary, only certain parts of the filter surface are active. This means that the filter consists of an arrangement of a large number of filter elements, for example in the form of strips. These filter elements can be manufactured monolithically from the substrate, for example by suitable manufacturing processes. The other (inactive) part of the filter surface is used to stabilize the filter membrane. This part is responsible for the ion beam casting a shadow. Therefore, in this arrangement, either the substrate or the filter must be moved to compensate for the shadowing effect. This arrangement allows to utilize a large filter surface (=reduced effects of filter degradation and thermal effects) and ensures illumination of the entire surface of the substrate. Figure 42 shows a filter with an inactive part and with mechanical scanning in one direction.

[0124] Point 15. Changing the doping profile in the substrate by using a sacrificial layer Furthermore, a sacrificial layer with a suitably selected thickness and stopping power can be applied to the substrate, so that the implantation profile is shifted in depth in the desired manner within the substrate. This type of sacrificial layer can also be used for masked ion implantation (see FIG. 43) and for unmasked ion implantation. In particular, this method makes it possible to "push" the undesired start of the doping profile from the substrate into the sacrificial layer, i.e. to embed the start of the profile in the sacrificial layer.

[0125] Fig. 43 shows the modification of the doping profile in the substrate obtained by a sacrificial layer in the case of a masked and energy filtered implant. In the example shown, the beginning of the implant profile is pushed into the sacrificial layer. In contrast to Fig. 43, this principle can be used as well for unmasked and energy filtered ion implants, i.e. implants where no masking layer is present.

[0126] Point 16. Lateral modification of the doping profile in the substrate by a sacrificial layer By applying a sacrificial layer with a suitable choice of stopping power and thickness variation over the wafer surface to the substrate, the implantation profile can be shifted as desired in depth into the substrate as a function of lateral position on the wafer. This type of sacrificial layer can be used for masked and also for unmasked ion implantation (see FIG. 44). In particular, the variation of implantation depth with a homogeneous doping profile can be advantageously used for edge termination of semiconductor components.

[0127] Figure 44 shows the lateral modification of the doping profile in the substrate by a sacrificial layer for unmasked and energy filtered ion implantation, where the lateral modification of the implantation depth is achieved by the lateral variation of the sacrificial layer thickness. This principle can be used analogously for masked and energy filtered implantation.

[0128] Point 17. Adaptation of profile transitions between several injection profiles Two or more doping profiles can be skillfully superimposed, resulting in the desired overall doping profile, especially in the areas of overlap. This technique is particularly advantageous for the growth and doping of multilayers. A typical example consists of the growth of several SiC epilayers and their energy filtered doping. Good contact between the layers needs to be guaranteed.

[0129] Point 18. Special arrangement of the multi-filter concept with coupled vibration motion A clever arrangement can be used so that lateral homogeneity of the distribution of ions is achieved despite the coupled oscillatory motion of the filter and the substrate, i.e. despite the absence of any relative vertical movement between the filter and the substrate. This type of arrangement is shown in Fig. 45. The wafer is guided by the x-direction rotation of the wafer wheel behind the substrate. The ion beam (not shown) is, for example, expanded in the x-direction and scans over the multi-filter surface by the vertical oscillatory motion of the implantation chamber. The filter surface consists of active filter areas and inactive holder areas. Arrangement (A) is an unfavourable arrangement. If we consider the illuminated filter surface for y1 and y2, then at y1 three filters are illuminated and at y2 no filters are illuminated at all. As a result, a laterally inhomogeneous stripe pattern is obtained on the wafer. Arrangement (B) shows a possible example of a better arrangement. Two filters are illuminated for both y1 and y2. This applies for all y. As a result, a laterally homogeneous doping on the wafer surface is achieved.

[0130] As shown in Figure 45, the vertical movement of the filter and the substrate in the y direction is coupled. The wafer is guided along the x direction behind the filter by the rotation of the wafer wheel. The ion beam (not shown) is expanded, for example, in the x direction and scans over the multi-filter surface by the vertical oscillatory movement of the implantation chamber. The filter surface consists of active filter areas and inactive holder areas. Arrangement (A) is a rather unfavourable arrangement. If we consider the illuminated filter surface for y1 and y2, then at y1 three filters are illuminated and at y2 no filters are illuminated at all. As a result, a laterally inhomogeneous stripe pattern is obtained on the wafer. Arrangement (B) shows a possible example of a better arrangement. Two filters are illuminated for both y1 and y2. This applies for all y. As a result, a laterally homogeneous doping on the wafer surface is achieved.

[0131] Point 19. Monitoring Another aspect aims to solve the problem of monitoring important parameters of the ion implantation modified by the energy filter. Such parameters are, for example, the minimum or maximum "projected range", the depth concentration distribution determined by the filter geometry, the (energy-dependent) angular distribution. Monitoring of other parameters, such as the implanted ion species, may also be useful. In particular, monitoring should be possible on the wafer where the ions are implanted or (simultaneously) on structures nearby the wafer. According to one aspect, the monitoring should be performed without requiring further processing of the monitoring structure or the wafer.

[0132] Monitoring can be performed by measuring optical parameters such as spectral absorption, spectral transmittance, spectral reflectance, change in refractive index, total absorption (wavelength range dependent on measurement device), and total transmission and reflection (wavelength range dependent on measurement device).

[0133] According to one embodiment, it is provided that for monitoring the implantation parameters, an arrangement of masks and substrate materials is used, which (1) are placed at appropriate positions on the surface to be implanted, e.g., on a wafer wheel, and (2) change their optical properties, e.g., as a result of ion implantation in an "as-implanted" manner, i.e., without the need for further post-processing. For example, this change is proportional to the implanted ion dose for a given ion species. The materials cited in (2) are, for example, PMMA (plexiglass), PMMA, SiC, LiNbO3, KTiOPO4, etc.

[0134] If the material optically sensitive to ionizing radiation is at the same time the material of the target substrate, the target substrate (eg a SiC wafer) can be used directly for optical monitoring.

[0135] In addition to changes in optical properties, materials such as PMMA are known to change their solubility in certain acids and solvents after irradiation with ions, and therefore the depth of the altered structure (or etch rate or resulting etch shape, etc.) after ion bombardment can be considered a measure of the implanted ion dose.

[0136] Monitoring other changes in physical parameters due to ion irradiation is contemplated, such changes may include, for example, mechanical properties of the monitored material, electrical properties of the monitored material, or nuclear-physical activation of the monitored material due to high energy ion irradiation.

[0137] According to one embodiment, the detection should proceed on the basis of a change in optical properties. This type of implementation is described below. In case it frequently happens that no monitoring is performed on the implanted target substrate, the implementation of a separate monitoring structure is proposed. The monitoring structure consists of an arrangement of a suitable substrate material with one or more mask structures. Examples are shown in Fig. 47 and Fig. 48.

[0138] As shown in Fig. 46, a monitoring structure or multiple monitoring structures (monitoring chips) are placed at a suitable location, such as on a wafer wheel. The readout of the monitoring chips is performed, for example, after implantation without further post-processing. In some cases, the mask needs to be removed from the monitoring substrate for the readout measurement. According to one embodiment, the mask is reusable.

[0139] The mask material and the substrate material of the monitoring chip can also be made of different materials. A criterion for the selection of the mask material is, for example, its compatibility with the material of the target substrate (to eliminate contamination caused by sputtering effects). Another criterion is the stopping power of the energetic ions, so that mask structures with high aspect ratios can be produced.

[0140] It is also possible that the mask material and the substrate material of the monitoring chip are manufactured from the same material. The mask and the substrate can also be manufactured monolithically, in which case it is usually not possible to reuse either the mask or the substrate.

[0141] Performance and characterization of mask structures after ion implantation: 1.Ion implantation performance modified by energy filters 2. Removal of the mask is possible but not necessary, since the readout measurement can also be performed by reflection from the back surface of the substrate.

[0142] 3.Optical measurement a. Absorption spectrum, resolved by wavelength b. Transmission spectrum, wavelength resolved c. Reflectance, wavelength resolved d. Simple overall absorption, i.e., not wavelength resolved e. Simple total transmission, i.e., not wavelength resolved f. Measurement of refractive index change g. Change in polarization 4. Comparison with a calibration curve or comparison standard and determining if the injection process occurred as expected.

[0143] Using the described monitoring structure, the following injection parameters can be tested:

[0144] A. Depth-dependent dose Therefore, this is a test for filter degradation and to determine if the implant dose is set correctly at the machine.

[0145] B. Maximum / minimum projected range This is therefore a test of the correct injection energy, a test of filter degradation, and a test of the accuracy of the generated filter structure.

[0146] C. Angular distribution of implanted ions This is therefore a test for filter degradation, a test for correct formation of the filter, and a test for correct geometric placement within the injection chamber. A. Monitoring the depth distribution of implanted ions

[0147] Point A. Depth-dependent dose 49 to 52 show, as an example, monitoring the depth distribution of the implanted ion dose set by an energy filter. In this example, the following simple assumptions apply:

[0148] The change in optical properties is caused only by the locally implanted ion dose and the intrinsic defects induced by it.

[0149] For example, ions passing only through depth region III with ion concentration C1 (FIG. 51) (so as to reach concentration region C2) will not result in any further change in the optical properties.

[0150] Precisely, it is conceivable that such a change in optical properties may be observed in PMMA as a result of, for example, electronic termination.

[0151] This is not an issue for assessability in principle, but in the examples of Figures 51 and 52 it is excluded for simplicity.

[0152] The mask structures shown in or described in Fig. 50 are arranged as staggered, i.e. "inclined" or continuous slopes, in terms of thickness and number, depending on the desired depth resolution. Thus, for maximum thickness, the following applies by way of example: "mask thickness" > Rp,max The lateral dimensions of the individual structures can range from square micrometers to square millimeters to square centimeters, depending on the requirements of the readout device.

[0153] Point B. Monitoring maximum projected range FIG. 53 shows a structure adapted for monitoring maximum projected range.

[0154] A similar structure using an evaluation procedure as described in A can also be used to measure or monitor the minimum projected range.

[0155] Point C. Monitoring the angular distribution of implanted ions Energy filters for ion implantation are known to produce an energy dependent spectrum of ion angles after passing through the filter.

[0156] In principle, it is true that for monoenergetic ions arriving perpendicular to the surface of the filter, the resulting lower energy ions after the filter will be scattered more strongly than the higher energy ones.

[0157] The resulting angular distribution is therefore a function of the filter geometry, changes in geometry over the life of the filter, the occurrence of channeling effects, the ion species used, the primary energy, the maximum and minimum energies of the resulting transmitted ions, and the geometry within the implantation chamber. By monitoring the angular distribution, it is possible to track all of these parameters.

[0158] For monitoring of individual parameters, different mask structures are proposed which can be arranged within the monitoring chip, as shown and described in Figures 55 to 58.

[0159] It should be noted that for the evaluation of the angular distribution, it is often only the aspect ratio of the mask features that is important.

[0160] Thus, the size of the openings in the mask structure for a thin mask, which is slightly thicker than the maximum projection range in the mask material, can be in the micrometer or sub-meter range.

[0161] Such monitoring structures are preferably arranged as an array of many individual structures so that a global optical evaluation (ie over a surface of several mm2 or cm2) can be performed.

[0162] In contrast, for the same aspect ratio and a mask thickness in the millimeter range, for example, the size of the openings can be in the millimeter or centimeter range. In these cases, it is also possible to evaluate individual structures that are not arranged in an array without special technical efforts.

[0163] Proposed mask structure: 1. Fixed mask thickness, mask openings of various shapes → changing aspect ratio; 2. Variable mask thickness, fixed geometry of mask opening → changing aspect ratio; 3. Combination of 1 and 2; 4. By arranging multiple arrays (or individual structures) of one, two or three different angles, the directional dependence of the angular distribution can be monitored.

[0164] A circular arrangement is also contemplated.

[0165] In addition to concentric rings, individual circles and circular rings of various dimensions, as shown in FIG. 58, are also particularly advantageous for monitoring the angular distribution of ions transmitted by the energy filter.

[0166] The essence of the last aspect described above is that the (essential) dose-dependent modification of the (preferred) optical parameters of the material is used for the "as-implanted" monitoring of the energy filter implantation process, so that by optical measurements (for example) the resulting implantation can be monitored as completely as possible with respect to its most important parameters, without the need for complex post-processing (for example annealing and application of metal contacts).

[0167] Thus, defective implants can be detected cheaply and quickly, and the affected wafers can be sorted out.

[0168] Figure 59 shows the skillful matching of the profile transition between two implantation profiles A and B, such that the resulting overall concentration profile can produce, for example, a desired homogeneous profile. This can be particularly advantageous for a two-layer layer system such as that shown in this figure (although this is not necessarily the case). Proposal for realization by the following sequence of processes: (1) doping the underlayer (implant B); (2) growing an upper layer; (3) Doping the top layer: While there are limited possibilities to configure the high-energy tail of implant A, the low-energy tail of implant B can be influenced, in particular, by the introduction of a sacrificial layer as described in "Point 15: Modifying the doping profile in the substrate by a sacrificial layer".

[0169] This is proposed to be achieved through the following process: (1) growing a sacrificial layer; (2) doping the underlayer (implant B); (3) removing the sacrificial layer; (4) growing an upper layer; (5) doping the top layer;

[0170] The above described concept makes it possible to develop manufacturing-worthy implantation methods for the semiconductor industry, i.e. economical application of the implantation method in industrial production processes. The concept described here makes it possible to realize in particular complex vertical doping concentration curves in a highly flexible way (multi-filter concept) with low angular distribution of the implanted ions, in addition to the homogeneous doping realized by simple triangular filter structures. In particular, all types of doping concentration curves can be approximated by the use of triangular filter structures in combination with collimator structures. Another important aspect concerns the suppression of artifacts that alter the ion current measurement on the substrate.

[0171] In conclusion, it should be pointed out once again that the measures described above in points 1 to 19 can be applied alone or in any desired combination with each other. For example, the described "end of life" detection can be applied to filters mounted on a frame, but also to filters mounted in other ways.

[0172] The wafers mentioned above may further be semiconductor wafers, but may also be composed of other implantable materials such as PMMA.

[0173] References [0] Energy filter for ion implantation systems. M. Rub, Research Report of the University of Applied Sciences (Ernst-Abbe-Hochschule) Jena, 2013 / 2014. [2] Constantin Csato, Florian Krippendorf, Shavkat Akhmadaliev, Johannes vonBorany, Weiqi Han, Thomas Siefke, Andre Zowalla, Michael Rub: Energy filter fortailoring depth profiles in semiconductor doping applications. Nucl. Instr.Meth., B, 2015, http: / / dx.doi / org / 10.1016 / j.nimb.2015.07.102. [4] Investigation of dopant profiles, losses and heating using an energy filterfor ion implantation. Krippendorf, Csato, Rub, DPG Spring Conference, Dresden,March 2014. [5] Energy filter for ion implantation. F. Krippendorf, C. Csato, T. Bischof,S. Bupta, W. Han, M. Nobst, University of Applied Sciences Jena; C. Ronning,Friedrich Schiller University Jena; R. Rupp, Infineon Technologies AG,Neubiberg; A. Schewior, University of Applied Sciences Jena; W. Wesch,Friedrich Schiller University Jena; W. Morgenroth, Institute for PhotonicTechnologies e.V., Jena; M. Rub, University of Applied Sciences Jena.Microsystem Technology Congress, Aachen, October 2014, "Energy filter forion implantation systems. Idea - preliminary experiments - Application, C. [6] C. Csato, T., Bischof, S., Gupta, W. Han, F. Krippendorf, W. Morgenroth, M.Nobst, C. Ronning, R. Rupp, A. Schewior, W. Wesch, M. Rub, June 12, 2013,Workshop "Ion Beams - Research and Application", 2013, LeibnitzInstitute for Surface Modification, Leipzig; M. Rub, B. Sc., T. Bischof, M.Sc.,C. Csato, B.Sc., S. Gupta, B.Sc., W. Han, M.Sc., F. Krippendorf, B.Sc., A.Schewior, B.Sc., C. Mose, Energy filter for ion implantation systems, researchreport of University of Applied Sciences Jena, 2011 / 2012. [7] EP 8030037 A1. [8] Rub: Energy filter for high-energy ion implantation, IP.com Disclosure No.:IPCOM000018006D, original publication date: December 1, 2001. Included in theprior art database: July 23, 2003 and Siemens AG, 2001, Siemens TechnicalReport, December 2001, 9 pages. [9] DE 10 2011 075 350 A1.

[10] J. Meijer, B. Burchard, High-energy ion projection for deep ionimplantation as a low-cost, high-throughput alternative for subsequent epitaxyprocesses. J. Vac. Sci. Technol., B22(1).

[11] U. Weber, G. Kraft: Design and construction of a ripple filter forsmoothed depth dose distribution in conformal particle therapy. Phys. Med.Biol., 44(1999), 2765-2775.

[12] Y. Takada et al.: A miniature ripple filter for filtering a ripple foundin distal part of a proton SOBP, Nuclear Instruments and Methods in PhysicsResearch A 524 (2004) 366-373.

[16] DE 19652463 C2.

[18] US 7,385,209 B2.

[19] US 2002-0050573 A1. [19-1] Energy filter for ion implantation systems. M. Rub, research report ofthe University of Applied Sciences Jena, 2013 / 2014. [19-2] DE 10239312 B4

[25] Materials Science-Poland, Vol. 24, No. 4, 2006.

[26] M. Nastasi et al.: Ion-Solid Interactions. Fundamentals and Applications.Cambridge University Press, 1996.

[27] O. Osman: Irradiation effects of swift heavy ions in matter. Dissertation,Essen, 2011.

Claims

1. irradiating a surface region of the wafer with an ion beam using an implanter; The injection device comprises: Filter Frame and 1. A method of implanting ions into a wafer comprising: a filter held by the filter frame and irradiated by an ion beam passing through the filter toward the wafer, the filter including at least one filter element that is a microstructured membrane, the filter having a surface area that is irradiated by the ion beam.

2. The method of claim 1 , wherein the surface area of ​​the filter onto which the ion beam is irradiated is greater than the surface area of ​​the wafer onto which the ion beam is irradiated.

3. The method of claim 2 , wherein the filter comprises a plurality of filter elements.

4. The method of claim 3 wherein the filter element is formed as a strip.

5. 5. The method of claim 3 or 4, wherein the filter includes inactive portions between the filter elements to stabilize the filter elements.

6. The method of claim 3 , wherein the wafer is moved in one direction during implantation.

7. The method of claim 3 further comprising expanding the beam area in front of the filter.

8. 3. The method of claim 2, wherein the entire surface area of ​​the filter irradiated by the ion beam is formed by a single filter element.

9. The method of claim 8 , wherein a diameter of the surface area of ​​the filter irradiated by the ion beam is greater than a diameter of the wafer.

10. The method of claim 8 , wherein the wafer is stationary during implantation.

11. The method of claim 8 , wherein the beam area is expanded before the filter.

12. 10. The method of claim 1, further comprising the steps of: positioning a monitoring structure proximate to the wafer; and implanting into the monitoring structure.

13. the implanter further comprising a collimator structure irradiated by the ion beam; The method of claim 1 , wherein the collimator structure is disposed in the transmitted beam after the filter.

14. 1. An implantation apparatus for implanting ions of an ion beam into a target substrate, comprising: A filter frame; a filter held by the filter frame; The implanter, wherein the filter is a microstructured membrane positioned and configured to be irradiated by the ion beam passing through the filter and towards the target substrate.

15. the implanter further comprising a collimator structure irradiated by the ion beam; 15. The implanter of claim 14, wherein the collimator structure is disposed in the transmitted beam after the filter.

16. 15. The injection device of claim 14, wherein the filter frame is held in a filter holder.

17. 16. The implanter of claim 15, wherein the collimator structure is disposed on the filter holder in the transmitted beam after the filter.

18. 16. The injection device of claim 15, wherein the collimator structure comprises a plurality of collimator units arranged in a predetermined pattern.

19. The injection device of claim 18 , wherein the collimator unit forms a lamellar or lattice shape in a top view.

20. 20. The injection device of claim 18, wherein the collimator unit is rectangular, circular, elliptical, hexagonal, or has another polygonal shape in a top view.

21. 20. The injection device of claim 18, wherein at least one of the collimator units comprises a tube having a length and a width, and wherein a ratio of the width to the length is less than 1, less than 2, less than 5, or less than 10.

22. A wall having an opening; a filter holder arranged in the region of the opening in the wall and having a receiving portion; a filter frame received in the receiving portion of the filter holder; a filter held in the filter frame, the filter configured to be irradiated by an ion beam passing through the filter.

23. 23. The injection system of claim 22, wherein the filter holder comprises a cooling device integrated within or disposed on the filter holder.

24. 24. The injection system of claim 23, wherein the cooling device comprises at least one coolant line.

25. 23. The implantation system of claim 22, further comprising an ion beam deflection system disposed in front of the aperture.

26. The filter holder is configured to hold the filter frame in a non-contact manner, 23. The injection system of claim 22, wherein the filter holder comprises at least one magnet for holding the filter frame.

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