Energy filter elements for ion implantation systems used in wafer manufacturing

Abstract

This invention provides an energy filter element for ion implantation systems used in wafer manufacturing. [Solution] The present invention relates to an injection device, an injection system, and a method. The injection device comprises a filter frame and a filter held by the filter frame, the filter being designed to be irradiated by an ion beam.

Description

Technical Field

[0001] The present invention relates to an implantation device provided with an energy filter (implantation filter) for ion implantation and its use, and an implantation method.

Background Art

[0002] By ion implantation, doping or the generation of defect profiles in any desired material, such as semiconductor materials (silicon, silicon carbide, gallium nitride), or optical materials (LiNbO3), can be achieved with a predefined depth profile within a depth range from a few nanometers to several hundred micrometers. In particular, generating a depth profile characterized by a depth distribution wider than the depth distribution of the doping concentration peak or defect concentration peak that can be obtained by single-energy ion irradiation, or generating a doping or defect depth profile that cannot be generated by one or a few simple single-energy implantations, is desirable.

Brief Description of the Drawings

[0003] [Figure 1] FIG. 1 is a diagram showing the basic principle of an energy filter. The energy of a single-energy ion beam is changed as a function of the point of incidence when passing through the microstructural energy filter component. The resulting energy distribution of the ions causes a change in the depth profile of the implanted substance in the substrate matrix. [Figure 2] FIG. 2 shows, on the left side, a wafer wheel, and the substrate to be implanted is fixed at a fixed position on this wafer wheel. During processing / implantation, the wheel rotates while tilted at 90°. Thus, the ion beam shown in green "writes" concentric circles on the wheel. To irradiate the entire surface of the wafer, the wheel is moved vertically during processing. FIG. 2 shows, on the right side, an energy filter attached to the region of the beam aperture. [Figure 3]Figure 3 shows schematic diagrams of various doping profiles (dopant concentration as a function of depth in the substrate) for different configurations of energy filter microstructures (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-shaped structure produces a triangular doping profile with increasing height as the depth in the substrate increases. [Figure 4] Figure 4 shows a cross-sectional view of the filter frame for holding the energy filter chip. [Figure 5] Figure 5 shows a filter frame for holding an energy filter element with a locking element, and a top view of the mounted energy filter. [Figure 6] Figure 6 shows a typical installation of a frame for holding an energy filter element within the beam path of an ion implanter. In this example, the filter holder is located on one side of the chamber wall. In this example, this side is the inside of the chamber wall, i.e., the side facing the wafer (not shown) during implantation. The frame with the filter tip inserted is pushed into the filter holder and then covers the opening in the chamber wall through which the ion beam passes during implantation. [Figure 7] Figure 7 shows a partial frame (left side of the figure) and a complete frame (right edge of the figure), each of which can be made of the same material (e.g., monolithic) as the energy filter and / or another material. [Figure 8] Figure 8 shows the use of one or more bars for mounting a filter frame surrounding a filter or any other passive scattering element. [Figure 9] Figure 9 shows the use of one or more suspension elements for mounting a filter frame surrounding a filter or any other scattering element. [Figure 10]Figure 10 shows the use of a magnetic field for mounting a filter frame surrounding a filter or any other scattering element. [Figure 11] Figure 11 shows a simple implementation of a multifilter. Three differently formed filter elements are combined within a filter holding frame to form a complete energy filter. The ion beam passes uniformly throughout 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 subprofiles arises from one of the three subfilters shown on the left, i.e., the subfilter with the corresponding number. [Figure 12] Figure 12 shows a detailed diagram of the multifilter concept. Three filter elements are shown as an example on the left. Four elements are described with numbers. 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 changing the surface dimensions of the individual filter elements. In this example, it is assumed that the filter and the substrate have the same energy-dependent stopping power. However, this is not usually the case. [Figure 13] Figure 13 shows the sum profile obtained when all the filter elements described in Figure 12 are assembled together as a complete filter with appropriate weighting and uniformly exposed to an ion beam of appropriate primary energy. [Figure 14] Figure 14 shows an exemplary arrangement of individual filter elements within a multifilter. The individual elements F1, F2, F3, etc., shown here are cut diagonally and directly attached to one another. [Figure 15] Figure 15 shows the arrangement of filters installed in an ion implantation system. Cooling lines, supplied with coolant by an external cooling device, are incorporated within a 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 time. Therefore, the unirradiated areas can be cooled by radiative cooling. This embodiment can also be configured as a multi-filter, as described above; that is, as a filter containing several different filter elements. In the illustrated example, the filtered frame vibrates in a direction perpendicular to the direction of the ion beam. Since the area of ​​the filter covered by the ion beam is smaller than the total surface area of ​​the filter, only a portion of the filter is exposed to the beam per unit time. This portion changes continuously due to the vibrational motion. [Figure 17] Figure 17 shows another configuration of the energy filter arrangement rotating around a central axis. In this case as well, since the irradiation per unit time is partial, unirradiated elements can be cooled. This embodiment can also be configured as a multi-filter. [Figure 18] Figure 18 schematically illustrates the "peak shift." By implanting ions into the energy filter with the help of a trapezoidal prism-shaped structure, a rectangular profile can be generated within the substrate. The initial peak is embedded in the energy filter. This implanted profile has the advantageous characteristic of starting immediately at the substrate surface, which is extremely important for the application of energy filters. [Figure 19] Figure 19 shows how ions are implanted into the PMMA substrate by an energy filter during static implantation. The ions disrupt the molecular structure of the PMMA. The subsequent development process reveals the energy distribution of the ions. Regions with high-energy deposition dissolve away. Regions with low or no ion energy deposition are not dissolved by the developer. [Figure 20] Figure 20 shows a monitoring system for identifying filters and monitoring their compliance with filter specifications (maximum temperature, maximum cumulative ion dose). [Figure 21]Figure 21 shows a collimator structure mounted on a filter holder. The aspect ratio determines the maximum angle α. If the available distance to the injection substrate is not sufficiently large, the collimator can consist of several collimator units arranged in a row with smaller apertures. These 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 positioned in the ion beam in a back-to-front configuration. When properly designed, the collimator has a favorable mechanical stabilization 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 positioned in the ion beam in a front-to-back configuration. [Figure 24] Figure 24 shows a collimator structure built directly on the filter. Depending on the filter layout and the required maximum angular distribution, the collimator structure can be lamellar, strip-shaped, tubular, or honeycomb-shaped. [Figure 25] Figure 25 shows a collimator structure directly constructed on a target substrate. Depending on the layout of the substrate structure and the required maximum angular distribution, the collimator structure can have a lamellar, strip, tubular, or honeycomb structure. [Figure 26] Figure 26 shows the doping profiles obtained using different collimator structures with the same filter. [Figure 27] Figure 27 shows the doping profiles obtained by multifilter with and without a collimator structure. [Figure 28]Figure 28 schematically shows the "inversion" of the filter. (A) The filter is used in its normal configuration, which means the microstructure is away from the beam. (B) The filter can be inverted, which means the microstructure is facing the beam. This has a favorable effect on the sputtering effect in the filter. [Figure 29] Figure 29 schematically illustrates the "slope" of the filter. If the energy filter is manufactured from an anisotropic material, a channeling effect may occur. This can be prevented by slouching the energy filter. [Figure 30] Figure 30 schematically shows various doping profiles (dopant concentration as a function of depth in the substrate) for various forms of energy filter microstructures (each case shown in side and top views). (A) A triangular prism-shaped structure produces a rectangular doping profile. (B) Smaller triangular prism-shaped structures produce 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, and the doping profile increases with increasing depth in the substrate. [Figure 31] Figure 31 shows various target profile shapes for the same primary ion and primary energy, based on different target materials. In each case, the filter material is silicon. [Figure 32] Figure 32 shows the change in shutdown power as a function of energy [4] (SRIM simulation). [Figure 33] Figure 33 shows the starting materials for a simple multilayer filter. Filter materials with appropriate stopping power are sequentially laid on top of each other by an appropriate deposition method. [Figure 34] Figure 34 shows how a complex dopant depth profile can be achieved even with a simple filter shape (here, a strip-shaped triangle) in a suitable configuration of a layered stack of materials with different stopping powers. [Figure 35]Figure 35 shows the general principle of constructing an energy filter from materials 1 to 6, where each individual filter structure has a different geometric shape. [Figure 36] Figure 36 shows the equilibrium charge state of ions (black line: Thomas-Fermi estimation; blue line: Monte Carlo simulation; red line: experimental result) as a function of the kinetic energy of ions passing through a thin film. Ion: sulfur; film: carbon

[27] . [Figure 37] Figure 37 shows the heating of an energy filter by ion bombardment. Under these conditions, 6 MeV C ions are present in an energy filter that is not transparent [2]. [Figure 38] Figure 38 shows an embodiment of the filter arrangement in which the filter is held in the filter frame at a defined (positive) potential with respect 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 [Figure 40] Figure 40 shows the arrangement for energy filter implantation, where complete irradiation of the stationary substrate is achieved by an ion deflection system in front of the filter and by selecting an appropriate distance (usually in the range of several cm to several m) between the filter and the substrate. [Figure 41] Figure 41 shows the arrangement for energy filter implantation, where a filter surface larger than the surface of the substrate is used to achieve complete irradiation of the substrate. The diameter of the irradiated filter area is larger than the diameter of the substrate. [Figure 42] Figure 42 shows a filter where only a part of it is active and involves mechanical scanning in one direction. [Figure 43] Figure 43 shows the change in the doping profile in the substrate by a sacrificial layer in the case of masked and energy-filtered implantation. In the example shown here, the start of the implantation profile is shifted into the sacrificial layer. This principle can be used in the same way as for unmasked and energy-filtered ion implantation. [Figure 44] Figure 44 shows the lateral modification of the doping profile within the substrate by the sacrificial layer in the case of unmasked and energy-filtered ion implantation. This principle can be used in the same way as masked and energy-filtered implantation. [Figure 45] Figure 45 shows the coupling of vertical movement in the y-direction between the filter and the substrate. The wafer is guided in the x-direction behind the substrate by the rotation of the wafer wheel. An ion beam (not shown) is extended, for example, in the x-direction and scans the entire surface of the multifilter as a result of vertical vibration of the injection chamber. This surface consists of an active filter region and an inactive holder region. The arrangement shown in (A) is an undesirable arrangement. Considering the filter surface irradiated at y1 and y2, three filters are irradiated at y1 and no filters are irradiated at y2. As a result, a transversely heterogeneous stripe pattern is obtained on the wafer. The arrangement shown in (B) is a possible example of a better arrangement. Two filters are irradiated at y1 and y2. This applies to all y values. As a result, transversely homogeneous doping is achieved across the entire surface of the wafer. [Figure 46] Figure 46 shows a wafer wheel with an array of wafers to be irradiated and a monitoring structure located between the wafers. [Figure 47] Figure 47 shows a monitoring mask with an example of the arrangement of various mask structures Ma1 to Ma10 that are transparent or partially transparent to the ion beam. [Figure 48] Figure 48 shows a cross-section of the surveillance mask and surveillance material. [Figure 49] Figure 49 shows an example of a depth profile of concentration generated using an energy filter. [Figure 50] Figure 50 shows an example of a mask structure for monitoring depth-dependent dose distribution. [Figure 51] Figure 51 shows the monitoring of the injection process using a monitoring structure. [Figure 52] Figure 52 shows the monitoring of the injection process using a monitoring structure. [Figure 53]Figure 53 shows the monitoring of the maximum projected range. [Figure 54] Figure 54 shows the mask structure. [Figure 55] Figure 55 shows another example of a mask structure. [Figure 56] Figure 56 shows another example of a mask structure. [Figure 57] Figure 57 shows a mask structure for monitoring asymmetrical angular distributions. [Figure 58] Figure 58 shows various arrangements of mask structures for detecting ion angular distributions in various directions. [Figure 59] Figure 59 shows a clever fit of the transition between two injection profiles A and B, resulting in an overall concentration profile that yields a desired profile, such as a homogeneous profile. This can be particularly beneficial in the case of a layered system consisting of two layers, as shown in the figure here (although it is not necessary).

[0004] The following is a proposed implementation through a series of processes: (1) The step of doping the lower layer (injection B), (2) Steps to develop the upper levels, and, (3) The step of doping the upper layer.

[0005] The configuration of the high-energy tail of injection A is limited. However, the low-energy tail of injection B can be influenced, in particular, by the introduction of a sacrificial layer, as described in "15: Modification of the doping profile in the substrate by a sacrificial layer".

[0006] The following is a proposed implementation through a series of processes: (1) Steps to increase the number of victims, (2) The step of doping the lower layer (injection B), (3) Step of removing the sacrificial layer, (4) Steps to develop the upper levels, (5) The step of doping the upper layer. [Modes for carrying out the invention]

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

[0008] Figure 2 shows a system for ion implantation. This system includes an implantation chamber on which multiple wafers can be placed on a wafer wheel. As the wafer wheel rotates during implantation, each wafer repeatedly passes through a beam aperture where an energy filter is located, allowing the ion beam to reach the implantation chamber and impact 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 a 90° tilt. Thus, the ions of the ion beam, shown in green, "write" concentric circles onto the wheel. To irradiate the entire surface of the wafer, the wheel is moved vertically during processing. The energy filter mounted on the beam aperture is shown on the right side of Figure 2.

[0009] Figure 3 illustrates the principle of how a number of different dopant depth profiles can be generated by the appropriate selection of filters, by showing several filter layouts or three-dimensional structures as examples. The individual filter profiles shown in Figure 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 (far left of the drawing) is shown for each case, as are a top view of the energy filter and a curve showing the change in the achieved dopant concentration versus wafer depth (as a function of depth). The wafer "depth" is the direction perpendicular to the wafer surface into which the ions are implanted. As shown in Figure 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 case (a) (therefore, 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 with increasing height as the depth in the substrate increases.

[0010] For many reasons, conventionally known energy filters (injection filters) or energy filter elements are not suitable for achieving high throughput, i.e., many wafers per hour. In particular, it is desirable to have high wafer throughput per hour, ease of handling, ease of manufacture, and the realization of desired profile shapes. Monolithic filters, i.e., statically or movablely mounted filters manufactured from solid blocks of material and individually mounted in the ion beam, are known from references [2],[3],[4],[5],[6],[7],[8],[9],

[10] . In contrast to silicon, the shape of the doped region of a SiC wafer is generally not altered by outward diffusion of the dopant profile [2],[4],[5],[6]. This is because of 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, for example, the comparative values ​​for silicon. For this reason, it has been economically impossible to realize doped regions with particularly high aspect ratios, i.e., doped regions with a small ratio of base surface area to depth.

[0011] The dopant depth profile of a semiconductor wafer can be generated by in-situ doping during epitaxial deposition or by (masked) single-energy ion implantation. In the case of in-situ doping, a high level of inaccuracy is possible. Even for homogeneous dopant profiles, the nature of the process means that significant deviations from ideal doping are expected on the wafer, i.e., from mid-to-edge. For gradient depth profiles, this inaccuracy also extends vertically to the doped region, because the local dopant concentration now depends on numerous process parameters such as temperature, local dopant gas concentration, topology, Prandtl boundary layer thickness, and growth rate. The use of a single-energy ion beam means that many separate implantations must be performed to obtain a dopant profile with acceptable vertical undulation. This technique can only be tuned to a certain extent and quickly becomes economically unfeasible.

[0012] An example of the present invention relates to the configuration of an energy filter element for an ion implantation system that enables the fulfillment of requirements for the use of energy filter elements in the industrial production of semiconductor components, particularly components based on SiC semiconductor materials. The manufacturing conditions for the use of the energy filter element are defined, for example, by the following embodiments.

[0013] 1. Technical ease of filter replacement In productive environments, such as factories, production is often carried out using ion implantation equipment operated by industrial workers ("operators") who are not trained technicians.

[0014] Energy filters are extremely fragile, microstructured membranes that are difficult to handle without damaging them. To make this filter technology economically viable, it should be ensured that, after a short period of training, even non-experts (i.e., non-technical individuals) can replace the filters like worn-out tools, or swap them with other filters within 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, the simple energy filters described in [1-6] produce only a constant profile. Complex filter structures, such as those described in Rub[8], are technically very sophisticated and difficult to realize according to the technological level of the manufacturing method. The goal is to achieve complex vertical profile shapes by using simple, i.e., easily manufactured filter structures.

[0016] 3. High-throughput cooling system combined with filter movement The manufacturing conditions, for example, typically involve an ion implanter (typical terminal voltage >1MV~6MV of a tandem accelerator) producing approximately 2 × 10⁻¹⁶ units per hour. 13 cm -2This means that more than 20-30 wafers with a 6-inch diameter should be manufactured with a fluence per wafer. To manufacture the required number of wafers under these circumstances, an ionic current of 1 pμA or more and up to several tens of pμA should be used, or a power of several watts or more, for example, 6 W / cm². 2 Filter (typical surface area is 1-2 cm²) 2 It needs to be placed on top. This will cause the filter to heat up. The problem is to cool the filter by proper means.

[0017] 4. Simple and low-cost manufacturing of filter structures to obtain a homogeneous and uniform depth profile. Filter structures can be manufactured by anisotropic wet chemical etching. In its simplest form, the filter structure consists of appropriately sized long triangular lamellae (e.g., 6 μm high, 8.4 μm spaced, and several millimeters long) arranged periodically on the thinnest possible film. Manufacturing triangular lamellae with sharp points is costly because the wet chemical anisotropic etching must be precisely controlled. Sharp points, i.e., non-trapezoidal lamellae, are costly because the etching rate and etching time must be precisely controlled to obtain pointed lamellae. In practice, this results in a considerable amount of process control work during etching. As a result of the expected non-uniform treatment during etching on a chip with hundreds of lamellae (the etching rate of a wet chemical process is never perfectly reproducible and is never homogeneous over a wide area), it leads to yield loss, i.e., imperfectly structured filter elements. The goal is to realize a simple and low-cost method for producing energy filters.

[0018] 5. High lateral homogeneity of the manufactured dopant region or defect region. The ion implantation energy filters described in the previously cited references [2],[3],[4],[5],[6],[7],[8],[9],

[10] have an internal three-dimensional structure that results in differences in the distance ions travel as they pass through the filter. These differences in travel distance, depending on the stopping power of the filter material, result in a change in the kinetic energy of the transmitted ions. Thus, a single-energy ion beam is transformed into a beam composed of ions with different kinetic energies. The energy distribution is determined by the shape and material of the filter; that is, the filter structure is transferred to the substrate by ion lithography.

[0019] 6. Monitoring the "end of life" of energy filters Due to nuclear interactions and thermal loading between the ion beam and the filter material, the typical service life of a filter is a result of each ion implantation process using energy filters. For a silicon energy filter with a support layer of approximately 2 μm thickness, a regular protrusion structure on the order of 8 μm, and an implantation process in nitrogen at 12 MeV with a current of approximately 0.1 pμA, the maximum yield is approximately 100 wafers (6 inches).

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

[0021] 7. Limitation of the angular distribution of transmitted ions For the fabrication of masked dopant regions, i.e., regions with limited lateral dimensions, especially in the case of high aspect ratios, it is necessary to restrict the angular spectrum of transmitted ions to avoid implanting ions beneath the masking layer.

[0022] 8. Minimizing filter wear due to sputtering effect

[0023] 9. Avoiding channeling effects (lattice induction effects) by arranging filters relative to the ion beam.

[0024] 10. Realization of complex dopant depth profiles using simple filter shapes.

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

[26] . This can lead to a positive or negative charge on the filter.

[0026] Simultaneously, secondary electrons with high kinetic energy can be generated by ion bombardment at the front or back of the filter.

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

[0028] The distance between the filter and the substrate in an ion accelerator (under high vacuum) is typically a few centimeters or less. That is, the diffusion of thermionic electrons (from thermionic emission) and the action of fast electrons (from ion bombardment) can alter the measurement of ion current on the substrate, for example, due to a Faraday cup installed there.

[0029] 12. Alternative manufacturing methods by injection molding, casting, or sintering References [2] to

[15] propose microtechnical methods for the manufacture of energy filters. In particular, they describe the use of lithography in combination with wet chemical etching or dry chemical etching for the manufacture of filters. For the manufacture of filters, an anisotropic wet chemical etching method using an alkaline etching solution (e.g., KOH or TMAH) on silicon is preferred.

[0030] In the case of filters manufactured by the method described last, the functional filter layer is made from single-crystal silicon. Therefore, when bombarded with high-energy ions, it must always be assumed that the channeling effect will, in principle, affect the effective energy loss within the filter layer in a way that is difficult to control.

[0031] 13. Arrangement for irradiating a stationary substrate Irradiation equipment should be used that allows for the irradiation of stationary material under energy filtering with high lateral homogeneity across the entire surface of the substrate. Reason: The terminal station of the irradiation system often does not have the full mechanical capability to scan the entire wafer (wafer wheel) with a point-like or nearly point-like beam spot. Conversely, many systems have, for example, an electrostatically expanded beam (= x-strip) that electrostatically scans the wafer (in the y-direction). In some cases, a partially mechanical scanner is used, i.e., the beam is expanded in the x-direction and the wafer is mechanically moved (slowly) in the y-direction.

[0032] 14. Arrangement for utilizing a large filter surface An irradiation device must be used that irradiates a stationary or movable substrate under energy filtering with high lateral homogeneity across the entire surface of the substrate, and that enables such irradiation over a larger filter surface. This reduces the effects of thermal and degradation on the filter.

[0033] 15. Modification of the doping profile within the substrate by a sacrificial layer. Energy filters are tools for manipulating doping profiles within a substrate. Under certain conditions, it is desirable to manipulate the doping profile generated within the substrate after the energy filter, i.e., downstream of the energy filter. In particular, it is desirable to "push" the beginning of the doping profile near the surface away from the substrate. This can be especially advantageous when the beginning of the dopant profile within the substrate cannot be precisely controlled by the filter for various reasons (particularly ion loss due to scattering). Such manipulation of the doping profile after the energy filter can be achieved by injection into a sacrificial layer on the substrate.

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

[0035] 17. Adapting profile transitions between several injection profiles For certain applications, it is desirable to join two or more profiles together along a "seam" at a certain depth, otherwise insulation exists between the layers. This problem arises particularly in layer systems that include a concentration "tail" where the lower end of the upper doping profile or the upper end of the lower doping profile tapers gently.

[0036] 18. Special arrangement of the multifilter concept for coupled oscillatory motion If the multifilter is mounted on a portion of a movable substrate chamber that can move linearly back and forth in front of the beam (for example, in the vertical scanning direction in the case of a rotating wafer disk), the multifilter can easily move relative to the beam simply by moving the substrate chamber. By using a magnetic or static scanning device that scans in one direction in front of the filter, a very large multifilter surface can be used, for example, equal to the product of the vertical vibration distance and the horizontal scanning distance. The motion 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" lines onto the wafer. As a result of the above arrangement, for example, the position of a horizontal irradiation line on the wafer is coupled to a vertical position on the multifilter. Gaps between individual filter elements result in, for example, non-uniformly doped lines on the wafer. Therefore, the arrangement of filter components in a multifilter must be selected so that lateral homogeneity is ensured despite the coupling of the linear motion of the filter and the substrate.

[0037] Examples of energy filters, injection devices, or components of injection devices 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.

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

[0039] Figures 4 and 5 show examples of the geometric and mechanical configuration of a filter frame. The filter held therein can have any desired surface structure selected according to the desired doping profile obtained with it. The filter holder and / or filter frame may be provided with a coating to prevent material abrasion from the filter frame and filter holder.

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

[0041] Figure 4 shows a cross-sectional view of a filter frame for holding an energy filter chip. The energy filter chip, also shown in Figure 4, can be attached to the frame by various means, such as using adhesive or mechanical springs. Figure 5 shows a top view of a filter frame for holding an energy filter element, also shown in Figure 5. The filter frame includes a locking element that allows the frame to be opened and closed to allow for filter replacement. Figure 6 shows an example of the installation of a frame for holding an energy filter element within the beam path of an ion implanter. Shown at the top of Figure 6 is a cross-section through the chamber wall and the filter holder positioned within it. In this example, the filter holder is positioned on the inner surface of the chamber wall, i.e., the side facing the wafer (not shown) during the implantation process. The ion beam passing through the opening in the chamber wall and the filter positioned in front of the opening during the implantation process is also schematically shown in Figure 6. The frame with the filter chip inserted into the filter holder covers the opening in the chamber wall through which the ion beam passes during the implantation process. This is shown at the bottom of Figure 6, which also shows a front view of the chamber wall with the filter holder attached.

[0042] The frame can be constructed from 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 from a material different from the filter material, such as metal. In this case, the filter can be inserted into the frame. In another example, the frame includes a monolithic frame and at least one additional frame made of a material different from the filter material attached to the monolithic frame. This additional frame is, for example, a metal frame.

[0043] As explained and illustrated above, and as shown on the right side of Figure 7, a frame can completely enclose a filter. In additional examples, the frame may not form a boundary around all (four) edges of the filter, but rather around only three, two (opposite), or one of the filter's edges. Therefore, in relation to this explanation, the term “frame” should be understood as both a three-dimensional frame that completely encloses the filter on all edges, and a partial frame that extends only around some of the filter's edges. Examples of such partial frames are also shown in Figure 7. Thus, Figure 7 shows various partial frames (left side of the figure) and a complete frame (right edge 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] An energy filter or any other scattering element can be mounted in the beam path of the injection device in various ways by its frame, which can be achieved according to one of the embodiments described above. Inserting the frame into the filter holder as described above is just one of several possibilities. Further possibilities are described below.

[0045] As shown in the example in Figure 8, the frame can be attached to the chamber wall using at least one bar. In this case, at least one bar functions as a filter holder. Figure 8 shows examples of attachment with one bar, two bars, and three bars. It is also clear that it is possible to use three or more bars.

[0046] As shown in another example in Figure 9, the frame can also be attached to the chamber wall by suspension brackets or suspension elements. These suspension elements are, for example, flexible and can be mounted between the frame and the chamber wall to ensure the frame is held firmly in place. In this example, the suspension elements function as filter holders. Figure 9 shows examples of mounting with one suspension element, two suspension elements, and three suspension elements. Of course, it is also possible to have three or more suspension elements.

[0047] In another example shown in Figure 10, the frame with the filter is held in a floating (non-contact) manner by magnets. For this purpose, magnets are attached to the front and rear 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 force, the frame floats between the magnets attached to the chamber wall and the magnets attached to the holder. The magnets on the filter frame can be realized, for example, by thermal deposition or any other layering method.

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

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

[0050] In other words, it has been proposed to decompose the desired doping profile into, for example, box profiles, and generate a triangular filter structure for each box profile. Then, the individual filter tips are mounted on a frame, for example, as shown in Figure 6.5.1, such that the area weighting corresponds to the appropriate dopant concentration for the box profile element in question. See Figure 6.5.4.

[0051] The decomposition of the dopant depth profile is not limited to the triangular structure shown here. Conversely, it can include additional structures, most commonly including slopes or convex or concave rising sides. The sides do not necessarily have to rise monotonically, but can also include valleys or depressions. A binary structure with a 90° flank angle is also conceivable.

[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 of eliminating the need for adhesive bonding between filters to block ions at the filter edges. Furthermore, this allows for optimal use of the irradiated surface. For the same overall filter dimensions and a given ion current, this has the effect of increasing wafer throughput.

[0053] Figure 11 shows a simple implementation of a multifilter. In this example, three filter elements of different shapes are combined within the frame of a filter holder to form a complete energy filter. The upper left of Figure 11 shows a cross-sectional view of the filter holder with the three filter elements, and the lower left of Figure 11 shows a top view of the filter holder with the three filter elements. The right side of Figure 11 shows the filter profile obtained with the coupled filter. When this filter is used as an injection filter, the ion beam passes uniformly through all of the individual filter elements, thus generating 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 arises from one of the three subfilters shown on the left, i.e., the subfilter identified by the same number.

[0054] Figure 12 illustrates, as an example, how three different filter elements, when combined, function as a multifilter. The figure shows the cross-sections of each individual filter element, examples of their dimensions, and doping profiles that can be obtained using the individual filter elements. In Figure 12, only the dimensions are shown for a fourth filter element (not shown) as an example. The weighting, i.e., the resulting concentration or doping profile, can be adjusted by changing the dimensions of the surface area of ​​the individual filter elements. In this example, we assume, though not necessarily, that the filter and substrate have the same energy-dependent stopping power. Figure 13 shows an example of a doping profile obtained when the four filter elements described based on Figure 12 are combined to form a multifilter and used for embedding. This sum profile results from the sum of the weighted filter elements across the surface in question. In this figure, we assume that the filter elements described based on Figure 12 are assembled with appropriate weighting to form a complete filter, uniformly exposed to an ion beam of appropriate primary energy, thus obtaining the shown sum profile.

[0055] In the example described based on Figure 11, the individual filter elements of the multifilter are separated from each other by a web of frames. As shown in another example in Figure 14, individual filter elements can also be directly adjacent to each other. Figure 14 shows a cross-sectional view of a multifilter with several adjacent filter elements F1, F2, F3. The multifilter is inserted into a filter frame. In this example, the individual filter elements F1, F2, F3 are cut diagonally and placed directly adjacent to each other.

[0056] Point 3. High-throughput cooling system combined with filter movement High wafer throughput for a given target doping can only be achieved by high ion current. Since approximately 20% to 99% of the ion beam's primary energy is deposited in the filter film, i.e., the portion of the injection filter through which the beam passes, the use of cooling methods has been proposed to prevent the filter temperature from rising excessively, even with high ion current.

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

[0058] a. Coolant flow within the filter holder This allows the heated filter tip to be cooled by heat dissipation. Figure 15 shows an example of such a cooled filter holder. Of particular note is a cross-section through a filter holder mounted on the chamber wall of an ion implanter. In this example, coolant lines are incorporated into the filter holder that houses the filter frame. Liquid coolant is supplied to these coolant lines by an external cooling device (not shown). Alternatively, or in addition to this, the coolant lines may be located on the surface of the filter holder (not shown).

[0059] b. Movement of the filter or ion beam For example, when using a rotating wafer wheel loaded with 10 to 15 wafers, it has been proposed that the filter or filter holder be configured to vibrate in rotational or linear motion. Alternatively, the ion beam can move electrostatically over the filter while the filter remains stationary.

[0060] In these modifications, the filter is only partially irradiated by the ion beam per unit time. As a result, the portion of the filter that is not irradiated at a particular moment is cooled by radiative cooling. Therefore, it is 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 time. Therefore, the unirradiated areas can be cooled by radiative cooling. This embodiment can also be configured as a multi-filter, i.e., a filter containing several different filter elements, as described above. In the example shown, the filtered frame vibrates in a direction perpendicular to the direction of the ion beam, which is shown schematically. Since the area of ​​the filter covered by the ion beam is smaller than the total area of ​​the filter, only a portion of the filter is irradiated per unit time. This portion changes continuously as a result of the vibrational motion.

[0062] Figure 17 shows an example of a filter arrangement with several filter elements supported by a rotating filter holder. Each individual filter element can be constructed in the same way, but they can also have different structures to obtain a multi-filter. As shown in Figure 17, each filter element traverses a circular path centered on the rotation axis (central axis) of the holder as the holder rotates. In this example as well, only partial irradiation per unit time occurs. That is, not all filter elements are irradiated simultaneously, so the unirradiated filter elements can be cooled.

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

[0064] For simple doping curves (e.g., homogeneous doping) that start from the surface of the substrate and require only simple protrusion structures, a simplified design and, consequently, a simplified manufacturing process are proposed here.

[0065] It is proposed that the microstructure film of the filter (e.g., a protruding structure) be configured to have flat areas on the protrusions instead of sharp points, and that the thickness of the film's support layer be dimensioned so that the formed low-energy dopant peaks are pushed into the filter's support layer and thus not embedded in the substrate. An example of this type of filter is shown in Figure 18. 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 are shown. As illustrated, a rectangular profile can be generated in the substrate by implanting ions into the energy filter using a trapezoidal prism-shaped structure. The initial peak is embedded in the energy filter; that is, there are no peaks in the dopant profile within the substrate. This implanted profile has the advantageous characteristic of starting immediately at the surface of the substrate, which can be extremely important for the application of energy filters.

[0066] As can be seen from the cross-section of the filter in Figure 18, this filter structure includes flat areas instead of sharp points. Therefore, the individual structural elements have a trapezoidal cross-section. This greatly simplifies the process technology required to realize the filter. For example, it is known that triangular structures can be generated in silicon by wet chemical etching using KOH or TMAH. For this purpose, the tips of the triangles must be masked by lithography. When manufacturing a complete chip, this leads to the problem that etching may penetrate under the lacquer or hard mask structure. Without the idea proposed here, this problem can only be solved by a perfect (and therefore complex and costly) process. The idea proposed here greatly simplifies the manufacturing of the filter structure. This also applies to modern plasma-assisted etching methods such as RIBE (Reactive Ion Beam Etching) and CAIBE (Chemically Assisted Ion Beam Etching).

[0067] Point 5. High lateral homogeneity of the manufactured dopant region or defect region. Lateral homogeneity can be important in static injection scenarios. When a rotating wafer disk (wafer wheel) is used with, for example, 11 wafers and a stationary ion beam, homogeneity 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, when the energies of the filter and ions are adjusted so that very low-energy ions (nuclear stationary state) exit the filter, large-angle scattering events occur, resulting in a wide angular distribution. When the energies of the filter and ions are adjusted so that only high-energy ions (electron state only, dE / dxelectron > dE / dxnuclear) exit the filter, the angular distribution is very narrow.

[0069] The minimum distance is characterized by the fact that the filter structure is not transferred to the substrate. That is, for example, given a given distribution of scattering angles of transmitted ions, these ions travel a transverse distance at least equivalent to the period of the lattice constant of the ion filter.

[0070] The maximum distance is determined by the loss of scattered ions, which can still be tolerated by the application of a given distribution of scattering angles, particularly at the edges of semiconductor wafers.

[0071] Figure 19 shows the results of an experiment in which ions were implanted through an energy filter during static implantation into a PMMA (methyl polyacrylate) substrate. Since the ions disrupt the molecular structure of PMMA, the subsequent development process reveals the energy distribution of the ions by dissolving the regions of high-energy deposition. Regions with low or no ion-induced energy deposition are not dissolved by the developer.

[0072] The idea proposed here is to generate high lateral doping homogeneity by precisely selecting the filter-substrate distance for both dynamic and static injection 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 filter degrades as a function of the accumulated injected ion dose.

[0074] When the critical ion dose is reached, the chemical composition, density, and shape of the filter are modified so that the impact on the resulting target profile can no longer be ignored. The critical ion dose depends on the filter material used, the type, energy, and shape of the ions implanted, and the acceptable range of variation (=specification) of the target profile.

[0075] Therefore, for each filter injection process using a given energy, ion species, profile, etc., specifications can be defined, including the maximum temperature and maximum permissible cumulative ion dose during injection. For example, the use of energy filters is provided to be monitored so that the filters are not used outside the specified permissible range, even when not being monitored by a technician. For this purpose, it is proposed that as soon as a filter is inserted into a filter holder on the injection device, each filter is detected based on an electronically readable signature, and this signature is read, for example, by a control computer. For this purpose, the signature is stored in electronically readable memory placed on the filter. The database stores, for example, the signatures of filters that can be used in a given injection device, the process to which the filter is applied (ion species, energy), and characteristics such as what cumulative dose and what maximum temperature is permissible to reach. 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 injection process.

[0076] Figure 20 shows a monitoring system for identifying filters and monitoring whether they comply with filter specifications (maximum temperature, maximum cumulative ion dose). Once a filter is identified by built-in sensors (charge integrator and temperature sensor), the filter's cumulative dose and temperature are continuously measured, for example. The injection process terminates when one of the specified parameters is reached or exceeded, i.e., when the filter becomes too hot or when the maximum permissible dose has been injected through the filter. That is, when a particular value no longer meets the specifications, a signal is sent to the control computer, which terminates the injection process.

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

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

[0079] Various examples are shown in Figures 21 to 25. Figure 21 shows a cross-sectional view through the chamber wall of the injection apparatus in the region of the beam aperture, a filter holder into which the filter is inserted and fixed to the chamber wall, and a collimator mounted on the side of the filter holder facing away from the chamber wall in this example. 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 and pass through the collimator. Segments of the ion beam emitted at a relatively large angle will hit the wall of the collimator and will not pass through it. If the available distance between the filter into which ions are implanted and the substrate is not sufficient for the desired aspect ratio, the collimator can also be composed of several collimator units having smaller apertures 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 top of the filter element. This type of element can be manufactured as a monolith or by microbonding. Figure 22 shows two examples of collimator structures placed directly on a filter. Since the collimator structure can act as a cooler with a surface area larger than the surface area of ​​the filter, this type of collimator structure placed directly on the filter can mechanically stabilize the filter and also have a cooling effect. Here, the maximum angle α is also defined by the aspect ratio of the individual collimator structures placed on the filter, each including length and width. The collimator structure can be attached to the filter, for example, by bonding using adhesive or by some similar method.

[0081] In the example shown in Figure 22, the collimator structure is positioned on the structured side of the filter, i.e., where the filter has raised and recessed areas. In this example, the structure is trapezoidal. Figure 23 shows a variation of the arrangement in Figure 22. In this example, the collimator surface is positioned on the unstructured side of the filter. In both cases, the collimator structure is positioned downstream of the filter with respect to the direction of the ion beam (indicated by arrows in Figures 21 and 22), and therefore the ion beam passes through the collimator structure only after passing through the filter.

[0082] Figure 24 shows top views of collimator structures in various examples. In the illustrated examples, the collimator structure is placed on a filter that has a lamellar structure when viewed from above. Each “filter lamellae” may have a triangular or trapezoidal cross-section, as already described above. However, the lamellar structure of the filter is just one example. Other types of filter structures mentioned above can also be used. Figure 24 shows examples on the left and in the center where the collimator structure is configured in strips; that is, it includes multiple parallel strips extending across the entire width of the filter. Each pair of adjacent strips forms a collimator, and the width of this collimator is determined by the distance between adjacent strips. The length of the collimator is determined by the height of the individual strips. The “height” of the strips is a dimension in the direction perpendicular to the plane of the drawing. The strips of the collimator structure may be perpendicular to the filter lamellae, as shown on the left side of Figure 24, or parallel to the lamellae, as shown in the center. On the right side of Figure 24, an example is shown where the collimator structure appears as a grid in the top view, resulting in the formation of multiple collimators whose geometric shapes are determined by the geometric shape of the grid. In the illustrated example, the individual collimators are rectangular, or more specifically square, in the top view, as the collimators are in the form of rectangular tubes. However, this is only one example. The grid can also be realized such that the individual collimators are circular, elliptical, or hexagonal (honeycomb-like) or have any other desired polygonal shape in the plan view.

[0083] Collimation by a hard mask on the target substrate In the case of masked injection, it is possible to apply masking to the target wafer to act as a collimator structure instead of, or in addition to, a collimator on the filter. The condition for this masking is that the stopping power of the masking must correspond to at least 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 constraints on the angular distribution are 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 described earlier and, therefore, depending on the layout of the substrate structure and the required maximum angular distribution, it may be, for example, lamellar, strip-shaped, tubular, or honeycomb-shaped. 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 lateral scattering but also the depth profile. This is shown in Figure 26, which displays the doping profiles of three different injection methods, each performed with the same filter but with a different collimator structure. In this example, each filter has a lamellar structure with a trapezoidal cross-section. However, this is just one example. On the left side of the figure, an injection method is shown in which injection is performed without a collimator structure. The injection profile obtained in this way starts at the surface of the substrate.

[0085] The center and right sides of Figure 26 show implantation methods in which implantation is performed on a collimator structure, with the aspect ratio of the collimator structure in the right example being higher than in the center example. As can be seen from the figure, the doping profiles obtained by these implantation methods start not on the surface of the substrate, but rather at a certain distance from it, and the higher the aspect ratio, the further the doping profile is from the surface and the flatter the rise. This is explained by the fact that the dopant profile in the region near the surface of the substrate is caused by ions that are more strongly stopped in the filter and therefore have lower energies. Such low-energy ions are scattered more strongly by the filter than high-energy ions, and low-energy ions have a wider angular distribution than high-energy ions. Therefore, the number of low-energy ions that can pass through the collimator structure is less than the number of high-energy ions, and the larger the aspect ratio of the collimator structure, the more pronounced the effect becomes and the smaller the maximum angle that ions can still allow to pass through the collimator structure.

[0086] Despite the collimator structure, the filter can be designed so that low-energy ions are "preferred" to generate a nearly homogeneous doping profile starting from the surface. That is, more low-energy ions pass through the filter than higher-energy ions. An example of this type of filter is shown in Figure 27. In this example, the filter has different filter regions, each with a maximum and minimum thickness. The maximum thickness is the same in all three regions, but the minimum thickness is different. This is achieved in the example by having trapezoidal structures in each of the individual regions, placed on bases with different heights or thicknesses, and therefore the heights of the trapezoidal structures are different. In the first section, the base is thinnest and the trapezoidal structure is tallest, resulting in the largest distance CD1 between adjacent structures in this section. In the third section, the base has the largest thickness and the trapezoidal structure is shortest, resulting in the smallest distance CD3 between adjacent structures in this section. 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 structure 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. Individual sections can be the same size in terms of their surface area, but they can also be different in size. It is also clear that it is possible to provide three or more sections with different minimum filter thicknesses.

[0087] Figure 27 shows on the left the implantation profile obtained by implantation using the filter described above, when implantation is performed without a collimator structure. This implantation profile starts at the surface, but the doping concentration decreases stepwise with increasing depth. In this figure, CD1 shows the region of the doping profile attributable to the first section of the filter, CD2 shows the region of the doping profile attributable to the second section of the filter, and CD3 shows the region of the doping profile attributable to the third section of the filter. Based on the doping profile, it can be seen that the thicker the minimum base thickness of the relevant section, the less depth the ions passing through the filter region in question penetrate into the substrate, i.e., their energy decreases. The doping profile also shows that more low-energy ions pass through this filter than high-energy ions. As mentioned above, low-energy ions are scattered more strongly than high-energy ions, and therefore fewer low-energy ions pass through the collimator structure than high-energy ions; thus, a nearly homogeneous doping profile starting from the surface can be obtained by using such a filter in combination with a collimator structure. This is shown on the right side of Figure 27, illustrating the implantation method using the described filter and collimator structure. The collimator structure in this example is placed on a circuit board, but it can also be placed on a filter.

[0088] Point 8. Reduction of filter wear due to sputtering effect. The injection configuration of the filter relative to the substrate: in some cases, the protrusions face the substrate, and in other cases, the protrusions face away from the substrate (→ sputtering, scattering during impact). Between the injection methods described above and those described below, the filter can be used in each case such that the microstructure of the filter faces the substrate, i.e., away from the ion beam as shown in Figure 28(a). Alternatively, the filter can be rotated so that the microstructure of the filter faces away from the substrate, i.e., towards the ion beam, as shown in Figure 28(b). The latter can have a favorable effect on the sputtering effect.

[0089] Point 9. Avoiding channeling by positioning filters relative to the ion beam. filter and / or substrate tilt As long as the filter and / or substrate are made of crystalline material, undesirable channeling effects can occur. That is, ions can achieve an increased range along a particular crystal direction. The magnitude and acceptance angle of the effect are functions of temperature and energy. The injection angle and crystallographic surface orientation of the starting materials used for the filter and substrate play an important role. In general, channeling effects cannot be reliably reproduced across the entire wafer because the above parameters may differ from wafer to wafer and from one injection system to another.

[0090] Therefore, channeling must be avoided. Channeling can be prevented by tilting the filter and substrate. Channeling in the filter or substrate can have a completely different effect on the depth profile of the injected dopant, especially when the filter and substrate are made of different materials.

[0091] Figure 29 schematically shows a filter tilted relative to the substrate during the injection process such that the base surface of the filter forms an angle greater than zero with the substrate surface. This angle is, for example, greater than 3°, greater than 5°, or greater than 10° but less than 30°. In particular, when the energy filter is manufactured from anisotropic material, it is possible to prevent or reduce the channeling effect in this way.

[0092] Point 10. Realizing complex dopant depth profiles with simple filter shapes. As described above, more complex dopant depth profiles can be achieved by adapting the geometric design of the filter elements. For the sake of simplicity in the following explanation, all types of scattering effects will be ignored.

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

[0094] For example, when silicon is used as the substrate material to be doped with boron, and the energy filter is constructed of a different material, the change in the dopant depth profile within the substrate is obtained in accordance with the change in the filter density and dE / dx as a function of the actual kinetic ion energy. A perfectly homogeneous, i.e., constant change in depth-direction doping is achieved only when the same material is used for both the filter and the substrate. This is shown in Figure 31, which illustrates the doping profiles for various substrate materials (target materials) obtained by the same implantation process, i.e., an implantation process with the same primary ions and the same primary energy. In each case, the filter material was silicon. The doping profiles differ as a result of the different substrate materials.

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

[0096] It has been proposed to adapt the energy-dependent changes in stopping power to a given surface shape, for example, by designing a filter as a multilayer system.

[0097] It is proposed that the change in stopping power as a function of ion energy (i.e., as a function of the vertical position on the filter protrusion with respect to a given ion species and primary energy) be modeled by the incident position on the filter (more precisely, the actual path of the ions through the filter and substrate) so that the total loss of kinetic energy is obtained overall (i.e., from the incidence of ions on the filter to the endpoint of the irradiated substrate). Thus, the energy loss in the filter is determined not only by the irradiated length of the filter material, but also by the position-dependent change in stopping power.

[0098] Therefore, using appropriate modeling and fixed geometry, it is possible to generate doping curves that increase or decrease in the depth direction, for example. Thus, the stopping power becomes a function of the lateral position. Examples of such filters are shown in Figures 33 to 35. In each of these figures, the lateral position is indicated by "y".

[0099] Figure 33 shows a multilayer starting material for a multilayer filter. In this embodiment, the starting material includes four different layers, shown as 1-4. However, the use of four layers is only an example. It is also possible to use fewer 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 for two layers to contain the same material and be separated by two or more layers made of different materials. The individual layers can be sequentially deposited or generated on top of each other by an appropriate deposition method.

[0100] With a proper configuration of layered stacks of materials having different stopping powers, complex dopant depth profiles can be realized even with simple filter geometry. Figure 34 shows a cross-section of a filter realized based on the starting material fabricated in Figure 33, and in the illustrated example, includes a base and triangular structures placed 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 they may be part of a pyramidal structure.

[0101] As shown in Figure 35, the filter may be realized such that several structures are arranged adjacent to each other in the lateral direction (y-direction), and these structures include stacked stacks having different geometric shapes and / or different layered stacks, i.e., stacks having different structures with respect to the individual layers and / or the sequence of materials in each layer. For example, six different materials are used in the illustrated filter, and these layers are shown as 1 to 6.

[0102] The selection is not limited to these materials, but for example, silicon, silicon compounds, or metals are suitable as materials for individual layers. Examples of silicon compounds include silicon carbide (SiC), silicon dioxide (SiO2), and silicon nitride (SiN). Suitable metals include, for example, copper, gold, platinum, nickel, and aluminum. In one example, at least one layer of silicon compound is grown on a silicon layer, and a metal layer is deposited from the gas phase on at least one layer of silicon compound. The metal layer can also be deposited directly onto the silicon layer. To obtain filters with different layers, it is also possible to fabricate various metal layers on each other by deposition.

[0103] Point 11: Electron suppression During the transmission of ions through a solid, it is known that electrons of the primary beam either remain in the solid or are absorbed by the ions. That is, depending on the properties of the filter material and the primary energy, the transmitted ions have, on average, higher or lower charge states after passing through the filter

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

[0104] Figure 36 shows the equilibrium charge state of ions as a function of the kinetic energy of ions in response to 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 surfaces 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), thermionic electrons are generated as a function of the temperature and work function of the filter material. This is shown in Figure 37, which illustrates the heating of the energy filter by ion bombardment. The curve shown is based on an experiment in which the filter was irradiated with high-energy carbon (C) ions of 6 MeV. In this case, the filter was an opaque energy filter [2].

[0106] The distance between the filter and the substrate in an ion accelerator (under high vacuum) is typically a few centimeters or less. Therefore, for example, the measurement of ion current on the substrate using a Faraday cup mounted therein is altered by the diffusion of thermionic electrons (from thermionic emission) and the action of fast electrons (from ion bombardment).

[0107] As mentioned earlier, from a filter perspective, both electron generation (primary ion stripping) and electron emission processes exist. Therefore, the potential of an implemented electrically isolated filter is not well defined. On the contrary, it changes during the injection process as a function of ion current, vacuum conditions, temperature, etc. A net negative charge promotes electron emission, while a net positive charge tends to suppress it. Various methods to prevent such charging are described below.

[0108] (a) Energy filter element at a specified (positive) potential It has been proposed that the energy filter be designed and mounted so that the filter is always at a specified 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 within the filter frame is held at a specified (positive) potential relative to the filter holder to suppress secondary electrons. The filter frame is connected to a voltage source and electrically isolated from the filter holder and the chamber wall of the injection device.

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

[0110] The maintained potential can be selected, for example, so that electron emission from the filter is completely suppressed, and therefore only the (positive) charge of the transmitted ion current is measured in a Faraday cup adjacent to or on the substrate. Typical values ​​for such (positive) potentials range from tens of volts to several thousand volts.

[0111] If the energy filter is highly ohmic due to its material composition, it has been proposed that the filter be provided with a thin, highly conductive layer on one or both sides, having a thickness ranging from a few nanometers to 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 to the side away from the substrate) does not cause any harmful contamination to the injected substrate material. For processing SiC substrates, this layer can be made of carbon, for example.

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

[0113] To reduce 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 so that thermionic emission does not occur as much as possible at a given temperature. The work functions of several elements are shown in Figure 39

[25] , Materials Science Poland, Vol. 24, No. 4, 2006. In particular, materials with work functions 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 during the filter design. Care must be taken to ensure that the applied layer (even if applied to a surface away from the substrate) does not cause any harmful contamination to the injected substrate material.

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

[0116] (a) In one example, it is provided that wet chemical anisotropic etching, which requires single-crystal material for manufacturing by a typical microtechnology process, can be replaced with dry chemical etching, meaning that polycrystalline or amorphous starting material is used for the filter film. Due to its material structure, the resulting filter exhibits improved properties with respect to channeling.

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

[0118] One advantage of using the method described above is that single-crystal filter films are typically not obtained, and therefore channeling is suppressed. Another advantage is the very wide range of available filter film materials. For example, the use of sintered SiC filter films is particularly advantageous for producing homogeneous doping profiles on SiC substrates.

[0119] Another advantage is that by using the molding method described above, the manufacturing cost of numerous filter elements can be significantly reduced compared to the manufacturing cost using microtechnology.

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

[0121] Point 14. Arrangement to utilize a large filter surface area. (a) Arrangement in which the entire filter surface is active Figure 41 shows an arrangement for energy filter injection (i.e., injection by energy filter) in which the beam area is enlarged by appropriate means and the irradiated filter surface area is larger than the substrate surface area. As a result, the substrate can be fully irradiated and a large filter surface can be used. The diameter of the irradiated filter area is larger than the diameter of the substrate. The substrate may be static or movable. This arrangement makes it possible to use a large filter surface (=reducing the effects of filter degradation and thermal effects) and ensures that the entire surface of the substrate is irradiated. The use of this type of arrangement is particularly advantageous when the required filter structure is "large". Doping high-voltage Si-IGBTs or Si power diodes with protons requires a penetration depth of more than 100 μm. Therefore, for this application, a filter structure with a "projection height" of >100 μm must be provided. Such a filter structure can be manufactured very easily with sufficient mechanical stability, even for large substrates (e.g., 6-inch or 8-inch).

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

[0123] (b) Arrangement in which a portion of the filter surface is inactive Initially, the same configuration described in Section 14(a) is used. This configuration involves expanding the beam area by appropriate means, resulting in an energy filter injection setup where the irradiated filter surface is larger than the substrate surface. Nevertheless, the entire filter surface is not active here. Conversely, only a portion of the filter surface is active. This means that the filter consists of an array of numerous filter elements, for example, in the form of strips. These filter elements can be manufactured monolithically from the substrate by, for example, an appropriate manufacturing process. The other (inactive) portion of the filter surface is used to stabilize the filter film. This portion is where the ion beam casts shadows. Therefore, in this configuration, either the substrate or the filter must be moved to compensate for the shadowing effect. This configuration allows for the use of a large filter surface (= reduction of filter degradation and thermal effects) and ensures that the entire substrate is irradiated. Figure 42 shows a filter with an inactive portion and accompanied by unidirectional mechanical scanning.

[0124] Point 15. Modification of the doping profile within the substrate by the sacrificial layer. Furthermore, since a sacrificial layer with appropriately selected thickness and stopping power can be applied to the substrate, the implanted profile is shifted in the depth direction within the substrate in the desired manner. This type of sacrificial layer can also be used for masked ion implantation (see Figure 43) and unmasked ion implantation. In particular, this method makes it possible to "push" undesirable beginning portions of the doping profile from the substrate into the sacrificial layer, i.e., to embed the beginning portions of the profile into the sacrificial layer.

[0125] Figure 43 shows the modification of the doping profile within the substrate resulting from the sacrificial layer in the case of masked and energy-filtered implantation. In this example, the beginning of the implantation profile is pushed into the sacrificial layer. This principle can be used in contrast to Figure 43, as in the case of unmasked and energy-filtered ion implantation, i.e., implantation without a masking layer.

[0126] Point 16. Lateral modification of the doping profile within the substrate by the sacrificial layer. By applying a sacrificial layer appropriately selected relative to the substrate, with appropriate stopping power and thickness variations on the wafer surface, the implantation profile can be shifted as desired in the depth direction within the substrate as a function of the lateral position on the wafer. This type of sacrificial layer can be used for both masked and unmasked ion implantation (see Figure 44). In particular, variations in the implantation depth of 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 within the substrate by a sacrificial layer in the case of unmasked and energy-filtered ion implantation. Here, the lateral modification of the implantation depth is achieved by changing the thickness of the sacrificial layer laterally. This principle can be used analogously to masked and energy-filtered implantation.

[0128] Point 17. Adapting profile transitions between several injection profiles. Two or more doping profiles can be skillfully superimposed, resulting in a desired overall doping profile, particularly in the overlapping region. This technique is especially advantageous for multilayer growth and doping. A typical example involves the growth of several SiC epitaxial layers and their energy-filtered doping. Good interlayer contact must be ensured.

[0129] Point 18. Special arrangement of the multifilter concept with coupled vibrational motion By using a clever arrangement, lateral homogeneity of the ion distribution can be achieved despite the coupled vibrational motion of the filter and substrate, i.e., despite the absence of relative vertical movement between the filter and substrate. This type of arrangement is shown in Figure 45. The wafer is guided by the rotation of a wafer wheel in the x-direction behind the substrate. An ion beam (not shown) is extended, for example, in the x-direction and scans the entire multi-filter surface by the vertical vibrational motion of the injection chamber. The filter surface consists of an active filter region and an inactive holder region. Arrangement (A) is an undesirable arrangement. Considering the irradiated filter surface for y1 and y2, three filters are irradiated for y1, and no filters are irradiated for y2. As a result, a laterally heterogeneous stripe pattern is obtained on the wafer. Arrangement (B) shows a possible example of a better arrangement. Two filters are irradiated for both y1 and y2. This applies to all y. As a result, laterally homogeneous doping is achieved on the wafer surface.

[0130] As shown in Figure 45, the vertical movement of the filter and substrate in the y-direction is coupled. The wafer is guided along the x-direction behind the filter by the rotation of a wafer wheel. An ion beam (not shown) is extended, for example, in the x-direction and scans the entire multi-filter surface by the vertical vibrational motion of the injection chamber. The filter surface consists of an active filter region and an inactive holder region. Arrangement (A) is a rather undesirable arrangement. Considering the irradiated filter surface for y1 and y2, three filters are irradiated for y1, and no filters are irradiated for y2. As a result, a transversely heterogeneous stripe pattern is obtained on the wafer. Arrangement (B) shows a possible example of a better arrangement. Two filters are irradiated for both y1 and y2. This applies to all y values. As a result, transversely homogeneous doping is achieved on the wafer surface.

[0131] Point 19. Surveillance Another embodiment is intended to address the problem of monitoring critical parameters of ion implantation that have been altered by an energy filter. Such parameters include, for example, the minimum or maximum "projection range," the depth concentration distribution determined by the geometric shape of the filter, and the (energy-dependent) angular distribution. Monitoring of other parameters, such as the ion-implanted ion species, may also be useful. In particular, monitoring must be possible on the wafer to which the ions are implanted, or (simultaneously) on (multiple) structures near the wafer. According to one embodiment, monitoring should be performed without requiring any 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, changes in refractive index, overall absorption (wavelength range dependent on the measuring instrument), and overall transmission and reflectance (wavelength range dependent on the measuring instrument).

[0133] In one embodiment, the arrangement of the mask and substrate material is provided for monitoring the above-mentioned implantation parameters. The arrangement of the mask and substrate material is (1) placed in an appropriate position on the implantation surface, e.g., on a wafer wheel, and (2) changes in their optical properties as a result of ion implantation, for example, in an "as-implanted" manner, i.e., without requiring 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 target substrate material is also optically sensitive to ion radiation, the target substrate (e.g., 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 ion irradiation. Therefore, the depth of the altered structure after ion irradiation (or etching rate or resulting etching shape, etc.) can be considered a measure of the injected ion dose.

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

[0137] According to one embodiment, detection should proceed based on changes in optical properties. This type of implementation is described below. If monitoring frequently fails to occur on the target substrate to be injected, the implementation of a separate monitoring structure is proposed. The monitoring structure consists of the arrangement of appropriate substrate materials having one or more mask structures. Examples are shown in Figures 47 and 48.

[0138] As shown in Figure 46, one or more monitoring structures (monitoring chips) are placed in a suitable location, such as on a wafer wheel. Reading of the monitoring chips is performed, for example, after injection without further post-processing. In some cases, it is necessary to remove the mask from the monitoring substrate for readout measurements. According to one embodiment, the mask is reusable.

[0139] The mask material and substrate material of the monitoring chip can also consist of different materials. Criteria for selecting the mask material include, for example, compatibility with the target substrate material (to eliminate contamination caused by sputtering effects). Another criterion is the stopping power of high-energy ions, which allows for the fabrication of mask structures with high aspect ratios.

[0140] It is also possible to manufacture the mask material and substrate material of the monitoring chip from the same material. The mask and substrate can also be manufactured monolithically. In this case, it is usually impossible to reuse either the mask or the substrate.

[0141] Performance and evaluation of mask structures after ion implantation: 1. Ion implantation performance modified by energy filters 2. Mask removal is possible but not always necessary, because readout measurements can also be performed by reflection from the back of the substrate.

[0142] 3.Optical measurement a. Absorption spectrum, wavelength-resolved b. Transmission spectrum, wavelength-resolved c. Reflectance, wavelength-decomposed d. Simple overall absorption, i.e., not wavelength-resolved. e. Simple overall transmission, i.e., unresolved wavelengths. f. Measurement of the change in refractive index Change in polarization of g. 4. Comparison with a calibration curve or reference standard, and determination of whether the injection process was carried out as expected.

[0143] By 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 a test to determine whether the injection dose is correctly set on the machine side.

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

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

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

[0148] Changes in optical properties arise solely from locally injected ion doses and the resulting intrinsic defects.

[0149] For example, ions that pass only through depth region III at ion concentration C1 (Figure 51) (so as to reach concentration region C2) do not cause any further change in optical properties.

[0150] More precisely, such changes in optical properties can be observed in PMMA as a result of, for example, electronic cessation.

[0151] • This is not a problem in principle regarding the possibility of evaluation, but it is excluded in the examples of Figures 51 and 52 for the sake of simplification.

[0152] The mask structure shown or described in Figure 50 is configured as "inclined surfaces" or continuous inclinations, i.e., staggered in thickness and number, depending on the desired depth resolution. Therefore, for the maximum thickness, the following applies as an example: "mask thickness" > Rp,max The lateral dimensions of individual structures can range from square micrometers to square millimeters to square centimeters, depending on the requirements of the reading device.

[0153] Point B. Monitoring of maximum projection range Figure 53 shows a structure suitable for monitoring the maximum projected range.

[0154] Similar structures using the evaluation procedure 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 generate energy-dependent spectra of ion angles after passing through the filter.

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

[0157] Therefore, the resulting angular distribution is a function of the filter's geometry, the change in its geometry over its lifespan, the occurrence of channeling effects, the ion species used, the primary energy, the maximum and minimum energies of the resulting transmitted ions, and the geometric arrangement within the implantation chamber. By monitoring the angular distribution, it is possible to track all of these parameters.

[0158] For monitoring individual parameters, different mask structures are proposed that can be placed within the monitoring chip, as illustrated and explained in Figures 55 to 58.

[0159] It should be noted that, for evaluating angular distribution, the only important factor is often the aspect ratio of the mask structure.

[0160] Therefore, the size of the opening in a mask structure for a thin mask that is slightly thicker than the maximum projection range of the mask material can be in the range of micrometers or submeters.

[0161] Such monitoring structures are preferably arranged as an array of numerous individual structures so that an overall optical evaluation (i.e., 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 opening can be in the millimeter or centimeter range. In these cases, it is also possible to evaluate individual structures that are not arranged in the array without special technical effort.

[0163] Proposed mask structure: 1. Fixed mask thickness, various mask opening shapes → change in aspect ratio; 2. Variable mask thickness, fixed geometry of mask opening → change in aspect ratio; 3.1 and 2 combination; 4. The directional dependence of the angle distribution can be monitored by arranging multiple arrays (or individual structures) consisting of 1, 2, or 3 different angles.

[0164] A circular arrangement is also a possibility.

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

[0166] The core of the last embodiment described above lies in the fact that (essential) dose-dependent changes in the (preferred) optical parameters of the material are used for "as-injected" monitoring of the energy filter injection process. As a result, by optical measurements (e.g.), the resulting injection can be monitored as completely as possible with respect to its most important parameters without requiring complex post-processing (e.g., application of annealing and metal-to-metal contact).

[0167] Therefore, it becomes possible to detect defective injections inexpensively and quickly, and to sort out the affected wafers.

[0168] Figure 59 shows a clever fit of profile transitions between two injection profiles A and B, and the resulting overall concentration profile can, for example, produce a desired homogeneous profile. This may be particularly advantageous (though not necessarily) for a two-layer system as shown in this figure. A proposed realization by the following series of processes: (1) The step of doping the lower layer (injection B), (2) Steps to develop the upper levels, (3) The step of doping the upper layer. The possibility of forming a high-energy tail of injection A is limited, but the low-energy tail of injection B can be affected, in particular by the introduction of a sacrificial layer, as described in "Point 15: Modification of the doping profile in the substrate by a sacrificial layer".

[0169] The following is a proposed implementation through a series of processes: (1) Steps to increase the number of victims, (2) The step of doping the lower layer (injection B), (3) Step of removing the sacrificial layer, (4) Steps to develop the upper levels, (5) The step of doping the upper layer.

[0170] The concepts described above enable the development of valuable injection methods for manufacturing in the semiconductor industry, i.e., economically applicable injection methods in industrial production processes. The concepts described here enable the realization of complex vertical doping concentration curves in a highly flexible method (multi-filter concept) with a low angular distribution of implanted ions, in addition to homogeneous doping achieved by a simple triangular filter structure. In particular, all types of doping concentration curves can be approximated by the use of a triangular filter structure combined with a collimator structure. Another important aspect concerns the suppression of artifacts that alter ion current measurements on the substrate.

[0171] In conclusion, it should be reiterated that the measures described above (points 1-19) can be applied individually or in any desired combination of each other. For example, the described "end of life" detection can be applied to filters mounted on a frame, but it can also be applied to filters mounted in other ways.

[0172] The wafers described above may also be semiconductor wafers, but they can also be made from other injection 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. The process includes the step of irradiating the surface region of the wafer with an ion beam using an injection device. The injection device is filter frame and A method for 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, wherein the filter includes at least one filter element which is a film with a microstructure, and the filter has a surface region irradiated by the ion beam.

2. The method according to claim 1, further comprising the steps of arranging a monitoring structure near the wafer and performing injection into the monitoring structure.

3. The injection device further includes a collimator structure irradiated by the ion beam, The method according to claim 1, wherein the collimator structure is positioned in the beam transmitted after the filter.

4. An implantation device for implanting ions from an ion beam into a target substrate, Filter frame and, The filter frame includes a filter held in the aforementioned filter frame, The aforementioned filter is a film with a microstructure, and the implantation device is arranged and configured such that it is irradiated by the ion beam that passes through the filter and is directed toward the target substrate.

5. The injection device further includes a collimator structure irradiated by the ion beam, The injection device according to claim 4, wherein the collimator structure is positioned in the beam transmitted after the filter.

6. The injection device according to claim 4, wherein the filter frame is held in a filter holder.

7. The injection apparatus according to claim 5, wherein the collimator structure is positioned on the filter holder in the beam transmitted after the filter.

8. The injection device according to claim 5, wherein the collimator structure comprises a plurality of collimator units arranged in a predetermined pattern.

9. The injection device according to claim 8, wherein the collimator unit forms a lamellar or grid-like shape when viewed from above.

10. The injection device according to claim 8, wherein the collimator unit has a rectangular, circular, elliptical, hexagonal, or other polygonal shape when viewed from above.

11. The injection device according to claim 8, wherein at least one of the collimator units comprises a tube having a length and a width, the ratio of the width to the length being less than 1, less than 2, less than 5, or less than 10.

12. A wall having an opening, A filter holder having a receiving portion is arranged in the region of the opening in the wall, A filter frame that is received in the receiving portion of the filter holder, An implantation system for implanting ions into a target substrate, comprising: a filter held in the filter frame, the filter configured to be irradiated by an ion beam passing through the filter.

13. The injection system according to claim 12, wherein the filter holder comprises a cooling device incorporated within or positioned on the filter holder.

14. The injection system according to claim 13, wherein the cooling device comprises at least one coolant line.

15. The injection system according to claim 12, further comprising an ion beam deflection system positioned in front of the opening.

16. The filter holder is configured to hold the filter frame in a non-contact manner. The injection system according to claim 12, wherein the filter holder comprises at least one magnet for holding the filter frame.

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