Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/02—Details
  • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
  • H01J37/05—Electron or ion-optical arrangements for separating electrons or ions according to their energy or mass
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
  • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
  • G21K1/025—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed radiation
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
  • G21K1/10—Scattering devices; Absorbing devices; Ionising radiation filters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/02—Details
  • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
  • H01J37/147—Arrangements for directing or deflecting the discharge along a desired path
  • H01J37/1472—Deflecting along given lines
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/3002—Details
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/317—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/317—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation
  • H01J37/3171—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation for ion implantation
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/317—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation
  • H01J37/3171—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation for ion implantation
  • H01J37/3172—Maskless patterned ion implantation
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/002—Cooling arrangements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/04—Means for controlling the discharge
  • H01J2237/047—Changing particle velocity
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/04—Means for controlling the discharge
  • H01J2237/047—Changing particle velocity
  • H01J2237/0475—Changing particle velocity decelerating
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/05—Arrangements for energy or mass analysis
  • H01J2237/057—Energy or mass filtering
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/30—Electron or ion beam tubes for processing objects
  • H01J2237/317—Processing objects on a microscale
  • H01J2237/31701—Ion implantation
  • H01J2237/31705—Impurity or contaminant control
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/30—Electron or ion beam tubes for processing objects
  • H01J2237/317—Processing objects on a microscale
  • H01J2237/31701—Ion implantation
  • H01J2237/31706—Ion implantation characterised by the area treated
  • H01J2237/3171—Ion implantation characterised by the area treated patterned
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/30—Electron or ion beam tubes for processing objects
  • H01J2237/317—Processing objects on a microscale
  • H01J2237/31701—Ion implantation
  • H01J2237/31706—Ion implantation characterised by the area treated
  • H01J2237/3171—Ion implantation characterised by the area treated patterned
  • H01J2237/31711—Ion implantation characterised by the area treated patterned using mask

Definitions

• the invention relates to an implantation arrangement with an energy filter (implantation filter) for ion implantation and its use and an implantation method.
• any materials such as semiconductors (silicon, silicon carbide, gallium nitride) or optical materials (LiNb03)
• doping or the generation of defect profiles in any materials can be achieved with predefined depth profiles in the depth range from a few nanometers to several 100 micrometers.
• Figure 1 illustrates the basic principle of an energy filter: a monoenergetic ion beam is modified in its energy as it passes through a microstructured energy filter component, depending on the point of entry. The resulting energy distribution of the ions results in a modification of the depth profile of the implanted substance in a substrate matrix.
• FIG. 2 shows on the left a wafer wheel on which substrates to be implanted are fixed. During processing / implantation, the wheel is tilted by 90 ° and rotated. The wheel is thus “described” in concentric circles by the ion beam indicated in green with ions.To irradiate the entire wafer surface, the wheel is moved vertically during the processing.
• Figure 2 shows a mounted energy filter in the region of the beam exit.
• FIG. 3 shows a schematic illustration of different doping profiles (doping concentration as a function of the depth in the substrate) for differently shaped energy filter microstructures (a) triangular prismatic structures produce a rectangular doping profile, (b) smaller triangular prismatic structures produce a less deeply distributed doping profile, (c) trapezoidal prismatic structures produce a rectangular doping profile with a peak at the beginning of the profile, (d) pyramidal Structures produce a triangular-shaped doping profile rising into the depth of the substrate
• FIG. 4 shows a cross-section of a filter frame for receiving an energy filter chip
• Figure 5 shows a plan view of a filter frame for receiving an energy filter element with closure element and mounted energy filter
• FIG. 6 illustrates a typical installation of a frame for receiving an energy filter element in the beam path of an ion implanter.
• the filter holder is disposed on one side of the chamber wall. In the example, this side is the inside of the chamber wall, that is, the side that faces the wafer (not shown) during implantation.
• the inserted into the filter holder frame with the filter chip covers the opening of the chamber wall through which occurs during implantation of the ion beam.
• Figure 7 shows a sub-frame (left in the figure) and full-frame (far right in the figure), each of which may be the same (e.g., monolithic) and / or other material than the energy filter.
• Figure 8 illustrates attachment of the filter frame with filter or any other passive scattering element through one or more webs.
• Figure 9 illustrates a mounting of the filter frame with filter or any other scattering element by a single or multiple suspension.
• Figure 10 illustrates a mounting of the filter frame with filter or any other scattering element by magnetic fields.
• FIG. 11 illustrates a simple realization of a multifuser.
• Three differently shaped filter elements are combined in a frame for filter holder to a whole energy filter.
• the ion beam sweeps all individual filter elements evenly.
• the dopant depth profile shown on the right thus arises.
• This profile contains three subprofiles numbered 1, 2, and 3. Each of these sub-profiles results from one of the three sub-filters shown on the left, from the sub-filter provided with the corresponding number.
• FIG. 12 illustrates a detailed illustration of the multifilter concept.
• On the left three filter elements are shown as examples. Four elements are numerically described. Each filter element results in a dopant depth profile for a given ion species and primary energy. The weighting, i. the resulting concentration is adjustable by the dimensioning of the surfaces of the individual filter elements. For the example, it was assumed that the filter and substrate have the same energy-dependent deceleration capability. In general, however, this is not the case.
• FIG. 13 shows a summation profile which results if all the filter elements described in FIG. 12 are combined with suitable weighting to form an overall filter and uniformly swept over by an ion beam of suitable primary energy.
• FIG. 14 shows an exemplary arrangement of individual filter elements in a multifilter.
• the individual elements Fl, F2, F3, etc. shown there are cut obliquely and are mounted directly on each other.
• FIG 15 shows a filter assembly incorporated in an ion implantation facility.
• the filter holder which accommodates the filter frame, cooling lines are integrated, which are supplied by an external cooling unit with coolant.
• the cooling lines could also be arranged on the surface of the filter holder (not shown).
• FIG. 16 shows an energy filter with a large area, which is only partially irradiated per unit of time.
• the non-irradiated areas can cool by radiation cooling.
• This embodiment is also configurable as a multifilter as described above. That is, as a filter having a plurality of different filter elements.
• the frame oscillates with the filter in a direction perpendicular to the beam direction of the ion beam.
• the area of the filter covered by the ion beam is less than the total area of the filter, so that only part of the filter is irradiated per unit of time. This part is constantly changing due to the pendulum movement.
• FIG. 17 shows a further embodiment of an arrangement of energy filters which rotate about a central axis. Also, only partially irradiated per unit time and the unirradiated elements can cool.
• This embodiment can also be designed as a multifilter.
• Figure 18 illustrates schematically a "shift of the peak.”
• Figure 19 shows how ions are implanted through an energy filter during a static implantation into a PMMA substrate.
• the ions destroy the molecular structure of the PMMA.
• a subsequent development process exposes the energy distribution of the ions. Areas of high energy deposition are removed. Areas less or without energy deposition by ions are not dissolved in the developer solution.
• FIG. 20 shows a control system for identifying the filter and for monitoring compliance with the filter specification (maximum temperature, maximum accumulated ion dose).
• Figure 21 shows a collimator structure which is fixed to a filter holder.
• the aspect ratio determines the maximum angle a.
• the collimator may also consist of a plurality of co-juxtaposed collimator units with a smaller opening. These may e.g. be arranged honeycomb
• Figure 22 shows a collimator structure which is constructed directly on the filter.
• the aspect ratio determines the maximum angle a.
• the filter is placed in back sides to front side configuration in ion beam.
• the collimator acts in an advantageous embodiment mechanically stabilizing on the filter and improves cooling due to the increased surface of the Fiterchips by radiation.
• Figure 23 shows collimator structure which is constructed directly on the filter. The aspect ratio determines the maximum angle a. In the example, the filter is placed in front to backside configuration in the ion beam.
• Figure 24 shows a collimator structure which is constructed directly on the filter.
• the collimator structure can be lamellar, strip-shaped, tubular or honeycomb-shaped - depending on the layout of the filter and the required maximum angular distribution.
• Figure 25 shows a collimator structure which is constructed directly on the target substrate.
• the collimator structure can be lamellar, strip-shaped, tubular or honeycomb-shaped - depending on the layout of the substrate structure and the required maximum angular distribution.
• Figure 26 illustrates doping profiles obtained with the same filter but different collimator structures.
• FIG. 27 illustrates doping profiles obtained by means of a multifilter during implantation with and without collimator structure.
• Figure 28 illustrates schematically "inverting the filter", (a) the filter is used in a regular array, ie the microstructures are pointing away from the beam, (b) the filter can be turned over, ie the microstructures face towards the beam Effects on sputtering effects in the filter.
• Figure 29 illustrates schematically a "tilting of the filter.” If the energy filter is made of anisotropic materials, the channeling effect can occur, which can be prevented by tilting the energy filter.
• FIG. 30 schematically shows various doping profiles (doping concentration as a function of depth in the substrate) for differently shaped energy filter microstructures (each shown in side view and top view), (a) triangular prismatic structures produce a rectangular doping profile, (b) smaller triangular prismatic structures produce a less depth distributed doping profile, (c) Trapezoidal prismatic structures produce a rectangular doping profile with a peak at the start of the profile. (d) Pyramidal structures produce a triangular-shaped doping profile rising into the depth of the substrate.
• FIG. 31 shows different target profile shapes with the same primary ion and the same primary energy, due to different target materials.
• the filter material is silicon in each case.
• Figure 32 illustrates the course of deceleration as a function of energy [4] (SPJM simulation).
• Figure 33 illustrates the starting material of a simple multilayer filter. Filter materials with suitable deceleration capability are sequentially stacked by suitable deposition techniques.
• FIG. 34 illustrates how, with a suitable configuration of the layer stack of materials with different deceleration properties, complex dopant depth profiles can be realized even with a simple filter geometry (here: strip-shaped triangles).
• Figure 35 illustrates a generalized construction of an energy filter, materials 1-6 and with different geometries of the individual filter structures.
• Figure 36 illustrates equilibrium charge states of an ion (black line:
• Figure 37 illustrates the heating of an energy filter by ion bombardment; 6MeV C ions in energy filters that are not transparent for these conditions [2].
• FIG. 38 shows an embodiment of a filter arrangement in which the filter in the filter frame is held at a defined (positive) potential with respect to the filter holder for the purpose of suppressing secondary electrons.
• Figure 39 illustrates work functions of some elements. [25] Materials Science-Poland, Vol. 24, no. 4, 2006
• FIG. 40 shows an arrangement for an energy-filter implantation in which an ion deflection system in front of the filter and a suitable distance between filter and substrate (typically schconce in the range of a few cm to a few m), the complete irradiation of a static substrate is achieved.
• FIG. 41 shows an arrangement for an energy filter implantation in which the larger surface of the energy filter can be used to achieve complete irradiation of the substrate compared to the substrate and a large filter surface is used.
• the irradiated filter area diameter is larger than the substrate diameter.
• Figure 42 illustrates a partially active one-way mechanical scan filter.
• FIG. 43 illustrates a modification of the doping profile in the substrate by means of a sacrificial layer in the case of a masked, energy-filtered implantation.
• the beginning of the implantation profile is pushed into the sacrificial layer.
• This principle can be used analogously for unmasked, energy-filtered ion implantation.
• FIG. 44 illustrates a lateral modification of the doping profile in the substrate by means of a sacrificial layer in the case of an unmasked, energy-filtered ion implantation.
• the lateral depth modification is due to the laterally different thickness of the sacrificial layer.
• the principle can be used analogously for masked, energy-filtered implantations.
• FIG. 45 illustrates a coupling of vertical movements in the y direction of the filter and the substrate.
• the wafers are guided by the rotation of the wafer wheel in the x-direction behind the substrate along.
• the ion beam (not shown) is, for example, widened in the x direction and is scanned by the vertical oscillating movement of the implantation chamber over the complete multifilter surface.
• the surface consists of active filter areas and inactive mounting areas.
• the arrangement shown in A) is an unfavorable arrangement. Considering the irradiated filter surface for yl and y2, 3 filters are irradiated at yl while no filter is irradiated at y2. As a result, a laterally inhomogeneous fringe pattern is obtained on the wafer.
• the arrangement shown in B) is a possible example of a better arrangement.
• 2 filters each are irradiated. This is true for all y.
• a laterally homogeneous doping over the wafer surface is achieved.
• FIG. 46 shows a wafer wheel with an arrangement of wafers to be irradiated, as well as monitoring structures between the wafers.
• FIG. 47 shows a monitoring mask with an exemplary arrangement of different ion beam transparent or partially transparent mask structures Mal-MalO.
• FIG. 48 shows a cross section through a monitoring mask and a monitoring material.
• Figure 49 shows an exemplary concentration depth profile made by an energy filter.
• FIG. 50 shows an example of a mask structure for monitoring the depth-dependent dose distribution.
• FIG. 51 illustrates the control of the implantation process by monitoring structures.
• Figure 52 illustrates the control of the implantation process by monitoring structures.
• FIG. 53 illustrates a monitoring of the maximum projected range.
• Figure 54 illustrates a mask structure.
• Figure 55 illustrates another example of a mask structure.
• Figure 56 illustrates another example of a mask structure.
• FIG. 57 illustrates a mask structure for monitoring asymmetric angular distributions.
• Figure 58 illustrates various arrangements of mask structures for detecting ion beam distributions in different directions.
• FIG. 59 illustrates the adaptation of a profile transition of two implantation profiles A and B in a skilful manner, so that the resulting overall concentration profile can, for example, produce a desired homogeneous profile.
• This can (but does not have to) be advantageous, in particular in the case of layer systems comprising 2 layers, as in the picture shown here.
• the design of the high-energy tail of implant A leaves only limited possibilities, but the low-energy tail of implant 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 sacrificial layer” a realization with the following process sequence: 1) growing sacrificial layer 2) doping the lower layer (implant B) 3) removing the sacrificial layer 4) growing the upper layer 5) doping the upper layer.
• FIG. 1 shows a method known from [7] for producing a depth profile.
• an implantation of an ion beam into a substrate takes place through a structured energy filter in an installation for ion implantation for the purpose of wafer processing.
• the resulting energy distribution of the ions leads to a modification of the depth profile of the implanted substance in the substrate matrix.
• This depth profile which is rectangular in the illustrated example, is also shown in FIG.
• FIG. 2 shows a system for ion implantation.
• This system includes an implantation chamber (implantation chamber) in which multiple wafers can be placed on a wafer wheel.
• the wafer wheel rotates during the implantation, so that the individual wafers repeatedly pass through a beam opening in which the energy filter is arranged and through which the ion beam passes into the implantation chamber, and thus into the wafers.
• the wafer wheel is shown, on which the substrates to be implanted are fixed.
• the wheel is tilted by 90 ° and rotated.
• FIG. 3 shows, by way of example, layouts or three-dimensional structures of filters in order to illustrate in principle how a multiplicity of different dopant depth profiles can be generated by a suitable choice of the filter.
• 3 filter profiles shown can be combined with each other to obtain more filter profiles and thus Dotiertiefenprofile.
• cross-sections of the energy filter in the left-hand illustrations in each case
• plan views of the energy filters and progressions of the doping concentration achieved over the depth (as a function of the depth) of the wafer are shown.
• the "depth" of the wafer is a direction perpendicular to the surface of the wafer being implanted.
• triangular-prismatic structures cause a rectangular doping profile
• smaller triangular-prismatic structures have a less profound rectangular doping profile than in case (a) (ie, the depth of the profile can be adjusted across the sizes of the structures )
• trapezium prismatic structures have a rectangular doping profile with a peak at the start of the profile
• pyramidal structures have a triangular doping profile rising into the depth of the substrate.
• dopants such as Al, B, N, P. These are many orders of magnitude below the comparative values of, for example, silicon. Due to this fact, it has not been possible to date to provide doping regions, especially those with high aspect ratios, i. small ratio of floor area to depth, economical to realize.
• Dopant depth profiles in semiconductor wafers can be made by in-situ doping during epitaxial deposition or by (masked) monoenergetic ion implantation.
• in-situ doping high inaccuracies can occur.
• process-related on the wafer ie from center to edge signifi- to expect deviations from the target doping.
• this inaccuracy also extends to the vertical direction of the doping region, since now the local dopant concentration depends on a large number of process parameters such as temperature, local doping gas concentration, topology, width of the Prandtl boundary layer, growth rate, etc.
• the use of monoenergetic ion beams means that many individual implants have to be performed to obtain doping profiles with acceptable vertical ripples. This approach is only partially scalable, it is very economically unprofitable very quickly.
• Examples of the invention relate to the design of an energy filter element for ion implantation systems, so that this corresponds to the requirements resulting from the application of the energy filter element in the industrial production of semiconductor devices, in particular for devices based on SiC semiconductor material.
• Production conditions are defined with regard to the use of energy filter elements, for example by the following aspects:
• the energy filter is a highly fragile microstructured membrane whose nondestructive handling is difficult.
• Novel semiconductor devices such as superjunction devices or optimized diode structures require a non-uniform doping process.
• the simple energy filters described in [1-6] only produce constant profiles.
• More complicated filter structures, such as those described in Hinb [8] are technically very complex and, according to the prior art, difficult to realize for productive tasks. It turns the Task to realize complicated vertical profile shapes with uncomplicated, ie easy to produce filter structures.
• production conditions mean that ion implanters (typical terminal voltage at tandem accelerators> 1MV to 6MV) should produce more than typically 20-30 wafers with 6 "diameter and surface doses per wafer of approximately 2E13cm-2 per hour
• ion currents of more than ⁇ up to some ⁇ are used or power of more than a few watts, eg 6W / cm-2, is deposited on the filter (typical area 1-2 cm 2 ). This leads to the heating of the filter.
• the object is to cool the filter by suitable measures.
• Filter structures can be made by anisotropic wet chemical etching.
• the filter structures consist of suitably dimensioned triangular long lamellae (for example 6 ⁇ high, 8.4 ⁇ spacing, length a few millimeters), which are arranged periodically on a membrane as thin as possible.
• the production of pointed triangular lamellae is cost-intensive, since the wet-chemical anisotropic etching must be precisely adjusted. Peak, i. Non-trapezoidal lamellae are expensive, since etching rates and etching times must be precisely matched to one another for pointed lamellae.
• the energy filters for ion implantation described in the cited references [2], [3], [4], [5], [6], [7], [8], [9], [10] have an internal 3-dimensional Structure that leads to path length differences of the ions in transmission through the filter. These path length differences produce, depending on the braking capacity of the filter material, a modification of the kinetic energy of the transmitted ions. A monoenergetic ion beam is thus converted into a beam of ions of different kinetic energy. The energy distribution is determined by the geometry and the materials of the filter, ie the filter structure is transferred into the substrate by means of ion lithography.
• the total number of wafers processed with a specific filter should be monitored.
• the angular spectrum of the transmitted ions must be limited in order to avoid a "subimplantation" of the masking layer.
• Electrons of the primary beam can be emitted or absorbed in the solid state, ie the transmitted ions depend on the properties of the filter material and the primary energy. On average, after passage through the filter, they have a higher or lower charge state [26]. This can lead to positive or negative charging of the filter.
• ion bombardment on both the front and the back of the filter can generate secondary electrons with high kinetic energy.
• the energy filter will heat up, see Fig. 6.5.24. Due to thermionic electron emission (Richardson-Dushman law) thermal electrons are generated depending on the temperature and the work function of the filter material.
• the distance (in high vacuum) of the ion accelerator between filter and substrate is typically only a few centimeters or less. That by diffusion of thermal electrons (from thermionic emission) and by the action of fast electrons (from ion bombardment), the measurement of the ion current at the substrate, for example by a Faraday Cup attached there, is falsified.
• microtechnical processes are proposed for the production of the energy filter.
• lithographic processes in combination with wet-chemical or dry-chemical etching processes are used to produce the filters.
• the anisotropic wet chemical etching process is resorted to using alkaline etching media (e.g., KOH or TMAH) in silicon.
• the functional filter layer is made of single crystal silicon.
• An irradiation arrangement is to be used which allows to irradiate a static substrate with high lateral homogeneity over the entire substrate surface in an energy-filtered manner.
• y-direction electrostatically expanded beam
• Partly also partially mechanical scanners are in use, ie widening of the beam in the x-direction and mechanical (slow) movement of the wafer in the y-direction.
• the energy filter is a tool for manipulating the doping profile in the substrate. Under certain conditions, manipulation of the producible doping profile in the substrate AFTER the energy filter is desirable. In particular, a "pushing out" of the near-surface beginning of the doping profile from the substrate is desirable, which may be particularly advantageous if the beginning of the doping profile in the substrate can not be adjusted correctly by the filter for various reasons (in particular loss of ions due to scattering) Doping profile manipulation after the energy filter can be done by implantation in a sacrificial layer on the substrate.
• a laterally variable doping profile in the substrate is desirable.
• the change in the implantation depth of a homogeneous doping profile for edge terminations in semiconductor components could be advantageously used.
• Such a lateral adjustment of the doping profile can take place by means of a laterally variable thickness sacrificial layer on the substrate.
• a multifold is attached to the moving part of a movable substrate chamber which moves in front of the beam with a linear pendulum motion (eg in the case of a rotating wafer disk with a vertical scanning device), movement of the multipurpose relative to the beam can easily occur be achieved by the movement of the substrate chamber.
• a magnetic or static scanning device in front of the filter in one direction then a very large Multifilterfiumblee can be used, which results, for example, as a product of vertical pendulum distance and horizontal scan distance.
• the movement of wafer and filter are coupled in this arrangement, which can lead to problems with regard to lateral doping homogeneity.
• this frame can be designed in such a way that it can be inserted at the ion implantation installation into a suitable frame holder preinstalled there.
• the frame protects the energy filler, allows easy handling and ensures electrical and thermal dissipation or electrical insulation (see Figure 36).
• the frame can be made by the manufacturer of the filter elements with the filter chip equipped in a dust-free environment and delivered in a dust-free packaging to the ion implantation unit.
• FIGS. 4 and 5 show an example of the geometric and mechanical design of a filter frame.
• the filter held therein may have any desired surface structure selected according to the desired doping profile to be achieved thereby.
• the filter holder and / or the filter frame may be provided with a coating which prevents material removal from the filter frame and filter holder.
• Filter frames and filter holders can be made of metals, preferably stainless steel or similar. be prepared. During the implantation process sputtering effects in the local environment of the energy filter must be expected due to scattered ions, i. it must be expected with near-surface removal of frame and filter holder material. Metal contamination on the substrate wafer could be the undesirable consequence.
• the coating prevents such contamination, the coating being of a non-contaminating material. Which substances are non-contaminating depends on the properties of the target substrate used. Examples of suitable materials include silicon or silicon carbide.
• FIG. 4 shows a cross-section of a filter frame for receiving an energy filter chip.
• the energy filter chip also shown in FIG. 4, can be fastened in the frame in various ways, for example by means of adhesive bonding by means of a vacuum-resistant, temperature-stable and highly thermally conductive adhesive or by a mechanical spring.
• Figure 5 shows a plan view of a filter frame for receiving an energy filter element, which is also shown in Figure 5.
• the filter frame has a closure element, through which the frame for changing the energy filter can be opened and closed.
• Figure 6 illustrates an example of incorporation of a frame for receiving an energy filter element into the beam path of an ion implanter. Shown in the upper part of Figure 6 is a cross section through the chamber wall and the filter holder arranged thereon.
• the filter holder is arranged on the inside of the chamber wall, ie the side which faces the wafer (not shown) during implantation.
• the ion beam passing during the implantation through the aperture in the chamber wall and the filter arranged in front of the aperture is also shown schematically in FIG.
• the inserted into the filter holder frame with the filter chip covers the opening of the chamber wall, through which occurs during implantation of the ion beam. This is shown in the lower part of Figure 6, which shows a plan view of the chamber wall with the filter holder attached thereto.
• the frame can be made of the same material as the filter.
• the frame can be made monolithic with the filter and referred to as a monolithic frame.
• the frame can also be made of a different material, such as the filter, such as a metal.
• the filter can be inserted into the frame.
• the frame includes a monolithic frame and at least one other frame of a different material than the filter attached to the monolithic frame. This further frame is for example a metal frame.
• the frame may completely surround the filter as explained and shown above and as shown on the right in FIG.
• the frame does not adjoin all (four) sides (edges) of the filter, but adjoins only three, two (opposite) or only one of the edges of the filter.
• a full frame that completely surrounds the filter on the sides (edges), but also a sub-frame that surrounds the filter only partially on the sides to understand. Examples of such subframes are also shown in FIG.
• FIG. 7 shows various subframes (on the left in the illustration) and a full frame (on the far right in the illustration).
• These frames may each consist of the same (e.g., monolithic) and / or other material than the energy filter.
• the energy filter or any other scattering element can be fastened by its frame, which can be realized according to one of the examples explained above, in various ways in the beam path of the Implanter.
• the above-mentioned insertion of the frame into a filter holder is just one of several possibilities. Other options are explained below.
• the frame may be secured to the chamber wall by at least one land.
• the at least one web serves as a filter holder. Illustrated in FIG. 8 are examples of attachments with only one web, with two bars and three bars. Of course, more than three bridges can be seen.
• the frame may also be secured to the chamber wall by suspensions or suspension elements.
• suspension elements are, for example, flexible and can be stretched between the frame and chamber wall such that the frame is held firmly.
• the suspension elements act as filter holders in this example. Shown in Figure 9 are examples of one-hanger, two-hanger and three-hanger mounts. Of course, more than three suspensions can be seen.
• the frame with the filter is held by magnets in a floating (non-contact) manner.
• magnets are fixed to a front and a back of the frame and the chamber wall such that in each case a magnet on the chamber wall or a holder attached to the chamber wall opposite a magnet on the frame, in each case opposite poles of the opposite magnets facing each other. Due to the magnetic forces, the frame is held suspended between the magnets attached to the chamber wall and the holder, respectively.
• the magnets on the frame of the filter can be realized, for example, by thermal evaporation or any other layering method.
• any desired doping profile in a semiconductor material can be achieved by the geometric design of an energy filter for ion implantation systems.
• the decomposition of a doping depth profile is not limited to the triangular structures shown here, but it may be further structures, which contain in the most general case bevels or convex or concave rising edges.
• the flanks do not necessarily have to be monotonically increasing, but may also contain valleys and depressions. Binary structures with flank angles of 90 ° are also conceivable.
• the filter elements are cut out "diagonally" and placed directly next to one another. ⁇ br /> ⁇ br />
• the advantage of oblique cutting is that no adhesive bond between the filters is required to block off ions at the edge of the filter, and in this way, the irradiated surface can be optimally utilized Overall filter dimensions and given ion current increase wafer throughput.
• FIG. 11 illustrates an example of a simple realization of a multifilter.
• three differently shaped filter elements are combined in a frame of the filter holder into a complete energy filter.
• FIG. 11 a cross section through the filter holder with the three filter elements is shown at the top left and
• FIG. 11 at the bottom left shows a plan view of the filter holder with the three filter elements.
• a filter profile is shown, which can be achieved with the combined filter.
• the ion beam uniformly passes over all individual filter elements, so that the dopant depth profile shown on the right in FIG. 11 is reached.
• This profile contains three subprofiles numbered 1, 2, and 3. Each of these sub-profiles results from one of the three sub-filters shown on the left, from the sub-filter provided with the corresponding number.
• FIG. 12 exemplifies the mode of operation of three different filter elements which can be combined to form a multifilter.
• Each figure illustrates a cross section through the individual filter elements, exemplary dimensions of these filter elements and by dopant profiles, as achieved by the individual filter elements can be.
• For a fourth, not shown filter element only exemplary dimensions are given in Figure 12.
• the weighting, ie the resulting concentration or the doping profile is adjustable by the dimensioning of the surfaces of the individual filter elements.
• FIG. 13 shows an example of a doping profile which can be obtained if the four filter elements explained with reference to FIG.
• FIG. 14 shows a cross section through a multifilter, which has a plurality of adjacent filter elements Fl, F2, F3 and which is inserted into a filter frame.
• the individual filter elements Fl, F2, F3 are sawed obliquely in the example and arranged directly adjacent to each other.
• High throughputs of wafers can only be achieved with high target ionizations for given target dopings. Since between about 20% to about 99% of the primary energy of the ion beam in the filter membrane, i. are deposited in the irradiated part of the implantation filter, the use of a cooling method is proposed, thereby preventing an excessive increase in the temperature of the filter even at high ion currents.
• Such cooling can be achieved, for example, by one or more of the following under a. to c.
• the measures described are: a. Coolant flow in the filter holder.
• FIG. 15 shows an example of such a cooled filter holder. Shown is in particular a cross section a filter holder attached to a chamber wall of an implanter.
• cooling lines are integrated, which are supplied by an external cooling device (not shown) with cooling liquid.
• the cooling lines can also be arranged on the surface of the filter holder (not shown).
• the ion beam can be electrostatically moved across the filter while the filter is stationary.
• the filter is irradiated only partially by the ion beam per unit time. This allows the currently unirradiated part of the filter via radiation cooling. Thus, in continuous operation averaged higher current densities can be realized with a given filter. Examples of how this can be realized are shown in FIGS. 16 and 17.
• FIG. 17 illustrates an energy filter with a relatively large area, which is only partially irradiated per unit of time.
• the non-irradiated areas can cool by radiation cooling.
• This embodiment is also configurable as a multifold as described above. That as a filter, which has several different filter elements.
• the frame oscillates with the filter in a direction perpendicular to the beam direction of the ion beam, which is shown schematically.
• the area of the filter covered by the ion beam is less than the total area of the filter, so that only part of the filter is irradiated per unit of time. This part is constantly changing due to the pendulum movement.
• Figure 18 shows an example of a filter assembly having a plurality of filter elements held by a rotating filter holder.
• the individual filter elements can each have the same structure, but can also be structured differently in order to obtain a multifunction.
• the individual filter elements move on rotation of the holder in a circular orbit about the axis of rotation (central axis) of the holder.
• only partial irradiation takes place per unit of time, ie not all filmed teretti irradiated simultaneously, so that the non-irradiated filter elements can cool.
• FIG. Shown is a cross section (left in the figure), a plan view (in the middle) and an example of a doping profile that can be achieved by the illustrated filter.
• FIG. Shown is a cross section (left in the figure), a plan view (in the middle) and an example of a doping profile that can be achieved by the illustrated filter.
• a rectangular profile can be created in the substrate.
• the initial peak is implanted in the energy filter, i. There is no peak of the doping profile within the substrate.
• the implant profile has the advantageous property that it begins directly at the substrate surface, which may be of crucial importance for the application of the energy filter.
• this filter structure has plateaus instead of spikes, so that the individual structural elements are trapezoidal in cross section.
• the aspect of lateral homogeneity may be essential in static implantation situations.
• the homogeneity is determined by the rotational and translational movement of the wafer disc relative to the ion beam.
• Filter-Substrate Distance The angular distribution of the transmitted ions is energy-dependent. Are filters and energy of the ions coordinated so that u.a. very low energy ions (nuclear deceleration regime) leave the filter, the width of the angular distribution is large, since large angle scattering events are common. If the filter and the energy of the ions are coordinated so that only high-energy ions (only in the electronic regime, dE / dxeiekton> dE / dxnukiear) leave the filter, the angular distribution is very narrow.
• a minimum distance is characterized in that the structure of the filter is not transferred to the substrate, i. e.g. for a given scattering angle distribution of the transmitted ions, they cover at least one lateral distance comparable to the period of the lattice constant of the ion filter.
• a maximum distance is determined by the loss due to scattered ions which can still be tolerated by the application (semiconductor component) for a given scattering angle distribution, in particular at the edge of the semiconductor wafer.
• Figure 19 shows the result of an experiment in which ions were implanted through an energy filter during static implantation into a PMMA (polymethylacrylate) substrate.
• the ions destroy the molecular structure of the PMMA, so that a subsequent development process, the energy distribution of the ions exposed so that areas of high energy deposition are resolved. Areas less or without energy deposition by ions are not dissolved in the developer solution.
• the idea proposed here is to produce a high lateral doping homogeneity with correct selection of the filter-substrate distance for both dynamic and static implantation arrangements.
• the filter is changed in its chemical composition, its density and its geometry so that the effects on the target profile to be realized can no longer be neglected.
• a specification including a maximum temperature during implantation and a maximum allowable accumulated ion dose may be defined.
• the signature is stored for this purpose, for example, in an electronically readable, arranged on the filter memory.
• a database stores, for example, the signatures of the filter which can be used on a particular implanter and their properties, for example for which process (ion type, energy) the filter is suitable and which accumulated dose and which maximum temperature can be achieved.
• the control computer can thus determine whether the filter is suitable for a planned implantation process.
• Figure 20 illustrates a control system for identifying the filter and monitoring compliance with the filter specification (maximum temperature, maximum accumulated ion dose). If the filter is identified by the built-in sensors (charge integra- Tor and temperature sensor), for example, permanently measured the accumulated ion dose and the temperature of the filter. The implantation process is terminated when one of the specified parameters is reached or exceeded, for example, when the filter becomes too hot or the maximum permissible dose has been implanted through the filter. That is, if the specification is violated, a signal is sent to the control computer, which terminates the implantation process.
• the filter specification maximum temperature, maximum accumulated ion dose
• masking may be applied to the target substrate.
• the co-animation can be effected by striated, tubular, latticed or hexagonal structures with high aspect ratios. which are placed in the transmitted beam after the energy filter The aspect ratio of these structures defines the allowed maximum angle.
• FIG. 21 shows a cross-section of an implanter chamber wall in the region of the jet opening, a filter holder fastened to the chamber wall with an inserted filter and a collimator, which in the example is fastened to a side of the filter holder facing away from the chamber wall.
• An aspect ratio of the collimator determined by the length and width of the collimator determines the maximum angle ⁇ relative to the longitudinal direction of the collimator below which the ion beam can be radiated into the collimator to pass the collimator. Shares of the ion beam, which are irradiated at larger angles, end at the wall of the collimator, so do not pass it.
• the collimator may also consist of a plurality of collimator units having a smaller opening arranged side by side. These may e.g. be arranged honeycomb-shaped.
• the collimator structure can also be arranged directly on the filter element.
• the production of such an element can be monolithic or by microstructure. bond process.
• Two examples of such a collimator structure arranged directly on the filter are shown in FIG.
• Such a collimator structure arranged directly on the filter can mechanically stabilize the filter and also have a cooling effect, since the collimator structure can act as a heat sink with a larger surface compared to the filter.
• the maximum angle ⁇ is also defined here by the aspect ratio of the individual collimator structures arranged on the filter, which each have a length and a width.
• the collimator structure may be attached to the filter, for example, by gluing, bonding, or the like.
• the collimator structure is arranged on the structured side of the filter, that is to say where the filter has elevations and depressions.
• the structures are trapezoidal in this example.
• FIG. 23 shows a modification of the arrangement of FIG. 22.
• the collimator structure is arranged on the unstructured side of the filter.
• the collimator structure in the beam direction of the ion beam (which is symbolized by the arrow in FIGS. 21 and 22) is arranged after the filter, that is, such that the ion beam passes through the collimator structure after passing through the filter.
• FIG. 24 shows plan views of collimator structures according to various examples.
• This collimator structure is arranged in the illustrated examples on a filter which has a lamellar structure in plan view.
• the individual "filter blades" may be triangular or trapezoidal in cross-section, for example, as previously explained.
• a lamellar structure of the filter is but one example. Any other filter structures as discussed above may also be used.
• FIG. 24 each shows an example in which the collimator structure is strip-shaped, that is to say has a plurality of parallel strips which each extend over the entire width of the filter. By two adjacent strips a collimator is formed, wherein the width of this collimator is determined by the distance of the adjacent strips.
• the length of the collimator is determined by the height of the individual strips.
• the "height" of the strips is their dimension in a direction perpendicular to the plane of the drawing.
• the stripes of the collimator structure may be perpendicular to the fins of the filter, as shown on the left in Fig. 24, or may be parallel to the fins, as shown in the center.
• the collimator structure is lattice-shaped in plan view, thereby forming a plurality of collimators.
• whose geometry is determined by the geometry of the grid.
• the individual collimators are rectangular in plan view, in particular square, so that the collimators are rectangular tubes. But this is only an example, the grid can also be realized so that the individual collimators in plan view are circular, elliptical or hexagonal (honeycomb) or have any other polygonal geometry.
• a mask acting as a KoUimator structure can be applied to the target wafer on the filter.
• a condition for this masking may be that the slowing down of the masking must be at least equal to the mean range of the transmitted ion beam in the target substrate material.
• the aspect ratio of the masking can be adjusted accordingly.
• Figure 25 shows an example of such a co-imimotor structure disposed directly on the target substrate.
• This KoUimator minimalist can have any of the previously discussed geometries, so for example, be lamellar, strip-shaped, tubular or honeycomb structure - depending on the layout of the substrate structure and the required maximum angular distribution.
• the aspect ratio of this KoUimator minimalist is the ratio of height (h in Figure 25) to width (b in Figure 25) of the recesses of the KoUimator Design forming mask on the substrate.
• the KoUimator Modell affect not only the scattering in the lateral direction, but also the depth profile.
• Figure 26 shows the doping profiles for three different implantation procedures, each performed with the same filter but different collimator structures.
• the filter in each case has a lamellar structure with a trapezoidal cross section. But this is just an example.
• an implantation method is illustrated in which implanted without KoUimator Modell. The implantation profile obtained thereby begins at the surface of the substrate.
• the filter can be designed such that ions with low energy are "preferred", ie more ions with lower energy pass through the filter than ions with higher energy.
• An example of such a filter is shown in FIG.
• the filter has different filter areas, each having a maximum and a minimum thickness. The maximum thickness is the same in all three areas, but the minimum thickness is different. This is achieved in the example in that the filter in the individual regions each have a trapezoidal structure arranged on a base region, wherein the height of the base is different in thickness or the trapezoidal structures have different heights.
• the thickness of the base is lowest and the trapezoidal structure highest, whereby a distance CD1 between adjacent structures in this section is greatest.
• the thickness of the base is the largest and the trapezoidal structure is the lowest, whereby a distance CD3 between adjacent structures in this section is the smallest.
• the thickness of the pedestal is between the thickness in the first section and the thickness in the third section, correspondingly, a height of the trapezoidal structure in that section is between the height in the first section and in the third section and a distance CD2 between adjacent structures in this section between the distance CD1 in the first section and the distance CD3 in the third section.
• the individual sections can be the same size in relation to their area but also be different sizes. In addition, of course, more than three sections can be provided with different minimum filter thicknesses.
• FIG. 27 shows in the left part an implantation profile which, when implanted with the described filter, is obtained when implanting without a collimator structure.
• This implantation profile begins at the surface, but the doping concentration gradually decreases with increasing depth.
• CD1 denotes a portion of the doping profile caused by the first portion of the filter
• CD2 denotes a portion of the doping profile caused by the second portion of the filter
• CD3 denotes a portion of the doping profile passing through the third portion of the filter is caused. It can be seen from the doping profile that the ions passing through the respective filter region penetrate less deeply into the substrate, so that their energy is lower, the greater the minimum thickness of the base of the respective section.
• the doping profile shows that more low energy ions pass through this filter than high energy ions.
• using such a filter in conjunction with a collimator structure may approximate homogeneous and on the surface beginning doping profile can be achieved.
• This is shown on the right in Figure 27, in which an implantation method using the illustrated filter and a collimator structure is shown.
• the collimator structure is in the example on the substrate, but can also be arranged on the filter.
• Ad 8 Low filter wear due to sputtering effects
• Implantation arrangement of the filter to the substrate, once spikes to the substrate, once spikes away from the substrate (- sputtering, scattering on impact).
• the filter can be used in each case such that the microstructures of the filter face the substrate, ie point away from the ion beam, as shown in FIG. 28 (a).
• the filter may also be rotated so that the microstructures of the filter are remote from the substrate, that is, toward the ion beam, as shown in Figure 28 (b). The latter can have beneficial effects on sputtering effects in the filter.
• Ad 9 Prevention of channeling effects due to the arrangement of the filter to the ion beam Tilting the filter and / or the substrate
• the filter and / or substrate are made of crystalline material, unwanted channeling effects may occur. That Ions can achieve an increased range along certain crystal directions.
• the size of the effects and the acceptance angle are temperature and energy dependent.
• the implantation angle, as well as the crystallographic surface orientation of the starting material used for filter and substrate play a crucial role. In general, the channeling effect can not be reliably reproduced over a wafer, as the above mentioned. Parameters from wafer to wafer and from implantation plant to implantation plant.
• Channeling should therefore be avoided. Tilting the filter and substrate can prevent channeling. Channeling in the filter or in the substrate can each have completely different effects on the depth profile of the implanted dopant, in particular if filter and substrate consist of different materials.
• Figure 29 schematically shows a filter which is tilted relative to the substrate during the implantation process such that a base of the filter with an area of the substrate makes an angle greater than zero.
• This angle is for example greater than 3 °, greater than 5 ° or greater than 10 ° and less than 30 °.
• the energy filter is made of anisotropic materials, this can be a channeling effect prevented or reduced.
• FIG. 30 shows a schematic illustration of different doping profiles (doping concentration as a function of the depth in the substrate) for differently shaped energy filters, which are each shown in side view and top view.
• (a) triangular-prismatic structures produce a rectangular-shaped doping profile
• (b) smaller triangular-prismatic structures produce a less depth-distributed doping profile than the larger triangular-shaped structures shown in (a).
• (c) trapezium-prismatic structures produce a rectangular doping profile with a peak at the start of the profile; and
• pyramidal structures produce a triangular doping profile rising into the depth of the substrate.
• modified dopant depth profiles result in the substrate in the design of the energy filter with different materials, depending on the density and course of dE / dx as a function of the current kinetic ion energy.
• a perfectly homogeneous, i. a constant course of the doping in the depth is achieved only with identical materials for filter and substrate.
• the filter material was silicon in each case.
• the doping profiles differ due to the different substrate materials.
• FIG. 32 illustrates the course of the deceleration capability as a function of the energy [4] (SRIM simulation) for the various substrate materials which are the basis of the illustration in FIG.
• the braking power thus becomes a function of the lateral position. Examples of such filters are shown in FIGS. 33 to 35.
• the lateral position is denoted by y in these figures.
• Figure 33 illustrates a multilayer feedstock for a multilayer filter.
• This starting material in the example comprises four different layers, designated 1 to 4. But using four layers is just one example. It is also possible to use less than or more than four different layers.
• the individual layers can differ not only in terms of the material used but also in terms of their thickness. It is also possible that two layers have the same material and are separated by two or more layers of other materials. The individual layers can be sequentially deposited on each other by suitable deposition processes.
• Figure 34 shows a cross-section of a filter realized on the basis of the starting material prepared in Figure 33, which in the illustrated example has a pedestal and triangular structures arranged on the pedestal. These triangular structures may be elongate in strip form, ie in a direction perpendicular to the plane of the drawing, or may also be part of pyramidal structures.
• the filter can also be realized by arranging a plurality of structures in the lateral direction (y-direction) side by side, which have different geometries and / or different layer stacks, i. Have layer stack with different structure with respect to the sequence of individual layers and / or the material of the individual layers.
• the illustrated filter uses six different materials, designated 1-6.
• silicon, silicon compounds or metals are, for example, silicon carbide (SiC), silicon oxide (S1O2) or silicon nitride (SiN).
• Suitable metals are, for example, copper, gold, platinum, nickel or aluminum.
• at least one layer of a silicon compound is grown on a silicon layer and applied to the at least one layer of a silicon layer.
• Compound a metal layer is evaporated.
• a metal layer can also be vapor-deposited directly onto a silicon layer. It is also possible to produce different metal layers on top of each other by vapor deposition, to thereby obtain different layers of the filter.
• Figure 36 illustrates the equilibrium charge states of an ion (Black line: Thomas Fermi estimate, Blue line: Monte Carlo simulations, Red line: Experimental results) as a function of the kinetic energy of the ion when irradiating a thin membrane.
• Ion sulfur
• membrane carbon.
• the distance (in high vacuum) of the ion accelerator between filter and substrate is typically only a few centimeters or less. That by diffusion of thermal electrons (from thermionic emission) and by the action of fast electrons (from ion bombardment), the measurement of the ion current at the substrate, for example by a Faraday Cup attached there, is falsified.
• FIG. 1 shows a cross-section of a filter arrangement in which this is ensured.
• the filter is held in the filter frame, for the purpose of suppression of secondary electrons, with respect to the filter holder at a defined (positive) potential.
• the filter frame is in this case connected to a voltage source and electrically insulated from the filter holder and the chamber wall of the implanter.
• the electrical potential of the filter holder can be regulated. For example, such that regardless of the charge balance that results from the implantation process, a constant potential is set during implantation with respect to the potential of the substrates to be implanted or the ground potential. For this purpose, a regulated supply of positive or negative charge by a current source can take place.
• the potential to be set can, in particular, be chosen so that, for example, the emission of electrons from the filter is completely suppressed, and thus only the (positive) charge of the transmitted ion current is measured in the Faraday cup next to or on the substrate.
• Typical values for such a (positive) potential are between a few 10V and a few 1000V.
• the energy filter is very high due to its material nature, it is proposed to cover the filter with a thin highly conductive layer with a thickness of a few nanometers to several tens of nanometers on one or both sides.
• the stopping power of this layer must be included in the design of the filter in the overall balance of Stoppingpower. It is important to ensure that the applied layer (even when applied to the side facing away from the substrate) in principle no harmful Contaminations caused in the substrate material to be implanted.
• the layer may consist of carbon, for example, for processing SiC substrates.
• the stopping power of this layer should be included in the design of the filter in the overall balance of Stoppingpower. It is important to ensure that the applied layer (even when applied to the side facing away from the substrate) in principle causes no harmful contamination in the substrate material to be implanted.
• Ad 12 Alternative manufacturing methods by injection molding, casting or sintering
• Implantation filters can be made by microfabrication techniques, such as lithography techniques in combination with wet chemical or dry chemical etching techniques.
• anisotropic wet-chemical etching processes using alkaline etching media (e.g., KOH or TMAH) in silicon can be used for filter production.
• the functional filter layer is made of monocrystalline silicon.
• the manufacturing process when designing the manufacturing process as a typical microtechnical process, it is intended to rely on dry chemical etching processes and to use polycrystalline or amorphous starting material for the filter membrane instead of wet chemical anisotropic etching processes which require single crystalline material.
• the resulting filter structurally has improved properties in terms of channeling due to its material structure.
• the filter In another example, it is intended not to produce the filter with a typical microtechnical process sequence, but to use imprinting, injection molding, casting and sintering methods.
• the core idea is to apply the processes mentioned in such a way that a mold or a mold insert defines the final shape of the energy filter membrane.
• the selected filter material is now processed in a known manner for the particular method, i. in a soft state (imprint), liquid state (injection molding and casting) or granular state (sintering processes) brought by the given mold, the mold insert, the stamp, etc. in the required geometry.
• a further advantage is that the use of the aforementioned molding methods can greatly reduce the cost of producing a large number of filter elements compared to microtechnical production.
• Figure 40 shows an arrangement for implantation into a substrate by an energy filter. This arrangement comprises a deflection device for the ion beam, which is arranged in front of the filter.
• the deflection of the ion beam that can be achieved by this deflector is tuned to the distance between the filter and substrate (typically in the range of a few cm to a few m) that the substrate completely, that is irradiated on its entire surface for the purpose of implantation can be.
• Figure 41 illustrates an arrangement for energy filter implantation (ie, energy filter implantation) in which the beam area has been increased by appropriate means and the irradiated filter area is greater than the substrate area, thereby achieving complete irradiation of the substrate and a large filter area can be used.
• the irradiated filter area diameter is larger than the substrate diameter.
• the substrate may be static or mobile.
• the filter consists of an arrangement of a number of, for example, strip-shaped filter elements. These filter elements can be produced monolithically from a substrate, for example by suitable manufacturing processes.
• the other (non-active) part of the filter surface is used to stabilize the filter membrane. This part shadows the ion beam. Therefore, either the substrate or the filter must be moved in this arrangement to compensate for the shading effects.
• Figure 42 illustrates a partially active one-way mechanical scan filter.
• Ad 15 Modification of the doping profile in the substrate by sacrificial layer
• a sacrificial layer can be applied to the substrate, whose thickness and stopping power is selected in a suitable manner, so that the Implantationspro fil is displaced in its depth in the substrate in the desired manner.
• a sacrificial layer can be used for masked ion implantation (see Figure 43) or even for unmasked ion implantation.
• an undesired beginning of a doping profile can be "pushed out" of the substrate into the sacrificial layer by implanting the beginning of the profile in the sacrificial layer.
• FIG. 43 illustrates a modification of the doping profile in the substrate by means of a sacrificial layer in the case of a masked, energy-filtered implantation.
• the beginning of the implantation profile is pushed into the sacrificial layer.
• This principle can be used analogously for an unmasked, energy-filtered ion implantation, ie an implantation in which, unlike in FIG. 43, no mask layer is present.
• Ad 16 Lateral modification of the doping profile in the substrate by means of a sacrificial layer
• a sacrificial layer is deposited on the substrate, the stopping power and thickness of which are selected over the wafer surface in a suitable manner, so that the implantation profile is displaced in its depth in the substrate as a function of the lateral position on the wafer in the desired manner.
• Such a sacrificial layer may be used for masked ion implantation or also for unmasked ion implantation (see Figure 44).
• the change in the implantation depth of a homogeneous doping profile can be advantageously used for edge terminations in semiconductor components.
• FIG. 44 illustrates a lateral modification of the doping profile in the substrate by means of a sacrificial layer in the case of an unmasked, energy-filtered ion implantation.
• a lateral modification of the implantation depth is achieved by a different thickness of the sacrificial layer in the lateral direction.
• the principle can be used analogously for masked, energy-filtered implantations.
• Two or more doping profiles can be cleverly overlapped, so that a desired Rescuedotierprofil arises especially in the region of the overlap.
• This technique is particularly advantageous in growing and doping multiple layers.
• a representative example is the growth of several SiC epi layers and respective energy-filtered doping. Here a good contact between the layers should be guaranteed.
• Ad 18 Special arrangement of the multifilter concept with coupled pendulum motion
• a clever arrangement can be used, so that despite coupled oscillating movement of filter and substrate, that is, no relative vertical movement between filter and substrate, a lateral homogeneity of the distribution of the ions is achieved.
• Such an arrangement is shown in FIG.
• the wafers are guided by the rotation of the wafer wheel in the x direction behind the substrate along.
• the ion beam (not shown) is, for example, widened in the x direction and is scanned by the vertical oscillating movement of the implantation chamber over the complete multifilter surface.
• the surface consists of active filter areas and inactive mounting areas.
• Arrangement A) is an unfavorable arrangement.
• the vertical movements in the y-direction are coupled by the filter and substrate.
• the wafers are guided by the rotation of the wafer wheel in the x-direction behind the substrate along.
• the ion beam (not shown) is, for example, widened in the x direction and is scanned by the vertical oscillating movement of the implantation chamber over the complete multifilter surface.
• the surface consists of active filter areas and inactive mounting areas.
• Arrangement A) is a rather unfavorable arrangement. Considering the irradiated filter surface for yl and y2, 3 filters are irradiated at yl while no filter is irradiated at y2. As a result, a laterally inhomogeneous fringe pattern is obtained on the wafer.
• Arrangement B shows a possible example of a better arrangement.
• 2 filters each are irradiated. This is true for all y.
• Ad 19 Monitoring
• Another aspect is to solve the problem of monitoring (monitoring) important parameters of the ion implantation modified by an energy filter.
• Such parameters are, for example, the minimum or maximum projected range, the depth concentration distribution set by the filter geometry and the (energy-dependent) angular distribution.
• the monitoring of other parameters, such as implanted ion species, etc. could also be useful.
• a monitoring should be possible in particular on the wafers to be implanted or on (parallel multiple) structures which are arranged in the vicinity of the wafer. According to one aspect, the monitoring should be carried out without further processing of the monitoring structures or the wafers.
• the monitoring can be performed by measuring optical parameters such as spectral absorption, spectral transmission, spectral reflectance, refractive index changes, global absorption (wavelength range of meter dependent) and global transmission, as well as reflection (wavelength range of meter dependent).
• optical parameters such as spectral absorption, spectral transmission, spectral reflectance, refractive index changes, global absorption (wavelength range of meter dependent) and global transmission, as well as reflection (wavelength range of meter dependent).
• the target substrate e.g., a SiC wafer
• the target substrate may be used directly for optical monitoring.
• the depth (or etch rate or resulting etch geometry, etc.) of an ion beam modified structure can be considered as a measure of the implanted ion dose.
• Monitoring of further changes of physical parameters by ion irradiation is conceivable. Such changes may be, for example, mechanical properties of the monitor material, electrical properties of the monitor material, or else the nuclear physical activation of the monitor material by high-energy ion irradiation.
• the detection is to take place via the change of optical properties.
• a monitoring structure consists of the arrangement of a suitable substrate material with one or more mask structures. Examples are shown in FIGS. 47 and 48.
• the monitoring structure or structures are arranged at a suitable location, for example on the wafer wheel, as shown in FIG.
• the monitoring chips are read out after implantation, for example without further post-processing. If necessary. the mask for the readout measurement must be separated from the monitoring substrate. In one aspect, the mask is reusable.
• Mask material and substrate material of the monitoring chip can be made of different materials.
• the criteria for selecting the mask material is, for example, compatibility with the material of the target substrates (to exclude contamination by sputtering effects) and a high energy ion deceleration capability such that high aspect ratio mask structures can be made.
• mask material and substrate material of the monitoring chip are made of the same material.
• Mask and substrate can also be made monolithic. In this case, neither a reuse of the mask nor the substrate is usually possible.
• the change in the optical properties is only produced by the locally implanted ion dose and the inherent defects caused thereby.
• ions which only pass through the depth region III with the ion concentration C1 (FIG. 51) (in order to reach the concentration range C2) do not lead to any further change in the optical properties. It would be conceivable that exactly such a change in the optical properties, for example in PMMA, would be observed by electronic braking. This is not a problem for the basic evaluability, but should be excluded in the example of FIGS. 51 and 52 for reasons of simplification.
• the mask structures shown or described in FIG. 50 are staggered in their thickness and number depending on the desired depth resolution, or in the form of an "inclined plane” or continuous ramp For example, for the greatest thickness: "thickness of the mask”> Rp, max.
• the lateral dimensions of the individual structures can be large, depending on the requirements of the read-out apparatus, from square micrometers over square millimeters to square centimeters.
• FIG. 53 shows a structure which is suitable for monitoring the maximum projected range.
• Analogous structures using evaluation procedures as described under A., are also used to measure or monitor the minimum projected range.
• the ion implantation energy filter produces an energy-dependent spectrum of ion angles after passing through the filter.
• the resulting angular distribution is thus a function of the filter geometry, the change in the geometry during the lifetime of the filter, the occurrence of channeling effects, the type of ion used, the primary energy, the resulting maximum and minimum energy of the transmitted ions and the geometric arrangement in the implantation chamber , All these parameters can be monitored by monitoring the angular distribution.
• the aperture sizes of the mask structures for thin masks which are only slightly thicker than the maximum projected range in the mask material, can be in the micrometer or sub-micrometer range.
• Such monitoring structures are preferably arranged as arrays, which consist of many individual structures in order to be able to carry out a global (ie on an area of several mm 2 or cm 2 ) optical evaluation.
• the opening sizes are in the millimeter or centimeter range. In these cases, the evaluation of individual structures that are not arranged in an array without excessive technical effort is possible.
• Circular arrangements are also conceivable.
• the core of the last-mentioned aspects is to apply the (essentially) dose-dependent modification of the (preferred) optical parameters of a material for the as implanted monitoring of the energy filter implantation process Parameters should be monitored as completely as possible, without a costly post-processing (eg annealing and application of metallic contacts) must be performed.
• FIG. 59 illustrates an adaptation of a profile transition of two implantation profiles A and B in a skilful manner, so that the resulting overall concentration profile can, for example, produce a desired homogeneous profile.
• This can (but does not have to) be advantageous, in particular in the case of layer systems comprising 2 layers, as in the picture shown here.
• the design of the high-energy tail of implant A leaves only limited possibilities, but the low-energy tail of implant 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 sacrificial layer” a realization with the following process sequence: 1) growing sacrificial layer 2) doping the lower layer (implant B). 3) removing the sacrificial layer 4) growing the upper layer. 5) doping of the upper layer.
• the concepts discussed above enable production-ready implantation methods for the semiconductor industry, i. an economical application of implantation methods in an industrial production process.
• the illustrated concepts allow, in particular, a very flexible (multifilter concept) realization of complex vertical doping concentration courses with a low angular distribution of the implanted ions.
• all types of doping concentration curves can be approximated through the use of triangular filter structures in conjunction with collimator structures.
• Another important aspect concerns the suppression of artifacts, which distort the ion current measurement on the substrate.
• Ad 1 to Ad 19 can each be used alone, but also in any combination with one another.
• the illustrated "end-of-life" detection may be applied to a frame held filter, but may be applied to an otherwise held filter.
• the above-explained wafer may be a semiconductor wafer, but may also be made of another material to be implanted, such as PMMA.
• IPCOM000018006E Original Publication Date: 2001-Dec-Ol Included in the Prior Art Database: 2003-Jul-23 or Siemens AG, 2001, Siemens Technology Report, Dec. 2001, 9 pages.

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