Ion implantation apparatus with energy filter having additional heat energy dissipation surface area

Abstract

An ion implantation device (20) includes an energy filter (25) having a thermal energy dissipating surface area, wherein the energy filter (25) includes a membrane, the membrane including a first surface and a second surface disposed opposite the first surface, the first surface being a structured surface.

Description

[0001] This application claims priority and benefit to Luxembourg patent application LU 101807, filed on May 15, 2020. The entire contents of Luxembourg patent application LU 101807 are incorporated herein by reference. Technical Field

[0002] The present invention relates to an apparatus for an ion implantation device, the apparatus comprising an energy filter (implantation filter) for ion implantation and its use, and an implantation method. Background Technology

[0003] Ion implantation is a method of doping or creating defect distributions in materials (such as semiconductors or optical materials) at depths predefined from a few nanometers to tens of micrometers. Examples of such semiconductor materials include, but are not limited to, silicon, silicon carbide, and gallium nitride. Examples of such optical materials include, but are not limited to, LiNbO3, glass, and PMMA.

[0004] Current needs include generating depth distributions for ion implantation that are wider than the depth distributions of doping or defect concentration peaks achievable through monoenergetic ion radiation, or generating doping or defect depth distributions that cannot be generated by one or a few simple monoenergetic implantations. In known prior art methods for generating depth distributions, structured energy filters are used, where the energy of the monoenergetic ion beam is modified as it passes through a microstructured energy filter element. The resulting energy distribution leads to the generation of ion depth distributions for the material. This is described, for example, in European Patent No. 0014516B1 (Bartko) or US Patent Application No. 2019 / 122850A1.

[0005] like Figure 1The diagram illustrates an example of such an ion implantation device 20, in which an ion beam 10 impinges on a structured energy filter 25. The ion beam source 5 can also be a cyclotron, a tandem accelerator, or a single-ended electrostatic accelerator. In other aspects, the energy of the ion beam source 5 is between 0.5 and 3.0 MeV / nucleus, or preferably between 1.0 and 2.0 MeV / nucleus. In one specific aspect, the ion beam source produces an ion beam 10 with an energy between 1.3 and 1.7 MeV / nucleus. The total energy of the ion beam 10 is between 1 and 50 MeV, in a preferred aspect between 4 and 40 MeV, and in a further preferred aspect between 8 and 30 MeV. The frequency of the ion beam 10 can be between 1 Hz and 2 kHz, for example between 3 Hz and 500 Hz, and in one aspect between 7 Hz and 200 Hz. The ion beam 10 can also be a continuous ion beam 10. Examples of ions in the ion beam 10 include, but are not limited to, aluminum, nitrogen, hydrogen, helium, boron, phosphorus, carbon, arsenic, and vanadium.

[0006] exist Figure 1 As can be seen, the energy filter 25 is made of a membrane with a triangular cross-sectional shape on the right side, but this type of form does not limit the invention, and other cross-sectional shapes can also be used. Since the upper ion beam 10-1 passes through region 25 of the energy filter 25... min It is the minimum thickness in the membrane of the energy filter 25, so the energy of the upper ion beam 10-1 is almost reduced when it passes through the energy filter 25. In other words, if the energy of the upper ion beam 10-1 on the left is E1, then the energy of the upper ion beam 10-1 on the right will have a substantially the same value E1 (i.e., the ion beam 10 loses only a little energy in the membrane due to the blocking power of the membrane).

[0007] On the other hand, the lower ion beam 10-2 passes through region 25 of the energy filter 25. max This is the thickest part of the membrane in the energy filter 25. The energy E2 of the lower ion beam 10-2 on the left is essentially absorbed by the energy filter 25, therefore the energy of the lower ion beam 10-2 on the right is reduced and lower than that of the upper ion beam, i.e., E1 > E2. As a result, the higher energy upper ion beam 10-1 can penetrate the substrate material 30 to a greater depth than the lower ion beam 10-2, leading to a different depth distribution in the substrate material 30, which is part of the wafer.

[0008] like Figure 1 As shown on the right, this represents the depth distribution. The hash triangle region shows the ion penetration into the substrate material at depths between d1 and d2. The Gaussian curve shows the depth distribution without the energy filter 25, and has a maximum at depth d3. It should be understood that depth d3 is greater than depth d2 because some energy of the ion beam 10⁻¹ is absorbed by the energy filter 25.

[0009] In the prior art, there are many known principles that can be used to manufacture the energy filter 25. Typically, the energy filter 25 is made of a bulk material, and its surface can be etched to create the desired pattern, for example... Figure 1 The diagram shows a triangular cross-sectional pattern. German patent DE 102016106119 B4 (Csato / Krippendorf) describes an energy filter made of material layers with different ion beam energy reduction characteristics. In Csato / Krippendorf's patent application, it is described that the depth profile produced by the energy filter will depend on the structure of the material layers and the surface structure.

[0010] In the applicant’s co-pending application DE 102019120623.5, an alternative structural principle is shown, the details of which are incorporated herein by reference, wherein the energy filter comprises spaced-apart microstructure layers connected together by vertical walls.

[0011] For the ion beam 10 that can be absorbed by the energy filter 25, its maximum power depends on three factors: the effective cooling mechanism of the energy filter 25; the thermomechanical properties of the membrane used to prepare the energy filter 25; and the material selection used to prepare the energy filter 25, which are also relevant. In a typical process, approximately 50% of the power is absorbed by the energy filter 25, but this can rise to 80% depending on the process conditions.

[0012] Figure 2 An example of an energy filter is shown, in which energy filter 25 is made of a triangular structured membrane mounted in a frame 27. In a non-limiting example, energy filter 25 may be made of a monolithic material, such as silicon on an insulator, comprising an insulating silicon dioxide layer 22, which, for example, is sandwiched between a silicon layer 21 (typically 2 to 20 micrometers thick, but can also be up to 200 micrometers) and a bulk silicon 23 (about 400 micrometers thick), and the insulating silicon dioxide layer 22 comprises a thickness of 0.2-1 micrometer. The structured membrane may be made of silicon, for example, but may also be made of silicon carbide or other carbon-based materials or ceramics.

[0013] To optimize wafer throughput in the ion implantation process for a given ion current of ion beam 10, thereby achieving efficient use of ion beam 10, preferably, only the membrane of energy filter 25 may be irradiated, without irradiating frame 27, where the membrane is in a fixed position. In practice, at least a portion of frame 27 may also be irradiated by ion beam 10 and thus heated. Frame 27 may indeed be completely irradiated. The membrane used to form energy filter 25 is heated, but due to its thinness (i.e., between 2 and 20 micrometers, but up to 200 micrometers), it has very low thermal conductivity. The membrane size is typically 2 x 2 cm. 2 and 35x35 cm 2 Between them, and corresponding to the wafer size. There is almost no thermal conduction between the film and the frame 27. Therefore, the overall frame 27 does not contribute to the cooling of the film, and the only relevant cooling mechanism of the film is thermal radiation from the film.

[0014] In addition to the thermal stress between the heated portions of the membrane forming the energy filter 25 and the frame, localized heating of the membrane within the energy filter 25 also generates thermal stress. Since energy is absorbed only from the ion beam 10 in portions of the membrane, localized heating can also lead to thermal stress within the membrane, potentially causing mechanical deformation or damage to the membrane 25. The heating of the membrane also occurs within a very short time, less than a second, typically on the order of milliseconds. The cooling effect generated in the un-radiated portions of the membrane will result in a temperature gradient within the energy filter 25. This cooling effect is particularly pronounced for pulsed ion beams 10 and scanning ion beams 10, and can even lead to unintended material modification (due to species implantation).

[0015] In the past, the problem of defects or material modifications was overcome by specifying safe operating conditions for use at compliant maximum ion doses, under which the problem would not occur. However, the long-term effects of mechanical deformation and film damage have not been addressed. Ignoring these long-term effects will lead to changes in the profile of the chip material, resulting in chips that must be discarded.

[0016] Therefore, improvements are needed to the cooling mechanism of the energy filter and the temperature uniformity of the filter and frame. Summary of the Invention

[0017] This paper teaches an ion implantation device including an energy filter, wherein the energy filter has an additional heat dissipation surface area to enable the energy filter to be cooled more effectively.

[0018] In one aspect of an ion implantation apparatus, an energy filter includes a membrane having a first surface and a second surface disposed opposite to the first surface. At least one of the first or second structured surface has microstructures thereon, forming additional heat dissipation surface regions. The spatial dimensions of the microstructures are between 3 and 5% of the spatial dimension of the structure on the first structured surface. However, these dimensions do not limit the invention. The microstructures have one of a randomly arranged structure or a structure with a triangular cross-section.

[0019] In another aspect of the ion implantation apparatus, the energy filter includes a plurality of membranes, including a first membrane and another membrane disposed at a distance from the first membrane, for example, located between the ion beam source and the substrate material. The ion implantation apparatus may further include positioning elements for moving the spacing between the plurality of membranes in a lateral or horizontal direction.

[0020] On the other hand, the ion implantation apparatus may further include a collimator disposed between one of the first or another film and the substrate material. The collimator absorbs ions scattered at an angle from the ion beam such that the ions reach their positions on the substrate with substantially the same energy, thereby achieving substantially the same penetration depth.

[0021] On another aspect of the ion implantation device, the housing of the ion implantation device also includes multiple conduits for conveying cooling fluid to reduce heating of the housing and to cool the housing, thereby cooling the frame and membrane of the ion implantation device.

[0022] The ion implantation device may also be equipped with multiple absorption elements that are in thermal contact with the housing to promote the absorption of thermal radiation. These absorption elements block visible and infrared light. Attached Figure Description

[0023] Figure 1 The operating principle of an ion implantation device with an energy filter known in the prior art is shown.

[0024] Figure 2 The structure of an ion implantation device with an energy filter is shown.

[0025] Figure 3A , Figure 3B and Figure 3C An energy filter with a microstructure is shown.

[0026] Figure 4A and Figure 4B Multiple membranes in the energy filter and open / closed collimation devices are shown.

[0027] Figure 5 The cooling system of the energy filter is shown. Detailed Implementation

[0028] The invention will now be described with reference to the accompanying drawings. It should be understood that the aspects of the invention described herein are merely illustrative and do not in any way limit the scope of the claims. The invention is defined by the claims and their equivalents. It should be understood that features in one aspect of the invention may be combined with features in different aspects of the invention.

[0029] Figure 3A , Figure 3B and Figure 3C The membrane structure of energy filter 25 according to one aspect of this document is shown. Figure 3A A structured membrane with a triangular cross-section, as described in the prior art, is shown. Figure 3B The microstructure on one side surface of the membrane 25 in the energy filter 25 is shown. Figure 3C The microstructures on both sides of the energy filter 25 are shown. In other words, the energy filter 25 has a membrane that, in addition to having a regular triangular cross-section, also has additional microstructures on one or more surfaces.

[0030] exist Figure 3A , Figure 3B and Figure 3C In the non-limiting example shown, the height h of the triangle is 16 micrometers and the spacing s is 20 micrometers. The energy filter 25 can have different dimensions; for example, the height can be between 1 micrometer and 200 micrometers, and the spacing can be between 1 micrometer and 400 micrometers.

[0031] The microstructure will affect the energy distribution of the ion beam 10 passing through the energy filter 25. However, assuming the energy distribution has a tolerance of 3-5%, the height of the microstructure can be 3-5% of the height h (labeled as mh in the figure, but not to scale), and the spacing of the microstructure can be 3-5% of the distance of the spacing s (labeled as ms in the figure, but not to scale). It should be understood that variations in the energy distribution will be influenced by the microstructures on both sides of the energy filter 20.

[0032] Microstructures are formed by etching the energy filter 20 from bulk material or by depositing material on a substrate. Many methods are known in the art. For example, patterning techniques such as photolithography, electron beam lithography, or laser beam lithography can be used to create masks on a substrate. Masks are made of photoresist, silicon dioxide, silicon carbide, chromium, or other materials. Wet chemical etching techniques use, for example, potassium hydroxide, TMAH (tetramethylammonium hydroxide), and other anisotropic etching solutions, plasma etching techniques, and ion beam etching.

[0033] Self-mask etching techniques can also be used, such as reactive ion etching under strong polymerization process conditions, or additives such as potassium hydroxide solution and isopropanol.

[0034] Self-mask deposition techniques, such as chemical vapor deposition in selective deposition mode or atomic layer deposition mode, can also be used.

[0035] Without a mask, the deposition or etching sequence of the layers is also known. This can be achieved using femtosecond laser ablation or focused ion beam deposition or material removal.

[0036] It is understandable that the formation of microstructures can be achieved by mechanically roughening the surface of the surface film 25, adding additional thin-layer materials such as silicon or carbon, or by using other techniques such as laser ablation.

[0037] The membrane structure of the energy filter 25 may have different structures and is not in the form of a triangular cross section. For example, the energy filter 25 may be formed from a series of pyramid shapes known in the art. Microstructures are then placed on the surface of the pyramid shapes.

[0038] The purpose of the microstructure is to provide a larger surface area for the membrane of the energy filter 25, which allows for greater thermal cooling of the energy filter 25.

[0039] Another aspect of the invention is as follows Figure 4A and 4B As shown, the energy filter 25 includes multiple membranes 400a-c, which are mounted in multiple frames 27 within a housing 410. The housing 410 may be made of steel with an inner coating of silicon carbide or other carbon materials. The inner coating is used to reduce or eliminate contamination of the semiconductor substrate. Figure 4A The energy filter 25 is shown to have multiple multi-layered bodies. Figure 4B An energy filter 25 with a membrane having a triangular cross-section is shown. The membrane of the energy filter 25 may also include, for example... Figure 3B and Figure 3C The microstructure shown.

[0040] Multiple membranes 400a-c, used to form the energy filter 25, are disposed in the housing 410. The multiple membranes 400a-c can be moved within the housing 410 along the direction of the ion beam 10 to change the spacing between each membrane 400a-b and between the membranes 400a-d and the substrate 30. Positioning elements 430, such as piezoelectric elements or micromotors, can be used to change the spacing in both the vertical and horizontal directions.

[0041] Figure 4A and 4BThe configuration also includes (optionally) a collimator 420 for collimating the ion beam 10 after it has passed through the plurality of membranes 400a-c. The end of the collimator 420 may be open or closed. It should be understood that each of the plurality of membranes 400a-c absorbs a portion of the energy of the passing ion beam 10; therefore, membranes 400a-c used to form the energy filter 25 will absorb less energy than a single membrane among membranes 400a, 400b, or 400c. The plurality of membranes 400a-c are cooled by thermal radiation.

[0042] Figure 4A and 4B The configuration of the energy filter 25 shown can also create different depth distributions for ions penetrating the substrate material 30. Figure 4A and Figure 4B The multiple membranes 400a-c shown are similar, but each of the multiple membranes 400a-c can have a different profile if required.

[0043] Figure 4A and Figure 4B The image shows three membranes 400a-c, but it's understandable that the number of membranes 400a-c could be increased. Increasing the number of membranes 400a-c would dissipate more energy. To avoid damage, it's assumed that the maximum energy dissipable in a single membrane 400a-c is 1.6 W / cm². 2 If the ion beam 10 has an energy of 10 MeV, and assuming that 50% of the energy is required to form a deposition pattern in the substrate material 30, then the ion current in the ion beam 10 is approximately 0.23 μA / cm. 2 Using five 400a-c membranes, assuming each membrane can absorb the same amount of energy, the maximum ion current would be 1.6 μA / cm. 2 .

[0044] Another aspect of the present invention is as follows Figure 5 As shown, an energy filter 25 is installed in a cooling housing 500. The cooling housing 500 has one or more conduits 510 in its wall 520, through which cooling fluid 530 passes. The cooling fluid 530 is, for example, water. Thermal radiation radiated from the energy filter 25 can be absorbed by the wall 520, and the heat is then dissipated through the cooling fluid 520.

[0045] On the other hand, the interior of wall 520 may have an absorption element 540, which may be, for example, a silicon or carbon-based material, and has a thickness in the range of micrometers to millimeters. The absorption element 540 absorbs radiant heat energy from energy filter 25.

[0046] Component reference numbers

[0047] 5 Ion Beam Source

[0048] 10 Ion Beams

[0049] 20 Ion Implantation Device

[0050] 21 silicon layers

[0051] 22 Silicon Dioxide Layer

[0052] 23. Bulk Silicon

[0053] 25 Energy Filters

[0054] 27 Filter Frame

[0055] 30 Substrate material

[0056] 400a-c membrane

[0057] 410 Housing

[0058] 420 collimator

[0059] 430 Positioning Element

[0060] 500 Cooling Housing

[0061] 510 catheter

[0062] 520 Wall

[0063] 530 Cooling fluid

[0064] 540 Absorption Element

Claims

1. An ion implantation device (20), characterized in that, The device includes an energy filter (25) having a heat dissipation surface region, wherein the energy filter (25) includes a membrane having a first surface and a second surface disposed opposite to the first surface, the first surface being a structured surface, and the ion implantation device (20) further includes a housing (410; 500) in which the energy filter (25) is mounted, and the housing (410, 500) further includes a plurality of absorption elements (540) in thermal contact with the housing (500) and blocking visible and infrared light.

2. The ion implantation device (20) according to claim 1, characterized in that, The first surface or the second surface has microstructures thereon and forms an additional heat dissipation surface region, wherein the spatial size of the microstructures is between 3 and 5% of the spatial dimension of the structure on the first surface.

3. The ion implantation device (20) according to claim 2, characterized in that, The microstructure has one of the following: a randomly arranged structure or a structure with a triangular cross-section.

4. The ion implantation device (20) according to claim 1, characterized in that, The energy filter (25) includes a plurality of membranes (400a-c), the plurality of membranes having a first membrane and another membrane disposed at a distance from the first membrane.

5. The ion implantation device (20) according to claim 4, characterized in that, It also includes an ion beam source (5), a substrate material (30), and a plurality of films (400a-c) disposed between the ion beam source (5) and the substrate material (30).

6. The ion implantation device (20) according to claim 4, characterized in that, It also includes a positioning element (430) for moving the spacing between the plurality of membranes (400a-c).

7. The ion implantation device (20) according to claim 5, characterized in that, It also includes a positioning element (430) for moving the spacing between the plurality of membranes (400a-c).

8. The ion implantation device (20) according to claim 4, characterized in that, It also includes a collimator (420) disposed between the first film (400a-c) or one of the other films and the substrate material (30).

9. The ion implantation device (20) according to claim 1, characterized in that, The structure of the first surface is either a structure with a triangular cross-section or a pyramidal structure.

10. The ion implantation device (20) according to claim 1, characterized in that, The energy filter (25) is made of silicon membrane.

11. The ion implantation apparatus (20) according to claim 1, characterized in that, The housing (500) also includes a plurality of conduits (510) for conveying cooling fluid (530).

12. The ion implantation device (20) according to claim 1, characterized in that, It also includes a filter frame (27), wherein the energy filter (25) is fixed by the filter frame (27).

13. A housing (500) for an energy filter (25) within an ion implantation device, characterized in that, The housing (500) includes a plurality of conduits (510) for conveying cooling fluid (530), wherein an energy filter (25) is installed in the housing (500), and the housing (500) also includes a plurality of absorption elements (540) that are in thermal contact with the housing (500) and block visible and infrared light.

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