METHOD FOR PRODUCING A GROUP III-V SUBSTRATE, IN PARTICULAR A GaAs AND INP SUBSTRATE

Abstract

The invention comprises a method for drying a wafer (W, W1, W2) immersed in a bath (1) and an undoped and doped wafer (W, W1, W2) according to the invention and a device for drying a wafer (W, W1, W2). It is ensured that the travel distance of the wafer (W, W1, W2) is as short as possible, only a small number of droplets remain attached to the wafer (W, W1, W2), and thus the wafer (W, W1, W2) has an oxide surface as uniform as possible, and the number / area of defect regions due to residual droplets attached after the Marangoni drying process can be minimized. Therefore, when passing through the water surface, the wafer (W) and the support (3, 31, 32) / the guiding devices (3a, 3a ', 3b, 3b', 3c, 3c ') are almost not contacted or ideally not contacted, so that continuous overflow can be maintained, that is, preferably, no water level drop exists when the wafer W is dried (and the support (3, 31, 32) is also ideally dried).

Description

Field of the Invention

[0001] The present invention relates to methods for producing improved III-V substrate surfaces and methods for producing III-V substrates themselves, where the materials GaAs and InP are of particular relevance. Background of the Invention

[0002] III-V substrates, especially gallium arsenide substrates and especially their wafers, are used in various applications and have increasing economic importance. Examples thereof include high-frequency amplifiers and switches as well as light-emitting components such as semiconductor lasers and diodes. In particular, transistors and diodes are mainly made of epitaxially grown single-crystalline compounds. The growth parameters can in particular be adjusted to the lattice. Lattice-matched epitaxy ensures high quality and low defect density. However, the quality depends not only on the conditions during epitaxy but also on the nature of the substrate itself, which usually affects the quality. In the case of gallium arsenide, in particular the problem of rapid formation of an oxide layer at the substrate surface occurs, which can form with an inhomogeneous composition (gallium oxide and arsenic oxide in different oxidation states) when no appropriate surface treatment takes place. The thermal properties of the oxides of different compositions are partly very different. However, for subsequent epitaxy processes, it is necessary to ensure that the oxide layer can be easily removed by heat treatment.

[0003] For example, the prior art document EP 2 629 319 A1 is known, which teaches that gallium arsenide in particular has significantly different physical and chemical surface properties compared to other semiconductors such as silicon. Since the surface of a gallium arsenide wafer contains gallium atoms and arsenic atoms that exhibit different chemical properties (also in terms of reactivity), the surface reactivity here is a special phenomenon: the surface layer can consist of gallium dioxide (Ga2O3), arsenic trioxide (As2O3), arsenic pentoxide (As2O5) and a small amount of elemental arsenic. When growing gallium arsenide, a specific method disclosed in this document needs to be used to fabricate the surface: treating with an ammonia solution, hydrogen peroxide and water, rinsing the wafer with deionized water, treating the wafer with an oxidizing agent, repeatedly rinsing the wafer with deionized water, treating the wafer with a dilute acid solution or a dilute base solution, re-rinsing the wafer with deionized water, and finally drying the wafer.

[0004] During the surface treatment of gallium arsenide, foreign particles can attach very easily, which is disadvantageous for the subsequent epitaxial process because they lead to an increase in the number of defects. Further prior art literature (Klaus Wolke et al., "Marangoni Wafer Drying Avoids Drawbacks", Solid State Technology, August 1996) reports the Marangoni drying method for silicon wafers. Marangoni drying is disclosed herein based on the physical force that causes a liquid to move away from a surface with a varying surface tension to establish equilibrium. A small amount of water (containing absorbed isopropyl alcohol) with a low surface tension moves into a large volume of liquid with a normal surface tension. For example, an isopropyl alcohol-nitrogen atmosphere with a lower surface tension can be used. In contrast, normal water has a higher surface tension. When a solid passes through the gas-liquid interface, such as when removing a wafer from a bath, the water tends to form a positive meniscus. The presence of a water-soluble material (such as isopropyl alcohol) in the atmosphere causes the solvent concentration in the meniscus to increase compared to the rest of the bath. When the wafer is pulled out of the bath, the water in the meniscus is pulled into the large volume of liquid, resulting in a completely dry wafer surface and no attached water droplets on the wafer surface, which may cause so-called water stains.

[0005] Therefore, the Marangoni effect originates from the difference in interfacial tension. The fluid (water in this case) then flows along the wafer in the direction of higher tension, which in turn causes the removal of water from the wafer and enables the wafer to be dried without residues. The Marangoni drying of semiconductor wafers relies on the spatial separation of the wafer and ultrapure water under the influence of a surface tension gradient in the interfacial layer where the ultrapure water contacts the wafer. This spatial separation can be achieved by lifting the wafer out of the ultrapure water-filled bath of a wet processing unit for semiconductor wafers or by lowering the water level.

[0006] In the document WO 2014 / 124980 A2, a production method for GaAs substrates and the gallium arsenide substrates produced thereby are disclosed, wherein the method includes Marangoni drying. It has been recognized that the combination of specific surface cleaning steps (acid cleaning, alkali cleaning, contact with an oxidant) and Marangoni drying helps to significantly improve the uniformity of the oxide surface compared to methods that do not involve a drying method based on subsequent Marangoni drying after the cleaning step. Thereby, the number of defects and the defect area on the wafer surface can be significantly reduced compared to methods that do not include Marangoni drying. Here, the area where the measurement signal obtained by a Candela ellipsometer is outside a defined threshold is regarded as the defect area. This is a standard function of the Candela ellipsometer and is directly output by the device.

[0007] Marangoni drying is particularly suitable for drying semiconductor wafers after wet chemical cleaning. In this case, the drying is preferably carried out uniformly over the entire surface and is substantially residue-free. Before the drying begins, the semiconductor wafer is usually arranged perpendicular to a process carrier disposed in a process bath filled with ultrapure water. Frequently, the bath involves the final bath of a so-called wet bench: a series of sequentially arranged liquid-filled baths in which the wafer undergoes the chemical and rinsing steps required for cleaning. In the high-throughput semiconductor industry, typically, after each expected process time is completed, the process carrier with the wafer is moved from one bath to another by an automated handling system.

[0008] There are various configurations for drying according to the Marangoni method. However, there is a common basic principle for all Marangoni methods: adding a liquid that reduces the surface tension of the water in the bath to the water surface. Usually, this involves isopropyl alcohol (isopropanol, abbreviated as IPA). The actual drying is carried out by the slow spatial separation of the wafer and the upper water layer that exhibits a reduced surface tension due to the presence of isopropyl alcohol. This spatial separation can be carried out in different ways, such as lifting the wafer out of the water, lowering the water level, or a combination of both. For good drying results, the relative removal speed of the wafer and the water level is in the range of, for example, 1 mm / s.

[0009] During Marangoni drying, water droplets (so-called residual droplets) can attach to the necessarily maintained contact point between the wafer and the clamping device as they cross the phase boundary, which can lead to a chemically altered oxide layer that has a negative impact on the crystalline quality of the epitaxial layer deposited on the wafer during device manufacturing. Drying the water in a delayed and uncontrolled manner may damage the wafer surface.

[0010] During the further processing of semiconductor wafers into electronic or optical devices, extremely surface-sensitive coating processes can be applied within the framework of so-called planar technology, in which thin semiconductor layers are deposited in single-crystalline form onto the surface of the wafer. This process (which is called epitaxy) places extremely high quality requirements on the surface of the semiconductor wafer.

[0011] The so-called III-V semiconductors, especially GaAs and InP, show distinguishing characteristics compared to silicon wafers, for example, in terms of altered surface tension, significantly increased surface reactivity, and more complex oxide layer chemical compositions. Additionally, the preferred further processing of these wafers by single-crystal coating with other III-V materials places higher demands on the lateral homogeneity of the oxide layer composition than for silicon wafers. Moreover, in the case of III-V semiconductor wafers, residual droplets may form more easily during Marangoni drying, and these residual droplets have a more negative impact on subsequent processes within the scope of device manufacturing. In the dry state, the surfaces of certain semiconductor wafers (especially GaAs and InP) are always covered by a thin amorphous oxide layer. This layer typically varies in thickness within the range between 1 and 2 nanometers (for InP, layer thicknesses below 1 nm may be possible), and thus consists of only a few atomic layers. During wet chemical cleaning and rinsing processes, the oxide layer undergoes complex changes, being removed, reformed, or having its composition altered. The oxide layer formed on the wafer surface after cleaning, rinsing, and drying processes has a passivation effect and is thermally removed from the wafer surface immediately before epitaxial coating in certain applications.

[0012] However, an ideal and laterally uniform composition of the oxide layer is an important requirement such that the starting surface remaining after thermal desorption of the oxide layer enables the layers to be deposited to achieve the best possible crystallographic coupling for epitaxy over the entire surface, thereby facilitating ideal current flow in the devices subsequently fabricated from these epitaxial layers.

[0013] The remaining, delayed, and uncontrolled drying water droplets after Marangoni drying result in an unfavorably altered composition of the oxide layer with partially crystalline regions in the corresponding areas at the wafer surface. In the thus disturbed areas of the wafer surface, incomplete desorption of the surface oxide may occur during desorption before the epitaxial process, leading to roughening of the wafer surface. As a result, the single-crystal growth of the functional layer is disturbed, leading to the development of crystal defects such as dislocations, grain boundaries, and twin lamellae. This ultimately disrupts the current flow in the devices fabricated from the epitaxially grown material and can potentially lead to yield losses.

[0014] In principle, there are several different possibilities for drying wafers after surface treatment and for lifting the wafers out of the bath for the Marangoni drying method.

[0015] In one embodiment, a wafer or wafer group is held in a water bath by a holder (a holding arrangement having rods). In this first embodiment, the rinse water (usually after cleaning with deionized water) is drained; however, within the scope of the present invention, it has been found that residual droplets often form at the contact points where the wafer or wafers are fixed to the holder, and at these contact points, uniform drying is disturbed. As a result, the quality of the surface layer of the oxide layer at the wafer surface is locally reduced, and the surface oxide layer becomes non-uniform, which leads to a reduction in the quality of the epitaxial layer grown later.

[0016] In a second embodiment, the wafer is lifted out of the water bath by a wedge that is pushed vertically upward, and the wafer is temporarily held by the wedge and a wafer holder, for example, in the lid of a dryer. Within the scope of the present invention, it has been found that in this embodiment, residual droplets can be prevented at a plurality of contact points. However, when passing through the water surface, there are usually droplets around the wedge. In addition, due to the fixed arrangement of the wafer holder in the lid of the dryer, drying is limited to certain wafer diameters.

[0017] In document WO 2001 / 078112 A1, another method for lifting a wafer or wafer group out of a cleaning bath is disclosed. Therein, there are two opposing gripping elements having receiving grooves facing each other, and when the wafer is lifted out of the water surface by a wedge, the gripping arms can grip these wafers.

[0018] In addition, document DE 199 243 02 A1 discloses a method for drying a substrate according to the Marangoni effect. Therein, during the lifting of the substrate, at least one additional fluid is laterally conveyed to the substrate and onto the processing fluid and is guided towards the area between the substrates.

[0019] In addition, document DE 10 359 320 A1 teaches a method for drying a substrate, wherein the substrate is lifted out of a bath containing a processing fluid, and a fluid that reduces the surface tension of the processing liquid is supplied to the processing liquid through at least two opposing supply devices facing each other, thereby causing control of the supply of the fluid that reduces the surface tension of the processing liquid such that the fluid is alternately supplied to the opposing supply devices.

[0020] Methods known from the prior art are generally complex in terms of equipment; these methods are still associated with drawbacks or are even deliberately accepted, i.e., when lifting the wafer out of the processing fluid, the residual droplets remain unchanged, which leads to the formation of "spots" on the wafer, which in turn can interfere with the subsequent epitaxial growth of a thicker crystal layer. Within the scope of the present invention, a "spot" refers to a surface defect generated by residual droplets attached to the wafer and detectable by a Candela surface ellipsometer. For example, compared to an area without such "spots", a "spot" refers to a chemically altered surface oxide layer composition at the wafer surface.

[0021] Accordingly, an object of the present invention is to provide a method that is not complex in terms of equipment and can be easily implemented, by which wafers of different sizes can be dried, and by which the formation of residual droplets during lifting of the wafer can be minimized or, if possible, completely avoided. Providing a very uniform oxide surface for III-V wafers can be regarded as an additional object of the present invention. Summary of the Invention

[0022] The above object is solved by a method according to claim 1, a III-V wafer according to claim 14 or 16, and a device for drying a wafer according to claim 18. Further advantageous embodiments of the present invention are the subject matter of the corresponding dependent claims.

[0023] Ellipsometer-based surface mapping performed using a Candela ellipsometer is used to characterize the surface properties of the corresponding wafer. The details of the corresponding measurements are accordingly explained in the description and examples.

[0024] Without limiting the present invention, the following items are provided to describe the main aspects, preferred embodiments, and special features of the present invention:

[0025] 1. A method for drying a wafer (W) located inside a bath (1) by using an arrangement including at least one wedge (2) and a pair of first lateral guiding means (3a, 3a'), a pair of second lateral guiding means (3b, 3b'), and a pair of third lateral guiding means (3c, 3c'), wherein the pair of first lateral guiding means (3a, 3a') is arranged below the pair of second lateral guiding means (3b, 3b'), and the pair of second lateral guiding means (3b, 3b') is arranged below the pair of third lateral guiding means (3c, 3c'), and wherein the method comprises the following steps:

[0026] i) Move at least one wedge (2) vertically upward until it reaches the wafer at the lowest point of the wafer, and move a pair of first lateral guiding devices (3a, 3a') and a pair of second lateral guiding devices (3b, 3b') vertically upward, wherein the wafer (W) contacts the pair of first lateral guiding devices (3a) and the pair of second lateral guiding devices (3b), wherein the upper region of the wafer (W) is lifted out of the bath (1), and wherein a pair of third lateral guiding devices (3c) do not contact the wafer;

[0027] ii) Move the wedge (2) vertically upward until the pair of first lateral guiding devices (3a, 3a') and the pair of second lateral guiding devices (3b, 3b') no longer contact the wafer (W), while still being below the liquid level of the bath (1), wherein a pair of third lateral guiding devices (3c, 3c') contact the wafer above the liquid level of the bath (1);

[0028] iii) Lift the wafer (W) above the liquid level of the bath (1), wherein a pair of third lateral guiding devices (3c, 3c') contact the wafer (W).

[0029] In one embodiment, the distance between the pair of first lateral guiding devices (3a, 3a') is less than the distance between the pair of second lateral guiding devices (3b, 3b'), and the distance between the pair of second lateral guiding devices (3b, 3b') is less than the distance between the pair of third lateral guiding devices (3c, 3c').

[0030] 2. The method for drying a wafer (W) according to item 1, further comprising the following steps:

[0031] iv) Move the wedge (2) vertically downward until the wafer (W) contacts at least one of the pair of first lateral guiding devices (3a) and the pair of second lateral guiding devices (3b);

[0032] v) Move the wedge (2) further vertically downward until it no longer contacts the wafer (W);

[0033] Simultaneously with step iv) and / or v) in parallel or after step v), the liquid level of the bath (1) is lowered until the liquid level is below the wedge (2).

[0034] 3. The method according to item 1 or 2, wherein the bath contains water and at least one additional surface tension reducing substance.

[0035] 4. The method according to item 3, wherein the at least one additional surface tension reducing substance is isopropyl alcohol.

[0036] 5. The method according to any one of items 2 to 4, wherein in step i), a pair of first lateral guiding devices (3a, 3a') and a pair of second lateral guiding devices (3b, 3b') are kept immersed in the bath (1), and at the end of step v), a pair of third lateral guiding devices (3c, 3c') preferably do not contact the wafer (W, W1, W2).

[0037] 6. The method according to any one of the foregoing items, wherein a pair of first lateral guiding devices (3a, 3a'), a pair of second lateral guiding devices (3b, 3b'), and / or a pair of third lateral guiding devices (3c, 3c') each consist of a pair of webs arranged in a manner that contacts opposite sides of the wafer (W).

[0038] 7. The method according to any one of the foregoing items, wherein a pair of first lateral guiding devices (3a, 3a'), a pair of second lateral guiding devices (3b, 3b'), and optionally a pair of third lateral guiding devices (3c, 3c') are also held by a carrier device (3d) such that the vertical movement of a pair of first lateral guiding devices (3a, 3a'), a pair of second lateral guiding devices (3b, 3b'), and optionally a pair of third lateral guiding devices (3c, 3c') always occurs synchronously.

[0039] 8. The method according to any one of the foregoing items, wherein in step i), a pair of first lateral guiding devices (3a, 3a') and a pair of second lateral guiding devices (3b, 3b') are kept immersed in the bath (1).

[0040] 9. The method according to any one of items 2 to 8 of the foregoing, wherein at the end of steps iv) and v), a pair of third lateral guiding devices (3c, 3c') do not contact the wafer (W).

[0041] 10. The method according to any one of the foregoing items, wherein step ii) further includes fixing the wafer by an additional gripping device (4) mounted above the liquid level of the bath (1).

[0042] 11. The method according to any one of the foregoing items, wherein the wedge (2) includes a suction device (6) to which a vacuum is applied when the upper tip of the wedge (2) is above the liquid level.

[0043] 12. The method according to item 11, wherein the suction device (6) represents an opening in the wedge (2, 2a, 2b).

[0044] 13. The method according to any one of the foregoing items, wherein the wedge (2) is made of plastic, preferably made of polyetheretherketone (PEEK).

[0045] 14. The method according to any one of the preceding items, wherein the wedge (2) has a surface structure that increases surface tension. Such a structure can be achieved, for example, by plasma treatment.

[0046] 15. The method according to any one of the preceding items, wherein a pair of first lateral guiding devices (3a, 3a'), a pair of second lateral guiding devices (3b, 3b') and a pair of third lateral guiding devices (3c, 3c') have notches.

[0047] 16. The method according to any one of items 1 to 15, wherein the lifting speed depends on the position of the lowest point of the wafer (W), and when the lowest point of the wafer (W) is lower than the liquid level by more than 1.2 cm, the lifting speed is between 0.8 and 1.2 mm / s, or when the lowest point of the wafer (W) is lower than the liquid level by less than 1.2 cm, the lifting speed is between 0.4 and 0.5 mm / s, and once the lowest point of the wafer (W) has reached the liquid level, the lifting speed is at least 30 mm / s, preferably at least 40 mm / s, more preferably at least 50 mm / s.

[0048] 17. The method according to any one of items 1 to 16, wherein a pair of first lateral guiding devices (3a, 3a'), a pair of second lateral guiding devices (3b, 3b') and a pair of third lateral guiding devices (3c, 3c') are mounted on a bracket (3), and the bracket (3) is moved in step i), and the wafer (W) is lifted above the liquid level of the bath (1) in step iii), wherein a pair of third lateral guiding devices (3c, 3c') and the wedge (2) contact the wafer (W).

[0049] 18. The method according to any one of items 1 to 16, wherein in all process steps, a pair of third lateral guiding devices (3c, 3c') are positioned above the liquid level and are capable of moving independently of a pair of first lateral guiding devices (3a, 3a') and a pair of second lateral guiding devices (3b, 3b'), and the third lateral guiding devices (3c, 3c') are capable of horizontal movement relative to each other.

[0050] 19. The method according to item 18, wherein in all process steps, the wedge (2) is kept below the liquid level.

[0051] 20. The method according to item 18 or 19, wherein in step iii), the distance between the points where the third lateral guiding devices (3c, 3c') contact the wafer continuously decreases.

[0052] 21. The method according to any one of items 18 to 20, wherein the third lateral guiding devices (3c, 3c') are adapted to perform horizontal movement relative to each other.

[0053] 22. The method according to any one of items 18 to 21, wherein the third lateral guiding device (3c, 3c') is eccentrically mounted or has an elliptical shape and is designed to perform a rotational movement.

[0054] 23. A group III-V wafer (W), wherein the oxide surface has a defect area of less than 25 mm 2 and wherein the group III-V wafer (W) is semi-insulating.

[0055] For many compounds (such as GaAs), semi-insulating means that the Fermi level is near the center of the bandgap. In the case of GaAs, in addition to doping with a certain amount of carbon (C), this can also be ensured by the intrinsic point defect EL2 (arsenic antisite on the gallium site). In the case of InP, doping with iron is required to produce semi-insulating properties.

[0056] The following conditions apply to the carrier concentration: when the carrier concentration is less than 1×10 10 cm -3 the wafer is considered semi-insulating, and when the carrier concentration is greater than 1×10 10 cm -3 the wafer is considered semiconductor. The determination of the carrier concentration is described in the standard "SEMI M39".

[0057] According to the standard "SEMI M87", for a semi-insulating wafer, the specific resistance is greater than 1×10 5 Ωcm, while a wafer having a value lower than this value can be considered semiconductor.

[0058] 24. The group III-V wafer (W) according to item 23, wherein the oxide surface has a defect area of less than 15 mm 2 , preferably less than 10 mm 2 , more preferably less than 5 mm 2 .

[0059] 25. A group III-V wafer (W) that is at least single-sided polished, dried and semi-insulating and has an oxide layer on the entire surface, wherein the surface having a changed surface oxide composition is less than 5 mm 2 compared to the rest of the entire surface of the group III-V wafer.

[0060] Here, the measurement is performed using a Candela surface ellipsometer with a measurement channel QAbsPhase.

[0061] 26. The group III-V wafer (W) according to item 23, 24 or 25, wherein the group III element is selected from Ga and In, and the group V element is selected from As and P.

[0062] 27. The group-III-V wafer (W) according to item 26, wherein the group-III-V wafer is composed of GaAs or InP, and wherein GaAs and InP may be undoped or doped with carbon (C) and iron (Fe), respectively.

[0063] 28. The group-III-V wafer (W) according to any one of items 23 to 27, wherein the resistivity is between 1×10 8 and 8×10 8 Ω·cm.

[0064] 29. The group-III-V wafer (W), wherein the oxide surface has a defect area of less than 25 mm 2 , and wherein the group-III-V wafer (W) is semiconductor.

[0065] Here, the measurement is performed by using a Candela surface ellipsometer with the measurement channel QAbsPhase.

[0066] The following conditions apply to the carrier concentration: when the carrier concentration is less than 1×10 10 cm -3 , the wafer is considered semi-insulating, and when the carrier concentration is greater than 1×10 10 cm -3 , the wafer is considered semiconductor. The determination of the carrier concentration is described in the standard "SEMI M39".

[0067] 30. The group-III-V wafer (W) according to item 29, wherein the group-III-V wafer (W) contains silicon or sulfur as a dopant.

[0068] 31. The group-III-V wafer (W) according to item 30, wherein the group-III-V wafer is a GaAs wafer and contains silicon as a dopant.

[0069] 32. The group-III-V wafer (W) according to item 30, wherein the group-III-V wafer is an InP wafer and contains sulfur as a dopant.

[0070] 33. The group-III-V wafer (W) that is at least single-sided polished, dried, and semi-insulating and has an oxide layer on the entire surface, wherein the surface with a changed surface oxide composition is less than 25 mm 2 compared to the rest of the entire surface of the group-III-V wafer.

[0071] Here, the measurement is also performed by using a Candela surface ellipsometer with the measurement channel QAbsPhase.

[0072] 34. The group-III nitride wafer (W) according to any one of items 29 to 33, wherein the carrier concentration is between 1×10 18 cm -3 and 9×10 18 cm -3 .

[0073] 35. The InP wafer (W) according to any one of items 29 to 34, wherein the oxide surface has a defect area of less than 20 mm 2 , preferably less than 15 mm 2 , more preferably less than 10 mm 2 , even more preferably less than 5 mm 2 .

[0074] 36. The group-III nitride wafer (W) according to any one of items 23 to 35, wherein the diameter of the wafer is at least 150 mm.

[0075] 37. The group-III nitride wafer (W) according to any one of items 23 to 36, wherein the diameter of the wafer is at least 200 mm.

[0076] 38. A GaAs wafer (W) doped with silicon and having a carrier concentration between 1×10 18 cm -3 and 3×10 18 cm -3 , wherein the surface oxide has a defect area of less than 25 mm 2 .

[0077] 39. An InP wafer (W) doped with sulfur and having a carrier concentration between 1.5×10 18 cm -3 and 9×10 18 cm -3 , and wherein the surface oxide has a defect area of less than 25 mm 2 .

[0078] 40. An InP wafer (W) doped with sulfur and having a carrier concentration between 1.5×10 18 cm -3 and 9×10 18 cm -3 , and wherein the surface oxide has a defect area of less than 20 mm 2 , preferably less than 15 mm 2 , more preferably less than 10 mm 2 , even more preferably less than 5 mm 2 .

[0079] 41. A group III-V semiconductor wafer (W) according to any one of items 23 to 39 or an InP wafer according to item 39 or 40, wherein the defective region is a continuous region.

[0080] 42. The group III-V semiconductor wafer (W) according to item 41, wherein at least a part of the defective region is in contact with the edge of the wafer.

[0081] 43. The group III-V semiconductor wafer (W) according to item 41 or 42, wherein at least a part of the defective region is at most 5 mm away from the edge of the wafer.

[0082] 44. The group III-V semiconductor wafer (W) according to any one of items 41 to 43, wherein the entire defective region is located within an annular region between the edge of the wafer and a virtual circular line that is at most 10 mm away from the edge of the wafer.

[0083] 45. The group III-V semiconductor wafer (W) according to any one of items 41 to 44, wherein the entire defective region is located within an annular region between the edge of the wafer and a virtual circular line that is at most 10.5 mm away from the edge of the wafer.

[0084] 46. The group III-V semiconductor wafer (W) according to any one of items 41 to 45, wherein the entire defective region is located within an annular region between the edge of the wafer and a virtual circular line that is at most 10 mm away from the edge of the wafer.

[0085] 47. The group III-V semiconductor wafer (W) according to any one of items 41 to 46, wherein the wafer has a straight grinding section or a notch at a part of the edge, and the defective region is opposite to the straight grinding section or the notch.

[0086] The straight grinding section or the notch serves as an "identification feature" for transferring the azimuthal orientation of the lattice determined by the wafer manufacturer by means of X-ray method to the exposure system in the lithography production line when the wafer is used for the production of electronic components (epitaxial layer growth, lithography, etc.) on the wafer.

[0087] 48. A device for drying a wafer, comprising:

[0088] A bath (1) containing a liquid;

[0089] A wedge (2);

[0090] At least one vertically movable support device (5);

[0091] wherein at least one bracket (3; 31, 32) can be mounted in the support device (5),

[0092] At least one bracket (3; 31, 32) comprises:

[0093] a pair of first lateral guiding devices (3a, 3a'), a pair of second lateral guiding devices (3b, 3b'), and a pair of third lateral guiding devices (3c, 3c'),

[0094] wherein the pair of first lateral guiding devices (3a, 3a') are arranged below the pair of second lateral guiding devices (3b, 3b'), and the pair of second lateral guiding devices (3b, 3b') are arranged below the pair of third lateral guiding devices (3c, 3c'), and

[0095] wherein the distance between the pair of first lateral guiding devices (3a, 3a') is less than the distance between the pair of second lateral guiding devices (3b, 3b'), and the distance between the pair of second lateral guiding devices (3b, 3b') is less than the distance between the pair of third lateral guiding devices (3c, 3c'),

[0096] wherein the wedge (2) is arranged below the support (3) and is vertically movable separately from the support device (5).

[0097] Here, vertically means moving out of or into the bath, i.e., parallel to the direction of gravity.

[0098] 49. The device according to item 48, wherein the wedge (2) is vertically movable independently of the support device (5) or the support (3).

[0099] 50. The device according to item 48 or 49, wherein the wedge (2) comprises at least two wedge parts (2a, 2b), and the two wedge parts (2a, 2b) are vertically movable independently of each other.

[0100] 51. The device according to item 50, wherein at least the first support (31) can be inserted into the support device (5) such that the center of at least the first support (31) is above the tip of the first wedge section (2a), and in addition, the second support (32) can be inserted such that the center of the second support (32) is above the tip of the second wedge section (2b).

[0101] 52. The device according to item 51, wherein the first support (31) is adapted to hold a wafer (W1) having a first diameter, and the second support (32) is adapted to hold a wafer (W2) having a second diameter, wherein the first diameter is less than the second diameter.

[0102] 53. The device according to any one of items 50 to 52, wherein the tip of the first wedge section (2a) and / or the second wedge section (2b) is formed as a triangle, preferably a right triangle.

[0103] 54. The device according to any one of items 50 to 53, wherein the first wedge section (2a) is divided into two parts and there are two sections, and the first wedge section (2a) and the second wedge section (2b) are arranged adjacent to each other. Description of the Drawings

[0104] The preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings below.

[0105] Figure 1 A Marangoni drying process according to the prior art is shown.

[0106] Figure 1 a) shows the arrangement structure of a wafer in a bath according to the prior art.

[0107] Figure 1 b) shows the sequence of process steps, and

[0108] Figure 1 c) shows the obtained wafer according to the prior art together with the corresponding residual droplets.

[0109] Figure 2 An additional process for Marangoni drying according to the prior art is shown.

[0110] Figure 2 a) shows the arrangement structure of a wafer in a bath according to the prior art.

[0111] Figure 2 b) shows the sequence of process steps, and

[0112] Figure 2 c) shows the obtained wafer according to the prior art together with the corresponding residual droplets.

[0113] Figure 3 A process for producing a clean and dry wafer (such as a GaAs wafer) using Marangoni drying according to an embodiment of the present invention is shown.

[0114] Figure 3 a) shows the arrangement structure of a wafer in a bath,

[0115] Figure 3 b) shows the sequence of process steps, and

[0116] Figure 3 c) shows the residual droplets at the contact points of the obtained wafer according to the embodiment of the present invention.

[0117] Figure 4Shows a process for producing a clean and dry wafer (such as a GaAs or InP wafer) using Marangoni drying according to another embodiment of the present invention. Figure 4 a) Shows the process steps, Figure 4 b) Shows the potential construction details for fixing the wafer above the liquid level.

[0118] Figure 5 Shows details of the exact sequence from Figure 4 step d) of the first variant.

[0119] Figure 6 Shows details of the exact sequence from Figure 4 step d) of the second variant.

[0120] Figure 7 Shows details of the exact sequence from Figure 4 step d) of the third variant.

[0121] Figure 8 Shows the concept of step d) from Figure 4 the fourth variant.

[0122] Figure 9 Shows another embodiment of the apparatus for drying the wafer.

[0123] Figure 10 Shows two examples of holders that can hold multiple wafers.

[0124] Figure 11 Show examples of evaluation routines for wafers or wafer groups, where the data acquired using a Candela surface ellipsometer can be processed accordingly.

[0125] Figure 12 Shows several examples of residual droplets or their residues that can be detected using a Candela surface ellipsometer and their areas measured accordingly.

[0126] Figure 13 Show another example of an evaluation routine for wafers or wafer groups, where the data acquired using a Candela surface ellipsometer can be processed accordingly.

[0127] Figure 14 Shows the comparison of the defect areas between a semi-insulating (undoped in this case) GaAs wafer dried using the process according to an embodiment of the present invention according to Figure 3 and a wafer dried using the process according to Figure 1 the process.

[0128] Figure 15 Shows the use according toFigure 3 Comparison of the defective regions of a semiconductor (doped with Si in this case) GaAs wafer dried by the process according to an embodiment of the present invention with a wafer dried by the process according to Figure 1 the process.

[0129] Figure 16 Shows the comparison of the defective regions of a semiconductor (doped with sulfur in this case) InP wafer dried by the process according to an embodiment of the present invention with a wafer dried by the process according to Figure 3 the process. Figure 1 the process.

[0130] Figure 17 Shows a view of the device for drying wafers as seen from above.

[0131] Figure 18 Shows a side view (in a different state) of the device for drying wafers according to another embodiment of the present invention.

[0132] Figure 19 Shows the comparison of the defective regions of a semi-insulating (doped with Fe in this case) InP wafer dried by the process according to an embodiment of the present invention with a wafer dried by the process according to Figure 3 the process. Figure 1 the process. Detailed Description

[0133] Figure 1 Shows the process for lifting one or more wafers W out of bath 1.

[0134] In Figure 1 a), bath 1 is shown (which contains deionized rinse water, for example, to which a surface active substance such as isopropyl alcohol has been added); wafer W is contained herein. Above the water surface, holding devices H and H' are provided, and wafer W is held by two pairs of lateral guiding devices 3a and 3a' and 3b and 3b'. Below the wafer, a corresponding wedge 2 is provided, which can move vertically and is used when lifting the wafer.

[0135] In Figure 1b), the process steps are described in more detail. In step a) of the process according to the prior art, the wafer W is located below the liquid level of the bath 1, and the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' are also located below the liquid level. The wedge 2 is located below the wafer W and does not contact it. In step b), during the upward movement of the first and second lateral guiding devices 3a, 3a', 3b, 3b', the wedge 2 moves closer to the wafer W. However, the wedge does not necessarily have to contact the wafer. A part of the wafer W is now located above the liquid level. However, the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' are still located below the liquid level. The wafer W is in a state where it cannot yet be held by the holding devices H and H'. It has not yet been lifted out of the bath. In step c), only the wedge 2 moves vertically upward and partially pushes the wafer W out of the water bath; the wafer W has contacted the holding devices H and H'. These holding devices can be provided, for example, in the lid of the dryer. However, the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' are still located below the liquid level and have not moved further relative to step b). Since the wedge 2 has pushed the wafer W further upward, the first lateral guiding devices 3a, 3a' no longer contact the wafer W, but the second lateral guiding devices 3b, 3b' still contact the wafer W. In step d), the wafer W is pushed further upward by the wedge 2 - now, the second lateral guiding devices 3b, 3b' also no longer contact the wafer W. However, the wafer W is still held by the holding devices H, H'.

[0136] In step e), the liquid is drained from the bath 1. The liquid level is below the wafer W. Thus, the wafer W has been dried. The water level of the bath is lowered, i.e., the water is drained, to ensure the drying of the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b'. The wedge 2 still contacts the wafer W. The first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' have not moved further relative to step c).

[0137] In step f), the surface of the water bath 1 is thus lowered so much that the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' and the wedge 2 are placed above the water level and have thus also been dried. The wedge 2 still contacts the wafer W.

[0138] In step g), the wedge 2 is being lowered. By the downward movement of the wedge 2, the wafer W is again held by the already dried first lateral guiding devices 3a, 3a' and second lateral guiding devices 3b, 3b' and thus comes into contact with them. In order to prevent the wafer W from coming into contact with the first lateral guiding devices 3a, 3a' and second lateral guiding devices 3b, 3b' when passing through the liquid level of the bath 1, the wafer W is pushed out of the first lateral guiding devices 3a, 3a' and second lateral guiding devices 3b, 3b' by the wedge 2 moving vertically upwards and is then held only by the holding devices H. Residual droplets between the wafer W and the first lateral guiding devices 3a, 3a' and second lateral guiding devices 3b, 3b' are prevented. The holding devices H, H' are now located above the water level and are therefore still dry and do not cause any residual droplets. When passing through the water surface, residual droplets can only exist between the wafer W and the wedge 2. However, a disadvantage of this method is that there is a challenging process management with very high requirements for the spatial adjustment of the various moving parts relative to each other, in particular for the wedge 2 and the first lateral guiding devices 3a, 3a' and second lateral guiding devices 3b, 3b'. Since the holding devices H, H' are continuously adjusted to one dimension of the wafer, wafers of different dimensions cannot be dried according to this method - a separate drying device would be required for each dimension.

[0139] Figure 1 c) clearly shows that the residual droplet T is present here at the lower edge of the wafer W, which occurs between the contact of the wafer W and the wedge 2.

[0140] Figure 2 An alternative process for drying single or multiple wafers from the bath 1 is shown, which is also known from the prior art.

[0141] Figure 2 a) clearly shows that the wafer W is further held by two pairs of first lateral guiding devices 3a, 3a' and second lateral guiding devices 3b, 3b'. These first lateral guiding devices and second lateral guiding devices are in turn located in the bath 1.

[0142] From Figure 2 b), the individual steps of the process are presented:

[0143] In step a), the wafer is located below the water surface and is held by the first lateral guiding devices 3a, 3a' and second lateral guiding devices 3b, 3b'. Here, the first lateral guiding devices 3a, 3a' and second lateral guiding devices 3b, 3b' have not yet been moved. The water bath 1 (which contains water with isopropanol enriched in its surface layer) is drained at a predetermined speed.

[0144] In step b), the liquid level is above a pair of second lateral guiding devices 3b, 3b'.

[0145] In step c), the water is below the wafer W, and the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' are above the liquid level.

[0146] Due to the contact between the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' when the liquid level is lowered, the contact points of the wafer with the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' often have residual droplets, which correspondingly and adversely affect the quality of the wafer. In addition, the quality of the epitaxial layer grown later is also negatively affected, which may lead to a lower yield of the component parts. However, the advantage of the method is that it is less technically challenging and it has the potential to dry wafers of different sizes.

[0147] Figure 2 c) shows the wafer W with residual droplets T at all four contact points.

[0148] Figure 3 A method for drying a wafer according to the present invention is shown.

[0149] In Figure 3 a), a state in which the wafer W is completely immersed in the bath 1 is shown. However, there are three pairs of lateral guiding devices 3a, 3a', 3b, 3b' and 3c, 3c' for holding the wafer here, wherein a pair of first lateral guiding devices 3a, 3a' are arranged below a pair of second lateral guiding devices 3b, 3b', and a pair of second lateral guiding devices 3b, 3b' are arranged below a pair of third lateral guiding devices 3c, 3c'. The distance between a pair of first lateral guiding devices 3a, 3a' is less than the distance between a pair of second lateral guiding devices 3b, 3b', and the distance between a pair of second lateral guiding devices 3b, 3b' is less than the distance between a pair of third lateral guiding devices 3c, 3c'. In Figure 3 a), the third lateral guiding devices 3c, 3c' do not contact the wafer W. The wedge 2 is provided below the wafer.

[0150] In Figure 3 b), the respective steps are described in more detail.

[0151] In step a), the wafer W is located below the liquid level of the bath 1 and is held by a pair of first lateral guiding devices 3a, 3a' and a pair of second lateral guiding devices 3b, 3b'. The wedge does not contact the wafer. A pair of third lateral guiding devices 3c, 3c' do not contact the wafer.

[0152] In step b), the wedge moves towards the wafer such that the tip of the wedge contacts the wafer.

[0153] In step c), the lateral guiding devices 3a, 3a', 3b, 3b' and 3c, 3c' as well as the wedge 2 move upwards. However, here, the third lateral guiding devices 3c, 3c' that have passed through the water surface do not contact the wafer, i.e., they do not touch the wafer. The wedge 2 still moves towards the wafer W and contacts the wafer, but still below the water surface.

[0154] In step d), the water level is still located between the pair of second lateral guiding devices 3b, 3b' and the third lateral guiding devices 3c, 3c'. However, the wafer W is only slightly lifted by the wedge 2 such that the wafer no longer contacts the first pair of lateral guiding devices 3a, 3a' and the second pair of lateral guiding devices 3b, 3b'. Instead, the wafer W contacts the third pair of lateral guiding devices 3c, 3c' above the liquid surface. Thus, the wafer is now held by the wedge 2 and the third pair of lateral guiding devices 3c, 3c'.

[0155] In step e), the wafer W, the tip of the wedge 2, and the first pair of lateral guiding devices 3a, 3a', the second pair of lateral guiding devices 3b, 3b' and the third pair of lateral guiding devices 3c, 3c' are all above the water surface.

[0156] In step f), the wedge 2 is being lowered and the wafer is held by the wedge 2 and the first pair of lateral guiding devices 3a, 3a' and the second pair of lateral guiding devices 3b, 3b' which are now dry. The third lateral guiding devices 3c, 3c' no longer contact the wafer W.

[0157] In step g), the water level has been lowered and the position of the wafer W relative to the three lateral guiding devices 3a, 3a', 3b, 3b' and 3c, 3c' and the wedge 2 has not changed compared to step f).

[0158] When passing through the water surface, there is only one contact point between the wafer W and the wedge 2, and residual droplets may appear at this contact point.

[0159] In Figure 3 c), the residual droplets are shown below at the contact point of the wedge 2, but it does not necessarily need to appear, and if it appears, it is smaller compared to the method according to Figure 1 and Figure 2 the method.

[0160] The moving speeds of the lateral guiding devices 3a, 3a', 3b, 3b' and 3c, 3c' and the wedge 2 are always coordinated such that the resulting moving speed of the wafer is always constant and can thus be controlled. The travel path of the wafer during lifting is the same as Figure 1It is relatively small, resulting in a shorter process time. Therefore, the contact time between the lower edge of the wafer W and the movable wedge 2 containing residual moisture is shortened by several minutes. As a result, the risk of forming residual droplets at the contact point is fundamentally reduced. Due to the short vertical distance between the wafer and the lateral guiding devices 3a, 3a', 3b, 3b' and 3c, 3c', the wafer and the lateral guiding devices can be dried almost simultaneously, which further shortens the process time. This leads to a significant increase in the productivity of the entire cleaning process, because drying usually represents the slowest process step and is therefore the limiting step of the entire process speed.

[0161] The adjustment workload for the setting and position correction of all components (the wedge and the lateral guiding devices) is significantly reduced, the complex alignment between the lateral guiding devices is omitted, and no inclined travel path is required. In addition, the risk that the wafer is subjected to mechanical stress without precise adjustment is reduced, which may lead to scratches on the wafer, damage to the wafer edge, and wafer breakage.

[0162] The reduced risk of residual droplets and mechanical stress of the wafer due to imprecise adjustment is particularly relevant for the drying of larger wafers (e.g., greater than 150 mm), because the unfavorable leverage ratio compared to a smaller wafer diameter would require a significantly increased adjustment workload and smaller tolerances to ensure consistent wafer quality.

[0163] Compared with Figure 1 the method in, the contact time between the wedge 2 and the wafer W can be shortened from several minutes to several seconds, which results in a sharp reduction in the probability of residual droplets occurring at the only remaining first contact point (between the wedge 2 and the wafer W). If these residual droplets still appear, they will also be significantly smaller.

[0164] Preferably, the wafer is lifted at a speed of about 1 mm / s. To dry the lower part of the wafer (about 1 cm), the lifting speed is significantly reduced to less than 0.5 mm / s to reduce contact with the droplets. The lifting speed is the speed at which the wafer moves relative to the liquid level. Since too large fluctuations in the water level may be reflected in the chemical composition of the oxide layer, this reduction in speed must be carried out gradually. When the lower edge of the wafer W just reaches the water level, the wafer W must be separated from the water level at a high speed (>30 mm / s, preferably >40 mm / s, more preferably >50 mm / s), and at the same time the wedge 2 must be separated from the lower edge of the wafer W in the opposite direction. Especially for n-doped GaAs, due to its high surface tension, this boundary condition must be precisely observed. Only in this way can it be prevented that on the one hand, the water from the water level and on the other hand, the residual moisture from the wedge 2 are pulled back onto the surface of the wafer again.

[0165] Figure 4Another embodiment of the method of Marangoni drying is shown. In particular, the sequence of process steps is shown in Figure 4 a). In step a), the wafer W is below the liquid level and is held by the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b'. The water bath 1 contains water that is rich in isopropyl alcohol at its surface. A pair of third lateral guiding devices 3c, 3c' is located above the liquid level and serves as (so to speak) a drying transfer unit. In step b), the wafer W is slightly lifted by the wedge 2, and a part of the wafer is above the water surface. The wedge 2 contacts the lower edge of the wafer W. Below the water surface, the wafer is still held by the lateral guiding devices 3a, 3a' and 3b, 3b', which have moved up a little. A pair of third lateral guiding devices 3c, 3c' still remains above the water surface and does not contact the wafer. In step c), the positions of the pair of first lateral guiding devices 3a, 3a' and the pair of second lateral guiding devices 3b, 3b' are kept constant. However, the wedge 2 has further lifted the wafer such that the wafer only contacts the pair of second lateral guiding devices 3b, 3b' and does not contact the pair of first lateral guiding devices 3a, 3a'. Compared with step b), the positions of the pair of third lateral guiding devices 3c, 3c' have not changed. In step d), the wafer W has been completely lifted out of the liquid bath. The wedge 2 does remain below the liquid level. Here, the pair of third lateral guiding devices 3c, 3c' has moved horizontally, and the distance between the third lateral guiding devices 3c, 3c' has become smaller. The third lateral guiding devices 3c, 3c' can have a holding function, or an additional gripping device 4 as Figure 9 shown (however, not shown in this figure) can be used to hold the wafer W above the liquid level. This third lateral guiding device or the additional gripping device holds the wafer W above the water surface. In step e), the liquid level is lowered by releasing water. In step f), the positions of the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' remain unchanged, but the pair of third lateral guiding devices 3c, 3c' is moving horizontally, the distance between the third lateral guiding devices 3c, 3c' increases again, and the wafer W is now at least resting on the wedge 2. From the moment when the third lateral guiding devices 3c, 3c' no longer contact the wafer, the wafer W is held by the wedge 2 and the second lateral guiding devices 3b, 3b'. Thus, the wedge 2 and all the lateral guiding devices 3a, 3a', 3b, 3b' and 3c, 3c' are dried. In step g), the wedge 2 is lowered such that the wafer W is again held by the pair of first lateral guiding devices 3a, 3a' and the pair of second lateral guiding devices 3c, 3b'.

[0166] In this method, there is a characteristic that the wafer passes through the water level without individual contact with any tool, that is, it does not contact any guiding devices 3a, 3a', 3b, 3b' and 3c, 3c' nor the wedge 2. In all process steps of wafer lifting, the wedge 2 remains below the liquid level, and a pair of third lateral guiding devices 3c, 3c' always remain above the liquid level and thus are never wetted.

[0167] Figure 4 b) Exemplarily shows how to additionally hold the wafer starting from step d). On the left side, the third lateral guiding devices 3c, 3c' are shown in a T shape, which results in the wafer W being better held. On the right side, the gripping device 4 can be seen, which can additionally hold the wafer W above the liquid level and can be adjusted to the wafer diameter.

[0168] Generally, the example of water in the discharge process bath of this method ( Figure 3 and Figure 4 ) then only takes effect when the wafer is completely above the liquid level. This allows a continuous flow of ultrapure water (so-called overflow). The surface of the liquid level (on which particles can float) is thus always well circulated and liquid exchange occurs. In the method according to Figure 2 , the liquid level is lowered while the wafer W is at least still partially in the bath. Then overflow at the liquid level is no longer possible, and particles can then easily accumulate there and attach to the dry wafer W - which then deteriorates the quality of the epitaxial layer.

[0169] Figure 5 A more detailed representation of the sequence from Figure 4 step d) according to the first variant is provided - showing the sub-steps so to speak. Here, it is shown that the wafer W is almost completely above the liquid level in step d-1). The wedge 2 is below the liquid level, and a pair of third lateral guiding devices 3c, 3c' are above the liquid level and adjacent to the wafer W. In steps d-2), d-3) and d-4), the distance between the pair of third lateral guiding devices 3c, 3c' continuously decreases, but the wedge 2 remains below the liquid level. In step d-3), the entire wafer is already above the water surface. In step d-4), the wafer has been moved slightly further upwards. Thus, the third lateral guiding devices 3c, 3c' are dry transfer units that always remain above the liquid level and thus are never wetted. Only the horizontal movement of the third lateral guiding devices 3c, 3c' is necessary. The wafer slides on the third lateral guiding devices 3c, 3c'.

[0170] Figure 6 A second variant from Figure 4A more detailed representation of the sequence of step d) - one could say showing sub - steps. Here, only the structure of the third lateral guiding devices 3c, 3c' is different. These third lateral guiding devices are oval and require horizontal movement and rotational movement to move the wafer W. Also here, only the lifting of the last few millimeters of the entire wafer W out of the liquid bath as shown in step d) of Figure 4 is described in particular detail. In step d - 1), the wafer abuts against two obliquely placed oval third lateral guiding devices 3c, 3c', where the long side of the oval abuts against the wafer. The wafer is almost completely lifted out of the water bath, with only one millimeter still immersed in the water. The wedge 2 is always underwater. Now, in step d - 2), the oval third lateral guiding devices 3c, 3c' rotate so that the wafer rotates a little further upwards. In steps d - 3) and d - 4), the third lateral guiding devices 3c, 3c' rotate further until the wafer is completely above the liquid level.

[0171] Figure 7 A more detailed representation of the sequence of step d) from Figure 4 is provided according to the third variant - one could say showing sub - steps. Here, the drying transfer unit (i.e., the third lateral guiding devices 3c, 3c') has an eccentric shaft. Horizontal movement and rotational movement are required to move the wafer W. In step d - 1), a small part of the wafer is still below the liquid level; in step d - 2), the third lateral guiding devices 3c, 3c' rotate, so the wafer moves slightly upwards; in step d - 3), the third lateral guiding devices 3c, 3c' have rotated further so that the wafer is already above the liquid level; in step d - 4), the wafer is lifted a little above the liquid surface. The wedge 2 always remains underwater.

[0172] Figure 8 A representation of AI - supported adaptive control for wafer lifting is shown. Here, a wafer W with radius R is shown, and in addition, a pair of third lateral guiding devices 3c, 3c' is shown asymmetrically. The interaction of the movement of the wedge 2 (not shown here), the third lateral guiding devices 3c, 3c' and the position of the wafer relative to the water level is particularly complex for the drying of wafers of different diameters. According to the conventional method, complex movement patterns must be developed and the machinery must be calibrated extensively for each diameter. Here, AI - supported adaptive control can be utilized. A camera (not shown here) records the wafers arranged in the holder, i.e., at least the first and the last wafers of the holder. The camera is fixed and mounted above the water surface, and the third lateral guiding devices 3c, 3c' are highlighted in color for easy image recognition. Then, a trained neural web - work with AI - based image recognition can determine the distance between the center of the wafer and the water level ( Figure 8 parameter z in Figure 8parameters x, y) in it, and the rotational positions of the possible third lateral guiding devices 3c, 3c'. Then, this data can control the program flow, especially the movement of the wedge 2 in the vertical direction, the movement of the third lateral guiding devices 3c, 3c' (horizontal movement and possible rotation), and can also correspondingly control other important process parameters (such as drainage or DI water supply). Monitoring of the first and last wafers in the carrier can detect the inclination of the carrier axis relative to the water surface plane and, if necessary, take appropriate countermeasures.

[0173] Figure 9 Another embodiment of a corresponding device for wafer drying is shown. In addition to the carrier 3 and the wedge 2, a gripping device 4 is provided, which is designed to grip the wafer until the wafer rises above the water surface. Once the gripping device 4 has gripped the wafer, the wedge 2 still underwater (not shown in the figure) can be lowered. The carrier and the gripper move upward at the same speed, and the wafer passes through the water surface without being held by the wedge 2 at the passing point. Thus, the formation of residual droplets is prevented. Here, a suction device 6 is provided within the wedge 2.

[0174] Figure 10 Two carriers are shown. Figure 10 a) shows a carrier 3 according to the prior art, which can be used, for example, in a method according to Figure 1 . Here, there are two head portions 3d, 3d', and between these two head portions, two pairs of lateral guiding devices 3a, 3a' and 3b, 3b' are arranged. The wafer W (not shown here) can be held by these lateral guiding devices. The first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' each have protrusions (not shown in detail here) - these protrusions form a comb-like structure that cannot hold a single wafer W (not shown here) - such that the wafers cannot contact or tilt each other. A pair of first lateral guiding devices 3a, 3a' is arranged below the second lateral guiding devices 3b, 3b'. The distance between a pair of first lateral guiding devices 3a, 3a' is less than the distance between the second lateral guiding devices 3b, 3b'. Figure 10 b) shows a carrier 3 that can be used in the method of the present invention according to Figure 3 . Compared with Figure 4 a), here, a pair of third lateral guiding devices 3c, 3c' is arranged above a pair of second lateral guiding devices 3b, 3b'. The distance between a pair of first lateral guiding devices 3a, 3a' is less than the distance between the second lateral guiding devices 3b, 3b', and the distance between a pair of second lateral guiding devices 3b, 3b' is less than the distance between the third lateral guiding devices 3c, 3c'. Therefore, there is a possibility of holding the wafer W (not shown here) at multiple points, which is different fromFigure 4 a) Different. The first lateral guiding devices 3a, 3a', the second lateral guiding devices 3b, 3b' and the third lateral guiding devices 3c, 3c' each have a protrusion (not shown in detail here) - the protrusion forms a comb structure that can hold a single wafer W (not shown here) - such that the wafers cannot contact or tilt each other.

[0175] Figure 11 A corresponding evaluation routine for measurement is shown, in which the uniformity of the oxide surface layer of the wafer according to the present invention can be evaluated: Using a Candela surface ellipsometer, an original data file is generated. Inside the software of the Candela ellipsometer, the corresponding contrast maximization is performed and applied to the entire map (for example, changing the contrast in an image processing software for pixel graphics until the droplet residue is clearly visible in the shown picture; here, it must be ensured that the area with the specific shape of the droplet stands out from its surroundings). Subsequently, the corresponding image file is exported. Then, for all wafers, manual marking of different contrast regions is performed, with particular attention paid to the edge regions. At the positions where residual droplets may form during the drying process due to the orientation of the wafer, for evaluation, a square with a width of 9 cm and a height of 1.9 cm is placed on the wafer. The droplets are identified and evaluated within this square. Thereby, it can be ensured that all possible residual droplets within a 1 cm-wide ring at the outer edge of the wafer are recorded. Compared with the ring (annular strip) where it may not be easy to distinguish the residual droplets from the possible laser markings at the front of the wafer during image processing, using the imaginary square is more useful and accurate. After that, image processing is used to perform the determination of the area of the defective region, in which the area can be measured accordingly. This measures the area of the defined region. Here, generally, the edge is not excluded for a specific region of the wafer - but the entire wafer can be further used - because the corresponding defects can be substantially avoided by the improved Marangoni drying method.

[0176] Here, the defective regions with residual droplets or the effects of their changes in the oxide layer composition are marked and measured based on the following criteria:

[0177] ‧ The region must be located on the edge of the wafer;

[0178] ‧ There is an irregular shape;

[0179] ‧ The region has a different brightness from the surrounding area (usually brighter than the surrounding area; smaller darker areas are also possible);

[0180] ‧ The shape of the region is typical of water residues (such as droplet shape, shape with spherical / elliptical / ovoid elements, elongated and branched shape).

[0181] This results in the frequency distribution of the identified defect areas.

[0182] Figure 12 Two examples of droplets at the wafer edge are shown, each of which is marked and whose area is measured. Here, it is difficult to perform an automatic evaluation because the contrast change in the wafer may occur, for example, through other effects (shown in black in Figure 12 ), but it must not be confused with the droplets at the wafer edge. Therefore, a manual evaluation must be performed here, in which it is always noted that the droplets originate from the edge of the wafer and the corresponding shape can also be logically assigned to the shape of the droplets. Accordingly, a completely angular shape cannot be assigned to the droplets. For example, an edge with fine serrated notches cannot be assigned to the droplets either, because the surface tension of water does not allow the development of such a shape. However, as Figure 12 shown in the left figure, a shape with an irregular edge section is possible. During drying of the wafer, contact with the support or wedge through the liquid surface results in defects due to the attached droplets, which may cause spots and thus "defects". However, according to the present invention, fewer spots are left, preferably only a single spot, and / or the overall spot area is minimized, while for drying methods according to the prior art, multiple and generally larger spot areas are usually left.

[0183] In Figure 13 an alternative to the evaluation routine is proposed. Here, the manual marking of different contrast regions is only performed for a few wafers, and then all the remaining wafers are evaluated by means of the training of a neural network, and the defect areas are evaluated accordingly here. Since the appearance of the droplet residues may have very different contrasts, the fragmentation of the droplet regions is carried out by means of a neural network. The neural network is trained using the TensorFlow-Keras platform. The UNet structure with a resnet34 backbone is used as the model (U-Net: Convolutional Networks for Biomedical Image Segmentation, Olaf Ronneberger, Philipp Fischer, Thomas Brox, arXiv 2015, https: / / doi.org / 10.48550 / arxiv.1505.04597; http: / / lmb.informatik.uni-freiburg.de / people / ronneber / u-net). For all images, the reasonableness of the segmented regions is visually inspected, and if necessary, it is added to the training dataset to retrain the network. This process is performed iteratively until the automatic segmentation matches the visual evaluation of more than 98% of all images. Then, the regions segmented in this way are automatically selected by conventional image processing (e.g., OpenCV: https: / / opencv.org / ) in a second step, and their areas are measured.

[0184] Thus, instead of evaluating the contrast based on a threshold, the contrast is evaluated visually or by a trained algorithm or neural network based on its range; here, the absolute value of the measured signal is not considered, but only the recognizability of the droplet area. The evaluation is performed outside the Candela ellipsometer.

[0185] Figure 14 The measurement results of the defect areas of two corresponding wafer sets of a semi-insulating, undoped GaAs wafer with a diameter of 150 mm are shown; on the right is the wafer dried using conventional Marangoni drying (according to Figure 1 ), and on the left is the wafer dried using the improved Marangoni drying according to the present invention ( Figure 3 ). For the undoped wafers, it can be shown that for the wafers produced according to the new method, the distribution of different defect areas is smaller, and the absolute defect area is smaller (less than 5 mm 2 ). The defect area corresponds to the area measured by surface measurement using a Candela ellipsometer. From a chemical perspective, there is an uneven composition of surface oxides - thus, the defect area is the area of surface oxides where the oxide composition is uneven. Since the droplet sizes in the data are not normally distributed, a conventional t-test cannot be performed. In these cases, it is suitable to use the Wilcoxon test which makes no assumptions about the underlying distribution. In this test, the sum of ranks of the observed values is calculated, which is approximately normally distributed and allows for statistical statements. Since the droplet sizes of the two methods are significantly different, a one-tailed test with a 0.95 confidence interval is performed. The parameter n represents the total number of values; if the p-value is below the typical value of 0.05, the null hypothesis can be rejected (in this case: the droplet size obtained by the method according to Figure 3 is larger than the droplet size obtained by the method according to Figure 1 ). Thus, a very small p-value (<0.0001) of the data very significantly indicates that the droplet size obtained by the method according to Figure 3 is smaller. The parameter W refers to the sum of ranks of one of the two groups.

[0186] Figure 15 The measurement results of the defect areas of two corresponding wafer sets of a semi-insulating silicon-doped GaAs wafer with a diameter of 150 mm are shown; on the right is the wafer dried using conventional Marangoni drying (according to Figure 1 ), and on the left is the wafer dried using the improved Marangoni drying according to the present invention ( Figure 3 ). Using the method according to the present invention, it can also be shown that for the Si-doped wafers, the diffusion is significantly smaller, and the defect area (less than 25 mm 2are significantly smaller. Since the droplet sizes in the data are not normally distributed, a conventional t-test cannot be performed. In such cases, the Wilcoxon test, which makes no assumptions about the underlying distribution, is suitable. In this test, the sum of the ranks of the observations is calculated, which is approximately normally distributed and allows for statistical statements. Since the droplet sizes of the two methods are significantly different, a one-tailed test with a 0.95 confidence interval is performed. The parameter n represents the total number of values; if the p-value is below the typical value of 0.05, the null hypothesis can be rejected (in this case: the droplet size obtained by the method according to Figure 3 is larger than the droplet size obtained by the method according to Figure 1 ). Thus, the very small p-value of the data (<0.0001) very significantly indicates that the droplet size obtained by the method according to Figure 3 is smaller. The parameter W refers to the sum of the ranks of one of the two groups.

[0187] Figure 16 shows the measurement results of the defect areas of two corresponding wafer groups of sulfur-doped InP wafers of a semiconductor with a diameter of 100 mm; on the right are the wafers dried using conventional Marangoni drying (according to Figure 1 ), and on the left are the wafers dried using the improved Marangoni drying according to the present invention ( Figure 3 ). Using the method according to the present invention, it can also be shown that for sulfur-doped wafers, the diffusion is significantly smaller, and the defect areas (less than 5 mm 2 ) are significantly smaller. The defect areas correspond to the areas measured by surface measurements using a Candela ellipsometer. From a chemical perspective, there is an inhomogeneous composition of the surface oxide - thus, the defect areas are areas of the surface oxide where the oxide composition is inhomogeneous. Since the droplet sizes in the data are not normally distributed, a conventional t-test cannot be performed. In such cases, the Wilcoxon test, which makes no assumptions about the underlying distribution, is suitable. In this test, the sum of the ranks of the observations is calculated, which is approximately normally distributed and allows for statistical statements. Since the droplet sizes of the two methods are significantly different, a one-tailed test with a 0.95 confidence interval is performed. The parameter n represents the total number of values; if the p-value is below the typical value of 0.05, the null hypothesis can be rejected (in this case: the droplet size obtained by the method according to Figure 3 is larger than the droplet size obtained by the method according to Figure 1 ). Thus, the very small p-value of the data (<0.0001) very significantly indicates that the droplet size obtained by the method according to Figure 3 is smaller. The parameter W refers to the sum of the ranks of one of the two groups.

[0188] In Figure 17In this case, an embodiment of a device for drying wafers according to the present invention is shown. Here, a support unit 5 is provided, in which a plurality of different brackets 3, 31, 32 can be suspended. The brackets themselves hold the wafers using guiding means (comb bars). In the current view, two first brackets 31 or one second bracket 32 can be suspended. The first bracket 31 is used for drying wafers with a smaller diameter compared to the bracket 32. Here, the wedge is composed of two first wedge sections 2a and one second wedge section 2b, which can move vertically separately from each other. The center of the first bracket 31 is directly above the tip of the first wedge section 2a, and the center of the second bracket 32 is above the tip of the second wedge section 2b. The first wedge section 2a and the second wedge section 2b also have corresponding protrusions 2c forming a comb-like structure. The second bracket 32 is provided for larger wafers, for example, with a diameter greater than or equal to 200 mm, and the protrusions 2c have a greater distance compared to the first bracket 31; thus, the bracket 32 is longer than the first bracket 31 and the same wedge cannot be used anymore to lift the wafer - different from wafers with a smaller diameter. The wedge sections 2a, 2b must be arranged centered relative to the brackets because they must capture the wafers at the lower points. Therefore, for example, according to the prior art, it is not possible to achieve the lifting of wafers with a diameter of up to 150 mm on the one hand and wafers with a diameter greater than or equal to 200 mm on the other hand in a dryer. In the device according to the present invention, separate wedge sections (2a for smaller wafers W1, 2b for larger wafers W2) with appropriately suitable lengths and appropriately adjusted distances of the protrusions 2c are used for smaller wafers (e.g., wafers with a diameter of 150 mm or less) and larger wafers (e.g., wafers with a diameter of 200 mm or more) respectively. Since the 200 mm wafer has a larger diameter, the distance of the protrusions 2c must be greater than in the case of a smaller wafer diameter so that they do not touch each other in the case where the wafer W2 is slightly tilted.

[0189] Figure 18 A side view of the wedge 2 of the device according to the present invention is shown. Here, in the left view, the structures of the first wedge section 2a and the second wedge section 2b are shown. In the central view, here a wafer W1 with a small diameter (e.g., a 3-inch or 150 mm wafer) is shown being lifted upward by the first wedge section 2a. In the right view, a larger wafer with a larger diameter W2 (e.g., a 200 mm wafer) is shown being lifted upward by the second wedge section.

[0190] Figure 19 The measurement results of the defect regions of two corresponding wafer groups of semi-insulating Fe-doped InP wafers with a diameter of 150 mm are shown; on the right is the use of conventional Marangoni drying (according to Figure 1The wafer to be dried, with the left side using improved Marangoni drying according to the present invention Figure 3 The wafer to be dried. For wafers doped with Fe, it can be shown that for wafers produced according to the existing method and the new method, the diffusion of different defect regions is equally small, and almost no defect regions can be seen. The defect regions correspond to the areas measured by surface measurements using a Candela ellipsometer.

[0191] The method for drying wafers according to the present invention includes a bath having an arrangement structure with at least one wedge and at least one support. The support has the following characteristics:

[0192] A pair of first lateral guiding devices 3a, 3a', a pair of second lateral guiding devices 3b, 3b', and a pair of third lateral guiding devices 3c, 3c'. The pair of first lateral guiding devices 3a, 3a' are arranged below the pair of second lateral guiding devices 3b, 3b', and the pair of second lateral guiding devices 3b, 3b' are arranged below the pair of third lateral guiding devices 3c, 3c'. The distance between the pair of first lateral guiding devices 3a, 3a' is preferably less than the distance between the pair of second lateral guiding devices 3b, 3b', and the distance between the pair of second lateral guiding devices 3b, 3b' is preferably less than the distance between the pair of third lateral guiding devices 3c, 3c'.

[0193] The method according to the present invention includes the following steps:

[0194] i) Move at least one wedge 2 vertically upward until it contacts the wafer at the lowest point of the wafer, move a pair of first lateral guiding devices 3a, 3a' and a pair of second lateral guiding devices 3b, 3b' vertically upward, wherein the wafer W contacts the pair of first lateral guiding devices 3a, 3a' and the pair of second lateral guiding devices 3b, 3b', wherein the upper region of the wafer W is lifted out of the bath 1, and the pair of third lateral guiding devices 3c, 3c' do not contact the wafer;

[0195] ii) Move the wedge 2 vertically upward until the pair of first lateral guiding devices 3a, 3a' and the pair of second lateral guiding devices 3b, 3b' no longer contact the wafer W, while still being below the liquid level of the bath 1, wherein the pair of third lateral guiding devices 3c, 3c' contact the wafer above the liquid level of the bath 1;

[0196] iii) Lift the wafer W above the liquid level of the bath 1, wherein the pair of third lateral guiding devices 3c, 3c' contact the wafer W.

[0197] Compared with the prior art (see Figure 1), in particular, the holding of the wafer is no longer achieved by fixed holding devices H and H' restricted within the wafer diameter (e.g., thus inside the cover of the dryer), but by a pair of third lateral guiding devices 3c, 3c'.

[0198] Therefore, when the water level correspondingly passes through the first and second lateral guiding devices, contact between the wafer and the first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' of the brackets 3, 31, 32 in particular is prevented. The wafers W, W1, W2 are held by the third lateral guiding devices 3c, 3c' located above the water level and already dried. During drying according to the invention, the vertical movement path of the wafer is significantly shorter and can be shortened to a few seconds. Therefore, significantly fewer and smaller droplets that may form when the wafer contacts the wedges 2, 2a, 2b occur. In the Candela measurement of the dried wafer according to this method, fewer and smaller residual droplets are found.

[0199] Preferably, the method according to the invention further comprises the following steps:

[0200] iv) moving the wedge 2 vertically downward until the wafer W contacts at least one of a pair of first lateral guiding devices 3a, 3a' and a pair of second lateral guiding devices 3b, 3b';

[0201] v) further moving the wedge 2 vertically downward until the wedge no longer contacts the wafer W;

[0202] Simultaneously with step iv) and / or v) in parallel or after step v), the liquid level of the bath 1 is lowered until the liquid level is lower than the wedge 2.

[0203] Correspondingly, the lateral guiding devices 3a, 3a', 3b, 3b' or the brackets 3, 31, 32 and the wedges 2, 2a, 2b can be dried until they are ready for subsequent drying operations of the wafer.

[0204] Preferably, the bath 1 contains water and at least one additional surface tension reducing substance, preferably isopropyl alcohol.

[0205] Thereby, it can be achieved that the Marangoni effect is optimally utilized in the method according to the invention.

[0206] Preferably, a pair of first lateral guiding devices 3a, 3a', a pair of second lateral guiding devices 3b, 3b' and / or a pair of third lateral guiding devices 3c, 3c' each consist of a pair of webs which are arranged to contact opposite sides of the wafers W, W1, W2 in different process steps. Thereby, it can be ensured that the wafers W, W1, W2 are held from the sides and do not contact each other during the drying process (i.e., they cannot topple over in the dryer either). Wafers that contact each other during drying may "stick" together and thereby prevent drying (i.e., the wafers will remain wet).

[0207] Preferably, a pair of first lateral guiding devices 3a, 3a' and a pair of second lateral guiding devices 3b, 3b' are immersed in the bath 1 in step i), and preferably, a pair of third lateral guiding devices 3c, 3c' do not contact the wafers W, W1, W2 at the end of step v).

[0208] Since there is contact only between the wedge and the wafer (or even no contact at all between the wafer and any guiding device or the wedge) at most when passing through the liquid level of the bath, it can be ensured that no droplets adhere to the wafers W, W1, W2 in the regions of the first, second and third guiding devices, which would correspondingly reduce the surface uniformity of the wafer surface.

[0209] Preferably, the wedges 2, 2a, 2b are provided with at least one suction device 6 at which a vacuum can be applied when the upper tips of the wedges 2, 2a, 2b are located above the liquid level. Thereby, it can be ensured that the remaining water at the tips of the wedges 2, 2a, 2b is sucked off so that droplets do not reach the wafers W, W1, W2 and thus can correspondingly cause non-uniformity of the oxide surface.

[0210] Preferably, the wedges 2, 2a, 2b have a surface structure that increases the surface tension. For example, the wedges 2, 2a, 2b can be manufactured therefrom by plasma treatment of PEEK. The increased surface tension of the wedges 2, 2a, 2b can cause residual droplets to remain at the wedges 2, 2a, 2b and not spread to the wafers W, W1, W2.

[0211] Preferably, the lifting speed depends on the position of the lowest point of the wafer, and if the lowest point of the wafer is more than 1.2 cm below the liquid level, the lifting speed is 0.8 to 1.2 mm / s, and if the lowest point of the wafer is less than 1.2 cm below the liquid level, the lifting speed is between 0.4 and 0.5 mm / s, which results in a significant reduction in the contact droplets. Since too large a fluctuation in the water level may be reflected in the chemical composition of the oxide layer, this speed reduction should be carried out gradually. Once the lowest point of the wafer W reaches the water level, the lifting speed is at least 30 mm / s (preferably 40 mm / s or 50 mm / s). Thereby, it is possible to prevent the water from the water level on the one hand and the residual moisture from the wedge on the other hand from being pulled onto the wafer surface again. At the same time, the wedge can be separated from the lower edge of the wafer in the opposite direction.

[0212] According to the embodiment, a pair of first lateral guiding devices 3a, 3a', a pair of second lateral guiding devices 3b, 3b' and a pair of third lateral guiding devices 3c, 3c' are arranged on the support 3, and the entire support 3 is moved in step i); in step iii), the wafer W is lifted above the liquid level of the bath 1, whereby a pair of third lateral guiding devices 3c, 3c' (already above the liquid level) and the wedge 2 contact the wafer W. When passing through the liquid surface, there is only one contact point between the wedge and the wafer - the droplet area can be minimized.

[0213] According to another embodiment, a pair of third lateral guiding devices 3c, 3c' are kept positioned above the liquid level in all process steps and are capable of moving independently of a pair of first lateral guiding devices 3a, 3a' and a pair of second lateral guiding devices 3b, 3b', and the third lateral guiding devices 3c, 3c' are capable of horizontal movement relative to each other. Thus, the third lateral guiding devices 3c, 3c' always remain dry and can hold the wafer W above the liquid level. When passing through the liquid level, accordingly, there is no contact point at all between the wedge and the wafer - then the droplet area can even be completely avoided. Preferably, the wedge 2 then remains below the liquid level in all process steps. This is the reason why there are no remaining residual droplets at the wafer in the area of the wedge.

[0214] Preferably, the distance between the points where the third lateral guiding devices 3c, 3c' contact the wafer in step iii) decreases continuously. Thereby, the wafer W can be vertically moved by the horizontal movement of the third lateral guiding devices 3c, 3c'. More preferably, the third lateral guiding devices 3c, 3c' are arranged to perform a horizontal movement relative to each other. More preferably, the third lateral guiding devices 3c, 3c' are eccentrically mounted or have an elliptical shape and are arranged to perform a rotational movement. Thereby, the vertical movement of the wafer can be caused by the rotational movement of the third lateral guiding devices 3c, 3c', and can be helpful in the region where the last wafer is lifted out of the bath (at this moment, the wedge 2 is not necessary for the vertical movement of the wafer, and the contact point of the wafer W - wedge 2 can be avoided when passing through the liquid surface).

[0215] Further process parameters may affect the uniformity of the oxide surface of III-V wafers:

[0216] ∙ As another parameter that needs to be controlled for Marangoni drying of residual droplets, the concentration of a substance that reduces the surface tension of ultrapure water (preferably isopropyl alcohol (IPA)) has emerged. Reducing the supply of IPA in the final stage of drying results in a larger vertical gradient in surface tension and a lower risk of residual droplet formation. Since the effect of reducing the IPA supply on the concentration of IPA in the gas phase and subsequently on the magnitude of the concentration gradient is delayed, it may be meaningful to gradually reduce the supply of IPA after the interfacial (liquid surface) has passed through the center of the wafer. In particular, for n-doped GaAs, it may be meaningful to significantly reduce the supply of IPA.

[0217] ∙ The gradient of IPA at the interface results from the interaction between the regulated IPA supply and the counter-overflow of deionized water (ultrapure water) in the process bath. At the same time, the intensity of the overflow affects the particles adhering to the wafer. Wafers made of InP have a higher surface tension (with the same pretreatment) and a significantly higher particle adhesion ability than GaAs. For a lower level of residual particles, for example, an overflow of ultrapure water of at least 0.1 l / h / cm 2 (per cm in the bath per hour 2 of the liquid surface area of 0.1 liter of ultrapure water) is necessary. For the reason that the concentration of IPA at the interface is sufficient, the overflow is only allowed to slightly exceed this value. At the same time, compared with GaAs, the IPA / N2 flow needs to be increased by 0.003 to 0.007 l / h / cm 2 to compensate for the larger IPA extraction caused by the overflow - so that the concentration of IPA remains stable at the interface.

[0218] ∙ In addition to the technical and chemical influencing factors of Marangoni drying itself, the treatment of III-V semiconductor wafers in the process bath before drying affects the quality of Marangoni drying and the size of the residual droplets that appear at the contact points at the lifting wedges. Depending on the cleaning sequence, the final cleaning step can consist of an acid, a base, or a neutral solution (e.g., via a nonionic surfactant). The pH value of the final chemical cleaning step before Marangoni drying determines the surface tension of the wafer surface during the drying process. To optimize drying, the concentration of IPA can be adjusted to the surface tension of the wafer to be dried. In this regard, hydrophobic wafers require less isopropanol than hydrophilic wafers (e.g., hydrophobic: <0.01 l / h / cm 2 IPA / N2, hydrophilic: e.g., >0.01 l / h / cm 2 IPA / N2). The adjustment of the surface tension of the wafer to be dried can be achieved, for example, by adding a small amount of acidic or basic additives.

[0219] The wafer according to the invention has an oxide layer on at least one surface. The surface has defect areas of less than 25 mm in the oxide layer 2 . The wafer is semi-insulating or semiconductor. The surface with the oxide layer is also referred to as the oxide surface.

[0220] For semi-insulating wafers, even smaller defect areas are possible: here, the defect areas are preferably below 15 mm 2 , more preferably below 10 mm 2 , even more preferably below 5 mm 2 . More preferably, such wafers are composed of preferably GaAs or InP, and even more preferably of undoped or carbon-doped GaAs or iron-doped InP.

[0221] The semiconductor wafer can be a GaAs wafer and contain silicon as a dopant, or an InP wafer and contain sulfur as a dopant.

[0222] Preferably, the defect areas are continuous areas, as Figure 12Exemplarily shown. Here, at least a part of the defect area can contact the edge of the wafer. Preferably, at least a part of the defect area is at most 5 mm away from the edge of the wafer. More preferably, at least a part of the defect area is located within an annular ring between the edge of the wafer and a virtual circular line that is at most 10 mm away from the edge of the wafer. Also preferably, the entire defect area is located within an annular ring between the edge of the wafer and a virtual circular line that is at most 10.5 mm away from the edge of the wafer. Even more preferably, the entire defect area is located within an annular ring between the edge of the wafer and a virtual circular line that is at most 10 mm away from the edge of the wafer. Optionally, the wafer has a straight grinding section or a notch at a part of its edge, and the defect area is positioned opposite to the straight grinding section or the notch.

[0223] The corresponding wafer can be produced by using the method according to the present invention, because during drying, droplets can be minimized, which results in a particularly small defect area.

[0224] The device for drying a wafer according to the present invention includes:

[0225] A bath 1 having a liquid;

[0226] A wedge 2;

[0227] At least one vertically movable support device 5,

[0228] wherein at least one holder 3; 31, 32 can be mounted in the support device 5,

[0229] The at least one holder 3; 31, 32 includes: a pair of first lateral guiding devices 3a, 3a', a pair of second lateral guiding devices 3b, 3b' and a pair of third lateral guiding devices 3c, 3c';

[0230] wherein a pair of first lateral guiding devices 3a, 3a' are arranged below a pair of second lateral guiding devices 3b, 3b', and a pair of second lateral guiding devices 3b, 3b' are arranged below a pair of third lateral guiding devices 3c, 3c', and wherein the distance between a pair of first lateral guiding devices 3a, 3a' is less than the distance between a pair of second lateral guiding devices 3b, 3b', and the distance between a pair of second lateral guiding devices 3b, 3b' is less than the distance between a pair of third lateral guiding devices 3c, 3c';

[0231] wherein the wedge 2 is arranged below the holder 3 and is vertically movable separately from the support device 5,

[0232] wherein the wedge 2 includes at least two wedge sections 2a, 2b, and wherein the two wedge sections 2a, 2b are vertically movable separately from each other,

[0233] At least the first support 31 can be suspended in the support device 5 such that the center of the first support 31 is positioned above the tip of the first wedge section 2a, and furthermore, the second support 32 can be suspended such that the center of the second support 32 is positioned above the tip of the second wedge section 2b.

[0234] Compared with the prior art, the two additional lateral guiding devices (the third lateral guiding devices 3c, 3c') result in the fact that these additional lateral guiding devices can hold the wafers W, W1, W2 from the side at the point when they rise above the liquid level, and thus, when the wafers W, W1, W2 have passed through the liquid level, holding can be achieved by the third lateral guiding devices 3c, 3c' (above the liquid level) and by the wedges 2, 2a, 2b (below the liquid level). The first lateral guiding devices 3a, 3a' and the second lateral guiding devices 3b, 3b' do not contact the wafers W, W1, W2 below the liquid level and also do not contact the wafers when passing through the liquid level, which is why the risk of droplet formation in these areas is avoided. In the device according to the invention, for smaller wafers (e.g., with a diameter of 150 mm or less) and larger wafers (e.g., with a diameter of 200 mm or more), separate wedge sections (2a for the smaller wafer W1, 2b for the larger wafer W2) with appropriately suitable lengths and appropriately adjusted distances of the protrusions 2c are used respectively. Since the 200 mm wafer has a larger diameter, the distance of the protrusions 2c must be greater than that in the case of a smaller wafer diameter so that the wafers W2 do not contact each other when they are slightly tilted. Such a device is suitable for drying wafers of various diameters without additional construction effort.

[0235] Example

[0236] Clean GaAs wafers using a wet chemical cleaning process - all wafers are pre-polished on both sides and finally polished on one side. Pre-cleaning is performed using NH3 and HCl. Final cleaning is performed using the method according to WO 2014 / 124980 A2: subject the wafers to alkaline cleaning (diluted NH3 solution plus megasonic waves), rinse with deionized water, and then dry using Marangoni drying.

[0237] Example 1:

[0238] Clean a semi-insulating undoped GaAs wafer with a diameter of 150 mm in a bath and then dry it using Marangoni drying. The undoped wafers are produced from crystals grown by the VGF process and have a resistivity of 1x10 8 to 8x10 8 Ω·cm. Using according to Figure 3The method of the present invention is used to dry 48 GaAs wafers. The process speed of the wafers is mostly 1 mm / s (which may vary for each stage of lifting, see above and claim 8). The "process speed" refers to the speed of the wafer relative to the water surface.

[0239] Comparative Example 1:

[0240] A semi-insulating undoped GaAs wafer with a diameter of 150 mm is cleaned in a bath and then dried using Marangoni drying. The undoped wafer is produced from a crystal grown by the VGF process and has a resistivity of 1x10 8 to 8x10 8 . 46 GaAs wafers are dried using the method (prior art) according to Figure 1 . The process speed of the wafers is mostly 1 mm / s (which may vary for each stage of lifting, see above and claim 8).

[0241] The comparison between Example 1 and Comparative Example 1 is shown in Figure 14 .

[0242] Example 2:

[0243] A silicon-doped GaAs wafer (semiconductor) with a diameter of 150 mm is cleaned in a bath and then dried using Marangoni drying. The doped wafer is produced from a crystal grown by the VGF process and has a Si doping with a carrier concentration of 1x10 18 to 3x10 18 cm -3 .

[0244] 84 silicon-doped GaAs wafers are dried using the method of the present invention according to Figure 3 . The process speed of the wafers is mostly 1 mm / s (which may vary for each stage of lifting, see above and claim 8).

[0245] Comparative Example 2:

[0246] A silicon-doped GaAs wafer (semiconductor) with a diameter of 150 mm is cleaned in a bath and then dried using Marangoni drying. 88 silicon-doped GaAs wafers are dried using the method (prior art) according to Figure 1 . The process speed of the wafers is mostly 1 mm / s (which may vary for each stage of lifting, see above and claim 8).

[0247] The comparison between Example 2 and Comparative Example 2 is shown in Figure 15 .

[0248] Example 3:

[0249] A sulfur-doped InP wafer (semiconductor) with a diameter of 100 mm is cleaned in a bath and then dried using Marangoni drying. The sulfur-doped wafer is produced from a crystal grown by the VGF process and has a carrier concentration of 1.5x10 18 to 9x10 18 cm -3 of sulfur doping. Nineteen sulfur-doped InP wafers are dried using the method of the present invention according to Figure 3 . The process speed of the wafers is mostly 1 mm / s (which can vary for each stage of lifting, see above and claim 8).

[0250] Comparative Example 3:

[0251] A sulfur-doped InP wafer (semiconductor) with a diameter of 100 mm is cleaned in a bath and then dried using Marangoni drying. The sulfur-doped wafer is produced from a crystal grown by the VGF process and has a carrier concentration of 1.5x10 18 to 9x10 18 cm -3 of sulfur doping. Twenty-nine InP wafers are dried using the method (prior art) according to Figure 1 . The process speed of the wafers is mostly 1 mm / s (which can vary for each stage of lifting, see above and claim 8).

[0252] A comparison between Example 3 and Comparative Example 3 is shown in Figure 16 .

[0253] Example 4:

[0254] An Fe-doped InP wafer (semi-insulating) with a diameter of 150 mm is cleaned in a bath and then dried using Marangoni drying. The Fe-doped wafer is produced from a crystal grown by the VGF process and has a carrier concentration of 2.8x10 7 to 3.8x10 7 cm -3 of iron doping. The resistivity is 4.9x10 7 to 8.7x10 7 Ωcm. The dislocation density is 290 to 480 cm -2 . Twenty-three InP wafers are dried using the method of the present invention according to Figure 3 . The process speed of the wafers is mostly 1 mm / s (which can vary for each stage of lifting, see above and claim 8).

[0255] Comparative Example 4:

[0256] Clean a 150 mm diameter Fe-doped InP wafer (semi-insulating) in a bath and then dry it using Marangoni drying. The Fe-doped wafer is produced from a crystal grown by the VGF process and has a carrier concentration of 2.8x10 7 to 3.8x10 7 cm -3 of Fe doping. The resistivity is 4.9x10 7 to 8.7x10 7 Ωcm.

[0257] The dislocation density is 290 to 480 cm -2 . Dry 12 InP wafers using the method according to Figure 1 (prior art). The process speed of the wafers is mostly 1 mm / s (which can vary for each stage of lifting, see above and claim 8).

[0258] A comparison of Example 4 and Comparative Example 4 is shown in Figure 19 .

[0259] Surface characterization of the wafers:

[0260] After drying, the surface properties of the wafers (oxide surface characteristics on the wafers) are characterized by an optical surface analyzer (Candela ellipsometer). To characterize the uniformity of the surface properties, the mapping of the measurement channel QAbsPhase of the Candela CS20 from company KLA was evaluated. The radial resolution of the Candela measurement is 50 μm, and the azimuthal resolution < 30 μm.

[0261] These mappings show bright and dark areas and stripe structures, which can be attributed to non-uniformities or generally to "defects". The intensity and quantity of the deviation from the background characterize the surface uniformity. In the evaluation of the droplet size, the contrast is not derived from a threshold, but is visually obtained based on their range or by a trained algorithm or neural web network (see above); here, the absolute value of the measurement signal is not considered, but only the clearly identifiable droplet area. And this evaluation is carried out outside the Candela ellipsometer. A boundary exclusion of a maximum of 0.5 mm is applied. The inward extension of the found droplets is at most about 1 cm, so the considered area covers a radius range between 65 mm and 74.5 mm for a 150 mm wafer and between 40 mm and 49.5 mm for a 100 mm wafer.

[0262] List of reference numerals

[0263] 1 bath

[0264] 2, 2a, 2b wedges

[0265] 2c protrusion

[0266] 3 Bracket

[0267] 31 First Bracket

[0268] 32 Second Bracket

[0269] 3a, 3a’ First Lateral Guide Device

[0270] 3b, 3b’ Second Lateral Guide Device

[0271] 3c, 3c’ Third Lateral Guide Device

[0272] 3d, 3d’ Head Section

[0273] 4 Gripping Device

[0274] 5 Support Device

[0275] 6 Suction Device

[0276] W Wafer

[0277] H, H’ Holding Device

Claims

1. A method for drying a wafer (W) located inside a bath (1), the drying being carried out by means of an arrangement comprising at least one wedge member (2) and a pair of first lateral guiding means (3a, 3a'), a pair of second lateral guiding means (3b, 3b') and a pair of third lateral guiding means (3c, 3c'). Among them, The pair of first lateral guiding means (3a, 3a') are arranged below the pair of second lateral guiding means (3b, 3b'), and the pair of second lateral guiding means (3b, 3b') are arranged below the pair of third lateral guiding means (3c, 3c'), and wherein the method comprises the following steps: i) Moving at least one wedge member (2) vertically upwards until it contacts the wafer at the lowest point of the wafer, moving the pair of first lateral guiding means (3a, 3a') and the pair of second lateral guiding means (3b, 3b') vertically upwards, wherein the wafer (W) contacts the pair of first lateral guiding means (3a, 3a') and the pair of second lateral guiding means (3b, 3b'), wherein the upper region of the wafer (W) is lifted out of the bath (1), and wherein the pair of third lateral guiding means (3c, 3c') do not contact the wafer; ii) Moving the wedge member (2) vertically upwards until the pair of first lateral guiding means (3a, 3a') and the pair of second lateral guiding means (3b, 3b') no longer contact the wafer (W), while still being below the liquid level of the bath (1), wherein the pair of third lateral guiding means (3c, 3c') contact the wafer above the liquid level of the bath (1); iii) Lifting the wafer (W) above the liquid level of the bath (1), wherein the pair of third lateral guiding means (3c, 3c') contact the wafer (W).

2. The method for drying a wafer (W) according to claim 1, further comprising the following steps: iv) Moving the wedge member (2) vertically downwards until the wafer (W) contacts at least one of the pair of first lateral guiding means (3a, 3a') and the pair of second lateral guiding means (3b, 3b'); v) Moving the wedge member (2) further vertically downwards until the wedge member no longer contacts the wafer (W); Simultaneously with step iv) and / or v) in parallel or after step v), lowering the liquid level of the bath (1) until the liquid level is below the wedge member (2).

3. The method according to claim 1 or 2, wherein The bath (1) contains water and at least one additional surface tension reducing substance, preferably isopropyl alcohol.

4. The method according to any one of the preceding claims, wherein, The pair of first lateral guiding means (3a, 3a') and the pair of second lateral guiding means (3b, 3b') and / or the pair of third lateral guiding means (3c, 3c') are constituted by a pair of webs which are arranged to contact opposite sides of the wafer (W, W1, W2).

5. The method according to any one of the preceding claims 2 to 4, wherein, The pair of first lateral guiding devices (3a, 3a') and the pair of second lateral guiding devices (3b, 3b') are kept immersed in the bath (1) in step i), and the pair of third lateral guiding devices (3c, 3c') preferably do not contact the wafers (W, W1, W2) at the end of step v).

6. The method according to any one of the preceding claims, wherein, The wedges (2, 2a, 2b) are provided with suction means (6) to which a vacuum can be applied when the upper tip of the wedges (2, 2a, 2b) is above the liquid level.

7. The method according to any one of the preceding claims, wherein, The wedges (2, 2a, 2b) have a surface structure that increases surface tension.

8. The method according to any one of claims 1 to 7, wherein The lifting speed depends on the position of the lowest point of the wafer (W), and when the lowest point of the wafer (W) is more than 1.2 cm below the liquid level, the lifting speed is between 0.8 mm / s and 1.2 mm / s, or when the lowest point of the wafer (W) is less than 1.2 cm below the liquid level, the lifting speed is between 0.4 mm / s and 0.5 mm / s, and once the lowest point of the wafer (W) has reached the liquid level, the lifting speed is at least 30 mm / s, preferably at least 40 mm / s, more preferably at least 50 mm / s.

9. The method according to any one of claims 1 to 8, wherein The pair of first lateral guiding devices (3a, 3a'), the pair of second lateral guiding devices (3b, 3b'), and the pair of third lateral guiding devices (3c, 3c') are provided on a support (3), and in step i), the support (3) is moved, and in step iii), the wafer (W) is lifted out and lifted above the liquid level of the bath (1), wherein the pair of third lateral guiding devices (3c, 3c') and the wedge (2) contact the wafer (W).

10. The method according to any one of claims 1 to 8, wherein The pair of third lateral guiding devices (3c, 3c') are positioned above the liquid level in all process steps and are capable of moving independently of the pair of first lateral guiding devices (3a, 3a') and the pair of second lateral guiding devices (3b, 3b'), and the third lateral guiding devices (3c, 3c') are capable of horizontal movement relative to each other.

11. The method according to claim 10, wherein, The wedge (2) remains below the liquid level in all process steps.

12. The method according to claim 10 or 11, wherein In step iii), the distance between the points where the third lateral guiding devices (3c, 3c') contact the wafer (W) continuously decreases.

13. The method according to any one of claims 10 to 12, wherein The third lateral guiding devices (3c, 3c') are eccentrically mounted or have an elliptical shape and are adapted to perform a rotational movement.

14. A III-V wafer (W, W1, W2), wherein: The oxide surface has defect regions smaller than 25 mm 2 and, wherein, the III-V group wafer (W) is semi-insulating or semi-conducting.

15. The III-V group wafer (W, W1, W2) according to claim 14, wherein, The oxide surface has defect regions smaller than 15 mm 2 , preferably smaller than 10 mm 2 , more preferably smaller than 5 mm 2 . Among them, the group III-V wafers (W, W1, W2) are semi-insulating and preferably composed of GaAs or InP, more preferably composed of undoped or carbon-doped GaAs or iron-doped InP.

16. The III-V wafer (W, W1, W2) according to claim 14, wherein: The III-V wafers are semiconductor, and wherein, the III-V wafers are GaAs wafers and contain silicon as a dopant, or wherein, the III-V wafers are InP wafers and contain sulfur as a dopant.

17. A device for drying wafers, comprising: a bath (1) having a liquid; a wedge (2); at least one support device (5) capable of vertical movement, wherein at least one support (3; 31, 32) can be mounted in the support device (5), the at least one support (3; 31, 32) includes: a pair of first lateral guiding devices (3a, 3a'), a pair of second lateral guiding devices (3b, 3b'), and a pair of third lateral guiding devices (3c, 3c'); Wherein, the pair of first lateral guiding devices (3a, 3a') are arranged below the pair of second lateral guiding devices (3b, 3b'), and the pair of second lateral guiding devices (3b, 3b') are arranged below the pair of third lateral guiding devices (3c, 3c'), and Wherein, the distance between the pair of first lateral guiding devices (3a, 3a') is less than the distance between the pair of second lateral guiding devices (3b, 3b'), and the distance between the pair of second lateral guiding devices (3b, 3b') is less than the distance between the pair of third lateral guiding devices (3c, 3c'), Wherein, a wedge (2) is provided below the support (3) and is vertically movable separately from the support device (5), Wherein, the wedge (2) comprises at least two wedge parts (2a, 2b), wherein the two wedge parts (2a, 2b) are vertically movable independently of each other, Wherein, at least the first support (31) can be suspended in the support device (5) such that the center of at least the first support (31) is above the tip of the first wedge section (2a), and in addition the second support (32) can be suspended such that the center of the second support (32) is above the tip of the second wedge section (2b).

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