Method for treating wafers and microplatelets, device for carrying out the method and ring for the method

Abstract

Method for treating an area on a wafer (17) or a microplatelet, comprising the steps: a) Providing a wafer (17) or a microplatelet, b) Placing the wafer (17) or microplatelet on a substrate (11), c) Providing material for a perimeter barrier around the area to be treated, d) Applying the material for the perimeter boundary so that a depression (3) is formed around the area to be treated, from which a liquid cannot escape and e) Filling the depression (3) with a treatment fluid, the treatment includes cleaning and removal of the treatment fluid by centrifugation, and wherein the material for the perimeter boundary according to step d) is attached such that there is a slope descending from the upper edge of the boundary to the area to be cleaned, the slope having an angle of inclination of 40°-50°.

Description

[0001] The invention relates to a method for treating an area on a wafer or a microplate, a device for carrying out this treatment and a special ring designed for a corresponding method.

[0002] When processing wafers, especially those containing electronic components, cleaning steps or surface modification steps for (partial) areas are often necessary. For example, thinning a wafer requires a cleaning step to remove residual material from the wafer surface. Surface modifications of specific areas of the wafer surface are also often desirable or necessary to prepare the surface for subsequent processing steps, such as making the surface hydrophilic in certain areas.

[0003] Wafers are often laminated onto a film commonly used in the semiconductor industry during processing. In such cases, the film itself is usually stretched over a frame. While immersion in a bath may be the preferred solution for cleaning or surface modification of a non-laminated wafer or corresponding microplatelets, processing a laminated wafer or corresponding microplatelets with liquid treatment agents may be limited. This can be due, for example, to the incompatibility of the treatment agents with the film and / or the frame supporting it.

[0004] For the state of the art, reference is made to the documents EP 1 005 071 A1, US 4 086 870 A, US 5 556 503 A, US 2006 / 0 185 695 A1 and US 2009 / 0 173 358 A1.

[0005] The object of the present invention was therefore to provide a gentle method for treating an area on a wafer or microplate, in which, in particular, the contact area of ​​a treatment fluid can be easily controlled and the treatment fluid can be effectively removed. Furthermore, it was particularly desirable that, within the framework of the method according to the invention, partial areas on a wafer (and even a microplate) could also be selectively treated with liquids. At the same time, it was also particularly desirable that the method according to the invention could be readily integrated into conventional wafer processing processes, that the treatment speed could be increased, and / or that treatment fluid could be saved.

[0006] This problem is solved according to the invention by a method for treating an area on a wafer or a microplate according to claim 1.

[0007] For the purposes of this invention, a surface is understood to be either a complete surface or a partial surface. If the object to be cleaned is a wafer, it essentially has three surfaces: a) a back surface, b) a front surface (on which the electronic components may be located), and c) a circumferential surface that extends around the wafer if it is circular. Those skilled in the art can, of course, apply these definitions analogously to microplates or non-circular wafers.

[0008] In accordance with the inventive method, it is therefore included that more than one of the surfaces of the object to be cleaned may be treated.

[0009] A method according to the invention is carried out such that, under the given process conditions, a treatment fluid does not escape uncontrollably from the recess. This can be achieved by gluing, mechanical fixing, suction by negative pressure, or by the weight of the circulating material or force exerted on this circulating material. In this context, a person skilled in the art can easily adapt further embodiments of the material attachment to the respective requirements.

[0010] A treatment according to the invention includes cleaning. However, it may be preferred that a treatment additionally includes a surface modification, e.g., in the sense of hydrophilization or hydrophobization. A treatment can also involve the application of a (possibly further) layer. Naturally, according to the invention, it is also possible to carry out several different treatments (e.g., cleaning and hydrophilization) in parallel or sequentially.

[0011] It has been found that the inventive method can be integrated surprisingly well into conventional processing methods for wafers and microplatelets. At the same time, it is advantageous that the depression precisely defines the contact area for the treatment fluid. This allows areas outside the depression, such as a frame on which a film is stretched that carries the wafer / microplatelet to be processed, to be protected from the treatment fluid.

[0012] Furthermore, it is advantageous that the exposure time of the treatment fluid is controlled and that it is avoided that treatment fluid has to be re-dosed because it escapes uncontrollably from the area in which it is supposed to act.

[0013] The perimeter boundary can be attached in such a way that the material does not come into contact with the treated wafer / microplate, thus creating a depression in the center of which (without contact with the edge) the wafer / microplate to be treated lies. However, it is also possible, and in many cases preferred, to attach the perimeter boundary so that the bottom of the depression is formed entirely by the wafer / microplate to be treated. In this case, the treatment fluid comes into contact only with the wafer / microplate and the perimeter boundary material, unless further devices or device components are specifically inserted into the resulting depression.If the wafer / microplate to be treated forms the bottom of the depression, it is preferred that the material for the circumferential boundary covers only 0.2–2 mm, preferably 0.5–1 mm, along the circumference of the wafer / microplate. This ensures that the substantial part of the wafer / microplate's surface is exposed to the treatment.

[0014] According to the invention, it is preferred that the material for the circumferential boundary is provided in the form of a ring. Such a ring is easy to place and, with appropriate design, particularly in the preferred form (see below), is especially suitable for ensuring a corresponding sealing function.

[0015] When the term "wafer" is used in the following text, it includes the term "microplatelet" unless explicitly stated otherwise.

[0016] For the execution of the inventive method, it is preferred that the wafer to be cleaned is laminated onto a film. Preferred films in this sense are standard dicing tapes or backgrinding tapes, such as those already used in semiconductor production processes. Specific examples are: Lintec: Adwill D-175, Adwill D-650, Adwill D-678 or Adwill E-8320; Ultron: Dicing Tape 1044R; similar tapes are available from Nitto Denko.

[0017] This film then serves as a substrate in step b) of the inventive method. The film itself is preferably stretched over a frame and (stretched over the frame) is preferably placed on a holding device. It is preferred that at least parts of the support surface of the holding device provided for the wafer / film are porous, so that the film (and thus also the wafer laminated onto it) can be drawn onto and stabilized by means of negative pressure on the support surface. At the same time, it may be preferred that the frame which stretches the film is additionally held on the device by means of a mechanical fixing.

[0018] According to the invention, the material for the circumferential boundary in step d) is attached in such a way that there is a slope descending from the upper edge of the boundary to the surface to be cleaned.

[0019] The slope has an angle of inclination of 40–50°, preferably 45°. This allows, within the framework of the inventive method, a depression to be created first by attaching the material for the circumferential boundary (preferably in the form of a ring). The treatment fluid is introduced into this depression and does not escape from it. After a suitable exposure time, the treatment agent can then be removed from the depression by centrifugal force. For this purpose, it is preferred that, in the inventive method, the entire depression, including the edge (and the bottom), is set into rotation so that the treatment fluid is ejected from the depression by means of centrifugal force. This is supported by a sloping incline according to the preferred form of the method.

[0020] It is further preferred according to the invention that the treatment effect of the treatment fluid is improved by vibration and / or by heating the treatment fluid.

[0021] According to the invention, the treatment includes cleaning. It is preferred according to the invention that the cleaning effect is enhanced by an ultrasonic transducer which is immersed in the treatment fluid after step e). This ultrasonic transducer sets the treatment fluid into vibration, so that it can exert its effect more effectively.

[0022] If, according to the invention, heating of the treatment fluid is to be used, it is possible to heat the treatment fluid before it comes into contact with the surface to be treated. However, it is also possible to heat the treatment fluid in the recess by direct or indirect heating, e.g., by means of IR radiation. Indirect heating can also be achieved, for example, by directly increasing the temperature of the surface to be treated. As already indicated above, it is preferred according to the invention that the treatment is a cleaning process. Particularly preferred in this context is that the cleaning process removes silicone-containing residues, especially silicone oil-containing residues.

[0023] The process according to the invention is also possible for wafers that have been thinned to a very high thickness, for example to a range of 10–50 µm. Furthermore, the process can also be used particularly well for wafers that have been thinned to a thickness above 50 µm, e.g. to thicknesses of 50–200 µm.

[0024] The method according to the invention can also be designed such that, in addition to spinning, the treatment fluid is extracted by means of a suitable device part.

[0025] Alternatively or additionally, the removal of the treatment fluid can be achieved, at least partially, by draining. For this purpose, a person skilled in the art will provide a draining device within the overall arrangement. This device can be located either at the edge of the depression or at the bottom of the depression, provided the depression is designed in such a way that not only the cleaning area is affected. Preferably, such a device consists of a valve to which a corresponding vacuum can be applied for suction, or a tap. If the draining device is designed to apply a vacuum for draining, it is also referred to as a suction device.

[0026] For the method according to the invention, it may also be preferred that the treatment fluid is collected after the action in such a way that it can be recycled.

[0027] Furthermore, in the method according to the invention, it may be preferred that the surface to be cleaned is dried by means of a nozzle using compressed air, inert gas or other suitable gases.

[0028] As further steps in the surface treatment process according to the invention, it may be preferred to introduce rinsing fluids into the depression once or several times after the actual treatment in order to remove any remaining treatment fluid. Preferred rinsing fluids in this sense are organic solvents such as isopropanol, ethanol, acetone, or even gasoline fractions, as well as water possibly containing additives such as detergents.

[0029] Treatment fluids to be used according to the invention include, for example, organic solvents for swelling or dissolving polymers located on wafers such as NMP, ethyl acetate, DMSO, acetone, gasoline fractions or alcohols, basic solutions such as aqueous sodium hydroxide, potassium hydroxide solutions or aqueous or alcoholic solutions of tetramethylammonium hydroxide, solutions for oxidizing metal and semi-metal surfaces such as nitric acid, fluoride-containing solutions such as hydrofluoric acid, tetrabutylammonium fluoride in butanone or potassium fluoride in dimethyl carbonate or preparations based on polydimethylsiloxanes containing additives such as organic solvents such as ethyl acetate, hexane or gasoline fractions and / or catalysts such as phosphonitrile chloride and its derivatives and / or noble metal catalysts.

[0030] Part of the invention is a device configured for carrying out a method according to the invention, particularly also in its preferred variants. This includes the fact that this device is particularly capable of applying the material for the circumferential boundary in such a way that a recess for a treatment fluid is created from which the treatment fluid does not escape.

[0031] Furthermore, part of the invention is a specially designed ring for a method according to the invention, wherein the ring has a circumferential surface sloping obliquely inwards from the upper edge and has a sealing feature in the area of ​​the lower edge of the obliquely sloping circumferential surface, selected from the group consisting of a contact surface, O-ring, sealing lip and recess for negative pressure, and wherein the slope has an angle of inclination of 40°-50°.

[0032] The sealing feature preferably consists of a circumferential edge that projects from the underside of the ring's inner circumference. The width of this circumferential edge is preferably 0.5–5 mm, more preferably 0.7–2 mm.

[0033] Alternatively or additionally, it may be preferable for the ring to be designed such that an O-ring seal is incorporated into it on the underside and around the entire inner circumference. In this case, the O-ring provides the seal. Suitable sealing materials include any elastic materials that are chemically compatible with the cleaning agent used.

[0034] As an alternative or in addition to O-ring seals, sealing lips or seals with other cross-sectional shapes may be considered; the expert will make an appropriate choice here.

[0035] Preferred embodiments of the ring according to the invention, the sealing lips and the groove in which the O-ring seal is located, can also be seen in the figures.

[0036] The sealing process can be ensured by applying pressure to the ring according to the invention. The sealing effect can be enhanced by selecting a suitable material for the ring. In many cases, sealing is also supported by laminating the surface to be cleaned (or the associated wafer) onto an elastic film. This elastic film yields slightly under pressure from the ring, thus reinforcing the sealing effect.

[0037] Special features of the ring according to the invention are described in the description of Fig. 2. Fig. 3 explained.

[0038] The invention is explained in more detail below using figures.

[0039] This presents Fig. 1 represents the situation after step e) in a method according to the invention.

[0040] Fig. 2a represents a ring according to the invention for the surface cleaning of a 200 mm wafer with corresponding dimensions.

[0041] Fig. Figure 2b depicts the situation onto which the ring according to the invention is applied, namely the cross-section of an annular frame onto which a film is stretched, carrying a laminated wafer. The inner diameter of the wafer frame is 243–250 mm.

[0042] Fig. Figure 3 shows two alternatives of the ring according to the invention, each as a half in cross-section. On the left side, a ring with a sealing surface of one mm (circumferentially) is shown, while on the right side, a ring is shown which has a recess 23 in the lower area that can be pressurized with a vacuum. In Fig. 1-3, the reference numerals mean the following: 1 Ultrasonic transducer 3. Recess with cleaning agent 5 rings 7 Mechanical fixing of the ring (and, if applicable, the frame) 9 frames Slide 11 13 Application point for negative pressure 15 Porous contact surface 17 Wafers to be cleaned (thinned) 19 Sealing lip 20 O-rings (circumferential) 21 Contact surface 23 Recess for negative pressure 25 Recess for frame 27 Extraction channel

[0043] In Fig. In 1, a wafer 17, which has undergone a thinning process, is laminated to a film 11 stretched over a frame 9. This film rests on a porous support surface 15, to which a vacuum 13 is applied, so that the film is fixed and stabilized on the support surface.

[0044] The ring 5 is positioned so that it forms a depression 3 around the wafer 17, into which a cleaning agent is poured. The sealing lip 19 is positioned so that it seals the depression against leakage of the cleaning agent.

[0045] An ultrasonic transducer 1 is immersed in the cleaning agent in the recess 3. Operation of the ultrasonic transducer causes the cleaning agent to vibrate, resulting in more intensive cleaning. In this way, the cleaning time can be reduced.

[0046] Ring 5 features a bevel that slopes downwards towards the thinned wafer. This allows the cleaning agent to be removed from the recess after the contact time by centrifugal force. For this purpose, the entire recess, including the ring and the porous contact surface (as well as any other contact surface areas), is set in rotation so that the centrifugal force ejects the cleaning agent from recess 3.

[0047] Fig. Figure 2 schematically shows an alternative design of a ring for a recess in the treatment of a 200 mm wafer. In this case, the ring is designed to seal the recess against the film on the wafer. For this purpose, a groove is machined into the ring, the middle diameter of which is smaller than the outer diameter of the wafer. A sealing cord is inserted into this groove, creating a seal between the ring and the wafer. This ensures that the cleaning fluid does not come into contact with the film in any way, allowing for greater flexibility in the choice of film material.

[0048] The dimensions are given as numerical values ​​(in mm) in the figure. The in Fig. The sealing ring 5 shown in Figure 2 is designed such that it has an O-ring 20 in a groove in the lower area of ​​the slope sloping down towards the surface to be cleaned. The O-ring is circumferential. The groove of the O-ring 20 is designed such that the boundary facing the inside of the ring is higher than the lowest point of the underside of the ring 5. The lowest point of the underside is the bearing surface 21. The bearing surface 21 is, in the case of the Fig. 2 a circumferential surface of 1 mm width.

[0049] The in Fig. The ring shown in Figure 2 is designed such that the O-ring 20 rests on the wafer in the sealing situation, while the contact surface 21 rests on the film onto which the wafer is laminated. However, it is also possible for the contact surface 21 to rest on the wafer in addition to the O-ring.

[0050] In connection with the Fig. 2. It should be noted that it is preferred that the bearing surface 21 is the lowest point of the underside of the ring 5.

[0051] Fig. Figure 3 shows a relatively simple version of the ring 5 according to the invention on the left side. It has a bearing surface 21 with a circumferential width of 1 mm. Furthermore, the ring 5 has a recess 25 for the frame. As can be seen from the Fig. As shown on the left side, a slope is provided from the inner end of the recess 25 to the support surface 21. This slope is designed to descend towards the inside of the ring. Instead of a slope, the transition can generally also be achieved by one or more steps. In the Fig.On the right side of the ring 5 according to the invention, a recess 23 is provided for negative pressure. This recess 23 forms a circumferential cavity that can be pressurized with negative pressure via the suction channel 27. This ring 5 also has a recess 25 for the frame.

[0052] When a vacuum is applied, the recess 23 for vacuum creates a corresponding suction force on the ring against the substrate. This ensures a seal. As an alternative to the suction channel 27, a seal can also be achieved if the substrate on which the ring 5 is placed is porous and can be subjected to a vacuum, so that the ring is drawn onto the substrate. This would be possible, for example, if the film onto which the wafer is laminated is perforated. For this type of seal, a recess 23 is not required.

Claims

[1] Method for treating an area on a wafer (17) or a microplatelet, comprising the steps: a) Providing a wafer (17) or a microplatelet, b) Placing the wafer (17) or microplatelet on a substrate (11), c) Providing material for a perimeter barrier around the area to be treated, d) Applying the material for the perimeter boundary so that a depression (3) is formed around the area to be treated, from which a liquid cannot escape and e) Filling the depression (3) with a treatment fluid, the treatment includes cleaning and removal of the treatment fluid by centrifugation, and wherein the material for the perimeter boundary according to step d) is attached such that there is a slope descending from the upper edge of the boundary to the area to be cleaned, the slope having an angle of inclination of 40°-50°. [2] Method according to claim 1, wherein the material for the circumferential boundary is a ring (5). [3] Method according to one of claims 1 to 2, wherein the treatment effect of the treatment fluid is improved by vibration and / or by heating the treatment fluid. [4] Method according to one of claims 1 to 3, wherein the cleaning effect is supported by an ultrasonic transducer (1) which is immersed in the treatment fluid according to step e). [5] Method according to any one of claims 1 to 4, wherein the depression (3) is designed such that its bottom is formed entirely by the wafer (17) or the microplate. [6] Method according to any one of claims 1 to 5, comprising the removal of treatment fluid by suction and / or drainage. [7] Device configured to carry out a method according to any one of claims 1 to 6. [8] Ring (5) for a method according to one of claims 2 to 6, wherein the ring (5) has a circumferential surface sloping inwards from the upper edge and has a sealing feature in the region of the lower edge of the sloping circumferential surface selected from the group consisting of a contact surface, O-ring, sealing lip (19) and recess for negative pressure (23), and wherein the slope has an angle of inclination of 40°-50°. [9] Ring (5) for a method according to one of claims 2 to 6 or according to claim 8, comprising a draining device or suction device (27).

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