Device for wet chemical processing of substrate surfaces

Abstract

A device (100) comprises a process chamber (101) for the wet-chemical processing of a substrate (103) located in the process chamber (101) with a process liquid (105) and at least one two-component spray nozzle (104) operated with a pressurized gas for spraying the process liquid (105) onto the substrate, which is arranged in the process chamber (101). In particular, it comprises a compressor (108) which is configured to draw in a process atmosphere (107) from the process chamber (101), compress it, and return it as a pressurized gas to the at least one two-component spray nozzle (104).

Description

BACKGROUND OF THE INVENTION

[0001] The invention described below relates to a device for the wet chemical processing of substrate surfaces. Description of the state of the art

[0002] Multilayer substrates with an integrated conductor structure find diverse applications in microelectronics. Well-known examples include printed circuit boards, chiplets, and interposers.

[0003] Printed circuit boards (PCBs) serve as a carrier for electronic components and ensure their electrical contact. Almost every electronic device today contains one or more PCBs.

[0004] Printed circuit boards (PCBs) consist of a flat substrate layer with a top and a bottom surface made of an electrically insulating material, as well as conductive traces on and / or within the substrate layer for electrically contacting electronic components. Examples of insulating materials used include fiber-reinforced plastics, plastic films, glass, or hard paper. The conductive traces themselves are typically made of a metal.

[0005] For simple circuits with limited space, often only one side of the substrate layer is equipped with conductive traces. However, more complex circuits frequently require more than one layer of conductive traces. In these cases, both sides of a substrate layer can be equipped with conductive traces. The conductive traces of the two layers are then usually electrically connected to each other via vias. For this purpose, holes can be drilled into the substrate layer and the hole walls metallized. Further dielectric layers with additional conductive trace layers can be applied to both sides of the substrate layer, which are in turn connected to each other and / or to the conductive traces formed on the substrate layer via vias.

[0006] A chiplet is a small, functional part of a larger microprocessor or system-on-a-chip (SoC). Instead of a large monolithic die (single chip) with a multitude of functions, a chiplet design divides different functional units into separate chips. These individual chips (chiplets) are then combined to form a multifunctional unit.

[0007] Interposers are substrates that physically and electrically connect different chips (such as chiplets). They are used as a kind of "adapter" between the chips and the actual substrate (e.g., a printed circuit board).

[0008] Chiplets and interposers also typically feature a multilayer structure with conductor structures in several layers. These conductor structures are separated by dielectric layers, and the dielectric layers are pierced by vias (vias) that electrically connect conductor structures in different layers. Like printed circuit boards, they generally comprise a flat substrate layer with a top and bottom surface made of an electrically insulating material, as well as conductive traces on and / or within the substrate layer for electrically contacting electronic components.

[0009] The production of the aforementioned multilayer substrates with the integrated conductor structure often involves a starting substrate which, in addition to the aforementioned carrier layer made of electrically insulating material, has an electrically conductive layer applied to it, from which the conductor tracks are formed. This is done, for example, in a multi-stage photolithography process using a photoresist, the solubility of which in a developer solution can be influenced by radiation, especially UV radiation.

[0010] In a typical process for fabricating conductive traces, the electrically conductive layer of the substrate is covered with a layer of photoresist. This photoresist layer can, for example, be laminated onto the conductive layer of the substrate. The photoresist layer is then exposed to radiation in an exposure step, with certain areas of the layer protected from radiation exposure by an exposure mask. Depending on the photoresist and developer solution used, either the exposed or the unexposed areas of the layer will be soluble in the developer solution after the exposure step and can be removed in a subsequent step.In this subsequent step, the development step, portions of the electrically conductive layer of the starting material are exposed. These can then be removed using a wet chemical etching solution in a further step, the etching step. The remaining traces of the electrically conductive layer form the desired conductor track structure. If necessary, this can be exposed and reinforced in a deposition step – for example, by electroplating a suitable metal.

[0011] After each chemical process step, the substrate is typically treated in a rinsing step with a rinsing medium, for example, highly purified, deionized water. If necessary, a drying step follows the rinsing step before the substrate is subjected to the next process step.

[0012] The multi-stage photolithographic processes, and in particular the etching, rinsing and deposition steps following the development step, can generally be carried out either as part of a batch process or as part of an inline process.

[0013] Inline processes ensure a tighter timeline. In these processes, the substrate to be processed is moved essentially continuously along a process line. Inline processes are therefore often also referred to as continuous processes. In most cases, it is conveyed like a conveyor belt over a roller array, where it is exposed to variable chemical and physical conditions in successive, not strictly separated processing sections of the process line, without having to leave the roller array. An example of such a section is in Fig. 2 of DE 10 2005 011 298 A1 is shown.

[0014] The surface treatments required in the described processes, using process fluids such as etching, rinsing, and developer solutions, are preferably carried out in enclosed process chambers using nozzles. The solutions are sprayed onto the respective substrate surface via stationary or moving nozzles.

[0015] For the wet chemical treatment of finely structured surfaces, the use of two-component spray nozzles has proven advantageous for increasing the kinetic energy of the spray jet and reducing droplet size. In two-component spray nozzles, the energy required to atomize the process fluid is generated by a high-velocity air or gas jet. This allows even viscous liquids to be transformed into a fine spray mist with droplet sizes of just a few micrometers, if required. The process fluid to be atomized is drawn in by a vacuum created inside the nozzle, based on the injector principle.

[0016] Two-component spray nozzles are preferably operated with compressed air. This must be supplied reliably and in sufficient quantity. However, for sensitive processes, such as etching steps in the aforementioned process chambers, where the quality of the compressed air can influence the process outcome, temperature control of the compressed air may be necessary. This requires a significant amount of energy and is therefore expensive. The energy invested is lost when the air is discharged from the process chamber. Furthermore, the discharged gas cannot be released into the environment without prior treatment, which is problematic given the typical quantities of several hundred cubic meters. 3 This presents a relevant problem every hour. SUMMARY OF THE INVENTION

[0017] The invention was based on the objective of providing an optimized device for the wet chemical processing of substrate surfaces that avoids or reduces the aforementioned problems.

[0018] To solve this problem, the invention proposes the device with the features mentioned in claim 1. Further developments of the invention are the subject of dependent claims.

[0019] An apparatus according to the invention is particularly suitable for carrying out wet chemical processes in the production of printed circuit boards, chiplets, interposers and the like, especially as described above. For example, the surface of a substrate comprising a carrier layer of an electrically insulating material and an electrically conductive metal layer applied thereto can be subjected to processing with an etching solution.

[0020] The device is characterized by the following features: a. It includes a process chamber for the wet chemical processing of a substrate located in the process chamber with a process fluid. b. It comprises at least one two-component spray nozzle operated with a printed gas for spraying the process liquid onto the substrate, which is arranged in the process chamber. c. It includes a compressor designed to draw in a process atmosphere from the process chamber, compress it, and return it as a pressurized gas to the at least one two-fluid spray nozzle.

[0021] The invention thus provides a device in which a compressor supplies the compressed gas to at least one two-component spray nozzle by compressing the process atmosphere of a process chamber, thereby eliminating the need for an external compressed gas supply. This offers numerous advantages: - Independence from external supply in terms of stability and quality. - The process atmosphere is extracted from the process chamber at the desired temperature and fed back into the process. - Balanced conditions regarding gas supply, which significantly reduces the amount of contaminated exhaust air that needs to be channeled and treated, ideally even to zero. - More stable process conditions in the process chamber due to a more constant process atmosphere.

[0022] The compressor is preferably a liquid ring compressor.

[0023] In another preferred embodiment, a screw compressor, for example, can be used as the compressor. A cleaning device is preferably installed upstream of this compressor on the vacuum side to remove corrosive components from the process atmosphere. Alternatively, instead of the cleaning device, it would also be conceivable to manufacture all components of the compressor that come into contact with the process atmosphere from a corrosion-resistant material, in particular titanium.

[0024] The principle of the liquid ring compressor is known from the prior art. Liquid ring compressors comprise a preferably cylindrical housing in which a star-shaped and eccentrically arranged impeller rotates. The housing contains a sealing fluid which, due to centrifugal force, forms a liquid ring concentric to the housing, sealing the impeller chambers. The impeller and housing do not touch.

[0025] The process fluid is, for example, an etching, rinsing, or developing solution. In the vast majority of cases, aqueous solutions are preferred. These may contain organic components (e.g., alcohol or acetone). In specific cases, however, organic solutions may also be preferred as process fluids.

[0026] The liquid ring compressor particularly preferably includes the process fluid as the sealing fluid.

[0027] The process atmosphere is preferably formed from the gas used to operate the at least one two-component spray nozzle and, in many cases, the process liquid used for wet chemical treatment of the substrate. The latter can be present in the process atmosphere in vaporized form or as droplets. The gas is preferably air. However, inert gases such as argon or nitrogen can also be used, as the use of a compressor allows for recirculation.

[0028] Preferably, the gas is compressed by the compressor to a pressure in the range of 2 bar to 10 bar.

[0029] Preferably, the compressor, in particular the liquid ring compressor, is characterized by the following feature: a. The parts of the compressor that come into contact with the process atmosphere are made of materials that are resistant to the process atmosphere.

[0030] This ensures long-term stability against the process gases. Such materials can be, for example, stainless steel or titanium. This is particularly advantageous, of course, if the sealing fluid in a liquid ring compressor is the process fluid itself, as described above.

[0031] In preferred embodiments, the device is characterized by the following feature: a. It comprises a temperature control device for temperature control of the printed gas. The temperature control device can be part of the at least one two-fluid spray nozzle, or part of the compressor, or arranged between the at least one two-fluid spray nozzle and the compressor.

[0032] In further preferred embodiments, the device is characterized by at least one of the following features: a. It includes a control unit that controls the speed of the compressor, in particular the liquid ring compressor. b. It includes a drain valve with a controllable cross-section. c. It includes a control unit that controls the cross-section of the drain valve.

[0033] Preferably, the control unit is able to control both the speed of the liquid ring compressor and the cross-section of the discharge valve. All of this serves the purpose of maintaining a constant gas pressure, particularly within the preferred range mentioned above.

[0034] In further preferred embodiments, the device is characterized by the following feature: a. It includes a droplet separator.

[0035] Preferably, the drain valve is arranged in conjunction with the droplet separator on the pressure side of the compressor to remove liquid residues from the compressed gas.

[0036] The device according to the invention preferably comprises a plurality of two-component spray nozzles, for example 10 to 200 two-component spray nozzles.

[0037] The at least one two-component spray nozzle is preferably coupled with at least one reservoir containing one or more different process fluids.

[0038] Furthermore, the device preferably comprises a transport and / or holding system with which the substrate to be processed can be held in the device, in particular in the process chamber, or transported through the process chamber.

[0039] Any method for the wet-chemical processing of substrate surfaces that can be carried out in the described apparatus is encompassed by the present invention.

[0040] Further features, details and advantages of the invention will become apparent from the claims and the summary, the wording of both of which is incorporated by reference into the description, the following description of preferred embodiments of the invention and the drawing. BRIEF DESCRIPTION OF THE DRAWING

[0041] An embodiment of the invention will now be explained in more detail with reference to the drawings. These show: Fig. 1: Preferred embodiment of a device according to the invention (schematic sectional view) Fig. 2: Schematic representation of a liquid ring compressor that can be used within the scope of the invention (sectional view). DESCRIPTION OF PREFERRED EXAMPLES

[0042] The in Fig. The device 100 shown in Figure 1 according to the invention comprises a process chamber 101 in which a substrate 103 to be treated, mounted on a transport system 102, can be transported through the process chamber 101. It passes through the two-component spray nozzle 104, by means of which the upper surface of the substrate 103 is sprayed with a process fluid 105. The process fluid 105 originates from the reservoir 106 and is supplied to the two-component spray nozzle 104 by means of a pump. Sprayed process fluid 105 can collect at the bottom of the process chamber 101 and is pumped back into the reservoir 106.

[0043] The process atmosphere 107 prevailing in process chamber 101 consists of air in which fine droplets of the process fluid 105 may be suspended. This air is drawn in by a compressor 108, compressed, and returned as a pressurized gas to the at least one two-fluid spray nozzle 104. The use of the compressor 108 thus enables a recirculation of the air.

[0044] For example, a liquid ring compressor can be used as the compressor 108. The compressor 108 is preferably driven by the electric motor 109. It has an adjustable drain valve 110 and a downstream droplet separator 111. In the case of a liquid ring compressor, process fluid 105, which can be drawn directly from the process chamber 101, is used as the sealing fluid within the liquid ring compressor 108.

[0045] The rotational speed of the electric motor 109, and thus of the impeller of the liquid ring compressor 108, as well as the function of the drain valve 110, can be controlled via a control device not shown here. This allows the compression pressure to be adjusted.

[0046] The in Fig. The liquid ring compressor 108 shown in Figure 2 comprises a star-shaped and eccentrically arranged impeller 122, which rotates around the drive shaft 124 in a cylindrical housing. The housing contains a sealing fluid which, due to centrifugal force, forms a liquid ring 123 concentric to the housing, sealing the impeller chambers of the impeller 122. A gas to be compressed is fed into the liquid ring compressor 108 via the inlet opening 121. Compressed gas can exit the liquid ring compressor 108 via the outlet opening 120. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2005 011 298 A1

[0013]

Claims

[1] Device (100) for wet chemical processing of substrate surfaces having the following features: a. It comprises a process chamber (101) for the wet chemical processing of a substrate (103) located in the process chamber (101) with a process fluid (105). b. It comprises at least one two-component spray nozzle (104) operated with a printed gas for spraying the process liquid (105) onto the substrate (103), which is arranged in the process chamber (101). c. It comprises a compressor (108) which is designed to draw in a process atmosphere (107) from the process chamber (101), compress it and return it as a pressurized gas to the at least one two-component spray nozzle (104). [2] Device for wet chemical processing of substrate surfaces according to claim 1 with the following additional feature: a. The compressor (108) is a liquid ring compressor. [3] Device for wet chemical processing of substrate surfaces according to claim 2 with at least one of the following additional features: a. The liquid ring compressor (108) comprises a sealing fluid. b. The liquid ring compressor (108) includes the process fluid (105) as a sealing fluid. [4] Device for wet chemical processing of substrate surfaces according to one of the preceding claims with the following additional feature: a. The parts of the compressor (108), in particular the liquid ring compressor, which come into contact with the process atmosphere (107), are made of materials that are resistant to the process atmosphere (107). [5] Device for wet chemical processing of substrate surfaces according to one of the preceding claims with the following additional feature: a. It includes a temperature control device for temperature control of the printed gas. [6] Device for wet chemical processing of substrate surfaces according to one of the preceding claims with at least one of the following additional features: a. It includes a control unit that controls the speed of the compressor (108), in particular the liquid ring compressor. b. It includes a drain valve (110) with a controllable cross-section. c. It includes a control unit that controls the cross-section of the drain valve (110). [7] Device for wet chemical processing of substrate surfaces according to one of the preceding claims with the following additional feature: a. It includes a droplet separator (111).

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