DE102007026082A1 - Method for the treatment of flat substrates and use of the method - Google Patents

Abstract

In order to process flat substrates such as printed circuit boards or silicon wafers (3) better in a horizontal passage in a treatment device (1) with treatment liquid (14), the treatment liquid (14) in a process step ozone (O <SUB> 3 </ SUB>) added. As a result, for example, printed circuit boards can be better removed from a resist or silicon wafers (3) can be better cleaned for solar cells.

Description

Field of application and status of the technique

The The invention relates to a method for the treatment of flat substrates in a horizontal passage through a treatment facility, various Uses of such a process and treated therewith Printed circuit boards or silicon wafers.

It Ozone is known for its strong oxidizing effect in many ways use, for example in drinking and wastewater treatment, Exhaust air purification or sterilization in medical technology. one The most important benefits of ozone is its compared to others strong oxidizing chemicals good environmental compatibility, rapid degradation in the atmosphere as well as relatively easy to produce.

Task and solution

Of the Invention is based on the object, an aforementioned method as well as applications mentioned above, which cause problems of the prior art can be avoided and in particular a Treatment of flat substrates, such as printed circuit boards or Solar cell wafers can be done in a novel way.

Is solved this object by a method having the features of the claim 1 and uses with the features of claims 8 to 11, 13, 14, 18 or 19 and a printed circuit board with the features of claim 21 or a silicon wafer with the features of claim 22. Advantageous As well as preferred embodiments of the invention are the subject of further claims and will be closer in the following explained. Some of the features listed below are explained only once. she but should be independent of it as well as the process as well as the uses or the printed circuit boards or Silicon wafers for solar cells can apply. The wording of the claims is by express Reference made to the content of the description.

According to the invention, it is provided that the substrates in the horizontal passage through a corresponding Treatment facility out or transported. At least one side of the Substrates with treatment liquid wetted or applied to this side. The treatment liquid According to the invention ozone is added or contains them Ozone in a certain concentration. Thus, in addition to the effect, the the treatment liquid in itself has on the substrate or its surface, the added ozone reinforce this effect or independently or additionally Have an effect to treat the substrate or to suitably to edit. The individual possibilities which effect the ozone has on different substrates or surfaces of the Substrates may have later to the individual uses explained in more detail.

Advantageous can the ozone of the treatment liquid gaseous be mixed. This has the advantage that the ozone at the simplest gaseous can be generated and also, in particular in water-based treatment fluids, gaseous can be mixed well.

In Further embodiment of the invention, it is advantageously provided that the ozone is generated directly at the treatment facility or in spatial Close to it. For this purpose, a corresponding generation device can be provided, as is known to those skilled in the art as an ozone generator is known, for example by a high voltage generator. This can in a treatment device according to the invention or device for implementation of the procedure to be part of the treatment facility. The advantage the use of ozone compared to other highly oxidizing Chemicals is that then long transport routes to a Treatment chamber of the treatment facility or other Mixing device in which the ozone of the treatment liquid is added, can be omitted.

The Ozone can either be generated from ambient air or beneficial from an oxygen supply. The advantage of generating from the ambient air is that then a corresponding oxygen supply or the like. can be omitted. Providing an oxygen supply is therefore advantageous because then because of the significantly higher oxygen content than in the ambient air of the ozone generator itself considerably more efficient can work.

Prefers a mixing device is provided, with which the ozone of the treatment liquid admixed becomes. For this purpose, the treatment liquid from the treatment device be brought out, so be led out in a separate circuit. In an advantageous static mixer, the ozone is admixed, for example, directly in gaseous State injected or initiated.

In a further embodiment of the invention, the treatment device may have a tank for a larger amount of treatment liquid. The treatment liquid can be removed from the tank for ozone addition and brought into the aforementioned mixing device for ozone addition. On the tank can be beneficial a degassing of the treatment liquid take place, so escaping gas are sucked. It can also be provided that after the admixing of ozone, the treatment liquid is introduced back into the tank, and then such a degassing or tank exhaust is particularly advantageous. By means of, for example, a feed pipe for this, possibly also with nozzles or injectors, which is arranged below a liquid level in the tank, the mixing of the ozone with the treatment liquid can be additionally supported. The path of the ozone or ozone gas bubbles through the treatment liquid to the surface should be as long as possible for improved ozone uptake of the treatment liquid.

alternative or additionally to a previously described suction of the tank can be a suction provided on a treatment chamber of the treatment device be. This prevents the release of ozone into the environment which reduces air pollution, especially for workers.

In Embodiment of the invention can be provided that the treatment liquid is circulated in a kind of cycle, between a tank, a treatment chamber of the treatment device in which the substrates with the treatment liquid be used, and a receptacle or the like., Which is advantageous located in the lower part of the treatment chamber.

to Determination of the concentration of ozone in the treatment fluid There are several options. On the one hand, the concentration in the aforementioned treatment chamber or receptacle are measured. Since usually a pump provided becomes a feeder of treatment liquid in the receptacle or in the treatment chamber, can measure concentration in front of the pump or behind the pump. Based on the measured ozone concentration, the ozone production or the admixture of ozone regulated in the treatment liquid become. The ozone production can be adapted to the ozone demand become. This may vary depending on the desired Use a different high ozone concentration provided be.

In Embodiment of the invention, it is possible that a treatment liquid chilled becomes. Such cooling can even be done below room temperature. By the admixture Of ozone, the effect of the treatment liquid can be enhanced. Furthermore, by cooling the treatment liquid extends the half-life of ozone, so that it will last longer in the treatment liquid stops, less is degraded and thus generated a total of less ozone must be increased or the recoverable ozone concentration can.

The Ozone concentration in the treatment liquid may vary depending on use be different. An ozone concentration is advantageous considered between 2 ppm and 30 ppm, particularly advantageous between 5 ppm and 10 ppm.

A the possible uses according to the invention a method described above is that a resist or photoresist by a stripping process of a printed circuit board is removed as a substrate. Particularly advantageous, the method be used according to a so-called pattern plating process. With that you can such areas of a resist are removed from a subsequently applied Copper structure partially enclosed or overlapped. As an ozone-containing appropriate treatment liquid the effect has that organic materials like the resist very are strongly attacked and dissolved in gaseous components can, So removing the resist is very possible. Thus, a removal even in partially closed cavities, as they arise in a pattern plating process can, very effective and residue-free.

A further use according to the invention is relatively simple in that PCBs are cleaned. Again, the strong effect of an ozone-containing can be advantageous treatment liquid on organic impurities such as residues of resist or the like. used become.

A further use according to the invention provides, for multi-layer printed circuit boards after drilling through the holes a method according to the invention with ozone-containing treatment liquid from resin smearing by drilling to clean. So can the Internal layers electrically conductive during the following processes be bonded by copper coating to the wellbore sleeves. This so-called desmear process is associated with potassium permanganate in the prior art high temperature, However, according to the invention with a ozone-containing treatment liquid performed much better become.

A another use according to a inventive aspect provides that substrates, in particular printed circuit boards, before coating with ozone-containing treatment liquid be treated for surface activation. This can improve the liability or improve the Wettability of the surface the substrates are reached.

A further use according to the invention sees a structuring of printed circuit board base material, for example Resin or polyimide film, before lamination or prior to electroless metallization before, for example, with a so-called chemical-copper process. For printed circuit boards that use a so-called semi-additive (SAP) or sequential build-up (SBU) procedures must be made the base material surface prior to applying a new conductive layer through a patterning process be prepared for liability improvement. This creates a microrough surface. Usual procedures are currently in, for example, glass fiber reinforced epoxy material or resin Coated Copper (RCC) a potassium permanganate process and polyimide a plasma process. According to the invention, these processes can be combined with a ozone-containing treatment liquid according to a procedures described above are performed much better.

A another use according to a inventive aspect provides a structuring of the free copper surface of Printed circuit boards before lamination processes. Before laminating single Inner layers of a multilayer printed circuit board is the copper surface for Liability improvement structured or prepared. In the prior art be for this performed special wet chemical processes, for example, the black oxide method or so-called substitute methods like Multibond. According to the invention, these Processes with an ozone-containing treatment liquid according to a procedures described above are performed much better.

Yet another use according to the invention provides that silicon wafers are treated in a production process for solar cells with ozone-containing treatment liquid. In the process, organic residues on the wafer surface can be removed. In this case, an oxide layer can be formed, the thickness of which depends on the concentration of ozone in the treatment liquid and the exposure time. Possibly. Foreign metals present on the wafer surface are incorporated into the newly formed oxide layer and removed from the wafer in a subsequent HF etching step with which the silicon oxide layer is removed. Thus, possible recombination sites for the electrons can be reduced and thus the efficiency of a finished solar cell can be increased. Further, by an ozone treatment on the wafer surface, the interfacial tension can be reduced since the surface is hydrophobic after the treatment. Basically, such a process may include the following steps:
Ozone treatment → Rinse → HF etching → Rinse

To the ozone treatment, the wafer can be rinsed, after an above-described HF etching step the wafer is rinsed in any case, it can also be dried become.

The above-described treatment of a silicon wafer with a method according to the invention can be carried out after a texturing process of the silicon wafers. In particular, the wafer can be rinsed several times beforehand and HCl and / or HF etched. Again, there is the possibility to rinse the wafer after an ozone treatment. Thus, both monocrystalline and multicrystalline silicon wafers can be treated. Basically, such a process may include the following steps:
Texturing → Rinse → KOH process → do the washing up → HCl / HF etching → rinse → ozone treatment → rinse → HF etching → Rinse → Dry

In a further embodiment of the invention, the above-described method for treating silicon wafers can be carried out after a phosphor glass etching process, before which phosphorus has been thermally baked for doping into the silicon. Here, it is necessary to perform a rinsing step after the phosphor glass etching process and before the ozone treatment. Basically, such a process may include the following steps:
HF etching (phosphorous glass etching) → rinsing → ozone treatment → rinsing → HF etching → rinsing → drying

In yet another embodiment of the invention, an edge isolation of the silicon wafer by etching can be carried out before said Phosphorglasätzprozess. In this case, HF and / or HNO _{3 can be} etched and rinsed several times. Here too, an ozone treatment according to the invention can then be carried out with a possible rinsing step. Basically, such a process may include the following steps:
Edge insulation (HF / HNO ₃ ) → Rinse → KOH process → Rinse → HF etching (Phosphor glass etching) → Rinse → Ozone treatment → Rinse → HF etching → Rinse → Dry

A further use of the method according to the invention described above can provide for structures in an antireflection layer to be cleaned on a silicon wafer, directly after the structures have been produced. This structuring can be carried out for example with a laser. When cleaning with ozone-containing treatment liquid, residues from structuring are removed from the silicon wafer, especially on the exposed emitter. This should be done before a metallization, in which then electrical contacts are introduced into the structure, in particular metallic contacts. Again, the admixture of ozone in the treatment liquid for cleaning the structures produced an improved cleaning effect. Basically, such a process may include the following steps:
Open the antireflection layer with laser → ozone treatment → rinse → HF etching → Rinsing → drying → metallization (for example, chemical Ni and light-induced galvanizing)

Yet another use according to the invention provides for carrying out a method described above after producing structures in an above-described antireflection layer of a silicon wafer, in which case the structuring takes place by masking the silicon wafer and then etching the exposed antireflection layer. A resist used for masking can be stripped off, preferably with NaOH. Subsequently, the treatment according to the invention of the silicon wafer in the structures produced for cleaning the same can be carried out with ozone-containing treatment liquid. Preferably, it is possible here that remaining impurities of the resist are removed. Basically, such a process may include the following steps:
Mask the silicon wafer with Inkjet → Etch the exposed lines in the antireflection layer → Stripping the resist → ozone treatment → Rinse → HF etching → do the washing up → dry → Metallization (for example, chemical Ni and light-induced galvanization)

These and other features go out the claims also from the description and the drawings, wherein the individual features each for alone or in the form of subcombinations an embodiment of the Invention and other fields be realized and advantageous also for protectable versions can represent for the protection is claimed here. The subdivision of the application into individual Sections and intermediate headings restrict the not in its generality among these statements.

Brief description of the drawings

embodiments The invention are shown schematically in the drawings and will be closer in the following explained. In the drawings show:

1 a schematic side view of a treatment device according to the invention with ozone production and mixing device and

2 a greatly enlarged sectional view through a printed circuit board after a pattern plating process.

Detailed description the embodiments

In 1 is a treatment facility 1 with a treatment chamber 12 shown in the areal substrates 3 , For example, printed circuit boards or silicon wafers for solar cells, can be treated. In the treatment facility 1 there is a transport system 2 , from below and optionally also above the web of the substrates 3 arranged transport rollers consists. Below the transport system 2 extends over the essential length of the treatment chamber 12 a receptacle 4 , Below this is an intermediate floor 5 provided from the receptacle 4 exiting treatment liquid 14 collects and via a piping system into a tank 15 passes. The Tank 15 forms the main supply of treatment liquid 14 for the treatment facility 1 ,

When passing through the substrates 3 with the transport system 2 through the treatment chamber 12 They are with their bottom of the treatment liquid 14 in the receptacle 4 wetted. In this case, for example, a cleaning or etching of the undersides of the substrates 3 as described above. It is both possible that the substrates 3 come into contact with the treatment liquid only with one side or its underside, as well as that they are completely submerged in the treatment liquid. This is due to a higher overflow of treatment liquid in the receptacle 4 reached. Likewise, spraying with treatment liquid through the illustrated nozzles 18 from above possible, but in principle also by other nozzles also or only from below. This is basically known in such treatment facilities.

Additionally, in a dipping system with overflow of treatment liquid in the receptacle 4 Schwalleinrichtungen be provided, which are similar to the nozzles shown 18 are formed. They are submerged in the treatment liquid and generate a flow by ejecting the treatment liquid under pressure, thus providing renewal of the treatment liquid to the substrate 3 and removing formed gas bubbles. Again, this is basically known in such treatment facilities. The swelling devices can be arranged at the top, bottom or on both sides.

The ozone concentration of the treatment liquid is measured using an ozone meter 8th measured, which is acted upon by a partial flow of the treatment liquid after a pump P1. Another or alternative such ozone meter 8th' can in the treatment chamber 12 be provided and the ozone concentration in the treatment chamber 12 or directly to the substrates 3 measure up.

In a second cycle is treatment liquid 14 from the tank 15 taken by a pump P2 and by a mixer 6 pumped. Alternatively, only with the pump P1 and valves, the treatment liquid can be divided into two partial streams. One part becomes a static mixer and then into the receptacle 4 or returned to the tank, the other part goes directly into the receptacle.

By means of an ozone generator 7 is generated from oxygen or O ₂ ozone, ie O ₃ . The oxygen supply can be done either from the ambient air or a separate oxygen tank, where it is not shown here. The generated ozone is from the ozone generator 7 either as shown in the mixing device 6 the treatment liquid mixed, and then in turn into the tank 15 recycled. Inside the tank 15 can be a kind of nozzle arrangement 17 or a feed pipe below the liquid level be provided for a particularly good mixing of the ozone-containing treatment liquid 14 with the in the tank 15 located. Alternatively, by the supply line shown in dashed lines, the ozone in the first described circuit behind the pump P1 and before the ozone meter 8th the treatment liquid 14 be mixed, so shortly before the introduction into the receptacle 4 , Then, the separate ozone addition in the treatment liquid 14 in the tank 15 omitted.

By means of a control 9 that work with both the ozone generator 7 as well as the ozone measuring devices 8th and 8th' connected, the ozone concentration in the treatment liquid 14 be set or regulated to a desired value, for example, the values mentioned above. Furthermore, the controller 9 additional tasks of the treatment facility 1 perform, for example, controlling the pump P1 or P2 and various valves or the like ..

At the top of the treatment chamber 12 there is a suction 11 , This sucks ozone-enriched air from the treatment chamber 12 which would otherwise escape into the ambient air. Again, the controller could 9 the strength of the suction 11 monitor and regulate if necessary.

The exact composition of the treatment fluid 14 as well as the desired ozone concentration therein can significantly affect the purpose and also the nature of the substrates 3 depend and are each set different and cheap.

Furthermore, a cooling device 10 provided that the treatment liquid 14 cools, beneficial in the tank 15 or by a heat exchanger in the circuit. As a result, a decomposition of the ozone can be slowed down, so that less ozone must be produced or with the existing generator power a higher ozone concentration is achieved. Of course, there is a sufficiently good effect and process reliability of the treatment of the substrates 3 with the treatment liquid 14 to pay attention.

In 2 is a circuit board 3 ' shown in high magnification. There are structures on it 19 that are formed by a resist. Between the individual structures 19 is copper in a pattern plating process 21 for tracks or the like. applied. This can be the copper 21 overhangs 22 about the structures 19 of the resist. This allows the top of the circuit board 3 ' reaching treatment liquid only to a part of the surface of the structure 19 arrive at their removal, so that the removal of the resist takes longer there or must be carried out with more aggressive treatment liquids. If this treatment liquid is now mixed with ozone as a possible use, then the structure becomes 19 from Resist particularly strongly attacked and dissolved, above all largely dissolved into gaseous components. This is particularly advantageous especially when the overhangs 22 even further about the structures 19 pass.

Claims (22)

Method for treating flat substrates ( 3 . 3 ' ), in particular printed circuit boards ( 3 ' ), in the horizontal passage through a treatment device ( 1 ), wherein on at least one side of the substrates ( 3 . 3 ' ) Treatment liquid ( 14 ), characterized in that the treatment liquid ( 14 ) Ozone (O ₃ ) is added. Method according to claim 1, characterized in that the treatment device ( 1 ) a tank ( 15 ) and the tank with treatment liquid ( 14 ), wherein the treatment liquid from the tank ( 15 ) and for ozone addition to the mixing device ( 6 ), preferably gas bubbles from the treatment liquid in the tank ( 15 ) and this gas is sucked out of the tank. Method according to claim 1 or 2, characterized in that the treatment liquid ( 14 ) between a treatment chamber ( 12 ) of the treatment facility ( 1 ) with a receptacle ( 4 ) for the treatment liquid ( 14 ) and a tank ( 15 ) is continuously circulated, preferably by means of a pump (P1). A method according to claim 3, characterized in that a concentration of ozone (O ₃ ) in the treatment liquid ( 14 ) in the receptacle ( 4 ) in the treatment facility ( 1 ) is measured, in particular after the pump (P1) for supplying treatment liquid ( 14 ) in the receptacle or in the collecting trough, wherein the ozone production is regulated depending on the measured ozone concentration, in particular is regulated to an adjustable constant value. A method according to claim 3, characterized in that an admixture of ozone (O ₃ ) in the treatment liquid ( 14 ) behind the pump (P1) and in front of the receptacle ( 4 ) of the treatment facility ( 1 ) takes place, the pump (P1) treatment liquid ( 14 ) from a tank ( 15 ) in the receptacle ( 4 ) pumps. Method according to one of the preceding claims, characterized in that the treatment liquid ( 14 ) is cooled ( 10 ), preferably below room temperature. Method according to one of the preceding claims, characterized characterized in that the ozone concentration is between 2 ppm and 30 ppm, preferably between 5 ppm and 10 ppm. Use of a method according to one of the preceding claims for removing a resist ( 19 ) of a printed circuit board ( 3 ' ) as a substrate, preferably after a pattern-plating process of the printed circuit board, in particular for removing regions of a resist which are formed by copper structures ( 21 . 22 ) are partially enclosed. Use of a method according to one of claims 1 to 7 for cleaning printed circuit boards ( 3 ' ). Use according to claim 9 for cleaning printed circuit boards ( 3 ' in multi-layer printed circuit boards after drilling the bores, wherein the bores or the surrounding areas of the circuit boards are cleaned by the ozone-containing treatment liquid of resin fouling by the drilling. Use of a method according to one of claims 1 to 7 for the surface activation of the substrates ( 3 . 3 ' ) before a coating to improve the adhesion or for better wettability. Use according to claim 11 for structuring Printed circuit board base material as a substrate, preferably of resin or Polyimide film as printed circuit board base material, before lamination processes or before an electroless metallization, in particular with a chemically-copper process. Use of a method according to one of claims 1 to 7 for structuring the free copper surface of printed circuit boards before lamination processes before, wherein preferably the copper surface before lamination of individual inner layers to a multilayer printed circuit board to improve adhesion is structured by the ozone-containing treatment liquid. Use of a method according to one of claims 1 to 7 for treating silicon wafers ( 3 ) for solar cells, wherein preferably the silicon wafers after treatment with ozone-containing treatment liquid ( 14 ) Are HF-etched and in particular then rinsed. Use according to claim 14, characterized in that the method after a texturing process of the silicon wafer ( 3 ), especially after multiple rinses and HCl / HF etching. Use of a method according to claim 14 after a phosphor glass etching process, before which phosphorus is doped into the silicon wafer ( 3 ), wherein in particular the silicon wafer ( 3 ) after the phosphor glass etching process and before treatment with ozone-containing treatment liquid ( 14 ) is rinsed. Use of the method according to claim 16, characterized in that, before the phosphor glass etching process, an edge insulation of the silicon wafers ( 3 ) by etching, preferably by HF / HNO ₃ etching and repeated rinsing. Use of a method according to one of claims 1 to 7 for cleaning structures in an antireflection coating on silicon wafers ( 3 ) directly after the structures have been produced, wherein in particular the structures are produced with a laser, whereby residues of the generation of the structures are removed and the exposed emitter of the silicon wafers ( 3 ) is cleaned prior to metallization, in which electrical contacts are introduced into the structure. Use of a method according to one of claims 1 to 7 after producing structures in an antireflection layer on a silicon wafer ( 3 by masking the silicon wafer and then etching the exposed antireflection layer, after which a resist for masking is removed, in particular by stripping with NaOH, and subsequently the silicon wafers are treated with ozone-containing treatment liquid (US Pat. 14 ) be treated. Use according to claim 19, characterized in that the free by structuring placed emitter of the silicon wafer ( 3 ), in particular remaining contaminants of the resist for masking the silicon wafer. Printed circuit board ( 3 ' ), characterized in that it has been treated by a method according to any one of claims 1 to 7. Silicon wafers ( 3 ), in particular for the production of solar cells, characterized in that it has been treated by a method according to one of claims 1 to 7.