EP0133304A1 - Device for treating a thin substrate with a fluid in a continuous flow process - Google Patents

Abstract

1. A device (10) for treatment of thin substrate (18) with liquid, comprising a container (12) preferably rectangular in section, open at the top and closed at the bottom, said container having slots (14, 16) on two opposite walls for guiding the substrate (18) horizontally or near-horizontally in the liquid and being arranged in an overflow vessel (20) from which a first line (22) having a pumping unit (30) exits, the free end (38) of said line terminating below the substrate in the container, characterized in that the free end (38) of line (22) is aligned with the underside of the substrate (18) to adjust the pressure acting on the substrate (18), that there is a second connection (32) between the overflow vessel (20) and the container (12) for controlled liquid discharge in the area of the container above the substrate (18), that a riser line (36) exits from the container below the substrate (18) and is connected to the container above the substrate, and that an overflow line (28) determining the liquid level exits from the container above the substrate.

Description

The invention relates to a device for treating thin substrates with liquid in a continuous process.

The handling and handling of especially large-format, thin, fragile plates with an extremely sensitive surface presents considerable difficulties in various areas of technology. For example, in the production of thin-layer semiconductor layers, thin glass plates, so-called substrates, vapor-coated with various substances, have to be exposed to a chemical immersion bath in order to form a semiconductor layer via a chemical exchange process. This process is very sensitive and is strongly influenced by the contact time in the bath and the bath movement. A uniform wet-chemical treatment of the entire surface in the production of large-format semiconductor layers can only be achieved in a continuous process.

It is possible to immerse the substrates vertically in immersion baths. However, this method is unsuitable for a uniform surface treatment, since the lower substrate edges when Immerse yourself first, and finally step out of the bathroom. However, especially with short diving times, a corresponding method is associated with considerable disadvantages.

The object of the present invention is to provide a device for treating substrates with liquid in a continuous process, which ensures that a uniform treatment of the surface takes place even with short treatment times, without the risk that the substrate in particular during the treatment is mechanically deformed, which would damage the substrate and thus render it unusable.

The object is inventively achieved in that the substrate horizontally or horizontally approximately up by the liquid _'oriented container is guided below the liquid level, said caused by the liquid column above the substrate hydrostatic pressure equal to or approximately equal to the to the bottom pressure acting on the substrate, which is determined by a liquid component which is introduced into the liquid in a controlled manner and impinges on the underside of the substrate.

In other words, a device is provided in which the substrate is subjected to a uniform pressure load during the treatment, which ensures that mechanical deformations cannot occur. This is achieved by passing the substrate horizontally through the liquid. The substrate is preferably received by a guiding device which ensures that neither transport rollers nor other stabilizing or guiding rollers are required during the transport through the liquid in order to guide the substrate through the liquid. The conveying speed of the substrate the device can then be set so that the liquid acts on the substrate over a period to be determined beforehand. In this context, it should be expressly pointed out that treating the substrate with the liquid can be referred to as floating with liquid. This buoyancy comprises various processes in a continuous process such as wetting, rinsing, degreasing, coating, etching or chemical conversion. Particularly in the case of processes such as rinsing (detachment effects), etching and chemical conversion, contact times that can be precisely observed, which can be in the range of seconds, are required.

The container, which is rectangular in section, open on the head side and closed on the bottom, has passage slots for the substrate on two opposite walls, the container being arranged in an overflow vessel, from which a first line having a conveying unit originates, the free end of which leads to the underside of the substrate is aligned, and for controlled liquid delivery into the area of the container above the substrate there is a (second) connection between the overflow vessel and the container, and below the substrate a riser leads from the container, which is connected to the container above the substrate.

In this case, the second line can advantageously be branched off from the first line after the conveying unit and have a throttle in the section leading to the container, so that liquid can be introduced into the container above the substrate in a controlled manner. Furthermore, the container is connected via an overflow line which determines the liquid level, into which the riser line opens, to a liquid reservoir which in turn is connected to an overflow vessel on the bottom side. A corresponding device ensures that the pressure conditions around the substrate passed through the container are set in such a way that mechanical deformation cannot occur, so that damage to the substrate is excluded.

In a further embodiment of the invention, gas nozzles are arranged both before the inlet slot and after the outlet slot, above and below the transport plane of the substrate. Inert gas can then be emitted from these gas nozzles over the entire width of the inlet or outlet slot, so that liquid emerging from the slots is pushed back, so that the substrate is essentially no longer exposed to the liquid after leaving the container.

The through slots of the container are dimensioned so that they are only slightly wider than the substrate thickness. If the substrates are guided exactly with the guide device mentioned above, which preferably consist of two V-rails, which hold the substrates on both sides and which in turn run in two rails which lead through the entry and exit slots, the respective slot should only total approx 2 mm thicker than the substrates themselves. The slot length itself results from the depth of the substrates to be treated.

Although the liquid portion to be dispensed onto the substrate could also be conducted at an angle deviating from 90 ° to the underside of the substrate, it has proven to be advantageous for the supply line for the surge material to be guided vertically upward into the container, so that the Exit of the liquid portion is also oriented perpendicular or almost perpendicular to the underside of the substrate to be treated. The line, the free end of which can be provided with slot nozzles for uniformly distributing the liquid portion onto the substrate, can preferably be brought up to 0.5 cm to 4 cm to the transport plane of the substrate. Furthermore, the surge intensity itself can be set by the delivery unit arranged in the line, for example a pump.

With the aid of the device according to the invention, the treatment times for thin, fragile substrates can be set such that times in the seconds range as well as in the minutes range result. This essentially depends on the transport speed of the substrate through the container and the dimensioning of the container itself.

• a) waagerechtes oder nahezu waagerechtes Hindurchführen des Substrats durch die Flüssigkeit unterhalb deren Oberfläche,
• b) Beschwallen der Unterseite des Substrats zum Behandeln dieses mit einem Flüssigkeitsanteil und
• c) Einstellen des Drucks oberhalb und unterhalb des Substrats in der Flüssigkeit in einem Umfang, daß auf das Substrat keine eine mechanische Deformation hervorrufende Druckdifferenz einwirkt bzw. nur in einem Umfang auftritt, der noch keine mechanische Deformation und damit Beschädigung des Substrats nach sich zieht.

A method for treatment such as wetting, rinsing, degreasing, coating, etching or chemical conversion of at least one surface of a thin substrate, such as a semiconductor layer in a liquid, is characterized in particular by the method steps,

• a) passing the substrate horizontally or almost horizontally through the liquid below its surface,
• b) flooding the underside of the substrate to treat it with a liquid portion and
• c) Adjusting the pressure above and below the substrate in the liquid to such an extent that no pressure difference causing mechanical deformation acts on the substrate or occurs only to an extent that does not yet result in mechanical deformation and thus damage to the substrate.

Further details, advantages and features of the invention result from the preferred exemplary embodiments shown in the drawing.

• Fig. 1 eine Prinzipdarstellung einer erfindungsgemäßen Vorrichtung,
• Fig. 2 eine Führungseinrichtung für ein Substrat und
• Fig. 3 eine Detaildarstellung von Fig. 1.

In Fig. 1 ist der prinzipielle Aufbau einer erfindungsgemäßen Vorrichtung 10 zum Beschwallen von dünnen zerbrechlichen Substraten 18 wie Halbleiterschichten mit Flüssigkeit dargestellt. Die Vorrichtung 10 umfaßt ein im Schnitt vorzugsweise rechteckiges Behältnis 12 mit diametral angeordneten Eintritts- und Austrittsschlitzen 14 bzw. 16, durch die das Substrat 18 durch das Behältnis 12 geführt werden kann. Das Behältnis 12 ist in einem Überlaufgefäß 20 angeordnet, von dem seinerseits bodenseitig Leitungen 22 und 24 ausgehen. Dabei ist die Leitung 24 mit einem Flüssigkeitsreservoir 26 verbunden, das seinerseits mit dem Behältnis 12 über eine Leitung 28 verbunden ist, wobei die Leitung 28 in dem Behältnis oberhalb des Schlitzes 14 und 16 mündet. Die Leitung 22 führt in das Behältnis 12 zurück und weist ein Förderaggregat wie eine Pumpe 30 auf. Von der Leitung 22 nach dem Förderaggregat 30 zweigt sodann eine weitere Leitung 32 ab, die gleichfalls in das Behältnis 12 mündet, gleichfalls oberhalb der Durchtrittsschlitze 14 und 16. In der Leitung 32 kann gegebenenfalls eine Drossel 34 angeordnet werden, um die über die Leitung 32 in das Behältnis 12 abzugebende Flüssigkeit im gewünschten Umfang einstellen zu können.Show it:

• 1 is a schematic diagram of a device according to the invention,
• Fig. 2 is a guide device for a substrate and
• 3 is a detailed view of FIG. 1.

1 shows the basic structure of a device 10 according to the invention for floating thin fragile substrates 18 such as semiconductor layers with liquid. The device 10 comprises a preferably rectangular section 12 with diametrically arranged inlet and outlet slots 14 and 16 through which the substrate 18 can be guided through the container 12. The container 12 is arranged in an overflow vessel 20, from which in turn lines 22 and 24 extend from the bottom. The line 24 is connected to a liquid reservoir 26, which in turn is connected to the container 12 via a line 28, the line 28 opening into the container above the slots 14 and 16. The line 22 leads back into the container 12 and has a delivery unit such as a pump 30. A further line 32 then branches off from line 22 to delivery unit 30, which likewise opens into container 12, also above passage slots 14 and 16. In line 32, a throttle 34 can optionally be arranged, around which line 32 line 32 is connected to be able to adjust the liquid to be dispensed into the container 12 to the desired extent.

Finally, a riser 36 extends from the bottom region of the container 12 and opens into the line 28. It should also be noted that the line 22 is introduced into the container 12 such that the section 38 guided in the container 12 is guided approximately in the longitudinal direction of the container 12 and thus the liquid emerging from the line 22 or 38 vertically or in strikes the substrate 18 guided through the slots 14 and 16 approximately perpendicularly.

Via the line 22, liquid originating from the liquid 26 or the overflow vessel 20 is pumped into the container 12 by means of the delivery unit 30 to such an extent that a liquid level is reached which extends to the connection 28 which corresponds to the height of the Liquid level specifies. Under these conditions, the line 32 and the riser 36 are filled at the same time. The liquid emerging from the passage slots 14 and 16 is taken up by the collecting vessel 20 and fed back to the circuit described above via the line 22 and the delivery unit 30. If a substrate 18 is now passed through the passage slots 14 and 16, the passage gaps 14 and 16 narrow, so that the proportion of the liquid entering the collecting container 20 is reduced. Although the delivery unit 30 can continue to operate with the same delivery rate, no one-sided pressure build-up from below onto the substrate 18 is produced, since excess liquid can flow back into the liquid reservoir 26 via the riser pipe 36 and the overflow line 28.

If the substrate 18 narrows both the inlet and the outlet slots 14 and 16, the liquid level and thus the hydrostatic pressure above the substrate 18 cannot drop due to leakage losses at the slots, since liquid 32 is continuously replenished via the line 32. In this case, however, an impermissible pressure rise cannot occur either, since the liquid level is predetermined by the overflow line 28. If necessary, the inflow into the region of the container 12 above the substrate 18 can be regulated to the required extent by means of the throttle 34.

With the device according to the invention there is recognizable for the first time the possibility of treating thin, fragile substrates by floating with simple means, without the risk of uncontrolled pressure conditions leading to destruction in the liquid in which the substrate is to be treated or swallowed prevalence.

So that the substrate 18 is not held mechanically by any transport rollers or by stabilizing or guiding rollers must be passed through the container 12, the substrate 18 is received by a holding device 36, as shown in Fig. 2, in a particularly noteworthy embodiment of the invention. The holding device consists of two rails 42 and 44 which receive the side edges 38 and 40 of the substrate 18 and which have mutually facing concave, preferably V-shaped recesses 46 and 48. From these recesses 46, 48, the side edges 38, 40 are received, so that now only the rails 42, 44 themselves have to be transported, that is to say in particular through the slots 14 and 16 of the container 12, to the substrate 18 in the Container 12 can treat existing liquid.

In order to ensure that the substrate 18 does not come into contact with the liquid outside of the container in an uncontrolled manner and in particular that too much liquid cannot escape through the through slots 14 or 16, as shown in FIG. 4, the slots 14 and 16 are preferably slot nozzles 50, 52, 54 and 56, from which an inert gas can flow out in the direction of the passage slots 14, 16 in order to be able to retain the liquid entrained by the substrate 18. The nozzles 50 to 56 are preferably arranged or designed with regard to their outlet opening in such a way that the entire width of the slots 14 and 16 is detected both below and above the substrate 18.

A treatment of thin, fragile substrates in which the device 10 according to the invention is used will be explained below using two examples. Further examples essential to the invention can be gathered from these examples.

example 1 Etching and rinsing process

One step in the production of, for example, cadmium sulfide / copper sulfide thin-film solar cells is the etching of the Cadmium sulfide layer for structuring the surface. A corresponding solar cell comprises a substrate support, for example in the form of a glass plate of size 30 x 30 cm with a thickness of approximately 1.5 mm. A metal film made of silver, for example, is vapor-deposited onto this glass plate and serves as the first electrical contact. A cadmium sulfide layer is then evaporated onto this metal film. To reduce reflections and to etch out grain boundaries, the surface of the cadmium sulfide layer must be roughened with an aqueous hydrochloric acid. Since this must be done briefly and very evenly, the device 10 according to the invention is to be used. An 18% hydrochloric acid with a temperature of 50 ° C is used as the liquid. For the substrate having the total thickness of 1.5 mm, a container 12 is used, the through-slots 14 and 16 of which are approximately 3 mm thick. The cadmium sulfide layer is then transported through the container 12 in such a way that it points in the direction of the bottom of the container 12. The distance between the slots 14 and 16 is chosen to be 4 cm. The substrate 18 is then received by a holding device 36, as shown in FIG. 2. With the aid of this holding device 36, the substrate 18 is guided through the slots 14 and 16 and through the liquid. The plate is transported through the liquid in about 15 seconds. In order to achieve optimal conditions or results, section 38 of line 22 ends approximately 2 cm below the transport plane of substrate 18. Section 38 has an approximately 30 cm wide slot nozzle at its end, the slots being approximately 1 mm long are. This selection of the slit nozzle ensures that the surface of the cadmium sulfide is evenly swollen by the aqueous hydrochloric acid. Subsequently, the substrate 18 is transported further in the same way by a corresponding device 10, but in which, instead of the etching solution, deionized water is present for rinsing.

Example 2 Chemical implementation

To form the cadmium sulfide / copper sulfide semiconductor layer, the cadmium ions in the upper boundary layer of the cadmium sulfide must be in a wet chemical exchange process can be exchanged for copper ions. For this purpose, the substrate with a structured cadmium sulfide surface specified in Example 1 can be transported through a device 10 in which there is a hydrochloric acid-copper chloride solution. The dimensions in terms of slot width, slot length, liquid level and distance between the slot nozzle and the lower surface of the substrate can have the same values as in Example 1. Advantageously, the chemical reaction device is located behind the device in which the cadmium sulfide surface has been rinsed with deionized water, so that the treatment of the substrate can be carried out continuously by passing through devices in accordance with the teaching of the invention arranged in a line. However, the speed of the substrate itself does not need to be changed if the reaction time is to be increased or decreased. Rather, in this case it is only necessary to change the distance within the respective container. The longer reaction time required for the exchange of the cadmium ions by copper ions can be achieved by choosing the depth of the container 12 in the transport direction 6 cm, whereas in the example 1 this was 4 cm.

Claims (8)

1. Device for treating thin substrate with liquid in a continuous process,
characterized,
that the substrate (18) is guided horizontally or approximately horizontally through a liquid-containing container (12) below the liquid level, the hydrostatic pressure caused by the liquid column above the substrate being equal to or approximately equal to the pressure acting on the underside of the substrate is determined by a portion of the liquid that is introduced into the liquid in a controlled manner and strikes the underside of the substrate. 2. Device according to claim 1,

characterized,
that the container (12), which is preferably rectangular in section, open at the top and closed at the bottom, has passage slots (14, 16) for the substrate (18) on two opposite walls, that the container is arranged in an overflow vessel (20), one of which Conveying unit (30) having (first) line (22) whose free end (38) is aligned with the underside of the substrate that for controlled Liquid discharge into the area of the container above the substrate there is a (second) connection (32) between the overflow vessel and the container, that a riser (36) extends from the container below the substrate and is connected to the container above the substrate, and that an overflow line (28) determining the liquid level starts from the container above the substrate. 3. Device according to claim 2,
characterized,
that the second line (32) branches off from the first line (22) after the delivery unit (30) and has a throttle (34). 4. The device according to claim 2,
characterized,
that the container (12) via the overflow line (28), into which the riser (36) opens, is connected to a liquid reservoir (26) which is connected on the bottom side to the overflow vessel (20). 5. The device according to claim 2,
characterized,
that the line (38) delivering the liquid portion to the underside of the substrate (18) is preferably provided with a slot nozzle for uniform distribution of the liquid portion onto the substrate. 6. The device according to claim 1 or claim 2,
characterized,
that the substrate (18) is received by a device (36) which is guided through the slots (14, 16) and preferably from two rails (42, 44) receiving the side edges (38, 40) of the substrate with a V-shape there are mutually facing recesses (46, 48) extending in the longitudinal direction of the device. 7. The device according to claim 1 or claim 2,
characterized,
that the container (12) in the area of the slots (14, 16) is surrounded by preferably inert gas on the substrate (18) through the slots emitting nozzles (50, 52, 54, 56). 8. A method for treatment such as wetting, rinsing, degreasing, coating, etching or chemical conversion of at least one surface of a thin substrate,
marked by
the procedural steps a) passing the substrate horizontally or almost horizontally through the liquid below its surface, b) flooding the underside of the substrate with a liquid portion and c) Adjusting the pressure above and below the substrate to such an extent that there is no pressure difference which causes mechanical deformation on the substrate.

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