APPARATUS FOR ELECTROLESS METALLIZATION OF A TARGET SURFACE OF AT LEAST ONE WORKPIECE, AND METHOD AND DIFFUSER PLATE FOR THIS PURPOSE

Abstract

The present invention relates to an apparatus (1) for the electroless metallization of a target surface of at least one workpiece (5), having a vessel (10) to accommodate a metallization solution having an inlet (15) and an outlet (16) for the metallization solution, and a holder (20) for accommodating the at least one workpiece (5) and can be arranged within the vessel (10), wherein at least one diffuser plate (30) is provided between the at least one inlet (15) and the holder (20) and has a multitude of diffuser openings (35) spaced apart in a plane of a plate (E), and wherein a movement device (40) is provided, which can move the diffuser plate (30) in at least one spatial direction in the vessel (10). The present invention further relates to a method for the electroless metallization of the target surface of the at least one workpiece (5).

Claims

1. An apparatus (1) for the electroless metallization of a target surface of at least one workpiece (5), comprising: a vessel (10) for receiving a metallization solution with an inlet (15) and an outlet (16) for the metallization solution, and a holder (20) for holding the at least one workpiece (5), which can be arranged in the vessel (10), wherein at least one diffuser plate (30) is provided between the at least one inlet (15) and the holder (20), which has a plurality of diffuser openings (35) spaced apart in a plane of a plate (E), and wherein a movement device (40) is provided, which can move the diffuser plate (30) in at least one direction in space in the vessel (10).

2. The apparatus (1) according to claim 1, characterized in that the movement device (40) has the diffuser plate (30) in at least one recurring movement in one of the spatial directions perpendicularly to the plane of a plate (E).

3. The apparatus (1) according to claim 1, characterized in that the receptacle (20) is movable in the vessel (10).

4. The apparatus (1) according to claim 1, characterized in that the holder (20) is provided by the movement device (40) or another movement device in the vessel (10) is mobile or that the holder (20) can be arranged in the vessel (10).

5. The apparatus (1) according to claim 1, characterized in that a first cross-sectional area (A1) of the diffuser opening (35) on a first side (31) of the diffuser plate (30) is larger than a second cross-sectional area (A2) on a second side (32) opposite the first side (31).

6. The apparatus (1) according to claim 5, characterized in that a ratio between the first cross-sectional area (A1) and the second cross-sectional area (A2) is at least 1.1, i.e. A1/A2≥1.1.

7. The apparatus (1) according to claim 1, characterized in that the diffuser openings (35) are aligned in the at least one spatial direction.

8. The apparatus according to claim 1, characterized in that the diffuser openings (35) are arranged in rows in the plane of a plate (E) and that adjacent rows are arranged so as to be offset to one another.

9. The apparatus according to claim 1, characterized in that the holder (20) can accommodate several workpieces (5) spaced apart in rows by gaps and/or that the diffuser openings (30) are directed into the gaps.

10. The apparatus (1) according to claim 1, characterized in that the diffuser plate (30) corresponds to the shape of the vessel (10).

11. The apparatus (1) according to claim 1, characterized in that the diffuser plate (30) has a frame (34), which projects out from the plane of a plate (E) of at least one of the pages (31, 32).

12. The apparatus (1) according to claim 11, characterized in that the frame (34) has flow means through which the metallization solution can be guided in the direction of the diffuser openings.

13. A method for the electroless metallization of a target surface of at least one workpiece (5), in particular with an apparatus (1) according to claim 1, comprising the following method steps: inserting at least one workpiece (5) into the holder (20), positioning the holder (20) in the vessel filled with a metallization solution, and flushing the at least one workpiece (5) with the metallization solution by moving the diffuser plate (30) in order to form jets formed by the diffuser openings (35) in the metallization solution.

14. The method according to claim 13, characterized in that the diffuser plate (30) is cyclically moved by the movement device (40) and that the jets exit alternately from the diffuser openings (35) and are generated by backflows flowing into the diffuser openings (35).

15. The method according to claim 13, characterized in that the holder (20) with the least one workpiece (5) in the vessel (10) is moved by the movement device (40) or that the holder (20) is moved with the least one workpiece (5) in the vessel (10) by a further movement device independently of the diffuser plate (30).

16. A diffuser plate (30) for the apparatus (1) according to claim 1.

Description

[0039] An embodiment according to the invention of an apparatus for the electroless metallization of a target surface of at least one workpiece and the associated method 5 are described in detail below with reference to the accompanying drawings. In the drawings:

[0040] FIG. 1 shows a simplified and schematic representation of an apparatus according to the invention for electroless metallization of at least one workpiece with a vessel for receiving a metallization solution, in which vessel a diffuser plate is movably arranged;

[0041] FIG. 2 shows an enlarged and schematic representation of the diffuser plate according to FIG. 1; and

[0042] FIG. 3 shows a schematic detail of the diffuser plate according to FIGS. 1 and 2.

[0043] The same or functionally identical parts are identified with the same reference signs below. For the sake of clarity, not all the same or functionally identical parts are provided with a reference number in the individual figures.

[0044] FIG. 1 shows an apparatus 1 for the electroless metallization of a target surface of at least one workpiece 5. Such workpieces are wafers (not shown) which are commonly used as a substrate or base plate for electronic components, inter alia for integrated circuits (IC), micromechanical components, or photoelectric coatings.

[0045] The apparatus 1 essentially consists of a vessel 10 for receiving a metallization solution (not shown) into which the workpieces 5 can be immersed for metallization.

[0046] In the exemplary embodiment, a plurality of workpieces 5 are arranged in holders 20, which are designed as so-called wafer carriers, in a perpendicular and upright manner.

[0047] The vessel 10 has a bottom side 11 and a top side 12 and is formed by a liquid-tight wall. While the top side 12 is essentially open, the remaining sides are closed, whereby the vessel 10 can receive the metallization solution. Furthermore, the vessel 10 has at least one inlet 15 and an outlet 16. A plurality of inlet lines 15 can preferably be provided, which are arranged in a distributed manner. Further preferably, the inlet 15 or the inlet lines 15 can be arranged on the bottom side. The outlet 16 is preferably arranged on the upper side, wherein the outlet 16 in the present case is designed as an overflow 18. The metallization solution can be continuously fed into the vessel 10 by means of the inlet 15, during which the outlet 16 is designed for preferably continuous removal of the metallization solution, as a result of which the metallization solution flows through the vessel from the inlet 15 to the outlet 16. In order to catch the metallization solution emerging through the overflow, the vessel 10 is arranged in an overflow vessel which surrounds the vessel 10. Like the vessel 10 itself, the overflow vessel is only shown schematically.

[0048] A diffuser plate 30 can be arranged in the vessel 10. The diffuser plate 30 can be a substantially planar plate which has a plane of a plate E which corresponds to the normal plane of the diffuser plate 30. The diffuser plate 30 has a first side 31 and a second side 32, the first side 31 facing the bottom 11 of the vessel 10 and the second side 32 the top side 12 of the vessel 10.

[0049] The diffuser plate 30 is movably arranged in the vessel 10 and can preferably be lifted and lowered between the bottom side 11 and the top side 12 in a direction parallel to a normal vector of the plane of a plate E, which preferably points in the vertical direction. To this end, the shape of the diffuser plate 30 is adapted to the shape of the vessel 10 and there is a gap or running gap formed between the diffuser plate 30 and the vessel 10.

[0050] The diffuser plate 30 divides the vessel 10 into a first area 13 and a second area 14, wherein the first area 13 includes a plenum between the bottom side 11 of the vessel 10 and the first side 31 of the diffuser plate 30 and the second area 14 comprises the area of the vessel 10, which extends from the second side 32 of the diffuser plate 30 to the upper side 12.

[0051] In the first area 13, a heater 42 can be arranged between the diffuser plate 30 and the inlet 15, which can be formed from a plurality of heating elements, which can be arranged in a stationary manner in the vessel 10 parallel to the diffuser plate 30. The heater 42 can regulate the temperature of the metallization solution in the vessel.

[0052] As can be seen from FIGS. 2 and 3, the diffuser plate 30 has a plurality of diffuser openings 35. The respective diffuser opening 35 completely breaks through the diffuser plate 30 and connects the first side 31 to the second side 32.

[0053] The diffuser openings 35 can—as in the illustrated embodiment—be arranged in a plurality of rows, which are arranged parallel and spaced apart from one another. In the respective row, the diffuser openings 35 are arranged at a first distance D1, preferably equidistantly along a straight line or in one or more concentric circles, so as to be spaced apart from one another. Adjacent rows run at a second distance D2. The second distance D2 is preferably smaller than the first distance D1 in order to achieve the 5 highest possible density of diffuser openings 35 on the diffuser plate 30.

[0054] FIGS. 2 and 3 also show that the diffuser openings 35 on the first side 31 and the second side 32 have different cross-sectional areas A1, A2. On the first side 31, the diffuser opening 35 has a first cross-sectional area A1 and on the second side 32, the diffuser opening 35 has a second cross-sectional area A2, wherein the first cross-sectional area A1 is preferably greater than the second cross-sectional area A2. The diffuser opening 35 can thus have a cone section through which the diffuser opening 35 has a cross-sectional taper between the first side 31 and the second side 32.

[0055] On the first side 31, a frame 34, which is formed in a circumferential manner along the side edge of the diffuser plate 30, protrudes from the plane of a plate E. As shown in FIG. 2, the frame 34 stands free from the first side 31 in the direction of the bottom side 11 and can have a chamfer designed as a flow conduction center, which can be arranged on the side facing away from the gap and by means of which the surface enclosed by the frame 34 is widened in the direction of the bottom side 11.

[0056] Furthermore, it can be seen from FIG. 2 that the diffuser plate 30 has holding means 36, through which the diffuser plate 30 is placed in the vessel 10 or can be immersed in the metallization solution. The holding means 36 comprise fastening means 37 on the side facing away from the diffuser plate 30.

[0057] The holding means 36 make it possible to immerse or submerge the diffuser plate 30 into the vessel 10. The holding means 36 are preferably designed in such a way that the fastening means 37 protrude from the top side 12 of the vessel 10 in the lowered state of the diffuser plate 30.

[0058] The apparatus 1 also has a movement device 40, which is arranged laterally next to the pool 10 in FIG. 1. The movement device 40 is connected via an agitation frame 45 to the fastening means 37 at the free end of the holding means 36. The movement device 40 can have a drive designed as desired, which can generate a movement that can be transmitted to the diffuser plate 30 by means of the agitation frame 45, the fastening means 37, and the holding means 36.

[0059] Preferably, the movement device 40 can raise and lower the diffuser plate 30 in the vessel 10, wherein, when the diffuser plate 30 is lowered, the diffuser plate 30 is moved in the direction of the bottom side 11 and the diffuser plate 30 is moved in the direction of the top side 12 when it is raised.

[0060] When the diffuser plate 30 is lowered, the metallization solution enclosed in the first area 13 is forced into the diffuser openings 35 and exits on the second side 32 from the respective diffuser opening 35 in a rapid, a so-called “jet”, which subsequently spreads out in the second area 14. When the diffuser plate 30 is raised, the metallization solution flows from the second area 14 in the direction of the first area 13, wherein the metallization solution that has flowed back is mixed in the first area 13 with the metallization solution supplied by the inlet 15. In this case, the heating 42 is surrounded by a flow, as a result of which the formation of bubbles at the heater 42 can be reduced and a homogeneous temperature distribution can be realized.

[0061] The larger cross-sectional areas A1 of the diffuser openings 35 on the first side 31 lead the metallization solution in the manner of a nozzle in the direction of the secand side 32, and when the diffuser plate 30 is lowered, gas bubbles are easily forced through the diffuser openings 35.

[0062] The movement device 40 can preferably lift and lower the diffuser plate 30 cyclically, as a result of which jets and backflows are formed alternately, which flush through the second area 14 of the vessel 10 and the metallization solution located there is thoroughly mixed. As a result, a local impoverishment of the metallization solution in the second area 14 is counteracted.

[0063] The holder 20 can be immersed through the open top side 12 in the metallization solution in the vessel 10. As can be seen from FIG. 1, the holder 20 is positioned on the side of the diffuser plate 30 facing the upper side 12 in the metallization solution in the vessel 10.

[0064] The holder 20 with the at least one workpiece 5 can be arranged on the side of the diffuser plate 30 facing the upper side 12 and positions the at least one workpiece 5 in such a way that the workpiece 5 is surrounded by the jets formed by the movement of the diffuser plate 30.

[0065] The holder 20 can follow a lowering and a lifting of the diffuser plate 30, which is why the distance between the at least one workpiece 5 and the diffuser plate 30 is constant during the electroless metallization of the workpiece 5. Alternatively, the holder 20 can be arranged in a stationary manner in the vessel 10 and the distance between the diffuser plate 30 and the holder 20 can be varied.

[0066] In order to electrolessly metallize a target surface of the at least one workpiece 5, the at least one workpiece 5 is first inserted into the holder 20. After the insertion of the at least one workpiece 5 into the holder 20, the holder 20 is positioned in the vessel 10 filled with a metallization solution, so that the workpieces 5 or the target surfaces of the workpieces 5 are completely lowered or lowered into the metallization solution or are completely surrounded by the metallization solution. As soon as the holder 20 is completely lowered into the metallization solution in the vessel 10, the at least one workpiece 5 is surrounded by the metallization solution by moving the diffuser plate 30 by means of the movement device 40 through the jets formed by the diffuser openings 35. In this case, it is also advantageous if, during the moving of the diffuser plate 30, the metallization solution is continuously fed through the inlet 15 into the vessel 10 and is equally discharged through the outlet 16. The flow rate through the inlet 15 is preferably about 5-20 l/min.

[0067] The diffuser plate 30 is preferably cyclically raised and lowered by the movement device 40, as a result of which jets exit repeatedly from the diffuser openings 35. The raising and lowering can be described as a sinusoidal or cyclic motion of approximately 20 periods, wherein the amplitude or the stroke of the diffuser plate 30 is about 30 mm. The jets mix the metallization solution in the second area 14 of the vessel 10 with the at least one workpiece 5, as a result of which a mixing of the metallization solution in this second area 14 counteracts a local impoverishment of the reactants of the metallization solution and the uniformity or layer thickness distribution on the target surface is improved.

TABLE-US-00001 List of reference numerals  1 Apparatus  5 Workpiece 10 Vessel 11 Floor area 12 Top side area 13 First area 14 Second area 15 Inlet 16 Outlet 18 Overflow 20 Holder 30 Diffuser plate 31 First side 32 Second side 34 Frame 35 Diffuser opening 36 Holding agent 37 Fastening means 40 Movement device 42 Heater 45 Agitation frame E Plane of a plate