JP5449920B2 - Electroless plating method - Google Patents

Description

  The present invention relates to an electroless plating method, and more particularly to an electroless plating method for a semiconductor wafer.

  In the fabrication of semiconductor devices, a passivation film is provided on the surface when the silicon (Si) wafer process is completed. This passivation film has a partially removed region, for example, an electrode mainly composed of aluminum (Al) is exposed. Then, in order to make an electrical connection with the outside through this electrode, an external metal is connected to the electrode.

  As a method for connecting an external metal, wire bonding is generally used. On the other hand, depending on the application, it may be advantageous in terms of resistance and heat dissipation to directly connect the lead frame and the electrode by soldering. However, since it is difficult to solder the lead frame and the electrode directly, for example, a Ni-P layer having a thickness of several μm in which several percent of phosphorus (P) is mixed with nickel (Ni), and surface oxidation A method of forming a gold (Au) layer for the purpose of prevention by an electroless plating process has been proposed. According to this electroless plating treatment method, since the Ni—P layer and the Au layer are deposited only on the aluminum, there is no need for patterning. Moreover, since the temperature at the time of plating is 100 ° C. or less, there is an advantage that a thermal problem in the process does not occur.

  Next, a conventional electroless plating method will be described. FIG. 7 is a cross-sectional view showing the structure of a plating apparatus used in a conventional electroless plating method. FIG. 8 is a cross-sectional view showing a cross-sectional structure taken along section line AA ′ of FIG. As shown in FIG. 7 or FIG. 8, in the plating apparatus, the plating tank 11 is filled with a chemical solution. A plurality of wafers 12 to be processed are arranged in the wafer cassette 13 so as not to contact each other. This wafer cassette 13 is immersed in the plating tank 11 so that the wafer 12 to be processed is perpendicular to the surface of the chemical solution.

  A chemical supply nozzle 14 is provided between the bottom of the plating tank 11 and the wafer cassette 13. The chemical solution supply nozzle 14 supplies the chemical solution sent from a pump (not shown) toward the chemical solution surface in the plating tank 11. As a result, the chemical solution flows between the processing target wafers 12 arranged in the wafer cassette 13. And the chemical | medical solution in the plating tank 11 is circulated. By circulating the chemical solution in this way, the film quality of the plating layer formed on the semiconductor device by the electroless plating process and the film quality such as the phosphorus concentration in nickel can be made uniform. In addition, the temperature and concentration of the chemical solution in the plating tank 11 that greatly affects the plating characteristics can be made uniform.

  The chemical solution overflowed from the plating tank 11 is collected by the outer tank 15. The outer tank 15 is provided outside the plating tank 11. The outer tank 15 is provided with a drain port 16 for draining the chemical solution. The chemical liquid drained by the drain port 16 is again supplied into the plating tank 11 from the chemical liquid supply nozzle 14 by a pump (not shown).

  Here, in order to deposit a layer having a uniform film thickness and film quality on the wafer 12 to be processed, it is important to flow a chemical at a uniform speed on the surface of the wafer 12 to be processed. However, considering the flow of the chemical liquid on a surface perpendicular to the wafer 12 to be processed, it is difficult to uniformly supply the chemical liquid from the chemical liquid supply nozzle 14 in the direction in which the wafers 12 to be processed are arranged. In other words, it is difficult to make the chemical flow rate between the processing target wafers 12 the same everywhere. Considering the flow of the chemical solution on a surface parallel to the wafer 12 to be processed, as shown in FIG. 7, the chemical solution is supplied from a relatively narrow region. Furthermore, drainage due to overflow is performed from around the upper end of the tank. For this reason, local vortices and convection are generated in the plating tank 11. Therefore, there is a problem that it is difficult to flow the chemical solution on the surface of the processing target wafer 12 at a uniform speed.

  Further, the technique shown in FIGS. 7 and 8 has a problem that the film thickness and the film quality uniformity of the Ni—P layer are greatly different depending on the supply flow rate of the chemical solution and the direction of the chemical solution supply nozzle 14 and are difficult to optimize. is there.

  Further, as another method of treatment with a chemical solution, a method is provided in which a chemical solution supply port is provided on the side wall of the cleaning tank, a chemical solution discharge port is provided on the opposite side wall, and a plurality of semiconductor substrates are inserted in parallel with the chemical solution surface. Has been proposed (see, for example, Patent Document 1 below). According to this method, for example, when cleaning a semiconductor substrate, particles adhering to the semiconductor substrate can be prevented from adhering to the adjacent semiconductor substrate.

JP-A-5-21413

  However, the technique of Patent Document 1 described above does not describe electroless plating treatment. For example, when it is used for electroless plating treatment, can the thickness and quality of the formed plating layer be uniform? There is a problem of not knowing whether or not. Further, since processing is performed only on the wafers arranged in one cassette, there is a problem that the number of wafers that can be processed at one time is limited.

  An object of the present invention is to provide an electroless plating treatment method capable of making the film thickness and film quality of a plating layer formed on a wafer uniform in order to eliminate the above-described problems caused by the prior art. Another object of the present invention is to provide an electroless plating method capable of performing electroless plating on a large number of wafers at once.

To solve the above problems and achieve an object, an electroless plating method according to this invention, a plurality of thin flat plates are arranged in parallel at appropriate intervals cassettes, chemical surface into the plating tank A cassette insertion step for inserting the flat plate with respect to the vertical direction, a plurality of openings, and the total area of the openings is approximately the same as the cross-sectional area of the pipe for supplying the chemical into the plating tank The flow of the chemical solution supplied from the pipe into the plating tank is rectified in a direction parallel to the chemical solution surface and the flat plate by passing the chemical solution through the opening of the rectifying means. , the cassette is immersed in the chemical solution, unrealized, the rectifying means and the plating layer forming step, the forming a plating layer on the flat plate, and where placed chemical outlet of the plating tank and of said cassette And Serial, characterized in that it is arranged between the location and the chemical drain outlet of the plating tank to be placed of the cassette.

Further, to solve the problem described above and achieve an object, an electroless plating method according to this invention, a plurality of cassettes are arranged in parallel a plurality of thin flat plate at appropriate intervals, plating tank A cassette insertion step of inserting the flat plate into the chemical solution surface so that the flat plate is perpendicular to the surface of the chemical solution, and a pipe having a plurality of openings, and a total area of the openings for supplying the chemical solution into the plating tank. By passing the chemical solution through the opening of the rectifying means having the same area as the area, the flow of the chemical solution supplied from the pipe into the plating tank is made uniform in a direction parallel to the chemical solution surface and the flat plate. while rectification, the cassette is immersed in the chemical solution, a plating layer forming step of forming a plating layer on the flat plate, only including, the rectifying means, chemical outlet of the plating tank and the cassette With place to be And, characterized in that it is arranged between the location and the chemical drain outlet of the plating tank to be placed with the cassette.

Further, an electroless plating method according to this invention is the invention described above, the in plating tank, immediately before each of said cassette, said rectifying means is disposed, which is arranged immediately before each of said cassette The flow of the chemical liquid flowing through each of the cassettes is rectified by the rectifying means.

Further, to solve the problem described above and achieve an object, an electroless plating method according to this invention, a plurality of cassettes are arranged in parallel a plurality of thin flat plate at appropriate intervals, plating tank A cassette insertion step of inserting the flat plate into the chemical solution surface so that the flat plate is perpendicular to the surface of the chemical solution, and a pipe having a plurality of openings, and a total area of the openings for supplying the chemical solution into the plating tank. By passing the chemical solution through the opening of the rectifying means having the same area as the area, the flow of the chemical solution supplied from the pipe into the plating tank is made uniform in a direction parallel to the chemical solution surface and the flat plate. A plating layer forming step of forming a plating layer on the flat plate by immersing the cassette in the chemical solution while rectifying, and the rectifying means is provided immediately before each of the cassettes in the plating tank. Arranged, Serial upstream of the flow of the liquid medicine flowing in the plating tank than rectifying means, is arranged stream guide means for agitating the liquid chemical in the upstream of the flow of the chemical solution flowing through each of the cassette, chemical by the diversion means Then, plating is performed while rectifying the flow of the chemical solution flowing through the cassette by the rectifying means .

Further, an electroless plating method according to this invention is the invention described above, the plating layer forming step, the metal mainly composed of aluminum on the surface of the flat plate is exposed regions, mainly nickel and phosphorus A plating layer as a component is formed electrolessly.

  According to each of the above inventions, each chemical flow in the plating tank is made parallel to the chemical liquid surface, and the wafer is inserted so as to be perpendicular to the chemical liquid surface and parallel to the chemical liquid flow. The chemical solution flows through the wafer at a uniform flow rate. Thereby, the film thickness and film quality of the plating layer formed on the wafer can be made uniform.

Moreover, according to each said invention, an electroless-plating process can be performed to a lot of wafers at once by arrange | positioning a several wafer cassette in a plating tank. For this reason, manufacturing cost can be held down.

Moreover, according to each said invention, the chemical | medical solution which flows into each wafer cassette can be rectified by the buffer board arrange | positioned just before each wafer cassette. Accordingly, even when a plurality of wafer cassettes are arranged in the plating tank, the flowed rectified chemicals flow through the respective wafer cassettes, so that the thickness and quality of the plating layer formed on the wafer can be made more uniform. Can do.

Moreover, according to each said invention, the chemical | medical solution which flows into each wafer cassette can be stirred by the baffle plate arrange | positioned between wafer cassettes. Therefore, since the chemical solution with no concentration bias flows in each wafer cassette, the film quality of the plating layer formed on the wafer can be made more uniform.

  According to the electroless plating method according to the present invention, there is an effect that the film thickness and film quality of the plating layer formed on the wafer can be made uniform. Moreover, according to this electroless plating treatment method, there is an effect that the electroless plating treatment can be performed on a large number of wafers at once.

1 is a cross-sectional view showing a structure of a plating apparatus used in an electroless plating method according to a first embodiment. 1 is a perspective view showing an electroless plating method according to a first embodiment. It is a top view which shows the structure of the plating apparatus used for the electroless-plating processing method concerning Embodiment 2. FIG. It is a top view which shows the structure of the plating apparatus used for the electroless-plating processing method concerning Embodiment 3. FIG. It is a perspective view which shows an example of the shape of a flow guide plate. It is a perspective view which shows another example of the shape of a flow guide plate. It is sectional drawing which shows the structure of the plating apparatus used for the conventional electroless-plating processing method. FIG. 8 is a cross-sectional view showing a cross-sectional structure along a cutting line AA ′ in FIG. 7.

  Exemplary embodiments of an electroless plating method according to the present invention will be described below in detail with reference to the accompanying drawings. Note that, in the following description of the embodiments and all the attached drawings, the same reference numerals are given to the same components, and duplicate descriptions are omitted.

(Embodiment 1)
FIG. 1 is a top view showing the structure of a plating apparatus used in the electroless plating method according to the first embodiment. As shown in FIG. 1, the plating tank 1 is provided with a chemical supply port 4 on the side wall. Moreover, the chemical | medical solution drain port 7 is provided in the side wall facing the side wall in which the chemical solution supply port 4 of the plating tank 1 was provided. By supplying the chemical solution into the plating tank 1 from the chemical solution supply port 4 and discharging the chemical solution from the chemical solution drain port 7, the flow of the chemical solution can be made parallel to the surface of the chemical solution.

  The buffer plate 6 is provided between the chemical solution supply port 4 and the place where the wafer cassette 3 is placed, and between the place where the wafer cassette 3 is placed and the chemical solution drain port 7. The buffer plate 6 makes the flow of the chemical liquid a uniform laminar flow from the chemical liquid supply port 4 side toward the chemical liquid drain port 7 side. The buffer plate 6 is a flat plate and is provided with a plurality of small-diameter openings. The total area of the openings of the buffer plate 6 is, for example, approximately the same as the cross-sectional area of the chemical solution supply port 4. The plating tank 1 having such a configuration is filled with a chemical solution.

  The wafer cassette 3 is a plurality of processed wafers 2 arranged in parallel at appropriate intervals. For this reason, in the wafer cassette 3, the wafers 2 to be processed are arranged so as not to contact each other. The wafer cassette 3 is arranged in the plating tank 1 so that the wafer 2 to be processed is perpendicular to the surface of the chemical solution and parallel to the flow of the chemical solution. Here, the wafer 2 to be processed is, for example, a silicon (Si) wafer and has a thickness of, for example, 100 μm or less.

  Next, the electroless plating method according to the first embodiment will be described. FIG. 2 is a perspective view illustrating the electroless plating method according to the first embodiment. As shown in FIG. 2, the plating tank 1 is filled with a chemical solution, and a chemical solution sent from a pump (not shown) is supplied from the chemical solution supply port 4 and drained from the chemical solution drain port 7. Moreover, the flow of the chemical solution is a uniform laminar flow from the chemical solution supply port 4 side to the chemical solution drain port 7 side by the buffer plate 6. The wafer cassette 3 is inserted into the plating tank 1 so that the wafer 2 to be processed is perpendicular to the surface of the chemical solution and parallel to the flow of the chemical solution. This reduces the resistance when the wafer 2 to be processed is immersed in the chemical solution.

  The flow of the chemical liquid that has passed through the wafer cassette 3 is again rectified by the buffer plate 6 and drained from the chemical liquid drain port 7. As a result, in the plating tank 1, the chemical solution flows in parallel with the chemical solution surface. Further, the chemical solution drained by the chemical solution drain port 7 is filtered, adjusted in concentration, and adjusted in temperature in a region not shown. In the temperature adjustment, for example, the chemical solution is set to approximately 70 ° C. And this chemical | medical solution is again supplied in the plating tank 1 from the chemical | medical solution supply port 4 with a pump. Here, for example, in the case of NiP plating, the wafer cassette 3 is immersed in a chemical solution for approximately 20 minutes.

  According to the electroless plating method according to the first embodiment, since the wafers 2 to be processed are arranged in parallel with the flow of the chemicals, the chemicals are almost uniformly flowed between the wafers 2 to be processed. Flows. Further, since the wafer 2 to be processed is as thin as 100 μm or less, the flow of the chemical solution is not greatly disturbed. Thereby, the film thickness and film quality of the plating layer formed on the processing target wafer 2 can be made uniform.

(Embodiment 2)
FIG. 3 is a plan view showing a structure of a plating apparatus used in the electroless plating method according to the second embodiment. As shown in FIG. 3, the plating apparatus used in the second embodiment has a plurality of wafer cassettes 3 shown in the first embodiment arranged in series with respect to the flow path. The wafer cassettes 3 are arranged at an appropriate interval.

  Next, the electroless plating method according to the second embodiment will be described. In the plating tank 1 filled with the chemical solution, a chemical solution sent from a pump (not shown) is supplied into the plating tank 1 through the chemical solution supply port 4, and from the chemical solution supply port 4 side to the chemical solution drain port 7 side by the buffer plate 6. It flows in a uniform laminar flow toward. A plurality of wafer cassettes 3 are inserted into the plating tank 1 so that the wafer 2 to be processed is perpendicular to the surface of the chemical solution and parallel to the flow of the chemical solution. This reduces the resistance when the wafer 2 to be processed is immersed in the chemical solution. And each wafer cassette 3 is arrange | positioned at an appropriate space | interval so that it may be in series with respect to a flow path. Thereby, the chemical liquid whose flow is rectified by the buffer plate 6 sequentially flows into the plurality of wafer cassettes 3. Then, the flow of the chemical solution is again rectified by the buffer plate 6 and drained from the chemical solution drain port 7. Further, the chemical solution drained by the chemical solution drain port 7 is filtered, adjusted in concentration, and adjusted in temperature in a region not shown. And this chemical | medical solution is again supplied in the plating tank 1 from the chemical | medical solution supply port 4 with a pump.

  According to the electroless plating method according to the second embodiment, the uniform flow of the chemical solution supplied from the chemical solution supply port 4 is disturbed by the wafer 2 to be processed. However, by arranging the wafer cassettes 3 at appropriate intervals, the flow disturbed by the upstream processing target wafer 2 becomes a uniform flow again before reaching the downstream processing target wafer 2. Accordingly, the flow of the chemical solution in each wafer cassette 3 is the same. For this reason, the chemical solution flows at a substantially uniform flow rate between the respective processing target wafers 2 arranged in the respective wafer cassettes 3. As a result, even in a plating apparatus in which a plurality of wafer cassettes 3 are arranged, the film thickness and film quality of the plating layer formed on each wafer to be processed 2 can be made uniform. Moreover, since it is possible to perform plating on a large number of wafers 2 to be processed in a single process, manufacturing costs can be reduced.

(Embodiment 3)
FIG. 4 is a plan view showing the structure of a plating apparatus used in the electroless plating method according to the third embodiment. As shown in FIG. 4, in the plating apparatus used in the third embodiment, a buffer plate 6 is disposed immediately before each wafer cassette 3 of the plating apparatus used in the second embodiment. Further, a flow guide plate 8 may be provided between the wafer cassettes 3. The flow guide plate 8 is attached to the plating tank 1 before the plating tank 1 is filled with the chemical solution. FIG. 5 is a perspective view showing an example of the shape of the flow guide plate. Since the shape of the flow guide plate 8 should just be able to stir a chemical | medical solution, it is not restricted to the shape shown to (a)-(d) of FIG. FIG. 6 is a perspective view showing another example of the shape of the flow guide plate. As shown in FIG. 6, the flow guide plate 8 may be composed of a plurality of sheets. Specifically, for example, a shape in which three flat plates are alternately arranged up and down may be used.

  Next, the electroless plating method according to the third embodiment will be described. First, before the plating tank 1 is filled with the chemical solution, the buffer plate 6 is arranged immediately before the place where each wafer cassette 3 is placed, and the flow guide plate 8 is placed between the places where the wafer cassette 3 is placed. . Next, a chemical solution sent from a pump (not shown) is supplied from the chemical solution supply port 4 into the plating tank 1 to fill the plating tank 1. Further, the chemical liquid whose flow is rectified by the buffer plate 6 flows in a uniform laminar flow from the chemical liquid supply port 4 side to the chemical liquid drain port 7 side. A plurality of wafer cassettes 3 are inserted into the plating tank 1 so that the wafer 2 to be processed is perpendicular to the surface of the chemical solution and parallel to the flow of the chemical solution. And each wafer cassette 3 is arrange | positioned at an appropriate space | interval so that it may be in series with respect to a flow path.

  Next, the flow of the chemical solution is rectified by the buffer plate 6. First, the chemical solution flows into the first wafer cassette 3. The chemical solution that has passed through the wafer cassette 3 is stirred by the flow guide plate 8 and the flow is rectified by the buffer plate 6. Then, it flows into the next wafer cassette 3. In this way, after the chemical solution flows into all the wafer cassettes 3, the flow is rectified again by the buffer plate 6 and drained from the chemical solution drain port 7. Further, the chemical solution drained by the chemical solution drain port 7 is filtered, adjusted in concentration, and adjusted in temperature in a region not shown. And this chemical | medical solution is again supplied in the plating tank 1 from the chemical | medical solution supply port 4 with a pump.

  According to the electroless plating method according to the third embodiment, since the buffer plate 6 is arranged immediately before each wafer cassette 3, the flow-rectified chemical solution is supplied to each wafer cassette 3. Therefore, the chemical solution flows at a substantially uniform flow rate between the respective processing target wafers 2 arranged in the respective wafer cassettes 3. Thereby, the film thickness and film quality of the plating layer formed on all the wafers 2 to be processed can be made more uniform than the electroless plating method according to the second embodiment.

  Further, according to the electroless plating method, the flow guide plates 8 are provided between the wafer cassettes 3. Therefore, for example, even when the concentration is biased due to the chemical solution flowing into the immediately preceding wafer cassette 3, it is stirred by the flow guide plate 8 and the concentration becomes uniform. Thereby, the film quality of the plating layer formed on the wafer 2 to be processed can be made more uniform than the electroless plating method according to the second embodiment.

  In the present specification, the method of forming a plating film on a silicon wafer by electroless plating has been described. However, the present invention is not limited to this. The present invention can also be applied, for example, when a plating layer is formed on a flat plate other than a silicon wafer by electroless plating.

  As described above, the electroless plating method according to the present invention is useful for performing electroless plating on a thin plate, and is particularly suitable for performing electroless plating on a semiconductor wafer.

DESCRIPTION OF SYMBOLS 1 Plating tank 2 Wafer to be processed 3 Wafer cassette 4 Chemical solution supply port 6 Buffer plate 7 Chemical solution drain port 8 Current guide plate

Claims (5)

A cassette insertion step of inserting a cassette in which a plurality of thin flat plates are arranged in parallel at appropriate intervals into the plating tank so that the flat plates are perpendicular to the chemical surface,
By passing the chemical solution through the opening of the rectifying means having a plurality of openings and the total area of the openings being about the same as the cross-sectional area of the piping for supplying the chemical solution into the plating tank, While rectifying the flow of the chemical solution supplied into the plating tank so as to be uniform in the direction parallel to the chemical solution surface and the flat plate, the cassette is immersed in the chemical solution, and a plating layer is formed on the flat plate. A plating layer forming step to be formed;
Only including,
The rectifying means is disposed between the chemical solution supply port of the plating tank and the place where the cassette is placed, and between the place where the cassette is placed and the chemical solution drain port of the plating tank. A characteristic electroless plating method. A cassette inserting step of inserting a plurality of cassettes in which a plurality of thin flat plates are arranged in parallel at appropriate intervals into the plating tank so that the flat plates are perpendicular to the surface of the chemical solution;
By passing the chemical solution through the opening of the rectifying means having a plurality of openings and the total area of the openings being about the same as the cross-sectional area of the piping for supplying the chemical solution into the plating tank, While rectifying the flow of the chemical solution supplied into the plating tank so as to be uniform in the direction parallel to the chemical solution surface and the flat plate, the cassette is immersed in the chemical solution, and a plating layer is formed on the flat plate. A plating layer forming step to be formed;
Only including,
The rectifying means is disposed between the chemical solution supply port of the plating tank and the place where the cassette is placed, and between the place where the cassette is placed and the chemical solution drain port of the plating tank. A characteristic electroless plating method.   In the plating tank, the rectifying means is arranged immediately before each cassette, and the flow of the chemical liquid flowing through each cassette is rectified by the rectifying means arranged immediately before each cassette. The electroless plating method according to claim 2. A cassette inserting step of inserting a plurality of cassettes in which a plurality of thin flat plates are arranged in parallel at appropriate intervals into the plating tank so that the flat plates are perpendicular to the surface of the chemical solution;
By passing the chemical solution through the opening of the rectifying means having a plurality of openings and the total area of the openings being about the same as the cross-sectional area of the piping for supplying the chemical solution into the plating tank, While rectifying the flow of the chemical solution supplied into the plating tank so as to be uniform in the direction parallel to the chemical solution surface and the flat plate, the cassette is immersed in the chemical solution, and a plating layer is formed on the flat plate. A plating layer forming step to be formed;
Including
In the plating tank, the rectifying means is disposed immediately before each of the cassettes, and the flow guiding means for stirring the chemical liquid is disposed upstream of the flow of the chemical liquid flowing in the plating tank than the rectifying means , upstream of the flow of the liquid medicine flowing through each of the cassette, after stirring the liquid medicine by the stream guide means, and performing plating while rectifying the flow of the liquid medicine flowing to the cassette by said rectifying means electroless plating method.   2. The plating layer forming step of electrolessly forming a plating layer mainly composed of nickel and phosphorus in a region where a metal mainly composed of aluminum is exposed on the surface of the flat plate. The electroless-plating processing method as described in any one of -4.

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