JP3971675B2 - Electroless plating equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electroless plating apparatus, and more particularly to an electroless plating apparatus that enables plating on an object to be plated having a small area.
[0002]
[Prior art]
In general electroless plating, the plating area of the object to be plated is on the order of cm ² to m ² , and those having a minute area of 1 cm ² or less are fine particles floating in the electroless plating solution. When the electroless plating reaction proceeds on these fine particles, the particles become enormous and settle in the plating tank while consuming the electroless plating solution, and then become the core for depositing metal in the plating tank. This is the main factor that significantly reduces the stability of the liquid.
For this reason, the conventional electroless plating solution has a composition that prevents metal deposition on fine particles by adding a stabilizer having an effect of suppressing precipitation of heavy metals, sulfur-containing organic compounds, nitrogen-containing organic compounds and the like. Yes.
[0003]
In addition, the conventional electroless plating equipment is equipped with a filter in the circulation flow path, and the electroless plating solution is circulated and filtered to collect fine particles to prevent particle growth and particle settling in the plating tank. Designed to be. In the above filter, the liquid flow rate is relatively large, and the above-mentioned stabilizer is sufficiently supplied to the collected particles, which are adsorbed on the particle surface, thereby suppressing metal precipitation. The plating tank has also been improved in the shape of the overflow tank, the circulation rate, the structure of the outlet, and the filter (Takao Nakayama, Surface Technology, 303-307, Vol. 42, No. 3, 1991). ).
Another factor causing unnecessary electroless plating reaction to proceed in the plating tank is local heating around the heater for adjusting the plating bath temperature. If the electroless plating solution around the heater is not sufficiently stirred, the temperature around the heater will rise locally, making it easier for the electroless plating reaction to proceed. As a result, plating particles are generated and the stability of the electroless plating solution is significantly reduced. In order to prevent such local heating, stirring of the electroless plating solution and sufficient liquid circulation are required, and the conventional electroless plating apparatus is based on flowing the electroless plating solution in the plating tank. Has been designed.
[0004]
Further, from the viewpoint of improving bath stability, as disclosed in JP-A-3-75378, circulation of a low-temperature plating solution having a high bath component concentration and circulation of a high-temperature plating solution having a low bath component concentration are performed. In combination, an electroless plating apparatus that replenishes the temperature and concentration of the plating solution separately to keep the plating solution in an inactive state or a state close to it and prevent metal from depositing in the piping and pumps of the circulation line. is there.
In this way, in the conventional electroless plating that assumes the order of cm ² to m ² as the plating area of the object to be plated, the plating of a small area is required on both sides of the electroless plating solution composition and the mechanism of the electroless plating apparatus. Precipitation was suppressed.
On the other hand, in the semiconductor device manufacturing process, LSI electrodes are formed by vacuum film formation or electroplating, but with the miniaturization of electrodes and the increase in wiring density, attention has been focused on electrode formation by electroless plating. Yes. In this case, the electrode, which is the object to be plated, has been refined to 0.0002 cm ^{2 at} the largest and 0.00005 cm ² or less at the smallest.
[0005]
[Problems to be solved by the invention]
The size of such a microelectrode is equivalent to the foreign matter (fine particles) in the above-described conventional electroless plating solution. For this reason, when electroless plating is performed on a semiconductor wafer having a microelectrode in a conventional electroless plating apparatus, a stabilizer having an effect of preventing precipitation is excessively supplied to the microelectrode by a liquid flow, and the shape of the plating deteriorates. In the worst case, there is a problem that plating is completely suppressed and precipitation stops. Therefore, the electroless plating on an object to be plated such as a microelectrode is preferably in a state where the flow of the electroless plating solution in the plating tank approaches as much as possible and the electroless plating solution is stationary.
However, when the flow of the electroless plating solution in the plating tank is stopped, the liquid temperature in the vicinity of the heater rises, metal deposition on the heater occurs due to local heating, or plating particles are generated in the electroless plating solution, There is a problem that the stability of the electroless plating solution is significantly reduced. For this reason, attempts have been made to achieve both metal deposition on the object to be plated, such as microelectrodes, and prevention of local heating, due to changes in the liquid circulation conditions and the installation of rectifying plates inside the plating tank. A preferable electroless plating apparatus has not been obtained.
[0006]
Further, the electroless plating apparatus disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 3-75378 has almost no change in bath component concentration in plating with a small area of 1 cm ² or less. It is difficult to make the inactive state, and it cannot be an effective measure for improving bath stability. Furthermore, in order to prevent metal deposition on the heater due to local heating, it is necessary to circulate the plating solution supplemented with temperature to the plating tank at a predetermined flow rate. Even if this is relaxed, it is difficult to bring the flow of the electroless plating solution close to a stationary state.
The present invention has been made in view of the above circumstances, and provides an electroless plating apparatus that enables plating on an object to be plated such as a microelectrode of 1 cm ² or less in a semiconductor device manufacturing process. The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve such an object, an electroless plating apparatus according to the present invention is an electroless plating apparatus that uses a minute area of 1 cm ² or less as an object to be plated, and includes a plating tank into which the object is to be plated, and a heater. A reserve tank in which the electroless plating solution overflowed from the plating tank to the reserve tank is circulated to the plating tank, and the electroless plating solution in the reserve tank is circulated. , with adjusting the electroless plating solution in the reserve tank to the desired liquid temperature, and a second circulation device order to prevent the plating particles generated at the metal deposition or electroless plating solution to the heater due to local heating wherein the circulation flow rate per unit area and unit time of the first said plating bath by circulating device is in the range of 1~30cm3 / cm2 · min, the the capacity V1 of the plating tank reservoir Volume ratio V1 / V2 of the capacitance of the probe tank V2 is set to such that structure in the range of 0.1 to 1.0.
[0008]
As a preferred aspect of the present invention, the first circulation device includes a pump and a flow meter disposed in the circulation flow path, and circulates by controlling the pump based on a flow velocity value measured by the flow meter. It was set as the structure provided with the control apparatus for adjusting a flow volume.
Moreover, as a preferable aspect of the present invention, the second circulation device is configured to include a pump and a filter.
In the present invention as described above, the first circulation device can circulate the electroless plating solution in the plating tank in a state close to a stationary state, and the second circulation device can remove the electroless plating solution in the plating tank. The electroless plating solution in the reserve tank can be circulated without affecting the circulation.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of an electroless plating apparatus of the present invention. In FIG. 1, an electroless plating apparatus 1 includes a plating tank 2 for introducing an object to be plated, and a reserve tank 3 provided with a heater 4 for adjusting a plating bath temperature. The plating tank 2 is provided with a low wall 2a ′ in a part of the wall 2a, and is configured such that the electroless plating solution overflows from the wall 2a ′. The reserve tank 3 is disposed at a position for receiving the electroless plating solution overflowed from the plating tank 2.
The electroless plating apparatus 1 includes a first circulation device 6 for circulating the electroless plating solution overflowed from the wall portion 2 a ′ of the plating tank 2 to the reserve tank 3 to the plating tank 2. The first circulation device 6 includes a pipe (circulation flow path) 6a connected from the vicinity of the bottom of the reserve tank 3 to the bottom of the plating tank 2, and a pump 6b and a valve 6c disposed in the middle of the pipe 6a. ing.
[0010]
In addition, the electroless plating apparatus 1 includes a second circulation device for circulating the electroless plating solution in the reserve tank 3. The second circulation device 8 includes a pipe (circulation flow path) 8a connected from the bottom of the reserve tank 3 to a substantially central part of the reserve tank 3, a pump 8b and a filter 8c disposed in the middle of the pipe 8a. It has.
The heater 4 disposed in the reserve tank 3 is for adjusting the temperature of the electroless plating solution in the reserve tank 3. Such a heater 4 is not particularly limited. For example, steam, hot water or the like is flowed into the pipe to heat the electroless plating solution that is in contact with the pipe, or cold water or the like is flowed into the pipe to be in contact with the pipe. The electroless plating solution may be cooled. Moreover, the heater 4 can also be set as the structure which heats the outer wall of the reserve tank 3 directly or indirectly via a heat medium.
[0011]
The first circulation device 6 controls the flow rate with a valve 6c, for example, so that the electroless plating solution is supplied from the reserve tank 3 to the plating tank 2 at a predetermined circulation flow rate independently of the second circulation device 8. Can be circulated. As will be described later, the electroless plating solution in the reserve tank 3 is adjusted to a predetermined liquid temperature by the heater 4 and the second circulation device 8, and therefore, by the circulation of the electroless plating solution by the first circulation device 6, The plating bath temperature in the plating tank 2 is also adjusted to a predetermined temperature. In the present invention, the circulation flow rate per unit area / unit time of the plating tank 2 by the first circulation device 6 is set to a range of 1 to ³⁰ cm ³ / cm ² · min, preferably 4 to 12 cm ³ / cm ² · min. . Thereby, the electroless plating solution in the plating tank 2 can be circulated in a state close to a stationary state. For this reason, it is possible to prevent the stabilizer having the effect of suppressing precipitation of heavy metals, sulfur-containing organic compounds, nitrogen-containing organic compounds, etc. contained in the electroless plating solution from being excessively supplied to the object to be plated with a small area. Stable metal deposition on the plated object is maintained and good electroless plating is possible. If the circulating flow rate per unit area / unit time of the plating tank 2 by the first circulation device 6 is less than 1 cm ³ / cm ² · min, it is difficult to adjust the temperature of the plating bath in the plating tank 2, and 30 cm ³ / cm ² · If it exceeds min, stable metal deposition on the object to be plated is hindered, which is not preferable.
The “unit area of the plating tank” at the above circulation flow rate means to divide by the horizontal sectional area (cm ² ) of the inner surface of the plating tank, and this horizontal sectional area is the depth of the plating tank. If it is not uniform in the vertical direction, the average value is taken as the horizontal sectional area.
[0012]
The second circulation device 8 can circulate the electroless plating solution from the bottom of the reserve tank 3 to the substantially central portion of the reserve tank 3 via the filter 8c by the pump 8b. The electroless plating solution in the reserve tank 3 is circulated by the second circulation device 8 so that the electroless plating solution in the reserve tank 3 is adjusted to a predetermined solution temperature, and metal deposition on the heater 4 by local heating or Further, the generation of plating particles in the electroless plating solution is prevented, and the stability of the electroless plating solution is improved.
In addition, the capacity | capacitance of the plating tank 2 in the electroless-plating apparatus 1 and the capacity | capacitance of the reserve tank 3 can be set suitably, for example, the capacity | capacitance V1 of the plating tank 2 is the range of 10-100L, and the capacity | capacitance V2 of the reserve tank 3 is 20 The capacity ratio V1 / V2 of both tanks can be set in the range of 0.1 to 1.0.
The material of the plating tank 2, the reserve tank 3, the pipe 6 a of the first circulation device 6, and the pipe 8 a of the second circulation device 8 is, for example, SUS, Teflon (registered trademark), PP (polypropylene), PPS (polyphenylene sulfide), and the like can be used. Moreover, said filter 8c can use what is used in the conventional electroless-plating apparatus, for example, a membrane filter etc. can be mentioned.
[0013]
FIG. 2 is a schematic configuration diagram showing another embodiment of the electroless plating apparatus of the present invention. In FIG. 2, the electroless plating apparatus 11 is the same as the above-described electroless plating apparatus 1 except for the first circulation device 7. Common members are assigned the same member numbers, and descriptions thereof are omitted.
The first circulation device 7 of the electroless plating apparatus 11 includes a pipe (circulation flow path) 7a connected from the vicinity of the bottom of the reserve tank 3 to the bottom of the plating tank 2, and a pump disposed in the middle of the pipe 7a. 7b, a flow meter 7c, and a control device 7d. In the first circulation device 7, the flow velocity value of the pipe 7a measured by the flow meter 7c is sent to the control device 7, and the control device 7d controls the pump 7b based on this flow velocity value to adjust the circulation flow rate. Also in this case, the circulation flow rate per unit area / unit time of the plating tank 2 by the first circulation device 7 is set in the range of 1 to ³⁰ cm ³ / cm ² · min, preferably 4 to 12 cm ³ / cm ² · min. For example, a personal computer or a programmable controller can be used as the control device 7d. The material of the pipe 7a of the first circulation device 7 can be the same as that of the pipe 6a described above.
The electroless plating apparatuses 1 and 11 described above are examples, and the present invention is not limited to these embodiments.
[0014]
【Example】
Next, the present invention will be described in more detail with specific examples.
[Example]
The plating bath volume (tank capacity when overflowing) is a polypropylene plating tank with a capacity of 20L and the polypropylene reserve tank with a capacity of 40L. Arranged. The reserve tank was equipped with a Teflon heater (a heater with a pipe coated with Teflon (registered trademark)) as a heater.
[0015]
A polypropylene pipe was provided so as to connect the vicinity of the bottom of the reserve tank and the bottom of the plating tank, and a pump and a flow meter (KARUMAN ACE, Inc. manufactured by Kakinomiya Seisakusho Co., Ltd.) were disposed in the middle of the pipe. Further, a control device was arranged so that the circulation flow rate could be adjusted by controlling the pump based on the flow velocity value of the pipe measured by this flow meter. Thus, the first circulation device was obtained.
In addition, a polypropylene pipe was provided so as to connect the bottom of the reserve tank and the center of the reserve tank, and a pump and a filter (membrane filter) were provided in the middle of the pipe to form a second circulation device.
Thereby, the electroless plating apparatus of the present invention as shown in FIG. 2 was obtained.
[0016]
Next, an electroless plating solution (Melplate NI-869 manufactured by Meltex Co., Ltd.) was poured into the plating tank and the reserve tank of the above electroless plating apparatus.
Subsequently, the circulation flow rate of the electroless plating solution in the reserve tank by the second circulation device was set to 400 L / hour, and it was heated by a heater to set the liquid temperature of the electroless plating solution in the reserve tank to 85 ° C. Further, the circulation flow rate per unit area / unit time of the plating tank by the first circulation device was set to 6 cm ³ / cm ² · min. Thereby, the plating bath temperature in a plating tank became 84-85 degreeC.
[0017]
Next, an object to be plated provided with a plurality of areas to be plated having a minute area (0.0001 cm ² ) was prepared. This object to be plated was immersed in a plating tank for 20 minutes, and electroless plating was applied to a part to be plated having a small area. After the electroless plating was completed, the object to be plated was lifted from the plating tank, and the formed plating pattern was observed. As a result, it was confirmed that an electrode having a uniform and good shape having a thickness of about 5 μm was formed on the above-mentioned minute area. In the reserve tank, local heating in the vicinity of the heater was prevented, and the electroless plating solution was highly stable.
[0018]
[Comparative Example 1]
The electroless plating was applied to the object to be plated in the same manner as in Example 1 except that the circulation flow rate per unit area / unit time of the plating tank by the first circulation device was set to 40 cm ³ / cm ² · min. .
As a result of observing the formed plating pattern, some defects were observed.
[0019]
[Comparative Example 2]
The plating bath amount (the tank capacity at the time of overflow) is 130L, and a SUS plating tank provided with a SUS heater (pipe made of SUS) as a heater, and the bottom of this plating tank and the central part of the plating tank A pipe made of SUS was provided so as to be connected, and a pump and a filter (membrane filter) were arranged in the middle of the pipe to form a circulation device. Thereby, an electroless plating apparatus having only one circulation system was obtained.
The same electroless plating solution as in the example was poured into the plating tank of this electroless plating apparatus and heated by a heater so that the plating bath temperature in the plating tank was 85 ° C. However, in order to prevent local heating in the vicinity of the heater, the electroless plating solution circulation flow rate per unit area / unit time of the plating tank was set to 60 cm ³ / cm ² · min.
Thereafter, in the same manner as in Example 1, electroless plating was performed on the object to be plated.
As a result of observing the formed plating pattern, a deposition failure was observed in a portion to be plated with a small area (0.0001 cm ² ), and the formed electrode had an abnormal shape, and some of the electrodes were not plated. There was an electrode that was a deposit.
[0020]
【The invention's effect】
As described above in detail, according to the present invention, a plating tank into which an object is to be plated, a reserve tank provided with a heater for adjusting the plating bath temperature, and an electroless overflow from the plating tank to the reserve tank An electroless plating apparatus including a first circulation device for circulating the plating solution to the plating tank and a second circulation device for circulating the electroless plating solution in the reserve tank, and the first circulation device. Since the circulation flow rate per unit area / unit time of the plating tank is set within the range of 1 to ³⁰ cm ³ / cm ² · min, the first circulation device closes the electroless plating solution in the plating tank to a stationary state. It can be circulated in a state, stable metal deposition on the object to be plated is maintained and good electroless plating is possible, and the second circulation device affects the circulation of the electroless plating solution in the plating tank. Give It is possible to circulate the electroless plating liquid in the reserve tank without the stability of the electroless plating liquid local heating is prevented is exhibited an effect of improving.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of an electroless plating apparatus of the present invention.
FIG. 2 is a schematic configuration diagram showing another embodiment of the electroless plating apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,11 ... Electroless-plating apparatus 2 ... Plating tank 3 ... Reserve tank 4 ... Heater 6 ... 1st circulation device 6a ... Pipe 6b ... Pump 6c ... Valve 7 ... 1st circulation device 7a ... Pipe 7b ... Pump 7c ... Flow meter 7d ... Control device 8a ... Piping 8b ... Pump 8c ... Filter

Claims (3)

In an electroless plating apparatus that uses a small area of 1 cm ² or less to be plated,
A plating tank for charging an object to be plated, a reserve tank in which a heater is disposed, a first circulation device for circulating an electroless plating solution overflowing from the plating tank to the reserve tank, to the plating tank; Circulate the electroless plating solution in the reserve tank, adjust the electroless plating solution in the reserve tank to the desired solution temperature, deposit metal on the heater by local heating, and generate plating particles in the electroless plating solution and a second circulation device order to prevent circulation flow rate per unit area and unit time of the plating tank according to the first circulation unit is in the range of 1~30cm3 / cm2 · min, the plating tank An electroless plating apparatus , wherein a capacity ratio V1 / V2 between the capacity V1 and the capacity V2 of the reserve tank is in a range of 0.1 to 1.0 .   The first circulation device includes a pump and a flow meter disposed in the circulation flow path, and a control device for controlling the pump based on a flow velocity value measured by the flow meter to adjust the circulation flow rate. The electroless plating apparatus according to claim 1, wherein the electroless plating apparatus is provided.   The electroless plating apparatus according to claim 1, wherein the second circulation device includes a pump and a filter.

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