JPH0270099A - Method and apparatus for electroplating - Google Patents

Abstract

PURPOSE:To precisely control both film thickness of a magnetic substance thin film and distribution of film thickness by arranging a plurality of coils in the vicinity of a base plate and measuring the change of impedance at every coil and changing current caused to flow through an electrode opposite to the base plate. CONSTITUTION:Coils 10-12 are arranged in the vicinity of the side opposite to the surface of a plated film 2 on a base plate 9 in a plating tank 1 and anodes 5-7 are allowed to correspond to the respective coils 10-12 and connected with the plating power sources 20-1-20-3. In this constitution, plating is started on the base plate 9 and AC is impressed to the coils 10-12 to generate eddy current and the change of impedance of the coils 10-12 due to this magnetic field is inputted to a data register 18 via an impedance measuring device 15. Then preset value of a film thickness range setting device 17 is compared with the measured value of the data register 18 by a comparator 19 and a command is sent to the power source of the anode correspondent to the coil wherein the data are deviated from the range and plating current is individually controlled. Thereby the high-quality magnetic substance plated film 2 is produced at high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to improvements in a magnetic plating method and apparatus.

(b) Conventional technology Ni/Kel iron alloy (permalloy), which is common as a magnetic thin film
A method of obtaining a film by electroplating in a magnetic field is widely used in industry, and the equipment used therefor includes a bath, a stirring device, a bath circulation bong, a magnetic field generator, and the like. With these devices, the film thickness and film thickness distribution are measured after plating is completed, so parameters that affect film thickness and film thickness distribution, such as ion concentration distribution in the plating bath, bath temperature, and plating current density, are kept as constant as possible. Then, by controlling the plating time, a plated film of a predetermined thickness was obtained.

However, the above plating parameters are difficult to measure and extremely difficult to maintain at constant values during plating, resulting in poor reproducibility and low productivity, making it difficult to obtain high-quality magnetic thin films at high yields. I'm wanted.

In contrast, the conventional method of obtaining a magnetic thin film with a predetermined thickness by plating while measuring the film thickness was (
1) A method of equipping a reciprocating stirring device with a coil and detecting changes in voltage or inductance that occur when cutting the magnetic flux passing through a plating film formed in a magnetic field; (2) Plating formed in a magnetic field. A method of arranging a coil around the film and measuring the amount of magnetic flux passing through the plating film, and (3)
There is a method in which a reciprocating stirring device is equipped with a coherent parallel light generator and a light intensity detector, and changes in intensity due to interference between the formed plating film and the light reflected from the base are detected. According to these methods, the thickness of the magnetic thin film can be controlled with high precision. However, recently, substrates on which magnetic thin films are to be formed have become larger, and even if the above-mentioned method is used, it is difficult to make the distribution of film thickness uniform on such substrates.

For example, in the methods (1) and (2) above, since the change in the total magnetic flux passing through the plating film is detected by a coil, the averaged film thickness of the plating film is measured. For this reason, some parts of the large substrate do not reach a predetermined film thickness, resulting in a decrease in yield. Furthermore, the distribution within the substrate of the portion where the film thickness does not reach a predetermined thickness is not reproducible, and productivity also decreases. Also, (3)
In this method, as the size of the substrate becomes larger, it becomes structurally difficult to maintain a constant distance between the light intensity detection device installed in the stirring device that moves back and forth over the substrate and the substrate on which the plating film is formed. Furthermore, it is structurally difficult to measure the film thickness distribution over the entire surface of the substrate.

Therefore, the present inventor proposed the use of electromagnetic induction as a method for measuring film thickness during plating, and a device for that purpose in the patent application filed in 1983-8.
It was proposed as No. 5850. As shown in Fig. 1, this method using electromagnetic induction involves placing a coil 3 near a substrate 9 on which a plating film 2 is to be formed, and applying an alternating current to the coil to generate an alternating current magnetic field during plating. An eddy current is generated in the membrane 2, and an impedance measurement device 15 detects a change in the impedance of the coil 3 due to the magnetic field created by this eddy current.

To measure the plating thickness of a magnetic thin film, it is necessary to increase the frequency of the alternating current applied to the coil. In the method used in the present invention, the frequency is 500 KHz-30MHz.
When set to z, thin films of 0.2 μm to 5 μm can be measured with high precision. Furthermore, as mentioned above, plating of magnetic thin films is generally carried out in a magnetic field of several tens to several thousand oersteds;
It has been found that by using a high frequency of Hz to 30 MHz, it is possible to detect electrical signals indicating changes in coil impedance without noise even in these magnetic fields.

By the way, the film thickness that can be measured using the electromagnetic induction method is within a limited range depending on the magnitude of the magnetic field generated by the coil 3. Therefore, by arranging multiple coils and switching the impedance change of each coil. If information on the film thickness of the entire surface of the substrate 9 is collected through detection, the film thickness distribution can be measured, and it is possible to prevent a case where a part of the substrate 9 does not reach a predetermined film thickness.

When a plurality of coils are arranged in this manner, mutual interference may occur depending on the shape and drive frequency of the coils, which is not desirable. Therefore, it is effective to measure by switching between multiple coils. In this method, multiple coils are not excited at the same time, so mutual interference does not occur. Furthermore, by devising the structure, dimensions, arrangement distance, etc. of the probe, it is possible to shorten the switching time. In other words, there are two types of coils that can be used in this method: probe type (inner magnetic type) and pot type (outer magnetic type), but in order to prevent interference in boat fishing, it is necessary to have a magnetic shielding effect on the outside of the core. A probe type with a ring (for example made of copper) is preferred. In addition, the frequency of the current used in such a coil is generally below the resonant frequency of the coil (for example! -10
MHz), but in the case of probe-type coils, in the case of a probe-type coil, if the core diameter is set to 0.5 mm or less, there will be no interference between adjacent coils even if the coils are placed close to each other with a distance of 10 mm or less. It can be measured without Furthermore, if the thickness of the ring surrounding the core of the probe-type coil is adjusted, it can operate at high frequencies of 10 MHz to 30 M112 without interference. Note that even with pot-shaped coils, if the diameter of the coil core was set to 3 mm or less, measurements up to 10111H2 were possible even if the coils were placed close to each other at 10 mm or less.

In magnetic plating, it is structurally difficult to arrange a detection coil on the substrate side on which the plating film is formed because the inside of the bathtub is stirred. Therefore, in the apparatus for carrying out the above method, the coil 3 is arranged on the back side of the substrate surface on which the plating film 2 is formed. Even so, with this method, it was possible to measure impedance changes corresponding to the thickness of a plating film formed on a ceramic substrate or a glass substrate with a thickness of several mm.

FIG. 2 shows a measuring device for carrying out the conventional measuring method by the inventor. Coils 10 to 12 are arranged near the opposite side of the plated film 2 of the substrate 9, and each coil is connected to an impedance measuring device 15 via a scanning device 14 that distributes driving alternating current and switches the detection output. ing.

Each coil 10-12 is hermetically sealed in a jig 21 that fixes the substrate 9, so that the plating solution 16 does not penetrate. The other structures of the plating tank 1 are not related to the present invention, and therefore their explanation will be omitted.

Each data measured by the impedance measurement device 15 is input to the data register 18, and is compared with the value set in the film thickness range setting device 17 by the comparison device 19,
If the conditions are met, the plating power source 20 is stopped.

Plating is performed in a permalloy plating bath with Ni2+, Fe2+ ion concentration, bath temperature, and plating current density within certain ranges (these conditions are not related to the present invention, so their explanations are omitted), and the current applied to the coil is frequency to 6
FIG. 3 is a graph showing the data obtained from the three coils when set to Mfh in terms of plating time and film thickness. In the figure, the horizontal axis shows the plating time, the vertical axis shows the plating film thickness, a is the data from the coil 11, and b is the data from the coil 1.
Data from 0 and C are data from coil 12.

From the figure, at the plating end point A using the conventional method, b and C
The data shows that the plating film thickness is still insufficient, and when plating is finished at time B when the output of all coils is within the predetermined film thickness range G, the plating film thickness inside the substrate is It can be seen that all of the film thicknesses are within the set film thickness range G. According to this method, the measurement accuracy of the film thickness was within ±0.1 μm.

FIG. 4 shows an example of the arrangement of coils for measuring the film thickness distribution of the plating film within the plane of the substrate 9. FIG. In the case of a 2-inch square substrate 9, nine coils 22 to 30 are arranged in a grid pattern at 20 mm intervals on the back side of the substrate, and each coil is connected to an impedance measuring device via a scanning device 14 as shown in FIG. 15, it was found that the distribution of the plating film thickness on the substrate could be measured with sufficient accuracy. By measuring the change in impedance of each of the coils 22 to 30 in this way, the thickness of the plating film on the entire substrate falls within the standard.

By the way, in the conventional measuring device as shown in Fig. 2, it was possible to determine the plating end point by measuring the film thickness distribution during plating using multiple coils, but it was possible to grasp the plating end point. It was not possible to control the variation in Therefore, as shown in Fig. 3, the overall processing time becomes longer due to variations in film thickness growth (vertical distance between asb and c), and the film thickness distribution is further improved by narrowing the 617'l1 width. I couldn't make it smaller.

(c) Purpose of the Invention The purpose of the present invention is to improve the shortcomings of the plating method as described above, perform plating while measuring the film thickness and film thickness distribution, and achieve a film with a predetermined thickness, especially on large substrates. The object of the present invention is to provide a method for obtaining a magnetic thin film with a uniform thickness distribution with even higher precision, and an apparatus therefor.

(D) Structure of the Invention According to the present invention, the electrode (anode) facing the substrate is divided corresponding to the plurality of coils, so that the entire area is equal to that of the electrode (cathode) including the substrate surface. Place it in That is, a portion of the anode (divided anode) facing the substrate at the coil position corresponds to one coil.

Then, the output detected from each coil is compared with a predetermined film thickness distribution range (for example, the difference between the center and the periphery is within 0.5 μm). As a result, the anode current of the part corresponding to the coil position determined to be out of range is controlled so that if it is below the range, it flows more than the current current, and if it exceeds the range, it flows less, so that the predetermined film thickness It becomes possible to perform plating while always satisfying the distribution.

- For example, when exceeding the range, 20% of the specified current
By controlling the flow to a certain extent, and conversely by flowing about 20% more than the predetermined current when the current was below the specified range, a plated film with a uniform thickness distribution could be obtained. However, since these conditions largely depend on the plating bath and plating conditions, there is an appropriate range for each case.

(E) Embodiment FIG. 5 shows an apparatus for carrying out the method according to the present invention. In the figure, the bathtub etc. are the same as those in FIG. 2. Anode 5
~7 are connected to the plating power supplies 20-1 to 20-3, respectively, and the anode 5 corresponds to the coil 10, the anode 6 corresponds to the coil 11, and the anode 7 corresponds to the coil 12.
A control system is included. The detection output from each coil is input to the data register 18 via the impedance measurement device 15. Here, the data is compared with the value set in the film thickness range setting device 17, and a command is sent to the power source of the anode corresponding to the coil whose data falls outside the range, thereby individually controlling the plating current. FIG. 6 shows data obtained from three coils when plating was performed using this apparatus and the frequency of the current applied to the coils was set to 6 MHz. a is data from coil 11, b is data from coil 10
C is the data from the coil 12. As can be seen from the figure, when the control system of FIG. 5 is used, the film thicknesses a-C are close to each other, and it can be seen that the plating time C falls within the predetermined film thickness range G. On the other hand, according to the conventional method, the data of the coil 12 becomes C' in FIG. 5, and the plating time C does not fall within the predetermined film thickness range G. It can also be seen that by adopting such a configuration, the width of the predetermined film thickness range G can be narrowed.

FIG. 7 shows an example of an anode divided corresponding to the coils arranged as shown in FIG. Anodes 31-39 are coils 22-
It is divided into positions corresponding to 30.

In this way, it is possible to control the plating film with a uniform film thickness distribution.

Nine coils 22 to 30 are arranged in a lattice shape at 20 mm intervals on a 2 inch square substrate 9, and opposing anodes 31 to 39
(each 20 mm square) are arranged corresponding to the coils 22 to 30, and plating is performed using the apparatus and control system shown in Figure 5 to achieve the necessary and sufficient plating film thickness distribution on the substrate. It was found that measurement can be controlled systematically.

(f) Effects of the invention By using the method and apparatus described above, plating can be performed while monitoring the film thickness distribution of magnetic plating, and a predetermined film thickness and film thickness distribution can be obtained over the entire plating substrate. This has made it possible to manufacture high-quality magnetic plated substrates at high yields.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a method for measuring plating film thickness used in the present invention. FIG. 2 is a diagram showing a conventional plating film thickness measuring device. Figure 3 is a graph showing an example of conventional plating film thickness measurement and end point control. FIG. 4 is a diagram showing an example of the arrangement of coils of the plating film thickness measuring device used in the present invention. FIG. 5 is a diagram showing a plating film thickness measurement and control device according to the present invention. FIG. 6 is a graph showing an example of measurement of plating film thickness, film thickness distribution control, and end point control according to the present invention. FIG. 7 is a diagram showing an example of the arrangement of anodes of the plating film thickness measuring device according to the present invention. 1. Bathtub, 2: Plating film, 3: Coil, 5-7: Anode, 9: Substrate, 10-12: Coil, 14: Scanning device, 15: Impedance measuring device, 17: Film thickness range setting device, 18 : data register, 19: comparator, 20: plating power supply, 20-
1 to 20-3: Metsuki power supply

Claims (2)

[Claims] (1) In magnetic thin film plating in a magnetic field, multiple coils are placed near the surface of the substrate on which the plating film will be formed, and the coils are driven at high frequency and the change in impedance is measured by switching for each coil. By monitoring the thickness and thickness distribution of the plating film, and controlling the thickness and thickness distribution of the plating by changing the current flowing through a part or the entire surface of the electrode facing the substrate according to the results. An electroplating method characterized by: (2) An apparatus for plating a magnetic thin film in a magnetic field, including a plurality of coils installed near the plating surface of a substrate to be plated, a high-frequency current generator for driving the coils, and an impedance of the coils. a switching device for selectively connecting the high frequency current generator to the coils in order to distribute the high frequency current to the plurality of coils, and a switching device for measuring the impedance of the plurality of coils. a switching device that selectively connects a measuring device to the coil; a device that monitors the thickness and thickness distribution of the plating film based on the measurement results of the impedance measuring device; and a device that controls the plating current according to the monitoring results; 2. An apparatus for carrying out the method according to claim 1, comprising a counter electrode that can change the distribution of plating current with respect to the substrate partially or over the entire surface.