JPH01287281A - Method for detecting end of etching of nickel-iron alloy film - Google Patents

Abstract

PURPOSE:To clearly judge the end of etching of an Ni-Fe alloy film on an electrically conductive substrate by measuring the potential difference between an electrode having chloride ion selectivity and the substrate. CONSTITUTION:When an Ni-Fe alloy film formed on an electrically conductive substrate 1 is patternwise dissolved and removed by etching with a ferric chloride soln. 6, an electrode 9 having chloride ion selectivity is placed opposite to the substrate 1 and used as a counter electrode and the potential difference between the substrate 1 and the electrode 9 is measured with an amplifier 10 for measuring potential difference. Since voltage becomes constant after the end of etching, the end of etching can be clearly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the field of electronics in which elements are formed using thin films, and particularly to a method for determining the end point when a Ni--Fe thin film is dissolved and removed by chemical etching.

Conventional technology In the field of electronics, a method is used in which a metal thin film formed on a substrate is covered with an organic polymer material called resist, and the remaining parts are etched using an etching solution. In this case, it is important to detect the end point in order to prevent etching from proceeding to areas that are originally intended to be left. As a method for detecting this end point, the method described by Hide et al.
,, vol, 132, No, 12゜2973-2
975 (1985)), there is a method of monitoring the current between the substrate and the platinum electrode.

Etching a Ni--Fe thin film formed on a substrate using an etching solution is performed, for example, in the manufacture of thin film magnetic heads, and a ferric chloride solution is used as the etching solution. End point detection is also important in this case. In such a case, it is possible to use a method such as measuring the current between the substrate and platinum as described above, but the platinum electrode is not suitable for oxidizing or reducing substances (e.g. re'', Fe'') in the solution.
”, Ni, etc.), making it difficult to detect a clear end point.

In this case, it is easy to consider monitoring the voltage between the platinum and the substrate, or the platinum rod potential is stable due to the effects of oxidizing and reducing substances. This method of measuring voltage requires that the etching solution be unaffected by oxidizing and reducing substances. Examples of this type of electrode include a sweet electrode called a comparative electrode or reference electrode, and a silver electrode called a comparison electrode or reference electrode.
Are there silver chloride electrodes or are these internal? It's called night @
This is also unsuitable because there is a risk that the 11 g or intoxicant may leach into the etching solution from within the substrate and, as a result, enter the semiconductor device.6 Problems to be Solved by the Invention When etching with a ferric chloride solution, if there is no way to clearly detect the end point of the etching, there is a risk that the etching will proceed beyond the portions that are not left. Therefore, it is necessary to clearly detect the end point of this and prevent over-etching.

However, it is an object of the present invention to provide a detection method that can clearly determine the end point of etching a metal film.

A second means to solve the problem and the inventor of the tree proceeded with research to achieve the above purpose, and (1)
With the method of detecting current, it is difficult to determine the end point of etching.

(2) In the method of detecting voltage, the counter electrode in which the voltage is always constant is heavy equipment.

(3) The voltage of electronically conductive electrodes such as platinum electrodes is not constant.

(4) Although the voltage is constant for sweet electrodes, silver chloride electrodes, etc., the etching solution may be contaminated.

(5) The etching solution consists of rec13 and MCI, which contains a large amount of C1- ions and has a constant concentration. Based on the knowledge that the voltage shows a constant voltage with respect to the ion concentration, it was discovered that the edging end point can be clearly detected by measuring the voltage difference between the substrate and the chloride ion selective electrode, and the present invention was achieved. However, in the present invention, the nickel-iron alloy film formed on the conductive substrate is removed by dissolving and removing the nickel-iron alloy film using 14-T ferric chloride solution. This is a method for detecting the etching end point of a nickel-iron alloy film, which is characterized in that a Hanawa ion-selective electrode is used as a means for detecting this, and the potential difference between a conductive substrate and the electrode is measured.

Etching solutions using ferric chloride contain a large amount of C biions with a constant 7 vacancy, so if a chloride ion-selective electrode is used in this solution, for example as a homogeneous membrane electrode or a liquid membrane electrode, the potential difference with the substrate will be constant. Therefore, the voltage can be measured using a Ni4e alloy film (e.g., the plated film 48 in 1(A) and Suba・
Once the ivy film 3) has been completely etched and soothed in the solution, the potential difference between the substrate and the chloride ion selective electrode becomes a constant value, so the end point of etching can be clearly detected. Hereinafter, the present invention will be explained in Examples 1 and 1-7, where the present invention will be explained in comparison with the conventional method and IS comparison 1-7. eC
The case of etching with h solution will be described.

FIG. 1(8) shows the cross-sectional structure of the thin film magnetic head element before etching, and FIG. 1(B) shows the cross-sectional structure after etching. That is, (8) the titanium sputtered film 2 formed on the substrate 1. A resist frame 5 is applied to the Ni--Fe sputtered film 3, followed by Ni--Fe plating 4a and 411), and the required portion 4b is covered with a cover 5', followed by immersion in an etching solution 6. on the other hand,
In (B), the dummy plating film 4a and the unnecessary N1-)e spa/vine film 3 have been removed by the etching process.6 Etching is performed using an etching solution with the following composition under the following conditions. degree 0.31101/, Q11C
1 concentration 0.01-0.001 mol/fJ
p++ Approximately 1.5 to 2.51 quality
A schematic diagram of the experimental setup for the test in which the 30°C current was monitored is shown in Figure 2, and the results are shown in the current-time correlation in Figure 3 (not shown in Figure 1). 1 is a substrate, 6 is a processing/soching solution, 7 is a Pt plate, and 8 is a current monitor. As shown in FIG. 3, in the current monitoring method, the current decreases as etching progresses, and although the progress can be seen, there is no clear end point.

On the other hand, the method of the present invention comprises a substrate] and a chloride ion electrode 9 as counter electrodes, and an amplifier 10 for measuring the difference between these voltages (Fig. 11 is an experimental apparatus, and Fig. 5 is a potential difference-time correlation diagram). ), it can be seen that the voltage becomes constant after the second point where etching ends, and the end point is extremely clear. Can be used to detect the end point of etching metal films using ferric solution6

[Brief explanation of the drawing]

FIGS. 1A and 1B are cross-sectional views of the thin film magnetic head element portion before and after etching, respectively. Figures 21 and 3 show the experimental equipment for monitoring current and the current-time correlation. FIGS. 4 and 5 are diagrams of an experimental apparatus and a potential difference-time correlation diagram for carrying out the voltage monitoring method of Rokunigi's invention. 1: Substrate 2: Titanium spun film 3
: N1-re sputtered film 4a/lb: Ni-metal plated film 5 Niresis l-5': Cover 6: Etching solution 7: Pt plate 8, current monitor 9: Chloride ion electrode 10' Potential difference measurement amplifier P: End point Location patent applicant Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] In etching to dissolve and remove a nickel-iron alloy film formed on a conductive substrate using a ferric chloride solution, chloride ion selection is used as a means to detect that the nickel-iron alloy film has been removed. 1. A method for detecting the end point of etching of a nickel-iron alloy film, the method comprising using a conductive electrode to measure the potential difference between a conductive substrate and the electrode.