JPS59169175A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To effectively remove only an improper electrode without affecting the influence to the other by covering the entire surface of a semiconductor device with a protective film, exfoliating only the film, and etching and removing the exposed electrode. CONSTITUTION:A medicine resistant protective film 6 having good sealability is uniformly coated on the overall main surface of a semiconductor substrate 1. Photoresist or polyimide resin is used as the protective film, it is cured by exposure or heating after coating. A damage is formed by a cutter only on the part of the protective film on the improper electrode 3a, removed, and the electrode 3a is exposed. Only the position of the electrode 3a is etched, and removed to remove the film 6. No possibility of damaging the normal electrode occurs, and no partial remainder of the improper electrode incompletely takes place.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a gate turn-off thyristor (hereinafter referred to as GT), for example.
Manufacture of semiconductor devices that have the function of cutting off current, such as transistors, electrostatic induction silices (abbreviated as O), and remove undesirable electrodes from among the plurality of divided electrodes provided on the main surface of the semiconductor substrate. Regarding the method.

[Prior art and its problems]

FIG. 1 shows, for example, a partial cross-sectional view of the element structure of a conventional GTO. In Figure 1, P type emitter (pE) + n type base (nB), p type base (pB) + n type emitter,
The silicon fast conductor substrate l consisting of four layers (no) has pB
A gate electrode 2 is provided on the layer, and a cathode electrode 3 is provided on the nE layer, and a contact electrode plate 4 is placed on the cathode electrode 3 so as to be in contact therewith. At this time, in order to prevent the gate electrode 2 and the cathode electrode 3 from short-circuiting through the contact electrode plate 4, heights are provided on the main surface of the silicon substrate 1. It is arranged very well.

In such a structure, if there is a defect indicated by the symbol A in the n2 layer below the cathode electrode 3, the cutoff signal will flow from the cathode electrode 3 to the gate electrode 2 through the defect A, and the current cutoff will not be performed effectively. In such a case, in order to prevent the main current from flowing through the nF layer with defect A, the cathode electrode (
As one countermeasure, a method of cutting and removing the defective electrode 3a (!: abbreviated as below) with a cutting tool is described in Japanese Patent Laid-Open No. 56-51867. FIG. 2 shows a situation in which a defective electrode 3a on a silicon substrate 1 is mechanically cut with a cutting tool 5. As shown in FIG.

However, if the emitter shape is complex or minute, this method carries the risk of damaging the surrounding normal cathode electrodes and even making the semiconductor device itself defective. However, it has the disadvantage that it is quite difficult to remove it reliably without affecting other parts and leaving no cutting residue.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method that eliminates the above-mentioned drawbacks and reliably removes only defective electrodes.

[Key points of the invention]

The present invention is achieved by covering the entire surface of a semiconductor device with a protective film, peeling off only the protective film on the defective electrode, and etching and removing the exposed electrode.

[Embodiments of the invention]

3 to 6 show the steps of the method according to the invention.

First, as shown in FIG. 3, a chemical-resistant adhesive 4I with good adhesion is uniformly applied to the entire main surface of the semiconductor substrate 1, which has been previously checked and marked by electrical measurement on the defective electrodes 3a. . As this chemical-resistant protective film, for example, photoresist, polyimide resin, etc. are used, and after coating, the anomalous film is cured by exposure to light or heating. Note that marks attached to defective electrodes are not shown.

Next, as shown in Fig. 4, only the marked portion of the protective film on the defective electrode 3a is scratched with a saw blade and most of it is removed, and the defective electrode 3a on the base of the removed portion is removed. expose. At this time, all the normal electrodes 3 are covered with the protective film 6, and only the defective electrode 3a to be removed is exposed. Alternatively, the protective film on the defective electrode 3a may be scratched with a knife to the extent that it reaches the underlying defective electrode 3a without having a large opening. Subsequently, the semiconductor substrate 1 in this state is placed on the etching jig 7 shown in FIG. 5 and immersed in a container 9 containing an etching solution 8. When these are pulled out of the container 9 after a predetermined time, the defective electrodes 3
Since only the portion a has been removed by etching, when the protective film 6 is finally removed, the state shown in FIG. 6 is obtained, and the process of the present invention is completed.

As a method for removing the protective film 6 on the defective electrode 2a, it is possible to use a photoetching method, but in practice, since the defective electrode to be removed exists in unspecified locations, it is necessary to fabricate a photomask. Photoetching is not suitable in this case as it is extremely inefficient to do so.

〔Effect of the invention〕

As explained above, according to the method of the present invention, normal electrodes are covered with a protective film with good adhesion, and only defective electrodes are reliably etched away, so even normal electrodes are not damaged. There is no risk of exposure, and there are no imperfections that could leave part of the defective electrode. In addition, regardless of the shape of the electrode, even if there are multiple defective electrodes, the etching process can be completed in one process, and by selecting the appropriate size of the etching container, a large number of defective electrodes can be removed at the same time. It has many advantages, such as extremely high processing efficiency because it can immerse many semiconductor devices.

[Brief explanation of drawings]

Figure 1 is a partial cross-sectional view of the GTO, Figure 2 is a conceptual diagram showing the cutting situation of a defective electrode, Figures 3 to 5 are process diagrams showing the procedure for attaching and removing the protective film according to the present invention, and Figure 6 is the completed product. It is a sectional view showing a state. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Gate electrode, 3... Cathode electrode, 3a... Defective electrode, 4... Contact electrode plate, 5... Bit, 6... Protective film, 7 ...Jig, 8
...Pa etching solution, 9...container. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1) A semiconductor comprising at least three layers of alternating conductivity types and a plurality of divided regions provided independently from each other in the uppermost layer, and an electrode film provided in each region. In manufacturing a semiconductor device, a method for selectively removing an electrode film belonging to a region having a defect among the divided regions to eliminate conduction of current to the region having the defect, the method comprising: After depositing a protective film over the entire main surface of the semiconductor substrate, the protective film is scratched to reach the electrode film only on the electrode film corresponding to the area having the defect, and the semiconductor substrate is etched with a semiconductor etching solution. A method for manufacturing a semiconductor device, characterized in that the electrode film belonging to the region having the defect is dissolved and removed by immersion in a liquid.