JPS62124744A - Etching method - Google Patents

Abstract

PURPOSE:To prevent the generation of insufficient etching by dipping a wafer in an etchant approximately half and generating largely moving bubbles on the surface of an etchant liquid through bubbling from the bottom. CONSTITUTION:Bubbles are generated from pipes 13a and 13b and holes 14a and 14b through etching, a large number of large bubbles 15 are also formed on the level of an etchant 12, and bubbles are generated successively from the pipes, thus gradually shifting bubbles 15 on the level upward. Accordingly, large bubbles 15 transfer along the surfaces of wafers 10, thus removing small bubbles, which are formed as the result of a chemical reaction among aluminum on the wafers and the etchant 12 and adhere on the surfaces of the wafers.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an etching method that can be used, for example, to form a metal film pattern for wiring in the manufacturing process of semiconductor devices, and in particular an etching method that can be used to partially cover a resist film. This invention relates to a wet etching method in which a wafer coated with an aluminum film is immersed in a phosphoric acid etchant to selectively corrode and remove the aluminum film.

(Prior Art) Conventionally, in manufacturing various semiconductor devices, aluminum films have been widely used as wiring patterns. When forming this aluminum wiring pattern, an aluminum film should be uniformly deposited on a wafer on which various semiconductor regions and insulating films have been formed, and a photoresist film should be deposited on this aluminum film and left as a wiring pattern. After selectively removing everything other than the photoresist film on the aluminum film, the wafer is loaded into a cassette that supports it in an almost vertical position, and the cassette is placed in a container containing a phosphoric acid etchant to perform etching. The portion of the aluminum film not covered by the photoresist film is removed by corrosion to form an aluminum wiring pattern.

(Problems to be Solved by the Invention) In the conventional etching method described above, the entire wafer is immersed in the etchant, but the chemical reaction between the etchant and aluminum generates air bubbles. adheres to the wafer surface. When air bubbles adhere to the wafer surface in this manner, the wafer surface in that area is no longer in contact with the etchant and cannot be etched, resulting in the disadvantage that a desired wiring pattern cannot be accurately formed. Particularly in recent years, the miniaturization of semiconductor devices has progressed, and accordingly, the wiring patterns have also been miniaturized, but the above-mentioned insufficient etching causes short circuits, which is a serious drawback that reduces the manufacturing yield of semiconductor devices.

In order to remove air bubbles that adhere to the wafer surface, for example, it is possible to install a stirring device to stir the etchant or move the wafer, but air bubbles are generated by the chemical reaction between the etchant and aluminum. Since air bubbles are extremely small, it is very difficult to remove them from the wafer surface.

The above-mentioned problems are not unique to etching metal films, but also occur when wet etching single crystal silicon, polycrystalline silicon, metal silicide, and the like.

The object of the present invention is to eliminate the above-mentioned conventional drawbacks, to effectively remove air bubbles that are generated by the chemical reaction between an etchant and the material to be etched and adhere to the wafer surface, and to be able to perform the etching at low cost using a simple device. The present invention is intended to provide an etching method that can perform the following steps.

(Means for Solving the Problems) In the etching method of the present invention, a wafer to be etched is placed in an etching container in an almost vertical state so that its lower half is covered with the etchant. Bubbling is performed from the bottom of the wafer.
It is characterized by generating relatively large bubbles that move upward along the surface of the portion not immersed in the etchant to remove small bubbles generated on the wafer surface by etching.

(Function) According to the above-described etching method of the present invention, many large bubbles are generated in the upper half of the wafer by bubbling, and since these bubbles move, they are generated by the chemical reaction of etching. Small air bubbles attached to the wafer surface are removed very effectively, and insufficient etching can be reliably eliminated.

Further, in a preferred embodiment of the present invention, bubbling is applied strongly to only one side of the wafer so that the wafer automatically rotates in that plane. In this way, the entire wafer can be etched uniformly without providing a separate means for rotating the wafer. In order to make this kind of rotational movement of the wafer more effective, the wafer
It is preferable to move the carrier up and down.

(Example) FIGS. 1A to 1C are a diagrammatic cross-sectional view, a plan view, and a vertical cross-sectional view showing the configuration of an example of an apparatus for carrying out the etching method according to the present invention, and FIG. 2 is a wafer used for the same.・
It is a perspective view showing a carrier.

As shown in FIG. 2, the wafer carrier I has a frame structure, and a large number of a3a and 3b are formed in the vertical direction on the inner surfaces of both side walls 2a and 2b. The inner surfaces of the side walls 2a and 2b are tapered inwardly at the bottom, so that the distance between the grooves 3a and 3b also decreases downward. The distance between the grooves 3a and 3b is slightly larger in the upper part than the diameter of the approximately circular wafer, and is smaller in the lower part. therefore? By inserting the wafer from above between n3a and n3b, the wafer 10 can be held in a predetermined position on the carrier in a substantially perpendicular state as shown in FIG. 1A. Furthermore, since the width of the grooves 3a and 3b is somewhat larger than the thickness of the wafer 10, the wafer can be smoothly inserted into and removed from the carrier, and the wafer can be held within the plane of the carrier. Can be rotated freely.

A desired semiconductor region and insulating film are formed, an aluminum film is roughly deposited thereon, and a wafer 10 coated with a resist film in a pattern corresponding to the desired electrode pattern is inserted into the grooves 3a and 3b of the carrier 1. and hold it. Next, the carrier 1 loaded with a large number of wafers 10 in this manner is placed into the processing/notching container 11. For this one container,
The phosphoric acid-based etchant 12 is contained so that approximately half of the wafer 10 is immersed in the carrier I. Furthermore, two pipes 13a and 13b are installed at the bottom of the container 11, and these pipes communicate with an air pump (not shown).

A large number of holes are made in these pipes 13a and 13b, and as shown in FIG. 1B, hole 1 made in pipe 13a
The number of holes 14b drilled in pipe 13b is larger than that in pipe 4a so that more bubbles are generated from pipe L3b, so that a strong bubbling effect is generated on one side of the wafer.

When etching is performed as described above, the pipe 13
Bubbles are generated from the holes 14a and 14b of holes 14a and 13b, and many large bubbles 1 are also formed on the liquid surface of the etchant 12.
5 is generated, and bubbles are generated later from the pipe, so the bubbles 15 on the liquid surface gradually move upward. As the large bubbles I5 move along the surface of the wafer 10, the small bubbles produced as a result of the chemical reaction between the aluminum on the wafer and the etchant 12 and attached to the surface of the wafer are removed.

On the other hand, the pipe 13b has more holes 1 than the pipe 13a.
4b will be opened and more air bubbles will be generated on one side of the wafer, so that the wafer 10 will rotate within the groove 3at3b of the carrier 1 due to the action of the air bubbles. That is, in FIG. 1A, wafer 1
0 will rotate counterclockwise. Such rotational action further promotes the relative movement between the wafer 10 and the bubbles 15, making it possible to more effectively remove small bubbles generated by chemical reactions and attached to the wafer surface, and to remove them uniformly over the entire wafer. Etching can be applied. In addition, the etchant is also subjected to a stirring action due to the bubbles rising inside the etchant 12.
Fresh etchant can always be applied to the wafer surface.

The present invention is not limited to the embodiments described above, but can be modified in many ways. For example, in the above-described embodiment, the carrier may be moved up and down in order to make the wafer rotation action by the bubbles even more effective. Furthermore, the wafer can be rotated automatically or manually by other means without rotating the wafer due to air bubbles. Also, it is not always necessary to have two pipes for bubbling, and one tree can have three pipes.
It is also possible to have more than one pipe, and instead of a pipe, a box with many holes can be placed at the bottom of the container.

Furthermore, although the above example shows the case where an aluminum film is etched with a phosphoric acid-based etchant, other metal films,
It can also be applied to wet etching of single crystal or polycrystalline silicon, metal silicide, etc.

(Effects of the Invention) According to the above-described etching method of the present invention, the wafer is half-immersed in the etchant and bubbling is performed from the bottom to generate large moving bubbles on the etchant liquid surface. Small air bubbles generated by chemical reactions during etching and attached to the wafer surface can be effectively removed from the wafer surface by large air bubbles, thus preventing insufficient etching and improving yield. moreover,
If bubbling is strongly applied to only one side of the wafer as in the embodiments described above, the wafer can be automatically rotated by the bubbles and etching can be performed uniformly.

[Brief explanation of drawings]

1A, B, and C are cross-sectional views, plan views, and vertical sectional views showing the configuration of an example of an apparatus for carrying out the etching method according to the present invention, and FIG. 2 is a perspective view showing a wafer carrier used therein. be. 1... Wafer carrier 2a, 2b... Side wall 3a, 3b-...
Groove 10...Wafer 11...Etching container 12...Etchant 13a, 13b.
...Pipe 14a, 14b...hole 15.
...When there is a large bubble.Applicant: Akira Sugimura, Patent Attorney, TDC Co., Ltd. Competence: Oki Sugimura, Patent Attorney Figure 1C Figure 2

Claims (1)

[Claims] 1. A wafer to be etched is placed in an etching container in an almost vertical state so that its lower half is immersed in etchant, and bubbling is performed from the bottom of the etching container to etch the wafer. An etching method characterized in that small air bubbles generated on the wafer surface by etching are removed by generating relatively large air bubbles that move upward along the surface of the portion not immersed in an etchant. 2. The etching method according to claim 1, wherein the wafer is rotated by bubbling.