1. Field of the Invention
The present invention relates to a technique of lithography and, particularly to a manufacturing method for semiconductor device wherein a stepwise taper is formed in a contract hole, that is, a opening portion, which is formed in an insulating film and metal, by the combination of a resist patterning process and a dry etching process.
2. Description of the Related Art
As is known, the degree of integration of the semiconductor element has been improved with the advance of a fine process technique of the semiconductor element. For the purpose of fining, the so-called multilayered wiring element has been generally used. In order to control leak current generated in the element, the necessary an interlayered insulating film is formed to have the thickness of 1 .mu.m or more regardless of quality. Thereby, the depth of the opening portion, which is formed in the interlayered insulating film, is increased.
As one of the fine process techniques, the frequency in use of a dry etching such as a reactive ion etching, in which an anisotropic etching is performed, is increased. For this reason, the side wall of the opening portion, which is formed in the interlayered insulating film, becomes almost vertical. Therefore, in a case where the inside of the opening portion cannot be completely embedded with the metal layer for wiring, which is deposited on the interlayered insulating film, the connection between the electrode in the opening portion and the external wiring layer is defective. To overcome this problem, there is known a method for forming taper in the opening portion contacting the wiring metal layer, that is, 20 to 30% of the entire depth, by using the combination of a chemical reaction or a physical etching.
Also, an image reversal process which can be used as the fine process technique was disclosed in Vacuum, Vol. 29, No. 12, 1989, page 585. Specifically, a mask, in which a layer interrupting light is formed, is superimposed at a predetermined position of a positive resist of a novolak type, an exposing process, which is a part of a photo engraving process, is provided therein, so that a photosensitive portion is formed therein other than the light interrupting layer of the mask. However, if this lamination layer is processed in ammonia atmosphere, the exposed and photosensitive indene carboxylic acid generates decarboxylic acid, insoluble indene is formed in alkali developer. If this phenomenon is used, a pattern to be originally formed is reversed. FIG. 1 illustrates an example of forming taper by the combination of the chemical etching and the physical etching. More specifically, a wiring layer forming of Al or Al alloy or an electrode 2 is directly or indirectly deposited on a semiconductor substrate 1 via a coating layer, and an interlayered insulating layer 3 is entirely deposited thereon.
Then, an opening portion 4 is formed on the interlayered insulating layer 3 by CDE process as a chemical etching, in which radical, which is generated by plasma generated by a magnetron tube, is moved to the distant position and RIE process as a physical etching. The edge of the opening portion 4 is etched in a certain horizontal and vertical isotropic direction by CDE process. Due to this, as is obvious from the drawing, a taper 6 is formed and a double edge is formed in positioning marks 5, which are used in an aligner process, as shown in FIG. 2. FIG. 2 is a plane view of the opening portion 4 for the positioning marks 5 seen from the above.
Moreover, FIG. 3 is a cross sectional view showing the opening portion 4 formed by providing image reversal process in the interlayered insulating layer 3. However, the side wall of the opening portion 4 is not vertically formed, and the double edge is formed in the positioning marks which are formed at the same with the above process. This causes the deterioration of the accuracy of the positioning.
In a case where the taper is formed in the opening portion 4 by the combination of the chemical etching and the physical etching, the positioning marks 5 are shaped similarly and the edges of the positioning marks look double as shown in FIG. 2. In general, to detect the positioning marks 5, reflected light of the irradiated laser is electrically compared between a setting coordinate and a measuring coordinate. Then, if the edges are discriminated several times, a plurality of detection signals are obtained, so that the positioning step fails or the accuracy of positioning is deteriorated.
Moreover, if the opening portion and the positioning marks are formed by use of the image reversal process, both the opening portion and the positioning marks are simultaneously formed, so that the taper 6 is formed in the positioning marks. As a result, since a detection signal having a clear waveform is not obtained, the accuracy of the positioning is deteriorated. In addition, regarding etching, it is difficult to set conditions such as an angle of a reverse taper and controllability and there is problem in reproductivity.