This application is related to Japanese application No. 2000-222703 filed on Jul. 24, 2000, whose priority is claimed under 35 USC xc2xa7 119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More particularly, the invention relates to processing of a barrier film at a contact hole etching step (etching step for forming a contact hole).
2. Description of the Related Art
In recent years, a semiconductor device has been made minute and multifunctional. With this, a phenomenon in which functions of various functional components formed in the semiconductor device are deteriorated by harmful elements, molecules, and the like, has become remarkable. As measures against this, there has been adopted a method for protecting the functional components against the harmful elements, molecules and the like by various protection films (barrier films). As constituent materials of the barrier films, Al2O3 (alumina), TiO2, TiN, TiON, Ta2O5, TaSiN, SiN and the like can be enumerated. One of these barrier films blocks the penetration of a harmful material by the dense film, and another takes a harmful material in the film to trap it. However, there is a problem that the barrier films prevent etching in a subsequent processing step or produce reactive secondary product materials (deposited materials) during the etching.
Hereinafter, an example of the prior art will be described with reference to FIGS. 3A to 3C.
First, a resist pattern 26 for contact hole formation is formed in a state where an NSG film 22, a BPSG film 23, an alumina film (barrier film) 24, and an NSG film 25 are deposited over a silicone (Si) substrate 21 on which various functional components (not shown) are formed (FIG. 3A). In this case, what is barriered by the alumina film 24 is not limited to a semiconductor component formed just on the Si substrate 21, but all functional components under the alumina film 24 are barriered.
Conventionally, in a subsequent contact hole etching, the alumina film and a Si oxide films (NSG film and BPSG film) are dry etched at the same time under normal conditions for etching the Si oxide films, for example, by a gas including a fluorine based gas in plasma etching such as RIE. As an example of existing techniques, although the alumina film is not used for a barrier, an example of Japanese Unexamined Patent Publication No. Hei. 8 (1996)-31932 discloses a similar step. In this case, etching is stopped in the alumina film, or a reactive secondary product material (deposited material) 27 produced from alumina is deposited on the bottom of a contact hole (FIG. 3B).
The deposited material prevents electrical contact between the Si substrate and a metal wiring of an upper layer, and must be removed before the wiring is formed in the contact hole. As a conventional method, the deposited material is removed by a treatment using chemicals (for example, EKC270 of EKC Technology Inc., etc.) capable of dissolving the deposited material, or by physically impacting inert molecules of Ar or the like, ions, radicals or the like to the deposited material to make scattering (called sputter etching, inverse sputtering, or the like).
However, the conventional methods have problems. That is, both the deposited material removal by the chemicals and the deposited material removal by the sputter etching have an etching rate with respect to the Si substrate of the bottom of the contact hole (see Table 1). Thus, there arise problems that a damage 28 is caused (FIG. 3C) at the bottom of the contact hole (surface of the Si substrate), and the contact resistance becomes unstable from fluctuation in the removable state of the deposited material.
As another example of the prior art, as in an embodiment of Japanese Unexamined Patent Publication No. Hei. 7 (1995)-273112, a method is also conceivable in which etching of the alumina film is carried out by changing a gas and by a gas containing chlorine. In the etching by the gas containing chlorine, the etching rate of the alumina film is fast, and an etching stop in the alumina film does not occur. However, the mechanism in which the deposited material is produced is not changed, and since a similar treatment for the deposited material becomes necessary, the superiority is not high.
Incidentally, in the foregoing description of the prior art and the problems, the same is the case with a barrier film (film made of TiO2, TiN, TiON, Ta2O5, TaSiN, or SiN) other than the alumina film.
As described above, in the etching of the contact hole containing the barrier film, it is necessary to obtain contact hole etching conditions under which the deposited material is not produced from the barrier film, or to conceive a method in which the deposited material is effectively and certainly removed without damage.
According to the present invention, there is provided a method of manufacturing a semiconductor device provided with a first insulating film and a barrier film on a conductive region and an opening portion in the first insulating film and the barrier film, the method comprising the steps of:
forming a first opening portion in the barrier film reaching the first insulating film;
forming a second insulating film at least on the first insulating film in the first opening portion; and
forming a second opening portion smaller than the first opening portion and reaching the conductive region by simultaneously boring a hole into the first insulating film and the second insulating film in the first opening portion.
One of the features of the present invention is that the barrier film is removed more extensively than the second opening portion in advance to suppress the production of a deposited material in the opening portion at the etching for forming the second opening portion (contact hole), so that the barrier film which causes deposit in the contact hole is not exposed at the etching of the second opening portion.
Further, according to the present invention, the step of forming the first opening portion in the barrier film reaching the first insulating film may comprise covering the barrier film with a third insulating film, forming a resist pattern by using a mask for forming the second opening portion, forming a pattern for forming the first opening portion on the third insulating film by using the resist pattern, and forming the first opening portion in the barrier film by using the pattern for forming the first opening portion.
According to the above method, since the formation of the first opening portion can be made by using the second opening portion formation mask, the number of masks to be used can be decreased.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.