The present invention relates to a manufacturing method of a semiconductor device and more particularly to a backside film which is formed by growing a film on both surface sides of a semiconductor substrate.
When a thin film is formed on a semiconductor substrate, the film is grown on either both of the obverse surface and the reverse surface of the semiconductor substrate (double-sided growth) or only the obverse surface thereof (single-sided growth), depending on the method of growing a film, the flow of the steps in the manufacturing method, the apparatus used therein and so forth.
For example, in the case that a polycrystalline silicon film to fabricate a gate electrode or the like, an insulating film to form a sidewall film, an interlayer insulating film or such is to be formed, as the film is generally grown by the LP-CVD (Low Pressure-Chemical Vapour Deposition) method, the deposition of the film proceeds not only on the obverse surface side of the semiconductor substrate but also on the reverse surface side thereof.
The backside film of this sort is, subsequently, removed by the following reasons.
Firstly, when another film is to be formed by the CVD method following formation of the foregoing film, the semiconductor substrate may not be able to be fixed onto a CVD apparatus satisfactorily, unless the backside film is removed. Secondly, in transporting the semiconductor substrate in the steps of a manufacturing method, the presence of any backside film may prevent the semiconductor substrate from attaching onto a transportation vehicle sufficiently. Thirdly, in the step of performing photolithography, if any backside film is left behind, focus at exposure may shift.
For the above reasons, when a thin film is grown on both surface sides of a semiconductor substrate in the conventional manufacturing method, the step of removing the backside film is performed before proceeding other steps. The semiconductor substrate is formed into a prescribed thickness by grinding from the reverse surface, after all other steps are completed.
However, in the methods of manufacturing a semiconductor device wherein a thin film is formed through double-sided growth and its backside film part is then removed, there are occasions in which waste matter and dust are generated in the steps subsequent to the step of the removal.
For instance, as shown in FIG. 4(a), after element isolation regions 502 are formed on a semiconductor substrate 501, a gate oxide film 503b is grown. Following that, as shown in FIG. 4(b), a polycrystalline silicon film 503 to fabricate gate electrodes is formed into a thickness of 200 nm or so. As the LP-CVD method is generally employed for the forming method, the polycrystalline silicon film 503 is grown on both of the obverse surface side and the reverse surface side of the semiconductor substrate 501. Consequently, etching is performed to remove a part of the polycrystalline silicon film 503 formed on the reverse surface side of the semiconductor substrate 501 and thereby a structure shown in FIG. 4(c) is obtained. In this instance, a portion of the polycrystalline silicon film lying on the edge section on the obverse surface side of the semiconductor substrate 501 may be, in part, removed therewith. The gate oxide film 503b on the reverse surface side can be also removed hereat, if circumstances require.
After that, as shown in FIG. 4(d), a silicide film 504 with a thickness of 200 nm or so is formed only on the obverse surface side of the semiconductor substrate, using the sputtering method.
The polycrystalline silicon film 503 and the silicide film 504 fabricated as described above are then etched and worked into gate electrodes, as shown in FIG. 4(c). In some cases, however, that etching conducted to form gate electrodes leaves a residue 505 behind, as shown in FIG. 4(e), which causes generation of waste matter and dust.
Further, after the gate electrodes are formed, for the purpose of forming sidewall films on the sidewalls of the gate electrodes, an insulating film 506 with a thickness of 250 nm or so is formed through double-sided growth by the LP-CVD method (FIG. 5(f)). Next, as shown in FIG. 5(g), the insulating film 506 lying on the side of the obverse surface is etched and sidewall films 506 are formed on the lateral faces of the gate electrodes 503a. After that, as shown in FIG. 5(h), the insulating film 506 formed on the side of the reverse surface of the semiconductor substrate is removed by means of etching, but, also on this occasion, a residue 507 may remain, as shown in FIG. 5(g), causing generation of waste matter and dust.
If waste matter and dust are generated, as described above, in the steps of manufacturing a semiconductor device, a sufficient yield may not be able to be attained, and besides an additional steps of etching to remove waste matter and dust may become necessary, which lowers productivity.
Further, because the step of removing the backside film is performed independently from the step of grinding the reverse surface of the semiconductor substrate finally, the manufacturing method may become unduly complicated and, in some cases, even satisfactory productivity cannot be achieved.
Further, in Japanese Patent Application Laid-open No. 266192/1997, there is disclosed a method wherein a film is formed on the obverse surface as well as the reverse surface of a wafer, and thereafter the foregoing film lying on the obverse surface of the foregoing wafer is subjected to etching, while the foregoing film lying on the reverse surface of the wafer is made to remain. Further, in the method described in that publication, as the steps of the method proceed, layers of polysilicon and other materials become overlaid on the reverse surface of the semiconductor substrate, and it is described therein that these layers are peeled off together after the step of the final heating treatment, namely, a high temperature treatment at 800xc2x0 C.-850xc2x0 C., which may exert thermal stress is completed.
Nevertheless, the main concern in that publication is thermal stress produced in the semiconductor substrate by the heat treatment when the semiconductor substrate has different numbers of films formed on the obverse surface and the reverse surface. Accordingly, this problem of thermal stress is solved by growing films equally on both of the obverse surface and the reverse surface and making qualities and thicknesses of these films on both surfaces identical, and nothing is mentioned therein to reduce the amount of waste matter and dust.
Moreover, although the films formed on the reverse surface of the semiconductor device are peeled off together after the heating steps are completed, grinding is not described to apply to the reverse surface of the semiconductor device. In effect, in a method of the publication, even after the backside films are peeled off, another film may be grown by a method without heat application, which may lead to formation of a backside film.
As set forth above, waste matter and dust brought about by removing the backside film which is formed through double-sided growth have not been hitherto regarded as a serious problem. Under such circumstances, the present inventors recognized waste matter and dust of this sort can be one of prime factors to lower yield and productivity in semiconductor device fabrication. Accordingly, an object of the present invention is to suppress generation of waste matter and attain satisfactory yield and productivity. Further, another object of the present invention is to achieve an improvement in productivity by performing the step of removing the backside film, concurrently with the step of grinding the reverse surface of the semiconductor substrate.
In light of the above problems, the present invention provides a method of manufacturing a semiconductor device, which comprises the steps of:
forming a first film on both of an obverse surface side and a reverse surface side of a semiconductor substrate; and
removing, by means of grinding, said first film formed on the reverse surface side of said semiconductor substrate as well as a part of said semiconductor substrate in depth from the reverse surface.
More specifically, the present invention provides a method of manufacturing a semiconductor device; which comprises the steps of
forming a polycrystalline silicon film into a thickness of not less than 50 nm but not greater than 150 nm on both of an obverse surface side and a reverse surface side of a semiconductor substrate;
forming, only on the obverse surface side of said semiconductor substrate, a silicide film into a thickness of not less than 50 nm but not greater than 200 nm over said polycrystalline silicon film;
working said polycrystalline silicon film and said silicide film into shape and thereby forming a gate electrode;
forming, on both of the obverse surface side and the reverse surface side of said semiconductor substrate, an insulating film for sidewall formation into a thickness of not less than 50 nm but not greater than 200 nm to cover said gate electrode;
etching said insulating film for sidewall formation which is formed on the obverse surface side of said semiconductor substrate and thereby forming a sidewall film on a lateral face of said gate electrode;
forming, only on the obverse surface side of said semiconductor substrate, an interlayer insulating film into a thickness of not less than 500 nm but not greater than 1.5 xcexcm to cover said gate electrode; and
removing, by means of grinding, said polycrystalline silicon film and said insulating film for sidewall formation, both of which are formed on the reverse surface side of said semiconductor substrate, as well as a part of said semiconductor substrate in depth from the reverse surface.
In the above manufacturing methods, any backside film formed through double-sided growth is not removed until fabrication of the obverse surface of the semiconductor substrate is completed, and, after completing the obverse surface fabrication, in the step of grinding the reverse surface of the semiconductor substrate, the backside films are also all removed by means of grinding. Further, as the method of growing a film, a method of single-sided growth, in other words, a method in which no film is allowed to grow on the reverse surface side of the semiconductor substrate, should be employed therein ,as long as circumstances permit. As a result, generation of waste matter can be well suppressed and satisfactory yield can be attained. Further, because it is unnecessary to perform any additional etching to remove waste matter, the manufacturing method becomes simplified and satisfactory productivity, provided. Furthermore, since the removal of the backside films is carried out along with final grinding of the reverse surface of the semiconductor substrate, the manufacturing method becomes simplified and productivity, enhanced.
In this manufacturing method of the present invention, any backside film formed through double-sided growth is not removed until fabrication of the obverse surface of the semiconductor substrate is completed, and, after completing the obverse surface fabrication, in the step of grinding the reverse surface, the backside films are removed together. As a result, even if the manufacturing method comprises the step of double-sided growth of a thin film, it can be avoided that a part of the film remains as waste matter on the wafer edge section while the obverse surface is fabricated, which facilitates to attain excellent yield and productivity.