1. Field of the Invention
The present invention pertains to a method for manufacturing a semiconductor device in which a fluorine-based gas is employed to etch contact holes followed by treatment of the etched contact holes with a nitrogen-containing plasma as a means of preventing the formation of reaction products from the etching procedure.
2. Description of the Prior Art
Semiconductor devices have a laminated structure, such as that shown in FIG. 20. Specifically, the semiconductor device is formed as a laminated structure, in which an SiO.sub.2 primary insulation layer 2, an aluminum-copper alloy conduction layer 3, and an SiO.sub.2 secondary insulation layer 4 are adhered in that sequence to a semiconductor wafer or substrate 1 of monocrystalline silicon. The conduction layer 3 is connected to an N.sup.+ region 1a of the P-type substrate 1 via thru-holes 2a, which are formed in the primary insulation layer 2. Thru-holes 4a are formed in the secondary insulation layer 4; the conduction layer 3 is connected to a bonding-pad conduction layer 5, which is attached to the secondary insulation layer 4, and extends through the thru-holes 4a into engagement with the conduction layer 3. A silicon nitride or silicon nitride/silicon dioxide protection layer 37 is attached to the bonding-pad conduction layer 5. A bonding pad 5a is provided at a location facing an opening 37a in the protection layer 37, which is formed by a standard photolithographic procedure. Thus, the bonding pad 5 a is electrically connected to the N.sup.+ region 1a of the substrate 1 through the conduction layer 3. Although there are other elements that are connected to the bonding pad by bonding wire, these other elements are not shown in FIG. 20.
The thru-holes 4a in the secondary insulation layer 4 are typically formed by dry etching through plasma etching with a fluorine-based gas such as C.sub.2 F.sub.6 /CHF.sub.3 or CF.sub.4. However, when plasma etching is carried out using a fluorine-based gas, exposure to air after the etching procedure is believed to generate, in several seconds, AlF.sub.m (OH).sub.3-m 56 in a location facing the thru-hole 4a on the surface of the conduction layer 3. Thus, there is an increase in contact resistance between the conduction layer 3 and the bonding-pad conduction layer 5 formed afterward. Thus, following the formation of the contact holes 4a, it is necessary to form the bonding-pad conduction layer 5 immediately, which is extremely problematic in terms of procedure control. The aforementioned AlF.sub.m (OH).sub.3-m is believed to form on the aluminum-copper alloy conduction layer 3 by a reaction between water in the air and residual fluorine. This reaction product is problematic in that it is difficult to distinguish it from the reaction products generated during other dry etching processes that involve chlorine-based gas. Below, the product generated on the surface of the aluminum alloy conduction layer in air after the fluorine-based gas plasma etching treatment (believed to be AlF.sub.m (OH).sub.3-m) will be referred to simply as "product."
It is an object of the present invention to provide a manufacturing method for making a semiconductor device wherein it is possible to control the generation of substances in the air, which are generated immediately following contact hole formation and which are a cause of increased contact resistance in the area of the contact hole. In this way, it will be possible, after the formation of the contact hole, to form, with sufficient freedom with respect to time, a conductive component connected through the contact hole, while preventing an increase in electrical resistance.