Thin-film resistor and method of fabrication

Abstract

A thin-film resistor has: 1. a resistance layer positioned on a dielectric layer, 2. a protective layer positioned on the resistance layer and having two openings on two ends of the resistance layer, 3. an insulating layer covering the upper and side surfaces of the protective layer, the side surfaces of the resistance layer, and the surface of the dielectric layer, the protective layer having two openings above the two openings of the protective layer, 4. two plugs positioned in the two openings of the insulating layer and the protective layer for electrically connecting to the two ends of the resistance layer, and 5. two conductive layers formed on the insulting layer and positioned on the two plugs, and which are used as two electrical wires for electrically connecting to the two ends of the resistance layer.

What is claimed is:  
     
         1 . A thin-film resistor positioned on a dielectric layer of a semiconductor wafer, the thin-film resistor comprising: 
 a resistance layer positioned in a predetermined area of the dielectric layer;    a protective layer positioned on the resistance layer in the predetermined area and comprising two openings on two ends, respectively, of the resistance layer;    an insulating layer formed on the semiconductor wafer and covering the upper and side surfaces of the protective layer, the side surfaces of the resistance layer, and the surface of the dielectric layer outside the predetermined area, the insulating layer comprising two openings respectively above the two openings of the protective layer;    two plugs respectively positioned in the two openings of the insulating layer and the protective layer for electrically connecting to the two respective ends of the resistance layer; and    two conductive layers formed on the insulting layer and respectively positioned on the two plugs, the two conductive layers being used as two electrical wires for electrically connecting to the two respective ends of the resistance layer.    
     
     
         2 . The thin-film resistor of    claim 1    wherein the resistance layer is formed of CrSi (chromium silicon), the protective layer is formed of silicon nitride by using a chemical vapor deposition method, the insulating layer is formed of silicon oxide by using a chemical vapor deposition method, and the dielectric layer is formed of borophosphosilicate glass (BPSG).  
     
     
         3 . The thin-film resistor of    claim 2    further comprising an isolating layer positioned in the predetermined area and between the resistance layer and the dielectric layer, the isolating layer isolating out-gassing produced by the borophosphosilicate glass of the dielectric layer to prevent the out-gassing from affecting the resistance of the resistance layer.  
     
     
         4 . The thin-film resistor of    claim 3    wherein the isolating layer is formed of silicon nitride or silicon oxide.  
     
     
         5 . The thin-film resistor of    claim 1    wherein the plug is formed from a tungsten layer.  
     
     
         6 . The thin-film resistor of    claim 5    further comprising the following two layers between each plug and each opening of the insulating layer and the protective layer: 
 a titanium layer positioned on the surface of each opening of the insulating layer and protective layer which is used as an adhesive layer; and  
 a titanium nitride layer positioned on the surface of the titanium layer which is used as a stumbling layer;  
 wherein when forming the tungsten layer, the titanium nitride layer is used to isolate the tungsten layer and the titanium layer.  
 
     
     
         7 . The thin-film resistor of    claim 1    wherein the two conductive layers are formed of a metallic alloy based on aluminum (Al).