JPH0714032B2 - Method of manufacturing thin film resistor - Google Patents

Description

The present invention relates to a manufacturing method for forming a thin film resistor in a monolithic integrated circuit device.

[Conventional technology]

Heretofore, when forming a thin film resistor in a monolithic integrated circuit device, NiCr, SiCr or the like having a low temperature coefficient and long-term stability has been used as a material thereof.

A manufacturing method for forming the thin film resistor will be described with reference to FIG. First, a P type base region 202, an N ⁺ type emitter region 203, and an N ⁺ type collector ohmic region 204 are formed on an N type semiconductor substrate 201, and a thermal oxide film 205 is grown on the surface thereof (FIG. 1 (a)). ).

Next, a contact window 20 is formed on each region of the NPN transistor 212.
After leaving 6 and forming a base oxide film 207 by oxidation, a nitride film 208 and an oxide film 209 are further formed by vapor phase growth (FIG. 2 (b)).

Next, the oxide film 209 inside the contact window 206 is removed, and the remaining oxide film 209 is used as a mask to form a nitride film 208 with hot phosphoric acid.
Is removed, and further the oxide film 209 and the underlying oxide film 207 located in the contact window 206 are simultaneously removed to open the inner contact window 214, and in this state, a thin film layer 210 of NiCr, SiCr or the like is formed on the entire surface of the semiconductor substrate. It is attached (Fig. 2 (c)).

Next, the thin film layers other than the thin film resistor are removed by photolithography to form a thin film resistor 211. After that, a metal wiring 213 is formed on the NPN transistor 212 and the thin film resistor 211 by using a metal such as aluminum, and an ohmic contact is obtained by heat treatment (FIG. 2 (d)).

By the way, according to the conventional manufacturing method, as shown in FIG. 2 (c), since the metal layer containing chromium is in contact with the silicon surface through the contact window 214, chromium contamination occurs. Chromium on the silicon surface is removed in the steps after FIG. 2 (c), but is not completely removed and remains in a trace amount. The subsequent heat treatment and thermal history after assembly adversely affect the transistor characteristics.

[Problems to be solved by the invention]

The present invention has been proposed in view of the drawbacks of the above-mentioned conventional example, and an object thereof is to provide a method of manufacturing a thin film resistor in which chromium does not directly contact the silicon surface.

[Means for solving problems]

A method of manufacturing a thin film resistor according to the present invention comprises the steps of forming a P-type region and an N-type region on a semiconductor substrate and forming a first thermal oxide film on the surface of the semiconductor substrate, the P-type region and the N-type region. Forming a first window in the first thermal oxide film on the region, forming a second thermal oxide film in the first window, vapor phase on the first and second thermal oxide films A step of forming a grown nitride film, a step of forming a second window in the vapor phase grown nitride film so as to be included in the first window, and a step of simultaneously forming the second thermal oxide film located in the second window. Removing step, forming a third thermal oxide film on the second window, forming a metal thin film layer on the surface of the semiconductor substrate, forming the metal thin film layer on a thin film resistor, the third step Removing the thermal oxide film, forming a metal wiring in the thin film resistor and the second window, and performing a heat treatment. And wherein the Ranaru.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a method of manufacturing a thin film resistor according to an embodiment of the present invention. First, a P-type base region 102, an N ⁺ -type emitter region 103, and an N ⁺ -type collector ohmic region 104 are formed on an N-type semiconductor substrate 101, and a thermal oxide film 105 is grown on the surface (FIG. 1 (a)).

Next, a contact window 10 is formed on each region of the NPN transistor 112.
6 is opened, and a nitride film 108 and an oxide film 109 are formed (FIG. 1 (b)).

Next, the oxide film 109 inside the contact window 106 is removed, and the remaining portion is used as a mask to remove the nitride film 108 with hot phosphoric acid. Further, the oxide film 109 and the underlying oxide film located on the contact window 106 are removed. 107 and 107 are removed at the same time to form a second contact window 114 inside. Further, this portion is again oxidized to form the underlying oxide film 120. In this state, a thin film layer 110 of NiCr, SiCr or the like is deposited on the entire surface of the semiconductor substrate (FIG. 3 (c)).

Next, the thin film layer 110 is etched by photolithography to form a thin film resistor 111. The thickness of the underlying oxide film is set so that the underlying oxide film 120 remains in the second contact window 114 during the etching of the thin film layer 110 at this time. After that, the underlying oxide film on the contact window 214 is removed, and NPN transistor 112 and thin film resistor 11 are formed by using a metal such as aluminum.
Metal wiring 113 is applied to 1 and an ohmic contact is obtained by heat treatment (FIG. 3 (d)).

〔The invention's effect〕

As described above, according to the present invention, since the metal thin film layer does not directly contact the silicon surface in the process, the silicon surface is not contaminated with chromium or the like contained in the metal. Therefore, it is possible to prevent deterioration of transistor characteristics due to subsequent thermal history.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a method of manufacturing a thin film resistor according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining a method of manufacturing a thin film resistor according to a conventional example. 101,201 ... N-type semiconductor substrate, 102,202 ... P-type base region,
103,203 ... N ⁺ type emitter region, 104,204 ... N ⁺ type collector ohmic contact region, 105,205 ... Field oxide film, 106,206 ... Contact window, 107,207 ... Base oxide film,
108,208 ... Vapor grown nitride film, 109,209 ... Vapor grown oxide film,
110, 210 ... Thin film layer, 111, 211 ... Thin film resistor, 112, 212 ... NPN
Transistors, 113, 213 ... Metal wiring, 114, 214 ... Second contact window, 120 ... Underlay oxide film.

Claims (1)

[Claims] 1. A step of forming a diffusion region in a semiconductor substrate, a step of forming a first thermal oxide film on the surface of the semiconductor substrate, a step of reaching the diffusion region in the first thermal oxide film on the diffusion region. Opening a first window, forming a second thermal oxide film on the surface of the diffusion region of the first window, forming a vapor phase growth nitride film on the first and second thermal oxide films An oxide film is formed on the vapor-grown nitride film and patterned, and a second window is formed in the vapor-grown nitride film using the oxide film as a mask so as to be included in the first window. The second film located on the second window at the same time as removing the film
Removing the thermal oxide film to expose the surface of the diffusion region, forming a third thermal oxide film on the exposed surface of the diffusion region of the second window, and forming a metal thin film on the surface of the semiconductor substrate. A step of forming the metal thin film into a thin film resistor, a step of removing the third thermal oxide film, a step of forming a metal wiring in the thin film resistor and the second window, and performing a heat treatment. A method of manufacturing a thin film resistor, comprising: