JPH03108376A - Buried zener diode and manufacture thereof - Google Patents

Abstract

PURPOSE:To simplify the manufacturing process by forming an anode diffusion layer on the top of an epitaxial layer, and forming a cathode diffusion layer below this, and also providing an emitter diffusion layer for cathode takeout on the top of the epitaxial layer. CONSTITUTION:A high concentration N-type emitter diffusion layer 21 for cathode takeout is formed on the top of an N-type epitaxial layer 3. Next, by a buried P mask, the similar patterning is done, and B is implanted therein and is diffused to form a high concentration P-type anode layer 22. Next, the resist pattern mask made by said buried mask is used as it is so as to form a high concentration N-type cathode layer 23. According to this manufacture, the layer 22 and the layer 23 are made with the same resist pattern mask, so photolithography for making a PN junction is required only one time. Moreover, the currents, which flow as breakdown occurs at the PN junction on the boundary between the layers 22 and 23, flow via the layer 3 and the layer 21, so the path is not affected by the depletion layer, and operation resistance decreases.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a Zener diode embedded in a monolithic IC (integrated circuit, hereinafter the same) and a method for manufacturing the same.

[Conventional technology]

The structure of a conventional Zener diode portion embedded in a monolithic IC is shown in FIG.

In this example, after forming a heavily doped N-type buried layer 2 on the upper surface of a P-type silicon substrate 1 and forming an epitaxial layer 3, an isolation 4 is formed by diffusion.

In the Zener diode portion, resist patterning is performed by a photolithography process using a buried P mask, and boron is implanted and then diffused to form a high concentration P type buried diffusion layer 5.

Next, similar patterning is performed using a base mask, and boron is implanted therein and then diffused to form a P-type base diffusion layer 6.

Next, similar patterning is performed using an emitter mask, and phosphorus is implanted therein and then diffused to form a highly doped N-type emitter diffusion layer 7.

Next, an oxide film 8 is formed by heat treatment, and an anode contact hole 9 and a cathode contact hole 10 are formed by etching.

Finally, an anode electrode 11 and a cathode electrode 12 are formed.

[Problem to be solved by the invention]

As described above, the Zener diode having the structure shown in FIG. 3 requires three photolithography steps using a mask.

Furthermore, in this Zener diode, the high concentration N type emitter diffusion layer 7 and the high concentration P type buried layer 5 are
Since the current flowing through the PN junction with the emitter diffusion layer 7 flows in the direction of the rear anode electrode 11 through the lower part of the emitter diffusion layer 7, there is a problem that the operating resistance increases due to the pinch effect caused by the depletion layer formed under the emitter diffusion layer 7. there were.

The present invention has been made in view of these points, and an object of the present invention is to provide a Zener diode that can simplify the manufacturing process and has low operating resistance, and a method for manufacturing the same.

[Means to solve the problem]

For this reason, the Zener diode of the present invention includes an anode diffusion layer formed on the upper surface of the epitaxial layer, a cathode diffusion layer formed on the lower surface of the anode diffusion layer so that the anode diffusion layer forms a PN junction, and the above-mentioned cathode diffusion layer. An emitter diffusion layer for taking out the cathode is formed on the upper surface of the epitaxial layer and connected to the cathode diffusion layer via the epitaxial layer.

Furthermore, the method for manufacturing a Zener diode of the present invention includes a step of forming an emitter diffusion layer for taking out the cathode on the upper surface of the epitaxial layer, a step of forming an anode diffusion layer on the upper surface of the epitaxial layer, and a step of forming an emitter diffusion layer for taking out the cathode on the upper surface of the epitaxial layer. A common resist pattern mask is used in the step of forming the anode diffusion layer and the step of forming the cathode diffusion layer.

〔Example〕

Examples of the present invention will be described below. FIG. 1 is a diagram showing the structure of a Zener diode in one embodiment.

Components that are the same as those shown in FIG. 3 are given the same reference numerals, and their explanations will be omitted.

In this embodiment, patterning is performed by a photolithography process using an emitter mask, and phosphorus is implanted therein and then diffused to form a high concentration N-type emitter diffusion layer 21 for taking out the cathode.

Next, similar patterning is performed using a buried P mask, and boron is implanted therein and then diffused by annealing to form a high concentration P type anode layer 22.

Next, using the resist pattern mask created by the above-mentioned buried mask as it is, phosphorus is implanted from above the high concentration anode layer 22 and then diffused by annealing to form a high concentration N-type cathode layer 23. At this time, an accelerating voltage is selected so that the phosphorus implantation reaches deeper than the highly doped P-type anode layer 22, and the highly doped P-type anode layer 22 is further diffused in the lateral direction by annealing.

After this, the anode electrode 11 and the cathode electrode 12 are formed by the same method as explained in FIG.

As described above, in this embodiment, the high concentration P-type anode layer 22 and the high concentration N-type cathode layer 23 are created using the same resist pattern mask, so only one photolithography process is required for creating the PN junction. .

Further, the current that flows due to breakdown occurring at the PN junction at the boundary between the highly doped P-type anode layer 22 and the highly doped N-type cathode layer 22 is transferred to the epitaxial layer 3 and the emitter diffusion layer 2.
1, the path is not affected by the depletion layer and the operating resistance is reduced.

〔Effect of the invention〕

As described above, the present invention has the advantage that the manufacturing process is simplified and a buried Zener diode with low operating resistance can be realized.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of a buried Zener diode according to an embodiment of the present invention, FIG. 2 is a flow chart showing an outline of the manufacturing process, and FIG. 3 is a diagram showing the structure of a conventional buried Zener diode. 4 are flowcharts showing the outline of the manufacturing process. 1...P-type silicon substrate, 2...buried layer, 3...
epitaxial layer, 4... isolation layer, 5.
... Buried layer, 6... Base diffusion layer, 7... Emitter diffusion layer, 8... Insulating film, 9... Anode contact hole, 10... Cathode contact hole, 11.
...Anode electrode, 12...Cathode electrode, 21...
・Emitter diffusion layer, 22... Anode diffusion layer, 23.
...Cathode diffusion layer.

Claims (2)

[Claims] (1) In a buried Zener diode built into a monolithic IC, an anode diffusion layer formed on the top surface of an epitaxial layer;
a cathode diffusion layer formed on the lower surface of the anode diffusion layer so as to form a PN junction with the anode diffusion layer; and a cathode formed on the upper surface of the epitaxial layer and connected to the cathode diffusion layer via the epitaxial layer. A buried Zener diode characterized by comprising an emitter diffusion layer for extraction. (2) A method for manufacturing a buried Zener diode to be incorporated into a monolithic IC, including a step of forming an emitter diffusion layer for taking out the cathode on the top surface of the epitaxial layer, and a step of forming an anode diffusion layer on the top surface of the epitaxial layer. and a step of forming a cathode diffusion layer below the anode diffusion layer, and a common resist pattern mask is used in the step of forming the anode diffusion layer and the step of forming the cathode diffusion layer. A method for manufacturing a featured embedded Zener diode.