JPS5816574A - Zener diode - Google Patents

Abstract

PURPOSE:To obtain a Zener diode with high stability, by providing a peak density profile with the width corresponding to the fluctuation width of the density profile on an N<+> type diffused region which is crossed therewith. CONSTITUTION:When forming the P<+> type diffused region 3, a plurality of times of boron impurity ion implantations are performed. The peak density of elongation-diffused impurity after an implantation is evenly formed by varying an implantation energy of each time and controlling a dope amount. In this process, the impurity density profile of the P<+> type region is formed in a trapezoid, and the diffusion depth for the N<+> type diffused region 4 is set to the central depth of the trapezoidal part. Thereby, the fluctuation of a breakdown voltage due to the dispersion of the P type impurity density or diffusion depth can be reduced.

Description

[Detailed description of the invention] The present invention relates to high stability voltage regulator diodes.

The NPN structure, which is commonly known as a constant voltage diode, has a 2M region 2 formed by Pg base diffusion on the surface of a substrate 1 consisting of an N [epitaxial layer, for example, and a deep region 1 in a part 1 of the NPN structure, which is usually known as a constant voltage diode. High concentration P+ layer 3,
A part of the surface of the 2-layer region 2 is filled with N by N++ emitter diffusion.
+ type region 4 is formed %+ m region 4 and P
PN with 臘 area 2 (or 3)! This method takes advantage of the constant breakdown voltage phenomenon caused by applying a voltage in the reverse direction. The impurity concentration profile of such a constant voltage diode is shown in FIG. 2, but in the surface breakdown type diode, breakdown occurs in the part of the figure due to the diffusion concentration of the P group region 2 on the low concentration side. In a bulk breakdown diode, P+ on the high concentration side
Breakdown occurs at point B where the impurity profiles of type region 3 and N+ type region 4 intersect. And in the former case, Pfi (
Pace) The breakdown voltage tends to vary depending on the diffusion concentration, and in the latter case, the breakdown voltage varies depending on the diffusion concentration of the P+ type region 3 and the diffusion depth K of the N+ type region 4 (it is influenced by the h□ of NpN). I couldn't avoid my shortcomings.

The present invention has been made to eliminate the drawbacks of the prior art described above, and its purpose is to provide a highly stable constant voltage diode, and also to provide a high-precision constant voltage diode with low drift even if it is a bulk breakdown type. The purpose is to obtain a voltage diode.

The voltage regulator diode according to the present invention is a NP shown in FIG.
In the N structure, as shown in FIG. For this reason, when forming the p+m+ dispersion region, K can be changed by implanting boron impurity ions multiple times and changing the implantation energy each time, as shown in Figure 4. R, □, fL□I fLPl,”
” and by controlling the dose amount, the peak quality of the stretched and diffused impurity after implantation is formed to be equal. This R, is the depth of the N++ diffusion layer formed by N+ diffusion (or secondary ion implantation) K. It is necessary to select a value close to Xj, and to decide the number of boron ion implantations in consideration of the fluctuation 11Xd of X3.

By employing the above process, the impurity peak concentration profile of the P+ type region is formed into a trapezoidal shape, and the N
++ By setting the diffusion depth Xj of the diffusion region to the center depth of the above-mentioned trapezoid, the breakdown voltage V due to variations in the P-type impurity concentration and Xj.

Fluctuations can be minimized. For example, in the case of the conventional device, the variation in breakdown voltage V was 6.5 ± 0.5 V (variation of about 10 fi), but with the present invention, the variation in breakdown voltage V is almost negligible. It is possible to supply a highly stable constant voltage diode regardless of the NpN hFI K.

The present invention can be applied to a PNP structure in addition to the NPN structure mentioned in the example.

The present invention has low drift and high precision even in the bulk breakdown type.
Constant voltage diode? This is something that can be achieved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a constant voltage diode with an NpN structure, Figure 2 is a curve diagram showing an example of an impurity concentration profile in a conventional constant voltage diode, and Figure 3 is an impurity concentration profile in a constant voltage diode according to the present invention. FIG. 4 is a curved section showing a part of the process for obtaining the P disk impurity concentration profile of FIG. 3. l...N type epitaxial (substrate), 2...P type region, 3...P+ type region 4...N+ type region Agent Patent attorney Susuki 1) Toshiyuki Daiichi Figure 1/2 Figure on Pal 7

Claims (1)

[Claims] 1. A second conductivity type impurity diffusion region is formed on the surface of the first conductivity type semiconductor substrate, and a first conductivity impurity high concentration diffusion region is formed on a part of the surface of the second conductivity type semiconductor substrate. In a constant voltage diode that utilizes the breakdown voltage phenomenon of a semiconductor junction between a first conductivity type diffusion region and a second conductivity type diffusion region, the peak portion of the impurity fineness profile of the second conductivity type diffusion region is shaped like a trapezoid. A constant voltage diode characterized in that the impurity concentration profile of the #11 conductive Nada high concentration film region intersects at this trapezoidal portion. 2. The constant voltage diode according to claim 1, wherein the second conductive diffusion region is formed by boron ion implantation K a plurality of times at different energies.