JPS6155974A - Constant-voltage diode - Google Patents

Abstract

PURPOSE:To adjust gate voltage from the outside, and to obtain precise stabilized voltage by forming a second diffusion region into a first diffusion region and shaping at least one diffusion region in high concentration into the second diffusion region. CONSTITUTION:A P type first diffusion region 2 is formed to the main surface of an N type semiconductor substrate 1, an N<+> type second diffusion region 3a shallower than the first diffusion region 2 is shaped into the first diffusion region 2, and at leat one N<++> type diffusion region, which is shallower than the diffusion region as the outside and has concentration higher than the diffusion region as the outside, is formed into the second diffusion region 3a. A gate electrode 5b is shaped onto an insulating film 4 so as to annularly cover the upper sections of the whole peripheries of the N<+> type diffusion region 3a and the N<++> type diffusion region 3b, and constant-voltage diode electrodes 5a are formed. The potential of the gate electrode 5b is biassed to a negative value to the N<+> type diffusion region 3a and the N<++> type diffusion region 3b from the outside, thus controlling carrier concentration in the surface of the region 3a, then changing breakdown voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a constant voltage diode, and particularly to a constant voltage diode suitable for semiconductor integrated circuits.

(Prior Art) Conventionally, a constant voltage diode for a semiconductor integrated circuit has a structure as shown in FIG. 5, in which 1 is an N-type semiconductor substrate, 2 is a Pi diffusion region, and 3 is an N+ diffusion region. , 4 is an insulating film, and 5 is an electrode. That is, since it is sufficient to prepare a negative set of PN junctions, it has been used very often. However, the stabilized voltage fluctuates greatly due to subtle variations in manufacturing conditions, making it impossible to obtain a highly accurate voltage regulator diode.

Furthermore, it has been impossible to obtain a desired stabilized voltage after manufacturing the integrated circuit, and its applications have been limited.

(Object of the Invention) The object of the present invention is to eliminate the drawbacks of the conventional voltage regulator diode as described above, to obtain a predetermined precise stabilization voltage, to obtain a wide variety of stabilization voltages, and to provide a stabilized The object of the present invention is to provide an excellent constant voltage diode that allows voltage selection.

(Structure of the Invention) The constant voltage diode of the present invention has a first diffusion region shallower than the first diffusion region within a first diffusion region of a second conductivity type formed on the main surface of a -conducting tm semiconductor substrate. a second diffusion region of a conductivity type, at least one diffusion region of a first conductivity type that is shallower and has a higher concentration than an outer diffusion region is provided inside the second diffusion region; an insulating film on the periphery of the first conductive type diffusion region and the first conductive type diffusion region, and the first conductive type second diffusion region and the It is configured to include an electrode formed to completely cover the periphery of at least one first conductivity type diffusion region.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIGS. 1(a) and 1(b) are a plan view and an xx' cross-sectional view of a first embodiment of the present invention. Figure 1 (a), (b)
As shown in FIG. 2, a P-type first diffusion region 2 is formed on the main surface of an N-type semiconductor substrate 1, and an N+-type first diffusion region 2, which is shallower than the first diffusion region 2, is formed inside the first diffusion region 2. Second diffusion area 3a
is formed, and the inside of the second diffusion region 3a is shallower than the outer diffusion region and has a high concentration of rr”.
At least one diffusion region of g is provided. In the case of FIGS. 1(a) and 1(b), an example is shown in which one high concentration diffusion region 3b is provided.

A gate electrode 5 is placed on the insulating film 4 so as to annularly cover the entire periphery of the N++ diffusion region 3a and the N''+ type diffusion region 3b.
It is constructed by forming a constant voltage diode electrode 5a.

In this embodiment, the potential of the gate electrode 5b is externally biased negatively with respect to the N++ diffusion region 3a and the N''+ type diffusion region 3b by pressing the button.
The main objective is to control the carrier concentration on the surface of the N+ m diffusion region 3a and change the breakdown voltage by negatively biasing the N+" type diffusion region 3bK. That is, if the gate voltage is N" type diffusion region 3a, When the N''11 diffusion region 3b is biased to a shallow negative voltage, breakdown occurs on the surface of the N+ diffusion region 3a, but as the negative bias of the gK gate electrode 5b is increased, the breakdown finally occurs. Since the surface of the N+ region 3a is reversed to a P fox, breakdown occurs on the surface of the N"fi diffusion region 3b, and the concentration of the N" type diffusion region 3b is higher than that of the N+ disk diffusion region 3a. In other words, the voltage regulator diode shown in Figure 2 has two types of stability that can be achieved by controlling the gate voltage. Figure 3 is a sectional view of the second embodiment of the present invention.The same reference numerals in Figure 3 as in Figure 1 indicate the same parts. is the first diffusion region 2 of P-o.
A second diffusion region 3a at the base of N+ is formed, which is shallower than the N+ diffusion region 2, and a N'' diffusion region 3b, which is shallower than the outer N++ diffusion region and has a high concentration, is formed. The structure up to this point is the same as in Figure 1, but in Figure 3 N
“Inside ICj!KN of type diffusion region 3b” W diffusion region 3b
Shallower N+++ type diffusion region 3 with high concentration
C is formed. That is, in a structure in which the number of NW diffusion layers is increased, two N-oxide diffusion regions are formed inside the second diffusion region, which are shallower than the outer diffusion region and have a higher concentration. 'C structure. In this way, Nfi
By increasing the number of diffusion layers, a more precise stabilization voltage can be obtained for the reasons explained above, and a wide variety of stabilization voltages can be obtained. That is, in the constant voltage diode having the structure shown in FIG. 3, three types of stabilizing voltages can be selected, as is clear from the relationship between the gate bias voltage and the stabilizing voltage shown in FIG.

Incidentally, in the above explanation, the first conductive gL reduction was explained using the N type, but it goes without saying that the fourth invention can be implemented as is even if the conductive board is replaced.

(Effects of the Invention) As explained above, according to the present invention, a desired stabilized voltage can be obtained regardless of the number of types, so a precise stabilized voltage can be obtained by adjusting the gate voltage ti externally after manufacturing the integrated circuit. It is also possible to easily change the stabilizing voltage after the integrated circuit is manufactured.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a plan view and a sectional view taken along line xx' of the first embodiment of the present invention, and FIG. 2 is a gate region potential and stabilizing voltage of the first embodiment of the present invention. FIG. 3 is a cross-sectional view of the second embodiment of the present invention, FIG. 4 is a diagram showing the relationship between the gate region potential and stabilizing voltage of the second embodiment of the present invention, and FIG. The figure is a cross-sectional view of an example of a conventional constant voltage diode. 1...NW semiconductor substrate, 2...P type diffusion region, 3a, 3b, 3c...N type diffusion region,
4...Insulating film, 5a... Constant voltage diode electrode, 5b... Gate electrode. Voltage 1 Zener voltage ↑ □ Gate 1 to 1 Hi Figure 4 弗 5 Section

Claims (1)

[Claims] A second diffusion region of the first conductivity type, which is shallower than the first diffusion region, is provided inside the first diffusion region of the second conductivity type formed on the main surface of the semiconductor substrate of the first conductivity type; providing at least one diffusion region of the first conductivity type which is shallower and has a higher concentration than the outer diffusion region inside the second diffusion region;
an insulating film is provided around the second diffusion region of the first conductivity type and the at least one first conductivity type diffusion region, and the second diffusion region of the first conductivity type and the 1. A constant voltage diode comprising: an electrode formed entirely around at least one first conductivity type diffusion region.