JP2515017B2 - Thyristor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thyristor made of polycrystalline silicon.

2. Description of the Related Art When a thyristor is formed on the same substrate while being electrically separated from an element formed on a semiconductor substrate, the isolation portion is not formed in the semiconductor substrate and the thyristor is formed on the oxide film formed on the surface of the semiconductor substrate. When the thyristor is made of polycrystalline silicon, the step of forming the isolation portion can be omitted. By the way, when a thyristor is made of polycrystalline silicon,
Since the mobility of carriers in polycrystalline silicon is smaller than that in silicon, the structure shown in FIGS. 4 and 5 is used for the purpose of normally operating the thyristor. That is, a gate region made of p-type polycrystalline silicon
Cathode regions 52 made of n-type polycrystalline silicon are arranged in an island shape within 51, and the original width of the gater region 51a between the n-type polycrystalline silicon region 53 and the cathode region 52 other than the cathode region 52 is set to be the same. It was made narrow so that the mobility of carriers would not be lowered. In FIGS. 4 and 5, 54 is a semiconductor substrate, 55 is a silicon oxide film formed on the surface of the semiconductor substrate 54, 56 is an anode region, and 57 to 59 are respective regions 51, 52,
Contact windows formed on 56, 60 to 62 are electrodes formed on the contact windows 57 to 59, and 63 is a silicon oxide film for electrode separation.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention According to the above conventional configuration, the cathode region 52
Is an n-type, the distance from the gate electrode 60 to the p-type region sandwiched between the n-type polycrystalline silicon region 53 and the cathode region 52, that is, the distance from the gate electrode 60 to the actual gate region 51a is long, Further, there is a problem that the current from the gate electrode 60 flows from the periphery of the cathode region 52 different from the original gate region 51a, thus increasing the gate current and causing a voltage drop to make it difficult for the thyristor to be in a conductive state. .

Therefore, an object of the present invention is to provide a thyristor capable of solving the above problems.

Means for Solving the Problems In order to solve the above problems, the thyristor of the present invention has p
An anode region made of n-type polycrystalline silicon, and an n-type polycrystalline silicon region formed outside the anode region,
A gate region formed outside the n-type polycrystalline silicon region and made of p-type polycrystalline silicon, and a cathode region arranged in an island shape in the gate region, and a gate formed in the gate region An electrode is arranged outside the cathode region opposite to the n-type polycrystalline silicon region and has a pn junction with the gate region on the side of the cathode region facing the n-type polycrystalline silicon region. Other than that, an isolation region having no polycrystalline silicon is provided in the other surface contact portion between the cathode region and the gate region.

Operation In the above configuration, since the isolation region was formed in the periphery of the cathode region other than the surface contact portion (pn junction) with the original gate region, when a voltage is applied to the gate electrode, the cathode region is not affected by the current. Since it flows from the gate region, it is possible to prevent excess current from flowing around the cathode region as in the conventional case.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The thyristor according to the present embodiment is formed of polycrystalline silicon on the oxide film formed on the surface of the semiconductor substrate. That is, a silicon oxide film 2 is formed on the surface of a semiconductor substrate 1, on which an anode region 3 made of p-type polycrystalline silicon, an n-type polycrystalline silicon region 4 of a predetermined width, and a p-type polycrystalline silicon region are sequentially formed. A gate region 5 made of polycrystalline silicon is formed side by side, and a plurality of cathode regions 6 are formed in an island shape in the gate region 5. Of course, the original gate region 5a is formed between the cathode region 6 and the n-type polycrystalline silicon region 4 other than the cathode region 6 with a narrow width. Further, in FIG. 1, 7,8,9 are contact windows formed in the respective regions 3, 5, 6,
Electrodes 10, 11, 12 are placed on these contact windows 7, 8, 9 respectively.
Are formed. Gate electrode 11 is arranged outside cathode region 6, that is, on the side opposite to n-type polycrystalline silicon region 4. Further, the pn of the portion of the cathode region 6 facing the n-type polycrystalline silicon region 4 is further
Isolation region b having no polycrystalline silicon at the surface contact portion between the cathode region 6 and the gate region 5 other than the junction a.
Are formed by etching. Reference numeral 13 is a silicon oxide film for separating electrodes.

According to the above configuration, the isolation region b is formed around the cathode region 6 except for the contact portion (pn junction portion) with the original gate region 5.
Therefore, when a voltage is applied to the gate electrode 11, a current flows into the cathode region 6 from the original gate region 5a, so that it does not flow from around the cathode region 6 as in the conventional case. Will not increase and there will be no voltage drop, so
It is possible to prevent the thyristor from becoming difficult to become conductive.

Here, FIG. 3 shows a specific example of the thyristor. In the thyristor shown in FIG. 3, a square anode region 21 is formed in the center, an n-type polycrystalline silicon region 22 is formed with a predetermined width around the anode region 21, and a gate region 23 is formed around the n-type polycrystalline silicon region 22. Eight square cathode regions 24 are formed in an island shape in the region 23 and at a position facing each side of the n-type polycrystalline silicon region 22, and the n-type polycrystalline silicon region 22 of each cathode region 24 is further formed. Separation regions b are formed around the three sides other than the part facing each other. In addition,
Each of the p-type regions 21 and 23 is formed by ion implantation of boron (acceleration energy 50 KeV, implantation amount 3 × 10 ¹³ cm ^-2 ),
The n-type regions 22 and 24 are formed by phosphorus ion implantation (acceleration energy 50 KeV, implantation amount 3 × 10 ¹⁵ cm ⁻² ).

As described above, according to the configuration of the present invention, since the isolation region is formed in the periphery of the cathode region other than the surface contact portion (pn junction) with the original gate region, when a voltage is applied to the gate electrode , Since the current flows from the original gate region to the cathode region, it does not flow from the surroundings of the cathode region as in the past, so the gate current does not increase and there is no voltage drop, so the thyristor conducts. It is possible to prevent the situation from becoming difficult.

[Brief description of drawings]

FIG. 1 is a plan view of the thyristor according to an embodiment of the present invention excluding the electrode portions, FIG. 2 is a sectional view of the thyristor, and FIG. 3 is a plan view of the thyristor excluding the electrode portions. FIG. 4 is a plan view of the conventional thyristor without the electrodes, and FIG. 5 is a sectional view of the thyristor. 3 ... Anode region, 4 ... N-type polycrystalline silicon region,
5,5a ... gate region, 6 ... cathode region, 11 ... gate electrode.

Claims (1)

(57) [Claims] 1. An anode region made of p-type polycrystalline silicon, an n-type polycrystalline silicon region formed outside the anode region, and a p-type polycrystalline region formed outside the n-type polycrystalline silicon region. The cathode having a gate region made of silicon and a cathode region arranged in an island shape in the gate region, and the gate electrode formed in the gate region being opposite to the n-type polycrystalline silicon region. The surface contact between the other cathode region and the gate region is left outside the region, leaving a pn junction with the gate region on the side of the cathode region facing the n-type polycrystalline silicon region. A thyristor with a polycrystalline silicon-free isolation region.