KR100486347B1 - Insulated-gate bipolar transistor - Google Patents

Abstract

The present invention discloses an insulated gate bipolar transistor (IGBT). This includes a first conductive semiconductor substrate, a buffer layer formed on the semiconductor substrate in a second conductivity type, an epi layer formed on the buffer layer in a second conductivity type, a base region formed on the epi layer in a first conductivity type, and the base region. First emitter regions within the second conductivity type and laterally spaced in the transverse direction and parallel to the longitudinal direction, second emitters within the base region and connecting the first emitter regions An emitter electrode shorting a region, a collector electrode connected to the semiconductor substrate, a base region between the first emitter regions, and the second emitter region, and a thickness of the emitter electrode is not constant around the second emitter region. In portions except the periphery of the second emitter region, the thickness is composed of a constant gate oxide film and a gate electrode formed on the gate oxide film. It is broken.

Description

Insulated-gate bipolar transistor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to power transistors, and more particularly to Insulated-Gate Bipolar Transistors (IGBTs).

Insulated Gate Bipolar Transistors (IGBTs) are power switching devices that require ideal conduction and switching losses and ideal breakdown voltages for desired switching operations. In addition, when the large current flows, the gate voltage is lowered below the threshold voltage to cut off the current.At this time, the current is not cut off and the voltage between the switch, that is, the voltage between the collector electrode and the emitter electrode does not become small, so the current continues to flow. As a result, conduction loss occurs, causing the temperature of the insulated gate bipolar transistor IGBT to rise, and as a result, the insulated gate bipolar transistor IGBT fails.

1 is a cross-sectional view illustrating a normal operating state of an insulated gate bipolar transistor (IGBT) according to the prior art.

Referring to FIG. 1, an insulated gate bipolar transistor (IGBT) is formed on a first conductive semiconductor substrate 1, a buffer layer 3 formed on the semiconductor substrate 1, and a second conductive type on the buffer layer 3. An epi layer 5 having a second conductivity type and having a concentration smaller than that of the buffer layer 3, a base region 7 formed with a first conductivity type well structure in the epi layer 5, and the base region 7. An emitter region 9 is formed within the second conductivity type and spaced apart from each other at predetermined intervals.

The collector electrode 17 is connected to the semiconductor substrate 1 and the emitter electrode 15 is shorted with the edge of the emitter region 9 including the base region 7 between the emitter regions 9. .

The gate electrode 11 is formed on the gate oxide film 10, in particular the epi layer 5, the other edge of the emitter region 9, the other edge of the emitter region 9 and the epi layer ( It is formed on the gate oxide film 10 corresponding to the base region 7 between 5).

The first conductivity type is a P type and the second conductivity type is an N type, so that the insulated gate bipolar transistor IGBT includes the emitter region 9, the base region 7, and the An NPN transistor composed of an epitaxial layer 5 and a base region 7, an epitaxial layer 5 / buffer layer 3, and a PNP transistor composed of the semiconductor substrate 1 are combined. Structure.

The operation principle of the insulated gate bipolar transistor (IGBT) formed as described above is as follows.

First, a negative voltage is applied to the gate electrode 11 and a positive voltage is applied to the collector electrode 17 to turn on the insulated gate bipolar transistor IGBT. A channel 19 is generated in the base region 7 corresponding to the lower portion of the electrode 11 so that the electrons e of the emitter region 9 flow through the channel 19 to the epi layer 5. .

Since the electron current flowing through the channel 19 to the epi layer 5 corresponds to the base current of the PNP transistor, the PNP transistor is turned on so that the hole h of the semiconductor substrate 1 becomes the buffer layer. (3), a hole current flowing to the emitter electrode 15 along the epi layer 5, the lower portion of the channel 19, and the lower portion of the emitter region 9 is generated.

As a result, the insulated gate bipolar transistor IGBT is turned on.

In order to turn off the insulated gate bipolar transistor IGBT, a negative voltage is applied to the gate electrode 11. As a result, the channel 19 does not occur so that the electron current and the hall current Since it does not occur, the insulated gate bipolar transistor IGBT is turned off.

Therefore, since the insulated gate bipolar transistor IGBT can control the turn on / off by changing the polarity of the voltage supplied to the gate electrode 11, normal operation is performed.

2 is a cross-sectional view illustrating an abnormal operating state of an insulated gate bipolar transistor (IGBT) according to the related art.

Referring to FIG. 2, a resistance (not shown) component is present in a hole current path flowing from the emitter region 9 to the emitter electrode 15, which increases as the hole current increases. A voltage greater than a threshold voltage between the emitter region 9 and the base region 7 is induced so that electrons e of the emitter region 9 do not pass through the channel 19 directly to the base. By flowing through the region 7 to the epi layer 5, the electron current flowing to the epi layer 5 becomes larger, and thus the base region 7, the epi layer 5 / buffer layer 3, and the The hole current of the PNP transistor formed of the semiconductor substrate 1 also increases.

In this state, even if the polarity of the voltage supplied to the gate electrode 13 is changed, electron current flowing from the emitter region 9 to the buffer layer 3 through the base region 7 is not removed. Therefore, the insulated gate bipolar transistor IGBT is not turned off.

In other words, the insulation gate bipolar transistor (IGBT) continues to flow current until the voltage between the collector electrode 17 and the emitter electrode 15 decreases, so that conduction loss occurs and the temperature rises, causing the device to fail. do.

Therefore, in order to solve the above problem, the difference between the potential of the emitter region 9 and the base region 7 corresponding to the lower portion of the emitter region 9 is determined by the emitter region 9 and the base region. It should be smaller than the threshold voltage with (7), in which the resistance of the emitter region 9 is increased to increase the potential of the emitter region 9.

An object of the present invention is to provide an insulated gate bipolar transistor (IGBT) having a large potential in the emitter region in order to prevent a phenomenon in which the turn-off of the device is not controlled due to generation of an electron current through the channel. .

In order to achieve the above object, the present invention, the first conductivity type semiconductor substrate; A second conductivity type buffer layer formed on the semiconductor substrate; An epitaxial layer formed on the buffer layer in a second conductivity type; A base region formed in the epi layer in a first conductivity type; First emitter regions of a second conductivity type in the base region and spaced apart in a transverse direction and parallel to the longitudinal direction; A second emitter region in the base region and of a second conductivity type and connecting said first emitter region; A collector electrode connected to the semiconductor substrate;

An emitter electrode shorting a base region between the first emitter regions and the second emitter region; A gate oxide film whose thickness is not constant around the second emitter region and whose thickness is constant except at the periphery of the second emitter region; And a gate electrode formed on the gate oxide film.

In the vicinity of the second emitter region, it is preferable that the thickness of the gate oxide layer on the first emitter region is smaller than the thickness of the gate oxide layer on the base region.

In portions other than the periphery of the second emitter region, it is preferable that the thickness of the gate oxide layer on the first emitter region and the thickness of the gate oxide layer on the base region and the epi layer is the same.

In addition, the epi layer is preferably smaller than the buffer layer concentration.

Therefore, in the insulated gate bipolar transistor (IGBT) according to the present invention, the emitter region close to the large portion of the gate oxide film serves as a resistor, so that the potential of the emitter region is increased, and as a result, the potential of the emitter region and the lower portion of the emitter region Since the potential difference of the base region of the transistor becomes small, an electron current that does not pass through the channel is generated, thereby preventing the phenomenon in which the turn-off of the device is not controlled.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 is a layout diagram of an insulated gate bipolar transistor (IGBT) according to the present invention.

Referring to FIG. 3, the emitter regions are spaced apart from each other on the longitudinally formed base region 57 and are formed in the longitudinal direction in parallel with the base region 57 in the longitudinal direction. The emitter region 59 is formed of a second emitter region 60 having a bridge shape so as to be connected laterally.

In other words, the emitter region has a structure in which the first emitter region 59 and the second emitter region 60 are connected in an H shape.

The contact hole 66 is separated from the first emitter region 59 between the first emitter region 59 and passes through the second emitter region 60 to the first emitter region 59. Parallel to, to form the emitter electrode. Thus, the emitter electrode is electrically connected to the base region 57 and the second emitter region 60.

A gate oxide film (not shown) is formed on the first emitter region 59, the second emitter region 60, the base region 57, and the epi layer 55, and the thickness thereof is the second. The emitter region 60 is formed differently in the periphery k and other portions.

The thickness of the gate oxide in the periphery k of the second emitter region 60 is larger than the thickness of the gate oxide in other portions, which is in the periphery k of the second emitter region 60. To increase the threshold voltage of the electrons e of the first and second emitter regions 59 and 60 do not flow to the periphery k of the second emitter region 60 but to the path indicated by the arrow. It is for.

Accordingly, the first emitter region 59 serves only as a resistance, and thus a first voltage obtained by multiplying the resistance of the electronic path by the electron current is represented.

4 is a cross-sectional view taken from line 4-4 'of the layout diagram of FIG.

Referring to FIG. 4, an insulated gate bipolar transistor (IGBT) is formed on a first conductive semiconductor substrate 51, a buffer layer 53 formed on the semiconductor substrate 51, and a second conductive type on the buffer layer 53. An epitaxial layer 55 formed in the second conductive type, a base region 57 formed in the epitaxial layer 55 in the first conductivity type, and a second conductive type in the base region 57 and spaced apart from each other by a predetermined interval. And a first emitter region 59 formed thereon.

The first conductivity type is a P type and the second conductivity type is an N type. The insulated gate bipolar transistor IGBT includes the emitter region 59, the base region 57, and the An NNP transistor formed of an epitaxial layer 55 and a PNP transistor formed of the base region 57, the epi layer 55 / buffer layer 53, and the semiconductor substrate 51 are coupled to each other. Structure.

The epi layer 55 is smaller than the concentration of the buffer layer 53.

The emitter electrode 67 is not in contact with the first emitter region 59 as is conventionally connected to the base region 57 between the first emitter region 59 and the collector electrode 69 is It is electrically connected to the semiconductor substrate 51.

The gate oxide layer 61 is formed to have a predetermined thickness on the first emitter region 59, the base region 57, and the epi layer 55 as in the related art, so that a negative voltage is applied to the gate electrode 63. Is applied, a channel (not shown) is formed in the base region 57 corresponding to the lower portion of the gate electrode 63, and electrons in the first emitter region 59 are transferred to the epi layer 55 through the channel. Will flow.

The gate electrode 63 is formed on the gate oxide layer 61 and surrounded by the insulating layer 65.

FIG. 5 is a cross-sectional view taken from 5-5 'of the layout diagram of FIG.

Referring to FIG. 5, except for the first and second emitter regions 59 and 60, the gate oxide layer 61, and the gate electrode 63 of the components of the insulated gate bipolar transistor IGBT, FIG. 4. Same as the structure of

That is, the first and second emitter regions 59 and 60 are formed in the base region 57 and electrically connected to the emitter electrode 67.

The gate oxide layer 61 is formed to have different thicknesses on the first and second emitter regions 59 and 60, the base region 57, and the epi layer 55. In particular, the gate oxide layer 61 may be formed. The thickness of the gate oxide layer 61 on the two emitter regions 59 and 60 is smaller than the thickness of the gate oxide layer 61 on the base region 57.

This is because a channel (not shown) is not formed in the base region 57 between the first and second emitter regions 59 and 60 and the epi layer 55 when a voltage is supplied to the gate electrode 63. This is to prevent electrons in the first and second emitter regions 59 and 60 from flowing into the epitaxial layer 55.

As a result, the gate input capacitance is reduced.

An operation principle of the insulated gate bipolar transistor IGBT will be described with reference to FIGS. 3 to 5 as follows.

First, a negative voltage is applied to the gate electrode 63 and a positive voltage is applied to the collector electrode 69 to turn on the insulated gate bipolar transistor IGBT. A channel is generated in the base region 57 corresponding to the lower portion of the electrode 63, and electrons e of the first and second emitter regions 59 and 60 flow along a path indicated by an arrow.

Accordingly, a first voltage obtained by multiplying the resistance of the first emitter region 59 by the electron current appears in the first emitter region 59.

Since the electron current flowing to the epi layer 55 corresponds to the base current of the PNP transistor, the PNP transistor is turned on so that the holes of the semiconductor substrate 51 are formed in the buffer layer 53 and the epi layer ( 55), a hole current flowing to the first emitter electrode 59 along the lower portion of the channel and the lower portion of the emitter region 59 is generated.

A resistance (not shown) component exists in the hole current path flowing from the lower portion of the first emitter region 59 to the emitter electrode 67 so that the hole current and the lower portion of the first emitter region 59 are lower than the first emitter region 59. The multiplied second voltage of the resistance is shown.

Therefore, since the first voltage is increased compared with the related art, the difference between the first voltage and the second voltage is small, and as a result, electrons in the first emitter region 59 are transferred to the base region under the gate electrode 63. The phenomenon that flows directly into the base region 57 without passing through the channel formed in the 57 does not appear.

The present invention is not limited to this, and it is apparent that many modifications are possible by those skilled in the art within the technical idea of the present invention.

As described above, in the insulated gate bipolar transistor (IGBT) according to the present invention, since the emitter region close to the large portion of the gate oxide film serves as a resistor, the potential of the emitter region is increased, and as a result, the potential of the emitter region is increased. Since the potential difference between the base region and the base region under the emitter region is small, it is possible to prevent the phenomenon in which the turn-off of the device is not controlled due to the generation of electron current through the channel.

1 is a cross-sectional view illustrating a normal operating state of an insulated gate bipolar transistor (IGBT) according to the prior art.

2 is a cross-sectional view illustrating an abnormal operating state of an insulated gate bipolar transistor (IGBT) according to the related art.

3 is a layout diagram of an insulated gate bipolar transistor (IGBT) according to the present invention.

4 is a cross-sectional view taken from line 4-4 'of the layout diagram of FIG.

FIG. 5 is a cross-sectional view taken from 5-5 'of the layout diagram of FIG.

Claims (4)

A first conductivity type semiconductor substrate; A buffer layer formed on the semiconductor substrate in a second conductivity type; An epitaxial layer formed on the buffer layer in a second conductivity type; A base region formed in the epi layer in a first conductivity type; First emitter regions of a second conductivity type formed in the base region and spaced apart from each other in a transverse direction and parallel in the longitudinal direction when viewed from an upper surface of the semiconductor substrate; A second emitter region of a second conductivity type formed in the base region and having a bridge shape connecting a predetermined portion of the first emitter region; A collector electrode connected to the semiconductor substrate; An emitter electrode shorting a base region between the first emitter regions and the second emitter region; A gate oxide film whose thickness is not constant around the second emitter region and whose thickness is constant except at the periphery of the second emitter region; And Insulated-Gate Bipolar Transistor (IGBT), comprising: a gate electrode formed on the gate oxide layer. The method of claim 1, wherein around the second emitter region Insulated gate bipolar transistor (IGBT), characterized in that the thickness of the gate oxide film over the first emitter region is smaller than the thickness of the gate oxide film over the base region. The method of claim 1, wherein the portion other than around the second emitter region Insulated gate bipolar transistor (IGBT), characterized in that the thickness of the gate oxide film over the first emitter region and the thickness of the gate oxide film over the base region and the epi layer. The method of claim 1, wherein the epi layer is Insulated gate bipolar transistor (IGBT), characterized in that less than the buffer layer concentration.

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