JPH0142636B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a semiconductor device such as a gate turn-off thyristor or a transistor in which conduction/disconnection of a main current can be controlled by a control current. It's about structure.

[Prior art]

In gate turn-off thyristors (hereinafter abbreviated as GTO) and transistors (hereinafter abbreviated as TRS),
The emitter layer is made up of a plurality of strip-shaped regions, and is exposed on one main surface of the semiconductor substrate together with the base layer adjacent thereto, with one main electrode film on each strip-shaped region and each strip-shaped region on the base layer. A control electrode film is in low-resistance contact so as to surround the semiconductor substrate, and the other main electrode film is in low-resistance contact with the other main surface of the semiconductor substrate.

To explain specifically using GTO as an example, the first
As shown in the figure, the semiconductor substrate 1 consists of a p-type emitter layer 2, an n-type base layer 3, a p-type base layer 4, and an n-type emitter layer, and the n-type emitter layer is divided into a plurality of strip-shaped regions 5. It is exposed together with the p-type base layer 4 on the upper main surface. On the lower main surface side, an anode electrode film 6 is provided on the p-type emitter layer 2, and on the upper main surface side, a cathode electrode film 7 is provided on each strip-shaped region 5.
A gate electrode film 8 is in low resistance contact with the p-type base layer so as to surround each strip-shaped region in a U-shape. On the upper main surface, a silicon oxide film 9 is provided as a surface stabilizing film in areas other than the areas where the electrodes 7 and 8 are in low resistance contact.

In addition, in Figure 1a, for ease of understanding, Figure 1b,
This silicon oxide film 9 shown in FIG. 1C is omitted, and although this is a plan view, each electrode 7, 8 is shaded.

The reason for adopting such a configuration is that when transitioning from a conductive state to a welded state, a turn-off signal is uniformly applied to each strip-shaped region 5, so that a quick transition operation can be expected.

However, the turn-off signal does not act uniformly on each strip-shaped region 5, and often fails to shift to the welt state, limiting the welt tolerance.

The reason is as follows.

According to the study results of turn-off destruction by the present inventors, turn-off failure will not occur unless the instantaneous values of the anode-cathode voltage and anode current exceed a certain limit line (locus) during turn-off. I understood. FIG. 2 shows an example of this limit line L. GTO operates safely within the shaded limit line. This area will be referred to as the safe operating area (hereinafter abbreviated as ASO).

The conventional GTO shown in Figure 1 had a narrow ASO and a small shear capacity.

The turn-off signal is applied such that the cathode electrode film 7 has a positive potential with respect to the gate electrode film 8 , and carriers in the p-type base layer 4 are extracted from the gate electrode film 8 . At this time, as shown in FIG. 1c, the carrier is pulled out from both sides of each strip-shaped region 5 in the width direction, and the conductive region contracts to the center of each strip-shaped region 5 accordingly. For this reason,
The resistance of the turn-off signal path becomes high and the turn-off signal that can be extracted is limited. This state lasts for a while, causing a sudden rise in temperature, which eventually leads to destruction.

Therefore, the voltage between the anode and cathode or the anode current had to be limited, and the shear breakage resistance was small.

As a means to improve the shrinkage resistance,
As shown in Publication No. 28750, it has been proposed to eliminate the center of the n-type emitter layer, but since the substantial area of the n-type emitter layer decreases, the on-voltage in the conductive state decreases. I had a problem with the price getting higher.

The above problems also occurred in TRS.

[Purpose of the invention]

An object of the present invention is to provide a semiconductor device with a wide ASO and a low on-voltage in a conductive state.

[Summary of the invention]

The present invention is characterized in that the semiconductor substrate has at least three adjacent semiconductor layers of different conductivity types, the first semiconductor layer is made up of a plurality of strip-shaped regions, and the second semiconductor layer is made up of each of the above-described semiconductor layers. A first main electrode is exposed on the first main surface of the semiconductor substrate together with the strip-like regions, a first main electrode is connected to each of the strip-like regions on the first main surface, a control electrode is connected to the second semiconductor layer, and the semiconductor substrate is exposed on the first main surface of the semiconductor substrate. In a semiconductor device in which the second main electrode is connected to the semiconductor layer on the second main surface side of the substrate, the region of the second semiconductor layer on one side in the width direction of each strip-shaped region is the same as that of the second semiconductor layer on the other side. The reason is that it is connected to the control electrode with a higher impedance than the other regions.

[Embodiments of the invention]

FIG. 3 shows a GTO that is an embodiment of the present invention. In FIG. 3, the same or equivalent parts as shown in FIG. 1 are given the same reference numerals.

The GTO shown in FIG. 3 differs from the GTO shown in FIG. 1 in that the gate electrode film is divided into two types, 8a and 8b. The gate electrode film (first control electrode means) 8a is connected to a control electrode (not shown), and the gate electrode film (second control electrode means) 8b is connected to the p-type base layer 4 between the gate electrode films 8a and 8b. It is connected to a control electrode (not shown) via a resistor and a gate electrode film 8a.

GTO or TRS where the emitter layer is divided into multiple parts
In this case, each emitter region is usually formed between the other emitter layer or collector layer.
There is an idea that it is a composite of GTO units and TRS units.

According to this idea, the GTO shown in Figure 3 is 4
Since it has four strip-shaped regions 5, it can be seen as a composite of four GTO units. each
The operation will be explained with reference to FIG. 4 assuming that the GTO units operate uniformly.

Figure 4 schematically shows the GTO unit in comparison to Figure 1c.

In FIG. 4, the same or equivalent parts as shown in FIGS. 1 and 3 are given the same reference numerals.

The resistance R in the p-type base layer 4 between the gate electrode films 8a and 8b is taken out to the outside of the semiconductor substrate 1, and the anode, cathode, and gate electrode films 6, 7, and 8 are
Assuming that the resistance at a and 8b can be ignored,
It is connected to an anode (first main electrode) A, a cathode (second main electrode) K, and a gate (control electrode) G.

That is, the p-type base layer region on one side (left side in the figure) in the width direction of the strip-shaped region 5 has a higher impedance (resistance R in the figure) than the p-type base layer region on the other side (right side in the figure). It has a configuration in which it is connected to gate G.

When the gate G is open and a voltage is applied that makes the anode A have a positive potential with respect to the cathode K, it is in a disconnected state. Here, when a voltage is applied to the cathode K so that the gate G has a positive potential and a turn-off signal is applied, a turn-off operation in a normal thyristor occurs. At this time, since there is a resistor R, the turn-off signal applied from the gate electrode film 8b side is smaller than the turn-off signal applied from the gate electrode film 8a side, but since the conduction region is expanded, the anode current is applied entirely in the strip-shaped region 5. seems to flow.

The turn-off signal is applied to the cathode K for the gate G.
is applied by applying a voltage that makes it a positive potential.

The flow of a turn-off signal, that is, a turn-off current, is shown in the p-type base layer 4 by i ₁ and i ₂ .

The p-type base layer 4 has sheet resistance. This is indicated by r ₁ and r ₂ along the path of the turn-off currents i ₁ and i ₂ . The sheet resistances r ₁ and r ₂ are subjected to conductivity modulation and have sufficiently small values when an anode current is flowing. Since the turn-off current i ₂ includes the resistor R, it is sufficiently smaller than the turn-off current i ₁ . Therefore, at the beginning of turn-off, carriers in the semiconductor substrate 1 are mainly extracted by the turn-off current _i1 , and as time passes, the carrier concentration in the center and right side of the figure continues to decrease, and the anode current will decrease overall. Internally, the anode current flows more to the left in the figure. The sheet resistance r ₁ gradually increases because the conductivity modulation weakens as the carrier concentration decreases. On the other hand, the sheet resistance r ₂ decreases due to the deviation of the anode current. Therefore the sheet resistance for sheet resistance r ₁
The difference between r ₂ and the sum of resistance R gradually weakens, turn-off current i ₁ decreases, and turn-off current i ₂ increases.

That is, the value of i ₂ /i ₁ =r ₁ /r ₂ +R gradually increases from approximately zero over time. The part where the anode current flows in a concentrated manner approaches the gate electrode film 8b, and the increased turn-off current i ₂ also pulls out the carriers, resulting in turn-off.

To summarize the above turn-off operation, due to the difference in turn-off current at the beginning of the turn-off operation, the carrier is pulled out unbalanced from one side and the other side in the width direction of the strip-shaped region, and at the end of the turn-off operation, the carrier is biased to one side. It can be said that it is pulled out from both sides.

The effects based on the above operation will be explained below.

First, you get a GTO with expanded ASO.

In the GTO according to the present invention, the carrier is biased to one side of the strip-shaped region 5 at the end of the turn-off operation, so the ability to pull out the carrier is not reduced, and therefore the turn-off operation is performed well and the ASO is expanded. it is conceivable that.

As mentioned above, ASO is an anode at turn-off.
According to the present invention, the second
The limit line L in the figure moves in the direction indicated by the arrow, and the shrinkage resistance improves. The inventors of the present invention confirmed this fact through experiments.

The more inductance L is included in the resistor R, the more the turn-off current i ₂ at the beginning of the turn-off operation is limited and the degree of unbalance increases. The turn-off current i ₂ increases and the ASO further expands.

Second, a GTO with low on-voltage can be obtained.

Since the strip-shaped region 5 is not provided with any means for reducing its substantial area as seen in Japanese Patent Publication No. 43-28750, the on-voltage in the conductive state is low. The higher the on-voltage, the greater the heat loss in the semiconductor substrate, the greater the risk of thermal breakdown, and the more difficult the turn-off operation becomes. Accordingly, in the present invention, a GTO with even greater breakdown strength can be obtained.

The conventional concept of GTO shown in Figure 1 is as follows:
Since the width of the strip-shaped region is made as small as possible so that the turn-off current acts from the beginning up to the center in the width direction, the area of the strip-shaped region is small, and therefore the number of strip-shaped regions is reduced. It had a lot of complex patterns.

According to the present invention, since the carrier is biased to one side, the width of the strip-shaped region can be increased, and the pattern on the cathode side can also be simplified.

In the embodiment shown in FIG. 3, due to the bonding of wires, leads, etc. that become the cathode K and gate G in FIG.
It is assumed that the gate signal is extracted from the bridge portion 7a side of the gate electrode film 7 and the gate signal is applied from the bridge portion 8c side of the gate electrode film 7. Both electrode films 7, 8a, and 8b have a small resistance. The further away from the bridging parts 7a and 8c the bridging part 7 becomes.
The resistance between a and 8c increases. Since more current flows in areas with lower resistance, each strip-shaped area 5
Looking at the distribution state in the semiconductor substrate in the longitudinal direction, the load current flows more toward the bridge portion 7a, and the gate signal flows more toward the bridge portion 8c.
In particular, regarding the turn-off current, the ratio of load current/turn-off current is small on the bridge portion 8c side and large on the bridge portion 7c side. Since the smaller the ratio of load current/turn-off current is, the easier the turn-off is, it can be said that there is a difference in the turn-off function in the longitudinal direction of each strip-shaped region 5.

Next, the turn-off operation will be explained taking into consideration the time passage explained in FIG. 4.

At the beginning of the turn-off operation, almost no turn-off current flows through the gate electrode film 8b.
The carriers are extracted exclusively through the gate electrode film 8a, and the area where the carriers move is biased toward the gate electrode film 8b. As the turn-off operation progresses, the turn-off current i ₁ flowing through the gate electrode film 8a
decreases, and the turn-off current i ₂ flowing through the gate electrode film 8b increases. The resistance component in the gate electrode film 8b, the lower end of the gate electrode film 8b, and the bridge portion 8
Comparing the resistance between the gate electrode film 8b and the gate electrode film 8b, the resistance at the gate electrode film 8b is sufficiently small, and the potential drop due to the turn-off current _i2 is almost negligible compared to the potential drop between the lower end of the gate electrode film 8b and the bridge portion 8c. Can be ignored. Therefore, the gate electrode film 8b is at approximately equal potential, and there is almost no distribution of the turn-off current i ₂ along the longitudinal direction of the strip-shaped region 5. Therefore, even if the turn-off current i ₁ initially pulls out the carriers with a difference in the longitudinal direction of the strip-shaped region 5, the turn-off current i ₂ pulls out the carriers almost equally in the final stage, so that The turn-off function becomes uniform depending on the direction, and a good turn-off operation can be obtained.

Since the gate electrode film 8b has the same potential as the p-type base layer 4 below, the gate electrode film 8b can be considered as a pressure equalizing material for the p-type base layer 4.

Conventionally, the length of the strip-shaped region 5 was limited in order to prevent the turn-off function from differing in the longitudinal direction of the strip-shaped region 5, but according to the present invention, the length of the strip-shaped region 5 was restricted. Due to the presence of the gate electrode film 8b, such restrictions can be eliminated, and the length of the strip-shaped region 5 can be set freely.

Next, a method of adding a resistance component using a semiconductor substrate will be explained.

FIG. 5 shows an area corresponding to the area surrounded by the dashed line in FIG. 3 as viewed from the upper left of FIG.

In this embodiment, similar to the conventional example shown in FIG.
The gate electrode film 8 is integrated. However, an n-type buried region 9 having the same conductivity type as the strip region 5 is provided along the longitudinal direction of the strip region 5 between the gate electrode film 8 on one side in the width direction of the strip region 5. There is. Because of the buried region 9, the turn-off current _i2 flows deeper within the p-type base layer ₄ than the turn-off current i1. Since the sheet resistance here is greater than the sheet resistance of the surface portion when the p-type base layer 4 is formed by a known diffusion technique, the turn-off currents i ₁ and i ₂ become unbalanced at the initial stage of the turn-off operation.

The buried region 9 may extend below a part of the gate electrode film 8 as shown by the dotted line.

The buried region 9 can be replaced by a groove 10 as shown in FIG.

FIG. 7 shows yet another embodiment. In this embodiment, a buried region 11 having the same conductivity type as the p-type base layer 4 and having a high impurity concentration is provided on one side of the strip-shaped region 5. The buried region 11 is in low resistance contact with the gate electrode film 8 at the end of the strip-shaped region 5 in the longitudinal direction. Turn-off current i ₁ flows through gate electrode film 8 , while turn-off current i ₂ flows through buried region 11 . Since the resistance in the buried region 11 is higher than the resistance in the gate electrode film 8, the turn-off currents i ₁ , i ₂
An imbalance occurs at the beginning of the turn-off operation.

In another embodiment shown in FIG. 8, the gate electrode film 8 is integrated as in the embodiment shown in FIG. 5, but the strip-shaped region 5 and the gate electrode film 8 on one side in the width direction The distance l ₁ between the strip regions 5 and the gate electrode film 8 on the other side in the width direction is set larger than the distance l ₂ between the strip regions 5 and the gate electrode film 8 on the other side in the width direction, and the sheet resistance of the p-type base layer 4 given by this distance difference is This difference causes an imbalance in the turn-off currents i ₁ and i ₂ at the beginning of the turn-off operation.

The embodiments shown in FIGS. 5 to 8 above are not limited to the forms shown in each figure, and can be combined arbitrarily.

Next, an application example of the present invention will be explained.

Addition of a lifetime killer to a semiconductor substrate and irradiation with radiation, which have been conventionally employed for speeding up, can also be applied to the present invention.

In addition, as an alternative to these speed-up methods,
The GTO has an anode-side emitter short-circuit structure disclosed in Japanese Patent Application Laid-Open No. 54-111790, etc., and this structure can also be applied to the GTO of the present invention.

As the semiconductor substrate, not only a rectangular one as shown in FIG. 3 but also a circular one as shown in FIG. 9 can be applied. In FIG. 9, the same or equivalent parts as those shown in FIGS. 1 and 3 are given the same reference numerals.

The circular semiconductor substrate 1 in FIG. 9 is provided with strip-shaped regions radially, and the cathode electrode films 7 are radially and independently in low-resistance contact thereon in a similar shape. Two strip-shaped regions form a pair, and the gate electrode film 8b on one side is in low-resistance contact with the p-type base layer between them. The gate electrode film 8a on the other side surrounds the paired strip-shaped regions.

In the example shown in FIG. 9, the strip-shaped regions are arranged in a single radial pattern, but in the case of a device with a large rated current, it is preferable to use a multiple radial arrangement.

FIG. 10 shows an example of FIG. 9 in which the p-type base layer has an etched-down structure. In this example, as shown in the figure, when the cathode 12 is pressed into contact with each cathode electrode film 7, insulation between each gate electrode film 8a, 8b and the cathode 12 can be ensured.

FIG. 11 is an example in which a GTO unit with a conventional structure and a GTO unit according to the present invention are installed side by side.

In FIG. 11, the same or equivalent components as those shown in FIGS. 1 and 3 are given the same reference numerals.

In the figure, five strip-shaped regions 5 are arranged side by side, and the strip-shaped region 5 at the right end in the figure is the first strip-shaped region 5.
As in the figure, gate electrode films 8a connected to the bridge portions 8c are arranged on both sides in the width direction, but other strip-shaped regions 5 are arranged on one side and the other side in the width direction, as in FIG. Gate electrode films 8a and 8b are arranged to provide unbalance.

In the strip-shaped region 5 at the right end, the carrier is pulled out in a well-balanced manner from both sides in the width direction at the beginning of the turn-off operation. In this case, since the amount of turn-off current acting on the remaining strip-shaped regions 5 is larger than that in the remaining strip-shaped regions 5, the GTO unit including the right-most strip-shaped region 5 attempts to complete turn-off quickly. At this time, each GTO unit including each of the other strip-shaped regions 5 is in a conductive state again, so the current flowing through the GTO unit including the right-most strip-shaped region easily transfers to the other GTO units and quickly turns off. complete. Each remaining inventive GTO unit then completes turn-off.

Since the GTO units other than the rightmost one bear the current of the rightmost GTO unit, this configuration can be adopted when there is sufficient ASO.

〔Effect of the invention〕

As explained above, according to the present invention, the carrier is unbalancedly pulled out from both sides of the strip-shaped region in the width direction at the beginning of the turn-off operation, and the ASO
It is possible to obtain a semiconductor device in which the on-state voltage is increased and the on-state voltage is low.

[Brief explanation of drawings]

Figure 1 shows a conventional GTO, in which a is a plan view on the cathode side, b is a vertical cross-sectional view along the -cutting line of a, c is a cross-sectional view along the -cutting line of a, and Fig. 2 3 is a diagram showing the relationship between the anode-cathode voltage and anode current in the GTO, FIG. 3 is a plan view of the cathode side of the GTO according to an embodiment of the present invention, and FIG. 4 is a diagram showing the turn-off operation mechanism of the GTO according to the present invention. Schematic diagram of the GTO unit explained in Figure 5~
Fig. 8 is a cross-sectional perspective view of main parts showing other embodiments of the present invention, and Fig. 9 is a GTO which is an example of application of the present invention.
FIG. 10 is a partial sectional view taken along the - cutting line of FIG. 9, and FIG. 11 is a plan view of the cathode side showing another application example of the present invention. 1... Semiconductor base, 2... P-type emitter layer, 3
... n-type base layer, 4 ... p-type base layer, 5 ...
N-type emitter layer strip-shaped region, 6... anode electrode film, 7... cathode electrode film, 8a, 8b... gate electrode film.

Claims (1)

[Claims] 1. A semiconductor substrate has at least three adjacent semiconductor layers having different conductivity types, the first semiconductor layer is composed of at least one strip-shaped region, and the second semiconductor layer is composed of at least one strip-shaped region. a first main electrode is exposed on the first main surface of the semiconductor substrate together with a shaped region, a first main electrode is provided on each of the strip-like regions of the first main surface, a control electrode is provided on the second semiconductor layer, and a control electrode is provided on the second semiconductor layer; In a semiconductor device in which a second main electrode is connected to a semiconductor layer on the front side, when the main current flowing between the first and second main electrodes is interrupted by a control current flowing between the control electrode and the first main electrode. , a first control electrode means for concentrating the conduction region of the current flowing in the semiconductor substrate on a part of the strip-shaped region of the first semiconductor layer; A semiconductor device having a second control electrode means for effectively extracting. 2. A semiconductor substrate has at least three semiconductor layers adjacent to a pair of main surfaces and having mutually different conductivity types, the first semiconductor layer consisting of a plurality of strip-shaped regions juxtaposed on the first main surface, and the second exposed on the first main surface so as to surround each strip-shaped region from the semiconductor layer,
A first main electrode is in low-resistance contact with each strip-shaped region on the first main surface, and is in contact with the second semiconductor layer on one side in a direction perpendicular to the longitudinal direction of each strip-shaped region along the longitudinal direction of the strip-shaped region. A plurality of first control electrodes are in low resistance contact, these first control electrodes are electrically connected to each other, and each strip-shaped region is attached to the second semiconductor layer on the other side in a direction perpendicular to the longitudinal direction of each strip-shaped region. a plurality of second control electrodes are in low resistance contact along the longitudinal direction of the
These second control electrodes are provided independently from the first control electrode, and the second control electrodes are provided on the second main surface of the semiconductor substrate.
A semiconductor device characterized in that main electrodes are in low resistance contact. 3. The semiconductor device according to claim 2, wherein the first control electrode and the second control electrode are connected to each other via an external resistor. 4 At least three semiconductor layers having different conductivity types adjacent to each other between a pair of main surfaces, the first semiconductor layer consisting of a plurality of strip-shaped regions juxtaposed on the first main surface, and the second semiconductor layer a semiconductor substrate exposed on the first main surface so as to surround each strip-shaped region; a plurality of first main electrodes in low-resistance contact with each strip-shaped region on the first main surface of the semiconductor substrate; a first main terminal electrically connected to each first main electrode; and a second main terminal in low resistance contact with a second main surface of the semiconductor substrate.
a main electrode; a second main terminal electrically connected to the second main electrode; and a second main terminal electrically connected to the first main surface of the semiconductor substrate. a control electrode in low resistance contact with the second semiconductor layer along the direction; and a second semiconductor between the strip region and the control electrode on one side in a direction perpendicular to the longitudinal direction of each strip region. A semiconductor device characterized in that the electrical resistance of one layer is greater than that on the other side. 5 The distance between the strip-shaped region and the control electrode on one side in a direction perpendicular to the longitudinal direction of each strip-shaped region is larger than that on the other side. The semiconductor device according to scope 4. 6. Claim 4, characterized in that a groove along the longitudinal direction of the strip-shaped region is formed in the second semiconductor layer on one side in a direction perpendicular to the longitudinal direction of each of the strip-shaped regions. semiconductor devices. 7. A region having a conductivity type opposite to that of the second semiconductor layer extending from the surface to the inside of the second semiconductor layer on one side in a direction perpendicular to the longitudinal direction of each of the strip-shaped regions in the longitudinal direction of the strip-shaped regions. 5. The semiconductor device according to claim 4, wherein the semiconductor device is formed along the lines.