JP2011049469A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device with improved withstand voltage characteristics, as regards a semiconductor device to which a high voltage is applied. <P>SOLUTION: The semiconductor device includes a first electrode formed on a semiconductor substrate, an annular second electrode formed around the first electrode, and a resistor connected to the first electrode and second electrode. The resistor is arranged in a spiral shape around the first electrode, and has a larger interval of a spiral on an outer peripheral side nearby the second electrode than that on an inner peripheral side connected to the first electrode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor device to which a high voltage is applied.

Patent Document 1 discloses a technique for improving the breakdown voltage performance of a high breakdown voltage MOSFET (Metal Oxide Semiconductor Field Effect Transistor) used by applying a high voltage.
FIG. 5 is a plan view of a high breakdown voltage MOSFET 900 and a cross-sectional view taken along line AB. In the technique disclosed in Patent Document 1, a circular drain electrode 111 and an annular source electrode 112 are formed on an n-type semiconductor substrate 101 as shown in FIG. A resistor 913 connected to each electrode is disposed between the source electrode 112 and the source electrode 112.

  The resistor 913 is arranged in a spiral shape from the drain electrode 111 toward the source electrode 112 provided on the outer periphery. According to the voltage applied between the drain electrode 111 and the source electrode 112, the electric field generated from the resistor 913 arranged in a spiral shape affects the semiconductor substrate 101 and stabilizes the electric field on the semiconductor substrate 101. Is.

FIG. 5B is a cross-sectional view taken along the line AB in FIG. 5A, an equipotential line between electrodes when a voltage is applied to the drain electrode 111 and the source electrode 112, and a graph showing an electric field. ing.
An n-type source region 105 and a drain region 107 having an impurity concentration higher than that of the semiconductor substrate 101 are formed on the n-type semiconductor substrate 101. The p-type base region 102 includes a source region 105 and also includes a p-type region 106 having a higher impurity concentration than the base region 102 in contact with the source region 105.

  The p-type offset region 103 includes the drain region 107 and is extended toward the source region 105. An n-type offset region 104 is formed on the offset region 103. On the offset region 104, a gate oxide film 108 and a field oxide film 109 formed on a channel portion between the offset region 103 and the base region 102 are formed.

  A gate electrode 110 is formed on the gate oxide film 108. A source electrode 112 is formed on the source region 105 and the region 106. A drain electrode 111 is formed on the drain region 107. A resistor 913 is disposed on the field oxide film 109 as shown in FIG. The resistor 913 has one end connected to the drain electrode 111 and the other end connected to the source electrode 112. On the field oxide film 109, an insulating interlayer film 114 including the resistor 913 and the gate electrode 110 is formed.

  In the MOSFET 900 configured as described above, by providing the resistor 913 as a field plate, the concentration of the electric field generated between the drain electrode 111 and the source electrode 112 is alleviated and the breakdown voltage characteristics are improved. At this time, the electric field generated in the offset regions 103 and 104 and the field oxide film 109 is determined according to the potential at each part of the resistor 913.

JP 2001-024191 A

  Although the resistor 913 is provided in order to reduce the concentration of the electric field between the drain electrode 111 and the source electrode 112, the potential difference between adjacent turns in the resistor 913 is as shown in FIG. The distance between the equipotential lines becomes narrower as compared with the vicinity of the drain electrode 111. This bias in potential difference appears as a bias in electric field strength, and the electric field strength is greatest near the source electrode 112. Here, the potential difference between the drain electrode 111 and the source electrode 112 is an integral value of the electric field strength, and is represented as the area Vb of the shaded area in the graph of FIG.

  The breakdown voltage of MOSFET 900 is determined based on the electric field strength in the vicinity of the source electrode 112 because the portion with the highest electric field strength is determined not to exceed the limit value Emax of the electric field strength that can withstand the structure. At this time, as shown in the graph of FIG. 5B, the electric field strength in the vicinity of the drain electrode 111 has a sufficient margin with respect to the limit value Emax of the electric field strength, and there is room for improving the breakdown voltage.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor device having improved breakdown voltage characteristics.

(1) In order to solve the above problem, the present invention provides a first electrode formed on a semiconductor substrate, a ring-shaped second electrode formed around the first electrode, the first electrode, A resistor connected to the second electrode, and the resistor is spirally disposed around the first electrode, and the spacing between the resistors is in accordance with the distance from the first electrode. A semiconductor device is characterized by having a widened portion.
(2) Further, the present invention is characterized in that, in the above-described invention, the resistor is widened as a space between the spirals becomes farther from the first electrode.
(3) Further, the present invention is characterized in that, in the above-described invention, the shape of the resistor is a self-similar shape.
(4) The spiral shape of the resistor has a declination angle θ relative to a straight line connecting the origin and a connection point where the resistor and the first electrode are connected in a polar coordinate system with the center of the first electrode as the origin. And a distance R from the center of the first electrode is
R = a · b ^ θ
(Where a is the radius of the first electrode, and b is an arbitrary constant), and is a logarithmic spiral satisfying the relationship.
(5) Further, in the present invention described above, the present invention is characterized in that the first electrode is formed in a circular shape, and the second electrode is formed in a circular shape.

  According to the present invention, the electric field generated between the first electrode and the second electrode to which a voltage is applied is affected by the voltage drop in the spiral resistor disposed between the electrodes, and is applied to a specific part. By distributing without concentrating, the semiconductor device can be prevented from being destroyed by the concentration of the electric field when a high voltage is applied, and the breakdown voltage characteristics of the semiconductor device can be improved.

FIG. 1 is a plan view of the semiconductor device 100 according to the first embodiment and a cross-sectional view taken along the line A′B ′. It is a figure which shows the resistor 113 which has a logarithmic spiral as a shape. It is a top view which shows the structure of the semiconductor device 200 of 2nd Embodiment. It is a top view which shows the semiconductor device 300 in 3rd Embodiment. FIG. 6 is a plan view of a high breakdown voltage MOSFET 900 and a cross-sectional view taken along line AB.

  Hereinafter, a semiconductor device in an embodiment of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a plan view of the semiconductor device 100 according to the first embodiment and a cross-sectional view taken along line A′B ′. Here, a case where the semiconductor device 100 is a MOSFET will be described. FIG. 1A is a plan view of the semiconductor device 100. FIG. 1B is a cross-sectional view of the semiconductor device 100 taken along line A′B ′, a graph showing equipotential lines when a voltage is applied between the electrodes, and an electric field between the electrodes.
As shown in FIG. 1A, in the semiconductor device 100, a circular drain electrode 111 and an annular source electrode 112 are formed on an n-type semiconductor substrate 101, and the drain electrode 111 and the source electrode 112 are Between them, the resistors 113 connected to the respective electrodes are arranged.

  The resistor 113 is arranged in a spiral shape from the drain electrode 111 toward the source electrode 112 provided on the outer periphery. For the resistor 113, a material having a high resistance value, for example, polysilicon, a thin metal, a polycrystalline semiconductor, a metal oxide, ceramics, glass, a conductive polymer, or the like is used. In addition, since parts other than the resistor 113 are the same as the configuration shown in FIG. 5, the corresponding parts are denoted by the same reference numerals (101 to 112, 114), and description thereof is omitted.

Here, the shape of the resistor 113 is a logarithmic spiral in which the distance between the spirals of the resistor 113 increases as the distance from the drain electrode 111 increases, that is, the spiral diameter increases toward the outer peripheral side. This logarithmic spiral is a curve represented by the following equation (1).
R = a · b ^θ (1)
However, θ is a deviation angle with respect to a straight line connecting the connection point connecting the drain electrode 111 and the resistor 113 to the origin in the polar coordinate system with the center of the drain electrode 111 as the origin. R is the distance from the origin in the polar coordinate system, a is the radius of the drain electrode 111, and b is an arbitrary constant that determines the density of the spiral of the logarithmic spiral.

FIG. 2 is a diagram showing a resistor 113 having a logarithmic spiral as a shape. The distances from the origin O to the points a, b, and c are r1, r2, and r3, respectively. However, the electrical resistivity of the resistor 113 is constant.
At this time, the length Lab of the resistor 113 from the point a to the point b, the distance Δab from the point a to the point b, the length Lbc of the resistor 113 from the point b to the point c, and the point b to the point b The distance Δbc to c is expressed by the following equations (2) to (5).

Lab≈2π {(r1 + r2) / 2} (2)
Δab = r2-r1 (3)
Lbc≈2π {(r2 + r3) / 2} (4)
Δbc = r3-r2 (5)

Here, if the current flowing through the resistor 113 when a voltage is applied to the point T1 and the point T2 is constant, the resistance value is proportional to the potential difference, the voltage difference Vab between the point a and the point b, and the point The voltage difference Vbc between b and point c is proportional to the length of the resistor 113 between each point.
Vab∝Lab (6)
Vbc∝Lbc (7)
Note that ∝ means that the left side is proportional to the right side.

Further, the electric field Eab between the point a and the point b and the electric field Ebc between the point b and the point c are expressed by the following equations (8) and (9).
Eab = Vab / Δab (8)
Ebc = Vbc / Δbc (9)

When the electric field Eab and the electric field Ebc are the same, the following equation (10) is established.
Vab / Δab = Vbc / Δbc (10)
Here, when the equations (2) to (7) are substituted into the equation (10), the following equation (11) is obtained.
(R1 + r2) / (r2-r1) = (r2 + r3) / (r3-r2) (11)

If formula (11) is expanded and arranged,
r1 / r2 = r2 / r3 (12)
It becomes. When the electric field strength is constant, the shape of the resistor 113 is a spiral having a radius that expands at a constant ratio, as shown in Expression (12). Such a spiral is generally known as a logarithmic spiral and is represented by the formula (1) in the polar coordinate system.

  By arranging the resistor 113 having a logarithmic spiral shape, the potential change between the drain electrode 111 and the source electrode 112 can be made constant as shown in FIG. The distribution can be made uniform. As a result, an electric field close to the upper limit that can be tolerated in the structure of the semiconductor device 100 can be applied from the vicinity of the drain electrode 111 to the vicinity of the source electrode 112, and the breakdown voltage characteristics can be improved.

  In addition, without increasing the distance between the electrodes in order to improve the withstand voltage characteristics, the withstand voltage characteristics can be improved by arranging the resistor 113 having a logarithmic spiral shape, and the semiconductor device 100 can be downsized. Can do.

  In the present embodiment, the case where the semiconductor device 100 is a MOSFET has been described. However, the present invention is not limited to a MOSFET. For example, a logarithmic spiral resistor is provided between an anode and a cathode of a diode to increase the breakdown voltage. May be. Further, the resistance element may have a high withstand voltage by forming the resistor in a logarithmic spiral shape with respect to the resistance element having two electrodes and a resistor connected to the electrodes. In this manner, by applying to various semiconductor devices, it is possible to prevent the electric field generated between the electrodes from being biased, and to improve the breakdown voltage characteristics.

Second Embodiment
FIG. 3 is a plan view showing the configuration of the semiconductor device 200 of the second embodiment. The semiconductor device 200 is a modification of the semiconductor device 100 of the first embodiment, and includes a polysilicon wiring 213 in which p-type regions 213a and n-type regions 213b are alternately provided in place of the resistor 113. It is a thing. Except for the above points, the configuration of the semiconductor device 200 is the same as the configuration of the semiconductor device 100, and thus the description thereof is omitted.
Like the semiconductor device 100 of the first embodiment, the polysilicon wiring 213 is provided between the drain electrode 111 and the source electrode 112, and the shape thereof is a logarithmic spiral.

  Since the semiconductor device 200 includes the polysilicon wiring 213 having a plurality of stages of pn diodes instead of the resistor 113, the flowing current can be made constant by the reverse saturation current of the pn diode, Leakage current of the semiconductor device 100 can be reduced and power consumption can be reduced.

<Third Embodiment>
FIG. 4 is a plan view showing a semiconductor device 300 according to the third embodiment. The semiconductor device 300 includes a high voltage circuit 301, a low voltage circuit 302, a low potential electrode 303, and a resistor 304.

The high voltage circuit 301 is a circuit that outputs a signal having a voltage of several hundred [V] to 1000 [V] with respect to a reference potential, for example, a ground potential. The low voltage circuit 302 outputs a signal for controlling the high voltage circuit 301. The voltage used in the low voltage circuit 302 is several [V] with respect to the ground potential [V].
The lower electrode 303 is an electrode that supplies a ground potential. The resistor 304 connects the high voltage circuit 301 and the low level electrode 303. Moreover, the shape of the resistor 304 is a logarithmic spiral, like the resistor 113 of the first embodiment.

  The semiconductor device 300 includes two circuits having different voltages, the high voltage circuit 301 and the low voltage circuit 302, as described above, and a high potential side electrode of the high voltage circuit 301 and a low potential electrode 303 are formed in a logarithmic spiral shape. The resistor 304 is connected. As a result, the electric field generated between the high voltage circuit 301 and the lower electrode 303 can be made uniform and concentration of the electric field can be prevented. In addition, since the electric field in the vicinity of the high voltage circuit 301 can be stabilized by the resistor 304 and the influence on the low voltage circuit 302 can be reduced, the high voltage circuit 301 and the low voltage circuit 301 are placed on the same silicon substrate. This makes it easy to make monolithic.

  In the first to third embodiments described above, the resistance of the resistor 113 as a whole may be increased by increasing the overall distance between the spirals of the resistor 113 (304) and the polysilicon wiring 213. . Thereby, the current (leakage current) flowing through the resistor 113 can be reduced, and power consumption can be reduced.

  In the first to third embodiments described above, the resistor 113 (304) and the polysilicon wiring 213 have been described as having a logarithmic spiral shape as a whole. However, the resistor 113 (304 ) And a part on the outer peripheral side including the outermost periphery of the polysilicon wiring 213 has a logarithmic spiral shape, and the other part has a shape other than the logarithmic spiral, for example, the spirals on the inner peripheral side are equally spaced. Good. In this case, at least the concentration of the electric field in the vicinity of the source electrode 112 and the lower electrode 303 can be avoided, and the breakdown voltage characteristics of the semiconductor device can be improved. Here, in the vicinity of the source electrode 112 and the lower electrode 303, at least in the resistor 113 (304) and the polysilicon wiring 213, the linear distance to the source electrode 112 and the lower electrode 303 is the drain electrode 111 and the high voltage circuit 301. This indicates a range shorter than the straight line distance up to.

  In the first to third embodiments described above, the intensity of the electric field generated between the electrodes is made uniform by applying the logarithmic spiral shape. However, the resistor 113 (304) and the polysilicon wiring 213 are used. On the other hand, without using a logarithmic spiral shape, the thickness of the resistor 113 (304) and the polysilicon wiring is increased as it approaches the outer peripheral portion, and the resistance value is changed to make the electric field strength between the electrodes uniform. You may make it.

  For example, in the resistor 913 of FIG. 5, the potential difference between the points 913a and 913b, the potential difference between the points 931b and 913c, and the potential difference between the points 913c and 913d are directed in the outer circumferential direction. The resistor 913 is thickened so that the resistance value from the point 913a to the point 913b, the resistance value from the point 913b to the point 913c, and the resistance value from the point 913c to the point 913d are the same. Thereby, even if it is a spiral of equal intervals, the same effect as a logarithmic spiral can be obtained.

  In the first to third embodiments described above, the resistor 113 (304) and the polysilicon wiring 213 have a spiral shape based on a circle. The drain electrode 111 and the high voltage circuit 301 may be wound in a spiral shape based on a racetrack. In this case, the interval between adjacent turns of the resistor 113 (304) has a shape that becomes wider as the distance from the center increases. The shape of the resistor 113 (304) is a self-similar shape. As a result, the electric field distribution between adjacent turns of the resistor 113 (304) arranged in an elliptical shape or an oval shape is uniform, and the concentration of the electric field can be prevented, as in the case of the logarithmic spiral shape. The withstand voltage characteristics can be improved.

  DESCRIPTION OF SYMBOLS 100 ... Semiconductor device, 101 ... Semiconductor substrate, 102 ... Base region, 103 ... Offset region, 104 ... Offset region, 105 ... Source region, 106 ... Region, 107 ... Drain region, 108 ... Gate oxide film, 109 ... Field oxide film 110 ... Gate electrode, 111 ... Drain electrode, 112 ... Source electrode, 113 ... Resistor, 114 ... Insulating interlayer film, 200 ... Semiconductor device, 213 ... Polysilicon wiring, 213a ... p-type region, 213b ... n-type Region 300 semiconductor device 301 high voltage circuit 302 low voltage circuit 303 low electrode 304 resistor 900 MOSFET 913 resistor

Claims (5)

A first electrode formed on a semiconductor substrate; an annular second electrode formed around the first electrode; and a resistor connected to the first electrode and the second electrode.
The resistor is arranged in a spiral shape around the first electrode, and an interval between spirals on the outer peripheral side in the vicinity of the second electrode is larger than an interval between spirals on the inner peripheral side connected to the first electrode. A semiconductor device characterized by its large size. The semiconductor device according to claim 1, wherein the resistor has a wider spiral distance as the distance from the first electrode increases. The semiconductor device according to claim 1, wherein the resistor has a self-similar shape. The spiral shape of the resistor has a declination angle θ relative to a straight line connecting the origin and a connection point where the resistor and the first electrode are connected in a polar coordinate system with the center of the first electrode as the origin, and The distance R from the center of the first electrode is
R = a · b ^ θ (where a is the radius of the first electrode and b is an arbitrary constant)
The semiconductor device according to claim 1, wherein the semiconductor device is a logarithmic spiral satisfying the relationship: 5. The semiconductor device according to claim 1, wherein the first electrode is formed in a circular shape, and the second electrode is formed in an annular shape.

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