JPH0618270B2 - Shutter-barrier barrier semiconductor device - Google Patents

Description

The present invention relates to a high breakdown voltage shutter barrier semiconductor device.

[Problems to be Solved by Prior Art and Invention]

The shutter barrier diode is widely used in a high-frequency rectifier circuit and the like by taking advantage of good high-speed response (high-speed switching characteristic) and low loss. But,
The breakdown voltage of the shutter barrier barrier diode (the breakdown voltage around the shutter barrier) is significantly lower than the bulk breakdown voltage (the breakdown voltage at the center of the shutter barrier).
There is a problem that it is difficult to increase the breakdown voltage.

Providing a field plate or a guard ring in order to solve this problem is known, for example, in the second edition of "Fixix of Semiconductor Devices" by S.M.J.E., USA. Also,
The use of both field plates and guard rings has already been done.

A shutter plate barrier diode having a field plate structure includes an n ⁺ type semiconductor region, an n type semiconductor region formed on the n ⁺ type semiconductor region, and a metal electrode capable of forming a shutter barrier formed on the n type semiconductor region (hereinafter referred to as a barrier electrode). Call)
An insulating layer formed on the n-type semiconductor region so as to surround the barrier electrode, a field plate provided on the insulating layer and connected to the barrier electrode, and an ohmic contact connected to the n ⁺ type semiconductor region. It consists of electrodes. When a reverse voltage is applied between the barrier electrode and the ohmic electrode, a depletion layer is generated between the barrier electrode and the n-type semiconductor region, and
A depletion layer is also generated in the n-type semiconductor region below the field plate due to the field effect of the field plate, and the concentration of the electric field on the peripheral portion of the barrier electrode is relieved, and the peripheral breakdown voltage of the Schottky barrier is improved. However, it was practically difficult to satisfactorily reduce the concentration of the electric field and significantly improve the breakdown voltage.

On the other hand, a Schottky barrier diode having a guard ring structure has a guard ring which is connected to the periphery of the barrier electrode in plan view and is formed of ap ⁺ type semiconductor region arranged so as to surround the barrier electrode. The p ⁺ type semiconductor region of the guard ring forms a pn junction with the n type semiconductor region.
When a reverse voltage is applied to the junction, the depletion layer spreads more effectively than around the shutter barrier. As a result, the breakdown voltage around the barrier electrode can be improved. However, since the structure is such that the Schottky barrier diode and the pn junction diode are arranged in parallel, when a forward voltage is applied and a forward current flows, a small number of carriers are injected at the pn junction portion, and High-speed response, which is one of the features, is reduced. Further, although the guard ring structure is widely used in combination with the field plate structure, it is still difficult to significantly increase the breakdown voltage.

In order to solve the above problems, it is known to form a resistance layer having a taper and a Schottky barrier effect around the Schottky barrier electrode.
No. 1463. According to this method
Certainly, high breakdown voltage is possible.

However, this patent publication does not disclose a technique for suppressing breakdown that occurs in a minute region at the outer peripheral edge of the resistance layer.

Therefore, an object of the present invention is to suppress the breakdown of the outer peripheral edge of the resistance layer in the Schottky barrier semiconductor device having a structure capable of increasing the breakdown voltage while ensuring high-speed response.

[Means for Solving the Problems] The present invention for achieving the above object includes a semiconductor region and a barrier electrode arranged on the semiconductor region so as to form a Schottky barrier between the semiconductor region and the semiconductor region. The Schottky barrier is disposed on the semiconductor region so as to surround the barrier electrode, is electrically connected to the barrier electrode, has a larger sheet resistance than the barrier electrode, and has a Schottky barrier between the barrier region and the semiconductor region. And a thin layer formed so as to obtain an outer peripheral edge region of the thin layer by ohmic contact with an outer peripheral edge region of the thin layer and a portion of the semiconductor region surrounding the outer peripheral edge of the thin layer, respectively. A Schottky barrier formed by the barrier electrode and a Schottky barrier formed by the thin layer are connected directly or via a pn junction. The present invention relates to Schottky barrier semiconductor devices.

[Operation] In the above invention, when a reverse voltage is applied between the barrier electrode and the semiconductor region, a depletion layer based on a shutter barrier between the barrier electrode and the semiconductor region and between the thin layer and the semiconductor region are formed. A depletion layer based on a rocket barrier is generated. Since the thin layer surrounds the barrier electrode, when the thin layer surrounds the barrier electrode adjacently, the two depletion layers are continuous with each other, and the guard ring of the p ⁺ type region is formed as in the example described later. When provided, the two depletion layers are continuous through the depletion layer of the pn junction. A potential gradient in which both the barrier electrode and the thin layer generate a Schottky barrier between the semiconductor region and the potential is gradually changed from the inner side to the outer side of the thin layer because the thin layer is a resistor. Occurs. As a result, the depletion layer can be spread so that the electric field is not concentrated on the peripheral edge of the barrier electrode, and the breakdown voltage is significantly improved.

By the way, when the connecting object according to the present invention is not provided so as to surround the thin layer, when a reverse voltage is applied, a breakdown occurs in a minute region at the outer peripheral end of the thin layer, and based on this, a reverse current is generated in the thin layer. Flowing through. The reverse current due to this minute breakdown is controlled and does not become so large because the thin layer is a resistor. However, due to the breakdown of the micro area, the micro area is burned out, and although it does not reach a defective level, it causes an increase in reverse current in the small signal area. On the other hand, the connection object according to the present invention (conductor or low resistance semiconductor, etc.)
In the case of having a thin film, since the periphery of the thin layer is electrically connected to the semiconductor region, breakdown does not occur here, the reverse current changes smoothly, and a Schottky barrier diode with less noise is provided. can do. Also,
Since the burnout does not occur, the characteristic fluctuation is reduced.

[First Embodiment] A shutter barrier diode according to a first embodiment of the present invention and a method for manufacturing the same will be described with reference to FIGS. 1 and 2.

First, as shown in FIG. 2 (A), GaAs (gallium arsenide)
A semiconductor substrate 21 made of is prepared. This semiconductor substrate 2
1 has a thickness of 300 μm and an impurity concentration of 1 to 3 × 10 ¹⁸ cm ⁻³
A thickness of 10 to 20 μm and an impurity concentration of 1 on the n ⁺ type region 22.
The n-type region 23 of up to 2 × 10 ¹⁵ cm ⁻³ is epitaxially grown.

Next, as shown in FIG. 2 (B), a thin layer 24 of Ti (titanium), that is, a Ti thin film, is formed by vacuum evaporation on the entire upper surface of the n-type region 23 made of n-type GaAs, and further on the entire upper surface. The Al (aluminum) layer 25 is continuously vacuum-deposited. The thickness of the Ti thin layer 24 is 50Å to 200Å (0.005 to 0.02 μm)
And is extremely thin. The Al layer 25 has a thickness of about 2 μm and the Ti thin layer 24
Is more than 100 times. Further, Au is formed on the lower surface of the n ⁺ type region 22.
The ohmic contact electrode 26 made of an alloy of (gold) -Ge (germanium) is formed by vacuum evaporation, and then 380
Heat treatment is performed at 10 ° C. for 10 seconds.

Next, as shown in Fig. 2 (C), A
A part of the l layer 25 is removed by etching to leave the Al layer 25a corresponding to the shutter barrier electrode which serves as the main forward current path. Further, the Ti thin layer 24 is removed from the peripheral region of the element by photo-etching, and is located under the Al layer 25a.
The Ti thin layer 24a and the Ti thin layer 24b surrounding and surrounding the Ti thin layer 24a are left. Since the Ti thin layers 24a and 24b are extremely thin films even if Ti itself is a conductor, the sheet resistance is 20 to 400.
It is a resistance layer of Ω / □, and has an order of magnitude higher resistance than the Al layer 25a.

Next, heat treatment is performed in air at 300 ° C. for 5 to 30 minutes. As a result, the Ti thin layer 24b not covered by the Al layer 25a is oxidized as shown in FIG.
The titanium oxide thin layer 28 shown in FIG. The Ti thin layer 24a below the Al layer 25a is not oxidized because it is masked by the Al layer 25a. Since both Al and Ti are metals that form a shock barrier between GaAs and Al, the Al layer 25a and the Al layer 25
The metal electrode composed of the Ti thin layer 24a located under a is referred to as a barrier electrode 27. As shown in FIG. 3, a titanium oxide thin layer 28 is arranged adjacent to the outer periphery of the barrier electrode 27 with the barrier electrode 27 at the center. Further, as shown in FIGS. 2 (D) and 3, an ohmic connection electrode 29 is arranged on the outer peripheral end side of the titanium oxide thin layer 28 so as to surround the titanium oxide thin layer 28 over the entire circumference. Has been done. The ohmic connection electrode 29 is made of an Au (gold) -Ge (germanium) alloy, is in ohmic contact (low resistance) with both the n-type region 23 and the titanium oxide thin layer 28, and has the n-type region 23 and the titanium oxide thin layer. It is a conductor that electrically connects 28. That is, the titanium oxide thin layer 28 and the n-type region 23 are electrically connected to each other via the ohmic connection electrode 29. In the barrier electrode 27, the Ti thin layer 24a is an extremely thin film.
It is not always clear how the Al layer 25a and the Ti thin layer 24a are involved in the formation of the shutter barrier. Further, the Ti thin layer 24a contributes to the improvement of the adhesiveness of the Al layer 25a to the n-type region 23 as a role other than the formation of the shutter barrier. The sheet resistance of the barrier electrode 27 is 1Ω.
/ □ or less is desirable, and in this embodiment, it is about 0.05Ω / □. The titanium oxide thin layer 28 according to the present invention shown in FIG. 2 (D) is larger than the layer thickness of the Ti thin layer 24b, and is approximately 75Å-.
It is 300 Å, and is a semi-insulating high resistance layer with a sheet resistance of 50 to 500 MΩ / □. That is, the titanium oxide thin layer 28 can be regarded as a perfect insulator TiO ₂ (titanium dioxide).
However, it is considered that the titanium oxide is a so-called oxygen-buer titanium oxide TiO _x (x is a numerical value smaller than 2) having less oxygen than TiO ₂ .

Subsequently, as shown in FIG. 1, the titanium oxide thin layer 28 is formed.
An insulating layer 30 for covering the semiconductor chip is provided to complete a semiconductor chip having a shutter barrier, that is, a power shutter diode diode chip. The insulating layer 30 is a plasma CV.
It is made of a silicon oxide film formed by the D (chemical vapor deposition) method. The insulating layer 30 may be replaced with a silicon nitride film formed by plasma CVD or photo CVD method, a polyimide resin film formed by coating method, or the like, but a silicon oxide film formed by plasma CVD method or photo CVD method is preferable. Atsuta Although illustration is omitted, Al
It is usual that, for example, a Ti layer and an Au layer are sequentially provided on the upper surface of the layer 25a to serve as a connecting electrode for the lead member.

The dimensions of each part in FIG. 3 are exemplified as follows. The width a of the barrier electrode 27 is about 900 μm, and the titanium oxide thin layer 2
8 has a width b of about 140 μm, the ohmic contact electrode 29 has a width c of about 30 μm, the titanium oxide thin layer 28 and the n-type region 23.
The distance d from the edge of is about 150 μm.

In this shutter barrier diode, not only a first shutter barrier occurs between the barrier electrode 27 and the n-type region 23, but also a second shutter barrier occurs between the titanium oxide thin layer 28 and the n-type region 23. Is formed.
The occurrence of the second shutter barrier was confirmed by the rectification characteristics, capacitance characteristics, saturation current characteristics, etc. of the shutter barrier diode. For example, when the area of the titanium oxide thin layer 28 is increased from zero, the saturation current I _S increases substantially in proportion to the sum of the areas of the titanium oxide thin layer 28 and the barrier electrode 27. It has been confirmed that this proportional relationship can be obtained at various temperatures of the shutter barrier diode. This means that a reverse current flows through the titanium oxide thin layer 28 at substantially the same current density as the barrier electrode 27. This phenomenon is caused by the titanium oxide thin layer 28 having substantially the same barrier height φ as the barrier electrode 27.
It clearly shows that it forms a cypress tree barrier with _B.

Next, the reverse voltage-reverse current characteristic of the shutter barrier diode according to the present invention will be described below. When the reverse voltage applied to the shutter barrier diode is gradually increased from zero volt, a very small saturation current I _S flows through the shutter barrier diode. At this time, a reverse current flows through the first shutter barrier based on the barrier electrode 27, and also a reverse current flows through the second shutter barrier based on the titanium oxide thin layer 28. The reverse voltage application circuit is connected to the barrier electrode 27, that is, the anode and the ohmic electrode 26, that is, the cathode, and is not directly connected to the titanium oxide thin layer 28 and the ohmic connecting electrode 29. Therefore, the current passing through the ohmic connection electrode 29 and the titanium oxide thin layer 28 flows into the barrier electrode 27. As the reverse voltage is increased, the reverse current I ₀ passing through the current path passing through the ohmic connection electrode 29 and the titanium oxide thin layer 28 and reaching the barrier electrode 27 increases. Since the titanium oxide thin layer 28 is a semi-insulating high resistance layer, current limitation is caused by the resistance component of the titanium oxide thin layer 28, so that the reverse current I ₀ gradually increases as the reverse voltage increases. Show the characteristics. Further, as the reverse current increases, the reverse current passing through the first shutter barrier based on the barrier electrode 27 and the second shutter barrier based on the titanium oxide thin layer 28 also gradually increases.

Since the voltage is applied not only to the barrier electrode 27 but also to the titanium oxide thin layer 28, the depletion layer 3 schematically shown in FIG.
1 is n under the barrier electrode 27 and the titanium oxide thin layer 28.
It occurs in the mold area 23. As the reverse voltage increases, the potential gradient in the lateral direction from the inner peripheral edge P ₁ to the outer peripheral edge P ₂ of the titanium oxide thin layer 28 gradually increases, and as a result, the titanium oxide thin layer 28 and the n ⁺ -type region The electric potential difference with respect to 23 decreases from the inner peripheral end P ₁ toward the outer peripheral end P ₂ . For this reason, the spread of the depletion layer 31 (the thickness in the vertical direction) is also the inner peripheral edge P ₁
Becomes smaller from the outer edge P ₂ toward the outer edge. Further, the surface of the n-type region 23 from the barrier electrode 27 to the titanium oxide thin layer 28 continues as a shutter barrier.
As a result of these, the gentle depletion layer 3 that alleviates the electric field concentration
1 is obtained, and the electric field concentration at the peripheral edge of the barrier electrode 27 is relaxed.

When the reverse voltage is about 250 V, a portion exceeding the critical electric field strength Ecrit occurs between the peripheral edge of the barrier electrode 27 and the ohmic electrode 26, causing breakdown, and the reverse current sharply increases.

In addition, if a Schottky barrier diode having a structure in which the ohmic connection electrode 29 is not provided is used, as the reverse voltage increases,
Breakdown occurs in a plurality of minute regions in the outer peripheral edge of the thin titanium oxide layer 28, and the reverse current increases stepwise.
In the Schottky barrier diode of FIG. 1 according to the present invention, the titanium oxide thin layer 28 and the n-type region 23 are ohmic-connected by the ohmic connecting electrode 29, and the titanium oxide thin layer is conductive when a reverse voltage is applied. No breakdown occurs at the outer edge of 28. A solid line characteristic curve of FIG. 5 shows a reverse voltage-reverse current characteristic of the Schottky barrier diode of FIG. 1 according to the present invention, and a broken line characteristic curve of a Schottky barrier diode having no ohmic connecting electrode 29. The reverse voltage-reverse current characteristic is shown. It can be seen that the reverse current changes smoothly in the Schottky barrier diode of FIG. 1 as compared with the structure without the ohmic connection electrode 29.

Further, in the case of the structure without the ohmic connection electrode 29,
When a breakdown occurs in a minute region at the outer peripheral edge of the titanium oxide thin layer 28, the reverse current accompanying the breakdown flows concentratedly in the minute region. As a result, the potential distribution in the lateral direction of the titanium oxide thin layer 28 due to the reverse current is not uniform over the entire circumference of the titanium oxide thin layer 28. In the Schottky barrier diode of FIG. 1 according to the present invention, the outer peripheral edge of the titanium oxide thin layer 28 and the n-type region 23 are formed.
And are connected in an ohmic manner all around. Therefore, from the outer peripheral edge P _{1 of the} titanium oxide thin layer 28 to the barrier electrode 27
The electric current to the titanium oxide thin layer 28 is substantially uniform over the entire circumference thereof. As a result, the potential distribution based on the reverse current from the inner peripheral edge P ₁ to the outer peripheral edge P ₂ of the titanium oxide thin layer 28 is substantially equal over the entire circumference of the ring-shaped titanium oxide thin layer 28. When the shutter barrier diode of this embodiment was used as a rectifying diode of a switching regulator having a switching frequency of 500 kHz, it was confirmed that a rectifying operation with extremely little noise was generated.
No decrease in the switching speed (high-speed response) due to the provision of the titanium oxide thin layer 28 was observed.

The shutter barrier diode of this embodiment has the following advantages.

(1) Since the titanium oxide thin layer 28 is a resistor having a high sheet resistance and is a material capable of forming a shutter barrier, a depletion layer that effectively relaxes the electric field concentration at the outer peripheral edge of the barrier electrode 27 is satisfactorily generated. . Therefore, the breakdown voltage can be significantly improved as compared with a Schottky barrier diode having a structure in which only a field plate or a guard ring is provided, or a Schottky barrier diode having a structure in which both a field plate and a guard ring are provided. The titanium oxide thin layer 28 of the Schottky barrier diode according to the present embodiment has the function of limiting the reverse current as well as the function of forming the depletion layer for alleviating the electric field concentration, similarly to the high resistance field plate made of polycrystal silicon. Have. However, unlike the high resistance field plate, the titanium oxide thin layer 28 of this embodiment can form a shutter barrier between itself and the n-type region 23. Therefore, the electric field concentration in the n-type region 23 below the boundary surface between the barrier electrode 27 and the titanium oxide thin layer 28 can be effectively relaxed, and the breakdown voltage is improved as compared with the conventional Schottky barrier diode having the high resistance field plate structure. To do.

(2) High-speed response is superior to the conventional Shoutoki barrier diode having a guard ring.

(3) The thermal instability of the characteristics found in the conventional Schottky barrier diode having a structure in which a field plate or a high resistance field plate is provided via an insulating layer has been resolved.

(4) The titanium oxide thin layer 28 is obtained by oxidizing the Ti thin layer 24b, which is the extended portion of the Ti thin layer 24a provided immediately below the Al layer 25a, and thus the target titanium oxide thin layer 28 can be easily formed. Can be obtained. In addition, the electrical connection between the barrier electrode 27 and the titanium oxide thin layer 28 can be easily and surely achieved.

(5) Since the ohmic connection electrode 29 is provided, the characteristic variation is small. That is, in the Schottky barrier diode having a structure without the ohmic connection electrode 29, the titanium oxide thin layer 28 is used.
In some cases, a current due to the breakdown flows intensively in a minute area on the outer peripheral edge of the, and the minute area is burned out. This burnout causes an increase in the reverse current in the small signal region although it does not reach a defective level in the BT test (test in which a reverse voltage is applied at a high temperature) and the like. In the Schottky barrier diode of this embodiment, as described above, the titanium oxide thin layer 28 and the n-type region 23 are substantially electrically connected to each other at the reverse voltage application level, and the above burnout does not occur, and No accompanying characteristic changes occur.

(6) Since breakdown does not occur at the outer peripheral edge of the titanium oxide thin layer 28, a reverse voltage-reverse current characteristic with a smoother change in reverse current can be obtained as compared with the structure without the ohmic connection electrode 29. Therefore, it is possible to provide a high breakdown voltage Schottky barrier diode for small signals with less noise.

(7) By providing the ohmic contact electrode 29 in a closed ring shape over the entire circumference of the titanium oxide thin layer 28, the potential distribution in the lateral direction of the titanium oxide thin layer 28 can be made substantially equal over the entire circumference. . Therefore, the concentration of the electric field can be effectively alleviated, the frequency of occurrence of products having a specified breakdown voltage or less is reduced, and the breakdown voltage yield can be further improved.

[Second Embodiment] Next, a shutter barrier diode according to a second embodiment of the present invention shown in FIG. 6 will be described. However, in FIG. 6 and FIG. 7 and FIG. 8 which will be described later, parts that are substantially the same as in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted.

The shutter barrier diode shown in FIG. 6 has an Al layer 25b and an Al layer.
The outer periphery of the barrier electrode 27 composed of the Ti thin layer 24c located under the layer 25b is covered with the Ti thin layer 24d and the titanium oxide thin layer 28.
And have a structure in which they are successively adjacently surrounded. The titanium oxide thin layer 28 and the barrier electrode 27 are electrically connected via the Ti thin layer 24d. Further, the outer peripheral end of the titanium oxide thin layer 28 is in ohmic contact with the n-type region 23 through an ohmic contact electrode 29 made of an Au--Ge alloy as in the case of the Schottky barrier shown in FIG. Here, the Ti thin layer 24d has a smaller sheet resistance than the titanium oxide thin layer 28, and forms a shock barrier between itself and the n-type region 23, and therefore acts as a part of the barrier electrode 27. Therefore, hereinafter, the Al layer 25b and the Ti thin layer 24 located below the Al layer 25b will be described.
The portion composed of c is the first barrier electrode 27a and the Ti thin layer 24.
The portion composed of d will be referred to as the second barrier electrode 27b.

In the shutter barrier diode of FIG. 6, the peripheral edge of the Al layer 25a is removed by etching after the step of FIG. 2 (D) to expose a part of the Ti thin layer 24a under the Al layer 25a to expose the second thin layer. It can be manufactured by obtaining the barrier electrode 27b.

In the Schottky barrier diode of FIG. 6, the stress concentration point and the electric field concentration point can be separated, and the withstand voltage yield can be further improved. That is, the relatively thick first barrier electrode 27
The stress due to the difference in the coefficient of thermal expansion between the a and n-type regions 23 is n
It occurs in the mold area 23. Since the second barrier electrode 27b and the titanium oxide thin layer 28 are extremely thin, these stresses are
It can be ignored as compared with that of the barrier electrode 27a. Therefore, the first barrier electrode 2 on the surface of the n-type region 23
At the lower part of the peripheral edge of 7a, a stress concentration point where the stress is concentrated occurs.

Further, an electric field concentration point is generated in the semiconductor region located below the boundary portion between the layers having greatly different sheet resistances. In the Schottky barrier diode shown in FIG. 5, an electric field concentration point is generated in the n-type region 23 below the boundary between the second barrier electrode 27b and the titanium oxide thin layer 28. N at the stress concentration point
Since the mold region 23 is strained, the critical electric field strength Ecrit that causes breakdown is lower than that in other portions. Therefore, if the electric field is concentrated at this stress concentration point, breakdown is more likely to occur. In the Schottky barrier diode of FIG. 6, since the electric field concentration point and the stress concentration point can be separated from each other as described above, the breakdown voltage can be further increased. The shutter barrier diode shown in FIG. 6 also has the effect of the shutter barrier diode shown in FIG. Further, it has an effect of increasing the reverse surge withstand capacity, though it is slightly less than that of the Schottky barrier diode shown in FIG.

[Third Embodiment] A shutter barrier diode according to a third embodiment of the present invention shown in FIG. 7 is a connection portion between the Ti thin layer 24a and the titanium oxide thin layer 28 of the shutter barrier diode shown in FIG. It has a structure in which a thick Ti thin layer 32 is provided under. The Ti thin layer 32 is an extremely thin film having a thickness of 100 to 400 Å at all times. In this case, the portion of the Ti thin layer 32 that is off the lower portion of the Al layer 25c can be considered as a part of the barrier electrode 27. Hereinafter, the portion including the Al layer 25c, the Ti thin layer 24a, and the thick Ti thin layer 32 is referred to as the first barrier electrode 27a and the thick Ti layer 32a.
The rest of the thin layer 32 will be referred to as the second barrier electrode 27b. The outer peripheral edge of the titanium oxide thin layer 28 is in ohmic contact with the n-type region 23 by an ohmic contact electrode 29 made of an Au-Ge alloy as in the Schottky barrier diode shown in FIG.

The shutter barrier diode shown in FIG. 7 has a thick Ti thin layer 3
By forming 2 on the n-type region 23 in advance by vacuum vapor deposition or the like, it can be manufactured by the same manufacturing method as in FIGS. 2B to 2D.

In the Schottky barrier diode of FIG. 7, the second barrier electrode 27b is formed of the thick Ti thin layer 32, so that the reverse surge withstand effect is more remarkable than that of the Schottky barrier diode of FIG. That is, when the resistance of the portion of the second barrier electrode 27b is large, the large current at the time of breakdown flows concentratedly on the peripheral portion of the first barrier electrode 27a, so that the surge withstand amount in the reverse direction becomes small. In this embodiment, the thickness of the second barrier electrode 27b is increased, and the resistance is further lowered than that of the Schottky barrier diode shown in FIG. 6, so that the second barrier electrode 27b serves as a passage for the reverse surge current. Works more effectively than a Schottky barrier diode. As a result, it is possible to alleviate that the reverse surge current disperses and flows in a plurality of locations on the outer peripheral end side of the second barrier electrode 27b and concentrates a large current as described above, thereby increasing the reverse surge withstand capability. . Further, in the peripheral portion of the first barrier electrode 27a where the Ti thin layer 32 is provided, a Schottky barrier having a barrier height φ _B larger than that of the Ti thin layer 24a is formed. Therefore, the peripheral breakdown voltage of the main shutter barrier is improved, and the breakdown voltage of the shutter barrier is further improved. It also has the effect of the shutter barrier diode shown in FIG.

[Fourth Embodiment] FIG. 8 shows a shutter barrier diode according to a fourth embodiment of the present invention. The Schottky barrier diode shown in FIG. 8 has a ring-shaped titanium oxide thin layer 28a on the surface of the n-type region 23, and further has a ring-shaped titanium oxide thin layer 28b thereon. Titanium oxide thin layers 28a, 28b
The outer peripheral ends of the respective electrodes are ohmic-connected to the n-type region 23 by ohmic-connection electrodes 29 made of Au-Ge alloy. Two Ti thin layers 24e located under the Al layer 25a,
Two Ti thin layers 24g, 24h corresponding to the extended portion of 24f
Acts as a part of the barrier electrode 27.
Two Ti thin layers 2 located under the layer 25a and the Al layer 25a
The metal electrode portion composed of 4e and 24f is referred to as a first barrier electrode 27a, and the metal electrode portion composed of two Ti thin layers 24g and 24h is referred to as a second barrier electrode 27b. The lower titanium oxide thin layer 28a is the upper titanium oxide thin layer 2
Since the degree of oxidation is stronger than 8b, the sheet resistance is higher than that of the upper titanium oxide thin layer 28b. Therefore, the current flowing through the upper titanium oxide thin layer 28b becomes larger than the current flowing through the lower titanium oxide thin layer 28a, and the potential gradient is mainly determined by the upper titanium oxide thin layer 28b. . Since the lower titanium oxide thin layer 28a has a high barrier height φ _B , it is possible to provide a Schottky barrier diode with a reduced saturation current I _{S and} a small reverse current level. Further, the inner peripheral edges of the upper titanium oxide thin layer 28b and the lower titanium oxide thin layer 28a do not coincide with each other, and are in a step shape. Therefore, the second barrier electrode 27b composed of the Ti thin layers 24g and 24h and the titanium oxide thin layers 28a and 2h are formed.
The sheet resistance at the boundary with 8b changes in two steps, and the electric field concentration at the lower part of the boundary can be alleviated, and the withstand voltage can be further improved. It is even better if the change in sheet resistance at this boundary is changed continuously. Further, similarly to the third embodiment, the reverse surge withstand capability can be increased as compared with the first and second embodiments. Further, it also has the effects of the first embodiment.

[Modification]

The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible, for example.

(1) The sheet resistance of the titanium oxide thin layers 28 and 28b varies in an effective range depending on the semiconductor chip structure and size, but is 10 kΩ / □ to 5000 MΩ / □, preferably 10 kΩ / □.
It should be selected from MΩ / □ to 1000 MΩ / □.

(2) When the width b of the titanium oxide thin layer 28 is about 10 μm or more, the effect of improving the withstand voltage appears, and when it is 30 μm or more, the effect becomes remarkable. However, in order to increase the yield to obtain a predetermined breakdown voltage, 100μ
It is more desirable to design it to be m or more. Width b is 500μ
Even if it is set to m or larger than this, a sufficient breakdown voltage improving effect can be obtained. Therefore, there is no upper limit of the width b, but even if the width b is 500 μm or more, not only a proportional increase in breakdown voltage cannot be expected, but also the semiconductor chip becomes large. Therefore, the width b is 30 to 500
It is desirable to set it in the range of μm.

(3) The connecting electrode is not limited to the ohmic connecting electrode 29 made of the Au-Ge alloy of the embodiment, but various modifications are possible. For example, an n ⁺ type region may be formed on the upper surface of the n type region 23 by epitaxial growth, and this may be used as a connection object (region) that electrically connects the thin titanium oxide layer 28 and the n type region 23. Further, a Ti thin layer may be formed adjacent to the n ⁺ type region formed on the upper surface of the n type region 23, and the n ⁺ type region and this Ti thin layer may be used as a connection object (region). The two semiconductor connection bodies described above have a higher resistance than the connection conductor made of an Au—Ge alloy, but when a reverse voltage is applied, the titanium oxide thin layers 28 and n are connected.
It can be regarded as a low resistance connection (short circuit) with the mold region 23.

(4) Connected objects (areas) do not continuously surround the entire circumference of the titanium oxide thin layer 28, but are a plurality of separated connected objects (areas).
The titanium oxide thin layer 28 may be surrounded by. In this case, the effect of stabilizing the potential distribution of the titanium oxide thin layer 28 can be satisfactorily obtained by setting the distance between the connected objects to 100 μm, preferably 50 μm or less.

(5) The film thickness of the Ti thin layer 24 in FIG. 2 (B) should be 20 Å or more in consideration of film thickness control, oxidation temperature, oxidation time and the like.
The upper limit is not limited as long as the above-mentioned predetermined sheet resistance is obtained, but when the Ti thin film is thermally oxidized to form a titanium oxide thin layer, the oxidation temperature and the oxidation time are taken into consideration.
Should be less than 00Å. The upper limit can be further expanded if strong oxidation such as plasma oxidation is performed.

(6) The oxidation temperature when the Ti thin layer 24 is oxidized to obtain the titanium oxide thin layer 28 is preferably 500 ° C. or lower.
When using a system electrode, the temperature is 380 ° C. or lower. The lower limit of the oxidation temperature is 200 ° C. or higher when the thermal oxidation method is used, but it may be a low temperature of room temperature or lower when the plasma oxidation is used. The oxidization time varies depending on the thickness of the Ti thin layer 24, the oxidization temperature, and the oxidative atmosphere, but it is desirable to be within the range of 5 seconds to 2 hours.

(7) Titanium oxide thin layers 28, 28a and 28b are formed by vapor deposition or sputtering of titanium oxide,
The Ti thin layers 24d, 24g, 24h and 32 may be replaced with titanium nitride layers having relatively high conductivity. The titanium nitride layer is formed by the Ti thin layers 24d, 24g, 2 using the Al layer as a mask.
It can be formed by nitriding 4h and 32.

(8) A titanium oxide thin layer is suitable as a thin layer having a high sheet resistance and generating a shock barrier, but it may be a thin oxide layer of a Ta (tantalum) -based material. Further, the Ti thin layer 24 and the titanium oxide thin layer 28 may be those to which In, Sn or the like is added.

(9) A structure combined with a guard ring may be used when strict high-speed response is not required or when a structure that prevents deterioration of high-speed response is prevented. For example, referring to the example of FIG. 1, a guard ring composed of ap ⁺ type region is formed in the n type region 23 below the junction between the barrier electrode 27 and the titanium oxide thin layer 28 to improve reverse surge withstand capability. It may have a structure. In this case, the first shutter barrier based on the barrier electrode 27 and the second shutter barrier based on the titanium oxide thin layer 28 are not directly continuous, but through the pn junction of the guard ring region, which is the same rectifying barrier as the shutter barrier. Will be continuous. When reverse voltage is applied, the first
The depletion layer based on the Schottky barrier and the depletion layer based on the second Schottky barrier are continuous through the depletion layer based on the pn junction between the p ⁺ type region and the n type region 23 to effectively relax the electric field concentration. Obtainable.

(10) The present invention is also applicable to a shutter barrier semiconductor device using a III-V group compound such as InP (indium phosphide) or silicon instead of GaAs.

(11) In the case of forming a Schottky barrier semiconductor device in an integrated circuit, a planer is provided in which an n ⁺ type region 22 is provided so as to surround the n type region 23 in an island shape and an ohmic electrode 26 is provided on the surface side of the n type region 23. It may be a structure.

(12) The n-type region 23 and the n ⁺ -type region 22 can be replaced with the p-type region.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a high breakdown voltage and high speed shutter barrier semiconductor device or a shutter barrier semiconductor device in which high breakdown voltage is achieved at a particularly high level. That is, a Schottky barrier semiconductor device capable of achieving a high breakdown voltage while ensuring high-speed response and suppressing the breakdown at the outer peripheral edge of the thin layer by the action of the connecting conductor that makes ohmic contact with the outer peripheral edge region of the thin layer. Can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing a shutter barrier diode according to a first embodiment of the present invention, FIG. 2 is a sectional view showing the shutter barrier diode of FIG. 1 in the order of manufacturing steps, and FIG. FIG. 4 is a plan view showing the state of (D), FIG. 4 is a partially enlarged sectional view of a Schottky barrier diode schematically showing a depletion layer, and FIG. 5 is a reverse voltage-reverse current of the Schottky barrier diode of FIG. FIG. 6 is a sectional view showing the shutter barrier diode of the second embodiment, FIG. 7 is a sectional view showing the shutter barrier diode of the third embodiment, and FIG. 8 is the fourth embodiment. FIG. 3 is a cross-sectional view showing the shutter barrier diode of FIG. 22 ... N ⁺ type region, 23 ... N type region, 24a ... Ti thin layer, 25a ... Al layer, 26 ... Ohmic electrode, 27 ...
... barrier electrode, 28 ... titanium oxide thin layer, 29 ... ohmic contact electrode.

Claims (1)

[Claims] 1. A semiconductor region, a barrier electrode disposed on the semiconductor region so as to form a Schottky barrier between the semiconductor region, and a barrier electrode disposed on the semiconductor region so as to surround the barrier electrode. A thin layer electrically connected to the barrier electrode, having a sheet resistance larger than that of the barrier electrode, and having a Schottky barrier with the semiconductor region; A connecting object electrically contacting the outer peripheral edge region of the thin layer and the semiconductor region by making ohmic contact with the outer peripheral edge region of the semiconductor layer and a portion of the semiconductor region surrounding the outer peripheral edge of the thin layer. The Schottky barrier semiconductor device characterized in that the Schottky barrier formed by the barrier electrode and the Schottky barrier formed by the thin layer are continuous directly or via a pn junction. Place