JPH01251656A - Schottky barrier semiconductor device - Google Patents

Abstract

PURPOSE:To realize a high breakdown strength structure, and obtain a Schottky barrier semiconductor device of high breakdown strength, by providing a barrier electrode formed on a semiconductor region, and a thin layer which is connected with a barrier electrode, has a sheet resistor larger than the barrier electrode, and is so formed that a Schottky barrier is formed between said film and the semiconductor region. CONSTITUTION:When an inverse voltage is applied between a barrier electrode 27 and a semiconductor region, two depletion layers 30 generate. The one is based on a Schottky barrier between the barrier electrode 27 and the semiconductor region. The other is based on a Schottky barrier between a thin layer 28 and the semiconductor region. Since the thin layer 28 surrounds the barrier electrode 27, the above two depletion layers 30 become continuous. Further, since the thin layer 28 is resistive, a potential gradient generates, whose value gradually changes, based on a backward current, from the inner periphery of the thin layer 28 toward the outer periphery. As the result, the electric field concentration in the semiconductor region in the vicinity of the periphery of the barrier electrode 27 is relaxed, so that the breakdown strength is remarkably increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high voltage Schottky barrier semiconductor device.

[Conventional technology and its problems Koschottky barrier diodes are widely used in high-frequency rectifier circuits, etc., due to their good high-speed response (high-speed switching characteristics), rectification characteristics with little noise generation, and low loss. There is. However, Schottky barrier diodes have the problem that the peripheral withstand voltage (withstand voltage around the Schottky barrier) is significantly lower than the bulk withstand voltage C (withstand voltage at the center of the Schottky barrier), making it difficult to increase the withstand voltage. .

In order to solve this problem, completely submerging the field plate or providing a guard ring is known, for example, from "Physics Op Semiconductor Devices J 2nd Edition" written by Niss M.C. in the United States. The use of both field plates and guard rings has also already been done.

A Schottky barrier diode with a field plate structure includes an n-type semiconductor region, an n-type semiconductor region formed on the n-type semiconductor region, and a barrier electrode below the Schottky barrier-formable electrode Cv formed on the n-type semiconductor region. call) and
an insulating layer formed to completely surround the barrier electrode on the n-type semiconductor region; a field plate provided on the insulation layer and connected to the barrier electrode; and an autank electrode connected to the n-type semiconductor region. Consists of. When a reverse voltage is applied between the barrier electrode and the ohmic electrode, a depletion layer is created between the barrier electrode and the n-type semiconductor region, and a depletion layer is also formed in the n-type semiconductor region under the field plate due to the field effect of the field plate. A depletion layer is generated, which alleviates the concentration of electric field in the semiconductor region near the periphery of the barrier electrode, and improves the breakdown voltage around the Schottky barrier.However, it effectively alleviates the concentration of electric field and significantly improves the breakdown voltage. This was difficult in practice.

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 made up of 10 p-type semiconductor regions arranged in a 51C manner to surround the barrier electrode.

The p-type semiconductor region of the guard ring is connected to the n-type semiconductor region and pn
When a junction is formed and a reverse voltage is applied to this pn junction,
The depletion layer spreads more effectively than around the Schottky barrier. As a result, the peripheral breakdown voltage of the barrier electrode can be improved. However, since the structure has a Schottky barrier diode and a pn junction diode arranged in parallel, when a forward voltage is applied and the head weight R, flows, the pn junction portion VC2
As a result, injection of minority carriers occurs, and the high-speed response, which is one of the characteristics of Schottky barrier diodes, deteriorates. Furthermore, it was difficult to completely improve the withstand voltage.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to realize a high-voltage structure that can significantly increase the breakdown voltage and hardly reduce high-speed response, thereby providing a high-voltage Schottky barrier semiconductor device.

Means for Solving the Problems] The present invention for solving the above problems and achieving the object described in J. a barrier electrode formed on the semiconductor region, and a sheet arranged on the semiconductor region so as to surround the barrier electrode, electrically connected to the barrier electrode, and larger than the barrier electrode. The present invention relates to a Schottky barrier semiconductor device having a resistive metal and a thin layer formed to form a Schottky barrier between the semiconductor region and the semiconductor region.

[For production]

According to the above invention, when a reverse voltage is generated between the barrier electrode and the semiconductor region, a depletion layer based on the Schottky barrier between the barrier electrode and the semiconductor region and a depletion layer between the thin layer and the semiconductor region. A depletion layer based on the Schottky barrier is generated. Since the thin layer surrounds the barrier electrode,
These two depletion layers are continuous. However, as shown in a modification example described later, when a pn junction such as a guard ring is provided in the semiconductor region so as to surround the barrier electrode, this pn junction
These two depletions J1 are continuous via a junction-based depletion layer. Further, since the thin layer is a resistor, a potential gradient is generated in which the potential gradually changes from the inner circumference side to the outer circumference side of the thin layer based on the reverse current. As a result of this, the electric field concentration in the semiconductor region near the periphery of the barrier electrode is alleviated, and the withstand voltage is significantly improved.

[First Embodiment] The Schottky barrier diode and its manufacturing method according to the first embodiment of the present invention are described in Sections 10-1, 2 and 3.
This will be explained based on the diagram.

First, as shown to the first merchant, GaAs ((jJ−
A semiconductor substrate 21 made of gallium oxide] is prepared. The semiconductor substrate 21 has a thickness of about 600 μm and an impurity concentration of 0.5 to
± of the n shadow area 22 of 2 x 10”cm with a thickness of 1
An n-shaded region 23 having a thickness of 0 to 20 μm and an impurity concentration of 1 to 2×10 15 cm 2 is epitaxially grown.

Next, as shown in Figure 1 a3), n'Jg GaA
A thin layer 24 of 'I'i (titanium), that is, a TiN film, is formed on the entire soil surface of the n-shaded area 26 consisting of s by vacuum evaporation, and then an AI (aluminum) layer 25 is continuously vacuum evaporated on the entire upper surface. do. The thickness of the Ti thin layer 24 is 50 to 200A.
(CJ, 005-0.02 tim) and is extremely thin.

The thickness of the AI island 25 is approximately 2 μm, and the thickness of the thin Ti layer 24 is approximately 2 μm.
It is 0 times or more. Furthermore, Au C is added to the lower surface of the n-shaded area 22
The electrode 26 of the ohmic contact made of an alloy of gold)-Ge (germanium) is formed by vacuum evaporation, and then 3
Heat treatment is performed at 80° C. for 10 seconds.

Next, as shown in FIG. 1(C) VC, 7 Oto etching is performed to A! A portion of the layer 25 is removed by etching, leaving an AIM 25a''f corresponding to the region where a Schottky barrier, which will become the main forward current path, is to be formed.Furthermore, the Ti thin layer 24 is removed from the peripheral region of the device by photoetching. , the Ti thin layer 24a below the AI layer 25a and the Ti thin layer 24b surrounding it are left.The Ti thin layer 24b is an extremely thin film even though Ti itself is a conductor. Therefore, the resistance layer has a sheet resistance of 20 to 400 Ω/hole, which is an order of magnitude higher in resistance than the %AI layer 25a.

Next, heat treatment is performed in air at 600° C. for 5 to 60 minutes. As a result, as shown in FIG. 10, the 1'i thin layer 24b, which is not covered with the Al layer 25a, is oxidized to become a titanium oxide thin layer 28, but the Ti thin layer 24b under the Al7tf 25a is oxidized to become a titanium oxide thin layer 28. 24a is not oxidized because it is masked by the AI layer 25a. Since both Al and Ti are metals that form a Schottky barrier with GaAs, they will be collectively referred to as the barrier electrode 27. Since the Ti thin layer 24a is an extremely thin film, the Ti thin sea island 24aA
It is not necessarily clear how the I layer 25a is involved in forming the Schottky barrier. In addition.

In addition to forming a Schottky barrier, the Ti thin film 24a contributes to improving the adhesion of the A1 layer 25a to the n-type suppressor region 26, and also serves as a titanium oxide thin layer 28 surrounding the barrier electrode 27 in a ring shape. It contributes to the electrical connection between and the AI layer 25a. The sheet resistance of the barrier electrode 27 is preferably 1 ohm/hole, and in this embodiment is about 0.050/hole. As shown in FIGS. 1 and 2, the thin titanium oxide layer 28 according to the present invention surrounding the AI layer 25a has a thickness that is approximately 75 mm larger than that of the thin Ti layer 24b.
A~300K, sheet resistance 50M~500MΩ
/ mouth is a semi-insulating high resistance layer. That is, the titanium oxide thin layer 28 is made of Ti02(2), which can be considered a perfect insulator.
Tiex is a so-called oxygen-poor titanium oxide that contains less oxygen than Ti0z (however, %
is considered to be a value that is two orders of magnitude smaller.

Next, as shown in FIG. 1 (2), the titanium oxide thin layer 28 is coated with a high-resolution Rffi 29 to complete a conductor chip having a Schottky barrier, that is, a Schottky barrier diode chip for power use. However, the insulating layer 29 is plus 7
CVD (chemical vapor depos)
The insulating layer 29 can be replaced with silicon nitride formed by plasma CVD or photo-CVD, a polyimide resin film formed by coating, etc. A silicon oxide film formed by plasma CVD or photo-CVD was suitable.

Although not shown in the drawings, it is common practice to sequentially provide, for example, a 1''i layer and an Au layer on the upper surface of the AI layer 25a, and use these as electrodes for connection to lead members.

Examples of dimensions of each part in FIG. 2 are as follows. The width a of the barrier electrode 27 is approximately 900 μm, and the thin titanium oxide layer 2
80 width is about 150 μm, titanium oxide thin layer 128 and n
The length C between the shadow area 23 and the edge thereof is approximately 150 μm. 2. Titanium oxide': By increasing the width of the 6J thin layer to approximately 10 μm or more, the effect of improving withstand voltage appears;
The effect becomes more noticeable when the distance is set to m or more. However, in order to increase the yield at which the specified withstand voltage can be obtained, 1.
It is more desirable to design it to 00 μrn or more. Even if @b is set to 500 μm or larger than this, a sufficient effect of improving the breakdown voltage can be obtained. Therefore, although there is no upper limit to the width of the semiconductor chip, even if the width of the semiconductor chip is increased to 500 μm or more, not only cannot a proportional increase in breakdown voltage be expected, but also m will occur as semiconductor chips become larger. Therefore, the width bTh3
It is desirable that the thickness be in the range of 0 to 500 μm.

In this Schottky barrier diode, not only a first Schottky barrier is formed between the barrier electrode 27 and the n-type shadow region 23, but also a second Schottky barrier is formed between the titanium oxide thin layer 28 and the n-type shadow region 23. A barrier is created. The occurrence of a Schottky barrier between the titanium oxide thin layer 28 and the n-shaded region 26 is due to the rectifying characteristics of the Schottky barrier diode.

Confirmed by capacity characteristics, saturation current characteristics, etc. for example,
When the area of the titanium oxide thin layer 28 is increased from zero, the saturation current is increased by the area of the titanium oxide thin layer 28 and the barrier electrode 2.
70 area increases approximately in proportion to the sum. It has been confirmed that this proportional relationship is obtained at various temperatures of the Schottky barrier diode. The fact that the saturation current changes approximately proportionally to the area of the sum of the titanium oxide thin layer 28 and the barrier electrode 27 means that between the barrier electrode 27 and the
This means that a reverse current flows through the titanium oxide thin layer 28 at a current density of . This phenomenon clearly shows that the titanium oxide thin layer 28 forms a Schottky barrier with barrier hide φB between the barrier electrode 27 and the path.

The solid line characteristic curve in FIG. 6 shows an example of reverse voltage-reverse current characteristics of the Schottky barrier diode shown in FIG. The reverse voltage-reverse current characteristics of a Schottky barrier diode having a structure in which the titanium oxide thin layer 28 is removed from the diode are shown. As is clear from the comparison of the two characteristic curves, the breakdown voltage of the Schottky barrier diode with a thin titanium oxide layer 28 according to the invention is approximately 250
v, and the breakdown voltage of a conventional Schottky barrier diode without a thin titanium oxide layer 28 is approximately 60
It can be seen that the titanium oxide thin layer 28 is responsible for significantly improving the breakdown voltage. Note that the breakdown voltage value (approximately 250 V) of the Schottky barrier diode having the titanium oxide thin layer 28 is based on the bulk breakdown voltage C.
It is considered that the voltage has reached a level approximately equal to (breakdown voltage at the center of the rear electrode 27).

Next, the reverse voltage-reverse current characteristics of the Schottky barrier diode according to the present invention will be explained in more detail.

When the reverse FI pressure applied to the Schottky barrier diode is gradually increased from zero, region 1 in Figure 3 first appears.
As shown in Figure 2, an extremely small saturation current (8) flows. At this time, a reverse current flows through the first Schottky barrier based on the barrier electrode 27 and the titanium oxide thin layer 28
A reverse current also flows through the second Schottky barrier based on . The reverse voltage application circuit is connected to the barrier electrode 27, ie, the anode, and the ohmic electrode 26, ie, the cathode, and the current passing through the titanium oxide thin layer 28 flows into the clear electrode 27. In the 30th region ■, the titanium oxide thin layer 28
Since the value of the current flowing through the titanium oxide thin layer 28 is small,
The potential difference between a point near and a point far from the barrier electrode 27 is not very large. That is, the potential gradient in the lateral direction of the titanium oxide thin layer 28 is small, and the potential of each part of the titanium oxide thin layer 28 is approximately equal to the potential of the barrier electrode 27.

When the reverse voltage is further increased to about 60 to 100 V, breakdown occurs in several minute regions at the outer periphery of the titanium oxide thin layer 28, and the reverse current becomes stepwise as shown at the region opening in FIG. To increase. One step of this staircase corresponds to breakdown of one outer peripheral edge of the thin titanium oxide layer 28. In the conventional Schottky barrier diode, breakdown in a minute region is triggered and a large reverse current flows, but in the Schottky barrier diode according to the present invention, no large reverse current flows. That is, since the titanium oxide thin layer 28 is a semi-insulating high resistance layer, a large increase in titanate current is suppressed. At the end of region n, the potential difference between the inner edge P1 of the titanium oxide thin layer 28 that is in contact with the barrier electrode 27 and the outer edge P2 that is far from the barrier electrode 27 becomes relatively large. As, titanium oxide thin layer 2
The potential difference between the circumference R1mP2 of No. 8 and the ohmic electrode 26 does not increase much even if the reverse voltage at the impression portion is increased.

Therefore, a new breakdown that occurs at one peripheral edge P2 will not occur. However, the breakdown that has already occurred at the peripheral edge P2 is maintained, and the reverse current based on this breakdown continues to flow through the titanium oxide thin layer 28t. In region (3), since no new breakdown occurs at the peripheral edge P2 of the titanium oxide thin layer 28, the first breakdown based on the barrier electrode 27 increases as the reverse voltage increases.
The reverse current through the Schottky barrier and the second Schottky barrier based on the thin tenter oxide layer 28 gradually increases.

If the titanium oxide source Nl28 is replaced with a resistor layer that does not form a Schottky barrier, for example, an n-type high-resistance GaAs layer, and the end of this resistor layer and the barrier electrode 27 are brought into ohmic contact, the opposite will occur. As the voltage increases, the reverse current (C leakage fi current) also increases significantly, and as a result, the withstand voltage also decreases. Since the titanium oxide thin layer 28 according to the invention not only has a high resistance but also forms a Schottky barrier, the leakage current suppression effect is greater than in the case of the resistor layer described above.

Since a voltage is applied not only to the barrier electrode 27 but also to the titanium oxide source N28vc, the depletion layer 3 schematically shown in FIG.
0 occurs in the n-shaded region 23 under the barrier electrode 27 and the thin titanium oxide layer 28. Titanium oxide thin layer 28 and n-shaded area 2
Since the potential difference between the depletion layer 60 and the depletion layer 60 becomes smaller from the inner circumferential end Pl toward the outer circumferential end P2, the extent (vertical thickness) of the depletion layer 60 also becomes smaller toward the outer circumferential end P2. Further, the surface of the n-shaded region 26 from the barrier electrode 27 to the titanium oxide thin layer 28 is continuous as a Schottky barrier. As a result, a gentle depletion layer 30 that can alleviate electric field concentration is obtained, making it difficult for the electric field to concentrate in the semiconductor region near the periphery of the barrier electrode 270. Therefore, as shown for the area, even if the reverse voltage applied between the pair of electrodes 26 and 27 increases, there will be a wide area where breakdown does not occur.

When the reverse voltage reaches about 250 V, a region exists between the periphery of the barrier electrode 27 and the ohmic electrode 26 where the critical electric field Ecrit k is exceeded, and breakdown occurs, and the reverse current increases as shown in region (3).

For comparison, the Ti thin layer 24b shown in FIG.
When we measured the reverse voltage-reverse current characteristics in the state before oxidation, we found that the Ti thin layer 24b was not a sufficiently high-resistance layer, so the reverse current was suppressed as shown at the region opening in Figure 3. As in the conventional case, a breakdown as shown by the dotted line occurred.

FIG. 11 shows the reverse saturation current density Jj flowing through the Schottky barrier generated by the titanium oxide thin layer 28 and the sheet resistance RS of the titanium oxide thin layer 28.

and shows the temperature dependence of the JS-Rs value. According to the experimental results, it is the Js/R8 value that determines the potential distribution of the titanium oxide thin layer 28 and determines the withstand voltage.
In practical use, pay attention to the JS/R8 value and use a thin layer of titanium oxide28.
All you have to do is design it. As shown in FIG. 11, the saturation flow density J8 increases greatly as the temperature rises. On the other hand, the sheet resistance RS decreases significantly as the temperature rises. As a result, fluctuations in JS and RS values due to temperature changes are small, and the breakdown voltage characteristics against temperature changes are stable. According to actual measurements, the breakdown voltage slightly increases as the temperature rises. This is considered to be due to the fact that the critical electric field Ecrit becomes higher as the temperature rises. If the titanium oxide thin layer 28
If the temperature coefficient of resistance is very small, such as a metal layer, even if a high breakdown voltage is obtained at room temperature, the JS/RS value will rise rapidly as the temperature rises, causing a drop in breakdown voltage at high temperatures.

The Schottky barrier diode of this example was used as a rectifier diode of a switching regulator with a switching frequency of 500 kHz.

Rectification operation with extremely low noise generation was confirmed.

Note that no decrease in switching speed (high-speed response) was observed due to the provision of the titanium oxide thin layer 28.

The advantages of this embodiment are summarized as follows.

Since the fi+ titanium oxide thin layer 28 is both a resistor and an object capable of forming a Schottky barrier, it can effectively alleviate the concentration of electric field at the periphery of the barrier electrode 27 and significantly increase the withstand voltage.

(2) Better high-speed response than conventional Schottky barrier diodes with guard rings.

+31 The thermal instability of the characteristics observed in conventional Schottky barrier diodes with field plates through an insulating layer has been eliminated. Furthermore, the titanium oxide thin layer 28 has strong shielding properties against ions entering from the outside. Furthermore, a drop in breakdown voltage due to temperature rise does not occur. Therefore, it has extremely high voltage stability and reliability.

T41 E)i thin layer 24 provided directly under the AI layer 25a
Since the titanium oxide groove/1i28 is obtained by oxidizing the Tj thin layer 2ab'l, which is the extended portion of a, the desired titanium oxide thin layer 28 can be easily obtained. Furthermore, electrical connection between the barrier electrode 27 and the titanium oxide thin layer 28 can be easily and reliably achieved.

[Second Embodiment] Next, a Schottky barrier diode according to a second embodiment of the present invention shown in FIG. 5 will be described. However, Section 5 (8)
In FIGS. 6 to 10 showing the sixth to seventh embodiments, which will be described later, the same parts as those in FIG.

The Schottky barrier diode shown in FIG.
a and a titanium oxide thin layer 28. but,
The titanium stepped thin layer 28 is not directly connected to A125a, but is connected via the T1 thin layer 2Ac. After the oxidation process to obtain the titanium oxide thin layer 28, this Ti thin layer 24c is formed by photoetching.
This is obtained by removing a portion of layer 25a. Since the Ti thin layer 24c is continuous with the Ti thin layer 24a and forms a Schmidt barrier between it and the n-bulk head region 26, this is also included as a part of the barrier electrode 27. In this way, Ti thin layer 2
When dc is provided, the pressure at 117 becomes even higher. That is, A
Since the I layer 25a and the n shadow region 26 are objects of different nature, the stress concentration point 31 due to the provision of the %A1 layer 25a
occurs below the periphery of the AI layer 25a.

The critical electric field Ecrit that causes breakdown at this stress concentration point 61 is lower than at other parts. Therefore, if the electric field concentrates on this stress concentration point 31, breakdown will occur even more easily. Therefore, in this embodiment, Ti
By providing the thin layer 24c, the titanium oxide thin layer 28
The inner circumferential end of the stress concentration point 61 is spaced apart from the stress concentration point 61. In the case of FIG. 1 (■), the electric field was concentrated at the lower part of the boundary between the barrier electrode 27 and the thin titanium oxide layer 28, which is of a different nature, but in FIG. An electric field concentration point 32 is generated at the lower part of the boundary between the titanium oxide thin layer 28 and the titanium oxide thin layer 28 having low conductivity. Since the electric field concentration point 62 is separated from the stress concentration point 61 in this way, breakdown occurs more than in the Schottky barrier diode with the structure shown in Figure 1 (■)! 7. It is less difficult, and the withstand pressure is higher.

Furthermore, since the sheet resistance of the %Ti thin layer 24c is orders of magnitude smaller than that of the titanium oxide thin layer 28, there is also the effect that the drop in breakdown voltage during ultra-high-speed switching is reduced.

[Sixth Example] In the Schottky barrier diode of the third example shown in FIG. layer 24d, 91
42 titanium oxide thin layer 28b.

A second Ti thin layer 24e for potential equalization and a third thin titanium oxide layer 28c are sequentially arranged in a ring shape, and are electrically connected to each other. Potential equalization A125b and 25C on the Ti1 layers 24d and 24e are made by leaving a part of the A1 layer 25 completely. That is, the AI shown in J in FIG.
During photoetching of the layer 25, the Ti thin layer 24d in FIG.
, 24eK, the AI layer 25b%25c remains and is used as a mask for preventing oxidation of the Ti thin ff12Ad, 24e.

Since the annular region consisting of the Ti 9 layers 24d, 24e and the A1 layers 25b, 25C has a high 41 property, it can become an equi' level distribution region. As a result, it is possible to completely correct the non-uniformity of the potential distribution in plan view on the surface of the n-shaded region 23, form a uniform depletion layer, and improve the breakdown voltage. In addition,
Ti thin/124d, 24e is titanium oxide thin layer 28a,
Since the conductivity is higher than that of 28b and 28c, the %AI layer 25b%25c'e may be removed because it exhibits the potential equalization effect even when alone.

Alternatively, the equipotential region may be formed only by using a thin titanium oxide layer in place of the Ti thin layers 24d and 24e, and using a conductor having a portion number corresponding to the At doves 25b and 25c. Also,
Under the Ti thin layers 24d and 24e, a p shadow region similar to a guard ring may be formed entirely alone or as an auxiliary potential equalization region. Further, one equipotential m region may be provided in one layer or three or more layers.

[Fourth Embodiment] The Schottky barrier diode shown in FIG.
A thin titanium oxide layer 2 is placed around the barrier electrode 27 consisting of c.
8a, 28b and the Ti thin layer 24d all in a ring shape, a shorting electrode 63 is provided to connect the second titanium oxide thin layer 28b and the n-shaded region 23. This shorting electrode 36 is
A layer of Au--Ge alloy and an Au layer are sequentially stacked on top of the soil of the Au-Ge alloy layer, and are in ohmic contact with the n-shaded region 23 made of GaAs.

When the short-circuit electrode 33 is provided in this way, the potential at the outer periphery of the titanium oxide thin layer 28b when a reverse voltage is applied becomes substantially the same as that of the n-shaded region 26, so breakdown occurs at this outer periphery. does not occur. Therefore, the noise that occurs when the Schottky barrier diode of FIG. 1 operates in region n of FIG. 3 does not occur in the diode of FIG. Since the periphery of the titanium oxide thin layer 28b is connected to the n-shaded region 23 by the electrode 33, current can flow therethrough relatively easily. Therefore, a current corresponding to the current in region (3) in FIG.
Thin layer 24d, titanium oxide thin layer 28a, and barrier electrode 27
can be obtained by a passage consisting of

[Fifth Example] The Schottky barrier diode of the fifth example shown in FIG.
k, and further has a ring-shaped titanium oxide thin layer 28d thereon.
, 28e, 28f and a ring-shaped potential equalizing Ti thin layer 2
It has 4h and 24i.

The upper titanium oxide thin layers 28d, 28e, 28f are made of Ti.
The Ti thin layer that was continuous with the thin layers 24g, 24h, and 24i was oxidized. Lower titanium oxide thin layer 28g
is the upper titanium oxide thin layer 28d.

The thickness of the upper titanium oxide thin layer 28d, 28e is approximately the same as that of the upper titanium oxide thin layer 28e, 28f, but the degree of oxidation is reduced.

Since it is stronger than 28f, the upper titanium oxide thin layers 28d, 28e, and 28fj also have a higher sheet resistance. Therefore, the upper titanium oxide thin layer 28d, the Ti thin layer 7m24
h, the current passing through the titanium oxide thin layer 28e1 Ti thin layer 24i and the titanium oxide thin layer 28f becomes larger than the current passing through the lower titanium oxide thin layer 28g, and the potential gradient is mainly determined by the upper layer. Ru. Since the lower titanium oxide thin layer 28g has a high barrier resistance φB, it is possible to provide a Schottky barrier diode with a small saturation current.

Although a portion of the titanium oxide thin layer 28f on the upper teeth is in contact with the n-type head mount 23, it may not be in contact therewith. In addition, the lower titanium oxide source 128g is also shown in Figures 6 and 7.
Ti thin layer for potential equalization as shown in the figure @24d, 2Ae
may be provided. Also.

The A1 layer may be left between the Ti thin layers 24h and 24i, as in the case of FIGS. 6 and 7.

[Sixth Example] The Schottky barrier diode of the sixth example shown in No. 9ryJ has an electrode layer 34 provided by vacuum evaporation on the barrier electrode 27 and insulating layer 29 having the same configuration as in FIG. It is. The peripheral edge 34a of this electrode layer 34 is connected to the insulating layer 29.
Since it faces the n-shade region 23 via the and titanium oxide thin layer 28, it functions as a field plate. As a result, both the breakdown voltage improvement effect based on the titanium oxide thin layer 28 and the breakdown voltage improvement effect based on the field plate can be obtained.

[Seventh Embodiment] The composite Schottky barrier diode of the seventh embodiment shown in FIG. A plurality of nine p-shaped headrests 66 are formed in the enclosed area in the form of islands.

The barrier electrode 27 and the p shadow regions 65 and 66 have a contact sound close to an auto-tack contact, and it can be considered that a Schottky barrier is not formed. Therefore, this composite Schottky barrier diode has a p-shaded region 35.36-n type head mounted 26-
A large number of pn junction diodes consisting of six stations in the n-shaded region 22 are connected in parallel to a Schottky barrier diode. The p shadow area 65 is.

This is a so-called guard ring. This composite Schottky barrier diode has pn junction diodes connected in parallel, which reduces the forward voltage drop when operated at high current density.

The forward and reverse surge resistance is increased, and the reverse current is also reduced. Although the high-speed response is reduced due to the parallel connection of pn junction diodes, it still exhibits an excellent high-speed response that is relatively close to that of a Schottky barrier diode. Of course, the provision of the titanium oxide thin layer 28 itself does not substantially reduce the high-speed response. Note that the p shadow regions 66 may be formed in a stripe shape, for example, so that the barrier electrodes 27 are alternately adjacent to the n-type square regions 23 and the p+-type regions 56 in a cross-sectional state. The structure of this embodiment is particularly effective when manufacturing a high voltage rectifier diode exceeding 200 V class using GaAs.

[Modified example]

The present invention is not limited to the above-described embodiments, but can be modified, for example, as follows.

The effective range of the sheet resistance of the fi+ titanium oxide thin layers 28.28a to 28f varies depending on the semiconductor chip structure and size, but is in the range of 10 to 5000 MΩ/unit, preferably 10 to 1000 MΩ/unit. should be selected.

(2) The thickness of the Ti thin layer 24 shown in FIG. 1(B) should be 20a or more, taking into consideration the % film thickness control, oxidation temperature, acid 116 hours, etc. There is no upper limit as long as the above-mentioned predetermined sheet resistance can be obtained, but when a Ti thin film is thermally oxidized to form a titanium oxide thin layer.

It should be 300X in consideration of the oxidation temperature and oxidation time. If strong oxidation such as plasma oxidation is used, this upper limit can be further expanded.

The oxidation temperature when f31 Ti thin/124 is oxidized to obtain the titanium oxide thin layer 28 is desirably 500° C. or lower, and 380° C. or lower when using an Au-based electrode. The lower limit of the oxidation temperature is set to 200° C. or higher when thermal oxidation is used, but it can be set to a low temperature below room temperature when plasma oxidation is used. The oxidation time varies depending on the thickness of the Ti thin layer 24, oxidation temperature, and oxidation atmosphere, but is preferably within the range of 5 seconds to 2 hours.

(4) Titanium oxide thin layers 28. Those corresponding to 28a to 28g are formed by vapor deposition or sputtering of titanium oxide, and Ti thin layers 240 to 24e, 24g to 24ji are titanium nitride layers with relatively high conductivity. may be replaced with

The titanium nitride layer may be formed by nitriding a thin layer of Ti using the A1 layer as a mask.

(Titanium oxide thin layer is suitable as a thin layer that has high sheet resistance and forms a Schottky barrier, but T
It can also be a thin oxide layer of a C tantalum) based material. Further, the Ti thin layer 24 and the titanium oxide thin layer 28 may be added with In'P Sn or the like. C
In this case, the thin layer is JS/R shown in FIG.
It is preferable to select a material that has a fairly large negative temperature coefficient of sheet resistance so that the s value changes within 101 times or less with respect to the temperature change in the practical range from 25° C. to 125° C. If the J8・R3 value falls within this range, the critical electric field Ec
Combined with the effect of the temperature dependence of rit, a drop in breakdown voltage at high temperatures does not become a problem.

(6) One of the main ways to improve reverse surge resistance
Alternatively, it can be combined with a guard ring consisting of a p-type region. To explain using the example of FIG. 5, the p shadow region is formed at a position from the Ti thin layer 24c to the titanium oxide thin layer 28 corresponding to the electric field concentration point 32, and is spaced apart from the AI layer 25a. In this way, forward current hardly flows into the p shadow region due to the resistance of the Ti thin layer 24c, and high-speed response does not deteriorate. When prioritizing improvement in reverse surge resistance, a guard ring is provided at the end of the AI layer 25a, as in the p-swelling region 35 in FIG. 10, since a drop in high-speed response is unavoidable.

When a guard ring structure is added, barrier electrode 27
A Schottky barrier based on a Schottky barrier titanium oxide thin layer 28 is continuous via a pn junction based on a guard ring, and a rectifying barrier (Schottky barrier b pn junction, etc.) near the periphery of the barrier electrode 27 is formed. )
continuity is maintained.

(7) The titanium oxide source 128 is usually formed in a closed ring shape so as to completely surround the barrier electrode 27. However, when a part of the Schottky barrier based on the barrier electrode 27 is made to have a high breakdown voltage with another high breakdown voltage structure, or when a part of the Schottky barrier based on the barrier electrode 27 is intentionally provided with a region that is likely to cause breakdown. etc., the titanium oxide thin layer 28 does not have to completely surround the barrier electrode 27'jk.

It is also applicable to a Schottky barrier semiconductor device using a [1-V group compound such as InP (indium phosphide) or silicon instead of f81 GaAs.

(When forming a Schottky barrier semiconductor device in a 91 integrated circuit, a planar structure is provided in which the n-shaded region 22 is provided so as to surround the n-shaded region 23 in an island shape, and the ohmic electrode 26 is provided on the surface side of the n-type region 230. You can also use it as

[101n shadow region 26 and n bulge region 22 can be replaced with p shadow region.

〔Effect of the invention〕

As described above, according to the present invention, the breakdown voltage can be significantly and reliably improved while maintaining the high speed response which is the greatest advantage of the Schottky barrier semiconductor device. Furthermore, the stability and reliability of its voltage resistance characteristics are also good.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a Schottky barrier diode according to a first embodiment of the present invention in the order of manufacturing steps. Figure 2 ('!, a plan view showing the state in Figure 1 0. Figure 6 is a reverse voltage-reverse current characteristic diagram of the Schottky barrier diode in Figure 1 ■. Figure 4 schematically shows the depletion layer. A partially enlarged cross-sectional view of a Schottky barrier diode. The fifth factor is a cross-sectional view showing the Schottky barrier diode of the second embodiment. FIG. 6 is a cross-sectional view showing the Schottky barrier diode of the third embodiment. A cross-sectional view showing a Schottky barrier diode according to a fourth embodiment. Fig. 8 is a cross-sectional view showing a Schottky barrier diode according to a fifth embodiment. Fig. 9 is a cross-sectional view showing a Schottky barrier diode according to a sixth embodiment. Fig. 10 is a cross-sectional view showing the composite Schottky barrier diode of the seventh embodiment. Fig. 11 shows the sheet resistance R8 of the titanium oxide thin layer and the reverse saturation current density Js flowing through the titanium oxide thin layer. It is a graph showing the temperature dependence of the product JS-R8. 22...n shadow area, 23...n shadow area, 24a...
- Ti thin layer, 25a... A1 layer, 26... Ohmic electrode, 27... Barrier electrode, 28... Titanium oxide thin layer, 29... Insulating layer. Agent: Nori Takano Figure 1: Compliance with Electricity (V) Figure 8: Amendment to Procedures, Figure 9. picture. 1985 Patent Application No. 285049 2 Name of the invention Schottky barrier semiconductor device 3 Relationship with the case of the person making the amendment Patent applicant's initiative 6 No increase in the number of inventions due to the amendment 1) Specification page 9 Add "less than" after "1Ω/mouth" in the 7th line. (2) In the 9th line of page 21 of the specification, ``by-'' is amended to ``by 1''.

Claims (1)

[Scope of Claims] [1] A semiconductor region; a barrier electrode formed on the semiconductor region so as to be able to generate a Schottky barrier between the semiconductor region; and a barrier electrode so as to surround the barrier electrode. disposed on the semiconductor region, electrically connected to the barrier electrode, has a sheet resistance greater than the barrier electrode, and is capable of creating a Schottky barrier between the semiconductor region and the semiconductor region. A Schottky barrier semiconductor device comprising: a thin layer formed thereon. [2] The thin layer is a high resistance film having a sheet resistance of 10 kΩ/□ or more. Schottky barrier semiconductor device. [3] The thin layer has a negative temperature coefficient of sheet resistance, and the product J_S・The Schottky barrier semiconductor device according to claim 1, wherein the value of R_S is within 100 times the change in temperature from 25°C to 125°C.