JPH01246868A - Schottky barrier semiconductor device - Google Patents

Abstract

PURPOSE:To increase breakdown strength along the periphery by a method wherein a second Schottky barrier is so formed as to surround a first Schottky barrier and connection is established directly or through the intermediary of a p-n junction. CONSTITUTION:An n<->-type region 24a under the periphery of a barrier metal electrode 30 is designed to be lower in impurity concentration than an n-type region 23 so that a depletion layer is prone to extend, upon application of a reverse voltage, along the periphery of the barrier metal electrode 30 where an electric field is easier to form than in the central part of the barrier metal electrode 30. Accordingly, breakdown strength may he enhanced along the periphery. Breakdown strength may be greatly enhanced thanks to a titanium oxide thin film 29, which in turn protects responsiveness from decreasing at a high speed. This design eliminates the heat-caused instability of performance characteristics in a field plate-provided Schottky diode.

Description

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

[Problems to be solved by conventional technology and invention] Schottky barrier diodes are widely used in high-frequency rectifier circuits, etc. by taking advantage of their high-speed response (C, high-speed switching characteristics), long length, and low finger loss (A). There is. However, Schottky barrier diodes have a notable phenomenon in which the peripheral breakdown voltage C (breakdown voltage around the Schottky barrier) is lower than the pulp breakdown voltage (breakdown voltage at the center of the Schottky barrier). #I has the problem of difficult voltage resistance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a Schottky barrier semiconductor device in which it is possible to make the peripheral breakdown voltages the same.

[Solve the spy ``V means of redemption]

In order to achieve the above object, the present invention includes a first semiconductor region, a conductive region of adhesive 2, and the first and second semiconductor regions.
barrier electrodes formed on the first and second semiconductor regions so as to form a first Schottky barrier and a second Schottky barrier, respectively, between the first and second semiconductor regions; The second semiconductor layer is made of a semiconductor material having a larger forbidden band energy width than that of the first semiconductor thin plate, and the first and second semiconductor heads are arranged such that the first Schottky barrier is connected to the second semiconductor thin plate. A Schottky barrier conductor, characterized in that the Schottky barrier is surrounded by a Schottky barrier, and the first Schottky barrier and the second Schottky barrier are connected to each other directly or via a pn junction. It is related to equipment.

[Function] The second semiconductor thin plate in the above invention, which has a larger forbidden band energy width (energy gap) than the first semiconductor thin plate, has a larger critical electric field strength.

Therefore, by arranging the second semiconductor head so as to surround the first semiconductor thin plate 5, the peripheral breakdown voltage of the first Schottky barrier can be increased.

[First Embodiment] A Schottky barrier diode and a method for forming layers thereof according to a first embodiment of the present invention will be explained based on FIGS.

In order to manufacture the Schottky barrier diode shown in Figure 1, GaAs is used as shown in Figure 2 (ARK).
A semiconductor substrate 21 made of (gallium arsenide) is prepared.

This semiconductor substrate 21 has a thickness of about 300 μm.

N-type thin plate 2 with impurity concentration of 1 to 3 X I Q”cm
2, thickness 10-20 μm, impurity concentration 1-2x
An n-shaded region 23 of 101 scm-' is epitaxially grown.

Next, as shown in FIG.
An n-shaded region 24 of AI GaAs (aluminium gallium arsenide) of cm is epitaxially grown. The n-shadow region 24 has an even lower impurity concentration than the n-shade region 26. Here, the MOCVD method (Metal C) is used to form the n-type head 24.
ChemicaI Vapcr Deposition
; organic metal vapor phase growth method) was adopted. That is, the semiconductor group 7fi21 is placed in a reaction vessel under reduced pressure, and G
a (Gallium) organometallic compound Ga (CH
s) S (trimethyl gallium) gas k Hy (hydrogen) gas is sent as a carrier gas to cause a thermal decomposition reaction, A I x Ga H-x As (x 4:
o, 4) Epitaxially grow crystals. In order to impart n-type properties, H2Se (hydrogen selenide) is fed together with the above gas to dope Se (selenium) as an n-type impurity into the AlGaAs crystal.

Next, as shown in Figure 2 Ω, one of the n-type headrests 24 is
11 to form a recess 25 by selectively etching the region where the Schottky barrier that is to become the main flow path is formed;
The n-shaped candy area 23 is exposed on the bottom surface of the recess 151'r25.

By using an etching solution that has a higher etching rate for Al0aAsK than for GaAs, the recess 15'
The bottom m1 of r25 can be made to substantially coincide with the boundary surface between the n-shade thin plate 23 and the n-shade area 24.

However, the bottom surface of the recess 1'9'r25 may be etched slightly beyond this boundary surface. A ring-shaped 1cn-shadow area 24a is formed on the peripheral side of the recess 25.

Next, as shown in Figure 2, #! - A 1゛i (natan) thin IvR26 is formed on the entire soil surface of the monument base 21 by vacuum deposition, and furthermore, the entire upper surface rA! (aluminum ξ) layer 2
．． 7. Continuously close the vacuum lid. The thickness of the 1゛i thin layer 26 is 30~20 OA (0,003~0.02 μm)
It is extremely thin. ,fart! The thickness of layer 27 is approximately 2 μm.

Furthermore, on the lower surface of the n-shaded region 22 there is Au (C gold) -Ge (
A low-resistance orthotac contact i4 pole 28 made of a germanium alloy is formed by vacuum evaporation, and then.

Heat treatment is performed at 680° C. for 10 seconds.

Next, as shown in FIG. 2(g), the Al eyebrow 27 is removed by photoetching to form an A1 layer 27a extending over the inner periphery of the recess P9r25 and the n shadow region 24a. Furthermore, the Ti thin layer 26 is removed from the peripheral area of the chip by photoetching, and the T layer below the AI layer 27a is removed.
The i thin layer 26a and the Ti thin layer 26b surrounding it in contact with it.
remain. Although the Ti thin layers 26a and 26b are conductors, since they are extremely thin films, the sheet resistance is 20 to 40.
0Ω/mouth resistance J noodles, AIJ cocoon 27aVc
The comparison is in terms of cylinder resistance.

Next, all the pieces are heat treated in air at 600°C for 5 to 30 minutes. By this tL, the AI layer 27a is coated with n and not covered with T.
The i thin layer 26b is oxidized to become a titanium oxide thin layer 29, but the Ti thin layer 26 masked by Al7127a
a is not oxidized. Here, both AI and Ti have a low impurity concentration (3aAs and low impurity concentration & (7) AI
Since GaAs is a metal that forms a Schottky barrier between layers, the AI layer 27a and the Ti thin layer 26a together will be referred to as the barrier pole or the barrier gold support as the pole 30.

Since the Ti thin layer 26a is an extremely thin film, the Ti thin N 26
It is not necessarily clear how A and AI skin 27a are each involved in the formation of the Schottky barrier. In addition, T4Hm26a is Al7127a n-type@region 2
6 and n- Improving adhesion to the shadow area 24a VC'4- Provides. Dimensions. 1゛i thin layer 26a has a barrier metal of about 30?
I-ring-shaped surrounding titanium oxide thin layer 29 and A! layer 27
Contributes to electrical contact and separation with a. It is desirable that the sheet resistance of the barrier metal electrode 30 is 1Ω/hole or less, and in this embodiment, the resistance is about 0.05Ω/hole. The thickness of the titanium oxide thin layer 29 is thought to be about 45 to 6 oooi, increasing from the thickness of the Ti thin #26b due to oxidation, but the exact value is not clear because it is difficult to measure.

The sheet resistance of the titanium oxide thin layer 29 is 1ON1 to 500
The titanium oxide thin layer 29 is a medium-insulating high-resistance layer. That is, the titanium oxide thin layer 29 is not 1'iCh (titanium dioxide), which can be considered a healthy insulator, but is a so-called oxygen-poor titanium oxide Tiex (x is a value smaller than 2), which has less oxygen than Ti (J2). )
It is thought that this is the case.

Subsequently, as shown in FIG. 1, the power Schottky barrier diode is completely destroyed by covering it with a titanium oxide thin layer 29 (J: total insulation 1-31). It should be noted that the insulating layer 31 is preferably a silicon oxide film formed by a plasma (VD) method or a photo-CVD method.
For example, on the soil surface of Al/Zeng 27a, there are ゛i layer and AuJ? I
! I is often provided at the 111st order and used as a connection electrode for the lead member.

The width a of the barrier metal pole 30 is about 1000 μm,
The width of the n-type g region 24a is approximately 320 μm.

The width C of the thin titanium oxide layer 29 is about 140 .mu.m, and the width d between the thin titanium oxide layer 29 and the periphery of the n-shaded region 24a is about 150 .mu.m.

In this Schottky barrier diode.

+1111 The Schottky barrier, which becomes the main path of the ill flow, has a barrier metal electrode 60 and an n shadow region 2 made of GaAs.
3 is the part that touches @. To be exact, Barrier Kinkaeden'I!
The opening where i60 and the n-shaded region 24a are in contact with each other may also be seen as part of the Schottky barrier, which is the main path of the wi current, but since the area is small, this can be ignored.

In the Schottky barrier diode shown in FIG. 1, a first Schottky barrier is formed between the barrier metal electrode 60 and the n-shaded region 23, and a second Schottky barrier is formed between the barrier metal electrode 30 and the n-type thin plate 24a. is formed. It was. There is also a sixth layer between the titanium oxide thin IWI 29 and the n-shadow region 24a.
A Schottky barrier is formed. Titanium oxide thin layer 2
9 abuts and surrounds the barrier metal electrode 60 so that the third Schottky barrier is continuous with the first and second Schottky barriers based on the barrier metal electrode 30. Therefore, the reverse voltage i EIJm-
f, the depletion layer extending from the first Schottky barrier, the depletion layer extending from the second Schottky barrier, and the depletion layer extending from the sixth Schottky barrier are continuous, resulting in a smooth depletion layer that alleviates electric field concentration. . Titanium oxide thin layer 2
The pressure-resistant structure according to No. 9 was invented by the inventors of the present application and others, and was published as % Application No. 62-307196 by the applicant of the present application. RLl, as the reverse voltage applied to the Schottky barrier diode is increased, the titanium oxide w1. Breakdown occurs at the outer periphery of layer 29. However, since the titanium oxide thin layer 29 is a high resistance layer, the increase in reverse current accompanying the breakdown is suppressed by the resistance of the titanium oxide thin layer 29. When a minute reverse current flows through the titanium oxide thin layer 29 due to breakdown, a potential gradient is generated in the titanium oxide thin layer 29, and a depletion layer that satisfactorily alleviates the 'w1 field concentration is obtained.

The noteworthy point of the Schottky barrier diode of this embodiment is that the barrier hide φB of the Schottky barrier is different between the central part and the peripheral part based on the barrier metal electrode 301C. The n-type dome 24a made of Al (3aAs) is GaA
The energy of the forbidden band +p than the n shadow region 26 consisting of s
Jd r energy gap) Eg is large. That is,
The energy gap Eg of AlxGa1-, cAs (x l-0,4) is about 1.9 eV.

(The energy gap Eg of 3aAs is about 1.4 eV
So, there it is.

Incidentally, a semiconductor with a large energy gap Eg has a larger critical electric field intensity Ecrit (electric field intensity when avalanche breakdown occurs) than a semiconductor with a small energy gap Eg. Therefore, the second Schottky barrier formed between the barrier gold Kaede@I30 and the n-shadow region 24 with a large energy gap EH is the barrier gold J/!
! 41iI@t30 and the small n-shaded region 23 of the energy gap 7EH have a higher breakdown voltage than the Schottky barrier of A1. That is, the breakdown voltage around the Schottky barrier is improved, and the Schottky barrier diode is made to have a high breakdown voltage.

Other advantages of this embodiment are summarized as follows.

(11) The impurity 6 degree of the nT-type region 24a at the lower part of the peripheral part of the barrier metal electrode 30 is lower than that of the n-shade region 23 at the lower part of the central part of the barrier metal electrode 30. Therefore, when reverse voltage is applied The depletion layer is more likely to extend in the peripheral portion where electric field concentration tends to occur than in the central portion of the barrier metal electrode 60. Therefore, the effect of improving one peripheral breakdown voltage is enhanced.

(Since 21GaAs and A I GaAs have good crystal lattice matching, epitaxial growth of the n1fjk region 24a is possible, and there is no inconvenience caused by forming the n shadow region 24a.
Since the OCVD method is used to form the shadow area 24a, mass production is good.

131 By providing the titanium oxide thin layer 29.

The breakdown voltage can be significantly increased compared to a conventional Schottky barrier diode having a high breakdown voltage structure in which a guard ring gI region is provided around the barrier metal electrode.

In addition, the problem of deterioration in high-speed response, which was a problem with Schottky barrier diodes provided with guard link mHR, has been resolved.

(4) By providing titanium oxide source #29.

The breakdown voltage can be significantly increased compared to a conventional Schottky barrier diode with a high breakdown voltage structure that includes a field plate with an insulating material interposed therebetween. Teta.

The thermal instability of the characteristics, which was a problem with Schottky barrier diodes having a field rating through an insulator, has been resolved.

[Second Embodiment] A Schottky barrier diode according to a second embodiment of the present invention shown in FIG. 4 will be described. However, in FIG. 4, parts that are substantially the same as those in FIGS. 1 to 3 are designated by the same reference numerals, and their explanations will be omitted.

Even if there are 3 in the Schottky barrier diode in Figure 4, the 1st
Prison Schottky barrier diode and four-way barrier gold*'
A first Schottky barrier is formed between the m-pole 60 and the n-shaded region 23, and the barrier metal electrode 60 and the n-type thin plate 24a
A second Schottky barrier is formed between the first Schottky barrier and the first Schottky barrier. This is because, like the Schottky barrier diode in Figure 1, the second Schottky barrier has a higher breakdown voltage than the first Schottky barrier.

A Schottky barrier diode with a high breakdown voltage can be realized because the peripheral breakdown voltage is reduced.

Furthermore, in the Schottky barrier diode shown in FIG. 4, two thin layers 26e, 26f and two thin titanium oxide layers 29 are formed in a ring shape on the outer periphery of the barrier metal t630.
a and 29b are sequentially arranged in contact with each other. Ti thin layer 2
6e, 26f and the titanium oxide thin layers 29a, 29b use barrier metal as the Ti layer located under the AI layer 27a of the pole 3o.
This corresponds to the study portion of the thin layers 26c and 26d. Therefore, the titanium oxide thin layers 29a, 29b are replaced by the Ti thin layers 26e, 2, respectively.
Valve 6f and electrically connect it to the barrier metal electric @160! has been done. Here, the thickness of 1"i to 26e forms a fourth Schottky barrier between the thin plate 24a and the n-shaped thin plate 24a. Therefore, barrier metal 1! The surfaces of the n-type thin plate 23 and the n-shaded region 24a from the pole 30 to the outer peripheral edge of the titanium oxide thin layer 29a are coated with barrier gold@1! First and second Schottky barriers based on the pole 30 and a fourth Schottky barrier and a third Schottky barrier based on titanium oxide VC are successively formed. As a result, when a reverse voltage is applied, a smooth depletion layer is obtained in which the depletion layers extending from each of these Schottky barriers are continuous and alleviate electric field concentration. Furthermore, a Ti thin layer 26e
, 26f, the electric field concentration point and the stress concentration point can be separated, and the withstand voltage yield is improved. That is, Tj thin N26
e, 26f is barrier metal 1! ! @! 30, and has a much smaller sheet resistance than the titanium oxide thin N7jI29a, 29b. Therefore.

The electric field concentration points are the Ti thin layers 26e and 26f and the titanium oxide thin layer/! It is located at the bottom of the boundary between 29a and 29b.

Stress concentration points are the barrier metal electrode 60 and the Ti thin layer 26e.

It is located at the bottom of the boundary part of 26f. Therefore, the critical ′M
, it is possible to move the electric field concentration point from a stress concentration point with low field strength Ecrjt, and the frequency of occurrence of products with a specified withstand voltage or less is reduced. Both housing and pressure yield are improved.

In addition, in the m4m Schottky barrier diode, the lower titanium oxide thin layer 29a is replaced with the upper titanium oxide thin layer 2.
It has stronger oxidation and thicker sheet resistance than 9b.

Therefore, the reverse current is mainly caused by the upper titanium oxide thin Wt
29b, the 11th position gradient is mainly determined by the upper titanium oxide thin layer 429b. Since the lower titanium oxide thin layer 29a has a high barrier hydride, the saturation current I8 becomes small, and as a result, a Schottky barrier diode with a reasonable reverse current level can be obtained.

Normally, the upper titanium oxide thin layer 29b has a T-shaped ring.
An equipotential region 61 consisting of an i-thin layer is provided. The equipotential region 31 is a region in which the thin Ti layer, which undergoes oxidation during the formation of the titanate thin layer 29b, remains as it is. In this equipotential region 61, titanium oxide thin layers 29a, 2
Compared to 9b, the conductivity is very high in VC, and the potential in the sacrum region is almost the same. As a result, n shadow area 26 and n-shadow area 24
The non-uniformity of the potential gradient seen in a plan view on the surface of a is corrected, and the breakdown voltage yield is improved.

Historically, the ends of the titanium oxide thin layers 29a and 29b are made of Au.
Connection region 6 made of (gold)Ge (germani, umium) alloy
2 is electrically connected to the n-type head mount 24a. Therefore, it is possible to provide a Schottky barrier diode with less noise caused by breakdown in a minute region of the outer circumferential line of the titanium oxide thin layer 29a. In the Schottky barrier diode shown in FIG. 1, a sharp current change due to breakdown occurring in a minute region at the outer periphery of the titanium oxide thin layer 29 may induce noise generation. This noise is not a problem in practical use, but if low noise is required (the Schottky barrier diode shown in FIG. 4 is more advantageous).

[Modified example]

The invention is not limited to the embodiments described above.

For example, the following transformations are possible.

In the Schottky barrier diodes shown in 11+1- and 2, the impurity concentration of the n-type e region 24a is
Even if it is selected to be equal to or larger than the n-type range, the effect of improving the peripheral breakdown voltage based on the difference in the energy gap Eg will not be recognized. However, as in the embodiment, it is more advantageous to form the n'' type region 24a, which has a lower impurity concentration than the n shadow region 26, in terms of improving the peripheral breakdown voltage.

(The 21n type region 24a is selected from a range of semiconductor materials that are capable of crystal growth in the n shadow region 23 and have a larger energy gap Eg than the n shadow region 260 conductor material.

The example of the combination of GaAs and AlGaAs as in the embodiment is an optimal example, but when the n-shaded region 23 is GaP (gallium phosphide), the n""-shaped region 24aσ? AI GaP (aluminum gallium phosphide) can be used as the conductor material.

(31 barrier Kinurekiden & 30 has Ag (ffM) and cuc
Various metal materials can be used, such as (copper).

14) The effective range of the sheet resistance of the titanium oxide thin layer 29 when adopting a high voltage resistance structure using a titanium oxide thin layer varies depending on the semiconductor chip structure and size, but is in the range of 10 to 5000Ω/unit. 8】Ω/mouth.

It should preferably be selected between 10 MΩ/mouth and ioooMΩ/mouth.

(5) The thickness of the Ti thin layer 26 in the second drawing is a thickness control.

The oxidation temperature, oxidation time, etc. should be taken into account and the oxidation temperature should be 2OA or more. Regarding the upper limit, what if the above prescribed sheet resistance can be obtained? There is no limit to this, but when a thin layer of titanium oxide is formed by thermally oxidizing an 'IIF' film.

Considering the oxidation temperature and oxidation time, it should be 600A or less. If you perform strong oxidation such as plasma oxidation,
This upper limit can be further expanded.

(6) Oxidize the dust thin layer 26 to form the titanium oxide thin layer 2
- The oxidation temperature when obtaining 9 is preferably 500°C or lower, and when using an Au thread electrode, it is 380°C or lower. 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. Oxidation time is 118
Thickness of layer 26, oxidation temperature.

It may vary depending on the oxidizing atmosphere, but it is best to keep it within the range of 5 seconds to 2 hours! Yes.

(7) Release the shape by vapor deposition or sputtering of mono-titanium oxide corresponding to the titanium oxide thin layer 29.29b,
The Ti thin fii 26e, 26f may be replaced with a titanium nitride layer having relatively high conductivity. The titanium nitride layer is A
Shaping can be achieved by nitriding the titanium oxide layer using one layer as a mask.

(8) Titanium dispersion thin / # is suitable as a thin layer that produces a Schottky barrier with a low sheet resistance.
The thin Ti layer 26 and the thin titanium oxide layer 29 and 29b can also be formed by adding In'P Sn or the like. good.

(9) A ring-shaped p shadow region may be formed as a guard ring in the n-type region 23 so as to be adjacent to the bottom periphery of the concave Ffr 25 . In this case, barrier metal II pole 30 and n
The Schottky barrier formed between the barrier metal 1 [pole 3o and the n-type candy region 24a] is not directly continuous but via a pn junction.

alJ When forming a Schottky barrier #84 body device in an integrated circuit, an n-shaded region 22 is provided so as to surround the n-shaded region 26 in an island shape, and the autotac electrode 28 is connected to the n-type a region 2.
It is also possible to adopt a brainer structure in which 3 VCs are provided on the front side.

Old Jn type header 23. N-type region 22 can be replaced with a p-type region.

〔Effect of the invention〕

As described above, according to the present invention, the peripheral breakdown voltages of the Schottky barrier can be made equal to each other, and a high breakdown voltage Schottky barrier #-conductor device can be provided.

[Brief explanation of the drawing]

FIG. 1 shows a Schottky barrier diode according to a first embodiment of the present invention. l′I view. FIG. 2 is a sectional view showing the Schottky barrier diode of FIG. 1 in the order of manufacturing steps. FIG. 6 is a plan view showing the state of the second drawing. FIG. 4 is a sectional view taken along the line-r of the Schottky barrier diode of the second embodiment. 22...n-shaped head, 26...n shadow area, 24a...
・n-Shadow area-26a-Ti thin 4.27 a-Al r
*, 28...Overhead electrode, 29...Titanium oxide thin layer, 30...Barrier metal plate.

Claims (1)

[Scope of Claims] [1] A first shot barrier and a second shot barrier are formed between a first semiconductor region, a second semiconductor region, and the first and second semiconductor regions, respectively. a barrier electrode formed on the first and second semiconductor regions so as to be able to perform the following steps, and the second semiconductor region is made of a semiconductor material whose forbidden band energy width is larger than that of the first semiconductor region. The first and second semiconductor regions are such that the first shot barrier is surrounded by the second shot barrier, and the first shot barrier and the second shot barrier are connected directly or via a pn junction. A shot barrier semiconductor device characterized in that the shot barrier semiconductor device is arranged such that