CN110212022A - A kind of groove structure junction barrier schottky diode - Google Patents

Abstract

The invention relates to a trench structure junction barrier Schottky diode, which comprises an anode electrode layer, an isolation medium layer, an N epitaxial layer, an N+ substrate layer and a cathode electrode layer from top to bottom, wherein the N epitaxial layer A plurality of trench structures are provided on the upper surface of the trench structure, and a P-type ion implantation region is formed inside the trench structure; the distance between adjacent trench structures decreases from the center to the edge of the upper surface of the N-epitaxial layer, and the plurality of P The shape and size of the type ion implantation regions are the same. The distance between adjacent trench structures of the trench structure junction barrier Schottky diode of the present invention tends to decrease from the center to the edge, thereby improving the conduction of the device during forward operation under the premise of ensuring the reverse leakage current Resistive characteristics improve device performance and reliability.

Description

A Junction Barrier Schottky Diode with Trench Structure

technical field

The invention belongs to the technical field of electronic components, in particular to a trench structure junction barrier Schottky diode.

Background technique

Schottky barrier diode is a device that uses the contact barrier between metal and semiconductor to work. It is suitable for high-frequency rectification, detection and mixing in low-voltage and high-current output applications, and it is used as a clamp in high-speed logic circuits. . A junction barrier Schottky diode (JBS) is a device that integrates multiple PN junction gates in the drift region of an ordinary Schottky diode. In the field of power electronics, JBS diodes have been widely used, which have the characteristics of good forward conduction characteristics and small reverse leakage current. Compared with the JBS diode, the trench junction barrier Schottky diode (TrenchedJuction barrier Schottky, TJBS) reduces the electric field of the Schottky contact region, so the diode leakage current is significantly reduced.

In the existing TJBS diode structure, the size of the Schottky contact area at different positions is the same. However, due to the different packaging areas contacted by different positions of the TJBS chip, the heat dissipation conditions at different positions of the TJBS chip are different, resulting in a temperature at the center of the TJBS chip greater than that around the chip. This temperature difference will lead to different carrier mobility in different positions of the TJBS chip, uneven current distribution, and local electromigration, which will affect the device reliability of the TJBS diode.

Contents of the invention

In order to solve the above problems in the prior art, the present invention provides a junction barrier Schottky diode with a trench structure. The technical problem to be solved in the present invention is realized through the following technical solutions:

The invention provides a trench structure junction barrier Schottky diode, which sequentially includes an anode electrode layer, an isolation dielectric layer, an N- epitaxial layer, an N+ substrate layer and a cathode electrode layer from top to bottom, wherein,

A plurality of trench structures are opened on the upper surface of the N-epitaxial layer, and a P-type ion implantation region is formed inside the trench structures;

The distance between adjacent trench structures decreases from the center to the edge of the upper surface of the N- epitaxial layer, and the shape and size of the plurality of P-type ion implantation regions are the same.

In one embodiment of the present invention, the plurality of groove structures are concentric ring structures.

In one embodiment of the present invention, the plurality of groove structures are all rectangular, and are distributed in an array structure on the upper surface of the N-epitaxial layer.

In one embodiment of the present invention, the distance between adjacent trench structures decreases continuously from the center to the edge of the upper surface of the N-epitaxial layer.

In one embodiment of the present invention, the distance between adjacent trench structures decreases in steps from the center to the edge of the upper surface of the N-epitaxial layer.

In one embodiment of the present invention, a first Schottky contact region is formed between the N-epitaxial layer and the anode electrode layer, and each of the P-type ion implantation regions is formed between the anode electrode layer second Schottky contact area.

In one embodiment of the present invention, the P-type ion implantation region is formed on both the bottom and the inner wall of the trench structure.

In an embodiment of the present invention, the groove depths of the plurality of groove structures are the same.

In one embodiment of the present invention, the distance between adjacent trench structures is greater than or equal to 3 μm.

Compared with prior art, the beneficial effect of the present invention is:

The trench structure junction barrier Schottky diode of the present invention increases the area of the Schottky contact region at the center of the device by making the distance between adjacent trench structures decrease from the center of the device to the edge, reducing the The area of the Schottky contact area at the edge of the device is reduced, so that the temperature difference between the center and the edge of the device is reduced under the premise of ensuring that the reverse leakage current and the forward conduction resistance do not degrade, and the local electromigration phenomenon is effectively suppressed. occurs, improving the reliability of the device.

Description of drawings

Fig. 1 is a schematic structural diagram of a trench structure junction barrier Schottky diode provided by an embodiment of the present invention;

FIG. 2 is a dimensioning diagram of a junction barrier Schottky diode with a trench structure provided by an embodiment of the present invention;

FIG. 3 is a dimensioning diagram of another junction barrier Schottky diode with a trench structure provided by an embodiment of the present invention;

Fig. 4 is a trench structure dimensional drawing of a junction barrier Schottky diode with a trench structure provided by an embodiment of the present invention;

5 is a schematic top view showing the distribution of P-type ion implantation regions provided by an embodiment of the present invention;

FIG. 6 is another schematic top view showing the distribution of P-type ion implantation regions provided by an embodiment of the present invention;

7a-7f are schematic diagrams of the preparation process of a junction barrier Schottky diode with a trench structure provided by an embodiment of the present invention.

The reference signs are as follows:

1-Anode electrode layer; 2-Isolation dielectric layer; 3-N-Epitaxial layer; 4-N+ substrate layer; 5-Cathode electrode layer; 6-Trench structure; 7-P-type ion implantation region; 9-Second Schottky contact area; 10-Ohm contact area.

Detailed ways

In order to further explain the technical means and effects of the present invention to achieve the intended purpose of the invention, the trench structure junction barrier Schottky diode proposed according to the present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

The aforementioned and other technical contents, features and effects of the present invention can be clearly presented in the following detailed description of specific implementations with accompanying drawings. Through the description of specific embodiments, the technical means and effects of the present invention to achieve the intended purpose can be understood more deeply and specifically, but the accompanying drawings are only for reference and description, and are not used to explain the technical aspects of the present invention. program is limited.

It should be noted that in this article, relational terms such as first and second etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or order between them. Furthermore, the terms "comprises", "comprises" or any other variation are intended to cover a non-exclusive inclusion such that an article or device comprising a set of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising a" does not exclude the presence of additional identical elements in the article or device comprising said element.

Embodiment one

Please refer to FIG. 1 . FIG. 1 is a schematic structural diagram of a junction barrier Schottky diode with a trench structure provided by an embodiment of the present invention. The trench structure junction barrier Schottky diode sequentially includes an anode electrode layer 1, an isolation dielectric layer 2, an N- epitaxial layer 3, an N+ substrate layer 4, and a cathode electrode layer 5 from top to bottom, wherein, in the N- epitaxial layer A plurality of trench structures 6 are etched on the upper surface of the trench structure 3, and a P-type ion implantation region 7 is formed inside the trench structures.

The isolation dielectric layer 2 surrounds the edge of the upper surface of the N-epitaxial layer 3 , and a plurality of trench structures 6 are provided on the surface of the N- epitaxial layer 3 inside the isolation dielectric layer 2 . Please refer to FIG. 4 . FIG. 4 is a dimensional diagram of a trench structure junction barrier Schottky diode provided by an embodiment of the present invention. In this embodiment, the shape and size of each trench structure 6 are equal, wherein, the width m ₁ ≤6.2 μm; the depth D ₁ ≤2.5 μm. In this embodiment, the isolation dielectric layer 2 is made of SiO ₂ material with a thickness in the range of 200-500 nm. The anode electrode layer 1 is arranged on the upper surface of the N- epitaxial layer 3 not covered by the isolation dielectric layer 2 and the upper surface of the isolation dielectric layer 2 , and covers the surface of the P-type ion implantation region 7 .

Further, in this embodiment, a first Schottky contact region 8 is formed between the N- epitaxial layer 3 and the anode electrode layer 1; a second Schottky contact region 8 is formed between each P-type ion implantation region 7 and the anode electrode layer 1 Schottky contact region 9 ; and an ohmic contact region 10 is formed between the contact surface of N+ substrate layer 4 and cathode electrode layer 5 .

Furthermore, the anode electrode layer 1 is composed of two layers of metal, wherein the upper metal is Al or Ag with a thickness of 2-5 μm, and the lower metal is Ti with a thickness of 50-100 nm. That is to say, the lower metal Ti directly covers the N-epitaxy layer 3 and the P-type ion implantation region 7, and form a first Schottky contact region 8 at the interface with the N- epitaxial layer 3, and form a second Schottky contact at the interface with the P-type ion implantation region 7 District 9.

The thickness and doping concentration of the N-epitaxial layer 3 can be specifically selected according to the conductor characteristics and breakdown characteristics of the device, usually in the range of 10-30 μm. For example, when the breakdown voltage of the device is required to be 1200V, the thickness of the N- epitaxial layer 3 can be selected as 10 μm. The N+ substrate layer 4 is usually a highly doped N-type silicon carbide substrate.

The cathode electrode layer 5 is also composed of two layers of metal, wherein the upper layer metal is metal Ni with a thickness of 50-100 nm, and the lower layer metal is a Ti/Ni/Ag alloy with a thickness of 2-5 μm. The bottom layer 4 is in contact, and an ohmic contact region 10 is formed at the interface with the N+ substrate layer 4 .

Further, the distance between adjacent trench structures 6 gradually decreases from the center to the edge of the upper surface of the N- epitaxial layer 3 , and the dimensions of the plurality of P-type ion implantation regions 7 are the same.

In the TJBS device, the package areas contacted by different positions are different, so that the heat dissipation conditions of different positions of the TJBS device are different. Since the larger the area of the N-type Schottky contact region, the greater the current density of the TJBS device, the greater the power of the TJBS device, and therefore the more serious the heat generation. By reducing the distance between adjacent trench structures 6 at the edge of the TJBS device, the area of the first Schottky contact region 8 at the edge is reduced, thereby reducing the Schottky contact region (including the Schottky contact region) formed with the anode electrode layer 1 The total area of the first Schottky contact area and the second Schottky contact area). In addition, the temperature at the edge of the device can be effectively reduced by taking advantage of the good heat dissipation characteristics at the edge of the TJBS device.

However, if the area of the first Schottky contact region 8 at the edge is simply reduced, the forward characteristics of the TJBS device will be weakened, so the trench structure junction barrier Schottky diode adjacent trench structure of this embodiment 6 gradually decreases from the center to the edge of the upper surface of the N-epitaxial layer 3, so that the area of the first Schottky contact region 8 gradually decreases from the center to the edge, that is, by increasing the first Schottky contact area of the center The area of the base contact region 8 reduces the area of the first Schottky contact region 8 at the edge, and reduces the temperature difference between the center and the edge of the TJBS device under the premise of ensuring that the reverse leakage current and the forward conduction resistance do not degrade , which effectively suppresses the occurrence of local electromigration, thereby improving the reliability of the device.

In this embodiment, please refer to FIG. 4 , the dimensions of the plurality of P-type ion implantation regions 7 are the same, that is, the width m ₂ and the junction depth D ₂ of each of the plurality of P-type ion implantation regions 7 are the same. A P-type ion implantation region 7 is formed on the bottom and the inner wall of the trench structure 6 . The thickness of the P-type ion implantation region 7 formed on the inner wall of the trench structure 6 is ≤0.6 μm.

Further, please refer to FIG. 2 . FIG. 2 is a dimensional diagram of a junction barrier Schottky diode with a trench structure provided by an embodiment of the present invention. In this embodiment, the distance between adjacent trench structures 6 decreases continuously from the center to the edge of the upper surface of the N − epitaxial layer 3 . As shown in the figure, the width of the first Schottky contact region 8 is represented by _WS1 , _WS2 , _{WS3, WS4, WS5, WS6 , WS7 , WS8 and WS9} from left to right. In this embodiment, the relationship between the width of the first Schottky contact region 8 is W _S1 <W _S2 <W _S3 <W _S4 <W _S5 >W _S6 >W _S7 >W _S8 >W _S9 . The distance between adjacent trench structures 6 is greater than or equal to 3 μm. That is, W _S1 ≥ 3 μm, W _S9 ≥ 3 μm.

In the trench structure junction barrier Schottky diode of this embodiment, the spacing between adjacent trench structures 6, that is, the width of the first Schottky contact region 8 increases continuously from the center to the edge, by increasing the first The area of the Schottky contact region 8 reduces the area of the first Schottky contact region 8 at the edge, and reduces the temperature difference of the TJBS device under the premise that the reverse leakage current and the forward conduction resistance are not degraded. , which effectively suppresses the occurrence of local electromigration, thereby improving the reliability of the device.

Further, please refer to FIG. 5 , which is a schematic top view showing the distribution of P-type ion implantation regions provided by an embodiment of the present invention. In this embodiment, the plurality of groove structures 6 are all concentric ring structures. The distance between the plurality of trench structures 6 gradually decreases from the middle to both sides, so that the area of the first Schottky contact region 8 between adjacent trench structures 6 gradually decreases. Correspondingly, the top view of each P-type ion implantation region 7 is also a concentric ring structure. Please refer to FIG. 6 . FIG. 6 is another schematic top view showing a P-type ion implantation region provided by an embodiment of the present invention. In other embodiments, each trench structure 6 has a rectangular shape and is distributed in a rectangular array on the upper surface of the N − epitaxial layer 3 . Correspondingly, the top view of each P-type ion implantation region 7 is also rectangular, distributed in a rectangular array. The distance between the plurality of trench structures 6 gradually decreases from the middle to the periphery, so that the area of the first Schottky contact region 8 between adjacent trench structures 6 gradually decreases.

The groove structure junction barrier Schottky diode of this embodiment, by increasing the distance between the adjacent groove structures at the center of the device and reducing the distance between the adjacent groove structures at the edge of the device, ensures the reverse Under the premise of no degradation of leakage current and forward conduction resistance, the temperature difference of the junction barrier Schottky diode of the trench structure is reduced, and the occurrence of local electromigration is effectively suppressed, thereby improving the reliability of the device.

Embodiment two

On the basis of the above-mentioned embodiments, this embodiment provides another way of distributing the trench structures. Please refer to FIG. 3 . FIG. 3 is a dimensional diagram of another junction barrier Schottky diode with a trench structure provided by an embodiment of the present invention. In this embodiment, the distance between adjacent trench structures 6 decreases stepwise from the center to the edge of the upper surface of the N-epitaxial layer 3 . As shown in the figure, the width of the first Schottky contact region 8 is represented by W ₁ , W ₂ , W ₃ , W ₄ , W ₅ , W ₆ , W ₇ , W ₈ and W ₉ from left to right. In this embodiment, the relationship between the width of the first Schottky contact region 8 is W ₁ =W ₂ <W ₃ =W ₄ <W ₅ >W ₆ =W ₇ >W ₈ = _S9 , and the adjacent trench structure 6 The pitch is greater than or equal to 3 μm. That is, W ₁ ≥ 3 μm and W ₉ ≥ 3 μm.

In the trench structure junction barrier Schottky diode of this embodiment, the spacing between adjacent trench structures 6, that is, the width of the first Schottky contact region 8 decreases stepwise from the center to the edge, that is, the device can be arranged from the center to the edge. The edge is divided into several regions. In the same region, the distance between adjacent groove structures 6 is different. In different regions, the distance between adjacent groove structures 6 is usually different, and the closer to the center, the adjacent The pitch of the trench structures 6 is larger. In this way, from the general trend of change, the spacing between adjacent trench structures 6, that is, the width of the first Schottky contact region 8 gradually increases from the center to the edge, and by increasing the first Schottky contact region 8 in the center reduce the area of the first Schottky contact region 8 on the edge, and reduce the temperature difference of the TJBS device under the premise of ensuring that the reverse leakage current and the forward conduction resistance do not degenerate, effectively suppressing the local electric current Migration occurs, thereby improving the reliability of the device.

Further, please refer to FIG. 6 , which is another schematic top view showing the distribution of P-type ion implantation regions provided by an embodiment of the present invention. In this embodiment, the plurality of trench structures 6 are all rectangular, and are distributed in a rectangular array on the upper surface of the N − epitaxial layer 3 . Correspondingly, the top view of each P-type ion implantation region 7 is also rectangular, distributed in a rectangular array. The distance between the plurality of trench structures 6 gradually decreases from the middle to the periphery, so that the area of the first Schottky contact region 8 between adjacent trench structures 6 gradually decreases.

Next, please refer to FIG. 7a-FIG. 7e. FIG. 7a-FIG. 7e are schematic diagrams of the preparation process of a junction barrier Schottky diode with a trench structure provided by an embodiment of the present invention. The preparation method of the trench structure junction barrier Schottky diode of this embodiment specifically includes the following steps:

Step 1: providing an N+ substrate layer 4 and epitaxially growing an N − epitaxial layer 3 on the upper surface of the N+ substrate layer 4 . Specifically, referring to FIG. 7a, a highly doped N-type silicon carbide substrate is selected as the N+ substrate layer 4, and the N+ substrate layer 4 is first cleaned by RCA standard, and then epitaxially grows N+ substrate layer 4 with a thickness of 10-30 μm on its upper surface. - epitaxial layer 3 .

Step 2: Please refer to FIG. 7b, etch trench structures 6 on the upper surface of the N-epitaxial layer 3 by photolithography and etching, the distance between the trench structures 6 gradually increases from the edge to the center, during the preparation At this time, trench structures 6 with different pitches can be etched by designing and using photomasks of different sizes. The specific spacing distribution has been described in detail in the foregoing embodiments, and will not be repeated here.

Step 3: forming a P-type ion implantation region in the trench structure 6 . Specifically, please refer to FIG. 7c, firstly, deposit 2 μm of SiO ₂ as a barrier layer; secondly, fill the trench structure 6 with P-type ion material through an ion implantation process; finally, in the middle of the P-type ion material A groove of a certain size is etched to form a P-type ion implantation region 7 with a concave cross section, and the P-type ion implantation region 7 covers the bottom and sidewalls of the trench structure 6 .

Step 4: Form a cathode electrode layer 5 on the lower surface of the N+ substrate layer 4. Specifically, please refer to FIG. Ni, and then sputter a layer of Ti/Ni/Ag alloy with a thickness of 2-5 μm to form the cathode electrode layer 5 , and the contact area between the N+ substrate layer 2 and the cathode electrode layer 5 is the ohmic contact area 10 .

Step 5: Form an isolation dielectric layer ₂ on the edge of the upper surface of the N-epitaxial layer 3. Specifically, referring to FIG. , etching the SiO ₂ isolation dielectric layer through a photolithography mask to form an isolation dielectric layer 2, so that the isolation dielectric layer 2 surrounds the upper surface of the N-epitaxial layer 3.

Step 6: Anode electrode layer 1 . Specifically, please refer to FIG. 7f, above the N- epitaxial layer 3, sputter Ti with a thickness of 50-100 nm by means of magnetron sputtering, and then sputter Al or Ag with a thickness of 2-5 μm to form an anode electrode layer 1, wherein, The lower layer of metal Ti directly covers the N- epitaxial layer 3, the SiO ₂ isolation dielectric layer and the P-type ion implantation region 7, and forms the first Schottky contact region 8 at the interface with the N-epitaxial layer 3. A second Schottky contact region 9 is formed at the interface of the type ion implantation region 7 .

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Orientation indicated by rear, left, right, vertical, horizontal, top, bottom, inside, outside, clockwise, counterclockwise, etc. The positional relationship is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, Therefore, it should not be construed as limiting the invention.

In the present invention, unless otherwise clearly specified and limited, a first feature being "on" or "under" a second feature may include direct contact between the first and second features, and may also include the first and second features Not in direct contact but through another characteristic contact between them. Moreover, "above", "above" and "above" the first feature on the second feature include that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. "Below", "beneath" and "under" the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (9)

1. a kind of groove structure junction barrier schottky diode, which is characterized in that from top to bottom successively include anode electrode layer (1), spacer medium layer (2), N- epitaxial layer (3), N+ substrate layer (4) and negative electrode layer (5), wherein

Multiple groove structures (6) are offered in the upper surface of the N- epitaxial layer (3), are formed in the inside of the groove structure P-type ion injection region (7)；

The spacing of the adjacent groove structure (6) is in reduction trend from the upper surface center of the N- epitaxial layer (3) to edge, and The geomery of multiple P-type ion injection regions (7) is all the same.

2. groove structure junction barrier schottky diode according to claim 1, which is characterized in that multiple groove knots Structure (6) is concentric ring structure.

3. groove structure junction barrier schottky diode according to claim 1, which is characterized in that multiple groove knots Structure (6) is rectangle, and is scattered in array structure in the upper surface of the N- epitaxial layer (3).

4. groove structure junction barrier schottky diode according to claim 1, which is characterized in that the adjacent groove knot The spacing of structure (6) reduces from the upper surface center of the N- epitaxial layer (3) to edge in a continuous manner.

5. groove structure junction barrier schottky diode according to claim 1, which is characterized in that the adjacent groove knot The spacing of structure (6) reduces from the upper surface center of the N- epitaxial layer (3) to edge in a step-wise manner.

6. groove structure junction barrier schottky diode according to claim 1, which is characterized in that

It is formed between the N- epitaxial layer (3) and the anode electrode layer (1) the first Schottky contact region (8), each p-type The second Schottky contact region (9) are formed between ion implanted region (7) and the anode electrode layer (1).

7. groove structure junction barrier schottky diode according to claim 1, which is characterized in that in the groove structure (6) bottom and inner wall has been respectively formed on the P-type ion injection region (7).

8. groove structure junction barrier schottky diode according to claim 1, which is characterized in that

The groove depth of the multiple groove structure (6) is all the same.

9. groove structure junction barrier schottky diode according to claim 1 to 8, which is characterized in that adjacent The spacing of the groove structure (6) is more than or equal to 3 μm.