JP2002170963A - Semiconductor element, semiconductor device, and method of manufacturing semiconductor element - Google Patents

Abstract

(57) Abstract: To provide a semiconductor element capable of achieving a high level of low loss and low cost. An n-type semiconductor region formed in a middle layer region of a semiconductor substrate (11). Drift region) 17 and semiconductor substrate 1
1 that is exposed at the bottom surface of the concave portion 16 formed on the other main surface 11B side of the semiconductor device 1 and is bonded to the n-type semiconductor region 17 and has an impurity density higher than that of the n-type semiconductor region 17
Semiconductor region 19 and one main surface 11 of semiconductor substrate 11
A p-type semiconductor region 18 exposed to the A side and joined to the n-type semiconductor region 17; a first main electrode layer 12 formed on an exposed portion of the p-type semiconductor region 18; and an exposed portion of the n-type semiconductor region 19 And the second main electrode layer 13 formed on the substrate. For this reason, the thickness of the main operation region of the element can be reduced, so that low loss can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to a semiconductor device, a semiconductor device (primary mounting body), and relates to a manufacturing method of a semiconductor device, more specifically, for example, power, such as low on-resistance R _on of the required power semiconductor diode The present invention relates to a power semiconductor element, a power semiconductor device (primary mounting body), and a method for manufacturing a power semiconductor element. Furthermore, the present invention relates to a high-frequency semiconductor element and a high-frequency semiconductor device (primary mounting body) that operate in a microwave or millimeter-wave band where the thickness of a substrate is a problem, and a method for manufacturing a high-frequency semiconductor element.

[0002]

2. Description of the Related Art Conventionally, a power diode element 1 as shown in FIG. 17 has been known as a semiconductor element. In this diode element 1, an n-type semiconductor region 3 having a relatively low impurity density is formed on one main surface 2A side of an n-type semiconductor substrate 2 having a relatively high impurity density by a known epitaxial growth method. . The n-type semiconductor region 3 functions as a drift region. On the surface of the n-type semiconductor region 3, a p-type semiconductor region 4 formed by diffusing a p-type impurity element is formed. Then, on the p-type semiconductor region 4,
The first main electrode layer 5 is formed so as to be electrically connected. The other main surface 2B of the n-type semiconductor substrate 2 has a second
The main electrode layer 6 is formed so as to be electrically connected.
The n-type semiconductor substrate 2 functions as a cathode region (second main electrode region), and the p-type semiconductor region 4 functions as an anode region (first main electrode region). Further, the first main electrode layer 5 functions as an anode electrode, and the second main electrode layer 6 functions as a cathode electrode.

[0003] In such a diode element 1, the n-type semiconductor region 3 constituting a drift region, since it is formed sufficiently thin as compared with the n-type semiconductor substrate 2 by epitaxial growth method, on-resistance R _on of the device And a low-loss diode is realized. Further, since the n-type semiconductor region 3 is formed by the epitaxial growth method,
A relatively steep impurity density gradient is obtained, and the reverse recovery time t _rr
Can be shortened.

[0004]

In the diode element 1 shown in FIG. 17, an n-type semiconductor region (drift region) 3 having a relatively low impurity density is formed by an epitaxial growth method. However, there is a problem that the cost is higher than the above.

Therefore, if the epitaxial growth method is not used, a predetermined semiconductor region is formed by introducing an impurity element into a semiconductor wafer purchased from the market by a thermal diffusion method or an ion implantation method. However, in this case, the following new problem occurs.

That is, in recent years, the diameter of a semiconductor wafer has been increased, and in the case of silicon, a large wafer of about 300 mm has been adopted. Accordingly, manufacturers of semiconductor wafers are no longer producing small diameter wafers such as 100 mm in diameter. As is well known, as the diameter of a semiconductor wafer increases, the thickness of the wafer increases accordingly. For a small diameter wafer such as 100 mm in diameter, the substrate thickness is about 300 μm to 450 μm or less.
For a large wafer of about 00 mm, the substrate thickness is about 1 mm,
Or more. That is, it is actually difficult to obtain a wafer having a small substrate thickness in the market.

For this reason, when the diode element 1 as shown in FIG. 17 is mass-produced using a large-diameter semiconductor wafer, an n-type semiconductor region (drift region) 3 is formed by the n-type semiconductor substrate. Therefore, the n-type semiconductor region 3
Increases in thickness. The portion corresponding to the n-type semiconductor substrate (cathode region) 2 in FIG. 17 is formed by the thermal diffusion method or the like from the back surface of the semiconductor wafer, and a deep diffusion layer of 100 μm or more is formed by the thermal diffusion method or the like. This is because it takes a long time and productivity is reduced. Therefore,
N-type semiconductor region 3 having a thickness substantially equal to the thickness of the semiconductor substrate 3
Will remain and be formed. n-type semiconductor region 3
Is a high-resistance layer having a relatively low impurity density. When the thickness of the substrate is increased, the on-resistance R _on is reduced, which is disadvantageous in opposition to an attempt to reduce the loss.

In a high-frequency semiconductor device operating in a microwave or millimeter-wave band, when the thickness of the substrate increases, the traveling time of carriers increases, and a problem arises that high-speed operation cannot be performed.

Further, the same applies to a power semiconductor element and a high-frequency semiconductor element.
Since the thermal resistance increases, there is a problem that the heat radiation effect is reduced. Even if the drift region (n-type semiconductor region) 3 of the diode element 1 as shown in FIG. 17 is formed by an epitaxial growth method, the thickness of the semiconductor substrate is unnecessarily large in the n-type semiconductor substrate (cathode). Since the region 2 exists, there is a problem that the thermal resistance increases and the heat radiation effect decreases.

The present invention has been made to solve the above problems. Therefore, an object of the present invention is to provide a semiconductor device that can achieve a high level of low loss and low cost.

Another object of the present invention is to provide a semiconductor device and a semiconductor device (primary package) in which a low loss and a low cost are achieved at a high level, and the heat dissipation and the mechanical strength of the device are improved. And a method for manufacturing a semiconductor device.

[0012]

In order to solve the above-mentioned problems, a first feature of the present invention is that a concave portion is formed on the other main surface side of a semiconductor base to thereby form a semiconductor portion of a main body portion serving as a semiconductor operation region. The feature is that the thickness of the substrate is reduced to reduce the loss and cost of the semiconductor element. That is, the first
The semiconductor device according to the features of (a), a semiconductor substrate,
(B) a first main electrode region having a higher impurity density than the semiconductor substrate formed on one main surface side of the semiconductor substrate;
(C) On the other main surface side of the semiconductor substrate, the cylindrical leg portion formed of the semiconductor substrate is left in the peripheral portion, and formed from the other main surface side of the semiconductor substrate to one main surface side. And a second main electrode region having a higher impurity density than the semiconductor substrate formed opposite to the first main electrode region on the other main surface side of the semiconductor substrate exposed at the bottom of the concave portion. And that it consists of In other words, the concave portion is formed at a substantially central portion on the other main surface side of the semiconductor substrate, and the cylindrical leg portion made of the semiconductor substrate is formed so as to surround the concave portion.

The first main electrode region and the second main electrode region form an operation region (main body portion) serving as a main current path of the semiconductor element. The “first main electrode region” means one of an anode region and a cathode region in a diode element. The “second main electrode region” means either a cathode region or an anode region that is not the first main electrode region in the diode element. Furthermore,
The “first main electrode region” means one of an emitter region and a collector region in a bipolar transistor element or an IGBT element. Heterojunction bipolar transistors (HB
T) Ultra-high frequency transistors operating in a microwave band, a millimeter wave band or a submillimeter wave band, such as elements, are also included. MO
In an IGFET element such as an SFET element, a MOSSIT element, or a high electron mobility transistor (HEMT) element, it means one of a source region and a drain region. In the case of a bipolar transistor element or an IGBT element, the "second main electrode region"
It means either the emitter region or the collector region that does not become the main electrode region, or in the IGFET element, it means either the source region or the drain region that does not become the first main electrode region. That is, if the first main electrode region is an anode region, the second main electrode region is a cathode region, and if the first main electrode region is an emitter region, the second main electrode region is a collector region. If the first main electrode region is a source region, the second main electrode region is a drain region. In a bipolar transistor element, an IGBT element, an IGFET element, and the like, a control electrode region of a base region and a control electrode layer such as a base electrode or a gate electrode are naturally added.

In the semiconductor device according to the first aspect of the present invention, since the concave portion is formed on the other main surface side of the semiconductor substrate, the main body portion substantially serving as the semiconductor operation region is formed to be thin. For example, even if a large-diameter semiconductor substrate (semiconductor wafer) is used as a starting base material, for example, a cathode region is a thin semiconductor region with a high impurity density and a cathode drift region is a semiconductor region made of a semiconductor substrate with a low impurity density. Since it can be configured, the on-resistance R _on can be reduced to achieve low loss. Even when a large-diameter semiconductor substrate (semiconductor wafer) is not used as a starting base material, it is easy to make the base material thinner than the starting base material. Effective for improvement. Further, since the impurity density between the second main electrode region having a high impurity density and the drift region having a low impurity density can be set to a relatively steep impurity density gradient, the reverse recovery time _trr of the semiconductor element can be reduced. It becomes possible. Further, since the cylindrical leg is formed, the main body is reinforced by the leg, and a decrease in mechanical strength can be suppressed even though the semiconductor operation region is made thin.

A semiconductor device (primary mounting body) according to a second aspect of the present invention has a support base provided with a protrusion for reinforcing a thin main body portion of a semiconductor element, thereby enhancing the attachment property and holding function of the semiconductor element, and It has a structure that enhances the heat dissipation effect. That is,
A semiconductor device according to a second aspect of the present invention is a semiconductor device including the semiconductor element described in the first aspect and a supporting base fixed to the semiconductor element. The supporting base fixed to the semiconductor element has a projection on one surface, and the projection is fitted into a recess of the semiconductor element.

In the semiconductor device according to the second aspect of the present invention, the semiconductor device is fixed in the recess formed on the other main surface side of the semiconductor element with the projection of the support base accommodated therein, so The transmission surface becomes large, and the heat radiation of the entire device becomes good. In addition, since the thin body portion is supported by the protruding portion, breakage of the semiconductor element can be reliably prevented, and the reliability of the semiconductor device can be improved. Further, as described in the first feature, it is easy to reduce the on-resistance R _on and the reverse recovery time _trr .

A third feature of the present invention is that each semiconductor region constituting a semiconductor element is formed by introducing an impurity element to manufacture a low-loss and low-cost semiconductor element. That is, the method for manufacturing a semiconductor device according to the third aspect of the present invention is characterized in that: (a) the first element having a higher impurity density than the semiconductor substrate by introducing the impurity element from one main surface side of the semiconductor substrate to a predetermined depth; Forming a main electrode region; and (b) leaving a cylindrical leg made of the semiconductor substrate on the other main surface side of the semiconductor substrate from the other main surface side of the semiconductor substrate. (C) forming a recess toward one main surface side; and (c) forming, on the other main surface side of the semiconductor substrate exposed at the bottom of the recess, a higher impurity than the semiconductor substrate facing the first main electrode region. Forming a second main electrode region having a high density.

In a method of manufacturing a semiconductor device according to a third aspect of the present invention, the first and second main electrode regions are formed by introducing an impurity element into a semiconductor substrate by a thermal diffusion method, an ion implantation method, or the like. The thickness of the semiconductor region sandwiched between the first and second main electrode regions can be reduced or made zero.
Therefore, the on-resistance R _on , the reverse recovery time _trr, and the heat radiation resistance can be reduced. In addition, since this structure can be realized without employing an expensive and complicated epitaxial growth method, the manufacturing is simplified and the cost can be reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of a semiconductor device, a semiconductor device, and a method of manufacturing a semiconductor device according to embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the thickness of each layer and their ratios are different from actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. In addition, it is needless to say that dimensional relationships and ratios are different between drawings.

(First Embodiment: Diode Element) FIGS. 1 and 2 are cross-sectional views of a diode element as a semiconductor element according to a first embodiment of the present invention. As shown in FIG. 1, a diode element 10a according to the first embodiment includes a semiconductor substrate (silicon substrate) 11 made of silicon (Si) and one main surface 11A of the semiconductor substrate 11.
A first main electrode region (anode region) 18 having a higher impurity density than the semiconductor substrate 11 formed on the side thereof, and a first main electrode region 18 having a higher impurity density than the semiconductor substrate 11 formed opposite the first main electrode region 18. And two main electrode regions (cathode regions) 19. In the diode element 10a, the n-type semiconductor region 17 composed of the semiconductor substrate 11 sandwiched between the first main electrode region 18 and the second main electrode region 19 functions as a cathode drift region. The other main surface 1 of the semiconductor substrate 11
On the 1B side, a concave portion 16 formed from the other main surface 11B side to the one main surface 11A side of the semiconductor base 11 is formed such that a cylindrical leg made of the semiconductor base 11 is left in the peripheral portion. Is formed. The second main electrode region 19 is formed on the semiconductor substrate 1 exposed at the bottom of the recess 16.
1 is formed on the other main surface 11B. Further, one main surface 11A side of the semiconductor substrate 11 and the other main surface 11B
A first main electrode layer (anode electrode layer) 12 and a second main electrode layer (cathode electrode layer) 13 are formed on both sides.

The diode element 10a according to the first embodiment is structurally roughly composed of a main body portion 14 and legs 15 as shown in FIG. Leg 15
Is formed in a cylindrical shape protruding downward from the entire periphery of the lower surface of the main body portion 14 (the other main surface side of the semiconductor substrate 11). That is, the leg portion 14 is formed in a cylindrical shape by forming the concave portion 16 inside the peripheral portion of the other main surface 11B of the thick semiconductor substrate (semiconductor wafer) 11 as will be described later. It has a peripheral portion of the semiconductor substrate 11. In the first embodiment, the case where the planar shape of the main body portion 14 is rectangular and the shape of the leg portion 14 is a rectangular cylindrical shape is exemplified. However, the present invention is not limited thereto. May be a cylindrical shape or the like.

FIG. 2 is a bottom view of the diode element 10a according to the first embodiment, and shows a structure in which the legs 14 are formed around the bottom edge of the diode element 10a. In the first embodiment, as shown in FIG. 1, the length (substrate thickness) dimension L1 of the semiconductor substrate 11 forming the leg portion 14 is larger than that of the semiconductor substrate 11 forming the main body portion. It is set to be longer than the thickness dimension L2.

The main body portion 14 includes a starting base material, that is, a semiconductor substrate 11 as a remaining portion after processing the semiconductor wafer.
For example, n as a drift region in which donor impurities such as phosphorus (P) and arsenic (As) are introduced at a low impurity density.
Semiconductor region 17 and one main surface 11 of semiconductor substrate 11
P-type semiconductor region 1 as a first main electrode region in which an acceptor impurity such as boron (B) is diffused from A
And an n-type as a second main electrode region formed by diffusing a donor impurity such as phosphorus (P) or arsenic (As) from the other main surface 11B side of the semiconductor substrate 11 to a high impurity density. A semiconductor region 19 is formed.

In the leg portion 15, the n-type semiconductor region 19 having a high impurity density formed in the main body portion 14 is extended so as to hang down from the entire peripheral portion thereof to form an n-type semiconductor region 19A. On the outside of the n-type semiconductor region 19A constituting the leg portion 15, an n-type semiconductor region 17A is formed extending downward so as to hang down from the entire peripheral portion of the n-type semiconductor region 17 of the main body portion 14. Are joined and surrounded. That is, the n-type semiconductor region 19 is formed by diffusing a donor impurity from the other main surface 11B side of the semiconductor substrate 11, and the leg 1
5 from the lower surface of the semiconductor substrate 11 to the lower surface of the semiconductor substrate 11
6 are formed with substantially the same diffusion depth over the entire surface.

In the diode element 10a according to the first embodiment, the second main electrode layer 13 is formed along the entire other main surface 11B of the semiconductor substrate 11. The thickness of the second main electrode layer 13 is not large enough to fill the entire recess 16. That is, the second main electrode layer 1
3 is formed relatively thin along the surface of the concave portion 16, and the concave portion 16 remains on the lower surface of the second main electrode layer 13.

In the diode element 10a according to the first embodiment of the present invention, a main operating region of a device serving as a main current path is formed in a main body portion 14 in which a semiconductor substrate 11 is formed to be thin. The total thickness of the drift region 17 and the cathode region 19 is reduced. That is,
Even when a large-diameter wafer is used as a starting base material, the main body portion 14 can be formed thin by forming the concave portion 16 on the other main surface 11B side of the semiconductor substrate 11. For this reason, even when the wafer is manufactured using a large-diameter wafer having a large substrate thickness as a starting material (base material), the diode element 10
a can be reduced. In addition, body part 1
By controlling the thickness of the high impurity density n-type semiconductor region 19 in 4, the on-resistance R _on of the element can be further reduced.

In the diode element 10a according to the first embodiment, the n-type semiconductor region 19 having a high impurity density is provided.
And the impurity density gradient between the n-type semiconductor region 17 having a low impurity density and the low impurity density can be made relatively steep, so that the reverse recovery time t
_rr can be shortened, and high-speed operation is facilitated.

Furthermore, in the diode element 10a according to the first embodiment, the semiconductor body 11
The main body portion 14 is reinforced by the leg portions 15 because the leg portions 15 which are left in a thick state are formed so as to protrude in a cylindrical shape. Therefore, it is possible to suppress a decrease in mechanical strength of the entire element despite the formation of the thin main body portion 14. Also, this leg 15
Can also function as a heat sink for the element, so that the heat dissipation of the diode element 10a can be improved.

The diode element 10a according to the first embodiment does not include a semiconductor region formed by the epitaxial growth method, and is formed substantially only by the impurity element diffusion step. In addition, the manufacturing cost can be kept low.

In the first embodiment, the leg 1
Although the length L1 is set to be longer than the thickness L2 of the main body portion 14, the length L1 of the leg portion 15 is appropriately changed depending on the thickness of the semiconductor wafer used as the starting base material.

[Semiconductor Device] FIG. 3 is a sectional view showing a semiconductor device (primary mounting body) 20 using the diode element 10a according to the first embodiment of the present invention. The semiconductor device 20 according to the first embodiment has a primary mounted body including the above-described diode element 10a, a support base 21 on which the diode element 10a is mounted, and a resin sealing body 22 covering the diode element 10a. It is.

The support base 21 is made of, for example, alumina (Al ₂
It is formed of a ceramic material such as O ₃ ) or aluminum nitride (AlN), a synthetic resin, or another material having high thermal conductivity and electrical insulation. In addition, at the position where the diode element 10a is mounted on the support base 21, a trapezoidal projection 23 that fits into the recess 16 of the diode element 10a is provided.
Are formed. On the periphery of the protruding portion 23 of the support base 21, a pad portion 24A of the wiring 24 patterned so as to be connected to an external terminal (not shown) is arranged.
The diode element 10a is connected to the pad portion 24A of the wiring 24 by the solder 25 in a state where the concave portion 16 is fitted to the projecting portion 23 of the support base 21, and the support base 2
Fixed to 1. The first of the diode element 10a
The main electrode layer 12 is connected to other external terminals via wires (not shown). In addition, the resin sealing body 22 can use various electric insulating resins such as an epoxy resin and a silicon resin.

In the semiconductor device 20 having such a configuration, the diode element 10a is fixed to the recess 16 formed on the other main surface of the semiconductor substrate 11 with the projection 23 of the support substrate 21 housed therein. Therefore, the diode element 10a
The contact surface area between the support and the support base 21 increases, and the thermal contact resistance decreases. For this reason, there is an advantage that heat dissipation is improved.

Further, the protrusion 23 of the support base 21
Since the thin main body portion 14 is supported, the mechanical strength of the main body portion 14 is increased, the elements are less likely to be damaged, and the reliability of the semiconductor device 20 can be improved.

[Method of Manufacturing Semiconductor Element] Next, a semiconductor element (diode element) according to the first embodiment of the present invention.
The manufacturing method of 10a will be described with reference to FIGS.
In the method of manufacturing the semiconductor element 10a according to the first embodiment, a large-diameter thick silicon wafer is used as a semiconductor base as a starting base material. For example, a substrate diameter of 500 μm to 700 μm at a wafer diameter of 150 mm, or a substrate thickness of 600 μm to 900 μm at a wafer diameter of 200 mm,
Further, a silicon wafer having a wafer diameter of 300 mm and a substrate thickness of 800 μm to 1 mm or more can be used.

(A) First, a silicon ingot grown by the FZ method, the CZ method, or the like is cut out, and as shown in FIG.
A silicon wafer (semiconductor substrate) 11 into which a type impurity element has been introduced is prepared. Then, as shown in FIG. 5, the silicon oxide films 26 and 27 are formed on one main surface 11A and the other main surface 11B of the semiconductor substrate (silicon wafer) 11 by thermal oxidation to a thickness of about 350 nm to 1 μm. Form.

(B) Next, a photoresist 28 is coated on the silicon oxide film 26 of the semiconductor substrate 11 by a known photolithography technique, and is exposed and developed to form a pattern of the photoresist 28. Then, as shown in FIG. 6, using this photoresist 28 as a mask,
An opening 26A is formed in the silicon oxide film 26 by performing wet etching or dry etching.

(C) Subsequently, after the photoresist 28 is removed, as shown in FIG. 7, an impurity-added thin film containing an acceptor impurity such as boron (B) is formed on one main surface 11A side of the semiconductor substrate 11. (Silicon oxide film, silicon nitride film, polysilicon film, etc.) 29 are deposited. Then, a p-type semiconductor region (anode region) 18 is formed by performing a heat treatment to perform selective diffusion to invert the conductivity type.
A gas phase diffusion method using a solid source such as boron nitride (BN) or a liquid source such as boron tribromide (BBr ₃ ) without using the impurity-added thin film may be used. Impurity ions such as ¹¹ B ⁺ and ⁴⁹ BF ₂ ⁺ are ion-implanted to 3 × 10 ¹⁵ cm ^−2.
A predetermined dose of about 5 × 10 ¹⁶ cm ⁻² or the like may be implanted, and then drive-in (heat treatment) to a desired depth may be performed.

(D) Next, after the impurity element source thin film 29 is removed by etching (or after boron glass or the like formed after drive-in is removed by etching), as shown in FIG. On one main surface 11A side and the other main surface 11B side, a silicon nitride film (Si ₃ N ₄ film) 51,
52 is deposited from 150 nm to 400 nm. As a result, the silicon nitride film 51 deposited on the one main surface 11A side of the semiconductor substrate 11 is a thin silicon oxide film (not shown) formed on the surface of the silicon oxide film 26 and the main surface 11A in the opening 26A. ) Is covered. The silicon nitride film 52 deposited on the other main surface 11B is stacked on the silicon oxide film 27.

(E) Thereafter, a photoresist 53 is applied to the other main surface 11B of the semiconductor substrate 11 on which the silicon nitride film 52 has been formed, and is exposed and developed to form a p-type semiconductor as shown in FIG. The photoresist 53 is patterned so that a position corresponding to the region 18 is opened.

(F) Then, using the photoresist 53 as a mask, the silicon nitride film 52 and the silicon oxide film 27 are selectively etched by reactive ion etching (RIE) or the like. At this time, the silicon oxide film 27 may be selectively etched by wet etching. Thereafter, after the photoresist 53 is stripped, anisotropic etching is performed using the silicon oxide film 27 and the silicon nitride film 52 as masks, and as shown in FIG. A recess 16 having a depth is formed. The other main surface 11B of the semiconductor substrate 11 is etched, for example, using potassium hydroxide (KOH).
Etching using an alkaline etching solution such as a mixed solution of ethylene chloride and ethylenediamine pyrocatechol, for example, boron trichloride (BCl ₃ ), silicon tetrachloride (SiCl ₄ ),
Anisotropic dry etching such as RIE using a chlorine-based etching gas such as phosphorus trichloride (PCl ₃ ) is performed. In the case of anisotropic etching, it should be noted that the plane orientation of the substrate 11 and the direction of the mask pattern are selected in a predetermined relationship. As shown in FIG. 10, a concave portion 16 having a predetermined depth may be formed on the other main surface 11B side of the semiconductor substrate 11 by a mechanical method such as sandblasting instead of anisotropic etching. In the case of a semiconductor device for a large current using the entire wafer as one device, the circular concave portion 16 can be formed by sandblasting while rotating the substrate 11. Furthermore, it is also possible to carry out a combination of a mechanical method such as sandblasting and anisotropic etching.

(G) Next, as shown in FIG. 11, after the silicon oxide film 26 and the silicon nitride film 52 formed on the other main surface 11B of the semiconductor substrate 11 are removed by etching, the exposed semiconductor substrate 11 is removed. On the other main surface 11B side, a donor impurity such as phosphorus (P) or arsenic (As) is diffused at a high concentration over the entire surface to form an n-type semiconductor region (cathode region) 19 having substantially the same depth over the entire surface. I do. in this case,
For example, an impurity-added thin film containing a donor impurity such as phosphorus (P) or arsenic (As) may be used, and a gas-phase diffusion method using a liquid source such as phosphorus oxychloride (POCl ₃ ) without using the impurity-added thin film. But it is good. Impurity ions such as ³¹ P ⁺ , ⁷⁵ As ⁺ are implanted by ion implantation at 3 × 10 ¹⁵ cm.
A predetermined dose such as ^{−2 to} 5 × 10 ¹⁶ cm ⁻² may be implanted from an oblique angle, and then drive-in (heat treatment) may be performed to a desired depth. As a result, the n-type semiconductor region 19 and p
The region between the semiconductor region 18 and the semiconductor region 18 becomes the n-type semiconductor region 17 having the intrinsic donor impurity density of the semiconductor substrate 11.

(H) Thereafter, as shown in FIG. 12, the silicon nitride film 51 on one main surface 11A side of the semiconductor substrate 11 is formed.
Using a photolithography technique and an etching technique, an opening 51A having substantially the same range as the opening 26A of the silicon oxide film 26 is formed, and a contact opening is opened.
In this case, the silicon nitride film 51 and the silicon oxide film 26 are selectively etched by RIE or the like using a photoresist (not shown) as a mask. At this time, the silicon oxide film 26 may be selectively etched by wet etching.

(I) Then, as shown in FIG. 13, a metal for an electrode is formed on one main surface 11A side and the other main surface side 11B of the semiconductor substrate 11 in which the contact opening is opened, for example, by a vacuum evaporation method. Or by using a sputtering method.
The first main electrode layer (anode electrode layer) 12 and the second main electrode layer (cathode electrode layer) 13 are formed by depositing to a predetermined thickness of about 10 μm to 10 μm, respectively. Then, the first main electrode layer 12 is patterned into a desired electrode shape as shown in FIG. 13 by using a lithography technique and an etching technique.

(V) Thereafter, the semiconductor substrate (semiconductor wafer) 11 is divided by dicing to complete the manufacture of the individual diode elements 10a.

(G) Further, as shown in FIG.
The semiconductor device 2 is soldered so that the recess 16 of the diode element 10a fits into the projection 23 of the semiconductor device 2.
0 is completed.

The diode element 10 manufactured as described above
a and the semiconductor device 20, the diode element 10a is formed on the other main surface 11B side of the semiconductor substrate 11 in the concave portion 1a.
6, the projecting portion 23 of the support base 21 is fixedly accommodated therein, so that good heat dissipation is achieved, and the projecting portion 23 supports the thin main body portion 14 of the diode element 10a. Is reliably prevented, and the reliability of the semiconductor device 20 can be improved.

[Modification 1 of Semiconductor Element] Here, the diode element 1 according to Modification 1 of the first embodiment described above.
0b will be described with reference to FIG. FIG.
In the diode element 10b shown in (1), portions having the same functions as those of the diode element 10a according to the first embodiment of the present invention are denoted by the same reference numerals, and description thereof is omitted. FIG.
Is different from the diode element 10a according to the above-described first embodiment only in the shape of the second main electrode layer 13, and the other configuration is the same as that of the above-described first embodiment.

That is, in the diode element 10 b according to the first modification of the first embodiment, the second main electrode layer 13 is provided only on the bottom surface of the concave portion 16 formed on the other main surface side of the semiconductor substrate 11. It is selectively formed. When the semiconductor device is manufactured by attaching the diode element 10b having such a configuration to the support base 21 as shown in FIG.
A pad portion 24A of a wiring 24 patterned to be connected to an external terminal (not shown)
Must be arranged. Then, with respect to such a supporting base 21, the diode element 10b assembles (assembles) the semiconductor device by fixing the second main electrode layer 13 to the top surface of the protrusion 23 via solder.
be able to. At this time, the inner peripheral surface of the recess 16 is
3 does not need to be fixed to the outer peripheral surface, a stress generated based on a difference in linear expansion coefficient between the semiconductor substrate 11 and the support substrate 21 is applied to a clearance (gap) formed between the concave portion 16 and the projecting portion 23. There is an advantage that it can be relaxed.

The operation and effect of the first modification are the same as those of the diode element 10a according to the first embodiment.

[Modification 2 of Semiconductor Element] FIG.
14 shows a diode element 10c according to a modification 2 of the embodiment. In the description of the second modification, the same portions and the portions that perform the same functions as those of the diode element 10a according to the first embodiment are the same as those of the diode element 10a according to the first embodiment. And the description is omitted. In the diode element 10c according to the second modification, the shape of the high impurity density n-type semiconductor region 19 formed on the other main surface 11B side of the semiconductor substrate 11 is as follows.
Diode element 10a according to the first embodiment described above
And different.

In other words, the semiconductor element 10 c according to the second modification of the first embodiment has the other main surface 11
On the B side, a high impurity density n-type semiconductor region 19 is
6 is selectively formed only in a region that is in contact with the bottom portion.
Therefore, the concave portion 1 on the other main surface 11B of the semiconductor substrate 11
6, a silicon oxide film 61 is formed on the inner peripheral surface and the surface around the concave portion 16. Then, the silicon oxide film 61
The portion corresponding to the bottom surface of the concave portion 16 of the
The main electrode layer 13 is formed so as to make ohmic contact with the n-type semiconductor region 19.

The above-mentioned n-type semiconductor region 19 may be formed by diffusing an impurity element from the region where the window of the silicon oxide film 61 is opened to a predetermined depth by a selective diffusion method.

The operation and effects of the second modification are the same as those of the diode element 10a according to the first embodiment.

(Second Embodiment: Bipolar Transistor Element) Next, a semiconductor element according to a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the present invention relates to a bipolar transistor (BJ).
T) Applied to an element.

As shown in FIG. 16, a bipolar transistor element 30 according to a second embodiment of the present invention has a semiconductor substrate (silicon substrate) 31 made of silicon and one main surface 31A side of the semiconductor substrate 31. The first main electrode region (emitter region) 40 having a higher impurity density than that of the semiconductor substrate 31 formed on the semiconductor substrate 31 and the other main surface 31B of the semiconductor substrate 31 are formed facing the first main electrode region 40. The second main electrode region (collector region) 41 has a higher impurity density than the semiconductor substrate 31. Further, in contact with the first main electrode region 40, the control electrode region (base region) 3
9, the control electrode region 39 and the second main electrode region 41.
A drift region (collector / drift region) 38 made of the semiconductor substrate 31 is formed between the two. On the other main surface 31B side of the semiconductor substrate 31, the semiconductor substrate 31
The main body 31 of the semiconductor substrate 31 is moved from the side of the other main surface 31B so that the cylindrical leg portion made of
A concave portion 37 is formed toward the A side. This recess 3
7, the other main surface 31B of the semiconductor substrate 31 exposed at the bottom
The second main electrode region 41 is formed. Further, a first main electrode layer (emitter electrode layer) 32 and a second main electrode layer 32 formed on one main surface 31A side of the semiconductor substrate (semiconductor substrate) 31 are formed.
It has a main electrode layer 33, a control electrode (base electrode) 33 formed in contact with the control electrode region 39, and a second main electrode layer (collector electrode layer) 34 formed on the other main surface 31B side. .

As shown in FIG. 16, the bipolar transistor element 30 according to the second embodiment is substantially constituted by a main body 35 and legs 36 in terms of structure. The leg 36 is provided on the lower surface of the main body 35 (the semiconductor base 31).
(The other main surface 31B side) is formed in a cylindrical shape protruding downward from the entire circumference. That is, the leg portion 36 is formed in a cylindrical shape by forming the concave portion 37 inside except for the peripheral edge of the other main surface 31B of the thick semiconductor substrate (semiconductor wafer) 31 as described later. It has a peripheral portion of a semiconductor substrate (semiconductor substrate) 31. In the second embodiment, the planar shape of the main body portion 35 is rectangular, and the shape of the leg portion 36 is a rectangular tube shape. However, the main body portion may have a planar circular shape, and the leg portion may have a cylindrical shape. Is the same as in the first embodiment.

In the main body portion 35, a starting base material, that is, a semiconductor substrate (semiconductor substrate) 31 as a remaining portion after processing of a semiconductor wafer is coated with a donor impurity such as phosphorus (P) or arsenic (As). An n-type semiconductor region 38 introduced at a high density; a p-type semiconductor region 39 in which an acceptor impurity such as boron (B) is diffused from one main surface 31A of a semiconductor substrate (semiconductor substrate) 31; For example, phosphorus (P) is formed in the semiconductor region 39 from the main surface 31A.
Formed by diffusing donor impurities such as arsenic and arsenic (As)
From the side of the other main surface 31B of the semiconductor substrate 40 and the semiconductor substrate (semiconductor substrate) 31, for example, phosphorus (P) or arsenic (A
An n-type semiconductor region 41 in which donor impurities such as s) are diffused to have a high impurity density is formed.

In the leg portion 36, an n-type semiconductor region 41 having a high impurity density formed in the main body portion 35 is formed so as to extend downward so as to hang down from the entire peripheral portion thereof. Outside the extended n-type semiconductor region 41A, the low impurity density n of the body portion 35 is formed.
N-type semiconductor region 38A extending so as to hang down from the entire peripheral portion of type semiconductor region 38
Are joined and surrounded. That is, the n-type semiconductor regions 41 and 41A having a high impurity density are formed by diffusing donor impurities from the other main surface 31B side of the semiconductor substrate (semiconductor substrate) 31 and from the lower surface of the legs 36 It is formed with substantially the same diffusion depth over the entire surface of the concave portion 37 formed on the lower surface of the base (semiconductor substrate) 31.

In the bipolar transistor element 30 according to the second embodiment, the above-mentioned second main electrode layer 34 is formed along the entire other main surface 1B side of the semiconductor substrate (semiconductor substrate) 31. . This second main electrode layer 34
It is formed relatively thin along the surface of the recess 37 without filling the entire recess 37. Therefore, the concave portion 37 remains on the lower surface of the second main electrode layer 34.

In the bipolar transistor element 30 according to the second embodiment of the present invention, a main operating region of a device is formed in a main body portion 35 having a thin semiconductor substrate (semiconductor substrate) 31 formed therein. Has become thinner. That is, even if a large-diameter wafer is used as a starting base material, the other main surface 3 of the semiconductor substrate (semiconductor substrate) 31 can be used.
By forming the concave portion 37 on the 1B side, the main body portion 35 is formed.
Can be formed thin. For this reason, even if the manufacturing is performed using a semiconductor wafer having a large diameter and a large substrate thickness, the loss of the bipolar transistor element 30 can be reduced. In addition, the on-resistance R _on of the element can be further reduced by controlling the impurity density of each layer and the thickness dimension of the region in the main body portion 35. or,
Even when a large-diameter semiconductor substrate (semiconductor wafer) is not used as a starting base material, it is easy to make the base material thinner than the starting base material. This is effective in improving the high-frequency characteristics and the heat radiation characteristics of the element 30. Further, since the impurity density between the second main electrode region having a high impurity density and the drift region having a low impurity density can be set to a relatively steep impurity density gradient, the reverse recovery time _trr of the semiconductor element can be shortened, The characteristics can be improved.

Further, in the bipolar transistor element 30 according to the second embodiment, the leg portion 36 in which the semiconductor substrate (semiconductor substrate) 31 is left thick from the main body portion 35 is formed.
Is formed so as to protrude into a cylindrical shape, so that the main body portion 35 is reinforced by the leg portions 36. Therefore,
As a whole, it is possible to suppress a decrease in mechanical strength even though the thin main body portion 35 is formed. Further, since the leg portion 36 can also function as a heat sink for the device, the heat dissipation of the bipolar transistor device 30 can be improved.

The bipolar transistor element 30 according to the second embodiment does not include a semiconductor region formed by the epitaxial growth method, and is formed substantially only by the impurity element diffusion step. Therefore, manufacturing costs can be kept low.

(Other Embodiments) The first and second embodiments have been exemplarily described above.
It should not be understood that the description and drawings forming part of the disclosure of the second embodiment limit the present invention. From this disclosure, various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art. For example, in the first and second embodiments of the present invention, the present invention is applied to the diode element and the bipolar transistor element as the semiconductor elements, respectively. However, the semiconductor element is manufactured using a large-diameter semiconductor wafer. MOSFET device, IG
BT element, thyristor element, GTO thyristor element, S
It goes without saying that the present invention can be applied to various semiconductor devices such as an I-thyristor device.

In the first and second embodiments of the present invention, the case where silicon is used as a semiconductor material has been described. However, the semiconductor material is not limited to silicon, but may be gallium arsenide (GaAs) or the like. May be used. For example, when the present invention is applied to an HBT or the like using a compound semiconductor material that operates in a microwave band or a millimeter wave band, it is possible to improve high-frequency characteristics and heat radiation characteristics.

In the first embodiment of the present invention, the semiconductor substrate 11 is n-type and the first main electrode region 18 is p-type.
Although the type and the second main electrode region 19 have been described as n-type, these conductivity types may be reversed. If the conductivity types are reversed, the first main electrode region 18 becomes a cathode region and the second main electrode region 19 becomes an anode region. Similarly, all of the conductivity types of the second embodiment may be reversed. or,
The semiconductor substrates 11 and 38 and the second main electrode regions 19 and 41 may be configured to have opposite conductivity types.

Further, in a certain case such as a Zener diode, the first embodiment may have a structure in which the first main electrode region 18 and the second main electrode region 19 are in direct contact with each other.

In the first embodiment, the diode element 10a in the semiconductor device 20 is sealed with resin. However, the diode element 10a may be sealed in a ceramic package. In addition, the above-described support base 2
One of the protrusions 23 may be provided with a heat dissipation via hole, and a heat dissipation fin may be provided on the back surface of the support base 21.
This is the scope of the present invention.

As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the matters specifying the invention according to the claims that are appropriate from the above description.

[0070]

As is apparent from the above description, according to the present invention, since the main operating region of the semiconductor element is formed in the thin main body, for example, a semiconductor substrate having a large diameter is used as a starting base material. This also has the effect of achieving low loss at a high level.

Further, according to the present invention, the thickness of the main operating region of the semiconductor device can be reduced, so that the high-frequency characteristics can be improved even in a semiconductor device for an ultra-high frequency operating in a microwave band or a millimeter wave band. is there. In these semiconductor devices for ultra-high frequency, a compound semiconductor material having a small diameter may be used.
It is also effective when the thickness is reduced to the following level.

Further, according to the present invention, since the main body of the semiconductor device is provided with the cylindrical legs, the mechanical strength of the entire semiconductor device is increased regardless of the thickness of the main body.

Further, according to the semiconductor device of the present invention,
By accommodating the protruding portions of the support legs in the recesses of the semiconductor element, the attachment of the semiconductor element is improved and the heat dissipation is improved.

Further, according to the method of manufacturing a semiconductor device according to the present invention, each semiconductor region can be formed in a step of introducing an impurity element by a thermal diffusion method or the like without the need for epitaxial growth. There is.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a bottom view showing the semiconductor device according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing the semiconductor device according to the first embodiment of the present invention.

FIG. 4 is a process cross-sectional view (No. 1) illustrating the process of manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 5 is a process sectional view (2) showing the step of manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 6 is a process sectional view (3) showing a step for manufacturing the semiconductor device according to the first embodiment of the present invention;

FIG. 7 is a process sectional view (part 4) showing a step for manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 8 is a process cross-sectional view (No. 5) showing the manufacturing process of the semiconductor device according to the first embodiment of the present invention.

FIG. 9 is a process cross-sectional view (part 6) illustrating the process of manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 10 is a process sectional view (part 7) showing the step of manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 11 is a process sectional view (8) showing a step for manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 12 is a process cross-sectional view (No. 9) showing the manufacturing process of the semiconductor device according to the first embodiment of the present invention.

FIG. 13 is a process sectional view (10) showing a step for manufacturing a semiconductor device according to the first embodiment of the present invention.

FIG. 14 is a cross-sectional view illustrating a semiconductor device according to Modification Example 1 of the first embodiment of the present invention.

FIG. 15 is a cross-sectional view illustrating a semiconductor device according to Modification 2 of the first embodiment of the present invention.

FIG. 16 is a sectional view showing a semiconductor device according to a second embodiment of the present invention.

FIG. 17 is a sectional view showing a conventional diode element.

[Explanation of symbols]

10a, 10b, 10c Diode element (semiconductor element) 11 Semiconductor base 12 First main electrode layer 13 Second main electrode layer 14, 35 Main body 15, 36 Leg 16, 37 Concave 17, 38 n-type semiconductor region (drift region) ) 18,40 p-type semiconductor region (first main electrode region) 19,41 n-type semiconductor region (second main electrode region) 20 semiconductor device 21 support base 23 protrusion 24 wiring 30 bipolar transistor element (semiconductor element) 33 control Electrode 39 Control electrode area

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 29/78 655 H01L 29/80 H 29/778 29/90 D 21/338 29/91 A 29/812 F 29 / 866 21/329

Claims (15)

[Claims] A semiconductor substrate; a first main electrode region having a higher impurity density than the semiconductor substrate formed on one main surface side of the semiconductor substrate; By leaving a cylindrical leg made of a semiconductor substrate in the periphery,
A concave portion formed from the other main surface side of the semiconductor base toward the one main surface side; and a first main electrode region formed on the other main surface side of the semiconductor base exposed at the bottom of the concave portion. And a second main electrode region having a higher impurity density than the semiconductor substrate formed opposite to the semiconductor substrate. 2. The semiconductor device according to claim 1, wherein the first main electrode region is of a first conductivity type, and the second main electrode region is of a second conductivity type opposite to the first conductivity type. 2. The semiconductor device according to 1. 3. The semiconductor device according to claim 1, further comprising a drift region formed of said semiconductor substrate between said first main electrode region and said second main electrode region. 4. The first main electrode region is of a first conductivity type, and has a second conductivity type between the first main electrode region and the drift region, which is a conductivity type opposite to the first conductivity type. 4. The semiconductor device according to claim 3, further comprising a control electrode region, wherein the second main electrode region is of the first conductivity type. 5. The semiconductor device according to claim 1, wherein said semiconductor substrate and said second main electrode region are of the same conductivity type. 6. The semiconductor device according to claim 1, wherein the second main electrode region is selectively formed on a part of the semiconductor substrate exposed at the bottom of the recess on the other main surface side. 5
The semiconductor device according to any one of the above items. 7. The semiconductor device according to claim 1, wherein the second main electrode region is formed on the other main surface side of the semiconductor substrate exposed at a bottom portion of the concave portion and a side wall portion of the concave portion. 6. The semiconductor device according to claim 5. 8. The semiconductor device according to claim 1, further comprising: a first main electrode layer in contact with said first main electrode region; and a second main electrode layer in contact with said second main electrode region. The semiconductor device according to any one of the above items. 9. The semiconductor device according to claim 7, wherein the second main electrode layer is selectively formed only on the bottom of the recess.
Or the semiconductor device according to 8. 10. The semiconductor device according to claim 7, wherein said second main electrode region is formed along a bottom portion of said concave portion and a side wall portion of said concave portion. 11. A semiconductor substrate, a first main electrode region formed on one main surface side of the semiconductor substrate and having a higher impurity density than the semiconductor substrate, and the other main surface side of the semiconductor substrate includes: A concave portion formed from the other main surface side to the one main surface side of the semiconductor substrate so as to leave a cylindrical leg portion made of a semiconductor substrate in a peripheral portion, and exposed to a bottom portion of the concave portion. A semiconductor element comprising, on the other main surface side of the semiconductor substrate, a second main electrode region having a higher impurity density than the semiconductor substrate formed opposite to the first main electrode region; A semiconductor device, comprising: a supporting base fixed to the semiconductor element, wherein the projecting part is fitted with the concave part of the semiconductor element. 12. The semiconductor device according to claim 11, wherein a wiring connected to an external terminal is formed on a surface of said support base. 13. The semiconductor device further includes a first main electrode layer in contact with the first main electrode region, and a second main electrode layer in contact with the second main electrode region. The layer and the wiring are electrically connected to each other.
13. The semiconductor device according to claim 1. 14. A step of introducing an impurity element from one main surface side of the semiconductor substrate to a predetermined depth to form a first main electrode region having a higher impurity density than the semiconductor substrate; On the main surface side, leaving a cylindrical leg made of the semiconductor substrate in the peripheral portion,
Forming a concave portion from the other main surface side of the semiconductor base toward the one main surface side; and forming the first main electrode on the other main surface side of the semiconductor base exposed at the bottom of the concave portion. Forming a second main electrode region having an impurity density higher than that of the semiconductor substrate in opposition to the region. 15. The method according to claim 14, wherein the second main electrode region is formed by diffusing the entire surface of the bottom and the side wall of the concave portion.