JP3027512B2 - Power MOSFET - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power MOSFET ,
In particular relates to technology for reducing electrical resistance, for example, relates valid by using those of high fever with a high output.

[0002]

2. Description of the Related Art Generally, power transistors and power I
2. Description of the Related Art Semiconductor devices having high output and high heat generation such as C are used in all fields of electronic devices and electric devices such as power supplies and switches of battery driving devices, automotive electric components, and motor driving control devices. Among such high-output and high-heat semiconductor devices, a conventional power transistor is described as an example in Japanese Patent Application Laid-Open No.
There is 9-25256. In this power transistor, a header for heat dissipation is integrally formed on a lead frame, a pellet is fixed on the header, and an electrode pad of the pellet and an inner lead are electrically connected by a bonding wire. And a part of the pellet, the inner lead group, and the header are resin-sealed by a resin-sealed body.

[0003]

In the conventional power transistor, the electric resistance of the bonding wire and the electric resistance of the aluminum wiring of the pellet (hereinafter referred to as the external resistance) and the resistance inside the pellet (hereinafter referred to as the external resistance).
It is called internal resistance. ) Is the ON resistance of the entire power transistor. Here, at the stage where the internal resistance is large, the external resistance hardly caused a problem. However, when technological innovation progresses and the internal resistance is reduced and improved to a level where the external resistance exceeds about 50% of the whole, the external resistance cannot be ignored.

An object of the present invention is to provide a power MOSFET capable of suppressing an external resistance component.

[0005] The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0006]

The outline of a typical invention among the inventions disclosed in the present application is as follows.

[0007] Means for solving the above-mentioned problems are as follows.
Arranged on the main surface on the side where the circuit elements of the conductor pellet are built
Source electrode and gate electrode, and the semiconductor pellet
A drain electrode disposed on a main surface of the unit opposite to the main surface.
Pole and the source electrode, gate electrode, and drain electrode.
Power having a plurality of inner leads connected to each other
-In the MOSFET, the source electrode is the gate
The contact area larger than the connection area between the electrode and the inner lead
The inner lead is connected to the inner lead through a connection having a flat area.
It is characterized by being connected mechanically and mechanically.

[0008]

According to the above means, the source electrode is connected to the gate electrode.
Connection plane larger than the connection plane area between the pole and inner lead
Electrical and mechanical connection to the inner lead through a connection having
The electrical resistance is reduced by the mechanical connection.
Because it is suppressed to a small value, the external resistance component is greatly reduced
Will be. In addition, the circuit elements of the semiconductor pellet
The source electrode located on the main surface on the
The direct connection to the inner lead
Since the connection is continued, the external resistance is greatly reduced as compared with the electrical connection by the bonding wire.
Also, the header is formed separately from the inner lead group.
Because the header can be formed using a material with good heat dissipation performance regardless of the material of the inner lead ,
The heat radiation performance for the body pellet can be improved.

[0009]

FIG. 1 shows a power MOS according to an embodiment of the present invention.
4A shows an FET , (a) is a partially cutaway plan view, and (b)
Is a front sectional view. FIG. 2 et seq. Are explanatory diagrams for explaining a method of manufacturing a power MOSFET according to one embodiment of the present invention.

[0010] In this embodiment, the engagement present invention Rupa word M
The OSFET (hereinafter, referred to as a transistor ) 1 has an MO
A semiconductor pellet (hereinafter, referred to as a pellet) 10 in which an SFET circuit is formed and formed in a small flat plate shape;
Three inner leads 35, 36, and 37 for electrically extracting the OSFET circuit to the outside, a header 41 for improving the heat radiation performance, a pellet 10, the inner lead group, and a part of the header 41 are resin-sealed. And a resin sealing body 44. Each inner lead 3 is provided on a main surface (hereinafter, referred to as an upper surface) on a side of the pellet 10 on which circuit elements are formed.
5, 36 and 37 are connection portions 25 and 2 formed from bumps.
6, 27 electrically and mechanically connected.
A header 41 is connected to the lower surface, which is the opposite main surface of the pellet 10. And this transistor 1
Is manufactured by the manufacturing method described below.

Hereinafter, a method of manufacturing a transistor according to an embodiment of the present invention will be described. With this description, the details of the configuration of the transistor 1 will be clarified.

In this method of manufacturing a transistor,
The pellet 10 shown in FIG. 2, the multiple lead frame 30 shown in FIG. 3, and the header shown in FIG. 4 are prepared in a pellet preparing step, a lead frame preparing step, and a header preparing step, respectively. .

The pellet 10 shown in FIG. 2 is divided (diced) into small square thin plates after appropriately forming a power MOSFET circuit in a wafer state in a so-called pre-process in a semiconductor device manufacturing process. It was produced by doing so. This pellet 1
Reference numeral 0 denotes a substrate 11 on which a gate 12 is formed of polysilicon with a silicon oxide film 13 underneath. A source 14 as a semiconductor diffusion layer is formed inside the substrate 11 corresponding to the outside of the gate 12 in the substrate 11, and a drain 15 is formed below the substrate 11.

An insulating film 16 made of a CVD oxide film or the like is formed on the substrate 11 so as to cover the gate 12 and the source 14. One contact hole 17 is formed so as to penetrate the gate 12. In the region of the insulating film 16 facing the source 14, three source contact holes 18 are arranged in a direction orthogonal to one side of the gate contact hole 17, and are formed to penetrate the source 14. I have.

Further, a gate electrode pad 19 is formed inside the gate contact hole 17, and a source electrode pad 20 is formed inside each source contact hole 18. These electrode pads 1
Nos. 9 and 20 are formed by depositing an aluminum material (aluminum or an alloy thereof) on the insulating film 16 by a suitable means such as sputtering deposition and then patterning the insulating film 16 by photolithography. In other words, since the aluminum material deposited on the insulating film 16 is filled in the contact holes 17 and 18, respectively, the electrode pads 19 and 20 formed by the filled portions are connected to the gate 12 and the source 14, respectively. Are electrically connected to each other. On the other hand, an electrode pad 21 for the drain 15 is provided on the lower surface of the substrate 11.
Are coated with an aluminum material.

On the gate electrode pad 19 and the three source electrode pads 20, a protective film 24 made of an insulating material such as phosphor silicate glass or polyimide resin is applied. Gate bumps 22 and source bumps 23 project from positions facing the electrode pad 19 for source and the electrode pad 20 for source, respectively. These bumps 22 and 23 include first underlayers 22a and 23a made of titanium (Ti) or the like,
Second underlayers 22b and 23 made of palladium (Pd) or the like
and main bodies 22c and 23 made of solder (Sn-Pb)
c.

The multiple lead frame 3 shown in FIG.
No. 0 is a thin plate made of a material having good conductivity such as iron-nickel alloy, phosphor bronze, or a copper alloy of the same material as the header, and is integrally formed by an appropriate means such as a punching press process or an etching process. I have. A plating process using tin (Sn), gold (Au), solder (Sn-Pb), or the like is performed on the surface of the
(Not shown) so that the electrical and mechanical connection action by the bumps 22 and 23 protruding from the base plate is properly performed. In the multiple lead frame 30, a plurality of unit lead frames 31 are arranged in a line in one direction.
However, only one unit is shown.

The unit lead frame 31 has a positioning hole 32
The outer frame 32 is provided with a pair of outer frames 32, and the two outer frames are arranged in parallel at a predetermined interval and are extended in series. Adjacent unit lead frames 31, 3
A pair of section frames 33 are arranged between the outer frames 32, 32 in parallel with each other and integrally formed between the outer frames. A substantially rectangular frame (frame) formed by these outer frames and section frames The unit lead frame 31 is configured in parentheses.

In each unit lead frame (hereinafter, sometimes referred to as a lead frame) 31, a dam member 34 is interposed between two section frames at a substantially central portion so as to be orthogonal and integrated. The dam member 34 is provided with three inner leads 35, 36, and 37 arranged at equal intervals in the length direction and projecting at right angles in one direction. At the tip of the central inner lead 35 (hereinafter, referred to as a first inner lead), a drain connection piece 35a is formed in the thickness direction as L.
It is formed to be bent in a letter shape. At one end of one inner lead 36 (hereinafter, referred to as a second inner lead), a gate connecting piece 36a is formed in a rectangular shape in the same plane. At the tip of the other inner lead (hereinafter, referred to as a third inner lead) 37, a source connection piece 37a is formed in a Y-shape in the same plane.

The dam member 34 has three outer leads 3
8, 39, 40 are three inner leads 35, 36, 37
, And project from each of the inner leads so as to be linearly continuous therewith. Then, adjacent outer leads and both section frames 3
Dams 34a for blocking the flow of the resin when a resin sealing body described later is formed are formed between the first and second dampers 3 and 33, respectively.

The header 41 shown in FIG. 4 is formed in a rectangular plate shape larger than the pellet 10 by using a material having good conductivity and heat conductivity such as a copper material (copper or copper alloy). ing. The header 41 has a mounting hole 4 for mounting the transistor on a printed circuit board or the like.
2 is arranged in the center near one of the short sides and is opened so as to penetrate in the thickness direction.

In the pellet bonding step, the pellet 10 and the header 41 prepared in advance as described above are provided on one main surface (hereinafter, referred to as an upper surface) of the header 41.
Then, the main surface of the pellet 10 on the side of the drain electrode pad 21 is bonded by a soldering layer 43 as a pellet bonding layer. As a solder material for forming the soldering layer 43, a solder material having a melting point equal to or higher than the melting point of the solder material used for the bumps 22 and 23 of the pellet 10 is used. As a method of forming the soldering layer 43, a method of heating the pellet 10 in a state where the pellet 10 is pressed against a solder foil (not shown) placed on the upper surface of the header 41 can be used.

Next, in the inner lead bonding step, an inner lead group is bonded to the main surface of the pellet 10 on the side opposite to the header 41, as shown in FIG. At this time, the multiple lead frames 30 are advanced in one direction by an inner lead bonding apparatus (not shown). In the inner lead bonding stage provided in the middle of the multiple lead frames 30 that are stepped forward, the pellets 30 face the unit lead frames 31 from below, and the respective bumps 22 and 23
Are connecting pieces 36a, 3a of the inner leads 36 and 37, respectively.
7a are assembled to the multiple lead frames 30 by being thermocompression-bonded with a bonding tool, respectively.

That is, when the respective bumps 22 and 23 are pressed against the respective inner leads 36 and 37 under heating, the solder of the bump bodies 22c and 23c is melted and the respective inner leads 36 and 37 are melted.
And 37. Then, after the solder is solidified, the gate connection portion 25 and the source connection are provided between the gate electrode pad 19 and each source electrode pad 20 of the pellet 10 and the second inner lead 36 and the third inner lead 37. Portions 26 are respectively formed. The gate connecting pad 25 electrically and mechanically connects the gate electrode pad 19 and the second inner lead 36, and the source connecting pad 26 connects the source electrode pad 20 and the third inner lead 36.
The inner lead 37 is electrically and mechanically connected, and the pellet connection is mechanically connected to the lead frame 31 by the mechanical connection, that is, the pellet 10 is fixedly assembled.

At the time of this inner lead bonding operation, the drain connecting portion piece 35a of the first inner lead 35 is formed.
Is soldered near the short side opposite to the mounting hole 42 of the header 41. With this soldered portion, the drain connection portion 27 is formed, and the drain connection portion 27 is formed.
Thus, the drain electrode pad 21 of the pellet 10 and the header 41 are electrically connected.

In the assembly of the header-attached pellet 10 and the multiple lead frames 30 assembled as described above, a resin sealing body 44 made of an insulating resin such as an epoxy resin is formed in the resin sealing body forming step. Each unit lead frame 31 is simultaneously molded using the transfer molding apparatus 50 shown in FIG.

The transfer molding apparatus shown in FIG. 6 includes a pair of upper dies 51 and lower dies 52 which are mutually clamped by a cylinder device or the like (not shown).
The upper mold cavity recess 5 is provided in the mating surface of the lower mold 52 and the lower mold 52.
A plurality of sets (only one set is shown) are submerged so that the cavity 3a and the lower mold cavity recess 53b cooperate with each other to form the cavity 53. In addition, on the ceiling surface of the upper mold cavity recessed portion 53a and the bottom surface of the lower mold cavity recessed portion 53b, mounting hole forming protrusions 60a and 60b for forming an attachment hole in the resin sealing body abut each other. As shown in FIG.

A pot 54 is opened on the mating surface of the upper mold 51, and the pot 54 has a cylinder device (not shown).
The plunger 55 which is moved forward and backward is inserted so that resin (hereinafter, referred to as resin) as a molding material can be fed. The cull 56 is a pot 5 on the mating surface of the lower mold 52.
4 and a plurality of runners 57 are radially arranged and laid so as to be connected to the pots 54, respectively. The other end of each runner 57 is connected to the lower cavity recess 53b, and a gate 58 is formed at the connection portion so that the resin can be injected into the cavity 53. In the mating surface of the lower mold 52, a rectangular shape slightly larger than the outer shape of the multiple lead frame 30 and having a dimension substantially equal to the thickness is formed so that the escape recess 59 can escape the thickness of the unit lead frame 31. It is submerged in depth.

The operation of molding the resin sealing body by the transfer molding apparatus configured as described above will be described. In the assembly according to the above configuration, the pellets 10 are placed in the escape recesses 59 submerged in the lower mold 52 and the lower mold cavity
3b, they are arranged and set so as to be accommodated respectively. Subsequently, the upper die 51 and the lower die 52 are clamped, and the resin 61 is moved from the pot 54 by the plunger 55 to the runner 5.
It is fed into each cavity 53 through 7 and a gate 58 and is press-fitted.

After the resin is injected, the resin 61 is thermally cured to form the resin sealing body 44. The upper mold 51 and the lower mold 52 are opened, and the resin is sealed by an ejector pin (not shown). The body 44 is released.

FIG. 7 shows an assembly of the multiple lead frame 30 and the resin sealing body 44 after release. Inside the resin sealing body 44 of this assembly, together with the pellet 10 and the three inner leads 35, 36, and 37, a part of the header 41 coupled to the lower surface of the pellet 10 is also in a resin-sealed state. Has become. In this state, the end face of the header 41 opposite to the pellet mounting surface is exposed from the surface of the resin sealing body 44, and the three outer leads 3
Reference numerals 8, 39, and 40 protrude at right angles from one short side surface of the resin sealing body 44. In addition, the resin sealing body 4
4, a mounting hole 45 is provided at a portion facing the header mounting hole 42.
Is formed and opened by the convex portions 60a and 60b.

In the lead frame cutting step (not shown), the outer frame 32, the section frame 33, and the dam 34a are cut off from the assembly formed with the resin sealing body 44 as described above. Thus, the transistor 1 shown in FIG. 1 is manufactured.

According to the above embodiment, the following effects can be obtained. (1) Since each inner lead is electrically and mechanically connected to the pellet by each connection portion, the electrical connection by the bonding wire can be abolished.
The external resistance can be greatly reduced as compared with the electrical connection by the bonding wire, and the performance of the power transistor can be improved.

(2) By eliminating the connection by the bonding wire, the size and weight of the power transistor package can be reduced.
Together with this, the performance of the power transistor can be improved.

(3) Since the header is separate from the inner lead group, the heat radiation performance of the header is improved by forming the header using a material having good heat radiation performance regardless of the material of the inner lead. In addition, the material of the inner lead can be selected optimally for the inner lead characteristic irrespective of the material of the header, and the quality and reliability of the power transistor can be further improved.

(4) By providing a plurality of connection pieces for the source electrode pad and the source inner lead,
Since a large current can flow through the source, the performance of the power transistor can be further improved.

(5) By molding the resin sealing body by the transfer molding method, it is possible to improve the performance that the resin sealing body should have such as moisture resistance, so that the quality and reliability of the power transistor can be improved. it can.

FIG. 8 shows a power M according to another embodiment of the present invention.
3A shows an OSFET, and FIG.
(B) is a front sectional view.

The second embodiment is different from the first embodiment in that
The point is that the resin sealing body 44A is formed by a potting method. That is, the resin sealing body 44A formed by the potting method has the pellets 10, the inner leads 35 and 36,
Only the necessary portions around the pellets 37 and the header 41 are sealed with resin. The inner leads 36 and 37 are made of an insulating adhesive tape or the like in order to prevent an external force from being accidentally applied to the inside of each of the inner leads 36 and 37 during the molding of the resin sealing body 44A. It is adhered to the header 41 by an adhesive 46.

According to the second embodiment, since the resin sealing body 44A is formed by the potting method, compared with the case where the resin sealing body is formed by the transfer molding method,
The cost can be reduced, and the entire package can be further reduced in size and weight.

Although the invention made by the inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

For example, the bumps are not limited to being provided on the pellet side, but may be provided on the inner lead side. Further, the bump body is not limited to being formed by solder, but may be formed by gold and connected to the inner lead by a gold-tin eutectic layer.

The pellet and the header are not limited to being connected by the soldering portion, but may be connected by a gold-tin eutectic layer or a conductive adhesive layer (such as a silver paste layer). However, it is desirable to form a joint having good thermal conductivity in consideration of the heat radiation effect of the pellet to the header.

The drain electrode pad is formed by the second pellet.
Not only is it arranged on the main surface (lower surface) side to be electrically connected to the header, but is also arranged on the same side as the gate electrode pad and the source electrode pad, and is electrically connected to the inner lead by a bump connection portion. You may connect.

The header is not limited to being bonded to the pellet before the inner lead bonding, but may be bonded to the pellet after the inner lead bonding or simultaneously with the inner lead bonding.

The shape, size, structure, etc. of the header are determined based on the required heat radiation performance, mounting form (for example, whether or not a retainer or a fastening bolt is used), the performance, size, shape, and the like of the pellet.
It is desirable to select according to various conditions such as the structure,
If necessary, radiation fins, bolt insertion holes, internal threads, and the like can be provided.

The material for forming the header is not limited to a copper-based material, but may be another metal material having good thermal conductivity such as an aluminum-based material.
In particular, it is desirable to use a material having excellent thermal conductivity, such as silicon carbide (Sic), and having a coefficient of thermal expansion substantially equal to that of silicon as the material of the pellet.

The present invention can provide an excellent effect when used in a power MOSFET which is required to have a high output and a low price and high heat radiation performance.

[0049]

The effects obtained by typical aspects of the invention disclosed in the present application will be briefly described as follows.

Since the inner lead is electrically and mechanically connected to the pellet by a connecting portion, the electrical connection by the bonding wire can be eliminated.
The external resistor-can be greatly reduced as compared with the electrical connection by the bonding wires, also by abolishing the electrical connection by the bonding wires, it is possible to compact lightweight package, power MOSF
The performance of the entire ET can be improved.

Further, the source electrode and the gate electrode are
With a connection area larger than the connection area with the
By connecting to the inner lead through the connection,
Since the air resistance can be suppressed small, the external resistance
Minutes can be greatly reduced. Also, if the header is
Since it is separate from the inner lead group , the heat dissipation performance of the header can be improved by forming the header using a material with good heat dissipation performance regardless of the material of the inner lead. In addition, the inner lead can be formed with an optimal material, and the quality and reliability of the semiconductor device can be improved.

[Brief description of the drawings]

1A and 1B show a power MOSFET according to an embodiment of the present invention, wherein FIG. 1A is a partially cutaway plan view, and FIG. 1B is a front sectional view.

FIGS. 2A and 2B show a pellet used in a method for manufacturing a power MOSFET according to one embodiment of the present invention, wherein FIG. 2A is a plan view and FIG.

FIG. 3 also shows a multiple lead frame,
(A) is a partially omitted plan view, and (b) is a front sectional view.

4A and 4B show a header after pellet bonding, in which FIG. 4A is a plan view, FIG. 4B is a front sectional view, and FIG.

FIG. 5 shows a state after inner lead bonding,
(A) is a partially omitted plan view, and (b) is a front sectional view.

6A and 6B show a resin sealing body forming step, in which FIG. 6A is a front sectional view, and FIG. 6B is a sectional view along line bb.

7A and 7B show a state after molding of a resin sealing body, wherein FIG. 7A is a partially omitted plan view and FIG. 7B is a front sectional view.

FIG. 8 is a power MOSFET according to another embodiment of the present invention.
(A) is a partially cut plan view, and (b) is a front sectional view.

[Explanation of symbols]

1: Power transistor ( power MOSFET ), 10
... pellet, 11 ... substrate, 12 ... gate, 1
3 ... silicon oxide film, 14 ... source, 15 ... drain,
16: insulating film, 17: contact hole for gate, 18
... Source contact hole, 19 ... Gate electrode pad, 20 ... Source electrode pad, 21 ... Drain electrode pad, 22 ... Gate bump, 23 ... Source bump, 24 ... Protective film, 25 ... Gate connection part , 26: source connection, 27: drain connection, 30: multiple lead frame, 31: unit lead frame, 32: outer frame,
33: section frame, 34: dam member, 35, 36, 3
7 ... inner lead, 38, 39, 40 ... outer lead,
41: header, 42: mounting hole, 43: soldering layer (pellet bonding layer), 44: resin sealing body by transfer molding method, 44A: resin sealing body by potting method, 45: mounting hole, 46: adhesive material , 50: transfer molding apparatus, 51: upper mold, 52: lower mold, 53: cavity, 54: pot, 55: plunger, 56: cull,
57: runner, 58: gate, 59: recess, 60a, 6
0b: convex portion, 61: resin.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-166984 (JP, A) JP-A-2-257660 (JP, A) JP-A-2-281737 (JP, A) JP-A-53-1979 135576 (JP, A) JP-A-5-121615 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/60 311 H01L 23/48 H01L 29/78

Claims (6)

(57) [Claims] 1. A semiconductor pellet circuit element is formed.
Electrode and gate electrode arranged on the main surface
And a main surface of the semiconductor pellet opposite to the main surface.
Drain electrode, the source electrode, and the gate electrode.
Multiple inner wires connected to each of the pole and drain electrodes
In the power MOSFET having a lead, the source electrode is connected to the gate electrode and the inner lead.
Connection area having a connection plane area larger than the connection plane area of
Electrically and mechanically connected to the inner lead through
A power MOSFET characterized in that: 2. The method according to claim 1, wherein the connection portion is a solder bump or a gold bump.
The power MO according to claim 1, comprising:
SFET. 3. The drain electrode and the inner lead
Are connected via a conductive adhesive or solder layer.
3. The power MOS according to claim 1, wherein:
FET. 4. The source electrode is connected by a solder bump.
Connected to the inner lead through the
The rain electrode is connected to the inner lead via a solder layer.
And the solder layer of the drain electrode is
Made of solder material with higher melting point than bump
The power according to claim 1, 2 or 3, wherein:
MOSFET. 5. The source electrode and the inner lead
Connected via a connection with multiple connection points
The package according to claim 1, 2, 3, or 4, wherein
Power MOSFET. 6. The drain electrode and the inner lead
Are connected via a header
Item 7. Power MOSFE according to item 1, 2, 3, 4, or 5
T.