KR0120186B1 - Buffer chip - Google Patents

Abstract

A buffer chip(32) smaller than a lead frame pad(31) is attached on a lead frame pad(31). After fixing a semiconductor chip(37) on the buffer chip(32) a process for hardening the adhesive is performed at the same time and perform wire bonding on a bonding pad(33) of the buffer chip(32) and on a bonding pad(38) of the semiconductor chip(37) and internal leads(34) by means of wave bonding or wedge bonding. The semiconductor processing is completed by performing epoxy molding and trimming forming process.

Description

Semiconductor device using buffer chip and manufacturing method thereof

1 (a) and (b) are a plan view of a main part and a sectional view of a main part of an embodiment of a conventional semiconductor device, respectively.

2 (a), 2 (b) and 2 (c) are a plan view of a main part and a side view of the main part, respectively, showing the defect of the wire bonded in the conventional semiconductor device.

3A and 3B are principal part plan views and major part perspective views, respectively, illustrating an embodiment of a semiconductor device using a buffer chip according to the present invention.

4 (a) and 4 (b) are a plan view of a main part and a perspective view of a main part of another embodiment of the semiconductor device using the buffer chip according to the present invention, respectively.

5 is a perspective view of principal parts showing still another embodiment of the semiconductor device using the buffer chip according to the present invention.

6 is a sectional view showing the main parts after EMC molding in FIG.

7 is a sectional view of the main portion after EMC molding in FIG.

8 is a sectional view of the main parts after EMC molding in FIG. 5;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method for manufacturing the same. More specifically, one or more buffer chips are bonded onto a lead frame pad by a liquid adhesive, and the semiconductor chips are laminated on the buffer chips to be bonded by a liquid adhesive. Afterwards, a semiconductor device using a buffer chip capable of high-density mounting by connecting a bonding pad and an internal lead of a semiconductor chip with a conductive wire by wave bonding, stitch bonding, or zig-zag bonding. And to a method for producing the same.

Recently, electronic devices are required to have high performance or multifunction according to miniaturization and slimness, and various semiconductor device mounting methods capable of efficiently mounting high-capacity memory devices in a limited internal space are in demand.

In addition, as the integration of semiconductor chips increases, the number of input / output terminals increases, so that the number of leads of semiconductor packages electrically connected to the input / output terminals increases.

Representative surface mount devices having outer leads in four directions to optimally satisfy the function of the semiconductor chip include QFP (Quad Flat Package) and PLCC (Plastic Leaded Chip Carrier).

The wire bonding method disclosed in U.S. Patent No. 4,875,618 as a wire bonding method in the manufacturing process of the apparatus having the outer lead in the four directions as described above is an example.

1 (a) and (b) are a plan view of a main part and a sectional view of a main part of an embodiment of a conventional semiconductor device.

Referring to FIG. 1A, the conventional semiconductor device includes a lead frame pad 11 used in a conventional semiconductor device, and a semiconductor chip 12 bonded on the lead frame pad 11 by silver-epoxy or the like. ), A bonding pad 13 formed on the semiconductor chip 12, and an end portion of the bonding pad 13 and the inner lead 14 which is part of the lead frame. The wire 15 is electrically connected by bonding.

Referring to FIG. 1B, the length L of the bonding wire for electrically connecting the bonding pad 13 and the internal lead 14 is in the shape of a wire loop, and thus, the bonding pad of the semiconductor chip ( 13 is defined as the straight line distance from the center of the wire ball formed on 13 to the point where it is wedge bonded to the end of the inner lead 14.

Therefore, in the wire bonding process in the manufacturing process of the semiconductor device as described above, since the wire 15 has a very long straight line distance, the wire sweeping, the short circuit between the wires, the sag of the wire, etc. The poor shape of the wire generally occurs.

FIG. 2A is a plan view of main parts describing wire-sweeping in each embodiment of the conventional semiconductor device, and FIG. 2B is a plan view of main parts in explaining a short circuit, and FIG. (c) is a side view of main parts showing sag phenomenon.

Referring to FIG. 2A, the conventional semiconductor device includes a lead frame pad 21 used in a conventional semiconductor device, and a semiconductor chip 22 bonded on the lead frame pad 21 by silver-epoxy or the like. ), The bonding pads 23 formed on the semiconductor chip 22 and the end recesses of the bonding pads 23 and the inner lead 24 which are part of the lead frame are electrically connected by ball 26 bonding. The wire 25 is comprised.

In this case, it can be seen that the wire 25 has a wire-sweeping phenomenon because the linear distance between the ball 26 and the inner lead 24 is very long.

Referring to FIG. 2B, the ball 26 bonded wires 25 electrically connecting the bonding pads 23 and the internal leads 24 of the semiconductor chip are short-circuited with adjacent wires. Able to know.

Referring to FIG. 2C, as described in FIG. 2A, the ball 26 bonded wires 25 electrically connecting the bonding pads 23 and the internal leads 24 of the semiconductor chip. ) Shows the deflection phenomenon.

However, when the length of the bonded wire exceeds 4.06mm (160mil), it is difficult to make a stable loop of wire. In particular, when the number of leads to be bonded is large and the spacing between the wires and adjacent wires is dense, it is difficult to form a stable loop of wire, and even if a slight wire sweeping phenomenon occurs, a short circuit between the wires causes a defect.

In the 208-lead QFP having an external lead spacing of 0.50 mm and a molded semiconductor device cross-sectional area of 28 x 28 mm 2, using the example of FIGS. 2A to 2C, the inner lead 24 is the number of centers of the semiconductor device. The gap between the ends of the inner lead 24 is smaller than 0.50 mm since they must be arranged toward.

Therefore, when the distance from the center of the ball 26 formed on the bonding pad 23 of the semiconductor chip 22 to an arbitrary point of the inner lead 24 that is wedge-bonded exceeds 4.06 mm, the inner lead 24 is removed. By closer to the center of the semiconductor device, the length of the wire can be shortened.

However, when the inner lead 24 is in close proximity, the width of the inner lead 24 is not only narrower, but also the semiconductor package manufacturing process is restricted due to the manufacturing limitations of the lead frame.

Thus, the minimum marginal width of the inner lead 24 of the wedge bonding point will vary somewhat depending on the wire diameter and capillary structure used but should be secured at least 0.080 mm.

However, in consideration of the tolerances in manufacturing the lead frame and the working error of the wire bonding apparatus, the minimum limit width must be 0.10 mm to ensure the stability of the wire bonding process. Therefore, when the width of the wedge bonding portion of the inner lead is set to 0.10 mm, the linear distance between the center of the bonding pad 23 of the individual semiconductor chip 22 to be bonded corresponding to 1: 1 and the wedge point of the inner lead 24 is 4.06. If it is more than mm, since the cross-sectional area of the semiconductor chip must be expanded, the effect of reducing the manufacturing cost and improving productivity by reducing the semiconductor chip 22 is excluded.

On the other hand, there is a problem even when the length of the wire is within 4.06 mm.

In general, when the length of the wire exceeds 3.05mm (120mil), it is defined as a long loop wire. In this case, even when a small impact is received from the outside, the deformation of the wire such as wire sweeping and shorting of the wire occurs, thereby causing a fatal defect. Easily triggered

Therefore, special care must be taken in handling, and in the mold process, the long wire bonded during the flow of the thermosetting epoxy resin (hereinafter referred to as EMC) in the desk state receives a lot of contact resistance, which also causes the wire shape. The risk of associated failures increases.

In order to prevent defects in the mold process, after the relay pad is installed on the lead frame pad, the semiconductor chip of the relay pad is mounted and wire bonded to shorten the length of the bonding wire, thereby making wire-sweeping and between the wires possible. Although defects caused by short circuits and sag of wires can be prevented, the lead frame is easily deformed or damaged due to thermal or mechanical forces applied in the process of forming a relay pad on the lead frame, thereby lowering the yield of the semiconductor device. .

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to adopt a wave wire bonding using a buffer chip, thereby essentially eliminating the defects of the wires which can be caused by the conventionally excessive problem. The present invention provides a semiconductor device using a buffer chip and a method of manufacturing the same, which can improve the manufacturing efficiency of the semiconductor chip pad and greatly alleviate the design constraints caused by the interference of the bonded wires in the semiconductor chip pad position design and the lead frame position design.

Another object of the present invention is to provide a method for manufacturing another semiconductor device by adopting a two-step wire bonding process using a buffer chip.

It is still another object of the present invention to provide a method for manufacturing a semiconductor device which can easily electrically connect a multi-bond pad formed in a zigzag pattern on a buffer chip with an internal lead having a fine pitch by zigzag wave wire bonding.

A feature of the semiconductor device according to the present invention for achieving the above objects is that the buffer chip is mounted on the die pad of the lead frame, the semiconductor on top of the buffer chip within the range that does not invade the bonding pads formed on the buffer chip After the chips are bonded, the bonding pads formed on the semiconductor chip, the bonding pads formed on the buffer chip, and the inner leads are wave bonded, and then molded with an epoxy mold compound to protect the two chips from the external environment. The point is to cut or bend the outer lead extending from the inner leads.

A feature of the method of manufacturing a semiconductor device according to the present invention for achieving the above objects is to bond a buffer chip using a liquid adhesive (non-conductive or conductive) on a lead frame pad, and a liquid adhesive on the buffer chip. Attaching the semiconductor chip using, and curing the adhesive; A wire bonding step of electrically connecting the bonding pads of the buffer chip, the bonding pads of the semiconductor chip, and internal leads with each other by a wave bonding or wedge bonding method; A molding process of molding the upper and lower portions of the lead frame to the resultant structure with an epoxy mold compound to protect it from the external environment; And a trimming / forming process for cutting or bending an outer lead extending from the inner leads.

Another feature of the semiconductor device according to the present invention is that the buffer chip is mounted on the die pad of the lead frame, and the semiconductor chip is adhered to the upper portion of the buffer chip within the range of not invading bonding pads formed in two rows on the buffer chip. Bonding pads formed on the semiconductor chip, bonding pads formed on the buffer chip, and internal leads in two rows are zigzag-wave-bonded, and then molded into an epoxy mold compound to protect the two chips from an external environment. The point is to cut or bend the outer lead extending from the inner leads.

Another feature of the method of manufacturing a semiconductor device according to the present invention for achieving the above objects is to bond a buffer chip having bonding pads arranged in two rows using a liquid adhesive on a lead frame pad, and onto the buffer chip. Bonding a semiconductor chip having bonding pads formed in one row using a liquid adhesive, and then curing the resin; A wire bonding step of electrically connecting the bonding pads of the buffer chip, the bonding pads of the semiconductor chip, and the inner leads with each other by a zigzag wave bonding or stitch bonding method; The resulting structure is provided with a molding process for molding the epoxy mold compound in order to protect the upper and lower parts of the lead frame from the external environment.

Hereinafter, an embodiment of a semiconductor device and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a semiconductor device according to the present invention, and FIG. 3 (a) is a plan view of the principal part of a first embodiment showing a wave wire bonding state between a bonding pad formed on a buffer chip and a bonding pad of a semiconductor chip. 3 (b) is a perspective view of main parts of FIG. 3 (a).

Referring to FIG. 3A, in the semiconductor device, the buffer chip 32 is bonded to the lead frame pad 31 used in the conventional semiconductor device by using an adhesive, and the buffer chip 32 is used. The semiconductor chip 37 with the integrated circuit thereon is bonded with the same adhesive as above.

The adhesive may use a liquid silver epoxy (Ag-Epoxy).

Here, the bonding pads 33 formed on the buffer chip 32 are formed to be the same as or larger than the bonding pads 38 of the semiconductor chip 37 mounted on the buffer chip 32. At this time, the buffer chip 32 is not larger than the lead frame pad 31 and has a thickness of 200 ~ 650㎛.

In addition, a ball is formed on the bonding pad 38 of the semiconductor chip 37 so that the wire 35 is wave-bonded with the bonding pad 33 of the buffer chip 32 by the movement direction of the capillary. (36), the wire 35 is wedgebonded at the end of the inner lead 34, which corresponds 1: 1 with the bonding pad 33, to end one cycle of the overall wire bonding. Accordingly, the wire 35 is first formed with a ball on the bonding pad 38 of the semiconductor chip 37, and then wave-bonded 36 to the bonding pad 33 of the buffer chip 32. Wedgebonding at the end of 34 to complete the electrical connection.

Here, the wire 35 that is wave-bonded 36 in the bonding pad 33 of the buffer chip 32 is a capillary, that is, a wire 35 made of gold (Au) and aluminum (Al) by pressure or ultrasonic vibration. Through the fusion between the metals of the bonding pads 33, the wires are electrically connected without breaking the wires.

The semiconductor device is manufactured by a series of package manufacturing processes described below, and the process is as follows.

The semiconductor device first uses a conductive or non-conductive liquid adhesive on the lead frame pad 31 to die attach the buffer chip 32 smaller than the lead frame pad 31, and then the buffer chip 32. After adhering the semiconductor chip 37 using an adhesive of the same property or an adhesive of different properties onto the semiconductor chip 37, a step of simultaneously curing the adhesive is performed.

Next, a wire electrically connecting the bonding pads 33 of the buffer chip 32, the bonding pads 38 of the semiconductor chip 37, and the internal leads 34 to each other by a wave bonding or wedge bonding method. Perform the bonding process.

The resulting structure is then subjected to a molding process in which the upper and lower portions of the lead frame are molded with an epoxy mold compound to protect it from the external environment.

Finally, the manufacturing of the semiconductor device is completed by performing a trimming / forming process of cutting or bending an external lead (not shown) extending from the internal leads 34.

A semiconductor device and a method of manufacturing the same according to the first embodiment described above may be more clearly understood with reference to the main cross-sectional view after EMC molding in FIG. 6, which will be described later.

FIG. 4 is a semiconductor device according to the present invention, and FIG. 4 (a) is a plan view of the principal part of a second embodiment showing a state in which a bonding pad formed on a buffer chip and a bonding pad of a semiconductor chip are two-step wire bonded. (b) is a principal part perspective view of FIG.

Referring to FIG. 4A, the basic configuration of the semiconductor device is similar to that of FIG. 4A, and the bonding pads 48 of the semiconductor chip 47 and the bonding pads 43 of the buffer chip 42 are similar to those of FIG. ) Are two steps of wedge wire bonding except that the rest of the configuration is the same as in FIG.

That is, in the semiconductor device described above, a buffer chip 42 is bonded to the lead frame pad 41 used in a conventional semiconductor device by an adhesive, and an integrated circuit is embedded on the buffer chip 42. 42) is glued together.

In addition, a ball is formed on the bonding pad 43 of the semiconductor chip 42 in which the integrated circuit is embedded, and thus the bonding pad 43 of the buffer chip 42 has a loop 45. In the first step, the ball is formed in a region where the bonding pad 43 of the same buffer chip 42 does not interfere with the wedge-bonded wire 45. One cycle of overall wire bonding is terminated by two steps bonding to the corresponding inner leads 44.

The semiconductor device according to the first embodiment described above may be more clearly understood by referring to the cross-sectional view of the main part after EMC molding in FIG. 7, which will be described later.

5 is a perspective view of a main part according to the third embodiment of the present invention, which shows a zigzag wave wire bonding state using bonding pads formed in two rows on a single layer buffer chip.

Referring to FIG. 5, the semiconductor device shows a wave wire bonded state as described in FIG. 3, but merely zigzags using bonding pads 53 arranged in two rows on the buffer chip 59. It is intended to be a wave wire bonding.

That is, in the semiconductor device, a semiconductor chip 57 in which a buffer chip 52 is bonded with an adhesive on a lead frame pad 51 used in a conventional semiconductor device, and an integrated circuit is embedded on the buffer chip 52. ) Is glued together.

Here, the buffer chip 52 is not larger than the lead frame pad 51 as in FIG. 3 and has a thickness of 200 to 650 µm.

In addition, a ball is formed on the bonding pad 53 of the semiconductor chip 57 in which the integrated circuit is embedded, and the bonding pad 53 is disposed at the edge of the buffer chip 52 by the movement direction of the capillary. ), The first step of wave wire bonding is finished, and the second step of wire bonding to the adjacent bonding pads 59 arranged therein is completed to complete the electrical connection.

The wire 55 of the wave bonding 56 at the bonding pads 53 and 59 of the buffer chip 52 is capillary, that is, the wire 55 made of gold (Au) and aluminum by pressure or ultrasonic vibration. Through the fusion between the metals of the bonding pads 53 and 59 made of (Al), they are electrically connected without breaking the wire.

The semiconductor device is manufactured by a series of package manufacturing processes described below, and the process is as follows.

First, the buffer chip 52 having the bonding pads 53 and 59 arranged in two rows using a non-conductive or conductive liquid adhesive on the lead frame pad 51 is bonded to the buffer chip 52. After adhering the semiconductor chips 57 having the bonding pads 58 arranged in a row using a liquid adhesive on the substrate, a process of simultaneously curing the liquid adhesive is performed.

Next, after performing the above process, the bonding pads 53 and 59 of the buffer chip 52 and the bonding pads 58 and the inner leads 54 of the semiconductor chip are zigzag-bonded or stitch bonded. A wire bonding process for electrically connecting each other is performed.

The resulting structure is then subjected to a molding process in which the upper and lower portions of the lead frame are molded with an epoxy mold compound to protect it from the external environment.

Finally, the semiconductor device as described above is completed by performing a trimming / forming process of cutting or bending an external lead (not shown) extending from the internal leads 54.

A semiconductor device and a method of manufacturing the same according to the third embodiment may be more clearly understood with reference to the cross-sectional view of the main part after EMC molding in FIG. 8, which will be described later.

On the other hand, the buffer chip used in FIGS. 3 to 5 is manufactured in a silicon wafer manufacturing process like a semiconductor chip in which an integrated circuit is embedded, but only a bonding pad is formed without an integrated circuit, and thus the manufacturing process is very simple. The manufacturing cost is also very low.

In addition, the buffer chip in the wafer state is separated into individual chips in a wafer cutting process of a conventional semiconductor manufacturing process, and the cross-sectional area (width × length) of the chip is not larger than the cross-sectional area of a lead frame pad or the like to be bonded, and the buffer chip Bonding pads are formed in an array of one or more rows in four or two directions from the edge of the chip.

In addition, as described above, the material of the buffer chip is made of the same silicon as the material of the semiconductor chip in which the integrated circuit is embedded, and the thickness is between 200 and 650 μm, and a metal may or may not be attached to the back side of the buffer chip. It's okay.

In addition, the bonding pad of the buffer chip is formed by securing a sufficient area so as not to be limited by wave bonding or two-stage bonding due to interference by a semiconductor chip bonded on the buffer chip, the bonding pad is a wire loop shape semiconductor chip It is formed inward so that it does not contact the edge of the edge and the edge of the buffer chip.

In addition, the wave wire bonding may be performed by using a dedicated wave wire bonder that is generally used, and the two-stage wire bonding may be performed by using a conventional general-purpose wire bonder.

6 is a cross-sectional view of the main part after EMC molding in FIG. 3, and the external lead OL is formed into a predetermined shape after the semiconductor device in FIG. 3 is molded by the EMC 30. FIG. In the cross-sectional view, the buffer chip 32 is interposed between the lead frame pad 31 and the semiconductor chip 37 to bond the bonding pad 38 and the internal lead 34 of the semiconductor chip 37 to the buffer chip 32. The loop shape of the bonded wire 35 after the wave bonding 36 is clearly shown as the wire 35 by the bonding pad 33.

FIG. 7 is a cross-sectional view of the main portion after EMC molding in FIG. 4, and the external lead OL is formed into a predetermined shape after the semiconductor device of FIG. 4 is molded by the EMC 40. FIG. Here, the cross-sectional view is similar to that of FIG. 6, with the buffer chip 42 interposed between the lead frame pad 41 and the semiconductor chip 47 to bond the pad 48 and the internal lead 34 of the semiconductor chip 47. ) Is a wire 45 by the bonding pad 33 of the buffer chip 32, and the loop shape of the bonded wire 45 after wedge bonding in two steps is clearly shown.

FIG. 8 is a cross-sectional view of the main part after EMC molding in FIG. 5, and the external lead OL is formed into a predetermined shape after the semiconductor device in FIG. 5 is molded by the EMC 50. FIG. Here, the cross-sectional view shows a bonding pad of the semiconductor chip 57 with a buffer chip 52 having bonding pads 56 and 59 arranged in two rows between the lead frame pad 51 and the semiconductor chip 57. Loop of bonded wire 55 after wave bonding in zigzag wave 58 with internal lead 54 by bonding pads 56, 59 of buffer chip 52 by bonding pads 56, 59. The shape is clearly shown.

As described above, the semiconductor device and the method of manufacturing the same according to the present invention employ wave wave bonding or wedge wire bonding in one and two steps using a buffer chip, and thus, warpage of wires caused by excessively long wires, Improving the mounting efficiency of semiconductor devices by fundamentally eliminating deficiencies that may be caused by sag, short-circuit between wires, and other wire length problems, and improving the mounting efficiency of the bonding pads of semiconductor chips and the interference of bonded wires in the design of lead frames. There is an advantage that a semiconductor device can be manufactured that can greatly alleviate the design limitation.

In addition, the semiconductor device and the method of manufacturing the same according to the present invention can easily perform wave wire bonding of fine pitch by bonding pads arranged in two or more zigzag rows at the edge of the buffer chip. It can be easily selected and used to increase the flexibility and practicality of the wire bonding operation, and in particular, the semiconductor device can be densified within the same area through a buffer chip between the semiconductor chip and the lead frame pad. .

As described above, the semiconductor device and the manufacturing method thereof according to the present invention may be changed according to the structure, use, and general specifications of the semiconductor chip and the device to which the present invention is applied, and therefore, the present invention is not limited to the present embodiment without departing from the technical spirit of the present invention. Obviously, various modulations are possible.

Claims (10)

A buffer chip is mounted on the die pad of the lead frame, and at least one semiconductor chip is adhered to the upper portion within the range of not invading the bonding pads formed on the buffer chip, and the bonding pads and the buffer formed on the semiconductor chip. After the bonding pads and the inner leads formed on the chip are wave bonded, the semiconductor chips and the buffer chip are molded with an epoxy mold compound to protect the semiconductor chip and the buffer from the external environment, and are formed by cutting or bending the outer leads extending from the inner leads. Semiconductor device. The semiconductor device of claim 1, wherein a bonding pad formed on the buffer chip is formed to be the same as or larger than a bonding pad of the semiconductor chip mounted on the buffer chip. The semiconductor device of claim 1, wherein the buffer chip is not larger than a lead frame pad and has a thickness of 200 μm to 650 μm. The semiconductor device of claim 1, wherein the bonding pads formed on the semiconductor chip, the bonding pads formed on the buffer chip, and internal leads are wedge bonded. Bonding a buffer chip to a lead frame pad using a liquid adhesive, bonding the semiconductor chip to a buffer chip using a liquid adhesive, and then curing the liquid adhesive; A wire bonding step of electrically connecting the bonding pads of the buffer chip, the bonding pads of the semiconductor chip, and internal leads with each other by a wave bond dealing or wedge bonding method; A molding process of molding the upper and lower portions of the lead frame to the resultant structure with an epoxy mold compound to protect it from the external environment; And a trimming / forming process of cutting or bending the outer lead extending from the inner leads. The method of manufacturing a semiconductor device according to claim 5, wherein the adhesive uses an epoxy in liquid phase. 6. The method of claim 5, wherein the adhesive uses a liquid nonconductive epoxy. Buffer chips are mounted on the die pad of the lead frame, and semiconductor chips are bonded to the top of the buffer chip within the range of not invading the bonding pads formed in two rows on the buffer chip, and bonding pads formed on the semiconductor chips. And two rows of bonding pads and inner leads formed on the buffer chip by zigzag wave bonding, and then molded into an epoxy mold compound to protect the two chips from the external environment, and cutting the outer leads extending from the inner leads. A semiconductor device formed by bending or bending. The semiconductor device of claim 7, wherein the buffer chip is not larger than a lead frame pad and has a thickness of 200 μm to 650 μm. Bonding the buffer chips having the bonding pads arranged in two rows using the adhesive on the lead frame pads, bonding the semiconductor chips having the bonding pads arranged in one row using the adhesive on the buffer chip, and then simultaneously applying the adhesive Curing step; A wire bonding step of electrically connecting the bonding pads of the buffer chip, the bonding pads of the semiconductor chip, and internal leads to each other by a zigzag wave bonding or stitch bonding method; A molding step of molding the resultant structure with an epoxy mold compound to protect the upper and lower portions of the lead frame from the external environment; And a trimming / forming process of cutting or bending an outer lead extending from the inner leads.