# Patent

## Title
Semiconductor package having reduced thickness

## Abstract

A semiconductor package is disclosed that comprises a chip paddle and a semiconductor chip that has a plurality of bond pads. The semiconductor chip is located on an upper surface of the chip paddle. Leads are formed at intervals along the perimeter of the chip paddle. The leads are in electrical communication with the bond pads. The semiconductor chip, the chip paddle and the leads are encapsulated by an encapsulation material. The height of the semiconductor package of the invention is minimized by half etching the chip paddle to reduce the thickness of the chip paddle such that the thickness of the chip paddle is less than the thickness of the leads. Preferably, the chip paddle of the present invention is about 25–75% of the thickness of the leads.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a divisional of U.S. application Ser. No. 09/687,585 entitled SEMICONDUCTOR PACKAGE HAVING REDUCED THICKNESS filed Oct. 13, 2000 now U.S. Pat. No. 6,696,747.


STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor package and, more particularly, but not by way of limitation, to a semiconductor package that has a reduced thickness.
2. History of Related Art
It is conventional in the electronic industry to encapsulate one or more semiconductor devices, such as integrated circuit dies, or chips, in a semiconductor package. These plastic packages protect a chip from environmental hazards, and provide a method and apparatus for electrically and mechanically attaching the chip to an intended device. Recently, such semiconductor packages have included metal leadframes for supporting an integrated circuit chip which is bonded to a chip paddle region formed centrally therein. Bond wires which electrically connect pads on the integrated circuit chip to individual leads of the leadframe are then incorporated. A hard plastic encapsulating material, or encapsulant, which covers the bond wire, the integrated circuit chip and other components, forms the exterior of the package. A primary focus in this design is to provide the chip with adequate protection from the external environment in a reliable and effective manner.
As set forth above, the semiconductor package therein described incorporates a leadframe as the central supporting structure of such a package. A portion of the leadframe completely surrounded by the plastic encapsulant is internal to the package. Portions of the leadframe extend internally from the package and are then used to connect the package externally. More information relative to leadframe technology may be found in Chapter 8 of the book Micro Electronics Packaging Handbook, (1989), edited by R. Tummala and E. Rymaszewski. This book is published by Van Nostrand Reinhold, 115 Fifth Avenue, New York, N.Y., which is herein incorporated by reference.
Once the integrated circuit chips have been produced and encapsulated in semiconductor packages described above, they may be used in a wide variety of electronic appliances. The variety of electronic devices utilizing semiconductor packages has grown dramatically in recent years. These devices include cellular phones, portable computers, etc. Each of these devices typically include a motherboard on which a significant number of such semiconductor packages are secured to provide multiple electronic functions. These electronic appliances are typically manufactured in reduced sizes and at reduced costs, which has resulted in increased consumer demand. Accordingly, not only are semiconductor chips highly integrated, but also semiconductor packages are highly miniaturized with an increased level of package mounting density.
According to such miniaturization tendency, semiconductor packages, which transmit electrical signals from semiconductor chips to motherboards and support the semiconductor chips on the motherboards, have been designed to have a size of about 1×1 mm.
One obstacle to reducing the thickness of conventional semiconductor packages is the internal leads are as thick as the chip paddle. Under the condition that the thickness of the internal leads is identical to that of the chip paddle, the bond pads on the semiconductor chip that is mounted onto the chip paddle are positioned at a far higher level than are the internal leads, so that the loop height of the conductive wires for connecting the semiconductor chip and the internal leads is elevated. The loop height results in an increase in a wire sweeping phenomenon that is caused by pressure of an encapsulation material during encapsulation of the package components.
Previously, techniques for reducing the thickness of semiconductor packages have been utilized, such as back-grinding techniques in which a semiconductor chip is ground down before being mounted on a chip paddle. The back-grinding process, however, deleteriously affects the semiconductor chip. For example, a semiconductor chip that is thinned in this manner is apt to undergo warping, which may result in damaging the internal integrated circuits. In addition, the semiconductor chip itself may be cracked during the back-grinding.
BRIEF SUMMARY OF THE INVENTION
The various embodiments of the present invention provide a semiconductor package that is extremely thin without the need for conducting a back-grinding process or at least for reducing the amount of back-grinding that is required. In one embodiment of the present invention, there is provided a semiconductor package comprising a semiconductor chip provided with a plurality of bond pads, a chip paddle bonded to the bottom surface of the semiconductor chip via an adhesive, a plurality of leads formed at regular intervals along the perimeter of the chip paddle and conductive wires for electrically connecting the bond pads of the semiconductor chip to the leads. A package body comprises the semiconductor chip, the conductive wires, the chip paddle and the leads that are preferably encapsulated by an encapsulation material. The chip paddle, the leads and the tie bars are externally exposed at their side surfaces and bottom surfaces. The chip paddle is half-etched over the entire upper surface of the chip paddle, which results in a thinner thickness than the leads. In one embodiment of the present invention, the half-etched chip paddle is about 25–75% as thick as the leads. Accordingly, by half-etching the entire upper surface of the chip paddle, the chip paddle itself is made thinner than the leads, leading to the slimming of the semiconductor package.



BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the method and apparatus of the present invention may be obtained by reference to the following detailed description, with like reference numerals denoting like elements, when taken in conjunction with the accompanying drawings wherein:
FIG. 1 is a cutaway perspective view of a semiconductor package incorporating the improved leadframe assembly of the present invention.
FIG. 2 shows a cross section of a semiconductor package wherein the semiconductor package has a chip paddle of reduced thickness according to one embodiment of the present invention; and
FIG. 3 shows a bottom plan view of the semiconductor package of FIG. 1.



The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the present invention and the figures.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIGS. 1, 2 and 3, a representative semiconductor package embodying aspects of the present invention is designated generally 10. Semiconductor package 10 comprises a semiconductor chip 12. Semiconductor chip 12 has a plurality of bond pads 14 on an upper surface of semiconductor chip 12 and along the perimeter of semiconductor chip 12. A die paddle or chip paddle 16 is bonded to a bottom surface of semiconductor chip 12 via an adhesive. At a corner of chip paddle 16 is a tie bar 20 (FIGS. 1 & 2), which extends outwards toward a respective corner of the semiconductor package 10. The tie bar 20 preferably also has a half-etched portion 21 (FIG. 1).
A plurality of leads 22 are located along the circumference of chip paddle 16. The chip paddle 16 and the leads 22 are externally exposed at their bottom surfaces (see FIG. 2). Additionally, the leads 22 are exposed on their side faces (see FIG. 1). The externally exposed portions of the chip paddle 16 and the leads 22 may be electroplated with a corrosion minimizing material such as, but not limited to, tin lead, gold, nickel palladium, tin bismuth, or other similar materials known in the art. Each of leads 22 has a half-etched portion 24 at an end facing the chip paddle 16. The upper surface of each of leads 22 may also be electroplated with an electrical conductivity enhancing material such as, for example, gold or silver. Conductive wires 26 provide an electrical pathway between the bond pads 14 of the semiconductor chip 12 and the leads 22. The semiconductor chip 12, the conductive wires 26, the chip paddle 16 and the leads 22 are encapsulated by an encapsulation material 28 to create a package body 30 whereas the chip paddle 16, the leads 22 and the tie bars 20 are externally exposed toward the downward direction of the semiconductor package 10. The encapsulation material 28 may be thermoplastics or thermoset resins, with the thermoset resins including silicones, phenolics, and epoxies.
An aspect of the various embodiments of the present invention resides in the formation of a half etched surface 32 over the entire upper surface of the chip paddle 16, so as to make the thickness of the chip paddle 16, designated h2 (FIG. 2), smaller than the thickness of the lead 22, which is designated h1 (FIG. 2). Preferably, the chip paddle 16 is about 25–75% as thick as the leads 22, but this range is presented for example only and should not be construed to limit the present invention.
It is also preferred that the formation of the half-etched surface 32 over the entire upper surface of the chip paddle 16 is conducted while a lower side area of the lead 22 is etched, e.g., to form half etched portion 24. However, the present invention is not limited to etching the top surface of chip paddle 16 and the half etched portion 24 of the leads 22 simultaneously.
By half-etching the entire upper surface of the chip paddle 16, the total height of the semiconductor package body 30 is reduced. When semiconductor chip 12 is mounted on the half-etched surface 32 of the chip paddle 16, the semiconductor chip 12 is positioned at a lower height than the semiconductor chip 12 would be if it were located on a non-etched chip paddle 16. Thus, the loop height of the conductive wires 26 is also lowered. An additional benefit is that the lower loop height of the conductive wires 26 decreases an occurrence of wire sweeping during encapsulation of the semiconductor package 10. Further, the low height of the semiconductor chip 12 results in decreasing the thickness of the semiconductor package 10.
The present invention has been described in an illustrative manner, and it is to be understood the terminology used is intended to be in the nature of descriptions rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings.
As described hereinbefore, the chip paddle 16 is made thinner than the leads 22 by half-etching the entire upper surface of the chip paddle 16, so that the total thickness of the semiconductor package 10 can be decreased. In addition, the height of semiconductor chip 12 with respect to the bottom surface of chip paddle 16 is reduced when the semiconductor chip 12 is mounted on the half-etched chip paddle 16. Consequently, the loop height of the conductive wires 26 is also lowered, which reduces wire sweeping during the encapsulation of the semiconductor package 10.
The following applications are being filed on the same date as the present application and are all incorporated by reference as if wholly rewritten entirely herein, including any additional matter incorporated by reference therein:












U.S. Pat/




application

First Named


Ser. No.
Title of Application
Inventor







6,646,339
Improved Thin and Heat
Jae Hun Ku



Radiant Semiconductor Package



and Method for Manufacturing


6,627,976
Leadframe for Semiconductor
Young Suk Chung



Package and Mold for Molding



the Same


6,475,827
Method for Making a
Tae Heon Lee



Semiconductor Package Having



Improved Defect Testing and



Increased Production Yield


6,639,308
Near Chip Size Semiconductor
Sean Timothy Crowley



Package


6,677,663
End Grid Array Semiconductor
Jae Hun Ku



Package


09/687,048
Leadframe and Semiconductor
Tae Heon Lee



Package with Improved Solder



Joint Strength


6,555,899
Semiconductor Package
Young Suk Chung



Leadframe Assembly and



Method of Manufacture


6,525,406
Improved Method for Making
Young Suk Chung



Semiconductor Packages









It is this believed that the operation and construction of the present invention will be apparent from the foregoing description of the preferred exemplary embodiments. It will be obvious to a person of ordinary skill in the art that various changes and modifications may be made herein without departing from the spirit and the scope of the invention.

## Claims

1. A method of fabricating a semiconductor package, comprising the steps of:
a) providing a leadframe which includes:
a die paddle having opposed, generally planar top and bottom surfaces; and
a plurality of leads which extend at least partially about the die paddle and each have opposed, generally planar upper and lower lead surfaces and an inner lead end;

b) etching the leadframe such that each of the leads includes a half etched portion which is formed in the lower lead surface, extends to the inner lead end, and defines a generally planar etched lead surface which is disposed in opposed relation to the upper lead surface and extends in generally co-planar relation to the top surface of the die paddle;
c) attaching a semiconductor chip to the top surface of the die paddle;
d) electrically connecting the semiconductor chip to at least one of the leads; and
e) at least partially encapsulating the leadframe and the semiconductor chip with an encapsulation material such that at least a portion of the lower lead surface of each of the leads is exposed in the encapsulation material.

2. The method of claim 1 wherein step (b) comprises etching the leadframe such that each of the leads has a lead thickness between the upper and lower lead surfaces thereof which exceeds a paddle thickness of the die paddle between the top and bottom surfaces thereof.

3. The method of claim 2 wherein step (b) comprises etching the entirety of the top surface of the die paddle and etching a portion of the lower lead surface of each of the leads in amounts sufficient to cause the lead thickness of each of the leads to exceed the paddle thickness and the top surface of the die paddle to extend in generally co-planar relation to the etched lead surface of each of the leads.

4. The method of claim 3 wherein the etching of the top surface of the die paddle and the etching of a portion of the lower lead surface of each of the leads to form the half etched portion therein is conducted simultaneously.

5. The method of claim 1 wherein step (d) comprises electrically connecting the semiconductor chip to the upper lead surface of at least one of the leads via a conductive wire which is encapsulated by the encapsulation material.

6. The method of claim 1 wherein step (e) comprises applying the encapsulation material such that the bottom surface of the die paddle is exposed therein.

7. The method of claim 6 wherein step (a) comprises providing a leadframe wherein the bottom surface of the die paddle and the lower lead surface of each of the leads extend in generally co-planar relation to each other.

8. The method of claim 6 further comprising the step of:
g) plating the bottom surface of the die paddle and the lower lead surface of each of the leads with a corrosion-minimizing material.

9. The method of claim 1 wherein step (e) comprises applying the encapsulation material such that at least a portion of the upper lead surface of each of the leads is exposed therein.

10. The method of claim 1 wherein step (a) further comprises plating the upper lead surface of at least one of the leads with an electrical conductivity enhancing material.

11. A method of fabricating a leadframe for use in a semiconductor package, comprising the steps of:
a) providing a die paddle having opposed, generally planar top and bottom surfaces, and a plurality of leads which extend at least partially about the die paddle and each have opposed, generally planar upper and lower lead surfaces and an inner end; and
b) etching the die paddle and the leads such that each of the leads includes a half etched portion which is formed in the lower lead surface, extends to the inner lead end, and defines a generally planar etched lead surface which is disposed in opposed relation to the upper lead surface and extends in generally co-planar relation to the top surface of the die paddle.

12. The method of claim 11 wherein step (b) comprises etching the die paddle and the leads such that each of the leads has a lead thickness between the upper and lower lead surfaces thereof which exceeds a paddle thickness of the die paddle between the top and bottom surfaces thereof.

13. The method of claim 12 wherein step (b) comprises etching the entirety of the top surface of the die paddle and etching a portion of the lower lead surface of each of the leads in amounts sufficient to cause the lead thickness of each of the leads to exceed the paddle thickness and the top surface of the die paddle to extend in generally co-planar relation to the etched lead surface of each of the leads.

14. The method of claim 13 wherein the etching of the top surface of the die paddle and the etching of a portion of the lower lead surface of each of the leads to form the half etched portion therein is conducted simultaneously.

15. The method of claim 11 further comprising the step of:
c) plating the bottom surface of the die paddle and the lower lead surface of each of the leads with a corrosion-minimizing material.

16. The method of claim 11 further comprising the step of:
g) plating the upper lead surface of at least one of the leads with an electrical conductivity enhancing material.

17. A method of fabricating a semiconductor package, comprising the steps of:
a) providing a leadframe which includes:
a die paddle having opposed, generally planar top and bottom surfaces; and
at least one lead which is disposed in spaced relation to the die paddle and has opposed, generally planar upper and lower lead surfaces and an inner end;

b) etching the leadframe such that the lead includes a half etched portion which is formed in the lower lead surface, extends to the inner lead end, and defines a generally planar etched lead surface which is disposed in opposed relation to the upper lead surface and extends in generally co-planar relation to the top surface of the die paddle; and
c) electrically connecting a semiconductor chip to the lead.

18. The method of claim 17 wherein step (b) comprises etching the leadframe such that the lead has a lead thickness between the upper and lower lead surfaces thereof which exceeds a paddle thickness of the die paddle between the top and bottom surfaces thereof.

19. The method of claim 18 wherein step (b) comprises etching the entirety of the top surface of the die paddle and etching a portion of the lower lead surface of the lead in amounts sufficient to cause the lead thickness of the lead to exceed the paddle thickness and the top surface of the die paddle to extend in generally co-planar relation to the etched lead surface of the lead.

20. The method of claim 19 wherein the etching of the top surface of the die paddle and the etching of a portion of the lower lead surface of the lead to form the half etched portion therein is conducted simultaneously.