Optical module package of flip chip bonding

Details Optical module package of flip chip bonding Optical module package of flip chip bonding

2002-06-27

2004-03-16

Williams, Alexander O. (Department: 2828)

Active solid-state devices (e.g., transistors, solid-state diode

Combined with electrical contact or lead

Flip chip

C257S432000, C257S433000, C257S434000, C257S680000, C257S728000, C257S724000, C257S725000, C257S738000, C257S737000, C257S779000, C257S772000, C385S052000, C385S088000

Reexamination Certificate

active

06707161

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical module package and a packaging method thereof, and more particularly, to a flip-chip-bonded optical module package and a packaging method thereof.
2. Description of the Related Art
In most cases, if electric signals of an optical device are allowed to be transmitted to the outside of the optical device by a conventional wire-bonding method and a chip of the optical device operates at a high speed of no less than 20 Gbps, electric parasitic components increase and the chip cannot show its desired speed. Accordingly, a flip chip bonding method capable of minimizing the distance between the chip of an optical device and a substrate, which are electrically connected to each other, must be used to minimize parasitic components between the chip of an optical device and the substrate.
FIG. 1
is a flowchart illustrating a conventional method of packaging an optical module using flip chip bonding. Referring to
FIG. 1
, a chip of an optical device is manufactured in step
10
. Next, solder balls, which transmit electric signals to the outside of the optical device chip, are deposited on a silicon wafer in step
12
. Next, the optical device chip is bonded to the silicon wafer by flip chip bonding in step
14
.
The silicon wafer, onto which a plurality of optical device chips are flip-chip-bonded, is cut, thereby forming an optical sub modules in step
16
. Next, an optical fiber is coupled with the optical device chip of the optical sub module in the manner of active alignment, thereby completing a flip-chip-bonded optical module package in step
18
. In order to actively align the optical device chip of the optical sub module with the optical fiber, the optical device is aligned with the optical fiber to provide a position at which the efficiency of the optical device chip to be optically coupled with the optical fiber is highest, and the optical device is fixed to the optical fiber using a laser welding method.
However, in the conventional method of packaging an optical module using flip chip bonding, the step of actively aligning the optical device chip of the optical sub module with the optical fiber requires much time and large expenditures. Accordingly, a new method, which is simpler and requires less expenditures than the conventional method of packaging an optical module using flip chip bonding, is required.
SUMMARY OF THE INVENTION
To solve the above-described problems, it is a first object of the present invention to provide a flip-chip-bonded optical module package which is capable of ensuring the electrical characteristics of a high speed optical device chip and easily increasing the efficiency of the optical device chip to be optically coupled with an optical fiber.
It is a second object of the present invention to provide a method of packaging an optical module using flip chip bonding which is capable of ensuring the electrical characteristics of a high speed optical device chip and easily increasing the efficiency of the optical device chip to be optically coupled with an optical fiber.
Accordingly, to achieve the first object, there is provided a flip-chip-bonded optical module package. The flip-chip-bonded optical module package includes an optical device chip which is comprised of an input/output pad formed on a substrate, an under bump metal layer formed on the input/output pad, and a solder bump formed on the under bump metal layer to transmit an electric signal to the outside. The flip-chip-bonded optical module package includes a silicon wafer through which a through hole is formed, on which an under ball metal layer is formed, and to which the optical device chip is flip-chip-bonded. The flip-chip-bonded optical module package includes a solder ball which is formed on the under ball metal layer and transmits an electrical signal from the solder bump to the outside, and an optical fiber which is inserted into the through hole and is optically coupled with the optical device chip. The through hole may be filled with an index matching material to increase the efficiency of the optical device chip coupled with the optical fiber. A lens may be inserted into the through hole to increase the efficiency of the optical device chip coupled with the optical fiber.
To achieve the second object, there is provided a method of packaging an optical module using flip chip bonding. An optical device chip, which is comprised of an input/output pad formed on a substrate, an under bump metal layer formed on the input/output pad, and a solder bump formed on the under bump metal layer to transmit an electric signal to the outside, is prepared. A silicon wafer is prepared to rearrange input/output terminals of the optical device chip and passively align an optical fiber with the optical device chip. A plurality of through holes are formed in the silicon wafer at predetermined intervals. An under ball metal layer is formed at the surface of the silicon wafer. A solder ball is formed on the under ball metal layer to transmit an electrical signal from the solder bump to the outside. The optical device chip is flip-chip-bonded to the silicon wafer. An optical sub module is manufactured by cutting the silicon wafer. The optical device chip is optically coupled with the optical sub module by inserting the optical fiber into the through hole of the optical sub module to be aligned with the optical device chip.
Preparing the optical device chip may include manufacturing optical devices each including an input/output pad formed on a substrate, forming an under bump metal layer on the input/output pad, forming a solder bump on the under bump metal layer on the input/output pad, and obtaining an individual optical device chip by cutting the substrate, on which the solder bump is formed.
The through hole may be formed by wet-etching or dry-etching the silicon wafer or polishing the back side of the silicon wafer and wet-etching or dry-etching the silicon wafer. The silicon wafer may be cut into individual wafers, on each of which an array of a plurality of optical device chips is formed. The optical fiber may be inserted into the through hole of the optical sub module in the manner of passive alignment, in which there is no need to operate an optical device.
As described above, according to the present invention, it is possible to sufficiently satisfy the electrical characteristics of a high speed optical device chip with the use of a flip chip bonding method. In addition, since an optical fiber is aligned with and inserted into a silicon wafer through a plurality of through holes formed perforating the semiconductor substrate, it is possible to increase the efficiency of an optical device chip to be optically coupled with the optical fiber.


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IEEE Transactions on Advanced Packaging, vol. 23, No. 2, May 2000, pp. 198-205.
Optical Fiber Array, 5 pages.
2001 Electronic Components and Technology Conference, 6 pages.

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