Semiconductor device manufacturing: process – Including control responsive to sensed condition – Optical characteristic sensed
Reexamination Certificate
2001-06-27
2002-08-27
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Including control responsive to sensed condition
Optical characteristic sensed
C438S016000, C438S029000, C438S046000
Reexamination Certificate
active
06440758
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and a method for bonding two semiconductor laser chips at narrow pitches on one submount in high accuracy. The present invention is utilized in an apparatus for bonding the two laser chips (for example, combination of a red chip and an infrared chip or the like) such as a combination laser die-bonder or the like.
One example of a conventional one-chip bonding apparatus is explained below. Conventionally, a semiconductor laser chip
4
is vacuum-sucked by using a vertically provided vacuum-suction collet
6
, peeled from a wafer sheet
1
, transferred to an intermediate stage
2
and passed as shown in
FIGS. 1 and 2
. On the intermediate stage
2
, a chip profile is recognized by image processing and then, a light-emission axis is recognized. A chip position is corrected in X, Y and &thgr; directions on the basis of this data.
After the chip position is corrected in the X, Y and &thgr; directions on the intermediate stage
2
, the chip is sucked again by using the suction collet
6
and transferred onto a submount
5
placed on a bonding stage
3
. The chip is bonded onto the submount
5
as it is with an adhesive or by thermo-compression bonding.
That is, the chip position is corrected only on the intermediate stage in the above-described conventional one-chip bonding apparatus. Therefore, when the chip is passed to the submount by using the collet after the position correction on the intermediate stage and the chip is mounted on the submount, a fine shift occurs. Thus, bonding position accuracy according to a specification (±2 &mgr;m or less) could not be ensured, thereby resulting in variations in a laser direction.
A method of efficiently fabricating a semiconductor laser without variations in a light-emitting direction in a die-bonding process of a semiconductor laser is disclosed in Japanese Patent Laid-Open Publication No. 7-202347. In this method, a laser chip is energized and allowed to emit light on the intermediate stage by using a probe. A light-emission axis direction is measured by image processing and the laser chip position is corrected on the basis of the measured value. When the light-emission axis direction is within a certain error range, the laser chip is sucked and transferred by a laser chip feed mechanism for die-bonding. Thus, the chip position accuracy is improved.
When a two-chip semiconductor laser device is fabricated, two kinds of light-emitting chips having different wavelengths are bonded on one submount with favorable accuracy. The chips
12
,
13
are bonded one by one in FIG.
3
A. When the second chip
13
is bonded, heat is applied to the first already bonded chip
12
at its junction and the clip
12
comes off. Therefore, the two chips need to be bonded at the same time.
In
FIG. 3B
, two conventional collets are simply arranged in a mirror image to constitute a two-chip bonding by using the one-chip bonding apparatus in
FIG. 2
so that two laser chips are die-bonded on a submount.
Since a specification for a distance between light-emission points is 100±2 &mgr;m in the two-chip semiconductor laser device, the chips need to be bonded so that a distance between the respective light-emission points
14
,
15
of the two laser chips
12
,
13
is 100±2 &mgr;m as shown in FIG.
4
. It is shown, however, that, since the collets are vertically disposed in a constitution shown in
FIG. 3B
, the collets interfere with each other and thereby the two chips cannot be bonded closely.
In the method disclosed in Japanese Patent Laid-open Publication No. 7-202347 as well, it is shown that, since the collets are vertically disposed, the collets interfere with each other and thereby the two chips cannot be bonded closely.
To prevent the collets from interfering with each other in the constitution where the collets are vertically disposed, a diameter of the main body of a collet might be made thinner than the chip profile. However, currently the diameter of the main body of the collet cannot be made thinner than the chip profile because a vacuum hole for vacuum-sucking a chip needs to be provided, rigidity larger than a certain level is required due to a load applied upon chip suction and chip bonding and the collet needs to be shaped so that position accuracy in attachment/replacement of the collet can be easily ensured.
As described above, when the above conventional devices are simply arranged laterally in a mirror image when a semiconductor laser device in which two laser chips are die-bonded on a submount is fabricated, there are disadvantages described below.
(1) Since the position is corrected only on the intermediate stage, a fine shift occurs after the correction on the intermediate stage when the chip is passed by using a collet or the chip is placed on the submount.
(2) The specification required distance (x in
FIG. 4
) between the light-emission points of the two chips is as narrow as 100 &mgr;m. Therefore, when the two chips are bonded at the same time, the normal vertical collets interfere with each other and thereby the two chips cannot be bonded at desired positions at the same time even if the light-emission point is positioned as closely to an end of the chip as possible.
SUMMARY OF THE INVENTION
The present invention was accomplished from the above viewpoints. Accordingly, an object of the present invention is to provide an apparatus and a method for bonding two semiconductor laser chips on one submount at narrow pitches in high accuracy.
In order to achieve the above object, there is provided a method of fabricating a semiconductor laser device wherein two semiconductor laser chips are die-bonded on one submount, comprising processes of placing the semiconductor laser chips on intermediate stages, allowing the semiconductor laser chips on the submount to emit light and measuring light-emission point positions and transferring the semiconductor laser chips through fixed points to prescribed positions on the submount.
That is, in the present invention, a position of each semiconductor laser chip is corrected by profile recognition and light-emission axis recognition on the intermediate stage, a voltage is applied to each chip by using a collet as an electrode on a bonding stage for bonding the chip on the submount to allow each of the two chips to emit light, the light-emission point position data is subjected to image processing, the position of each of the two chips is finally corrected by a high-resolution precision positioning mechanism driven by a piezo-electric element of a bonding head on the basis of the data and then bonding is performed. Thus, according to the fabricating method of the present invention, a two-chip semiconductor laser device can be fabricated in high bonding accuracy.
In one embodiment of the present invention, the method comprises a process of measuring light-emission point positions and light-emission axis directions of the semiconductor laser chips placed on the intermediate stages.
In one embodiment of the present invention, the method comprises a process of correcting positions and directions of the intermediate stages on the basis of the results of measuring the light-emission point positions and light-emission axis directions of the semiconductor laser chips placed on the intermediate stages.
In one embodiment of the present invention, the method comprises processes of sucking the two semiconductor laser chips from respective wafer sheets or a chip tray by using collets, transferring the collets through fixed points by a fixed-point transfer movement mechanism and placing the two semiconductor laser chips on the respective intermediate stages, correcting positions of the two semiconductor laser chips on the respective intermediate stages, sucking the two semiconductor laser chips again, transferring the chips through fixed points and mounting the chips on the submount, energizing the two semiconductor laser chips on the submount to allow the chips to emit light and measuring a distance between the light-emiss
Itoh Yoshiyuki
Kanishi Hiroshi
Tamaishi Masayuki
Nixon & Vanderhye P.C.
Roman Angel
Sharp Kabushiki Kaisha
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