JPS61181176A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the short circuit of a junction due to the creeping-up of conductive paste while obtaining sufficient die bonding strength by bonding an silicon substrate with the base of a semiconductor chip, from a side surface of which the junction is exposed, through a silver paste layer and die-conding the silicon substrate side onto a stem substrate through conductive adhesives. CONSTITUTION:A GaAlAs infrared LED has a P-type GaAlAs layer 1, an N-type GaAlAs layer 2 and an aluminum electrode 3, and an silicon substrate 12 is bonded onto the back of the P-type GaAlAs layer 1 through a silver paste layer 11. on die bonding, conductive paste 4 is applied onto a mount section in a stem substrate 5 as a mounting agent, and a LEF pellet is fixed. Conductive adhesives 4 also creep up along the side wall of the LED chip at the time. A distance up to a junction surface from the base of the chip is made longer than a conventional GaAlAs infrared LED pellet by several hundred 4mum, thus preventing the situation, in which a P-N junction is short-circuited by creeping-up conductive paste 4, approximately completely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical semiconductor device, and particularly to an improvement in a die bonding configuration suitable for a GaAlAs infrared light emitting device.

[Technical background of the invention]

When packaging an optical semiconductor device such as a light emitting diode (LED), as in the case of other semiconductor devices such as a memory, a step of die bonding the LED pellet to a stem substrate is included.

Conventionally, this die bonding has been performed as shown in FIGS. 2(A) to 2(D).

Figure 1 (A) shows a conventional infrared LE using GaAI As.
It is a sectional view showing a D chip. In the figure, 1 is a P-type GaA I As layer. On the P-type layer 1 is an N-type G layer.
An aA I As layer 2 is formed, and both layers form a PN junction that becomes a light emitting region. Furthermore, an electrode 3 made of aluminum is formed on the surface of the N-type layer 2. The PN junction structure in this GaAI As infrared LED pellet consists of the above-mentioned P-type layer 1 on a GaASI plate (not shown).
and an N-type layer 2 are sequentially epitaxially grown, and then the GaAs 1 plate is removed. Therefore, the distance d1 from the bottom of the chip to the bonding surface is shorter than the distance d2 from the bonding surface in a normal semiconductor device. Note that the reason for removing the GaAs substrate in this manner is to avoid light absorption by the GaAs substrate and improve light emission output.

When die-bonding the above LED pellets onto the stem substrate shown in FIG. 2 (8), first apply the conductive adhesive 4
was dropped on the mounting site on the stem substrate 5, and the same figure (C)
The LED pellet is glued thereon as shown in FIG.

At this time, the conductive adhesive 4 creeps up along the side surface of the LED chip due to its surface tension, and the LED chip is fixed in the shape shown in FIG.

By the way, if the conductive adhesive 4 creeps up to the PN junction surface of the LED chip, the P-type layer 1 and the N-type layer 2 will be short-circuited and the LED will no longer function. Distance d to the joint surface! The risk of this is great for QaAIAS infrared LEDs, which have a small amount of water, so in this case, a polyimide-based silver paste with a small creep-up is used as the conductive adhesive 4, and by reducing the amount used, the mounting agent This prevents short circuits caused by creeping up.

[Problems with the background technology] However, polyimide silver paste cures quickly after application, so if left for a long time, the viscosity deteriorates significantly, making it less compatible with the pellets, and the strength decreases due to variations in mounting work. There was a problem where some items were not retained. Further, since the amount of conductive adhesive used is reduced as described above to prevent creeping up, there is a problem in that the pellets are likely to peel off due to the influence of the above-mentioned viscosity deterioration.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and is intended to prevent short-circuiting of the bond due to the creeping up of conductive paste in die bonding when assembling optical semiconductor devices such as LEDs, and to provide a sufficient amount of conductive adhesive. The purpose is to obtain die bonding strength using a chemical agent.

[Summary of the invention]

The optical semiconductor device according to the present invention is made of first conductivity type GaAIAS.
A semiconductor chip having a PN junction consisting of a second conductivity type GaAlAs layer and a second conductivity type GaAlAs layer and with the junction exposed on the side surface, and a silicon substrate bonded to the bottom surface of the semiconductor chip via a silver paste layer. The invention is characterized in that the silicon substrate side is die-bonded onto the stem substrate via a conductive adhesive.

In the above-mentioned optical semiconductor device of the present invention, since a silicon substrate is bonded to the back side of a conventional semiconductor chip, the distance to the PN junction is longer by the thickness of the silicon substrate, which is usually several hundred - Even when used, it is possible to prevent short circuits between the joints due to creeping up.

Furthermore, since a silver paste layer is interposed between the GaAl As layer and the silicon substrate, when the present invention is applied to an LED, the light generated by the GaAl As bonding is reflected by this silver paste layer. Since the light is taken out to the outside without being absorbed in the silicon substrate, the same light emitting output as before can be obtained.

[Embodiments of the invention]

FIG. 1(A) is a sectional view showing an embodiment in which the present invention is applied to a GaAlAs infrared LED. In the same figure, 1
is a P-type GaAIAS layer, 2 is an N-type GaAIAS layer, and 3 is an aluminum electrode, and the structure of this part is the second one.
It is exactly the same as the conventional LED pellet shown in Figure (A).On the other hand, in this embodiment, a silicon substrate 12 is bonded to the back surface of the P-type GaAI As layer 1 via a silver paste layer 11, and this structure Figure 2 (A) shows the added points.
This is different from conventional infrared LED pellets.

When assembling the infrared LED pellet of the above embodiment into a package, die bonding can be performed in a conventional manner as shown in FIGS. 1(B) to 1(D). That is, first, as shown in the same figure (B), after applying the conductive paste 4 as a mounting agent on the mounting part of the stem substrate 5, as shown in the same figure (C), the LE
All you have to do is fix the D pellet.

In this case as well, the conductive adhesive 4 creeps up along the side wall of the LED chip as shown in FIG.
Since the distance from the bottom of the chip to the bonding surface is several hundred meters longer than in the case of a pellet, it is possible to almost completely prevent the PN junction from being short-circuited by the conductive paste 4 that has climbed up. As a result, the following effects can be obtained in the above embodiment.

First, since a sufficient amount of conductive paste 4 can be used without shorting the bond, sufficient die bonding strength can be obtained for the LED chip, and problems such as subsequent peeling can be avoided. .

Second, since there is no need to use a polyimide adhesive that exhibits little creeping up as a mounting agent, die bonding can be performed using an epoxy silver paste as in the case of other semiconductor devices. Therefore, there are problems when using polyimide-based silver paste, namely, the curing speed after application is fast, so if it is left for a long time, the viscosity deteriorates significantly and the compatibility with the pellet becomes poor, and the strength is not maintained due to variations in mounting work. It is possible to avoid problems such as items appearing that were not specified.

Thirdly, in the conventional case, it was necessary to perform a visual inspection on all the pieces to check for short circuits in the joints due to silver paste creeping up, but in the above embodiment, such an inspection is not necessary. Therefore, working time can be significantly shortened and productivity can be improved.

Note that in the above embodiment, when infrared light generated at the PN junction enters the silicon substrate 12, the light emission output extracted to the outside is reduced due to light absorption by the silicon.

However, in the above embodiment, since the light is interposed by the silver paste layer 11, the light is reflected by the silver paste layer 11 and does not enter the silicon substrate 12, so that the same light emitting output as the conventional one can be obtained. .

〔Effect of the invention〕

As detailed above, in the optical semiconductor device according to the present invention,
In die bonding when assembling semiconductor chips, it has remarkable effects such as preventing short circuits due to conductive paste creeping up and ensuring die bonding strength by using a sufficient amount of conductive adhesive. That's what you get.

[Brief explanation of drawings]

FIG. 1(A) is a sectional view showing an embodiment in which the present invention is applied to a GaAI AS infrared LED, and FIG. 1(B) to (
D) is an explanatory diagram showing the die bonding method, and Figures 2 (A) to (D) are explanatory diagrams showing the structure of a conventional GaAJAS infrared LE[) chip and problems when die bonding it. be. 1-P type GaAl AS layer, 2-N type GaAIAS layer,
3... Aluminum electrode, 4... Mounting agent, 5...
... Stem substrate, 11... Silver paste layer, 12 Silicon substrate. Applicant's agent Patent attorney Takehiko Suzue No. 1 Figure 2 Tadashi

Claims (1)

[Claims] First conductivity type GaAlAs layer and second conductivity type GaAl
A semiconductor chip having a PN junction made of an As layer and with the junction exposed on the side surface, and a silicon substrate bonded to the bottom surface of the semiconductor chip via a silver paste layer, the silicon substrate side An optical semiconductor device characterized in that the above is die-bonded onto a stem substrate via a conductive adhesive.