JPH0554260B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a die bonding method for bonding a semiconductor laser chip onto a submount.

[Technical background of the invention and its problems]

Recently, optical digital audio disks ( Digital Audio Discs ) have been put into practical use and are about to be mass produced. Along with this, the semiconductor lasers incorporated in digital audio disks are also required to be superior in terms of price, lifespan, and performance. Therefore, automatic semiconductor laser manufacturing equipment has been developed to satisfy these demands. One of the important parts of this automatic manufacturing equipment is a die bonding equipment for bonding a semiconductor laser chip onto a submount. FIG. 1 shows a die bonding apparatus generally used for semiconductor lasers, in which a submount 2 made of, for example, copper or silicon is vacuum-adsorbed onto a preheater 1 having a built-in heating wire. Then, a semiconductor laser chip (generally GaAlAs type) 4 vacuum-adsorbed to the tip of a capillary 3 above the submount 2 is positioned on the submount 2 and pressurized. The vicinity of the joint between the semiconductor laser chip 4 and the submount 2 is electrically heated to 200 to 350°C by the preheater 1, and the Au
-Die bonding was performed by melting bonding insert materials such as Sn-based and Au-Si-based materials.
However, according to such a conventional die bonding method, heating is performed using a heating wire built into the preheater 1, so it takes a long time (for example, 30 to 60 seconds) to raise the bonding part to the bonding temperature. was necessary. In addition, once the temperature of submount 2 rises, the cooling time is also slow, so it takes time for the bonding insert material to solidify after melting. It had to be held in position with precision. As a result, in the conventional die bonding method, the bonding time was too long (120 seconds or more), significantly reducing production efficiency. In addition, the emission characteristics of semiconductor laser chips change due to thermal strain, so
When the bonding time is long as in the above-described conventional method, thermal strain often remains, which is a factor in reducing the reliability of the semiconductor laser.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and provides a die bonding method that can bond a semiconductor laser chip to a submount with high efficiency and reliability without leaving any residual thermal strain. The purpose is to

[Summary of the invention]

The present invention provides a die bonding method for die bonding a semiconductor laser chip held on a capillary to a submount placed on a mounting table, in which the semiconductor laser chip held on the capillary and the semiconductor laser chip held on the capillary are bonded together. A preheating step is provided in which the submount on which the held semiconductor laser chip is placed is preheated by spraying heated inert gas, and a heating element is provided to heat at least one of the capillary and the submount. A heating step of instantaneously heating at least one of the capillary and the submount by supplying power to a heating element, and a heating step after the preheating step to intervene between the semiconductor laser chip and the submount. a step of die bonding the semiconductor laser chip and the submount by melting the bonding insert material, and a step of raising the capillary at the same time as stopping power supply to the heating element and stopping the preheating. A die bonding method is provided.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail based on examples with reference to the drawings.

FIG. 2 shows a die bonding apparatus used in the die bonding method of this embodiment. A suction hole 6 connected to a vacuum source (not shown) is bored in the base 5, which is an X-Y table, and is open on the upper surface of the base 5. This base 5 is driven by a stepping motor (not shown) and is positioned at a predetermined position by a control signal from an arithmetic control section. Further, on the upper surface of this base 5, a heating element 7 made of a material such as Mo or stainless steel is fixedly installed. An installation surface 9 on which a submount 8 is placed is formed on the upper surface of the central portion of the heating body 7 (dimensions are, for example, 25 mm in length, 3 mm in width, and 1.5 mm in thickness). That is, the heating body 7 serves as a mounting table on which the submount 8 is mounted.
The heating body 7 also has a mounting surface 9 that communicates with the suction hole 6.
A through hole 10 is provided to allow the submount 8 to be vacuum-adsorbed. Further, the heating element 7 is electrically connected to a welding power source (not shown), and by supplying power to the heating element 7, the heating element 7 is controlled to be heated to 200 to 500 degrees Celsius. In addition, the heating body 7
For example, a temperature sensor 7a such as a thermocouple is installed in the center of the
is buried and electrically connected to the control mechanism of the welding power source. On the other hand, a metal capillary 11 is disposed above the heating body 7 so as to be movable up and down.
A vacuum suction hole 12 is opened at the tip of the capillary 11 so as to face the submount 8 held by the heating body 7, and a semiconductor laser chip 13 is vacuum suctioned therein. moreover,
A gas heater 14 is provided on the side of the capillary 11. This gas heater 14 consists of a heat-resistant tube 16 whose tip is formed into a nozzle and has a heating wire 15 built therein, and is connected to a source of an inert gas (not shown) such as argon gas or nitrogen gas. Then, the semiconductor laser chip 13 which is die-bonded from the nozzle of the gas heater 14 and the submount 8, that is, the bonding site, are
Preheating is performed by spraying inert gas at 200-300℃.

Next, a die bonding method using the die bonding apparatus configured as described above will be explained. First, for example, in capillary 11
GaAlAs semiconductor laser chip 13 (dimensions are, for example, 400 μm long, 250 μm wide, 80 to 130 μm thick)
m) is vacuum-adsorbed, and a submount 8 made of, for example, copper or silicon (dimensions are, for example, 2 mm in length, 1.2 mm in width, and thickness) is placed on the mounting surface 9 of the heating element 7.
220μm) by vacuum adsorption. Then, the base 1 is moved to position the submount 8. At this time, inert gas heated to 200 to 300°C is blown out from the gas heater 14 in the direction of the arrow 17 in FIG. The submount 8 placed on the
heated to ℃. Then, the capillary 11 is lowered and the semiconductor laser chip 13 is pressed against the submount 8 with a force of about 10 g. Then,
A large current (200 to 800 A) is supplied from the welding power source to the heating element 7 for 1 to 5 seconds. automatically controlled). Then, the heating body 7 is heated to a preset temperature (200 to 500°C). As a result, any of the Au-Sn brazing material, Au-Si brazing material, In brazing material, or Su-Pb brazing material deposited on the surface of the submount 8 and interposed between it and the semiconductor laser chip 13 is determined. This bonding insert material is melted, and the semiconductor laser chip 13 is die-bonded to the submount 8. When the power supply and the blowing of inert gas from the gas heater 14 are stopped, the bonding part is rapidly cooled to room temperature. Therefore, since the bonding insert material also solidifies immediately, the capillary 11 can be raised almost at the same time as the power supply is stopped, and die bonding can be completed.
In this way, the die bonding method of this embodiment can instantaneously raise the temperature of the bonding area to the required temperature by supplying power, and can quickly cool the bonding area immediately after the die bonding is completed, so the die bonding time can be reduced. Can be shortened. Moreover, since the heating time is short, no thermal distortion remains in the semiconductor laser chip 13, and the quality and reliability of the semiconductor laser is improved. In addition, as a result of reliable bonding, it is possible to perform scrubbing, semiconductor lasers, etc.
There is no need to press the chip 13 against the submount 8 with a high pressure, and there is no risk of damage to the semiconductor laser chip 13.

FIG. 3 shows a die bonding apparatus used in a die bonding method according to another embodiment of the present invention. A hole 20 is bored and opens on the upper surface of the base 19. This base 19 is driven by a stepping motor (not shown) and is positioned at a predetermined position by a control signal from an arithmetic control section. Furthermore, a preheater 21 is fixedly installed on the upper surface of this base 19. A mounting surface 23 on which a submount 22 is mounted is formed on the upper surface of this preheater 21 . In other words, the brake heater 21 is the submount 22
It serves as a mounting table on which to place items. The preheater 21 also has a mounting surface 23 that communicates with the suction hole 20.
A through hole 24 opening to the submount 22 is bored.
It is designed to be vacuum adsorbed. Furthermore, a heating wire 25 is built into the preheater 21 to preheat the submount 22 to 100 to 200°C. On the other hand, a metal capillary 26 is disposed above the preheater 21 so as to be movable up and down.
At the tip of this capillary 26, so as to face the submount 22 held by the preheater 21,
The vacuum suction hole 27 is open and the semiconductor laser
The chip 28 is vacuum-adsorbed. The tip of the capillary 26 is formed into a V-shape and is inserted into the center of the lower end of a heating body 29 (having dimensions of, for example, 3 mm in width and 1.5 mm in thickness) made of, for example, Mo or stainless steel. The opening end of the vacuum suction hole 27 of the capillary 26 is connected to the heating body 2.
It has been drilled since 9. Further, the heating body 29 is adapted to be raised and lowered integrally with the capillary 26. And the heating body 29 is
The heating element 2 is electrically connected to a welding power source (not shown).
By supplying power to the heating element 9, the heating element 29 is heated to 300 to 500°C. A temperature sensor 29a, such as a thermocouple, is embedded in the vicinity of the capillary 26 of the heating body 29, and is electrically connected to the control mechanism of the welding power source.

Next, a die bonding method using the die bonding apparatus having the above configuration will be explained. First, a GaAlAs semiconductor laser chip 28, for example, is vacuum-adsorbed onto the capillary 26, and the preheater 21, which has been preheated to 100 to 200°C,
The submount 22 is vacuum-adsorbed onto the mounting surface 23 of the submount 22 . Then, the base 1 is moved to position the submount 22. Next, Capillary 26
is lowered together with the heating element 29, and the semiconductor laser chip 28 is placed about 10cm above the submount 22.
Press with about g. Therefore, a large current (200 to 800 A) is applied from the welding power source to the heating element 29 for 1 to 5 seconds.
(The power supply time is automatically controlled so that the temperature is maintained at a predetermined temperature for a set time using the temperature detection signal from the temperature sensor 29a as a feedback signal. ) Then, the heating body 29 is heated to a preset temperature (300 to 500°C).
As a result, it is deposited on the surface of the submount 22 and interposed between it and the semiconductor laser chip 28.
The bonding insert material made of either Au-Sn brazing material, Au-Si brazing material, In brazing material, or Sn-Pb brazing material is melted and the submount 22
And the semiconductor laser chip 28 is definitely a die.
Bonded. When the power supply to the heating element 29 and the preheating of the preheater 21 are stopped, the bonding part is rapidly cooled to room temperature. Therefore, since the bonding insert material also solidifies immediately, the capillary 26 can be raised almost as soon as the power supply to the heating element 29 is stopped, and die bonding can be completed. As described above, the die bonding method of this embodiment can instantaneously raise the temperature of the bonding part to the required temperature, and can also rapidly cool it immediately after die bonding is completed, so that it can be used in the same way as in the previous embodiment. be effective.

Furthermore, the gist of the present invention also applies when the heating elements 7 and 29 are used together, that is, when the heating element 29 is provided on the capillary side, a submount is placed on the heating element 7, and power is supplied at the same time for die bonding. is within the range of Further, in the second embodiment, the preheater 21 and the gas heater may be used together for preheating.

〔Effect of the invention〕

The present invention enables heating to the required temperature for die bonding in an extremely short time by supplying a large current to a heating element provided near the bonding site. This can be reduced to approximately 1/10 of the time required using the electric heating method, significantly improving production efficiency. Also, because the heating time is short, no harmful thermal distortion remains in the semiconductor laser chip. Furthermore, since reliable bonding is possible, there is no need for scrubbing or pressing the semiconductor laser chip against the submount with high pressure, which eliminates the risk of damaging the semiconductor laser chip. Therefore, the die bonding method of the present invention improves the quality and reliability of the semiconductor laser.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional die bonding method, FIG. 2 is an explanatory diagram of main parts of a die bonding apparatus used in a die bonding method according to an embodiment of the present invention, and FIG. 3 is an explanatory diagram of a die bonding apparatus according to an embodiment of the present invention. FIG. 7 is an explanatory diagram of the main parts of a die bonding apparatus used in a die bonding method of another embodiment. 7: heating body (mounting table), 8, 22: submount, 11, 26: capillary, 13, 28: semiconductor laser chip, 21: preheater (mounting table), 29: heating body.

Claims (1)

[Claims] 1. In a die bonding method in which a semiconductor laser chip held in a capillary is die-bonded to a submount placed on a mounting table, the capillary, the semiconductor laser chip held in this capillary, and this held A preheating step is performed in which the submount on which the semiconductor laser chip is placed is sprayed with heated inert gas to preheat it, and a heating element is provided to heat at least one of the capillary and the submount, and power is supplied to the heating element. By performing a heating step of instantaneously heating at least one of the capillary and the submount, and a heating step after the preheating step, the bonding between the semiconductor laser chip and the submount is bonded.・It is characterized by having a step of melting the insert material and die bonding the semiconductor laser chip and the submount, and a step of raising the capillary at the same time as stopping power supply to the heating body and stopping the preheating. die bonding method.