JP2998769B2 - Bonding material for mounting semiconductor element and method of mounting semiconductor element using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding material for mounting an optical semiconductor device used in the fields of optical communication and optical information processing, and a method for mounting a semiconductor device using the same.

[0002]

2. Description of the Related Art In recent years, the demand for semiconductor lasers has been increasing in many fields, and commercialization of GaAs-based and InP-based lasers has been actively promoted. These have realized high performance, high reliability, and low cost, and have expanded the application range due to advances in crystal growth, process technology, and packaging technology. In particular, it can be said that package technology has contributed most to low cost through mass production. Moreover,
The final performance and reliability of the device are greatly affected by the packaging technology, and many improvements and contrivances have been made to date.

[0003] Optical semiconductor elements such as semiconductor lasers are often configured as shown in FIG. 3 in order to reduce the thermal resistance when assembled into a package. That is, a material having excellent heat conductivity such as copper is used for the heat sink 1, and indium 2, which is a soft metal, is soldered to alleviate mechanical strain caused by a difference in thermal expansion coefficient between the optical semiconductor element 50 and the heat sink 1. It is used as a material.

Usually, the heat sink 1 has a simple structure brazed integrally with the stem 8, and this mounting method is called direct bonding. In a package assembled by this method, for example, in the case of a semiconductor laser, a low thermal resistance of about 40 ° C./W can be easily obtained. However, direct bonding requires solder thickness controllability and flatness due to indium 2. That is, if the indium 2 serving as the solder layer is too thin, the bonding strength is reduced, and if it is too thick, the indium 2 swells to the side surface of the optical semiconductor element 50, and the pn junction is covered. Is caused. Indium 2
If the surface has irregularities, the adhesion of the optical semiconductor element 50 becomes insufficient and a gap is formed between the optical semiconductor element 50 and heat dissipation is hindered.

Therefore, in order to satisfy these requirements, it is necessary to form the indium 2 by controlling the film thickness to 2 to 3 μm by vacuum evaporation. However, as described above, since the heat sink 1 as the vapor deposition section is integral with the stem 8, the heat sink 1 other than the vapor deposition section such as the wiring post 7 must be masked one by one to prevent indium from adhering. Has the disadvantage that it becomes complicated.

In order to solve the above problems, a method of mounting a semiconductor device shown in FIG. 4 has been proposed (Japanese Patent Application No. 3-17 / 1991).
489). In this method, indium 2 is once
E is deposited on an E-film (ethylene-tetrafluoroethylene copolymer) 11, and the iron 6 is
By pressing the film from the film 11 side and transferring the indium 2, the process can be simplified, and a significant cost reduction of the product can be expected. Moreover, since ETFE, which is thermally stable and has an appropriate elastic modulus, is used, the indium is cut well and the reproducibility is excellent.

[0007]

However, in the method using indium transfer described above, a fluorine-based resin such as ETFE is used for the transfer film. The surface generally has irregularities of several μm due to manufacturing and processing problems. It has been found that the irregularities not only strengthen the adhesion to the indium, but also bring a fluorine or carbon compound, which is a material of the film, into the vicinity of the surface of the transfer film during transfer.

FIG. 5 shows the state of indium before and after transfer. If there are large irregularities on the surface of the film 11, the adhesion to the indium 2 thereon becomes strong and transfer becomes difficult.
If the transfer is performed forcibly, the protruding portion 12 of the film 11 is torn off together with the indium 2, and it is considered that the stripped member 11a of the film 11 is present on the surface of the transferred indium 2. Further, when a local temperature rise of the film 11 is caused by ultrasonic waves or the like, thermal decomposition is promoted, and similarly, constituent elements of the film 11 are detected.

[0009] These irregularities on the film surface vary depending on the film manufacturer and lot, and this has made the indium transfer process unstable. When the irregularities are large, the amount of impurities on the surface of the transferred indium is increased as described above, and this causes a problem of initial poor adhesion to the semiconductor element or poor adhesion after long-time energization.

Accordingly, the present invention provides a bonding material for mounting a semiconductor element which facilitates the transfer of indium from a film, enables a clean surface of the transferred indium, and realizes a stable adhesion strength. It is an object of the present invention to provide a method for mounting a semiconductor device using a semiconductor device.

[0011]

In order to achieve the above-mentioned object, a first object of the present invention is to provide a semiconductor device using a fluorine-based resin having a surface unevenness of 0.1 μm or less for a transfer film for depositing indium. Of the bonding material for mounting.

Further, a second object of the present invention is to provide a transfer film on which indium is vapor-deposited, which is composed of two main layers of a fluorine-based resin and a thin polyimide layer, and is arranged so that indium is vapor-deposited on the polyimide layer. Of the bonding material for mounting the semiconductor element.

Further, a third kind of solution is to dispose one main surface of the bonding material for mounting a semiconductor element described in the first or second problem solving means on a base, A surface of a semiconductor element in which a metal containing indium on one principal surface of the bonding material is transferred onto the base by pressing a surface with a pressing member, and a semiconductor element is installed on the base via the metal containing indium. Implementation method.

[0014]

In the structure of the bonding element for mounting a semiconductor element according to the first means for solving the problem, the unevenness of the surface of the fluorine-based resin is small, so that the adhesion to the indium is weak.
The release of the fluorine compound to the transfer film surface during transfer to the heat sink is suppressed.

[0015] In the structure of the bonding material for mounting a semiconductor element according to the second means for solving the problem, since the contact with the indium is polyimide which is thermally stable and has high mechanical strength,
Even when a local temperature rise occurs due to ultrasonic waves or the like, the detachment of the film constituent elements to the transferred indium surface is suppressed. In addition, the mechanical strength of the entire film is improved, so that the film is hardly stretched and the mass production process is stabilized.

The method for mounting a semiconductor element according to the third aspect of the present invention is a very simple process in which one main surface of a bonding material is placed on a base, and pressure is applied from the other main surface by a pressing member. As a result, a large amount of indium can be transferred with almost no fluorine or carbon compound.

[0017]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the measurement results of the irregularities on the surface of ETFE (ethylene tetrafluoroethylene) used as the transfer film in the first invention. (a) shows the case where the unevenness used in this example is 0.1 μm or less, and (b) shows the case where the unevenness is about 0.4 μm at the maximum for comparison. The indium 2 is transferred to the heat sink 1 while applying pressure and ultrasonic waves from the ETFE side in the same manner as in FIG. The transfer was performed on the samples (a) and (b) under the same conditions, but (a) was clearly transferred and (b) was only partially transferred.

The following Table 1 summarizes the results of elemental analysis of the surface of the transferred indium by photoelectron spectroscopy.
Here, attention is paid only to the ratio F _1S / In _{3P of} photoelectron detection to indium (In) of fluorine (F). It can be seen that sample (a) has a much smaller relative amount of fuso than (b). In addition, in the case of (b), the adhesion between the indium and the film is so strong that the indium is not transferred clearly. As in (a), it is necessary to increase the pressure and the output of ultrasonic waves in order to perform clear transfer, but in that case, the amount of fluorine in (b) seems to increase further.

[0020]

[Table 1]

As described above, by using a film having a small unevenness on the surface, the transferred indium surface can be cleaned, and the adhesion strength between the semiconductor element and the heat sink can be increased to obtain a highly reliable semiconductor element. . (Embodiment 2) A second embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows the structure of a bonding material for mounting a semiconductor element according to a second embodiment. The transfer film is a 50μm thick ETF
It is composed of two layers, E10 and a polyimide layer 30 having a thickness of 5 μm. Then, 2 μm of indium 2 is deposited on the polyimide layer 30. The thermal decomposition temperature of polyimide is
Since the temperature is 500 ° C. or higher, which is significantly higher than that of the fluororesin, even if there is a local temperature rise due to ultrasonic waves at the time of transfer, thermal decomposition does not occur and the film elements are not separated. Therefore, a clean indium surface can be obtained even when transferring at a high temperature or applying high-power ultrasonic waves. Also,
The tensile strength of polyimide is about twice that of ETFE at room temperature.
If it is ℃, it will be nearly 4 times. Therefore, even if the polyimide layer 30 is thin as in this embodiment, the tensile strength of the entire film can be increased by about 40%. However, if the polyimide layer 30 is too thick, the deformation in the thickness direction when the film is pressed by the transfer iron is lost, so that the indium cutting is deteriorated or the transfer is only partially performed, which is not desirable.

[0023]

As is clear from the description of the above embodiment, according to the present invention, the transferred indium has a clean surface almost free of compounds of fluorine and carbon, and a stable transfer process can be realized. Therefore, a semiconductor device having low thermal resistance and high reliability can be realized with good yield.

[Brief description of the drawings]

FIG. 1 is a view showing a measurement result of surface unevenness of an ETFE film used in the present invention.

FIG. 2 is a sectional view showing a configuration of a bonding material for mounting a semiconductor element according to the present invention.

FIG. 3 is a perspective view showing a conventional semiconductor device direct bonding configuration.

FIG. 4 is a transfer process diagram of a conventional bonding material for mounting a semiconductor element.

FIG. 5 is a sectional view showing a state of indium before and after transfer using a conventional bonding material for mounting a semiconductor element.

[Explanation of symbols] 1 heat sink 2 indium 10 ETFE film 30 polyimide layer

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yukinobu Morita No. 2-3, Kodemmacho, Nihonbashi, Chuo-ku, Tokyo Inside Oji Tobi Co., Ltd. (56) References JP-A-62-143496 (JP, A) JP-A-2 JP-A-65143 (JP, A) JP-A-2-37727 (JP, A) JP-A-3-183179 (JP, A) JP-A-4-6661 (JP, A) JP-A-6-52822 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01S 3/18 H01L 21/52 H01L 23/40

Claims (3)

(57) [Claims] 1. A bonding material for semiconductor element mounting for depositing a metal containing indium on a heat-resistant film and transferring it onto a mounting substrate while applying pressure, wherein the heat-resistant film has a surface unevenness of 0.1 μm or less. A bonding material for mounting semiconductor elements using a flat fluorocarbon resin. 2. A bonding material for mounting a semiconductor element for vapor-depositing a metal containing indium on a heat-resistant film and transferring it onto a mounting substrate while applying pressure, wherein the heat-resistant film is made of a fluorine-based resin and polyimide. A bonding material for mounting semiconductor elements using a multi-layer film and a metal containing indium deposited on the polyimide surface. 3. A bonding member for mounting a semiconductor element according to claim 1, wherein one main surface of the bonding member is mounted on a base, and another main surface of the bonding member is pressed by a pressing member to form the bonding member. A method of mounting a semiconductor element, comprising transferring a metal containing indium on one principal surface onto the base, and installing a semiconductor element on the base via the metal containing indium.