Heat radiating component and semiconductor device provided with the same

Abstract: Disclosed herein is a semiconductor laser provided with a heat radiating component which is improved in heat radiating property. The semiconductor laser comprises a heat radiating component for radiating heat which is generated in operation. In this heat radiating component, a polycrystalline diamond layer (3) synthesized by vapor deposition is formed on the upper surface of a stem (4). A semiconductor laser element (1) is brazed/bonded onto the surface of the vapor-deposited polycrystalline diamond layer (3) through a brazing filler metal (2). Also disclosed herein is a heat radiating component having a thermal expansion coefficient being coincident to that of an LSI chip to be mounted thereon, which is excellent in heat radiating property.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a heat radiating component and a semiconductor device provided with the same, and more specifically, it relates to a heat radiating component for dissipating heat which is generated from a semiconductor element such as a semiconductor laser element or an LSI chip, and a semiconductor device provided with such a heat radiating component. Description of the Background Art In general, well known is a heat radiating component for dissipating heat which is generated from a semiconductor element such as a semiconductor laser element or an LSI chip. For example, the range of application of a semiconductor laser is rapidly widened in the field of optical communication, optical memory and the like. In response to this, technology development has been made in order to increase the output or reduce the wavelength of such a semiconductor laser. Under such circumstances, the heating value of a semiconductor laser element is apt to be increased. Thus, the semiconductor laser element is disadvantageously deteriorated in reliability, and its life is reduced. To this end, there has been developed a semiconductor laser which is provided with a heat radiating component of a heat conductive material, in order to dissipate heat generated from the semiconductor laser element. Fig. 1 is a block diagram showing a conventional semiconductor laser which is provided with a heat radiating component. Referring to Fig. 1, the conventional semiconductor laser comprises a stem 4, a submount 5 which is mounted on a prescribed upper surface region of the stem 4 through a brazing filler metal 6, and a semiconductor laser element 1 which is mounted on a prescribed upper surface region of the submount 5 through another brazing filler metal 2. The brazing filler metal 6 is adapted to bond the submount 5 to the stem 4, while the other brazing filler metal 2 is adapted to bond the semiconductor laser element 1 to the submount 5. Table 1 shows materials and shapes of the semiconductor laser element 1, the submount 5, the brazing filler metals 2 and 6, and the stem 4 respectively. Element 1 Material Compound Semiconductor Composed of Ga, As, In, P, Al or the like Shape up to 0.5 mm square Submount 5 Material Si, AlN, BeO, Cu-W Alloy, Cu-Mo Alloy, SiC, cBN polycrystalline Substance or Single-Crystalline Diamond Shape up to 1 mm square, 0.2 to 0.5 mm Thick Brazing Filler Metals 2 & 6 Element Side (2) Au-Sn Alloy, Pb-Sn alloy or In Stem Side (6) Au-Si Alloy or Pb-Sn Alloy Stem 4 Material Cu, Cu-W Alloy, Cu-Mo Alloy or Cu-W-Mo Alloy Shape 5 to 15 mm Square In operation, heat which is generated from the semiconductor laser element 1 is transmitted to the stem 4 through the submount 5, to be radiated. The submount 5 is adapted to efficiently transmit the heat generated from the semiconductor laser element 1 to the stem 4. Therefore, the submount 5 is made of a material having high thermal conductivity, such as a Cu-W alloy, a polycrystalline substance of cBN (cubic boron nitride) or single-crystalline diamond shown in Table 1, for example. In the conventional semiconductor laser, however, the brazing filler metal 6 is interposed between the submount 5 and the stem 4, to inevitably resist against the thermal conduction from the submount 5 to the stem 4. In the conventional semiconductor laser, therefore, it has been difficult to attain efficient heat radiation due to such interposition of the brazing filler metal 6. When the submount 5 is made of high-priced single-crystalline diamond or the like, its size is considerably reduced as compared with the upper surface of the stem 4. Consequently, the thermal conduction surfaces of the submount 5 and the stem 4 are so reduced that thermal diffusion mainly progresses vertically along the direction of depth of the stem 4 and no sufficient thermal diffusion is attained in the transverse direction. Also when the submount 5 is made of single-crystalline diamond, therefore, it is difficult to attain sufficient heat radiation efficiency. On the other hand, the brazing filler metal 2 which is interposed between the submount 5 and the semiconductor laser element 1 is prepared from an Au-Sn alloy, a Pb-Sn alloy or the like. However, such a material has a high thermal expansion coefficient. When the temperature of the semiconductor laser element 1 is increased upon operation, therefore, the semiconductor laser element 1 is extremely distorted by heat. Such heat distortion leads to abnormal operation of the semiconductor laser element 1 or reduction of its operation life. In general, therefore, it has been difficult to provide a heat radiating component which has an excellent radiation effect and a semiconductor laser which has excellent operation characteristics. Further, it has been difficult to effectively prevent heat distortion of a semiconductor element such as a semiconductor laser element or an LSI chip, which is bonded by a brazing filler metal having a high thermal expansion coefficient. Further, the article "Diamond-Film Synthesis Using DC Plasma Jet CVD" in Fujitsu Scientific & Technical Journal, vol. 25 no. 1, March 1989, pages 44-51, discloses a method of producing a heat sink, comprising the steps of: Creating a 1 mm thick diamond film in a CVD process, cutting the diamond film into a 2.5 x 2.5 x 0.5 mm 3 chip by using a YAG laser, polishing the surface of the chip and metallizing Pi, Pt and Au-Sn thin films on the surface of the chip by sputtering, and soldering a InGaAsP laser diode on the diamond chip, and finally attaching the chip to a copper stem. JP-A-62196858 discloses a semiconductor device comprising a diamond covered with a Ti layer by a sputtering method. A titanium nitride layer is formed as a reaction preventive layer on the Ti layer. A Pt layer is formed on the titanium nitride layer, and an Au-Sn layer is formed as a fusion-bonding metal on the uppermost layer. A semiconductor element is mounted on the Au-Sn. This arrangement is made to prevent Ti from reacting with Sn. Further, 400 Solid State Technology 34 (1991) February, No 2, West Ford, MA, US pages 89 to 91 discloses a heat radiating component comprising the features of the precaracterizing portion of claim 1. SUMMARY OF THE INVENTION An object of the present invention is to improve the heat radiating property of a heat radiating component. Another object of the present invention is to improve the heat radiating property of a heat radiating component while preventing heat distortion of a semiconductor element mounted thereon. Still another object of the present invention is to improve operating characteristics of a semiconductor device by an excellent heat radiating effect. A further object of the present invention is to prevent operation failures in an LSI package and increase its operation life. The above object is solved by a heat radiating component comprising the features defined in claim 1. Preferred embodyments of the invention are defined in the dependent claims. Preferably the mounting surface of the stem is entirely covered with the polycrystalline diamond layer which is formed by vapor deposition. Thus, no brazing layer is required between the vapor-deposited polycrystalline diamond layer and the stem, whereby efficiency of thermal conduction from the former to the latter can be improved. Further, the vapor-deposited polycrystalline diamond layer having high thermal conductivity is adapted to cover the overall mounting surface of the stem or a part thereof with a wider area as compared with the contour of the semiconductor element, whereby thermal conduction surfaces are so widened that heat generated from the semiconductor element is diffused along the direction of depth of the stem as well as along the plane of the mounting surface of the stem. According to the invention, the polycrystalline diamond layer is formed on at least one surface of the substrate base material and the single metallization bonding layer of at least one metal selected from Au, Ag, Si, Ge, Sn, Pb and In is mounted on a prescribed surface region of the polycrystalline diamond layer so that the semiconductor element is mounted on its surface, while the thermal expansion coefficient of the overall heat radiating component is set at a prescribed value within a range of 4 x 10 -6 to 6 x 10 -5 /°C under temperatures ranging from the room temperature to 400°C to easily coincide with that of the semiconductor element since the materials for and the thicknesses of the metal bonding layer, the polycrystalline diamond layer and the substrate base material are properly selected and set at prescribed values respectively. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates the sectional structure of a conventional semiconductor laser; Fig. 2 illustrates the sectional structure of a semiconductor laser according to the present invention; and Fig. 3 illustrates the sectional structure of another LSI package according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 2, a semiconductor laser according to the present invention comprises a stem 4, a vapor-deposited polycrystalline diamond layer 3 which is formed on the upper surface of the stem 4 by vapor deposition, and a semiconductor laser element 1 which is bonded onto the surface of the vapor-deposited polycrystalline diamond layer 3 through a brazing filler metal 2. Table 2 shows materials and shapes of the semiconductor laser 1, the vapor-deposited polycrystalline diamond layer 3, the brazing filler metal 2 and the stem 4 respectively. Element 1 Material Compound Semiconductor Composed of Ga, As, In, P, Al or the like Shape up to 0.5 mm square Submount 3 Material Polycrystalline Diamond Synthesized by Vapor Deposition (Thermal Conductivity: 500 to 2000 W/m·K, Specific Resistance: at least 10 9 Ω·cm) Shape 10 to 500µm Thick, Covering Upper Surface of Stem Brazing Filler Metals 2 Au-Sn Alloy, Pb-Sn Alloy or In Stem 4 Material Cu, Cu-W Alloy, Cu-Mo Alloy, Cu-W-Mo Alloy, W, Mo, SiC Sintered Body, Si 3 N 4 Sintered Body or AlN Sintered Body Shape 5 to 15 mm Square The vapor-deposited polycrystalline diamond layer 3 is formed over the entire upper surface of the stem 4. Therefore, heat which is generated from the semiconductor laser element 1 is transmitted to the vapor-deposited polycrystalline diamond layer 3, to be diffused along the direction of depth and the transverse direction in its interior. The heat is further diffused from the interface between the vapor-deposited polycrystalline diamond layer 3 and the stem 4 toward the interior of the stem 4. Namely, a region of the stem 4 contributing to heat radiation is widened as compared with the conventional semiconductor laser shown in Fig. 1. Thus, it is possible to attain effective heat radiation. According to the present invention, the thermal conductivity of the vapor-deposited polycrystalline diamond layer 3 is preferably 500 to 2000 W/m·K, since no sufficient thermal conduction is attained if the thermal conductivity is not more than 500 W/m·K, while it is impossible to form a polycrystalline diamond layer whose thermal conductivity exceeds 2000 W/m·K with the current technology. Further, the specific resistance of the vapor-deposited polycrystalline diamond layer 3 is preferably at least 10 9 Ω·cm. This is the condition which is necessary for ensuring insulability. The thickness of the vapor-deposited polycrystalline diamond layer 3 is preferably within a range of 10 to 500 µm, since no effective radiation can be attained if the thickness is not more than 10 µm, while the heat radiating effect is not remarkably improved but the cost is increased if the thickness exceeds 500 µm. Due to the employment of the vapor-deposited polycrystalline diamond layer 3 having high thermal conductivity, the stem 4 may be made of W, Mo, an SiC sintered body, an Si 3 N 4 sintered body, an AℓN sintered body or the like, in addition to the conventional material-of Cu, a Cu-W alloy, a Cu-Mo alloy or a Cu-W-Mo alloy. Description is now made on Examples which were made on the basis of the aforementioned essence of the present invention in order to confirm the effect thereof. Example 1 Polycrystalline diamond was synthesized on an upper surface of 5 mm by 10 mm of a Cu stem by performing microwave plasma CVD (chemical vapor deposition) for 8 hours under the following conditions: Raw Material Gas (Flow Rate) H 2 500 scan CH 4 20 sccm Gas Pressure 70 Torr Microwave Oscillation Output 600 W Thus, it was possible to cover the overall upper surface of the stem with a polycrystalline diamond layer of 50 µm in thickness. This polycrystalline diamond layer had thermal conductivity of 1600 W/m·K, and specific resistance of 10 10 Ω·cm. Then, a Ga-Aℓ-As optical semiconductor element (semiconductor laser element) of 0.2 mm square was brazed/bonded onto the upper surface of the polycrystalline diamond layer with a brazing filler metal of an Au-Sn alloy, thereby preparing a semiconductor laser (A). In order to evaluate the heat radiating effect of the stem, the semiconductor laser (A) was continuously oscillated with an output of 200 mW and the temperature rise of the semiconductor laser element was measured. On the other hand, comparative example was prepared by employing a single-crystalline synthetic diamond layer of 0.75 mm square having thermal conductivity of 2000 W/m·K as a submount which was provided on the surface of a stem. The single-crystalline synthetic diamond layer was brazed onto the surface of the stem, and a semiconductor laser element similar to the above was further brazed/bonded onto the surface of the single-crystalline synthetic diamond layer, to prepare a semiconductor laser (B). Then, the temperature rise of the semiconductor laser element was measured. In the comparative semiconductor laser (B), the submount was bonded onto the stem by a brazing filler metal of an Au-Si alloy. On the other hand, the semiconductor laser element was bonded onto the submount by another brazing filler metal of an Au-Sn alloy. Table 3 shows the results of the tests for evaluating the heat radiating effects. Temperature of Semiconductor Element (°C) Inventive Sample (A) 35 Comparative Sample (B) 80 Referring to Table 3, it is understood that the temperature of the semiconductor laser element included in the inventive semiconductor laser (A), which was provided with the polycrystalline diamond layer formed on the upper surface of the stem, was extremely lower than that of the comparative semiconductor laser (B), which was provided with the submount of the single-crystalline synthetic diamond layer. Thus, it is understood that the inventive semiconductor laser (A) has an excellent heat radiating effect. Example 2 In Example 2, an SiC stem of 15 mm by 10 mm was employed to synthesize polycrystalline diamond on its upper surface through thermal CVD. In more concrete terms, a linear tungsten filament of 0.5 mm in diameter and 100 mm in length was employed as a thermoionic emission material, to synthesize the polycrystalline diamond by carrying out thermal CVD for 20 hours under the following conditions: Raw Material Gas (Flow Rate) H 2 300 sccm C 2 H 2 15 sccm Gas Pressure 80 Torr Filament Temperature 2150°C Filament-to-Substrate Distance 6 mm Substrate Temperature 920°C Consequently, it was possible to cover the overall upper surface of the stem with a polycrystalline diamond layer of 150 µm in thickness. This polycrystalline diamond layer had thermal conductivity of 800 W/m•K and specific resistance of 5 x 10 9 Ω•cm. Then, an In-Ga-As-P semiconductor laser element of 0.3 mm square was brazed/bonded onto the upper surface of the polycrystalline diamond layer by a brazing filler metal of an In alloy, to prepare a semiconductor laser (C). In order to evaluate the heat radiating effect of the stem, the semiconductor laser (C) was continuously oscillated for 6000 hours with an initialization output of 25 mW. The time change of the laser output was measured under this condition. Comparative example was prepared by employing a single-crystalline natural diamond layer of 1 mm square having thermal conductivity of 1200 W/m•K as a submount which was mounted on the surface of the same stem as the above. In more concrete terms, the single-crystalline natural diamond layer was brazed onto the surface of the stem and a semiconductor laser element was brazed/bonded onto the surface of the single-crystalline natural diamond layer, to prepare a semiconductor laser (D). Then, the semiconductor laser (D) was evaluated. As to this semiconductor laser (D), the submount was bonded onto the stem by a brazing filler metal of an Au-Si alloy, while the semiconductor laser element was bonded onto the submount by another brazing filler metal of an In alloy. Table 4 shows the results of the test for evaluating the heat radiating effects. Laser Oscillation Output (mW) Immediately After Oscillation 100Hr 500Hr 1800Hr 4000Hr 7000Hr Inventive Sample (C) 250 253 248 249 251 248 Comparative Sample (D) 250 248 251 240 225 203 Referring to Table 4, it has been clarified that the inventive semiconductor laser (C) exhibited extremely small time change of the laser output as compared with the comparative semiconductor laser (D). This means that the inventive semiconductor laser (C) can efficiently radiate heat generated from the semiconductor laser element. Example 3 In Example 3, various materials were employed for preparing stems. Table 5 shows the materials for the stems and conditions for synthesizing polycrystalline diamond layers covering the upper surfaces of the stems. The polycrystalline diamond layers were synthesized by a thermal filament method under the conditions shown in Table 5. Table 6 shows properties of the polycrystalline diamond layers covering the upper surfaces of the stems. No. Material of Stem Gas Composition/F low Rate (sccm) Gas Pressure (Torr) Filament Temperature (°C) Stem Temperature (°C) Synthesizing Time (h.) E Cu-Mo Alloy CH 4 20 120 1,900 850 22 H 2 500 F Cu C 2 H 2 50 85 2,100 950 55 H 2 600 G AlN Sintered Body CH 4 20 145 2,200 700 80 H 2 500 H Cu-W-Mo Alloy CH 4 50 90 2,050 1,020 24 H 2 600 I Al 2 O 2 Sintered Body CH 4 20 200 1,950 880 46 H 2 500 J SiC Sintered Body C 2 H 2 50 50 2,180 930 87 H 2 600 No. Thickness (µm) Thermal Conductivity (W/m·K) Specific Resistance (Ω·cm) E 15 800 8 x 10 11 F 3 1,500 6 x 10 9 G 80 300 3 x 10 12 H 250 1,800 2 x 10 10 I 380 1,200 5 x 10 9 J 55 750 5 x 10 6 Then, Ga-Aℓ-As optical semiconductor elements (semiconductor laser elements) of 0.3 mm square were brazed/bonded onto the upper surfaces of the polycrystalline diamond layers, thereby preparing semiconductor lasers (E) to (J). In order to evaluate heat radiating effects of the stems, the semiconductor lasers (E) to (J) were continuously oscillated with outputs of 180 mW, and the temperature rises of the semiconductor elements were measured. Table 7 shows the results of the tests for evaluating the heat radiating effects. No. Temperature of Semiconductor Element (°C) No. Temperature of Semiconductor Element (°C) E 30 H 25 F 70 I 28 G 80 J Incapable of Stable Laser Oscillation Referring to Table 7, it is understood that the temperatures of the semiconductor laser elements provided in the semiconductor lasers (F), (G) and (J) were too high to attain sufficient heat radiating effects of the stems. This may be because the thickness of the polycrystalline diamond layer was too small in the semiconductor laser (F). In the semiconductor laser (G), it is conceivable that thermal conductivity of the polycrystalline diamond layer was too low to sufficiently transmit the heat generated from the semiconductor laser element to the stem. In the semiconductor laser (J), the semiconductor laser element was incapable of attaining stable laser oscillation, conceivably because the specific resistance of the polycrystalline diamond layer was too small. On the other hand, it is understood that the stems provided in the semiconductor lasers (E), (H) and (I) efficiently radiated heat since the semiconductor laser elements were at low temperatures. An LSI chip according to an aspect of the present invention is now described. Fig. 3 is a sectional view showing the LSI package according to this aspect of the present invention. Referring to Fig. 3, this LSI package comprises an LSI chip 15, which is mounted on a prescribed surface region of a polycrystalline diamond layer 13 through a metal bonding layer 14 alone. The following Examples were made in order to confirm the effect of the LSI package shown in Fig. 3. Example 4 Polycrystalline diamond was synthesized on an Si substrate of 20 mm square having a thickness of 1.5 mm by performing microwave plasma CVD for 10 hours, under the following conditions: Raw Material Gas (Flow Rate) H 2 200 sccm CH 4 5 sccm Gas Pressure 80 Torr Microwave Oscillation Output 600 W The upper surface of the Si substrate recovered after the aforementioned synthesis was covered with a polycrystalline diamond layer of 0.1 mm in thickness. The surface of this layer was further covered with a bonding material of an Au-Sn alloy in a thickness of 30 µm, to prepare a heat radiating substrate (K2). An Si LSI chip of 15 mm square was mounted on the heat radiating substrate (K2), which in turn was subjected to performance evaluation. Comparative example (L2) was prepared in a similar manner to the above, except for that the heat radiating substrate was prepared from AℓN of the same shape as the above. Another comparative example (M2) was prepared in a conventional structure with a bonding material of silver paste. These comparative examples (L2) and (M2) were also subjected to performance evaluation. The performance evaluation was made by carrying out thermal shock tests and measuring heat resistance values, under the following conditions: Thermal Shock Test Each of the aforementioned heat radiating substrates carrying the LSI chips was alternately dipped in organic solvents which were set at temperatures of 125°C and -55°C repeatedly by 100 times, and a damaged state of each LSI chip was observed. Heat Resistance Measurement Electric power of 3 W was applied to each LSI chip, and the temperature of the LSI chip was measured with an infrared thermometer when the same entered a stationary state. Table 10 shows the results. Sample Result of Thermal Shock Test Result of Measurement of Heat Resistance (LSI Temperature) Inventive Sample K2 Not Damaged 30°C Comparative Sample L2 Cracked After 80 Times 70°C Comparative Sample M2 Cracked After 20 Times 50°C Referring to Table 8, it is understood that the inventive sample (K2) exhibited small difference in thermal expansion coefficient with respect to the LSI chip substantially with no heat distortion dissimilarly to the conventional examples, while exhibiting an excellent heat radiating property. Example 5 A gas obtained by mixing H 2 , C 2 H 6 and Ar in ratios of 8:1:1 was supplied into a reaction tube, which was provided with a Cu-Mo alloy substrate of 25 mm square having a thickness of 1 mm, at a flow rate of 500 sccm, and its pressure was adjusted to 135 Torr. Then, a high frequency of 13.56 MHz was supplied from a high frequency generator for exciting the mixed gas and generating plasma, thereby synthesizing polycrystalline diamond for 30 hours. The high frequency was outputted at 800 W. The upper surface of the substrate recovered after the aforementioned synthesis was covered with a polycrystalline diamond layer of 0.03 mm in thickness. The surface of this layer was further covered with a bonding material layer of an Au-Si alloy so that its thickness was 40 µm, thereby preparing a heat radiating substrate (N2). A GaAs LSI chip of 18 mm square was mounted on this heat radiating substrate (N2), which in turn was subjected to performance evaluation. Comparative examples (02) to (T2) were prepared by combining bonding materials and heat radiating substrate materials shown in Table 11, to be subjected to performance evaluation. This performance evaluation was made by carrying out thermal shock tests and measuring heat resistance values similarly to Example 4. Table 9 shows the results. Sample Result of Thermal Shock Test Result of Measurement of Heat Resistance (LSI Temperature) Bonding Material No. Substrate Material Material Thickness Inventive Sample N2 Cu-Mo Alloy Covered with Diamond Au-Si 30µm Not Damaged 25°C Comparative Sample O2 Cu-Mo Alloy Au-Si 25µm Cracked After 60 Times 50°C Comparative Sample P2 AlN Sintered Body Au-Si 35µm Cracked After 20 Times 50°C Comparative Sample Q2 Cu-Mo Alloy Silver Paste 45µm Cracked After 80 Times 75°C Comparative Sample R2 Cu-Mo Alloy Au-Sn 40µm Cracked After 70 Times 55°C Comparative Sample S2 SiC Sintered Body Au-Si 15µm Cracked After 30 Times 60°C Comparative Sample T2 AIN Sintered Body Silver Paste 25µm Cracked After 60 Times 60°C Referring to Table 9, it is understood that the inventive sample (N2) exhibited small difference in thermal expansion coefficient with respect to the LSI chip substantially with no heat distortion dissimilarly to the comparative examples, while exhibiting an excellent heat radiating property. Summarized, the heat radiating component preferably comprises the polycrystalline diamond layer having high thermal conductivity vapor-deposited entirely over the upper surface of the stem, whereby efficiency of thermal conduction from the semiconductor laser element is so improved that it is possible to suppress characteristic deterioration caused by heat which is generated from the semiconductor laser element. Further, the heat radiating component comprises the polycrystalline diamond layer formed on at least one surface of the substrate base material which is made of one material selected from metals and ceramics, the metallization bonding layer being made of at least one metal selected from Au, Ag, Si, Ge, Sn, Pb and In is formed on a prescribed surface 5 region of the polycrystalline diamond layer so that the semiconductor element is mounted on its surface, and the thermal conductivity of the overall heat radiating substrate is set at a prescribed value within a range of 4 x 10 -6 to 6 x 10 -5 /°C under temperatures ranging from the room temperature to 400°C by properly selecting the materials for the metallization bonding layer, the polycrystalline diamond layer and the substrate base material and setting the thicknesses thereof at prescribed values respectively. Thus, it is possible to easily form the heat radiating substrate to have a thermal expansion coefficient which coincides with that of an LSI chip to be mounted thereon as well as an excellent heat radiating property. Further, the heat radiating component preferably comprises the stem having the mounting surface for receiving the semiconductor laser element thereon, and the vapor-deposited polycrystalline diamond layer covering the mounting surface of the stem. The semiconductor laser element is brazed/bonded onto the surface of the vapor-deposited polycrystalline diamond layer, whereby efficiency of thermal conduction from the semiconductor laser element is so improved that it is possible to prevent characteristic deterioration caused by heat which is generated from the semiconductor laser element. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.

Claims: A heat radiating component having a mounting surface for receiving a semiconductor element (1; 15), said heat radiating component comprising: a stem (4; 12), and a vapor-deposited polycrystalline diamond layer (3; 13) provided on said stem (4; 12), wherein said semiconductor element (1; 15) is mountable on said diamond layer (3; 13), and wherein said vapor-deposited polycrystalline diamond layer (3; 13) is formed on an upper surface of said stem (4; 12) by vapor deposition, and wherein said stem (12) is made of one material selected from metals and ceramics; and wherein a metallization bonding layer (14) is formed on a prescribed surface region of said polycrystalline diamond layer for receiving said semiconductor element on its surface, characterized in that said metallization bonding layer is a single layer being made of at least one material selected from Au, Ag, Si, Ge, Sn, Pb and In; wherein materials for and thicknesses of said metallization bonding layer, said polycrystalline diamond layer and said substrate base material are properly selected and set at prescribed values respectively for setting the thermal expansion coefficient of overall said heat radiating component at a prescribed value within a range of 4 x 10 -6 to 6 x 10 -5 /°C under temperatures ranging from the room temperature to 400°C. The heat radiating component according to claim 1, wherein said stem is formed by a sintered body being mainly composed of at least one material selected from Si, Mo, W, a Cu-W alloy, a Cu-Mo alloy, a Cu-Mo-W alloy and AIN. The heat radiating component in accordance with claim 1, wherein said vapor-deposited polycrystalline diamond layer (3; 13) is formed to cover overall said mounting surface of said stem (4; 12). The heat radiating component in accordance with claim 1, wherein said vapor-deposited polycrystalline diamond layer (3; 13) has a thermal conductivity of at least 500 W/m•K and not more than 2000 W/m•K. The heat radiating component in accordance with claim 1, wherein said vapor-deposited polycrystalline diamond layer (3; 13) has a specific resistance of at least 10 9 Ω•cm. The heat radiating component in accordance with claim 1, wherein said vapor-deposited polycrystalline diamond layer (3; 13) has a thickness of at least 10 µm and not more than 500 µm.

Inventors: IGUCHI TAKAHISA, NAKAI TETSUO, NAKAMURA TSUTOMO, IGUCHI, TAKAHISA, NAKAI, TETSUO, NAKAMURA, TSUTOMU, Iguchi, Takahisa, c/o Itami Works Sumitomo El., Nakai, Tetsuo, c/o Itami Works Sumitomo El., Nakamura, Tsutomo, c/o Itami Works Sumitomo El.
Applicants: SUMITOMO ELECTRIC INDUSTRIES, SUMITOMO ELECTRIC INDUSTRIES, LTD.
Application year: 1992
Main classification: H01L23
IPC codes: H01L23