JPH0585868A - Sputtering film-bearing member and its production - Google Patents

Abstract

PURPOSE:To obtain the title member improved in soldering affinity by formation of a sputtering film with a texture of granule-stacked structure on a solid ceramic member having a sputtering target and specific angle through bias sputtering technique. CONSTITUTION:A solid ceramic member (e.g. of rectangular parallelepiped) consisting of e.g. AlN sintered compact is set on e.g. a parallel flat plate-type autorotation/revolution-type sputtering device. Using Ar gas, at each specified substrate revolution and autorotation numbers and substrate temperature, a specified power's RF together with 2KW of DC sputtering power is applied on the space between the substrate and a chamber to make a successive film formation from the ground side of Ti, Ni and Au films on the upper surface and four sides of the substrate through bias sputtering technique. Thus, a ductile, continuous and high-density film is formed on the upper surface of the substrate and a high-granular density film of granular structure is formed on each of the four sides, resulting in favorable soldering affinity for the member, leading to soldering with high reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member having a sputtered film and a method for manufacturing the member, and more particularly to improving solder wettability of a sputtered film formed on the surface of ceramics such as an aluminum nitride sintered body. Is.

[0002]

2. Description of the Related Art With the recent miniaturization and high integration of electronic devices, how to remove heat generated from various semiconductor elements mounted on these devices including IC chips is extremely important. This has been a problem, and various proposals have been made in terms of component design, circuit design, materials, and the like. Recently, an aluminum nitride sintered body has been used as a substrate material for a semiconductor such as a highly integrated IC. When used as a substrate for a semiconductor package, a silicon chip is usually placed on an aluminum nitride substrate, its upper surface is hermetically covered with ceramics such as aluminum nitride, and a lead frame connected to the silicon chip is attached to the aluminum nitride substrate and the lead frame. Pull out to the outside through the joint with the covering ceramics. Then, a metallization layer is formed on each of the joining surfaces of the aluminum nitride substrate and the ceramics covering the aluminum nitride substrate in order to improve adhesion, and the lead frame portion is further soldered. Therefore, this metallized layer is required to have excellent solder wettability.

[0003]

A sputtering method is adopted as a method for forming the metallized layer. However, according to the study by the present inventors, the conventional sputtered film has the following problems with respect to solder wettability. That is, the sputtered film formed on the surface parallel to the surface of the sputtering target (hereinafter simply referred to as the target) (hereinafter referred to as the “main surface”) has no problem in solder wettability, but for example, on the surface perpendicular to the sputtering target. It was found that the sputtered film formed was inferior in solder wettability to the parallel surface. It was speculated that this was due to some difference in the sputtered film on the surface perpendicular to the main surface. Regarding the modification of the sputtered film, for example, as shown in JP-A-59-229480, in order to form a good quality film on the substrate with good uniformity, the diameter of the target should be increased, or the substrate should be rotated or revolved. It has been proposed to give a complicated motion or to install a plurality of flat targets with a certain inclination angle with respect to the cathode electrode or the high frequency electrode. However, in both cases, the uniformity of the film formed on the main surface of the flat substrate is examined. Further, JP-A-2-138456 discloses a description of forming a sputtered film having a layered structure of granular crystals and columnar crystals on the surface of a Si wafer by applying a specific bias sputtering method for the purpose of improving the so-called step coverage. ing. However, this step coverage has been studied for steps on the order of microns, and can be considered to be about film formation on almost the main surface. Moreover, the solder wettability is unknown. As a sputtering method for surfaces other than the main surface, a barrel-type sputtering method has been put into practical use as a film forming method for small capacitors. In this method, for example, a large number of bases each having a size of about 1 mmφ × 3 mml are put in a basket, and sputtering is performed while rotating the basket. In this method, there is a drawback that the substrates are likely to collide with each other and cracks and cracks are easily generated, and the sputtering efficiency is poor because a film is formed in an extra place such as a basket. As described above, in the conventional sputtering, film formation on a flat surface such as a Si wafer is mainly considered, and there are few examples of sputtering on a three-dimensional object, and the above-mentioned barrel type sputtering is observed. The barrel method has a problem that cracks and cracks are likely to occur and the sputtering efficiency is poor. Therefore, an object of the present invention is to provide a member having a sputtered film having good solder wettability formed on the surface other than the main surface. Another object of the present invention is to provide a method for producing such a member with high efficiency without causing chipping or cracking.

[0004]

In solving the above-mentioned problems, the present inventor first clarified the influence of the film-forming direction on the surface to be sputtered. As shown in FIG. 11, the side surface of the AlN ceramic was polished from the flat surface at angles of 30 °, 60 °, and 90 °, and ordinary DC sputtering was performed on the polished portion. Ar
Pressure is 0.7 Pa, substrate revolution is 4.5 rpm, rotation is 16.2 rp
m, and the substrate temperature was 250 ° C. Sputtering power is DC only 2
kW was applied. The sputtered film thickness on the main surface of the substrate is Ti 4000 Å, Ni 20000 Å, and Au 3500 Å. 12, 30 and 60 in FIGS. 12, 13 and 14, respectively.
The SEM photograph of the surface of the sputtered film on the corner side surface polished to 90 ° is shown. The polishing angle of the corner side is 30 °, 60 °, 90 °
It can be seen that the growth direction of the sputtered film inclines upward in the photograph as it becomes larger, and gaps begin to form between the grains. Figure 1
5, FIG. 16 and FIG. 17 show SEM photographs of the cross section of the sputtered film on the square side surfaces polished to 30 °, 60 ° and 90 °, respectively. It can be seen that as the angle increases, gaps start to form between the grains of each sputtered film, and the columnar organization of the film is promoted. FIG. 18 shows the side surface of the AlN ceramics 30 ° from the flat surface.
The evaluation results of solder wettability of the sputtered film formed on the surface polished at 60 ° and 90 ° are shown below. It can be seen that as the angle increases, the solder wetting spread becomes smaller and the solder wettability becomes worse. The solder wettability is evaluated according to the method described in Examples below. FIG. 19 is a diagram schematically showing the structure of a sputtered film when the angle is 90 °, and the arrow in the figure indicates the sputter direction. The sputtered film on the upper surface of the substrate has a columnar dense structure, but the side surface forms a shadow to the film formation on the lower side adjacent to the upper side in the figure as the film grains grow. Areas that are difficult to be formed between upper and lower particles are formed (shadow effect). As a result, the unevenness of the film becomes severe, and the Au film, which is the third layer, is Ni, which is the second layer.
The entire surface of the membrane cannot be covered. Therefore, Ni
Is presumed to have been oxidized in the air and the solder wettability has deteriorated. Therefore, in order to improve the solder wettability, it is necessary to form a systematically dense film on the surface perpendicular to the main surface. Therefore, the present inventor further studied,
It has been found that the bias sputtering method can form a dense film systematically on the surface perpendicular to the main surface and improve the solder wettability. That is, the present invention is a three-dimensional member having a sputtered film formed on the surface thereof, the substrate of the three-dimensional member is ceramics, and the sputtered film structure has a grain deposition structure. A member having a sputtered film characterized in that the sputtered film is a three-dimensional member formed on the surface, the sputtered film structure has a grain deposition structure, and a solder layer is formed on the sputtered film, And the sputtered film is a three-dimensional member formed on the surface, the base of the three-dimensional member is ceramics, the sputtered film structure has a grain deposition structure, and a solder layer is formed on the sputtered film. The angle between the member having the sputtered film and the sputter surface of the sputter target is 60 to 90.
When a sputtered film is formed on the surface of a ceramic substrate having a surface of 90 °, a method of manufacturing a member having a sputtered film, characterized in that a bias sputtering method is adopted, and an angle formed by the sputtering target and the sputtered surface is 60 degrees. ~
This is a method for producing a member having a sputtered film, which is characterized in that a sputtered film is formed on a surface of 90 ° by a bias sputter method, and then the sputtered film is soldered.

[0005]

[Function] In the sputtering without applying the bias, the film grows in a columnar shape as described above to cause the shadow effect.
According to the bias sputtering method, since a film is formed while performing reverse sputtering, the film has a particle deposition structure and a shadow effect does not occur. Therefore, the film surface becomes flatter, and a film having a high density and few voids can be obtained by observing the cross-sectional structure of the film. Such a film, for example, has less oxidation from the film surface than the columnar structure, good solder wettability,
It has a more reliable effect.

[0006]

EXAMPLES The present invention will be described in detail below based on examples. (Embodiment 1) As shown in FIG. 3, AlN ceramics of 10 mm square and 2 mm thick are provided with Ti, Ni, and
The Au film was sequentially formed from the base side. The film formation was performed by bias sputtering using a parallel plate type revolving sputtering device. Ar pressure is 0.6 Pa, substrate revolution is 9.5 rp
m, rotation was 34.2 rpm, substrate temperature was 315 ° C. when Ti and Ni were formed, and Au was 250 ° C. Sputtering power was DC power of 2 kW, and 0.5 kW of RF was simultaneously applied between the substrate and the chamber. The film thicknesses of Ti and Ni on the main surface of the substrate are 5000 Å and 15000 Å, respectively, and Au is 350
The film was formed so as to have 0 angstrom. 1 and 2 are microstructure photographs of the cross section of the side surface of the substrate and the upper surface of the substrate of the film thus obtained, observed by SEM. On the main surface of the substrate, a continuous, high-density film having high malleability is formed. The film on the side surface of the substrate shows a granular structure on all four side surfaces, and a continuous and high-density film is formed between the particles. 1 in the figure is T
i film, 2 is a Ni film, and 3 is an Au film. To see the characteristics of the film, the solder wettability of the film was evaluated. 10 solder
% Sn-90% Pb solder was used. 1mm square solder 8
The 4, placed on a substrate side portion, 20% H ₂
Soldering was performed by holding at 380 ° C. for 10 minutes in an atmosphere of −80% N ₂ . The solder wettability was evaluated by the width L of the spread portion of the solder after soldering, as shown in FIG. Table 1 is a summary of the evaluation results. The solder spread width on the side surface of the substrate is 5 to 10 mm, and it can be seen that the solder wettability is improved as compared to the conventional case where no bias is applied as shown in FIG. .. The AlN ceramics are individually set in a flat substrate holder during sputtering, one by one, and they do not collide with each other, and of course, cracks or cracks do not occur. In addition, the film was immediately formed with high efficiency without being blocked by a basket or the like. The unit of Table 1 is mm.

[Table 1] (Example 2) The same conditions as in Example 1 were used except that the RF output for bias applied between the substrate and the chamber was set to 0.2 kW, which is lower than in Example 1. An evaluation was made. FIG. 6 is a microstructure photograph of the cross section of the side surface of the substrate of the film thus obtained, observed by SEM. Similar to Example 1, a continuous and high-density film is formed between the grains, but it can be seen that the grain structure is slightly weaker than that of Example 1, and the density is lowered. This is the bias R. F. It is presumed that the output was low. The results of evaluation of the solder wettability of the above-mentioned film by the same method as in Example 1 are shown in Table 1. The solder wettability of 3500A is 4 to 8 mm, and although the solder wettability is slightly inferior to that of Example 1,
It shows good solder wettability as compared with the conventional case where no bias is applied. (Conventional example) 10 mm square × 2 mm thick Al as in Examples 1 and 2
Ti, Ni, and Au films were formed on N ceramics. For film formation, the same apparatus as in Examples 1 and 2 was used, and sputtering was performed only in DC. Sputter power is 2kW for DC power
The substrate was electrically connected to the chamber and grounded. Ar pressure, substrate rotation speed, substrate temperature, Ti, Ni, Au
The film thickness and the like are the same as those in Examples 1 and 2. FIG. 7 and FIG. 8 are microstructure photographs of the cross section of the substrate main surface and the substrate side surface of the film thus obtained, observed by SEM. As with the first and second embodiments, the film on the main surface of the substrate is formed as a continuous and high-density film having high malleability. However, unlike Examples 1 and 2, the film on the side surface of the substrate has a columnar structure, and clear voids are seen between the columnar particles. In the figure, 1 is Ti
The film, 2 is a Ni film, and 3 is an Au film. The solder wettability of the film is evaluated in the same manner as in Examples 1 and 2, and the results are shown in Table 1. It is understood that the solder spreadability is 3 to 7 mm and the solder wettability is poor. FIGS. 9 and 10 are SEM photographs of the surface of the side surface of the AlN ceramic substrate with bias powers of 0 and 0.5 kW, respectively. It can be seen that in the sputtered film formed without applying a bias, gaps are seen between the crystal grains, but in the sputtered film formed by bias sputtering, the gaps are small and the film structure is dense. It should be noted that the gaps between the aggregate units of a large number of crystal grains are Al
It is understood that this is a portion corresponding to a crystal grain boundary of N ceramics, and the gap caused by this crystal grain boundary is smaller when no bias is applied. (Example 3) Ti, Ni, and Au films were sequentially formed on the upper surface and the entire side surface of Si ₃ N ₄ ceramics having a diameter of 10 mm and a thickness of 2 mm from the base side. The Ti film was formed by DC sputtering with a sputtering power of 2 kW. The Ni and Au films were subjected to bias DC sputtering by applying DC power of 2 kW to the target. Ar pressure is 0.8 Pa,
The number of revolutions of the substrate was 4 rpm, the rotation was 14.4 rpm, and the substrate temperature during sputtering was 250 ° C. for all of Ti, Ni, and Au. The film thicknesses of Ti, Ni and Au on the main surface of the substrate were 4000, 20000 and 3500 angstroms. As in Examples 1 and 2, the film on the main surface of the substrate is a film having a high spreadability, which is continuous and has a high density. The side surface of the substrate also has a grain structure, and a film having continuous inter-grain and high density. Been formed. The solder wettability of the above film was evaluated in the same manner as in Example 1, and as a result, the solder spreads to 2/3 of the circumferential portion and shows good solder wettability. Although the embodiments and the like of the present invention have been described above, the sputtering apparatus used in the present invention is not limited to the parallel plate type revolving / revolving sputtering apparatus. It is also effective for other types of sputtering equipment such as equipment. Also, the structure of the film is T
Not limited to i, Ni and Au, Cr-Ni-Au,
Other configurations such as Ti-Cu-Au, Cr-Cu-Au, and Ti-Pt-Au may be used, and other than the three-layer structure is also effective.

[0007]

According to the present invention, it is possible to obtain a film having a high film density and a high solder wettability on a three-dimensional object with high efficiency and without causing cracks or cracks.

[Brief description of drawings]

FIG. 1 is an S showing a cross section of a film on a side surface of a substrate obtained in Example 1.
It is a metal microstructure photograph by EM (30000 times).

FIG. 2 SE showing a cross section of the film on the main surface of the substrate obtained in Example 1
It is a metal microstructure photograph by M (30000 times).

FIG. 3 shows the shape of the substrate used in Example 1.

FIG. 4 is a diagram showing a solder wettability evaluation method used in Examples and Comparative Examples.

FIG. 5 is a diagram showing a solder wettability evaluation method used in Examples and Comparative Examples.

FIG. 6 is an S showing a cross section of the film on the side surface of the substrate obtained in Example 2;
It is a metal microstructure photograph by EM (30000 times).

FIG. 7 is a metal microstructure photograph by SEM showing the main surface of the substrate obtained in Comparative Example 1 (30000 times).

8 is an S showing a cross section of the film on the side surface of the substrate obtained in Comparative Example 1. FIG.
It is a metal microstructure photograph by EM (30000 times).

FIG. 9 is a micrograph of a metal microstructure obtained by observing the surface of a side surface film formed by a conventional bias-free sputtering method with an SEM (10000 times).

FIG. 10 is a metal microstructure photograph of the surface of a side surface film formed by a biased sputtering method observed by SEM (10000 times).

FIG. 11 is a diagram showing the shape of a substrate used for investigating the relationship between the angle of a film-formed surface and the property of the film.

FIG. 12 is a photograph of a metal microstructure of a side surface of a sputtered film formed by ordinary DC sputtering, observed by SEM (10000 times).

FIG. 13 is a photograph of a metal microstructure of a side surface of a sputtered film formed by normal DC sputtering, observed by SEM (10000 times).

FIG. 14 is a metal microstructure image of a side surface of a sputtered film formed by normal DC sputtering, observed by SEM.
(10000 times).

FIG. 15 is a micrograph of a metal microstructure obtained by observing a cross section of a sputtered film by ordinary DC sputtering with an SEM (200
00 times).

16 is a photograph of a metal microstructure obtained by observing a cross section of a sputtered film formed by normal DC sputtering with an SEM (300
00 times).

FIG. 17 is a micrograph of a metal microstructure obtained by observing a cross section of a sputtered film by ordinary DC sputtering with an SEM (300
00 times).

FIG. 18 is a graph showing evaluation results of solder wettability.

FIG. 19 is a diagram schematically showing the structure of a film formed by bias sputtering.

[Explanation of symbols]

 1 Ti Film 2 Ni Film 3 Au Film 10 Base 11 Main Surface 12 Side 13 Solder Preform 14 Solder Spread

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Hayashida 2326 Imai, Ome-shi, Tokyo Hitachi, Ltd. Device Development Center

Claims (8)

[Claims] 1. A member having a sputtered film, characterized in that the sputtered film is a three-dimensional member formed on the surface, the base of the three-dimensional member is ceramics, and the sputtered film structure has a grain deposition structure. .. 2. A member having a sputtered film according to claim 1, wherein the ceramic is an aluminum nitride sintered body. 3. A sputtered film, which is a three-dimensional member having a sputtered film formed on its surface, wherein the sputtered film has a grain deposition structure and a solder layer is formed on the sputtered film. A member having. 4. A three-dimensional member having a sputtered film formed on its surface, a substrate of the three-dimensional member is ceramics, a sputtered film structure has a grain deposition structure, and a solder layer is formed on the sputtered film. A member having a sputtered film. 5. The member having a sputtered film according to claim 4, wherein the ceramic is an aluminum nitride sintered body. 6. A sputtering film characterized by employing a bias sputtering method when forming a sputtering film on a surface of a ceramic substrate having an angle of 60 to 90 ° with a sputtering surface of a sputtering target. A method of manufacturing a member having. 7. A sputtering method, characterized in that a film is formed by sputtering with a bias sputtering method on a surface having an angle of 60 to 90 ° with a sputtering surface of a sputtering target, and then soldering is performed on the sputtering film. A method for manufacturing a member having a film. 8. The method for producing a member having a sputtered film according to claim 7, wherein the substrate on which the sputtered film is formed is an aluminum nitride sintered body.