JP2008153523A - Method of manufacturing cap structure, and semiconductor device sung the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a cap structure having an eyelet portion that is capable of effectively preventing occurrence of stray light, is thermally stable, and transmits light, and having an optically transmissive member fitted thereto. <P>SOLUTION: The method of manufacturing a cap structure comprises the steps of: preparing a cap body having an eyelet portion; performing underlying plating under the cap body; applying Sn-Ni plating on the underlying plating; applying Zn-Ni plating on the Sn-Ni; annealing the cap body which is formed with a Zn-Ni plating coating under a high temperature; and depositing an optically transmissive member on the annealed eyelet portion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a cap structure. More specifically, the present invention relates to a cap structure that can prevent stray light inside a cap structure when used as a cover in a semiconductor device including a light emitting element and / or a light receiving element. It relates to the manufacturing method. The present invention also relates to a semiconductor device using such a cap structure as a cover.

  In an optical device using laser light, a semiconductor device on which a laser diode is mounted is used for receiving and emitting laser light. Such a semiconductor device is usually configured by mounting a laser element for light emission and a monitor element on a stem, and in order to hermetically seal the element, the upper surface of the semiconductor device is covered with a cap with a light transmission window. ing. In such a semiconductor device, laser light incident on the inside of the semiconductor device from the light transmission window of the cap or laser light emitted from the laser element for light emission toward the light transmission window is generated inside the cap of the semiconductor device. There is a problem of generating stray light that is reflected and causes noise and malfunction of the semiconductor device.

  Conventionally, in order to avoid the problem of noise and malfunction due to stray light, a method of suppressing irregular reflection of light by making the inner surface of the cap and the surface of the stem black has been generally performed. As such a method, for example, the present applicant applies a method of blackening the plating film by performing cobalt or cobalt alloy plating on the cap body and heating in an oxidizing atmosphere (Patent Document 1), or blacking the cap body. A method (Patent Document 2) has already been proposed in which a nickel plating film is formed and blackened by heating in the atmosphere. However, in the case of these methods, since the method of heating the plating is adopted in order to make the inner surface of the cap or the like black, there is a problem that the number of steps increases and becomes complicated. A method newly developed by the present applicant to solve such problems and to effectively suppress stray light is the cap manufacturing method described in Patent Document 3.

  In the method described in Patent Document 3, after a base plating film 124 is formed on a cap body 120 having a light transmission hole 122 as shown in FIG. 1 (A), the cap body as shown in FIG. 1 (B). A light transmission window 119 is joined to 120 so as to cover the light transmission hole 122 using a low melting point glass 118. Next, as shown in FIG. 1C, Sn-Ni plating 126 is applied to the cap body 120 to which the light transmission window 119 is bonded, thereby forming a first black film on the surface of the base plating film 124. Subsequently, Zn—Ni plating 128 is performed, and a second black film is formed on the first black film. Here, nickel plating suitable for reaction with the low melting point glass is used for forming the base plating film.

JP-A-6-252281 (Claims) JP-A-7-7098 (Claims) JP 2003-204006 (Claims, FIG. 1)

  According to the method described in Patent Document 3, stray light can be more effectively suppressed as a result of the effective combination of the light-absorbing action of the first black film and the light-absorbing action of the second black film. effective. However, it has been found that this method still has problems to be solved. For example, low melting point glass is used as a bonding material when a light transmission window is bonded to the cap body, but it can be used when the low melting point glass is weak to a plating solution or a pretreatment solution used in a subsequent plating step. There are restrictions on low melting glass. In particular, this method cannot be used for products using low-melting glass with low chemical resistance. In addition, since the plating method is used after the light transmission window is joined, dirt is likely to adhere to the light transmission window, necessitating a cleaning process by polishing, or the light transmission window itself may be damaged in some cases. There is also a case. Further, during the plating process, metal impurities contained in the low-melting glass tend to elute into the plating solution, which tends to cause deterioration of the plating solution and thereby shorten the life of the solution. Furthermore, it was considered that the light transmissive window was joined after a series of plating steps. In this method, for example, the light transmissive window was directly incorporated into a cap subjected to Zn-Ni plating and joined with a low melting point glass. In this case, the gas from the plating adversely affects the bonding force, and not only does the bonding fail, but there is a problem that the light transmission window and the cap are severely contaminated by the heat applied during the bonding.

  Accordingly, the object of the present invention is to solve the above-mentioned problems and effectively prevent the generation of stray light in the internal cavity covered with the cap, and is thermally stable, and the appearance of the obtained cap Is to provide a method for producing a cap that is good and free from variations.

  Another object of the present invention is to provide a semiconductor device using the cap thus obtained.

  These and other objects of the present invention will be understood from the following detailed description.

  As a result of diligent research, the present inventor has used a specific material suitable for the configuration of the cap and uses an annealing process after a series of plating processes, so that a light transmission window can be formed on the cap after plating without any problems. The present invention was completed by discovering that it can be joined.

One aspect of the present invention is a method of manufacturing a cap structure including an eyelet part for light transmission and a light-transmitting member attached to the eyelet part.
Preparing a cap body with an eyelet,
Forming a base plating on the cap body;
Applying Sn-Ni plating on the base plating;
Applying Zn-Ni plating on the Sn-Ni plating;
Annealing the cap body after forming the Zn-Ni plating film at a high temperature;
There is a method for manufacturing a cap structure, comprising: welding a translucent member to an eyelet portion after annealing.

  According to another aspect of the present invention, there is provided a semiconductor device including at least one light emitting element and / or light receiving element, wherein the element mounting surface of the semiconductor device is manufactured by the manufacturing method of the present invention. The semiconductor device is hermetically sealed with a cap body.

  According to the present invention, as will be understood from the following detailed description, when the cap structure is hermetically sealed to the semiconductor device, the generation of stray light in the internal cavity of the semiconductor device covered with the cap structure is effective. Therefore, problems such as noise and malfunction due to stray light can be solved. In addition, the cap structure can be manufactured thermally and stably, the appearance of the obtained cap is good, the product does not vary, and the yield is good. Moreover, since there is no restriction | limiting in the low melting glass used as a joining material, a cap structure can be manufactured easily at low cost. Furthermore, since the translucent member is welded after the series of plating steps is completed, it is possible to prevent deterioration of the plating solution and shortening of the life of the solution, as well as preventing discoloration and contamination of the cap structure. it can.

  Furthermore, since the cap structure of the present invention has various characteristics as described above in addition to high airtightness and thermal conductivity, various semiconductor devices including a light emitting element and a light receiving element alone or in combination, for example, The cap structure of the present invention can be advantageously used for a semiconductor laser, a vehicle-mounted sensor, and the like.

  While the present invention can be advantageously implemented in various forms, preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, this invention is not limited to the following embodiment.

  The present invention resides first in a method of manufacturing a cap structure. Here, the cap structure covers the element mounting surface in a semiconductor device including a light emitting element and a light receiving element and hermetically seals the cap structure. And a translucent member mounted. This manufacturing method is carried out in the following series of steps.

(1) To prepare a cap body provided with an eyelet part.
(2) Form a base plating on the cap body.
(3) Applying Sn-Ni plating on the base plating.
(4) Applying Zn-Ni plating on Sn-Ni plating.
(5) The cap body after forming the Zn—Ni plating film is annealed at a high temperature.
(6) A light-transmitting member is welded to the annealed eyelet part.

2 (A) to 2 (C) sequentially show a method for manufacturing a cap structure according to the present invention. First, as shown to FIG. 2 (A), the cap main body 11 provided with the eyelet part 12 is prepared. The cap body 11 has an internal cavity 13 formed inside thereof. The shape of the cap body 11 is not limited, and the cap body 11 can be arbitrarily changed according to the shape and mounting position of the semiconductor device to which the cap body 11 is attached. Usually, the surface of the cap body 11 is horizontal as shown in FIG. Although not shown, it is an inclined, rectangular or cylindrical article. The size of the cap body 11 is, for example, about 2.9 to 4.0 mm (length) × about 7.2 to 7.3 mm (width) × about 2.8 to 2.9 mm (high) when the cap body 11 is rectangular. That is). The cap body 11 is typically an eyelet in which a metal or an alloy thereof having excellent thermal conductivity is formed into a cap shape by press molding or other molding methods, and a laser beam or other light passes above the cap body 12. A portion (light transmission hole) 12 is formed. The material suitable for forming the cap body 11 is not limited to the following materials, but iron (Fe), iron-nickel (Ni) alloy, iron-nickel-cobalt (FeNiCo) alloy, and the like can be used. FeNiCo-based alloy (coefficient of thermal expansion: about 70 × 10) that is commercially available as “Kovar®”, generally having the same thermal expansion coefficient as that of the translucent member (glass), and suitable for joining and use. ^-7 / ° C) is particularly useful.

  Next, the base plating 14 is formed on the prepared cap body 11. The base plating 14 is not particularly limited as long as the corrosion resistance of the cap body 11 can be improved and Sn-Ni plating can be suitably formed thereabove. Examples of the base plating include nickel plating, and nickel plating is particularly useful. The base plating can be formed by a conventional technique such as electroless plating or electrolytic plating, and the thickness is usually about 2 to 5 μm. The composition and plating conditions of the nickel plating bath for forming the base can be arbitrarily changed according to the purpose.

  After the base plating is formed, an Sn—Ni plating 16 and a Zn—Ni plating 18 are sequentially formed on the base plating 14 as shown in FIG. These two plating films are black films for preventing stray light formed on the surface of the cap body 11. When forming a black film on the cap body 11, first, the Sn—Ni plating 16 is formed on the surface of the base plating 14 of the cap body 11. The Sn—Ni plating 16 can be formed by a conventional method by electroless plating or electrolytic plating, and its thickness is usually about 2 to 5 μm, and typically about 3 to 4 μm. The composition and plating conditions of the Sn—Ni plating bath can be arbitrarily changed according to the purpose.

  After the Sn—Ni plating 16 is formed, a Zn—Ni plating 18 is formed on the plating film. The Zn—Ni plating 18 can be formed by electroless plating or electrolytic plating by a conventional method, and about half the thickness of the Sn—Ni plating 16 is sufficient. A thickness of the order is advantageous. The thickness of the Zn—Ni plating 18 is usually about 1 to 2.5 μm, and typically about 1.5 to 2 μm. The composition and plating conditions of the Zn—Ni plating bath can be arbitrarily changed according to the purpose.

  In the cap structure according to the present invention, the black coating on the inner wall is formed in such a two-layer structure, thereby utilizing the light absorbing action by the Sn—Ni plating 16 and the light absorbing action by the Zn—Ni plating 18. As a result, the irregular reflection of the laser beam can be prevented better than the conventional cap for a semiconductor device, and the stray light can be more effectively suppressed. More specifically, in the case of a black film having such a two-layer structure, reflection of laser light in the vicinity of 780 nm can be suitably suppressed by forming the first black film by the Sn—Ni plating 16. By providing the second black film by the Zn—Ni plating 18, irregular reflection of laser light in a low wavelength band of 650 nm or less can be suitably suppressed. In addition, since the Zn—Ni plating 18 can be formed on a rough surface with many irregularities due to relatively large crystal grains, the blackness of the black film can be increased and incident on the cap body 11. Laser light can be effectively absorbed, in other words, stray light can be effectively suppressed by this.

  In the practice of the present invention, when the Sn—Ni plating 16 and the Zn—Ni plating 18 are sequentially formed, the cap body 11 that is the workpiece is plated for the Zn—Ni plating 18 from the plating bath on which the Sn—Ni plating 16 is applied. Move to bath and plate inside. In this Zn—Ni plating, it is important to deposit a plating film stably and evenly on the surface of the cap body 11 to eliminate variations in appearance and to improve the adhesion of the plating film. For example, in the case of performing Zn—Ni plating by an electrolytic method, if the plating is performed while simply applying a DC voltage between the plating electrodes, the voltage between the electrodes gradually increases, and a product having a good appearance cannot be obtained. For this reason, suitable electrolytic Zn-Ni plating is performed by controlling the voltage between the plating electrodes to be maintained at a constant voltage, or by applying a voltage pulsed so that the voltage between the plating electrodes is constant. It is preferable to consider so that the By forming the Zn—Ni plating 18 on the surface of the cap body 11 in this way, the surface of the cap body 11 can be covered with a black film having a high concentration. Even if there is unevenness, these unevennesses can be prevented from appearing in the appearance of the product, and the appearance and appearance of the final product can be improved.

  After completion of the Zn—Ni plating, the cap body is annealed at a high temperature. The annealing step is essential in the method of the present invention, and with this step, the above-mentioned effects specific to the present invention can be achieved. The annealing process can be performed using a conventional technique using a general heating furnace. For example, the heating furnace can be a continuous furnace or a vacuum furnace. Moreover, it is preferable that the pressure at the time of annealing is under vacuum or atmospheric pressure. Furthermore, the atmosphere during annealing is preferably a reducing atmosphere (for example, hydrogen, argon, nitrogen, etc.) or under vacuum. Although the temperature and time of the annealing step can be widely changed depending on the desired effect, etc., a temperature of about 600 to 800 ° C. and a time of about 30 to 60 minutes are usually preferable, and more preferably about 650 to 700 ° C. And a time of about 30 minutes.

  After the completion of the annealing step, the translucent member 13 is welded to the eyelet portion 12 of the cap body 11 as shown in FIG. The translucent member 13 may be rectangular or circular, and can be adjusted to the opening of the fuzzet portion 12. Although the size of the translucent member 13 can be widely changed, when the size is rectangular, the size is usually about 2.9 to 4.6 mm (vertical) × about 7.2 to 7.3 mm (horizontal). ) × about 2.8 to 2.9 mm (height). The translucent member 13 is preferably glass, and more preferably glass having substantially the same thermal expansion coefficient as that of the cap body 11. Suitable glass includes, for example, hard glass such as borosilicate glass.

  When the translucent member 13 is welded to the eyelet part 12, various bonding agents 19 can be used, but low melting point glass is preferable, and lead-free low melting point glass is more preferable. This is because, in the case of lead, there is a problem that lead contained in the low melting point glass deteriorates the environment. In the practice of the present invention, bismuth (Bi) -based low melting glass can be used particularly advantageously.

  The welding of the translucent member 13 using the low melting point glass 19 can be performed using a conventional technique. For example, the welding process can be performed by plating the eyelet part and annealing and then welding a low melting point glass. By doing so, plating after welding can be eliminated. Through such a welding step, the cap structure 10 of the present invention as shown in FIG. 2C can be manufactured. As can be understood from the above description, the cap structure 10 can effectively suppress the reflection of laser light on the inner surface of the cap main body 10 and the semiconductor device (not shown), It becomes possible to suppress the occurrence of malfunction.

  In another aspect, the present invention is a semiconductor device including at least one light emitting element and / or a light receiving element, and the element mounting surface of the semiconductor device is any one of claims 1 to 6. The semiconductor device is hermetically sealed with a cap structure manufactured by the manufacturing method described in 1. above. Examples of the semiconductor device include a semiconductor laser. Such a semiconductor device can be advantageously used in fields such as an optical pickup, optical communication, in-vehicle sensor, transistor, and IC.

  FIG. 3 is a cross-sectional view showing one embodiment of a semiconductor device using the cap structure of the present invention. As shown, the semiconductor device 30 includes a stem 31 on which a laser element 35 is mounted via a copper block (heat sink) 36. Although the stem 31 is not shown for simplification of explanation, it is preferable to have the above-described two-layer black film as in the case of the cap body 11, thereby preventing stray light and providing good light absorption. Can be obtained. As described above, the cap structure 10 is formed by welding the translucent member (glass) 17 to the eyelet portion 12 with the low melting point glass 19 on the cap body 11, and is joined to the stem 31 by laser welding or resistance welding. ing. The stem 31 can be made of iron, an iron-nickel alloy, an iron-nickel-cobalt alloy, or the like, but can preferably be made of the same material as the cap body 11. The stem 31 has a lead pin 31 attached through a through hole (not shown) that penetrates the stem 31 in the thickness direction. The laser element 35 is mounted on the side surface of the heat sink 36, and although not shown, the laser element 35 and the lead pin 32 are electrically connected.

  In the illustrated semiconductor device 30, the entire inner surface of the internal cavity 13 of the semiconductor device 30 that houses the laser element 35 by the cap structure 10 and the stem 31 overlaps the first black film 16 and the second black film 18. Therefore, it is possible to prevent the reflection of the laser beam on the entire inner surface of the semiconductor device 30 and to effectively suppress the stray light. Further, according to the present invention, since the black film is uniformly formed on the surface of the cap body 11 and the surface of the stem 31, when the cap structure 10 and the stem 31 are joined by laser welding, resistance welding, or the like, These can be reliably bonded, the adhesion between the cap structure 10 and the stem 31 can be improved, and the hermetic sealing degree of the semiconductor device 30 can be improved.

  Subsequently, the present invention will be described with reference to examples thereof. Needless to say, the present invention is not limited to these examples.

Example 1
In this example, a cap structure was produced as described with reference to FIG.

  An iron-nickel-cobalt alloy (trade name “KOVAL (registered trademark)”) was press-molded to produce a rectangular cap. A square eyelet (opening) for allowing laser light to pass through was formed on the top of the cap. First, base plating was performed on the entire surface of the cap. The base plating was nickel plating, and was formed to a thickness of about 3 μm by electroless plating.

  Next, Sn—Ni plating was formed on the base plating by electrolytic plating. The thickness of the Sn—Ni plating was about 0.3 μm. Subsequently, Zn-Ni plating was further formed by electrolytic plating on the formed Sn-Ni plating. The thickness of the Zn—Ni plating was about 0.15 μm. The photograph on the left side of FIG. 4 shows the state of the cap after Zn-Ni plating. The cap was then placed in an annealing furnace and heated in a reducing atmosphere (hydrogen) at a temperature of about 650 ° C. for about 40 minutes. The lower center photograph in FIG. 4 shows the state of the upper surface of the cap after annealing. As understood from this photograph, the appearance of the Zn—Ni plating film is as good as before annealing, and no defects are generated.

  After completion of the annealing step, a light transmission window made of hard glass was welded to the eyelet portion of the cap using bismuth-based low-melting glass to obtain a target cap structure. The photograph on the lower right side of FIG. 4 shows the state of the lower surface of the cap after welding the light transmission window. As can be understood from this photograph, the appearance changed to matte dark brown by heating during welding, but this discoloration is not a problem. This cap structure is welded neatly without bubbles being taken into the welding surface.

[Measurement of reflectance]
When the reflectance (%) on the inner surface of the cap after Zn-Ni plating and annealing was measured, the results plotted in FIG. 5 were obtained. As understood from this measurement result, in the case of this example, in addition to suitable suppression of reflection of laser light near 780 nm derived from the presence of Sn—Ni plating, the effect derived from Zn—Ni plating, that is, Further, prevention of irregular reflection of laser light in a low wavelength band of 650 nm or less can be effectively achieved. It can also be seen that this light reflection characteristic is comparable to the light reflection characteristic of the cap after Zn-Ni plating shown in FIG. 5 (the annealing step is omitted). Furthermore, it can also be seen that the conventional cap with only the electrolytic Ni plating shown in FIG. 5 provides only a very poor light reflection characteristic as compared with the above two examples.

  Furthermore, from the measurement results of the reflectance as described above, in the cap of this example, the annealing was performed after the Sn-Ni plating and the Zn-Ni plating were sequentially stacked on the surface of the cap body, and further annealed. It can be seen that stray light can be suppressed more effectively than when the processing is omitted.

[Consideration of reaction state]
In this example, no defect occurred even though the annealing process was performed subsequent to the plating, but rather a good welding of the light transmission window to the eyelet part of the cap could be achieved. This bonding effect is considered to be derived from the reactivity of the low melting point glass used as the bonding material, and after the light transmission window was welded, the release surface after peeling the light transmission window from the cap structure was photographed as a composite map. . FIG. 6A is a photograph of the peeled surface of the light transmission window (glass portion), and FIG. 6B is a photograph of the peeled surface of the cap body (eyelet portion). From these photographs, it can be seen that ZnBi is mainly composed of the peeled surface of the glass part, and ZnBi and Sn are mainly composed of the peeled surface of the eyelet part.

  Further, when the cross section of the cap structure after plating and annealing was photographed as a composite map, the photograph shown in FIG. 7 was obtained. As can be seen from this photograph, a thin Sn layer is formed, Zn, Sn and Bi react well, and good welding of the light transmission window to the eyelet portion is completed.

Comparative Example 1
Although the method described in Example 1 was repeated, in this example, the cap structure was manufactured by omitting the annealing step for comparison. With respect to the obtained cap structure, the cap was observed according to the method described in Example 1, and the light reflection characteristics of the inner surface of the cap were measured. The results shown in FIGS. 4 and 5 were obtained.

  The upper photograph in the center of FIG. 4 shows the state of the upper surface of the cap after welding the light transmission window. As can be seen from this photograph, it can be seen that the appearance of the Zn-Ni plating film is mottled by heating during welding and is unsuitable as a commercial product. The photograph on the upper right side of FIG. 4 shows the state of the lower surface of the cap after the light transmission window is welded. As understood from this photograph, a large number of bubbles are generated by the gas from the plating on the welding surface of the light transmission window. The light reflection characteristics of the inner surface of the cap were acceptable as shown in FIG.

It is sectional drawing which showed the well-known method for manufacturing the cap for semiconductor devices later on. It is sectional drawing which showed the manufacturing method of the cap structure by this invention later on. It is sectional drawing which showed one embodiment of the semiconductor device using the cap structure of this invention. It is the photograph which showed the cap structure after plating and after translucent member welding, the state of the cap structure after ZnNi plating on the left side, the state of the cap structure without annealing treatment above the center and the right side, and the center and the right side The state of the cap structure after annealing is shown below. It is the graph which plotted the measurement result of the reflectance in the cap main body after carrying out plating and / or annealing treatment on different conditions. FIG. 6A is a photograph showing a peeled surface after peeling the light transmitting window from the cap structure as a composite map after welding the light transmitting window. FIG. 6A shows the light transmitting window (glass) and FIG. Shows the cap body (eyelet part), and FIG. 6C shows the elemental structure. It is the photograph which showed the cross section of the cap structure after plating and annealing as a composite map, FIG. 7 (A) shows a cross-sectional structure and FIG. 7 (B) shows the structure of an element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cap structure 11 Cap main body 12 Eyelet part 13 Internal cavity 14 Base plating 16 Sn-Ni plating 17 Translucent member 18 Zn-Ni plating 19 Low melting glass 30 Optical apparatus

Claims (10)

A method of manufacturing a cap structure including an eyelet part for light transmission and a light transmitting member attached thereto,
Preparing a cap body with an eyelet,
Forming a base plating on the cap body;
Applying Sn-Ni plating on the base plating;
Applying Zn-Ni plating on the Sn-Ni plating;
Annealing the cap body after forming the Zn-Ni plating film at a high temperature;
A method of manufacturing a cap structure, comprising: welding a translucent member to the eyelet portion after annealing.   The manufacturing method according to claim 1, wherein the cap body is made of a metal or an alloy thereof.   The manufacturing method according to claim 1, wherein the cap body is made of a FeNiCo-based alloy.   The manufacturing method according to claim 1, wherein the translucent member is made of a glass material.   The manufacturing method according to claim 1, wherein the annealing step is performed in a vacuum or a reducing atmosphere at a temperature of 500 to 800 ° C. for 30 to 60 minutes.   The manufacturing method according to any one of claims 1 to 5, wherein the eyelet part and the translucent member are welded through low-melting glass.   The manufacturing method according to claim 1, wherein the low-melting glass is a bismuth-based low-melting glass.   The manufacturing method according to any one of claims 1 to 7, wherein a semiconductor device including a light emitting element and / or a light receiving element is hermetically sealed with the obtained cap body.   A semiconductor device including at least one light emitting element and / or light receiving element, wherein the element mounting surface of the semiconductor device is manufactured by the manufacturing method according to claim 1. A semiconductor device which is hermetically sealed with a structure.   The semiconductor device according to claim 9, wherein the semiconductor device is a semiconductor laser.