JP3619128B2 - Manufacturing method of optical semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an optical semiconductor device, and more specifically, the distance between the microlens and the optical element can be made constant by controlling the thickness of a transparent sealing resin layer on which a microlens is disposed. The present invention relates to a method for manufacturing an optical semiconductor device.
[0002]
[Prior art]
As shown in FIG. 5, as an optical signal input / output device for maintaining a form called a chip size package (CSP) and enabling input / output of a large number of optical signals, an LSI chip (semiconductor integrated package) is used. A structure in which a surface optical element 52 such as a surface light emitting element or a surface light receiving element is connected to a circuit 51 via a solder bump 53 is proposed (Japanese Patent Application No. 11-138605). In this apparatus, the electrodes 58 formed on the LSI chip 51 are connected to solder bumps 57 via metal posts 56 and are fixed on a printed circuit board (not shown) by the solder bumps 57. Further, the electrode 58 and the metal post 56 are provided in the mold resin 55, and form a chip size package having a package function such as relaxation of stress applied to the LSI chip 51 and pitch conversion. ing.
[0003]
The surface optical element 52 is flip-chip mounted on the LSI chip 51 with the light input / output direction directed toward the printed circuit board (downward in FIG. 5), but in order to improve the reliability of the element. Resin sealing with a transparent sealing resin 54 is performed. In this manner, a semiconductor device having not only an input / output of an electrical signal but also a mechanism for inputting / outputting an optical signal is configured.
[0004]
In addition, Japanese Patent Application No. 11-138605 discloses the structure shown in FIG. 6 as an optical semiconductor device having an optical signal input / output mechanism. In this structure, the surface optical element 62 flip-chip mounted on the LSI chip 61 is molded by a transparent resin 63 and packaged. Electrical connection with the printed circuit board 68 is made through the interposer 64 and flat leads 65 extending to the outside of the package. The light beam transmitted through the transparent resin 63 used in the mold is collimated by the microlens 66 formed on one surface of the transparent resin 63 and is optically coupled with high efficiency. An optical connection between 62 and the optical waveguide 67 is realized.
[0005]
The optical semiconductor device having such a configuration is characterized in that a decrease in optical coupling efficiency due to misalignment hardly occurs when a package is mounted on a printed board. Similarly, in the surface light-receiving element or the array thereof, by forming the microlens array 66, collimated light propagating from the printed circuit board 68 side can be focused and guided to the surface light-receiving element with high efficiency. It is.
[0006]
[Problems to be solved by the invention]
The microlens array is formed directly on the light input / output portion of the surface optical element or on the surface of a transparent sealing resin layer provided for the purpose of sealing the surface optical element. In the formation of the microlens array, it is particularly important to maintain high controllability and flexibility of the formation position. For example, in order to convert output light from a surface light-emitting element into collimated light having a diameter of several hundreds of micrometers, a microlens having an appropriate focal length and aperture diameter must be provided. The output light from the surface light-emitting element varies greatly depending on its structure. For example, some light-emitting diodes (LEDs) have a full width at half maximum exceeding 100 °, while some surface-emitting lasers have an angle of 10 ° or less. .
[0007]
In order to perform desired beam conversion by adding microlenses to these various optical elements and to realize downsizing of the package, not only microlens groups having various focal lengths are prepared, It is necessary to accurately control the position of the microlens with respect to the optical element, particularly the distance between the optical element and the microlens.
[0008]
In many cases, the microlens or the array thereof is formed at a position corresponding to the light input / output portion of the optical element on the surface of the transparent sealing resin layer. Therefore, in order to improve the optical coupling efficiency by the microlens array and sufficiently expand the tolerance for the positional deviation, it is necessary to arrange the microlens array at a predetermined position with high accuracy. It is indispensable to control the thickness of the transparent sealing resin layer interposed between the lens array and the optical element with high accuracy and to sufficiently flatten the surface.
[0009]
It is an object of the present invention to sufficiently control the thickness of the transparent sealing resin layer and flatten the surface, and to seal the optical element with a sealing resin with high accuracy. An object of the present invention is to provide a method of manufacturing an optical semiconductor device capable of forming a microlens in a portion with a high degree of freedom.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the optical semiconductor device manufacturing method of the present invention uses a dispenser method or an ink jet method to add a liquid transparent resin and solidify it, thereby sealing the optical semiconductor element and the microlens. It is characterized by performing formation and dam formation .
[0013]
The resin that can be used as the photo-curable resin is a resin that is cured by irradiation with ultraviolet rays, visible light, infrared rays, or the like, and is transparent or has little absorption with respect to light in a wavelength region to be used. A resin prepared by adding a photopolymerization initiator to an acrylic resin, a silicon resin, or a polyimide resin and being cured by desired light in the range of ultraviolet to infrared can be used. In particular, an ultraviolet curable epoxy resin in which a photopolymerization initiator is added to adjust a refractive index and a curing shrinkage rate is most preferable in practical use.
[0014]
In the present invention, after forming a recess having a predetermined depth in the substrate, an optical semiconductor element to be sealed is formed in the recess, and a liquid transparent resin is formed in the recess using a dispenser system or an ink jet system. Are continuously or intermittently discharged to immerse the optical semiconductor element in the transparent resin, solidify the transparent resin to form a transparent encapsulating resin layer, and then the optical element included in the optical semiconductor element. A liquid transparent resin was dropped on the surface of the transparent encapsulating resin layer above by a dispenser method or an ink jet method, and the dropped liquid transparent resin was formed by the surface tension of the liquid transparent resin. The microlens is formed by solidifying while holding the spherical surface . Since the thickness of the transparent sealing resin layer is determined by the depth of the concave portion or the amount of the transparent resin placed in the concave portion, the distance between the microlens and the optical element is increased by controlling these. It can be easily controlled with accuracy.
[0015]
In this case, for example, as shown in FIG. 4, a recess having a desired depth formed on the surface of the substrate 13, an optical semiconductor element formed in the recess, and the above-described recess formed in the recess. An optical semiconductor device having a transparent sealing resin layer 33 covering the optical semiconductor element, and a microlens 20 formed on the surface of the transparent sealing resin layer 33 above the optical elements 12a and 12b of the optical optical semiconductor element. Is formed.
[0016]
In addition, instead of forming the recess and forming an optical semiconductor element therein, a dam having a predetermined height is formed on the substrate, and an optical semiconductor element to be sealed formed on the substrate is formed. Surrounded by the dam . Next, a liquid transparent resin is discharged into the dam continuously or intermittently using a dispenser method or an ink jet method, and the optical semiconductor element is immersed in the transparent resin . Next, after solidifying the transparent resin to form a transparent sealing resin layer, a liquid transparent resin is dispensed on the surface of the transparent sealing resin layer above the optical element included in the optical semiconductor element. The liquid transparent resin dropped by the ink jet method is solidified in a state where the spherical surface formed by the surface tension of the liquid transparent resin is held to form a microlens . Also in this case, the transparent resin layer and the microlens can be formed by a dispenser method or an ink jet method, and thus are practically preferable. The thickness of the transparent sealing resin layer, and therefore the distance between the microlens and the optical element, depends on the depth of the dam or the amount of liquid transparent resin placed in the dam, and by controlling these, The distance can be controlled easily and with high accuracy.
Furthermore, the said dam can also be formed using a photocurable resin. In this case, an optical semiconductor element to be sealed and a dam shape surrounding the optical semiconductor element and having a predetermined height by discharging liquid transparent resin continuously or intermittently using a dispenser system or an inkjet system After that, the transparent resin is solidified to form a dam having a predetermined height on the substrate. In this case, the dam, the transparent sealing resin layer, and the microlens can be formed using a common method, which is practically preferable.
[0017]
In this case, for example, as shown in FIG. 3, an optical semiconductor element formed on the surface of the substrate 13 and a desired height formed so as to surround the optical semiconductor element on the surface of the substrate. On the surface of the dam 32, the transparent sealing resin layer 33 covering the optical semiconductor element formed in the dam 32, and the transparent sealing resin layer 33 above the optical elements 12a and 12b of the optical semiconductor element Thus, an optical semiconductor device having the microlens 20 formed in the above is formed.
[0018]
In the case where the recess is formed and used, and in the case where the dam is formed and used, a photocurable resin or a thermosetting resin can be used as the transparent resin. As the thermosetting resin, an epoxy resin, an acrylic resin, a silicon resin, or a polyimide resin can be used. As the photocurable resin, an optical semiconductor element is placed in a liquid resin and irradiated with light. The same method as in the above method can be used.
[0019]
In addition, in the light irradiation with respect to the said photocurable resin, light intensity can be suitably selected in the range for 10 second-5 minutes by the thickness of a resin layer for several mW / cm < ² >-several hundred W / cm < ² >. When exposed for a long time (1 minute or more) with a relatively low light intensity (several tens of mW / cm ² ), the resin layer surface has less irregularities and good flatness. Further, the uncured portion may be removed by dissolving with an organic solvent such as ethyl alcohol or blowing off by blowing air.
[0020]
Examples of the microlenses, or to form a lens-shaped object having a condensing action, or it is possible to use by mounting the pre-molded object transparent sealing resin layer, in the present invention, the A lens-like object having a condensing function is formed from a transparent resin dropped on the transparent resin layer and used as a lens.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Reference Example A reference example of the present invention will be described with reference to FIGS. 1 and 2. As shown in FIG. 2, the optical semiconductor device formed by the present reference example, LSI chip 11, a plurality of surface faces the light emitting element is constituted by an array arranged light emitting elements 12a and a plurality of surfaces having a semiconductor integrated circuit An optical semiconductor device having an optical signal input / output function is configured by housing the surface light receiving elements 12b configured by arraying the light receiving elements in a package (not shown).
[0022]
The LSI chip 11, the surface light emitting element 12 a, and the surface light receiving element 12 b are mounted on the electric wiring substrate 13 and are electrically connected to each other by the connection conductor 14. Further, connection leads 15 are formed on the peripheral edge of the LSI chip 11 and connected to the wiring film 16. Solder bumps 18 are formed in an area array on the wiring film 16 and used for connection to a printed circuit board (not shown). Further, an elastomer 17 is inserted between the LSI chip 11 and the wiring film 16 to absorb stress applied to the LSI chip 11 and protect the LSI chip 11. The surface optical elements 12 a and 12 b are sealed with a transparent sealing resin 19, and a microlens 20 is formed on the surface of the transparent resin 19.
[0023]
The output light 12c from the surface light emitting element 12a is transmitted through the transparent sealing resin 19 and then collimated by the microlens 20 with high efficiency with an optical waveguide (not shown) provided on the printed circuit board side in advance. Photocoupled. A photocurable resin was used as the transparent sealing resin 19, and the surface optical device 12 was mounted on the electric wiring substrate 13 and electrically connected to the connection conductor 14, and then manufactured using an optical modeling method.
[0024]
This manufacturing method will be described in detail with reference to FIG. In FIG. 1, for the sake of simplicity, the LSI chip 11 is not shown, and only the planar optical element 12 is mounted on the electric wiring board. First, as shown in FIG. 1A, an ultraviolet curable epoxy resin is placed in a container 22 as an uncured liquid photocurable resin 21, and an electric wiring board 13 on which a surface optical element 12 is mounted. Was put in the photocurable resin liquid 21. At this time, the stage 23 is adjusted so that the light emitting surface or the light receiving surface of the surface optical element 12 is positioned at a predetermined depth from the liquid surface of the photocurable resin liquid 21. The depth corresponds to the thickness of the transparent sealing resin layer 19 on the surface optical element, and the thickness determines the distance between the surface optical element and the microlens.
[0025]
In this state, after using the exposure mask 24 having an opening larger than that of the surface optical element 12 and exposing the ultraviolet ray from the upper surface by the light irradiation device 25, the irradiated portion of the photocurable resin 21 is cured and solidified. Then, the uncured portion was removed, and as shown in FIG. 1B, a structure in which the planar optical element 12 was resin-sealed with the cured photocurable resin 21b was formed.
[0026]
Next, the microlens 20 was formed on the surface of the transparent sealing resin 19 made of the cured photocurable resin 21b, and the optical semiconductor device having the BGA package structure shown in FIG. 2 was manufactured. As a method for forming the microlens 20, after resin sealing with the transparent sealing resin 19, an ultraviolet curable resin liquid is dropped onto the surface of the transparent sealing resin 19 by a dispenser or an ink jet method, and the liquid The method of curing the resin to form a lens while maintaining the spherical surface formed by the surface tension is particularly effective from the viewpoint of ease of formation and freedom of formation.
[0027]
Alternatively, after the desired portion of the photocurable resin 21 is cured to form the photocurable resin 21b, the electric wiring on which the surface optical element 12 covered with the photocurable resin 21b is driven by driving the stage 23 is mounted. In this state, the substrate 13 may be lowered, and the light beam from the light irradiation device 25 may be finely condensed to cure only a very small region of the uncured photocurable resin 21. In this way, the microlens 20 and the cured photocurable resin 21b (corresponding to the transparent sealing resin 19 in FIG. 2) can be integrally formed.
[0028]
Further, the microlens array can be formed by fixing a microlens array formed on a glass substrate, such as a flat microlens array, on the transparent sealing resin 19.
[0029]
In this reference example , the light-emitting element 12 is uncured so that the distance between the upper surface of the light-emitting element 12 and the liquid surface of the uncured photocurable resin 21 is equal to the thickness of the transparent sealing resin layer. The liquid photo-curing resin 21 was allowed to settle so that the exposure process was performed only once. However, if the stage 23 is driven intermittently or continuously to perform multiple exposures and the curing depth per operation is reduced, the effects of shrinkage and curing depth during curing are reduced, and after curing. The surface flatness could be further improved.
[0030]
Example 1
FIG. 3 shows an example of the structure of a resin-encapsulated optical semiconductor device having an optical signal input / output mechanism formed according to the present invention. In the present embodiment, an LSI chip 11 having a semiconductor integrated circuit, a surface light emitting element 12a configured by arranging a plurality of surface light emitting elements in an array, and a surface light receiving element configured by arranging an array of a plurality of surface light receiving elements. An optical semiconductor device having an optical signal input / output function is configured by housing 12b in a package (not shown).
[0031]
The LSI chip 11, the surface light emitting element 12 a, and the surface light receiving element 12 b are mounted on the electric wiring substrate 13 and are electrically connected to each other by the connection conductor 14. Further, a lead frame 31 is formed on the peripheral edge of the electric wiring board 13 and used for connection to a printed board (not shown).
[0032]
On the electrical wiring board 13, a dam 32 made of resin is formed so as to include the LSI chip 11 and the surface optical elements 12a and 12b on the inner side. A region surrounded by the resin dam 32 is filled with a transparent resin 33, and the LSI chip 11 and the surface optical elements 12a and 12b are sealed to protect them from stress such as heat and impact. The reliability of the chip is improved by enhancing the environmental resistance.
[0033]
Further, the microlens array 20 is formed on the surface of the transparent resin 33. The distance between the surface optical elements 12a and 12b and the microlens 20 is defined by the thickness of the transparent resin layer 33 used for sealing. This thickness depends on the height of the dam 32 and the sealing resin. It can be easily adjusted by the supply amount of 33.
[0034]
As a method of forming the dam 32, for example, the surface type optical elements 12a and 12b and the LSI chip 11 are discharged while discharging an appropriate amount of photocurable resin liquid continuously or intermittently using a dispenser or an ink jet system. A method was used in which the stage was driven so as to enclose it into a dam shape and then cured by light irradiation. This forming method is very effective because it can be similarly applied to the subsequent sealing step using a transparent resin and the formation of a microlens.
[0035]
Further, spacers made of resin, metal, or ceramic prepared in advance may be arranged side by side on the wiring board 13, and these spacers may be used as dams.
Since these dams 32 are used to define the thickness of the transparent sealing resin layer 33, they need not be transparent with respect to the wavelength used. The surface flattening of the transparent sealing resin layer 33 can be easily realized by, for example, using a resin having a low viscosity or a low surface tension. Furthermore, not only such a method using the free liquid surface of the resin, but also a transparent substrate having a flat surface is brought into contact, and light irradiation is performed therethrough to cure the resin, and then the transparent substrate is removed. Even if this method is used, the surface flattening can be easily realized and is practical. The microlens 20 is the same as the method shown in the above reference example , that is, an ultraviolet curable resin liquid is dropped onto the surface of the transparent sealing resin layer 33 by a dispenser or an inkjet method, and the surface tension of the liquid is It was formed using a method of curing the resin to form the microlens 20 while maintaining the formed spherical surface .
[0036]
In this embodiment, the dam 32 is formed so as to include the planar optical elements 12a and 12b and the LSI chip 11 inside, but only the planar optical elements 12a and 12b are included inside, and the LSI chip 11 is outside. The dam 32 may be formed so that In this case, not only the flat package structure using the lead frame 31 shown in FIG. 3, but also a ball grid array type package using solder bumps arranged in an area array or a chip size package (Chip Size Package; CSP).
[0037]
Example 2
FIG. 4 is a diagram showing the structure of a semiconductor device formed in the second embodiment of the present invention. As shown in FIG. 4, the semiconductor device formed in this embodiment includes an LSI chip 11 on which a semiconductor integrated circuit is manufactured, a surface light emitting element 12a configured by arraying surface light emitting elements, and a surface light receiving element. The surface light receiving elements 12b configured in an array are mounted on a BGA package substrate 41 provided with recesses in advance, and an area array package structure in which these are sealed with a transparent resin 32 is provided.
[0038]
The thickness of the sealing resin 42 is defined by the depth of the concave portion provided in the BGA package substrate 41 and the liquid amount of the transparent resin 42 placed in the concave portion. The distance between the elements 12a and 12b and the microlens 20 can be controlled to a desired value. Further, the surface of the sealing resin 42 could be flattened by a method such as using a low-viscosity resin as in Example 1. The microlens 20 was also formed using the same method as in Example 1 above. Further, not only the BGA package substrate but also a package substrate in which a concave portion can be formed on the surface can be used in the same manner. Furthermore, a pin grid array type package and a concave butterfly type package can be used in the same manner.
[0039]
【The invention's effect】
As is apparent from the above description, according to the present invention, when a resin-encapsulated optical semiconductor device having an optical signal input / output mechanism is manufactured, the distance between the optical element and the microlens and the position of the microlens are high. It can be controlled with accuracy. Furthermore, not only for chip protection but also for resin sealing by controlling the thickness and surface flatness of the transparent sealing layer, the microlens required for beam conversion of input / output light has a high degree of freedom. Thus, a semiconductor device having various forms of optical signal input / output mechanisms can be formed at low cost.
[Brief description of the drawings]
FIG. 1 is a view for explaining a resin sealing method in a reference example of the present invention.
FIG. 2 is a cross-sectional view of a semiconductor device formed in a reference example of the present invention.
FIG. 3 is a view showing a cross-sectional structure of a semiconductor device formed in a first embodiment of the present invention.
FIG. 4 is a diagram showing a cross-sectional structure of a semiconductor device formed in a second embodiment of the present invention.
FIG. 5 is a diagram schematically showing a first example of the structure of a conventional optical semiconductor device.
FIG. 6 is a diagram schematically showing a second example of the structure of a conventional optical semiconductor device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... LSI chip, 12 ... Surface type optical element, 12a ... Surface light emitting element array, 12b ... Surface light receiving element array, 12c ... Output light beam from surface light emitting element, 13 ... Wiring board, 14 ... Connection conductor, 15 ... Connection Lead, 16 ... Wiring film, 17 ... Elastomer, 18 ... Solder bump, 19 ... Transparent sealing resin, 20 ... Microlens, 21 ... Connection lead, 22 ... Solder bump, 31 ... BGA package substrate, 32 ... Transparent resin, 32b ... transparent resin surface, 33 ... solder bump, 41 ... transparent resin.

Claims (4)

A step of discharging a liquid transparent resin onto a substrate continuously or intermittently using a dispenser method or an ink jet method to form a dam, an optical semiconductor element to be sealed by solidifying the transparent resin, and the light Forming a dam having a predetermined height on the substrate, surrounding the semiconductor element, and discharging the liquid transparent resin into the dam continuously or intermittently using the dispenser method or the ink jet method. A step of immersing the optical semiconductor element in the transparent resin in the dam, a step of solidifying the transparent resin in the dam to form a transparent sealing resin layer, and a light of the optical semiconductor element On the surface of the transparent encapsulating resin layer above the element, a liquid transparent resin is dropped by a dispenser method or an ink jet method, and the dropped liquid transparent Fat, solidified while holding the spherical surface formed by the surface tension of the transparent resin of the liquid, a method of manufacturing an optical semiconductor device which comprises a step of forming a microlens. The method for manufacturing an optical semiconductor device according to claim 1 , wherein the transparent resin is a photocurable resin or a thermosetting resin. 3. The method of manufacturing an optical semiconductor device according to claim 2 , wherein the thermosetting transparent resin is an epoxy resin, an acrylic resin, a silicon resin, or a polyimide resin. 3. The method of manufacturing an optical semiconductor device according to claim 2 , wherein the photocurable transparent resin is an epoxy resin, an acrylic resin, a silicon resin, or a polyimide resin to which a photopolymerization initiator is added.

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