JPH0878560A - Semiconductor device - Google Patents

Abstract

PURPOSE: To avoid the scattering of low melting point glass in relation to a semiconductor device in the composition of fixing a cap to a package using a glass material. CONSTITUTION: Within a semiconductor device composed of a substrate 22 internally sealing a semiconductor chip 21 and a cap 23 while the substrate 22 and the cap 23 are junctioned with each other using a low melting point glass 32, a scattering preventive bump 33 as a scattering proventing mechanism of the low melting point glass 32 is provided on the junction part 28 of the substrate 22 and the cap 23 at the arrangement position of the semiconductor chip 21 nearer than that of the low melting point glass 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device having a structure in which a cap is fixed to a package by using a glass material.

Generally, erasable ROM (Read Only Mem)
An EPROM (Erasable Programmable ROM) is known as an ory.

In this EPROM, it is necessary to irradiate the semiconductor chip with ultraviolet rays in order to erase the written information. Therefore, the cap provided in the EPROM package is provided with a window for transmitting ultraviolet rays, and the ultraviolet ray irradiation position formed on the upper surface of the semiconductor chip is irradiated with ultraviolet rays through the window. Has been done.

Further, if dust adheres to the ultraviolet irradiation position of the semiconductor chip, there is a possibility that the erasing process of the EPROM cannot be reliably performed. Therefore, EP
In order to improve the erasing characteristics of the ROM, it is necessary to prevent dust from adhering to the ultraviolet irradiation position of the semiconductor chip.

[0005]

2. Description of the Related Art FIGS. 9 and 10 are schematic configuration diagrams of conventional semiconductor devices 1 and 2. The semiconductor device 1 has a leadless package structure, and the semiconductor device 2 has a DI structure.
It has a P (Dual In-line Package) type package structure. It should be noted that components common to the respective drawings will be described with the same reference numerals.

The semiconductor device 1 is an EPROM, and is roughly a semiconductor chip 3, a substrate 4, a cap 5,
It is composed of the side notch 6. The semiconductor chip 3 is an EPROM chip and a ceramic substrate 4
It is mounted in the cavity 7 formed in. On the upper surface of the semiconductor chip 3, an erasing section 3a is formed which is irradiated with ultraviolet rays.

The substrate 4 is formed of a multilayer ceramic, and internal wiring (not shown) is arranged in each layer. Further, side notches 6 serving as external connection terminals are provided on the outer peripheral side surface of the substrate 4, thus forming a leadless type package. The semiconductor chip 3 is the wire 8
Is connected to the internal wiring provided inside the substrate 4, and the internal wiring is connected to the side notch 6.

The cap 5 is made of ceramic,
An ultraviolet light transmitting window 9 for transmitting ultraviolet light is formed at a position facing the erasing portion 3a of the semiconductor chip 3 at the center thereof. The cap 5 covers the upper opening of the substrate 4, and by joining the cap 5 to the substrate 4,
A package that seals the semiconductor chip 3 is formed. As the bonding material (sealing material) for bonding the substrate 4 and the cap 5, the low melting point glass 10 (shown in satin) was used.

The semiconductor device 1 having the leadless package structure shown in FIG. 9 and the DIP shown in FIG.
In the semiconductor device 1 having side molds, the side notches 6 are provided in the substrate in the semiconductor device 1, whereas in the semiconductor device 2, the side notches 6 a extend downward from both side portions of the substrate 4. Differ in that

[0010]

The above-mentioned semiconductor devices 1 and 2 (EPROM) have the same characteristics as those of the semiconductor devices 1 and 2 when dust is attached to the erasing portion 3a of the semiconductor chip 3 which is irradiated with ultraviolet rays. There is a possibility that the erasing process cannot be performed reliably. Therefore, in order to improve the erasing characteristics of the semiconductor devices 1 and 2, it is necessary to configure so that dust does not adhere to the erasing portion 3a of the semiconductor chip 3.

However, in the conventional semiconductor devices 1 and 2, the substrate 4 and the cap 5 are provided in the erasing portion 3a of the semiconductor chip 3.
There is a problem that the low-melting-point glass 10 that joins and is scattered, and the scattered low-melting-point glass 10 deteriorates the erasing characteristics of the semiconductor devices 1 and 2.

As one of the causes of the scattering of the low melting point glass 10, it is conceivable that a thick film printing method is used as a method of disposing the low melting point glass 10 at the bonding position of the substrate 4 or the cap 5.

That is, as a method of disposing the low melting point glass 10 at a predetermined bonding position of the substrate 4 or the cap 5, a paste mixed with a powder of the low melting point glass is used to form a thick film using a mask having openings only at the bonding portions. The film is printed, and then the firing process is performed to remove the binder in the paste.
As a result, the low melting point glass 10 is attached to the substrate 4 or the cap 5.
Is arranged at a predetermined joining position.

However, since the above-mentioned mask uses the mesh member, the trace of the mesh remains on the low melting point glass 10 formed after printing and firing. That is, the formed low-melting-point glass 10 has a sharp portion at its tip.

The pointed portion formed on the low melting point glass 10 is rubbed and chipped when the cap 5 is attached to the substrate 4, and the chipped low melting point glass 10 is scattered to the erased portion 3a of the semiconductor chip 3. However, the erasing characteristics are deteriorated by the fact that they are fixed by heat during the subsequent sealing process.

As a means for solving this, it is conceivable to set the firing temperature of the firing treatment carried out after thick film printing to a high value to completely melt the low melting point glass 10. When the low-melting glass 10 is completely melted, the low-melting glass 10 has a spherical shape due to the surface tension generated at the time of melting, so that it is possible to prevent a sharp portion from being generated on the surface of the low-melting glass 10.

Therefore, even if the cap 5 rubs the low-melting glass 10 when the cap 5 is placed on the substrate 4, the low-melting glass 10 has a spherical shape, so that no chipping occurs and the low melting point is low. The glass 10 is the erasing portion 3a of the semiconductor chip 3.
It can be prevented from scattering.

However, according to the experimental results of the present inventor, although the scattering of the low melting point glass 10 can be prevented to some extent by increasing the firing temperature as described above,
It was found that the low melting point glass 10 still scatters in the erasing portion 3a of the semiconductor chip 3 due to the temperature at the time of heating for sealing, and the erasing characteristics deteriorate.

The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor device capable of preventing the low melting glass from scattering.

[0020]

In order to solve the above problems, the present invention is characterized by taking the following means.

According to a first aspect of the present invention, there is provided a semiconductor device comprising a substrate which encapsulates a semiconductor chip therein and a cap, and a package in which the substrate and the cap are joined by a joining member. In the joining position with the cap, a scattering prevention mechanism for preventing the joining member from scattering is provided at a position closer to the placement position of the semiconductor chip than the placement position of the joining member.

The invention according to claim 2 is characterized in that the joining member is made of a low melting point glass.

Further, the invention of claim 3 is characterized in that the scattering prevention mechanism is constituted by a projection formed on the substrate.

Further, the invention of claim 4 is characterized in that the scattering prevention mechanism is constituted by a projection formed on the cap.

Further, the invention of claim 5 is characterized in that the scattering prevention mechanism is formed of crystallized glass interposed between the substrate and the cap.

[0026]

The above-mentioned means operate as follows.

According to the first aspect of the present invention, a scattering prevention mechanism for preventing the scattering of the bonding member at the bonding position between the substrate and the cap and at a position closer to the semiconductor chip mounting position than the bonding member mounting position. By providing, the scattering prevention mechanism prevents the joining member from scattering toward the semiconductor chip,
Therefore, it is possible to prevent the joining member from scattering on the semiconductor chip.

According to the second aspect of the present invention, by using the low melting point glass as the joining member, the substrate and the cap can be joined easily and reliably. Also,
Since low-melting-point glass has the property that scattering easily occurs,
It is possible to effectively function the scattering prevention mechanism, and it is possible to prevent the low melting point glass from scattering on the semiconductor chip while maintaining the bondability between the substrate and the cap.

Further, according to the invention of claim 3 or 4, since the scattering prevention mechanism is constituted by the projection formed on the substrate or the cap, the scattering prevention mechanism can be realized with a simple structure.

Further, according to the invention of claim 5, since the scattering prevention mechanism is composed of crystallized glass interposed between the substrate and the cap, the crystallized glass has a function of preventing scattering of the bonding member. Since it has both the bonding function of bonding the substrate and the cap, it is possible to prevent the bonding member from scattering while improving the bonding property of the substrate and the cap.

[0031]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a sectional view showing a semiconductor device 20 which is a first embodiment of the present invention. This semiconductor device 20 is an EP
This is a ROM, and in the example shown in the figure, an example adopting a leadless type package structure is shown.

The semiconductor device 20 is roughly composed of a semiconductor chip 21, a substrate 22, a cap 23, and side notches 24. The semiconductor chip 21 is E
This is a PROM chip, and at the center of the upper surface of this semiconductor chip 21, an erasing portion 21a is formed which is irradiated with ultraviolet rays when erasing the information once written. An electrode pad 25 is formed on the upper surface of the semiconductor chip 21 surrounding the erased portion 21a. The semiconductor chip 21 having the above structure is mounted in the cavity 26 formed in the substrate 22.

The substrate 22 is a multilayer ceramic substrate, and each layer is provided with internal wiring (not shown). Cavity 26 in which semiconductor chip 21 of this substrate 22 is mounted
A stepped portion 27 is formed at the upper position, and a joining portion 28 to which the cap 7 described later is joined is formed above the stepped portion 27. In addition, side notches 24 that serve as external connection terminals are provided on the outer peripheral side surface of the substrate 22, thus forming a leadless type package.

An electrode portion 29 is formed on the step portion 27 formed on the substrate 22, and the electrode pad 25 formed on the semiconductor chip 21 and the electrode portion 29 are electrically connected by a wire 30. Further, the electrode portion 29 is connected to the internal wiring provided therein, and the side notch 2
4 is also connected. Therefore, the semiconductor chip 21
It is configured to be electrically connected to the side notch 24 via the wire 30, the electrode portion 29, and the internal wiring.

Further, the cap 23 is the substrate 22 described above.
Of the upper surface of the substrate 22 and is bonded to the bonding portion 28 formed on the substrate 22. This cap 23 is also made of ceramic, and its coefficient of thermal expansion is matched with that of the substrate 22. Further, an ultraviolet ray transmitting window 31 that transmits ultraviolet rays is formed at a position facing the erasing portion 21 a formed on the semiconductor chip 21 in the central portion of the cap 23.

As the bonding material (sealing material) for bonding the substrate 22 and the cap 23 described above, the low melting point glass 32 (shown in satin) is used in this embodiment. Low melting point glass 32
Is easily used because it melts at a relatively low temperature (400 ° C. to 500 ° C.), and because it has good bondability with ceramics, is commonly used as a bonding material for ceramic packages.

The low melting point glass 32 is provided on the joint portion 28 formed on the substrate 22. Low melting point glass 3
As a method for arranging 2 in the joint portion 28, first, in the present embodiment, the thick film printing method is used. Specifically, a paste containing low-melting-point glass powder is printed on the bonding portion 28 of the substrate 22 with a thick film using a mask having openings only at the positions of the bonding portion 28, and then firing processing is performed. The binder in the paste is removed, so that the low melting glass 32
Are disposed on the cap 23. After that, the semiconductor chip 2
1 is mounted and the substrate 22 to which the wire 30 is connected and the cap 23 are sealed.

The firing temperature is set higher than the melting temperature of the low melting point glass 32 so that no trace of the mesh of the mask is left on the low melting point glass 32 disposed on the cap 23. Thus, by setting the firing temperature to a temperature higher than the melting temperature of the low melting point glass 32, when the cap 23 is attached to the substrate 22, the low melting point glass 32 can be prevented from being chipped due to traces of the mesh, and the semiconductor chip can be prevented. Two
It is possible to prevent the low melting point glass 32 from scattering on the erasing portion 21a of No. 1 and adhere to the erasing portion 21a due to heating during sealing, and to improve the erasing characteristics of the semiconductor device 20. However, as described above, the scattering of the low melting point glass 32 cannot be completely prevented only by raising the firing temperature.

Therefore, in the semiconductor device 20 according to the present embodiment, as shown in the enlarged view of FIG. 2, the low melting point glass 32 is formed at the joining portion 28 where the substrate 22 and the cap 23 are joined.
A scattering prevention protrusion 33 is provided as a scattering prevention mechanism for preventing the low melting point glass 32 from scattering at a position closer to the position where the semiconductor chip 21 is arranged than the position at which the semiconductor chip 21 is disposed.

The anti-scattering projection 33 is formed integrally with the substrate 22 and is formed annularly on the upper surface of the joint portion 28 having a rectangular frame shape in plan view. Therefore, the anti-scattering projection 33 contacts the bottom surface of the cap 23 with the cap 23 mounted on the substrate 22. In addition, the scattering prevention protrusions 3
Since 3 is formed in a ring shape, the cap 23 is attached to the substrate 2
In a state in which the anti-scattering projection 33 is attached to the cap 23 and is attached to the cap 2, the cavities 26 are defined with respect to the outside.

Therefore, in order to dispose the low melting point glass paste on the joint portion 28, the low melting point glass 3 is placed on the cap 23.
2 is thick-film printed and then fired. After that, the low melting point glass 32 is mounted on the substrate 22 and then fired.
Even if it is melted, it is possible to reliably prevent the melted low melting point glass 32 from being scattered inside the cavity 26 due to the presence of the scattering prevention projections 33. Therefore, the low melting point glass 32 does not adhere to the erasing portion 21a formed on the semiconductor chip 21, and the erasing characteristics of the semiconductor device 20 during ultraviolet irradiation can be improved.

The formation of the above-mentioned scattering prevention protrusions 33 is
The substrate 22 may be formed by press molding in a material state and then firing. To form the substrate 22 using the green sheet method, the scattering prevention protrusions 33 are formed on the uppermost green sheet. It may be formed by stacking green sheets having a shape corresponding to the above, and performing firing treatment on the green sheets. Thus, the formation of the scattering prevention protrusions 33 can be performed collectively in the step of forming the substrate 22, and therefore the formation of the scattering prevention protrusions 33 is not difficult.

FIG. 3 shows a semiconductor device 20a which is a modification of the semiconductor device 20 shown in FIGS.

The present modification is characterized in that a recess 34 is formed at a position facing the shatterproof projection 33 of the cap 23. In this way, the scattering prevention protrusions 3
By forming the concave portion 34 at a position facing the No. 3, the anti-scattering projection 33 formed on the substrate 22 is inserted into the concave portion 34 formed on the cap 23, so that the low melting point glass 32 is scattered. It can be prevented more reliably. Further, the engagement between the scattering prevention protrusion 33 and the recess 34 can be used as positioning when the cap 23 is arranged on the substrate 22, and the assembling property of the semiconductor device 20 can be improved.

FIGS. 4 and 5 show a semiconductor device 40 which is a second embodiment of the present invention.

In each drawing, the same components as those of the semiconductor device 20 according to the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

The semiconductor device 40 according to the second embodiment is characterized in that the cap 41 is provided with a scattering preventing projection 42 which serves as a scattering preventing mechanism. This shatterproof projection 42
Is configured to come into contact with the joint portion 44 of the substrate 43 when the cap 41 is disposed on the joint portion 44 of the substrate 43.

As described above, the anti-scattering mechanism is not limited to the substrate 22, but the cap 41 may be provided with the anti-scattering projection 42. Even if the cap 41 is provided with the shatterproof protrusions 42, like the semiconductor device 20 according to the first embodiment, the melted low melting point glass 3 is used.
2 can be surely prevented from scattering inside the cavity 26, so that the erasing portion 21 formed on the semiconductor chip 21 can be prevented.
It is possible to prevent the low melting point glass 32 from adhering to a, and improve the erasing characteristics of the semiconductor device 20 during ultraviolet irradiation.

Since the cap 41 is also made of ceramic as described above, the shatterproof protrusion 42 can be easily formed on the cap 41.

FIG. 6 shows a semiconductor device 40a which is a modification of the semiconductor device 40 shown in FIGS. 1 and 2 in the second embodiment.

The present modification is characterized in that a recess 45 is formed at a position facing the shatterproof protrusion 42 of the substrate 43. By thus forming the recess 45 at a position facing the shatterproof protrusion 42, the shatterproof protrusion 42 formed on the cap 41 is inserted into the recess 45 formed on the substrate 43. It is possible to more reliably prevent the low melting point glass 32 from scattering.
Further, the engagement between the anti-scattering projection 42 and the recess 45 can also be used for positioning the cap 41 and the substrate 43.

7 and 8 show a semiconductor device 50 which is a third embodiment of the present invention.

Also in this embodiment, the same components as those of the semiconductor device 20 according to the first embodiment described above are designated by the same reference numerals and the description thereof will be omitted.

The semiconductor device 50 according to the third embodiment is characterized in that a crystallized glass 53 is provided between the substrate 51 and the cap 52 as a scattering prevention mechanism. The position where the crystallized glass 53 is arranged is also selected on the joint 28 so as to be closer to the position where the semiconductor chip 21 is arranged than the position where the low melting point glass 32 is arranged.

The crystallized glass 53 is glass which is crystallized by being heated unlike the ordinary glass. Then, once crystallized, it does not melt even if it is heated up to the melting point of ordinary glass, and maintains a solidified state. Therefore, even if a heat treatment is performed to melt the low-melting glass 32, the crystallized glass 53 is in a solidified state even when the low-melting glass 32 is in a molten state, so that the crystallized glass 53 has a low melting point. It can be used as a scattering prevention mechanism that prevents the glass 32 from scattering.

Since the crystallized glass 53 has a bonding property, the crystallized glass 53 can be used as a bonding member for bonding the substrate 51 and the cap 52 together. Therefore, the crystallized glass 52 has a scattering prevention function of preventing the low melting point glass 32 from scattering, and the substrate 51 and the cap 52.
Since it has both the bonding function of bonding and the bonding function, it is possible to prevent the scattering of the low melting point glass 32 while improving the bonding property between the substrate 51 and the cap 52.

In this embodiment, the semiconductor device 20,
Although the EPROM has been described as an example of 40 and 50,
The application of the present invention is not limited to EPROMs, but can be widely applied to semiconductor devices using light, ultraviolet rays, infrared rays, etc. (for example, optical laser elements, photodiodes, CCDs, etc.).

[0059]

As described above, according to the present invention, the following various effects are exhibited.

According to the invention of claim 1, a scattering prevention mechanism for preventing the scattering of the bonding member at the bonding position between the substrate and the cap and at a position closer to the semiconductor chip mounting position than the bonding member mounting position. By providing, the scattering prevention mechanism prevents the joining member from scattering toward the semiconductor chip,
Therefore, it is possible to prevent the joining member from scattering on the semiconductor chip.

According to the second aspect of the present invention, by using the low melting point glass as the joining member, the substrate and the cap can be joined easily and reliably. Also,
Since low-melting-point glass has the property that scattering easily occurs,
It is possible to effectively function the scattering prevention mechanism, and it is possible to prevent the low melting point glass from scattering on the semiconductor chip while maintaining the bondability between the substrate and the cap.

Further, according to the invention of claim 3 or 4, since the scattering prevention mechanism is constituted by the projection formed on the substrate or the cap, the scattering prevention mechanism can be realized with a simple structure.

Further, according to the invention of claim 5, since the scattering preventing mechanism is constituted by the crystallized glass interposed between the substrate and the cap, the crystallized glass has a function of preventing the scattering of the bonding member. Since it has both the bonding function of bonding the substrate and the cap, it is possible to prevent the bonding member from scattering while improving the bonding property of the substrate and the cap.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor device that is a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing the vicinity of the junction in the semiconductor device according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a semiconductor device which is a modification of the semiconductor device according to the first embodiment of the present invention.

FIG. 4 is a sectional view of a semiconductor device according to a second embodiment of the present invention.

FIG. 5 is an enlarged cross-sectional view showing the vicinity of the junction in the semiconductor device according to the second embodiment of the present invention.

FIG. 6 is a sectional view showing a semiconductor device which is a modification of the semiconductor device according to the second embodiment of the present invention.

FIG. 7 is a sectional view of a semiconductor device according to a third embodiment of the present invention.

FIG. 8 is an enlarged cross-sectional view showing the vicinity of a bonding portion in a semiconductor device which is an eighth embodiment of the present invention.

FIG. 9 is a cross-sectional view showing an example of a conventional semiconductor device.

FIG. 10 is a cross-sectional view showing an example of a conventional semiconductor device.

[Explanation of symbols]

 20, 20a, 40, 40a, 50 Semiconductor device 21 Semiconductor chip 21a Erasing part 22, 43, 51 Substrate 23, 41, 52 Cap 24 Side notch 26 Gaviness 27 Stepped part 28,44 Joint part 30 Wire 31 Ultraviolet transmission window 32 Low Melting point glass 33,42 Shatterproof projections 34,45 Recesses 53 Crystallized glass

Claims (5)

[Claims] 1. A semiconductor device comprising a package which is composed of a substrate for encapsulating a semiconductor chip inside and a cap, and which is formed by joining the substrate and the cap with a joining member. The joining position of the substrate and the cap. The semiconductor device is characterized in that a scattering prevention mechanism for preventing scattering of the bonding member is provided at a position closer to the position where the semiconductor chip is disposed than the position where the bonding member is disposed. 2. The semiconductor device according to claim 1, wherein the joining member is a low melting point glass. 3. The semiconductor device according to claim 1, wherein the scattering prevention mechanism is a protrusion formed on the substrate. 4. The semiconductor device according to claim 1, wherein the scattering prevention mechanism is a protrusion formed on the cap. 5. The semiconductor device according to claim 1, wherein the scattering prevention mechanism is crystallized glass interposed between the substrate and the cap.