JPS6025828B2 - magnetic bubble memory chip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic bubble memory chip, and an object of the present invention is to prevent the electromigration phenomenon occurring in the conductor pattern of a magnetic bubble memory chip by dissipating local heat generation.

The degree of integration of magnetic bubble memory devices has also been significantly improved, and along with this, permalloy patterns for transferring magnetic bubbles and conductor patterns for flowing control currents have also become finer.

For this reason, in the conductor pattern, the current density locally becomes high at the cross-sectional area of the conductor pattern, causing a phenomenon called electromigration, which eventually leads to disconnection of the conductor pattern. It may come to that. In other words, in the conductor pattern,
If there is a localized area with a small cross-sectional area, the current density at that area becomes high, generating Joule heat and increasing the temperature. However, if electricity is applied for a long time in such a high-temperature area, the metal of the conductor material will Ions are gradually taken away and stored elsewhere. Therefore, at the location where the atoms of the conductive material have been taken away, the electromigration phenomenon continues in a vicious cycle, and the cross-sectional area of the conductive material becomes smaller by 4.0 mm, eventually leading to a wire breakage. Conversely, where atoms of the conductive material accumulate, there is a risk of short-circuiting the wiring. Several solutions to the electromigration phenomenon have been proposed, but most of them are attempts from the material standpoint.

By the way, the life span of a conductor due to the electromigration phenomenon, that is, the MTF (mean time
The fail mountain e) is proportional to 1/e-E/Kt. Here, E is activation energy, k is Borckmann's constant, and T is temperature. In this way, the higher the temperature, the more intense the electromigration becomes, which shortens the life of the conductor. Therefore, the present invention suppresses the temperature rise in the part where the electromigration phenomenon occurs.
The aim is to prevent the electromigration phenomenon and extend the life of the conductor. In order to suppress heat generation in the area where the electro-migration phenomenon occurs, the present invention provides a magnetic bubble memory chip with a heat dissipation layer made of a material with excellent heat conduction as a neck layer, thereby suppressing the local heat generation in the conductor pattern. The heat is transmitted to the heat dissipation layer and is dissipated.

Next, each embodiment of the present invention will be described in detail.

In FIG. 1, reference numeral 11 denotes a heat dissipation layer, and the heat dissipation layer 11 is a neck layer on the back surface of the magnetic bubble chip, that is, on the surfaces of the two legs of the substrate. Therefore, the layer structure of the chip in this case is GG
On the LPE magnetic thin film 3 formed on the G (gadolinium gallium garnet) substrate 2, there are formed a first sublayer 4, a conductor pattern 5, a second sublayer 6, a permalloy pattern 7 for bubble transfer, and a protective layer 8. are stacked in the order of
A heat dissipation layer 11 is provided on the back surface of the Q-type substrate 2. The heat dissipation layer 11 is made of a material with excellent thermal conductivity, such as AI-Cu.
It is constructed by depositing Ag, Cu, etc. by vapor deposition or sputtering, or by adhering a foil or plate of a material with good thermal conductivity. According to this configuration, since the thicknesses of the first spacer layer 4, bubble material 3, and substrate 2 interposed between the conductor pattern 5 and the heat dissipation layer 11 are extremely small, the heat locally generated in the conductor pattern 5 is One base layer 4
The heat is effectively transmitted to the heat dissipation layer 11 via the bubble material 3 and the substrate 2, and is further diffused over the entire surface of the heat dissipation layer 11. Therefore, localized heat generation in the conductor pattern is effectively radiated, and temperature rise in the heat generating portion is suppressed. This inactivates the electromigration phenomenon and extends the life of the conductor pattern. In this embodiment, when mounting the chip on the plane, the heat dissipation layer 11 side may be die-bonded to the plane, or the chip may be turned upside down and the protective film 8 side may be face-down bonded onto the plane. . FIG. 2 shows an example in which the heat dissipation layer 12 is provided between the first spacer layer 4 and the bubble material 3; Since only the first spacer layer 4 exists, and the distance between them is shortened, heat transfer to the heat dissipation layer is more effective than in the case of FIG.

FIG. 3 shows an example in which the heat dissipation layer 13 is provided in the same layer as the conductor pattern 5.

That is, the heat dissipation layer 13 is provided on the same surface, away from the conductor pattern, by utilizing an empty position in the chip where there is no conductor pattern. Since the ratio of the conductor pattern to the chip area is extremely small, a heat dissipation layer with a sufficiently large area can be obtained. Furthermore, the heat dissipation layer can be formed in the same process as the conductor pattern by simply changing the mask shape, so there is no increase in the number of manufacturing steps. In FIG. 4, contrary to FIG. 1, a heat dissipation layer 14 is provided on the uppermost layer, that is, on the protective layer 8.

That is, a material with excellent thermal conductivity is deposited on the protective layer 8 by sputtering or vapor deposition to form the heat dissipation layer 14. In this case, since the heat dissipation layer 14 is close to the permalloy pattern 7 for magnetic bubble transfer, a nonmagnetic material is used so as not to exert a magnetic influence on the permalloy pattern 7. As described above, according to the present invention, by laminating and providing a heat dissipation layer directly on a magnetic bubble chip, a structure is explored in which localized heat generation in the conductor pattern is transmitted to the heat dissipation layer and dissipated by the heat dissipation layer. Therefore, even if the conductor pattern has a locally small cross-sectional area, the temperature will not rise to a high temperature. Therefore, activation of the electromigration effect can be prevented, the conductor pattern will not be disconnected, and the reliability of the magnetic bubble chip can be ensured. Furthermore, local heat generation in the conductor pattern is suppressed within the magnetic bubble chip by the heat dissipation layer of the present invention;
By mounting the chip on a ceramic or metal plane, heat is transferred to the plane and dissipated more effectively.

[Brief explanation of the drawing]

1 to 4 of the drawings are cross-sectional views showing different embodiments of the magnetic bubble chip according to the present invention, respectively. In the figure, 11...14 are heat dissipation layers, 2 is a substrate, 3 is a bubble material, 4 and 6 are spacer layers, 8 is a protective layer, 5 is a conductor pattern, and 7 is a permalloy pattern. Figure 1: Blinds Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A magnetic device characterized in that a heat dissipation layer with good thermal conductivity is arranged on a magnetic bubble memory chip, and the heat dissipation layer is configured to dissipate and alleviate localized heat generated by a conductor. Bubble memory chip.