JP2773635B2 - Method for manufacturing In bump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an In bump for use in a hybrid type device.

[0002]

2. Description of the Related Art A hybrid type device in which several types of devices are combined by using In bumps, such as a photodetection device including an IC and a photodiode, is generally used in a two-dimensional manner. It has an arrayed structure, in which columns of In called "In bumps" are formed in each pixel of each device, and pressure is applied while facing the In bumps to join the two devices. For forming the In bump, for example, a first resist pattern is formed on the device, a metal film for supplying a plating current is deposited, and a second resist pattern is formed. It is done in a way that makes you. In
The shape of the bump is a cylinder, for example, a pixel size of 25 μm.
In the case of m pitch, the diameter of the In bump is about 10 μm and the height is about 20 μm. What is important in the method of connecting devices with In bumps is to make the shape of the In bumps uniform in order to keep the connection state of each pixel constant.
As described above, when an In bump having a height of about 20 μm is formed by plating, the height of the In bump varies due to a difference in growth rate.

As a method of suppressing the height variation, as described in Japanese Patent Laid-Open No. 17339/1992, ion milling is performed after forming a second resist pattern.
A method has been proposed in which a redeposition film of a base metal is formed on the inner peripheral surface of a hole opened in a resist so as to achieve uniform plating growth of In.

In order to make the shape of the In bump uniform, a method of heating and melting the In bump after the growth of plating to adjust the shape has also been used. For example, as in the invention described in Japanese Patent Application Laid-Open No. 4-16831, the sample is annealed at 250 ° C. for 30 minutes in an inert gas atmosphere with the resist or polyimide pattern left after the bump is formed to soften and dissolve the solder bump. A method has been proposed.

[0005]

However, in the above-mentioned Japanese Patent Application Laid-Open No. 4-17339, it is necessary that the underlying metal beaten out by the ion milling process adheres uniformly to the inner peripheral surface of the resist hole. To achieve this, the ratio of the hole depth to the hole diameter (aspect ratio)
Must be small. In this publication, hole diameter 2
The depth of the hole is about 10 μm for 0-30 μm,
Since the aspect ratio is at most 0.5, it is possible to achieve uniform plating growth of In. However, hole diameter 10μ
hole depth is about 20μm and aspect ratio is 2
In this case, ions cannot sufficiently reach the bottom surface of the hole during the ion milling process, and therefore, a redeposition film having a sufficient thickness can be uniformly formed on the inner peripheral surface of the hole. There is a problem that can not be.

Further, in the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 4-16831, the resist or polyimide pattern cannot be easily removed after annealing at 250 ° C. for 30 minutes. Had. That is, if the pattern is a resist, the pattern is altered and carbonized, and cannot be easily removed even by using a release agent. If the pattern is polyimide, imidization is almost 1
It progresses by 00% and becomes difficult to remove. In any case, it is difficult to achieve the object by this method.

To avoid this problem, it is considered effective to remove the resist pattern using an organic solvent or a developing solution after the plating growth and remove the base metal using an acid-based etching solution, and then heat and melt the In bump. But In
When the bump is heated and melted, the bump becomes a crushed sphere as shown in FIG. 3 (d), so that the shapes can be made uniform, but there is a problem that the diameter becomes wider than after plating growth. That is, as the pixel size becomes smaller, the distance between In bumps becomes shorter, so that adjacent In bumps are connected to each other, resulting in a short circuit of the pixel.

An object of the present invention is to provide a method for manufacturing an In bump capable of preventing the diameter of the In bump from expanding.

[0009]

The method of manufacturing an In bump according to the present invention is characterized in that a metal film having a melting point higher than that of In is formed on the side surface of the In bump, and then the shape is made uniform by heating and melting. The refractory metal film is formed on the side surface of the In bump by reattachment of the plating electrode metal by ion milling or by electroless plating. Due to the presence of this metal, I
Even if the n bumps are melted by heating, the shapes can be made uniform without increasing the diameter of the In bumps.

[0010]

【Example】

(Embodiment 1) The present invention will be described with reference to FIG. In order to form an In bump by a plating method, first, as shown in FIG. 1A, a first resist pattern 4 is formed on a device 1 by a PR method. Next, a plating electrode 5 for supplying a plating current is deposited on the device 1 using a deposition method. In this case, the type of the plating electrode 5 needs to be such that In plating easily grows, has a higher melting point than In, and has an appropriate hardness.
Cu, Ni, Pt, Sn or the like can be used. Next, the second layer resist pattern 6 is formed again by the PR method, the device 1 is immersed in a plating solution, and an electric current is supplied through the plating electrode 5, and the cavity of the first layer resist pattern 4 and the second layer resist pattern 6 is formed. To form an In bump 7. When the In bump 7 has grown up to the upper part of the second resist pattern 6, the device 1 is taken out of the plating solution and plating growth is completed. Next, as shown in FIG. 1B, only the second-layer resist pattern 6 is etched by an RIE method using O ₂ gas, or the entire surface of the device 1 is irradiated with ultraviolet rays or the like by an exposure machine to form a developer. Remove by immersion. Then, the plating electrode 5 is exposed, and is removed by etching using an ion milling device as shown in FIG. When the plating electrode 5 is etched by the ion milling method, the plating electrode 5 is beaten out by ions such as Ar and adheres again to the side surface of the In bump, and the plating electrode 5 is removed.
Is formed. After the etching of the plating electrode 5 is completed, the first-layer resist pattern 4 is removed by the RIE method using an O ₂ gas or an organic solvent. For example, it is heated at a temperature of 150 to 170C. At this time, as shown in FIG. 1D, a redeposition film 8 of the plating electrode 5 is formed on the side surface of the In bump 7, and since the redeposition film 8 does not melt at the above temperature, the In bump 7 is It is possible to process into a shape in which only the bump head is rounded without spreading in the radial direction.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2A, an In bump 7 is formed by the same method as described above. In the case of this embodiment, as shown in FIG. 2B, the device 1 is heated in air at a temperature of 80 to 100 ° C. for 10 to 30 minutes,
An oxide film 9 is formed on the head of n bump 7. Next, FIG.
In (c), the second resist pattern 6 is removed by the same method as described above. When the plating electrode 5 is exposed, FIG.
As shown in (d), the plating electrode 5 is removed with an etching solution. As the etchant, one having selectivity of In and etching is desirable. For example, when the plating electrode 5 is Au, an etchant containing potassium iodide is preferable. Next, the device 1 is immersed in an electroless plating solution,
A plating film is formed around the substrate. At this time, since the oxide film 9 is formed on the top of the In bump, no plating film is formed by electroless plating. Next, as shown in FIG. 2E, the device 1 is immersed in hydrochloric acid or hydrofluoric acid diluted with pure water to remove the oxide film 9 formed on the top of the In bump, and the first resist pattern 4 is changed to acetone. Remove with an organic solvent such as Finally, when the device 1 is heated by the same method as described above, the In bump 7 can be processed into a shape in which only the bump head is rounded without spreading in the radial direction as shown in FIG.

[0012]

As described above, in the In bump of the present invention, a metal layer having a melting point higher than that of In is formed on the side surface of the bump by ion milling or electroless plating of the underlying metal film, thereby heating the In bump. When melting, the shapes of the In bumps can be made uniform while easily suppressing the expansion of the diameter.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of an In bump forming process of the present invention.

FIG. 2 is a sectional view showing an embodiment of an In bump forming process of the present invention.

FIG. 3 is a cross-sectional view showing a conventional In bump forming process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Device 2 Device electrode 3 Protective film 4 1st-layer resist pattern 5 Plating electrode 6 2nd-layer resist pattern 7 In bump 8 Re-adhesion film of plating electrode 5 9 Oxide film 10 Plating film by electroless plating 12 Shorted In bump

Claims (2)

(57) [Claims] In a method for manufacturing an In bump having a metal film made of a high melting point metal on a side surface of the In bump, the metal film is re-adhered to the side surface of the In bump by ion milling of a plating electrode metal. A method for producing an In bump, wherein the bump is heated and melted at 170 ° C. 2. A method for producing In bump having a metal film made of a refractory metal on the side surface of the In bump, In vans
After an oxide film is formed on the top of the bump , a metal film is formed on the side surface of the In bump by electroless plating, and the oxide film is removed.
And then heating and melting the bump at 150 ° C. to 170 ° C.