JPS60192351A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide laminated thin films with high bonding strength by a method wherein an Si evaporation film as an intermediate layer is laid between thin films to be diffused mutually therewith. CONSTITUTION:Ti 4, Cu 5 and Ni 8 to be base metals are respectively laminated as the first, second and third layers to join these thin film layers. The films Ti 4 and Cu 5 are interfacially junctioned at relatively low junction strength by means of laying an Si evaporation film 13 between the interface thereof. The active Si evaporation film 13 may be diffused mutually with the Ti 4 and Cu 5 at relatively low temperature of around 400 deg.C to form a silicide easily providing said films Ti 4 and Cu 5 with solid bonding. The Si evaporation film 13 provided with sufficiently thin thickness no exceeding 0.1mum may easily make a junction electrically ohmic. The characteristics of a semiconductor element may not be deteriorated since only an extremely thin Si film is added thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a method for laminating thin films such as metal and insulating films provided on a semiconductor device.

[Prior art and its problems]

For example, in semiconductor devices such as flip chips having a multilayer electrode structure and Schottky diodes having a laminated structure of a barrier metal and an insulating film.

It is desirable that thin film-to-thin film bonding is performed between metals, insulating films, or metals and insulating films, and these are strongly bonded.

In general, three types of bonding are known for bonding these thin films: interface bonding, interdiffusion bonding, and intermediate layer bonding.

Interfacial bonding involves intermolecular and atomic interactions that occur between two amounts of substances that are in contact with each other, i.e., electrostatic or Van d
This is an er Waals-like interaction, and the bonding strength mainly depends on the state of the interface between the two materials at the time of bonding. Therefore, in order to improve the bonding strength between thin films through interfacial bonding, careful attention must be paid to the surface treatment of the surfaces to be bonded, the atmosphere and degree of vacuum during the formation of the thin film formed on these surfaces, and the optimum conditions are required. However, when forming a thin film deposited by ordinary resistance heating or electron beam heating, it is difficult to reproduce the good condition of the deposition surface and the problem is that it is difficult to control the surface condition. There is. A known alternative to vapor deposition is sputtering, in which the surface is treated by sputter cleaning before sputtered thin film formation, which has the advantage of improving bonding properties due to the kinetic energy of the sputtered atoms. Although this method is effective for forming a thin film for interfacial bonding, it has the problem of sputtering damage to the base on the side to be bonded. Therefore, by simply forming a thin film by vapor deposition or sputtering and bonding the thin film to a film to be bonded at an interface, sufficient bonding strength cannot be obtained, resulting in a lack of reliability of the semiconductor element.

Interdiffusion bonding involves heating thin films of interfacially bonded metals to a higher temperature to cause interdiffusion between the thin films at the bonding interface.
This is due to the metallic bonding of the alloy layer formed by this interdiffusion, and although the bonding strength is higher than that of interface bonding, the problem with the bonding strength is the strength of the alloy layer itself, so interdiffusion is likely to occur. Constituent metals must be selected, and high-temperature processing is not applicable to devices that involve processes that are impossible.

For example, the intermediate layer junction is At,! :5i02 and other thin films, an intermediate layer made of A L x Os is formed between the two thin films, and this intermediate layer is made of At film and S i O,
Since the bond is shared with the film, a bond with high strength can be obtained, and it is effective when bonding metals that are easily oxidized or metals that are easily oxidized and an oxide film. However, in this case as well, effective bonding can only be achieved with metals that are easily oxidized, and cannot be achieved with any thin film.

For example, FIGS. 1A-1E are cross-sectional views showing the process of forming protruding electrodes of a conventionally well-known flip chip.

FIG. 1 shows a step A in which a surface protection film 3 such as Si02 with a thickness of 1 μm is formed on the At wiring 2 with a thickness of 1 μm provided on the surface of the St substrate 10, and a window is opened. For example, the thickness of the base metal of the first layer is 0.5
μm thick Ti film 4 and second layer base metal, for example, 1 μm thick
Step B of depositing a Cu film 5, Step C of applying a photoresist 6 to form a solder region and removing unnecessary parts,
Step D of removing the photoresist 6 and applying the photoresist 7 again to areas other than the solder area, applying a third layer of base metal Nl plating 8, performing, for example, Pb-an based solder alloy plating, and removing the resist 7. After that, the solder plating layer is reflowed to form the protruding electrode 9, which is roughly divided into process E.

The hemispherical solder protrusion electrode 9 formed in the contact hole portion of the flip chip thus obtained has a first layer of KTi4, a second layer of Cu5, and a third layer of Ni as base metals.
8 are stacked and the respective thin film layers are bonded. In this case, the wiring metals A42 and Ti4. and 5
An intermediate layer is formed at the bonding interface between the surface protective film 3 of in2 and Ti 4 to form an intermediate layer bond, and Cu 5
The bonding interfaces between and Ni 8, and Ni 13 and solder 9 are mutual diffusion bonding, and have a relatively high bonding strength among these thin film laminates, but the bonding between Tp + 4 and C[15 is simply an interfacial bonding. Only relatively low bonding strength can be obtained. Therefore, the protruding solder electrode of a flip chip having such a thin film laminated structure has the disadvantage that peeling occurs at the interface between the underlying metal T14 and Cu5.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks, be able to be applied to bonding thin films of any material without being affected by the interfacial characteristics between the thin films, and have high bonding strength without causing any adverse effects on the characteristics of semiconductor devices. The purpose of the present invention is to provide a method for laminating thin films without causing any adverse effects.

[Summary of the Invention] When laminating thin films such as metal or oxide films provided in a semiconductor element, the present invention interposes an extremely thin 81 vapor deposited film between the thin film layers to increase the thickness of the laminated thin film by interdiffusion and forming an intermediate layer. This provides bonding strength.

[Embodiments of the invention]

The present invention will be explained below based on examples.

2A to 2E show the case where the method of the present invention is applied to the process of forming protruding electrodes of a flip chip similar to that shown in FIG. 1, and parts common to those in FIG. 1 are represented by the same reference numerals. The steps in FIG. 2A-H correspond to those in FIG.
The process different from the one shown in the figure is the base metal Ti 4 of the first layer in Figure 2B.
A Si vapor deposited film 13 having a thickness of approximately 0.05 μm is interposed between the base metal 5 of the second layer and the base metal 5 of the second layer.

As explained in FIG. 1, the Ti film 4 and Cu film 5 are bonded at an interface where Cu 5 is attached to the evaporated surface of Ti 4, and the bonding strength is low, so a Si evaporated film is attached to these interfaces. Since the Si vapor deposited film is active unlike single-crystal Si, Ti 4
These compounds easily form silicide by interdiffusion with and Cu 5, and the formation of a silicide layer with Ti film 4
A strong bond between the film and the Cu film 5 can be obtained. In this case, by making the thickness of the Si vapor deposited film 13 sufficiently thin, a spot-like ohmic bond can be easily obtained.
It is preferable that the thickness be less than m.

FIG. 3 shows a partial cross-sectional view of a Schottky pad, in which the method of the present invention is applied.

In FIG. 3, the barrier metal 11 provided on the substrate 1o 81 often forms an overoxide portion so as to partially cover the top of the Si oxide film 12. In FIG. However, various metals are used as the barrier metal depending on the characteristics of this Schottky barrier diode, so if MO is used as the barrier metal, the bonding surface between the MO and the 81 oxide film may not have sufficiently high strength. There is. Therefore, in this case, one eight-layer vapor deposited film 14 is provided between the barrier metal 11 and the St oxide W 12 as shown in FIG. That is, MO film 1
1 and the Si oxide film 12 alone, a strong bond cannot be obtained by interposing the Si vapor deposited film 14 to form MO silicide at the interface with the MO film 11 and oxygen at the interface with the Si oxide film 12. Sufficient bonding strength is obtained by forming a shared intermediate layer.

〔Effect of the invention〕

As explained in the examples above, when laminating and bonding various thin films to semiconductor devices, even if sufficient bonding strength cannot be obtained by combining thin films that do not easily diffuse into each other, it is possible to By interposing one layer of Si film, it is possible to form a diffusion layer or an intermediate layer and increase the bonding strength. Therefore, if a peeling phenomenon occurs in the laminated thin film of a semiconductor element, it will be a problem. Metal, regardless of the type of thin film.
It can be combined with any thin film such as oxide, and bonding these with a Si thin film in between can be easily done at a relatively low temperature, and only requires adding an extremely thin 81 film. This has the advantage that the characteristics of the semiconductor element are not impaired at all.

[Brief explanation of the drawing]

Figure 1 is a process diagram of the protruding electrode of a conventional flip chip;
The figure is a process diagram of a protruding electrode of a flip chip to which the method of the present invention is applied, and FIG. 3 is a partial sectional view of a Schottky diode to which the method of the present invention is applied. 1.10... Silicon substrate, 3.12... Oxide film,
4...Ti film, 5...Cu film, 8...Nr plating, 9...Figure 1

Claims (1)

[Claims] 1) When forming electrodes, wiring, or a surface protective film by laminating conductive, semiconductive, or insulating thin films on a predetermined region of the surface of a semiconductor substrate, a small number of thin films to be laminated A method of manufacturing a semiconductor device characterized by forming a thin film of silicon on one layer and then layering the next thin layer on top of that. 2. A method for manufacturing a semiconductor device according to claim 1, wherein the thickness of the silicon thin film is 0.1 μm or less.