JPS58192351A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the damage of Al wiring, and to improve the reliability and yield of the device by etching a barrier metal as a foundation under the state in which a noble metal thin-film of specific thickness or less is left on a barrier metal layer. CONSTITUTION:An Al electrode pad 2 on a semiconductor substrate 1 is coated with a protective film 3, and a Ti layer 4 and an Au film 9 of not more than 1,000Angstrom thickness are evaporated onto the film 3 and the pad 2. A resist mask 6 is executed, the surface is plated with Au, and a bump electrode 8 is formed. When the mask 6 is removed and the surface of the substrate is exposed in an H2O2 group liquid, an etching liquid intrudes through defects such as the pin holes of the thin-film 9, and etches the foundation barrier metal 4, but Al is hardly etched. Accordingly, the Au thin-film 9 floats from the surface of the substrate in sections except a pad section. The thin-film 9 under an unstable state is removed easily through ultrasonic washing under the state. According to the constitution, an unnecessary Au thin-film is removed easily, Al wiring is not damaged by the severe etching liquid, and the reliability and yield of the device can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a semiconductor device in which protruding electrodes are provided on electrode pads of a chip.

In order to connect circuit elements built into a semiconductor chip with external circuits, electrodes and pads are usually fabricated on the surface around the chip, and protruding electrodes (bumps) are fabricated on the electrode pads to connect the tips of inner leads and By connecting the tips of beam leads, etc., a semiconductor device equipped with lead wires for external connection is manufactured. Au bumps are used as this kind of protruding electrodes.
Solder bumps are widely used, and the manufacturing process of conventionally used Au bumps will be described first.

In FIG. 1(a), reference numeral 1 denotes a semiconductor substrate into which circuit elements such as transistors and resistors are incorporated using conventionally known semiconductor manufacturing techniques. On the surface of the substrate, there is an AI between circuit elements.
! AI using the chip peripheral area in conjunction with wiring! The electrode pad 2 is formed, and the surface of the substrate is covered with a passivation film 3 except for the pad 20 portion. On the substrate 1 covered with the passivation film 3, Ti or T
A base barrier metal layer 4 made of an i-alloy, followed by a g-layer pass 7 metal layer 5f' made of a noble metal are deposited by sequential vapor deposition.
As shown in the figure (crane), a photoresist 6 is then applied, and a window opening lower is formed at a position corresponding to the electrode pad 2 through a photolithography process. Au bumps 8 are formed thereon, the resist 6 is removed, and the formed Au bumps 8 are removed.
Upper barrier metal layer 5 and base barrier metal layer 4 using as a mask
are sequentially removed by etching to produce a semiconductor device equipped with protruding electrodes 8 as shown in FIG. 1(c).

Here, the two-layer barrier metal layers 4 and 5 are composed of Au bumps 8
And AI! It prevents mutual diffusion with electrode pads 1 and 2, and also prevents At
It is provided to improve the adhesion with the electrode pad 2 and the adhesion with the Au bump 8 by plating. Pt, Au, and Pt are combinations of barrier metal materials suitable for this purpose.
An example is a combination of two or three layers of a noble metal such as d and Ti or a Ti alloy.

Especially when Au is used as the protruding electrode,
',,'4 The noble metal of the upper layer L-5 barrier metal is an indispensable layer in forming the barrier metal layer because it improves the adhesion with the metal layer and the metallization property. However, commonly used Pt
, AujPd, and the like have excellent acid resistance and alkali resistance, and on the other hand, such properties become an obstacle in the manufacturing process of semiconductor devices. That is, unnecessary portions of the base barrier metal and noble metal deposited over the surface of the semiconductor substrate must be removed, except for the portions that will become barrier metal regions for the protruding electrodes. However, due to the above-mentioned properties, it is extremely difficult to chemically remove precious metals by etching them. A dry etching method is used.

However, in the former type of chemical etching, the etchant penetrates through the thin part of the step part, the pinhole part of the film, the interface of the bump part, etc. before the precious metal is completely removed.
The Al electrode pads 2 and wiring provided on the lowest layer are eroded, causing disconnection and poor contact.

The problem was that it was long and the work efficiency was extremely low.

The present invention has been made in view of the problems in the process of manufacturing protruding electrodes in the conventional semiconductor device rltK, and the present invention will now be described with reference to Examples.

To summarize the present invention, the upper part of the barrier metal layer is composed of a comparatively thin noble metal layer, and after the conductor serving as the protruding electrode is fabricated, the underlying barrier metal of the F layer is etched with the noble metal layer remaining. , and then remove unnecessary noble metal parts floating from the substrate surface.

In FIG. 2(a), the surface of the semiconductor substrate l is coated with AI! as in the conventional process described above. The electrode pad 2 is formed and covered with a passivation film 3, and Ti for barrier metal is formed on the passivation film 3 and the electrode pad 2.
Or base metal layer 4 made of Ti alloy and Au s P
A noble metal layer 9 made of Pd or Pd is formed. In particular, the noble metal layer 9 is formed to have a thickness of xoooX or less, preferably 700 Å or less. The thin film can be formed by controlling the time during vapor deposition so that the thickness is less than 100A, or by dry etching a relatively thick noble metal film with plasma or by chemically etching it with an aqua regia-based etchant. This can be obtained by reducing the thickness to 1000 Å or less.

The substrate surface covered with the thin noble metal film 9 is shown in FIG.
) After a photoresist 6 is applied and patterned by photolithography, Au plating for the protruding electrodes 8 is performed, and electrodes continuous to the noble metal layer 9 are formed. Next, the unnecessary resist 6 is removed to obtain the substrate surface shown in FIG.
The substrate surface is exposed to a solution of Hlo, an alloy etchant. Since the noble metal layer 9 is formed thin in advance as described above, it contains many defects such as pinholes and step parts, and the etchant penetrates through these parts and etches the underlying barrier metal 4. be exposed. The etching solution for removing the underlying barrier metal 4 is as follows:
The etching speed for A7 K is extremely slow, and AI! is rarely eroded.

As a result of the progress of etching of the underlying barrier metal layer 4, the noble metal layer 9 becomes floating from the substrate surface except for the bonding at the electrode pad portion, as shown in FIG. 2(d). In this state, the substrate 1 is then subjected to ultrasonic cleaning in a solvent.

During the ultrasonic cleaning process, the noble metal layer portion from which the underlying barrier metal was removed was physically peeled off, and as shown in Figure 2, unnecessary barrier metal portions were removed. Obtain a semiconductor device. Usually, a step is formed in the deposited barrier metal layer at the electrode pad portion, so that it can be easily removed by applying the ultrasonic waves.

Removal of the noble metal layer 9 using ultrasonic waves has no risk of damaging the Al electrodes and wiring, compared to conventional etching, and is also possible since they have already been produced. The amount of Au protruding electrodes to be etched is also small, and the influence on other parts can be significantly reduced. In addition, the above-mentioned cleaning process also has a cleaning effect because the water that has adhered up to the previous process is replaced with alcohol.

Although the barrier metal layer according to the present invention is thinner than that of the noble metal layer produced through the conventional process, it has no effect on the effect of bonding the At electrode pad and the Au protruding electrode portion. There are many obstacles.

As described above, according to the present invention, in a semiconductor device in which a protruding electrode is formed through a barrier layer, the upper noble metal layer of the barrier metal layer is formed to have a relatively thin thickness of 1 cm, and the underlying barrier metal layer is formed with the noble metal layer remaining. By etching, the unnecessary precious metal layer can be easily removed, and the reliability and yield of semiconductor devices can be significantly improved without damaging the Al wiring by harsh etching solutions or the like. Furthermore, there is no need to use a highly dangerous etching solution during the manufacturing process, making processing easier.

[Brief explanation of the drawing]

FIGS. 1(a) to (c) are cross-sectional views showing conventional manufacturing processes;
FIGS. 2(a) to 2(e) are cross-sectional views showing embodiments of the present invention. 1: Semiconductor substrate, 2: At electrode pad, 4: Base barrier metal, 9: Prize MW, 8: Projection electrode. Agent Patent Attorney Aihiko Fukushi (2 others) 1\1) N-False\. 258-

Claims (1)

[Claims] L. In a method for manufacturing a semiconductor device in which a protruding electrode is formed on an electrode pad on a chip through a multilayer barrier metal layer whose upper layer is a noble metal, a protruding electrode is formed on an underlying barrier metal layer.
A process of depositing a noble metal film with a thin film thickness of 00λ or less, a process of depositing a conductor for a protruding electrode on the noble metal film, and etching the base barrier metal layer using the conductor as a mask and leaving the upper noble metal layer. a step of removing;
1. A method for manufacturing a semiconductor device, comprising the step of physically removing an upper noble metal floating and remaining from a base barrier metal layer.