JPH04255252A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a protective film formation method through which a protective film is formed on a cover insulating film which coats a chip, where the protective film can be deposited equally in thickness throughout a wafer and devices, and especially an opening provided to the protective film at a bonding pad uniform in size and stable in shape can be formed. CONSTITUTION:A first process in which a bonding pad 4 of conductive film is formed on a semiconductor substrate 1, a second process in which a cover insulating film 5 is deposited on the substrate 1 covering the bonding pad 4, a third process in which a bonding pad window is provided to the cover insulating film 5 to enable the surface of the bonding pad 4 to be exposed, a fourth process in which a spin-on-glass film 8 is applied onto the substrate 1 to flatten the surface of the substrate 1, a fifth process in which a polyimide film 6 is deposited on the substrate 1, and a sixth process in which an opening is bored in the polyimide film 6 and the spin-on-glass film 8 above the bonding pad window are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a protective film on a cover insulating film coated on a chip.

In recent years, in order to improve the reliability of semiconductor devices by protecting the chip surface and improving moisture resistance, it has become necessary to cover the conventional cover insulating film with a polyimide film as a protective film.

The present invention meets this need and can be used to form a stable protective film, particularly in bonding pad areas.

0004

[Prior Art] In conventional examples, the difference in the thickness of the polyimide film at the bonding pad portion between two-layer aluminum (Al) wiring and three-layer aluminum wiring is about 1.5 to 2 μm.
When trying to dissolve the polyimide film to expose the pad, it was not possible to dissolve it within the same dissolution time.

Furthermore, even within the same wafer, the polyimide film is 2 μm thicker on the scribe line than on the bonding pad.
When the polyimide film on the bonding pad is melted and removed to a regular size, a polyimide film with a thickness of 2 μm remains on the scribe line.

On the other hand, if an attempt is made to completely dissolve the polyimide film on the scribe line, the size of the opening on the bonding pad will increase by about 2 μm and the shape will become distorted. FIGS. 2A and 2B are cross-sectional views illustrating a conventional example.

In FIG. 2(A), 1 is silicon (S
i) Wafer, 2 is the first layer Al wiring, 3 is the interlayer insulating film, which is a phosphosilicate glass (PSG) film, 4 is the second layer Al wiring, 5 is the cover insulating film, which is a PSG film, and 6 is the protective film, which is a polyimide film. , 7 are resist films for pad window openings.

[0008] Here, the Al wirings 2 and 4 are bonding pads. A pad window is opened in the PSG film 5 using ordinary lithography, and the surface of the second layer Al wiring 4 is exposed. A polyimide film 6 is spin-coated thereon.

A resist film 7 is deposited thereon, and the bonding pad portion is exposed by projection exposure or contact exposure. In FIG. 2B, after exposure, the resist film 7 at the pad window opening is dissolved with an alkaline developer, and the polyimide film 6 is also dissolved with the same developer.

At this time, the coating thickness of the polyimide film 6 on the bonding pad portion is thicker than that on the cover PSG film 5, and the dissolution time of the polyimide film 6 changes each time the number of layers of the multilayer wiring changes. .

Furthermore, as described above, the polyimide film 6 remains in deep parts such as scribe lines.

0012

[Problems to be Solved by the Invention] Therefore, it is necessary to deposit a polyimide film with the same thickness within the wafer and between different types of devices.

The purpose of the present invention is to enable a protective film to be deposited with the same thickness within a wafer and between different types of wafers, and in particular to stabilize the opening dimensions and shape of the protective film in the bonding pad area. do.

[0014]

[Means for Solving the Problem] The above problem is solved by forming a bonding pad (4) made of a conductive film on a semiconductor substrate (1), and forming the bonding pad (4) on a semiconductor substrate (1).
a step of depositing a cover insulating film (5) on the substrate, a step of opening a bonding pad window in the cover insulating film (5) to expose the surface of the bonding pad (4); A spin-on glass film (8
) to planarize the surface of the substrate, and then depositing a polyimide film (6) on the substrate.
This is achieved by a method for manufacturing a semiconductor device characterized by comprising a step of opening the polyimide film (6) on the bonding pad window and the spin-on glass film (8).

[0015]

[Operation] The present invention makes the etching conditions of the polyimide film uniform on the wafer by applying the polyimide film to a uniform thickness on the substrate after flattening the SOG film by spin coating.

As a result, the bonding pad window can be opened with high precision, and the polyimide film can be etched without leaving residues on deep parts of the substrate such as scribe lines.

The combination of the SOG film and the polyimide film was adopted after confirming that there was no problem in terms of reliability and moisture resistance, and that it was no different from the conventional case of using a polyimide film alone. Note that it is more effective if the thickness of the SOG film on the flat part is as thin as possible.

[0018]

Embodiment FIGS. 1A and 1B are cross-sectional views illustrating an embodiment of the present invention. In Fig. 1(A), 1 is a Si wafer, 2 is a first layer Al wiring with a thickness of 4000 Å,
3 is an interlayer insulating film, which is a 1 μm thick PSG film, 4 is a 7000 Å thick second layer Al wiring, 5 is a cover insulating film, which is a 1 μm thick PSG film, 6 is a protective film, which is a 1 μm thick polyimide film, 7 is a resist film with a thickness of 4 μm for pad window opening, and 8 is a flattening film made of spin-on glass (SOG).
It is a membrane.

Here, the Al wirings 2 and 4 are bonding pads. A pad window is opened in the PSG film 5 using ordinary lithography, and the surface of the second layer Al wiring 4 is exposed. On top of that, an SO layer with a thickness of 3000 Å is formed on the cover insulating film 5.
G film 8 is spin coated and the substrate surface is flattened.

Further, a resist film 7 is deposited thereon, and the bonding pad portion is exposed by projection exposure or contact exposure. In FIG. 2B, after exposure, the resist film 7 at the pad window opening is dissolved with an alkaline developer, and the polyimide film 6 is also dissolved with the same developer.

Next, using the resist film 7 remaining after development as a mask, CF4/CHF3/O2 (100/100
SOG film 8 is opened by performing quasi-anisotropic etching using a gas of /50 SCCM), and then resist film 7 is removed by O2 plasma ashing.

FIG. 2C shows the pad portion in which the polyimide film 6 and the SOG film 8 have been opened through the above steps.

[0023]

[Effects of the invention] The protective film can now be deposited with the same thickness within the wafer and between different types, and the protective film can now be etched stably without leaving any residue deep on the wafer. Ta.

[0024] In particular, the uniformity of the opening size and the stability of the shape of the protective film in the bonding pad portion were achieved. As a result, it became possible to form a stable protective film with excellent moisture resistance on the chip, contributing to improved reliability of semiconductor devices.

[Brief explanation of the drawing]

[Fig. 1] Cross-sectional view explaining one embodiment of the present invention

[Figure 2
] Cross-sectional view explaining a conventional example

[Explanation of symbols]

1 Si wafer 2 1st layer Al wiring 3. PSG film as interlayer insulation film 4 2nd layer Al wiring 5 PSG film as cover insulating film 6 Polyimide film as a protective film 7 Resist film 8 SOG film with flattening film

Claims (1)

[Claims] 1. A step of forming a bonding pad (4) made of a conductive film on a semiconductor substrate (1), and depositing a cover insulating film (5) on the substrate to cover the bonding pad (4). a step of opening a bonding pad window in the cover insulating film (5) to expose the surface of the bonding pad (4), and then applying a spin-on glass film (8) on the substrate to form a bonding pad window on the substrate. A step of flattening the surface and then depositing a polyimide film (6) on the substrate.
A method for manufacturing a semiconductor device, comprising the steps of: depositing a polyimide film (6) on the bonding pad window and opening the spin-on glass film (8).