JPS60113944A - Semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE:To enable to avoid a conductive layer from being damaged when apertures are formed in an IC in a structure, wherein the conductive layer is coated on the surface of the semiconductor substrate, the conductive layer is covered with an insulating film and a protective film, the apertures are formed, and the conductive layer is made to expose, by a method wherein a stopper layer consisting of a material, which is strong for each etching liquid or gas for the insulating film and the protective film, is readily provided between the conductive layer and the insulating film. CONSTITUTION:A field insulating film 2 is coated on an Si substrate 1, a polycrystalline Si layer 3, which is used for a fuse, etc., is deposited thereon and cutting parts 3a for using as a fuse respectively are formed at parts, where intersect orthogonally to the longitudinal direction of the layer 3. For forming the cutting parts 3a, an SiO2 interlayer oxide film 4 and an Si3N4 film 4 are laminatedly coated on the Si layer 3, a PSG film 6 is formed on the whole surface including the layer 3 and the films 4 and 5, and an aperture 6a is bored in the PSG film 6 corresponding to the cutting parts 3a. Following that, an SiO passivation film 7 is coated on the whole surface, an aperture 7 a is again bored, and the film 5 made to expose is removed using CF4+O2 gas, and furthermore, the film 4 is also removed using mixed liquid of HF and NH4F.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to semiconductor integration technology, and relates to a technology that is effective when used, for example, in forming a fuse opening in a semiconductor device.

[Background Art] For example, in a semiconductor memory device such as a 256-bit dynamic RAM (random access memory), the yield of chips is improved by switching a memory column containing a defective bit in the memory array with a spare memory column. Redundant circuits are sometimes provided to improve performance.

In order to switch to this redundant circuit, a fuse made of polysilicon or the like is formed on the main surface of the semiconductor substrate through an insulating film such as a silicon oxide film, and depending on whether or not this fuse is blown, the switching to the redundant circuit is performed. It is proposed to perform a switching setting.

In this case, the fuse can be blown by applying a voltage of about 20 V to both ends to cause an overcurrent to flow, or by irradiating it with a laser.

By the way, in the current semiconductor manufacturing technology, SiO□ is finally deposited on the surface of the substrate by plasma deposition, etc.
A film-like passivation film is formed. Therefore,
As mentioned above, in a semiconductor integrated circuit having a fuse, after forming a passivation film, a hole is made in the part of the fuse, and a current is applied to the fuse to break it and scatter it, causing it to be scattered by the surrounding passivation film. It is necessary to protect circuit elements etc. from the material of the fuse.

However, as mentioned above, the fuse is formed using polysilicon, and the PSG film (phosphorus silicon
When a passivation film such as a glass film) or a SiO film is formed by plasma deposition, freon (CF
4) If windows are opened in the PSG film and passivation film by dry etching using gas, C2F6 gas, etc., the polysilicon fuses will also be damaged by the etching gas, and fuses that do not need to be cut will deteriorate. It was found that this caused some inconveniences, such as

Therefore, we prepared a molyb silicide (MOS) film on the polysilicon fuse as a stopper when etching the PSG film.
i2) A two-layer stopper layer consisting of a polysilicon layer and a polysilicon layer, and an aluminum layer that is resistant to Freon gas are formed. Using this aluminum layer as a stopper, a window in the passivation film is etched, and a molybsilicide layer is used as a stopper to open a window in the passivation film.
The present inventors have developed a method of opening a window in the SG film without damaging the polysilicon fuse.

However, when the fuse opening is structured as described above, the stopper layer must be provided in two layers.
The structure is complicated, and each stopper layer must be etched separately, making the process complicated. In addition, the etching solution for the aluminum layer, which serves as a stopper, is difficult to penetrate into the opening with a relatively small area, so there is a risk that the aluminum layer cannot be etched sufficiently. Glabella oxide film (S
It has been found that because the selectivity to iO2) is small, there is a risk that the underlying polysilicon fuse may also be damaged.

[Object of the Invention] An object of the present invention is to provide a semiconductor integration technology that has remarkable effects not seen before.

Another object of the present invention is to prevent the fuse from being damaged by etching when forming an opening for exposing the fuse cutting portion by a simple process change when applied to a technology for forming fuses in semiconductor integrated circuits, for example. It is to make it.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the Invention] Representative inventions disclosed in this application will be summarized as follows.

That is, the present invention provides a semiconductor integrated circuit in which, for example, a polysilicon fuse is formed on the main surface of a semiconductor substrate via an insulating film, and a PSG film and a passivation film are formed on the polysilicon fuse. A T1 to Ride film is provided between the film and the insulating film.
-By using the Ride film as a common stopper layer when opening the window for the PSG film and the passivation film, it is possible to protect the polysilicon fuse from etching when opening the window just by providing one stopper layer. This aims to achieve the above purpose of

[Embodiment] FIGS. 1 to 5 show an embodiment in which the present invention is applied to forming a polysilicon fuse on the main surface of a substrate in a semiconductor integrated circuit, together with a process.

In this embodiment, polysilicon is deposited onto a field oxide film 2 formed by thermal oxidation on the main surface of a single semiconductor substrate 1 such as a silicon chip, and then photoetched to form a field oxide film 2 as shown in FIG. Then, a polysilicon fuse 3 having a relatively narrow cut portion 3a in the center is formed (FIG. 2).

Then, the surface of this polysilicon fuse 3 is thermally oxidized to form a thin interlayer oxide film 4, and then a T1 to Ride film (Si3N
4) is deposited and unnecessary portions are removed by photo-etching to form a T1-ride film 5 on the interlayer oxide film 4 on the surface of the polysilicon fuse 3 so as to cover the cut portion 3a.

Then, a PSG film 6 which will become an interlayer insulating film is placed on top of it by CVD.
Deposition is performed by method D (chemical vapor deposition method). Next, dry etching is performed on the PSG film 6 using CHF 3+02 gas to form contact holes at both ends of the fuse 3, and at the same time,
An opening 6a is formed in the center of the fuse (FIG. 3).

Thereafter, aluminum is deposited on the entire surface of the PSG film 6, and then photoetched to form aluminum wiring (not shown). Then, after forming a passivation film 7 such as a silicon nitride film (SIO film) on the entire surface by plasma deposition, dry etching using C2F6 gas is performed to remove the cut portion 3a at the center of the fuse 3.
An opening 7a is formed in the passivation film 7 so as to expose it, resulting in the state shown in FIG.

After that, oxygen was added to the Freon gas (CF4+02
) The nitride film 5 on the glabellar oxide film 4 on the surface of the polysilicon fuse 3 is removed using gas.

Next, hydrofluoric acid (HF) and ammonium fluoride (NH4F)
By performing etching with an aqueous solution called buffered hydrofluoric acid, which is a mixture of As shown in the figure, the cut portion 3a of the polysilicon fuse 3 is exposed.

According to the above embodiment, the nitride film 5 formed by plasma deposition serves as a stopper when forming the opening 6a in the PSG film 6 by dry etching using CHF3+02 gas, and also serves as a stopper when forming the opening 6a in the PSG film 6 by dry etching using CHF3+02 gas. It also serves as a stopper when forming the opening 7a in the passivation film 7 by dry etching.
Even if the polysilicon fuse 3 is thin, there is no risk of damage to the polysilicon fuse 3. That is, in the above embodiment, the nitride film 5 serves as a common stopper for the etching of the PSG film 6 and the passivation film 7.

Moreover, the etching rate of the silicon nitride film with (CF4+02) gas is more than 5 to 6 times faster than that of the interlayer oxide film (Si02 film), so when dry etching the nitride film 5 with (CF4+02) gas, Also, the thin interlayer oxide film 4 is not destroyed and the underlying polysilicon fuse 3 is not damaged.

As a result, the structure of the polysilicon fuse opening becomes simple, and damage to the polysilicon fuse during the opening can be prevented with only slight changes in the process.

Regarding the process of the dynamic RAM mentioned above, the electrode of the capacitor for storing information charges is formed in the first layer of polysilicon, and the wiring of the first layer is formed in the second layer of polysilicon. Two-layer polysilicon technology has already been proposed by the applicant. Therefore, in such a dynamic RAM, the structure and process of the above embodiment are applied to the fuse for switching and setting the redundant circuit, and the polysilicon fuse 3 is formed simultaneously with the formation of the first polysilicon layer, and the wiring In order to insulate from the second polysilicon layer, the surface of the first polysilicon layer is thermally oxidized to form an interlayer oxide film 4, and then a nitride film 5 is formed by plasma deposition.
form. If the opening 6a of the PSG film 6 is formed at the same time as the contact hole of the aluminum wiring is formed, the polysilicon fuse having the excellent structure as described above can be used as a dynamic RAM without changing the process. It can be provided on a semiconductor substrate on which a semiconductor substrate is formed.

However, the polysilicon fuse 3 can also be formed from a second polysilicon layer instead of the first layer. In that case, since it is not necessary to form an oxide film for insulation on the surface of the second polysilicon layer, a structure can be obtained in which the interlayer oxide film 4 in FIG. 4 is omitted.

Even in this case, there is no problem because the etching gas (CF4+02) for removing the nitride film 5 has a high selectivity to polysilicon.

Note that in the above embodiment, due to the relationship between the etching gas for the PSG film as the insulating film 6 formed on the polysilicon fuse 3 and the etching gas for the SiC film as the passivation film 7, plasma is applied to the film 1 as a brim layer. Although a deposited T-Ride film 5 is used, it goes without saying that if the insulating film, passivation film, or etching gas is changed, the material of the stopper layer can be changed accordingly.

[Effect] In a semiconductor integrated circuit in which a polysilicon fuse is formed on the main surface of a semiconductor substrate via an insulating film, and an insulating film and a passivation film are formed on the polysilicon fuse,
Since a nitride film is provided between the polysilicon fuse and the insulating film, this nitride film serves as a common stopper layer when opening windows in the insulating film and passivation film, and also serves as a common stopper layer for forming windows between the insulating film and the passivation film. Due to the effect of increasing the etching rate difference between the film etching gas stopper layer and the polysilicon fuse,
A simple process change has the advantage of protecting the polysilicon fuse from etching during window opening.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, in the above embodiments, the fuse was made of polysilicon.

It can also be applied when the fuse is formed of a conductor made of aluminum or the like.

[Field of Application] In the above explanation, the invention made by the present inventor will mainly be explained in terms of the field of application, which is the background of the invention, which is dynamic RAM.
Although the present invention has been described as being applied to a technique for forming a fuse opening in , it is not limited thereto, and can also be applied to, for example, a technique for forming an electrode such as a bonding pad having an opening in a semiconductor integrated circuit.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the shape of a fuse formed on the whole surface of a semiconductor substrate, and FIGS. 2 to 5 are examples of the structure of a fuse opening and its manufacturing method according to the present invention. FIG. 2 is a sectional view taken along line A-A in FIG. 1, showing the steps in order of knee distance. 1... Semiconductor substrate, 2... Insulating film (field oxide film), 3... Conductive layer (fuse), 3a...
・Cut section, 4... Interlayer oxide film, 5... Stopper layer (nitride film), 6... Insulating film (PSG film)
, 7... passivation film, 6a, 7a... opening. Figure 1 A = Figure 2 Figure 3 Figure a Figure 4 Figure 5

Claims (1)

[Claims] 1. A semiconductor in which an insulating film and a protective film are formed on a conductive layer formed on one main surface of a semiconductor substrate, and an opening is formed above the conductive layer. In integrated circuit devices,
A semiconductor integrated circuit device characterized in that a stopper layer made of a material resistant to both the etching solution or the etching gas of each of the insulating film and the protective film is formed between the conductive layer and the insulating film. . 2. The conductive layer is a polysilicon fuse, the insulating film is a phosphorus silicon glass film, and the protective film is a silicon oxide film, and the stopper layer is made of a nitride film formed by plasma deposition. A semiconductor integrated circuit device according to claim 1, characterized in that: 3. The semiconductor integrated circuit device according to claim 1 or 2, wherein the fuse is formed from the first layer of polysilicon in a dynamic RAM employing two-layer polysilicon technology.