JPS6195556A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve reliability and prevent deterioration in element characteristic through suppression of generation of cracks in protection film by forming said protection to be formed on a metal wiring layer in such a manner that the characteristic changes in the thickness direction. CONSTITUTION:A protection film 8 is given the structure that concentration of phosphorus (a) contained changes in the direction of thickness. For example, the minimum phosphorus concentration is set to about 0.5mol% and the maxi mum concentration is set to 6mol%. Such constitution can be attained, for example, on the occasion of forming the protection film 8 by the CVD method, the concentration of PH3 gas to be mixed to the SiH4 gas is changed continuous ly with the time. It is desirable that the phosphorus concentration (a) changes at least in a period in the direction of thickness. Thereby, since the protection film 8 has the structure that PSG thin films in different phosphorus concentrations are integrally formed in multilayer structure, the film as a whole has the structure that the soft portion by high phosphorus concentration and the hard portion by low phosphorus concentration are integrated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a semiconductor device, and particularly to a semiconductor device in which a protective film for metal wiring is improved.

[Background technology]

2. Description of the Related Art In semiconductor devices such as ICs and LSIs, a metal wiring layer 1 (usually a metal wiring layer) is used to electrically connect between elements formed on the main surface of a semiconductor substrate and between electrode pads for external connection. In order to protect this Al wiring layer from external moisture, heat, external force, etc., 7-inch aluminum wiring layer is placed on the A-e wiring layer. A protective film called phosphor is formed, and Si glass containing phosphorus, that is, a PSG film is generally used.

By the way, the present inventors conducted various studies regarding this protective film, and found that in semiconductor devices that had undergone thermal history, many cracks occurred in the protective film, and through these cracks, moisture (moisture), air, etc. It has become clear that accidents that degrade the reliability of semiconductor devices, such as penetrating layers and corroding them, are likely to occur. The cause of this crack is the thermal expansion of the A2 wiring layer due to thermal history.
It is thought that when the PSG film contracts, it is unable to follow it due to the difference in coefficient of thermal expansion, and the internal stress generated based on this difference causes cracks to occur in the PSG film.

, -, the present inventors examined the properties of the PSG film without changing the requirements related to the PSG film.

It was found that when the concentration of phosphorus contained is low, it becomes hard, and when the degree of phosphorus is increased, it becomes flexible. It has also been found that the characteristics change by changing the production rate. Based on this result, we examined the reliability of a protective film with a uniform quality, and found that when the phosphorus concentration of a PSG film changes, increasing the phosphorus concentration reduces the occurrence of cracks; It has been found that a large amount of phosphorus is eluted by moisture and becomes phosphoric acid, which may corrode the A2 pad (wire bonding opening). Incidentally, a column describing the insulating film forming technology in detail is ``Micro Devices,'' published by Nikkei McGraw-Hill, Inc., 8mura Electronics Special Edition, August 22, 1980, P, 124-P, ]28.

[Purpose of the invention]

An object of the present invention is to provide a semiconductor device that suppresses the occurrence of cracks in a protective film, improves reliability, and does not cause deterioration of device characteristics.

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

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, by configuring the protective film formed on the metal wiring layer so that its characteristics change in the thickness direction, cracks in the protective film due to deformation of the metal wiring layer can be prevented by the overall effect of the combination of each characteristic. The aim is to prevent this and improve reliability.

[Embodiment 1] FIG. 1 shows an example in which the present invention is applied to an MO8 type semiconductor device, in which a field oxide film 2.
A gate oxide film 3 is formed, and a gate electrode 4 is formed thereon. In addition, impurities (such as arsenic) are diffused on the main surface to form source/drain regions 5.5, which together with the gate electrode 4 constitute a MOS transistor. An interlayer insulating film 6 such as a silicon oxide film is formed on the gate electrode or source/drain region 5.5, and then the source/drain region 5.5 is formed.
Through holes are formed in the drain regions 5, 5, and A is formed here.
Two wiring layers 7.7 are formed to electrically connect the MOS transistors. Then, a protective film (panosivation film) 8 made of KPSG is formed over the entire surface to cover the A2 wiring 11 7.

This protective film 8 has a structure in which the concentration of phosphorus contained in 5IC1 is varied in the thickness direction, as shown schematically with a characteristic diagram of a part of the second pressure. Phosphorus concentration is at least 0.5m
The range is about 1%, maximum is 6mo1%, and in this example, it is 0 with a periodic rate of change (θ degree/R degree) similar to a sine wave curve.
The degree is changing.

Such a configuration is such that, for example, when forming the protective film 8 by the CVD method, the pH is mixed with the S i H4 gas.

It is sufficient to continuously change the gas concentration (supply meter) as the day progresses. Note that it is preferable to configure the structure so that the change in phosphorus concentration is small (in one cycle in each direction).

According to the above configuration, the protective film 8 is made of PS with different phosphorus concentrations.
Since the G thin film is made up of multiple layers and an integral structure, the film as a whole has a structure in which a flexible part due to a high phosphorus concentration and a stiff part due to a low phosphorus concentration are integrated. . Therefore, even if the lower A2 wiring layer 7 is thermally expanded or contracted, this deformation is absorbed by the flexibility of the high phosphorus concentration, or a small deformation force is suppressed by the hardness of the low phosphorus concentration, thereby restraining the deformation. As a result, internal stress in the protective film 8 is suppressed, the occurrence of cranks is suppressed, and reliability is improved.

In addition, since the phosphorus concentration (average concentration) of the protective film 8 as a whole can be suppressed to the same level or lower than that of the conventional method, it does not adversely affect the device.

[Embodiment 2] FIG. 3 is a diagram showing the main parts of another embodiment of the present invention together with its characteristics. As schematically shown in the same figure, this protective film 8A changes the 0 degree phosphorus of PSG to an inclined state,
As a result, the protective film 8A has a configuration in which the concentration changes not only in the thickness direction but also in the planar direction. For example, as shown in FIG.
Nozzles 1 with different pH and gas ejection amount are installed in the upper part of the inside of O.
1a to lli are arranged side by side, and the movable table 1 is placed in this lower position.
The silicon substrate 1 placed on the table 12 can be formed by CVD film formation without moving in one direction. Various concentration distributions can be obtained by returning the book etc.

In this embodiment as well, the lower layer AJ? Deformation of the wiring layer 7 can be absorbed or restrained by the phosphorus concentration characteristics, and in particular, in this example, it is absorbed not only in the thickness direction but also in the planar direction.

Since the restraint can be performed, the occurrence of cracks can be more effectively suppressed.

〔effect〕

(f) Since the phosphorus concentration of the protective film made of PSG is changed in the thickness direction to change the characteristics in the thickness direction, deformation in the F2 wiring layer can be absorbed in the flexible part and suppressed in the hard part. This prevents the generation of internal stress in the protective film, inhibits the generation of cracks, and improves reliability.

(2) Since the phosphorus concentration is changed not only in the thickness direction but also in the plane direction, it can effectively absorb and restrain the plane of the wiring layer, increasing the effect of suppressing cracks. Be able to do that.

(3) Since the phosphorus concentration is varied between the highest and lowest levels, the phosphorus content of the protective film as a whole can be suppressed, and the adhesive etc. will not deteriorate.

Although the invention made by the present inventor has been specifically explained above based on examples, it is understood that the present invention is not limited to the above-mentioned examples, and that various changes can be made without departing from the gist of the invention. Not even 5. For example, the phosphorus concentration may be changed stepwise in the thickness direction or in the planar direction.

[Application field]

In the above explanation, the invention made by the present inventor is mainly applied to a PSG film of an MQS type semiconductor device, which is the background field of application. It can also be applied to type semiconductor devices. In addition, not only PSG but also plasma Si
It can also be applied to six films of xNy and plasma 5ixOy, and the 0 degrees of these N and O can be changed. Furthermore, in addition to changing the concentration of the film, the rate of film formation can also be changed.
The properties of the membrane may also be altered.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment to which the present invention is applied, FIG. 2 is a schematic diagram showing an enlarged view of the main part along with its characteristics, and FIG. 3 is a diagram similar to FIG. 2 of another embodiment. FIG. 4 is a schematic diagram of an apparatus for explaining the manufacturing method of the structure of the embodiment shown in FIG. 1...Silicon substrate, 4...Gate electrode, 5...Source/drain region, 6...Interlayer insulating film, 7...People! Wiring layer, 8.8A Protective film, IO-・chamber, lla~
lli...nozzle, 12...movable table. Agent 9F Burial Officer Akio Takahashi 1-・No.
1 Figure 2? /′

Claims (1)

[Claims] 1. A semiconductor device comprising a protective film formed on a metal wiring layer such as Al, characterized in that the characteristics of the protective film are varied in the direction of its thickness. Device. 2. The semiconductor device according to claim 1, wherein the characteristics are also changed in the plane direction. 3. The semiconductor device according to claim 1 or 2, wherein the protective film is Si glass containing phosphorus, and the concentration of phosphorus is varied. 4. The semiconductor device according to any one of claims 1 to 3, wherein the protective film is formed at a rate of change.