JPH0637113A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the electric characteristics of a semiconductor device by preventing the occurrence of a defect caused by cracks by selectively injecting hydrogen into the active layer of the MOS element of the semiconductor device by effectively masking hydrogen irradiation while the occurrence of cracks due to the difference in coefficient of thermal expansion between a mask and its substrate is suppressed. CONSTITUTION:A semiconductor device which has good electric characteristics and in which no defect is generated is manufactured by selectively performing hydrogen passivation only on an MOS element in a required area by using a mask 8 composed of an SiOxNy film and preventing the occurrence of defects, such as cracks, etc., in the interlayer insulating layer 5 which is the substrate of the mask 8, PSG film 7, etc.

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 hydrogen-passivating an active layer to terminate its dangling bond with hydrogen.

[0002]

2. Description of the Related Art In recent years, a technique for manufacturing a semiconductor device in which an amorphous silicon film or a polycrystalline silicon film is formed as an active layer on an insulating substrate or an insulating layer has been intensively studied.

Such a semiconductor device has a thin film transistor (hereinafter, referred to as a thin film) in order to pursue high integration.
Transistor; abbreviated as TFT) has been studied, and some have begun to use it. For example, a MOS element in a cell portion of SRAM or a cell portion of EPROM is a typical example. Furthermore, the use as a drive circuit element of a liquid crystal display device in which a semiconductor element is formed on an insulating substrate such as quartz or glass has been studied, and it has already been used in part.

However, at present, the characteristics of a MOS element using an amorphous silicon film or a polycrystalline silicon film are worse than the characteristics of an element formed in a single crystal, and various studies have been made to improve the characteristics. For example, low mobility, high threshold voltage, high leakage current, etc. are examples of those having a large adverse effect due to the crystal defect.

As a means for improving the characteristic deterioration due to these crystal defects, particularly in the polycrystalline silicon layer, hydrogen plasma irradiation is performed to terminate the defects, and the dangling bonds are terminated with hydrogen atoms to improve the characteristics. The method of bringing is known.

However, if such hydrogenation (hydrogen passivation) is excessively performed, for example, n-type TF
In the T element, the threshold voltage shifts to the negative side and V _G = 0V
Also in this case, there is a phenomenon that a current flows and the characteristic becomes like a depletion type.

Therefore, in a liquid crystal display device, for example,
Switching TF for applying voltage of pixel portion to liquid crystal in pixel
For the T element, hydrogen passivation is actively performed for the purpose of improving switching characteristics by reducing the drain leak current, and the TFT element of the liquid crystal driving circuit integrally formed on the substrate outside the pixel portion is A manufacturing method of suppressing hydrogen passivation in order to avoid depletion due to excessive passivation has been studied.

As a manufacturing method for selectively performing such plasma treatment, a mask is provided on a portion where hydrogen passivation is to be suppressed while avoiding a portion where hydrogen passivation should be positively performed, and is covered with the mask. A method of introducing hydrogen into a non-existing part can be considered. The mask used at this time has good masking properties against hydrogen plasma irradiation, good process consistency, and can be easily processed by conventional semiconductor-related film formation techniques such as film formation and patterning, and its film peeling. It goes without saying that what can be done is preferable.

In the region where the dangling bond is terminated by introducing hydrogen from the window which is not covered with the mask, it is necessary to form the dangling bond by a low temperature process to the extent that hydrogen is not released. Under such circumstances, it has been confirmed that, for example, a SiN _x film that can be formed at a relatively low temperature has good mask characteristics against hydrogen plasma irradiation.

However, the SiN _x film has a hard film quality,
Further, the residual stress may cause a crack called a crack in the underlying SiO ₂ film or the like. The main cause of this is considered to be the difference in the coefficient of thermal expansion. For example, the coefficient of linear expansion of quartz (SiO ₂ ) is 0.4 × 10 ^-6 / ° C.
On the other hand, SiN _x is 4 to 7 × 10 ⁻⁶ / ° C., which is 10 times or more different. Therefore, using the SiN _x film as a mask, SiO
When it is formed on _two films, means for alleviating this difference in linear expansion coefficient is required, but using such means complicates the manufacturing process and also complicates the structure of the semiconductor device. There is a problem of becoming a thing.

[0011]

Thus, in the case of using the conventional SiN _x film as the mask during hydrogen passivation, although the mask characteristics are good,
A crack called a crack is generated due to a difference in thermal expansion coefficient between the SiN _x film of the mask and the underlying layer such as a SiO ₂ film as an underlying layer, and the crack causes a disconnection or a chipped pattern in wiring of a semiconductor device. There was a problem that defects such as poor connection occurred.

The present invention has been made to solve such a problem, and an object thereof is to suppress the occurrence of cracks due to the difference in the coefficient of thermal expansion between the mask and the underlying layer thereof. It is intended to manufacture a semiconductor device having improved electrical characteristics by effectively masking hydrogen irradiation and selectively introducing hydrogen into an active layer of a MOS element of the semiconductor device to avoid generation of defects due to cracks. .

[0013]

A method of manufacturing a semiconductor device according to the present invention comprises a step of forming an active layer from an amorphous silicon film or a polycrystalline silicon film to perform element isolation to form a plurality of MOS elements, and oxygen. A step of arranging a mask made of a silicon nitride layer containing Al so as to avoid a MOS element that performs hydrogen passivation among the plurality of MOS elements; and irradiating the active layers of the plurality of MOS elements with hydrogen plasma to remove hydrogen And a step of performing hydrogen passivation by diffusion.

The silicon nitride film contains 0.1% oxygen.
It is preferable to set the atomic concentration to be 15% or less.

The above-mentioned hydrogen plasma irradiation is conducted at 200 ° C.
It is preferable to carry out the above-mentioned work atmosphere.

[0016]

In the present invention, a SiN _x film containing oxygen as a mask for hydrogen plasma irradiation, that is, a mask made of a SiO _x N _y film having a small residual stress and a sufficient masking effect for hydrogen, is formed by hydrogen passivation. Are masked by arranging them in a region where the masking is not performed, and the active layer of the MOS element in the region not covered by this mask is irradiated with hydrogen plasma for hydrogen passivation.

In this way, hydrogen mask passivation is selectively applied only to the MOS elements in the necessary regions by using the mask made of SiO _x N _y film, and at the same time, the underlying film of the mask is not cracked. Thus, it is possible to manufacture a semiconductor device having good electric characteristics and avoiding the occurrence of defects.

The mask according to the present invention consists SiO _x N _y film, the SiO _x N _y film, mask characteristic against hydrogen is like a normal the SiN _x film good and normal the SiN _x film The residual stress is Si because it has a looser bond
Since it is smaller than the N _x film, it can be used as a base Si during the manufacturing process.
It rarely causes cracks and the like in the O ₂ film. As a result, the above-described operation is realized.

However, if the contained oxygen concentration is too high, the mask becomes less effective as a hydrogen barrier, so that the oxygen concentration has an appropriate concentration value.

The inventors of the present invention have studied a film that reduces the difference in expansion coefficient from an underlying layer such as an interlayer insulating layer so as not to generate cracks. As a result, the SiN _x film contains a small amount of oxygen, so-called SiO _x N. It was confirmed that it was effective to form a _y- film and use this film as a mask for hydrogen passivation. Furthermore, we tried film formation while changing the oxygen partial pressure, and examined what kind of oxygen partial pressure shows good mask characteristics against hydrogen passivation. Moreover, the relationship between the optimum oxygen concentration and the barrier effect against hydrogen was examined. As a result, the oxygen concentration is 0.1% or more 15
It was confirmed that the atomic concentration of not more than% was suitable.

Further, the present inventors have confirmed that the hydrogen passivation can be performed more effectively if the hydrogen plasma irradiation at the time of hydrogen passivation is performed in a working atmosphere of 200 ° C. or higher.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the manufacturing method of the present invention will be described in detail below with reference to the drawings.

In describing a method of manufacturing a TFT semiconductor device, as a typical example thereof, in this embodiment, a liquid crystal display formed by arraying a plurality of MOS elements formed on a transparent insulating substrate such as a quartz substrate. The semiconductor device for the device was adopted.

First, the structure of a semiconductor device manufactured by the manufacturing method of the present invention will be described. In the portion of the MOS device exposed by avoiding the mask 8 made of the SiO _x N _y film, which is a mask at the time of hydrogen passivation, and exposed to hydrogen plasma to introduce and diffuse hydrogen into the active layer 2, As shown in FIG. 1 (a), an active layer 2 having an element-isolated shape is arranged on a quartz substrate 1, a gate insulating layer 3 is formed so as to cover the active layer 2, and phosphorus is deposited on the active layer 2. A gate electrode 4 made of polycrystalline silicon added to have low resistance is formed, and an interlayer insulating layer 5 made of a silicon oxide film is formed thereon. Then, a contact hole for making contact with the source and drain of the active layer 2 is formed, an Al film containing 0.5% of Si is formed as the wiring 6 by a sputtering method, and the wiring is formed by patterning. 6 is formed. And PSG film (Phospho-Silicate Glass) for reducing the step difference of the layer structure in the MOS device
7 is arranged so as to cover it.

Then, as shown in FIG. 1B, the portion of the MOS element where it is desired to avoid introducing and diffusing hydrogen into the active layer 2 is temporarily masked with a SiO _x N _y film when irradiated with hydrogen plasma. 8 is arranged as a mask for hydrogen passivation, and the mask 8 made of this SiO _x N _y film serves as a barrier for hydrogen introduction and diffusion to the active layer 2. Its film thickness is 2000 angstroms.

Since the mask 8 made of the SiO _x N _y film is a jig for a mask during hydrogen passivation and does not directly participate in the operation of the semiconductor device, it is peeled off from the MOS element after hydrogen plasma irradiation. However, the mask 8 made of this SiO _x N _y film does not necessarily have to be stripped as in the present embodiment, and if there is no problem in the process alignment of the semiconductor device, it is left as it is without being stripped. Good.

Next, a method of manufacturing the semiconductor device of the present invention will be described.

Amorphous silicon is deposited on the substrate such as the quartz substrate 1 by the LPCVD method, and the amorphous silicon is deposited at a low temperature of about 600.degree.
After solid phase growth was performed for a time to form a polycrystalline silicon layer, element isolation was performed in an island shape to form an active layer 2.

Then, a gate insulating layer 3 is formed by thermal oxidation so as to cover the gate insulating layer 3, and a gate electrode 4 is formed on the gate insulating layer 3 by using polycrystalline silicon having a low resistance by adding P (phosphorus).
Was formed.

After that, self-alignment with the gate insulating layer 3 was performed to ion-implant the active layer 2 at a predetermined position using an ion-implanting device to form a source region and a drain region.

After activation of impurities by high temperature annealing, a low temperature oxide film was formed as an interlayer insulating layer 5 by the CVD method.

After that, a contact hole for making contact with the source and drain wiring 6 is formed, and Si is
A 0.5% Al film was formed by a sputtering method and patterned to form source and drain wirings 6.

Then, a PSG film 7 was deposited in order to reduce the step difference of the layer structure in the MOS device. However, this PSG film can be omitted in view of device characteristics.

Then, SiO is formed by using the plasma CVD method.
After forming a film of _x N _y , this is patterned to form S
A mask 8 made of an iO _x N _y film was formed. The film thickness is 2000
Angstrom.

Plasma CV is used to form this SiO _x N _y film.
The reason why D is used is that it can be formed at a lower temperature than the LPCVD method by thermal decomposition, the film is denser than the sputtering method, and that the film contains hydrogen. The gas used is Si if it is a conventional SiN _x film.
A mixed gas of N ₄ , NH ₃ and H ₂ (diluted with N ₂ ) is used. In the manufacturing method of the present invention, N ₂ O is added to this in a flow rate ratio of NH 3.
2.5 times ₃ was added.

Using the mask 8 made of this SiO _x N _y film as a mask, the hydrogen plasma irradiation to the MOS element was performed for about 1 hour. That is, the SiO _x N _y film is left on the n-channel TFT portion of the MOS element serving as a drive circuit of the liquid crystal display device, and the p-channel portion and the pixel portion switching n-threshold are used as a window portion (opening portion) for plasma irradiation. The top of the channel is removed by dry etching and Si
The O _x N _y film was patterned to form a mask 8 made of a SiO _x N _y film, and hydrogen was applied to the p channel portion and the pixel n channel portion only by hydrogen plasma irradiation. This plasma irradiation is performed with a hydrogen partial pressure of 0.5 to
The heating was performed by placing a heating wire around the vacuum chamber with rr and a power of 150 W and heating the vacuum chamber at a low pressure atmosphere of 270 ° C. for 1 hour.

Thereafter, while heating at 350 ° C., hydrogen is diffused inside the amorphous silicon film of the active layer 2 and then SiO _x N.
_The mask 8 made of the _y film was peeled off.

At this time, in the normal SiN _x film, the base SiO
₂ undergoes cracking, but that would be generated and permeation during subsequent chemical processing corrode wiring of the signal lines or the like made of Al or Cr is confirmed, SiO _x in accordance with the present invention The present inventors have confirmed that the mask 8 made of the N _y film does not cause such a crack.

In order to dispose a transparent electrode (not shown) on the upper portion, a contact hole with the underlying silicon layer was formed, a transparent electrode was formed by a sputtering method, and then this was patterned.

Even if hydrogen passivation is performed after the transparent electrode is formed, the hydrogen passivation effect is almost the same, but the transparent electrode is damaged by the plasma irradiation. Therefore, the transparent electrode was formed after the hydrogen plasma irradiation. Of course, the present inventors confirmed that the termination effect of dangling bonds due to hydrogen plasma irradiation is not reduced even after the transparent electrode is formed because it is not necessary to raise the temperature during film formation because of the sputtering method. ing.

Then, a TFT substrate provided with such a semiconductor device and a counter substrate (not shown) are bonded to each other, and liquid crystal (not shown) is injected into the gap between the two substrates to sandwich them.
The exterior assembly was performed to obtain a liquid crystal display device.

In the semiconductor device manufactured in this way,
Fig. 2 shows the measurement results of electrical characteristics by hydrogen plasma irradiation.
Shown in.

As is clear from FIG. 2, the electrical characteristics of the MOS switching element are remarkably improved, such as the reduction of the leakage current and the improvement of the rise (switching characteristic) of the drain current _ID with respect to the gate voltage V _G. It was confirmed.

FIG. 3 shows the electrical characteristics of the MOS element covered with the mask 8 made of SiO _x N _y film.
It was confirmed that there was almost no change before and after the hydrogen passivation treatment, and that the mask 8 made of the SiO _x N _y film was highly effective as a mask for hydrogen.

From another experiment, the mask 8 made of SiO _x N
It was confirmed that when the atomic concentration of oxygen in the _y film was about 15% or more, the properties as a silicon nitride film were weakened and the effect as a mask was weakened. On the contrary, it was confirmed that in the SiO _x N _y film having an oxygen concentration of about 0.5 to 1% or less, cracks were formed in the underlying oxide film after the plasma irradiation treatment. Therefore, as a mask, SiO _x N _y
It was confirmed that the optimum atomic concentration of oxygen contained in the film 8 should be 0.5% or more and 15% or less.

Although the amorphous silicon film is used as the material of the active layer in this embodiment, the material is not limited to this. For example, a polycrystalline silicon film may be used.

[0047]

As described in detail above, according to the present invention,
It is possible to selectively perform hydrogen plasma irradiation treatment only on the necessary parts, and thereby, hydrogen passivation is performed to suppress the leakage current to a low level, and a good threshold voltage characteristic is avoided by avoiding the debrising phenomenon due to hydrogen passivation. It is possible to realize a semiconductor device having both the secured MOS element. Moreover, at that time, since it does not cause cracks in the interlayer insulating layer, which is the base layer of the mask, it is possible to prevent corrosion of metal wiring such as Al due to chemical solution soaking into cracks during chemical solution treatment during subsequent wet etching. Therefore, it is possible to provide a highly reliable semiconductor device while avoiding the occurrence of defects such as disconnection.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a MOS element of a semiconductor device manufactured by a manufacturing method of the present invention.

FIG. 2 is a diagram showing electrical characteristics of a MOS element which is hydrogen passivated by using the method for manufacturing a semiconductor device of the present invention.

FIG. 3 is a diagram showing electrical characteristics of a MOS element in a region covered with a mask according to the method for manufacturing a semiconductor device of the present invention.

[Explanation of symbols]

1 ... Quartz substrate, 2 ... Active layer, 3 ... Gate insulating layer, 4 ... Gate electrode, 5 ... Interlayer insulating layer, 6 ... Drain and source wiring, 7 ... PSG film, 8 ... Mask composed of SiO _x N _y film

Claims (3)

[Claims] 1. A step of forming an active layer from an amorphous silicon film or a polycrystalline silicon film to perform element isolation to form a plurality of MOS elements, and a mask made of a silicon nitride layer containing oxygen. MO for hydrogen passivation among MOS devices
Manufacturing of a semiconductor device comprising: a step of arranging to avoid the S element, and a step of irradiating hydrogen plasma to active layers of the plurality of MOS elements to diffuse hydrogen to perform hydrogen passivation. Method. 2. The silicon nitride layer contains 0.1% to 15% of oxygen.
The element is contained at the following atomic concentration:
A method for manufacturing a semiconductor device as described above. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the hydrogen plasma irradiation is performed in a working atmosphere at 200 ° C. or higher.