JPH08242000A - Semiconductor device and fabrication thereof - Google Patents

Abstract

PURPOSE: To enable layers for insulation and protection to steadily exhibit their primary functions and also avoid deterioration of device function while effectively reducing a trap level of an active layer made of polycrystalline silicon. CONSTITUTION: In a semiconductor device comprising an active layer 3 made of polycrystalline silicon, a plurality of interlayer insulating films 4, 7, metal layers 5, 8, 10 and a protection layer 9, as a material of at least one of interlayer insulating layers 4, 7 or a protective layer 9, a ceramic precursor polymer including hydrogen which is not previously required is used. Thereby, hydrogen is released during the baking to form ceramic precursor polymer and this hydrogen is coupled for termination with a dangling bond of silicon atom of the active layer 3 made of polycrystalline silicon, resulting in the stabilized condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device comprising an active layer made of polycrystalline silicon, a plurality of insulating layers, a metal layer and a protective layer, and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a conventional semiconductor device of this type, for example, a MOS type thin film transistor (TF) used in an active matrix and a peripheral driving circuit of a liquid crystal display device is used.
T), etc., but the active layer in which the channel of this TFT is formed is generally made of polycrystalline silicon.

This polycrystalline silicon generally has a large number of trap levels due to grain boundaries and intragranular defects, but in the above-mentioned applications, dangling existing particularly at the crystal grain boundaries and grains. The trap level caused by a ring bond (unbonded hand) or a bond strain between silicon atoms causes an adverse effect such as an increase in the threshold value in the current-voltage characteristics of the TFT and a decrease in the sharpness of the subthreshold region. I know that.

As a countermeasure against this, conventionally, hydrogen is bonded to a dangling bond of silicon atoms in the channel portion (so-called hydrogenation treatment) to reduce the trap level.

As the above-mentioned hydrogenation treatment, conventionally, for example, Japanese Patent Publication No. 4-57098 and Japanese Patent Publication No. 62-
The one shown in Japanese Patent No. 45712 is known.

In the above hydrogenation treatment, a plasma silicon nitride film containing hydrogen is formed as a protective layer above the active layer of the TFT by a plasma CVD method, and then thermal annealing is performed.

The above hydrogenation treatment is to anneal the completed TFT with hydrogen plasma.

[0008]

The conventional TFT described above has the following problems.

First, in the hydrogenation treatment, hydrogen contained in the plasma silicon nitride film as the protective layer is lost, so that the film becomes less dense and, for example, the interlayer insulating property is deteriorated and electrostatic breakdown easily occurs. However, the original function of the protective layer is deteriorated, such as cracking.

On the other hand, in the hydrogenation treatment, plasma damage remains on each layer constituting the TFT, which has a bad influence such as deterioration of switching characteristics.

Therefore, it is an object of the present invention to effectively reduce the trap level in an active layer made of polycrystalline silicon in a semiconductor device while constantly exhibiting the original function of an insulating or protective layer. It is also possible to avoid deterioration of the device function.

It is another object of the present invention to manufacture a semiconductor device exhibiting excellent characteristics without increasing the number of separate steps in the method of manufacturing a semiconductor device.

[0013]

A first semiconductor device of the present invention comprises an active layer made of polycrystalline silicon, a plurality of interlayer insulating layers, a metal layer and a protective layer. At least one or the protective layer is formed of a ceramic precursor polymer that releases hydrogen by firing and is converted into ceramics.

A second semiconductor device of the present invention is used as an element constituting a switching element of a switching matrix for driving a liquid crystal layer and a driver circuit for driving the switching element, and a liquid crystal driving electrode and other elements. The insulating layer that insulates the electrode from the electrode is formed of a ceramic precursor polymer that releases hydrogen by firing and is converted into ceramics.

The ceramic precursor polymer described above contains Si, N, and H as the main components, and it is preferable that the firing be performed in an atmosphere containing oxygen. According to a method of manufacturing a semiconductor device of the present invention, at least one of the interlayer insulating layers or a protective layer of the semiconductor device including an active layer made of polycrystalline silicon, a plurality of interlayer insulating layers, a metal layer and a protective layer is formed. A method of applying a solution of a ceramics precursor polymer, which releases hydrogen by firing to be converted into ceramics, on the underlying layer in a layered manner, and by firing the applied solution, it is converted into ceramics. In addition, a step of hydrogenating the underlayer with a generated gas released during firing is included.

It is preferable that the solution of the above-mentioned ceramics precursor polymer contains Si, N, and H as the main components, and the firing step is performed in an atmosphere containing oxygen.

[0017]

In summary, in the present invention, a ceramic precursor polymer containing hydrogen, which is not a necessary element, is used in advance, and hydrogen released during firing is used for stabilizing the active layer made of polycrystalline silicon. .

Further, in the first and second semiconductor devices of the present invention, the hydrogen is released when the ceramic precursor polymer is used to form at least one of the interlayer insulating layers or the protective layer. It is in a stable state because it is bonded and terminated to dangling bonds of silicon atoms existing inside the active layer and at the interface between the active layer and layers above or below the active layer.

In the method of manufacturing a semiconductor device according to the present invention, hydrogen released during the process of forming at least one of the existing interlayer insulating layers or the protective layer is used inside the active layer made of polycrystalline silicon and Since the dangling bonds of the silicon atoms existing at the interface between the active layer and the layer above or below the active layer are bonded and terminated, the active layer and the layer above or below it become stable. Moreover, the denseness of at least one of the interlayer insulating layers or the protective layer is ensured.

Therefore, in the present invention, the composition of the insulating or protective layer does not become unstable as in the conventional hydrogenation treatment, and it is not necessary to use the conventional hydrogenation treatment. There is no need to increase the number of processes.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the embodiments shown in FIGS. Here, as a semiconductor device, a MOS type TFT 40 used for an active matrix of a liquid crystal display device as shown in FIG. 4 is taken as an example. 1 and 2 relate to an embodiment of the present invention.
2 is a sectional structure view of the TFT, and FIG. 2 is a manufacturing process drawing of the TFT shown in FIG.

In the figure, reference numeral 1 is a glass substrate, and a base coat layer 2 for preventing diffusion of impurities from the glass substrate 1 is laminated on the surface of the glass substrate 1.

In a required area on the surface of the base coat layer 2,
The active layer 3 is laminated in an island shape. The active layer 3 is separated into a channel region 3A and an N-type source region 3B and drain region 3C.

The surfaces of the exposed portions of the active layer 3 and the base coat layer 2 are covered with a gate insulating layer 4 of silicon oxide having a substantially uniform thickness along the irregularities. On the surface of the gate insulating layer 4, a gate electrode 5 made of aluminum is formed in a region directly above the channel region 3A of the active layer 3. The gate electrode 5 is covered with an anodized layer 6.

The exposed portion of the gate insulating layer 4 and the surface of the anodized layer 6 are covered with an insulating layer 7 of silicon oxide having a substantially uniform thickness along the irregularities. On the surface of the insulating layer 7, a source electrode 8 made of aluminum is formed in a region directly above the source region 3B of the active layer 3. The source electrode 8 is connected to the source region 3B of the active layer 3 through a contact hole 11 continuously provided in the insulating layer 7 and the gate insulating layer 4.

On the exposed part of the insulating layer 7 and the surface of the source electrode 8, a protective layer 9 made of silicon oxide is laminated relatively thickly so that the surface of the protective layer 9 becomes flat. The protective layer 9 is obtained by applying and firing a ceramics precursor polymer that releases hydrogen by firing and is converted into ceramics such as silicon oxide. This ceramic precursor polymer contains Si, N, and H as main components as shown in the following chemical formula 1. Specifically, it is preferable to use Tonen polysilazane manufactured by Tonen Corporation.

[0027]

Embedded image

A pixel electrode 10 made of ITO is partially laminated on the flat surface of the protective layer 9 described above. The pixel electrode 10 is connected to the drain region 3C of the active layer 3 through a contact hole 12 continuously provided in the protective layer 9, the insulating layer 7 and the gate insulating layer 4.

Next, a method of manufacturing the TFT having the above structure will be described with reference to the process chart of FIG.

1 mm thick by sputtering method
The base coat layer 2 made of alumina or silicon oxide having a substantially uniform film thickness (100 nm) is laminated on the surface of the substrate 1 made of quartz glass.

A substantially uniform film thickness (50 to 150 n) is formed on the entire surface of the base coat layer 2 by the plasma CVD method.
m, for example, 100 nm) of an amorphous silicon film is laminated. This is polycrystallized by performing thermal annealing at 600 ° C. in a nitrogen atmosphere, and then patterned to obtain an active layer 3 made of polycrystalline silicon [FIG.
(See (a)].

A gate insulating layer 4 made of silicon oxide and having a substantially uniform film thickness (100 nm) is laminated on the entire surface of the exposed portions of the active layer 3 and the base coat layer 2 by a sputtering method. Then, a substantially uniform film thickness (6) is formed on the entire surface of the gate insulating layer 4 by the sputtering method.
An aluminum film (containing 0.1 to 2% of silicon) having a thickness of 00 to 800 nm, for example 600 nm, is laminated. By patterning this aluminum film, the gate electrode 5 having a required size is obtained [see FIG. 2 (b)]. In addition,
As the above-mentioned sputtering conditions, the target is Si
O ₂ and the substrate temperature is 200 to 400 ° C., for example 350
℃, the atmosphere is oxygen and argon, argon /
Oxygen = 0 to 0.5, for example 0.1 or less.

By anodizing the surface of the gate electrode 5, the gate electrode 5 is covered with the anodized layer 6 [see FIG. 2 (c)]. This anodic oxidation is performed by immersing the object in an ethylene glycol solution containing tartaric acid in an amount of 1 to 5%. The thickness of the anodized layer 6 can control the length of the offset gate region of the active layer 3 which is a post process.

Using the anodized layer 6 as a mask, N-type impurities such as phosphorus are implanted by an ion doping method,
In a nitrogen atmosphere, thermal annealing is performed at 450 ° C. to diffuse the active layer 2 to form an N-type source region 3B and drain region 3C in the active layer 2. The portion of the active layer 3 excluding the source region 3B and the drain region 3C becomes the channel region 3A [see FIG. 2 (d)]. As ion doping conditions, the doping gas is PH ₃ , the acceleration voltage is 60 to 90 KV, for example, 80 KV, and the dose amount is 1 × 10 ¹⁵ to 8 × 10 ¹⁵ cm ⁻² , for example, 2 × 10 ¹⁵ cm.
^-2 .

An insulating layer 7 made of silicon oxide having a substantially uniform film thickness (600 nm) is laminated on the exposed portion of the gate insulating layer 4 and the entire surface of the anodized layer 6 by plasma CVD [FIG. reference〕.

Contact holes 11 are formed by patterning the gate insulating layer 4 and the insulating layer 7 directly above the source region 3 B of the active layer 3. Thereafter, the source electrode 8 made of aluminum and connected to the source region 3B is formed at a required position on the surface of the insulating layer 7 [FIG.
(F)].

By a spin coating method, a ceramic precursor polymer solution, for example, Tonen Polysilazane manufactured by Tonen Co., Ltd., is layered (1 μm) on the exposed surface of the insulating layer 7 and the entire surface of the source electrode 8 so that the surface becomes substantially flat.
And heat treatment at 400 ° C. in an air atmosphere (or an atmosphere containing oxygen) to release hydrogen and ammonia and convert them into silicon oxide [see FIG. 2 (g)]. Hydrogen and ammonia released at this time are bonded to dangling bonds of silicon atoms existing inside the active layer 3 made of polycrystalline silicon and at the interface between the active layer 3 and the gate insulating layer 4. Therefore, this dangling bond is terminated, resulting in a decrease in the trap level near the center of the forbidden band. Moreover, the composition of the protective layer 9 made of the converted silicon oxide becomes dense.

Contact holes 12 are formed by patterning the gate insulating layer 4, the insulating layer 7 and the protective layer 9 directly above the drain region 3 C of the active layer 3. After that, the pixel electrode 10 made of ITO and connected to the drain region 3C is formed in a required region on the surface of the protective layer 9 (see FIG. 1).

In the TFT manufacturing method described above,
The difference from the conventional method is that the material of the protective layer 9 is changed, and the number of steps is not increased.

In the manufacturing method of the above embodiment, the gate insulating layer 4 and the aluminum layer to be the gate electrode 5 are continuously formed in the step, but they may be formed in different steps. it can. Further, as shown in FIG. 3, the gate insulating layer 4 may be left according to the width of the gate electrode 5 and the other portions may be removed.

Further, in the TFT of the above-mentioned embodiment, the protective layer 9 is formed of a ceramic precursor polymer that releases hydrogen during firing. Instead of or in addition to this, the gate insulating layer which is an interlayer insulating layer is used. At least one of 4 and the insulating layer 7 may be formed of the above-mentioned ceramic precursor polymer. That is, at least one of the protective layer 9, the gate insulating layer 4, and the insulating layer 7 may be formed of the above-mentioned ceramic precursor polymer.

[0042]

According to the present invention, as in the conventional hydrogenation treatment, hydrogen, which is a necessary element for the composition of the protective layer, is released by thermal annealing to stabilize the active layer made of polycrystalline silicon. Alternatively, unlike the conventional hydrogenation treatment, hydrogen is not injected into the constituent elements of the semiconductor device by hydrogen plasma to stabilize the active layer made of polycrystalline silicon of the semiconductor device. At least one of the layers or the material of the protective layer is a ceramic precursor polymer containing hydrogen which is not a necessary element in advance, and at the same time as the formation thereof, the active layer made of polycrystalline silicon is stabilized.

Therefore, according to the present invention, in the process of forming at least one of the interlayer insulating layers or the protective layer, the inside of the active layer made of polycrystalline silicon and this active layer and the layers above or below the active layer are formed. Hydrogen is bonded to the dangling bond of silicon atoms existing at the interface and is terminated, resulting in a stable state and destabilizing the composition of the insulating and protective layers as in the conventional hydrogenation treatment. And like traditional hydrotreating,
There is no need to increase the number of separate processes. Therefore, in the present invention, the trap level in the active layer made of polycrystalline silicon can be effectively reduced without waste, and the original function of the insulating or protective layer can be constantly exhibited and the device function is deteriorated. Will be able to avoid.

[Brief description of drawings]

FIG. 1 is a sectional structural view showing a TFT of an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of the TFT of the embodiment.

FIG. 3 is a sectional structural view showing a TFT of another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of an active matrix of a general liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Base coat layer 3 Active layer 3A Channel region of active layer 3B Source region of active layer 3C Drain region of active layer 4 Gate insulating layer (interlayer insulating layer) 5 Gate electrode 6 Anodized layer 7 Insulating layer (interlayer insulating layer) ) 8 Source electrode 9 Protective layer 10 Pixel electrode 40 TFT

Claims (5)

[Claims] 1. A semiconductor device comprising an active layer made of polycrystalline silicon, a plurality of interlayer insulating layers, a metal layer and a protective layer, wherein at least one of the interlayer insulating layers or the protective layer is hydrogenated by firing. A semiconductor device, which is formed of a ceramic precursor polymer that emits and converts into ceramics. 2. A semiconductor device comprising a switching element of a switching matrix for driving a liquid crystal layer and an element constituting a driver circuit for driving the switching element, wherein a liquid crystal driving electrode and another electrode are insulated from each other. The semiconductor device is characterized in that the insulating layer is formed of a ceramics precursor polymer that releases hydrogen by firing to be converted into ceramics. 3. The ceramic precursor polymer is S
3. The semiconductor device according to claim 1, wherein i, N, and H are the main components, and the firing is performed in an atmosphere containing oxygen. 4. A method of forming at least one of said interlayer insulating layers or a protective layer for a semiconductor device comprising an active layer made of polycrystalline silicon, a plurality of interlayer insulating layers, a metal layer and a protective layer. , A step of applying a layered solution of a ceramics precursor polymer that releases hydrogen to convert it to ceramics by firing on the underlayer, and converts the applied solution into ceramics by firing and releases it during firing And a step of hydrogenating the underlayer with the generated gas. 5. The semiconductor device according to claim 4, wherein the ceramic precursor polymer solution contains Si, N, and H as main components, and the firing step is performed in an atmosphere containing oxygen. Manufacturing method.