JPH04332130A - Manufacture of semiconductor element - Google Patents

Abstract

PURPOSE:To form a boundary state between a semiconductor layer and an insulating film in high quality of substantially the same degree as that obtained by a thermal-oxidation process without necessity of a high temperature process. CONSTITUTION:After a semiconductor layer 2 is formed on a substrate 1, a lacer beam is emitted from a laser in an oxidative atmosphere thereby to form a thin oxide layer 3 as a first oxide layer on the layer 2. Then, a second oxide layer 4 is formed on the layer 3 by irradiating it with a laser beam from a laser or by a CVD method.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to thin film transistor elements (TFTs) used in LCD displays, integrated circuits, etc.
) and silicon-on-insulator devices (SOI).

0002

[Prior Art] Generally, when producing a thin film transistor element such as a MOS transistor, there is a step of forming a gate insulating film on a semiconductor layer on a substrate, which increases the integration and speed of the semiconductor element. In order to provide such excellent characteristics, the formation technology of the semiconductor layer and the insulating film such as the gate insulating film formed thereon is extremely important.

By the way, to form an insulating film on a semiconductor layer, a thermal oxidation process at a temperature of about 1000°C is usually used, and by using this high temperature process, the bond between the semiconductor layer and the insulating film is improved. Although it is possible to improve the interface condition, on the other hand, it is a high temperature process,
There are problems such as limitations on the types of substrates that can be used and the diffusion of unnecessary impurities into the semiconductor layer.

[0004] Various techniques have been proposed to avoid such problems. For example, JP-A-61-26327
In No. 3 (hereinafter referred to as Conventional Example 1), the surface of the semiconductor layer was made amorphous by ion implantation, an oxide film was formed by CVD method, etc., and then heat treatment was performed at a temperature of 600°C for about 3 hours. A technique has been disclosed in which annealing is performed to improve the interface state between a semiconductor layer and an oxide film.

Furthermore, in Japanese Patent Application Laid-Open No. 119974/1983 (hereinafter referred to as Conventional Example 2), a gate insulating film is formed on a semiconductor layer by deposition, and after forming the gate insulating film,
A technique for performing annealing by laser light irradiation has been disclosed.

[0006] Also, Japanese Patent Application Laid-Open No. 62-71276 (hereinafter referred to as
Conventional Example 3) discloses a technique for forming a gate insulating film on a semiconductor layer by the ECR method.

[0007]

[Problems to be Solved by the Invention] By using the above-mentioned technology, it is possible to form an insulating film without using a high temperature process of about 1000°C, and it is possible to form an insulating film on a somewhat wider range of substrates than when using a thermal oxidation process. It is possible to select the desired amount, and it is also possible to prevent impurity diffusion into the semiconductor layer to some extent.

However, when using the above-mentioned technology, it is difficult to create a good interface between the semiconductor film and the insulating film compared to a thermal oxidation process that requires a high temperature of about 1000°C. There were drawbacks.

That is, in Conventional Example 1, the oxide film is formed by CVD.
Since the semiconductor layer is formed by a method such as a method, there is a limit to the ability to modify the interface state between the semiconductor layer and the oxide film. By making the semiconductor layer amorphous, we aim to improve its compatibility with the oxide film, but it is difficult to significantly improve the interface state with thermal annealing at a temperature of 600°C for about 3 hours. It is.

On the other hand, in Conventional Example 2, since annealing is performed using heat generated by a laser beam process, it is expected that a better quality interface state can be obtained than in Conventional Example 1. However, in Conventional Example 2, since the gate insulating film is formed by deposition on the semiconductor layer, it is essentially impossible to realize a good interface depending on the atmosphere during deposition, pretreatment, etc.

Furthermore, in Conventional Example 3, ECR is formed on the semiconductor layer.
Since the gate insulating film is simply provided by the method, it is not possible to obtain an interface state superior to that in Conventional Examples 1 and 2.

As described above, conventionally, it has been impossible to create a good interface between the semiconductor layer and the insulating film without using a high-temperature process such as a thermal oxidation process.

[0013] The present invention provides a semiconductor device that can create an interface state between a semiconductor layer and an insulating film of almost the same quality as that obtained by a thermal oxidation process, without requiring a high-temperature process. The purpose is to provide a manufacturing method for.

[0014]

[Means for Solving the Problems] According to the present invention, a first insulating layer and a second insulating layer are sequentially formed on a semiconductor layer, and the first insulating layer is oxidized by an optical process. A second insulating layer is formed on the first insulating layer by CVD.
It is characterized by being formed by a deposition process using a method or an optical process.

FIGS. 1A to 1C are diagrams showing an example of the manufacturing process of a semiconductor device according to the present invention. In this manufacturing process example, after forming the semiconductor layer 2 on the substrate 1 (see FIG. 1(a)),
A thin oxide layer 3 is formed as a first oxide layer on the surface of the semiconductor layer 2 by irradiation with a laser beam from a laser in an oxidizing atmosphere (see FIG. 1(b)). Next, a second oxide layer 4 is formed on the first oxide layer 3 by irradiation with a laser beam from a laser or by a CVD method.
(see Figure 1(c)).

In the steps of FIGS. 1(b) and 1(c),
Prior to forming the first oxide layer 3 and the second oxide layer 4, the surfaces of the semiconductor layer 2 and the first oxide layer 3 are etched by changing the gas atmosphere and using the same optical process to form the interface. It is important to perform cleaning in advance.

In addition, in the process shown in FIG. 1(b), it is important that the heat generated by the laser beam is efficiently absorbed by the surface of the semiconductor layer 2, and for this purpose it is necessary to emit a laser beam with a relatively short wavelength. It is best to use a laser that By using such a laser, the outermost surface of the semiconductor layer 2 is brought into a molten state, and this outermost surface reacts with the oxidizing gas, whereby the thin first oxide layer 3 can be created. for example,
When a thin oxide layer is desired due to higher integration,
It is possible to sufficiently finish this first oxide layer 3 to a thin film thickness of about several hundred angstroms.

In the above manufacturing process example, it is assumed that the semiconductor layer 2 is formed on the substrate 1 in the process shown in FIG. In this case, the steps shown in FIGS. 1(b) and 1(c) may be performed on this wafer (for example, a silicon wafer).

[0019]

EXAMPLES The present invention will be explained in more detail below using examples.

Example 1 In Example 1, quartz glass was used as the substrate, and a polycrystalline silicon thin film of 1000 Å was deposited on this insulating substrate by the LPCVD method under conditions of a pressure of 0.1 Torr and a temperature of 630°C.
It was formed to a certain thickness. Thereafter, in a Cl2 gas atmosphere at a pressure of 10 Torr, the polycrystalline silicon thin film is irradiated with 1 to 5 shots of a laser beam with a wavelength of 248 nm from a KrF excimer laser at an output intensity of 10 mJ/cm2 to etch the surface of the polycrystalline silicon thin film. did. Then, C
After removing 12 gas and reducing the degree of vacuum to about 1/107 Torr, O2 gas was introduced. Atmosphere O2 gas: 10
SCCM, with the pressure maintained at 10 Torr, the above Kr
A laser beam with a wavelength of 248 nm is irradiated from an F excimer laser with an output intensity of 200 mJ/cm2 to the etched polycrystalline silicon thin film, and the surface of the silicon thin film is approximately 100 Å thick.
An oxide film (first insulating layer) was formed. After that, O
In addition to 2 gases, 10 SCCM of Si2H6 gas was introduced, and the wavelength 248n from the same KrF excimer laser as above was used.
m laser beam is irradiated to form a second insulating layer on the first insulating layer.
A SiO2 layer with a thickness of 1000 Å was formed as an insulating layer.

Example 2 In the second example, a thermal oxide film with a thickness of about 1000 Å was formed on a silicon wafer cut out in the (100) direction and having a resistivity of 0.1 Ω·cm. Using the base body as a substrate, a polycrystalline silicon thin film was formed on this substrate to a thickness of about 1000 Å under the same conditions as in Example 1. Next, O3 gas is introduced, and the atmosphere is changed to O3 gas: 10S.
While maintaining CCM and pressure at 1 Torr, a laser beam with a wavelength of 248 nm was irradiated from a KrF excimer laser onto the polycrystalline silicon thin film to form an oxide film (first insulating layer) of about 200 Å on the surface of the silicon thin film. After that, Si
A SiO2 layer having a thickness of 1000 Å was formed as a second insulating layer by the LPCVD method under the conditions of H4 gas: 10 SCCM, O2 gas: 10 SCCM, and a temperature of 400°C.

In Examples 1 and 2, SiO2 layers, ie, insulating films, were formed as the first and second oxide layers on the silicon thin film (semiconductor layer) as described above. The SiO2 layer thus formed has a level at the interface with the silicon thin film of a low order of about 1010 (1/cm2 eV), and is formed by a thermal oxidation process that requires a high temperature of about 1000°C. It was found that the interface properties were comparable to those of thermal oxide films, and it was confirmed that an optical process using an excimer laser is an effective method. In particular, although good interface properties can be obtained, the temperature is considerably lower than that during the thermal oxidation process (for example, about 200°C).
Since the insulating film can be formed using the same method, a wide range of substrates can be selected, and process conditions can be significantly relaxed.

[0023]

[Effects of the Invention] As explained above, according to the present invention,
A first insulating layer is formed on the semiconductor layer by an oxidation process using a photo process, and a second insulating layer is formed on the first insulating layer by CVD.
Since it is formed by a deposition process using the D method or an optical process, it is possible to create an interface state between the semiconductor layer and the insulating layer that is of the same quality as a thermal oxidation process. It is possible to form an insulating film at a temperature considerably lower than that of the conventional method.

[Brief explanation of drawings]

FIGS. 1(a) to 1(c) are diagrams showing the manufacturing process of a semiconductor device according to the present invention.

[Explanation of symbols]

1 Board 2 Semiconductor layer 3 First oxide layer 4 Second oxide layer

Claims (1)

[Claims] 1. A first insulating layer and a second insulating layer are sequentially formed on a semiconductor layer, the first insulating layer is formed by an oxidation process using an optical process, and the second insulating layer is formed by an oxidation process using an optical process. A method of manufacturing a semiconductor device, characterized in that an insulating layer is formed on the first insulating layer by a deposition process using a CVD method or an optical process.