JP3182226B2 - Method for manufacturing conductive polycrystalline silicon film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polycrystalline silicon film by irradiating an energy beam.

[0002]

2. Description of the Related Art In recent years, research on thin film semiconductors used in thin film solar cells, display elements for liquid crystal displays, and the like has been actively conducted. This is not possible with conventional single-crystal semiconductors, in which a thin-film semiconductor of this kind can be easily formed on a surface of an inexpensive insulating substrate, for example, glass or quartz, or ceramics, and can be formed over a large area. This is because it has excellent features.

In particular, a method of irradiating a high energy beam such as a laser to an amorphous semiconductor typified by an amorphous silicon film to polycrystallize the same to obtain a higher quality polycrystalline semiconductor is described. Attention has been paid to the fact that it is a low-temperature and dry process, so that it is easy to introduce into a device manufacturing process and a relatively reliable semiconductor can be obtained.

[0004] A method for producing a polycrystalline silicon film by irradiation with an energy beam is described in detail, for example, in Applied Electronic Properties Subcommittee Research Report No. 427, pp. 31-35.

[0005]

However, in many cases, the film formed by using the above energy beam is a so-called non-doped film, and it is difficult to apply the film to the formation of a conductive polycrystalline silicon film. .

[0006] This is based on the fact that it was difficult to increase the electrical conductivity, which is important as a film characteristic of the conductive polycrystalline silicon film, by polycrystallization by irradiation with an energy beam. In other words, an amorphous silicon film doped with a conductivity type determining impurity such as phosphorus or boron is used as a starting material, and polycrystallization occurs even when irradiated with an energy beam. This is because activation of the conductivity-type determining impurity does not sufficiently occur.

For this reason, even if an attempt is made to use a conductive polycrystalline silicon film as a constituent material of a device, the above-described method of forming using an energy beam cannot be used. There has been no choice but to use a conductive polycrystalline silicon film formed by a solid phase growth method. However, since the conductive polycrystalline silicon film formed by these manufacturing methods generally has a low conductivity, it is necessary to reduce the resistance by increasing the thickness of the conductive polycrystalline silicon film when using the film. And so on, which is a major problem in the device manufacturing process.

[0008]

The characteristic feature of the production method of the present invention is that the production method is carried out at a heating temperature of 200 to 400.degree.
Contains 5 to 10 atomic% of impurities for determining conductivity type and has a film thickness of 5
The purpose is to irradiate an energy beam to an amorphous silicon film having a thickness of not more than 00 °.

[0009]

According to the present invention, first, an amorphous silicon film to be polycrystallized is heated to 200 to 400 ° C., so that heat is easily generated in the film and the film thickness is reduced to 500 °.
By the following, heat based on the irradiated energy beam can be distributed over the entire film, and as a result, polycrystallization of the amorphous silicon film can be efficiently promoted.

[0010] By setting the conductivity type determining impurity in the amorphous silicon film in the range of 0.5 to 10 atomic%,
It becomes possible to obtain a sufficiently high conductivity as a polycrystalline silicon film after the energy beam irradiation.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is used in the manufacturing method of the present invention.
Includes impurities determining conductivity type contained in amorphous silicon film
Irradiate an energy beam to each of the films
Showing the relationship with the sheet resistance of a single-crystal silicon film
FIG. For comparison, the figure shows the energy beam illumination.
(A) when the substrate temperature at the time of
(B) when performed at room temperature without treatment
You. The amorphous silicon film used in this sample was
A film having a thickness of about 500 ° formed by a plasma CVD method.
Energy beam, the irradiation intensity is about 30
0mJ / cm ^TwoArF laser was used. Table 1 shows that
Typical formation condition of amorphous silicon film used in the present invention
The case is shown.

[0012]

[Table 1]

According to FIG. 1, the sheet resistance sharply decreases as the content of phosphorus, which is a conductivity type determining impurity, in the film increases from 0.01 at% to 1 at%, and particularly, the substrate is heated. It can be seen that sheet (a) has a smaller sheet resistance than room temperature (b). Practical sheet resistance range of 10 ² (Ω) as wiring material for devices
/ □), it is preferable that the impurity content be 0.5 atomic% to 10 atomic%.

Here, the reason why 10 atomic% or more is not adopted is that if the impurity content exceeds 10 atomic%, the impurity becomes more than the solid solubility limit with silicon. The reason for this is that the function as described above is not fulfilled.

Next, the relationship between the thickness of the amorphous silicon film and the sheet resistance after irradiation with the energy beam will be described. FIG. 2 is a characteristic diagram showing such a relationship. FIG. 2 also shows the relationship with the average crystal grain size of the formed polycrystalline silicon film. Incidentally, in preparing this sample, the substrate heating temperature during energy beam irradiation was set to about 400 ° C., and the energy beam irradiation conditions were as shown in FIG.
It is the same as in the case of.

The conductivity type determining impurities of this sample include:
Phosphorus having an impurity amount of about 1 atomic% was used, and the average crystal grain size was measured by using an image observed by a transmission electron microscope.

According to FIG. 1, as the film thickness decreases, the average crystal grain size increases remarkably, and the half-surface sheet resistance gradually decreases. Moreover, the state of the decrease in the sheet resistance shows a saturation tendency in the vicinity of the film thickness exceeding about 500 °. This indicates that it is extremely important to control the thickness of the amorphous silicon film as a starting material when forming a polycrystalline silicon film by irradiation with an energy beam.

Accordingly, considering that the larger the grain size is, the better the film quality is. Considering that the thickness of the amorphous silicon film is about 500 ° or less, the sheet resistance is sufficiently small and the grain size is small. It turns out that a big thing is obtained.

FIG. 3 shows the relationship between the substrate heating temperature during energy beam irradiation and the sheet resistance of the polycrystalline silicon film after irradiation. The sample used for this had a film thickness of about 5
00 °, the energy beam is about 300 mJ /
A cm ² ArF laser was used.

According to FIG. 1, as the substrate heating temperature increases, the sheet resistance of the formed polycrystalline silicon film gradually decreases. This is based on the fact that the crystal grain size has increased due to the high substrate temperature.

From the above, when an amorphous silicon film is used as a starting material, and an energy beam is applied to the amorphous silicon film to obtain a conductive polycrystalline silicon film, the amorphous silicon film Conductivity type determining impurity amount in,
It can be seen that the film thickness and the substrate heating temperature during energy beam irradiation are important parameters. Especially 2
An amorphous silicon film having a conductivity type determining impurity of 0.5 to 10 atomic% and a thickness of 500 ° or less at a heating temperature of 00 to 400 ° C. is used as a starting material by this energy beam irradiation. It can be seen that the method is suitable for a method for manufacturing a polycrystalline silicon film.

Next, an example of a semiconductor device using the method of manufacturing a polycrystalline silicon film of the present invention will be described. The semiconductor device used in the embodiment is a thin film transistor, which will be described below with reference to an element structure diagram for each manufacturing process (FIG. 4).

In the first step shown in FIG. 1A, a silicon oxide film (2) having a thickness of about 1 μm is formed on an insulating substrate (1) such as non-alkali glass by a normal pressure CVD method. The silicon oxide film is provided in order to prevent the influence of the energy beam performed in a later step from affecting the substrate (1).

Next, the second step shown in FIG. 2B is a step of forming an amorphous silicon film which is a starting material of the manufacturing method of the present invention.
00 ° n ⁺ type amorphous silicon film (forming temperature of about 400
C. and a phosphorus content of about 1%), and patterning is performed so that the n ⁺ -type amorphous silicon film remains in portions to become the source and drain regions (s) and (d).
The heat treatment is performed for about 1 hour in the range described above. Thereby, the amorphous silicon film (3) as the starting material is completed.

In this heat treatment in this step, when the energy beam is irradiated in the subsequent step, hydrogen contained in the amorphous silicon (3) explodes explosively due to heat by the energy beam. The purpose is to release hydrogen in the film in advance in order to suppress film roughness caused by the film.

Then, in the third step shown in FIG.
An amorphous silicon (3) as a starting material is irradiated with an ArF laser (4) at a substrate heating temperature of 400 ° C. at an intensity of about 300 mJ.
/ Cm ² . Thereby, the conductive polycrystalline silicon film (3 ′) obtained by the present invention is obtained.

Next, in a fourth step shown in FIG. 2D, a conductive polycrystalline silicon film (3 ') provided so as to correspond to the source / drain regions (s) and (d) is substantially at the center. In order to form a channel region, amorphous silicon (5) serving as a channel layer is formed by a plasma CVD method and then patterned, and the above-described heat treatment for hydrogen release is performed on the amorphous silicon (5). To the amorphous silicon (5)
Laser irradiation (6) is performed for polycrystallization. The laser used here is an excimer laser having an intensity of about 250 mJ / cm ² .

In a fifth step shown in FIG. 3E, a silicon oxide film 7 for a gate insulating film and a gate electrode 8 are formed on the polycrystalline amorphous silicon 5. An n ⁺ -type amorphous silicon film is formed by sputtering and plasma CVD, respectively, and is patterned into a desired shape. Using the patterned gate electrode (8) as a mask, offset between a channel and a drain and between a channel and a source are performed. After the region (9) is ion-implanted with phosphorus to reduce the leakage current to a concentration of about 0.01%, the gate electrode material n
^An excimer laser (about 300 mJ / cm ² ) (10) is applied to activate the phosphorus of the ⁺ type amorphous silicon film (8) and the phosphorus ion-implanted into the offset region. Such irradiation simultaneously brings about polycrystallization of the n ⁺ -type amorphous silicon film (8).

Finally, in the sixth step shown in FIG.
After a silicon oxide film (11) serving as a protective film is formed, contact holes are formed, and source and drain electrodes (12) and (13) are formed by a conventionally known method.

In the embodiment, the source of the thin film transistor,
When forming the drain conductive layer and the gate electrode material,
Although the polycrystalline silicon film of the present invention is used, it goes without saying that it may be used as a wiring material in a semiconductor device.

Also, although the description has been made using an amorphous silicon film formed by a plasma CVD method as a starting material, the present invention is not limited to this.
A VD method, a normal pressure CVD method, or a non-doped amorphous silicon film may be subjected to ion implantation or the like to obtain a desired impurity content.

Although a relatively general-purpose phosphorus has been described as the conductivity-type determining impurity, a series of trends regarding the conductivity-type determining impurity described above are the same for other boron, arsenic, and the like. These may be selected according to the device to be applied.

Further, in the embodiment of the present invention, an ArF laser was used as an energy beam for polycrystallization. However, the present invention is not limited to this laser, and other lasers such as XeCl and KrF may be used. You may.

[0034]

According to the manufacturing method of the present invention, by heating an amorphous silicon film to be polycrystallized to 200 to 400.degree. C., heat is easily generated in the film. By doing so, the heat based on the irradiated energy beam can be spread over the entire film, and the conductivity-type-determining impurity in the amorphous silicon film is set in the range of 0.5 to 10 atomic%. This makes it possible to obtain a sufficiently high conductivity as a polycrystalline silicon film irradiated with energy beams.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram illustrating the relationship between the content of impurities determining the conductivity type contained in an amorphous silicon film and the sheet resistance of a manufactured polycrystalline silicon film for explaining the manufacturing method of the present invention. .

FIG. 2 is a characteristic diagram illustrating the relationship between the thickness of an amorphous silicon film and the sheet resistance for explaining the manufacturing method of the present invention.

FIG. 3 is a characteristic diagram illustrating a relationship between a substrate heating temperature at the time of energy beam irradiation and the sheet resistance value for explaining the manufacturing method of the present invention.

FIG. 4 is a cross-sectional view of an element structure for each step for explaining a manufacturing step of a semiconductor device using the manufacturing method of the present invention.

[Explanation of symbols]

 (a) ... substrate heating temperature 400 ° C (b) ... room temperature

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/20 H01L 21/3205

Claims (1)

(57) [Claims] 1. A heating method at a heating temperature of 200 to 400.degree.
Containing a conductivity type determining impurity of 10 to 10 atomic% and a film thickness of 500
(4) A method for producing a conductive polycrystalline silicon film, which comprises irradiating the following amorphous silicon film with an energy beam.