KR19990006994A - Growth method and CVD apparatus of polycrystalline silicon film - Google Patents

Abstract

The present invention discloses a method for growing a polycrystalline silicon film, which enables optimization of many factors such as processability, diffusion characteristics, and roughness of the film surface and interface, and a CVD apparatus for efficient and rapid implementation of the growth method. have.

The method of growing a polycrystalline silicon film includes raising the film forming temperature to a predetermined temperature higher than its starting temperature after a predetermined time has elapsed from the start of growth, or repeatedly increasing the film forming temperature from a low temperature while film growth is continued. Growing a film to a predetermined film thickness, wherein the CVD apparatus is provided with a movable heat shield plate or tube that can be inserted between the heater and the substrate as a heat source.

Description

Growth method and CD device of polycrystalline silicon film

The present invention relates to a method of growing a polycrystalline silicon film and a CVD apparatus used in the growing method.

A polycrystalline silicon (hereinafter referred to as poly-Si) film on an amorphous insulating film that can be used for semiconductor devices such as LSI can be grown and deposited by chemical vapor deposition (CVD). However, the conventional film growth has been made while keeping the film growth conditions constant.

In addition, the conventional CVD apparatus used for film growth is slow in response to temperature change, and it is difficult to change the film growth conditions during the thin film growth process and to repeatedly change the film forming conditions during the film formation process.

With the recent miniaturization of LSI, there is a need to adjust the concentration distribution of roughness and dopant on the interface and surface of poly-Si film more precisely and precisely. Furnace is unable to optimize many factors such as processability, diffusion properties, and roughness of the surface and interface of the membrane.

It is a first object of the present invention to provide a method for growing a polycrystalline silicon (poly-Si) film which enables optimization of many factors such as workability, diffusion characteristics, roughness of surfaces and interfaces.

It is a second object of the present invention to provide a CVD apparatus for effective and rapid implementation of the growth method.

1 is a schematic diagram for explaining the first embodiment of the present invention, (a) is a film growth state at the growth temperature of 510 ℃, (b) is a film growth state at the growth temperature of 510 to 620 ℃, (C ) Represents the film growth state at the end point.

Figure 2 is a schematic diagram for explaining the prior art.

Figure 3 is a schematic view for explaining the reaction tube pressure-sensitive CVD apparatus of the present invention, (a) is a state in which the thermal radiation shielding tube is installed in a position to avoid the cracks, (b) the thermal radiation shielding tube covers the cracking zone Indicates a state installed at the location.

4 is a schematic view for explaining a back heater type ultra-high vacuum CVD apparatus of the present invention, (a) is a state in which the thermal radiation shielding plate is avoided the substrate, (b) is a position in which the thermal radiation shielding plate covers the substrate Indicates the state.

5 is a schematic view for explaining a conventional reaction tube pressure reduction CVD apparatus.

Explanation of symbols on the main parts of the drawing

1 substrate 10 heater

3: a-Si 11: crack zone

4: poly-Si I 13: reaction tube

5: transition layer 14: thermal radiation shielding tube

6: poly-Si II 15: thermal radiation shielding plate

A method of growing a polycrystalline silicon (poly-Si) film of the present invention is a method of growing a polycrystalline silicon film in which a polycrystalline silicon film is grown by a CVD method on a substrate such as an amorphous insulating film. Thereafter, the polycrystal comprises a step of raising the film forming temperature to a predetermined temperature higher than the start temperature, or growing the film to a predetermined thickness by repeating the operation of raising the film forming temperature from a low temperature while continuing the film growth. It is a growth method of a silicon film.

The CVD apparatus of the present invention is an apparatus for effective and rapid implementation of the growth method, and is an apparatus for depositing a thinner film on a substrate by the CVD method, and is a movable thermal radiation shield plate which can be inserted between a heater as a heat source and the substrate. Or a tube is provided.

The silicon film grown by CVD on the amorphous layer becomes poly-Si or a-Si depending on the growth temperature. The poly-Si obtained by crystallizing a-Si film by heat treatment is different from the film grown from the starting point in the grain orientation and diameter. Furthermore, the orientation and diameter of the grains in the film grown as a poly-Si film from the starting point depend on the growth conditions. In the method of the present invention, by causing such a change substantially in the depth direction of the poly-Si film, optimization of many factors such as workability, diffusion characteristics, roughness of the surface and the interface can be realized in the poly-Si film. According to this method, if the film is formed by repeating the operation of raising the film forming temperature from a low temperature, it is possible to cause the above change in the depth direction of the poly-Si film.

In order to promptly change the above-mentioned film forming conditions, in particular, the film growth temperature, without impairing the temperature uniformity with the CVD apparatus, a thermal radiation shielding tube or plate can be inserted between the heater and the substrate as a heat source. The heat radiation from the heater can be cut off immediately. That is, the film growth temperature change can be effectively realized by the CVD apparatus in which the thermal radiation shield tube or the plate is provided between the heater and the substrate.

In a preferred embodiment of the method according to the invention, for example, at a low growth temperature (substrate temperature), which is an amorphous silicon growth condition or a growth condition of polycrystalline silicon, a constant time for the film to be deposited at 1 nm or more from the film growth start point. While the film is grown, the film is grown to a predetermined thickness by immediately or continuously changing the growth temperature (substrate temperature) to a higher temperature, which is a polycrystalline silicon growth condition, while continuing the film growth.

According to another preferred embodiment, when the film growth at a high temperature described above reaches a predetermined film thickness, while the film growth is continued, the growth temperature (substrate temperature) may be amorphous silicon growth condition or polycrystalline silicon growth condition. After immediate or continuous change to low temperature, the film is formed at low temperature until the desired film thickness is reached. Then, the film formation at the high temperature described above is performed again until the predetermined thickness is reached. The operation of raising the film forming temperature from a low temperature can be repeated several times as necessary.

In another embodiment of the method of the present invention, the flow rate of the film-forming raw material gas is changed to a flow rate different from the initial flow rate at the time of film growth after the predetermined time has elapsed from the film growth start point while continuing the film growth described above. The film is grown until a predetermined film thickness is achieved by repeating such a flow rate change or by repeating such an operation and increasing the film forming temperature from the low temperature.

In the preferred embodiment of the CVD apparatus of the present invention, for example, in the case of the reaction tube LP-CVD apparatus, a space is formed between the heater and the reaction tube, and for example, a movable thermal radiation shield tube made of tantalum is provided. do. When the method of the present invention is carried out using this apparatus, the blocking tube is placed at a position covering the crack zone, which is the film forming point, at the start of film growth, and it is necessary to sharply increase the film forming temperature after a predetermined time. If present, the position of the barrier pipe is moved up or down to be in a position to avoid cracks. When it is necessary to form a film by repeating the operation of raising the film forming temperature from a low temperature, such temperature increase can be promptly performed by repeating the movement of the blocking tube.

For example, when the apparatus of the present invention is a back heater type UHV-CVD apparatus, a movable thermal radiation shielding plate is provided between the heater and the substrate. In the case of carrying out the method of the present invention using this apparatus, at the start of film growth, the film is formed by placing the blocking plate at a position covering the substrate and moving the blocking plate to a position avoiding the substrate after a predetermined time elapses. The temperature can rise quickly. By repeatedly moving the position of the blocking plate, the operation of raising the film forming temperature from the low temperature can be repeated.

Using the CVD apparatus of the present invention, it can be easily understood that a poly-Si film is grown at the start of film growth, and after a predetermined time, the film formation temperature is effectively and quickly lowered to grow an a-Si film thereon. .

Hereinafter, a detailed embodiment of the present invention will be described with reference to the drawings.

Example 1

First, an example of carrying out the method of the present invention using a conventional reduced pressure CVD apparatus will be described as an exemplary embodiment.

On the SiO ₂ film ₂ on the surface of the Si substrate 1, film growth started under the condition that the flow rate of silane was 800 sccm and the film formation temperature was 510 ° C (see Fig. 1 (a)). After 5 minutes, the silane flow rate was set back to 300 sccm and the film forming temperature of 620 ° C., and after about 20 minutes, the actual growth temperature reached 620 ° C. (see FIG. 1 (b)). The film growth was continued for 30 minutes while maintaining the silane flow rate at 640 sccm and the film formation temperature of 620 ° C. to complete the film formation (see FIG. 1 (c)). In the above step, when the temperature was 510 DEG C, the a-Si film 3 was deposited to a thickness of 10 nm (see Fig. 1 (a)), and the a-Si film crystallized during the temperature rise, so that the transition layer 5 Was deposited (see FIG. 1 (b)). At the final point of film growth at 620 DEG C for 30 minutes, as shown in Fig. 1 (c), a 300 nm thick poly-Si film (poly-Si I film (4) + transition layer (5) + poly) -Si II film 6) was formed. That is, in the formed poly-Si films 4 + 5 + 6, the transition layer 5 exists at a depth of 200 to 250 nm, and the poly-Si I film 4 and poly having different orientations under and above the transition layer, respectively. -Si II film 6 is present.

Compared with the conventional technology, i.e., the poly-Si film 9 (see Fig. 2) in the case where film formation is continued at a constant temperature of 620 캜, the poly-Si film obtained in this embodiment is better. The reason is that the roughness of the interface between the poly-Si film (9) and the SiO ₂ film (2) in the conventional method can be reduced and reaches the SiO ₂ (2) upon ion implantation into the poly-Si film (9). This is because the amount of dopant can be reduced.

The growth conditions of the above embodiments should be optimized according to the type of equipment or raw material gas, but in general, the above tendency is observed between the increase and decrease of the conditions and the film quality.

Since the poly-Si film formed as described above does not have a barrier or a low conductive layer that inhibits carrier movement between the layers, when the poly-Si film is used as the gate electrode of the MOS transistor, excellent yield, performance, and reliability are obtained. Combined MOS transistors can be manufactured.

The above embodiment is a case where a conventional reduced pressure CVD apparatus is used, but when a more rapid condition change is required, the following apparatus of the present invention can be used.

Example 2

An example of a reaction tube reduced pressure CVD apparatus is shown in FIG. 3. A space was formed between the heater 10 and the reaction tube 13, and a tantalum movable thermal radiation shielding tube 14 was provided in the space.

When carrying out the method of the present invention using this apparatus, at the start of film growth, the blocking tube 14 is located at the position shown in Fig. 3 (b), and when it is necessary to raise the growth temperature quickly, The blocking tube 14 is moved to the position shown in Fig. 3 (a). If necessary, by repeating the positional movement of the barrier tube 14 between the positions shown in Figs. 3 (b) and 3 (a), a rapid change in the film growth temperature can also be repeated.

Example 3

An example of a back heater type ultra high vacuum CVD apparatus is shown in FIG.

Between the heater 10 and the board | substrate 12, the tantalum movable thermal radiation shield 15 was arrange | positioned.

In carrying out the method of the present invention using this apparatus, at the start of film growth, the blocking plate 15 is located at the position shown in Fig. 4B, and when it is necessary to raise the growth temperature quickly, The blocking plate 15 is moved to the position shown in Fig. 4A. As in the case of the second embodiment, the rapid change of the film growth temperature can also be repeated by repeating the position shift of the blocking plate 15 between the positions shown in FIGS. 4 (b) and 4 (a).

In the conventional reaction tube pressure reducing CVD apparatus shown in Fig. 5, it takes several minutes to increase or decrease the growth temperature. However, the growth temperature can be changed in one minute or less with the CVD apparatus of the present invention as described above. Thus, for example, it is possible to grow a poly-Si film having a thickness of 150 nm, which is composed of a lower layer having a structure shown in FIG. 1 and an upper layer having a structure different from that shown in FIG. In addition, by using the growth method of the present invention, a poly-Si film having a structure of FIG. 1 and having a thickness of 50 nm was formed three times, so that a 150-nm-thick poly-Si film was formed as described above. Can be obtained using

According to the present invention, a poly-Si film can be obtained in which the optimization of many factors such as workability, diffusion characteristics, roughness of the surface and the interface, etc. is realized in the manufacture of a semiconductor device.

Claims (7)

In the method for growing a polycrystalline silicon film by growing a polycrystalline silicon film by a CVD method on a substrate such as an amorphous insulating film, the predetermined temperature higher than the start temperature after a predetermined time has elapsed from the growth start point while the film growth is continued. A method of growing a polycrystalline silicon film, comprising the steps of raising the film forming temperature or repeating the operation of raising the film forming temperature from a low temperature until a predetermined thickness. 2. The film of claim 1, wherein the film is grown at a low growth temperature (substrate temperature), which is an amorphous silicon growth condition or a polycrystalline silicon growth condition, for any time during which the film is deposited to 1 nm or more from the film growth initiation point, and the film is formed. A process for growing a polycrystalline silicon film, wherein the growth temperature (substrate temperature) is changed immediately or continuously to a high temperature which is a polycrystalline silicon growth condition to grow the film up to a predetermined film thickness. 3. When the film growth at a high temperature reaches a predetermined film thickness, the film growth is continued, and the growth temperature (substrate temperature) is set to a low temperature, which is the amorphous silicon growth condition or the polycrystalline silicon growth condition. A method of growing a polycrystalline silicon film, wherein the film formation is carried out immediately or continuously and the film formation is carried out at the low temperature until the predetermined film thickness is reached, and the film formation is performed again until the predetermined film thickness is reached at the high temperature. . The method of growing a polycrystalline silicon film according to claim 3, wherein the operation of raising the film forming temperature from a low temperature is repeated several times as necessary. 2. The flow rate according to claim 1, wherein the gas flow rate of the film forming source gas is changed to a flow rate different from the initial flow rate at the film growth start point after a predetermined time elapses from the growth start point while continuing the film growth. A method of growing a polycrystalline silicon film, wherein the film is grown to a predetermined film thickness by repeating the change and using this operation in combination with the operation of raising the film forming temperature from the low temperature. A CVD apparatus for depositing a thin film by a CVD method on a substrate, the CVD apparatus comprising a movable thermal radiation shield plate or a tube that can be inserted between a heater as a heat source and a substrate. A method of growing a polycrystalline silicon film, which is carried out by any one of claims 1 to 5, using the CVD apparatus according to claim 6.