JPH04142030A - Manufacture of semiconductor film - Google Patents

Abstract

PURPOSE:To grow a single crystal having a wide area by a method wherein a thin-film structure is irradiated, through an optical fiber, with a laser beam radiated from a laser oscillation apparatus. CONSTITUTION:A laser beam is introduced into an optical fiber 3; a thin-film structure body 6 is irradiated with the laser beam radiated from the exist of the optical fiber 3. That is to say, when the laser beam is introduced into the optical fiber 3, it is reflected repeatedly while it is passed through the optical fiber 3. When it is radiated form the exist of the optical fiber 3, it is changed to a distribution having a region where its optical intensity is nearly definite. In this case, in order to grow a crystal whose grain size is large, it is preferable that the optical intensity distribution of the laser beam has a flat distribution rather than a Gaussian distribution. Thereby, it is possible to manufacture a single-crystal film whose grain size is large.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor film used for manufacturing semiconductor integrated circuit devices, etc.
The present invention relates to a method for manufacturing a semiconductor film called a silicon on inductor structure. [0002] The semiconductor film produced according to the present invention can be used in many fields such as highly integrated LSIs, high voltage devices, radiation resistant devices, and three-dimensional integrated circuits. JP-A-4-142030 Ca) If the semiconductor single crystal film to be grown is not made of silicon, for example, G
The semiconductor film grown in the present invention is not limited to silicon, as even a compound semiconductor such as aAs is generally called an SOI structure. [0003]

[Conventional technology]

There are various methods for SOI structure formation technology, one of which is
One of them is the laser beam recrystallization method. In the laser beam recrystallization method, an amorphous or polycrystalline semiconductor film formed on a base such as an insulating film is melted by a laser beam, and crystal growth is performed while moving the melted portion. In addition,
The term recrystallization is used not only when the original semiconductor film to be melted and turned into a single crystal is polycrystalline but also when it is amorphous. [0004] The light intensity distribution of a laser beam usually has a Gaussian distribution, so if the thin film structure of the semiconductor film is irradiated as it is, melted, and the molten part is moved, the irradiation will occur as the molten part cools. As cooling progresses from the periphery to the center of the region, a large number of crystal nuclei are generated and their growth surfaces meet, making it impossible to obtain a large single crystal. [0005] Therefore, as one method to solve this problem, a method of making the temperature distribution of molten silicon bimodal (also referred to as M-type) to enable crystal growth from a single nucleus has been studied. There is. As a method to make the light intensity distribution of a laser beam bimodal, methods such as splitting one laser beam or combining two laser beams have been proposed (these laser beam recrystallization methods A general explanation is "SOI Structure Formation Technology" published by Sangyo Tosho Co., Ltd., 1986, 35-43.
(see page). [0006]

[Problem to be solved by the invention]

When the laser beam is processed into a bimodal shape, (A) in Figure 10
The temperature distribution shown in is obtained. At this time, two laser spots having Gaussian intensity distributions are placed adjacent to each other to obtain a bimodal beam. When the thin film structure is irradiated with a bimodal laser beam, crystal growth progresses from the central portion where the temperature is low to the end portions where the temperature is high, as shown in FIG. 10(B). [0007] Therefore, in order to enlarge the single crystal region, (C) in FIG.
If the distance between the two laser spots is increased as shown in Figure 2, the temperature of the central low-temperature portion may drop to below the melting point of silicon. In this case, good recrystallization cannot be performed. [0008] If the laser output is increased as shown in FIG. 10(D),
If the temperature were to be raised, the temperature at the peak portion would rise excessively, and the molten silicon would scatter, making it impossible to perform good recrystallization. [0009] As a result, the upper limit of the width of a single crystal that can be formed using the conventional laser beam recrystallization method is about 20 μm, and the width cannot be increased beyond that, making it difficult to increase the operating rate of manufacturing equipment. It is. [0010] An object of the present invention is to easily realize a method of manufacturing a single crystal film having a larger dalene size using a laser beam recrystallization method at a relatively low cost. [00113

[Means for Solving the Problems] The present invention provides a method for recrystallizing a semiconductor film by irradiating a thin film structure having an amorphous or polycrystalline semiconductor film formed on a base with a laser beam. A laser beam is introduced into an optical fiber, and the thin film structure is irradiated with the laser beam emitted from the exit of the optical fiber. [0012] In order to concentrate the energy of the laser beam, the laser beam emitted from the optical fiber exit is focused on the thin film structure using a lens. [0013] In order to process the light intensity distribution of the laser beam into a desired shape such as a bimodal shape, a part of the laser beam emitted from the optical fiber exit is shielded from the laser beam with an opaque or semi-transparent mask. do. [0014] In the present invention, the optical fiber input ends are bundled in a substantially circular shape on the input side between the laser beam input side and the thin film structure,
On the exit side, an optical fiber bundle is provided in which the output ends of the optical fibers are arranged with a spread in a direction perpendicular to the relative scanning direction of the laser beam, and the laser beam is introduced into this optical fiber bundle. The thin film structure is irradiated with a laser beam emitted from the laser beam. [0015]Operation: The laser beam emitted from the laser device has a Gaussian light intensity distribution as shown in FIG. 5(A). When a laser beam is introduced into an optical fiber, it is repeatedly reflected while passing through the optical fiber, and when it is emitted from the exit of the optical fiber, the distribution changes to the one shown in Figure 5 (B), where the light intensity is approximately constant. . In order to grow crystals with a large dalein size, it is more convenient for the light intensity distribution of the laser beam to have a flat distribution than a Gaussian distribution. [0016] When the laser beam emitted from the optical fiber exit is focused by a lens, the area of the melted portion becomes smaller but the temperature becomes higher. [0017] By blocking a part of the laser beam emitted from the optical fiber exit with a mask, the light intensity distribution of the laser beam is processed into a bimodal shape as shown in FIG. 5(C). I can do it. (C) is more convenient than (B) for single crystal growth When expanded, a wide single crystal film is formed with one laser beam scan. [0019]

【Example】

FIG. 1 represents one embodiment. 1 is a laser device, for example, a continuous wave argon ion laser device with an output of about 3W. 3 is an optical fiber that irradiates the laser beam Be to the thin film structure 6 including the semiconductor film; 2 is the laser beam Be emitted from the laser device 1;
This is a lens that condenses the light and guides it to the input end face of the optical fiber 3. [00201 The optical fiber 3 consists of a core 4 at the center and a cladding 5 surrounding it.The core 4 is exposed at the input end face of the optical fiber 3, and the input end face prevents scattering and diffuse reflection of light. Polished sufficiently to prevent this from occurring. The material for the optical fiber 3 is preferably quartz glass. [0021] The diameter of the core 4 of the optical fiber 3 is approximately several 1100 At, for example, approximately 400 μm. The diameter of the laser beam Be focused by the optical lens 2 is approximately 8 times the diameter of the core 4.
Set it to about 0%. It is desirable that the entrance end face of the core 4 be perpendicular to the axis of the optical fiber 3, and that the optical axis of the focused laser beam Be be perpendicular to the end face of the core 4. [0022] An example of the thin film structure 6 is shown in FIG. 10 is, for example, a silicon single crystal substrate, on which a thermal oxide film 11 is formed to a thickness of, for example, 0.8 to 1 μm, and a polycrystalline silicon film 12 is formed on it to a thickness of, for example, about 0.5 μm by the LPCVD method. A Si02 film 13 is deposited thereon by CVD to a thickness of, for example, about 0.3 μm. This thin film structure has an SOI structure, and is irradiated with a laser beam, melted, and the melted region moves, thereby turning the polycrystalline silicon film 12 into a single crystal. [0023] Next, the operation of the embodiment shown in FIG. 1 will be described. The laser beam Be introduced into the core 4 of the optical fiber 3 is repeatedly reflected as it travels through the core 4, and is emitted from the other end face of the optical fiber 3 having a length of, for example, about 1 m.
The OI substrate 6 is irradiated. [0024] The light intensity distribution of the laser beam Be at the A-A' line position is the B-B' line position after passing through the optical fiber 3, which has a Gaussian distribution as shown in FIG. The light intensity distribution at this time becomes a distribution having a substantially uniform intensity region as shown in FIG. 5(B). If we use an optical fiber 3 whose core 4 has a diameter of about 400 μm, the optical fiber shown in FIG. 5(B)
Approximately 40011 m due to the laser beam light intensity distribution
It is possible to obtain a single crystal region with a width of . [0025] FIG. 3 shows a second embodiment. In FIG. 3, the laser beam Be emitted from the optical fiber 3
The light is focused by an optical lens 7 and irradiated onto the SOI substrate 6. [0026] In FIG. 3, the laser beam Be emitted from the optical fiber 3
When the SOI substrate 6 is irradiated with the laser beam, the light intensity of the laser beam is insufficient and the polycrystalline silicon film of the substrate 6 is not sufficiently melted, or when there is a limit to the intensity of the laser beam that can be oscillated by the laser oscillator. It is valid. [0027] FIG. 4 shows a third embodiment. In FIG. 4, a part of the laser beam Be is blocked by a mask 8 that is opaque or semi-transparent. As a result, the light intensity distribution of the beam spot 9 irradiated onto the SOI substrate 6 can be varied in intensity, and the light intensity distribution can be processed. By using the mask 8 having a pointed tip as shown in FIG. 4, a bimodal light intensity distribution as shown in FIG. 5C can be obtained. [0028] FIG. 6 shows a fourth embodiment. An optical fiber bundle 20 is arranged on the SOI substrate 6 on the side where the laser beam is incident. The optical fiber bundle 20 is a bundle of a large number of optical fibers 22 each having a core diameter of about 10 μm. In the optical fiber bundle 20, its light incidence side 20a
The input ends of the optical fibers 22 are bundled so that the space between the optical fibers is the smallest and the overall outer shape is approximately circular, and the light output side 2 of the optical fiber bundle 20 is
The optical fibers 22 of 0b are not bundled, but are arranged on a straight line in a direction perpendicular to the relative scanning direction 24 of the laser beam and the substrate 6. [0029] At the lower part of the exit side of the optical fiber bundle 20, the SOI substrate 6 is placed on a support stand that can move in the scanning direction 24. [0030] The exit side end face of the optical fiber bundle 20 and the surface of the SOI substrate 6 may or may not be parallel. In addition, the distance between the exit side end face of the optical fiber bundle 20 and the surface of the SOI substrate 6, and the interval (pitch) between the exit end faces of the optical fibers 22 arranged in a straight line are determined by the laser beam incident on the optical fiber east entrance side 20a. It is determined empirically from the power and intensity distribution formed by the laser beam 28 emitted from one optical fiber exit. That is, the exit end 2 of the optical fiber bundle is arranged so that the light intensity distribution of the laser beam irradiated onto the surface of the SOI substrate 6 is shaped like a bow, as shown in FIG.
Set 0b. [0031] A laser beam 26 is incident on the entrance end 20a of the optical fiber bundle. For example, an argon laser beam is used as the laser beam 26, and is made to enter the entrance ff120a of the optical fiber bundle perpendicularly. The laser power is, for example, 20W. It is preferable that the diameter of the laser beam 26 to be irradiated is made sufficiently larger than the incident cross-sectional area of the entrance side 20a of the optical fiber bundle. [0032] Next, the operation of this embodiment will be explained. The SOI substrate 6 is supported so that the distance between the end face of the exit side 20b of the optical fiber bundle and the surface of the SOI substrate 6 is constant, and the SOI substrate 6 is heated and held at about 600° C., and scanned in the direction of the arrow 24. An argon laser 2 is emitted from the entrance side of the optical fiber bundle 20.
6, the laser beam introduced into the optical fiber bundle 20 travels through each optical fiber 22, reaches the optical fiber exit lined up in a straight line, and from there becomes a laser beam 28 that hits the SO■ substrate 6. irradiate. 30 is an irradiation spot. The polycrystalline silicon substrate film is melted by laser beam irradiation, a melted portion 32 is generated, and as the SOI substrate 6 moves, the melted portion 32 is cooled and a single crystal film 34 is formed. [0033] In addition to the thin film structure shown in FIG. 2, a glass substrate may be used instead of the silicon substrate 10. Also,
A silicon nitride film may be used instead of the silicon oxide films 11 and 13 in FIG. 2, or a two-layer structure of a silicon oxide film and a silicon nitride film may be used. [0034] In the embodiment of FIG. 6, a YAG laser, a C*2 laser, or the like may be used in place of the argon laser in order to obtain a large output laser beam. [0035] The number of optical fibers 22 included in the optical fiber bundle 20 is not particularly limited, and may be set to a number that is easy to handle. [0036] In the embodiment of FIG. 6, the exit side 20b of the optical fiber bundle 20 is
Although they are arranged in rows, they can be arranged in two rows on the exit side, or
The laser spots 30 may be arranged and irradiated in three rows as shown in FIG. [0037] Furthermore, in order to make the density of the irradiated laser spot different depending on the location, for example, as shown in FIG. can also be formed. In FIG. 9, 30 is an irradiated laser spot, 32 is a melted region of the thin film structure, and 34 is a single crystallized region. [0038]

【Effect of the invention】

In the laser beam recrystallization method of the present invention, a laser beam emitted from a laser oscillation device is irradiated onto a thin film structure through an optical fiber, so that the light intensity distribution of the laser beam after passing through the optical fiber has a substantially uniform shape. distribution. This makes it possible to grow a single crystal over a wider area than when irradiating with a laser beam having a Gaussian distribution. [0039] There is a device called a homogenizer that makes the light intensity distribution uniform. In this method, a beam with a Gaussian distribution is divided by a pipe rhythm and then combined to create a uniform laser beam. However, homogenizer devices are complicated and generally very expensive, including the use of a large number of optical lenses. In contrast, in the present invention, an optical fiber is used to create a laser beam with a uniform intensity distribution, so the apparatus is inexpensive and simple. [0040] If a laser beam is passed through an optical fiber and then focused by a lens, laser melting can be performed even with a small output laser oscillation device. 1. By processing the light intensity distribution of the laser beam emitted from the optical fiber using a mask. The light intensity distribution can be processed into a distribution shape suitable for single crystal growth, such as a bimodal shape, and more stable crystal growth can be achieved. [0041] By guiding the laser beam using an optical fiber bundle and making it spread in the direction perpendicular to the scanning direction on the exit side, it is possible to form a wide single crystal with -degree scanning. , it is possible to increase the operating rate of manufacturing equipment.

[Brief explanation of the drawing]

[Figure 1] FIG. 2 is a schematic front view showing one embodiment.

FIG. 2 is a cross-sectional view showing a substrate with an SOI structure used in the same example.

[Figure 3] FIG. 3 is a schematic front view showing main parts of a second embodiment.

FIG. 4 is a schematic perspective view showing a laser beam and a mask in a third embodiment.

FIG. 5 is a diagram showing the light intensity distribution of a laser beam, (A)
is the light intensity distribution when emitted from the laser oscillation device, (B
) is the light intensity distribution of the laser beam emitted from the optical fiber,
(C) shows a bimodal light intensity distribution when a mask is used.

[Figure 6] It is a schematic perspective view which shows a 4th Example.

7 is a diagram showing the temperature distribution of the laser beam irradiation area in the embodiment of FIG. 6. FIG.

FIG. 8 is a plan view showing a laser beam irradiation spot in still another embodiment.

FIG. 9 is a plan view showing a laser beam irradiation spot and an SOI substrate in still another example.

[Figure 101] A diagram showing a conventional bimodal light intensity distribution, in which (A) is the spot shape, (B) is the temperature distribution when the laser beam is used, and (C) is the diagram when the beam spot is expanded. Temperature distribution (D) represents the temperature distribution when the laser output is increased. [Explanation of symbols] Laser oscillation device optical lens 22 Optical fiber Core of optical fiber Optical fiber cladding SOI substrate Condensing lens mask 30 Laser beam substrate Silicon single crystal substrate 26° Thermal oxide film Polycrystalline silicon film SiO2 film Optical fiber bundle e Laser beam

[Document core]

drawing

[Figure 1]

[Figure 2]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 7]

[Figure 81 [Figure 9]

[Figure 10]

Claims (4)

[Claims] Claim 1: A method for recrystallizing a thin film structure having an amorphous or polycrystalline semiconductor film formed on a base by irradiating the semiconductor film with a laser beam, wherein the laser beam is introduced into an optical fiber. and irradiating the thin film structure with a laser beam emitted from the exit of the optical fiber. 2. The method of manufacturing a semiconductor film according to claim 1, wherein the laser beam emitted from the optical fiber exit is focused onto the thin film structure using a lens. 3. The semiconductor according to claim 1, wherein a part of the laser beam emitted from the optical fiber exit is shielded from the laser beam by an opaque or semi-transparent mask to process the light intensity distribution of the laser beam. Membrane manufacturing method. 4. A method of recrystallizing the semiconductor film by irradiating a laser beam onto a thin film structure having an amorphous or polycrystalline semiconductor film formed on a base, wherein the laser beam incident side and the thin film Optical fibers are arranged in such a manner that the input ends of the optical fibers are bundled in a substantially circular shape on the input side between the structures, and the output ends of the optical fibers are arranged spread out in a direction perpendicular to the relative scanning direction of the laser beam on the exit side. A method for manufacturing a semiconductor film, comprising: providing a bundle of optical fibers, introducing a laser beam into the bundle of optical fibers, and irradiating the thin film structure with the laser beam emitted from an exit of the bundle of optical fibers.