JPH0521342A - Thin film semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent fluctuation of a boundary between a melted part and a solid layer and a beat-up occurring at the time of solidifying the melted part in the case of manufacturing a thin film semiconductor device to be recrystallized by a band region melting and recrystallizing method by approaching an interval of semiconductor thin films recrystallized in a DELTA stripe state on a substrate. CONSTITUTION:A polycrystalline silicon 2 is deposited on a quartz glass 1, and miniaturized by a photolithography technique. An interval between stripes is set to 50mum or less, and a width of the stripe is set to 300mum or less. A surface protective layer is deposited. It is band region-recrystallized with an Ar laser light as a light source. Thus, a polycrystalline silicon 22 becomes a light absorption layer at the time of crystallizing the band region to be converted to heat thereby to prevent radiation of the heat. That is, diffusion of heat is protected, a temperature distribution in the short direction in the stripes becomes low in the central direction and high at both sides. Thus, the recrystallization is started from the center, and a stable faucet growth can be realized.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of manufacturing a thin film semiconductor device using a zone melting recrystallization method and a thin film semiconductor obtained thereby.

[0002]

2. Description of the Related Art A scanning circuit portion of an image reading device such as a one-dimensional photo sensor elongated for image reading or a two-dimensional photo sensor having a large area, liquid crystal (LC), electrochromic material (EC), or electro. It has been proposed that a driving circuit portion of an image display device using a luminescent material (EL) uses a thin film transistor formed by using a silicon thin film formed on a predetermined substrate as a material, as the size of these devices increases. . As the silicon thin film used for forming these transistors,
Amorphous or polycrystalline silicon thin films are often used. The reason is that these materials can be formed on a large-area substrate relatively easily. In recent years, there has been an increasing demand for higher speeds and higher functions for these devices, and along with this, it has become necessary to improve the performance of the thin film transistors of the drive section. However, the mobility of a thin film transistor using amorphous silicon or polycrystalline silicon as an active layer is 0.1
˜1.0 cm ² / v · sec, a polycrystalline silicon thin film transistor is 1.0 to 10 cm ² / v · sec, and the mobility of a transistor formed of single crystal silicon is ˜60.
It is far below 0 cm ² / v · sec. for that reason,
There is a growing need to form single crystal silicon thin films on large area substrates. The technology for forming a single crystal silicon thin film on an insulating material has been actively researched as an SOI technology in recent years, but since many of them have been mainly aimed at improving the performance of integrated circuits, the focus of the research is on silicon wafers. It is aimed at the realization of a three-dimensional LSI using. In the case of the above-mentioned reading or image display device, glass or the like capable of forming a relatively large area that can be formed on a silicone wafer is often used as a substrate material because of the demand for increasing the area. Although there are few studies on the formation of a single crystal silicon thin film on such a glass substrate, a polycrystalline silicon thin film is formed on a quartz glass substrate, and a SiO ₂ layer is formed as a surface protection layer on the polycrystalline silicon thin film. When the polycrystalline silicon layer sandwiched between the glass substrate and the SiO ₂ surface protective layer is melted and recrystallized, a (100) -oriented single crystal recrystallized film is obtained. Such a method is based on the zone melting recrystallization method.
It is referred to as "stallization; hereinafter abbreviated as ZMR method). As a method of melting the polycrystalline silicon layer,
Strip heater method, high frequency heating carbon susceptor method,
Examples include halogen lamp method and laser heating method. ZMR
When performing, the polycrystalline silicon or amorphous silicon is sequentially formed on the quartz substrate, and then the surface protection layer such as Si.
An O ₂ layer or the like is deposited, but with a polycrystalline silicon or amorphous silicon deposited on the entire surface, ZM
When R is performed, due to the surrounding environment (slight vibration, fluctuation of heat source, etc.), many developments (bead up phenomenon) in which the melted silicon instantaneously solidifies into a circle due to surface tension are observed.
Also, due to slight fluctuations in the solid-liquid interface of the molten silicon, many occurrences of Glen Bundary, sub-Glen Boundary, etc. are observed. Conventionally, as one of the methods for solving these problems, there is a method of disposing a Si ₃ N ₄ film, which is a stripe-shaped antireflection film, on SiO ₂ of a surface protective layer.
In this method, the temperature of the silicon melt below the Si ₃ N ₄ film is raised to delay recrystallization during ZMR and concentrate defects such as Glen Bundary and Sub-Glen Bundary. However, in this method, the effect of the antireflection film of the Si ₃ N ₄ film is not observed remarkably due to slight variations in film thickness and changes in film quality, and the yield is decreased due to an increase in fine processing steps. There is a problem of causing it. As another conventional solution method, a polycrystalline or amorphous silicon layer is finely processed into a connecting island shape having a certain regularity or a rectangular stripe shape by using a photolithography technique, and then ZMR is performed. At that time, if the distance between the stripes is large, the temperature on both sides of the stripe is lowered due to the heat radiation on both sides of the stripe, and the single crystal growth by ZMR in the stripe starts from both sides. Is polycrystal, and there are many defects near the center. In fact, when building a device inside the stripe,
There is a drawback that both sides cannot be used, and the device area cannot be effectively used. On the contrary, if the stripe width is too large, the bead up phenomenon occurs due to the surface tension of the Si melt as described above.

[0003]

It is an object of the present invention to manufacture a thin film semiconductor device recrystallized by a zone melting recrystallization method, to fluctuate an interface between a melted portion and a solid layer, and to cause a bead-up that occurs during solidification of the melted portion. The point is to prevent the phenomenon.

[0004]

According to a first aspect of the present invention, a recrystallized semiconductor thin film is provided on a substrate in a large number of stripes, the distance between the stripes is 50 μm or less, and the width of the stripe is 300 μm or less. And a thin film semiconductor device. According to a second aspect of the present invention, a polycrystalline or amorphous semiconductor layer is provided in a stripe shape on a substrate, a distance between the stripes is 50 μm or less, a width of the stripe is 300 μm or less, and then a surface protective layer is formed thereon. The present invention relates to a method for manufacturing a thin film semiconductor device, characterized in that the polycrystalline or amorphous semiconductor layer is recrystallized by a zone melting recrystallization method after forming the film. A stop heater, a high-frequency heating carbon susceptor, a halogen lamp, and a laser beam, which are conventionally used as a heating source in the ZMR method, all heat and absorb the light into the substrate to melt and recrystallize silicon. All of these light sources, except lasers, can be considered as classical light sources and have a wavelength distribution in their intensity. The distribution of this wavelength is
Although it depends on the temperature of the light source, the melting point of silicon (1425
In the case of heating to (.degree. C.), it has a peak value between 0.5 and 1.0 .mu.m. The peak values of these wavelengths are in the range absorbed by silicon, and therefore, the above-mentioned light source can be used to perform melt recrystallization of silicon. In the case of stably forming a single crystal, recrystallization nucleation must occur at one place. When melting and recrystallizing a striped silicon thin film on a substrate such as a transparent quartz glass substrate as in the present invention, the peak wavelength of the heat source is not absorbed by the quartz glass substrate, and therefore the quartz glass substrate Not enough heating.
In such a situation, the cooling of the stripe-shaped silicon thin film may start from both ends of the stripe, resulting in a polycrystalline silicon stripe, or it may be single-crystallized only in a narrow area in the central part and polycrystalline in the periphery. Sex comes out. The inventors of the present invention have considered the state of a single crystal of a striped silicon thin film on a quartz glass substrate by the ZMR method as described above, and even if the substrate is not sufficiently heated, recrystallization is performed at the center of the stripe. Good results have been obtained by placing a stripe of silicon close to the periphery of the single crystallizing stripe in order to be able to start with. The present invention has been made under such a background. FIG. 4 schematically shows the states of recrystallization temperature when the stripes are independent and when the stripes are close to each other.
In the case of a single stripe, since the quartz glass substrate is not sufficiently heated, heat escapes from both ends of the stripe, and the temperature distribution becomes as shown in (c), so crystallization is as shown in (a). Start at both ends of the stripe. On the other hand, when the number of stripes is three, the central stripe is affected by the heat escaping from the stripes at both ends, and the heat is hard to escape to both ends. This situation is emphasized as the number of stripes increases, and by optimizing the conditions, the temperature of the central stripe becomes lower than that of both ends of the stripe as shown in (d), and the single crystal formation is Therefore, a preferable temperature distribution can be formed. Therefore, as shown in (b), solidification of the central stripe starts from the central portion.

Silicon will be described in detail as the semiconductor thin film of the present invention. However, the present invention is not limited to silicon, and the periodic rate is not limited to silicon.
Group IV, III-V, II-VI group simple substances or compound semiconductors, whose crystal structure is applicable to all materials having a diamond structure or a zinc blend structure. Other than Ge, SiC, BN, BP,
BAs, AlP, AlSb, GaP, GaAs, GaS
b, InP, InAs, InSb, ZnS, ZnSe,
ZnTe, CdS, CdSe, CdTe, CdHg and the like. There is no special limitation as long as it is a material that has a different wavelength of light absorption from the semiconductor layer and does not generate heat itself during zone melting and recrystallization, but if a thin film semiconductor is used as an optical sensor or CCD element, it must be a transparent material. Is preferred. Quartz glass is a typical material, but SiO ₂ , Al ₂ O ₃ , T
Examples thereof include iO ₂ , ZrO ₂ , Si ₃ N ₄ , BN, TiC, SiC, borosilicate glass, lead glass, and aluminosilicate glass.

The present invention will now be described in detail with reference to the drawings. In FIG. 1, reference numeral 1 is a mirror-finished transparent quartz glass as a support. This transparent quartz glass substrate is fused quartz or synthetic quartz, and the thickness is usually 0.3 to 5 mm.
And preferably 0.5 to 1.5 mm. 2 is an amorphous or polycrystalline silicon thin film. This layer is S
Using iH ₄ , Si ₂ H ₆ , SiF ₄ , and SiCl ₄ , heat C
VD, ECR, photo CVD, LPCVD, plasma CVD
The film thickness is 0.1 μm to 5 μm, preferably 0.2 μm to 1.0 μm. The recrystallized silicon layer is finely processed into a stripe shape by using photolithography. The distance between stripes is 50
It is not more than μm, preferably not more than 30 μm. or,
The stripe width is 300 μm or less, preferably 200
μm or less. The SiO ₂ surface protective layer 3 is indispensable for forming a single crystal silicon thin film by the melt recrystallization method. In the present invention, the surface protective layer is, for example, SiO _{2 formed} by a chemical vapor deposition method (CVD method), and S
iH ₄ , Si ₂ H ₆ , SiF ₄ , SiCl ₄ , N ₂ O, O ₂ ,
With _{NO 2, N 2 O 4,} N 2 O 5, CO 2, CO, normal pressure C
It is deposited by VD, photo CVD, ECR, LPCVD. As the surface protective layer, in addition to SiO ₂ , SiO, Si ₃ N
₄ , SiN, etc. can also be used. This film thickness is 0.
It is 5 μm to 5 μm, preferably 1.0 μm to 2.0 μm. As described above, the thin film semiconductor material of polycrystalline silicon or amorphous silicon film to be single-crystallized is formed by the melt recrystallization method. Next, this polycrystalline or amorphous silicon thin film is formed into a single crystal silicon thin film by a melt recrystallization method. The melt recrystallization method used at this time is one of the methods introduced conventionally. As a linear beam forming method, an Ar laser heating zone melting recrystallization method, a halogen lamp heating method, or the like is used. Here, the ZMR apparatus used this time is shown in FIGS. FIG. 2 is a schematic diagram of an apparatus when an Ar laser is used as a ZMR heating source. 6
Is an Ar laser having a wavelength of 5145Å which is a heat source, 5 is a cylindrical lens for beam shaping, 4 is a sample prepared in FIG. 1, 8 is a sample moving stage for ZMR, 7 is a sample temperature, and feedback is provided to the heat source 6. It is a controller to call. The sample 4 is placed on the stage 8 and an Ar laser beam is irradiated from above, and ZMR is performed by moving the sample stage 8 to obtain a single crystal silicon thin film having (100) orientation on the surface. At that time, the controller 7 feeds back the output of the Ar laser 6 so that the temperature of the region irradiated with the laser light becomes constant. Since the Ar laser is a light source having a wavelength of 5145 Å, it penetrates the surface protective layer SiO ₂ and the quartz substrate and absorbs the amorphous or polycrystalline silicon layer. For that reason, only the silicon layer is heated and rises above the melting point of silicon,
Recrystallization is performed through the cooling process. FIG. 3 is a schematic diagram of an apparatus when a halogen lamp is used as a ZMR heating source. Reference numeral 11 denotes a halogen lamp that is linearly focused and has a peak at a wavelength of 1.0, and moves in the direction of arrow 12. Reference numeral 13 is a sample prepared in FIG. 1, and 14 is a parallel light halogen lamp having a peak at 1.0 μm for preheating. The light of the halogen lamp passes through the surface protective layer SiO ₂ and the quartz substrate and is absorbed by the amorphous or polycrystalline silicon layer. This 1.0 μm light absorbs free carriers when the temperature becomes high, and only the silicon layer is heated to a temperature higher than the melting point of silicon and recrystallized through a cooling process.

[0007]

EXAMPLES Example 1 The configuration of a substrate for Example 1 will be described with reference to FIG.
The support 1 was made of mirror-polished transparent quartz glass having a thickness of 1 mm. Polycrystalline silicon 2 is deposited on quartz glass 1 by LPCVD to a thickness of 0.35 μm, and then fine processing is performed by using a photolithography technique. The distance between stripes is 0 to 100 μm, and the width of stripe is 150 μm.
m was constant. However, fine processing was not performed when the distance between the stripes was 0 μm. After depositing this polycrystalline silicon 2, a surface protective layer (SiO ₂ ) 3 is deposited by LPCVD to a thickness of 1.5 μm. Using the apparatus shown in FIG. 2 for the above sample, using Ar laser light as a heating source, input power 10 W, scan speed 1 mm / sec
Zone recrystallization (ZMR). The film forming conditions for each layer are as follows. That is, the polycrystalline silicon 2 is LPC
A film was formed by VD method using SiH ₄ gas and N ₂ gas as a carrier gas at a flow rate ratio of 1/10 at a substrate temperature of 650 ° C. and a deposition pressure of 1 Torr. The surface protection layer 3 is LPCVD
Method using SiH ₄ gas and N ₂ O gas at a flow rate ratio of 1/5
The film was formed at 0, a substrate temperature of 750 ° C., and a deposition pressure of 1.8 Torr. In Table 1, the stripes and the intervals between the stripes were evaluated. The evaluation items include the surface orientation of the recrystallized region, the ratio of the recrystallized (single crystal) region in the stripe, and the surface property of the recrystallized film (however, the surface roughness (Ra) is used for the description of the surface property). Evaluated and Ra <200
Å is ○, 200Å <Ra <1000Å is △, Ra ≧
1000 Å is described as x. ], And the occurrence rate of the bead-up phenomenon. From the above results, stripe width 150 μm
If the stripes are present at a distance of at least 40 μm or less, then good results are obtained. If the stripe spacing increases, the effect of heat protection is not observed and crystallization proceeds from both sides, increasing the proportion of polycrystals.

[Table 1]

Example 2 As the support 1, a transparent quartz glass plate having a thickness of 1.5 mm, which was mirror-polished, was used. Plasma CVD on transparent quartz glass 1
0.5 μm of amorphous silicon 2 is deposited by photolithography, and then microfabrication is performed by using photolithography technology. The distance between stripes is 5 μm, and the width of stripes is 5 μm.
To 300 μm. After depositing this amorphous silicon 2, a surface protective layer (SiO ₂ ) 3 is deposited by LPCVD to a thickness of 1.5 μm. Using the halogen lamp light as a heating source for the above sample, the upper heater power 3
Zone recrystallization (ZMR) is performed at kw, lower heater power 2 kw × 3, and scan speed 0.5 mm / sec.
The film forming conditions for each layer are as follows. Amorphous silicon 2 is formed by plasma CVD using SiH ₄ gas and carrier gas N ₂
Using gas, gas flow ratio 1/10, substrate temperature 300 ° C,
The film was formed at a pressure of 1 Torr. In addition, the surface protective layer 3 has a thermal CV.
SiH ₄ gas and O ₂ gas were used in the D method, the flow rate ratio was 1/60,
A film was formed at a substrate temperature of 450 ° C. In Table 2, the stripe width was evaluated. As the evaluation items, the surface orientation of the recrystallized region, the ratio of the single crystal region in the stripe, the surface property of the recrystallized film (however, surface roughness (Ra) was used for the description of the surface property, and Ra < 200Å is set as ○, 200Å <Ra <1000Å is △, Ra ≧ 1000
Write Å as ×. ], And the occurrence rate of the bead-up phenomenon. From the above results, when the stripe-to-strip interval is fixed at 5 μm, the stripe width is 300 μm or less, which is a good result. As the stripe width increases, the rate of beat-up increases and the disappearance of silicon is observed. It is considered that this was because the surface tension of the melt of silicon became large and could not be suppressed by the surface protective layer.

[Table 2]

[0009]

[Effects] According to the present invention, by bringing the semiconductor stripes closer to each other, the polycrystalline or amorphous semiconductor layer becomes a light absorption layer at the time of ZMR, is converted into heat, and prevents radiation of heat. . In other words, heat diffusion is protected, the temperature distribution in the short direction within each stripe is low in the central direction, high on both sides, recrystallization starts from the central part, and stable facet growth, which is important for ZMR, is realized. it can. As a result, the bead-up phenomenon does not occur on the entire surface of the stripe, and there are no defects such as Glen Bundary and Sub-Glen Bundary.
0) An oriented recrystallized semiconductor thin film can be realized. Further, the step of depositing the antireflection film is not required, and the steps can be shortened and the yield can be improved. The effect of preventing heat radiation by using stripes as a light absorption layer by placing the stripes close to each other cannot be realized by using a silicon wafer as a substrate.
This is a unique phenomenon caused by disposing a semiconductor layer on a substrate. The reason for this is that when a silicon wafer is used as the support, light such as Ar laser light, halogen lamp light, and carbon susceptor radiated light by the high frequency heating method is absorbed by the silicon wafer, which is the support, and the silicon wafer itself is absorbed. Heat is generated over the entire surface, and the effect of the present invention cannot be realized. On the other hand, when a substrate having semiconductor layers having different light absorption wavelengths is used as a support, light absorption does not occur in the support, and light absorption occurs only in the polycrystalline or amorphous semiconductor layer, so that the stripes are close to each other. The effect by that can be expressed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a layer structure before or after zone melting recrystallization of a thin film semiconductor device of the present invention.

FIG. 2 shows an example of an Ar laser heating zone melting and heating apparatus used in the present invention.

FIG. 3 shows an example of a halogen lamp heating zone melting and heating apparatus used in the present invention.

FIG. 4 is a diagram for explaining the principle of the present invention,
The state of the solid-liquid interface when (a) is a single stripe,
(B) shows the state of each solid-liquid interface in the case of three stripes, (c) and (d) are (a) and (b), respectively.
Shows the temperature distribution corresponding to.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 2 Semiconductor layer (a layer that is polycrystalline or amorphous before zone melting recrystallization and is a layer that becomes single crystal by recrystallization) 3 Surface protective layer 4 Sample 5 Cylindrical lens 6 Ar laser generator 7 Controller 8 Sample moving stage 11 Upper focal light lamp 12 Arrow indicating the moving direction of upper focal light lamp 13 Sample 14 Lower parallel light lamp

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical location // H01L 21/268 Z 8617-4M (72) Inventor Goichi Otaka Takadate Kumanodo, Natori City, Miyagi Prefecture 10 Ricoh Applied Electronics Research Laboratories, Inc. in the 5th place of the character (72) Inventor Takeshi Hino Takadate Kumanodou, Natori City, Miyagi Prefecture 10 Ricoh Applied Electronics Research Laboratories, Inc. of the 5th place (72) invention Sato Yukito Takadate Kumano-do, Natori City, Miyagi Prefecture 10 5th place in the upper area of the Ricoh Applied Electronic Research Laboratory Co., Ltd.

Claims (4)

[Claims] 1. A recrystallized semiconductor thin film is provided on a substrate in a large number of stripes, the interval between the stripes is 50 μm or less, and the width of the stripe is 300 μm or less. Thin film semiconductor device. 2. The thin film semiconductor device according to claim 1, wherein the semiconductor thin film is a silicon thin film. 3. The thin film semiconductor device according to claim 1, wherein the substrate is transparent quartz. 4. A polycrystalline or amorphous semiconductor layer is provided in a stripe shape on a substrate, a distance between the stripes is 50 μm or less, a width of the stripe is 300 μm or less, and then a surface protective layer is formed thereon. And then recrystallizing the polycrystalline or amorphous semiconductor layer by a zone melting recrystallization method.