JPH07335901A - Fabrication of semiconductor device - Google Patents

Abstract

PURPOSE:To rationalize the fabrication process of a semiconductor device by utilizing an antireflection film effectively. CONSTITUTION:When a semiconductor device is fabricated, a film deposition process is performed at first to deposit a thin semiconductor film 2 on an insulating substrate 1. A coating process is then performed to deposit an antireflection film 3 for laser light 4 on the thin semiconductor film 2. Subsequently, an irradiation process 15 performed to irradiate the thin semiconductor film 2 with a laser light 4 through the antireflection film 3 to crystallize the thin semiconductor film 2 and to make compact the antireflection film 3. Finally, a fabrication process is performed to integrate a thin film transistor using the crystallized thin semiconductor film as an active region and the compacted antireflection film as a gate insulating film. When the coating process is performed, a desired region on the thin semiconductor film 2 may be coated with the antireflection film 3 and the plane of the thin semiconductor film 2 may be divided into crystallized and non-crystallized regions by varying the irradiation efficiency of the laser light 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device. Specifically, it relates to a crystallization technique of a semiconductor thin film using laser light irradiation. More specifically, it relates to a technique for effectively utilizing an antireflection film for laser light.

[0002]

2. Description of the Related Art As a high-resolution display, a large-sized and high-definition liquid crystal display panel using a polycrystalline silicon thin film transistor as a switching element is considered promising. In order to mass-produce a large-scale high-definition liquid crystal display panel using a polycrystalline silicon thin film transistor, it is essential to establish a low temperature process that can adopt a low-priced glass substrate. A technique that has been widely expected as a low-temperature process technique is a technique of irradiating a semiconductor thin film such as amorphous silicon with laser light to form high-quality polycrystalline silicon on a low-melting-point glass substrate. FIG. 8 is a schematic view showing an example of a conventional laser light irradiation method. The semiconductor device to be processed has a laminated structure in which a semiconductor thin film 102 is formed on a transparent insulating substrate 101. The semiconductor thin film 102 is made of, for example, amorphous silicon. A laser beam 104 is irradiated onto a predetermined area section 103 provided on the semiconductor thin film 102.
Since the laser output is comparatively small, it is 1 per laser irradiation.
A narrow area of about 00 μm ² is processed. Therefore, in order to process the semiconductor thin film 102 having a large area as the screen size increases, the laser light 104 is scanned or the laser irradiation region is moved stepwise, so that the entire semiconductor thin film 10 is processed.
It was irradiating 2. That is, the energy density is increased by narrowing the laser irradiation region to some extent, whereby the semiconductor thin film 102 made of amorphous silicon or polycrystalline silicon having a relatively small grain size is completely melted and its grain size is increased. Was there. Since the laser light is scanned or moved in steps, the irradiation time per chip is relatively long and the throughput is reduced. Further, when the irradiation of laser light is scanned, a temperature difference is locally generated, and the variation in crystal grain size becomes large. This causes variations in electrical characteristics of the thin film transistor such as mobility and threshold voltage.

FIG. 9 is a schematic view showing another example of a conventional laser light irradiation method. This is to divide the semiconductor thin film 102 into planes and selectively provide crystallization sections and non-crystallizing sections, which is disclosed in, for example, Japanese Patent Laid-Open No. 60-245124. That is, the plurality of preset area sections 103 are sequentially irradiated with the laser beam 104 to form crystallized areas, and the other areas become non-crystallized areas. In this method, laser light irradiation is selectively performed many times, and it is necessary to set the coordinates of the laser irradiation system each time, and the throughput remains at a relatively low level.

[0004]

By the way, conventionally, in the case of performing crystallization by laser light irradiation, it is general to previously form an antireflection film on the surface of a semiconductor thin film. The antireflection film can improve the absorption efficiency of the irradiation energy of laser light, and is effective in completely melting the semiconductor thin film and promoting its crystallization. However, in the conventional method, the used antireflection film is removed by etching or the like, and a thin film transistor or the like is integratedly formed thereon by applying a semiconductor process. Therefore, an object of the present invention is to effectively utilize the antireflection film in order to make the manufacturing process of the semiconductor device efficient.

[0005]

In order to achieve the above-mentioned object of the present invention, the following two means are taken. That is, according to the first aspect of the present invention, the semiconductor device is manufactured by the following steps. First, a film forming process is performed to form a semiconductor thin film on an insulating substrate. Next, a coating process is performed to form an antireflection film for the laser light on the semiconductor thin film. Subsequently, an irradiation step is performed to irradiate the semiconductor thin film with laser light through the antireflection film to crystallize the semiconductor thin film and at the same time densify the antireflection film. Finally, a processing step is performed to form a thin film transistor by using the crystallized semiconductor thin film as an active region and the densified antireflection film as a gate insulating film. In the coating step, for example, SiO ₂ , S
The antireflection film is formed using at least one inorganic material selected from iN and SiON. These inorganic materials are converted into a gate insulating film in a later process.

According to the second aspect of the present invention, the semiconductor device is manufactured by the following steps. First, a film forming process is performed to form a semiconductor thin film on an insulating substrate. Next, a coating step is performed to selectively form an antireflection film for laser light on a desired area of the semiconductor thin film. Then, an irradiation step is performed to simultaneously irradiate the area covered with the antireflection film and the area not covered with the laser beam simultaneously to form a crystallized area and a non-crystallized area in plane division. Finally, a treatment step is performed to separately form thin film transistors having different electric characteristics in the crystallized area and the non-crystallized area. For example, a thin film transistor having a large current driving capability is integrally formed in the crystallized area, while a thin film transistor having a small current driving capacity is integrally formed in the non-crystallized area. In this case, it is possible to additionally form a pixel electrode in a matrix in the non-crystallized area and connect it to the thin film transistor having a small current driving capability to form a pixel array section. On the other hand, a thin film transistor having a large current drive capability included in the crystallized area can be connected to form a peripheral circuit section for driving the pixel array section. Through these steps, a semiconductor device suitable for a drive substrate of an active matrix display device can be manufactured.

[0007]

In the first aspect of the present invention, SiO ₂ , SiN, S
The semiconductor thin film is irradiated with laser light through an antireflection film composed of iON or the like to crystallize the semiconductor thin film and at the same time densify the antireflection film. On the other hand, a semiconductor process is applied to integrally form a thin film transistor having a crystallized semiconductor thin film as an active region. At this time, the densified antireflection film is not removed but is converted to a gate insulating film for effective use. As a result, the manufacturing method of the semiconductor device can be made efficient and the throughput can be improved.

In the second aspect of the present invention, the antireflection film is selectively formed so as to overlap the desired area of the semiconductor thin film. After that, the area covered with the antireflection film and the area not covered with the antireflection film are collectively irradiated with laser light to form crystallized areas and non-crystallized areas in a plane division manner. Compared with the conventional method shown in FIG. 9, by making good use of the antireflection film, it is possible to separately form a crystallized region and an non-crystallized region in one irradiation step, which leads to an improvement in throughput.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic view showing a first embodiment of a semiconductor device manufacturing method according to the present invention. In this manufacturing method, a film forming step is first performed to form the semiconductor thin film 2 on the insulating substrate 1. The semiconductor thin film 2 is made of, for example, amorphous silicon or polycrystalline silicon having a relatively small grain size.
Next, a coating process is performed to form an antireflection film 3 for the laser light on the semiconductor thin film 2. As the antireflection film 3, for example, at least one selected from SiO ₂ , SiN, and SiON, or a plurality of layers of inorganic materials thereof are used. As a film forming method, for example, SiO ₂ is formed at normal pressure. Alternatively, at a substrate temperature of 400 ° C, 0.1 Torr
LTO (LOW TEMPER) at a pressure of about 10 Torr
ATURE OXIDE) SiO ₂ may be formed.
Further, SiO ₂ , SiN or SiON may be formed by plasma CVD. In any case, this antireflection film 3 is formed to have a thickness of, for example, about 50 nm for the purpose of increasing the absorption efficiency of laser light irradiation performed in a later step. Next, an irradiation step is performed to irradiate the semiconductor thin film 2 with the laser beam 4 through the antireflection film 3 to crystallize the semiconductor thin film 2 and simultaneously densify the antireflection film 3. In this example, a one-shot laser pulse is used as the laser beam 4, and the semiconductor thin film 2 is completely melted and crystallized by one irradiation. Finally, a processing step (semiconductor process) is performed to form a thin film transistor by using the crystallized semiconductor thin film 2 as an active region and the densified antireflection film 3 as a gate insulating film.

The antireflection film 3 generally made of SiO ₂ , SiON or the like is a thermal SiO film usually used as a gate insulating film.
_{Since the} film is formed at a lower temperature (for example, 600 ° C. or lower) as compared with ₂ , the densification is not sufficiently performed in the initial stage. Therefore, a localized level density (trap level) exists inside the antireflection film 3. This indicates that the interface fixed charge density existing between the underlying semiconductor thin film 2 and the antireflection film 3 thereon also increases. In the present invention, since the antireflection film 3 itself is instantaneously heated to near the melting temperature (1200 ° C.) of the silicon constituting the semiconductor thin film 2 by laser light irradiation, the inorganic material itself such as SiO ₂ , SiN, SiON is also melted and solidified. This makes it possible to obtain film characteristics comparable to those of thermal SiO _{2 which} is conventionally used as a gate insulating film. For example, wavelength is 300nm-350nm, energy density is 200mJ /
cm ^{2 to} 400 mJ / cm ² and pulse width 20 nsec to 200
By irradiating a laser pulse of nsec for one shot, crystallization of the semiconductor thin film and densification of the antireflection film are achieved at the same time.

FIG. 2 is a schematic view showing a modification of the method for manufacturing the semiconductor device shown in FIG. In this example, the laser light 4 is divided into a plurality of times and the semiconductor thin film 2 is irradiated stepwise. For example, a laser pulse whose irradiation range is narrowed is moved step by step. Thereby, high-density irradiation energy is applied to the semiconductor thin film 2 and the antireflection film 3.
Can be added to.

FIG. 3 is a schematic partial sectional view showing a structural example of a thin film transistor included in a semiconductor device manufactured by the manufacturing method shown in FIG. In this example, a planar type thin film transistor is formed. As shown,
A semiconductor thin film 12 forming an element region of a thin film transistor is formed on a transparent insulating substrate 11. The semiconductor thin film 12 is made of silicon crystallized by the above-mentioned laser light irradiation. A gate electrode 14 made of an alloy of aluminum and silicon or the like is patterned on the semiconductor thin film 12 via a gate insulating film 13. As described above, the gate insulating film 13 uses the antireflection film densified by the irradiation of laser light. Gate electrode 14
An n-type impurity is implanted in the semiconductor thin film 12 at a high concentration on both sides thereof to form a source region and a drain region of the thin film transistor. A channel region is provided between the two.
The thin film transistor having such a configuration is covered with the first interlayer insulating film 15 made of PSG or the like. A wiring 16 made of metal aluminum or the like is patterned on the wiring 16 and is electrically connected to the source region and the drain region of the thin film transistor through the contact hole. The wiring 16 is further covered with a second interlayer insulating film 17 made of PSG or the like. A passivation film 18 made of P-SiN or the like is further formed thereon.

Table 1 below shows data comparing a gate insulating film formed according to the present invention with a conventional gate insulating film. The gate insulating film formed according to the present invention is LT
It is the one converted from the antireflection film with OSIO ₂ . On the other hand, as a conventional gate insulating film, typical thermal SiO ₂ is cited. The inter-layer breakdown voltage of the conventional gate insulating film is 40 V, whereas the gate insulating film of the present invention is about 38 V, which is almost comparable. Further, the etching rate showing the film density is 1.6 nm / sec in the conventional gate insulating film, while it is approximately 1.5 nm / sec in the gate insulating film according to the present invention. You can see that it is comparable. Further, the interface fixed charge density: Qss of the conventional gate insulating film is 1 × 10 ¹⁰ (1 / cm ² eV), whereas the gate insulating film produced according to the present invention is 2 × 10 ¹⁰ (1 / It is about cm ² eV), and it can be seen from an orderly viewpoint that the density of fixed charges at the interface is sufficiently reduced as a result of densification by laser light irradiation.

[Table 1]

FIG. 4 is a graph showing the electrical characteristics of the thin film transistor formed according to the present invention, which is shown by the curve A. The curve B represents thin film transistor characteristics when an antireflection film which has not been densified by laser light irradiation is used as a gate insulating film. In this graph, the horizontal axis represents the gate voltage VGS and the vertical axis represents the drain current IDS. As is clear from the graph, the current driving capability is remarkably improved and the leakage current is also reduced when the laser beam is densified. It is considered that this is caused by the decrease in interface state density accompanying the densification of the gate insulating film.

Next, a second embodiment of the semiconductor device manufacturing method according to the present invention will be described with reference to FIG. First, a film forming process is performed to form the semiconductor thin film 22 on the transparent insulating substrate 21. Next, a coating process is performed to selectively form the antireflection film 23 for the laser light on the desired area of the semiconductor thin film 22. Then, an irradiation step is performed to irradiate the area 24 covered with the antireflection film and the area 25 not covered with the laser beam 26 together to form the crystallized area 24 and the non-crystallized area 25 in a plane division manner. Finally, a processing step is performed to separately form thin film transistors having different electric characteristics in the crystallized area 24 and the non-crystallized area 25. For example, crystallization area 2
A thin film transistor having a large current driving capability is integratedly formed in 4, and a thin film transistor having a small current driving capability is integrally formed in the non-crystallized area 25. Of course, the anti-reflection film left in the crystallized area 24 may be used to process the gate insulating film of the thin film transistor.

When a large area semiconductor thin film (for example, a silicon thin film) is irradiated with a laser beam, a thin film transistor having characteristics different from those of a crystalline silicon transistor may be needed locally. For example, a device with a low leak current such as an amorphous silicon transistor can be used as an active element for pixel switching. If this device can be formed at the same time as the peripheral drive circuit section, it can be used in the laser light irradiation process. Mass production efficiency is dramatically improved. However, a driving circuit used for an active matrix type display device or the like needs an electron mobility similar to that of crystalline silicon. For this reason, conventionally, it was not possible to perform simultaneous laser light irradiation. In order to make this possible, the present invention adopts a structure in which the antireflection film is selectively formed only in the crystallizing region and the antireflection film is removed in the other regions. This promotes crystallization in the area coated with the antireflection film. The other areas are left as substantially amorphous silicon because the irradiation energy of the laser beam cannot be absorbed efficiently. After that, a semiconductor process may be applied to integrally form thin film transistors having different electric characteristics in both areas. According to the present invention, it is not necessary to selectively and repeatedly irradiate the laser beam, so that mass production efficiency is improved.

FIG. 6 shows an application example of the method of manufacturing the semiconductor device shown in FIG. 5, and schematically shows the method of manufacturing the display semiconductor chip. First, a film forming step is performed to form a semiconductor thin film 52 on a transparent insulating substrate 51 made of a glass material having a relatively low melting point (for example, 600 ° C. or lower). The semiconductor thin film 52 is amorphous or polycrystalline having a relatively small grain size in the precursor state, and is made of, for example, amorphous silicon or polycrystalline silicon. Next, a series of treatments including heat treatment of the semiconductor thin film 52 is performed, and the area section 5 for one chip is
A thin film transistor is integratedly formed on 3. In this embodiment, the pixel array section 54 is provided in the area section 53, and the horizontal scanning circuit 55 and the vertical scanning circuit 56 are provided as peripheral circuits for driving the pixel array section 54.
Is included. A thin film transistor is integrally formed on each of these. Finally, pixel electrodes for one screen are formed in a matrix in the pixel array section 54 to form the display semiconductor chip 5.
Complete 7. This is incorporated into an active matrix type liquid crystal panel or the like as a display drive substrate.

In this embodiment, the area section 53 is irradiated with the laser pulse 58 in one shot, and the semiconductor thin film 52 for one chip is collectively heat-treated. For example, when the semiconductor thin film 52 is amorphous silicon in the precursor state, it is once melted by batch heating and then crystallized to obtain polycrystalline silicon having a relatively large grain size. When the semiconductor thin film 52 is a polycrystal with a relatively small grain size in the precursor state, it can be melted by batch heating and then recrystallized to be converted into a polycrystal with a relatively large grain size. As the laser pulse 58, for example, excimer laser light can be used. Since the excimer laser light is a strong pulsed ultraviolet light, it is absorbed by the surface layer of the semiconductor thin film 52 made of silicon or the like and raises the temperature of that portion, but does not heat the insulating substrate 51. Insulating substrate 51
A plasma CVD silicon film or the like that can be formed at a low temperature can be selected as the precursor film to be formed on. On the transparent insulating substrate 51 made of a glass material, for example, a plasma C having a thickness of 30 nm
When a VD silicon film is formed, the melting threshold energy when irradiated with XeCl excimer laser light is 130 mJ / cm
It is about ² . 220mJ to melt the entire film thickness
Energy of about / cm ² is required. The time from melting to solidifying is about 70 ns.

In this embodiment, the antireflection film is not provided in the area where the pixel array section 54 is formed, while the horizontal scanning circuit 5 is used.
5, an anti-reflection film is formed in advance on a portion where peripheral circuit portions such as 5 and the vertical scanning circuit 56 are formed. This makes it possible to form a non-crystallized area and a crystallized area at the same time. In the non-crystallized area, a matrix-shaped pixel electrode is additionally formed and connected to a thin film transistor having a small current driving capability to form a pixel array section 54. A horizontal scanning circuit 55 and a vertical scanning circuit 56 for driving the pixel array unit 54 are built by connecting thin film transistors having a large current driving capability included in the crystallization area.

Finally, the constituent materials of the antireflection film which is a characteristic element of the present invention will be listed. That is, SiO ₂ , SiO
N, SiN, PSG, P- SiO 2: H, P-SiO
N: H, P-SiN: H, P-PSG: H, BPSG,
Polyimide, Ta ₂ O ₅ , CrO ₂ , Al ₂ O ₃ , Al
SiO ₂ , MoTaO ₂ , W _x O _1-x , TiO ₂ , PZ
T etc. are mentioned. These materials can be used alone or in combination. FIG. 7 shows a multilayer antireflection film. That is, the semiconductor thin film 72 formed on the transparent insulating substrate 71 is covered with the antireflection film 73 having a three-layer structure. The material of each layer can be appropriately selected from the substances listed above.

[0021]

As described above, according to the first aspect of the present invention, the semiconductor thin film is irradiated with the laser beam through the antireflection film to crystallize the semiconductor thin film and at the same time, to make the antireflection film dense. Turn into. After that, by forming the thin film transistor by using the crystallized semiconductor thin film as an active region and the densified antireflection film as a gate insulating film, the manufacturing process of the semiconductor device can be shortened, which can contribute to mass production. According to the second aspect of the present invention, the area covered with the antireflection film and the area not covered with the antireflection film are collectively irradiated with the laser beam, and the crystallized area and the non-crystallized area are separately formed in a plane division manner. As a result, there is an effect that the semiconductor crystallization process by laser light irradiation is shortened in time and mass production becomes possible.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of a semiconductor device manufacturing method according to the present invention.

FIG. 2 is a schematic diagram showing a modified example of the first embodiment.

FIG. 3 is a cross-sectional view showing a structure of a thin film transistor included in a semiconductor device manufactured according to the present invention.

FIG. 4 is a graph showing electrical characteristics of the thin film transistor shown in FIG.

FIG. 5 is a schematic view showing a second embodiment of the semiconductor device manufacturing method according to the present invention.

FIG. 6 is a schematic diagram showing an application of the second embodiment.

FIG. 7 is a cross-sectional view showing a multilayer structure of an antireflection film.

FIG. 8 is a schematic diagram showing an example of a conventional laser light irradiation method.

FIG. 9 is a schematic diagram showing another example of a conventional laser light irradiation method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Semiconductor thin film 3 Antireflection film 4 Laser light 11 Insulating substrate 12 Semiconductor thin film 13 Gate insulating film 14 Gate electrode

Front Page Continuation (72) Inventor Shizuo Nishihara 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Hisao Hayashi 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation Shares In the company

Claims (11)

[Claims] 1. A film forming step of forming a semiconductor thin film on an insulating substrate, a coating step of forming an antireflection film for laser light on the semiconductor thin film, and a laser on the semiconductor thin film via the antireflection film. An irradiation step of irradiating light to crystallize the semiconductor thin film and at the same time densify the antireflection film, and a thin film transistor is integrated using the densified antireflection film as the active region and the gate insulating film. A method of manufacturing a semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein in the coating step, the antireflection film is formed using at least one inorganic material selected from SiO ₂ , SiN and SiON. 3. In the coating step, a desired area of the semiconductor thin film is selectively covered with an antireflection film, and the irradiation efficiency of laser light is changed to form a crystallized area and a non-crystallized area in a plane division manner. The method for manufacturing a semiconductor device according to claim 1. 4. In the processing step, thin film transistors having a relatively large current driving capability are integrated and formed in the crystallization area,
4. The method of manufacturing a semiconductor device according to claim 3, wherein thin film transistors having a relatively small current driving capability are integrally formed in the non-crystallized area. 5. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of forming pixel electrodes in a matrix in an integrated manner by connecting to thin film transistors. 6. A film forming step of forming a semiconductor thin film on an insulating substrate, a coating step of selectively forming an antireflection film for laser light on a desired area of the semiconductor thin film, and a coating step of coating with an antireflection film. The irradiation step of irradiating the uncovered area and the uncovered area with laser light all at once to form the crystallized area and the non-crystallized area in a plane division, and the crystallized area and the non-crystallized area have different electric characteristics. A method for manufacturing a semiconductor device, which includes a process step of separately forming a thin film transistor. 7. The manufacturing of a semiconductor device according to claim 6, wherein in the processing step, a thin film transistor having a large current driving capability is integrally formed in the crystallized area and a thin film transistor having a small current driving capacity is integrally formed in the non-crystallized area. Method. 8. A thin film transistor having a large current drive capability included in the crystallized region, in which a pixel electrode in a matrix form is additionally formed in the non-crystallized region and connected to the thin film transistor having a low current drive capability to form a pixel array section. 8. The method of manufacturing a semiconductor device according to claim 7, further comprising the step of connecting the lines to form a peripheral circuit section for driving the pixel array section. 9. The method of manufacturing a semiconductor device according to claim 6, wherein the processing step includes a step of processing into a gate insulating film of a thin film transistor using the antireflection film left in the crystallized area. 10. A drive substrate for a display in which a thin film transistor and a pixel electrode are integrated and formed, wherein the thin film transistor is formed by using a semiconductor thin film and an antireflection film, and the semiconductor thin film has an antireflection film interposed therebetween. And is crystallized by being irradiated with laser light to form an active region of the thin film transistor, and the antireflection film is densified by being irradiated with laser light to form a gate insulating film of the thin film transistor. Drive substrate for display. 11. A drive substrate for a display, comprising a thin film transistor integratedly formed on a semiconductor thin film and pixel electrodes integratedly formed in a matrix, wherein the semiconductor thin film has a partially coated antireflection film interposed therebetween. It is subjected to collective irradiation with laser light and is plane-divided into a crystallized region and a non-crystallized region. In the non-crystallized region, a thin film transistor having a small current driving capability and a pixel electrode are integrated and formed to constitute a pixel array section. A display driving substrate, wherein thin film transistors having a large current driving capability are integrated and formed in the crystallized area to form a peripheral circuit portion to drive the pixel array portion.