JP2004356637A - Tft and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide excellent performance TFTs (thin-film transistors) which can solve the conventional problems especially relating to the manufacturing method of a crystal TFT, using excimer laser annealing and the related TFT. <P>SOLUTION: A semiconductor island used as active region is formed, and insulating coating film used as gate insulated film is formed on it. Semiconductor film and the insulating coating film are treated by laser annealing, at the same time. As a result of this, the semiconductor island grows transversely in crystallization, in all directions, and the insulating coating film is turned quality high in simultaneously. Moreover, regarding the patterning of the semiconductor film, it can be patterned, without using resist in such a way that a light irradiating the semiconductor through a mask makes an extremely thin oxide film formed partially on the surface, and the semiconductor film, in which the ultra-thin oxide film is not formed on the surface, is removed by gas-phase etching executed, after the formation in a state with the semiconductor film being kept in an oxygen atmosphere. A high performance single crystal TFT, superior in transistor characteristics and of proper yield, can be manufactured, in such a manner that these processes are executed continuously, without exposing to conditions which not exposed by atmosphere. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

DETAILED DESCRIPTION OF THE INVENTION

Industrial applications

The present invention relates to a thin film transistor, and more particularly, to a method of manufacturing a crystalline thin film transistor using excimer laser annealing and such a thin film transistor.

First, words used in the present specification will be described.

In this specification, in principle, "semiconductor" refers to materials such as silicon (silicon, Si) and germanium, and "transistor" refers to elements such as vacuum tubes and switches formed using these semiconductors. Shall be referred to as a typical thing. The energy beam refers to a beam of light, laser light, electron, X-ray, or the like.

In recent years, research and development of an active matrix liquid crystal display element (LCD) or an active matrix organic EL display element that independently drives each pixel using a thin film transistor (hereinafter also referred to as “TFT”) have been actively performed. . This TFT is roughly classified into a polycrystalline silicon thin film transistor (hereinafter, also referred to as “poly-Si TFT”) and an amorphous silicon thin film transistor (hereinafter, also referred to as “a-Si TFT”).

Since polycrystalline silicon thin film transistors have high mobility, it is expected that not only driving of pixels but also peripheral driving circuits and further information processing circuits will be integrated on glass in the future.

It is said that in order to form a sufficiently high-speed information processing circuit using a thin film transistor, the electron mobility needs to be 500 cm ² / vs or more, which is close to that of single crystal silicon. In order to realize such a high-performance thin film transistor, it is necessary to manufacture a high-quality silicon film and a gate insulating film. However, at present, only a polycrystalline silicon film can be obtained with respect to a silicon film, and the crystal grain boundary becomes a scattering center of electrons, so that the presence of the crystal grain boundary lowers the mobility. On the other hand, as for the gate insulating film, fixed charge and interface states increase due to low-temperature deposition. In addition, in the current manufacturing method, one photolithography step is performed to form an active region semiconductor island of a transistor before the gate insulating film is deposited, and this step damages the semiconductor / gate insulating film interface. The quality of the interface between the insulating film and the semiconductor / gate insulating film not only fluctuates the threshold voltage of the transistor but also lowers the mobility. Therefore, in order to obtain high-performance TFT characteristics, it is necessary to minimize the grain boundaries in the channel portion of the TFT and to form a good gate insulating film and a good silicon / gate insulating film interface.

As a method of forming a polycrystalline thin film at a low temperature of 500 ° C. or less at present, there is a method of irradiating an amorphous silicon film with an excimer laser to melt and then crystallize when solidifying. This method is considered to be a promising method because it does not cause thermal damage to the glass substrate. However, in this method, the grain size is small, and it is difficult to control the positions of the crystal grains, so that it is difficult to realize a single crystal TFT.

As a solution to such a problem, recently, a crystal is grown in a lateral direction, and a channel of a transistor is arranged in parallel with the lateral crystal growth direction to eliminate a crystal grain boundary that crosses when a carrier passes through the channel. Has demonstrated that the mobility can be increased to 400 cm 2 / vs or more. For this reason, in recent years, techniques for realizing lateral crystal growth and using it for TFTs have been actively developed. In general, the lateral crystal growth may be performed by generating a temperature gradient in the silicon film, so that the crystal grows laterally from a low temperature portion to a high temperature portion. The main method is to vary the laser intensity spatially. For example, a mask method that locally blocks laser light and a phase shift method that generates laser light interference have been devised. However, these methods need to modulate the laser light source, require expensive optical devices, and increase the manufacturing cost of the thin film transistor. Further, position control of crystal grains for generating lateral crystal grains where desired is not realized by a simple method. Currently, the production of the first-generation low-temperature polycrystalline polysilicon thin-film transistors has begun, but this uses a first-generation laser annealing device that randomly generates crystals by irradiating the semiconductor film with uniform laser light. However, this laser annealing apparatus cannot easily realize lateral crystal growth and control of crystal grain position. If lateral growth and crystal grain position control can be realized with this apparatus, it is not necessary to purchase a new expensive laser annealing apparatus, and the invention of a new method using uniform laser light in the first generation laser annealing apparatus. Is desired.

On the other hand, regarding the formation of a high-quality gate insulating film of a thin film transistor, since the manufacturing temperature of the transistor is limited to 500 ° C., which is the substrate heat-resistant temperature, a sufficiently satisfactory method of manufacturing an insulating film has not been established. Regarding the deposition of the insulating film, a PECVD method can be considered, but in this method, the insulating film is damaged by the plasma. At present, a method of depositing an insulating film by ECR-PECVD or a method of annealing the insulating film with high-pressure steam or oxygen plasma after depositing the insulating film have been devised in order to reduce the damage caused by the plasma. The apparatus is expensive, and in the latter case, the problem of complicating the process remains.

In addition to these methods, a method was devised in which a silicon nitride film deposited at a low temperature was irradiated with a laser and then annealed at a high temperature. However, only the surface was annealed, so that this method did not provide a sufficient effect of improving the insulating film.

Further, in a manufacturing process of a top gate type thin film transistor which is currently generally used, first, a semiconductor island to be a transistor active layer is patterned by photolithography, and then a gate insulating film is formed on the surface. However, in this photolithography process, the surface of the semiconductor film includes various steps such as application of a resist and exposure to the air, during which the surface of the semiconductor film is contaminated or dust adheres. Therefore, the interface between the semiconductor film and the gate insulating film cannot be kept clean, resulting in a decrease in transistor characteristics and inconvenience. In the conventional patterning method using a resist, surface contamination of the resist to the semiconductor film and exposure to the air are inevitable, so no resist is used, and from the deposition of the semiconductor film to the patterning of the semiconductor island and the deposition of the gate insulating film. In the meantime, a new patterning method that does not require exposure to the air is desired.

An object of the present invention is to provide a thin film transistor having excellent performance by solving such a problem.

Means for solving the problem

First, means for crystallizing a semiconductor film will be described with reference to the cross-sectional views of FIGS. Regarding the directions in the figure, the directions of xyz are shown on the left side. The substrate 10 is placed parallel to the xy directions. First, an SiO 2 film is deposited as a passivation film 15 on the substrate 10. After that, a semiconductor film 20f is deposited on the passivation film 15, and then the semiconductor film 20f is patterned into a semiconductor island 20 to be an active region of the thin film transistor as shown in FIG. The process from the formation of the semiconductor film 20f to the patterning of the semiconductor island 20 is referred to as a semiconductor island formation process. Although the surface shape of the semiconductor island 20 will be described later, the shape is shown in FIGS. 10A to 10D. Subsequently, an insulating coating film 30a is formed on the surface of the semiconductor island 20, as shown in FIG. This is referred to as a coating film forming step.

Subsequently, the laser light 40 is incident on the substrate. This is a crystallization step. At this time, the laser light may be incident from one surface of the substrate 10 on which the semiconductor island 20 is formed as shown in FIG. 1D, or the semiconductor light may be incident on the substrate 10 as shown in FIG. The same effect can be obtained even if the light is incident from the opposite side of the surface on which the island 20 is formed. When a semiconductor island is irradiated with a laser beam and melted, there is a lateral heat outflow 50a and a downward heat outflow 50b around the semiconductor island 20, whereas there is only a downward heat outflow 50b in the center of the island. The temperature drop around the island is faster than that at the center of the island. Therefore, crystal nuclei are generated in the peripheral portion of the semiconductor island ahead of the central portion and grow laterally toward the central portion of the semiconductor island.

FIGS. 11 (a) to 11 (d) show aspects of crystal grains after crystallizing the semiconductor islands 20 having various shapes shown in FIGS. 10 (a) to 10 (d). When the island width in the y direction and the island width in the x direction are the same, a large grain boundary 201a generated by collision of crystal growth exists in an X shape. On the other hand, in FIG. 11B in which the difference between the island width in the x direction and the island width in the y direction is large, a grain boundary parallel to the x direction is formed by exposing both ends 201c of the semiconductor island in the x direction and having one center 201b. Only. Therefore, when manufacturing a transistor with this structure, as shown in FIG. 7B or FIG. 8B, the carrier traveling direction of the channel of the transistor is set to the y direction having a narrow lateral width, and the central grain extending in the x direction is formed. If a channel is formed avoiding the boundary 201b, a crystal grain boundary where carriers cross in the channel can be eliminated. At both ends of the island in the x direction, there is a crystal grain boundary 201c traversed by carriers. However, the effect can be reduced by increasing the difference in width between the island in the x direction and the y direction. Thus, the performance of the transistor can be dramatically improved. Further, since the surface of the channel region of the semiconductor island 20 is extremely flat, the characteristics of the transistor become more uniform.

Furthermore, if the semiconductor island 20 is formed into a saw-like shape on the long side as shown in FIG. 10C, after crystallization, crystal grains generated in the concave portion 20x are generated in the convex portion 20y as shown in FIG. 11C. Since the particles reach the center of the semiconductor island 20 earlier than the crystal grains, the number of crystal grains can be controlled.

Further, when the semiconductor peninsula 210 is formed in the semiconductor island 20 as shown in FIG. 10D, the crystal nucleus is preferentially generated from the semiconductor peninsula 210 and moves in the direction indicated by the arrow in FIG. As a result, the semiconductor island 20 is monocrystallized.

The crystal growth can be controlled not only by the shape of the semiconductor island 20 shown in FIGS. 10A to 10D but also by changing the shape.

In a subsequent transistor manufacturing process, the insulating coating film 30a formed on the semiconductor island 20 in FIG. 1C can be used as it is as a gate insulating film. Since the insulating coating film 30a is simultaneously annealed at a high temperature when the semiconductor island 20 is irradiated with the laser 40 in FIG. 1D, good insulating characteristics, low interface states, fixed charges, and the like are obtained. Contributes to higher performance.

In the case where the insulating coating film 30a does not have a light absorbing property for the laser beam 40, however, the lateral crystal growth distance is limited to about 2 microns. If the width of the semiconductor island 20 in the y direction shown in FIGS. 10B and 10C is twice or more the distance in which the lateral crystal growth is possible, the lateral crystal growth distance from the peripheral portion toward the center is possible. However, the lateral crystal growth cannot reach the center of the island, and a microcrystalline region 205 is generated at the center of the island due to the generation of crystal nuclei as shown in FIG.

On the other hand, regarding the semiconductor island 20 shown in FIG. 10D, the distance from the connection portion 220 between the semiconductor island 20 and the semiconductor peninsula 210 to the peripheral portion of an arbitrary semiconductor island 20 is larger than the lateral crystal growth distance of 2 μm. Even in a long case, as shown in FIG. 11 (f), a microcrystalline region 205 due to the generation of a crystal nucleus occurs in a portion separated from the connection portion 220 by 2 μm or more. Therefore, when crystallizing the semiconductor island 20 having a large size, it is necessary to use a method of increasing the crystal growth distance.

Therefore in order to increase the lateral crystal growth distance by extending the melting time of the semiconductor island 20 in the present invention, 1000~40000cm ^-1 with respect to the laser beam to be irradiated as shown in FIG. 1 (e), preferably 4000 to A translucent film 30b having an absorption coefficient of 14000 cm ^-1 was formed on the coating film 30a. FIG. 2 shows the dependence of the lateral crystal growth distance on the thickness of the translucent film 30b. Here, the absorption coefficient of the translucent film was 12000 cm ⁻¹ .

FIG. 2 shows that the lateral crystal growth distance increases with the thickness of the translucent film 30b. Then, the lateral crystal growth distance is extended by the thickness of the translucent film 30b, and the larger semiconductor islands 20 shown in FIGS. 10A to 10D can be laterally grown. For example, in FIGS. 10B and 10C, when the island width of the semiconductor island 20 in the y direction is 10 μm or more, the lateral crystal growth distance needs to be 5 μm or more. When the thickness is 300 nm or more, the generation of the microcrystalline region 205 shown in FIG. 11E can be prevented. Alternatively, in the case of FIG. 10D, when the distance from the base portion 220 of the semiconductor peninsula 210 and the semiconductor island 20 to an arbitrary end of the semiconductor island 20 is 5 μm, the lateral crystal growth distance needs to be 5 μm or more. Therefore, the thickness of the translucent film 30b may be set to 300 nm or more from FIG.

Since the insulating coating film 30a and the translucent film 30b have undergone laser annealing, they have good insulating properties. Therefore, when a transistor is subsequently formed, at least a part of the insulating coating film 30a or at least a part of the insulating coating film 30a and the translucent film 30b can be used as it is as a gate insulating film of the transistor.

Next, in the case of patterning the semiconductor island 20 in FIG. 1B as a problem of the conventional technology, the surface of the semiconductor island 20 is easily contaminated by photolithography using a conventional resist, and therefore, when the transistor is manufactured, It has been mentioned above that a perfect semiconductor / gate insulating film interface cannot be obtained. In the present invention, when the surface of an amorphous semiconductor film is oxidized or a part of the amorphous semiconductor film is changed to a crystalline phase, the etching rate is lower than that of the original amorphous semiconductor film. Invented that the film can be patterned.

FIG. 3 shows the etching rate of the atomic hydrogen silicon film. The etching rates of the amorphous silicon film, the crystalline silicon film, and the silicon oxide film were significantly different. Therefore, selective etching between the amorphous silicon film, the crystalline silicon film, and the silicon oxide film can be performed. Here, the patterning method using the difference in etching rate between the silicon film and the silicon oxide film is referred to as a surface oxidation patterning method, and the patterning method using the difference in etching rate between an amorphous silicon film and a crystalline silicon film is referred to as a phase conversion patterning method. And

First, the surface oxidation patterning method will be described with reference to FIG. As shown in FIG. 4A, a light beam 41 passing through the photomask 3 is irradiated while the semiconductor film 20f is kept in an atmosphere of oxygen 2. Then, an oxide film 22 is formed on the surface of the semiconductor film 20f where the light beam 41 has been irradiated. At this time, the pattern of the photomask 3 that transmits light is transferred to the silicon film as the surface oxide film 22. Thereafter, as shown in FIG. 4 (b), when the oxide film 22 is vapor-phase etched with atomic hydrogen 1 or the like, the etching rate of the oxide film 22 is much lower than that of the semiconductor film 20f. Can be selectively removed. As a result, the semiconductor islands 20 are formed according to the pattern of the photomask 3 that allows the light to pass.

Next, a phase conversion patterning method will be described with reference to FIG. First, as shown in FIG. 5A, the amorphous semiconductor film 20f is irradiated with the laser 40 through the photomask 3. Then, the portion irradiated with the laser beam becomes the crystallized semiconductor film 20g. That is, the pattern of the photomask 3 that passes light is transferred as a crystalline semiconductor. Thereafter, as shown in FIG. 5B, a portion which is not a crystalline semiconductor is selectively removed using atomic hydrogen 1 or the like. As a result, the semiconductor islands 20 are formed according to the pattern of the photomask 3 that allows the light to pass.

In the above description, atomic hydrogen 1 was used as an etching gas. However, the same effect can be obtained by using a plasma of a hydrogen fluoride gas, such as a carbon fluoride gas such as CF4 and NF4, or a nitrogen fluoride gas.

Although a new method of patterning a semiconductor film has been described above, it is needless to say that the present invention is not limited to a semiconductor and can be applied to patterning of a metal film.

By combining inventions such as the new semiconductor film crystallization method, gate insulating film forming method, and patterning method described above, at least the formation of the semiconductor film of FIG. 1A, the patterning of the semiconductor island of FIG. The process up to the formation of the gate insulating film in FIG. 1C can be completed without being exposed to the air.

FIG. 6 shows an example of a multi-chamber semiconductor device manufacturing apparatus capable of realizing the present invention. The manufacturing procedure of the semiconductor device will be described with reference to FIGS. First, SiO 2 is deposited as a passivation film 15 on the surface of the substrate 10 in FIG. Subsequently, the substrate 10 is transported to the vapor deposition chamber 113 in FIG. 6 to form the semiconductor film 20f. After that, the substrate 10 is transferred to the laser irradiation exposure chamber 112 in FIG. 6, and according to the surface oxidation patterning method, as shown in FIG. Then, a surface oxide film was formed on a part of the surface of the semiconductor film 20f according to a photomask. Alternatively, according to the phase conversion patterning method, as shown in FIG. 5B, a laser beam is passed through a photomask and made incident on the semiconductor film 20f, and a part of the semiconductor film 20f is crystallized according to the photomask.

Subsequently, the substrate 10 is transferred to the vapor-phase etching chamber 118 shown in FIG. 6, and the semiconductor film 20f having no oxide film 22 formed on the surface as shown in FIG. 4B, or as shown in FIG. 5B. The semiconductor film 20f, which has not been converted into the crystal, is removed by vapor phase etching to form a semiconductor island 20 as shown in FIG. The surface shape of the semiconductor island 20 may be any of FIGS.

Subsequently, the substrate 10 is transported to the vapor deposition chamber 114, and an insulating coating film 30a, a translucent film 30b, and the like are deposited on the surface as shown in FIG. Thereafter, the substrate 10 may be exposed to the atmosphere, but the semiconductor device manufacturing apparatus of FIG. 6 can be used even in the subsequent laser annealing stage. The substrate is transported again to the laser irradiation exposure chamber 112 in FIG. 6 and irradiated with the laser light 40 as shown in FIG. 1D or 1F to crystallize the semiconductor island 20. Thus, a series of processes can be completed without being exposed to the atmosphere. According to this method, particularly, the quality of the interface between the semiconductor island 20 and the gate insulating film 30a can be ensured, and a high-performance transistor with high yield and high uniformity can be formed.

Of course, another metal film deposition chamber is attached to this multi-chamber and a metal film or a low-resistance semiconductor film to be a gate electrode is successively deposited, and the gate electrode is deposited in the same manner as the patterning method shown in FIGS. Can be patterned. In FIG. 6, the laser irradiation exposure chamber 112 may also be used as a gas phase etching chamber. The present invention is not limited to thin film transistors, but can be applied to any thin film device.

Embodiment of the Invention

Hereinafter, a thin film semiconductor device and a method of manufacturing the same according to an embodiment of the present invention will be described in detail.

(Embodiment 1) In Embodiment 1, a method for manufacturing a transistor of the present invention will be described with reference to FIGS. First, in FIG. 1A, a silicon oxide film is deposited as a passivation film 15 on a glass substrate 10 by PECVD using TEOS (tetraethoxysilane) at 300 ° C. to a thickness of 300 nm. Subsequently, an amorphous silicon film is deposited as a semiconductor film 20f by LPCVD using disilane as a raw material at 50 ° C. to a thickness of 50 nm. Then, as shown in FIG. 1B, the amorphous silicon film was patterned to form a semiconductor island 20. Here, the surface shape of the semiconductor island 20 is as shown in FIGS. 10 (a), (b), (c) and (d). Here, the main body of the semiconductor island 20 has a size of 1 μm × 2 μm to 15 μm × 30 μm. Next, as shown in FIG. 1C, a SiO ₂ film is formed as an insulating coating film 30 a on the semiconductor island 20 at 300 ° C. and 100 nm by PECVD using TEOS (tetraethoxysilane) and oxygen and nitrogen as raw materials. Deposited. Then, as shown in FIG. 1E, a laser beam is applied to the surface of some of the semiconductor islands 20 at 300 ° C. using TMS (tetramethylsilane), PECVD using oxygen and nitrogen as raw materials as a semitransparent film 30b. A 40 nm SiON film having an absorption coefficient of 10,000 cm ⁻¹ was formed at a thickness of 500 nm.

First, in the structure shown in FIG. 1D, the semiconductor island 20 was irradiated with a laser beam 40 to be crystallized. When the surface shape of the semiconductor island 20 is 4 μm or less in the y direction in FIGS. 10A to 10C, the crystal growth state of the semiconductor island after crystallization is shown in FIGS. As shown in FIG. 11C, when the island width in the y-direction exceeds this dimension, the microcrystalline region 205 is generated as shown in FIG. Alternatively, in the case where the shape of the semiconductor island is as shown in FIG. 10D and the distance from the connection portion 220 between the semiconductor peninsula 210 and the semiconductor island 20 to an arbitrary end of the semiconductor island is 2 μm or less, the semiconductor after laser annealing is performed. Although the island 20 is monocrystallized as shown in FIG. 11D, if the size exceeds this size, a microcrystallized region 205 is formed in a part of the semiconductor island 20 as shown in FIG. 11F. As shown in FIG. 1E, the surface of FIG. 1C is made of SiON as a translucent film 30b in order to prevent the generation of the microcrystallized region shown in FIGS. 11E and 11F. The film was deposited. Here, the SiON translucent film 30b was deposited at 300 ° C. and 500 nm by PECVD using TEOS (tetraethoxysilane), oxygen and nitrogen as raw materials. Absorption coefficient of the semi-transparent film Of2000-20000cm ^-1 with respect to the laser beam to be irradiated, preferably with those 4000-12000cm ^-1. Then, as shown in FIG. 1F, the semiconductor island 20 was irradiated with a laser beam 40 to achieve crystallization. As a result, the semiconductor islands 20 shown in FIGS. 10A to 10D crystallized as shown in FIGS. 11A to 11D.

Subsequently, a process for manufacturing a top gate transistor is started, but the semiconductor island 20 shown in FIGS. 11B to 11D is left as an active layer of the transistor. As shown in FIG. 1D, an insulating coating film 30a is formed on the semiconductor island 20, and this is used as it is as a gate insulating film of the transistor. Alternatively, when the translucent film 30b is formed on the surface as shown in FIG. 1F, the translucent film 30b is selectively etched to obtain the structure shown in FIG. Also in this case, the insulating coating film 30a was a gate insulating film.

Next, a manufacturing process of the transistor will be described with reference to FIGS. First, for example, a Ta metal film was deposited on the insulating coating film 30a of FIG. 1D by using a sputter deposition method, and then the Ta metal film was patterned to form a gate electrode 60. Here, the shape of the gate electrode 60 is determined by the shape of the semiconductor island 20 shown in FIGS. 11B to 11D.

First, the case of the structure of the semiconductor island 20 in FIGS. 11B and 11C will be described. In this case, the gate electrode 60 can have a dual gate structure shown in FIGS. 7A and 7B or a single gate structure shown in FIGS. 8A and 8B. In these cases, the gate electrode 60 is arranged so as to avoid the central grain boundary 201b of the semiconductor island 20. On the other hand, if the shape of the semiconductor island 20 is as shown in FIG. 11D, since the semiconductor island is a single crystal, the gate electrode 60 may be a single gate or a multi-gate. FIGS. 9A and 9B show examples in which a single gate is arranged. Also in the present embodiment, the gate electrode 60 is arranged as shown in FIGS.

In a subsequent step, as shown in FIGS. 7C, 7D, 8C, 8D, or 9C, 9D, the source 20b and the drain of the silicon island are formed using the gate electrode 60 as a mask. Acceptor ions or donor ions were implanted in a self-aligned manner by ion implantation at the location 20c and at the junction of both channels near 201b.

Thereafter, as shown in FIGS. 7 (e) and (f), FIGS. 8 (e) and (f), or FIGS. 9 (e) and (f), 500 nm of SiO ₂ is formed by TECVD using TEOS as the interlayer insulating film 90. It is formed by the PECVD method. Then, the dopants in the source / drain regions 20b and 20c and the channel coupling portion were activated and the interlayer insulating film 90 was reformed by annealing with laser or furnace. A contact hole 87 in the source / drain region was formed, and a source electrode 70 and a drain electrode 80 were formed through the contact hole, thereby completing the TFT.

According to the thin film transistor device according to the present invention, the channel formed immediately below the gate electrode does not have a crystal grain boundary extending in a direction perpendicular to the direction in which carriers move, and the gate insulating film is formed by a conventional low-temperature deposition method. Since the characteristics are remarkably improved as compared with the above film, the thin film transistor can be manufactured as a transistor having high-performance switching characteristics comparable to a single crystal transistor, and having no variation in transistor characteristics. In the case where the surface shape of the semiconductor island 20 is as shown in FIG. 11B or FIG. 11C, the mobility of the TFT was 360 cm 2 / vs, and good characteristics were obtained. On the other hand, when the surface shape of the semiconductor island 20 was as shown in FIG. 11D, the mobility of the TFT was 460 cm 2 / vs, and further excellent characteristics were obtained.

(Embodiment 2) The present invention relates to a new patterning method for patterning a semiconductor film without using a resist and without being exposed to the atmosphere, which will be described with reference to FIGS. 1A to 1F show a process of manufacturing a transistor. FIG. 6 shows a multi-chamber type semiconductor device manufacturing apparatus used in the embodiment. The semiconductor device manufacturing apparatus shown in FIG. 6 includes a plurality of chambers (chambers), one or more vapor deposition chambers 113 or 114 for depositing a thin film, and a laser irradiation exposure chamber 112 for irradiating a laser to the thin film. A gas phase etching chamber 118 for etching a thin film, a substrate transfer means 121, an exhaust device 119 for evacuating the inside of each chamber, and a delivery chamber 116 for introducing and removing a substrate. Further, a pre-processing chamber 117 can be attached as pre-processing of the substrate.

First, the substrate 10 is introduced into the delivery chamber 116 of the multi-chamber semiconductor device manufacturing apparatus, transferred to the pretreatment chamber 117 through the stock chamber 115, and subjected to substrate cleaning. Thereafter, the substrate is carried into a vapor deposition chamber 114 where a thin film can be deposited by PECVD, and a silicon oxide film is used as a passivation film 15 on a glass substrate 10 using TEOS (tetraethoxysilane) as a raw material, as shown in FIG. Deposited 300 nm at 300 ° C. by PECVD. Subsequently, the wafer was carried into a vapor-phase deposition chamber 113 where a PECVD thin film could be deposited using silane as a raw material, and an amorphous silicon film having a thickness of 50 nm was deposited as a semiconductor film 20f. After the deposition of the amorphous silicon film, the surface of the amorphous silicon film is hydrogen-terminated and hardly oxidized, and this state can be maintained at room temperature for several hours.

After that, the substrate 10 is carried into the laser irradiation exposure chamber 112, and the amorphous silicon film 20f is irradiated with the laser light 41 as the light 41 through the photomask 3 in an oxygen atmosphere as shown in FIG. Here, the light 41 is 0.01 mJ / cm2 to 800 mJ / cm2, preferably 1 mJ / cm2 to 400 mJ / cm2, and the number of times of irradiation may be one or more. After light irradiation, amorphous silicon is oxidized by oxygen in the atmosphere in a portion exposed to light 41, and a silicon oxide film 22 is formed on the surface. In this state, the substrate is transported to the vapor phase etching chamber 118. In the vapor phase etching chamber 118, hydrogen is decomposed into atomic hydrogen while the tungsten filament is kept at 1200 to 2600 ° C., preferably 1800 to 2100 ° C. Then, as shown in FIG. 4B, the silicon film 20f on which the oxide film 22 is not formed on the surface is etched by atomic hydrogen. As a result, the silicon island 20 could be patterned. Here, the shape of the silicon island 20 may be any of FIGS. 10B, 10C, and 10D. Next, the substrate 10 is carried into the PECVD vapor deposition chamber 114, and an SiO ₂ film is formed on the patterned silicon island 20 as an insulating coating film 30a by TEOS (tetraethoxysilane) as shown in FIG. ) Was deposited to a thickness of 100 nm by using PECVD using as a raw material. Subsequently, an SiON film is deposited as a translucent film 30b at 300 ° C. by using PECVD using TMS (tetramethylsilane), oxygen and nitrogen as raw materials. The semi-transparent film absorption coefficients for the laser beam 40 to be irradiated 2000-20000cm ^-1, desirably used was the 4000-12000cm ^-1. It was a SiON film of 12000 cm ^-1 and was formed to a thickness of 500 nm.

Subsequently, the substrate 10 was introduced into the laser irradiation exposure room 112, and the semiconductor island 20 was irradiated with the laser light 40 as shown in FIG. 1D or 1F. As a result, the semiconductor island 20 was crystallized as shown in FIGS. 11 (b), (c) and (d).

Subsequently, a thin film transistor was manufactured, and the subsequent processes were manufactured in the same process as in Example 1.

In the second embodiment, at least a semiconductor film forming step of depositing a semiconductor film 20f, a semiconductor island forming step of patterning a semiconductor film to form a semiconductor island 20, and an insulating coating film of forming an insulating coating film 30a. Can be performed without exposure to the air, which leads to improved device performance, reduced variation in device performance, improved yield, and improved productivity. As a result of carrying out Example 2, good characteristics were obtained in which the mobility of the n-type transistor was 560 cm 2 / vs, the S value was 0.2 V / dec, and Vth was 0.1 V. In addition, in this method, variation in threshold voltage was within 50 mV, and a uniform transistor characteristic distribution was obtained.

Embodiment 3 The present invention relates to a new patterning method for patterning a semiconductor film without using a resist and without being exposed to the atmosphere, which will be described with reference to FIGS. 1A to 1F show a process of manufacturing a transistor. FIG. 6 shows a multi-chamber type semiconductor device manufacturing apparatus used in the embodiment. The semiconductor device manufacturing apparatus shown in FIG. 6 includes a plurality of chambers (chambers), one or more vapor deposition chambers 113 or 114 for depositing a thin film, and a laser irradiation exposure chamber 112 for irradiating a laser to the thin film. And a gas phase etching chamber 118 for etching a thin film, a substrate transfer means 121, an exhaust device 119 for evacuating the inside of each chamber, and a delivery chamber 116 for introducing and removing a substrate. Further, a pre-processing chamber 117 can be attached as pre-processing of the substrate.

First, the substrate 10 is introduced into the delivery chamber 116 of the multi-chamber semiconductor device manufacturing apparatus, transferred to the pretreatment chamber 117 through the stock chamber 115, and subjected to substrate cleaning. Thereafter, the substrate is carried into a vapor deposition chamber 114 where a thin film can be deposited by PECVD, and a silicon oxide film is used as a passivation film 15 on a glass substrate 10 using TEOS (tetraethoxysilane) as a raw material, as shown in FIG. Deposited 300 nm at 300 ° C. by PECVD. Subsequently, the wafer was carried into a vapor deposition chamber 113 where PECVD thin film deposition using silane as a raw material was possible, and an amorphous silicon film was deposited to a thickness of 50 nm as a semiconductor film 20f as shown in FIG.

Thereafter, the substrate 10 is carried into the laser irradiation exposure chamber 112, and the amorphous silicon film 20f is irradiated with the laser light 40 through the photomask 3 as shown in FIG. Here, the laser light 40 is 10 mJ / cm2 to 800 mJ / cm2, preferably 100 mJ / cm2 to 600 mJ / cm2, and the number of times of irradiation may be one or more. After the light irradiation, the portion irradiated with the laser light 40 is phase-converted from amorphous silicon to crystalline silicon 20g. In this state, the substrate 10 is transferred to the vapor phase etching chamber 118. In the vapor phase etching chamber 118, hydrogen is decomposed into atomic hydrogen while the tungsten filament is kept at 1200 to 2600 ° C., preferably 1800 to 2100 ° C. Then, as shown in FIG. 5B, the amorphous silicon film 20f that has not undergone phase conversion is etched by atomic hydrogen. Thereby, the silicon island 20 was formed. Here, the shape of the silicon island 20 may be any of FIGS. 10B, 10C, and 10D.

Next, the substrate 10 is carried into the PECVD vapor deposition chamber 114, and an SiO ₂ film is formed on the patterned silicon island 20 as an insulating coating film 30a by TEOS (tetraethoxysilane) as shown in FIG. ) Was deposited to a thickness of 100 nm by using PECVD using as a raw material. Subsequently, an SiON film is deposited as a translucent film 30b at 300 ° C. by using PECVD using TMS (tetramethylsilane), oxygen and nitrogen as raw materials. The semi-transparent film absorption coefficients for the laser beam 40 to be irradiated 2000-20000cm ^-1, desirably used was the 4000-12000cm ^-1. It was a SiON film of 12000 cm ^-1 and was formed to a thickness of 500 nm.

Subsequently, the substrate 10 was introduced into the laser irradiation exposure room 112, and the semiconductor island 20 was irradiated with the laser light 40 as shown in FIG. 1D or 1F. As a result, the semiconductor island 20 was crystallized as shown in FIGS. 11 (b), (c) and (d).

Subsequently, a thin film transistor was manufactured, and the subsequent processes were manufactured in the same process as in Example 1.

In the third embodiment, at least a semiconductor film forming step of depositing the semiconductor film 20f, a semiconductor island forming step of patterning the semiconductor film to form the semiconductor island 20, and an insulating coating film of forming the insulating coating film 30a. Could be performed without exposure to the air, which led to improved device performance, reduced variation in device performance, improved yield, and improved productivity. As a result of carrying out Example 2, good characteristics were obtained in which the mobility of the n-type transistor was 550 cm 2 / vs, the S value was 0.2 V / dec, and Vth was 0.1 V. In addition, in this method, variation in threshold voltage was within 50 mV, and a uniform transistor characteristic distribution was obtained.

Further, in the above description, the non-LDD structure is described as an example of the structure of the polycrystalline thin film transistor, but other structures such as an LDD structure and a GOLD structure can be similarly implemented.

In the above description, an excimer laser beam was used as the laser beam. Regarding the wavelength, the same result was obtained using any of 248, 308, and 351 nm.

The technical scope of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the spirit of the present invention. For example, the type of a specific film constituting each part of the TFT can be appropriately changed.

The invention's effect

A semiconductor island serving as an active region is formed, and an insulating coating film serving as a gate insulating film is formed thereon. Then, the semiconductor film and the insulating coating film are simultaneously laser-annealed. As a result, the semiconductor island grows in the lateral direction in all regions, and at the same time, the quality of the insulating coating film is improved. As for the patterning of the semiconductor film, while the semiconductor film is maintained in an oxygen atmosphere, light is irradiated to the semiconductor film through a mask to partially form an ultrathin oxide film on the surface, and thereafter, selective vapor phase etching is performed. By removing the semiconductor film on which the surface ultrathin oxide film is not formed, the semiconductor film can be patterned without using a resist. By continuously performing the above steps without exposing to air, a thin film transistor with excellent transistor characteristics and high yield can be manufactured.

(A)-(f) is sectional drawing of the process drawing which shows an example of the manufacturing method of the thin film semiconductor device by the Example of this invention. FIG. 3 is a diagram showing the dependence of the translucent film thickness on the lateral crystal growth distance FIG. 3 is a diagram illustrating an etching rate of amorphous silicon, crystalline silicon, and silicon oxide with respect to atomic hydrogen. (A) and (b) are views showing a novel semiconductor film patterning method of the present invention. (A) and (b) are views showing a novel semiconductor film patterning method of the present invention. FIG. 2 is a view showing a multi-chamber type semiconductor device manufacturing apparatus for performing a series of processes up to a semiconductor film forming step, a semiconductor island forming step, and an insulating coating film without being exposed to the air in the present invention. 3A to 3F are process diagrams illustrating an example of a method for manufacturing a thin film semiconductor device according to an embodiment of the present invention. 3A to 3F are process diagrams illustrating an example of a method for manufacturing a thin film semiconductor device according to an embodiment of the present invention. 3A to 3F are process diagrams illustrating an example of a method for manufacturing a thin film semiconductor device according to an embodiment of the present invention. (A)-(d) is a figure which shows the surface shape of a semiconductor island in the process of FIG.1 (b). (A)-(f) is a figure which shows the aspect of the crystal growth after laser irradiation of a semiconductor island in the process of FIG.1 (d).

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Hydrogen atom 2 Oxygen or nitrogen 3 Photomask 4 Projection lens system 10 Glass substrate 15 Passivation film 20f Semiconductor film 20g Polycrystalline semiconductor film 20 Semiconductor island 20a Channel region 20b Source region 20c Drain region 22 Oxide film or nitride film or oxynitride Film 30 Insulating coating film 30a Buffer film 30b Translucent film 50a Lateral heat outflow 50b Vertical heat outflow 110 Laser light source 111 Lens system 112 Laser irradiation exposure room 113 Vapor deposition chamber 114 Vapor deposition chamber 115 Stock chamber 116 Delivery room 117 Pretreatment chamber 118 Gas phase etching chamber 119 Exhaust device 121 Substrate transfer means 201a X-shaped crystal grain boundary 201b Semiconductor island center crystal grain boundary 201c Semiconductor crystal x-direction crystal grain boundary 205 Microcrystal region 210 Semiconductor peninsula 220 Connection between semiconductor island and semiconductor peninsula 0 gate electrode 70 source electrode 80 drain electrode 90 interlayer insulating film 87 contact hole

Claims (14)

A semiconductor island forming step of forming a semiconductor film on a substrate and further processing to form a semiconductor island, a coating film forming step of forming an insulating coating film on the surface of the semiconductor island, and laser irradiating the semiconductor island A method for manufacturing a semiconductor transistor, comprising: a crystallization step of crystallizing; and a device forming step of forming a semiconductor transistor from the semiconductor island. 2. The method according to claim 1, wherein at least a part of the insulating coating film is used as a gate insulating film of a semiconductor transistor in the device forming step. 3. The semiconductor transistor according to claim 1, wherein the insulating coating film in the step of forming the coating film includes a translucent film having an absorption coefficient of 4000 cm ⁻¹ to 20,000 cm ^{−1. 4.} Method 2. The insulating coating film in the coating film forming step, wherein the insulating coating film includes a silicon oxide film and a translucent film having an absorption coefficient of 4000 cm ^-1 to 20,000 cm ^-1. Item 4. The method for manufacturing a semiconductor transistor according to item 2 or 3. The semiconductor island forming step includes: a semiconductor film forming step of forming an amorphous semiconductor film on a substrate; a phase conversion step of irradiating the semiconductor film with a laser through a photomask to crystallize the semiconductor film; 5. A selective etching step in which an amorphous semiconductor film that has not been crystallized in the conversion step is etched to leave only a crystallized semiconductor film. Semiconductor manufacturing method The semiconductor island forming step includes: a semiconductor film forming step of forming an amorphous semiconductor film on a substrate; and irradiating a light passed through a photomask with the amorphous semiconductor film kept at least in an oxygen atmosphere. 3. The method according to claim 1, further comprising: a surface oxidation step of oxidizing the surface of the amorphous semiconductor film according to the photomask pattern; and a selective etching step of etching the amorphous semiconductor film whose surface has not been oxidized. 5. The method for manufacturing a semiconductor transistor according to claim 3 or claim 4. The selective etching process is to selectively remove an exposed amorphous semiconductor film using atomic hydrogen generated by decomposing hydrogen molecules with a tungsten filament heated to 1200 to 2600 degrees Celsius. 7. The method of manufacturing a semiconductor transistor according to claim 1, wherein the semiconductor transistor is manufactured by using the method described in claim 1 or claim 2 or claim 3 or claim 4 or claim 5 or claim 6. 5. The method according to claim 1, wherein at least the steps from the step of forming a semiconductor island to the step of forming a coating film are continuously performed without exposure to the air. 8. The method for manufacturing a semiconductor transistor according to claim 5, 6, or 7, 5. The method according to claim 1, wherein at least the steps from the step of forming a semiconductor island to the step of forming a coating film are continuously performed without exposure to the air. An apparatus for manufacturing a semiconductor transistor according to claim 5, 6, or 7, Irradiating the amorphous semiconductor film with a laser through a photomask to crystallize it according to the photomask pattern; and etching the amorphous semiconductor film that has not been crystallized in the phase conversion step. A method for patterning a semiconductor film, comprising: a selective etching step for leaving only a crystallized semiconductor film. An oxidizing step of irradiating light through a photomask with the amorphous semiconductor film kept at least in an oxygen atmosphere to oxidize the surface of the amorphous semiconductor film according to the photomask pattern; and that the surface was not oxidized. A method of patterning a semiconductor film, comprising: a selective etching step of etching an amorphous semiconductor film. The vapor-phase etching process is characterized in that the amorphous semiconductor film is selectively etched with atomic hydrogen generated by decomposing hydrogen molecules with a tungsten filament heated to 1200 to 2600 degrees Celsius. A method for patterning a semiconductor film according to claim 10 or claim 11. 13. The semiconductor film according to claim 1, wherein the semiconductor film is a silicon film, a germanium film, or a silicon and germanium compound. 4. The method according to claim 1, wherein the insulating coating film is a silicon oxide film, a silicon nitride film, or a silicon oxynitride film.

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