JP5284669B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a semiconductor device and a manufacturing method thereof.

In recent years, an integrated circuit using an SOI (Silicon On Insulator) substrate instead of a bulk silicon wafer has been developed. By taking advantage of the features of the thin single crystal silicon layer formed on the insulating layer, the transistors in the integrated circuit can be formed completely separated from each other, and the transistors can be made fully depleted, High-value-added semiconductor integrated circuits such as high integration, high-speed driving, and low power consumption can be realized. In the development of such an LSI using an SOI substrate, the operating frequency can be improved and the processing capability can be improved by reducing the chip area by using a multilayer wiring technique.

In recent years, a method of forming a single crystal silicon layer on a supporting substrate made of glass by using a smart cut method has been proposed (for example, see Patent Document 1). Since the glass substrate can have a larger area than a silicon wafer and is inexpensive, it is possible to manufacture a large-area and inexpensive SOI substrate by using the glass substrate as a base substrate.

A technique for forming a bottom-gate thin film transistor by applying a technique for manufacturing an SOI substrate (see, for example, Patent Document 2) and a technique for forming a dual-gate thin film transistor (for example, see Patent Document 3) are known. As described above, the transistor in which the gate electrode is formed on the smooth surface side of the silicon wafer has a small defect density in the channel portion and exhibits good characteristics.
JP 11-163363 A JP 2000-106333 A JP 2002-57309 A

As described above, it is effective to use the smart cut method to form a transistor in which a single crystal semiconductor layer typified by a single crystal silicon layer is formed over a supporting substrate and the single crystal semiconductor layer is an active layer. Some of such transistors have an insulating layer (gate insulating film) and a conductive layer (gate wiring, gate electrode) between the single crystal semiconductor layer and the supporting substrate.

As an example of this step, after providing an insulating layer (gate insulating film) and a conductive layer (gate wiring, gate electrode) on a silicon wafer, a bonding layer with a support substrate may be formed thereon, At this time, it is necessary to flatten the bonding layer in order to attach the bonding layer to the support substrate. In order to planarize the bonding layer, there is a method of performing film thinning by surface polishing or dry etching (referred to as an etch back process), but a step is provided by a conductive layer (gate wiring, gate electrode). It is difficult to ensure sufficient flatness of the bonding layer by the treatment, and the number of steps for flattening increases.

In addition, when a substrate made of a material having a high thermal linear expansion coefficient such as glass is used as a large substrate, the amount of warpage of the substrate increases due to the difference in stress coefficient between the gate electrode and the substrate in the heat treatment in the manufacturing process. There may be a problem that the substrate cannot be transferred to the process apparatus. Further, in the process of bonding the silicon wafer on which the conductive layer is formed and the support substrate, bonding failure may occur.

An object of the present invention is to provide a semiconductor device in which a conductive layer is formed between a single crystal semiconductor layer and a supporting substrate, and the amount of warpage of the supporting substrate due to heat is small.

An object of the present invention is to provide a semiconductor device with high productivity and a manufacturing method thereof in a semiconductor device in which a conductive layer is formed between a single crystal semiconductor layer and a supporting substrate.

The semiconductor device of the present invention has a structure in which a conductive layer is formed between a single crystal semiconductor layer and a supporting substrate, and a gate insulating film is formed between the single crystal semiconductor layer and the conductive layer, A gap is provided between the conductive layer and the support substrate. In this structure, the first insulating layer is formed between the single crystal semiconductor layer and the supporting substrate. The first insulating layer is not formed between the conductive layer and the single crystal semiconductor layer. The film thickness of the first insulating layer is larger than the film thickness of the conductive layer.

In the structure of the semiconductor device, a second insulating layer may be provided between the conductive layer and the gap. That is, the second insulating layer may be in contact with the first insulating layer or the conductive layer. A third insulating film may be formed between the support substrate and the first insulating layer.

In the method for manufacturing a semiconductor device of the present invention, a gate insulating film is formed over a single crystal semiconductor substrate, an embrittlement layer is formed over the single crystal semiconductor substrate, and a conductive layer is left over the conductive layer. The first insulating layer is formed thereon, the resist is removed together with the first insulating layer on the resist, the single crystal semiconductor substrate and the supporting substrate are bonded together, and the embrittled layer is formed. The single crystal semiconductor substrate and the support substrate are separated from each other at the boundary. In this configuration, the first insulating layer is formed to have a thickness greater than that of the conductive layer. A method of removing both the first insulating layer and the resist is referred to as a lift-off method. Note that the order of the step of forming the gate insulating film and the step of forming the embrittlement layer may be first. Through the above steps, a convex step in a bonding layer provided by a conductive layer (a gate wiring or a gate electrode) that causes a bonding failure when the single crystal semiconductor substrate and the supporting substrate are bonded can be removed.

The manufacturing method of the semiconductor device can shorten the process as compared with the method for removing the convex step of the bonding layer described below. That is, first, the resist after the conductive layer is formed is peeled off, the first insulating layer is formed so as to be in contact with the conductive layer, and the resist mask is exposed so that the convex step of the bonding layer provided by the conductive layer is exposed. This is a step of forming and removing the convex bonding layer using dry etching or wet etching. In this step, the number of masks and the bonding layer etching step are increased as compared with the lift-off method which is a method for manufacturing a semiconductor device of the present invention.

In the structure of the method for manufacturing a semiconductor device, the second insulating layer may be formed so as to be in contact with the first insulating layer or the conductive layer formed over the single crystal semiconductor substrate. Note that a third insulating film may be formed on the surface of the support substrate.

In any case, when the single crystal semiconductor substrate and the support substrate are bonded to each other, the surfaces thereof are in contact with each other, but the support substrate is not in contact with the region where the gap is formed. However, the area where the gap is formed is substantially the same as the area where the conductive layer is formed, and the area of the gap is in contact with each other when the single crystal semiconductor substrate and the support substrate are bonded together. Since it is smaller than the area, it can be bonded without defective bonding. In such a semiconductor device configuration, when the temperature of the semiconductor device rises, even if the expansion / contraction ratios of the conductive layer and the support substrate are different, the gap relaxes the strain, so that the substrate warps or the film peels off. , Defects due to the difference in expansion / contraction rate can be reduced.

In addition, as described above, in the method for manufacturing a semiconductor device of the present invention, when the single crystal semiconductor substrate and the supporting substrate are bonded to each other, a gap generated by forming the conductive layer and a step caused by the gap are flattened. It can be pasted together without becoming. That is, the planarization process can be omitted, and productivity can be improved.

Moreover, the following effects can be additionally expected by such a configuration. That is, when the support substrate has flexibility, or when the semiconductor element is transferred to the flexible substrate, the gate wiring can be prevented from being broken due to bending. In addition, when the support substrate is a silicon substrate, parasitic capacitance generated between the gate electrode and the support substrate can be reduced. In addition, when conductive polycrystalline silicon is used for the gate electrode, it is possible to reduce the change in threshold voltage of the element due to diffusion of alkali metal such as sodium from the support substrate into the gate electrode. In addition, when a reflective layer made of a highly reflective metal film is formed on the surface of the support substrate, parasitic capacitance between the reflective layer and the gate electrode can be reduced. Further, when conductive polycrystalline silicon is used for the gate electrode, since there is a hollow, light from the back surface of the support substrate (for example, backlight light) can be reflected at the interface between the support substrate and the hollow. The variation of the threshold voltage due to the change in the work function can be suppressed. Further, even when a support substrate has a large area and uniform planarization treatment is difficult, the planarization treatment can be omitted and bonding can be performed. Therefore, a highly reliable semiconductor device without a bonding defect is provided. Can do.

In a semiconductor device in which a conductive layer is formed between a single crystal semiconductor layer and a supporting substrate, a gap is provided between the conductive layer and the supporting substrate. A highly reliable semiconductor device can be provided.

In a method for manufacturing a semiconductor device in which a conductive layer is formed between a single crystal semiconductor layer and a supporting substrate, the insulating layer formed over the conductive layer is removed by a lift-off method, thereby planarizing the surface of the single crystal semiconductor substrate Processing can be omitted, and a manufacturing method of a highly productive semiconductor device can be provided.

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below. Note that in the structures of the present invention described below, the same reference numerals are used in different drawings. In this specification, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics.

(Embodiment 1)
In this embodiment mode, an example of a method for manufacturing a semiconductor device of the present invention will be described with reference to FIGS. More specifically, a substrate processing method used for the SOI substrate will be described with reference to FIG. A method for manufacturing an SOI substrate will be described with reference to FIG.

First, a single crystal semiconductor substrate 110 is prepared. As the single crystal semiconductor substrate 110, for example, a semiconductor substrate made of a Group 4 element such as silicon, germanium, silicon germanium, or silicon carbide can be used. Of course, a substrate made of a compound semiconductor such as gallium arsenide or indium phosphide may be used. In this embodiment, a single crystal silicon substrate is used as the single crystal semiconductor substrate 110. The size of the single crystal semiconductor substrate 110 is not limited. For example, a circular semiconductor substrate such as 8 inches (200 mm), 12 inches (300 mm), and 18 inches (450 mm) can be processed into a rectangle and used. Note that in this specification, a single crystal means that the crystal structure is formed with a certain regularity and the crystal axes are in the same direction in any part. That is, it does not matter about the number of defects.

First, a single crystal semiconductor substrate 110 is prepared (see FIG. 1A).

After the single crystal semiconductor substrate 110 is washed, an insulating layer 112 is formed on the surface of the single crystal semiconductor substrate 110. The thickness of the insulating layer 112 is preferably 10 nm to 400 nm.

Examples of the material forming the insulating layer 112 include silicon oxide, silicon nitride, silicon oxynitride, and silicon nitride oxide. As a method for forming the insulating layer 112, a CVD method, a sputtering method, a method using oxidation (or nitridation) of the single crystal semiconductor substrate 110, and the like can be given.

Next, the single crystal semiconductor substrate 110 is irradiated with an ion beam 140 made of ions accelerated by an electric field through the insulating layer 112, and an embrittled region is formed in a region at a predetermined depth from the surface of the single crystal semiconductor substrate 110. 114 is formed (see FIG. 1B). The depth of the region where the embrittled region 114 is formed can be controlled by the acceleration energy of the ion beam 140 and the incident angle of the ion beam 140. Note that the embrittlement region 114 is formed in a region having a depth approximately equal to the average penetration depth of ions.

The thickness of the single crystal semiconductor layer separated from the single crystal semiconductor substrate 110 is determined by the depth at which the above-described embrittlement region 114 is formed. The depth at which the embrittlement region 114 is formed is from 50 nm to 500 nm, preferably from 50 nm to 200 nm, from the surface of the single crystal semiconductor substrate 110.

When ions are implanted into the single crystal semiconductor substrate 110, an ion implantation apparatus or an ion doping apparatus can be used. In the ion implantation apparatus, a source gas is excited to generate ion species, the generated ion species are mass-separated, and an ion species having a predetermined mass is injected into a workpiece. The ion doping apparatus excites a process gas to generate ion species, and implants the generated ion species into a workpiece without mass separation. Note that an ion doping apparatus provided with a mass separator can also perform ion implantation with mass separation, as in the case of an ion implanter. In this specification, only one of the ion implantation apparatus and the ion doping apparatus is specified particularly when it is necessary to use the ion implantation apparatus, and if not particularly specified, any apparatus may be used for ion implantation. I will do it.

The ion implantation process in the case of using an ion doping apparatus can be performed, for example, under the following conditions.
・ Acceleration voltage: 10 kV to 100 kV (preferably 30 kV to 80 kV)
・ Dose amount 1 × 10 ¹⁶ / cm ² or more and 4 × 10 ¹⁶ / cm ² or less ・ Beam current density ² μA / cm ² or more (preferably 5 μA / cm ² or more, more preferably 10 μA / cm ² or more)

In the case of using an ion doping apparatus, a gas containing hydrogen can be used as a source gas in an ion implantation process. By using the gas, H ⁺ , H ₂ ⁺ , and H ₃ ⁺ can be generated as ionic species. When hydrogen gas is used as a source gas, it is preferable to implant a large amount of H ₃ ⁺ . Specifically, it is preferable that the ion beam 140 includes 70% or more of H ₃ ⁺ ions with respect to the total amount of H ⁺ , H ₂ ⁺ , and H ₃ ⁺ . Moreover, it is more preferable that the ratio of H ₃ ⁺ ions is 80% or more. By increasing the ratio of H ₃ ^{+ in} this manner, the embrittlement region 114 can contain hydrogen at a concentration of 1 × 10 ²⁰ atoms / cm ³ or more. This facilitates separation from the embrittled region 114. Further, by implanting a large amount of H ₃ ⁺ ions, the ion implantation efficiency is improved as compared with implanting H ⁺ and H ₂ ⁺ . That is, the time required for driving can be shortened. In addition, by using H ₃ ⁺ , the average penetration depth of ions can be reduced, so that the embrittled region 114 can be formed in a shallow region.

When using an ion implantation apparatus, it is preferable to implant H ₃ ⁺ ions by mass separation. Of course, H ⁺ or H ₂ ⁺ may be implanted. However, when an ion implantation apparatus is used, since ion species are selected and implanted, the efficiency of ion implantation may be reduced as compared with the case where an ion doping apparatus is used.

In addition to the gas containing hydrogen, the source gas in the ion implantation process is a rare gas such as helium or argon, a halogen gas typified by fluorine gas or chlorine gas, or a halogen compound gas such as fluorine compound gas (for example, BF ₃ ). One or more kinds of gases selected from the above can be used. When helium is used as the source gas, the ion beam 140 with a high proportion of He ⁺ ions can be generated by not performing mass separation. By using such an ion beam 140, the embrittled region 114 can be efficiently formed.

Further, the embrittlement region 114 can be formed by performing the ion implantation process a plurality of times. In this case, the source gas may be different for each ion implantation process, or the same source gas may be used. For example, after ion implantation is performed using a rare gas as a source gas, ion implantation can be performed using a gas containing hydrogen as a source gas. Alternatively, ion implantation may be performed first using a halogen gas or a halogen compound gas, and then ion implantation may be performed using a gas containing hydrogen gas.

Although the example in which the embrittled region 114 is formed after the insulating layer 112 is formed is described above, the insulating layer 112 may be formed after the embrittled region 114 is formed. At this time, it is possible to avoid generation of defects and contamination of impurities due to the ion implantation process in the insulating layer 112. Note that in the case where the insulating layer 112 is formed by oxidation (or nitridation) of the single crystal semiconductor substrate 110, the insulating layer 112 is formed under a temperature condition that does not change the embrittlement layer.

After the embrittlement region 114 is formed, the conductive layer 116 is formed with a thickness of 50 to 200 nm (see FIG. 1C). The conductive layer 116 can be formed by a CVD method, a sputtering method, or the like. Specifically, materials such as aluminum, tungsten, titanium, tantalum, molybdenum, nickel, chromium, niobium, platinum, copper, gold, silver, manganese, neodymium, carbon, and silicon can be used. Alternatively, an alloy containing the above material as its main component or a compound containing the above material may be used. The conductive layer 116 may have a single-layer structure or a stacked structure. In this embodiment mode, molybdenum is formed to a thickness of 100 nm.

Next, a resist 120 for processing the conductive layer 116 into a predetermined shape is formed. The resist 120 is formed with a thickness of 0.5 to 3 μm. Next, the conductive layer 116 is etched by a method such as dry etching or wet etching, so that the conductive layer 118 processed into a predetermined shape is formed (see FIG. 1D). Note that the resist 120 is not removed at this point. Next, an insulating film 122 made of silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, or the like is formed by a CVD method or a sputtering method (see FIG. 1E). At this time, although the insulating film is also formed on the resist 120, the resist 120 is not formed on the side wall of the resist 120 because the resist 120 has a sufficient thickness. The insulating film is formed under the condition that the resist is not lost or largely deformed due to the substrate temperature or the like.

Next, the resist is removed, and the insulating film 122 over the resist is removed by a lift-off method, so that a first insulating layer 124 is formed (see FIG. 1F). In this manner, the first insulating layer 124 is formed in a portion other than the conductive layer 118.

Next, the second insulating layer 126 is formed over the first insulating layer 124 (see FIG. 1G).

Since the second insulating layer 126 is a layer that forms a bond in bonding, the surface thereof preferably has high flatness. As such a second insulating layer 126, for example, a silicon oxide film formed by a chemical vapor deposition method using an organosilane gas can be used. Further, a silicon nitride film may be used. Further, the second insulating layer 126 may have a stacked structure including a plurality of layers. For example, a blocking layer formed using a material capable of suppressing entry of an impurity element into the semiconductor layer may be formed between the layer having high flatness and the first insulating layer 124. Examples of the material forming the blocking layer include silicon nitride, silicon nitride oxide, aluminum nitride, and aluminum nitride oxide. Of course, silicon oxide, silicon oxynitride, and other insulating materials may be used. Note that although the example in which the second insulating layer 126 is formed is described in this embodiment mode, the second insulating layer 126 may be formed as long as the surface flatness is sufficiently ensured at the stage where the first insulating layer 124 is formed. Formation of layer 126 may be omitted.

Next, the base substrate 100 is prepared (see FIG. 2A). As the base substrate 100, a light-transmitting glass substrate used in a liquid crystal display device or the like can be used. A glass substrate having a strain point of 580 ° C. or higher and 680 ° C. or lower (preferably 600 ° C. or higher and 680 ° C. or lower) may be used. The glass substrate is preferably an alkali-free glass substrate. For the alkali-free glass substrate, glass materials such as aluminosilicate glass, aluminoborosilicate glass, and barium borosilicate glass are used, for example.

As the base substrate 100, a glass substrate, a ceramic substrate, a substrate made of an insulator such as a quartz substrate or a sapphire substrate, a substrate made of a semiconductor such as silicon, a substrate made of a conductor such as metal or stainless steel, or the like is used. You can also.

Although not shown in this embodiment mode, an insulating layer may be formed on the surface of the base substrate 100. By providing the insulating layer, in the case where an impurity (such as an alkali metal or an alkaline earth metal) is contained in the base substrate 100, the impurity can be prevented from diffusing into the semiconductor layer. The insulating layer may have a single layer structure or a laminated structure. Examples of the material forming the insulating layer include silicon oxide, silicon nitride, silicon oxynitride, and silicon nitride oxide.

In this specification, oxynitride is a substance having a higher oxygen content than nitrogen as its composition, and nitride oxide is a substance having a higher nitrogen content than oxygen as its composition. Say. For example, silicon oxynitride refers to oxygen of 55 atomic% to 65 atomic%, nitrogen of 1 atomic% to 20 atomic%, silicon of 25 atomic% to 35 atomic%, and hydrogen of 0.1 atomic% to 10 atomic%. A substance contained in an atomic percent or less range. In addition, silicon nitride oxide means oxygen of 15 atomic% to 30 atomic%, nitrogen of 20 atomic% to 35 atomic%, silicon of 25 atomic% to 35 atomic%, and hydrogen of 15 atomic% to 25 atomic%. Substances included in the following ranges.

After that, the base substrate 100 and the single crystal semiconductor substrate 110 (see FIG. 2B) are attached to each other (see FIG. 2C). Specifically, after the surfaces of the base substrate 100 and the second insulating layer 126 are cleaned by a method such as ultrasonic cleaning, the surface of the base substrate 100 and the surface of the second insulating layer 126 are placed in contact with each other. To do. Then, pressure treatment is performed so that a bond is formed between the surface of the base substrate 100 and the surface of the second insulating layer 126. As a bonding mechanism, a mechanism related to van der Waals force or a mechanism related to hydrogen bonding may be considered.

Here, before the bonding is formed, the surface of the base substrate 100 or the second insulating layer 126 may be subjected to oxygen plasma treatment or ozone treatment to make the surface hydrophilic. By this treatment, a hydroxyl group is added to the surface of the base substrate 100 or the second insulating layer 126, so that a hydrogen bond can be formed at the bonding interface.

Next, the base substrate 100 and the single crystal semiconductor substrate 110 which are bonded are subjected to heat treatment so that the bonding is strong. The heating temperature at this time needs to be a temperature at which separation in the embrittled region 114 does not proceed. For example, it can be less than 400 ° C., preferably 300 ° C. or less. The heat treatment time is not particularly limited, and optimal conditions may be set as appropriate based on the relationship between the treatment speed and the bonding strength. In this embodiment mode, heat treatment is performed at 200 ° C. for 2 hours. Here, it is also possible to locally heat only the region related to bonding by irradiating the region related to bonding with microwaves. Note that the heat treatment may be omitted when there is no problem in bonding strength.

A gap 150 is formed between the base substrate 100 and the second insulating layer 126 in the portion where the conductive layer 118 is formed at the interface between the base substrate 100 and the single crystal semiconductor substrate 110 bonded in this manner. . At this time, although the gap 150 depends on the shape thereof, if it is 50% or less of the area of the single crystal semiconductor substrate 110, bonding failure does not occur even in the bonding step.

Next, the single crystal semiconductor substrate 110 is separated into the single crystal semiconductor layer 128 and the single crystal semiconductor substrate 130 in the embrittlement region 114 in FIG. 2C (see FIG. 2D). The single crystal semiconductor substrate 110 is separated by heat treatment. The temperature of the heat treatment can be based on the heat resistant temperature of the base substrate 100. For example, when a glass substrate is used as the base substrate 100, the heating temperature is preferably 400 ° C. or higher and 650 ° C. or lower. Note that heat treatment may be performed at 400 ° C to 700 ° C for a short time. Note that in this embodiment, heat treatment is performed at 600 ° C. for 2 hours.

By performing the heat treatment as described above, a volume change of minute holes formed in the embrittled region 114 occurs, and a crack occurs in the embrittled region 114. As a result, the single crystal semiconductor substrate 110 is separated along the embrittled region 114. Since the second insulating layer 126 is bonded to the base substrate 100, the single crystal semiconductor layer 128 separated from the single crystal semiconductor substrate 110 remains on the base substrate 100. Further, since the bonding interface between the base substrate 100 and the second insulating layer 126 is heated by this heat treatment, a covalent bond is formed at the bonding interface, and the bonding force between the base substrate 100 and the second insulating layer 126 is further increased. improves.

In the semiconductor substrate formed as described above, the surface of the single crystal semiconductor layer 128 has defects due to the separation process or the ion implantation process, and the flatness thereof is impaired. In the case of forming a bottom gate structure using the single crystal semiconductor substrate 110 of the present invention, a channel is formed at the interface between the single crystal semiconductor layer 128 and the insulating layer 112 serving as a gate insulating film, and the interface has a defect density. Small and smooth. Therefore, even if the defect density on the surface of the single crystal semiconductor layer 128 is high and the flatness is impaired, the device characteristics are not greatly affected. Therefore, it is not always necessary to repair or flatten the defects. However, in the case of a dual gate structure in which gate electrodes are provided above and below the single crystal semiconductor layer 128, a thin gate insulating layer having a high withstand voltage is formed on the surface of the uneven single crystal semiconductor layer 128. It is difficult. In addition, in the case where a defect exists on the surface of the single crystal semiconductor layer 128, the localized state density at the interface with the gate insulating layer is increased. A process of reducing 128 defects is performed. In this manner, a desired element structure or a defect repair or planarization process on the surface of the single crystal semiconductor layer 128 is performed as necessary.

In this embodiment, the flatness of the single crystal semiconductor layer 128 is improved and defects are reduced by irradiation with the laser light 142 over the single crystal semiconductor layer 128 (see FIG. 2E). By irradiation with laser light 142 from the upper surface side of the single crystal semiconductor layer 128, the upper surface of the single crystal semiconductor layer 128 is melted. After melting, the single crystal semiconductor layer 128 is cooled and solidified, whereby a single crystal semiconductor layer with improved flatness on the upper surface is obtained. In this embodiment, since the laser beam 142 is used, the base substrate 100 is not directly heated. That is, the temperature rise of the base substrate 100 can be suppressed. Therefore, a substrate with low heat resistance such as a glass substrate can be used for the base substrate 100. Of course, the base substrate may be heated within the allowable temperature range. By heating the base substrate, the surface density of the semiconductor layer after separation from the support substrate and the energy density of the laser beam necessary to reduce defects can be reduced, so the laser light irradiation area is expanded. Can improve tact.

Here, melting of the single crystal semiconductor layer 128 by irradiation with the laser light 142 is preferably partial melting. This is because, when completely melted, there is a high possibility that the crystallinity is lowered due to disordered nucleation after the liquid phase is formed and the crystallinity is lowered. On the other hand, by partial melting, crystal growth proceeds from a solid phase portion that is not melted. Thereby, defects in the semiconductor layer can be reduced. Here, complete melting means that the single crystal semiconductor layer 128 is melted to the vicinity of the lower interface to be in a liquid state. On the other hand, partial melting in this case means that the upper portion of the single crystal semiconductor layer 128 is melted to be in a liquid phase, but the lower portion is not melted and remains in a solid phase.

A pulsed laser is preferably used for the laser light irradiation. This is because high-energy pulsed laser light can be instantaneously oscillated, and it becomes easy to create a partially molten state. The oscillation frequency is preferably about 1 Hz to 10 MHz. More preferably, it is 10 Hz or more and 1 MHz or less. As the above-mentioned pulsed laser, Ar laser, Kr laser, excimer (ArF, KrF, XeCl) laser, CO ₂ laser, YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, GdVO ₄ laser, Y ₂ O ₃ Laser, ruby laser, alexandrite laser, Ti: sapphire laser, copper vapor laser, gold vapor laser, or the like can be used. In order to partially melt, it is preferable to use a pulsed laser, but it is not limited to this. That is, the use of a continuous wave laser is not excluded. As the continuous wave laser, Ar laser, Kr laser, CO ₂ laser, YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, GdVO ₄ laser, Y ₂ O ₃ laser, ruby laser, alexandrite laser, Ti: There are sapphire laser, helium cadmium laser and the like.

The wavelength of the laser light 142 needs to be a wavelength that is absorbed by the single crystal semiconductor layer 128. The wavelength may be determined in consideration of the skin depth of the laser light. For example, it can be in the range of 250 nm to 700 nm. The energy density of the laser light 142 can be determined in consideration of the wavelength of the laser light 142, the skin depth of the laser light, the thickness of the single crystal semiconductor layer 128, and the like. The energy density of the laser beam 142 may be set in the range of 300 mJ / cm ² or more and 800 mJ / cm ² or less, for example. The range of the energy density is an example when a XeCl excimer laser (wavelength: 308 nm) is used as a pulsed laser.

Irradiation with the laser beam 142 can be performed in an atmosphere containing oxygen such as an air atmosphere or an inert atmosphere such as a nitrogen atmosphere. In order to irradiate the laser beam 142 in an inert atmosphere, the laser beam 142 may be irradiated in an airtight chamber and the atmosphere in the chamber may be controlled. In the case where a chamber is not used, a nitrogen atmosphere can be formed by spraying an inert gas such as nitrogen gas on the surface to be irradiated with the laser light 142.

Here, the effect of improving the flatness of the single crystal semiconductor layer 128 is higher than that in an air atmosphere when the inert gas is used in an inert atmosphere such as nitrogen. In addition, the inert atmosphere has a higher effect of suppressing the generation of cracks and ridges than the air atmosphere, and the usable energy density range of the laser beam 142 is widened. Note that the irradiation with the laser beam 142 may be performed in a vacuum. When the laser beam 142 is irradiated in a vacuum, the same effect as irradiation in an inert atmosphere can be obtained.

After irradiation with the laser light 142 as described above, a thinning process for reducing the thickness of the single crystal semiconductor layer 128 may be performed. In order to reduce the thickness of the single crystal semiconductor layer 128, an etching process (etchback process) in which one or both of dry etching and wet etching are combined may be applied. For example, if the single crystal semiconductor layer 128 is a layer made of a silicon material, a dry etching process using SF ₆ and 0 ₂ in the process gas, it is possible to thin the single crystal semiconductor layer 128.

In this embodiment mode, the etching treatment may be performed after the surface is flattened by laser light irradiation, but the present invention is not construed as being limited thereto. For example, etching may be performed before laser light irradiation. In this case, the unevenness and defects on the surface of the semiconductor layer can be reduced to some extent by the etching treatment. Moreover, you may apply the said process to both before and after irradiation of a laser beam. Further, the laser light irradiation and the above process may be repeated alternately. As described above, by using a combination of laser light irradiation and etching treatment, unevenness and defects on the surface of the semiconductor layer can be significantly reduced. Of course, it is not always necessary to use the above-described etching treatment or heat treatment.

Through the above steps, a gap is formed over the support substrate, and a conductive layer is provided thereover, whereby the amount of warpage of the support substrate is reduced, and a highly reliable SOI substrate including the single crystal semiconductor layer 132 thereon is manufactured. (See FIG. 2F).

(Embodiment 2)
In this embodiment, a manufacturing process of a bottom-gate thin film transistor using an SOI substrate in which a conductive layer is provided over a supporting substrate and the single crystal semiconductor layer 132 is provided over the supporting substrate as in Embodiment 1 will be described. Show.

First, with reference to Embodiment 1, a conductive layer 118 is formed over the supporting substrate 100, and an insulating layer 112 and a single crystal semiconductor film 132 are formed over the conductive layer 118. Here, the insulating layer 112 is a gate insulating film 202, and the conductive layer 118 is a gate electrode 204. Next, as illustrated in FIG. 3A, the single crystal semiconductor film 132 is formed into an island shape by a photolithography technique and a dry etching method, whereby the island-shaped single crystal semiconductor layer 206 is formed.

Next, as illustrated in FIG. 3B, an impurity imparting one conductivity type is added to the island-shaped single crystal semiconductor layer 206, so that a source region and a drain region 208 (not distinguished in the drawing) are formed. The crystalline semiconductor layer 206 is assigned to the source / drain region 208 and the active layer 207. In this embodiment mode, the concentration of phosphorus or boron is added to the source region and the drain region 208 at 1 × 10 ¹⁹ to 1 × 10 ²¹ cm ⁻³ . Accordingly, it functions as a source region and a drain region 208 and can make ohmic contact with a conductive layer formed thereon.

For that purpose, first, a resist mask is formed over at least the island-shaped single crystal semiconductor layer 206 except the region to which phosphorus or boron is added. The resist mask is formed by a photolithography technique. Here, an oxide film is formed on the surface of the island-like single crystal semiconductor layer 206 by an ozone water cleaning process or the like to improve the resist coating property, and the applied resist is exposed and developed to form a resist mask. Form. Next, phosphorus or boron is added by ion doping or ion implantation, and the resist is removed and removed. In the present invention, since a thin film transistor is formed using an island-shaped single crystal semiconductor layer 206 formed over an insulating film, a CMOS can be manufactured without an element isolation step. In order to form an n-channel transistor and a p-channel transistor, the above treatment is performed as separate steps of a treatment for adding phosphorus and a treatment for adding boron.

In the above, phosphorus or boron is added by an ion doping method or an ion implantation method, but a semiconductor film (not shown) to which an impurity imparting one conductivity type is added is formed on a desired single crystal semiconductor film by a CVD method or the like. A source region and a drain region 208 may be formed by film formation. At this time, after the formation, a resist mask is formed, a source region and a drain region 208 are formed by dry etching, and then the resist is removed. However, at this time, in a region where a semiconductor film to which an impurity imparting one conductivity type is added is not formed over the single crystal semiconductor film, the film thickness is reduced by overetching.

Next, a conductive layer 210 is formed over the source and drain regions 208 and the gate insulating film 202. The conductive layer 210 is formed by a sputtering method, a CVD method, a printing method, a droplet discharge method, an evaporation method, or the like. The conductive layer 210 may have a laminated structure of a barrier film made of a high melting point material such as molybdenum, titanium, tungsten, and nitrides thereof, and a conductive film using a low resistance material such as aluminum. After a resist mask is formed on the previous conductive layer 210, the conductive layer 210 is etched to form a pair of wirings (functioning as a source electrode and a drain electrode) as shown in FIG. Note that when the source region and the drain region 208 are formed by a CVD method or the like, the conductive layer 210 and the source region and the drain region 208 may have the same shape in some cases. At this time, if both layers are processed at once with the same resist mask, the resist mask forming step can be reduced once.

Next, dry etching may be performed under a condition that the exposed island-shaped single crystal semiconductor layer surface 212 is not damaged and the etching rate for the island-shaped single crystal semiconductor layer surface 212 is low. By this step, it is possible to remove the etching residue on the island-shaped single crystal semiconductor layer surface 212 of the source region and the drain region, the residue of the resist mask, and the contamination source in the apparatus used for removing the resist mask, The insulation between the source region and the drain region can be ensured. As a result, leakage current of the thin film transistor can be reduced, and a thin film transistor with low off-state current and high withstand voltage can be manufactured. For example, chlorine gas may be used as the etching gas.

Through the above steps, a transistor using a single crystal semiconductor layer can be formed.

In the semiconductor device of this embodiment, auxiliary wiring can be further formed over a pair of wirings. The auxiliary wiring is for connecting the gate electrode 204 or the conductive layer 210. At this time, as illustrated in FIG. 4A, the protective insulating film 214 is formed over the conductive layer 210, the source and drain regions 208, and the gate insulating film 202. The protective insulating film 214 can be formed in a manner similar to that of the gate insulating film 202. Note that the protective insulating film 214 is used to prevent entry of contaminant impurities such as organic substances, metal substances, and water vapor floating in the air, and is preferably a dense film.

Next, the insulating film 216 is formed over the protective insulating film 214. Here, the insulating film 216 is formed using a photosensitive organic resin. Next, the insulating film 216 is exposed to light using a photomask and developed to form the insulating film 216 exposing the protective insulating film 214. Next, the protective insulating film 214 is etched using the insulating film 216 as a mask to form a contact hole exposing a part of the wiring. The contact hole may be provided so as to open the gate insulating film 202 and reach the gate electrode 204.

Next, a wiring 218 is formed as illustrated in FIG. The wiring 218 can be formed in the manner in which the conductive layer 210 is formed. Although the wiring 218 is in contact with the conductive layer 210 in FIG. 4B, the wiring 218 may be formed in contact with the gate electrode 204.

Note that this embodiment can be combined with any of the following embodiments as appropriate.
(Embodiment 3)

In this embodiment mode, as shown in Embodiment Mode 1, a manufacturing process of a dual-gate thin film transistor using an SOI substrate in which a conductive layer is provided over a supporting substrate and a single crystal semiconductor layer 132 is provided thereover is provided. Show about. In a dual-gate thin film transistor, an electric field in a vertical direction from a gate electrode to a channel can be reduced by sandwiching an active layer of a semiconductor layer between two upper and lower electrodes. Therefore, carrier mobility is improved and off-current is reduced. Further, since the channel regions are formed at both upper and lower ends of the active layer, there is an advantage that the on-current in transistor characteristics can be increased and the S value can be improved.

First, as in Embodiment Mode 2, the conductive layer 118 is formed over the supporting substrate 100, and the insulating layer 112 and the single crystal semiconductor film 132 are formed over the conductive layer 118. However, here, the insulating layer 112 is a first gate insulating film 250, and the conductive layer 118 is a first gate electrode 251. Next, an island-shaped single crystal semiconductor layer 206 is formed from the single crystal semiconductor film 132. Next, an impurity imparting one conductivity type is added to the island-shaped single crystal semiconductor layer 206, so that the source and drain regions 208 are formed. Also here, the concentration of phosphorus or boron is added to the source region and the drain region 208 at 1 × 10 ¹⁹ to 1 × 10 ²¹ cm ⁻³ as in the second embodiment. As a result, the island-shaped single crystal semiconductor layer 206 is assigned to the source and drain regions 208 and the active layer 207.

Next, as illustrated in FIG. 5A, a second gate insulating film 252 is formed over the first gate insulating film 250 and the active layer 207. The second gate insulating film 252 can be formed in a manner similar to that of the first gate insulating film 250, and examples of the material thereof include silicon oxide, silicon nitride, silicon oxynitride, and silicon nitride oxide. Moreover, it is good also as a laminated structure which consists of these materials. Here, silicon oxide is formed to a thickness of 100 nm.

Next, a second gate electrode 254 is formed over the second gate insulating film 252. The second gate electrode 254 can also be formed by a film formation method and a processing method similar to those of the first gate electrode 251. Here, molybdenum is used as a material to form a film with a thickness of 150 nm.

Here, the film types or film thicknesses of the first gate insulating film 250 and the second gate insulating film 252 are not necessarily the same. The film types of the first gate electrode 251 and the second gate insulating film 254 are not necessarily the same. By changing the type and thickness of these films, the effect of the potential applied to the first gate electrode 251 and the second gate insulating film 254 on the transistor characteristics can be changed, and the transistor characteristics can be controlled in detail. can do.

Next, an interlayer insulating film 256 is formed over the second gate insulating film 252 and the second gate electrode 254. The interlayer insulating film 256 can be formed in a manner similar to that of the insulating film 216 in Embodiment 2. A contact hole is provided in the interlayer insulating film 256, and a wiring to be formed later is disposed so as to reach the source and drain regions 208, the first gate electrode 251, or the second gate insulating film 254. . At this time, using the interlayer insulating film 256 as a mask, the first gate insulating film 250 and the second gate insulating film 252 at the bottom of the contact hole dry are dry-etched or wet-etched to form the first gate electrode 251 or the second gate-insulating film 252. The second gate insulating film 254 is exposed.

Next, a wiring 258 is formed as illustrated in FIG. The wiring 258 can be formed in the manner in which the conductive layer 210 is formed. In FIG. 5B, the wiring 258 is connected to the source and drain regions 208; however, the wiring 258 may be formed so as to be connected to the first gate electrode 251 or the second gate electrode 254.

The dual-gate thin film transistor may be driven by connecting the first gate electrode and the second gate electrode and applying the same potential, or different between the first gate electrode and the second gate electrode. Control may be performed independently by applying a potential. Alternatively, the threshold voltage of the transistor may be controlled by fixing the potential of one of the first gate electrode and the second gate electrode.

As described above, a dual-gate thin film transistor in which a gap is formed on a supporting substrate and a conductive layer is provided thereover can reduce the amount of warpage of the supporting substrate. Note that this embodiment can be combined with any of the following embodiments as appropriate.

(Embodiment 4)
In this embodiment, an example in which an element substrate that can be used for a display device is formed using the semiconductor device formed in Embodiment 2 will be described. Of course, it is possible to form not only the second embodiment but also the third embodiment.

As shown in FIG. 6A, a pixel electrode 300 is formed instead of the wiring 218 in FIG. Here, after a conductive film is formed over the insulating film 216, the conductive film is etched using a resist mask formed by a photolithography process using a photomask, whereby the pixel electrode 300 is formed. Although this embodiment will be described with reference to FIGS. 6A to 6B, the gate electrode is not described because it has a degree of freedom to be routed under the gate insulating film.

The pixel electrode 300 includes indium oxide including tungsten oxide, indium zinc oxide including tungsten oxide, indium oxide including titanium oxide, indium tin oxide including titanium oxide, indium tin oxide, indium zinc oxide, and oxidation. A light-transmitting conductive material such as indium tin oxide to which silicon is added can be used.

The pixel electrode 300 can be formed using a conductive composition containing a conductive high molecule (also referred to as a conductive polymer). The pixel electrode formed using the conductive composition preferably has a sheet resistance of 10,000 Ω / □ or less and a light transmittance of 70% or more at a wavelength of 550 nm. Moreover, it is preferable that the resistivity of the conductive polymer contained in the conductive composition is 0.1 Ω · cm or less.

As the conductive polymer, a so-called π-electron conjugated conductive polymer can be used. For example, polyaniline or a derivative thereof, polypyrrole or a derivative thereof, polythiophene or a derivative thereof, or a copolymer of two or more kinds thereof can be given.

Here, as the pixel electrode 300, an indium tin oxide film is formed by a sputtering method, and then a resist is applied over the indium tin oxide. Next, the resist is exposed and developed using a sixth photomask to form a resist mask. Next, the pixel electrode 300 is formed by etching indium tin oxide using a resist mask.

FIG. 6B is a plan view of one pixel of an example of the display device of this embodiment. FIG. 6A corresponds to a cross-sectional view taken along the line QR of FIG. In FIG. 6B, one of the wirings has a shape in which a source region or a drain region surrounds the other (specifically, a U shape or a C shape). In this element structure, the area of the region where carriers move can be increased as compared with an element structure in which the source and drain are symmetrical. That is, this corresponds to an increase in the width of the channel, so that the amount of current flowing through the element can be increased, and the area occupied by the element can be reduced.

Further, in the case of a liquid crystal display device, a lower layer of the wiring 302 connected to the signal line is a source region, a lower layer of the wiring 304 connected to the pixel electrode is a drain region, and the area of the source region facing the drain region is a drain electrode. A U-shaped or C-shaped structure larger than the area facing the source electrode (that is, a shape in which the source region surrounds the drain in a curved shape with an insulating film in the upper surface shape), thereby forming a gate electrode (gate wiring) ) And the drain region can be reduced. For this reason, the fluctuation (feedthrough) of the pixel electrode potential due to the parasitic capacitance of the element can be suppressed. In addition, a display device using the structure can improve the response speed of the pixel. In particular, in the case of a thin film transistor formed in a pixel of a liquid crystal display device, the voltage drop of the pixel electrode can be reduced, so that the response speed of the liquid crystal material can be increased.

In this embodiment mode, since the transistor characteristics required for the pixel transistor and the driver transistor are different, it is not necessary to use a dual gate type for both. For example, the pixel transistor may be a transistor having a gate on one side, for example, a bottom gate, and the driver transistor may be a dual-gate thin film transistor. Further, a channel region is formed by forming a non-single-crystal semiconductor layer in the pixel transistor, and a channel region is formed in the single-crystal semiconductor layer formed in the present invention in the driver transistor. good.

Through the above steps, a thin film transistor and an element substrate that can be used for a display device, which have a gap over the support substrate and reduce the amount of warpage of the support substrate by providing a conductive layer thereover, can be formed. it can.

According to this embodiment, a thin film transistor with excellent characteristics such as mobility, on-state current, S value, and off-state current can be manufactured. As a result, the drive frequency of the display device can be increased, and it is possible to sufficiently cope with an increase in panel size and an increase in pixel density.

(Embodiment 5)
In this embodiment mode, electronic devices using the semiconductor device of the present invention, particularly a display device, will be described with reference to FIGS.

As an electronic device manufactured using the semiconductor device (especially a display device) of the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, an audio playback device (car audio component etc.), a computer, Reproducing a recording medium such as a game machine, a portable information terminal (mobile computer, cellular phone, portable game machine, electronic book, etc.), an image reproducing apparatus (specifically, Digital Versatile Disc (DVD)) equipped with a recording medium, And a device provided with a display capable of displaying the image).

FIG. 7A illustrates a television receiver or a personal computer monitor. A housing 901, a support base 902, a display portion 903, a speaker portion 904, a video input terminal 905, and the like are included. The semiconductor device of the present invention is used for the display portion 903. According to the present invention, a semiconductor device with improved wiring flexibility and improved integration can be manufactured; therefore, a high-performance television receiver or personal computer monitor can be provided.

FIG. 7B illustrates a digital camera. An image receiving portion 913 is provided on the front portion of the main body 911, and a shutter button 916 is provided on the upper surface portion of the main body 911. Further, a display portion 912, operation keys 914, and an external connection port 915 are provided on the back surface portion of the main body 911. A semiconductor device of the present invention is used for the display portion 912. According to the present invention, a high-performance digital camera can be provided.

FIG. 7C illustrates a laptop personal computer. A main body 921 is provided with a keyboard 924, an external connection port 925, and a pointing device 926. In addition, a housing 922 having a display portion 923 is attached to the main body 921. The semiconductor device of the present invention is used for the display portion 923. According to the present invention, a high-performance notebook personal computer can be provided.

FIG. 7D illustrates a mobile computer, which includes a main body 931, a display portion 932, a switch 933, operation keys 934, an infrared port 935, and the like. The display portion 932 is provided with an active matrix display device. A semiconductor device of the present invention is used for the display portion 932. According to the present invention, a high-performance mobile computer can be provided.

FIG. 7E illustrates an image reproducing device. The main body 941 is provided with a display portion B 944, a recording medium reading portion 945, and operation keys 946. Further, a housing 942 having a speaker portion 947 and a display portion A 943 is attached to the main body 941. Each of the display portion A 943 and the display portion B 944 uses the semiconductor device of the present invention. According to the present invention, a high-performance image reproducing device can be provided.

FIG. 7F illustrates an electronic book. The main body 951 is provided with operation keys 953. A plurality of display portions 952 are attached to the main body 951. The semiconductor device of the present invention is used for the display portion 952. According to the present invention, a high-performance electronic book can be provided.

FIG. 7G illustrates a video camera. A main body 961 is provided with an external connection port 964, a remote control receiving unit 965, an image receiving unit 966, a battery 967, an audio input unit 968, and operation keys 969. A housing 963 having a display portion 962 is attached to the housing. A semiconductor device of the present invention is used for the display portion 962. According to the present invention, a high-performance video camera can be provided.

FIG. 7H illustrates a mobile phone, which includes a main body 971, a housing 972, a display portion 973, a sound input portion 974, a sound output portion 975, operation keys 976, an external connection port 977, an antenna 978, and the like. A semiconductor device of the present invention is used for the display portion 973. According to the present invention, a high-performance mobile phone can be provided.

FIG. 8 is an example of a configuration of a portable electronic device 1000 that has both a telephone function and an information terminal function. 8A is a front view, FIG. 8B is a rear view, and FIG. 8C is a development view. The portable electronic device 1000 has both functions of a telephone and an information terminal, and is an electronic device called a smartphone that can perform various data processing in addition to voice calls.

The portable electronic device 1000 includes a housing 1001 and a housing 1002. A housing 1001 includes a display portion 1011, a speaker 1012, a microphone 1013, operation keys 1014, a pointing device 1015, a camera lens 1016, an external connection terminal 1017, and the like. The housing 1002 includes a keyboard 1021, an external memory slot 1022, and a camera. Lens 1023, a light 1024, an earphone terminal 1025, and the like. An antenna is incorporated in the housing 1001. In addition to the above structure, a non-contact IC chip, a small recording device, or the like may be incorporated.

The display portion 1011 incorporates the semiconductor device of the present invention. Note that the video (and the display direction) displayed on the display unit 1011 varies depending on the usage mode of the portable electronic device 1000. In addition, since the camera lens 1016 is provided on the same surface as the display portion 1011, a voice call with video (so-called videophone) is possible. Note that the speaker 1012 and the microphone 1013 can be used for recording, reproduction, and the like without being limited to voice calls. When taking a still image and a moving image using the camera lens 1023 (and the light 1024), the display unit 1011 is used as a viewfinder. The operation keys 1014 are used for making and receiving calls, inputting simple information such as e-mail, scrolling the screen, moving the cursor, and the like.

The housings 1001 and 1002 which overlap with each other slide and can be developed as illustrated in FIG. 8C to be used as an information terminal. In this case, smooth operation using the keyboard 1021 and the pointing device 1015 is possible. The external connection terminal 1017 can be connected to various cables such as an AC adapter and a USB cable, and enables charging and data communication with a computer or the like. In addition, a recording medium can be inserted into the external memory slot 1022 to support storage and movement of a larger amount of data. In addition to the above functions, a wireless communication function using an electromagnetic wave such as infrared rays, a television reception function, or the like may be provided. According to the present invention, a high-performance portable electronic device can be provided.

As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields. Note that this embodiment can be combined with any of the above embodiments as appropriate.

It is a figure shown about the processing method of a semiconductor substrate. It is a figure shown about the manufacturing method of a semiconductor substrate. 8A to 8D are cross-sectional views illustrating a method for manufacturing a semiconductor device of the present invention. 8A to 8D are cross-sectional views illustrating a method for manufacturing a semiconductor device of the present invention. 8A to 8D are cross-sectional views illustrating a method for manufacturing a semiconductor device of the present invention. FIG. 11 is a cross-sectional view illustrating a method for manufacturing a display device of the present invention. FIG. 11 illustrates an electronic device using a semiconductor device. FIG. 11 illustrates an electronic device using a semiconductor device.

Explanation of symbols

100 base substrate

Claims (8)

Forming a first insulating film on the single crystal semiconductor substrate;
Irradiating the single crystal semiconductor substrate with ions to form an embrittled region;
Forming a conductive film on the first insulating film after forming the embrittled region;
Forming a resist on the conductive film;
Etching the conductive film using the resist as a mask to form a conductive layer processed into a predetermined shape;
Forming a second insulating film having a thickness larger than that of the conductive layer on the first insulating film and the resist;
Removing the resist and removing the second insulating film on the resist by a lift-off method;
Forming a third insulating film on the second insulating film and the conductive layer;
Bonding the single crystal semiconductor substrate and the support substrate so that a gap is formed between the third insulating film in a region overlapping the conductive layer and the support substrate;
Forming a semiconductor layer over the supporting substrate by performing heat treatment and separating the single crystal semiconductor substrate along the embrittled region. Forming a first insulating film to be a first gate insulating film on a single crystal semiconductor substrate;
Irradiating the single crystal semiconductor substrate with ions to form an embrittled region;
Forming a conductive film on the first insulating film after forming the embrittled region;
Forming a resist on the conductive film;
Etching the conductive film using the resist as a mask to form a conductive layer to be a first gate electrode;
Forming a second insulating film having a thickness larger than that of the conductive layer on the first insulating film and the resist;
Removing the resist and removing the second insulating film on the resist by a lift-off method;
Forming a third insulating film on the second insulating film and the conductive layer;
Bonding the single crystal semiconductor substrate and the support substrate so that a gap is formed between the third insulating film in a region overlapping the conductive layer and the support substrate;
Forming a semiconductor layer over the support substrate by performing heat treatment and separating the single crystal semiconductor substrate along the embrittled region;
Etching the semiconductor layer to form an island-shaped semiconductor layer;
Adding an impurity imparting one conductivity type to the island-shaped semiconductor layer to form a source region and a drain region;
Forming a fourth insulating film to be a second gate insulating film on the island-shaped semiconductor layer;
Forming a second gate electrode over the fourth insulating film. In claim 1,
Etching the semiconductor layer to form an island-shaped semiconductor layer;
Adding an impurity imparting one conductivity type to the island-shaped semiconductor layer to form a source region and a drain region;
Forming a source electrode on the source region and a drain electrode on the drain region;
Performing a dry etching process on the exposed surface of the island-shaped semiconductor layer between the source electrode and the drain electrode. In claim 2 or claim 3,
The top surface shape of the island-shaped semiconductor layer is a method for manufacturing a semiconductor device in which one of the source region and the drain region surrounds the other. In any one of Claims 1 thru | or 4,
A method for manufacturing a semiconductor device, comprising: etching a surface of the semiconductor layer to reduce irregularities or defects on the surface of the semiconductor layer and then irradiating the surface of the semiconductor layer with a laser beam to planarize the semiconductor layer. In any one of Claims 1 thru | or 5,
The method for manufacturing a semiconductor device, wherein the gap is 50% or less of the area of the single crystal semiconductor substrate. In any one of Claims 1 thru | or 6,
In the step of forming the embrittled region, the single crystal semiconductor substrate is irradiated with ions using a halogen gas or a halogen compound gas, and then irradiated with ions using a gas containing hydrogen gas to form the embrittled region. A method for manufacturing a semiconductor device. In any one of Claims 1 thru | or 7,
In the step of forming the semiconductor layer over the support substrate, the embrittlement region is formed by irradiating microwaves to the bonding region between the single crystal semiconductor substrate and the support substrate to increase the bonding strength and then performing the heat treatment. A method for manufacturing a semiconductor device in which the single crystal semiconductor substrate is separated along a line.

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