JP2008028405A - Semiconductor thin-film reforming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exclusively irradiate desired regions with a laser beam by suppressing position deviation between a stage and a substrate. <P>SOLUTION: A semiconductor thin-film reforming apparatus includes a gastight vessel which can accommodate a substrate coated with a semiconductor material on a prescribed substrate setting section, a light source that radiates a light for irradiating the semiconductor material to heat the semiconductor material to a predetermined heat-treatment temperature, a light transmitting window provided on a wall of the gastight vessel for introducing the light from the light source into the gastight vessel by transmitting through the window, a holding means provided on the substrate setting section for fixing and holding the substrate on the substrate setting section, and a pressure controlling means for controlling the atmospheric pressure inside the gastight vessel during the light irradiation so as not to be lower than the vapor pressure of the semiconductor material melted by heating with the light irradiation, wherein the vapor pressure depends on the temperature of the melted semiconductor material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor thin film reformer, and in particular, a semiconductor thin film reformer using a laser crystallization technique (a technique for polycrystallizing an amorphous semiconductor material deposited on a substrate by irradiating a laser beam). It relates to the device.

  Conventionally, a field effect thin film transistor (TFT) formed on a glass substrate or the like is frequently used as a driving element for a display, a sensor, a printing device, or the like. Representative techniques for forming such TFTs include hydrogenated amorphous silicon TFT technology and polycrystalline silicon TFT technology.

In the former, the maximum temperature of the manufacturing process is about 300 ° C., and carrier mobility of about 1 cm ² / Vsec is realized. This technology is used for manufacturing a switching transistor of each pixel in an active matrix type (AM-) liquid crystal display (LCD). Note that the AM-LCD has a driving TFT for each pixel, and an LCD that drives the TFT of each pixel by a driver integrated circuit (IC, LSI formed on a single crystal silicon substrate) arranged around the screen. Since each pixel has a switching TFT, compared to passive matrix LCDs that send electrical signals for driving liquid crystals from the peripheral driver circuit, crosstalk is reduced and good image quality can be obtained. Have.

On the other hand, for the latter, for example, a quartz substrate is used, and by using a high temperature process similar to an LSI of about 1000 ° C., a carrier mobility of 30 to 100 cm ² / Vsec can be obtained. Realization of such high carrier mobility, for example, when applied to a liquid crystal display, the pixel TFT for driving each pixel and the peripheral drive circuit section can be simultaneously formed on the same glass substrate, thereby reducing the manufacturing process cost. And there is an advantage related to miniaturization of LCD. That is, when the TFT and the peripheral drive circuit are connected by using tab connection or wire bonding as in the prior art, the connection between the AM-LCD substrate and the peripheral driver integrated circuit due to the downsizing and high resolution of the LCD. It is difficult to cope with the narrowing of the pitch. However, such a polycrystalline silicon TFT technology has an advantage in terms of downsizing, but has a problem that an inexpensive low softening point glass that can be used in the former process cannot be used when a high temperature process is used.

Therefore, in order to solve the above problems, it is necessary to reduce the temperature in the polycrystalline silicon TFT process, and a technique for forming a polycrystalline silicon film at a low temperature by applying a laser crystallization technique has been actively researched and developed. For example, Patent Document 1 discloses a technique in which an amorphous silicon thin film on an amorphous substrate is crystallized by irradiating a short wavelength pulse laser beam and applied to a thin film transistor. According to this method, it is possible to crystallize amorphous silicon without increasing the temperature of the entire substrate. Therefore, a semiconductor element or a semiconductor integrated circuit is manufactured on a large area such as a liquid crystal display and an inexpensive substrate such as glass. There is an advantage that you can. However, as described in the above publication, irradiation intensity of about 50 to 500 mJ / cm ² is required for crystallization of an amorphous silicon thin film by a short wavelength laser.

On the other hand, the light emission output of currently available pulse laser devices is about 1 J / pulse at maximum, and the area that can be irradiated at one time is only about ² to ²⁰ cm ² even by simple conversion. Therefore, in order to crystallize the entire surface of the substrate having a substrate size of 47 × 37 cm ² , for example, at least 87 to 870 points need to be irradiated with laser. In addition, if the substrate size is increased to 1 m square, the number of irradiation points is similarly increased. Furthermore, the beam shape irradiated to the substrate is a line shape (length: 100 to 300 mm, width: about 1 to 0.1 mm), and the beam is scanned in the width direction so that the beam scanning direction is two axes (x axis and Attempts have been made to change from the y-axis) to the 1-axis (x-axis).

In general, these laser crystallizations are realized by a pulse laser irradiation apparatus having a configuration as shown in FIG.
FIG. 14 is an explanatory view showing a conventional ELA apparatus. As shown in the figure, the laser light supplied from the pulsed laser light source 1401 is defined by optical elements such as mirrors 1402, 1403, 1405 and a beam homogenizer 1404 installed to make the spatial intensity uniform. The silicon thin film 1407 on the glass substrate 1408 that is an irradiated body is reached through the optical path 1406. In general, since one irradiation range is smaller than that of a glass substrate, laser irradiation is performed on an arbitrary position on the substrate by moving the glass substrate 1408 on the xy stage 1409. Instead of using the xy stage 1409, a configuration in which the above-described optical element group is moved, or a combination of the optical element group and the stage can be used.

It is also possible to irradiate the beam while moving the Y stage on which the substrate is arranged, by making the beam irradiation shape into a linear shape having a length equivalent to one side of the substrate. At this time, the movement of the stage and the supply of the pulsed light are performed in the following procedure.
1) Simultaneously with the stage moving at a constant speed, the pulse laser is oscillated and supplied at a constant period.
2) Repeat (the stage is moved by one step and stopped) + (one pulse laser is supplied).

  FIG. 15 is an explanatory diagram showing a conventional irradiation method when the beam irradiation shape is rectangular. Since one irradiation range 1502 is generally smaller than that of a glass substrate, laser irradiation is performed on an arbitrary position on the substrate by moving the glass substrate 1501 on the xy stage. Instead of using the xy stage, a configuration in which the movement of the optical element group (for example, the X direction) and the movement of the stage (the Y direction) may be used. By using such a method, the crystallized regions 1503 are sequentially formed. The stage movement and supply of pulsed light at this time are performed in the following procedure. Reference numeral 1504 denotes a laser introduction window provided in the chamber.

3) Simultaneously with the stage moving at a constant speed, the pulse laser is oscillated and supplied at a constant period.
4) (Stage is moved by one step on the stage and stopped) + (pulse laser is supplied for one pulse or more) is repeated.

As described above, the moving means of the substrate stage is used in laser crystallization using a linear beam or a rectangular beam.
Laser irradiation may be performed in a vacuum chamber or in a high purity gas atmosphere in a vacuum chamber. Further, if necessary, it has a cassette 1410 containing a glass substrate with a silicon thin film and a substrate transport mechanism 1411 as shown in FIG. 14, and the substrate can be mechanically taken out and stored between the cassette and the stage. When the above-described method is used, the glass substrate is only disposed on the xy stage, and no means for fixing and holding the glass substrate is used.

Japanese Patent Publication No.7-118443

However, in order to increase the beam utilization efficiency, the laser irradiation point is reduced by irradiating only the desired area with the laser and avoiding the irradiation to the part that does not need the laser irradiation (for example, the margin when cutting the device). However, it is necessary to increase the utilization efficiency of the laser beam. For this purpose, it is necessary to match the device creation region and the laser irradiation region, and it is necessary to prevent the substrate from being displaced on the stage. In particular, in order to control the irradiation position based on the coordinate system of the stage, it is indispensable to prevent deviation. In addition, when the glass substrate is bent due to the formation of a semiconductor thin film or the substrate is heated, the focus is shifted. Therefore, it is necessary to bring the substrate into close contact with the stage in order to correct the deflection.
The present invention is for solving such a problem, and a semiconductor thin film reforming apparatus capable of irradiating only a desired region with a laser by suppressing positional deviation between the stage and the substrate. The purpose is to provide.

  A semiconductor thin film reforming apparatus according to the present invention is installed in a sealed container having a substrate placement portion for placing a substrate having a semiconductor thin film and a light transmission window for transmitting laser light, and outside the sealed container. Laser beam irradiation means for irradiating laser light for melting and heating the semiconductor thin film through the light transmission window, holding means for fixing and holding the substrate on the substrate mounting portion, and the sealed container By adjusting the gas flow rate supplied to the inside, the atmospheric pressure in the sealed container at the time of irradiation with the laser light is controlled to be equal to or higher than the vapor pressure defined by the temperature of the melted and heated semiconductor thin film. A pressure control unit; an alignment mechanism for adjusting alignment of the substrate fixedly held by the substrate platform with respect to the optical axis of the laser beam; and the substrate platform with respect to the laser beam. A focusing mechanism that adjusts the position of the fixedly held substrate in the focusing direction; and a mask stage that enables the laser light to be irradiated onto the substrate through an optical mask. The mask stage includes the alignment adjustment and When the focusing is completed, the laser beam irradiation unit starts moving to irradiate the laser beam to a desired position on the substrate, and the laser beam irradiation unit performs the alignment adjustment after the mask stage starts moving. The laser beam is irradiated in consideration of an offset amount for exposure at a point distant from the position.

Moreover, this invention includes the structure shown below as another aspect.
That is, the alignment mechanism and the focusing mechanism adjust the position of the substrate in the alignment and focusing directions so that the error accuracy of the exposure position of the substrate falls within the range of 0.1 to 100 μm.
The holding means is a reduced pressure adsorption means.
The holding means is an electrostatic adsorption means.
The substrate is a glass substrate, and the semiconductor thin film is a silicon thin film.
The present invention further includes means for introducing nitrogen or inert gas into the sealed container and means for introducing oxygen gas into the sealed container.
The semiconductor thin film reformer is used for manufacturing a field effect thin film transistor.
The field effect thin film transistor is used as a driving element of an active matrix liquid crystal device.

  Therefore, by using the present invention, displacement of the substrate is prevented and the irradiation position can be precisely controlled, so that the number of laser irradiation points can be reduced and the utilization efficiency of the laser beam can be increased. In particular, when the stage has a coordinate system and the irradiation position is controlled based on the coordinate system, the effect of preventing the deviation is great. Further, since the substrate is fixed to the stage even under a condition in which the glass substrate is bent due to the formation of a semiconductor thin film or the heating of the substrate, the deflection can be corrected and the defocusing of the beam can be prevented.

  As described above, the present invention provides a sealed container provided with a substrate placement portion for placing a substrate having an amorphous semiconductor thin film and a light transmission window for transmitting laser light, and outside the sealed container. A laser beam irradiation unit that is installed and irradiates a laser beam for melting and heating the amorphous semiconductor thin film through the light transmission window; and a holding unit for fixing and holding the substrate on the substrate mounting portion; By adjusting the flow rate of gas supplied into the sealed container, the atmospheric pressure in the sealed container at the time of irradiation with the laser light is controlled by the vapor pressure defined by the temperature of the melted and heated amorphous semiconductor thin film. Pressure control means for controlling to be as described above is provided.

  Therefore, by using the present invention, displacement of the substrate is prevented and the irradiation position can be precisely controlled, so that the number of laser irradiation points can be reduced and the utilization efficiency of the laser beam can be increased. In particular, when the stage has a coordinate system and the irradiation position is controlled based on the coordinate system, the effect of preventing the deviation is great. Further, since the substrate is fixed to the stage even under a condition in which the glass substrate is bent due to the formation of a semiconductor thin film or the heating of the substrate, the deflection can be corrected and the defocusing of the beam can be prevented.

Next, an embodiment of the present invention will be described with reference to the drawings.
In the laser crystallization process, it is necessary to prevent the mixing of metal impurities other than the semiconductor material to be used. Similar to other processes used in the semiconductor device manufacturing process, for example, the CVD process, 10 to 5 torr (Note that 1 torr = 1) /(7.50062×10 ⁻³ ) Pa, the same shall apply hereinafter) and a vacuum vessel capable of high vacuum evacuation is required. In the CVD process, after high vacuum evacuation, a source gas, carrier gas, etc. controlled to about 10 ⁻⁴ to 10 ⁻¹ torr are introduced, and a reaction precursor is formed using heat or plasma as a gas decomposition means. A desired film is formed on the substrate. On the other hand, in the laser crystallization process, a reactive gas is not particularly required. Therefore, in a high vacuum atmosphere exceeding 10 ⁻⁵ torr or an inert gas atmosphere controlled to about 10 ⁻⁴ to 10 ⁻¹ torr. That process has been implemented. However, when the laser crystallization process is used for mass production, the semiconductor material is heated and heated by laser irradiation, and the semiconductor material atoms are vaporized and adhere to the laser introduction window. As a result, the laser transmittance decreases, and the irradiation intensity There is a problem that changes with time.

  Therefore, in the present embodiment, as a means for solving such a problem, the pressure of the inert gas introduced into the chamber is set high up to about atmospheric pressure, so that the semiconductor material adheres to the gas introduction window. To prevent. Further, since the friction with the stage is smaller than that in a high vacuum atmosphere and the substrate is likely to be displaced on the stage, the substrate is fixedly held on the stage using a predetermined holding means. Since it is in a high-pressure atmosphere around atmospheric pressure, a decompression suction means (such as a vacuum chuck) can be used as this holding means. Of course, other means may be used instead of the reduced pressure suction means, and for example, an electrostatic suction means may be used.

  In addition, as a standard for a high-pressure atmosphere around the atmospheric pressure such as the above-described inert gas, a pressure about the vapor pressure of the semiconductor material is required. This is because the semiconductor material gas density on the surface of the semiconductor material is about ½ or less and becomes smaller near the laser introduction window.

  FIG. 1 is an apparatus cross-sectional view showing an embodiment of the present invention. As shown in the figure, a laser beam 101 supplied from a laser light source is supplied to a mask 102 through an optical element group such as a beam homogenizer and a mirror. The beam 103 that has passed through the mask 102 is formed into a desired beam shape by an opening pattern formed in the mask 102, and is irradiated onto the surface of the substrate 107 through a projection lens (not shown) and a window 104. The amorphous semiconductor thin film deposited on the substrate 107 in advance, that is, the unirradiated region 106 is melted and recrystallized by laser irradiation to become an irradiated region 105 that is a crystalline thin film. The substrate 107 is fixedly held on the stage 110 by the holding means 109. The vacuum vessel including the above devices is controlled in atmospheric pressure by a pressure control device 112 and connected to a vacuum vessel 111 having a substrate transfer means via a gate valve 108. That is, the pressure control device 112 controls the atmospheric pressure in the container at the time of light irradiation so that the vapor pressure defined by the temperature of the semiconductor material melted and heated by the light irradiation does not fall below.

  FIG. 2 is a sectional view of an apparatus showing an embodiment of the present invention. As shown in the figure, the substrate 201 is transferred onto the pins of the substrate up-and-down mechanism 207 by a substrate transfer means (not shown). The stage 202 has a stage (guide portion) 203 and a pin passage opening 204 for roughly positioning the substrate 201. An adsorption port 205 provided for fixing the substrate is connected to an adsorption exhaust line 206. After the substrate transfer means is retracted, the substrate up-and-down mechanism is lowered and the substrate 201 is placed on the stage 202 before and after closing the gate valve for isolating the atmosphere and introducing the gas. At this time, the suction mechanism is activated, and the substrate 201 is fixedly held on the stage 202.

  FIG. 3 is a perspective view showing an embodiment of the present invention. The pulsed UV light supplied from the first excimer laser EL1 and the second excimer laser EL2 is guided to the homogenizer opt20 'via the mirrors opt3, opt3' and the lenses opt4. Here, the beam intensity profile is shaped by the optical mask opt21 so as to have a desired uniformity, for example, an in-plane distribution of ± 5%. Note that the intensity profile and total energy amount of the original beam supplied from the excimer laser may vary from pulse to pulse, so the intensity on the optical mask is more sensitive to spatial distribution and variations between pulses. It is desirable to provide a mechanism for homogenization. Further, as the homogenizer opt 20 ', those using a fly-eye lens or a cylindrical lens are generally used.

  The light pattern formed by the optical mask is irradiated onto the substrate sub0 installed in the vacuum chamber C0 through the reduction projection exposure apparatus opt23 'and the laser introduction window W0. The substrate sub0 is placed on the substrate stage S0, and the optical pattern can be exposed to a desired region, for example, the pattern transfer region ex0, by moving the substrate stage S0 (moving in the X or Y direction in the drawing). it can. Although FIG. 3 shows a reduction projection optical system, an optical system that performs enlargement projection at the same magnification may be used in some cases. Further, the optical mask may be placed on a mask stage (not shown), and the optical mask may be moved to irradiate a desired position on the substrate.

  Next, a mechanism necessary for irradiating a substrate with a desired light pattern under desired conditions will be exemplified. Since adjustment of the optical axis requires fine adjustment, a method of adjusting the position of the substrate by fixing the optical axis once adjusted is shown. The position of the substrate irradiation surface with respect to the optical axis needs to correct the position in the focal (Z) direction and the perpendicularity to the optical axis. Accordingly, among the θxy inclination correction direction, θxz inclination correction direction, θyz inclination correction direction, X exposure area movement direction, Y exposure area movement direction, and Z focusing direction in the figure, θxy inclination correction direction, θxz inclination correction direction, θyz The degree of perpendicularity to the optical axis is corrected by adjusting the tilt correction direction. Further, by adjusting the Z focusing direction, the substrate irradiation surface is arranged and controlled at a position corresponding to the focal depth of the optical system.

  FIG. 4 is a side view showing the adjustment and the substrate alignment mechanism. With respect to the L0 exposure axis, an optical mask opt21, a reduced projection exposure apparatus opt23 ', and a laser introduction window W0 are arranged as shown in FIG. The substrate sub0 disposed in the vacuum chamber C0 is disposed on the heater H0 with a substrate suction mechanism and the substrate XYZθxyθxzθyz stage S0 ′. Although a vacuum chamber is used, actual light irradiation is preferably performed in an atmosphere of inert gas, hydrogen, oxygen, nitrogen, or the like replaced after evacuation, and the atmospheric pressure is a pressure around atmospheric pressure. Also good. By using a heater with a substrate adsorption mechanism, substrate heating conditions of about room temperature to 400 ° C. can be selected during light irradiation. By setting the atmospheric pressure to the atmospheric pressure as described above, the substrate can be adsorbed by the vacuum chuck function, so that the displacement can be prevented even if the substrate stage moves in the chamber. Even if there is sled or deflection, it can be fixed to the substrate stage. Furthermore, it is possible to minimize the depth of focus shift due to substrate warpage or deflection due to heating.

  The laser interferometers i1 and i2 measure the alignment of the substrate and the position in the Z direction of the substrate via the measurement window Wi and the measurement mirror opt-i. For alignment, the alignment mark on the substrate is measured using the off-axis microscope m0, the microscope light source Lm, and the microscope element opt-m, and the desired exposure position can be measured using the substrate position information by the laser interference system. Although the off-axis method is illustrated in FIG. 2 described above, a through lens (Through The Lens) method or a through mask (Through The Mask) method (or a reticle method) can be applied. Further, by determining linear coordinates from a plurality of measurement points using the least square method, it is possible to take means for averaging measurement errors that occur during measurement.

  5A to 5C are explanatory views showing the relationship between the mask pattern and the alignment mark. The mask used for exposure is composed of a mask msk1 (non-exposure part) and a mask msk2 (exposure part). For example, when an excimer laser is used as a light source, a film that absorbs and reflects ultraviolet light, such as a metal such as aluminum, chromium, and tungsten, or a dielectric multilayer film, is formed on a quartz substrate that transmits ultraviolet light. Is used to form a pattern. The silicon film is exposed according to a desired pattern on the mask (indicated by the white portion in FIG. 5A), and the exposed silicon portion 502 is included in the non-exposed silicon portion 501 as shown in FIG. 5B. Is formed. At this time, it is possible to expose a pre-designed position on the silicon thin film by performing exposure after alignment adjustment so that the on-mask mark mrk1 matches the on-substrate mark mrk2, if necessary.

In the thin film transistor forming process using the silicon thin film, when the exposure process is the first process that requires positioning (that is, when the alignment mark is not formed in advance), the exposure formation mark is formed during the exposure process to the silicon thin film. By simultaneously exposing mrk3, an alignment mark using an optical color difference between a-Si and crystalline Si can be formed. Therefore, a transistor, a desired mechanism, and a function can be formed in a desired region subjected to exposure modification by performing photolithography or the like in a later process using this mark as a reference. FIG. 5C shows a state where a Si oxide film is formed on the silicon thin film after the exposure process and a desired region of the silicon layer is removed by etching. The Si removal portion 503 is a region where the laminated silicon film and Si oxide film are removed by etching, and a shape in which silicon oxide films 504 and 505 are laminated on the non-exposed silicon portion 501 and the exposed silicon portion 502 is shown. ing. Thus, by forming an island-shaped structure made of a silicon film covered with an oxide film, channel / source / drain regions of thin film transistors separated between elements and marks necessary for alignment in subsequent steps can be formed.

  6A and 6B are timing charts showing main operations. In Control Example 1, the substrate is moved to a desired exposure position by the operation of the substrate stage. Next, focusing and alignment operations are performed to precisely adjust the exposure position. At this time, for example, adjustment is performed so as to enter a desired setting error accuracy of about 0.1 μm to 100 μm. When the operation is completed, light irradiation to the substrate is performed. When these series of operations are completed, the substrate moves to the next exposure region, and after irradiation of necessary portions on the substrate is completed, the substrate is replaced and a predetermined series of processing is performed on the second processing substrate. .

  On the other hand, in the control example 2, the substrate is moved to a desired exposure position by the operation of the substrate stage. Next, focusing and alignment operations are performed to precisely adjust the exposure position. At this time, for example, adjustment is performed so as to enter a desired setting error accuracy of about 0.1 μm to 100 μm. When the operation is completed, the operation of the mask stage is started. In order to avoid variation in the amount of movement step at the start, the light irradiation to the substrate is a chart that is started after the start of the mask stage operation. Of course, since exposure is performed at a point away from the alignment position due to the movement of the stage, it is needless to say that the amount of offset needs to be considered in advance. It is also possible to start the operation of the light source earlier than the light irradiation to the substrate, and when the stability of the output intensity of the light source increases, the shutter or the like is opened to perform the light irradiation to the substrate. In particular, when an excimer laser is used as a light source and a usage method in which an oscillation period and a stop period are repeated, it is known that the initial several tens of pulses are particularly unstable. When it is not desired to irradiate the beam, a method of blocking the beam in accordance with the operation of the mask stage can be adopted. When these series of operations are completed, the substrate moves to the next exposure region, and after irradiation of necessary portions on the substrate is completed, the substrate is replaced and a predetermined series of processing is performed on the second processing substrate. .

  FIG. 7 is a side view showing an embodiment (semiconductor thin film reformer) of the present invention. The plasma CVD chamber C2, the laser irradiation chamber C5, and the substrate transfer chamber C7, and the substrate transfer through the gate valves GV2 and GV5 without contacting the atmosphere outside the apparatus, in an inert gas, nitrogen, hydrogen, This is possible in an atmosphere of oxygen or the like and in a high vacuum, reduced pressure, or pressurized state. In the laser irradiation chamber, a substrate is placed on a substrate stage S5 that can be heated to about 400 ° C. using a chuck mechanism. In the plasma CVD chamber, the substrate is placed on the substrate holder S2 that can be heated to about 400 ° C. In this example, the silicon thin film 701 formed on the glass substrate Sub0 is introduced into the laser irradiation chamber, and the silicon thin film on the surface is modified to the crystalline silicon thin film 702 by the laser irradiation and is transferred to the plasma CVD chamber. Is shown.

  The laser beam introduced into the laser irradiation chamber is a laser combining optical device in which the beams supplied from the first excimer laser EL1 and the second excimer laser EL2 pass through the first beam line L1 and the second beam line L2. It reaches the substrate surface via opt1, mirror opt11, transmission mirror opt12, laser irradiation optical device opt2, homogenizer opt20, optical mask opt21 fixed to optical mask stage opt22, projection optical device opt23, and laser introduction window W1. Although two excimer lasers are illustrated here, one or more desired number of light sources can be installed. In addition to the excimer laser, a pulse laser such as a carbon dioxide laser or a YAG laser, or a CW light source such as an argon laser and a high-speed shutter may be used to supply the pulse.

  On the other hand, in the plasma CVD chamber, the RF electrode D1 and the plasma confinement electrode D3 form the plasma formation region D2 away from the region where the substrate is disposed. A silicon oxide film can be formed on the substrate by supplying, for example, oxygen and helium to the plasma formation region and silane gas using the source gas introduction device D4.

  FIG. 8 is a top view showing an embodiment (semiconductor thin film reforming apparatus) of the present invention. The load / unload chamber C1, the plasma CVD chamber C2, the substrate heating chamber C3, the hydrogen plasma processing chamber C4, the laser irradiation chamber C5, and the substrate transfer chamber C7 are connected through gate valves GV1 to GV6, respectively. The laser beam supplied from the first beam line L1 and the second beam line L2 is irradiated onto the substrate surface via the laser synthesis optical device opt1, the laser irradiation optical device opt2, and the laser introduction window W1. Further, gas introduction devices gs1 to gs7 and exhaust devices vent1 to vent7 are connected to the respective process chambers and transfer chambers, and supply of desired gas species, setting of process pressure, exhaust, and vacuum are adjusted. As shown by the dotted lines in the figure, the processing substrates sub2 and sub6 are arranged on a plane.

  FIG. 9 is a side view schematically showing the plasma CVD chamber C2 of FIG. Electric power is supplied to the high frequency electrode RF2 from the high frequency power source RF1 (high frequency of 13.56 MHz or higher is suitable). Plasma is formed between the electrode RF3 with a gas supply hole and the high-frequency electrode, and the radical formed by the reaction passes through the electrode with the gas supply hole and is guided to the region where the substrate is disposed. Another gas is introduced by the planar gas introduction device RF4 without being exposed to plasma, and a thin film is formed on the substrate sub2 through a gas phase reaction.

The substrate holder S2 is designed to heat from room temperature to about 500 ° C. with a heater or the like. As shown in FIG. 9, by using an exhaust device vent2, a gas introduction device gs2, an oxygen line gs21, a helium line gs22, a hydrogen line gs23, a silane line gs24, a helium line gs25 and an argon line gs26, oxygen radicals and silane gas are removed. A silicon oxide film can be formed by reaction. When film formation was performed under conditions of a substrate temperature of 300 ° C., a pressure of 0.1 torr, an RF power of 100 W, a silane flow rate of 10 sccm, an oxygen flow rate of 400 sccm, and a helium flow rate of 400 sccm, the fixed oxide film charge density (5 × 10 ¹¹ cm ⁻² ) The formation of a silicon oxide film having good characteristics has been confirmed.

  Further, a better oxide film can be formed by increasing the ratio of oxygen flow rate to silane. As a form of the plasma CVD chamber, not only the parallel plate type RF plasma CVD apparatus as described above but also a method not using plasma such as low pressure CVD or atmospheric pressure CVD, or a microwave or ECR (Electron Cycrotron Resonance) effect was used. It is also possible to use a plasma CVD method.

Furthermore, when the plasma CVD apparatus shown in FIG. 9 is used for forming a thin film other than a silicon oxide film, the following raw materials can be used as necessary gas species. That is, for the formation of the Si ₃ N ₄ silicon nitride film, N ₂ (nitrogen) (or ammonia), Ar (argon) as the carrier gas, SiH ₄ (silane), argon as the carrier gas, or the like can be used. A source gas such as H ₂ (hydrogen) and silane, hydrogen (argon as a carrier gas) and SiF ₄ (tetrafluorosilane) (argon as a carrier gas) can be used for forming the Si silicon thin film. Although not a film formation process, hydrogen plasma treatment of a silicon thin film or a silicon oxide film is also possible using hydrogen plasma.

  FIG. 10 is a cross-sectional view showing the manufacturing process of the TFT. An embodiment in which an alignment mark is provided in advance and laser irradiation corresponding to the alignment mark is performed will be described.

  (A) A substrate cover film T1 and a silicon thin film T2 are sequentially formed on a glass substrate sub0 from which organic substances, metals, fine particles, and the like have been removed by cleaning. As the substrate cover film T1, silane and oxygen gas are used as raw materials by LPCVD (Low Pressure Chemical Vapor Deposition), and a silicon oxide film of 1 μm is formed at 450 ° C. By using the LPCVD method, it is possible to cover the entire outer surface of the substrate except for the substrate holding region (not shown). Alternatively, plasma CVD using TEOS (tetraethoxysilane) and oxygen as raw materials, atmospheric pressure CVD using TEOS and ozone as raw materials, plasma CVD as shown in FIG. A material capable of preventing diffusion of impurities harmful to semiconductor devices including glass having a reduced alkali metal concentration as much as possible, quartz / glass having a polished surface, and the like is effective as the substrate cover film.

The silicon thin film is formed by LPCVD with a thickness of 75 nm at 500 ° C. using Si ₂ H ₆ (disilane) gas as a raw material. In this case, since the concentration of hydrogen atoms contained in the film is 1 atomic% or less, film roughness due to hydrogen release in the laser irradiation process can be prevented. Alternatively, the substrate temperature, the (hydrogen) / (silane) flow rate ratio, the (hydrogen) / (tetrafluorosilane) flow rate ratio, and the like can be obtained by using the plasma CVD method as shown in FIG. It is possible to form a silicon thin film having a low hydrogen atom concentration by adjusting In order to form the alignment mark T9, patterning is performed by photolithography and etching, and the alignment mark T9 is formed on the substrate. Next, a mark protective film T10 is formed to protect the alignment mark T9, and then a silicon thin film T2 is formed.

  (B) The substrate prepared in the above step (a) is introduced into the thin film forming apparatus of the present invention after undergoing a cleaning step for removing organic substances, metals, fine particles, surface oxide films and the like. Irradiation with the laser beam L1 modifies the desired region of the silicon thin film T2 to a crystallized silicon thin film T2 '. Laser crystallization is performed in an atmosphere of high purity nitrogen of 700. Torr of 99.9999% or more, and oxygen gas is introduced after completion of laser irradiation. At the time of laser light exposure, it is adsorbed and fixed to the substrate stage, and a desired area is exposed based on the alignment mark. Thereafter, the alignment of the next process can be performed based on an alignment mark provided in advance or an alignment mark (not shown) formed by crystallized silicon thin film patterning.

  (C) The substrate that has undergone the above steps is transferred to the plasma CVD chamber through the substrate transfer chamber after the gas is exhausted. As the first gate insulating film T3, a silicon oxide film is deposited to a thickness of 10 nm at a substrate temperature of 350 degrees using silane, helium, and oxygen as source gases. Thereafter, hydrogen plasma treatment or heat annealing is performed as necessary. The processing up to this point is processed by the thin film forming apparatus according to the present embodiment.

  (D) Next, an island of a silicon thin film and a silicon oxide film laminated film is formed using photolithography and etching techniques. At this time, it is preferable to select an etching condition in which the etching rate of the silicon oxide film is higher than that of the silicon thin film. As shown in FIG. 10, when the pattern cross section is formed in a stepped shape (or tapered shape), gate leakage can be prevented and a highly reliable thin film transistor can be provided.

  (E) Next, after cleaning for removing organic substances, metals, fine particles, etc., a second gate insulating film T4 is formed so as to cover the island. Here, a silane and oxygen gas were used as raw materials by LPCVD, and a silicon oxide film was formed to a thickness of 30 nm at 450 ° C. Alternatively, it is also possible to use plasma CVD using TEOS (tetraethoxysilane) and oxygen as raw materials, atmospheric pressure CVD using TEOS and ozone as raw materials, plasma CVD as shown in FIG.

Next, an n ⁺ silicon film of 80 nm and a tungsten silicide film of 110 nm are formed as gate electrodes. The n ⁺ silicon film is preferably a crystalline phosphorus-doped silicon film formed by plasma CVD or LPCVD. Thereafter, a patterned gate electrode T5 is formed through photolithography and etching processes. In the subsequent steps, one of the following two steps (f1 or f2) can be used depending on the structure of the transistor to be formed.

(F1), (f2) Next, impurity implantation regions T6, T6 ′ are formed using the gate as a mask. When forming a CMOS circuit, in combination with photolithography n ⁺ region is required n ^- separately formed channel TFT ^- p requiring channel TFT and the p ⁺ region. Methods such as ion doping that does not perform mass separation of implanted impurity ions, ion implantation, plasma doping, and laser doping can be employed. At that time, depending on the application and impurity introduction method, impurities are introduced while leaving or removing the silicon oxide film on the surface as shown in (f1) and (f2).

  (G1), (g2) Interlayer isolation insulating films T7, T7 'are deposited, contact holes are opened, metal is deposited, and metal wiring T8 is formed by photolithography and etching. As the interlayer isolation insulating film, a TEOS-based oxide film, a silica-based coating film, or an organic coating film that can be flattened can be used. The contact hole opening can be applied by photolithography and etching, and the metal wiring can be applied with a low-resistance aluminum, copper, an alloy based on them, or a high melting point metal such as tungsten or molybdenum. By performing the above steps, a thin film transistor with high performance and reliability can be formed.

FIG. 11 is a timing chart showing the embodiment of the present invention.
12 and 13 are flowcharts showing the laser processing. As shown in FIGS. 11A and 12, the substrate is introduced into a laser processing chamber that is sufficiently evacuated. After closing the gate valve and stopping the gas flow with the substrate transfer chamber (or other processing chamber such as load lock chamber, silicon thin film forming chamber), nitrogen (or inert gas such as argon, hydrogen, or a mixed gas thereof) ). At this time, it is desirable to control the nitrogen pressure to be constant without stopping the exhaust, but it is also possible to close the gas introduction valve when the exhaust pressure is stopped or when a certain pressure is reached after gas introduction (not shown). Here, the substrate is fixed by suction. The stage on which the substrate is placed is moved to a predetermined position, and if necessary, after waiting for the pressure and the temperature of the substrate heater to reach a predetermined state (not shown), laser irradiation to the substrate is started. .

  A desired region is laser-irradiated (recrystallized) by moving the substrate stage or the irradiation beam, and then oxygen is introduced. Furthermore, the laser introduction window is irradiated with laser light while preventing the laser irradiation to the effective area on the processing substrate by using the movement of the substrate stage or an optical shutter mechanism disposed in the vacuum apparatus. The introduction window irradiation, oxygen supply, and nitrogen supply are stopped simultaneously or sequentially to increase the displacement. After the substrate adsorption is released and the pressure in the laser irradiation chamber is exhausted to a predetermined range, the gate valve connected to the substrate transfer chamber is opened and the substrate is discharged.

On the other hand, the following forms can also be used. As shown in FIGS. 11B and 13, the substrate is introduced into a laser processing chamber that is sufficiently evacuated. After closing the gate valve and stopping the gas flow with the substrate transfer chamber (or other processing chamber such as load lock chamber, silicon thin film forming chamber), nitrogen (or inert gas such as argon, hydrogen, or a mixed gas thereof) ). Here, the substrate is fixed by suction. The stage on which the substrate is arranged is moved to a predetermined position, and if necessary, after waiting for the pressure and the temperature of the substrate heater to reach a predetermined state (not shown), laser irradiation to the substrate is started. After moving the substrate stage or the irradiation beam to irradiate (recrystallize) a desired region with laser, the supply of nitrogen is stopped and oxygen is introduced. The substrate transfer chamber is previously controlled to a predetermined pressure in an oxygen atmosphere, and when the pressure in the laser irradiation chamber reaches a predetermined pressure, the gate valve is opened and the substrate is discharged. After transporting the substrate, the laser introduction window is irradiated with laser light. The introduction window irradiation, oxygen supply, and nitrogen supply are stopped simultaneously or sequentially to increase the displacement.

  In the above-described form, oxygen is supplied by a gas purifier or a gas cylinder so that the purity of the inert gas, nitrogen, hydrogen, etc. constituting the mixed gas alone is 99.9999%. High purity gas was used. Immediately after laser crystallization, high-purity oxygen is introduced into the vacuum apparatus to form a natural oxide film having a low impurity concentration on the surface, and the impurity silicon surface (laser in the laser irradiation chamber, substrate transfer chamber, film formation chamber, etc.) The surface of the silicon thin film after crystallization is in a very active state, and even if it is not sufficiently controlled in the vacuum atmosphere, impurities can easily adhere to the surface. . At this time, compared with the case where active gases such as radicals and ions are used, the efficiency in a single process is inferior, but there is an effect that the incorporation of impurities adhering to the inner wall of the apparatus can be reduced. As a result, we succeeded in improving the overall production efficiency by suppressing the decrease in the device operation rate due to the cleaning and maintenance in the device. In addition, since the carbon present in the silicon oxide film and the silicon oxide film interface can be reduced, it is possible to manufacture a thin film transistor having a small leak current by using the present apparatus and the present manufacturing method.

  The present invention can be applied to a semiconductor thin film reforming apparatus using a laser crystallization technique.

It is an apparatus sectional view showing an embodiment of the invention. It is an apparatus sectional view showing an embodiment of the invention. It is a perspective view which shows embodiment of this invention. It is a side view which shows the alignment mechanism of a board | substrate. (A)-(C) It is explanatory drawing which shows the relationship between a mask pattern and an alignment mark. (1) and (2) are timing charts showing main operations. It is a side view which shows embodiment (semiconductor thin film modifier) of this invention. It is a top view which shows embodiment (semiconductor thin film modifier) of this invention. It is a side view which shows the outline of the plasma CVD chamber C2 of FIG. It is sectional drawing which shows the manufacturing process of TFT. It is a timing chart showing embodiment of this invention. It is a flowchart which shows embodiment (laser processing) of this invention. It is a flowchart which shows embodiment (laser processing) of this invention. It is explanatory drawing which shows the conventional ELA apparatus. It is explanatory drawing which shows the conventional irradiation method at the time of making the irradiation shape of a beam into a rectangle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Laser, 102 ... Mask, 103 ... Beam which passed through mask, 104 ... Window, 105 ... Irradiated area, 106 ... Unirradiated area, 107 ... Substrate, 108 ... Gate valve, 109 ... Holding means, 110 ... Stage, DESCRIPTION OF SYMBOLS 111 ... Vacuum container provided with board | substrate conveyance means, 112 ... Pressure control apparatus, 201 ... Board | substrate, 202 ... Stage, 203 ... Stage (guide part), 204 ... Pin passage port, 205 ... Adsorption port, 206 ... Adsorption exhaust line, 207 ... Substrate up / down mechanism, EL1 ... first excimer laser, EL2 ... second excimer laser, opt20 '... homogenizer, opt21 ... optical mask, opt23' ... reduced projection exposure apparatus, opt3, opt3 '... mirrors, opt4 ... Lenses, W0 ... laser introduction window, C0 ... vacuum chamber, sub0 ... substrate, S0 ... substrate stage, ex ... Pattern transfer area, θxy, θxz, θyz ... Tilt correction direction, X, Y ... Exposure area movement direction, Z ... Focusing direction, L0 ... Path optical axis, H0 ... Heater with substrate suction mechanism, S0 '... Substrate XYZθxyθxzθyz stage , I1, i2 ... laser interferometer, m0 ... off-axis microscope, Lm ... light source for microscope, opt-m ... element for microscope, msk1 ... mask (non-exposed part), msk2 ... mask (exposed part), mrk1 ... on mask Mark, mrk2 ... mark on substrate, mrk3 ... exposure formation mark, 501 ... non-exposed Si, 502 ... exposed Si, 503 ... Si removal part, 504,505 ... Si oxide film, C2 ... plasma CVD chamber, C5 ... laser irradiation chamber C7: substrate transfer chamber, GV2, GV5: gate valve, S2: substrate holder, S5: substrate stage, Sub0: glass substrate, 7 DESCRIPTION OF SYMBOLS 1 ... Silicon thin film, 702 ... Crystalline silicon thin film, D1 ... RF electrode, D2 ... Plasma formation area | region, D3 ... Plasma confinement electrode, D4 ... Source gas introduction apparatus, opt1 ... Laser synthetic | combination optical apparatus, opt11 ... Mirror, opt12 ... Transmission Mirror, opt2 ... laser irradiation optical device, opt20 ... homogenizer, opt21 ... optical mask, opt22 ... optical mask stage, opt23 ... projection optical device, C1 ... load / unload chamber, C3 ... substrate heating chamber, C4 ... hydrogen plasma chamber, GV1 to GV6: gate valve, gs1 to gs7 ... gas introduction device, vent1 to vent7 ... exhaust device, sub2, sub6 ... treatment substrate, RF1 ... high frequency power supply, RF2 ... high frequency electrode, RF3 ... electrode with gas supply hole, RF4 ... flat surface Mold gas introduction device, gs21 ... oxygen line, gs2 2 ... helium line, gs23 ... hydrogen line, gs24 ... silane line, gs25 ... helium line, gs26 ... argon line, L0 ... laser beam, T1 ... substrate cover film, T2 ... silicon thin film, T2 '... crystallized silicon thin film, T3 ... first gate insulating film, T4 ... second gate insulating film, T5 ... patterned gate electrode, T6, T6 '... impurity implanted region, T7, T7' ... interlayer isolation insulating film, T8 ... metal wiring, T9: Alignment mark, T10: Mark protective film.

Claims (8)

A hermetically sealed container having a substrate placement portion for placing a substrate having a semiconductor thin film and a light transmission window for transmitting laser light;
A laser beam irradiation means that is installed outside the sealed container and irradiates a laser beam for melting and heating the semiconductor thin film through the light transmission window;
Holding means for fixing and holding the substrate on the substrate mounting portion;
By adjusting the flow rate of the gas supplied into the sealed container, the atmospheric pressure in the sealed container at the time of irradiation with the laser light is equal to or higher than the vapor pressure defined by the temperature of the melted and heated semiconductor thin film. Pressure control means to control,
An alignment mechanism for adjusting the alignment of the substrate fixedly held on the substrate mounting portion with respect to the optical axis of the laser beam;
A focusing mechanism that adjusts a position in a focusing direction of the substrate fixedly held on the substrate mounting portion with respect to the laser beam;
A mask stage capable of irradiating the substrate with the laser light through an optical mask,
The mask stage starts moving to irradiate the laser beam to a desired position on the substrate when the alignment adjustment and the focusing are completed.
The laser beam irradiation unit irradiates the laser beam in consideration of an offset amount for exposure at a point away from the alignment adjustment position after the mask stage starts to move. Reformer. In claim 1,
The alignment mechanism and the focusing mechanism adjust the position of the alignment and focusing direction of the substrate so that the error accuracy of the exposure position of the substrate falls within a range of 0.1 to 100 μm. apparatus. In claim 1 or 2,
The semiconductor thin film reforming apparatus, wherein the holding means is a reduced pressure adsorption means. In claim 1 or 2,
The semiconductor thin film reforming apparatus, wherein the holding means is an electrostatic adsorption means. In claim 1 or 2,
The substrate is a glass substrate;
The semiconductor thin film reforming apparatus, wherein the semiconductor thin film is a silicon thin film. In claim 5,
A semiconductor thin film reforming apparatus further comprising means for introducing nitrogen or an inert gas into the sealed container and means for introducing oxygen gas into the sealed container. In claim 1 or 2,
The semiconductor thin film reforming apparatus is used for manufacturing a field effect thin film transistor. In claim 1 or 2,
The field effect thin film transistor is used as a driving element of an active matrix liquid crystal device.

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