JP2013030542A - Evaluation method of amorphous semiconductor film, and method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluation method of an amorphous semiconductor film which evaluates and manages an amorphous silicon (a-Si) film during a manufacturing process of a flat panel display, in the context of improvement in performance of the flat panel display.SOLUTION: In an evaluation method of an amorphous semiconductor film, laser light is radiated from a laser light radiating means 36 to a sample 32 in which an a-Si film is formed on a glass substrate. A microwave is radiated from a microwave radiating means 38 to each of sampling points on the sample 32 to which laser light is radiated, and reflection intensity is measured using a reflection wave detecting means 40. Based on the measurement result of reflection intensity at each sampling point, uniformity of physical property in the a-Si within a substrate surface is evaluated.

Description

  The present invention relates to a method for evaluating physical properties of an amorphous semiconductor film, and a method for manufacturing a semiconductor device manufactured using the amorphous semiconductor film.

  In a panel-like display device such as a liquid crystal display, a thin film transistor (TFT) is formed on a glass substrate, and each TFT is selected and a pixel signal is applied using the TFT as a switch element. A semiconductor film made of amorphous silicon (a-Si) has been widely used as an active layer serving as a channel in a TFT. Polycrystalline silicon (polycrystalline) having high carrier mobility has been used so far. Attempts to change to a semiconductor film made of silicon (poly-Si) have been made, and a low temperature poly-silicon (LTPS) technology capable of forming a film at a low temperature has been developed.

The LTPS film is usually formed by a process of laser crystallization of an a-Si film. LTPS makes it possible to use an inexpensive glass substrate having a low deformation temperature, and is more suitable for increasing the size of the substrate than high-temperature polysilicon technology. Here, the electron mobility μ of LTPS is about 30 to 300 cm ² / V · s, and the electron mobility μ of a-Si is about 0.5 to 1.0 cm ² / V · s. While it is about two digits larger, its width is also large. This wide range of electron mobility is caused by laser crystallization, and reflects the difference in crystal grain boundary size and defect density.

  As a technique for evaluating the crystallinity of this LTPS film, the following Non-Patent Document 1 discloses a method using a microwave-photo-conductivity decay (μ-PCD). The μ-PCD method irradiates a semiconductor as a sample with laser light to generate carriers (electrons and holes) in the semiconductor and irradiates microwaves, and changes the carrier density according to the reflection intensity of the microwaves. Observe. Since the resistivity of the semiconductor decreases as the carrier density increases, the reflectance of the microwave irradiated to the laser irradiation position changes in proportion to the carrier density. Since the lifetime until the generated carriers disappear due to recombination reflects the physical characteristics of the sample, the crystal state of the sample can be measured in a non-contact and non-destructive manner based on the time change of the reflectance of the microwave. .

  On the other hand, in the manufacture of a semiconductor device such as a flat panel display (FPD) using an a-Si film, it has not been conventionally performed to measure the physical characteristics of the a-Si film in a non-destructive manner. The reason may be that the a-Si film is not accompanied by crystallization that causes a large variation in characteristics unlike the LTPS film, and the necessity of measuring the characteristics on the production line is low. Conventionally, after the product is completed, the device characteristics are evaluated by inspection of lighting of the display, etc., and the Fourier transform infrared spectrophotometer (FT-IR) and secondary ion mass spectrometer (SIMS) are applied to the cut sample. Evaluation of physical properties of amorphous semiconductors using analytical techniques such as Rutherford backscattering spectroscopy (RBS) and electron spin resonance (ESR) has been performed as necessary.

Shingo Sumie et al., “Evaluation of Crystal Defects in Low-Temperature Polysilicon TFT Process: Application of Lifetime Measurement Technology”, Kobe Steel, Vol. 57, no. 1, 2007, pp8-16.

  In general, semiconductor devices are highly integrated and driven at high speed. In the FPD, as the screen is enlarged, higher definition is achieved by increasing the number of pixels, and high-speed driving is achieved by improving the dynamic resolution and increasing the frame rate corresponding to 3D video display. a-Si is still widely used especially in large FPDs because of its merit that the manufacturing cost is lower than LTPS. Unlike the LTPS film, the characteristics of the a-Si film, like the above-described electron mobility, are not affected by the crystallization process. However, among the above-mentioned product trends, there are strict requirements for the target range for the physical property value of the a-Si film and the uniformity of the physical property value in the plane of the glass substrate. By the way, the size of the glass substrate continues to expand, and the size of the 10th generation (G10) is about 3 m square.

  The present invention has been made in order to meet the above-mentioned demands in a production line such as an FPD, and an amorphous semiconductor film formed in a manufacturing process of a semiconductor device that can meet the demands. An evaluation method and a method for manufacturing a semiconductor device manufactured using the amorphous semiconductor film are provided.

  The amorphous semiconductor film evaluation method according to the present invention includes a laser beam irradiation step of irradiating a laser beam to an evaluation target substrate in which an amorphous semiconductor film is formed on a substrate made of an insulator, and the evaluation target. Microwave irradiation step of irradiating each sampling point irradiated with the laser light on the substrate with microwaves following the laser light irradiation step and measuring the reflection intensity, and measurement of the reflection intensity at each sampling point And an evaluation step for evaluating uniformity of physical properties of the amorphous semiconductor film within the substrate surface based on the result.

  A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device including a film forming step of forming an amorphous semiconductor film on a substrate, and the method includes: The laser light irradiation step of irradiating the evaluation target substrate having the amorphous semiconductor film formed thereon with laser light, and the laser light irradiation step at each sampling point where the laser light of the evaluation target substrate is irradiated Subsequently, the microwave irradiation step of irradiating the microwave and measuring the reflection intensity, and the measurement result of the reflection intensity at each sampling point of the evaluation target substrate, the amorphous in the substrate surface And evaluating the uniformity of the physical properties of the semiconductor film and detecting defects in the film formation process before the completion of the manufacture of the semiconductor device.

  Another method of manufacturing a semiconductor device according to the present invention includes a step of forming a gate electrode of a thin film transistor on a substrate made of an insulator, and an insulating film formation for covering the gate electrode and forming a gate insulating film on the substrate. A method of manufacturing a semiconductor device using the thin film transistor, comprising: a film process; and a semiconductor film forming process of forming an amorphous semiconductor film on the gate insulating film and forming an active layer of the thin film transistor. A specimen in which the gate insulating film and the amorphous semiconductor film are stacked on the substrate in the insulating film forming step and the semiconductor film forming step in parallel with the manufacture of the thin film transistor to prepare a sample substrate A laser beam irradiation step for irradiating the sample substrate with a laser beam; and each sampling point where the laser beam is irradiated on the sample substrate. The microwave irradiation step of irradiating the microwave subsequent to the light irradiation step and measuring the reflection intensity thereof, and the measurement result of the reflection intensity at each sampling point of the sample substrate, An evaluation step of evaluating uniformity of physical properties of the amorphous semiconductor film and detecting defects in the semiconductor film formation process before the completion of the manufacture of the semiconductor device, and the semiconductor device during the manufacture of the semiconductor device It is possible to cope with defects in the film formation process.

  Still another method of manufacturing a semiconductor device according to the present invention includes a semiconductor film forming step of forming an amorphous semiconductor film on a substrate made of an insulator, and reducing the hydrogen content in the amorphous semiconductor film. And a laser crystallization step of crystallizing the amorphous semiconductor film after the dehydrogenation step by laser light irradiation to form a polycrystalline semiconductor film as an active layer of a thin film transistor, A method of manufacturing a semiconductor device using the thin film transistor, wherein the amorphous semiconductor film is formed on the substrate in the semiconductor film formation step in parallel with the manufacture of the thin film transistor, and in the dehydrogenation step A specimen preparation step for preparing a specimen substrate by reducing the hydrogen content in the amorphous semiconductor film, a laser light irradiation step for irradiating the specimen substrate with laser light, and the specimen substrate A microwave irradiation step of irradiating each sampling point irradiated with the laser light with a microwave following the laser light irradiation step and measuring a reflection intensity thereof, and the reflection intensity at each sampling point of the sample substrate On the basis of the measurement results, an evaluation step for evaluating the degree of dehydrogenation of the amorphous semiconductor film and its uniformity in the substrate surface before the laser crystallization step, and the dehydrogenation in the evaluation step And an additional dehydrogenation step of performing an additional dehydrogenation process when deficiency is detected.

  Another method of manufacturing a semiconductor device according to the present invention includes a step of forming a gate electrode of a thin film transistor on a substrate made of an insulator, and an insulating film formation for forming a gate insulating film on the substrate so as to cover the gate electrode. A semiconductor film forming step of forming an amorphous semiconductor film to be an active layer of the thin film transistor on the gate insulating film; a source electrode of the active layer and the thin film transistor on the amorphous semiconductor film; And a ohmic layer film forming step of forming a low-resistance amorphous semiconductor film serving as an ohmic contact layer between the drain electrode and the drain electrode, and a method of manufacturing a semiconductor device using the thin film transistor, In parallel with the manufacture of the substrate, the gate insulating film and the low-resistance amorphous semiconductor film are stacked on the substrate in the insulating film forming step and the ohmic layer forming step. A sample preparation step for preparing a sample substrate, a laser light irradiation step for irradiating the sample substrate with laser light, and a laser light irradiation step for each sampling point irradiated with the laser light on the sample substrate Subsequently, the microwave irradiation step of irradiating the microwave and measuring the reflection intensity thereof, and the measurement result of the reflection intensity at the respective sampling points of the sample substrate, the low resistance non-intensity within the substrate surface is measured. And evaluating the uniformity of the physical properties of the crystalline semiconductor film to detect defects in the ohmic layer deposition process before the completion of the manufacture of the semiconductor device, and the ohmic layer during the manufacturing of the semiconductor device It is possible to cope with defects in the film forming process.

  According to the method for evaluating an amorphous semiconductor film of the present invention, the physical properties of the amorphous semiconductor film can be promptly measured nondestructively after the film formation. Further, according to the method for manufacturing a semiconductor device of the present invention, the amorphous semiconductor film can be evaluated without waiting for completion of a TFT, FPD, or the like using the amorphous semiconductor film. That is, before performing the process following the formation of the amorphous semiconductor film. Since it is possible to determine the quality of the amorphous semiconductor film and deal with the defect, it is possible to avoid the occurrence of unnecessary subsequent work using the defective amorphous semiconductor film and improve the yield of the semiconductor device. Is possible.

FIG. 3 is a schematic vertical sectional view of an example of a TFT formed on an array substrate of an IPS liquid crystal panel. It is a schematic diagram explaining the amorphous semiconductor film evaluation apparatus used in the embodiment of the present invention. It is a schematic diagram which shows the vertical cross-section of the sample substrate in 1st Embodiment. It is a graph which shows the measurement result by the evaluation apparatus about the sample board | substrate which formed the a-Si film | membrane with the CVD apparatus before a maintenance. It is a graph which shows the measurement result by the evaluation apparatus about the sample board | substrate which formed the a-Si film with the CVD apparatus after a maintenance. End of the sample substrate after the maintenance of the CVD apparatus is a graph _showing, V _g -I _d characteristics of the TFT in the central portion and the end portion of the sample substrate before maintenance. It is a SIMS profile measured about the section | slice of the center part and edge part of the sample board | substrate before the maintenance of a CVD apparatus. It is a flowchart which shows the outline of the manufacturing process of a liquid crystal display. It is a schematic diagram explaining the manufacturing method of the liquid crystal display in 2nd Embodiment. It is a graph which shows the relationship between the hydrogen content of the a-Si film in the sample substrate in 3rd Embodiment, and reflection intensity. It is a schematic diagram which shows the vertical cross-section of the sample substrate in 3rd Embodiment. It is a graph which shows the relationship between the reflection intensity and dangling bond density immediately after film-forming of an a-Si film and after dehydrogenation. It is a schematic diagram explaining the manufacturing method of the liquid crystal display in 3rd Embodiment. It is a graph which shows the relationship between the reciprocal number of 4 terminal resistivity of n ⁺ a-Si film | membrane, and reflection intensity regarding 4th Embodiment. It is a graph which shows the relationship between the reciprocal number of 2 terminal resistance value of n ^<+> a-Si film | membrane, and reflection intensity regarding 4th Embodiment. It is a graph which shows the relationship between on-current and reflection intensity about TFT using the n ⁺ a-Si film of different film-forming conditions. It is a schematic diagram explaining the manufacturing method of the liquid crystal display in 4th Embodiment. It is a schematic diagram explaining the manufacturing method of the liquid crystal display in 5th Embodiment. It is a schematic diagram explaining the manufacturing method of the liquid crystal display in 6th Embodiment.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  The principle of the amorphous semiconductor film evaluation method and the evaluation apparatus according to the embodiment will be described.

  The liquid crystal panel of the liquid crystal display device includes an array substrate on the backlight side, a color filter substrate on the display surface side, and a liquid crystal layer sealed in a gap therebetween. For example, in an IPS (In-Plane Switching) type liquid crystal panel, the orientation of the liquid crystal layer is controlled for each pixel by a voltage applied to a pixel electrode disposed on the surface of the array substrate on the liquid crystal layer side.

  FIG. 1 is a schematic vertical sectional view of an example of a TFT formed on an array substrate of an IPS liquid crystal panel. The TFT 2 is provided at each portion where a plurality of scanning signal lines (not shown) arranged in the vertical direction of the screen and a plurality of data signal lines (not shown) arranged in the horizontal direction of the screen intersect. The TFT 2 has an inverted staggered structure, the gate electrode 6 of the TFT 2 is formed on the surface of the glass substrate 4, and an active layer 10 that becomes a channel portion of the TFT 2 is laminated thereon with a semiconductor film via a gate insulating film 8. In this embodiment, the semiconductor film is an a-Si film. A drain electrode 14 and a source electrode 16 are connected to the active layer 10 through an ohmic contact layer 12, respectively. The surface of the TFT 2 facing the liquid crystal layer is covered with a protective film 18, and the pixel electrode 20 formed on the surface of the protective film 18 is connected to the source electrode 16 through a contact hole 22 formed in the protective film 18. On the other hand, the gate electrode 6 is connected to the scanning signal line, and the drain electrode 14 is connected to the data signal line.

  A signal for controlling on / off of the TFT 2 is applied to the scanning signal line, and a voltage signal for controlling the liquid crystal layer is applied to the data signal line. The TFT 2 functions as a switch element that controls the intermittent connection between the data signal line and the pixel electrode 20 according to the signal of the scanning signal line. When the TFT 2 is turned on, a voltage signal corresponding to the image signal is applied to the pixel electrode 20 from the data signal line. Is done.

The gate insulating film 8 and the protective film 18 are each made of a silicon nitride film (SiNx). Hereinafter, g-SiNx means the gate insulating film 8, and PAS-SiNx means the protective film 18. The ohmic contact layer 12 is made of low-resistance a-Si (n ⁺ a-Si) doped with n-type impurities at a high concentration to reduce resistance. Incidentally, the pixel electrode 20 is formed of an ITO (Indium Tin Oxide) film which is a transparent conductive film. A common electrode 24 made of ITO is disposed under the pixel electrode 20, and the potential of the common electrode 24 is set by a common line 26 made of the same metal film as the gate electrode 6.

When the on-characteristics of the TFT 2 deteriorate in the liquid crystal display device, the luminance may be lowered due to insufficient writing of the data signal to the pixel. The main factors of deterioration of the on-characteristics of TFT are (a) film thickness and film quality of the g-SiNx film, (b) ease of passage of charges as the active layer of the a-Si film (semiconductor physical properties), (c) n ⁺ Resistance value and carrier density of a-Si film.

  Regarding the factor (a), the on-characteristics deteriorate in the region where the g-SiNx film is thick.

  Regarding the factor (b), the on-characteristics are improved as the a-Si film has (i) high purity, (ii) a low dangling bond amount, and (iii) an atomic structure through which electrons easily pass. Here, the dangling bond is an unpaired electron that is not involved in the bond in the covalent atomic structure of a-Si, and has the property of hindering the movement of charges during TFT operation.

Regarding the factor (c), if the resistance value of the n ⁺ a-Si layer is sufficiently low as an ohmic contact layer, the on-characteristic is good.

The present invention relates to the evaluation of an amorphous semiconductor film. For example, in the TFT 2 of FIG. 1, an a-Si film forming an active layer 10 and an n ⁺ a-Si film forming an ohmic contact layer 12 are evaluated. In addition, it is possible to detect the on-characteristic failure associated with the above factors (b) and (c) during the manufacture of the liquid crystal display device and to deal with it.

  The amorphous semiconductor film according to the present invention is evaluated by an evaluation apparatus using the μ-PCD method. The basic principle of this apparatus is the same as that of the apparatus conventionally used for evaluating the crystallinity of the LTPS film. However, as already mentioned, the amorphous semiconductor film has a carrier mobility much higher than that of the polycrystalline semiconductor film. Since the reflection intensity of the microwave becomes very small, higher sensitivity than that of the LTPS film measurement is required. Devices that enable such highly sensitive measurements have recently been developed and provided. For example, differential μ-PCD is used as a technique for achieving high sensitivity.

  FIG. 2 is a schematic diagram illustrating the amorphous semiconductor film evaluation apparatus 30 used in the present embodiment. The outline of the μ-PCD method and the evaluation apparatus 30 will be described with reference to FIG. The evaluation apparatus 30 includes a stage 34 on which a sample 32 is placed, a laser beam irradiation means 36, a microwave irradiation means 38, and a reflected wave detection means 40. In the figure, each of the vertical sections of the stage 34 on which the sample 32 is placed is shown. Means 36, 38, 40 are represented. The laser light irradiation means 36 includes, as a light source, a pulse laser that excites and outputs a third harmonic (wavelength 349 nm) of YLF (lithium, yttrium fluoride) with a semiconductor laser, and pulses the target position of the sample 32 with an optical system. A laser beam with a width of about several tens of nS is irradiated. The microwave irradiating means 38 includes a microwave oscillator, a waveguide, and the like that output a microwave with a frequency of 26 GHz oscillated using a Gunn diode. In the differential μ-PCD method, the microwave output from the oscillator is branched into two, and one waveguide guides the microwave to the irradiation position of the laser light and extracts the reflected wave, and the other waveguide. Introduces the microwave to a position not irradiated with laser light and extracts the reflected wave. The reflected wave detection means 40 generates a signal indicating the reflectance at the target position of the sample 32 based on the difference in intensity between the two reflected waves. As described above, since the differential μ-PCD method is a method for extracting only the change in the physical properties of the sample 32 due to the irradiation of the laser beam, the disturbance due to the noise of the microwave oscillator and the mechanical vibration can be canceled and high sensitivity can be realized. .

When laser irradiation is performed on the sample 32 in which the semiconductor film 44 is formed on the insulating substrate 42, excess carriers (electron / hole pairs) are generated in the semiconductor film 44, and after the lifetime determined by the physical characteristics of the semiconductor film 44. , Recombine and disappear. Since the generation of excess carriers increases the conductivity of the sample 32, the reflectance of the microwave at that position changes corresponding to the density of excess carriers. As described above, the μ-PCD method measures the lifetime in a non-contact / non-destructive manner from the time change of the reflectance of the microwave. The stage 34 can move two-dimensionally in a horizontal plane, and can change the measurement target position on the sample 32 to create a map in the substrate plane. In this evaluation method, an amorphous material such as an a-Si film or an n ⁺ a-Si film is used based on the reflection intensity (reflectance) of the microwave at each sampling point of the sample 32 or a map of the lifetime in the substrate surface. The physical property value of the high-quality semiconductor film, the presence or absence of variation in the substrate surface, or the uniformity is estimated and evaluated.

Basically, the reflectivity R increases as the density of excess carriers increases, and thus the reflectivity V at a certain measurement time increases as the lifetime τ increases. The V value is affected by the thickness of the a-Si layer, the amount of impurities, the dangling bond density, the atomic structure, and the like. Further, regarding the n ⁺ a-Si layer, values such as doping amount and resistivity are also affected. Of these factors, the film thickness is not related to the physical properties of the a-Si layer or the like, but all others are related to the semiconductor physical properties and the physical properties of the ohmic contact layer. That is, assuming that the film thickness is constant, the V value reflects the on-characteristics of the TFT, such as mobility μ and on-current I _on, and thus the above-described writing deficiency can be evaluated based on the V value. For example, the uniformity of the on-characteristics of the TFT can be evaluated based on the mapped V value.

  The principle of the evaluation method and the evaluation apparatus according to the present invention have been described above. Hereinafter, an evaluation form of an amorphous semiconductor film to which the present invention is applied and experimental results will be described. Further, an embodiment of a manufacturing method to which the present invention is applied to an FPD which is an example of a semiconductor device formed using an amorphous semiconductor film will be described.

[First embodiment]
The present embodiment relates to an a-Si film evaluation method. Here, an example applied to the evaluation of the a-Si film used for the active layer 10 of the TFT formed on the array substrate of the liquid crystal panel will be described. In the manufacturing process of the liquid crystal panel, the TFT 2 shown in FIG. 1 is formed on the glass substrate. A sample substrate 50 as a sample 32 is formed substantially in parallel with the step of forming the TFT 2. The sample substrate 50 is formed in the same size as the liquid crystal panel. FIG. 3 is a schematic diagram showing a vertical cross-sectional structure of the sample substrate 50 in the present embodiment. The SiNx film 52 (thickness) formed by the film formation process of the gate insulating film 8 on the glass substrate 4 (thickness 0.7 mm). 370 nm), the a-Si film 54 (thickness 160 nm) formed by the film formation process of the active layer 10, and the SiNx film 56 (thickness 480 nm) formed by the film formation process of the protective film 18 are sequentially formed by CVD (Chemical Vapor Deposition: Chemical vapor deposition) Each layer of the sample substrate 50 is basically formed on the entire surface of the substrate, and the next layer is laminated without patterning.

  A liquid crystal panel and a sample substrate 50 were prepared using a substrate (82 cm wide and 46 cm long) on which an active layer 10 (or a-Si film 54) was formed before and after maintenance for a CVD apparatus operated for a considerable period of time. .

  For the liquid crystal panel, a lighting test was performed by inputting an image signal of a uniform halftone image. Here, in order to compare with the sample substrate 50, a liquid crystal panel having the same position on the mother glass as the sample substrate 50 is used. Since the difference in on-characteristics of the TFT 2 tends to be noticeable in a low temperature state, the lighting test was performed at -20 ° C. As a result, in the liquid crystal panel in which the active layer 10 was formed with the CVD apparatus before maintenance, it was visually confirmed that the brightness in the region of about 5 cm at the right end was significantly reduced, and the occurrence of uneven brightness in the screen was confirmed. It was done. On the other hand, in the liquid crystal panel in which the active layer 10 was formed by a CVD apparatus after maintenance, luminance nonuniformity was not observed in the screen, and it was confirmed that the liquid crystal panel was healthy.

  4 and 5 are graphs showing the results of measuring the sample substrate 50 with the evaluation apparatus 30, and FIG. 4 relates to the sample substrate 50 in which the a-Si film 54 is formed by the CVD apparatus before maintenance. FIG. 5 is after maintenance. Although the measurement was performed two-dimensionally on the entire substrate surface (XY surface) using the stage 34, for the sake of illustration, the measurement result along the substrate lateral direction is shown here. The horizontal axis of the graph represents the coordinate in the horizontal direction (X direction) on the substrate, and the vertical axis represents the measured value of the reflection intensity V of the microwave, indicating the value at the center in the vertical direction (Y direction) of the substrate. ing.

  Two types of changes in the amount of reflected light appear in the measurement results shown in FIG. 4 corresponding to before maintenance. One is a gentle distribution in which the value is low on the left side of the substrate and gradually increases from the left side toward the center. The other is a distribution in which the value decreases remarkably as it approaches the right end. Here, the reflection intensity signal was 112 mV at the center in the X direction, but was 82 mV at the right end. The former gentle distribution is considered to reflect the film thickness distribution in which the a-Si film thickness is thin in the left half of the map and becomes thicker as it approaches the outer periphery. The region with the small value at the right end corresponds to the low-luminance region of the liquid crystal panel described above, and the film quality of the a-Si film is poor, and as a result, the TFT characteristics are degraded in the liquid crystal panel. It is done.

  In the measurement results in FIG. 5 corresponding to the post-maintenance, the observed luminance decrease at the right end of the substrate was not observed in the case of FIG. On the other hand, the tendency that the reflection intensity V gradually rises from the left end of the substrate to the right, which is considered to be a film thickness distribution, similarly exists, and reaches a relatively large reflection intensity (127 mV) in the right end region.

In order to clarify the cause of the luminance failure at the end before maintenance, the TFT characteristics in the sample region of the liquid crystal panel were evaluated, and the sample region was cut out from the sample substrate 50 to examine the amount of impurities. The following three locations Sm1, Sm2, and Sm3 were set as sample regions.
Sm1: Right end after CVD maintenance (where the above V value was 127 mV)
Sm2: Center before CVD maintenance (where the above V value was 112 mV)
Sm3: Right end before CVD maintenance (where the V value was 82 mV)

Figure 6 shows by comparison, _V g -I _d characteristics of the TFT corresponding to each sample area. The horizontal axis of the graph is the gate voltage V _g (gate-source voltage V _gs ), and the vertical axis is the drain current I _d (source-drain current I _ds ). FIG. 6A shows the measurement result for the TFT in the region Sm1, FIG. 6B shows the measurement result for the region Sm2, and FIG. 6C shows the measurement result for the region Sm3. The channel width W of the TFT was 1000 μm, the channel length L was 5 μm, the drain-source voltage V _ds was set to 10.1 V, and measurements were performed at three temperatures of 20 ° C., 0 ° C., and −20 ° C. .

6, sample Sm3, compared with Sm1, Sm2, any temperature, even lower value of on-current _{I d} in the gate voltage _{V g,} which shows that the TFT characteristics are deteriorated.

FIG. 7 shows SIMS profiles measured for the sections of the sample substrate 50 in the regions Sm2 and Sm3. The left graph corresponds to Sm2, and the right graph corresponds to Sm3. The horizontal axis of the graph is the depth from the sample surface, and the ranges indicated by the notation of PAS-SiNx, Si, and g-SiNx from the surface side along the horizontal axis are SiNx film 56, a-Si film 54, and SiNx, respectively. This is the depth range of the film 52. The vertical axis represents the yield, the right axis corresponds to the ion count value, and the left axis corresponds to the element concentration. Of the observed elements, the profiles for hydrogen (H), nitrogen (N), silicon (Si), and fluorine (F) with high yields are shown. FIG. 7A shows the measurement results for the sample section in the region Sm2, and FIG. 7B shows the measurement results for the region Sm3. The major difference between Sm2 and Sm3 is the N and F profiles. When compared with the content in the a-Si layer, N is about 7 times, F is about 20 times, and there are more at the end (Sm3) than at the center (Sm2). In quantifying the content of N and F, assuming that the density of atoms in the Si layer is 5.0 × 10 ²² atoms / cc, the atomic concentration of N in the center is 0.06 at%, and F atoms The concentration is 0.006 at%, and N is 0.40 at% and F is 0.14 at% at the end. In particular, the content of N at the edge is a considerably large value as an impurity. In each layer of PAS-SiNx and g-SiNx, F is about five times larger at the end than at the center.

Although not shown, oxygen (O) and carbon (C) have no significant difference between the center and the end, and sodium (Na), aluminum (Al), potassium (K), calcium (Ca), iron (Fe) The copper (Cu) elements were below the lower limit of detection, and phosphorus (P) was about the same at the center and at the end (about 10 ¹⁵ atoms / cc).

  From the measurement and analysis of the TFT characteristics and SIMS profile described above, defects such as uneven brightness of the liquid crystal panel may be caused by deterioration of physical properties of the a-Si film due to local increase of impurities in the substrate surface. I understood.

  The evaluation method of the present invention using the μ-PCD method detects the presence of a physical property deterioration portion of the a-Si film in the substrate surface using the sample substrate 50, and the luminance on the liquid crystal panel associated therewith. It is possible to estimate the occurrence of deficiencies and uneven brightness. That is, when the reflection intensity V measured on the sample substrate 50 is smaller than the threshold value measured in advance by the comparison between the liquid crystal panel and the sample substrate 50 as described above, the sample substrate 50 is manufactured in parallel. It can be determined that there is a risk of insufficient luminance for the array substrate. In addition, when the fluctuation range of the reflection intensity in the substrate surface is equal to or larger than the threshold value obtained by measurement in advance, it can be determined that there is a possibility of uneven brightness. As described above, when a defect such as insufficient brightness or uneven brightness in the liquid crystal panel is predicted in the evaluation at the stage of preparing the sample substrate 50, for example, the subsequent manufacturing process is stopped and the CVD apparatus is maintained. It is possible to take measures such as

  Here, the μ-PCD method is affected by the presence of a conductor under the semiconductor layer. Therefore, in the above-described embodiment, as the sample substrate 50, a substrate on which a metal film for forming the gate electrode 6 is not formed is formed in parallel with the array substrate for manufacturing the liquid crystal panel, and the sample substrate 50 is used as the evaluation apparatus 30. Measured with However, even in the array substrate, there is a region where no metal film is disposed under the a-Si film. Such a region exists, for example, in a portion other than the image region and the peripheral circuit formation region, and such a region is likely to exist on the edge of the substrate. When the a-Si film 54 is formed, the region where the metal film does not exist below is found along the edge of the substrate, or provided in advance by design, and the spot-like laser beam of the evaluation apparatus 30 and It is possible to evaluate the uniformity of the physical properties of the a-Si film in the array substrate by irradiation with microwaves.

[Second Embodiment]
The present embodiment relates to a method for manufacturing a liquid crystal display using a TFT in which an active layer 10 is formed of an a-Si film. FIG. 8 is a flowchart showing an outline of a manufacturing process of a liquid crystal display, and includes a TFT array process, a color filter (CF) process, a cell process, and a module (MD) process. The TFT array process is a process for forming an array substrate by repeatedly forming a structure such as a TFT on a glass substrate by repeating a photolithography process and a film forming process. Specifically, after patterning the gate electrode 6, a g-SiNx film (gate insulating film 8), an a-Si film (active layer 10), and an n ⁺ a-Si film (ohmic contact layer 12) are continuously formed using a CVD apparatus. A film is formed, and the active layer 10 and the ohmic contact layer 12 are patterned. Furthermore, after forming the drain electrode 14, the source electrode 16, the protective film 18, and the contact hole 22, an ITO film is formed and patterned to form the pixel electrode 20.

  The CF process is a process of forming a color filter substrate by forming a black matrix and color filters such as red (R), green (G), and blue (B) on a glass substrate.

  The cell process is a process in which the array substrate manufactured in the TFT array process and the color filter substrate manufactured in the CF process are combined, and a liquid crystal material is put therebetween. Specifically, an alignment film made of polyimide is printed on the liquid crystal side surfaces of both substrates, and a rubbing process is performed. Further, assembly including sealing agent application, substrate bonding, and liquid crystal injection is performed. In general, the TFT array process and the CF process are performed using a large-area mother glass, and after assembling them, a plurality of liquid crystal panels produced in the mother glass are cut out. A polarizing plate is attached to each cut liquid crystal panel.

  The MD process is a process for completing a liquid crystal display by assembling a backlight, a driving power source and the like to the liquid crystal panel. Specifically, a driver IC is mounted, a backlight is attached, etc., and finally a lighting inspection is performed.

  FIG. 9 is a schematic diagram for explaining a method of manufacturing a liquid crystal display in the present embodiment. As the glass substrate, an actual substrate for actually producing the array substrate and an evaluation substrate for producing the sample 32 are prepared. For example, a part of a plurality of glass substrates (mother glass) constituting a production lot is used as an evaluation substrate, an evaluation target lot is defined for each predetermined number of lots, and a part of the glass substrate is set as an evaluation substrate. be able to.

As in the first embodiment, the TFT 2 shown in FIG. 1 is formed on the glass substrate 4 that is a real substrate. On the other hand, a sample substrate is manufactured using an evaluation substrate in parallel with the process of manufacturing the TFT 2. Specifically, a gate metal (GM) film 72 is formed on the actual substrate 70 by sputtering (S100), and this is patterned to form, for example, the gate electrode 6 (S102). After the gate electrode 6 is formed, the g-SiNx film 74, the a-Si film 76, and the n ⁺ a-Si film 78 are continuously formed using a CVD apparatus (S104). FIG. 9 shows a schematic vertical sectional structure 80 in the vicinity of the gate electrode 6 of the array substrate that has undergone the above steps.

  In the process up to this point for the actual substrate 70, the g-SiNx film 74 and the a-Si film 76 are formed on the evaluation substrate 90 to produce a sample substrate (S110). This film forming step S110 uses the same CVD apparatus as the film forming step S104 on the actual substrate 70, and the g-SiNx film 74 and the a-Si film 76 on the evaluation substrate 90 are formed under the same conditions as in the actual substrate 70. Is done. FIG. 9 shows a schematic vertical sectional structure 92 of the sample substrate.

  In the manufacturing method of the liquid crystal display according to the present embodiment, when the sample substrate is manufactured in parallel with the three-layer continuous film forming step S104 on the actual substrate 70, the sample substrate is used next and based on the evaluation method described in the first embodiment. The physical properties of the a-Si film 76 are evaluated (S112). Specifically, the sample substrate is set in the evaluation apparatus 30 described above, and laser light irradiation and microwave irradiation are performed, for example, a map of the reflection intensity V is measured. And based on the measurement result of the said evaluation apparatus 30, it detects that the physical property degradation part of an a-Si film exists in a board | substrate surface, and estimates the generation | occurrence | production of the brightness | luminance deficiency and brightness nonuniformity in a liquid crystal display accompanying it. For example, when the reflection intensity V measured on the sample substrate is smaller than the threshold value measured in advance by comparison with the lighting inspection of the liquid crystal panel as described in the first embodiment, the sample substrate is manufactured in parallel with the sample substrate. It can be determined that there is a risk of insufficient luminance for the actual substrate being used. In addition, when the fluctuation range of the reflection intensity in the substrate surface is equal to or larger than the threshold value obtained by measurement in advance, it can be determined that there is a possibility of uneven brightness.

Subsequent to the patterning step (S106) of the n ⁺ a-Si film 78 and the a-Si film 76 following the film forming step S104 on the actual substrate 70, the a-Si film is obtained as a result of the physical property evaluation S112 of the a-Si film. This is performed when it is determined that the film forming process 76 is good. On the other hand, if the film forming process is determined to be defective as a result of the physical property evaluation S112, the cause of the defect, the maintenance of the CVD apparatus, and the like are performed without performing subsequent processing (S114).

  As described above, the a-Si film forming process performed at an extremely early stage of the liquid crystal display manufacturing process is evaluated at an early stage such as before moving to the next process, thereby quickly grasping the problem of the line. be able to. For example, when a quality defect is detected by evaluation using a sample substrate, it is avoided that many subsequent steps are wasted on the actual substrate of the work-in-process manufactured in parallel with the sample substrate. it can. Conventionally, the defect is detected in a considerably later process such as a lighting inspection. Therefore, in a subsequent lot between the occurrence of a-Si film deposition defect in a certain lot and the lighting inspection. Where there is a possibility that defective work-in-progress will continue to be produced, it can be prevented by the manufacturing method of the present invention. Thus, according to the method for manufacturing a liquid crystal display of the present invention, yield and line productivity are improved.

  In the above embodiment, until the evaluation result of the a-Si film using the sample substrate is obtained, the execution of the step S106 immediately after the step S104 in which the a-Si film 76 is formed on the real substrate 70 is stopped. However, it is permissible in the present invention to proceed with the actual substrate 70 until the evaluation result is obtained.

[Third embodiment]
The present embodiment relates to a method for manufacturing a liquid crystal display using a TFT in which an active layer 10 is formed of an LTPS film. As in the second embodiment, this embodiment also relates to the process of forming the active layer 10 of the TFT in the TFT array process among the manufacturing processes of the liquid crystal display shown in FIG.

  The LTPS film of the active layer 10 is formed by crystallizing an a-Si film formed by a CVD apparatus. In the case of using the laser crystallization method, it is known that there is a possibility that a film called ablation may be destroyed unless the laser irradiation is performed after removing hydrogen in the a-Si film.

  Hereinafter, the results of experiments and analysis performed on the influence of hydrogen contained in the a-Si film will be described.

FIG. 10 is a graph showing the relationship between the reflection intensity V and the hydrogen content in the a-Si film formed by the CVD apparatus, with the horizontal axis representing the reflection intensity V and the vertical axis representing the hydrogen content in terms of atomic concentration. It is. FIG. 11 is a schematic diagram showing a vertical cross-sectional structure of a sample used in this measurement. On a 6-inch φ quartz substrate, a SiN film (thickness 148 nm), a SiO ₂ film (thickness 170 nm), and a-Si It has a structure in which films (thickness 50 nm) are sequentially stacked by a CVD apparatus. Several types of samples having different hydrogen contents in the structure were prepared, and the reflection intensity V in the measurement region was measured for each sample. FIG. 10 plots the maximum value, minimum value, and peak value (average value) of the reflection intensity V of each sample, and shows regression lines 120, 122, and 124 for the maximum value, minimum value, and peak value, respectively. Yes. As shown in FIG. 10, the reflection intensity V and the hydrogen content are in a proportional relationship. Therefore, it was found that the reflection intensity V was measured by the evaluation device 30 described above, and the hydrogen content in the a-Si film could be evaluated from the measured value.

  FIG. 12 is a graph showing the relationship between the reflection intensity V and the dangling bond density in the a-Si film, where the horizontal axis represents the reflection intensity V and the vertical axis represents the dangling bond density. Each a-Si film was measured immediately after film formation and after dehydrogenation. The dangling bond density and the reflection intensity V differ greatly immediately after film formation and after dehydrogenation. Specifically, a measurement result having a low dangling bond density and a high reflection strength V is obtained immediately after film formation, and a measurement result having a high dangling bond density and a low reflection strength V is obtained after dehydrogenation. Obtained. The measurement result immediately after film formation is because the lifetime τ of carriers generated by laser irradiation of the evaluation apparatus 30 is relatively long because hydrogen in the film terminates dangling bonds in the a-Si film. . On the other hand, after dehydrogenation, hydrogen terminated is eliminated and dangling bonds increase, so that the carrier lifetime τ is shortened and the reflection intensity V is decreased.

  From the experiment and analysis results, it can be seen that the evaluation device 30 can evaluate the amount of hydrogen in the a-Si film.

Next, experimental results regarding crystallization by laser irradiation after dehydrogenation will be described. A SiNx film (thickness 150 nm), a SiO ₂ film (thickness 170 nm), and an a-Si film (thickness 55 nm) are sequentially stacked on a 6-inch φ quartz substrate (thickness 0.625 mm) using a CVD apparatus. The sample is irradiated with laser light. The laser changed the irradiation output by 5 W in the range of 50 to 85 W, and measured the reflection intensity V in the irradiated region and non-irradiated region at each output. In the region where the irradiation output is 60 W or more, the lifetime of carrier τ is increased due to the crystallization of the a-Si film, and the reflection intensity V is increased as compared with the non-irradiated region of the laser beam. On the other hand, the reflection intensity V decreased in the entire irradiation area of 50 W and in the area of about half of 55 W as compared with the non-irradiation area. This is because the dangling bond density in this region was increased as a result of further rapid dehydrogenation due to the instantaneous rise in temperature within the range where crystallization was not performed by irradiation with a weak laser. From this experimental result, it was found that dehydrogenation treatment can be performed by irradiating a weak laser beam. Moreover, it is shown that the phenomenon in which hydrogen has escaped from the a-Si film can be confirmed by the evaluation apparatus 30.

FIG. 13 is a schematic diagram for explaining a method of manufacturing a liquid crystal display in the present embodiment. Similar to the second embodiment, an actual substrate and an evaluation substrate are prepared as glass substrates. A TFT having an active layer made of an LTPS film is formed on a glass substrate which is a real substrate. Here, the LTPS TFT is a bottom gate type, and a GM film 152 is formed on the actual substrate 150 by sputtering (S180), and this is patterned to form, for example, a gate electrode 154 (S182). After the formation of the gate electrode 154, a g-SiNx film 156, a g-SiO ₂ film 158 (gate oxide film), and an a-Si film 160 are successively formed using a CVD apparatus (S184). Thereafter, an annealing furnace is used to anneal at a high temperature not higher than the melting point of the glass substrate, for example, about 450 ° C. to perform a dehydrogenation process (S186). Incidentally, laser annealing causes the above-described ablation due to bumping of hydrogen, and is not used for the dehydrogenation process at this stage. FIG. 13 shows a schematic vertical sectional structure 162 in the vicinity of the gate electrode 154 of the actual substrate that has undergone the above steps.

In parallel with the above-described process for forming TFTs on the actual substrate 150, a sample substrate is created using the evaluation substrate 170. In the process up to the dehydrogenation process S186 for the actual substrate 150, the evaluation substrate 170 is formed with the g-SiNx film 156, the g-SiO ₂ film 158, and the a under the same CVD apparatus and the same conditions as the film formation process S184 of the actual substrate 150. A Si film 160 is formed (S190). Thereafter, the a-Si film 160 on the evaluation substrate 170 is also subjected to a dehydrogenation process under the same conditions as the dehydrogenation process S186 on the actual substrate 150 to produce a sample substrate (S192). FIG. 13 shows a schematic vertical sectional structure 172 of the sample substrate.

  In the method for manufacturing a liquid crystal display according to this embodiment, when a sample substrate is manufactured in parallel with the three-layer continuous film forming step S184 and the dehydrogenation treatment S186 on the actual substrate 150, the sample substrate is used next and described in the first embodiment. The physical properties of the a-Si film 160 are evaluated based on the evaluation method (S194). Specifically, the sample substrate is set in the evaluation apparatus 30, laser light irradiation and microwave irradiation are performed, and for example, a map of the reflection intensity V is measured.

  And based on the knowledge obtained by the experiment etc. which were mentioned above, the amount of hydrogen in the a-Si film 160 of a sample substrate or its in-plane distribution is evaluated from the measurement result of the said evaluation apparatus 30. FIG. For example, using the experimental results of FIG. 10, it is determined whether the reflection intensity V in the sample substrate surface is a value indicating that the hydrogen content in the a-Si film 160 is sufficiently reduced, and dehydration is performed. It is determined whether the raw process is good. If the dehydrogenation process is satisfactory, the actual substrate 150 is advanced to the Si layer laser crystallization process next to the dehydrogenation process S186 (S188). On the other hand, when it is determined that the dehydrogenation is insufficient, for example, the dehydrogenation process S186 for maintaining the temperature at about 450 ° C. is performed again using an annealing furnace. The re-dehydrogenation treatment S186 here can be performed by laser annealing with a low irradiation power when the amount of hydrogen has already decreased to some extent and the risk of ablation is low, based on the knowledge in the above-described experiment. This method can complete the treatment in a shorter time than the treatment by the annealing furnace. In order to accurately determine whether or not this laser annealing can be applied, it is necessary to confirm the amount of hydrogen after dehydrogenation, but the physical property evaluation S194 using the μ-PCD method makes this possible.

  As described above, the LTPS film dehydrogenation process performed at an extremely early stage of the liquid crystal display manufacturing process is evaluated before moving to the next laser crystallization process. To reduce the amount of hydrogen, avoid ablation in laser crystallization, and improve the yield.

  Conventionally, in the LTPS TFT manufacturing process, the importance of managing the Si film after crystallization of the a-Si film has been recognized, and evaluation using the μ-PCD method has been used for the management. However, the management of the CVD-formed a-Si film as a starting material before crystallization is equally important. In the LTPS TFT manufacturing process of this embodiment, the management of the a-Si film is the same as that of the above-described present invention. This is preferably performed using an evaluation method.

[Fourth embodiment]
As in the second embodiment, the present embodiment relates to a method for manufacturing a liquid crystal display using a TFT in which an active layer 10 is formed of an a-Si film. In the second embodiment, after the GM film patterning S102, the a-Si film 76 among the g-SiNx film 74, the a-Si film 76, and the n ⁺ a-Si film 78 that are continuously formed is formed on the sample substrate. The quality was judged. On the other hand, in this embodiment, the n ⁺ a-Si film 78 is formed on the sample substrate, and the quality is determined.

Specifically, the quality of the n ⁺ a-Si film 78 as the ohmic contact layer 12 can be evaluated based on, for example, the resistance value among the physical properties. An n ⁺ a-Si film (thickness 25 nm) was produced on a G6 glass substrate (thickness 0.7 mm) under different conditions, and the reflection intensity V was about 10 cm square area at the center and end of the glass substrate. The 4-terminal resistivity and the 2-terminal resistance value were measured. The film formation conditions of the n ⁺ a-Si film were changed by changing the percentage of phosphine (PH ₃ ) gas mixed with the monosilane (SiH ₄ ) gas used for CVD, and the flow rate ratio of PH ₃ / SiH ₄ was 2.8 to 4.6%. In this way, four stages of samples were prepared in 0.6% steps. Samples were prepared and measured before and after maintenance of the CVD apparatus.

14 and 15 are scatter diagrams showing the measurement results of the respective samples, and show the correlation between the reflection intensity V of the n ⁺ a-Si film and the resistance. The horizontal axis represents the reflection intensity V in both FIGS. The vertical axis in FIG. 14 is a value proportional to the inverse of the 4-terminal resistivity, and the vertical axis in FIG. 15 is a value proportional to the inverse of the 2-terminal resistance value. 14 and 15, it can be seen that the resistance tends to be small when the reflection intensity V is large, and it can be determined that the physical property as the ohmic contact layer 12 is good as the reflection intensity V is large. By the way, in this measurement, the flow rate ratio of PH ₃ / SiH ₄ was 2.8%, and the measured value of the reflection intensity V at the edge of the substrate immediately before maintenance was high.

The evaluation of the n ⁺ a-Si film by the evaluation device 30 has the following characteristics. First, since phosphorus (P) is doped, there are more carriers than in the a-Si film, and accordingly, the reflectance of the microwave is increased, and a large reflection intensity V is observed. In addition, the measurement value is increased according to the amount of carriers present under the influence of the P content, the activation rate, and the like. That is, the greater the measured value, the lower the resistivity.

Using the n ⁺ a-Si film under some sample conditions described above, TFTs as shown in FIG. Specifically, an n ⁺ a-Si film was produced with a PH ₃ / SiH ₄ flow rate ratio of 2.8% and 4.6% before maintenance of the CVD apparatus. For the TFT at the center and the TFT at the end of the substrate, the drain-source voltage V _ds is set to 0.1 V, and V _g −I _d at three temperatures of 20 ° C., 0 ° C. and −20 ° C. Characteristics were measured. Figure 16 is a gate in the characteristics - and the drain current I _d source voltage V _gs at 23V, shows the relationship between the reflection intensity V, the horizontal axis reflection intensity V, the vertical axis is the drain current I _d . From the results shown in FIG. 16, the value of the on-current I _d decreases as the measurement temperature decreases, but the on-current I _d tends to decrease when the reflection intensity V of the n ⁺ a-Si film is small at any temperature. Appears. That is, the low reflection intensity V of the n ⁺ a-Si film means that the resistance value of the ohmic contact layer 12 between the active layer 10 and the drain electrode 14 and the source electrode 16 in FIG. 1 is high. The on-current value of the TFT becomes small.

From the experiment and analysis results, it was found that the physical properties of the n ⁺ a-Si film in the a-Si TFT manufacturing process can be managed by the evaluation device 30.

FIG. 17 is a schematic diagram for explaining a method of manufacturing a liquid crystal display according to this embodiment. Similar to the second embodiment, an actual substrate and an evaluation substrate are prepared as glass substrates. A TFT having an active layer made of an a-Si film is formed on the glass substrate which is the actual substrate 70. The TFT is the same as that of the second embodiment, and the description of the actual substrate 70 in FIG. 17 (the left half in the figure) is the same as the left half in FIG. The difference from the second embodiment is that a g-SiNx film 74 and an n ⁺ a-Si film 78 are continuously formed on the evaluation substrate 200 in a sample substrate manufactured in parallel with the actual substrate 70. (S210). In this film forming step S210, a film is formed under the same conditions as the actual substrate 70 using the same CVD apparatus as the film forming step S104 on the actual substrate 70. FIG. 17 shows a schematic vertical sectional structure 202 of the sample substrate.

In the liquid crystal display manufacturing method of the present embodiment, when a sample substrate is manufactured in parallel with the three-layer continuous film forming step S104 on the actual substrate 70, the sample substrate is then used based on the evaluation method described in the first embodiment. The physical properties of the n ⁺ a-Si film 78 are evaluated (S212). Specifically, as in the second embodiment, a map of the reflection intensity V is measured for the sample substrate. And based on the knowledge obtained by the experiment etc. which were mentioned above, the resistance of the n ^<+> a-Si film 78 of a sample substrate or its in-plane uniformity is evaluated from the measurement result of the said evaluation apparatus 30. FIG. For example, it is determined whether the resistance of the n ⁺ a-Si film 78 in the sample substrate surface is sufficiently small or uniform, and it is determined whether or not the n ⁺ a-Si film 78 is satisfactorily formed. To do.

Subsequent to the film formation step S104 in the real substrate ^70, n + a-Si patterning the film 78 and the a-Si film 76 (S106) and subsequent steps, the result of evaluation of the physical properties S212 in the ⁿ + a-Si film, ^{n +} This is performed when it is determined that the film formation process of the a-Si film 78 is good. On the other hand, if it is determined that there is a problem such as an increase in resistance as a result of the physical property evaluation S212, it is determined that there is some abnormality in the CVD apparatus or the film formation condition setting is incorrect, and the apparatus maintenance or conditions Is reset (S214).

As described above, the n ⁺ a-Si film forming process performed at the very early stage of the liquid crystal display manufacturing process is evaluated at an early stage, such as before moving to the next process, so that the problem of the line can be quickly found. I can grasp it. Therefore, the same effect as the second embodiment can be obtained. That is, for example, when a quality defect is detected by evaluation using a sample substrate, many subsequent steps are wasted on the actual substrate of the work-in-process manufactured in parallel with the sample substrate. Can be avoided. Further, conventionally, such a defect is detected in a considerably later process such as lighting inspection, and a defect is not detected in a subsequent lot after the occurrence of a-Si film deposition defect in a certain lot until the lighting inspection. If there is a possibility that the work-in-progress will continue to be produced, it can be prevented according to the production method of the present invention. Thus, according to the method for manufacturing a liquid crystal display of the present invention, yield and line productivity are improved.

It should be noted that, as in the second embodiment, it is allowed to proceed the process for the actual substrate 70 to some extent until an evaluation result of the n ⁺ a-Si film using the sample substrate is obtained.

[Fifth Embodiment]
This embodiment relates to a method of manufacturing a liquid crystal display using a TFT in which an active layer 10 is formed of an a-Si film, as in the second and fourth embodiments. In the second embodiment, the quality of the a-Si film 76 formed on the sample substrate is determined, and in the fourth embodiment, the n ⁺ a-Si film 78 is formed on the sample substrate to determine the quality. On the other hand, in this embodiment, in parallel with the process for the actual substrate, the two types of sample substrates are produced and the quality is determined.

  FIG. 18 is a schematic diagram for explaining a method of manufacturing a liquid crystal display in the present embodiment. Similar to the second to fourth embodiments, an actual substrate and an evaluation substrate are prepared as glass substrates. A TFT having an active layer made of an a-Si film is formed on the glass substrate which is the actual substrate 70. The TFT is the same as in the second and fourth embodiments, and the description of the actual substrate 70 in FIG. 18 (the left half in the figure) is the same as the left half in FIGS. 9 and 17.

In the present embodiment, two evaluation substrates are prepared, and a sample substrate similar to that of the second embodiment having the vertical cross-sectional structure 92 is prepared using one evaluation substrate 90 (S110), and the other evaluation substrate 200 is prepared. A sample substrate similar to that of the fourth embodiment having the vertical cross-sectional structure 202 is prepared using S (S210). The film forming steps S110 and S210 are formed under the same conditions as the actual substrate 70 using the same CVD apparatus as the film forming step S104 on the actual substrate 70. Then, based on the evaluation method described in the first embodiment using each sample substrate, the physical property evaluation of the a-Si film 76 and the physical property evaluation of the n ⁺ a-Si film 78 are performed as in the second and fourth embodiments. (S220). Then, when the film formation process of the a-Si film 76 and the film formation process of the n ⁺ a-Si film 78 are satisfactory, the process is performed on and after the process S106 on the actual substrate 70. On the other hand, when it is determined that the film formation process of the a-Si film 76 or the film formation process of the n ⁺ a-Si film 78 is defective, maintenance of the CVD apparatus is performed (S222).

As described in the second and fourth embodiments, the film formation process of the a-Si film and the n ⁺ a-Si film performed at the very initial stage of the liquid crystal display manufacturing process is evaluated at an early stage. An effect is obtained.

[Sixth Embodiment]
The present embodiment relates to a method for manufacturing a semiconductor device in which an a-Si film formed on a glass substrate is annealed with a laser to form a crystalline silicon film, and a transistor or the like is formed using the crystallized Si film.

  The mobility of a poly-Si film such as LTPS is larger than that of an a-Si film, but is smaller than that of single crystal Si. Therefore, in order to increase the speed of elements such as transistors, there is a technique in which an a-Si film is melted and crystallized by laser annealing to form a single crystal (c-Si) film or a pseudo c-Si film. If this technique is used, a c-Si film can be formed on a large-area glass substrate.

  In the present embodiment, an example will be described in which a TFT formed on an array substrate of a liquid crystal display is formed using a c-Si film formed on a glass substrate by the technique. In a TFT using a c-Si film, the c-Si film forms an active layer, on which a gate electrode, a drain electrode, and a source electrode are formed.

  FIG. 19 is a schematic diagram for explaining a method of manufacturing a liquid crystal display in the present embodiment. In this manufacturing method, unlike the second to fifth embodiments described above, it is not necessary to prepare an evaluation substrate separately from the actual substrate, and the actual substrate itself is used for the evaluation.

  A SiNx film 252 serving as a contamination prevention film and an a-Si film to be crystallized are continuously formed on the surface of the glass substrate 250, which is an actual substrate, by a CVD apparatus (S270). Here, the SiNx film 252 is provided to prevent impurities that deteriorate the characteristics of the semiconductor film from the glass substrate 250 from diffusing into the a-Si film during laser annealing.

  Before laser annealing, dehydrogenation is performed on the a-Si film to prevent ablation (S272). Thereafter, the a-Si film is crystallized by irradiating laser light to form a c-Si film 254 (S274). FIG. 19 shows a schematic vertical sectional structure 256 of the sample substrate.

  In the liquid crystal display manufacturing method of this embodiment, when the a-Si film is crystallized, it is based on the evaluation method described in the first embodiment before subsequent processing such as patterning of the formed c-Si film. Then, the crystallinity of the c-Si film 254 is evaluated (S276). Specifically, the actual substrate after the laser crystallization treatment is set in the evaluation apparatus 30, laser light irradiation and microwave irradiation are performed, and for example, a map of the reflection intensity V is measured.

  As described in the third embodiment, crystallization of the a-Si film increases the carrier lifetime τ and increases the reflection intensity V. Therefore, the crystallinity of the c-Si film 254 can be evaluated based on the reflection intensity V.

Therefore, when it is determined that the crystal is favorably crystallized from the reflection intensity V, the subsequent processes for the actual substrate such as the c-Si film patterning process S278 and the SiO ₂ film forming S280 to be the gate insulating film are started. The On the other hand, if it is determined that the crystallization process is defective, such as insufficient crystallization or non-uniformity, the laser crystallization apparatus is maintained (S282).

  As described above, regarding the film formation process of the c-Si film by crystallization of the a-Si film that is performed at an extremely early stage of the manufacturing process of the liquid crystal display, before forming an element such as a transistor using the c-Si film. The evaluation improves the yield of the liquid crystal display and the productivity of the line as described in the above embodiment.

2 TFT, 4,250 glass substrate, 6,154 gate electrode, 8 gate insulating film, 10 active layer, 12 ohmic contact layer, 14 drain electrode, 16 source electrode, 18 protective film, 20 pixel electrode, 22 contact hole, 30 Evaluation device, 32 samples, 34 stages, 36 laser light irradiation means, 38 microwave irradiation means, 40 reflected wave detection means, 50 sample substrate, 52, 56, 252 SiNx film, 54, 76, 160 a-Si film, 70 150, actual substrate, 72,152 gate metal film, 74,156 g-SiNx film, 158 g-SiO ₂ film, 78 n ⁺ a-Si film, 254 c-Si film.

Claims (5)

A laser beam irradiation step of irradiating a laser beam to an evaluation target substrate in which an amorphous semiconductor film is formed on a substrate made of an insulator;
A microwave irradiation step of irradiating each sampling point irradiated with the laser light of the evaluation target substrate with a microwave subsequent to the laser light irradiation step and measuring a reflection intensity thereof,
Based on the measurement result of the reflection intensity at each sampling point, an evaluation step for evaluating the uniformity of physical properties of the amorphous semiconductor film within the substrate surface;
A method for evaluating an amorphous semiconductor film, comprising: In a method of manufacturing a semiconductor device including a film forming step of forming an amorphous semiconductor film on a substrate,
A laser beam irradiation step of irradiating a laser beam to an evaluation target substrate in which the amorphous semiconductor film is formed on a substrate made of an insulator by the film forming step;
A microwave irradiation step of irradiating each sampling point irradiated with the laser light of the evaluation target substrate with a microwave subsequent to the laser light irradiation step and measuring a reflection intensity thereof,
Based on the measurement result of the reflection intensity at each sampling point of the substrate to be evaluated, the uniformity of the physical properties of the amorphous semiconductor film in the substrate surface is evaluated, and the defect in the film formation process is determined as the semiconductor device. An evaluation step to detect before the manufacturing of
A method for manufacturing a semiconductor device, comprising: Forming a gate electrode of a thin film transistor on a substrate made of an insulator; forming an insulating film on the substrate so as to cover the gate electrode; and forming an amorphous film on the gate insulating film A method of manufacturing a semiconductor device using the thin film transistor, comprising: forming a semiconductor film; and forming a semiconductor film forming step of forming an active layer of the thin film transistor.
In parallel with the manufacture of the thin film transistor, a sample preparation step for preparing a sample substrate by laminating the gate insulating film and the amorphous semiconductor film on the substrate in the insulating film forming step and the semiconductor film forming step; ,
A laser beam irradiation step of irradiating the sample substrate with a laser beam;
A microwave irradiation step of irradiating each sampling point irradiated with the laser light of the specimen substrate with a microwave following the laser light irradiation step and measuring a reflection intensity thereof,
Based on the measurement result of the reflection intensity at each sampling point of the sample substrate, the uniformity of the physical properties of the amorphous semiconductor film within the substrate surface is evaluated, and the semiconductor film formation process is determined to be defective. An evaluation step to detect prior to completion of device manufacture;
And a method for manufacturing a semiconductor device, wherein a defect in the semiconductor film forming step can be dealt with during the manufacturing of the semiconductor device. A semiconductor film forming step for forming an amorphous semiconductor film on a substrate made of an insulator; a dehydrogenation step for reducing a hydrogen content in the amorphous semiconductor film; and the non-hydrogenation step after the dehydrogenation step. A method of manufacturing a semiconductor device using the thin film transistor, including a laser crystallization step of forming a polycrystalline semiconductor film as an active layer of the thin film transistor by crystallizing the crystalline semiconductor film by laser light irradiation. ,
In parallel with the manufacture of the thin film transistor, the amorphous semiconductor film is formed on the substrate in the semiconductor film formation step, and the hydrogen content in the amorphous semiconductor film is reduced in the dehydrogenation step. A specimen preparation step for preparing a specimen substrate;
A laser beam irradiation step of irradiating the sample substrate with a laser beam;
A microwave irradiation step of irradiating each sampling point irradiated with the laser light of the specimen substrate with a microwave following the laser light irradiation step and measuring a reflection intensity thereof,
Based on the measurement result of the reflection intensity at each sampling point of the sample substrate, the degree of dehydrogenation of the amorphous semiconductor film and the uniformity in the substrate surface are evaluated before the laser crystallization step. An evaluation step;
An additional dehydrogenation step of performing an additional dehydrogenation process when the lack of dehydrogenation is detected in the evaluation step;
A method for manufacturing a semiconductor device, comprising: Forming a gate electrode of the thin film transistor on a substrate made of an insulator; forming an insulating film on the substrate so as to cover the gate electrode; and forming the gate electrode of the thin film transistor on the gate insulating film. A semiconductor film forming step of forming an amorphous semiconductor film to be an active layer, and a low-resistance layer to be an ohmic contact layer between the active layer and the source electrode and the drain electrode of the thin film transistor on the amorphous semiconductor film; A method of manufacturing a semiconductor device using the thin film transistor, including an ohmic layer film forming step of forming a resistive amorphous semiconductor film,
In parallel with the manufacture of the thin film transistor, a sample substrate is manufactured by stacking the gate insulating film and the low-resistance amorphous semiconductor film on the substrate in the insulating film forming step and the ohmic layer forming step. Steps,
A laser beam irradiation step of irradiating the sample substrate with a laser beam;
A microwave irradiation step of irradiating each sampling point irradiated with the laser light of the specimen substrate with a microwave following the laser light irradiation step and measuring a reflection intensity thereof,
Based on the measurement result of the reflection intensity at each sampling point of the sample substrate, the uniformity of physical properties of the low-resistance amorphous semiconductor film within the substrate surface is evaluated, and a defect in the ohmic layer deposition process is determined. An evaluation step to detect before the completion of manufacturing the semiconductor device;
A method of manufacturing a semiconductor device, which is capable of coping with defects in the ohmic layer film forming process during the manufacturing of the semiconductor device.

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