JP2007188953A - Method for manufacturing polycrystal silicon layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing polycrystal silicon layer ensuring a large mobility. <P>SOLUTION: A substrate to be processed is formed by laminating an amorphous silicon oxide layer on an amorphous silicon layer. The amorphous silicon oxide layer is subjected to dehydrogenation process within the vacuum atmosphere to isolate hydrogen molecule. A naturally oxidized film is not formed because the surface is not oxidized during the dehydrogenation process of the amorphous silicon oxide layer. It is no longer required to remove the naturally oxidized film on the surface by cleaning the amorphous silicon oxide film with hydrofluoric acid. The amorphous silicon oxide layer may be annealed with the excimer laser under the condition that the naturally oxidized film does not exist on the surface. A polysilicon layer showing the mobility can be obtained as the layer that may be used as the active layer of a thin film transistor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a polycrystalline silicon layer using laser annealing.

  In recent years, in an active matrix liquid crystal display device, since a semiconductor active layer can be formed on a large glass substrate with good uniformity and at a relatively low temperature, as a switching element of a display pixel provided in a matrix in this liquid crystal display device, A thin film transistor (TFT) using amorphous silicon as a semiconductor active layer is used. Thin film transistors formed on a glass substrate provided with these display pixels are used not only for these display pixels but also for driving circuit elements provided around the liquid crystal display device.

  However, as the thin film transistor of these driving circuit elements, a thin film transistor using polycrystalline silicon having a higher field effect mobility as a semiconductor active layer than a thin film transistor using amorphous silicon as a semiconductor active layer is used. The polycrystalline silicon used as the semiconductor active layer of this thin film transistor is irradiated with an energy beam such as a XeCl excimer laser beam toward the thin film amorphous silicon laminated on the glass substrate, thereby excimer laser annealing. Anneal: ELA) and melted and recrystallized.

  Here, the excimer laser beam irradiation is performed in a vacuum atmosphere or an inert gas atmosphere such as nitrogen for the purpose of preventing the entry of impurities from the atmosphere that causes unstable operation of the thin film transistor. Further, when polycrystalline silicon is formed from amorphous silicon by irradiating an energy beam in an atmosphere containing oxygen as in the air, irregularities are formed on the surface of the polycrystalline silicon. The surface becomes rough. In the protruding portion formed on the surface of the polycrystalline silicon, electric field concentration is likely to occur, and the coverage of the gate insulating layer laminated on the polycrystalline silicon is lowered to cause breakdown voltage degradation. Therefore, it is related to the reliability and yield of the thin film transistor.

  In order to prevent the surface roughness of the polycrystalline silicon, the excimer laser beam is irradiated in a vacuum atmosphere or an inert gas atmosphere such as nitrogen. That is, when this excimer laser beam is irradiated in a vacuum atmosphere or an inert gas atmosphere such as nitrogen, impurities are prevented from being mixed into the polycrystalline silicon, and the surface of the polycrystalline silicon can be smoothed. However, when the excimer laser beam is irradiated in an inert gas atmosphere such as a vacuum atmosphere or nitrogen, it is necessary to irradiate an excimer laser beam having a higher energy density than when the excimer laser beam is irradiated in the air. The crystal grain size in polycrystalline silicon does not grow. If the crystal grain size in the polycrystalline silicon is small, it is not easy to form a high-performance thin film transistor with high mobility.

Therefore, as an annealing method of this kind of polycrystalline silicon, a film to be processed to be laminated on a glass substrate has a two-layer structure, and the amorphous silicon laminated on the glass substrate is sublimated so as to contain oxygen. Amorphous silicon oxide formed from a mixed gas of nitrogen oxide and silane gas is stacked. Further, the amorphous silicon oxide is dehydrogenated to release hydrogen molecules in the amorphous silicon oxide, and then a vacuum atmosphere or an inert gas atmosphere such as nitrogen is directed toward the amorphous silicon oxide. Among them, a configuration in which an excimer laser beam is irradiated and laser annealing is performed to form polycrystalline silicon is known (for example, see Patent Document 1).
JP 2003-17505 A

  However, in the polycrystalline silicon annealing method described above, when amorphous silicon oxide is dehydrogenated to release hydrogen molecules in the amorphous silicon oxide, the surface of the amorphous silicon oxide is naturally exposed. An oxide film is formed. For this reason, when amorphous silicon oxide is irradiated with an excimer laser beam and laser annealing is performed with this natural oxide film formed on the surface, the polycrystal formed by laser annealing of this amorphous silicon oxide There is a problem that the crystal grain size in silicon does not grow and it is not easy to make polycrystalline silicon having a high mobility.

  The present invention has been made in view of these points, and an object of the present invention is to provide a method for manufacturing a polycrystalline silicon layer that can increase mobility.

  In the present invention, an amorphous silicon layer is formed on an insulating substrate, an amorphous silicon oxide layer is formed on the amorphous silicon layer formed on the insulating substrate, and the amorphous silicon layer on the insulating substrate is formed. The hydrogen molecules in the amorphous silicon oxide layer formed on the porous silicon layer are liberated in a vacuum atmosphere, and each of the amorphous silicon oxide layer from which the hydrogen molecules are liberated and the amorphous silicon layer are laser-annealed. Then, it is crystallized into a polycrystalline silicon layer.

  Then, after forming an amorphous silicon layer on the insulating substrate, an amorphous silicon oxide layer is formed on the amorphous silicon layer. Next, after releasing hydrogen molecules in the amorphous silicon oxide layer in a vacuum atmosphere, each of the amorphous silicon oxide layer and the amorphous silicon layer is crystallized by laser annealing to form a polycrystalline silicon layer. To do.

  Further, an amorphous silicon layer is formed on the insulating substrate, hydrogen molecules in the amorphous silicon layer formed on the insulating substrate are liberated, and the amorphous silicon layer from which the hydrogen molecules are liberated is released. An oxide film formed on the surface is removed, an amorphous silicon oxide layer is formed on the amorphous silicon layer from which the oxide film on the surface has been removed, and the amorphous silicon layer on the insulating substrate and Each of the amorphous silicon oxide layers is crystallized by laser annealing to form a polycrystalline silicon layer.

  Then, after an amorphous silicon layer is formed on the insulating substrate, hydrogen molecules in the amorphous silicon layer are liberated. Next, after removing the oxide film formed on the surface of the amorphous silicon layer, an amorphous silicon oxide layer is formed on the amorphous silicon layer. Thereafter, each of the amorphous silicon oxide layer and the amorphous silicon layer is crystallized by laser annealing to form a polycrystalline silicon layer.

  According to the present invention, the surface of the amorphous silicon oxide layer is oxidized by releasing hydrogen molecules in the amorphous silicon oxide layer formed on the amorphous silicon layer on the insulating substrate in a vacuum atmosphere. Hydrogen molecules in the amorphous silicon film can be liberated without forming a layer. In addition, since the oxide film formed on the surface of the amorphous silicon layer formed on the insulating substrate is removed and then the amorphous silicon oxide layer is formed on the amorphous silicon layer, this amorphous An amorphous silicon oxide layer can be formed on the amorphous silicon layer in a state where no oxide layer is formed on the surface of the silicon layer. Therefore, the amorphous silicon oxide layer and the amorphous silicon oxide layer are crystallized by laser annealing each of the amorphous silicon oxide layer and the amorphous silicon oxide layer without forming an oxide layer on the surface of each of the amorphous silicon layer and the amorphous silicon oxide layer. Therefore, a polycrystalline silicon layer having high mobility can be easily formed.

  The configuration of the first embodiment of a liquid crystal display device having a polycrystalline silicon layer according to the present invention will be described below with reference to FIGS.

  In FIG. 6, reference numeral 1 denotes a liquid crystal panel as a liquid crystal display device. The liquid crystal panel 1 is a liquid crystal display (LCD) and includes an array substrate 2 having a rectangular flat plate shape. The array substrate 2 has a glass substrate 3 that is an insulating substrate as a light-transmitting substrate having a substantially transparent light-transmitting property. On the surface of the glass substrate 3, a plurality of scanning lines (not shown) spaced in parallel at equal intervals along the width direction of the glass substrate 3 and parallel at equal intervals along the vertical direction of the glass substrate 3. A plurality of signal lines spaced apart from each other are orthogonally wired and provided in a lattice shape.

  Furthermore, a pixel 4 is provided in each of the regions partitioned and surrounded by these scanning lines and signal lines. These pixels 4 are formed in a matrix in an image display area (not shown) on the glass substrate 3. Further, each of these pixels 4 is provided with a thin film transistor (TFT) 5 as a switching element, a pixel electrode 6, and an auxiliary capacitor (not shown) which is a pixel auxiliary capacitor as a storage capacitor. Here, each of these pixel electrodes 6 is electrically connected to and controlled by the thin film transistor 5 in the same pixel 4.

An undercoat layer 7 is formed on the entire surface of the glass substrate 3. The undercoat layer 7 includes a silicon nitride layer 8 which is a first coat layer formed by being laminated on the glass substrate 3, and an oxidation as a second coat layer laminated on the silicon nitride layer 8. And a silicon layer 9. Specifically, the silicon nitride film 8 is made of silicon nitride (SiN _x ), and the silicon oxide film 9 is made of silicon oxide (SiO _x ).

  Further, on the silicon oxide film 9 of the undercoat layer 7, an island-shaped active layer 11 which is a semiconductor layer composed of a polysilicon (p-Si) layer 10 as a polycrystalline silicon layer is provided. . The active layer 11 has a thickness dimension of about 48 nm, for example. A channel region 12 is provided at the center in the width direction of the active layer 11, and a source region 13 and a drain region 14 are provided on both sides of the channel region 12. Further, a gate insulating film 15 is formed on the undercoat layer 7 including the active layer 11, and a gate electrode 16 is stacked on the gate insulating film 15 facing the channel region 12 of the active layer 11. The gate electrode 16 is integrally connected to the scanning line. The gate electrode 16, the gate insulating film 15, and the active layer 11 constitute a thin film transistor 5.

  Further, an interlayer insulating film 17 as a protective layer is laminated on the gate insulating film 15, and the gate electrode 16 on the gate insulating film 15 is covered with the interlayer insulating film 17. The interlayer insulating film 17 and the gate insulating film 15 have first contact holes 18 and 19 that pass through the interlayer insulating film 17 and the gate insulating film 15 and communicate with the source region 13 and the drain region 14 of the active layer 11. Is provided. A source electrode 21 is stacked on the interlayer insulating film 17 covering the first contact hole 18 penetrating the source region 13 of the active layer 11, and the source electrode 21 is electrically connected to the source region 13 of the active layer 11. Has been. Further, a drain electrode 22 is laminated on the interlayer insulating film 17 covering the first contact hole 19 penetrating the drain region 14 of the active layer 11, and the drain electrode 22 is electrically connected to the drain region 14 of the active layer 11. It is connected.

  Further, a passivation film 23 as a protective layer is laminated on the interlayer insulating film 17, and the source electrode 21 and the drain electrode 22 on the interlayer insulating film 17 are covered with the passivation film 23, respectively. The passivation film 23 is provided with a second contact hole 24 that penetrates the passivation film 23 and communicates with the drain electrode 22. Then, the pixel electrode 6 is laminated on the passivation film 23 covering the second contact hole 24, and the pixel electrode 6 is electrically connected to the drain electrode 22 through the second contact hole 24. Further, an alignment film 25 made of alignment-treated polyimide is laminated on the passivation film 23, and the pixel electrode 6 on the passivation film 23 is covered with the alignment film 25.

  Further, a counter substrate 31 is disposed to face the alignment film 25. The counter substrate 31 includes a glass substrate 32 as an insulating substrate having a substantially transparent translucency. A color filter layer 33 as a colored layer is laminated on the entire surface of the glass substrate 32 facing the alignment film 25, and a counter electrode 34 as a common electrode as a common electrode is laminated on the color filter layer 33. . Further, an alignment film 35 made of alignment-treated polyimide is laminated on the counter electrode 34. A liquid crystal composition 37 is injected into a liquid crystal sealing region 36 which is a gap between the alignment film 25 of the array substrate 2 and the alignment film 35 of the counter substrate 31 to provide a liquid crystal layer 38 as a light modulation layer. Thus, the liquid crystal panel 1 is configured.

  Next, a manufacturing apparatus for manufacturing the liquid crystal panel 1 provided with the polysilicon layer 10 of the first embodiment will be described.

  In FIG. 1, reference numeral 41 denotes a CVD (Chemical Vapor Deposition) apparatus as a film forming apparatus. The CVD apparatus 41 is a so-called single wafer type and a multi-chamber type, and includes a transfer chamber 42 as a hollow main body having a hexagonal shape in plan view. Further, on one side surface of the transfer chamber 42, a hollow transfer-in / out chamber 43 having a square shape in a plan view for carrying the glass substrate 3 in or out of the transfer chamber 42 is provided. Further, on one side surface of the transfer chamber 42 adjacent to the one side surface where the carry-in / out chamber 43 is provided, the glass substrate 3 transferred from the transfer chamber 42 is hollow in a rectangular shape in plan view for film formation temperature maintenance. A film formation heating chamber 44 is provided. The film formation heating chamber 44 is internally maintained at a temperature of, for example, 350 ° C., and the substrate temperature of the glass substrate 3 conveyed to the film formation heating chamber 44 is heated to, for example, a film formation temperature of 350 ° C. .

Further, on one side surface of the transfer chamber 42 adjacent to the film forming and heating chamber 44, a hollow film is formed in a rectangular shape in plan view in which the glass substrate 3 heated to the film forming temperature in the film forming and heating chamber 44 is transferred. A chamber 45 is provided. The film forming chamber 45 is provided on one side surface of the transfer chamber 42 located on the opposite side to the side where the carry-in / out chamber 43 is provided. In the film forming chamber 45, the silicon nitride layer 8 and the silicon oxide layer 9 are stacked on the transferred glass substrate 3 to form the undercoat layer 7. Further, in the film forming chamber 45, an amorphous silicon layer (a-Si) 27, which is an amorphous silicon layer as an amorphous semiconductor layer, is laminated on the undercoat layer 7 to a thickness of 45 nm, for example. Next, the film formation chamber 45 is formed on the amorphous silicon layer 27 under the condition that the gas flow ratio of nitrous oxide gas (N ₂ O) and silane gas (SiH ₄ ) is 1.5. An amorphous silicon oxide layer 28, which is an amorphous silicon oxide layer as a layer, is continuously laminated on the amorphous silicon layer 27 to a thickness of, for example, 3 nm to form a substrate 29 to be processed.

A dehydrogenation chamber 46 for dehydrogenation heating, which is a hydrogen treatment chamber as a hollow heating chamber having a rectangular shape in plan view, is provided on one side surface of the transfer chamber 42 facing the film formation chamber 45. The interior of the dehydrogenation chamber 46 is maintained at a temperature of 500 ° C., for example. The substrate to be processed 29 stacked up to the amorphous silicon oxide layer 28 in the deposition chamber 45 is transferred to the dehydrogenation chamber 46 via the transfer chamber 42. Further, the inside of the dehydrogenation chamber 46 is maintained in a vacuum atmosphere having a degree of vacuum of, for example, 1 × 10 ⁻³ Pa or less, and the substrate 29 to be processed is placed in the vacuum atmosphere for about 5 minutes, for example. Then, the amorphous silicon oxide layer 28 of the substrate 29 to be processed is dehydrogenated to release hydrogen molecules in the amorphous silicon oxide layer 28. At this time, in the dehydrogenation treatment of the amorphous silicon oxide layer 28 in the dehydrogenation chamber 46, the natural oxide film A does not grow on the surface of the amorphous silicon oxide layer 28.

  Further, on one side surface of the transfer chamber 42 facing the film formation heating chamber 44, a hollow cooling chamber 47 having a rectangular shape in a plan view is provided in which the substrate 29 to be processed dehydrogenated in the dehydrogenation chamber 46 is transferred. It has been. The cooling chamber 47 is filled with, for example, argon gas (Ar) at a pressure of 100 Pa, and the substrate to be processed 29 transferred into the cooling chamber 47 is cooled to a predetermined temperature.

  On the other hand, in FIG. 4, reference numeral 51 denotes an ELA (Excimer Laser Anneal) apparatus as an excimer laser annealing apparatus. The ELA apparatus 51 crystallizes the amorphous silicon layer 27 and the amorphous silicon oxide layer 28 by a laser annealing method. An ELA chamber 52 which is a silicon layer 10 and has a hollow processing chamber is provided. The ELA chamber 52 is filled with nitrogen, which is an inert gas, and maintained in a nitrogen atmosphere. In the ELA chamber 52, each of the undercoat layer 7, the amorphous silicon layer 27 and the amorphous silicon oxide layer 28 is laminated by the CVD apparatus 41, and the surface of the amorphous silicon oxide layer 28 is washed with water. The substrate 29 to be processed is loaded.

  Further, on the upper side of the ELA chamber 52, a laser as a laser irradiation means for irradiating the surface of the amorphous silicon oxide layer 28 of the substrate 29 to be processed installed in the ELA chamber 52 with a XeCl excimer laser beam E. An irradiation unit 53 is installed. Therefore, the substrate 29 to be processed is loaded and installed below the laser irradiation unit 53 in the ELA chamber 52 with the surface of the amorphous silicon oxide layer 28 facing the laser irradiation unit 53.

  Therefore, the ELA apparatus 51 is configured such that the natural oxide film A does not exist on the surface of the amorphous silicon oxide layer 28 of the substrate 29 to be processed, and the substrate 29 to be processed transferred into the ELA chamber 52 of the ELA apparatus 51. An excimer laser beam E is irradiated from the laser irradiation unit 53 in the ELA chamber 52 toward the surface of the amorphous silicon oxide layer 28, and the amorphous silicon layer 27 and the amorphous silicon oxide layer 28 are irradiated by the excimer laser beam E irradiation. Each of these is excimer laser annealed and recrystallized to form a polysilicon layer 10.

  Next, a method for manufacturing the polycrystalline silicon layer according to the first embodiment will be described.

  First, as a first step, the glass substrate 3 is carried in from the carry-in / out chamber 43 of the CVD apparatus 41 shown in FIG. 1, and this glass substrate 3 is transferred to the film-forming heating chamber 44 via the transfer chamber 42 of the CVD apparatus 41. Transport. At this time, the glass substrate 3 transported into the film formation heating chamber 44 is heated to a film formation temperature of, for example, 350 ° C. in the film formation heating chamber 44.

  Next, the glass substrate 3 is transferred from the film formation heating chamber 44 to the film formation chamber 45 through the transfer chamber 42. In this film forming chamber 45, as shown in FIG. 2, a silicon nitride film 8 is laminated on the glass substrate 3, and then a silicon oxide film 9 is laminated on the silicon nitride film 8 to form an undercoat. Layer 7 is formed.

  Further, in the film forming chamber 45, after an amorphous silicon layer 27 having a thickness of, for example, about 45 nm is formed on the undercoat layer 7, the amorphous silicon layer 27 is continuously formed. An amorphous silicon oxide layer 28 having a thickness of about 3 nm, for example, is laminated on the layer 27 under the condition that the gas flow ratio of nitrous oxide gas and silane gas is 1.5 to form a substrate 29 to be processed.

Thereafter, the substrate 29 to be processed is transferred from the film formation chamber 45 to the dehydrogenation chamber 46 via the transfer chamber 42. Then, in this dehydrogenation chamber 46, the substrate 29 to be processed is placed for about 5 minutes in a vacuum atmosphere of a vacuum degree of 1 × 10 ⁻³ Pa or less, for example, and the amorphous silicon oxide layer of the substrate 29 to be processed 28 is dehydrogenated, and hydrogen molecules in the amorphous silicon oxide layer 28 are liberated. At this time, in the dehydrogenation treatment of the amorphous silicon oxide layer 28 in the dehydrogenation chamber 46, the surface of the amorphous silicon oxide layer 28 is not oxidized and the natural oxide film A does not grow.

  Further, the substrate 29 to be processed is transferred from the film forming chamber 45 to the cooling chamber 47 via the transfer chamber 42. Then, in this cooling chamber 47, the substrate 29 to be processed is cooled to a predetermined temperature with argon gas having a pressure of 100 Pa, for example. Here, even when the substrate to be processed 29 is cooled in the cooling chamber 47, the surface of the amorphous silicon oxide layer 28 of the substrate to be processed 29 is not oxidized, so that a natural oxide film is formed on the surface of the amorphous silicon oxide layer 28. A doesn't grow.

  Thereafter, as a second step, after the substrate 29 to be processed is transferred from the cooling chamber 47 to the loading / unloading chamber 43 via the transfer chamber 42 and taken out from the CVD apparatus 41, as shown in FIG. Pure water W is sprayed from the spray nozzle 48 toward the surface of the amorphous silicon oxide layer 28 of the substrate 29 while the substrate 29 is rotated left counterclockwise L, and the surface of the amorphous silicon oxide layer 28 is moved forward. Washed with water as a wash.

  Further, as a third step, as shown in FIG. 4, the substrate 29 to be processed is transferred into the ELA chamber 52 of the ELA apparatus 51 and set at a predetermined position in the ELA chamber 52.

  In this state, the excimer laser beam E is irradiated from the laser irradiation unit 53 of the ELA apparatus 51 toward the surface of the amorphous silicon oxide layer 28 of the substrate 29 to be processed in the ELA chamber 52, as shown in FIG. The amorphous silicon layer 27 and the amorphous silicon oxide layer 28 on the substrate 29 to be processed are recrystallized by excimer laser annealing to form the polysilicon layer 10 by the irradiation of the excimer laser beam E.

  Here, the characteristics of the polysilicon layer 10 were examined. As a result, the surface of the polysilicon layer 10 did not have unevenness that could be visually recognized. That is, as a pre-cleaning, the substrate 29 is not washed with the hydrofluoric acid aqueous solution F, but the substrate 29 is washed with water, so that the amorphous silicon oxide layer 28 of the substrate 29 is not damaged. It depends. Further, on the surface of the polysilicon layer 10, only relatively low protrusions of 5 nm or more and 7 nm or less were formed. Further, the polysilicon layer 10 has grown to a relatively large particle size of, for example, 0.5 μm or more and 1.0 μm or less.

  Here, as a comparative example shown in FIGS. 15 to 21, as shown in FIG. 15, the undercoat layer 7 on the glass substrate 3, the amorphous silicon layer 27 having a thickness of 45 nm, for example, and the thickness having a thickness of 5 nm, for example. The substrate to be processed 29 in which the amorphous silicon oxide layers 28 are sequentially laminated is placed in a dehydrogenation apparatus as an oven which is a heating device (not shown), and the substrate 29 to be processed is heated to 500 ° C. in an atmosphere of nitrogen atmosphere. A dehydrogenation step is performed in which the hydrogen molecules in the amorphous silicon oxide layer 28 of the substrate 29 are desorbed by heating at a temperature for about 1 hour.

  At this time, in this dehydrogenation step, the temperature when the substrate 29 to be processed is dehydrogenated is relatively high, and the atmosphere when the substrate 29 to be processed is dehydrogenated is in the atmosphere. As shown, the surface of the amorphous silicon oxide layer 28 of the substrate 29 to be processed is oxidized, and a natural oxide film A is formed on the surface of the amorphous silicon oxide layer 28. When the surface of the amorphous silicon oxide layer 28 is irradiated with the excimer laser beam E and the excimer laser annealing is performed in a state where the natural oxide film A exists on the surface, the particle diameter is 0.1 μm or less. The polysilicon layer 10 is in a crystalline state.

  Therefore, in the case of the thin film transistor 5 in which the polysilicon layer 10 is the active layer 11, the mobility of the thin film transistor 5 becomes too small, so that the polysilicon layer 10 cannot be used as the active layer 11 of the thin film transistor 5. End up. That is, in order to have the mobility required for the thin film transistor 5, the particle size of the polysilicon layer 10 which becomes the active layer 11 of the thin film transistor 5 needs to be 0.3 μm or more.

  For this reason, as shown in FIG. 17, the surface of the amorphous silicon oxide layer 28 of the substrate 29 to be processed is washed with a hydrofluoric acid aqueous solution F to remove the natural oxide film A existing on the surface of the amorphous silicon oxide layer 28. Then, as shown in FIG. 18, the amorphous silicon oxide layer 28 needs to be subjected to excimer laser annealing. Then, as the cleaning of the substrate 29 to be processed with the hydrofluoric acid aqueous solution F, the 1% by mass concentration of the hydrofluoric acid aqueous solution F is applied to the center of the surface of the substrate 29 to be processed while the substrate 29 is rotated leftward horizontally. In general, spin cleaning is performed by removing the natural oxide film A formed on the surface of the amorphous silicon oxide layer 28 of the substrate 29 to be processed by being dropped from the spray nozzle 49 and cleaned. Then, after removing the natural oxide film A on the surface by this spin cleaning, the amorphous silicon oxide layer 28 of the substrate 29 to be processed is subjected to excimer laser annealing to form a polysilicon layer 10 as shown in FIG. Yes.

  Here, when the characteristics of the polysilicon layer 10 manufactured in this one comparative example were examined, as shown in FIG. 20, radial spiral irregularities could be visually recognized on the surface of the polysilicon layer 10. This radial spiral unevenness is considered to be affected by the flow of the hydrofluoric acid aqueous solution F because the flow of the hydrofluoric acid aqueous solution F rotates clockwise during the spin cleaning of the substrate 29 to be processed. Further, in order to investigate the radial spiral unevenness in more detail, the grain size and the height of the protrusion at the points O, A and B shown in FIG. 20 of the polysilicon layer 10 on the substrate 29 to be processed are shown. Measurement was performed with a scanning electric microscope and an atomic force microscope.

  As a result, as shown in FIG. 21, the grain size of the polysilicon layer 10 was about 0.8 μm at the center of the substrate 29 to be processed, but gradually approaches the periphery of the substrate 29 to be processed. It became small and was about 0.4 μm at point B. On the other hand, the height of the protrusions was about 6 nm at the O point, but about 10 nm at the B point, which was higher than the particle size. Therefore, it has been found that the unevenness of the height of the protrusion can be visually recognized in the radial spiral unevenness. However, the height of the protrusion is about 30% lower than a typical value of 10 μm or more and 15 μm or less, which indicates the usefulness of the method shown in this comparative example.

  The amorphous silicon oxide layer 28 itself as well as the natural oxide film A formed at the center of the substrate 29 due to the radial spiral irregularities formed on the surface of the polysilicon layer 10 in the above comparative example. Will also be removed from the periphery. The unevenness of the removal of the natural oxide film A and the amorphous silicon oxide layer 28 causes unevenness on the surface of the polysilicon layer 10. That is, the amorphous silicon oxide layer 28 itself is also removed together with the natural oxide film A during cleaning with the hydrofluoric acid aqueous solution F depending on the composition of the amorphous silicon oxide layer 28.

  Therefore, since it is not easy to remove only the natural oxide film A formed on the surface of the amorphous silicon oxide layer 28 with good uniformity, cleaning with the hydrofluoric acid aqueous solution F is used as the removal of the natural oxide film A. As long as it is not easy to eliminate unevenness formed on the surface of the polysilicon layer 10 formed by the excimer laser annealing of the amorphous silicon oxide layer 28.

  Therefore, as in the first embodiment described above, the undercoat layer 7, for example, the amorphous silicon layer 27 having a thickness of about 45 nm, and about 3 nm, for example, are formed on the glass substrate 3 in the film forming chamber 45 of the CVD apparatus 41. Then, the amorphous silicon oxide layer 28 of the thickness 29 is sequentially laminated to form the substrate 29 to be processed, and then the amorphous silicon oxide layer 28 of the substrate 29 to be processed is removed in a vacuum atmosphere in the dehydrogenation chamber 46 of the CVD apparatus 41. Dehydrogenation treatment was performed to release hydrogen molecules in the amorphous silicon oxide layer 28.

  As a result, the surface of the amorphous silicon oxide layer 28 is not oxidized during the dehydrogenation process of the amorphous silicon oxide layer 28 of the substrate 29 to be processed in the dehydrogenation chamber 46, and the surface of the amorphous silicon oxide layer 28 is not oxidized. Natural oxide film A is not formed. Therefore, it is not necessary to clean the amorphous silicon oxide layer 28 of the substrate 29 to be processed with the hydrofluoric acid aqueous solution F and remove the natural oxide film A formed on the surface of the amorphous silicon oxide layer 28.

  For this reason, the amorphous silicon oxide layer 28 of the substrate 29 to be processed is washed with water and then subjected to excimer laser annealing in a nitrogen atmosphere by the ELA apparatus 51 to form the polysilicon layer 10, whereby the surface of the amorphous silicon oxide layer 28 is obtained. The amorphous silicon oxide layer 28 can be subjected to excimer laser annealing in the absence of the natural oxide film A. As a result, the polysilicon layer 10 has a relatively large particle size of 0.3 μm or more, specifically 0.5 μm or more and 1.0 μm or less, which is a particle size usable as the active layer 11 of the thin film transistor 5. Can be. Therefore, the polysilicon layer 10 having a high mobility that can be used as the active layer 11 of the thin film transistor 5 is obtained.

  Furthermore, the amorphous silicon oxide layer 28 of the substrate 29 to be processed is not washed with the hydrofluoric acid aqueous solution F as a pre-cleaning before the excimer laser annealing. The silicon layer 28 itself is not removed during cleaning with the hydrofluoric acid aqueous solution F. Therefore, since the amorphous silicon oxide layer 28 of the substrate 29 to be processed is not reduced before the excimer laser annealing, the thickness of the amorphous silicon oxide layer 28 can be reduced.

  At the same time, since the film thickness damage of the amorphous silicon oxide layer 28 of the substrate 29 to be processed does not occur, the surface of the polysilicon layer 10 formed by excimer laser annealing the amorphous silicon oxide layer 28 is, for example, 5 nm to 7 nm. Only the following relatively low protrusions are formed, and unevenness that can be visually recognized on the surface of the polysilicon layer 10 is not formed.

  As a result, it is possible to manufacture the polysilicon layer 10 having a low projection height, a large particle size, and a uniform particle size. Accordingly, since the mobility is high and the deterioration of the breakdown voltage of the gate insulating film 15 of the thin film transistor 5 due to the formation of the protrusion on the surface can be reduced, the thin film transistor 5 with a high yield can be manufactured.

  In the first embodiment, the substrate 29 to be processed is taken out from the CVD apparatus 41, washed with water, and then transported into the ELA chamber 52 of the ELA apparatus 51, and the amorphous silicon oxide layer of the substrate 29 to be processed. Although the excimer laser annealing of 28 is performed, the ELA chamber 52 of the ELA apparatus 51 is integrally formed on one side surface of the CVD apparatus 41 facing the carry-in / out chamber 43 as in the second embodiment shown in FIG. It is also possible to perform excimer laser annealing on the amorphous silicon oxide film 28 of the substrate 29 to be processed without removing the substrate 29 to be processed from the CVD apparatus 41.

  In this case, the inside of the ELA chamber 52 of the CVD apparatus 41 is maintained in a vacuum atmosphere. Further, in the ELA chamber 52, the substrate 29 to be processed in which the hydrogen molecules in the amorphous silicon oxide layer 28 are liberated in a vacuum atmosphere in the dehydrogenation chamber is not taken out of the CVD apparatus 41 but is immediately taken out. It is conveyed through. The upper side surface of the ELA chamber 52 is a substantially transparent incident window glass that transmits the excimer laser beam E irradiated from the laser irradiation unit 53 installed above the ELA chamber 52 into the ELA chamber 52. An annealing window 61 is provided. The annealing window 61 is formed in a rectangular shape in plan view larger than the glass substrate 3 of the substrate 29 to be processed.

  Further, in the ELA chamber 52, a stage (not shown) on which the substrate 29 to be processed transferred into the ELA chamber 52 is installed is swingably mounted via a swing mechanism. This stage is provided so that the substrate 29 to be processed is installed horizontally and the substrate 29 to be processed can be swung horizontally. Therefore, in the ELA chamber 52, the substrate to be processed 29 from which the hydrogen molecules in the amorphous silicon oxide layer 28 are released is transferred in the dehydrogenation chamber 46 of the CVD apparatus 41 and placed on the stage. Further, in the ELA chamber 52, the amorphous silicon oxide layer 28 of the substrate 29 to be processed is irradiated from the laser irradiation unit 53 through the annealing window 61 while the stage is swung. The amorphous silicon layer 27 together with the amorphous silicon oxide layer 28 is subjected to excimer laser annealing to form the polysilicon layer 10.

  Then, the substrate 29 to be processed that has been subjected to excimer laser annealing in the ELA chamber 52 is transferred to the cooling chamber 47 via the transfer chamber 42. In the cooling chamber 47, the substrate 29 to be processed is cooled by argon gas, and then transferred to the loading / unloading chamber 43 through the transfer chamber 42 and taken out of the CVD apparatus 41.

  As a result, the characteristics of the polysilicon layer 10 were examined. As in the first embodiment, the height of the protrusions formed on the surface was low, the grain size was large, and the grain size was uniform. It was a silicon layer 10.

  Further, the substrate to be processed 29 in which the hydrogen molecules in the amorphous silicon oxide layer 28 are liberated in the dehydrogenation chamber 46 of the CVD apparatus 41 is immediately transported to the ELA chamber 52 without being taken out of the CVD apparatus 41. In the ELA chamber 52, the amorphous silicon oxide layer 28 of the substrate 29 to be processed is subjected to excimer laser annealing continuously in a vacuum atmosphere following dehydrogenation. As a result, the amorphous silicon oxide layer 28 can be subjected to excimer laser annealing in a state in which the natural oxide film A does not exist on the surface of the amorphous silicon oxide layer 28 of the substrate 29 to be processed, so that it is the same as in the first embodiment. An effect can be produced.

  Further, the amorphous silicon oxide layer 28 of the substrate 29 to be processed is excimer laser annealed to form the polysilicon layer 10, and then the substrate 29 to be processed is transferred to the cooling chamber 47 and cooled. As a result, the possibility of the formation of the natural oxide film A on the surface of the amorphous silicon oxide layer 28 of the substrate 29 to be processed is eliminated as much as possible when the substrate 29 to be processed before the excimer laser annealing is cooled in the cooling chamber 47. it can.

  Further, as in the third embodiment shown in FIGS. 8 to 14, in the film forming chamber 45 of the CVD apparatus 41 shown in FIG. 8, the undercoat layer 7 is formed on the glass substrate 3 as shown in FIG. Then, for example, an amorphous silicon layer 27 having a thickness of 45 nm can be sequentially formed to be a substrate 29 to be processed, and the substrate 29 to be processed can be taken out from the CVD apparatus 41 after being cooled in the cooling chamber 47. In this case, the substrate 29 to be processed taken out from the CVD apparatus 41 is transported into a dehydrogenation apparatus (not shown) and heated in a nitrogen atmosphere at a temperature of 500 ° C. for about 1 hour as a second step. As a result, hydrogen molecules in the amorphous silicon layer 27 of the substrate 29 to be processed are desorbed, and bumping at the time of excimer laser annealing of the amorphous silicon layer 27, so-called ablation, is suppressed. At this time, when hydrogen molecules are desorbed from the amorphous silicon layer 27 of the substrate 29 to be processed in the dehydrogenation apparatus, a natural oxide film A is formed on the surface of the amorphous silicon layer 27 as shown in FIG. Will be formed.

  After that, the substrate 29 to be processed is taken out from the dehydrogenation apparatus, and as shown in FIG. 11, the hydrofluoric acid having a concentration of 1% by mass from the spray nozzle 49 toward the surface of the amorphous silicon layer 27 of the substrate 29 to be processed. An aqueous solution F is sprayed to remove the natural oxide film A formed on the surface of the amorphous silicon layer 27. At this time, the natural oxide film A formed on the surface of the amorphous silicon oxide layer 28 is compared with the case where the natural oxide film A formed on the surface of the amorphous silicon oxide layer 28 is removed by washing with the hydrofluoric acid aqueous solution F. A can be removed uniformly.

  Further, as a third step, the substrate 29 to be processed is again transferred to the CVD apparatus 41 and introduced, and the temperature of the substrate 29 to be transferred into the film forming chamber 45 of the CVD apparatus 41 is about room temperature. As shown in FIG. 12, the amorphous silicon layer of the substrate 29 to be processed is formed in the film forming chamber 45 in a state where the growth of the natural oxide film A due to the heating of the amorphous silicon layer 27 of the substrate 29 to be processed is suppressed. An amorphous silicon oxide layer 28 having a thickness of, for example, about 3 nm is laminated on the layer 27 under the condition that the gas flow ratio of nitrous oxide gas and silane gas is 1.5.

  Next, after the substrate 29 to be processed is taken out from the CVD apparatus 41, the surface of the amorphous silicon oxide layer 28 of the substrate 29 to be processed is washed with water, and then the substrate 29 is subjected to the ELA apparatus 51 as shown in FIG. Each of the amorphous silicon oxide layer 28 and the amorphous silicon layer 27 of the substrate 29 to be processed is subjected to excimer laser annealing while being introduced into the ELA chamber 52 and introduced into the ELA chamber 52 in a nitrogen atmosphere. Thus, the polysilicon layer 10 is formed as shown in FIG.

  At this time, since the amorphous silicon oxide layer 28 before annealing of the substrate 29 to be processed is not dehydrogenated, it is considered that ablation of hydrogen molecules in the amorphous silicon oxide layer 28 may occur. The film thickness of the silicon layer 28 is comparatively thin as about 3 nm, and by laminating the amorphous silicon oxide layer 28 on the amorphous silicon layer 27, there is little possibility that ablation of hydrogen molecules in the amorphous silicon oxide layer 28 will occur. .

  As a result, when the characteristics of the polysilicon layer 10 formed on the substrate 29 to be processed were examined, the film thickness of the amorphous silicon oxide layer 28 of the substrate 29 to be processed was maintained without damage. Similar to the embodiment, the polysilicon layer 10 had a low protrusion height, a large particle diameter, and a uniform particle diameter formed on the surface. Since the amorphous silicon layer 27 and the amorphous silicon oxide layer 28 can be respectively excimer laser annealed in a state where the natural oxide film A does not exist on the surface of each of the amorphous silicon layer 27 and the amorphous silicon oxide layer 28 of the substrate 29 to be processed. The same operational effects as those of the first embodiment can be obtained.

  In each of the above embodiments, the method of manufacturing the polysilicon layer 10 used for the active layer 11 of the thin film transistor 5 of the liquid crystal panel 1 has been described. However, various methods such as plasma display devices other than the liquid crystal panel 1 and organic electroluminescence display devices are used. It can also be used correspondingly as a manufacturing method of the polysilicon layer 10 used for the active layer of the switching element of the image display device and the active layer of other semiconductor elements.

It is explanatory drawing which shows the CVD apparatus used for the manufacturing method of the polycrystalline silicon layer of the 1st Embodiment of this invention. It is explanatory drawing which shows the state which formed the amorphous silicon layer and the amorphous silicon oxide layer on the insulating substrate with the CVD apparatus same as the above. It is explanatory drawing which shows the state which rinses an amorphous silicon oxide layer same as the above. It is explanatory drawing which shows the state which laser-anneales an amorphous silicon oxide layer same as the above. It is explanatory drawing which shows the state which the amorphous silicon oxide layer same as the above crystallized. It is explanatory sectional drawing which shows the liquid crystal display device which has a polysilicon layer same as the above. It is explanatory drawing which shows the CVD apparatus used for the manufacturing method of the polycrystalline silicon layer of the 2nd Embodiment of this invention. It is explanatory drawing which shows the CVD apparatus used for the manufacturing method of the polycrystalline silicon layer of the 3rd Embodiment of this invention. It is explanatory drawing which shows the state which formed the amorphous silicon layer on the insulating substrate with the same CVD apparatus. It is explanatory drawing which shows the state which carried out the dehydrogenation process of the amorphous silicon layer same as the above. It is explanatory drawing which shows the state which wash | cleans an amorphous silicon layer same as the above with hydrofluoric acid. It is explanatory drawing which shows the state which formed the amorphous silicon oxide layer on the amorphous silicon layer same as the above. It is explanatory drawing which shows the state which laser-anneales an amorphous silicon oxide layer same as the above. It is explanatory drawing which shows the state which the amorphous silicon oxide layer same as the above crystallized. It is explanatory drawing which shows the state which formed the amorphous silicon layer and the amorphous silicon oxide layer on the insulating substrate of one comparative example. It is explanatory drawing which shows the state which carried out the dehydrogenation process of the amorphous silicon oxide layer same as the above. It is explanatory drawing which shows the state which wash | cleans an amorphous silicon oxide layer same as the above with hydrofluoric acid. It is explanatory drawing which shows the state which laser-anneales an amorphous silicon oxide layer same as the above. It is explanatory drawing which shows the state which the amorphous silicon oxide layer same as the above crystallized. It is explanatory drawing which shows the nonuniformity of the surface of a polysilicon layer same as the above. It is a graph which shows the relationship between the position of a polysilicon layer same as the above, a particle size, and the height of protrusion.

Explanation of symbols

3 Glass substrate as an insulating substrate
10 Polysilicon layer as polycrystalline silicon layer
27 Amorphous silicon layer as amorphous silicon layer
28 Amorphous silicon oxide layer as amorphous silicon oxide layer A Natural oxide film as oxide film

Claims (5)

Forming an amorphous silicon layer on an insulating substrate;
Forming an amorphous silicon oxide layer on the amorphous silicon layer formed on the insulating substrate;
Free hydrogen molecules in the amorphous silicon oxide layer formed on the amorphous silicon layer on the insulating substrate in a vacuum atmosphere;
A method for producing a polycrystalline silicon layer, wherein the amorphous silicon oxide layer from which hydrogen molecules are liberated and the amorphous silicon layer are crystallized by laser annealing to form a polycrystalline silicon layer. 2. The surface of the amorphous silicon oxide layer from which hydrogen molecules are liberated in a vacuum atmosphere is washed with water, and then each of the amorphous silicon oxide layer and the amorphous silicon layer is laser-annealed. The manufacturing method of the polycrystalline silicon layer of description. 2. The laser annealing of each of the amorphous silicon oxide layer and the amorphous silicon layer is performed in a vacuum atmosphere in succession to the liberation of hydrogen molecules in the amorphous silicon oxide layer in a vacuum atmosphere. The manufacturing method of the described polycrystalline silicon. Forming an amorphous silicon layer on an insulating substrate;
Liberates hydrogen molecules in the amorphous silicon layer formed on the insulating substrate;
Removing the oxide film formed on the surface of the amorphous silicon layer from which the hydrogen molecules have been released;
Forming an amorphous silicon oxide layer on the amorphous silicon layer from which the oxide film on the surface has been removed;
A method for producing a polycrystalline silicon layer, wherein each of the amorphous silicon layer and the amorphous silicon oxide layer on the insulating substrate is crystallized by laser annealing to form a polycrystalline silicon layer. 5. The method for producing a polycrystalline silicon layer according to claim 4, wherein the surface of the amorphous silicon oxide layer is washed with water, and then each of the amorphous silicon oxide layer and the amorphous silicon layer is laser-annealed. .

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