KR20030008752A - The method of crystallization of amorphous silicon for liquid-crystal display - Google Patents

Abstract

PURPOSE: A method for forming polysilicon for LCD is provided to increase a size of grain and obtain an uniform thin film by performing a rapid thermal process or an ultraviolet process for amorphous silicon including a very small amount of metallic material. CONSTITUTION: A metallic material is included into amorphous silicon in order to crystallize the amorphous silicon in a solid state. A plurality of cores are formed to crystallize the amorphous silicon. The plural cores are moved to a side portion in order to crystallize the amorphous silicon. A grain boundary(12) formed by colliding the crystallized polysilicon grains(11) to each other. A very small amount of metallic material is included into the amorphous silicon by using the amorphous silicon layer, a buffer layer, an ion implanting method, plasma, and a solution including metal.

Description

The method of crystallization of amorphous silicon for liquid-crystal display}

According to the present invention, amorphous silicon containing a very small amount of metal (10 ¹² to 10 ¹⁴ cm ^-2 ) is crystallized by rapid heat treatment or ultraviolet (UV) to uniformly spaced nucleation and laterally crystallized from the nucleus to macroscopic grains. A method for obtaining a uniform polycrystalline silicon thin film.

Most of the devices using polycrystalline silicon are used in active devices of active matrix liquid crystal displays (AMLCDs) and switching devices and peripheral circuits of electro-luminescence devices. In this case, in the production of a thin film transistor using polycrystalline silicon, a deposition polycrystalline silicon, a technique using high temperature heat treatment, or a laser heat treatment technique is used. The laser heat treatment method is capable of low temperature processing and can realize high field effect mobility. However, since an expensive laser equipment is required, many alternative technologies have been studied.

Currently, the method of recrystallization using metal has been studied in various ways because it has the advantage of fast crystallization at a lower temperature than typical solid phase crystallization. Recrystallization using metal largely includes metal induced crystallization and metal induced lateral crystallization. However, when metal is used, the device characteristics are degraded due to metal contamination of the transistor device. Alternatively, to reduce the amount of metal to a minimum and to form a high quality polycrystalline silicon thin film, metal ions are reduced through ion implanters (10 ¹⁴ to 10 ¹⁶ cm ^-2 ), or thin films are deposited as thin as 0.5 nm. Techniques for forming a high quality film using high temperature treatment, rapid heat treatment or laser have been developed. However, with the current technology, the grain size, which is the most important factor in polycrystalline silicon, is small, the uniformity is not good, and there are many problems in large area.

In the present invention, polysilicon thin film is prepared by uniformly dispersing a disilicide (MSi ₂ ) that acts as a crystallization nucleus in a solid state by rapid heat treatment or ultraviolet (UV). It aims at forming at intervals and crystallizing to the side to obtain a macro grain and a uniform thin film.

Features of the invention for this purpose is the metal content in the thin film by chemical vapor deposition (CVD) or plasma (Plasma) sputtering (sputtering) method for making an amorphous silicon thin film containing a trace amount of metal (10 ¹² ~10 ¹⁴ cm ^{- 2} ) can form a thin film. The trace metal layer is positioned on a glass substrate or on a glass substrate by forming a buffer layer (oxide film, nitride film), and then on the amorphous silicon thin film layer, first forming a micro metal thin film on the glass substrate, forming amorphous silicon, and then recrystallization. And forming a buffer layer (nitride film, oxide film) on the glass substrate, depositing a very small amount of metal, and then forming an amorphous silicon thin film layer. In addition, using a gas containing a small amount of metal can be produced by chemical vapor deposition method or plasma chemical vapor deposition method.

The amorphous silicon thin film containing a trace amount of the metal thin film is uniformly formed with the disilide (MSi ₂ ) nucleus of the metal by rapid heat treatment or ultraviolet (UV), and crystallized to the side to meet the neighboring grain to form grain boundaries. Manufacturing a polycrystalline silicon thin film.

1 is an example according to the present invention, a photograph showing the number of nuclei (sedimentation) of the die silicide (NiSi ₂ ) according to the nickel deposition time observed with a reflector microscope. FIG. 1A shows a trace metal thickness of 5 × 10 ¹² cm ⁻² , 1B shows 1 × 10 ¹³ cm ⁻² , and FIG. 1C shows 5 × 10 ¹³ cm ⁻² , followed by forming a trace metal thin film at 10 ° C. Photo of polycrystalline silicon thin film formed by holding for seconds

2 is a reflector photomicrograph of a process in which grain crystallizes laterally from a nickel disilicide nucleus (precipitation) according to the present invention. 2A, 2B and 2C are photographs obtained by crystallization at 750 for 1 second, 8 seconds and 20 seconds of rapid heat treatment holding time, respectively.

Figure 3 is a schematic diagram of a process of crystallizing an amorphous silicon thin film containing a trace amount of metal according to the present invention by rapid heat treatment. FIG. 3A shows a trace metal thin film deposition step after metal sputtering, FIG. 3B shows a metal dissilicide precipitation step serving as a crystallization nucleus, and FIG. 3C shows a grain boundary formation step that crystallizes laterally from the nucleus and encounters neighboring grains.

4 is an example according to the present invention, macroscopic grain photograms of polycrystalline silicon rapidly heat-treated after sputtering the nickel content per area on amorphous silicon less than 10 ¹² cm ^-2 . 4A and 4B are reflecting microscope photographs at magnifications of 200 and 500 times, respectively.

5 is an example of the present invention, the optical image of the polycrystalline silicon rapidly heat-treated after sputtering the nickel content per area on the amorphous silicon of 10 ¹⁴ cm ^-2 or more

6 is an example according to the present invention, the number of nickel dissilicide nuclei (sedimentation) per cm ² according to the nickel sputtering time

7 is an example according to the present invention, the number of nickel dissilicide nuclei (sedimentation) per 1 cm ² according to the rapid heat treatment temperature

8 is an example according to the present invention, the Raman scattering spectrum of the crystallized polycrystalline silicon thin film after rapid heat treatment of the amorphous silicon thin film containing a trace amount of metal

9 is an example of the present invention, X-ray diffraction spectrum of a crystallized polycrystalline silicon thin film after rapid heat treatment of amorphous silicon containing a small amount of nickel thin film

10 is a bright field image and an electron diffraction pattern of a transmission electron microscope of polycrystalline silicon grown laterally from a nickel disilicide nucleus after rapid heat treatment.

<Description of the symbols for the main parts of the drawings>

11. Grain. 12. Amorphous silicon thin film.

21. Grain boundaries.

31. Trace Metal Thin Films

32. Amorphous Silicon Thin Film

33. Precipitate of metal disilicide (MSi2) acting as a crystallization nucleus

34. Polysilicon Grain Region 35. Grain Boundary Region

41. Polysilicon Thin Film

FIG. 1 is a photograph of crystallization from the nucleus formed laterally from a nucleus formed by nickel disilicate (NiSi ₂ ) precipitation with nickel sputtering time over an amorphous silicon thin film thickness of 50 nm. According to secondary ion mass spectroscopy (SIMS), FIG. 1A shows a nickel concentration per area of 5 × 10 ¹² cm ^-2 , FIG. 1B shows 1 × 10 ¹³ cm ^-2 , and FIG. 1C shows 5 × 10 ¹³ cm ^-2. After forming a trace amount of the metal thin film having a polycrystalline silicon thin film formed by maintaining for 10 seconds at 750 degrees. Di silicide, depending on the metal deposition time (NiSi _2), it can be seen that the increase in the number of grains 11 of the polycrystalline silicon to the increase in the number of precipitates (Precipitate), die silicide forming the nuclei in the amorphous silicon (12) (NiSi ₂₎ It can be seen that the distance between the precipitations becomes uniformly narrow.

FIG. 2 shows the formation of uniform disilicide (NiSi ₂ ) nuclei with a thickness of 5 μm to 20 μm after rapid heat treatment in a thin film containing 5 × 10 ¹² cm ⁻² per area of nickel metal, and growth of crystals from the nucleus to the side. Giving.

2A to 2C are photographs obtained by crystallization for 1 second, 8 seconds and 20 seconds of rapid heat treatment holding time at 750 degrees, respectively. As the retention time increases, crystals grow laterally from the nucleus. As the side surface is grown from the precipitated nuclei of nickel disiicide (NiSi ₂ ), it is shown that the grain boundary 21 is formed by hitting the adjacently grown grain 11 as shown in FIGS. 2C and 2D. In Fig. 2C, the grain 11 crystallization size is 20 mu m on average. As can be seen from the photo, the neighboring grains 11 show that the grain boundary 21 is formed by hitting each other.

3 shows a diagram schematically illustrating FIG. 2. Precipitated metal dissilicide (NiSi2) is formed by nucleating amorphous silicon 32 containing a very small amount (5x10 ¹² cm ^-2 ) of metal 31 on the substrate through rapid thermal treatment at 550 ° C for 5 minutes. A schematic of 33 is shown in FIGS. 3A and 3B. 3C shows that the grain boundary 35 is formed by crystallizing laterally as the NiSi ₂ precipitate is moved laterally from the nucleus to the neighboring grain 34.

FIG. 4 is a macro grain photomicrograph of polycrystalline silicon rapidly heat treated at 700 degrees after sputtering to less than 10 ¹² cm ^{−2 of} nickel content on amorphous silicon. 4A and 4B are reflecting microscope photographs magnified 200 times and 500 times, respectively. Since the amount of sputtered nickel is less than 10 ¹² per area, it restricts nickel migration, so that it does not meet neighboring grains, but is isolated in a high temperature heat-treated polycrystalline silicon thin film 41 and laterally separated from one nickel disilicide nucleus (precipitation). Growing to form a circular grain (11).

5 is an optical photograph of polycrystalline silicon rapidly heat-treated at 700 degrees after sputtering at a nickel content of 10 ¹⁴ cm ⁻² or more on amorphous silicon. If the amount of sputtered nickel is more than 10 ¹⁴ per area, the precipitation of nickel disiicide increases, which prevents the deposition and lateral growth of neighboring disilicide. As a result, a polycrystalline silicon thin film with a small grain is obtained as shown in the photograph.

FIG. 6 shows the number of nickel dissilicide deposited per cm ² according to plasma sputtering time exposed on amorphous silicon. The nickel-sputtered amorphous silicon thin film was held at 700 degrees for 10 seconds and the number of small grains formed in the thin film heat-treated 10 times in succession was divided by the area. As time goes on, it can be seen that the number of precipitation of the nickel dissilicide growing in the nucleus increases linearly. This nuclear density is proportional to the amount of nickel contained in amorphous silicon.

FIG. 7 shows the number of nickel disilisad precipitates per cm ² depending on the rapid heat treatment temperature after nickel concentration of 5 × 10 ¹² cm ⁻² sputtered on amorphous silicon. Grain per 1 cm ² of thin film heat-treated at 650 ° C for 3 consecutive 5 minutes, at 700 ° C for 10 consecutive 10 seconds, and at 750 ° C for 10 seconds 2 times The average value of the number growing is shown. In fact, one would count the number that appears on a 5x5cm ² per cm ^2. As a result of rapid heat treatment at high temperature, the number of precipitation of nickel disilicide (NiSi ₂ ) growing into the nucleus increases, and as a result, it can be seen that the grain size is smaller than the grain size of the crystallized thin film at 650 or 700 degrees. It can be seen that the size of the critical nucleus required for crystallization decreases with increasing temperature.

8 shows Raman scattering properties of crystallized polycrystalline silicon. The crystallization position of the optical phonon mode of the polycrystalline silicon thin film appears at a wavelength of 520 cm ⁻¹ . It is a polycrystalline silicon thin film which is crystallized by rapid heat treatment five times in a row at 750 degrees for 20 seconds. In FIG. 4, the crystallization position is 520.60 cm ⁻¹ , which is considered to be a good crystallization characteristic.

FIG. 9 shows an X-ray diffraction spectrometer (XRD) of a polysilicon thin film continuously thermally treated by maintaining an amorphous silicon thin film containing 5 × 10 ¹² cm ⁻² of nickel at 700 degrees for 20 seconds. It can be seen that the rapid thermally treated thin film grows in the (111) direction more than the (220) and (311) directions. Therefore, it means that the polycrystalline silicon obtained by the present invention is mostly grown in the (111) direction.

10A and 10B show a bright field image and an electron diffraction pattern of a polycrystalline silicon thin film having a diameter of 20 μm measured by a transmission electron microscope. In the electron diffraction pattern, the dots are clear in a circular shape, showing a single crystal phase with good crystallinity and almost no defects.

The present invention is an amorphous silicon thin film containing a small amount of metal (M) in the grain size and uniformity, which is a problem when the amorphous silicon thin film is crystallized into a polycrystalline silicon thin film, recrystallized using rapid heat treatment or ultraviolet (UV). It is a new method to replace laser technology because it can make nuclei formed at the uniform process at uniform intervals and can make large and uniform polycrystalline silicon thin film size of polycrystalline silicon grain. Polycrystalline silicon according to the present invention can be applied to the manufacture of flat panel displays, solar cells, semiconductor devices and the like.

Claims (22)

In the method of crystallizing amorphous silicon, Incorporating metal (M) into the amorphous silicon to crystallize the amorphous silicon in the solid state; and The metal makes several nuclei for crystallization and Crystallizing amorphous silicon as the nuclei move laterally; and And crystallizing the polycrystalline silicon grains to impart grain boundaries to each other. The method of claim 1, A small amount of amorphous silicon (10 ¹² ~10 ¹⁴ cm ^-2) of the amorphous silicon buffer layer or so as to include a metal (nitride film, oxide film) and Crystallization method of amorphous silicon characterized by using ion implantation, plasma, metal contact or solution containing metal on amorphous silicon stack The method according to claim 1, In order to control the formation interval of disilicide (MSi ₂ ) nucleus of metal, the metal forms an average concentration of 10 ¹² to 10 ¹⁴ cm ^-2 per area and forms the nucleus using a high temperature process, rapid heat treatment, or ultraviolet (UV) light. The method of claim 2, Ion implantation and using a solution containing the metal or the plasma process for forming a metal trace (10 ¹² ~10 ¹⁴ cm ^-2) to the surface and A method of using a high temperature heat treatment or ultraviolet (UV) absorption using a thin film containing a metal (10 ¹² ~10 ¹⁴ cm ^-2) of the small amount of crystallizing amorphous silicon The method of claim 3, wherein Crystallization method of amorphous silicon, characterized in that using a shadow mask when depositing a small amount of metal thin film The method of claim 1, Method for crystallizing amorphous silicon, characterized in that the metal (M) and silicon (Si) forms a metal die silicide (MSi ₂ ) mass in order for the metal to form a crystallization nucleus The method of claim 6, Crystallization method of amorphous silicon, characterized in that the metal disilicide (MSi ₂ ) is nickel disilicide (NiSi ₂ ) The method of claim 1, In order to make the metal nucleus, the vacuum pressure is maintained at 550 to 800 degrees in the atmosphere of nitrogen (or oxygen, nitrogen and hydrogen mixed gas, argon) at 1mtorr to 760torr for 1 to 1000s or continuously rapid heat treatment and nitrogen at atmospheric pressure. (Or oxygen, nitrogen and hydrogen mixed gas, argon) crystallization method of the amorphous silicon, comprising the step of raising the temperature of the amorphous silicon 350 ~ 650 degrees in the atmosphere The method of claim 1. In order to move the nucleus to the side, the sample temperature is maintained between 500 and 1200 degrees in a nitrogen (or oxygen, nitrogen and hydrogen mixed gas, argon) atmosphere using a high temperature process, rapid heat treatment, or laser under atmospheric conditions. Crystallization method of amorphous silicon characterized by holding for ˜10 hours The method of claim 1, Crystallization of amorphous silicon using a surface-treated thin film using acetone, methanol, hydrofluoric acid (HF) or an etchant to clean the surface after nucleation The method of claim 1, Crystallization method of amorphous silicon, characterized in that the generation of nuclei for crystallization and applying an electric field to the sample to enhance the lateral movement of the crystallization nuclei The method of claim 1, Crystallization method of amorphous silicon, characterized in that the crystallization at a constant rate from the nucleus when the nucleus moves to crystallize the amorphous silicon for crystallization The method of claim 1, A method of crystallizing amorphous silicon, characterized in that two grains collide to form a straight grain boundary. In the method of crystallizing amorphous silicon, Forming a metal thin film (10 ¹² to 10 ¹⁴ cm ^-2 ) on the glass substrate first; Depositing amorphous silicon on the metal thin film; Forming a nucleus for crystallization by the metal in contact with the amorphous silicon; The nucleus is laterally moved to crystallize amorphous silicon and And crystallizing the polycrystalline silicon grains to impart grain boundaries to each other. In the method of crystallizing amorphous silicon, Depositing amorphous silicon containing 10 ¹² to 10 ¹⁴ cm ^{-2 in} nickel in a gas phase; In order to heat the amorphous silicon to form a plurality of NiSi ₂ agglomerates Heating the amorphous silicon, Heating the amorphous silicon to continuously crystallize the amorphous silicon while the crystallization nuclei move laterally, The crystallized grains of the amorphous silicon, characterized in that the impingement to each other to form a crystal boundary. In the method of crystallizing amorphous silicon, Depositing amorphous silicon containing 10 ¹² to 10 ¹⁴ cm ^-2 in a vapor phase state, First heating the amorphous silicon to 350 to 800 degrees; and A method of crystallizing amorphous silicon by heating the heated amorphous silicon in the second 500 to 1200 degrees. In the method of crystallizing amorphous silicon, Depositing amorphous silicon containing 10 ¹² to 10 ¹⁴ cm ⁻² in a gaseous state, Crystallization method of the amorphous silicon, characterized in that it comprises the step of heating 400 to 1200 degrees in the state of the amorphous silicon in the electric field The method according to any one of claims 14, 15, 16 and 17, Crystallization method of amorphous silicon, characterized in that the ultraviolet (UV) is used to heat-treat the amorphous silicon The method according to any one of claims 15, 16 and 17, To include nickel in amorphous silicon, A method of crystallizing amorphous silicon, characterized in that the heating of the nickel, the nickel in the gas phase is included in the deposition of amorphous silicon The method according to any one of claims 15, 16 and 17. To include nickel in amorphous silicon, A method of crystallizing amorphous silicon, characterized in that the molecules containing nickel are heated to be included in the deposition of amorphous silicon in the gas phase. The method according to any one of claims 15, 16 and 17. To include nickel on amorphous silicon, Crystallization method of amorphous silicon, characterized in that the vapor deposition on the amorphous silicon by heating the molecule containing nickel The method according to any one of claims 15, 16 and 17, To include nickel on amorphous silicon, A method of crystallizing amorphous silicon, characterized in that the solid state containing nickel is brought into contact with amorphous silicon.