CN204332909U - A kind of preparation facilities of low-temperature polysilicon film - Google Patents

Abstract

The utility model discloses a kind of preparation facilities of low-temperature polysilicon film, this device inductively produces highdensity plasma based on the planar spiral winding of copper pipe coiling under high frequency RF power source excitation, improve concentration and the energy of reaction active groups in Polysilicon film deposition, can be less than high speed deposition polysilicon membrane under the substrate temperature of 350 DEG C, maximum sample size can reach 140mm × 140mm.Meanwhile, the induction coil of this device is separated with reaction zone by quartz window, and plasma energetic ion group can be avoided the bombardment damage of electrode, reduces the metallic pollution prepared in material.In addition, carry out magnetic confinement at cylindrical reaction chamber annular magnet array plasma of arranging outward, improve plasma uniformity, can be used for the making of the silica-based function film of Large-Area-Uniform and device.

Description

A kind of preparation facilities of low-temperature polysilicon film

Technical field

The utility model relates to a kind of preparation facilities of low-temperature polysilicon film, refers to the silica-base film deposition of material equipment at thin-film transistor (Thin Film Transistor, TFT) and thin film solar cell field with extensive use value especially.

Background technology

Polysilicon membrane (p-Si) on structurally ordered degree between monocrystalline silicon and amorphous silicon.The raising of the degree of order makes the electric property of polysilicon membrane have very large lifting compared to amorphous silicon membrane, and as higher electron mobility, (low temperature polycrystalline silicon electron mobility is amorphous silicon more than 400 times, up to 200cm ²/ Vsec), lower dark current and the thermal stability of Geng Jia.Thin-film transistor TFT drive circuit is key one step improving liquid crystal display (LCD) quality.At present, based on cost control reason, most of tft array still adopts the manufacture of cheap amorphous silicon membrane (a-Si).As adopted polycrystalline SiTFT (p-Si TFT) technology, TFT device volume will be less, improve " aperture opening ratio " of single pixel, and then strengthen display brightness, reduce energy consumption.And, p-Si TFT drive IC can be integrated with glass substrate, avoid the separation design of traditional a-Si TFT, the connector quantity between drive IC and glass substrate is made to be reduced to less than 200 from about 4000 of a-Si TFT, display screen can do lighter and thinner, reduce modular manufacture cost, improve the job stability of device, also adapt with the development trend of notebook computer and dull and stereotyped computer light thinning.In film photovoltaic field, as adopted polysilicon membrane to substitute amorphous silicon membrane, being expected the photoelectric conversion efficiency and the job stability that improve device, promoting the industrialization process of film photovoltaic device.At present, amorphous silicon (a-Si) is though thin film solar cell achieves industrialization, but be limited by structural stability and the electric property of a-Si material, this class component conversion efficiency is generally lower than 8%, far below the main flow efficiency of more than 20% of monocrystalline silicon, and there is serious light-induced degradation (S-W) effect, competitive advantage is always not obvious for many years.Therefore, adopting the more stable polysilicon membrane of the better structure of electric property to substitute amorphous silicon membrane and manufacture semiconductor device, is the inevitable requirement of semiconductor industry.

In early days, for obtaining polysilicon membrane, normal employing high-temperature technology technology, as rapid thermal annealing (Rapid Thermal Annealing, RTA) or high temperature solid-state crystallization (Solid Phase Crystalline, SPC).Technological temperature is now at least more than 800 DEG C, and simple glass softening melting early occurs and cannot use at all, only has and uses the better quartz substrate of heat resistance.But quartz glass is often expensive and size is less, the needs of large scale display floater and the manufacture of large area film photovoltaic device cannot be adapted to.For this reason, most of manufacturer can only select cheap a-Si thin-film material to manufacture TFT device or solar cell.

At present, develop low temperature polycrystalline silicon (Low Temperature Polycrystalline Silicon, LTPS) technology and become industry common recognition.The existing prevailing technology technology of LTPS has two kinds: metal-induced lateral crystallization method (Metal Induced Lateral Crystallization, MILC) and Excimer-Laser Crystallization method (Excimer Laser Annealing, ELA).The common ground of two kinds of methods needs on substrate, deposit a-Si film (being generally the plasma enhanced CVD preparation by low pressure chemical vapor deposition or capacitance coupling type) in advance, impel a-Si film crystallization by thermal annealing or local laser heating again, obtain polysilicon membrane.Relative to high temperature crystallization processes such as rapid thermal annealing (RTA), solid phase crystallizations (SPC), both all achieve the significantly decline of crystallization temperature, generally can complete conversion under the technological temperature of 500 ~ 600 DEG C.As; Chinese patent " a kind of method of transversely inducing and crystallizing low-temperature polycrystalline silicon film " (CN10185378 A) provides a kind of MILC technology, adopt nickel as catalyst inert protective gas environment, at 590 DEG C annealing within 1 hour, obtain polysilicon membrane.Chinese patent (CN102709160 A) then provides a kind of ELA technology to obtain low-temperature polysilicon film, and this manufacture method is carried out quasi-molecule laser annealing to amorphous silicon layer and obtained polysilicon membrane, and crystallite dimension is comparatively large, is evenly distributed.

But MILC and ELA all needs prefabricated a-Si film, then changes polysilicon membrane into by later stage crystallization process, in fact there is many shortcomings.Such as, MILC easily causes metallic pollution, and the process time reaches a few hours.The shortcoming of ELA is that crystallite dimension is responsive to laser power, is not suitable for the crystallization of large area uniform film and equipment cost is high.Meanwhile, be limited to the strong absorption ability of a-Si film to laser energy, the polysilicon membrane thickness that ELA crystallization is formed is generally less than 100nm.

For simplifying the production process of semiconductor device, reduce manufacturing cost, people attempt to be no more than under 350 DEG C of substrate temperatures Direct precipitation low-temperature polysilicon film in inexpensive glass or plastic.At present, most of device level Si film all adopts chemical vapour deposition technique (Chemical Vapor Deposition, CVD) to prepare.Compared to physical method, Si thin film crystallization quality prepared by chemical method is higher, and even particle size distribution, photoelectric properties are best.CVD technique will realize Direct precipitation low-temperature polysilicon film, needs greatly to improve SiH, SiH ₂deng the activity of reactive group, namely improve its mobility at substrate surface.The glow discharge mode of decomposition reaction gas many employings better effects if.But the plasma density of traditional capacitance manifold type glow discharge is lower by (~ 10 ⁹cm ^-3), electric discharge air pressure higher (more than 100Pa), when preparation for Si film, deposit film mostly is amorphous state, still need high annealing crystallization, and deposition rate is low, film thickness uniformity is poor, be difficult to the bombardment damage avoiding heavy dose of ion pair growing surface, is not suitable for preparing high-quality large area uniform film.In recent years, inductively coupled plasma (Inductively Coupled Plasma, ICP) is subject to extensive concern due to the high-density plasma that can maintain Large-Area-Uniform under lower air pressure (can reach 0.1Pa).The film deposition rate of ICP-CVD technology is high, and deposit film crystalline quality is good, is a kind of low-temperature polysilicon film Directly depositing with better development prospect.

Chinese patent " a kind of low temp polysilicon film device and manufacture method and equipment " thereof (CN 100537838 C) and " plasma deposition apparatus and method for the manufacture of polysilicon " (CN101512042 B) all proposes the process route that a kind of ICP of employing plasma directly prepares low temperature polycrystalline silicon, obtains good crystalline quality.But due to ICP discharge mechanism reason, plasma often marginal density is large, and middle section is little, and deposited film thickness is uneven.In addition, the bombardment of ICP intermediate ion to electrode brings pollution also very important.The utility model is the ICP-CVD silica-base film depositing device proposing a kind of novel electrode structure, and by optimizing electrode modes of emplacement and Magnetic control array, obtain uniform high-density plasma, for the preparation of Large-Area-Uniform high-quality polycrystalline silicon film material provides a kind of important device.

Summary of the invention

For improving the uniformity of ICP-CVD equipment depositing silicon base film, improve thin film crystallization quality, the utility model provides a kind of ICP-CVD precipitation equipment, the glow discharge loop construction simplicity of design of this device, and separated by dielectric layer and reative cell, adopt magnetic confinement technology simultaneously, improve plasma uniformity.

The technical solution adopted in the utility model is: (1) adopts planar spiral inductor coil as sparking electrode.This loop construction is simple, can excite uniform plasma, be conducive to improving the crystalline quality and thickness evenness of preparing film; (2) discharge mode of external is adopted.By quartz medium floor, planar spiral winding is separated with Polysilicon film deposition room, eliminates energetic ion in plasma and, to the bombardment of electrode material surface, effectively avoid electrode material to the pollution of depositing silicon base film; (3) for providing plasma uniformity further, adopting annular magnet array to carry out magnetic confinement to the plasma produced, improving the plasma uniformity of two dimensional surface above thin film deposition, be adapted to the preparation of large area uniform film; (4) H is adopted ₂dichlorosilane (the SiCl of dilution ₂h ₂) as key reaction source gas.SiCl ₂h ₂replace traditional SiH ₄more easily decompose, fail safe is higher, contributes to improving deposition rate; (5) H plasma cleans thin film deposition substrate.Substrate cleaning Du Genggao after cleaning, contributes to the surface mobility and the nucleation rate that improve reaction active groups.

The utility model adopts the simple discharge coil of structure, by supplementary meanss such as modes of emplacement, magnetic confinement technology, obtain uniform ICP plasma, by selecting suitable reaction source gas and the process to substrate surface, make ICP-CVD device can realize the deposition of Large-Area-Uniform high-quality polysilicon membrane at low temperatures.

Accompanying drawing explanation

Fig. 1 is the crystal structure schematic diagram of monocrystalline silicon, amorphous silicon and polysilicon;

Fig. 2 is traditional ICP-CVD installation drawing;

Fig. 3 the utility model proposes the ICP-CVD equipment schematic diagram being applicable to Large-Area-Uniform silica-base film deposition;

Fig. 4 is that planar spiral inductor coil is connected vertical view, relevant portion size with water power;

Fig. 5 is reative cell outer ring magnet array schematic diagram;

Fig. 6 is the arc-shaped magnet shape and scale diagrams that adopt.

Embodiment

Below in conjunction with accompanying drawing, the utility model will be further described.

See Fig. 1, the Si atom periodic arrangement of single crystal silicon material, the degree of order is the highest.Amorphous silicon is short-range order and longrange disorder, and material structure defect is many, and the motion of electric charge is easily subject to capturing of defect or scattering, and carrier mobility is lower.Polycrystalline silicon material can regard the system of many little monocrystalline compositions as, and little intra-die is complete ordering, and intercrystalline exists boundary.Compared to amorphous silicon, polysilicon, except at grain boundary, is monocrystalline silicon characteristic substantially.

Fig. 2 is traditional ICP-CVD equipment.Reactor quartz ampoule is made, and excites generation plasma by the high frequency coil be looped around outside quartz ampoule.Its principle is: the radio-frequency current of alternation causes the magnetic field of alternation, and then convolution electric field of inducting, electronics does circumnutation under the effect of electric field, adds the collision probability with neutral gas molecule, therefore can produce the plasma (>10 higher than CCP density ¹¹cm ^-3).This apparatus structure is simple, and reactor internal contamination is few, but electric field and air flow method inequality, and if uniformity is poor during large-area film deposition, general area is limited with diameter 10cm.For meeting the needs of large area film deposition, its ICP electric discharge device need be improved.

Fig. 3 is a kind of modified model ICP-CVD device that the utility model proposes.The inductance coil of this device is separated by dielectric layer window and plasma, can avoid the sputtering of ion pair discharge coil.For improving plasma uniformity, outside reative cell, a circle annular magnet of having arranged, to provide magnetic confinement, improves the plasma uniformity above sample stage.Sample stage is connected with grid bias power supply, to promote that reaction active groups is to the movement on its surface, and then improves deposition rate.Bias voltage can regulate.The utility model adopts high-purity H ₂dichlorosilane (the SiCl of dilution ₂h ₂) as key reaction source gas, concentration is 10%.Again by the SiCl of dilution ₂h ₂h high-purity with another road ₂jointly pass into reative cell, by regulating the flow-rate ratio of two kinds of gases, dynamic regulates SiCl ₂h ₂concentration.Two-way gas is all controlled by standard mass flow controller.Before Polysilicon film deposition, first pass into H ₂gas, makes H plasma clean thin film deposition substrate.Substrate cleaning Du Genggao after cleaning, contributes to the surface mobility and the nucleation rate that improve reaction active groups.

Fig. 4 is planar spiral winding and the water power connection vertical view thereof of the employing of this device.For improving plasma uniformity, employing external diameter is that hollow high-purity copper tube coiling of 6mm forms planar spiral winding, copper pipe thickness of pipe wall 1mm in 3 weeks.Coil diameter 200mm, the quartz window being 3mm by thickness is separated with plasma slab, and being positioned over external diameter is in 300mm vacuum chamber.Based on this size, the maximum low-temperature polysilicon film preparing 140mm × 140mm of this equipment.One end of helical coil is connected with radio-frequency power supply by matching box, the direct ground connection of the other end.The copper pipe of helical coil is inner without the need to insulating sleeve, can directly water flowing cooling.Radio-frequency power supply power 1000W, frequency 13.56MHz.By the capacitance adjustment to matching box, ICP system can be made under certain air pressure to produce glow discharge.

Fig. 5 is the arrangement schematic diagram of vacuum chamber outer ring magnet array.Around vacuum chamber, place one piece of arc-shaped magnet every 45 °, totally 8 magnet are formed.Magnet array provides extra balance magnetic confinement for reative cell inside, avoids plasma too to concentrate on certain region, improves the overall uniformity of plasma.

Fig. 6 is fixed on arc-shaped magnet structural representation outside vacuum chamber and size thereof.For guaranteeing to fit with outer wall precision, the specialized designs arc-shaped magnet of this kind of structure.Magnet outer arc is about 20mm, is 7.6 ° to the center subtended angle of vacuum chamber.Arc-shaped magnet sheet thickness is about 5mm.Half sector, left and right is respectively N pole and S pole.By arc-shaped magnet array, in vacuum chamber, provide a braided magnetic field, can retrain the motion of electronics, avoid plasma too to concentrate on ate electrode or adjacent edges, improve overall uniformity.

Claims (7)

1. the preparation facilities of a low-temperature polysilicon film, this device adopts inductively-coupled discharge mode to decompose source gas and produces reaction active groups, active group is adsorbed onto substrate surface and then synthesised polycrystalline silicon thin film, it is characterized in that: induction coil is separated by medium window and plasma slab, and arrange annular magnet array outward to provide magnetic confinement at reative cell.

2. the preparation facilities of a kind of low-temperature polysilicon film according to claim 1, is characterized in that: reaction source gas adopts high-purity H ₂the concentration of dilution is the dichlorosilane of 10%, by high-purity H ₂further dilution, its concentration can change between 0% ~ 10%.

3. the preparation facilities of a kind of low-temperature polysilicon film according to claim 1, is characterized in that: substrate is connected with the DC bias source of pressure-adjustable, substrate and inductance coil distance can regulate between 60 ~ 100mm, and substrate growth temperature is below 350 DEG C.

4. the preparation facilities of a kind of low-temperature polysilicon film according to claim 1, it is characterized in that: induction coil is the planar spiral structures of two dimension, coil diameter 200mm, being positioned over external diameter is in the vacuum chamber of 300mm, but is that the quartz window of 3mm and plasma slab separate by thickness.

5. the preparation facilities of a kind of low-temperature polysilicon film according to claim 1, is characterized in that: the copper tube coiling that induction coil is 6mm by external diameter forms for 3 weeks, copper pipe thickness of pipe wall 1mm, and copper pipe is inner without the need to installing the direct water flowing cooling of insulating sleeve additional.

6. the preparation facilities of a kind of low-temperature polysilicon film according to claim 1, is characterized in that: with the mutually level vacuum chamber outer wall of plasma slab on to arrange annular magnet array, place one block of magnet every 45 °, totally 8 magnet are formed.

7. the preparation facilities of a kind of low-temperature polysilicon film according to claim 1, it is characterized in that: annular magnet array is made up of arc-shaped magnet sheet, its thickness is 5mm, half sector, left and right is respectively N pole and S pole, outer arc length 20mm, the center subtended angle of outer arc length to vacuum chamber is 7.6 °, fits with vacuum chamber outer wall precision.