CN103757695A - Sidewall heat compensation device of polysilicon directional solidification device - Google Patents

Abstract

The invention provides a sidewall heat compensation device of a polysilicon directional solidification device, relating to polysilicon. The invention provides the sidewall heat compensation device of the polysilicon directional solidification device, which can greatly reduce energy consumption and cost, enable equipment to be simple and reliable, keep the polysilicon rising along the horizontal direction before solidification and realize excellent purification quality. The sidewall heat compensation device is provided with a top cover, a heating device, a housing, a heat preservation layer, a crucible and a heat dissipation plate, wherein the top cover is arranged at the top of the housing, the heating device and the crucible are arranged in a cavity of the housing, the heating device is arranged above the crucible, and the edge of the heating device extends to the upper part of the cavity; the heat preservation layer wraps the outer side and the bottom in the cavity, a silicon solution is contained in the crucible, and the heat dissipation plate is arranged under the crucible and closely jointed with the crucible.

Description

A kind of sidewall heat compensation device of polysilicon directional freezing equipment

Technical field

The present invention relates to polysilicon, especially relate to a kind of sidewall heat compensation device of polysilicon directional freezing equipment.

Background technology

In the today of advocating low-carbon emission reduction, sun power has become the green energy resource receiving much concern.Polysilicon is current most widely used solar cell material.Generally, in the process of metallurgy method purifying solar energy level polysilicon (6N level), directional freeze is an important step of removal of impurities, and at present, conventional directional solidification process has two kinds: heat-exchanging method (HEM) and Bridgman method (Bridgman).In the world, numerous production of polysilicon business have adopted heat-exchanging method as companies such as Japanese capital pottery, Bayer Bitterfeld GmbH, French Ford Wa Ke, and in directional freeze process, the solidified front of silicon can maintenance level rise, and refining effect is good.But the equipment complex and expensive of heat-exchanging method, in process of setting, the induction coil heating apparatus of top and sidewall needs a direct-open, and relies on bottom forced heat radiation to form the vertical temperature gradient of directional freeze, and this has caused the huge loss of electric energy.And the Bridgman method that GT Solar provides, crucible and heating unit need relative movement, and this has increased the complicacy of equipment undoubtedly, also requires more high reliability and wearing quality.

The domestic Dai Xin that is engaged in the research of metallurgy method purifying polycrystalline silicon etc. (wears prosperous, Du Haiwen, Zhang Junyan, Wang Feng. the impact of graphite heater in polysilicon directional freezing technique. electronics manufacturing engineering, 2012,2:106-109) comparative studies heater top, side well heater and three kinds of different well heaters of top-side well heater, think that top-side well heater of current employing can obtain good efficiency and solidified front (solid-liquid phase interface) in polysilicon melting and crystal growing process.This is very similar to heat-exchanging method, all adopts Multi-surface heating to build the thermograde of vertical direction, guarantees directional freeze purification quality, but also brought, equipment is complicated, the problem of high energy consumption simultaneously.And general conventional apparatus for directional solidification only adds at top and holds thermal source, in process of setting, sidewall leaks heat, causes solidified front to present spill, has a strong impact on the purification quality of polysilicon.

Collateral security purification quality, and reduce costs the angle with energy consumption, the latent heat of solidification that makes full use of top firing device and silicon maintains directional freeze thermal field, keeps the horizontal configuration of solidified front, is the developing direction of metallurgy method purifying polycrystalline silicon.

Summary of the invention

The object of the invention is to that the heating arrangement that exists for existing solar-grade polysilicon apparatus for directional solidification is complicated, energy consumption is huge, solidified front is difficult for the shortcomings such as maintenance level, provide can significantly reduce energy consumption and cost, equipment simple and reliable, can keep that polysilicon solidified front level rises, the sidewall heat compensation device of the superior in quality a kind of polysilicon directional freezing equipment of purifying.

The present invention is provided with top cover, heating unit, housing, thermal insulation layer, crucible, heating panel; Described top cover is located at the top of housing, and heating unit and crucible are located in the cavity of housing, and heating unit is located at crucible top, and the edge of heating unit extends to cavity top; Described thermal insulation layer is wrapped in outside and the bottom in cavity, holds silicon liquid in crucible, and heating panel is placed under crucible and with crucible and fits tightly.

The edge of described heating unit preferably extends to cavity top and higher than cavity hatch 3～10mm.

The thickness of described thermal insulation layer can be 100～350mm.

Described cavity can be axially symmetric structure, cavity is centered around outer side the close contact of crucible, the section of cavity is up-narrow and down-wide gradual change type triangular structure of right angle, the inclined-plane of described triangular structure of right angle can be after plane the curved surface of indent a little, the vertical surface of triangular structure of right angle is vertical with bottom surface, and the angle on bottom surface and inclined-plane can be 73 °～78 °.

The present invention is the principle in the internal reflection of class right-angle triangle cavity, refraction, coupling according to heat, the thermal coupling that equipment top firing device, silicon liquid upper surface and crucible wall are distributed, in silicon process of setting, crucible wall dispersed heat compensates, make the heat flow density flowing out from sidewall be reduced to the order of magnitude that approaches 0, be equal to desirable thermal insulation, form vertical orientation temperature of solidification gradient, guarantee that the level of solidified front rises.

The present invention takes full advantage of top heater and silicon liquid solidifies the heat of the heat compensation sidewall loss of distributing, to reach the effect of sidewall thermal insulation.Both the side heaters of heat-exchanging method (HEM) can be omitted, and again without the running gear of Bridgman method (Bridgman), and good refining effect can be reached, not only simplified construction, and saves energy consumption greatly.The present invention makes polysilicon in directional freeze process, and solidified front (solid-liquid phase interface) maintenance level always rises, suitable with the refining effect of heat-exchanging method and Bridgman method, but structure simplifies greatly, and energy consumption also significantly reduces.Therefore use the present invention can obtain larger economic benefit and social benefit.

Accompanying drawing explanation

Fig. 1 is the schematic perspective view of the embodiment of the present invention.

Fig. 2 is the schematic top plan view of the embodiment of the present invention.

Fig. 3 is the diagrammatic cross-section of the embodiment of the present invention.

Fig. 4 is the perspective diagram of the embodiment of the present invention.

Embodiment

As illustrated in fig. 1 and 2, the embodiment of the present invention is provided with top cover 1, heating unit 2, housing 3, thermal insulation layer 4, crucible 8, heating panel 11.Described top cover 1 is located at the top of housing 3, and heating unit 2 and crucible 8 are located in the cavity 5 of housing 3, and heating unit 2 is located at crucible 8 tops, and the edge of heating unit 2 extends to cavity 5 tops; Described thermal insulation layer 4 is wrapped in outside and the bottom in cavity 5, holds silicon liquid 9 in crucible 8, and heating panel 11 is placed under crucible 8 and with crucible 8 and fits tightly.

The edge of described heating unit 2 extends to cavity 5 tops and higher than cavity 5 opening 3～10mm.

The thickness of described thermal insulation layer 4 is 100～350mm.

Described cavity 5 is axially symmetric structure, cavity 5 is centered around outer side the close contact of crucible 8, the section of cavity 5 is up-narrow and down-wide gradual change type triangular structure of right angle, the inclined-plane 6 of described triangular structure of right angle can be after plane the curved surface of indent a little, the vertical surface 7 of triangular structure of right angle is vertical with bottom surface 10, and the angle on 10Yu inclined-plane, bottom surface 6 can be 73 °～78 °.

Because top cover 1 is placed in main body top, housing 3 is wrapped in outside, and therefore support structure and protection are provided.

As shown in Figures 3 and 4, heating unit 2 is installed on directly over crucible 8, and edge extends to heat compensation cavity 5 tops, higher than cavity 5 opening 3～10mm, for keeping surface temperature and the heating cavity 5 of silicon liquid 9; Thermal insulation layer 4 is wrapped in outside and the bottom of heat compensation cavity 5, thick 100～350mm; Heat compensation cavity 5 is axially symmetric structure, be centered around outer side the close contact of crucible 8, cavity 5 sections are upper narrow opening (width 20～50mm), the gradual change class triangular structure of right angle of bottom wider (width 200～300mm), inside has three, is respectively inclined-plane 6, vertical surface 7, bottom surface 10, wherein, internal surface 6 can be plane, can be also the curved surface of indent a little, and face 6 is 73 °～78 ° with the angle of face 10; Silicon liquid 9 is contained among crucible 8; Heating panel 11 is placed under crucible 8, fits tightly with crucible 8.

The present invention can be according to the specific requirement of output, the size of bi-directional scaling device.

Below provide some examples of sidewall heat compensation device.

Embodiment 1

Heating unit (graphite heater) is installed higher than 4～6mm place, crucible top, and the cavity cross-section upper opening of heat compensation device is 30mm, and bottom lengths is 200mm, and inclined-plane and bottom surface angle are 78 °.In cavity inner surface, inclined-plane adopts high compactness, resistant to elevated temperatures black fiber sheet material, and surfaceness is between Ra6.3～Ra12.5; The vertical surface contacting with crucible adopts high-intensity graphite cake to make, and surfaceness is Ra3.2; Cavity bottom surface adopts stupalith, and surface finish is processed, surface roughness Ra 0.1.

Embodiment 2

Heating unit (graphite heater) is installed higher than 8mm place, crucible top, and the cavity cross-section upper opening of heat compensation device is 20mm, and bottom lengths is 250mm, and inclined-plane and bottom surface angle are 73 °.In cavity inner surface, inclined-plane and vertical surface all adopt high-intensity graphite sheet to make, and surfaceness is respectively Ra6.3 and Ra3.2; Cavity bottom surface adopts stupalith, and surface finish is processed, surface roughness Ra 0.2.

Embodiment 3

Heating unit (graphite heater) is installed higher than 5mm place, crucible top, and the cavity cross-section upper opening of heat compensation device is 40mm, and bottom lengths is 220mm, the slight indent in inclined-plane, with bottom surface angle be 75 °.In cavity inner surface, inclined-plane adopts high compactness, resistant to elevated temperatures black fiber sheet material, and surfaceness is Ra12.5; The vertical surface contacting with crucible adopts high-intensity graphite cake to make, and surfaceness is Ra1.6; Cavity bottom surface adopts stupalith, and surface finish is processed, surface roughness Ra 0.05.

Ultimate principle of the present invention is as follows:

Get a certain section of sidewall heat compensation device, establishing inside cavity inclined-plane is face I, and vertical surface is face II, and bottom surface is face III, and top firing device surface is face IV.Because cavity is heated by well heater, more than temperature can reach 1000K, inner air is very thin, can think in cavity and be similar to vacuum, meets the law that conducts heat between grey surface:

wherein,

for passing through each surperficial heat flow density in cavity, ε _ifor each surface heat radiant emittance, σ is Stefan-Boltzmann constant, J _ifor each surface launching heat density, T _ifor each internal surface temperature,

angle factor for mutual relationship between surface.

That is:

In cavity, angle, the cavity size relation of ⅠYu bottom surface, inclined-plane III have determined angle factor

value, and material kind, the surfaceness of internal surface have determined thermal radiation emissivity ε _ivalue.Therefore, properly design cavity geometry and select suitable inner lining material, can make by the heat flow density of vertical surface II in cavity

value is 0, and because vertical surface II and crucible wall fit tightly mutually, therefore, the heat by crucible outer side wall is also 0, by this system of equations, can obtain one group of theoretical value:

$\left\{\begin{array}{c}{\stackrel{\‾}{F}}_{11}=0,{\stackrel{\‾}{F}}_{12}=\frac{1}{2},{\stackrel{\‾}{F}}_{13}=\frac{1}{3},{\stackrel{\‾}{F}}_{14}=\frac{1}{6}\\ {\stackrel{\‾}{F}}_{21}=\frac{1}{2},{\stackrel{\‾}{F}}_{22}=0,{\stackrel{\‾}{F}}_{23}=\frac{3}{10},{\stackrel{\‾}{F}}_{24}=\frac{2}{10}\\ {\stackrel{\‾}{F}}_{31}=\frac{5}{9},{\stackrel{\‾}{F}}_{32}=\frac{1}{3},{\stackrel{\‾}{F}}_{33}=0,{\stackrel{\‾}{F}}_{34}=\frac{1}{9}\\ {\stackrel{\‾}{F}}_{41}=\frac{5}{11},{\stackrel{\‾}{F}}_{42}=\frac{4}{11},{\stackrel{\‾}{F}}_{43}=\frac{2}{11},{\stackrel{\‾}{F}}_{44}=0\end{array}\right.$ With $\left\{\begin{array}{c}{\mathrm{\ϵ}}_I=0.92\\ {\mathrm{\ϵ}}_{\mathrm{II}}=0.8\\ {\mathrm{\ϵ}}_{\mathrm{III}}=0.23\\ {\mathrm{\ϵ}}_{\mathrm{IV}}=0.9\end{array}\right.$

Binding isotherm value and engineering are actual, and the angle of ⅠYu bottom surface, inclined-plane III is got 73 °～78 °, inclined-plane I, vertical surface II, thermal radiation emissivity ε corresponding to bottom surface III _iget respectively: 0.9～0.95,0.75～0.85,0.2～0.25.Therefore, crucible wall is just equal to desirable adiabatic condition, and polysilicon has formed the thermograde of vertical direction at process of setting, and solidified front maintenance level well rises.

Integral body of the present invention is the pyramid structure of flat-top, and top cover is made by fine and close refractory fibrous material; Using graphite sheet as the base material of heat compensation cavity, and its section is upper narrow opening, the gradual change cavity configuration that bottom is wider, cavity configuration is totally class right-angle triangle, wherein, the inclined-plane of inside cavity can be plane, can be also the curved surface of indent a little.The material of the different thermal radiation emittance of heat compensation cavity liner, as required, can select fiberboard, graphite cake, refractory brick, the differing materials such as pottery; Cavity outer side covers has thermal insulation layer and device case, and thermal insulation layer can adopt refractory brick, refractory fibre or resistant to elevated temperatures porous material, and device case adopts 4～10mm Plate Steel.Top is provided with heating unit, and heating unit can adopt graphite heating plate, is placed in directly over crucible, and extends to cavity top, higher than cavity open top 3～10mm, by thermal radiation, heating and thermal insulation is carried out in silicon liquid surface and inside cavity, and power is adjustable.Heat compensation inside cavity is buried thermopair underground, and collecting temperature signal transfers to temperature controlling system and processes; Temperature controlling system comprises thermopair, signal collection and analysis equipment, microcomputer, thermosistor etc., can be controlled voluntarily by temperature controlling system the output rating of cavity top firing device, also can carry out manual intervention control.

The present invention is around being arranged on directional freeze crucible outside, and both fit tightly by contact surface; Can facilitate installation and removal, be conducive to the repacking of conventional apparatus for directional solidification; Silicon liquid can be by slowly pouring directional freeze crucible into after the fusing of other equipment, and carry out forced-ventilation heat radiation by the heating panel of crucible bottom, silicon directional freeze from bottom to top gradually in container, the highly purified polysilicon of cooling rear acquisition.

Claims (5)

1. a sidewall heat compensation device for polysilicon directional freezing equipment, is characterized in that being provided with top cover, heating unit, housing, thermal insulation layer, crucible, heating panel; Described top cover is located at the top of housing, and heating unit and crucible are located in the cavity of housing, and heating unit is located at crucible top, and the edge of heating unit extends to cavity top; Described thermal insulation layer is wrapped in outside and the bottom in cavity, holds silicon liquid in crucible, and heating panel is placed under crucible and with crucible and fits tightly.

2. a kind of sidewall heat compensation device of polysilicon directional freezing equipment as claimed in claim 1, the edge that it is characterized in that described heating unit extends to cavity top and higher than cavity hatch 3～10mm.

3. a kind of sidewall heat compensation device of polysilicon directional freezing equipment as claimed in claim 1, the thickness that it is characterized in that described thermal insulation layer is 100～350mm.

4. a kind of sidewall heat compensation device of polysilicon directional freezing equipment as claimed in claim 1, it is characterized in that described cavity is axially symmetric structure, cavity is centered around outer side the close contact of crucible, and the section of cavity is up-narrow and down-wide gradual change type triangular structure of right angle.

5. a kind of sidewall heat compensation device of polysilicon directional freezing equipment as claimed in claim 4, the inclined-plane that it is characterized in that described triangular structure of right angle is the curved surface of indent a little after plane, the vertical surface of triangular structure of right angle is vertical with bottom surface, and the angle on bottom surface and inclined-plane is 73 °～78 °.

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