CN201506845U - Heat shield for single crystal furnace - Google Patents

Abstract

The utility model relates to an important device in a single crystal furnace thermal system, in particular to a heat shield used for a single crystal furnace, which is provided with an outer heat shield, an inner heat shield and a thermal insulation layer positioned between the outer heat shield and the inner heat shield that are fixedly connected, wherein the taper of the outer heat shield ranges from 0.16 to 0.23, and the taper of the inner heat shield ranges from 0.52 to 0.63. Through adjusting the tapers of the inner and the outer heat shields and changing the thickness of the thermal insulation layer, the shielding effect is better, and the growth rate of silicon single crystal is higher; the taper of the outer heat shield is smaller, the bottom part of the outer heat shield is substantially flat, the flow rate of argon gas is increased, the volatilization of impurities like SiO is enhanced, the growth environment of the silicon single crystal is improved, and both the yield and quality of the silicon single crystal are improved.

Description

Heat shield for single crystal furnace

Technical field

The utility model relates to an important device in the hot system of single crystal growing furnace, specifically is a kind of heat shield for single crystal furnace.

Background technology

The hot system of czochralski silicon monocrystal is open the earliest, and mainly the shape and structure by well heater is aided with the thermal field drawing silicon single-crystal that outer heat-preservation cylinder insulation forms.Present thermal field has upgraded to the system of enclosed, comprise graphite crucible, well heater, heat-preservation cylinder, insulation cover, lagging material and heat shielding, furnace hearth plate etc., the bottom of furnace hearth plate and be lagging material on every side, the lagging material in the heat-preservation cylinder and the heat-preservation cylinder outside is supported on the furnace hearth plate, upper and lower insulation cover is installed on the heat-preservation cylinder, and heat shielding is installed in the lid mouth of insulation cover.The use of heat shielding makes hot system become closed hot system, is equipped with the use of upper and lower insulation cover simultaneously, has effectively reduced heat energy loss, guarantees making full use of of heat energy; In addition, the existence of heat shielding is wanted to guide argon gas to be directed flow, guarantees always to be full of the freshest argon gas around silicon liquid and the crystal, makes silicon single-crystal atmosphere protection growth down around.But present heat shielding shield effectiveness is not fine, the directed flow speed of argon gas is the highest can only to reach 2-8m/s, heat shielding next top outside the impurity such as SiO that produce in the process of growth of silicon single crystal can be deposited on influences the growing environment of silicon single-crystal, and then influences the yield and the quality of silicon single-crystal.

The utility model content

The technical problems to be solved in the utility model is: in order to improve shield effectiveness, improve the speed of growth of silicon single-crystal and get rid of the impurity such as SiO that produce in the process of growth, a kind of heat shield for single crystal furnace is provided.

The technical scheme that its technical problem that solves the utility model adopts is: a kind of heat shield for single crystal furnace, have outer heat shielding, internal heat shield and outside thermal insulation layer between heat shielding and the internal heat shield, outer heat shielding is fixedlyed connected with internal heat shield, the tapering of outer heat shielding is 0.16-0.23, and the tapering of internal heat shield is 0.52-0.63.

Described internal heat shield and outer heat shielding all adopt isostatic pressing formed graphite to make.

The material of described thermal insulation layer is soft felt.

The beneficial effects of the utility model are: by adjusting inside and outside heat shielding tapering, change insulation layer thickness, make shield effectiveness better, silicon monocrystal growth speed is faster; Outer heat shielding tapering diminishes, and outer heat shielding bottom is slightly flat, has increased the argon gas flow velocity, has strengthened the volatilization of impurity such as SiO, has improved the growing environment of silicon single-crystal, has improved silicon single-crystal yield and quality.

Description of drawings

Below in conjunction with drawings and Examples the utility model is further specified.

Fig. 1 is a structural representation of the present utility model.

Fig. 2 is a temperature profile on the crystal axis that obtains by simulation before and after heat shielding is improved.

Fig. 3 is a temperature profile on the melt axis that obtains by simulation before and after heat shielding is improved.

Wherein: 1. outer heat shielding, 2. internal heat shield, 3. thermal insulation layer, 4. molybdenum screw, 5. insulation cover.

Embodiment

As shown in Figure 1, a kind of heat shield for single crystal furnace, have outer heat shielding 1, internal heat shield 2 and outside thermal insulation layer 3 between heat shielding 1 and the internal heat shield 2, it is big that the tapering of internal heat shield 2 becomes, and outer heat shielding 1 tapering diminishes, thermal insulation layer 3 thickenings, internal heat shield 2 taperings are 0.52-0.63, the tapering of outer heat shielding 1 is 0.16-0.23, and internal heat shield 2 and outer heat shielding 1 all adopt isostatic pressing formed graphite to make, and the material of middle thermal insulation layer 3 is soft felt.Earlier outer heat shielding 1, internal heat shield 2 contrapositions are installed in advance during use, dose needed soft carpet veneer then outside between heat shielding 1, the internal heat shield 2, outer heat shielding 1 and internal heat shield 2 close after completing, fix by molybdenum screw 4, be placed in after whole heat shielding assembles on insulation cover 5 internal orifices, so just form an enclosed hot system that helps silicon monocrystal growth.

A technical characterictic is that outer heat shielding 1 tapering diminishes, internal heat shield 2 taperings become big in the utility model, and this makes that thermal insulation layer 3 is thicker, and the shield effectiveness of heat shielding is better, and the longitudinal temperature gradient of thermal field is bigger, and silicon monocrystal growth speed is faster.In order to prove the above-mentioned validity of this heat shielding, here we have set up a model by the STR simulation software, before and after being improved by simulation on the crystal axis temperature profile Fig. 3 and improve before and after temperature profile Fig. 4 on the melt axis, as shown in Figure 3, improvement back liquid-solid interface place's crystalline thermograde thermograde compared with before-improvement is big; As shown in Figure 4, the thermograde of liquid-solid interface place melt is constant substantially before and after the improvement; According to equation

$V_{\mathrm{crys}}=\frac{1}{{\mathrm{\ρ}}_{\mathrm{crys}}\mathrm{\ΔH}}({\mathrm{\λ}}_{\mathrm{crys}}\frac{{\∂T}_{\mathrm{crys}}}{\∂n}-{\mathrm{\λ}}_{\mathrm{melt}}\frac{\∂T_{\mathrm{melt}}}{\∂n})$

Calculating learns that improving the back crystalline growth velocity increases, and actual tests result has verified that also analog result is correct.

Another technical characterictic is that the design of outer heat shielding 1 bottom slightly flattens in the utility model, outer heat shielding 1 tapering diminishes, the spacing between outer heat shielding 1 and the graphite crucible wall has been compressed in the two variation, make the argon gas flow velocity of flowing through herein accelerate (analog result shows that the argon gas mean flow rate increases to 3-10m/s by the 2-8m/s before improving), the SiO that produces in silicon fusing and the silicon monocrystal growth process and other impurity is easier is pulled away, so that these impurity sedimentary amount in heat shielding 1 next top outside reduce, even a small amount of deposition is arranged, because the runner port area reduces, the probability that impurity such as SiO are fallen in the molten bath also reduces, thereby improved the growing environment of silicon single-crystal, helping silicon single-crystal grows under the state of good lattice, improve silicon single-crystal yield and quality, have the excellent popularization utility value.

Claims (3)

1. heat shield for single crystal furnace, have outer heat shielding (1), internal heat shield (2) and be positioned at outer heat shielding (1) and internal heat shield (2) between thermal insulation layer (3), outer heat shielding (1) is fixedlyed connected with internal heat shield (2), it is characterized in that: the tapering of outer heat shielding (1) is 0.16-0.23, and the tapering of internal heat shield (2) is 0.52-0.63.

2. heat shield for single crystal furnace according to claim 1 is characterized in that: described internal heat shield (2) and outer heat shielding (1) all adopt isostatic pressing formed graphite to make.

3. heat shield for single crystal furnace according to claim 1 is characterized in that: the material of described thermal insulation layer (3) is soft felt.

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