CN1003380B - Method and equipment for pulling single crystal silicon in non-liner magnetic field - Google Patents

Abstract

The present invention relates to a method for pulling single crystals in magnetic fields and a single crystal furnace. A spiral pipe of the single crystal furnace is divided into two groups with different internal diameters, and an armature of the spiral pipe is manufactured into the shape of a furnace wall and is simultaneously used as the furnace wall of the whole furnace body, the armature, an upper end cover and a lower cover of the furnace body and a magnetic loop are in a totally enclosed structure, and the spiral pipe is supported by a lifter and can move vertically relative to a crucible. In crystal pulling, the crucible is positioned on the upper end or the lower end of a magnetic field generated by the spiral pipe and is provided with a loudspeaker-shaped non-linear area for obtaining maximal inhibiting effect on melted silicon heat convection, the furnace wall in a fully enclosed structural is used as the armature, and smaller direct-current power sources can obtain larger magnetic field intensity.

Description

Non-linear magnetic field pulling single crystal silicon method and device thereof

The invention belongs to the method and the equipment therefor of pulling monocrystal silicon in magnetic field.

The silicon crystal of using in microelectronics industry had been started before 30 years since its production technology, and its basic process of production does not just take place significantly to change.Yet, in recent years, with the unicircuit the developing rapidly of microelectronics of representative, the silicon crystal that is used to make unicircuit and other semiconducter device has been proposed more and more higher requirement.Crystal technique has become the centrostigma of industrial applied research, and has constituted one of main pillar of modern microelectronics industry.

With the Grown by CZ Method silicon crystal time, often exist thermal convection (referring to JRCorruthersScmiconductor, Silicon, 1977, P61) this convection current or nature or be forced to.Natural convection makes the variation of solidification rate be difficult to control, (referring to AFWitt, at al, JElectrochSoc, Vol122, NO.2) thus cause near the uneven distribution of diffusion boundary layer thickness crystal one melt interface, these variations cause crystalline periodically unordered and microcosmic and macroscopic ununiformity; The heterogeneity of convection current causes producing temperature oscillation in molten silicon, and oscillation amplitude increases with the increase of thermograde.These temperature variation with owing to the inhomogeneous fringe spacing that forms of the impurities concentration distribution in the crystal is relevant, as shown in Figure 1.Because the existence of temperature instability, lead at crystal-melt interface place and to change local growth and melt back.This growth is solidified and the melt back phenomenon, in the allomeric formation of microdefect relevant, Fig. 2 is illustrated in when making Si the curly grain that the microdefect because of material produces.Especially concentration and the distribution at silicon intermediate gap oxygen is to cause fault, and heat such as dislocation loop and throw out induce the reason of defective.Therefore, desire improves quality of semiconductor devices and yield rate, need accurately control the concentration and the distribution of oxygen.

Suitable applying a magnetic field can obtain the effective monitoring to thermal convection, and the concentration of oxygen and distribution are tended towards stability.

Nineteen fifty-three Thompson is to the interaction between conductive fluid and magnetic field, done theoretically and analyzed (referring to WB.Thompson phil, Mag, Ser7, Vol42, NO335(1951)) conclusion that draws thinks, utilizes magnetic field to increase the viscosity of conductive melt effective exercise, can control the intensity of free convection easily.According to Lenz's law: when the conductor cutting magnetic line movement, in conductor, produce induced current, the motion of the magnetic field resistance conductor of induced current.Same principle can be applicable to the convective motion of silicon melt in the magnetic field.

Magnetic field both can change the convection action of silicon melt, had also just controlled quartzy fusion speed indirectly and the transporting of interface, can obtain 2 * 10 with the magnetic field single crystal growing furnace according to reports ¹⁷/ centimetre ³The crystal of low oxygen concentration can be eliminated swirl defect, fault, oxide precipitation and produce relevant phenomenons such as hot alms giver, thereby can obviously improve the homogeneity (, openly speciallyying permit the clear 58-190891(1983 of communique (A)) of material, the Yi Zeshen good fortune referring to Gang Cunmao, openly specially permit the clear 56-104791(1981 of communique (A)), T, Suzuki, at al, UK Patent, Aplication GB 21029267A(1983) and2059932(A))

11 in the total accompanying drawing of this specification sheets.Fig. 1 represents the impurity striation in the czochralski silicon monocrystal.Fig. 2 is illustrated in the curly grain that produces because of the microdefect in the material when making Si.Fig. 3 represents the relation of oxygen level and magneticstrength in the silicon chip.Fig. 4 represents to add the improved situation of silicon single-crystal homogeneity behind the magnetic field.Fig. 5 is the transverse magnetic field single crystal growing furnace schematic diagram that is made of hollow saddle-type coil, and 1 is furnace main body among the figure, and 2 is electro-magnet, and 3 is direct current power source.Fig. 6 adds the transverse magnetic field single crystal growing furnace schematic diagram that armature constitutes by iron core, and 1 is the Ar import among the figure, and 2 is that silicon single-crystal 3 is stay-warm case, and 4 is magnetic pole, and 5 are molten silicon.

The vertical magnetic field single crystal growing furnace schematic diagram that Fig. 7 is made up of two groups of fixed air core coils, 1 is body of heater among the figure, and 2 is coil, and 3 is direct current power source.

The vertical magnetic field single crystal growing furnace schematic diagram that Fig. 8 is made up of one group of fixation hollow spiral tube, 1 is crystal among the figure, and 2 is spiral tube, and 3 is well heater, and 4 is crucible, 5 are molten silicon.

Fig. 9 is the synoptic diagram of molten silicon thermal convection in the crucible.

Figure 10 is the method synoptic diagram of pulling monocrystal silicon in non-linear magnetic field, and 1 is molten silicon among the figure, and 2 be crucible, and 3 is magnetic line of force, and 4 is crystal ingot, 5 be crucible on magnetic field, 6 is that crucible is in the lower end, magnetic field.

Figure 11 is the adjustable magnetic field single crystal growing furnace schematic diagram in the totally enclosed spiral tube of outer wall position, and 1,2 is hydraulic actuator among the figure, 3 is magnet ring, and 4,5 is spiral tube, and 6 is water cooler, 7 is cooling water outlet, and 8 is the cooling water inlet, and 9,10,11 for being used for the porthole of various objectives, 12 is stay-warm case, and 13 is heating member, and 14 is the crucible holder, 15 are molten silicon, and 16 is crucible, and 17 is internal protecting wall, 18 is the body of heater upper end cover, and 19 is the body of heater lower end cover, and 20 is armature.

Fig. 3 is with oxygen content change rule in the CZ silicon single-crystal of transverse magnetic field drawing.Fig. 4 adds one of homogeneity is improved in the silicon single-crystal behind the magnetic field microtexture example (referring to TSuzuki, at al, Semiconductor Silicon(1981)) add as seen therefrom that the oxygen level in the monocrystalline tends towards stability behind the magnetic field, the homogeneity of material improves.

Currently mainly take dual mode when magnetic field is used to draw the CZ silicon single-crystal, a kind of mode is to use transverse magnetic field, be the signal schematic diagram of transverse magnetic field single crystal growing furnace as shown in Figure 5 and Figure 6, but transverse magnetic field is more serious to the influence of heating member.Another kind of mode is to draw the CZ silicon single-crystal with vertical magnetic field, equipment used as shown in Figure 7 and Figure 8 (referring to Georgy Fiegl, Solid State Teohnoiogy, Vol26, NO.8(1983) P.121, and Keigo Hoshikava Jap J.Appl.Phys., VOL.21,9, L545-547(1982) (1982) or Chinese translation: Zhang Xiujun translates, semi-conductor magazine, 1983,5, P52).This vertical magnetic field single crystal growing furnace though solved the influence of transverse magnetic field to heating member, has weakened the controllability of temperature fluctuation.This is because vertical magnetic field is bigger than the B part to the restraining effect of the convection current of the part of the A among Fig. 9, in addition, the formation of this class vertical magnetic field, all be that air core coil with no iron core and armature produces, therefore need very big power source (generally at 60-7QKW) could produce enough magneticstrengties, cause very big energy consumption.

In order to overcome the shortcoming and defect of transverse magnetic field and vertical magnetic field single crystal growing furnace, the nonlinear area that the present invention uses magnetic field that spiral tube produces comes pulling monocrystal silicon, to obtain the as far as possible big inhibition effect of magnetic field, designed a kind of single crystal growing furnace that uses this method to be achieved simultaneously to molten silicon thermal convection.

Main points of the present invention are to utilize the spiral tube group with different interior warps to produce magnetic field, and the magnetic line of force of the top and bottom in this magnetic field has outside open hydraucone shape respectively, as shown in figure 10.When pulling monocrystal, adjust the relative position of spiral tube and crucible, make crucible be in the nonlinear area of upper end, magnetic field or lower end toroidal.In this zone, the movement locus of magnetic line of force direction and molten silicon thermal convection approaches quadrature, thereby can obtain the molten big as far as possible inhibition effect of silicon thermal convection.

For this method is achieved, the present invention has designed the adjustable magnetic field single crystal growing furnace in the totally-enclosed spiral tube of a kind of outer wall position, this single crystal growing furnace is by three hydraulic actuators, magnet ring, spiral tube armature, body of heater is end cap up and down, crucible, stay-warm case, parts such as heating member and crucible holder are formed, spiral tube has 11 groups, and 5 groups of the upper end have bigger internal diameter, and its internal diameter is 380 millimeters, 6 groups of the lower end have less internal diameter, its internal diameter is 350 millimeters, is separated by by water cooler between every group of 11 groups of spiral tubes, and the spiral tube group is carried a load on the back by magnet ring, magnet ring is supported by three synchronous hydraulic actuators, when crystal pulling, can adjust spiral tube group and crucible relative position, make crucible be in the nonlinear area in magnetic field that spiral tube produces, thereby effectively suppress the thermal convection of molten silicon by hydraulic actuator.Another characteristics of this single crystal growing furnace are the shapes that is made into the furnace wall as the armature of spiral tube, while is as the outer furnace wall of whole body of heater, the end cap up and down of body of heater also is to make with ferromagnetic material, it and furnace wall and magnet ring constitute enclosed magnetic loop, to increase magneticstrength to greatest extent and to reduce leakage magnetic flux, in the body of heater upper end, be provided with three vision slits, so that the control of observation operation when the seeding shouldering and isodiametric growth process.Vision slit 9 is again the fire door of equipment such as heating member heat-insulation system etc. in filling raw material and the loading and unloading stove simultaneously, makes easy to operate.

Because spiral tube added armature, and body of heater makes full-closed structure, therefore the magnetic field that only just can produce 1500-2000 Gauss with the direct current power source of 10KW.The present invention selects the top condition of crystal pulling by the relative position of adjusting screw pipe and crucible, introduces in monocrystalline thereby control oxygen preferably, reduces and draws the temperature fluctuation that thermal convection causes in the prosperous process.For producing the higher silicon crystal of integrity, created condition.Because the appropriate design on the furnace binding can be saved the energy greatly, reduce production costs simultaneously, thereby obtain bigger benefit economically.

Claims (2)

1, a kind of in non-linear magnetic field the method for pulling monocrystal Si, it is characterized in that this non-linear magnetic field is formed by the magnetic field superposition of the spiral tube group generation of two groups of different diameters, two spiral tube groups are supported by jacking system, in this magnetic field during crystal pulling, the crucible that molten silicon is housed is placed in the spiral tube group, adjusting jacking system makes the spiral tube group move with respect to crucible, make crucible place the linearity region and the nonlinear area in stack magnetic field respectively, the adjustment program should guarantee that the movement locus of magnetic line of force direction and molten silicon thermal convection approaches quadrature all the time.

2, a kind of single crystal growing furnace of implementing the described method of claim 1 comprises the jacking system magnet ring, the spiral tube group, water cooler, stay-warm case, heating member, the crucible holder, crucible, internal protecting wall, end cap up and down, armature, it is characterized in that spiral tube group (4) and spiral tube group (5), have different internal diameters, each spiral group is made up of discrete winding, be separated by by water cooler (6) between the winding, armature (20) is made furnace wall shape, with spiral tube group (4,5) cover on wherein armature (20) and end cap (18 up and down, 19) and magnet ring (3) constitute a closed magnet circuit, have vision slit (11) on the armature (20), internal protecting wall has vision slit (9 on (17), 10).

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