JP2003128492A - Method for producing polycrystalline silicon for semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems of deformation of a shape including a horizontal cross section, development of a popcorn and fluctuation of an outer diameter, not by ventilation from the upper part of a furnace nor using a multiple nozzle as is in conventional ventilation from the bottom part of the furnace at a low cost and economically. SOLUTION: In producing the polycrystalline silicon for the semiconductor using a chlorosilan as a raw material by gas-phase growth, the surface temperature of the rod is maintained within the range between 950 and 1,050 deg.C and the feeding rate of the raw material gas per unit surface area is regulated within the range between 3.5×10<-4> and 9.0-×10<-4> mol/cm<2> min in reaction time zone when the rod surface area is 20% or more of that at the end of the reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a silicon single crystal.
Manufacture of semiconductor grade polycrystalline silicon used for manufacturing materials
About the method. [0002] 2. Description of the Related Art Silicon material, which is a material for semiconductor devices, is used.
Crystals are mainly made of polycrystalline silicon
Manufactured by the key method, the polycrystalline silicon is
It is mainly manufactured by a vapor growth method called Siemens method.
ing. Semiconductor grade polycrystalline silicon by Siemens method
In the manufacture of blast furnaces, multiple cylinders are placed in a bell jar type reactor.
A core rod is installed and heated by electricity. In this state,
Mixing of trichlorosilane and hydrogen as raw material gas in furnace
By supplying gas, the surface of the silicon core rod is sealed.
Recon precipitates and the core rod grows. Supply of raw material gas and
Gas discharge is usually performed from the bottom of the furnace where the furnace structure is simple.
You. Production of such semiconductor grade polycrystalline silicon
Now, in order to improve productivity, the reactor was enlarged and
For example, the number of silicon core bars to be installed is several tens to one hundred
More than ten are being done. That is, many at once
Production by depositing a large amount of polycrystalline silicon
This improves the performance. [0005] However, the size of such a reactor has been increased and
According to this increase in the number, while productivity will increase,
The gas supply to the silicon rod surface becomes uneven,
Or irregularities called popcorn on the surface,
The problem of defective shape such as non-uniform rod diameter occurs
I do. This shape defect reduces the yield when collecting products.
Causes popcorn, and furthermore, irregularities called popcorn
May cause abnormal growth and reduced cleaning of the rod surface.
You. As a measure for solving this problem, a special
No. 6,172,093 discloses that a plurality of
And a plurality of source gas nozzles at the top of the furnace.
It describes that the gas outlets are evenly arranged. Ma
Japanese Patent No. 2867306 discloses a silicon rod.
An upper nozzle for supplying raw material gas toward the upper part,
For the lower part that supplies raw material gas toward the lower part of the recon rod
A technique using a nozzle in combination is described. [0007] SUMMARY OF THE INVENTION However, these
The solution for the shape defect has the following problems. [0008] JP-A-6-172093 describes
Is to supply raw material gas from the bottom of the furnace and
The gas outlets are evenly distributed in the
Cannot be sufficiently eliminated. In other words,
In order to extinguish it,
The amount of source gas needs to be secured. Raw materials
If the supply amount is small, the precipitation of silicon crystals becomes insufficient and
The surface shape deteriorates. When the raw material supply becomes excessive, the raw material gas
Removes heat from the electrically heated silicon rod.
The temperature of the silicon rod drops locally,
The horizontal cross-sectional shape of the rod is
Become [0009] The deterioration of the horizontal cross-sectional shape is due to its cross-sectional shape.
Does not become a perfect circle, and causes ovalization and egret.
This deterioration not only reduces the yield, but also reduces the axial
Increases variation in diameter and reduces polycrystalline silicon rod
When used as a charge rod or additional charge rod
, Cracks during melting of raw material due to increase in residual stress and falls
Increase the risk of doing. The deterioration of the surface shape is caused by popcorn.
Is not sufficiently resolved due to
No. In addition to these, Japanese Patent Application Laid-Open No. 6-172093
According to the measures described in the official gazette, a gas outlet is
However, the upper part of the furnace is
Exhaust pipes where polymer adheres to the upper part of the furnace
Is not realistic. On the other hand, it is described in Japanese Patent No. 2867306.
Measures to effectively suppress irregularities on the rod surface
For each of the upper and lower nozzles,
An independent gas supply system must be provided,
An increase in equipment costs due to the complicated structure becomes a problem. Also,
When adopting the double tube type nozzle described in the publication,
The cost of processing consumable nozzles
The number of nozzles per furnace in large furnaces
There is a big economic problem. An object of the present invention is to improve the horizontal cross-sectional shape,
The problem of shape deterioration including top cone generation and variation in outer diameter
That can be solved economically without spending equipment costs
It is an object of the present invention to provide a method for producing graded polycrystalline silicon. [0014] [MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
In addition, the present inventors did not rely on the improvement of the furnace equipment,
We plan to suppress shape deterioration by changing
The experiment was repeated. As a result, control of rod surface temperature and
Shape by controlling the raw gas supply rate
It has been found that deterioration can be suppressed. That is, the supply amount of the raw material gas to the reactor is
Until this is essentially constant throughout the reaction,
It was simply increased as the rod grew, but this
Strict control of the feed rate according to the increase of the rod surface area
By controlling the furnace, the existing gas can be used without improving the furnace equipment.
In the form of supply and discharge of gas (as supply and discharge of furnace bottom)
Deterioration of horizontal cross-sectional shape of silicon rod, popcorn
Generation and deterioration of the shape including variation in outer diameter are suppressed.
You. The reason is as follows. As described above, in order to eliminate the deterioration of the shape,
Requires the necessary amount of material gas per polycrystalline silicon surface area.
Needs to be secured. That is, the raw material supply amount is small
Insufficient deposition of silicon crystals causes deterioration of surface shape
I do. If the material supply becomes excessive, the horizontal cross-sectional shape of the rod
Worsens. Use the same amount of source gas throughout the reaction
When supplied, before the reaction where the surface area of the silicon rod is small
In the period, the raw material gas amount becomes excessive and the rod
The cross-sectional shape deteriorates. On the other hand, the surface area of the silicon rod is
In the latter half of the reaction, the amount of source gas is
The surface shape of the metal deteriorates. However, as the rod grows,
Increases the gas supply over the entire reaction period.
To secure the required amount of source gas per rod surface area.
From both the horizontal cross-sectional shape and the surface shape
The effect that shape deterioration is reduced can be obtained.
Conventionally, the gas supply was increased with the rod growth
Was partly done, but the supply was simply
It is set from the point of mass balance, and from the point of surface shape,
The supply per unit area was significantly short. Method for producing semiconductor-grade polycrystalline silicon of the present invention
The law was developed based on this knowledge,
Semiconductor-grade bonding by vapor phase growth method using rosilanes as raw material
Rod surface area at the end of the reaction when producing crystalline silicon
In the reaction time zone of 20% or more of
Maintain in the range of 950 to 1050 ° C.
The raw material gas supply amount per unit surface area is 3.5 × 10^-Four~
9.0 × 10^-Fourmol / cm^Twois managed within the range of min.
You. Rod surface temperature and raw material per unit surface area
The rod surface area ends the reaction during the maintenance period of the feed gas supply
The reaction time zone of 20% or more of the time is the rod surface area
Is less than 20% at the end of the reaction,
The maintenance is not important. That is, the rod table
At the beginning of the reaction when the area is less than 20% at the end of the reaction,
Rod surface temperature and source gas supply per unit surface area
Does not significantly affect the rod shape. why
Then, if the seed core of polycrystalline silicon is mass-produced industrially,
Normally from a polycrystalline silicon rod for easy processing
The cut-out square bar of several mm is used. Silicon lock
Current density during heating of the rod is high at the center of the rod cross section.
The rod surface temperature is the distance from the center to the rod surface.
The effect of separation is great. At the beginning of the reaction, the rod cross section is square
Due to differences in the distance from the rod center to the surface
Rod surface temperature is not stable. Therefore, the rod shape
The rod surface temperature and unit area
Of raw material gas does not significantly affect rod shape
It is. The rod surface area is 20% or more at the end of the reaction.
During the reaction time, the rod surface temperature was set to 950 to 105
It is necessary to maintain the temperature within the range of 0 ° C during this reaction time.
When the pad surface temperature is lower than 950 ° C., the silicon crystal
Because the deposition rate is extremely low and productivity is
Not a target. If the temperature exceeds 1050 ° C., precipitation of silicon crystals
Is sufficient, but popcorn on the surface is extremely low.
At the end, the rod surface shape is significantly deteriorated. The amount of source gas supplied per unit surface area
Is 3.5 × 10^-Four~ 9.0 × 10^-Fourmol / cm^Twowithin min
3.5 × 10^-Fourmol / cm^TwoIf less than min
Indicates that the raw material gas supply to the rod surface is
Popcorn is generated, and the surface shape is deteriorated. 9.0
× 10^-Fourmol / cm^TwoIf the min.
The surface temperature decreases, and the rod near the gas supply port has an agglomeration.
Is generated and the horizontal cross-sectional shape deteriorates.
The yield with respect to the supplied amount is deteriorated. Method for producing semiconductor-grade polycrystalline silicon of the present invention
The method is effective for large furnaces where rod shape deterioration is remarkable.
Especially for furnaces with 30 or more rods (60)
It is. [0022] DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.
It will be described based on the following. FIG. 1 is preferably used to carry out the method of the present invention.
FIG. 1 is a configuration diagram of a reaction furnace to be used. The reactor 10 has a jacket structure at the furnace bottom 11.
Is a bell jar furnace covered with a bottomless furnace body 12 of FIG. Furnace bottom 1
A large number of silicon core rods 20 are provided on 1. Many
Several silicon core rods 20 are connected in a gate shape as two sets.
And electrically connected in series to a power supply (not shown).
Connected. In operation, a large number of silicon core rods 20 pass through.
The predetermined reaction temperature is maintained by electric heating. This state
Then, the raw material is introduced into the furnace from the gas supply nozzle 11a of the furnace bottom 11.
Gas is supplied. Furnace gas is supplied to the furnace.
The gas is discharged from the furnace bottom 11 through the gas discharge port 11b to the outside of the furnace.
Next is discharged. The source gas is, for example, trichlorosilane
It is a mixed gas of hydrogen. Gas supply nozzle 11a and gas
The discharge ports 11b are dispersedly arranged in the furnace bottom 11. By this operation, a large number of silicon core rods 2
, Silicon crystals are precipitated on each surface of the silicon core rod 20.
Grows to produce polycrystalline silicon. Manufacturing of semiconductor-grade polycrystalline silicon of this embodiment
In the manufacturing method, the table of the silicon rod 21 growing during the operation is displayed.
The surface temperature is detected. In addition, the silicon rod 21
The surface area is measured. The surface temperature of the silicon rod 21 depends on the furnace body 1
2 Measure with a radiation thermometer from the observation window provided in
Can be. In the case of temperature measurement with a radiation thermometer, use the observation window
If you can see even part of the silicon rod 21 from
Silicon rods located near the center as possible
Practical temperature measurement is also possible for 21. Observation window
If cloudy weather is an obstacle to temperature measurement,
Hydrogen gas at all times to prevent contamination,
It is effective to make the window position far away so that it is hard to receive radiant heat
It is. Another temperature measurement method is disclosed in Japanese Patent Application No. 11-32.
There is a method (described later) filed under No. 4000. For measuring the surface area of the silicon rod 21
As a method, there is an estimation method using gas chromatography. This is Hara
Gas supply and the amount of gas discharged from the reactor
Analyze composition using graphs, etc., and determine the weight of the generated silicon
You. The rod diameter is determined from the amount of silicon produced and the length of the core rod.
Calculate and calculate the surface area. Otherwise
For example, there is a direct measurement from the observation window. This is an observation window
This method directly measures the diameter of the silicon rod. B
If there are many rods and the rods overlap each other,
The diameter of the silicon rod arranged on the circumference becomes a representative value.
Still another method is disclosed in Japanese Patent Application No. 11-324000.
There is a method (to be described later) filed by the applicant. Filed in Japanese Patent Application No. 11-324000
Method, the diameter of the silicon rod at a particular point in time
At a specific time from the resistivity of the silicon rod obtained using
First step of estimating the silicon rod temperature at a point
And the silicon rod temperature estimated in the first step
Silicon after a predetermined time elapses from the vapor growth rate obtained
A second step of estimating the rod diameter;
The estimated diameter of the silicon rod in
And a third step of updating the silicon rod diameter to a later diameter.
Return. By setting the first specific point as the reaction initiation period
High accuracy in the transition of silicon rod diameter and surface temperature
Can be estimated. Manufacturing of semiconductor-grade polycrystalline silicon of the present embodiment
In the fabrication method, the silicon rod measured in this way
21 in the reaction time zone of 20% or more at the end of the reaction
The surface of the growing silicon rod 21 detected
The temperature is controlled at 950 to 1050C. Also measured
Calculated using the surface area of the silicon rod 21
Source gas supply per unit surface area of pad is 3.5 × 10
^-Four~ 9.0 × 10^-Fourmol / cm^TwoIt is managed within the range of min.
Specifically, as the surface area of the silicon rod 21 increases,
Supply of raw material gas
I do. Adjust the flow rate of the raw material gas supplied to the reactor 10
As a method, a flow meter attached to the supply pipe (specifically,
Is a mass flow meter).
The flow rate is increased by opening and closing the valve so that the
It is common to reduce. Adjust the measured data to the specified value
Valve control for computer control (PDI system)
Etc.) may be adopted. The surface temperature of such a silicon rod 21
And the maintenance of the supply of raw material gas per unit surface area
Source gas supply and gas discharge from the furnace bottom as before
Of the silicon rod surface
Is controlled. Further, unevenness of the rod diameter is suppressed. More water
Deterioration of the flat cross-sectional shape is suppressed. [0032] EXAMPLES Next, examples of the present invention will be described.
The effect of the present invention is clarified by comparing with an example.
You. In each example, the number of rods is 72 (36 pairs).
And Silicon mandrel is 9mm square, product rod diameter
Is 130 mm. As a raw material gas,
The run was diluted to 8 times the molar ratio with hydrogen gas and supplied to the reactor.
Paid. Reaction with a rod surface area of 20% or more at the end of the reaction
In the time zone, the rod surface temperature is 990 to 1010 ° C.
Maintained. And raw material gas per unit surface area
The supply amount was controlled as shown in FIG. Comparative Example 1 and Comparative Example 2 in FIG.
And Conventional Example 2. In these examples, almost all phases of the reaction
The raw material gas was controlled at a constant supply rate over the period. others
Therefore, the raw material gas supply per unit surface area
It decreases greatly with the increase of the surface area to surface area ratio,
In the reaction time zone where the surface area ratio is 20% or more, 3.5
× 10^-Four~ 9.0 × 10^-Fourmol / cm^Twodeviating from min
did. As a result, in Comparative Example 1, the raw material gas was initially
Due to the large supply, egrets occurred and even in the second half
The shape could not be recovered. In Comparative Example 2, initially
Egret occurs, popcorn with uneven surface in the second half
did. The minimum value of the surface area ratio is the surface area of the silicon core bar.
About 9%, which corresponds to In Example 1 and Example 2, the rod surface area
By increasing the supply of source gas as the
In the reaction time zone where the surface area ratio is 20% or more,
3.5 x 10 gas supply^-Four~ 9.0 × 10^-Fourmol / cm^Twom
It was managed within the range of in. Manufactured polycrystalline silicon lock
The surface of the metal was smooth without irregularities. Rod diameter is 130
mm ± 2 mm. Horizontal cross section is almost perfect circle
Egre does not occur near the source gas supply port due to its shape
Was. In Comparative Examples 3 and 4, the surface area ratio was 2
The supply amount of the source gas in the reaction time zone of 0% or more is 3.5
× 10^-Fourmol / cm^Twoless than min, produced polycrystalline
The surface of the silicon rod has large irregularities, and between the irregularities
Resulted in a pinhole-like hole. The rod diameter is
There is a variation of 10mm in diameter between near and far from the spout
Was. The horizontal cross section is not a perfect circle, and the difference between the major axis and the minor axis is 5
mm elliptical shape. In Comparative Example 5, the surface area ratio was 20% or more.
The supply amount of source gas in the time zone is 9.5 × 10^-Fourmol /
cm^Two11 × 10 over min^-Fourmol / cm^Twomin. Manufacture
The surface of the polycrystalline silicon rod is smooth without irregularities
there were. The rod diameter was stable with little variation,
Regarding the horizontal cross-sectional shape, there is no
Occurred. The deposition rate of polycrystalline silicon was
Worse by 10%. Comparative Example 6 is Conventional Example 3. In this example,
Source gas supply in the reaction time zone where the surface area ratio is 20% or more
The salary is managed at a constant level, but the managed amount is 3.5 ×
10 ^-Fourmol / cm^Two2.0 × 10 below min^-Fourmol / cm^Twoin min
there were. The surface of the manufactured polycrystalline silicon rod is
Top cones were generated and the shape was extremely deteriorated. Horizontal section
There is no egret, but not a perfect circle, slightly elliptical
Became. [0039] As described above, the semiconductor of the present invention
The method for producing high-grade polycrystalline silicon uses chlorosilanes as a raw material.
Of semiconductor grade polycrystalline silicon by vapor phase growth method
When the rod surface area is more than 20%
During the working hours, the rod surface temperature is set to 950-1050.
° C, and per rod unit surface area
Source gas supply rate is 3.5 × 10^-Four~ 9.0 × 10^-Fourmol /
cm^TwoBy controlling within the range of min,
Deterioration, popcorn generation, bad shape including outer diameter variation
The problem of gasification, regardless of the use of exhaust gas at the top of the furnace or the use of a compound nozzle,
To spend equipment costs by using the same furnace bottom supply and exhaust
Can be solved economically.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a reactor suitably used for carrying out the method of the present invention. FIG. 2 is a graph showing a relationship between a rod surface area ratio and a source gas supply amount. [Description of Signs] 10 Reactor 11 Furnace bottom 12 Furnace body 20 Silicon mandrel 21 Silicon rod

Claims (1)

Claims 1. When a semiconductor grade polycrystalline silicon is produced by a vapor phase growth method using chlorosilanes as a raw material, a rod surface is required to be in a reaction time zone in which a rod surface area is 20% or more at the end of the reaction. The temperature is maintained within the range of 950 to 1050 ° C., and the supply amount of the raw material gas per unit surface area of the rod is controlled within the range of 3.5 × 10 ^{−4 to} 9.0 × 10 ⁻⁴ mol / cm ² min. A method of manufacturing semiconductor-grade polycrystalline silicon.