JP2003192487A - Method and apparatus for growing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To grow a large diameter and high quality single crystal. <P>SOLUTION: When the single crystal 19 is grown by a Czochralski method, a raw material melt is heated according to a heating temperature pattern that is determined by estimating the change with the passage of time of the diameter of the single crystal against the heating temperature pattern from the response characteristics of the diameter of the single crystal caused by the heating temperature of a heating means 15 for heating the raw material melt and then controlling so that the estimated value of the diameter coincides with the target value of the diameter previously set against the pulling length or the pulling time. The heating temperature pattern is determined by finely dividing the heating temperature changing in the growing process of the single crystal 19 every a specified time, then identifying the change amount of the diameter against each step-like change amount, estimating the diameter of the single crystal by superimposing these change amounts of the diameter, comparing the estimated values with the target diameter, and adjusting so as to eliminate the error. In a growth apparatus, the heating means is controlled by a control means according to the heating temperature pattern based on the growing method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to a single crystal such as a silicon single crystal by the Czochralski method (including a magnetic field application Czochralski method equipped with a device for applying a magnetic field to a raw material melt. The same applies hereinafter). TECHNICAL FIELD The present invention relates to a single crystal growth method and a single crystal growth apparatus grown from a raw material melt, and in particular, to a single crystal growth method and a single crystal growth method for improving the setting of a heating temperature pattern for heating a raw material melt for controlling the diameter of the single crystal. .

[0002]

2. Description of the Related Art There are various methods for growing a single crystal, and the most typical pulling method among them is the Czochralski method. In the growth of a silicon single crystal by the Czochralski method, as is well known, a seed crystal is immersed in a silicon raw material melt, and from this state, the seed crystal is pulled while controlling the pulling rate and the heating temperature of the raw material melt. As a result, a cylindrical silicon single crystal is grown below the seed crystal. And from the grown silicon single crystal,
A silicon wafer that is a material of a semiconductor device is collected.

In growing such a silicon single crystal, the diameter of the single crystal is controlled. As a conventional technique for controlling the diameter of a single crystal, a method for automatically controlling the diameter of a single crystal characterized by feeding back a deviation between a measured value of a single crystal diameter and a set value to a melt temperature or a pulling rate (special feature) Kai 57-175794). As represented by this method, the conventional method for controlling the diameter of a single crystal is a dynamic control in which the deviation of the diameter of the single crystal during pulling is fed back to the heater temperature for heating the raw material melt or the pulling rate. Further, Japanese Patent Laying-Open No. 4-149092 describes a method and a device for controlling the growth of a cone portion, but the present technique is also a dynamic control for controlling the diameter by operating the heater temperature during pulling.

The reason why the dynamic control is emphasized as the diameter control in the above conventional technique is as follows. That is, since there is a slight individual difference in the single crystal growth device for each device, the heating characteristics differ for each device. Further, even with a single manufacturing apparatus, differences in heating characteristics will occur due to changes over time in the parts that make up the manufacturing apparatus and replacement of parts. For this reason, the heater temperature pattern of the heating means set in advance is only one guide, and the diameter control must rely on dynamic control during pulling.

[0005]

The problem with the prior art relating to the above diameter control lies in the dynamic control carried out during the pulling of the single crystal. When controlling the deviation of the diameter by feeding it back to the heating temperature, it takes a long time from the operation of the heating temperature to the effect on the diameter of the single crystal. Therefore, it is difficult to control the desired diameter. Now that the diameter of the single crystal has become large, the time required to act on the diameter of the single crystal is further extended, and the difficulty is further increased.

On the other hand, when the deviation of the diameter is fed back to the pulling rate, the time from the operation of the pulling rate to the action on the diameter of the single crystal becomes short. However, it has been found that as the quality of the single crystal becomes higher, the correlation between the pulling speed and the quality becomes stronger, and it has been found that the allowable pulling speed deviation is very narrow. Therefore, the pulling speed cannot be controlled so much. That is, the diameter can be controlled by manipulating the pulling speed, but if the pulling speed is manipulated easily, the quality of the single crystal will be deteriorated, which will result in a fall.

As described above, as the diameter of a single crystal is increased and the quality thereof is improved, the problem of dynamic diameter control has become apparent. Further, as a problem that has been pointed out in the past, good diameter control is indispensable in order to suppress an increase in material loss due to outer peripheral grinding and to prevent deterioration in yield rate due to defective diameter.

From the above, the importance of diameter control independent of dynamic control during pulling has become more important as the diameter and quality have been further improved.

The present invention has been made in view of the above problems, and provides a heating temperature setting means for determining the diameter of a single crystal before pulling it, thereby maintaining the quality of the single crystal and improving the diameter defect. It is an object of the present invention to provide a single crystal growth method and a single crystal growth apparatus that perform diameter control to suppress yield failure due to

[0010]

In order to solve the above problems, a method for growing a single crystal according to a first invention is a heating means for heating a raw material melt when growing a single crystal by the Czochralski method. From the response characteristics that the heating temperature affects the diameter of the single crystal, the change over time of the single crystal diameter with respect to the heating temperature pattern is predicted, and the diameter predicted value and the preset target diameter value for the pulling length or pulling time are It is characterized in that the raw material melt is heated based on the heating temperature pattern determined by adjusting so as to match.

With the above structure, by heating the raw material melt based on a predetermined heating temperature pattern, it becomes possible to grow a single crystal having a large diameter while controlling its diameter accurately. This method for growing a single crystal is particularly suitable for controlling the shape of the shoulder portion up to the straight body portion that is the target diameter of the product.

The heating temperature pattern is obtained by subdividing the heating temperature, which changes during the growth process of a single crystal, at regular time intervals to specify the diameter change amount corresponding to each step change amount, and superimposing these diameter change amounts. It is desirable to make a determination by comparing the diameters of the single crystals that can be combined with the target diameter and adjusting them so as to eliminate those errors.

With the above structure, it is possible to absorb the influence of the heating temperature pattern on the diameter, which is different for each crystal growing device or for each history of the parts constituting the crystal growing device.
That is, by finely measuring the diameter of the single crystal in which the heating temperature is subdivided and the temperature (step change amount) changed in each part is changed, fine adjustment can be performed. As a result, the diameter of the single crystal that can be created by superimposing the amount of change in diameter at each part can be finely adjusted, and finely adjusted to eliminate the error from the target diameter, producing the best heating temperature pattern. can do.

The apparatus for growing a single crystal according to the second aspect of the invention comprises a heating means for heating the raw material melt based on a preset heating temperature pattern when growing the single crystal by the Czochralski method. The crystal growing apparatus is characterized by including control means for controlling the heating means according to the heating temperature pattern determined based on the single crystal growing method according to the invention.

With the above structure, by heating the raw material melt on the basis of the finely adjusted best heating temperature pattern, it becomes possible to grow a single crystal having a large diameter while controlling its diameter accurately. .

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A single crystal growing method and a growing apparatus according to the present invention will be described below.

[Single Crystal Growth Method] First, a single crystal growth method according to the present embodiment will be described.

The method for growing a single crystal according to the present embodiment is one in which, in the Czochralski method, heating control is performed based on a preset heating temperature pattern instead of the conventional dynamic control described above. When growing a single crystal by the Czochralski method, from the response characteristics of the heating temperature of the heating means for heating the raw material melt to the diameter of the single crystal, predict the change over time of the single crystal diameter with respect to the heating temperature pattern, The heating temperature pattern of the heating means is determined by adjusting the predicted value and the preset target diameter value for the pull-up length or pull-up time so that they match each other. And, the method for growing a single crystal that performs heating control based on this heating temperature pattern is also an effective method for controlling the diameter of the straight body part to be constant, but in particular, the straight body part that is the target diameter of the product is It is the most suitable method for controlling the shape of the shoulder.

Specifically, when a single crystal (semiconductor single crystal or the like) is grown from a raw material melt by the Czochralski method,
The heating temperature pattern of the heating means that is set to have a desired diameter with respect to the pulling length or pulling time is optimized, and then a single crystal is grown based on this heating temperature pattern.

In order to realize this, the following processing is performed. First, the effect of the heating temperature of the heating means on the diameter of the single crystal is formulated.

The basic formula is a diameter change amount corresponding to a step change amount of the heating temperature of the heating means, and can be expressed by the following formula (1). Here, the diameter change amount is d, the temperature decrease amount of the heating means is ΔT, the proportional constant is K, the time constant is T, and the dead time is L. Further, the subscript i corresponds to the order of steps when the heating temperature pattern continuously set with respect to time is divided into steps at regular time intervals.

[0022]

[Equation 1] A typical example of this equation is shown in the graph of FIG.

If the heating temperature pattern to be set is subdivided at regular intervals, it is possible to calculate the amount of change in diameter corresponding to each step-like change amount (temperature difference in each subdivided portion). . This conceptual diagram is shown in FIGS. 3 and 4. FIG. 3 is an example in which the heating temperature pattern is subdivided into steps at regular intervals. Here, the heating temperature is a relative temperature with the heating temperature at the start of the shoulder process as the reference temperature of 0 ° C. FIG. 4 shows the diameter change amount corresponding to each step change amount of the heating temperature pattern subdivided into the step shape of FIG. For example, the diameter change amount corresponding to ΔT1 shown in FIG. 3 is d1 in FIG. ΔT in FIG.
Similarly, 2 and ΔT3 respectively correspond to d2 and d3 in FIG. The diameter of the single crystal can be finally predicted as shown in FIG. 5 by superimposing the diameter variation amounts of FIG. Here, when the diameter of the single crystal is D, the following equation (2) is established.

D (t) = Σdi (t) (2) The prediction accuracy of the diameter depends on the prediction model. The parameters required for this prediction model are determined based on the actual track record. The influence of the heating temperature pattern on the diameter has individual differences, and differs depending on the crystal growing apparatus or the history of the parts constituting the crystal growing apparatus. Conversely speaking, for each crystal growth device,
Alternatively, if a single crystal is grown under the same conditions for each history of the components that make up the crystal growing apparatus, a single crystal having the same diameter can be repeatedly obtained. Therefore, by determining the parameters of the prediction model for each of the same conditions, it is possible to correspond to each crystal growing device or each history (change with time) of the components forming the crystal growing device. The same condition data is created by accumulating the operating conditions of the crystal growing apparatus, the usage status of the components constituting the crystal growing apparatus, and the actual pulling value of the single crystal. Other data will be added to the database as needed. As a result, the numerical values under various conditions are made into a database for each crystal growing device and each component constituting the crystal growing device. Then, by specifying the states of the crystal growing apparatus and the parts constituting the crystal growing apparatus based on this database, it becomes possible to instantaneously extract the heating temperature pattern corresponding thereto.

In the present embodiment, the parameters of the model are the proportional constant, the time constant, and the dead time corresponding to each step, as described above. That is, if the number of steps is N, 3 × N is the number of parameters required for the model. These model parameters are determined so that the predicted diameter value matches the actual diameter value based on the actual heating temperature and the actual diameter value.

Next, a method of determining the heating temperature pattern will be described. The diameter for this heating temperature pattern is predicted using the above prediction model, that is, the diameter prediction model for which model parameters have already been determined. Then, the heating temperature pattern is reviewed until the prediction error becomes equal to or less than the desired setting value, and the heating temperature pattern when the diameter prediction error becomes equal to or less than the desired setting value is obtained in order to obtain the desired diameter pattern. It is determined as an optimized heating temperature pattern.

The method of determining the heating temperature pattern will be specifically described with reference to the flowchart shown in FIG. First,
A heating temperature pattern is set (step S1). This heating temperature pattern is set to an approximate value for the first time. From the second time onward, set the value slightly different from the previous value. Next, the predicted value of the diameter is specified by referring to the set heating temperature pattern with the prediction model (step S2). Next, it is judged whether or not the error between the expected value of the diameter and the target value is less than or equal to a desired set value (step S3).
If it is not below the desired set value, step S1
And step S2 are repeated. If it becomes less than the desired set value, the heating temperature pattern is determined (step S4).

A database of the determined heating temperature pattern of the heating means is set and set in the control panel of the crystal growing apparatus to grow a single crystal. That is, the single crystal is pulled based on the heating temperature pattern set corresponding to the pull length or pull time.

As a result, it becomes possible to pull the single crystal having a good diameter controllability while maintaining the quality of the single crystal.

A good diameter control is possible even for a large diameter single crystal, and a large diameter and high quality single crystal can be grown. As a result, the yield rate is improved and the manufacturing cost can be reduced.

[Single Crystal Growth Apparatus] Next, a crystal growth apparatus will be described with reference to the drawings. FIG. 6 is a configuration diagram of the crystal growth apparatus according to the present embodiment.

The crystal growing apparatus comprises a cylindrical furnace body 11. A quartz crucible 12 is provided in the center of the furnace body 11.
Are arranged. The quartz crucible 12 is filled with a raw material melt 13 in which a single crystal raw material is melted. Crucible 12
A heating means 1 for heating the raw material melt 13 is provided around the periphery of the
5 is provided.

Above the furnace body 11, a cylindrical casing 11a elongated from the furnace body 11 is connected. A wire 17 is hung in the casing 11 a so as to be concentric with the rotation shaft 14 of the crucible 12. A seed holder 17a is attached to the lower end of the wire 17, and a seed crystal 17b is attached to this. And seed crystal 1
7b is immersed in the raw material melt 13 in the quartz crucible 12, and the seed crystal 17b is raised while rotating the crucible 12 and the seed crystal 17b from this state, so that the silicon single crystal 19 is grown thereunder.

Due to the rotation and raising of the seed crystal 17b,
At the top of the casing 11a, the wire rotating device 20
And a wire lifting device 21.

The wire rotating device 20 includes a wire rotating motor 23, a drive pulley 24, a driven pulley 25, and a belt 26. The drive pulley 24 is attached to the rotating shaft of the wire rotating motor 23. The driven pulley 25 is connected to the wire 17 via the wire lifting device 21. The belt 26 is stretched around the drive pulley 24 and the driven pulley 25 to connect the wire rotating device 20 and the wire elevating device 21. As a result, the wire rotating device 20 directly rotates the wire lifting device 21, and indirectly through the wire lifting device 21.
It is designed to rotate 7.

The wire lifting device 21 comprises a wire lifting motor 28 and a bobbin 29. The wire lifting motor 28 is coupled to the bobbin 29 by a gear so as to rotate the bobbin 29. The wire 17 is wound around the bobbin 29. As a result, the bobbin 29 is rotated by driving the wire lifting motor 28, and the wire 1 wound around the bobbin 29 is rotated.
7 is moved up and down.

An elevating means 30 is constituted by including the wire 17, the wire rotating device 20, and the wire elevating device 21.

An observation window 11b is provided in the upper portion of the furnace body 11, and a diameter sensor 31 is installed on the side facing the single crystal 19 with the observation window 11b interposed therebetween. The diameter sensor 31 is connected to the image processing unit 32, and the measurement / detection means 33 is configured to include them.

A control board 40 is connected to the heating means 15 and the wire lifting motor 28. This control panel 40 is
By controlling the heating means 15 and the wire lifting motor 28, the heating temperature and the pulling length or pulling time of the single crystal are controlled by preset values. That is, the pulling rate and the heating temperature of the heating means 15, which strongly influence the diameter of the single crystal and the quality of the single crystal, are controlled in a pattern preset on the control board 40 during the pulling of the single crystal. Has become.

As the method for determining the heating temperature pattern for controlling the diameter which is important in the present invention, the above-mentioned single crystal growing method was used. It was determined by using a predictive model to predict the diameter of single crystals. That is, in the control panel 40,
A CPU, a memory, and the like are provided, and the processing functions of the above-described single crystal growing method are stored. Specifically, the control panel 4
0 controls the wire rotating motor 23 and the wire elevating motor 28 at a set value, and the heating means 15
Was controlled based on the heating temperature pattern determined by the above single crystal growth method.

Specifically, the heating temperature pattern of 120 minutes was divided into steps of 1 minute, and 360 model parameters were determined. At this time, the standard deviation of the diameter prediction error by the prediction model was 0.32 mm.

Next, when the heating temperature pattern determined by the above method was set on the control panel 40 of the crystal growing apparatus and the single crystal was pulled up, good results were obtained. That is, it was possible to manufacture a single crystal having good diameter controllability while maintaining the quality of the single crystal. An example of this is shown in FIG.

[0043]

As described in detail above, according to the single crystal growth method and the single crystal growth apparatus of the present invention, it is possible to maintain the quality of the single crystal and to pull up the single crystal having a good diameter controllability. It will be possible.

In particular, it becomes possible to control the diameter of a single crystal having a large diameter well, and it is possible to grow a high quality single crystal having a large diameter. As a result, the yield rate is improved and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a flowchart for determining a heating temperature pattern.

FIG. 2 is a basic diagram showing modeling of a diameter change amount.

FIG. 3 is a graph showing an example of subdivision of a heating temperature pattern.

FIG. 4 is a graph showing each amount of change in diameter corresponding to each heating temperature.

FIG. 5 is a graph for predicting the diameter of a single crystal.

FIG. 6 is a configuration diagram showing a growing apparatus used in the single crystal growing method according to the embodiment of the present invention.

FIG. 7 is a graph showing an example of manufacturing a single crystal.

[Explanation of symbols]

11: furnace body, 11a: casing, 11b: observation window,
12: crucible, 13: raw material melt, 15: heating means, 17:
Wire, 17a: seed holder, 17b: seed crystal, 1
9: Single crystal, 20: Wire rotating device, 21: Wire lifting device, 23: Wire rotating motor, 24: Drive pulley,
25: driven pulley, 26: belt, 28: wire lifting motor, 29: bobbin, 30: lifting means, 31: diameter sensor, 32: image processing unit, 33: measuring / detecting means, 4
0: Control panel.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koji Kato             2201 Kamioda, Oita, Kohoku-cho, Kishima-gun, Saga Prefecture             Sumitomo Metal Industries, Ltd. Sitix Business Division             Within F-term (reference) 4G077 AA02 BA04 CF10 EA02 EG20                       EH04 EH10 HA12 PF02 PF16

Claims (3)

[Claims] 1. When growing a single crystal by the Czochralski method, from the response characteristics that the heating temperature of the heating means for heating the raw material melt influences the diameter of the single crystal, the change of the single crystal diameter with time with respect to the heating temperature pattern is shown. Predicting, heating the raw material melt based on a heating temperature pattern that is determined by adjusting the predicted diameter value and the preset target diameter value for the pulling length or pulling time to match Method for growing single crystal. 2. The method for growing a single crystal according to claim 1, wherein the heating temperature pattern is divided into heating temperatures that change during the growing process of the single crystal at regular intervals to correspond to individual step-like changes. By specifying the diameter change amount to be compared, by comparing the diameter of the single crystal made by superimposing these diameter change amount and the target diameter, by adjusting to eliminate those errors,
A method for growing a single crystal characterized by determining. 3. A single crystal growing apparatus comprising a heating means for heating a raw material melt based on a preset heating temperature pattern when growing a single crystal by the Czochralski method. A single crystal growth apparatus comprising: a control means for controlling the heating means according to the heating temperature pattern determined based on the single crystal growth method described in 1.