JPH11278983A - Cutting of crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cutting a crystal, intended for reducing cutting frequency and avoiding the derivation of thin-walled products associated with the cutting operation, by estimating the oxygen concentration distribution in the axial direction of a single crystal grown by CZ process based on the relevant past results and then determining the positions to be cut at based on the oxygen concentration distribution thus estimated. SOLUTION: This method for cutting a crystal comprises the following procedure: the past operational results in respective ovens are stored in a host computer 20; when the operational conditions for the respective ovens for producing a targeted item are inputted, a computer 10 receives the operational results corresponding to the respective ovens from the host computer 20 and stores them in a database; using the above operational results, oxygen concentration distribution characteristics are prepared; using these characteristics, the oxygen concentration distribution in the axial direction of a single crystal to be grown is estimated; the computer 10 determines a range within which the single crystal can be made into a successful product based on the quality specification (oxygen concentration distribution) of the product which has received orders and the estimated oxygen concentration range; while considering order volume, the product is assorted starting from the priority level; thereby the product can be exhaustively taken from the whole single crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crystal cutting method used for collecting a product from a single crystal such as silicon produced by the CZ method.

[0002]

2. Description of the Related Art A silicon single crystal used as a material of a semiconductor device is industrially manufactured mainly by a CZ method. The CZ method is, as is well known, a method in which a seed crystal is immersed in a silicon raw material melt contained in a quartz crucible, and the seed crystal is pulled up while rotating the seed crystal and the quartz crucible in opposite directions. In this method, a single crystal of silicon is grown.

Incidentally, specific resistance and oxygen concentration are important as the quality of a silicon single crystal. For this reason, demands for these characteristics from the user side are very fine and severe, and therefore, the types of products manufactured by the manufacturers are extremely diverse. And
On the manufacturer side, products of the type that satisfies the required quality (target type) are manufactured industrially using multiple pulling furnaces according to the order status. This is the basic situation of mass production of single crystals.

[0004] However, it is a very difficult technology to economically produce a product of the quality required by the user. This is because, in a single grown single crystal, few parts satisfy the required quality, and many parts that do not meet the required quality are treated as loss (dissolved raw material with low economic value), so that the yield in product extraction is low. Because it is very low.

That is, in the production of a silicon single crystal using the CZ method, as shown in FIG. 1A or FIG.
Due to the segregation of the doping element as the pulling proceeds, the specific resistance of the grown single crystal changes in the pulling axis direction. In addition, the oxygen concentration of the single crystal also changes in the pulling axis direction due to a decrease in the amount of the melt as the pulling proceeds. For these reasons, there are very few parts (target parts) that satisfy the required quality in both the specific resistance and the oxygen concentration, and usually about 50%.

In order to solve this problem, for example, it has been considered to collect a plurality of types of products having different required qualities from one grown single crystal. That is, one single crystal is distributed to a plurality of types of products by utilizing the variety of required quality of products. Then, the applicant has made this distribution as follows.

[0007] As shown in FIG.
Is cut and removed. Blocks 41 and 42 of predetermined length (for example, 200 mm)
・ Cut equally. Measure the oxygen concentration at each cutting position,
Obtain the oxygen concentration at both end faces of each block.

Now, in blocks 41 and 42, the oxygen concentration at both end surfaces satisfies the oxygen specification of the target product, and block 43
Then, it is assumed that only the oxygen concentration at one end surface satisfies the oxygen specification of the target variety, and the oxygen concentration at the other end surface deviates from the oxygen specification of the target variety. If you do, block 4
1, 42 are directly collected as target varieties. As for the block 43, the block 43 is cut again at a position where it returns to the one end from the other end surface. This re-cutting is called cutback, and the cutting margin L is determined based on the rate of deviation of the oxygen concentration from the required specifications. That is, when the deviation rate is large, the cutback is made large, and when the deviation rate is small, the cutback is reduced.

When the cutting back is completed, the oxygen concentration is measured again at the cutting position. If the measured value satisfies the required specifications, the main unit 43a is collected as a target product. If the measured value does not satisfy the required specifications, the main unit 43a is switched back again. Thus block 4
Collect the target variety from 3. The thin portion 43b derived from the cutback is transferred to another type together with other blocks 44. Here, switching back is performed appropriately.

[0010]

According to such a product sampling method, a plurality of types of products are sampled from a single single crystal, and the yield is improved as compared with a case where only the target type is sampled. However, since cutting is repeatedly performed on one single crystal, not only is it inefficient, but also the cutting blade is severely worn and the cutting tool cost is increased. In addition, a large number of thin blocks are generated along with the cutback. Since these thin blocks often cannot be cut into wafers as they are, a plurality of thin blocks are laminated and provided for cutting as a block having a sufficient thickness, but the lamination requires time and effort.

An object of the present invention is to provide a crystal cutting method capable of greatly reducing the number of cuts at the time of product sampling and also avoiding the derivation of a thin product accompanying the cutting.

[0012]

In the mass production of single crystals by the CZ method, as described above, a plurality of pulling furnaces are used to manufacture products of the same kind, but the single crystals grown in each furnace are used. The quality distribution in the axial direction of the crystal, particularly the oxygen concentration distribution, differs greatly as shown in FIGS. 1 (a) and 1 (b). This is due to deterioration of parts, slight differences in furnace body characteristics, and inaccuracies in instruments, but regardless of the cause, even if it is attempted to pull up products with the same characteristics in each furnace, the axial The oxygen concentration distribution is greatly different, and even in the same furnace, the oxygen concentration distribution changes with each pulling. For this reason, it is considered impossible to accurately estimate the oxygen concentration distribution of the single crystal. Therefore, in the case of collecting a product from the single crystal, the oxygen concentration was actually measured by cutting as described above.

However, when the variation in the oxygen concentration distribution among furnaces and the change in the same furnace were investigated in detail, the oxygen concentration distribution characteristics of each furnace became clear by using the past operation data of each furnace. As a result, it has been found that the oxygen concentration distribution of a single crystal can be estimated with such high accuracy that it can be used for sorting single crystals, and the present invention has been completed.

According to the single crystal cutting method of the present invention, a single crystal is grown by the CZ method, and the oxygen concentration distribution in the axial direction of the single crystal to be grown is estimated from past operation results. Determining the cutting position based on this is a structural feature.

In the crystal cutting method of the present invention, it is preferable that the cutting position is determined so that a plurality of types of products having different oxygen concentration specifications are collected from the grown single crystal.

It is preferable that the oxygen concentration distribution characteristics in the crystal axis direction are grasped in a plurality of pulling furnaces, and the cutting position is determined based on the oxygen concentration distribution of the single crystal predicted from the characteristics.

In this case, it is preferable to update the oxygen concentration distribution characteristics of each pulling furnace every time the unit is pulled up by using the actually measured data of the oxygen concentration distribution of the single crystal.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

The crystal cutting method according to the embodiment of the present invention comprises:
It is used for production control of single crystals, and more specifically, for efficient product extraction from single crystals grown in a plurality of pulling furnaces. This production management is executed by the computer 10 as shown in FIG. The computer 10 is connected to the host computer 20 and the host computer 2
By exchanging information between the two, the processing of FIG. 3 is performed to finally indicate the cutting position of the single crystal. The instruction information is transmitted to the plurality of processing terminals 30, 30,.

The information received from the host computer 20 includes the order status, the product in process status, the quality record,
There are operation data, product specifications, etc. Information transferred to the host computer 20 includes single crystal cutting position information, quality sample extraction information, assignment instruction information, and the like.

The computer 10 includes a database for storing various information necessary for the operation received from the host computer 20, information generated in the computer 10 such as oxygen concentration distribution, operation processing result data, and the like. I have.

The manager successively inputs the quality specification, quantity and desired delivery date of the ordered product into the computer 10. In operation, the type with the highest priority is determined based on the current order status, and as a target type, the crystal is grown in multiple pulling furnaces to satisfy the order quantity of the type. Then, the manager inputs the operating conditions of each furnace for producing the target product to the computer 10 and instructs the distribution of the products. Then, the computer 10 extracts necessary information from the host computer 20 and executes the three programs shown in FIG. 3, that is, the priority data generation, the oxygen concentration table generation, and the crystal production system.

In the generation of the priority data, the priority is determined based on the desired delivery date of the product, the difficulty of the training, and the like. The determined priorities are stored in the database of the computer 10.

In preparing the oxygen concentration table, the oxygen concentration distribution is estimated as the internal quality of the single crystal grown in each furnace. Hereinafter, this step will be described in detail. Although the specific resistance and the oxygen concentration are important as the internal quality of the product, for convenience of explanation, only the oxygen concentration which is most difficult to manage will be described in detail.

The host computer 20 stores past operation results (operation conditions, oxygen concentration distribution, etc.) in each furnace. When operating conditions of each furnace for manufacturing a target product are input, the computer 10
The operation results corresponding to the operation conditions are stored in the host computer 20.
And store it in the database. Next, an oxygen concentration distribution characteristic (table for estimating the oxygen concentration distribution) is created using the operation results, and cultivation is performed using the oxygen concentration distribution characteristic (a table for estimating the oxygen concentration distribution) of each furnace. The oxygen concentration distribution in the axial direction of the single crystal is estimated.

Specifically, based on the quality performance data and the pulling performance data, 10
Oxygen specifications for batches, actual oxygen results, specification component sizes,
Generate intermediate data with edited feed amount. From the intermediate data, the average value of the actual oxygen data is obtained for each furnace / oxygen specification, rearranged in the axial direction of the single crystal, and registered as table data. By operating the registered oxygen concentration table, the oxygen concentration distribution is estimated, for example, every 1 mm. An example of the created oxygen concentration table is shown in Table 1, and the oxygen concentration distribution estimated from the table is shown in FIG.

[0027]

[Table 1]

In the crystal production system, products are sorted using the estimated internal quality distribution and the determined priorities.

That is, assuming that the quality specifications of the products stored in the computer 10 are shown in Table 2 and the estimated oxygen concentration distribution is shown in FIG. 4A, the distribution is performed as follows.

[0030]

[Table 2]

The type A is a main type (target type) designated with a predetermined oxygen concentration and has the highest priority. Each of the types a, b, c, d,... Is a sub-type designated with a predetermined oxygen concentration, and has lower priority than the main type A in order.

In the product distribution, the computer 10 first determines the quality specification (oxygen concentration distribution) of the ordered product and the estimated oxygen concentration range as shown in FIG.
Determine the range in which a single crystal can be commercialized. The target variety A can be collected from near the top of the single crystal to the middle. The product type a having the second highest priority has a high oxygen concentration and can be collected from the top of the single crystal.
The varieties b and d having the third and fifth priorities have a relatively low oxygen concentration and can be collected from the middle part of the single crystal to the vicinity of the bottom. In particular, the varieties b have a narrow range of oxygen concentration and strict quality specifications. It is a variety. Variety c with the fourth highest priority is
It has the lowest oxygen concentration and can be collected from the vicinity of the bottom of the single crystal. The product e having the sixth priority has a wide range of oxygen concentration and can be collected from almost the entire length of the single crystal.

Once the possible range of commercialization is determined, FIG.
As shown in (c-1), the final distribution of the products is performed from the priority order while taking the order quantity into consideration. That is, the variety A, which is the target variety, is allotted to all the available positions. The type a having the second priority is assigned to the top of the single crystal avoiding the overlapping part with the type A. The product type b having the third highest priority is preferentially allocated to the remaining portion. Subsequently, the varieties c, d, and e having the fourth, fifth, and sixth priorities are preferentially allocated to the remaining parts.

In the case where the order quantity of the product e is large, FIG.
As shown in 2), part of the type c is replaced with the type e. In addition, when the order quantity of the product type d is large, FIG.
As shown in 3), part of the type c is replaced with the type d.

Thus, the product is completely extracted from the entire single crystal in accordance with the order status, the yield when extracting the product from the single crystal is remarkably improved, and there is no excess or deficiency in the order.

In addition, in each furnace, single crystals are grown aiming at the type A, but since their oxygen concentration distributions are not the same, products that cannot be collected in one furnace can be collected in another furnace. By comprehensively sorting the single crystals grown in step (1), even in actual operation, products are collected from the single crystals with little or no excess or deficiency with respect to orders.

When a single crystal is grown in each furnace, the single crystal is cut according to the determined distribution. Further, the oxygen concentration of the single crystal is measured at the cutting position, and the data is fed back to the computer 10.

Strictly speaking, the oxygen concentration distribution characteristic (table for estimating the oxygen concentration distribution) in each furnace changes every time one single crystal is grown. For this purpose, the latest measured data is fed back to the computer 10. The computer 10 always creates an oxygen concentration distribution characteristic (a table for estimating the oxygen concentration distribution) using a predetermined number of latest data (for example, the latest 10 data). Thereby, the oxygen concentration distribution of the single crystal grown in each furnace is estimated with high accuracy.

[0039]

As described above, according to the crystal cutting method of the present invention, a single crystal is grown by the CZ method, and the quality distribution in the axial direction of the grown single crystal is estimated from past operation results. By determining the cutting position of the single crystal based on the obtained quality distribution, it is possible to directly cut out multiple types of products with different required oxygen concentration specifications when collecting products from the single crystal without excess or deficiency. Therefore, there is no need for equal-length cutting for actually measuring the oxygen concentration of the single crystal, and no need for cutting back. Therefore, the number of cuts at the time of product sampling can be greatly reduced, and the cost of the cutting tool for the cut can be significantly reduced. Further, since the derivation of a thin product due to the cutting can be avoided, the number of steps for cutting a single crystal into a wafer can be reduced.

[Brief description of the drawings]

FIG. 1 is a chart schematically showing a specific resistance distribution and an oxygen concentration distribution of a single crystal.

FIG. 2 is an apparatus configuration diagram of a production management system using a crystal cutting method according to an embodiment of the present invention.

FIG. 3 is a flowchart showing software of the production management system.

FIG. 4 is a conceptual diagram of a crystal cutting method in the production management system.

FIG. 5 is a conceptual diagram of a conventional crystal cutting method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Computer 20 Host computer 30 Information terminal 40 Single crystal 41, 42 .. block

Claims (4)

[Claims] 1. A method for growing a single crystal by the CZ method,
A crystal cutting method characterized by estimating the oxygen concentration distribution in the axial direction of a single crystal to be grown from past operation results and determining a cutting position based on the estimated oxygen concentration distribution. 2. The crystal cutting method according to claim 1, wherein a cutting position is determined in order to collect a plurality of types of products having different oxygen concentration specifications from the grown single crystal. 3. The cutting position is determined based on the oxygen concentration distribution characteristics in the crystal axis direction in a plurality of pulling furnaces and based on the oxygen concentration distribution of the single crystal predicted from the characteristics. Item 3. The crystal cutting method according to Item 1 or 2. 4. The crystal cutting method according to claim 3, wherein the oxygen concentration distribution characteristics of each of the pulling furnaces are updated every time the unit is pulled up, using the actually measured data of the oxygen concentration distribution of the single crystal.