阅读说明：本技术 直拉法生长硅单晶过程中测量晶体直径的方法 (Method for measuring crystal diameter in process of growing silicon single crystal by Czochralski method ) 是由 傅林坚 高宇 夏泽杰 陈丽婷 叶刚飞 胡建荣 李林 沈文杰 曹建伟 于 2019-10-11 设计创作，主要内容包括：本发明涉及单晶硅生产技术,特别涉及直拉法生长硅单晶过程中测量晶体直径的方法。包括以下步骤：(1)设置CCD摄像机,根据原始热场设计获得参照物直径Ф<Sub>1</Sub>,晶体实际直径,记为Ф；(2)晶体实际生长过程中,CCD摄像机计算得到图像中参照物直径记为φ1,参照物在硅熔体表面的倒影直径φ2,晶体与液面交界面图像,将此时晶体直径记为φ；(3)CCD捕捉到图像中参照物在液面垂直投影直径可近似计算φ<Sub>3</Sub>＝(φ<Sub>1</Sub>+φ<Sub>2</Sub>)/2,直径Ф<Sub>1</Sub>＝Ф<Sub>3</Sub>,图像中φ/φ<Sub>3</Sub>＝Ф/Ф<Sub>3</Sub>＝Ф/Ф<Sub>1</Sub>,即Ф＝Ф<Sub>1</Sub>×(φ/φ<Sub>3</Sub>)＝Ф<Sub>1</Sub>×[2φ/(φ<Sub>1</Sub>+φ<Sub>2</Sub>)]。本发明装置最终实现准确测量晶体直径和实时测量,从而提高晶体直径控制精度和工艺稳定性。(The invention relates to a monocrystalline silicon production technology, in particular to a method for measuring the crystal diameter in the process of growing silicon single crystal by a Czochralski method. The method comprises the following steps: (1) setting a CCD camera to obtain the diameter phi of the reference object according to the original thermal field design 1 The actual diameter of the crystal is recorded as phi; (2) in the actual growth process of the crystal, calculating by a CCD camera to obtain a diameter of a reference object in an image as phi 1, a reflection diameter phi 2 of the reference object on the surface of the silicon melt, and an interface image of the crystal and a liquid level, wherein the diameter of the crystal at the moment is recorded as phi; (3) the diameter of the vertical projection of the reference object on the liquid level in the image captured by the CCD can be approximately calculated 3 ＝(φ 1 +φ 2 ) 2, diameter phi 1 ＝Ф 3 Phi/phi in the picture 3 ＝Ф/Ф 3 ＝Ф/Ф 1 I.e. phi ═ phi- 1 ×(φ/φ 3 )＝Ф 1 ×[2φ/(φ 1 +φ 2 )]. The device of the invention finally realizes the accurate measurement of the crystal diameterAnd the real-time measurement is carried out, so that the control precision of the crystal diameter and the process stability are improved.)

1. A method for measuring a crystal diameter in growing a silicon single crystal by the Czochralski method, comprising the steps of:

(1) arranging a CCD camera outside an observation window of a Czochralski method silicon single crystal growing furnace, wherein the CCD camera is connected with a computer through a signal wire, and the CCD camera transmits the shot image signals of the reference substance and the surface of the silicon melt to the computer for data conversion and image measurement; wherein the reference object diameter phi is obtained according to the original thermal field design₁The actual diameter of the crystal is recorded as phi;

(2) in the actual growth process of the crystal, after a CCD camera shoots an image of a certain moment in the growth process of the silicon single crystal, calculating to obtain the diameter of a reference object in the image as phi 1, the reflection diameter phi 2 of the reference object on the surface of the silicon melt, and the image of the interface between the crystal and the liquid level, wherein the diameter of the interface is equal to the diameter of the crystal, and the diameter of the crystal at the moment is recorded as phi;

(3) approximate calculation phi of vertical projection diameter of reference object on liquid level in CCD captured image₃＝(φ₁+φ₂)/2，φ₃The actual diameter of the reference object projected on the liquid level is equal to the diameter phi of the reference object₁＝Ф₃Thus phi/phi in the image₃＝Ф/Ф₃＝Ф/Ф₁I.e. phi＝Ф₁×(φ/φ₃)＝Ф₁×[2φ/(φ₁+φ₂)]。

2. The method of claim 1, wherein the reference object is a draft tube.

Technical Field

The invention relates to a monocrystalline silicon production technology, in particular to a method for measuring the crystal diameter in the process of growing silicon single crystal by a Czochralski method.

Background

In the growth of silicon single crystals by the Czochralski method, it is often necessary to calibrate the diameter of the crystal grown from the silicon melt in order to control the product quality. The commonly used method of measuring the diameter of a crystal is to use a caliper in which a telescope is combined with a caliper. After the caliper is fixed on an observation window on a furnace body, an operator aligns a scale in the telescope with one side edge of the crystal and reads the scale, then moves the telescope transversely until the scale is aligned with the other side edge of the crystal, the scale is read again, and the difference of the two readings is the diameter of the crystal. However, the method is influenced by the subjective effect of operators and the error of the scale, the measured diameter of the single crystal has an error, the diameter of the crystal cannot be measured in real time, and a real-time control basis cannot be provided for the production of the single crystal.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a method for measuring the crystal diameter in the process of growing silicon single crystals by a Czochralski method.

In order to solve the technical problem, the solution of the invention is as follows:

there is provided a method for measuring a crystal diameter in growing a silicon single crystal by the Czochralski method, comprising the steps of:

(1) a CCD camera is arranged outside an observation window of the silicon single crystal furnace grown by the Czochralski method, and the CCD camera is connected with the observation window through a signal wireThe CCD camera can transmit the shot image signals of the reference object and the surface of the silicon melt to the computer, and carry out data conversion and image measurement; wherein the reference object diameter phi is obtained according to the original thermal field design₁The actual diameter of the crystal is recorded as phi;

(2) in the actual growth process of the crystal, after a CCD camera shoots an image of a certain moment in the growth process of the silicon single crystal, calculating to obtain the diameter of a reference object in the image as phi 1, the reflection diameter phi 2 of the reference object on the surface of the silicon melt, and the image of the interface between the crystal and the liquid level, wherein the diameter of the interface is equal to the diameter of the crystal, and the diameter of the crystal at the moment is recorded as phi;

(3) the diameter of the vertical projection of the reference object on the liquid level in the image captured by the CCD can be approximately calculated₃＝(φ₁+φ₂)/2，φ₃The actual diameter of the reference object projected on the liquid level is equal to the diameter phi of the reference object₁＝Ф₃Thus phi/phi in the image₃＝Ф/Ф₃＝Ф/Ф₁I.e. phi ═ phi-₁×(φ/φ₃)＝Ф₁×[2φ/(φ₁+φ₂)]。

As an improvement, the reference object is a guide shell.

Description of the inventive principles:

in the invention, the diameter phi of the lower edge of the guide cylinder₁For known parameters, the crystal diameter can be calculated by corresponding the relevant size in the measured image to the crystal size.

1. Data preparation

Obtaining the lower edge diameter phi of the guide shell according to the original thermal field design₁The computer processes the image captured by the CCD to obtain the diameter phi of the lower edge of the guide shell in the image₁The diameter phi of the inverted image of the guide cylinder on the liquid surface₂The vertical projection diameter phi of the guide shell on the liquid level₃Crystal diameter phi.

2. Principle explanation

In the actual spatial position, the vertical projection of the guide shell on the liquid level and the crystal aperture are both located on the plane of the melt surface. So that the CCD captures the projection and the crystal aperture in the imageRatio of diameter (phi/phi)₃) Is equal to its actual diameter ratio phi/phi₃. Meanwhile, the actual projection diameter is equal to the actual diameter (phi) of the guide cylinder₁＝Ф₃) And calculating the actual diameter of the crystal according to the proportional relation.

3. Measuring process

In the method, on the basis of the relationship: phi is phi₁×(φ/φ₃)＝Ф₁×[2φ/(φ₁+φ₂)]

Compared with the prior art, the invention has the beneficial effects that:

the invention takes the lower edge of the guide flow cylinder with a fixed diameter in the crystal growth thermal field as a reference object, and finally realizes accurate measurement of the crystal diameter and real-time measurement by calibrating the crystal diameter obtained by CCD scanning through the numerical value, thereby improving the control precision of the crystal diameter and the process stability.

Drawings

FIG. 1 is a schematic view of an apparatus for growing a silicon single crystal by the Czochralski method which is common in the prior art;

FIG. 2 is a silicon melt surface image taken by a CCD camera.

FIG. 3 is a schematic diagram of the principle of measurement and calculation of the crystal diameter in the present invention.

Reference numerals in the drawings: 1-crystal, 2-draft tube, 3-quartz crucible, 4-graphite crucible and 5-silicon melt; 6-boundary position of crystal and melt, 7-lower edge of guide cylinder inversing on surface of melt, 8-lower edge of guide cylinder, 9-CCD camera, 11-projection of guide cylinder on liquid surface, 12-reflection of guide cylinder, 13-crystal aperture and 14-CCD image.

Detailed Description

The following describes the implementation of the present invention in detail with reference to the accompanying fig. 1-3 and the embodiments.

The crystal diameter measuring method of the present invention is used in the czochralski silicon single crystal growth process in a thermal field structure, captures a reference object image, a reference object reflection image, and an aperture image of the interface position of the crystal 1 and the silicon melt 5 using the CCD9, and obtains an accurate numerical value of the diameter of the crystal 1 by processing the images. The reference object used in this embodiment is a guide cylinder 2, and in specific applications, a member of known size such as a quartz crucible 3, a graphite crucible 4, etc. as in the member of fig. 1 may be used.

The method specifically comprises the following steps:

(1) arranging a CCD camera 9 outside an observation window of a silicon single crystal growing furnace by a Czochralski method, connecting the CCD camera 9 with a computer through a signal wire, transmitting the shot image signals of the surfaces of the guide cylinder 2 and the silicon melt 5 to the computer, and performing data conversion and image measurement, wherein the actual diameter of the lower edge 8 of the guide cylinder is recorded as phi₁The aperture 13 at the boundary position 6 between the crystal 1 and the melt is approximately equal to the actual diameter of the crystal 1 and is marked as phi;

(2) in the actual growth process of the crystal 1, after a CCD camera 9 shoots a CCD image 14 at a certain moment in the growth process of the silicon single crystal, the diameter of the guide cylinder 2 in the image is calculated and recorded as phi₁The diameter phi of the reflection of the lower edge of the guide shell on the surface of the melt is 7₂The image of the interface between the crystal 1 and the liquid level, the diameter of the interface is equal to the diameter of the crystal 1, and the diameter of the crystal 1 at the moment is recorded as phi;

(3) based on the principle of mirror reflection, the melt level is equivalent to a mirror surface, and the diameter of the vertical projection of the guide cylinder 2 on the melt level in the image captured by the CCD camera 9 can be approximately calculated₃＝(φ₁+φ₂)/2，φ₃The diaphragm is positioned on the same plane as the diaphragm in the step (1), and the actual diameter of the projection of the guide cylinder 2 on the liquid level is equal to the diameter phi of the guide cylinder 2₁＝Ф₃Thus phi/phi in the image₃＝Ф/Ф₃＝Ф/Ф₁I.e. phi ═ phi-₁×(φ/φ₃)＝Ф₁×[2φ/(φ₁+φ₂)]

The specific calculation process is exemplified below by way of introducing specific data.

(1) The actual diameter phi of the lower edge 8 of the known guide shell₁＝270mm；

(2) The image captured by the CCD camera 9 is calculated by phi₁＝162.24mm、φ₂＝161.03mm、φ＝126.31mm；

(3) Approximate calculation of phi₃＝(φ₁+φ₂)/2＝(162.24mm+161.03)/2＝161.635mm

(4) The growth of the silicon single crystal is photographed by a CCD camera 9After the image at a certain moment in the process, measuring phi in the image₁、φ₂And phi are 162.24mm, 161.03mm, 126.31mm, respectively;

(5) calculating the actual diameter of crystal 1₁×(φ/φ₃)＝162.24mm×(126.31mm/161.635mm)＝207.61mm

(6) After the completion of the growth of the crystal 1, the diameter of the crystal 1 was actually measured at the same position to be 207.85 mm.

It should also be noted that the above-mentioned list is only of specific embodiments of the invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.