CN108977879B - High-purity quartz crucible for single crystal and preparation method thereof - Google Patents

Abstract

The invention relates to the field of monocrystalline silicon equipment manufacturing, and aims to provide a high-purity quartz crucible for monocrystalline and a preparation method thereof. The crucible comprises a crucible body; the crucible body comprises a crucible side wall and a crucible bottom; the upper part of the side wall of the crucible is provided with an annular three-layer structure parallel to the cross section of the crucible, and the rest part of the crucible body is of a double-layer structure. The method comprises (1) preparing a double-layer structure; (2) and throwing the quartz sand on the outermost layer into a graphite mold which rotates and is not poured into the quartz sand part by using a forming machine, then throwing the synthetic quartz sand on the outermost layer, and finally throwing the high-purity synthetic quartz sand on the quartz sand of the whole mold to form a third layer. (3) And melting the two-layer and three-layer structures by adopting a high-temperature arc method. The crucible provided by the invention does not need to introduce a Ba coating on the inner surface of the crucible, so that the influence of impurities on the quality of the silicon rod is avoided, and the service life of the crucible can be effectively prolonged.

Description

High-purity quartz crucible for single crystal and preparation method thereof

Technical Field

The invention belongs to the field of monocrystalline silicon equipment manufacturing, and particularly relates to a high-purity quartz crucible for single crystals and a preparation method thereof.

Background

The CZ method is the mainstream method for producing the monocrystalline silicon at present, polycrystalline silicon is put into a quartz crucible container, the polycrystalline silicon is heated and melted, then the rotating seed crystals are contacted with the liquid level of the melted silicon liquid, and the monocrystalline silicon rod is grown through the working procedures of seeding, shouldering, isometric diameter, ending and the like. In the process of pulling the single crystal, particularly in the seeding and shouldering stages, the phenomenon of liquid level vibration of silicon liquid can be generated sometimes, and in serious cases, the phenomenon of incapability of seeding and shouldering can be directly caused.

The liquid level vibration is generally considered to be caused by reaction of silicon liquid and a quartz crucible to generate SiO gas. Particularly, in the high-purity synthetic quartz crucible, the vibration is more obvious, because the inner surface of the high-purity synthetic quartz crucible is not subjected to Ba coating treatment, a uniform cristobalite protective layer cannot be formed, and the activity of the synthetic quartz is higher than that of natural quartz, the synthetic quartz crucible reacts with silicon liquid more violently, and the possibility of generating liquid level vibration is higher.

At present, three main ways for solving the problem of liquid level vibration during crystal pulling are provided: 1. manufacturing a Ba coating on the inner surface of the crucible; 2. increasing the bubble content of the transparent layer; 3. defects such as tiny pits are made on the inner surface of the crucible. The greatest disadvantage of mode 1 is that the Ba coating is also an impurity in relation to the silicon bath, and when the requirements on the quality of the silicon rod are very high, the Ba coating can carry impurities into the silicon bath, thereby affecting the quality of the silicon rod. The biggest defect of the mode 2 is that when the bubbles of the transparent layer are too much, the bubbles expand and are broken, so that SiO2 fragments are brought into the silicon liquid, and crystal growth abnormality is caused to break. Mode 3 has the greatest disadvantage that as the pulling time increases, the defects on the inner surface are consumed by reaction with the silicon melt, and the level vibration improvement capability for multiple pulls is limited.

In patent document 1 (japanese patent No. 4338990), it is mentioned that the use of natural quartz sand at the position where the synthetic quartz crucible is in contact with the initial liquid surface of the silicon liquid can suppress the liquid surface vibration of the silicon liquid, but this process is difficult to mold, and since the natural quartz sand has a lower purity than the synthetic sand, the natural quartz is dissolved into the silicon liquid to increase the possibility of the silicon liquid being contaminated with metal.

Patent document 2 (shin-Etsu quartz Co., Ltd., silica vessel for pulling up silicon single crystal and process for producing the same: China, 104395509.2015-03-04) discloses that the use of crystalline silica sand or a mixture of crystalline and amorphous silica sand at the position where the synthetic quartz crucible is in contact with the initial liquid surface of the silicon melt can effectively suppress the liquid surface vibration during pulling up the silicon single crystal, but this process is also difficult to form, and the crystalline silica sand is melted at high temperature and then rapidly cooled, and is likely to be converted into vitreous silica, so that the effect of suppressing the liquid surface vibration is limited.

Patent document 3 (jp 2000 a-219593) discloses that the infrared transmittance of the quartz crucible wall is 3% to 10% to suppress the liquid surface vibration, but this method has a limited effect on suppressing the liquid surface vibration of a large quartz crucible.

In patent document 4 (japanese patent No. 4390461), it is mentioned that the increase of the bubble content at the contact position of the quartz crucible with the initial liquid surface of the silicon liquid can suppress the liquid surface vibration; however, the method has the great disadvantage that the bubble expansion is serious along with the increase of the crystal pulling time, the etching of the silicon liquid to the crucible is increased, and the crucible cannot be fed and pulled for many times, so that the service life of the crucible is shortened.

In patent document 5 (jp 2011-one 105552), it is mentioned that a large number of tiny pits are formed at the initial contact position of the quartz crucible and the liquid level of the silicon liquid to suppress the vibration of the liquid level, but the tiny pits tend to be smooth along with the etching of the silicon liquid, so that the effect of suppressing the vibration of the liquid level tends to be weakened when a second silicon rod or even a third silicon rod is drawn.

In patent document 6 (international publication No. WO 2011/158712), it is mentioned that the inner surface of the quartz crucible is sandblasted by high purity natural sand to manufacture a quartz crucible having a certain roughness on the inner surface, which can suppress the vibration of the liquid level, the manufacturing process of the crucible is complicated, the yield is low, and the same disadvantages as the quartz crucible disclosed in patent document 5 exist, namely, the effect of suppressing the vibration of the liquid level tends to be weakened when the rough surface of the inner surface of the crucible tends to be smooth after being etched by the silicon liquid.

Patent document 7 (jp 2012-17240 a) mentions that the vibration of the liquid level of the silicon liquid can be suppressed by introducing hydrogen gas during the melting process to increase the hydroxyl content of the inner surface of the crucible to form an inner surface with a hydroxyl content of 500-1000 ppm, but the crucible has a high hydroxyl content, which causes a decrease in the viscosity of quartz, resulting in a decrease in the strength of the crucible body, and the crucible is likely to deform at high temperatures.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a high-purity quartz crucible for single crystals and a preparation method thereof.

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

provided is a high-purity quartz crucible for single crystal, comprising a crucible body; the crucible body comprises a crucible side wall and a crucible bottom; the upper part of the side wall of the crucible is provided with an annular three-layer structure parallel to the cross section of the crucible, and the rest part of the crucible body is of a double-layer structure;

the three-layer structure sequentially comprises a transparent quartz layer, a bubble transition quartz layer and an opaque quartz layer from inside to outside; and the structural boundary between adjacent layers is obvious, and no transition zone exists.

The inner layer of the double-layer structure is a transparent quartz glass layer, and the outer layer is an opaque quartz glass layer containing bubbles.

As an improvement, the crucible is of a three-layer structure in the height range of 0.05H-0.3H from the port of the crucible body downwards, wherein H is the distance from the port of the crucible body to the bottom end.

As an improvement, in the three-layer structure, the bubble rate of the transparent quartz layer is lower than 0.01%; the bubble rate of the bubble transition quartz layer is 0.01-0.1%.

The bubble content is measured by specific gravity. Cut out of a quartz crucible for a unit volume (1 cm)³) The mass of the quartz piece (2) is a, the mass of the quartz piece per unit volume not containing bubbles is B2.21, and the bubble content is (1-a/B) × 100%.

As an improvement, in the three-layer structure, the Al content in the transparent quartz layer is 1-20 ppb, and the transparent quartz layer is made of high-purity synthetic quartz sand; the Al content of the bubble transition quartz layer is 1-20 ppm, and the bubble transition quartz layer is made of Al-doped synthetic quartz sand.

As an improvement, in the three-layer structure, the thickness of the transparent quartz layer is 1-2 mm, and the thickness of the bubble transition quartz layer is 2-3 mm.

As an improvement, in the double-layer structure, the Al content in the opaque quartz glass layer of the outer layer is 20-30 ppm.

The invention also provides a preparation method of the high-purity quartz crucible for the single crystal, which comprises the following steps:

(1) preparing a double-layer structure: the quartz sand is poured into a rotating mould, notably: the port of the mould is downward within a certain range, and quartz sand is not poured into the mould; melting the quartz sand by adopting a high-temperature arc method, and forming an opaque quartz glass layer and a transparent quartz glass layer in a vacuumizing mode in the melting process; the quartz sand can adopt high-alumina natural quartz sand, and the content of Al element is increased by the aluminum doping process.

(2) Firstly throwing quartz sand with 20-30 ppm of Al content at the outermost layer into a graphite mold which rotates and is not poured into a quartz sand part by using a forming machine, then throwing synthetic quartz sand with 1-20 ppm of Al content onto the quartz sand at the outermost layer, and finally throwing high-purity synthetic quartz sand with 1-20 ppb of Al content onto the quartz sand of the whole mold to form a third layer.

(3) And melting the two-layer structure and the three-layer structure by adopting a high-temperature arc method to form the high-purity quartz crucible for the single crystal.

It should be noted that: the preparation method comprises the following steps: in the step (1), the two-layer structure of the quartz crucible is respectively a bubble layer (opaque layer) and a transparent layer, the two-layer structure of the crucible is realized by a vacuum pumping mode, and the thickness of the transparent layer can be determined by the vacuum pumping time, which is a known technology. And the boundary between the two layers of structures is obvious, and no transition zone exists.

The quartz sand mentioned in the step (2) means natural quartz sand, that is, natural ore processed and synthetic quartz sand is SiO2 chemically synthesized, and its purity is very high, but the synthetic sand in this patent is aluminum-doped and the high-purity synthetic quartz sand is non-aluminum-doped synthetic quartz sand. In addition, the quartz sand does not contain any doped adhesive and is completely attached to the die by the rotating centrifugal force of the die, which is a common method of the prior crucible, the collapse phenomenon can not occur, and a uniform synthetic quartz sand layer can be formed by a forming machine. The molding machine can customize or purchase commercially available equipment, such as the model TSVC vacuum conveyor equipment, the brand TRUSTAR manufactured by Shenzhen Chengtong technology Limited.

The invention principle is as follows:

the invention provides a quartz crucible with a three-layer structure at a specific position, wherein the specific position is a position corresponding to the liquid level of molten silicon liquid during silicon rod production. The difference of Al contents of the three-layer structure is large, the viscosity of quartz sand is directly influenced by the Al content, and when the viscosity of the quartz sand is large, the elimination of bubbles is not facilitated, so that the bubble content of the bubble transition layer in the invention is higher than that of a common transparent layer. When crystal pulling is carried out, due to the existence of high temperature, bubbles begin to expand, the high transparent layer with extremely low Al content on the inner layer has low viscosity, and a slight uneven interface can be formed under the influence of the expansion of the bubbles on the bubble transition layer, and the interface can be used as a gasification center of SiO to prevent the silicon liquid from being overheated, so that the problem of liquid level vibration is avoided.

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

the crucible of the invention does not need to introduce a Ba coating on the inner surface of the crucible, thereby avoiding the influence of impurities on the quality of the silicon rod, and because the bubble content of the high transparent layer is extremely low, the crucible does not need to worry about abnormal crystal growth caused by the bubble rupture in the transparent layer, thereby effectively prolonging the service life of the crucible.

Drawings

FIG. 1 is a sectional view showing a structure of a quartz crucible of the present invention.

In the figure: 10-opaque quartz glass layer; 11-a layer of transparent quartz glass; 12-bubble transition quartz layer; 13-a transparent quartz layer; 14-crucible side wall; 15-a transition section; 16-crucible bottom; 17-opaque quartz layer.

Detailed Description

Example 1

A quartz crucible for single crystal growth has a double-layer structure. The outer opaque layer is made of common natural high-purity quartz sand, the inner transparent layer is made of high-purity synthetic quartz sand, the thickness of the transparent layer formed by the inner synthetic quartz sand is 2.5mm, the quartz crucible is used for pulling monocrystalline silicon, and the pulling time is 120 h.

And (3) test results: obvious liquid level vibration of silicon liquid occurs in the crystal pulling seeding process, and the crystal is difficult to form, and the vibration lasts until shouldering is finished.

Example 2

A quartz crucible for single crystal growth is of a double-layer structure and comprises an opaque layer made of common natural high-purity quartz sand, a bubble transition layer made of high-purity aluminum-doped synthetic quartz sand and a high transparent layer made of high-purity synthetic quartz sand from outside to inside in sequence, wherein the thickness of the transparent layer formed by the high-purity synthetic quartz sand is 2.5mm, the quartz crucible is used for pulling single crystal silicon, and the pulling time is 120 hours.

And (3) test results: slight liquid level vibration occurs in the crystal pulling and seeding process, which is not beneficial to crystal formation, but no liquid level vibration of silicon liquid occurs in the shouldering process.

Example 3

A high-purity quartz crucible for single crystal comprises a crucible side wall and a crucible bottom; the side wall of the crucible is provided with an annular three-layer structure parallel to the cross section of the crucible, and the rest part of the crucible body is of a double-layer structure; the three-layer structure is arranged in the height range of 0.05H-0.3H from the port of the crucible body downwards, wherein H is the distance from the port of the crucible body to the bottom end. The three-layer structure sequentially comprises a transparent quartz layer, a bubble transition quartz layer and an opaque quartz layer from inside to outside; the transparent quartz layer has a bubble rate of 0.001 to 0.01%, preferably 0.005%, an Al content of 1 to 20ppb, preferably 5ppb, and a thickness of 1 mm; the bubble rate of the bubble transition quartz layer is 0.01-0.1%, preferably 0.1%, the Al content is 1-20 ppm, preferably 15ppm, the thickness is 2mm, and the Al content of the opaque quartz layer is 20-30 ppm, preferably 25 ppm. The inner layer of the double-layer structure is a transparent quartz glass layer, and the outer layer is an opaque quartz glass layer containing bubbles.

The quartz crucible is used for pulling monocrystalline silicon, two rods are pulled by adopting multiple feeding, the pulling time of the first silicon rod is 120 hours, and then the second silicon rod is continuously pulled.

And (3) test results: in the process of drawing the two silicon rods, the phenomenon of liquid level vibration of silicon liquid does not occur, but in the process of drawing the second silicon rod, the phenomenon of difficult seeding occurs, and the analysis on the crucible after the crystal is pulled shows that the inner surface of the crucible at the position of the three-layer structure has a bubble perforation phenomenon, the thickness of the push side high transparent layer is too thin, and the push side high transparent layer reacts with the silicon liquid and is consumed, so that a bubble transition layer is exposed in the silicon liquid, and the seeding is difficult due to the breakage of bubbles.

Example 4

A high-purity quartz crucible for single crystal comprises a crucible side wall and a crucible bottom, wherein the crucible is composed of a double-layer structure, but the double-layer structure in the height range of 0.05H-0.3H from a crucible body port downwards is different from the double-layer structure of other bodies, wherein H is the distance from the crucible body port to the bottom end. The double-layer structure comprises a transparent quartz layer and an opaque quartz layer from inside to outside in sequence; the transparent quartz layer has a bubble rate of 0.001-0.01%, preferably 0.005%, an Al content of 1-20 ppb, preferably 5ppb, and a thickness of 2 mm; the Al content of the opaque quartz layer is 20-30 ppm, preferably 25 ppm.

The quartz crucible was used for pulling single crystal silicon for a pulling time of 120 h.

And (3) test results: obvious liquid level vibration occurs in the seeding process, and the vibration lasts to the shouldering process.

Example 5

A high-purity quartz crucible for single crystal comprises a crucible side wall and a crucible bottom; the side wall of the crucible is provided with an annular three-layer structure parallel to the cross section of the crucible, and the rest part of the crucible body is of a double-layer structure; the three-layer structure is arranged in the height range of 0.05H-0.3H from the port of the crucible body downwards, wherein H is the distance from the port of the crucible body to the bottom end. The three-layer structure sequentially comprises a transparent quartz layer, a bubble transition quartz layer and an opaque quartz layer from inside to outside; the bubble rate of the transparent quartz layer is 0.001-0.01%, preferably 0.005%, the Al content is 1-20 ppm, preferably 5ppm, and the thickness is 2 mm; the bubble rate of the bubble transition quartz layer is 0.01-0.1%, preferably 0.1%, the Al content is 1-20 ppm, preferably 15ppm, the thickness is 2mm, and the Al content of the opaque layer is 20-30 ppm, preferably 25 ppm. The inner layer of the double-layer structure is a transparent quartz glass layer, and the outer layer of the double-layer structure is an opaque quartz glass layer containing bubbles.

The quartz crucible is used for pulling monocrystalline silicon, two silicon rods are pulled by adopting multiple feeding, the pulling time of the first silicon rod is 120 hours, and then the second silicon rod is continuously pulled.

And (3) test results: in the process of drawing two silicon rods, the phenomenon of liquid level vibration of silicon liquid does not occur, other abnormalities do not occur in the process of drawing a second silicon rod, and the inner surface of the drawn crucible is not perforated by bubbles after being analyzed.

It is noted that the actual scope of the invention encompasses not only the disclosed embodiments, but also all equivalent ways of practicing or implementing the invention under the claims.

Claims (2)

1. A high-purity quartz crucible for single crystal comprises a crucible body; the crucible is characterized in that the crucible body comprises a crucible side wall and a crucible bottom; the upper part of the side wall of the crucible is provided with an annular three-layer structure parallel to the cross section of the crucible, and the rest part of the crucible body is of a double-layer structure;

the three-layer structure is arranged in the height range of 0.05H-0.3H from the port of the crucible body downwards, wherein H is the distance from the port of the crucible body to the bottom end; the three-layer structure sequentially comprises a transparent quartz layer, a bubble transition quartz layer and an opaque quartz layer from inside to outside; in the three-layer structure, the Al content in the transparent quartz layer is 1-20 ppb, the Al content in the bubble transition quartz layer is 1-20 ppm, and the Al content in the opaque quartz layer is 20-30 ppm; the bubble rate of the transparent quartz layer is lower than 0.01 percent, and the bubble rate of the bubble transition quartz layer is 0.01 to 0.1 percent; the thickness of the transparent quartz layer is 1-2 mm, and the thickness of the bubble transition quartz layer is 2-3 mm;

the inner layer of the double-layer structure is a transparent quartz glass layer, and the outer layer of the double-layer structure is an opaque quartz glass layer containing air bubbles; in the double-layer structure, the Al content in the opaque quartz glass layer of the outer layer is 20-30 ppm.

2. A method for preparing a high-purity quartz crucible for single crystal is characterized in that,

the crucible body comprises a crucible side wall and a crucible bottom; the upper part of the side wall of the crucible is provided with an annular three-layer structure parallel to the cross section of the crucible, and the rest part of the crucible body is of a double-layer structure;

the three-layer structure is arranged in the height range of 0.05H-0.3H from the port of the crucible body downwards, wherein H is the distance from the port of the crucible body to the bottom end; the three-layer structure sequentially comprises a transparent quartz layer, a bubble transition quartz layer and an opaque quartz layer from inside to outside; in the three-layer structure, the Al content in the transparent quartz layer is 1-20 ppb, the Al content in the bubble transition quartz layer is 1-20 ppm, and the Al content in the opaque quartz layer is 20-30 ppm; the bubble rate of the transparent quartz layer is lower than 0.01 percent, and the bubble rate of the bubble transition quartz layer is 0.01 to 0.1 percent; the thickness of the transparent quartz layer is 1-2 mm, and the thickness of the bubble transition quartz layer is 2-3 mm;

the inner layer of the double-layer structure is a transparent quartz glass layer, and the outer layer of the double-layer structure is an opaque quartz glass layer containing air bubbles; in the double-layer structure, the Al content in the opaque quartz glass layer of the outer layer is 20-30 ppm;

the preparation steps of the high-purity quartz crucible for the single crystal are as follows:

(1) preparing a double-layer structure: the quartz sand is poured into a rotating mould, notably: in the local range with the downward port of the mold, quartz sand is not required to be poured; melting the quartz sand by adopting a high-temperature arc method, and forming an opaque quartz glass layer and a transparent quartz glass layer in a vacuumizing mode in the melting process;

(2) firstly throwing quartz sand with 20-30 ppm of Al content at the outermost layer into a graphite mould which rotates and is not poured into a quartz sand part by using a forming machine, then throwing synthetic quartz sand with 1-20 ppm of Al content onto the quartz sand at the outermost layer, and finally throwing high-purity synthetic quartz sand with 1-20 ppb of Al content onto the quartz sand of the whole mould to form a third layer;

(3) and melting the two-layer structure and the three-layer structure by adopting a high-temperature arc method to form the high-purity quartz crucible for the single crystal.

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