CN111101194A

CN111101194A - Crystal growth method of monocrystalline silicon crystal bar

Info

Publication number: CN111101194A
Application number: CN201811267643.7A
Authority: CN
Inventors: 沈伟民; 范进
Original assignee: Zing Semiconductor Corp
Current assignee: Zing Semiconductor Corp
Priority date: 2018-10-29
Filing date: 2018-10-29
Publication date: 2020-05-05
Also published as: TW202016367A

Abstract

The invention provides a crystal growing method of a monocrystalline silicon crystal bar, which sequentially comprises an equal-diameter stage and a finishing stage, wherein the height of the finishing stage is increased by controlling the finishing speed and/or temperature of the finishing stage so as to enable the BMD density at the top and the bottom of the equal-diameter stage to be consistent. The crystal growing method of the monocrystalline silicon crystal bar can avoid unnecessary waste of the crystal bar, thereby improving the production efficiency.

Description

Crystal growth method of monocrystalline silicon crystal bar

Technical Field

The invention relates to the technical field of semiconductors, in particular to a crystal growing method of a monocrystalline silicon crystal bar.

Background

With the development of science and technology and the continuous emergence of new electronic products, the demand of large-diameter monocrystalline silicon is rapidly increased. The method for growing single crystal silicon crystal mainly includes Czochralski method (CZ), floating zone method (FZ) and epitaxial method. The Czochralski method and the floating zone method are used for growing the monocrystalline silicon bar material, and the epitaxial method is used for growing the monocrystalline silicon film. Among them, the single crystal silicon grown by the czochralski method is mainly used for semiconductor integrated circuits, diodes, epitaxial wafer substrates, solar cells, and the like, and is currently the most common single crystal silicon growth method.

The single crystal silicon is prepared by the Czochralski method, namely, in a crystal growing furnace, a seed crystal is immersed into silicon melt contained in a crucible, the seed crystal and the crucible are rotated and simultaneously pulled, so as to perform seeding, shouldering, shoulder rotating, diameter equalizing and ending at the lower end of the seed crystal in sequence, and a single crystal silicon crystal rod is obtained. In the process, the crystal growth without crystal defects is difficult to realize, and the crystal bar which cannot meet the quality requirement of manufacturing the positive plate cannot be put into use, so that waste is caused, and the production cost is increased.

Therefore, it is necessary to provide a method for growing a single crystal silicon ingot to solve the above problems.

Disclosure of Invention

In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

Aiming at the defects of the prior art, the invention provides a crystal growing method of a monocrystalline silicon crystal bar, which sequentially comprises an equal-diameter stage and a final stage, wherein the height of the final stage is increased by controlling the final speed and/or temperature of the final stage so as to make the BMD density at the top and the bottom of the equal-diameter stage consistent.

Illustratively, the height of the trailing section is no less than 1/3 the diameter of the constant diameter section.

Illustratively, the ending speed is a pull speed.

Illustratively, the temperature is a heater temperature.

Illustratively, the ending speed and the temperature are adjusted simultaneously in the ending stage, and the diameter change of the ending section is controlled in real time.

Illustratively, the average value of the ending speed ranges from 0.6mm/min to 0.7 mm/min.

Illustratively, the equal diameter stage is preceded by a seeding stage and a shouldering stage.

Illustratively, the growing method is a czochralski method.

The crystal growing method of the monocrystalline silicon crystal bar can avoid unnecessary waste of the crystal bar, thereby improving the production efficiency.

Drawings

The following drawings of the invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

In the drawings:

fig. 1 is a schematic view showing a silicon single crystal ingot obtained by a conventional method for growing a silicon single crystal ingot.

Fig. 2 is a schematic view of a single crystal silicon ingot obtained by a method for growing a single crystal silicon ingot according to an embodiment of the present invention.

Fig. 3 is a schematic view showing a crystal growth furnace used in a method for growing a silicon single crystal ingot from a silicon single crystal ingot according to an embodiment of the present invention.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

It is to be understood that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals refer to like elements throughout.

It will be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it can be directly on, adjacent to, connected or coupled to the other elements or layers or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

Spatial relational terms such as "under," "below," "under," "above," "over," and the like may be used herein for convenience in describing the relationship of one element or feature to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, then elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "under" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

Embodiments of the invention are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region shown as a rectangle will typically have rounded or curved features and/or implant concentration gradients at its edges rather than a binary change from implanted to non-implanted region. Also, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation is performed. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the present invention.

In order to provide a thorough understanding of the present invention, a detailed structure will be set forth in the following description in order to explain the present invention. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed.

The preparation method of the existing single crystal silicon ingot is mainly a Czochralski method, and the main process steps of the method comprise the stages of seeding, shouldering, equalizing diameter and ending. In the production of single crystal silicon by the Czochralski method, oxygen is the impurity having the highest content in silicon and is present in a supersaturated state in the silicon single crystal. During thermal processing in device fabrication, oxygen in the silicon nucleates growth at defects or impurities, forming Bulk Micro Defects (BMDs). In order to meet the quality requirements of a silicon wafer cut from a single crystal silicon ingot, the density of BMDs in the ingot needs to be maintained stable. However, in view of economic cost (such as power consumption, length of time used, etc.), a relatively sharp ending is generally adopted at present, as shown in fig. 1. As a result, the cooling time of the BMD nucleation temperature at the bottom of the constant diameter section varies, resulting in unstable BMD density in this portion, which does not meet the quality requirements for forming a positive film, resulting in waste.

In view of the above problems, the present invention provides a method for growing a single crystal silicon ingot, which comprises an isometric section and a finishing section in this order, wherein the height of the finishing section is increased by controlling the finishing speed and/or temperature of the finishing section so as to maintain the BMD nucleation density of the isometric section stable. The crystal growing method of the monocrystalline silicon crystal bar can avoid unnecessary waste of the crystal bar, thereby improving the production efficiency.

In the following description, for purposes of explanation, specific details are set forth in order to provide a thorough understanding of the present invention. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed. [ exemplary embodiments ]

The method for growing a single-crystal silicon ingot according to an embodiment of the present invention will be described in detail with reference to fig. 2 and 3.

As shown in fig. 2, the crystal growth method provided by the present invention sequentially comprises an equal-diameter stage and a finishing stage, wherein the height of the finishing stage is increased by controlling the finishing speed and/or temperature of the finishing stage, so that the BMD density at the top and bottom of the equal-diameter stage is consistent. According to the method provided by the invention, the height of the tail section is increased, the BMD nucleation density of the whole equal-diameter section is consistent, and the uneven BMD nucleation density at the bottom of the equal-diameter section caused by rapid tail ending is avoided, so that the unnecessary waste of crystal bars is avoided, and the production efficiency is improved.

Specifically, a crystal growth furnace is provided first, and a silicon material is heated and melted into a silicon melt in the crystal growth furnace.

As shown in FIG. 3, the crystal growth furnace for growing silicon single crystals by the Czochralski method comprises a furnace body 301, wherein a heating device and a pulling device are arranged in the furnace body 301. The heating device comprises a quartz crucible 302, a graphite crucible 303 and a heater 304. The quartz crucible 302 is used for holding a silicon material, such as polysilicon. In which the silicon charge is heated to a silicon melt 305. The graphite crucible 303 is wrapped around the outside of the quartz crucible 302 for providing support to the quartz crucible 302 during heating, and the heater 304 is disposed outside the graphite crucible 303. A heat shield 306 is disposed above the quartz crucible 302, and the heat shield 306 has a downward-extending inverted conical shield surrounding the growth region of the silicon single crystal 307, so as to block direct heat radiation of the heater 304 and the high-temperature silicon melt 305 to the growing single crystal silicon ingot 307 and reduce the temperature of the single crystal silicon ingot 307. Meanwhile, the heat shield can also enable the downward-blown argon to be intensively and directly sprayed to the vicinity of a growth interface, so that the heat dissipation of the monocrystalline silicon crystal bar 307 is further enhanced. The furnace body 301 is also provided with heat insulating materials, such as carbon felt, on the side wall.

The pulling device comprises a seed shaft 308 and a crucible shaft 309 which are vertically arranged, the seed shaft 308 is arranged above the quartz crucible 302, the crucible shaft 309 is arranged at the bottom of the graphite crucible 303, a seed crystal is arranged at the bottom of the seed shaft 308 through a clamp, and the top of the seed shaft is connected with a seed shaft driving device, so that the seed shaft can rotate and pull upwards slowly. A crucible shaft driving device is provided at the bottom of the crucible shaft 309, so that the crucible shaft 309 can drive the crucible to rotate.

When single crystal growth is performed, firstly, a silicon material is put into the quartz crucible 302, then the crystal growth furnace is closed and vacuumized, and protective gas is filled into the crystal growth furnace. Illustratively, the protective gas is argon gas, the purity of the argon gas is more than 99.99%, the pressure is 0.05MPa, and the flow rate is 70L/min. Then, heater 304 is turned on and heated to a melting temperature of 1420 ℃ or higher, so that the silicon material is completely melted into silicon melt 305 within 20 min.

Next, the seed crystal is immersed in the silicon melt 305, rotated and slowly pulled by the seed shaft 308, so that silicon atoms grow along the seed crystal as a single crystal silicon ingot 307. The growth process sequentially comprises the stages of seeding, shouldering, shoulder rotating, equal diameter and ending.

Specifically, the seeding stage is first performed. That is, after the silicon melt 305 is stabilized to a certain temperature, the seed crystal is immersed in the silicon melt and raised at a certain pulling rate, so that silicon atoms grow along the seed crystal into a narrow neck with a certain diameter until the narrow neck reaches a predetermined length. Illustratively, the pull rate ranges from 1.5mm/min to 2.5mm/min, the neck length is 1.2 to 1.4 times the diameter of the ingot, and the neck diameter ranges from 5mm to 7 mm.

And after the thin neck reaches a preset length, entering a shouldering stage, wherein the formed conical crystal bar is the shouldering section of the crystal bar. In the shouldering stage, the temperature and the crystal pulling rate are gradually reduced, so that the diameter of the crystal bar is gradually increased until the diameter of the crystal bar reaches a preset value.

When the diameter of the monocrystalline silicon ingot reaches a preset value, the diameter-equaling stage is carried out, and the cylindrical ingot formed in the stage is the diameter-equaling section of the ingot. Specifically, the crucible temperature, the pulling speed, the crucible rotating speed and the crystal rotating speed are adjusted to stabilize the growth rate and keep the crystal diameter unchanged until the crystal pulling is finished.

And finally, entering a final stage. During the ending, the lifting speed is increased, and the temperature of the silicon melt 305 is increased at the same time, so that the diameter of the crystal bar is gradually reduced to form a conical shape, and finally the crystal bar is separated from the liquid level. In the process, the height of the ending section is increased by controlling the ending speed and/or temperature in the ending stage, so that the BMD density at the top and the bottom of the constant-diameter section is consistent, and the phenomenon that the BMD density at the bottom of the constant-diameter section is unstable due to rapid ending is avoided. Wherein the ending speed is a pulling speed. Specifically, the movement of the crystal bar in the crystal growing process comprises pulling along the axial direction of the crystal bar and rotating the crystal bar around the axis of the crystal bar, the pulling speed and the rotating speed correspond to each other, and the ending speed is the pulling speed in the ending speed. The temperature is the heater temperature, i.e., the height of the finishing section is increased by controlling the temperature of the heater 304. And finally, lifting the finished crystal bar to the upper furnace chamber, cooling for a period of time, and taking out to finish a growth cycle. In one embodiment, the ending speed and temperature are adjusted simultaneously during the ending phase, and the diameter change of the ending section is controlled in real time. Illustratively, the average value of the ending speed ranges from 0.6mm/min to 0.7mm/min, e.g. 0.65 mm/min.

In a preferred embodiment, the height of the tail section is greater than 1/3 times the diameter of the constant diameter section. When the height of the tail section is larger than or equal to 1/3 of the diameter of the equal-diameter section, the cooling time of the BMD nucleation temperature of the whole equal-diameter section is ensured not to be changed greatly, so that the BMD nucleation density of the equal-diameter section is stable, and unnecessary waste of the equal-diameter section is avoided.

In one embodiment, temperature control and pull rate control are performed simultaneously during the end-up process to control the diameter change of the end-up section in real time until the end of single crystal silicon ingot 307 is free from silicon melt 305. An image acquisition device (such as a CCD camera) can be used for acquiring images at the three-phase intersection of the monocrystalline silicon crystal rod 307 and the silicon melt 305 in the crystal growing furnace, and then a computer is used for processing the images to obtain the diameter of the monocrystalline silicon crystal rod 307 and feeding the diameter back to the control system to control crystal growing. Specifically, during crystal growth, a bright ring is generated at the solid-liquid interface of single-crystal silicon ingot 307 and silicon melt 305 due to release of latent heat. The CCD camera acquires the image signal of the bright ring, and transmits the signal to the computer system after analog-to-digital conversion, and the image processing program in the computer system processes the single crystal growth image to acquire the measured diameter of the single crystal silicon ingot 307.

Thus, the description of the steps related to the method for growing a single crystal silicon ingot according to the embodiment of the present invention is completed. It is understood that the method for growing a single crystal silicon ingot of the present embodiment includes not only the above-described steps but also other necessary steps before, during or after the above-described steps, which are included in the scope of the growing method of the present embodiment.

The present invention has been illustrated by the above embodiments, but it should be understood that the above embodiments are for illustrative and descriptive purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, which variations and modifications are within the scope of the present invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. The crystal growing method of the monocrystalline silicon crystal bar is characterized by comprising an equal-diameter stage and a final stage in sequence, wherein the height of the final stage is increased by controlling the final speed and/or temperature of the final stage, so that the BMD density of the top and the bottom of the equal-diameter stage is consistent.

2. The crystal growth method according to claim 1, wherein the height of the end section is not less than 1/3 of the diameter of the constant diameter section.

3. The crystal growth method according to claim 1, wherein the finishing speed is a pulling speed.

4. The crystal growth method according to claim 1, wherein the temperature is a heater temperature.

5. The crystal growth method according to claim 1, wherein the finishing speed and the temperature are adjusted simultaneously in the finishing stage, and the diameter change of the finishing section is controlled in real time.

6. The crystal growth method according to claim 1, wherein the average value of the finishing speed is in the range of 0.6mm/min to 0.7 mm/min.

7. The crystal growth method according to claim 1, further comprising a seeding stage and a shouldering stage before the constant diameter stage.

8. The crystal growth method according to any one of claims 1 to 7, wherein the crystal growth method is a Czochralski method.