TW202016367A - A crystal growth method of single crystalline silicon ingot (2) - Google Patents

Abstract

The present application provides a crystal growth method of single crystalline silicon ingot. Said method comprising an equal-diameter growth step and a tail growth step, wherein, in the tail growth step, a growing rate and/or a temperature is controlled to increase a height of the tail, in order to make the bulk microdefect (BMD) be consistency from top to bottom of the equal-diameter section of the ingot. By applying the method of the present application, the process efficiency is enhanced and the waste of the obtained silicon ingot is avoided.

Description

Method for growing single crystal silicon ingot (2)

The invention relates to the field of semiconductor technology, in particular to a method for growing single crystal silicon ingots.

With the development of technology and the continuous emergence of new electronic products, the demand for large-diameter single crystal silicon has grown rapidly. The growth methods of single crystal silicon crystals mainly include the Czochralski method (CZ), the zone melting method (FZ) and the epitaxial method. The Czochralski method and the zone melting method are used to grow single crystal silicon rods, and the epitaxial method is used to grow single crystal silicon thin films. Among them, the single crystal silicon grown by the Czochralski method is mainly used for semiconductor integrated circuits, diodes, epitaxial wafer substrates, solar cells, etc. It is currently the most common single crystal silicon growth method.

The single crystal silicon is prepared by the Czochralski method, that is, in the crystal growth furnace, the seed crystal is immersed in the silicon melt contained in the crucible, and the seed crystal is pulled while rotating the seed crystal and the crucible, so that the seed crystal is sequentially introduced at the lower end of the seed crystal Crystal, put shoulder, turn shoulder, equal diameter and finish, get single crystal silicon ingot. In the above process, it is difficult to realize the crystal growth without crystal defects, and the crystal rods that cannot meet the quality requirements for manufacturing the positive film cannot be put into use, thus causing waste and increasing production costs.

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

A series of concepts in simplified form were introduced in the summary of the invention, which will be explained in further detail in the detailed description section. The summary of the present invention does not mean trying to define the key features and necessary technical features of the claimed technical solution, nor does it mean trying to determine the protection scope of the claimed technical solution.

In view of the deficiencies of the prior art, the present invention provides a method for growing a single crystal silicon ingot, the growing method includes an equal-diameter stage and a finishing stage in sequence, wherein, by controlling the finishing speed and/or temperature of the finishing stage Increase the height of the finishing section to make the density of bulk micro defects (BMD) at the top and bottom of the equal-diameter section consistent.

Exemplarily, the height of the finishing section is not less than 1/3 of the diameter of the equal-diameter section.

Exemplarily, the closing speed is a pulling speed.

Illustratively, the temperature is the heater temperature.

Exemplarily, 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.

Exemplarily, the average value of the finishing speed ranges from 0.6 mm/min to 0.7 mm/min.

Exemplarily, before the equal-diameter stage, a seeding stage and a shoulder-releasing stage are also included.

Exemplarily, the crystal growth method is a Czochralski method.

The method for growing single crystal silicon ingots provided by the invention can avoid unnecessary waste of ingots, thereby improving production efficiency.

In the following description, a large number of specific details are given in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features known in the art are not described.

It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments presented herein. Rather, providing these embodiments will make the disclosure 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. The same reference numerals denote the same elements throughout.

It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on the other element or layer On, adjacent to, connected to, or coupled to 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" another element or layer, there are no intervening elements or Floor. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and/or portions, these elements, components, regions, layers and/or portions 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. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer, or section discussed below can be represented as a second element, component, region, layer, or section.

Spatial relationship terms such as "below", "below", "below", "below", "above", "above", etc. It can be used here for the convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientations shown in the figures, the spatial relationship terms are intended to include different orientations of the device in use and operation. For example, if the device in the drawings is turned over, then elements or features described as "below" or "under" or "under" will be oriented "above" the other elements or features. Thus, the exemplary terms "below" and "below" can include both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or other orientation) and the spatial descriptors used herein interpreted accordingly.

The terminology used herein is for describing specific embodiments only and is not intended to be a limitation of the present invention. As used herein, the singular forms "a", "an", and "said/the" are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "composition" and/or "comprising", when used in this specification, determine the existence of the described features, integers, steps, operations, elements and/or components, but do not exclude one or more other The presence or addition of features, integers, steps, operations, elements, components, and/or groups. As used herein, the term "and/or" includes any and all combinations of the listed items.

Embodiments of the invention are described herein with reference to cross-sectional views that are schematic diagrams of ideal embodiments (and intermediate structures) of the invention. In this way, a change from the shown shape due to, for example, manufacturing techniques and/or tolerances can be expected. Therefore, the embodiments of the present invention should not be limited to the specific shapes of the regions shown here, but include shape deviations due to, for example, manufacturing. For example, an implanted area shown as a rectangle generally has round or curved features and/or implant concentration gradients at its edges, rather than a binary change from the implanted area to the non-implanted area. Likewise, 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 proceeding. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to display the actual shape of the regions of the device and are not intended to limit the scope of the present invention.

In order to thoroughly understand the present invention, detailed structures will be proposed in the following description, in order to explain the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may have other embodiments.

At present, the preparation method of the single crystal silicon ingot is mainly the Czochralski method, and its main process steps include seeding, shoulder laying, equal diameter, and finishing stages. In the process of preparing single crystal silicon by the Czochralski method, oxygen is the impurity with the highest content in silicon and is in a supersaturated state in the silicon single crystal. During the thermal processing of device manufacturing, oxygen in silicon will nucleate and grow at defects or impurities, forming bulk micro defects (BMD). In order to meet the quality requirements of the subsequent silicon wafers cut from single crystal silicon ingots, it is necessary to maintain the density of the BMD in the ingots to be stable. However, due to the consideration of economic costs (such as electricity consumption, length of time, etc.), the current rapid closure is generally adopted, as shown in Figure 1. As a result, the cooling time of the BMD nucleation temperature at the bottom of the equal-diameter section has changed, resulting in unstable BMD density in this part, so that this part cannot meet the quality requirements for forming positive films, resulting in waste.

In view of the above problems, the present invention provides a method for growing a single crystal silicon ingot, the growing method includes an equal diameter stage and a finishing stage in sequence, wherein the finishing stage is increased by controlling the finishing speed and/or temperature of the finishing stage The height of the segment is to keep the BMD nucleation density of the equal-diameter segment stable. The method for growing single crystal silicon ingots provided by the invention can avoid unnecessary waste of ingots, thereby improving production efficiency.

In order to thoroughly understand the present invention, detailed structures and/or steps will be proposed in the following description, in order to explain the technical solution proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may have other embodiments.

[Exemplary embodiment]

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

As shown in FIG. 2, the method for growing crystals provided by the present invention includes an equal diameter stage and a finishing stage in sequence, wherein the height of the finishing stage is increased by controlling the finishing speed and/or temperature of the finishing stage to make the equal diameter section The BMD density at the top and bottom is the same. According to the method provided by the present invention, by increasing the height of the finishing section, the BMD nucleation density of the entire equal-diameter section is consistent, to avoid uneven BMD nucleation density at the bottom of the equal-diameter section due to rapid finishing, thereby avoiding unnecessary waste of crystal rods. Increased production efficiency.

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

As shown in FIG. 3, the crystal growth furnace is used to grow a silicon single crystal by the Czochralski method, and includes a furnace body 301, and a heating device and a pulling device are provided in the furnace body 301. The heating device includes a quartz crucible 302, a graphite crucible 303, and a heater 304. Among them, the quartz crucible 302 is used to contain silicon material, such as polycrystalline silicon. The silicon material is heated into silicon melt 305 therein. The graphite crucible 303 is wrapped on the outside of the quartz crucible 302 to provide support for the quartz crucible 302 during the heating process, and the heater 304 is disposed on the outside of the graphite crucible 303. A heat shield 306 is provided above the quartz crucible 302. The heat shield 306 has an inverted conical screen surrounding the growth area of the silicon single crystal 307, which can block the growth of the heater 304 and the high temperature silicon melt 305. The direct thermal radiation of the crystalline silicon ingot 307 lowers the temperature of the single crystal silicon ingot 307. At the same time, the heat shield can also make the blowing down argon gas be directly sprayed near the growth interface, further enhancing the heat dissipation of the single crystal silicon rod 307. The side wall of the furnace body 301 is also provided with thermal insulation material, such as carbon felt.

The pulling device includes a vertically arranged seed crystal shaft 308 and a crucible shaft 309, the seed crystal shaft 308 is arranged above the quartz crucible 302, the crucible shaft 309 is arranged at the bottom of the graphite crucible 303, and the bottom of the seed crystal shaft 308 is installed by a clamp The top of the seed crystal is connected to the seed crystal shaft driving device, so that it can slowly pull upward while rotating. 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 growing a single crystal, first put silicon material in the quartz crucible 302, then close the crystal growth furnace and evacuate, and fill the crystal growth furnace with protective gas. Exemplarily, the protective gas is argon, whose purity is 99.99% or more, the pressure is 0.05 MPa (Mpa), and the flow rate is 70 liters/minute (L/min). Then, the heater 304 is turned on and heated to a melting temperature above 1420°C, so that the silicon material is completely melted into silicon melt 305 within 20 minutes.

Next, the seed crystal is immersed in the silicon melt 305, and the seed crystal is rotated and slowly pulled by the seed axis 308, so that the silicon atoms grow into a single crystal silicon rod 307 along the seed crystal. The growth process includes the stages of seeding, shoulder laying, shoulder turning, equal diameter, and finishing.

Specifically, the seeding stage is performed first. That is, when the silicon melt 305 stabilizes to a certain temperature, the seed crystal is immersed in the silicon melt, and the seed crystal is raised at a certain pulling speed, so that the silicon atoms grow along the seed crystal into a thin neck of a certain diameter until the thin neck reaches Scheduled length. Exemplarily, the pulling speed range is 1.5 mm/min-2.5 mm/min, the length of the neck is 1.2-1.4 times the diameter of the ingot, and the diameter of the neck is 5 mm-7 mm.

After the narrow neck reaches a predetermined length, it enters the shoulder laying stage, and the tapered ingot formed in this stage is the shoulder laying section of the ingot. In the shoulder-releasing stage, the temperature and the pulling rate are gradually reduced to gradually increase the diameter of the ingot until the diameter of the ingot reaches a predetermined value.

When the diameter of the single crystal silicon ingot reaches a predetermined value, it enters the equal-diameter stage, and the cylindrical ingot formed at this stage is the equal-diameter segment of the ingot. Specifically, the crucible temperature, pulling speed, crucible rotation speed and crystal rotation speed are adjusted to stabilize the growth rate and keep the crystal diameter unchanged until the crystal pulling is completed.

Finally, enter the closing stage. When finishing, speed up the lifting rate and increase the temperature of the silicon melt 305, so that the diameter of the ingot gradually becomes smaller, forming a conical shape, and finally leave the liquid surface. In this process, the height of the finishing section 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 section is consistent, and the occurrence of the bottom of the equal-diameter section due to rapid closing is avoided. The phenomenon of unstable BMD density. Wherein, the closing speed is the pulling speed. Specifically, the movement of the ingot during the crystal growth process includes pulling along the axis of the ingot and rotation of the ingot around its own axis, corresponding to the pulling speed and the rotating speed, and the ending speed is the pulling speed therein. The temperature is the heater temperature, that is, the height of the finishing section is increased by controlling the temperature of the heater 304. Finally, the finished crystal rod is lifted to the upper furnace chamber to cool down for a period of time, and then a growth cycle is completed. In one embodiment, the finishing speed and temperature are adjusted simultaneously in the finishing stage, and the diameter change of the finishing section is controlled in real time. Exemplarily, the average value of the finishing speed ranges from 0.6 mm/min to 0.7 mm/min, for example, 0.65 mm/min.

In a preferred embodiment, the height of the finishing section is more than 1/3 of the diameter of the equal-diameter section. When the height of the finishing section is greater than or equal to 1/3 of the diameter of the equal diameter section, it can ensure that the cooling time of the BMD nucleation temperature of the entire equal diameter section does not change greatly, so that the BMD nucleation density of the equal diameter section is stable, avoiding The unnecessary waste of equal-diameter sections.

In one embodiment, the temperature control and the pulling speed control are simultaneously performed during the finishing process, and the diameter change of the finishing section is immediately controlled until the end of the single crystal silicon rod 307 is separated from the silicon melt 305. You can use an image acquisition device (such as a CCD camera) to collect the image of the three-phase junction between the single crystal silicon rod 307 and the silicon melt 305 in the crystal growth furnace, and then use the computer to process the image to obtain the single crystal The diameter of the silicon ingot 307 is fed back to the control system to control the crystal growth. Specifically, during crystal growth, a bright ring is generated at the solid-liquid interface between the single crystal silicon ingot 307 and the silicon melt 305 due to the 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. The image processing program in the computer system processes the single crystal growth image to obtain the single crystal silicon rod 307 Measured diameter.

So far, the introduction of the relevant steps of the method for growing a single crystal silicon ingot according to an embodiment of the present invention is completed. It can be understood that the method for growing a single crystal silicon ingot of this embodiment not only includes the above steps, but also includes other required steps before, during or after the above steps, which are all included in the method for growing crystals of this embodiment. In the range.

The method for growing single crystal silicon ingots provided by the invention can avoid unnecessary waste of ingots, thereby improving production efficiency.

The present invention has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for purposes of illustration and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, those skilled in the art can understand that the present invention is not limited to the above-mentioned embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications fall within the scope of protection claimed by the present invention. Within range. The protection scope of the present invention is defined by the appended claims and their equivalent scope.

301: furnace body

302: Quartz crucible

303: Graphite crucible

304: Heater

305: Silicon melt

306: Hot screen

307: silicon single crystal

308: Seed axis

309: Crucible shaft

FIG. 1 shows a schematic diagram of a single crystal silicon ingot obtained by a conventional method for growing a single crystal silicon ingot.

FIG. 2 shows a schematic diagram of a single crystal silicon ingot obtained by a method for growing a single crystal silicon ingot provided by an embodiment of the present invention.

FIG. 3 shows a schematic diagram of a crystal growth furnace used in the crystal growth method of a single crystal silicon rod provided by an embodiment of the present invention.

Claims (8)

A method for growing a single crystal silicon ingot, wherein the growing method includes an equal diameter stage and a finishing stage in sequence, wherein the height of the finishing stage is increased by controlling the finishing speed and/or temperature of the finishing stage to Make the density of BMD at the top and bottom of the equal diameter section consistent. The method for growing crystals according to item 1 of the patent application scope, wherein the height of the finishing section is not less than 1/3 of the diameter of the equal-diameter section. The crystal growth method as described in item 1 of the patent application range, wherein the finishing speed is the pulling speed. The crystal growth method as described in item 1 of the patent application range, wherein the temperature is a heater temperature. The method for growing crystals according to item 1 of the patent application scope, wherein the finishing speed and the temperature are simultaneously adjusted in the finishing stage, and the diameter change of the finishing section is controlled in real time. The crystal growth method as described in item 1 of the patent application range, wherein the average value of the finishing speed ranges from 0.6 mm/min to 0.7 mm/min. The crystal growth method as described in item 1 of the patent application scope, wherein, before the equal-diameter stage, a seeding stage and a shoulder-releasing stage are further included. The crystal growth method according to any one of the items 1 to 7 of the patent application range, wherein the crystal growth method is a Czochralski method.

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