CN115233293A

CN115233293A - Lightly doped P-type silicon single crystal and preparation method thereof

Info

Publication number: CN115233293A
Application number: CN202210877742.7A
Authority: CN
Inventors: 陶莹
Original assignee: Beijing Maizhuji Technology Co ltd
Current assignee: Beijing Maizhuji Technology Co ltd
Priority date: 2022-07-25
Filing date: 2022-07-25
Publication date: 2022-10-25

Abstract

The invention relates to the technical field of silicon crystal growth, in particular to a lightly doped P-type silicon single crystal and a preparation method thereof. Melting a silicon raw material into a silicon melt, and introducing hydrogen and nitrogen into the silicon melt to dope the hydrogen and the nitrogen into the silicon melt; after doping, crystal pulling is carried out by a P-type Czochralski method to obtain a silicon single crystal. According to the preparation method, before the silicon crystal grows, hydrogen and nitrogen are simultaneously doped into the melt of the silicon raw material, so that the concentration of oxide precipitates in the monocrystalline silicon wafer before epitaxy is greatly improved, and the radial uniformity of BMD of the silicon single crystal can be greatly improved. While increasing the BMD concentration, harmful defect stacking faults can be avoided. After the silicon single crystal is made into an epitaxial wafer, the silicon single crystal can meet the requirements of all advanced logic elements and is beneficial to improving the yield.

Description

Lightly doped P-type silicon single crystal and preparation method thereof

Technical Field

The invention relates to the technical field of silicon crystal growth, in particular to a lightly doped P-type silicon single crystal and a preparation method thereof.

Background

The PP-silicon epitaxial wafer (PP-epi wafer) is mainly used in logic chips or devices (logic devices). In advanced logic chip applications, the silicon epitaxial wafer is required to haveAt least at a concentration higher than 5E8 cm ^-3 The radial uniformity of the oxide precipitates (Bulk Micro Defects, abbreviated as BMD) must be good. The effect of a sufficiently high BMD is to increase the resistance to thermal stress of the silicon epitaxial wafer, to avoid overlay error, and to provide sufficient gettering.

However, in general, PP-si epitaxial wafer cannot reach more than 5e8 cm because of the high temperature process of extending to 1100C, which causes many BMD small embryos (BMD cycle) to be destroyed by high temperature ^-3 。

In order to solve this problem, the prior art has adopted adding nitrogen during the growth of P-type Czochralski (Czochralski) silicon crystals. The BMD concentration in the silicon single crystal can be greatly supplied due to the existence of nitrogen, so that the BMD concentration in the PP-silicon epitaxial wafer prepared by the silicon single crystal can reach 5E8 cm ^-3 The above. However, the silicon single crystal to which nitrogen is added has the following problems:

(1) In special applications, a higher 1E9 cm is required ^-3 In the above BMD, it is necessary to increase the nitrogen concentration greatly, and when the nitrogen concentration is high, a very harmful micro defect, i.e., stacking fault, is generated on the silicon single crystal, and such a defect seriously affects the yield of the downstream chip manufacturing, particularly the yield of the logic chip.

(2) In a silicon single crystal to which only one element of nitrogen is added, the BMD distribution is not uniform in the radial direction, and the BMD concentration at the edge tends to be greatly reduced. This also affects the yield of the chip.

Disclosure of Invention

The invention aims to solve the technical problem of providing a lightly doped P-type silicon single crystal and a preparation method thereof.

The technical scheme for solving the technical problems is as follows:

the invention relates to a preparation method of a lightly doped P-type silicon single crystal, which comprises the steps of melting a silicon raw material into a silicon melt, and introducing hydrogen and nitrogen into the silicon melt to dope the hydrogen and the nitrogen into the silicon melt; after doping, crystal pulling is carried out by a P-type Czochralski method to obtain a silicon single crystal.

The invention can be realized by the following further technical scheme:

further, the introduction of nitrogen gas and hydrogen gas into the silicon melt is stopped before crystal pulling is performed.

Further, after the temperature of the silicon melt is stabilized, hydrogen and nitrogen are doped into the silicon melt.

The invention provides a lightly doped P type silicon single crystal which is prepared by the preparation method.

Further, in the silicon single crystal, the concentration of hydrogen atoms in the silicon single crystal is 1E13 to 1E14 cm ^-3 The concentration of nitrogen atoms in the silicon single crystal is 1E13 to 1E14 cm ^-3 。

Further, oxide precipitates in the silicon single crystal are uniformly distributed, and the concentration of the oxide precipitates is 1E9 cm or more ^-3 。

The invention provides a crystal pulling furnace for preparing a lightly doped P-type silicon single crystal, which comprises an auxiliary chamber, wherein a hydrogen input pipeline and a nitrogen output pipeline are communicated with the auxiliary chamber, and mass flow controllers are respectively arranged on the hydrogen input pipeline and the nitrogen input pipeline.

Further, the nitrogen input pipeline is positioned above the hydrogen input pipeline.

Further, an argon inlet is further formed in the auxiliary chamber and is located above the nitrogen input pipeline.

The furnace further comprises a furnace chamber, wherein a crucible is arranged in the furnace chamber, and a heater is arranged on the lower side of the crucible; the top of the furnace chamber is in communication with the sub-chamber, and the sub-chamber is located above the crucible.

The invention has the beneficial effects that:

(1) In the preparation method, before the silicon crystal growth is carried out by adopting a P-type Czochralski method (Czochralski), hydrogen and nitrogen are simultaneously doped into a melt of a silicon raw material, so that the concentration of oxide precipitates (BMD) in a single crystal silicon wafer before the epitaxy is greatly improved;

(2) The preparation method can greatly improve the radial uniformity of the BMD of the silicon single crystal;

(3) The preparation method can avoid the generation of harmful defect stacking faults (stacking faults) while improving the BMD concentration;

(4) The silicon single crystal has high BMD concentration and uniform distribution by doping hydrogen and nitrogen, and can meet the requirements of all advanced logic elements after being made into an epitaxial wafer, thereby being beneficial to improving the yield;

(5) The crystal pulling furnace is characterized in that the auxiliary chamber is respectively provided with a hydrogen input pipeline and a nitrogen input pipeline, and the pipelines are respectively provided with a mass flow controller which can control the input flow and pressure of hydrogen and nitrogen, so that the concentration of hydrogen and nitrogen in silicon melt is controlled.

Drawings

FIG. 1 is a schematic view of the crystal pulling furnace of the present invention;

FIG. 2 is a graph showing the concentration distribution of BMD in silicon single crystals of examples and comparative examples, which are the production method of a lightly P-doped silicon single crystal of the present invention.

In the drawings, the reference numbers indicate the following list of parts:

1. a sub-chamber; 11. a hydrogen input conduit; 12 nitrogen gas input pipeline; 13. an argon inlet;

2. a mass flow controller;

3. a furnace chamber; 4. a crucible; 5. a heater.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth to illustrate, but are not to be construed to limit the scope of the invention.

The preparation method of the lightly doped P-type silicon single crystal comprises the steps of melting a silicon raw material into silicon melt, doping hydrogen and nitrogen into the silicon melt, and after doping, pulling crystal by adopting a P-type Czochralski method to obtain the silicon single crystal.

In the method of the present invention, hydrogen and nitrogen are simultaneously doped into a melt of a silicon raw material before silicon crystal growth by a P-type Czochralski method (Czochralski method), so that the concentration of oxide precipitates (BMDs) in a single crystal silicon wafer before epitaxy is greatly increased, stacking faults (stacking faults) are not generated, and the radial uniformity of BMDs can be greatly improved. After the silicon wafer is made into an epitaxial wafer, the requirements of all advanced logic elements can be met, and the yield is improved.

The preparation method of the invention dopes nitrogen and hydrogen in silicon single crystal at the same time, the principle is that hydrogen atom is an element with high diffusion coefficient in the crystal lattice of silicon. Since it is much smaller in size than silicon atoms, the addition of hydrogen to the silicon lattice induces the generation of more BMD. And because of its high diffusion coefficient, hydrogen atoms can diffuse out of the silicon surface during the epitaxial high temperature process up to 1100 ℃, thus not causing adverse effects in the application of logic elements.

The silicon feedstock of the present invention may be any specific conventional electronic grade silicon feedstock, the power of the specific molten silicon feedstock being set according to the specific thermal field conditions. The introduction amount of the hydrogen and the nitrogen is based on the final concentration in the silicon single crystal, and in the actual production, the specific introduction amount can be properly adjusted due to different specific specifications of equipment such as a crystal pulling furnace and the like.

The addition of hydrogen and nitrogen is carried out by a gas phase addition method. When hydrogen and nitrogen are added to the crystal pulling furnace, the hydrogen and nitrogen dissolve in the silicon melt, and the hydrogen and nitrogen in the silicon melt further enter the silicon ingot during crystal pulling. During crystal pulling, a large amount of inert gas is always circulated, and only negligibly small amounts of hydrogen and nitrogen are dissolved into the silicon melt after the addition of hydrogen and nitrogen is stopped.

Since it is necessary that hydrogen and nitrogen are dissolved in the silicon melt, it is necessary to start adding hydrogen and nitrogen after the silicon raw material is completely melted. The addition is generally resumed at the stage when the silicon melt reaches a stable temperature. The addition of hydrogen and nitrogen is stopped before the crystal pulling begins, otherwise the rate of crystallization is affected. The stabilization temperature is a necessary stage in the process of pulling single crystal silicon, and the specific temperature of the stage varies according to different equipment and requirements, but is a conventional setting in the art. In addition, the silicon melt in a large crucible has a large area on the surface, the temperature of each position is different, and the temperature in the central area of the crucible is 5-10 ℃ higher than the melting point of silicon.

The lightly doped P-type silicon single crystal is prepared by the preparation method.

In the silicon single crystal, the concentration of hydrogen atoms in the silicon single crystal is 1E13 to 1E14 cm ^-3 The concentration of nitrogen atoms in the silicon single crystal is 1E13 to 1E14 cm ^-3 。

The silicon single crystal has a uniform distribution of oxide precipitates and a concentration of the oxide precipitates of not less than 1E9 cm ^-3 。

The epitaxial wafer prepared by the silicon single crystal has high concentration of BMD and can not cause adverse effect on the application of logic elements.

In addition to the introduction of hydrogen and nitrogen for doping, argon is often introduced as a protective gas during the preparation. Thus, the entire gas phase in the production process includes hydrogen, nitrogen and argon. The specific concentration of nitrogen or hydrogen to be doped in the silicon melt can be adjusted by controlling the volume of the introduced hydrogen or nitrogen. Taking hydrogen as an example, the partial pressure of hydrogen is related to the volume fraction of hydrogen in the whole gas phase and the total pressure, and the total pressure can be measured by a pressure measuring device on the crystal pulling furnace; the specific calculation method is as formula (1):

（1）

in the formula (1), k is a Henry constant, and the equilibrium concentration of hydrogen dissolved in the silicon melt is proportional to the partial pressure of hydrogen in the gas phase according to Henry's law, and is calculated as in the formula (2):

（2）

partial pressure can be obtained through the volume fraction and total pressure of hydrogen in the gas phase through the formula, and the concentration of hydrogen dissolved in the silicon melt is calculated according to the partial pressure. While the volume fraction of hydrogen in the gas phase can be controlled, the total pressure can be measured. The concentration of nitrogen can also be calculated by the above procedure.

Therefore, based on the principle, the invention also provides a crystal pulling furnace for preparing the lightly doped P type silicon single crystal.

The crystal pulling furnace comprises an auxiliary chamber 1 and a crystal pulling device, wherein the crystal pulling device is positioned in the auxiliary chamber 1, and the upper end of the crystal pulling device is provided with a crystal pulling device. The auxiliary chamber 1 is communicated with a hydrogen input pipeline 11 and a nitrogen output pipeline 12, and the hydrogen input pipeline 11 and the nitrogen input pipeline 12 are respectively provided with a mass flow controller 2; the mass flow controllers 2 are respectively arranged on the hydrogen input pipeline 11 and the nitrogen input pipeline 12, so that the flow rate of the introduced hydrogen and nitrogen can be controlled, and the concentration of the hydrogen and the concentration of the nitrogen in the silicon melt can be regulated and controlled.

Preferably, the nitrogen input pipe 12 is located above the hydrogen input pipe 11; since nitrogen is heavier than hydrogen, the nitrogen input pipe 12 is arranged above the hydrogen input pipe 11, and when the nitrogen and the hydrogen are introduced, the nitrogen can press the hydrogen down, so that the hydrogen can be better doped into the silicon melt.

Preferably, the auxiliary chamber 1 is also provided with an argon inlet 13; the argon is introduced for pressure regulation, so that the oxidation of parts in the furnace can be prevented, and the tail gas emission and heat extraction can be facilitated; an argon inlet 13 is located above the nitrogen inlet line 12.

Preferably, the furnace also comprises a furnace chamber 3, a crucible 4 is arranged in the furnace chamber 3, and a heater 5 is arranged at the lower side of the crucible 4; the top of the furnace chamber 3 communicates with the sub-chamber 1, and the sub-chamber is located above the crucible 4.

The technical solution of the present invention is illustrated by the following specific examples.

Examples

The crystal pulling furnace is adopted to prepare the hydrogen and nitrogen doped silicon single crystal, and the specific operation steps are as follows:

silicon raw material is charged into a crucible 4 in a furnace chamber 3 and heated to melt the entire amount of the silicon raw material to obtain a silicon melt. After the temperature of the silicon melt is stabilized, corresponding gas is respectively introduced through the argon inlet 13, the nitrogen input pipeline 12 and the hydrogen input pipeline 11. The flow rates of hydrogen and nitrogen are controlled by mass flow controllers 2, respectively.

And (3) calculating the volumes of the hydrogen and the nitrogen by adopting a formula (1) and a formula (2) in a reverse way according to the concentrations of the hydrogen and the nitrogen in the final silicon single crystal so as to obtain the flow rates of the hydrogen and the nitrogen. Meanwhile, in the actual preparation process, fine adjustment is carried out according to the actually detected concentration.

After the introduction of hydrogen and nitrogen was completed, crystal pulling was started to obtain a hydrogen and nitrogen-doped 300 mm silicon single crystal.

Comparative example

The silicon single crystal was produced using the same silicon raw material and crystal pulling method as in example, in this comparative example, only nitrogen was doped.

The BMD concentrations of the silicon single crystals obtained in examples and comparative examples were measured, respectively, and the results of the measurements are shown in fig. 2.

As can be seen from fig. 2, BMD concentrations at a plurality of positions in the radial direction from the center of the single crystal silicon were measured. It can be seen that the BMD concentration of the silicon single crystal of the example was higher at each position than that of the silicon single crystal of the comparative example. Meanwhile, the fluctuation of the BMD concentration of the silicon single crystal of the example was small, while the fluctuation of the BMD concentration of the comparative example was large.

As can be shown by the above examples and comparative examples, the present invention has a higher BMD concentration using a hydrogen and nitrogen doped silicon single crystal, and at the same time, BMD is uniformly distributed on the silicon single crystal.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on orientations or positional relationships shown in the drawings, which are merely for convenience of description and simplification of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

In the present invention, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the second feature or the first and second features may be indirectly contacting each other through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A preparation method of lightly doped P-type silicon single crystal is characterized in that a silicon raw material is melted into a silicon melt, and hydrogen and nitrogen are introduced into the silicon melt to dope the silicon melt with hydrogen and nitrogen; after doping, crystal pulling is carried out by a P-type Czochralski method to obtain a silicon single crystal.

2. The method for producing a lightly P-doped silicon single crystal as defined in claim 1, wherein the introduction of nitrogen gas and hydrogen gas into the silicon melt is stopped before the pulling.

3. The method for producing a silicon single crystal according to claim 1, wherein the silicon melt is doped with hydrogen gas and nitrogen gas after the temperature of the silicon melt is stabilized.

4. A lightly P-doped silicon single crystal, which is prepared by the preparation method of any one of claims 1 to 3.

5. The lightly P-doped silicon single crystal according to claim 4, wherein the concentration of hydrogen atoms in the silicon single crystal is 1E13 to 1E14 cm ^-3 The concentration of nitrogen atoms in the silicon single crystal is 1E13 to 1E14 cm ^-3 。

6. The lightly P-doped silicon single crystal according to claim 5, wherein the concentration of oxygen precipitates in the silicon single crystal is uniformly distributed in a radial direction of the silicon single crystal, and the maximum concentration of the oxygen precipitates is 1E9 cm or more ^-3 。

7. A crystal pulling furnace for preparing the lightly doped P type silicon single crystal as claimed in any one of claims 4 to 6, characterized by comprising an auxiliary chamber (1) and a crystal pulling device, wherein the auxiliary chamber (1) is communicated with a hydrogen input pipeline (11) and a nitrogen output pipeline (12), and the hydrogen input pipeline (11) and the nitrogen input pipeline (12) are respectively provided with a mass flow controller (2).

8. A crystal pulling furnace for producing a lightly P-doped silicon single crystal as claimed in claim 7, characterized in that the nitrogen gas feed conduit (12) is located above the hydrogen gas feed conduit (11).

9. A crystal pulling furnace for producing a lightly doped P-type silicon single crystal as claimed in claim 8, characterized in that an argon inlet (13) is further provided to the sub-chamber (1), the argon inlet being located above the nitrogen gas feed pipe (12).

10. A crystal pulling furnace for preparing a lightly doped P-type silicon single crystal according to any one of claims 7 to 9, characterized by further comprising a furnace chamber (3), wherein a crucible (4) is arranged in the furnace chamber (3), and a heater (5) is arranged on the lower side of the crucible (4);

the top of the furnace chamber (3) is communicated with the bottom of the auxiliary chamber (1), and the auxiliary chamber (1) is positioned above the crucible (4).