TWI628316B - Methods for forming monocrystalline silicon ingot and wafer - Google Patents

Abstract

The invention provides a method for forming single crystal silicon and a wafer. When a single crystal silicon ingot is formed by the Czochralski method, a gas containing deuterium gas and nitrogen gas is passed into the molten silicon to cause deuterium. Atoms and nitrogen atoms are stored in the gaps between the single crystal silicon ingots. After the wafers are formed using the single crystal silicon ingots, the deuterium can diffuse out of the device formed on the wafers and combine with the dangling bonds at the interface to form a relatively large Stable structure, thus avoiding the penetration of hot carriers, reducing the leakage current, improving the performance and reliability of the device; In addition, the straight pull single crystal silicon ingot with a suitable nitrogen concentration can be formed in the wafer body after one-step high temperature annealing. High-density oxygen precipitation forms a clean area with a certain width on the near surface of the wafer. As the nitrogen concentration increases, the radial distribution of oxygen precipitation in the wafer becomes more uniform, which can improve the performance of the wafer.

Description

Method for forming single crystal silicon ingot and wafer

The present invention relates to the field of single crystal growth and semiconductor manufacturing in the Czochralski method, and more particularly to a method for forming single crystal silicon ingots and wafers.

Single crystal silicon, which is a starting material for manufacturing semiconductor devices, is usually grown into a cylindrical single crystal silicon ingot using the crystal growth technology of the Czochralski (CZ) method (also known as the straight-draw technology). Single crystal silicon ingots are processed into wafers through a series of wafer processing processes such as slicing, etching, cleaning, and polishing.

According to the Czochralski method, the silicon wafer is heated and melted in a single crystal furnace in a crucible, and a rod-shaped seed crystal (called a seed crystal) with a diameter of only 10 mm is immersed in the melt, and the seed crystal is slightly rotated. Ascending upward, the silicon atoms in the melt will continue to crystallize on the previously formed single crystal and continue its regular atomic arrangement. If the entire crystallization environment is stable, crystals can be formed again and again, and finally a single-crystal silicon single crystal with a cylindrical arrangement of atoms, that is, a silicon single-crystal silicon ingot.

Molten silicon is contained in quartz crucibles and is often contaminated by a variety of impurities, one of which is oxygen. At the melting temperature of silicon, oxygen penetrates into the crystal lattice until it reaches a predetermined concentration, which is generally determined by the solubility of oxygen in silicon at the melting temperature of silicon and the actual segregation coefficient of oxygen in solidified silicon. Crystal growth The concentration of oxygen infiltrating the silicon ingot over a long period of time is greater than the solubility of oxygen in the solidified silicon at typical temperatures used in the manufacture of semiconductor devices. As the crystal grows from the molten silicon and cools, its oxygen solubility decreases rapidly, and oxygen saturates in the cooled silicon ingot.

The silicon ingot is cut into wafers. The interstitial oxygen remaining in the wafer grows into an oxygen precipitate during the subsequent thermal process. The presence of oxygen precipitation in the active area of the device can reduce the integrity of the gate oxide and cause unnecessary substrate leakage currents.

An object of the present invention is to provide a method for forming a single crystal silicon ingot and a wafer, which can reduce oxygen precipitation and improve the performance of subsequent devices.

In order to achieve the above object, the present invention provides a method for forming a single crystal silicon ingot, comprising the steps of: providing polycrystalline silicon fragments, putting the polycrystalline silicon fragments into a crucible for melting and passing a gas, the gas including deuterium and Nitrogen; a single crystal silicon ingot is formed by using a magnetic field Cheby's crystal pulling method.

Further, in the method for forming a single crystal silicon ingot, the gas introduced is a mixed gas of deuterium, nitrogen, and argon.

Further, in the method for forming a single crystal silicon ingot, the partial pressure of the deuterium gas ranges from 1% to 80%.

Further, in the method for forming a single crystal silicon ingot, a partial pressure range of the nitrogen gas is 1% to 80%.

Further, in the method for forming a single crystal silicon ingot, the density of nitrogen atoms in the formed single crystal silicon ingot ranges from 1 × 10 ¹² atoms / cm 3 to 8 × 10 ¹⁸ atoms / cm 3.

Further, in the method for forming a single crystal silicon ingot, the density range of the deuterium atoms in the formed single crystal silicon ingot is 1 × 10 ¹² atomic cubic centimeters to 8 × 10 ¹⁸ atoms / cubic centimeters.

Further, in the method for forming a single crystal silicon ingot, the magnetic field-added Cheshire pull method includes the steps of: placing the doped polycrystalline silicon fragments in a crucible to melt at a predetermined temperature; A seed crystal is used to pull the crystal upward at a predetermined pulling rate, and when the length of the fine crystal reaches a predetermined length, the pulling rate is reduced to enter the shoulder-releasing step; during the shoulder-releasing step, the pulling speed is reduced to maintain a linear cooling rate to form a predetermined diameter After the single-crystal silicon ingot is passed, the shoulder is turned into the same diameter step. When the diameter of the single-crystal silicon ingot grows to a predetermined requirement, it is quickly raised upward to cool down in time. At the same time, the linear cooling is stopped, and the crucible is given a rising rate. Adjust the pulling speed control. After the single crystal silicon ingot diameter is relatively stable, open the automatic isometric control program and enter the automatic isometric control stage.

Further, in the method for forming a single crystal silicon ingot, a diameter of the single crystal silicon ingot is controlled by the crystal pulling rate and a predetermined temperature.

Further, in the method for forming a single crystal silicon ingot, the magnetic field strength is 1000 to 5000 Gauss.

The invention also proposes a method for forming a wafer. A single crystal silicon ingot is used as a raw material to form a wafer. The single crystal silicon ingot is formed using the method for forming a single crystal silicon ingot as described above. The wafer contains Deuterium and nitrogen are doped with atoms, and the wafer is subjected to a high-temperature annealing process.

Further, in the method for forming a wafer, the method includes the steps of sequentially performing thinning, surface grinding, polishing, edge processing, and cleaning processing on the single crystal silicon ingot to form a wafer.

Further, in the method for forming a wafer, a temperature range of the high-temperature annealing process is 800 degrees Celsius (° C) to 2000 degrees Celsius (° C).

Compared with the conventional technology, the beneficial effects of the present invention mainly include: when a single crystal silicon ingot is formed by using the Chai's crystal pulling method, a gas containing deuterium and nitrogen is introduced into the molten silicon, so that the deuterium atoms and nitrogen Atoms are stored in the gaps between the single crystal silicon ingots. After the wafers are formed using the single crystal silicon ingots, when a device is formed on the wafer, deuterium can diffuse out and combine with dangling bonds at the interface to form a more stable structure. In order to avoid the penetration of hot carriers, reduce the leakage current, improve the performance and reliability of the device; In addition, the straight-drawing single-crystal silicon ingot with a suitable nitrogen concentration can form high-density oxygen in the wafer after one-step high temperature annealing. The precipitation forms a clean area of a certain width on the near surface of the wafer. As the nitrogen concentration increases, the radial distribution of oxygen precipitation in the wafer becomes more uniform, which can improve the performance of the wafer.

S100‧‧‧ provides polycrystalline silicon fragments. The polycrystalline silicon fragments are placed in a crucible to be melted and passed into a gas, which includes deuterium and nitrogen.

S200‧‧‧Single-crystal silicon ingot by magnetic field Cheby pull method

FIG. 1 is a flowchart of a method for forming a single crystal silicon ingot according to an embodiment of the present invention.

The method for forming the single crystal silicon ingot and wafer of the present invention will be described in more detail below with reference to the schematic diagrams, which show the preferred embodiments of the present invention. It should be understood that those skilled in the art can understand the present invention described herein. Modifications are made while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as a broad understanding of those skilled in the art, and not as a limitation on the present invention.

In the interest of clarity, not all features of an actual embodiment are described. In the following description, well-known functions and structures are not described in detail because they may confuse the present invention with unnecessary details. It should be considered that in the development of any practical embodiment, a large number of implementation details must be made to achieve the developer's specific goals, such as by a system or business-related restriction, by a The embodiment is changed to another embodiment. In addition, it should be considered that such development work may be complicated and time-consuming, but it is only routine work for those with ordinary knowledge in the art.

The invention is described more specifically in the following paragraphs by way of example with reference to the drawings. The advantages and features of the present invention will become clearer from the following description and the scope of patent application. It should be noted that the drawings are all in a very simplified form and all use inaccurate proportions, which are only used to facilitate and clearly explain the purpose of the embodiments of the present invention.

Please refer to FIG. 1. In this embodiment, a method for forming a single crystal silicon ingot is proposed, which includes steps: S100: providing polycrystalline silicon fragments, placing the polycrystalline silicon fragments in a crucible for melting and passing in a gas, The gas includes deuterium and nitrogen; S200: a single crystal silicon ingot is formed by using a magnetic field Chai's crystal pulling method.

In step S100, the polycrystalline silicon fragments can be polycrystalline silicon or fragments of silicon wafers containing impurities. To refine using such silicon wafers, firstly, the silicon wafers need to be placed in a quartz crucible for melting, so as to form monocrystalline silicon subsequently. Ingot to remove some impurities. Specifically, the melting temperature and the manufacturing process are similar to those in the prior art, and details are not described herein.

Gas injection is performed on the melted polycrystalline silicon fragments, and the gas includes deuterium and nitrogen; specifically, the gas may be a mixed gas of deuterium, nitrogen, and argon. The partial pressure range of the deuterium gas is 1% to 80%, and the partial pressure range of the nitrogen gas is 1% to 80%. Specifically, it can be determined according to the requirements of the manufacturing process, which is not limited herein.

In one embodiment, the density of nitrogen atoms in the formed single crystal silicon ingot ranges from 1 × 10 ¹² atoms / cm 3 to 8 × 10 ¹⁸ atoms / cm 3 (how many atoms are contained in each cm 3). In one embodiment, the density of deuterium atoms in the formed single crystal silicon ingot ranges from 1 × 10 ¹² atoms / cm 3 to 8 × 10 ¹⁸ atoms / cm 3.

When the magnetic field is used to form a single crystal silicon ingot by the Cheby pull method, the molten polycrystalline silicon fragments are doped with deuterium and nitrogen, so that the deuterium and nitrogen are stored in the gap between the single crystal silicon ingots, which is conducive to upgrading subsequent devices. Performance.

In step S200, a single-crystal silicon ingot is formed by using a magnetic field Chai's crystal pulling method.

Wherein, the magnetic field-added Cheshire crystal pulling method includes the steps of: placing the doped polycrystalline silicon fragments in a crucible to melt at a predetermined temperature; and using a seed crystal to pull the crystal upward at a predetermined pulling rate until fine When the crystal length reaches a predetermined length, reduce the pulling rate and enter the shoulder-releasing step; in the shoulder-releasing step, reduce the pulling speed and maintain a linear cooling rate to form a single-crystal silicon ingot of a predetermined diameter, and then enter the shoulder equalizing step; After the diameter of the single crystal silicon ingot grows to a predetermined requirement, it is quickly raised upwards, and the temperature is reduced in a timely manner. At the same time, the linear cooling is stopped, and the crucible is given a rising rate. Slowly adjust the pull speed control according to the rate of change of the diameter. , Open the automatic isometric control program and enter the stage of automatic isometric control.

The diameter of the single crystal silicon ingot is controlled by the crystal pulling rate and a predetermined temperature. The diameter of the single crystal silicon ingot can be determined according to the needs of the manufacturing process, and is not limited herein. Wherein, the added magnetic field strength is 1000 to 5000 Gauss, for example, 3000 Gauss.

In another aspect of this embodiment, a method for forming a wafer is also proposed. A single crystal silicon ingot is used as a raw material to form a wafer, and the single crystal silicon ingot is formed using the single crystal silicon ingot as described above. The wafer is doped with deuterium and nitrogen, and the wafer is subjected to a high-temperature annealing process.

Specifically, the method for forming a wafer includes the steps of: performing thinning, surface grinding, polishing, edge processing, and cleaning processing on the single crystal silicon ingot in order to form a wafer.

The temperature range of the high-temperature annealing process is 800 ° C to 2000 ° C, for example, 1000 ° C. After one-step high-temperature annealing, a high-density oxygen precipitation can be formed in the wafer body, and a clean area with a certain width can be formed on the near surface of the wafer. To improve wafer performance.

In summary, in the method for forming a single-crystal silicon ingot and a wafer provided in the embodiments of the present invention, when a single-crystal silicon ingot is formed by using the Chai's method, a molten silicon containing deuterium and nitrogen is passed through. The gas allows the deuterium and nitrogen atoms to be stored in the gap between the single crystal silicon ingots. After the wafer is formed using the single crystal silicon ingots, the deuterium can diffuse out of the device formed on the wafer and carry out dangling bonds with the interface. Combined to form a more stable structure, thereby avoiding the penetration of hot carriers, reducing leakage current, and improving the performance and reliability of the device; In addition, a straight-pull single-crystal silicon ingot with a suitable nitrogen concentration is subjected to a one-step high temperature annealing, A high-density oxygen precipitation can be formed in the circle and a clean area of a certain width can be formed on the near surface of the wafer. As the nitrogen concentration increases, the radial distribution of oxygen precipitation in the wafer becomes more uniform, which can improve the performance of the wafer.

The content of the specific embodiments described above is used to describe the present invention in detail. However, these embodiments are only used for illustration and are not intended to limit the present invention. Those skilled in the art can understand that various changes or modifications made to the present invention without departing from the scope defined by the scope of the attached patent application fall into a part of the present invention.

Claims (10)

A method for forming a single crystal silicon ingot, which comprises the steps of: providing polycrystalline silicon fragments, putting the polycrystalline silicon fragments into a crucible for melting and introducing a gas, the gas including deuterium and nitrogen; A partial pressure range of the deuterium gas is 1% to 80%, and a partial pressure range of the nitrogen gas is 1% to 80%; and a single crystal silicon ingot is formed by using a magnetic field Czochralski method. The method for forming a single crystal silicon ingot according to item 1 of the scope of patent application, wherein the gas is a mixed gas of deuterium, nitrogen, and argon. The method for forming a single crystal silicon ingot according to item 1 of the scope of patent application, characterized in that the density range of the nitrogen atoms in the formed single crystal silicon ingot is 1 × 10 ¹² atoms / cm 3 to 8 × 10 ¹⁸ atoms / Cubic centimeters. The method for forming a single crystal silicon ingot as described in item 1 of the scope of the patent application, wherein the density of the deuterium atoms in the formed single crystal silicon ingot ranges from 1 × 10 ¹² atoms / cm 3 to 8 × 10 ¹⁸ atoms / Cubic centimeters. The method for forming a single crystal silicon ingot according to item 1 of the scope of the patent application, characterized in that the magnetic field Cheshire pull method includes the step of placing the doped polycrystalline silicon fragments in a crucible. Melting at a predetermined temperature; using a seed crystal to pull up the crystal at a predetermined pulling rate, and when the length of the fine crystal reaches a predetermined length, reducing the pulling rate and entering a shoulder-releasing step; reducing the pulling speed in the shoulder-releasing step to maintain a linearity After the single crystal silicon ingot of a predetermined diameter is formed, the temperature is reduced, and then the shoulder is turned into the same diameter step. After the diameter of the single crystal silicon ingot has grown to a predetermined requirement, it is quickly raised upwards to reduce the temperature in time. According to the rate of change of the diameter, slowly adjust the pull speed control. After the single crystal silicon ingot diameter is relatively stable, open the automatic isometric control program and enter the automatic isometric control stage. The method for forming a single crystal silicon ingot according to item 5 of the scope of the patent application, wherein the diameter of the single crystal silicon ingot is controlled by the pulling rate and a predetermined temperature. The method for forming a single crystal silicon ingot according to item 5 of the scope of patent application, wherein the magnetic field strength is 1000 to 5000 Gauss. A method for forming a wafer, wherein a single crystal silicon ingot is used as a raw material to form a wafer, characterized in that the single crystal silicon ingot is formed by using the method described in item 1 of the scope of patent application, and the wafer contains deuterium and Nitrogen is doped, and the wafer is subjected to a high-temperature annealing process. The method for forming a wafer according to item 8 of the scope of patent application, characterized in that it comprises the steps of: sequentially thinning the single crystal silicon ingot, surface grinding, polishing, edge processing and cleaning processing to form a wafer . The method for forming a wafer according to item 8 of the scope of patent application, wherein the temperature range of the high-temperature annealing process is 800 ° C to 2000 ° C.