CN111364098A

CN111364098A - Doping device for heavily-doped Czochralski single crystal

Info

Publication number: CN111364098A
Application number: CN201811605948.4A
Authority: CN
Inventors: 李超; 崔彬; 方峰; 王学锋; 郑沉; 邓德辉
Original assignee: Grinm Semiconductor Materials Co Ltd
Current assignee: Grinm Semiconductor Materials Co Ltd
Priority date: 2018-12-26
Filing date: 2018-12-26
Publication date: 2020-07-03

Abstract

The invention discloses a doping device for re-doping Czochralski single crystals. The side wall of the quartz bell jar in the doping device is composed of a plurality of quartz walls, a plurality of holes are respectively formed on the quartz walls positioned on the inner side of the outer wall, and the holes on the two adjacent layers of quartz walls are distributed in a mutually staggered mode. Wherein, the arrangement mode of the plurality of layers of quartz walls is as follows: the starting point of the top part descends layer by layer from inside to outside. The quartz wall inside the outer wall is preferably two layers. The doping device changes the thermal motion mode of the doping gas molecules by improving the structure of the quartz bell jar, and the doping gas molecules can exist in the quartz bell jar for a longer time. Under the same doping time and conditions, the method is more favorable for doping gas molecules to be dissolved into the silicon material, and can obviously improve the doping efficiency.

Description

Doping device for heavily-doped Czochralski single crystal

Technical Field

The invention relates to a doping device for remixing Czochralski single crystals, belonging to the technical field of single crystal silicon drawing.

Background

Currently, semiconductor silicon materials can be divided into heavily doped silicon single crystals and lightly doped silicon single crystals. The resistivity value of the pulled single crystal is determined by the doping level of the selected doping element, the higher the doping level of the doping element, the lower the resistivity of the single crystal. Low-resistivity single crystals with large doping amount are called heavily doped silicon single crystals; on the other hand, if the doping amount of the doping element is small, the silicon single crystal is called lightly doped silicon single crystal.

The heavily doped silicon single crystal is used for manufacturing a Schottky diode of a switching power supply of a super large scale integrated circuit and a special electronic device of a field control high frequency power electronic device, and a modern power grid control system requires circuits with small volume, fast conversion, high voltage resistance, military control and guidance, requires strong high frequency resistance and small volume, is a preferred product, is a new material urgently needed by special industries such as national economic development, national defense and the like of China, generally adopts an N/N- +, P/P- + -epitaxial structure in the COMS process, combines the epitaxial structure taking a heavily doped silicon wafer as a substrate with an internal gettering process, and is an effective way for solving latch-up effect in the integrated circuit and soft failure caused by α particles.

When the heavily doped low-resistivity silicon single crystal is pulled, the doping amount required to be doped is relatively large. At present, the main doping agents are arsenic, phosphorus and antimony which have strong volatility, and volatile matters generated by the arsenic, the phosphorus and the antimony have strong harm to human bodies and the environment. As dopant, arsenic is attracting attention from a number of material manufacturers As an ideal dopant. Arsenic, however, is highly volatile, and a large amount of dopant is volatilized during incorporation into a silicon melt, while impurities incorporated during growth of a silicon single crystal are continuously volatilized through the melt surface. The volatilized dopant not only affects the accuracy of doping, but also brings much trouble to subsequent work. As is well known, arsenic is a toxic materialSubstances, particularly oxides thereof, e.g. As₂O₃Pi Shuang is called Pi Shuang, which is a highly toxic substance. Therefore, the difficulty of environmental protection treatment is very great in the technology of preparing heavily arsenic-doped silicon single crystal. Therefore, when arsenic is selected as a dopant, a doping method and a doping apparatus different from those of the conventional method must be developed to reduce the emission of arsenic from the source.

Among many parameters of heavily doped monocrystalline silicon, resistivity is the most basic and the most important, and with the increasing competitive pressure of the semiconductor industry, the control of the product on the resistivity range is gradually accurate, so that the doped arsenic is increased continuously.

In the doping process, arsenic is dissolved into the silicon material as much as possible, and a single crystal product with lower resistivity can be pulled within the same crystallization time. As shown in fig. 1 and 2, fig. 1 is a schematic structural view of a quartz bell jar used in a conventional doping apparatus, and fig. 2 is a top view thereof. When the quartz bell jar is adopted for doping, the doping process has some defects:

1. after the arsenic is sublimated at high temperature, gas molecules are volatilized rapidly, the gas molecules continuously move around at high temperature (as shown by arrows in figure 1), the gas molecules reversely impact the liquid level after contacting the quartz bell jar, and a large part of gas molecules which are not fused into the silicon material are lost from gaps between the quartz bell jar and the liquid level, so that the doping efficiency is reduced.

2. Volatile matters can be attached to a vacuum pipeline, the pipeline can be partially blocked for a long time, the normal operation of a vacuum system is influenced, the atmosphere is not smooth, the crystallization is influenced, and the extracted arsenic is harmful and toxic substances and causes harm to the outside.

Disclosure of Invention

The invention aims to provide a doping device for heavily doping Czochralski single crystals, which improves the movement mode of gas molecules by improving the structure of a quartz bell jar in the device so as to improve the doping efficiency.

In order to achieve the purpose, the invention adopts the following technical scheme:

a doping device for re-doping Czochralski single crystal is provided, wherein the side wall of a quartz bell jar in the doping device is composed of a plurality of quartz walls, a plurality of holes are respectively formed on the quartz walls positioned at the inner side of the outer wall, and the holes on two adjacent quartz walls are distributed in a mutually staggered mode.

Wherein, the arrangement mode of the plurality of layers of quartz walls is as follows: the starting point of the top part descends layer by layer from inside to outside.

Wherein the quartz wall located inside the outer wall is preferably two layers.

The invention has the advantages that:

the doping device changes the thermal motion mode of the doping gas molecules by improving the structure of the quartz bell jar, and the doping gas molecules can exist in the quartz bell jar for a longer time. Under the same doping time and conditions, the method is more favorable for doping gas molecules to be dissolved into the silicon material, and can obviously improve the doping efficiency.

Drawings

Fig. 1 is a schematic structural diagram of a conventional doping apparatus.

Fig. 2 is a top view of the doping apparatus of fig. 1.

Fig. 3 is a schematic structural diagram of a doping apparatus according to the present invention.

Fig. 4 is a top view of the doping apparatus of fig. 3.

Detailed Description

The present invention is further described with reference to the following drawings, which are not meant to limit the scope of the invention.

The doping device for re-doping Czochralski single crystal uses an improved quartz bell jar structure. The side wall of the quartz bell jar is composed of a plurality of layers of quartz walls, and the arrangement mode of the plurality of layers of quartz walls is as follows: the starting point of the top of the quartz wall descends layer by layer from inside to outside. Several holes are formed on several quartz walls on the inner side of the outer wall. The holes on the two adjacent quartz walls are distributed in a mutually staggered mode.

As shown in fig. 3 and 4, the quartz wall on the inner side of the outer wall is two layers, and the holes on the two layers are staggered with each other. As shown by the arrows in fig. 3, when the quartz bell jar structure is used for doping, the gas molecules after arsenic sublimation continuously impact the quartz wall under the action of heat, one part of the molecules are rebounded, the other part of the molecules enter the quartz interlayer through the holes, and the molecules repeatedly collide with the wall to rebound and enter the holes after losing part of kinetic energy until the molecules completely rebound after impacting the quartz wall at the outermost layer.

In the process of gas molecule thermal motion, the frequency of mutual collision of molecules is greatly increased compared with the frequency before improvement, the molecules collide the wall for multiple times to weaken the molecular kinetic energy, so the average free energy of the molecules is reduced, the average free path is shortened, and the gas molecules of arsenic exist in the bell jar for a longer time. Under the same doping time and conditions, gas molecules are more favorably dissolved into the silicon material, and the aim of improving the doping efficiency is fulfilled.

Brief introduction to the doping Pattern

Stabilizing and doping the molten silicon material under the following specific conditions:

pressure: flow rate of 20 to 100 Torr: 20-100slpm power: 60-85KW

Crystal transformation: crucible rotation at 0-5 rpm: crucible position at 1-5 rpm: -20-20mm

And placing the doping device in a furnace body auxiliary chamber, communicating the gas after purification with the pressure reduced to the main chamber, enabling the distance between the doping device and the liquid level to be 15-20mm, taking the doping time about 5-8 minutes based on the completion of arsenic volatilization, lifting the doping device to the auxiliary chamber after doping is completed, carrying out isolated cooling, taking out the doping device, purifying the auxiliary chamber, and communicating the main chamber to carry out crystal pulling.

Examples

The specific conditions for stabilizing and doping the molten silicon material in this example are as follows:

pressure: flow rate of 80 Torr: 60slpm Power: 80KW

Crystal transformation: crucible rotation at 0 rpm: l rpm crucible position: -40mm

And placing the doping device in a furnace body auxiliary chamber, communicating the gas after purification with pressure reduced to the main chamber, enabling the distance between the doping device and the liquid level to be 15mm, enabling the doping time to be about 5 minutes based on the completion of arsenic volatilization, lifting the doping device to the auxiliary chamber after doping is completed, carrying out isolated cooling, taking out the doping device, purifying the auxiliary chamber, and communicating the main chamber to carry out crystal pulling.

Taking a 20-inch thermal field 6-inch [111] crystal orientation single crystal as an example, the resistivity data of the head of the single crystal under the same doping amount and crystallization time (6-8 hours) and the crystallization conditions of different doping devices are counted as follows:

the original doping device: a single-layer cylindrical quartz bell jar with an inner diameter of 150mm, a wall thickness of 3mm and a height of 330 mm;

the doping device is improved: three layers of cylindrical quartz bell jars with the inner diameter of 150mm, the wall thickness of 3mm and the width of an inner interlayer and an outer interlayer of 30mm,

the height is 330mm, 300mm, 270mm, and the diameter of the staggered arrangement of inner wall holes is 15 mm.

Results

From the result of the resistivity data, the doping efficiency can be improved by about 9.5% by using the improved doping device for doping, and the purpose of reducing the dosage of the dopant is achieved in the resistivity single crystal with the same specification.

Claims

1. A doping device for heavily doping Czochralski single crystals is characterized in that the side wall of a quartz bell jar in the doping device is composed of a plurality of quartz walls, a plurality of holes are respectively formed on the quartz walls positioned on the inner side of the outer wall, and the holes on the two adjacent layers of quartz walls are distributed in a mutually staggered mode.

2. A doping apparatus for heavily doping a czochralski single crystal as set forth in claim 1, wherein the plurality of quartz walls are arranged in such a manner that: the starting point of the top part descends layer by layer from inside to outside.

3. The doping apparatus for heavily doping a Czochralski single crystal as set forth in claim 1, wherein the quartz wall located inside the outer wall is two-layered.