CN115020200A - Preparation method of 300mm substrate for improving ultra-thick epitaxial edge defects - Google Patents

Preparation method of 300mm substrate for improving ultra-thick epitaxial edge defects Download PDF

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CN115020200A
CN115020200A CN202210748314.4A CN202210748314A CN115020200A CN 115020200 A CN115020200 A CN 115020200A CN 202210748314 A CN202210748314 A CN 202210748314A CN 115020200 A CN115020200 A CN 115020200A
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substrate
edge
silicon oxide
oxide film
epitaxial
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吴泓明
钟佑生
李云鹏
王文博
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Zhengzhou Hejing Silicon Materials Co ltd
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Zhengzhou Hejing Silicon Materials Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02002—Preparing wafers
    • H01L21/02005—Preparing bulk and homogeneous wafers
    • H01L21/02008—Multistep processes
    • H01L21/0201—Specific process step
    • H01L21/02021—Edge treatment, chamfering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02002—Preparing wafers
    • H01L21/02005—Preparing bulk and homogeneous wafers
    • H01L21/02008—Multistep processes
    • H01L21/0201—Specific process step
    • H01L21/02016—Backside treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02002—Preparing wafers
    • H01L21/02005—Preparing bulk and homogeneous wafers
    • H01L21/02008—Multistep processes
    • H01L21/0201—Specific process step
    • H01L21/02019—Chemical etching
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention discloses a preparation method of a 300mm substrate for improving ultra-thick epitaxial edge defects, which comprises the following steps: s1, growing a layer of silicon oxide film on the back surface of a 300mm substrate after double-sided polishing and before final polishing; and S2, performing ring etching on the edge region position of the silicon oxide film. The method effectively prevents the reaction between the back of the substrate close to the edge and the growth gas when the epitaxial layer grows, can prevent the Silicon reduce from forming at the edge of the back, can avoid the adhesion phenomenon between the substrate and the Susceptor, and improves the quality of the edge of the back of the substrate.

Description

Preparation method of 300mm substrate for improving ultra-thick epitaxial edge defects
Technical Field
The invention belongs to the technical field of silicon substrate processing, and particularly relates to a preparation method of a 300mm substrate for improving ultra-thick epitaxial edge defects.
Background
With the vigorous development of integrated circuit technology in the fields of new energy automobiles, high-speed rails, photovoltaics, industry and the like, the market demand for high-voltage power semiconductor devices is more and more vigorous, and meanwhile, in the manufacturing of the high-voltage power devices, the substrate type is inevitably gradually transferred to a 300mm large-diameter substrate along with the reduction of the production cost of the 300mm large-diameter substrate, and the 300mm large-diameter substrate focuses more on the defect improvement of edges so as to improve the utilization rate of the substrate. However, the influence on the quality of the power semiconductor mainly comes from three aspects, namely the design capability based on the understanding of the system knock-how (know-how); the difference of front-end processing, namely the difference of process level of the substrate manufacturing link; the third is the difference of the back-end process, i.e. the difference of the chip packaging process level.
In the substrate manufacturing process, in consideration of flatness, a 300mm substrate basically needs to be subjected to double-sided polishing and final polishing, and a substrate applied to a high-voltage power device often needs to be grown to an ultra-thick Thickness (THK)>40 μm) to improve the withstand voltage of the device. However, during the growth of the ultra-thick epitaxial layer, the growth gases TCS (trichlorosilane) and H are generated due to the long time required 2 Meanwhile, the defect may be generated by diffusing to the edge of the back surface of the substrate, and the adhesion may be generated at the contact position of the edge of the back surface of the substrate and the Susceptor (base) of the epitaxial tool, which not only increases the risk of fragments in the unloading process of the tool, but also may cause the defect of Bridging-Like at the edge of the substrate, as shown in fig. 1, which affects the quality of the epitaxial wafer and may seriously cause the crack of the epitaxial wafer.
On the other hand, the prior art refers to heavily doped As (arsenic) and P (phosphorus) (generally referring to resistance)<0.5ohm cm) substrate, is subjected to a high temperature stage of epitaxy, often by depositing a layer of dopant to a thickness of 0.5ohm cm on the back of the substrate before final polishing in order to prevent out-diffusion of dopant
Figure BDA0003720274890000021
If the thin film at the edge of the back surface of the substrate is not uniform or the thin film at the edge is not completely removed and remains, the thin portion of the thin film or the portion not covered by the thin film is easily exposed (the thin portion of the thin film may be exposed due to pre-epitaxial treatment or other reasons such as scratches, etc.), and when the epitaxial layer is grown, the growth gas at the position of the thin film is induced to proceed along the exposed substrateAnd the other areas can not be deposited due to the existence of the back sealing film, so that a similar Nodule defect, namely Silicon Nodule, different from the Bridging-Like defect is formed, as shown in FIGS. 2-3, and the back sealing film does not need to be added for the lightly doped substrate.
Disclosure of Invention
The invention aims to provide a method for preparing a 300mm substrate for improving the defect of the ultra-thick epitaxial edge in order to overcome the defects of the prior art.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a 300mm substrate for improving ultra-thick epitaxial edge defects comprises the following steps:
s1, growing a layer of silicon oxide film on the back surface of a 300mm substrate after double-sided polishing and before final polishing;
and S2, performing ring etching on the edge region position of the silicon oxide film.
Preferably, the thickness of the substrate is 700-800 mm, and the thickness of an epitaxial layer of an epitaxial wafer manufactured by the substrate is more than 40 μm;
in step S1, the thickness of the silicon oxide film is
Figure BDA0003720274890000022
Preferably, the ring etching region in step S2 includes a chamfer on the back surface of the substrate and an edge-most region in the back surface plane, and the ring etching width is 0.1-1 mm.
Preferably, the silicon oxide film is grown in step S1 by a chemical vapor deposition method.
Preferably, the chemical vapor deposition method comprises the following steps:
under the protection of inert gas, SiH with the volume ratio of 1 (8-14) is used 4 And O 2 And growing the silicon oxide film on the back of the substrate under the conditions of normal atmospheric pressure and 400-500 ℃.
Preferably, step S2 is performed by performing the ring etching in a liquid phase or a gas phase.
Preferably, the liquid phase ring etching step includes firstly covering the silicon oxide film layer on the back of the substrate with an HF acid corrosion resistant article, exposing only the region to be etched on the edge of the substrate, then soaking the substrate in an HF solution with the mass percentage of 4-7% for 50-150 s, and finally removing the HF acid corrosion resistant article.
Preferably, the step of gas phase ring etching is to face the back of the substrate upwards, then cover the HF acid corrosion resistant article on the silicon oxide thin film layer on the back of the substrate, expose only the region to be etched at the edge of the substrate, and introduce HF gas to perform ring etching.
Therefore, the method not only effectively prevents the reaction between the back surface of the substrate close to the edge and the growth gas when the epitaxial layer grows, but also prevents the formation of Silicon reduce at the edge of the back surface, thereby avoiding the adhesion phenomenon between the substrate and the suscepter and improving the quality of the edge of the back surface of the substrate.
Drawings
FIG. 1 is a photograph of a prior art substrate under a microscope for observing defects in the edge location of the backside after deposition of an ultra-thick epitaxial layer;
FIGS. 2 to 3 are photographs of Silicon reduce defects observed under different magnification microscopes in the prior art;
FIG. 4 is a schematic view showing the positions of defects of Silicon nitride and Bridging-Like generated when a 300mm substrate is epitaxially grown;
FIG. 5 is a schematic illustration of the silicon oxide film growth and ring etch locations of the present application;
FIG. 6 is a photograph of the edge position of the backside of a substrate after deposition of an ultra-thick epitaxial layer improved by the method of the present invention under a microscope.
Detailed Description
The invention provides a preparation method of a 300mm substrate for improving ultra-thick epitaxial edge defects, which comprises the following steps:
s1, growing a layer of silicon oxide film (LTO film) on the back of a substrate after double-sided polishing and before final polishing;
and S2, performing ring etching on the edge area position of the silicon oxide film.
According to the method, a layer of silicon oxide film grows on the back surface of the 300mm substrate after double-side polishing and before final polishing, and during subsequent substrate epitaxy, due to the blocking effect of the silicon oxide film, growth gas can be effectively prevented from being deposited at the contact position of the edge of the back surface of the substrate and a Susceptor (base), so that the contact position of the substrate and the Susceptor (base) is further prevented from being adhered, and the defect of a bridge shape (Bridging-Like) is also avoided. Meanwhile, in practical production, it is found that, for a lightly doped large-size substrate such as a 300mm substrate, a slight scratch may also be caused by the polishing action of the epitaxial gas HCl or other reasons when performing an ultra-thick epitaxy, so that a part of the Silicon oxide film in a thinner region at the chamfer (wafer level) of the substrate is removed, but the removal of the Silicon oxide film at the edge is not complete due to the action, and a great part of the Silicon oxide film still remains intact, so that a defect of a Silicon Nodule is generated, and the defect of the Bridging-Like and the defect position of the Silicon Nodule are shown in fig. 4. Therefore, in order to prevent the occurrence of the root-shaped defect during epitaxy, the method and the device perform ring etching on the edge region of the grown silicon oxide film at the same time, and completely remove the thin film layer on the edge, so that no residual silicon oxide film is induced in subsequent external delay, the root-shaped defect cannot be formed even if a small amount of growth gas is deposited on the edge, and the performance of the substrate and the epitaxial wafer is not obviously influenced.
As shown in fig. 5, a Silicon oxide film on the back surface of the substrate is grown to cover the back chamfer and the back plane, in order to prevent the occurrence of bridging defects, the Silicon oxide film should be covered at the contact position of the back surface of the substrate and the pedestal (the position close to the edge of the back plane of the substrate), and in order to prevent the occurrence of Silicon nitride defects, the Silicon oxide film on the back chamfer of the substrate is removed (the Silicon oxide film covered by the Silicon oxide film before etching is a film resistant to HF acid corrosion, during the etching process, the Silicon oxide film on the covered position of the film resistant to HF acid corrosion is retained, the Silicon oxide film on the exposed position is soaked in HF acid to be etched and removed, and then the film resistant to HF acid corrosion is removed), and the Silicon oxide film with a width of about 0.01-0.09 mm closest to the edge of the back plane on the outer side of the connection with the pedestal is also removed.
According to the method, the silicon oxide film deposition and the ring etching are carried out after double-side polishing and before final polishing, if the silicon oxide film deposition and the ring etching are carried out after the final polishing, the damage to a polished surface can be caused by the deposition, and the deposition is carried out before the final polishing, so that the damage to the front side of the substrate caused by LTO deposition can be removed by the final polishing.
Therefore, the method not only effectively prevents the reaction between the back surface of the substrate close to the edge and the growth gas when the epitaxial layer grows, but also prevents the formation of Silicon reduce at the edge of the back surface, thereby avoiding the adhesion phenomenon between the substrate and the contact position (Susceptor) and improving the quality of the edge of the back surface of the substrate.
After the invention aims at improving a 300mm double-sided polished substrate and finishing the growth of a thick epitaxial layer, the edge appearance of the substrate is greatly improved, and the quality of an epitaxial wafer is improved, as shown in a specific figure 6 (the product is from example 1).
The thickness of the epitaxial layer of the ultra-thick epitaxial wafer is generally larger than 40 mu m, the thickness of the corresponding substrate is about 700-800 mm, and the thickness of the grown silicon oxide film is preferably selected
Figure BDA0003720274890000051
If the silicon oxide film is too thick, the cost increases and the throughput decreases, and if it is too thin, the silicon oxide film is etched away by the vapor phase epitaxial gas during the epitaxial deposition.
Preferably, the step S2 includes etching the ring with a width of 0.1-1 mm, including the chamfer of the back surface of the substrate and the edge area in the back surface plane.
Step S1 is preferably performed by a chemical vapor deposition method, and further, the chemical vapor deposition method specifically includes the following steps: under the protection of inert gas, SiH with the volume ratio of 1 (8-14) is used 4 And O 2 And growing the silicon oxide film on the back of the substrate under the conditions of normal atmospheric pressure and 400-500 ℃.
Compared with a thermal oxidation method, the chemical vapor deposition method requires lower temperature, and compared with a plasma chemical vapor deposition method, the chemical vapor deposition method does not need special plasma equipment. Moreover, the silicon oxide film layer obtained by the chemical vapor deposition method not only has higher growth rate, but also has density which can completely meet the requirements of the subsequent epitaxial process, and the production capacity is higher, and the normal pressure and the low temperature in the production process are safer.
Preferably, step S2 is performed by performing the ring etching in a liquid phase or a gas phase.
Preferably, the liquid phase ring etching step is to cover the substrate back silicon oxide thin film layer with an HF acid corrosion resistant article such as an HF acid resistant thin film, to expose only the region to be etched at the edge of the substrate (the diameter of the cover thin film is generally slightly larger than the diameter of the substrate back horizontal plane, HF acid will permeate to the position of the substrate back horizontal inner edge during etching, to etch away the silicon oxide thin film at the substrate back horizontal inner edge), then to soak in an HF solution with a mass percentage of 4-7% for 50-150 s, and finally to remove the acid resistant thin film.
Preferably, the step of vapor phase ring etching is to firstly make the back side of the substrate face upwards, then cover the HF acid corrosion resistant article such as the corrosion resistant disk on the silicon oxide film layer on the back side of the substrate, only expose the area to be etched on the edge of the substrate, and introduce HF gas to perform ring etching.
Preferably, liquid phase corrosion is adopted, and the silicon oxide film subjected to liquid phase corrosion is more regular relative to the gas phase edge.
Example 1
Taking a lightly-doped phosphorus substrate (the diameter is 300mm, the back chamfer width is 0.9mm) with the resistance value of 1-10 ohm cm after double-side polishing, and using SiH with the volume ratio of 1:9 under the protection of nitrogen inert gas 4 And O 2 Growing a layer with the thickness of
Figure BDA0003720274890000061
Then an acid-resistant film with a diameter of 298.3mm is used to cover the LTO layer on the back side of the substrate, only the LTO on the edge part of the substrate is exposed, then the substrate is soaked in a 5% HF solution for etching for 100s, and finally the acid-resistant film is torn off, and the measured ring etching width is about 0.95mm (including the back chamfer width + the in-plane etching width).
The processed substrate is taken for epitaxy, the untreated substrate with double-side polishing is taken for comparison, the thickness of epitaxy is 50 mu m, the edge appearance of the substrate and the edge appearance of the substrate are observed under a microscope, and the results are shown in figures 1 and 4.
Example 2
Taking a lightly-doped phosphorus substrate (the diameter is 300mm, the back chamfer width is 0.15mm) with the resistance value of 1-10 ohm cm after double-side polishing, and using SiH with the volume ratio of 1:12 under the protection of nitrogen inert gas 4 And O 2 Growing a layer with the thickness of
Figure BDA0003720274890000062
Then an acid-resistant film of 299.8mm diameter was used to cover the LTO layer on the back side of the substrate, exposing only the LTO on the edge portion of the substrate, then immersed in a 5% HF solution for 100 seconds of etching, and finally the acid-resistant film was torn off, the ring etching width being measured to be about 0.2mm (including the back chamfer width + in-plane etching width).
Example 3
Taking a lightly-doped phosphorus substrate (the diameter is 300mm, the back chamfer width is 0.45mm) with the resistance value of 1-10 ohm cm after double-side polishing, and using SiH with the volume ratio of 1:14 under the protection of nitrogen inert gas 4 And O 2 Growing a layer with the thickness of
Figure BDA0003720274890000063
Then an acid-resistant film of 299.2mm diameter was used to cover the LTO layer on the back side of the substrate, exposing only the LTO on the edge portion of the substrate, then immersed in a 5% HF solution for 100 seconds of etching, and finally the acid-resistant film was torn off, the ring etching width being measured to be about 0.5mm (including the back chamfer width + in-plane etching width).
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (8)

1. A preparation method of a 300mm substrate for improving ultra-thick epitaxial edge defects is characterized by comprising the following steps:
s1, growing a layer of silicon oxide film on the back surface of a 300mm substrate after double-sided polishing and before final polishing;
and S2, performing ring etching on the edge region position of the silicon oxide film.
2. The method for preparing a 300mm substrate for improving ultra thick thickness epitaxial edge defects of claim 1,
the thickness of the substrate is 700-800 mm, and the thickness of an epitaxial layer of an epitaxial wafer manufactured by the substrate is more than 40 mu m;
in step S1, the thickness of the silicon oxide film is
Figure FDA0003720274880000011
3. The method for preparing a 300mm substrate for improving ultra thick thickness epitaxial edge defects as claimed in claim 2,
step S2 the ring etching area includes the substrate back chamfer angle and the edge area in the back plane, the ring etching width is 0.1-1 mm.
4. The method for preparing a 300mm substrate with improved ultra-thick epitaxial edge defects according to claim 1,
and step S1, growing the silicon oxide film by chemical vapor deposition.
5. The method of claim 4, wherein the step of chemical vapor deposition is as follows:
under the protection of inert gas, SiH with the volume ratio of 1 (8-14) is used 4 And O 2 And growing the silicon oxide film on the back of the substrate under the conditions of normal atmospheric pressure and 400-500 ℃.
6. The method for preparing a 300mm substrate with improved ultra-thick epitaxial edge defects according to claim 1,
step S2 is a liquid or vapor phase ring etch.
7. The method for preparing a 300mm substrate with improved ultra-thick epitaxial edge defects according to claim 6,
the liquid phase ring etching step is that firstly, HF acid corrosion resistant objects are covered on the silicon oxide film layer on the back surface of the substrate, only the area to be etched on the edge of the substrate is exposed, then the substrate is placed in HF solution with the mass percentage of 4-7% to be soaked for 50-150 s, and finally the HF acid corrosion resistant objects are removed.
8. The method for preparing a 300mm substrate with improved ultra-thick epitaxial edge defects according to claim 6,
the gas phase ring etching step is that firstly, the back surface of the substrate faces upwards, then, HF acid corrosion resistant articles are covered on the silicon oxide film layer on the back surface of the substrate, only the area to be etched on the edge part of the substrate is exposed, and HF gas is introduced for ring etching.
CN202210748314.4A 2022-06-29 2022-06-29 Preparation method of 300mm substrate for improving ultra-thick epitaxial edge defects Pending CN115020200A (en)

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