Monitoring sheet for monitoring epitaxial film thickness and preparation method thereof

Abstract

According to the monitoring piece for monitoring the thickness of the epitaxial film and the preparation method of the monitoring piece, the doped layer reflects infrared light, the epitaxial film layer transmits the infrared light, and the resistivity of the doped layer is 1 / 3-1 / 2 of the resistivity of the epitaxial film layer epitaxially arranged on the doped layer, so that the thickness of the epitaxial film is monitored. Therefore, when the thickness of the epitaxial film layer is measured by adopting the Fourier transform infrared spectroscopy, the thickness of the epitaxial film layer can be accurately measured, and a substrate layer with heavy doping concentration is not used, so that the manufacturing cost is greatly reduced, and the problem that a monitoring sheet for monitoring the thickness of the epitaxial film in the prior art is relatively high in cost and high in expense is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a monitoring sheet for monitoring epitaxial film thickness and a preparation method thereof. Background Art

[0002] The usual epitaxy is a single-layer epitaxial structure. If the epitaxy thickness needs to be accurately measured, a low-doped epitaxial film layer needs to be deposited on a substrate with a high doping concentration. The thickness of the epitaxial film layer is measured using Fourier transform infrared spectroscopy (FT-IR). The substrate and the epitaxial film layer have different refractive indices due to different doping concentrations. When the optical path difference between the light beam reflected from the surface of the epitaxial film layer and the light beam reflected from the substrate interface is an integer multiple of half a wavelength, the maximum and minimum values ​​can be observed in the reflection spectrum. According to the extreme peak position of the interference fringes in the reflection spectrum, the optical constant of the sample and the incident angle, the corresponding epitaxial film thickness can be calculated. The lightly doped epitaxial film layer is relatively transparent to the infrared spectrum with a wavelength range of 2.5μm to 50μm, but the heavily doped substrate acts as a reflective surface for radiation within this range. Therefore, infrared reflection technology can be used to determine the thickness of the epitaxial film layer. The monitoring film used to monitor the thickness of the epitaxial film in the prior art is generally expensive. Summary of the invention

[0003] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a monitoring piece for monitoring epitaxial film thickness and a preparation method thereof, so as to solve the problem that the monitoring piece for monitoring epitaxial film thickness in the prior art is relatively high in cost.

[0004] To achieve the above-mentioned purpose and other related purposes, the present invention provides a monitoring film for monitoring the thickness of an epitaxial film, wherein the monitoring film comprises a substrate layer and a doping layer from bottom to top; wherein the doping concentration of the doping layer is greater than the doping concentration of the substrate layer, the resistivity of the doping layer is 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer epitaxially grown on the doping layer, and the doping concentration of the doping layer reflects infrared light with a wavelength in the range of 2.5 μm to 50 μm, and the doping concentration of the epitaxial film layer transmits infrared light with a wavelength in the range of 2.5 μm to 50 μm.

[0005] Optionally, the thickness of the doping layer is greater than 300 nm.

[0006] Optionally, the doping concentration of the doping layer is greater than 1E18 atoms / cm 3 .

[0007] Optionally, the doping concentration of the substrate layer is less than 1E15 atoms / cm 3 .

[0008] Optionally, the materials of the substrate layer and the doping layer are silicon, and the doping ions of the doping layer are antimony ions.

[0009] The present invention provides a method for preparing a monitoring sheet for monitoring epitaxial film thickness, which is used to prepare the monitoring sheet for monitoring epitaxial film thickness as described in any one of the above, and the preparation method comprises:

[0010] providing a substrate;

[0011] Ion implantation is performed on the upper surface of the substrate to a preset thickness to form a doping layer, wherein the preset thickness is less than the thickness of the substrate; wherein the resistivity of the doping layer is 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer epitaxially grown on the doping layer, and the doping concentration of the doping layer reflects infrared light with a wavelength in the range of 2.5 μm to 50 μm, and the doping concentration of the epitaxial film layer transmits infrared light with a wavelength in the range of 2.5 μm to 50 μm.

[0012] Optionally, before forming the doping layer on the upper surface of the substrate, the method also includes cleaning the upper surface of the substrate to remove impurities on the upper surface of the substrate, and etching the upper surface of the substrate to remove the oxide layer on the upper surface of the substrate.

[0013] Furthermore, the method for cleaning the upper surface of the substrate comprises immersing the substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of (0.8-1.2): (0.8-1.2): (4.5-5.5) at 120°C-150°C for 8 minutes-12 minutes; the method for etching the upper surface of the substrate comprises immersing the substrate in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of (10-50): 1 at 20°C-25°C for 20 seconds-40 seconds.

[0014] Optionally, the material of the substrate is silicon, and the doping ions of the doping layer are antimony ions.

[0015] Furthermore, the implantation energy of the ion implantation is 1500keV to 2000keV, and the implantation dose of the ion implantation is greater than 2E15 atoms / cm 2 .

[0016] As described above, the monitoring film for monitoring epitaxial film thickness and the preparation method thereof of the present invention have the following beneficial effects: the monitoring film for monitoring epitaxial film thickness of the present invention makes the doped layer reflect infrared light, makes the epitaxial film layer transmit infrared light, and makes the resistivity of the doped layer be 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer epitaxially grown on the doped layer, so that when the thickness of the epitaxial film layer is measured by Fourier transform infrared spectroscopy, the thickness of the epitaxial film layer can be accurately measured, and the use of a substrate layer with a heavy doping concentration can be avoided, which greatly reduces the production cost and solves the problem of high cost and expense of the monitoring film for monitoring epitaxial film thickness in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is a schematic diagram of the cross-sectional structure of a monitoring sheet for monitoring epitaxial film thickness and an epitaxial film layer of the present invention.

[0018] Figure 2 Shown is a schematic flow chart of a method for preparing a monitoring sheet for monitoring epitaxial film thickness according to the present invention.

[0019] Figure 3 Schematic diagram showing the test points for the thickness of the epitaxial film.

[0020] Component number description

[0021] 11 Substrate

[0022] 12 Doping layer

[0023] 13 Epitaxial film

[0024] Steps S1 to S2 DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] See also Figures 1 to 3 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0027] This embodiment provides a monitoring sheet for monitoring epitaxial film thickness, such as Figure 1As shown, the monitoring film includes a substrate layer 11 and a doping layer 12 from bottom to top; wherein, the doping concentration of the doping layer 12 is greater than the doping concentration of the substrate layer 11, the resistivity of the doping layer 12 is 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer 13 epitaxially grown on the doping layer, and the doping concentration of the doping layer 12 reflects infrared light with a wavelength in the range of 2.5 μm to 50 μm, and the doping concentration of the epitaxial film layer transmits infrared light with a wavelength in the range of 2.5 μm to 50 μm.

[0028] The monitoring film for monitoring the thickness of the epitaxial film of the present embodiment makes the doped layer reflect infrared light, makes the epitaxial film layer transmit infrared light, and makes the resistivity of the doped layer be 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer epitaxially grown on the doped layer. Therefore, when the thickness of the epitaxial film layer is measured by Fourier transform infrared spectroscopy, the thickness of the epitaxial film layer can be accurately measured, and the use of a substrate layer with a heavy doping concentration can be avoided, which greatly reduces the manufacturing cost and solves the problem of high cost and expense of the monitoring film for monitoring the thickness of the epitaxial film in the prior art.

[0029] The principle of measuring the thickness of the epitaxial film layer 13 by Fourier transform infrared spectroscopy is based on the interference effect generated when infrared light passes through the epitaxial film layer 13 and the doped layer 12. When the infrared light is irradiated to the interface between the epitaxial film layer 13 and the doped layer 12, it is reflected to form two beams of light reflected from the upper surface of the doped layer 12 and the upper surface of the epitaxial film layer 13. When these two beams of light meet in space, interference will occur to form an interference pattern. The preset thickness of the doped layer 12 ensures the stability and observability of the interference pattern. The preset thickness of the doped layer 12 can enhance the interference effect, thereby improving the accuracy of the measurement. If the preset thickness of the doped layer 12 is too thin, the interference effect may not be obvious enough, resulting in difficulty in accurately parsing the interference pattern, thereby affecting the accuracy of the thickness measurement. In this embodiment, it is preferred that the film thickness of the doped layer 12 is greater than 300nm to improve the accuracy of the film thickness measurement and reduce the measurement error.

[0030] As an example, in order to reduce the cost, the substrate 11 may be doped with a concentration less than 1E15 atoms / cm 3 The substrate 11 may be silicon, germanium, silicon carbide, gallium arsenide or indium phosphide, etc. The material type of the substrate 11 may be selected according to specific functions and application scenarios, and is not excessively limited here. In this embodiment, a lightly doped substrate is preferably used, i.e., the doping concentration is less than 1E15 atoms / cm 3 Such lightly doped silicon substrate is more commonly used and has lower cost, and can reduce the production cost of the monitoring sheet for monitoring the thickness of the epitaxial film.

[0031] The type of ion implantation can be N-type or P-type. As an example, N-type doping ions can be pentavalent ions such as nitrogen, phosphorus, arsenic, and antimony, and P-type doping ions can be trivalent ions such as boron, aluminum, gallium, and indium. The selection is made according to actual needs and is not excessively limited. In this embodiment, antimony ions are selected to dope the lightly doped silicon substrate to form the doping layer 12, and in this embodiment, the doping concentration is preferably greater than 1E18 atoms / cm 3 The doping layer 12 can reflect the infrared light beam due to the higher doping concentration.

[0032] This embodiment also provides a method for preparing a monitoring sheet for monitoring epitaxial film thickness, which is used to prepare the monitoring sheet for monitoring epitaxial film thickness, but is not limited thereto. Other suitable preparation methods are also possible. The above content can be quoted in its entirety here, and will not be described in detail below for the purpose of brevity. Figure 1 and Figure 2 As shown, the preparation method comprises:

[0033] S1, providing a substrate 11;

[0034] S2, ion implantation is performed on the upper surface of the substrate 11 to form a doping layer 12 of a preset thickness, and the preset thickness is less than the thickness of the substrate 11; wherein the resistivity of the doping layer 12 is 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer 13 epitaxially grown on the doping layer 12, and the doping concentration of the doping layer 12 reflects infrared light with a wavelength in the range of 2.5 μm to 50 μm, and the doping concentration of the epitaxial film layer 13 transmits infrared light with a wavelength in the range of 2.5 μm to 50 μm.

[0035] The preparation method of the monitoring film for monitoring the thickness of the epitaxial film of the present embodiment makes the doped layer reflect infrared light, makes the epitaxial film layer transmit infrared light, and makes the resistivity of the doped layer be 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer epitaxially grown on the doped layer. Therefore, when the thickness of the epitaxial film layer is measured by Fourier transform infrared spectroscopy, the thickness of the epitaxial film layer can be accurately measured, and the use of a substrate layer with a heavy doping concentration can be avoided, which greatly reduces the production cost and solves the problem of high cost and expense of the monitoring film for monitoring the thickness of the epitaxial film in the prior art.

[0036] It should be noted here that if Figure 1 As shown, in this embodiment, the upper surface of the substrate 11 is a surface close to the doping layer 12 .

[0037] Combine the following Figure 1 and Figure 2 The method for preparing the monitoring sheet for monitoring the thickness of the epitaxial film of this embodiment is described in detail.

[0038] First, S1 is performed to provide a substrate 11. As an example, in order to reduce the cost, the substrate 11 can be selected to have a doping concentration less than 1E15 atoms / cm 3 The substrate 11 may be silicon, germanium, silicon carbide, gallium arsenide or indium phosphide, etc. The material type of the substrate 11 may be selected according to specific functions and application scenarios, and is not excessively limited here. In this embodiment, a lightly doped substrate is preferably used, i.e., the doping concentration is less than 1E15 atoms / cm 3 Such lightly doped silicon substrate is more commonly used and has lower cost, and can reduce the production cost of the monitoring sheet for monitoring the thickness of the epitaxial film.

[0039] Then, S2 is performed, in which ions are implanted into the upper surface of the substrate 11 to form a doping layer 12 with a preset thickness, and the preset thickness is less than the thickness of the substrate 11; wherein the resistivity of the doping layer 12 is 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer 13 epitaxially grown on the doping layer 12, and the doping concentration of the doping layer 12 reflects infrared light with a wavelength in the range of 2.5 μm to 50 μm, and the doping concentration of the epitaxial film layer 13 transmits infrared light with a wavelength in the range of 2.5 μm to 50 μm.

[0040] As an example, before forming the doping layer 12 on the upper surface of the substrate 11, the upper surface of the substrate 11 is cleaned to remove impurities on the upper surface of the substrate 11, and the upper surface of the substrate 11 is etched to remove the oxide layer on the upper surface of the substrate 11.

[0041] Specifically, the method for cleaning the upper surface of the substrate 11 includes immersing the substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of (0.8-1.2): (0.8-1.2): (4.5-5.5) at 120° C. to 150° C. for 8 minutes to 12 minutes to remove organic matter, metal and other impurities on the upper surface of the substrate 11. The method for etching the upper surface of the substrate 11 includes immersing the substrate in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of (10-50): 1 at 20° C. to 25° C. for 20 seconds to 40 seconds to remove the oxide film on the upper surface of the substrate 11.

[0042] It should be noted that, in this embodiment, the upper surface of the doped layer 12 is the side close to the epitaxial film layer 13, and the upper surface of the epitaxial film layer 13 is the side away from the doped layer 12. The doped layer 12 is formed by ion implantation, and the doping concentration and film thickness of the doped layer 12 can be controlled by precisely controlling the implantation dose and implantation energy of the ion implantation. The type of the ion implantation can be N-type or P-type. As an example, the N-type doping ions can be pentavalent ions such as nitrogen, phosphorus, arsenic, and antimony, and the P-type doping ions can be trivalent ions such as boron, aluminum, gallium, and indium. The specific selection is based on actual needs, and no excessive restrictions are made here. In this embodiment, antimony ions are implanted into the upper surface of the substrate 11, and the implantation energy of the implantation doping is controlled to be 1500keV~2000keV, and the implantation dose of the implantation doping is greater than 2E15 atoms / cm 2 , so as to form a doping concentration greater than 1E18 atoms / cm on the upper surface of the substrate 11 3 , and the doping layer 12 having a film thickness greater than 300 nm can make the doping layer 12 reflect the infrared light beam due to the higher doping concentration, thereby reducing the measurement error.

[0043] As a specific example, as shown in Table 1, the measurement results of using the monitoring piece for monitoring epitaxial film thickness of this embodiment to measure the film thickness of the epitaxial film layer 13 with a preset target thickness of 6 μm, the measurement averages of the two monitoring pieces for monitoring epitaxial film thickness are 5.971 μm and 5.967 μm respectively. The measurement points are as follows: Figure 3 As shown, the measuring points include the center point of the epitaxial film layer 13 and eight points equidistantly distributed on the epitaxial film layer 13. The layout of the measuring points can provide comprehensive information on the film thickness of the center and edge regions of the epitaxial film layer 13, which can be used to evaluate the thickness uniformity of the thin film on the epitaxial film layer 13. Those skilled in the art know that when the preset target thickness is 6 μm, the mean value of the results measured at the nine measuring points is between 5.935 μm and 6.065 μm, which means that the monitoring is qualified. Therefore, the monitoring sheet for monitoring the epitaxial film thickness of this embodiment can be used as a monitoring sheet for monitoring the film thickness of the epitaxial film layer 13.

[0044]

[0045] Table 1

[0046] In summary, the present invention provides a monitoring sheet for monitoring epitaxial film thickness and a preparation method thereof, by making the doped layer reflect infrared light, making the epitaxial film layer transmit infrared light, and making the resistivity of the doped layer 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer epitaxially on the doped layer, so that when the thickness of the epitaxial film layer is measured by Fourier transform infrared spectroscopy, the thickness of the epitaxial film layer can be accurately measured, and the use of a substrate layer with a high doping concentration is avoided, which greatly reduces the production cost and solves the problem of high cost and high expense of the monitoring sheet for monitoring epitaxial film thickness in the prior art. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0047] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A monitoring sheet for monitoring epitaxial film thickness, characterized in that: The monitoring film includes a substrate layer and a doping layer from bottom to top; wherein, the doping concentration of the doping layer is greater than the doping concentration of the substrate layer, the resistivity of the doping layer is 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer epitaxially grown on the doping layer, and the doping concentration of the doping layer reflects infrared light with a wavelength in the range of 2.5 μm to 50 μm, and the doping concentration of the epitaxial film layer transmits infrared light with a wavelength in the range of 2.5 μm to 50 μm.

2. The monitoring sheet for monitoring epitaxial film thickness according to claim 1, characterized in that: The thickness of the doping layer is greater than 300 nm.

3. The monitoring sheet for monitoring epitaxial film thickness according to claim 1, characterized in that: The doping concentration of the doping layer is greater than 1E18 atoms / cm 3 .

4. The monitoring sheet for monitoring epitaxial film thickness according to claim 1, characterized in that: The doping concentration of the substrate layer is less than 1E15 atoms / cm 3 .

5. The monitoring sheet for monitoring epitaxial film thickness according to claim 1, characterized in that: The materials of the substrate layer and the doping layer are silicon, and the doping ions of the doping layer are antimony ions.

6. A method for preparing a monitoring sheet for monitoring epitaxial film thickness, for preparing the monitoring sheet for monitoring epitaxial film thickness as claimed in any one of claims 1 to 5, characterized in that: The preparation method comprises: providing a substrate; Ion implantation is performed on the upper surface of the substrate to a preset thickness to form a doping layer, wherein the preset thickness is less than the thickness of the substrate; wherein the resistivity of the doping layer is 1 / 3 to 1 / 2 of the resistivity of the epitaxial film layer epitaxially grown on the doping layer, and the doping concentration of the doping layer reflects infrared light with a wavelength in the range of 2.5 μm to 50 μm, and the doping concentration of the epitaxial film layer transmits infrared light with a wavelength in the range of 2.5 μm to 50 μm.

7. The method for preparing a monitoring sheet for monitoring epitaxial film thickness according to claim 6, characterized in that: Before forming the doping layer on the upper surface of the substrate, the method also includes cleaning the upper surface of the substrate to remove impurities on the upper surface of the substrate, and etching the upper surface of the substrate to remove the oxide layer on the upper surface of the substrate.

8. The method for preparing a monitoring sheet for monitoring epitaxial film thickness according to claim 7, characterized in that: The method for cleaning the upper surface of the substrate comprises: immersing the substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of (0.8-1.2): (0.8-1.2): (4.5-5.5) at 120° C. to 150° C. for 8 minutes to 12 minutes; the method for etching the upper surface of the substrate comprises: immersing the substrate in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of (10-50): 1 at 20° C. to 25° C. for 20 seconds to 40 seconds.

9. The method for preparing a monitoring sheet for monitoring epitaxial film thickness according to claim 6, characterized in that: The material of the substrate is silicon, and the doping ions of the doping layer are antimony ions.

10. The method for preparing a monitoring sheet for monitoring epitaxial film thickness according to claim 9, characterized in that: The implantation energy of the ion implantation is 1500keV to 2000keV, and the implantation dose of the ion implantation is greater than 2E15 atoms / cm 2 .

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