Method for determining trace As component in InGaAsP
By epitaxially growing multiple InGaAsyP1-y layers on a GaAs substrate, and utilizing the relationship between the corrosion rate and composition of a mixed solution of HCl and water, the problem of quantitatively measuring trace amounts of As components in thin-layer InGaAsP was solved, thus improving the stability and accuracy of the epitaxial process.
Patent Information
- Application Number
- CN202511520877.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-23
- Publication Date
- 2026-01-16
AI Technical Summary
Existing technologies make it difficult to quantitatively test the trace As composition in thin InGaAsP layers, especially those with a thickness of less than 40 nm, which makes it difficult to guarantee the stability of subsequent device processes.
By epitaxially growing multiple InGaAsyP1-y epitaxial layers with different compositions on a GaAs substrate, the relationship between corrosion rate and composition in a mixed solution of HCl and water was established, and the corrosion rate was measured to determine the composition of the thin InGaAsy0P1-y0 epitaxial layer.
This method enables quantitative testing of trace As components in thin InGaAsP layers, improving the stability and accuracy of subsequent epitaxial processes.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of semiconductor manufacturing, and particularly relates to a method for determining a trace As component in InGaAsP. BACKGROUND
[0002] For a GaAs-based pHEMT epitaxial structure, an InGaP etching stop layer is usually added in the epitaxial structure to improve the flatness of wet etching in subsequent device preparation processes. In the molecular beam epitaxy growth process of the epitaxial structure, the InGaP etching stop layer is usually directly grown on the arsenide epitaxial layer, and the growth process involves switching of the group V element As to P. If the As pressure is too high when the arsenide is grown or the interruption time is too short when the switching is performed, the InGaP layer may contain a trace amount of As, forming an InGaAsP layer.
[0003] Because a conventional concentration of HCl solution has a very high selectivity ratio for the InGaP layer and the arsenide layer (for example, a GaAs layer, the etching rate is almost zero), the HCl solution is usually used to etch and remove the InGaP etching stop layer. The etching rate of the HCl solution for the InGaP layer is usually about 15 nm / min to 30 nm / min according to different temperatures and concentrations, and the thickness of the InGaP layer as the etching stop layer is usually less than 40 nm, so the InGaP layer can be completely removed within 2-3 minutes. However, when the InGaP layer contains a trace amount of As to become an InGaAsP layer, the etching rate of the HCl solution for the InGaAsP layer will be significantly reduced as the As content increases. In particular, for an InGaAsP layer with an As content of more than 20%, the etching rate of the HCl solution for the InGaAsP layer is almost zero. Therefore, in mass production, in order to ensure the stability of the subsequent device process, it is desirable to control the content of the trace amount of As contained in the InGaP layer within a certain range (for example, within a range that almost does not affect the etching rate of the HCl solution for the InGaP layer) during the molecular beam epitaxy growth process, which requires quantitative determination of the As component in the InGaAsP layer containing a trace amount of As.
[0004] In conventional techniques, for a relatively thick (for example, a thickness greater than or equal to 100 nm) InGaAsP layer, the As component can be jointly determined by X-ray diffraction combined with PL spectrum, however, when the thickness of the InGaAsP layer is relatively thin (for example, a thickness less than 40 nm), the intensity of the test peak reflecting the As component in the test result curve of either X-ray diffraction test or PL spectrum test will be very weak, and the test peak for characterizing the As component in the thin InGaAsP layer is difficult to identify due to the influence of the test peaks formed by other epitaxial layers in the epitaxial structure, so that the As component cannot be determined by using these test means.
[0005] Therefore, it is necessary to provide a method for realizing quantitative test of trace As component in thinner InGaAsP layer. SUMMARY
[0006] The present application aims at providing a method for determining trace As component in InGaAsP to solve the problem of quantitative test of trace As component in thin InGaAsP layer.
[0007] To achieve the above object, the technical scheme adopted by the present application is as follows: The present application provides a method for determining trace As component in InGaAsP, which comprises the following steps: Step a, for a plurality of different y values in the range of 0<y<0.02, epitaxially growing corresponding InGaAs y P 1-y epitaxial layers on a GaAs substrate to obtain a plurality of epitaxial samples, the thickness h of the InGaAs y P 1-y epitaxial layer being a preset value, and 100 nm≤h≤500 nm; Step b, using a preset etching solution to etch the plurality of epitaxial samples respectively to obtain the corresponding etching rate of each component y, performing data fitting to obtain the corresponding relationship between etching rate and component y, the preset etching solution being a mixed solution of HCl and water, the volume ratio of HCl to water being in the range of 0.8:1 to 2:1; Step c, for an InGaAs y0 P 1-y0 epitaxial layer sample on the arsenide epitaxial layer, the thickness of which is less than 40 nm and the component y0 thereof is less than 0.02, using a preset etching solution to etch the InGaAs y0 P 1-y0 epitaxial layer, and determining the corresponding etching rate, and then determining the component y0 in the InGaAs y0 P 1-y0 epitaxial layer according to the corresponding relationship determined in step b.
[0008] Optionally, the components of In in the InGaAs y P 1-y epitaxial layer and the InGaAs y0 P 1-y0 epitaxial layer are both 0.485.
[0009] Optionally, 100 nm≤h≤300 nm.
[0010] Optionally, the plurality of epitaxial samples are grown by fixing the P beam size and adjusting the As beam size to achieve the change of the composition y, and the composition y in each of the plurality of epitaxial samples is determined by both X-ray diffraction and PL spectrum.
[0011] Optionally, the etching processes in steps b and c are both performed at the same preset etching temperature, and the preset etching temperature ranges from 20 to 25 DEG C and is controlled by a water bath.
[0012] Optionally, in step c, the InGaAs y0 P 1-y0 The thickness of the epitaxial layer sample ranges from 5 nm to 30 nm.
[0013] Optionally, in the preset etching solution, the volume ratio of HCl to water is 1:1.
[0014] The beneficial effects of the present application include: The present application provides a method for determining the trace As composition in InGaAsP, which comprises the following steps: a, epitaxially growing a plurality of InGaAs y P 1-y epitaxial layers corresponding to different y values in the range of 0<y<0.02 on a GaAs substrate to obtain a plurality of epitaxial samples, wherein the thickness of the InGaAs y P 1-y epitaxial layer is a preset value, and 100 nm≤h≤500 nm; b, using a preset etching solution to etch each of the plurality of epitaxial samples to obtain the etching rate corresponding to each composition y, performing data fitting to obtain the corresponding relationship between the etching rate and the composition y, wherein the preset etching solution is a mixed solution of HCl and water, and the volume ratio of HCl to water ranges from 0.8:1 to 2:1; c, for an InGaAs y0 P 1-y0 epitaxial layer sample with a thickness less than 40 nm and a composition y0 less than 0.02 on an arsenide epitaxial layer, using a preset etching solution to etch the InGaAs y0 P 1-y0 epitaxial layer and determining the corresponding etching rate, and determining the composition y0 in the InGaAs y0 P 1-y0 epitaxial layer according to the corresponding relationship determined in step b. The present application grows a relatively thick InGaAs y P 1-y epitaxial layer containing trace As, establishes the corresponding relationship between the etching rate and the trace As composition, and determines the composition y0 in a thin InGaAs y0 P 1-y0The epitaxial layer only needs to measure the etching rate, and the component y0 of the epitaxial layer can be determined according to the corresponding relationship, the quantitative test of the trace As component in the thin layer InGaAsP epitaxial layer is realized, and the subsequent epitaxial process is optimized and improved. BRIEF DESCRIPTION OF DRAWINGS
[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.
[0016] Figure 1 A flowchart of the method for determining the trace As component in InGaAsP provided by the embodiments of the present application is shown. DETAILED DESCRIPTION
[0017] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present application.
[0018] In conventional technology, for the InGaAsP layer with a relatively large thickness (for example, the thickness is greater than or equal to 100 nm), the As component can be determined by X-ray diffraction combined with PL spectrum. In particular, when the rates of the group III elements In and Ga have been calibrated, the As component can be determined only by X-ray diffraction. However, when the thickness of the InGaAsP layer is relatively small (for example, the thickness is less than 40 nm), the intensity of the test peak reflecting the As component in the test result curve of the X-ray diffraction test or the PL spectrum test is very weak, and the test peak formed by other relatively thick epitaxial layers in the epitaxial structure is also affected, so that it is difficult to identify the test peak for characterizing the As component in the thin layer InGaAsP layer, and thus the As component cannot be determined by using these test means. Therefore, it is necessary to provide a method for realizing the quantitative test of the trace As component in the relatively thin InGaAsP layer.
[0019] Figure 1 A flowchart of the method for determining the trace As component in InGaAsP provided by the embodiments of the present application is shown, as shown in Figure 1 The method for determining the trace As component in InGaAsP provided by the present application includes: Step a, epitaxially growing corresponding InGaAs on GaAs substrate for a plurality of different y values in the range of 0 < y < 0.02 y P 1-y Epitaxial layer, to obtain a plurality of epitaxial samples.
[0020] InGaAs y P 1-y The thickness h of the epitaxial layer is a preset value, and 100 nm ≤ h ≤ 500 nm.
[0021] It should be noted that the trace amount in the present application refers to the component of As in the InGaAsP material layer satisfying the following range: greater than 0 and less than 0.02, that is, the proportion of As in the five elements is less than 2%.
[0022] In order to accurately test the InGaAs y P 1-y The thickness h of the epitaxial layer is usually thick, for example, h ≥ 100 nm. If the thickness h is too thick (for example, h > 500 nm), it will cause unnecessary waste of growth time and material, and increase the cost of the experiment. Therefore, the thickness h can be limited to 100 nm ≤ h ≤ 500 nm, and optionally, 100 nm ≤ h ≤ 300 nm. For example, h can be equal to 200 nm or 300 nm. If the thickness is thin, as previously described, the As component cannot be quantitatively determined due to the too weak test peak intensity of the reaction As component. The plurality of epitaxial samples are grown by fixing the P beam current and adjusting the As beam current to change the component y. The component y in each of the plurality of epitaxial samples is determined by both X-ray diffraction and PL spectrum. Alternatively, the rates of In and Ga can also be calibrated in advance, and in the case where the rates of In and Ga are known, the components of In and Ga in the InGaAsP layer are also known, at this time, only X-ray diffraction is required to determine the component of As in the InGaAsP layer.
[0023] In actual growth, the As component is changed by fixing the P beam current and adjusting the As beam current, and the component y of As in the grown InGaAs y P 1-y Epitaxial layer is measured by relevant test means. By adjusting the As beam current, a plurality of epitaxial samples with the component y in the range of 0 < y < 0.02 can be obtained, and the components y of As in these epitaxial samples are known after measurement. It should be understood that the proportions of In and Ga in these epitaxial samples are fixed. Since the lattice constant of In 0.485 Ga 0.515 P matches the lattice constant of the GaAs substrate, and the InGaAs y P 1-yThe content of As in the epitaxial layer is very small, so the InGaAs in the above plurality of epitaxial samples is optionally y P 1-y The composition of In in the epitaxial layer is all 0.485.
[0024] Step b, using a preset etching solution, respectively etching the plurality of epitaxial samples to obtain the etching rate corresponding to each composition y, and performing data fitting to obtain the corresponding relationship between the etching rate and the composition y.
[0025] The preset etching solution is a mixed solution of HCl and water, and the volume ratio of HCl to water is in the range of 0.8:1 to 2:1. For example, in the preset etching solution, the volume ratio of HCl to water is 1:1.
[0026] The etching solution with a volume ratio of HCl to water of 1:1 has an etching rate of about 20 nm / min to 30 nm / min for InGaP without As. When the InGaP layer contains a small amount of As to become an InGaAsP layer, the etching rate of the HCl solution for the InGaAsP layer will decrease significantly with the increase of the content of As. In other words, when the InGaAsP layer contains a small amount of As, the etching rate of the HCl solution for the InGaAsP layer is very sensitive to the change of the As composition. However, when the As composition is further increased, the etching rate of the HCl solution for the InGaAsP layer is no longer sensitive to the change of the As composition because the etching rate is already very low at this time. In particular, for the InGaAsP layer with an As content of more than 20%, the etching rate of the HCl solution for it no longer changes with the As composition, and the etching rate is almost zero.
[0027] For the InGaAsP layer containing a small amount of As (As composition less than 0.02), different As compositions correspond to different etching rates, and the etching rate is very sensitive to the content of As, so for the preset etching solution, the etching rate corresponding to different As compositions can be tested, and the corresponding relationship between the etching rate and the As composition y can be established by data fitting. For the measurement of the etching rate, a part of the surface of the sample can be covered and protected by photoresist, then the sample is etched by the etching solution for a certain time (for example, 2-5 minutes), then the photoresist is removed to form an etching step, and then a conventional commercial step meter is used to accurately measure the height of the formed step, and then the corresponding etching rate can be calculated. The vertical resolution of the conventional commercial step meter is about 0.1 nm, which can fully meet the accuracy requirements of the method of the present application in testing the height of the etching step.
[0028] Step c, for the arsenide epitaxial layer, the InGaAs with a thickness less than 40 nm and a composition y0 less than 0.02 y0 P1-y0 An epitaxial layer sample is etched with the preset etching solution y0 P 1-y0 The epitaxial layer, and the corresponding etching rate is determined, and the composition y0 of the InGaAs in the epitaxial layer is determined according to the corresponding relationship determined in step b. y0 P 1-y0 The epitaxial layer, and the corresponding etching rate is determined, and the composition y0 of the InGaAs in the epitaxial layer is determined according to the corresponding relationship determined in step b.
[0029] The arsenide epitaxial layer in the present application may, for example, be a GaAs epitaxial layer.
[0030] For the InGaP etching barrier layer in the GaAs-based pHEMT structure, the thickness is usually less than 40 nm. Optionally, the InGaAs y0 P 1-y0 The thickness of the epitaxial layer sample ranges from 5 nm to 30 nm. When growing the GaAs-based pHEMT structure by molecular beam epitaxy, after the arsenide layer (for example, GaAs) is grown, the InGaP layer is grown. If the As pressure is too high when growing the arsenide or the interruption time is too short when switching, a trace amount of As may be contained in the InGaP, thereby forming InGaAs with a thickness less than 40 nm y0 P 1-y0 Epitaxial layer, where the trace amount of As is not desired. Therefore, if the InGaP layer contains a trace amount of As, it is desirable to quantitatively determine the composition of As to facilitate subsequent improvement of the epitaxial process. InGaAs y0 P 1-y0 The composition y0 of the trace amount of As in the InGaAs epitaxial layer is less than 0.02, or y0 is less than 0.01 or less. As described previously, for InGaAs with a thickness less than 40 nm y0 P 1-y0 Epitaxial layer, the composition y0 of the trace amount of As cannot be directly quantitatively tested by conventional means such as X-ray diffraction or PL spectrum.
[0031] For the InGaAs y0 P 1-y0 Epitaxial layer, the InGaAs can be etched with the preset etching solution in step b at the same etching temperature as in step b. y0 P 1-y0 Epitaxial layer (a portion of the surface is protected with photoresist to form an etching step), since the thickness of the InGaAs y0 P 1-y0 Epitaxial layer is thin, so it can only be etched for a short time (for example, 5 seconds to 20 seconds), and the maximum etching time is no more than the time required to completely remove the InGaAs y0 P 1-y0The time required for the epitaxial layer is determined, and the corrosion step height is measured using a profilometer to calculate the corresponding corrosion rate. Since the correlation between corrosion rate and As composition was established in step b, the corrosion rate can be calculated based on InGaAs. y0 P 1-y0 The corrosion rate corresponding to the epitaxial layer is used to quantitatively determine the composition y0.
[0032] To match the lattice constant of the GaAs substrate, the In composition in the InGaP epitaxial layer (as a corrosion barrier layer) is typically calibrated to 0.485. Therefore, the InGaAs formed after the introduction of unintentional trace amounts of As... y0 P 1-y0 The In composition in the epitaxial layer is also 0.485.
[0033] Optionally, the corrosion processes in steps b and c are carried out at the same preset corrosion temperature, which ranges from 20°C to 25°C, and is controlled by a water bath.
[0034] In summary, this application achieves this result by growing a relatively thick InGaAs layer containing trace amounts of As. y P 1-y Epitaxial layers were used to establish a correlation between corrosion rate and trace As composition, specifically for thin-layer InGaAs. y0 P 1-y0 By measuring the corrosion rate of the epitaxial layer, its composition y0 can be determined according to the corresponding relationship, realizing the quantitative testing of trace As components in the thin InGaAsP epitaxial layer, which is beneficial to the optimization and improvement of subsequent epitaxial processes.
[0035] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A method for determining trace As components in InGaAsP, characterized in that, The method includes: Step a: For multiple different y values within the range of 0 < y < 0.02, grow corresponding InGaAs y P 1-y epitaxial layers on a GaAs substrate to obtain multiple epitaxial samples, where the thickness h of the InGaAs y P 1-y epitaxial layer is a preset value, and 100 nm ≤ h ≤ 500 nm; Step b: Using a preset etching solution, the multiple epitaxial samples are etched and tested to obtain the etching rate corresponding to each component y. Data fitting is performed to obtain the correspondence between the etching rate and component y. The preset etching solution is a mixed solution of HCl and water, and the volume ratio of HCl to water ranges from 0.8:1 to 2:
1. Step c: For InGaAs with an arsenide epitaxial layer thickness less than 40 nm and composition y0 less than 0.02 y0 P 1-y0 The epitaxial layer sample was etched using a pre-set etching solution. y0 P 1-y0 The epitaxial layer is determined, and the corresponding etching rate is identified. Then, based on the correspondence determined in step b, the InGaAs is determined. y0 P 1-y0 The component y0 in the epitaxial layer.
2. The method for determining trace As components in InGaAsP according to claim 1, characterized in that, InGaAs y P 1-y Epitaxial layer and InGaAs y0 P 1-y0 The In composition in the epitaxial layer is 0.
485.
3. The method for determining trace As components in InGaAsP according to claim 1, characterized in that, 100 nm ≤ h ≤ 300 nm.
4. The method for determining trace As components in InGaAsP according to claim 1, characterized in that, During the growth process of the multiple epitaxial samples, the component y is changed by fixing the P beam current and adjusting the As beam current. The component y in each of the multiple epitaxial samples is determined by both X-ray diffraction and PL spectroscopy.
5. The method for determining trace As components in InGaAsP according to claim 1, characterized in that, The corrosion processes in steps b and c are carried out at the same preset corrosion temperature, which ranges from 20°C to 25°C and is controlled by a water bath.
6. The method for determining trace As components in InGaAsP according to claim 1, characterized in that, In step c, InGaAs y0 P 1-y0 The thickness of the epitaxial layer samples ranges from 5 nm to 30 nm.
7. The method for determining trace As components in InGaAsP according to claim 1, characterized in that, The volume ratio of HCl to water in the pre-defined corrosion solution is 1:1.