Method for determining growth temperature of epitaxial layer in molecular beam epitaxy system

Abstract

The invention provides a method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system, and relates to the technical field of semiconductor manufacturing. The method comprises the following steps: growing an InGaAsP epitaxial layer at a plurality of growth temperatures; testing and determining each As component; the function relation of data fitting is used as the corresponding relation between the growth temperature and the As component; at the first temperature, growing an InGaAsP epitaxial layer on the InGaAs epitaxial layer; measuring an As component, and calculating a corresponding growth temperature as a second temperature according to the corresponding relationship; the growth temperature when other epitaxial layers grow on the InGaAs epitaxial layer is equal to the reference temperature minus (the second temperature minus the first temperature). Through the obtained corresponding relation, the additional influence of heat absorption of the InGaAs epitaxial layer with the specific thickness on the growth temperature can be calculated, the growth temperature when other epitaxial layers grow on the InGaAs epitaxial layer is determined based on the additional influence, and the product quality can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing, and in particular to a method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system. Background Art

[0002] In the material growth process of molecular beam epitaxy (MBE), the growth temperature of the epitaxial layer is a key process parameter that affects the quality of epitaxial products. Usually, the molecular beam epitaxy system heats the substrate tray through a tray heating device, and senses the temperature through a thermocouple set between the substrate tray and the tray heating device. The system obtains the sensed temperature and performs heating control.

[0003] To determine the process parameters of a complex epitaxial layer structure, it is usually decomposed into multiple simple calibration structures, and the calibration structure is grown to obtain the optimal growth temperature of the calibration structure (that is, the corresponding thermocouple temperature), and the growth temperature is applied to the complete epitaxial structure. However, for the growth of an epitaxial layer on an InP substrate, when InGaAs material has been grown on the epitaxial layer, due to the small bandgap width of the InGaAs material, a large amount of thermal radiation will be absorbed, causing the surface temperature of the epitaxial layer to rise. Since the thermocouple is located on the back of the substrate and the thermocouple is non-contact with the substrate, this surface temperature increase is usually difficult to be quantitatively and accurately sensed by the thermocouple, and it is difficult to accurately feed back to the temperature control system, resulting in the optimal temperature (thermocouple temperature) of other epitaxial layers determined based on the calibration structure being inconsistent with the optimal temperature when other epitaxial layers are grown on the InGaAs epitaxial layer, which may lead to degradation of the epitaxial layer growth quality. Summary of the invention

[0004] The object of the present invention is to provide a method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system in view of the above-mentioned deficiencies in the prior art, so as to solve the problem of determining the temperature of other epitaxial layers grown on an InGaAs epitaxial layer.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: The present invention provides a method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system, the method being used to determine the growth temperature when growing other epitaxial layers on an InGaAs epitaxial layer of a first preset thickness, the method comprising: Step a: growing InGaAs of a second preset thickness on an InP substrate at a plurality of different growth temperatures. y P 1-y epitaxial layers to obtain multiple epitaxial wafers; Step b, testing the plurality of epitaxial wafers respectively to determine the value of the As component y in each epitaxial wafer, thereby obtaining a plurality of y values; Step c, performing data fitting on the multiple different growth temperatures and the multiple y values, and using the function relationship obtained by fitting as the corresponding relationship between the growth temperature and the As component; Step d: Continue to grow an InGaAs epitaxial layer of a second preset thickness on the InGaAs epitaxial layer of the first preset thickness. y P 1-y epitaxial layer, and measured to determine the composition y, where InGaAs y P 1-y The growth temperature of the epitaxial layer is a first temperature; Step e, calculating the growth temperature corresponding to the component y determined in step d in the corresponding relationship, and using the corresponding growth temperature as the second temperature; Step f, when growing other epitaxial layers on the InGaAs epitaxial layer of the first preset thickness, the growth temperature = reference temperature - (second temperature - first temperature), where the reference temperature is a predetermined growth temperature for growing other epitaxial layers on an InP substrate without an InGaAs epitaxial layer.

[0006] Optionally, the other epitaxial layer includes one of the following: an InP epitaxial layer, an InGaAs epitaxial layer, an InAlAs epitaxial layer, and an InGaAsP epitaxial layer.

[0007] Optionally, the InGaAs epitaxial layer of the first preset thickness is an InGaAs epitaxial layer with a fixed In composition or a combined InGaAs epitaxial layer formed by stacking a plurality of InGaAs epitaxial layers with different In compositions.

[0008] Optionally, the In composition in the InGaAs epitaxial layer of the first preset thickness is in a range of greater than or equal to 0.4 and less than or equal to 0.55.

[0009] Optionally, the InGaAs epitaxial layer of the first preset thickness is an InGaAs epitaxial layer with an In composition fixed at 0.53.

[0010] The beneficial effects of the present invention include: The method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system provided by the present invention comprises: step a, growing InGaAs of a second preset thickness on an InP substrate at a plurality of different growth temperatures, y P 1-yStep b, testing the plurality of epitaxial wafers respectively to determine the value of the As component y in each epitaxial wafer, thereby obtaining a plurality of y values; step c, performing data fitting on the plurality of different growth temperatures and the plurality of y values, and using the function relationship obtained by fitting as the corresponding relationship between the growth temperature and the As component; step d, continuing to grow an InGaAs epitaxial layer of a second preset thickness on the InGaAs epitaxial layer having grown the first preset thickness y P 1-y epitaxial layer, and measured to determine the composition y, where InGaAs y P 1-y The growth temperature of the epitaxial layer is the first temperature; step e, calculate the growth temperature corresponding to the component y determined in step d in the corresponding relationship, and use the corresponding growth temperature as the second temperature; step f, the growth temperature when growing other epitaxial layers on the InGaAs epitaxial layer of the first preset thickness = reference temperature - (second temperature - first temperature), and the reference temperature is the predetermined growth temperature of other epitaxial layers grown on the InP substrate without the InGaAs epitaxial layer. This method obtains the corresponding relationship between the InGaAsP epitaxial layer component and the growth temperature, and then grows and measures the InGaAsP component on the InGaAs layer, so as to calculate the additional influence of the InGaAs epitaxial layer endothermic on the actual growth temperature, based on which the growth temperature when growing other epitaxial layers on the InGaAs epitaxial layer can be determined, which is conducive to improving product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0012] Figure 1 A flow chart of a method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system provided by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] To determine the process parameters of a complex epitaxial layer structure, it is usually decomposed into multiple simple calibration structures. By growing the calibration structure, the optimal growth temperature of the calibration structure (that is, the corresponding thermocouple temperature) is obtained, and the growth temperature is applied to the complete epitaxial structure. However, for the growth of an epitaxial layer on an InP substrate, when an InGaAs material has been grown on the epitaxial layer, due to the small bandgap width of the InGaAs material, a large amount of thermal radiation will be absorbed, causing the surface temperature of the epitaxial layer to rise. Since the thermocouple is located on the back of the substrate and the thermocouple is non-contact with the substrate, this surface temperature increase is usually difficult to be quantitatively and accurately sensed by the thermocouple, and it is difficult to accurately feed back to the temperature control system, resulting in the optimal temperature (thermocouple temperature) of other epitaxial layers determined based on the calibration structure being inconsistent with the optimal temperature when other epitaxial layers are grown on the InGaAs epitaxial layer, which may lead to degradation of the growth quality of the epitaxial layer. Therefore, it is necessary to propose a method for determining the growth temperature when other epitaxial layers are grown on an InGaAs epitaxial layer.

[0015] Figure 1 A flow chart of a method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system provided by an embodiment of the present invention is shown.

[0016] The method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system provided by the present invention is used to determine the growth temperature when growing other epitaxial layers on an InGaAs epitaxial layer of a first preset thickness, and the substrate used for the growth is an InP substrate, such as Figure 1 As shown, the method includes: Step a: growing InGaAs of a second preset thickness on an InP substrate at a plurality of different growth temperatures. y P 1-y epitaxial layers to obtain multiple epitaxial wafers; In the growth of step a, the component of In is a known component that is pre-calibrated and fixed, so the temperature of the indium source furnace and the temperature of the gallium source furnace remain unchanged. And at the multiple different growth temperatures, the As beam equivalent pressure and the P beam equivalent pressure are both fixed. If the growth temperature remains unchanged, then since the As beam equivalent pressure and the P beam equivalent pressure remain unchanged, the corresponding As component y will also remain unchanged. However, since the growth temperature is changed, the desorption of As and P will be affected by the growth temperature, resulting in different As components y obtained at different temperatures. Generally speaking, the higher the growth temperature, the more severe the P desorption will be, and thus the higher the As component. It should be understood that in the multiple growths of step a, except for the different growth temperatures, the other process parameters are the same. In step a, a second preset thickness of InGaAs is grown on an InP substrate. y P 1-y The epitaxial layer refers to the InGaAs layer with a second preset thickness grown directly on the InP substrate. yP 1-y Epitaxial layer, on InP substrate and InGaAs y P 1-y There is no other epitaxial layer structure growing between the epitaxial layers.

[0017] It should be noted that the growth temperature described in this application refers to the thermocouple temperature sensed by the thermocouple arranged between the substrate support plate and the support plate heating device.

[0018] Step b: testing the plurality of epitaxial wafers respectively to determine the value of the As component y in each epitaxial wafer, thereby obtaining a plurality of y values.

[0019] Step c: performing data fitting on the multiple different growth temperatures and the multiple y values, and using the functional relationship obtained by fitting as the corresponding relationship between the growth temperature and the As component.

[0020] Through steps a to c, the corresponding relationship between the growth temperature and the As component can be obtained.

[0021] Step d: Continue to grow an InGaAs epitaxial layer of a second preset thickness on the InGaAs epitaxial layer of the first preset thickness. y P 1-y epitaxial layer, and measured to determine the composition y, where InGaAs y P 1-y The growth temperature of the epitaxial layer is a first temperature.

[0022] In step d, an InGaAs epitaxial layer of a first preset thickness and an InGaAs epitaxial layer of a second preset thickness may be continuously grown on the InP substrate. y P 1-y The first temperature here is the preset thermocouple temperature. Since the InGaAs epitaxial layer absorbs heat, the surface temperature of the epitaxial layer increases. That is, when the thermocouple temperatures are all the first temperature, the InGaAs in step d y P 1-y The actual growth temperature of the epitaxial layer is higher than that of InGaAs grown directly on InP substrate. y P 1-y The actual growth temperature of the epitaxial layer will result in the actual component y being higher than the expected value (i.e., InGaAs grown directly on an InP substrate y P 1-y composition value in epitaxial layer).

[0023] It should be understood that in step d, the second preset thickness of In is grown. x0 Ga 1-x0 As y P 1-yDuring the epitaxial layer growth process, the indium source furnace temperature, the gallium source furnace temperature, the As beam equivalent pressure, and the P beam equivalent pressure are the same as those in step a.

[0024] Optionally, the InGaAs epitaxial layer of the first preset thickness is an InGaAs epitaxial layer with a fixed In component or a combined InGaAs epitaxial layer formed by stacking a plurality of InGaAs epitaxial layers with different In components. The range of the In component in the InGaAs epitaxial layer of the first preset thickness is greater than or equal to 0.4 and less than or equal to 0.55. Optionally, the InGaAs epitaxial layer of the first preset thickness is an InGaAs epitaxial layer with a fixed In component of 0.53.

[0025] Step e: calculating the growth temperature corresponding to the component y determined in step d in the corresponding relationship, and taking the corresponding growth temperature as the second temperature.

[0026] Using the corresponding relationship, the second temperature corresponding to the component y determined in step d can be calculated, that is, when the InGaAs is grown on the InGaAs layer with the first preset thickness at the first temperature, y P 1-y The effect of the epitaxial layer is equivalent to growing InGaAs directly on the InP substrate at the second temperature. y P 1-y The effect of the epitaxial layer. Therefore, the contribution of the heat absorption of the InGaAs layer of the first preset thickness is equivalent to the difference between the second temperature and the first temperature. The amount of heat absorbed by the InGaAs layer is usually closely related to the thickness of the InGaAs layer. The thicker the InGaAs layer, the greater the amount of heat absorbed.

[0027] Step f, when growing other epitaxial layers on the InGaAs epitaxial layer of the first preset thickness, the growth temperature = reference temperature - (second temperature - first temperature), the reference temperature is a predetermined growth temperature for growing other epitaxial layers on an InP substrate without an InGaAs epitaxial layer. Optionally, the other epitaxial layers include one of the following: an InP epitaxial layer, an InGaAs epitaxial layer, an InAlAs epitaxial layer, and an InGaAsP epitaxial layer.

[0028] The reference temperature may be the optimal temperature obtained when other epitaxial layers are directly grown on the InP substrate for calibration. Similarly, the reference temperature here is also the thermocouple temperature. When other epitaxial layers are grown on the InGaAs epitaxial layer of the first preset thickness, the surface temperature of the epitaxial layer increases because the InGaAs epitaxial layer absorbs heat. Therefore, in order to offset the deviation of the actual growth temperature from the optimal growth temperature caused by the temperature increase, the reference temperature - (second temperature - first temperature) may be used as the growth temperature when other epitaxial layers are grown on the InGaAs epitaxial layer of the first preset thickness.

[0029] The method obtains the corresponding relationship between the InGaAsP epitaxial layer composition and the growth temperature, then grows and measures the InGaAsP composition on the InGaAs layer, and can calculate the additional influence of the InGaAs epitaxial layer endothermicity on the actual growth temperature. Based on this, the growth temperature when growing other epitaxial layers on the InGaAs epitaxial layer can be determined, which is beneficial to improving product quality.

[0030] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system, characterized in that: The method is used to determine the growth temperature when growing other epitaxial layers on an InGaAs epitaxial layer of a first preset thickness, and the method comprises: Step a: growing InGaAs of a second preset thickness on an InP substrate at a plurality of different growth temperatures. y P 1-y epitaxial layers to obtain multiple epitaxial wafers; Step b, testing the plurality of epitaxial wafers respectively to determine the value of the As component y in each epitaxial wafer, thereby obtaining a plurality of y values; Step c, performing data fitting on the multiple different growth temperatures and the multiple y values, and using the function relationship obtained by fitting as the corresponding relationship between the growth temperature and the As component; Step d: Continue to grow an InGaAs epitaxial layer of a second preset thickness on the InGaAs epitaxial layer of the first preset thickness. y P 1-y epitaxial layer, and measured to determine the composition y, where InGaAs y P 1-y The growth temperature of the epitaxial layer is a first temperature; Step e, calculating the growth temperature corresponding to the component y determined in step d in the corresponding relationship, and using the corresponding growth temperature as the second temperature; Step f, when growing other epitaxial layers on the InGaAs epitaxial layer of the first preset thickness, the growth temperature = reference temperature - (second temperature - first temperature), wherein the reference temperature is a predetermined growth temperature for growing the other epitaxial layers on an InP substrate without an InGaAs epitaxial layer.

2. The method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system according to claim 1, characterized in that: The other epitaxial layer includes one of the following: an InP epitaxial layer, an InGaAs epitaxial layer, an InAlAs epitaxial layer, and an InGaAsP epitaxial layer.

3. The method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system according to claim 1, characterized in that: The InGaAs epitaxial layer of the first preset thickness is an InGaAs epitaxial layer with a fixed In composition or a combined InGaAs epitaxial layer formed by stacking a plurality of InGaAs epitaxial layers with different In compositions.

4. The method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system according to claim 3, characterized in that: The In composition of the InGaAs epitaxial layer of the first preset thickness is in a range of greater than or equal to 0.4 and less than or equal to 0.

55.

5. The method for determining the growth temperature of an epitaxial layer in a molecular beam epitaxy system according to claim 4, characterized in that: The InGaAs epitaxial layer of the first preset thickness is an InGaAs epitaxial layer with an In composition fixed at 0.53.

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