Method for determining process parameters of molecular beam epitaxy beryllium doping

Abstract

The application provides a method for determining molecular beam epitaxy beryllium doping process parameters, and relates to the technical field of semiconductor manufacturing. The method comprises the following steps: A, growing multiple calibration structures with different doping layer thicknesses at a Be source furnace temperature of a first temperature, and measuring the doping concentration of the corresponding calibration structure; B, performing data fitting by using a preset model to obtain fitting parameters; C, calculating y1 and comparing y1 and N0; D, adjusting the first temperature value according to the comparison result, repeating A to C, and stopping until the absolute value of (y1-N0) / N0 is less than a preset threshold. The application establishes the corresponding relationship between the doping thickness and the measured doping concentration by using the preset model, so that the measured results of the calibration structure can be used to directly determine the process parameters corresponding to the base region layer with the expected doping concentration, thereby avoiding the problem of the measured doping concentration deviation of the base region caused by the replacement of the Be source furnace, and improving the performance stability of the epitaxial materials and devices of different batches.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and specifically to a method for determining the process parameters of beryllium doping in molecular beam epitaxy. Background Technology

[0002] For InP-based HBT devices with a heavily beryllium (Be)-doped InGaAs layer in the base region, the base doping concentration directly determines the base resistance and significantly affects the device's current gain and frequency characteristics. Therefore, maintaining the stability of the base doping concentration during the large-scale molecular beam epitaxy production of InP-based HBT device epitaxial materials is crucial for ensuring stable device performance.

[0003] Before each batch of InP-based HBT epitaxial material is grown using molecular beam epitaxy, a doped calibration structure needs to be grown, and the doping concentration of the calibration structure is measured using a Hall effect meter. Based on the Hall effect measurement results of the doped calibration structure, the Be source furnace temperature corresponding to the desired doping concentration in the base region is determined. However, the base layer in InP-based HBT structures is typically thin (e.g., less than or equal to 35 nm), and the concentration is usually greater than 1 × 10⁻⁶. 19 cm -3 To ensure the accuracy of Hall effect measurements (due to the presence of a depletion layer during testing), the thickness of the doped calibration structure is typically greater than or equal to 75 nm. If the doping concentration is low, a thicker doped calibration structure is required. When using a Be source furnace for doping, the instantaneous doping concentration is initially higher than expected for a short period after the furnace baffle is opened, before settling back to a stable state. Therefore, when the Be source furnace temperature determined by the conventional calibration method is used for base layer doping, the actual doping concentration of the base layer usually differs from the measured doping concentration of the doped calibration structure; the actual doping concentration is often higher than expected. However, when the Be source furnace is stable over a long period, a stable correspondence exists between the actual doping concentration of the base layer and the measured doping concentration of the doped calibration structure. In this case, the conventional calibration method described above is reliable and feasible.

[0004] However, when different batches of beryllium doping are grown using different Beryllium source furnaces (e.g., when changing molecular beam epitaxy equipment), the transient responses of different Beryllium source furnaces differ. This causes a change in the correspondence between the actual doping concentration of the base layer and the measured doping concentration of the doping calibration structure. In this case, even if the measured doping concentration obtained using the doping calibration structure is consistent with that of previous batches, the actual doping concentration of the corresponding grown base layer will still deviate compared to before, resulting in changes in device performance parameters. This necessitates re-establishing the correspondence between device parameters and calibration results, increasing production and testing costs. Therefore, a novel method for determining beryllium doping process parameters is needed to ensure that the actual doping concentration of the base region remains stable across different batches or different beryllium doping source furnaces. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a method for determining the process parameters of beryllium doping in molecular beam epitaxy, thereby solving the problem of accurate calibration of beryllium doping process parameters.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for determining the process parameters of beryllium doping in molecular beam epitaxy. This method is used to determine the Be source furnace temperature when growing a Be-doped layer in a semiconductor device structure. The expected doping concentration of the Be-doped layer is a preset concentration N0, and the thickness h0 of the Be-doped layer ranges from 20 nm to 35 nm. The method includes: Step A: At the first temperature of the Be source furnace, multiple Be-doped calibration structures with different doped material layer thicknesses are grown using a molecular beam epitaxy system, and the doping concentration of the corresponding Be-doped calibration structure is measured. The doped material layer of the Be-doped calibration structure is the same as that of the Be-doped layer, and the thickness of the doped material layer is greater than or equal to 75 nm. The first temperature is the initial temperature determined based on empirical data. Step B: Use the preset model y=a / x+b to fit the data to obtain the fitting parameters a and b, where x represents the thickness of the doped material layer of the Be-doped calibration structure, and y represents the measured doping concentration corresponding to x. Step C: Calculate y1 = a / h0 + b, and compare y1 with N0; Step D: Adjust the value of the first temperature according to the comparison result in step C, and repeat steps A to C under the new first temperature condition until the absolute value of (y1-N0) / N0 is less than the preset threshold. Then, determine the Be source furnace temperature when growing the Be doped layer in the semiconductor device structure according to the final value of the first temperature.

[0007] Optionally, the doping concentration of the Be-doped calibration structure is measured using a Hall effect meter.

[0008] Optionally, the thickness of the doped material layer in the Be-doped calibration structure ranges from 75 nm to 300 nm.

[0009] Optionally, in step A, the thicknesses of the plurality of Be-doped calibration structures are 75 nm, 150 nm, and 300 nm, respectively.

[0010] Optionally, in step A, the first temperature is a Be source furnace temperature determined based on a pre-obtained relationship curve between the Be doping concentration and the Be source furnace temperature, such that the expected doping concentration of any of the plurality of Be doped calibration structures is equal to m×N0, where m is a preset coefficient and the range of m is 0.7. <m<0.9。

[0011] Optionally, the value of the first temperature can be adjusted based on the comparison result in step C. Specifically, this includes: calculating N0 / y1, and then calculating and determining the specified doping concentration N based on the pre-obtained relationship curve between the Be doping concentration and the Be source furnace temperature. z It becomes N0 / y1×N z At that time, the change in Be source furnace temperature ΔT is used as the first temperature, and then the sum of the first temperature and ΔT is used as the adjusted value to specify the doping concentration N. z This indicates the measured doping concentration of the Be-doped calibration structure with the thinnest doped material layer among the multiple Be-doped calibration structures described in step A.

[0012] Optionally, determining the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure based on the final value of the first temperature includes: using the final value of the first temperature as the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure; or Based on the final values ​​of y1 and N0, and historical data on the impact of adjusting the value of the first temperature on y1, the final value of the first temperature is revised again, and the revised first temperature is used as the Be source furnace temperature when growing the Be doped layer in the semiconductor device structure.

[0013] Optionally, the Be-doped layer is a Be-doped InGaAs material layer.

[0014] Optionally, the growth rate V of the Be-doped layer B The range is 0.5 μm / h ≤ V B ≤1 μm / h.

[0015] Optionally, the growth rate of the doped material layer is the same as that of the Be-doped layer.

[0016] The beneficial effects of this invention include: The method for determining beryllium doping process parameters provided by this invention is used to determine the Be source furnace temperature when growing a Be-doped layer in a semiconductor device structure. The expected doping concentration of the Be-doped layer is a preset concentration N0, and the thickness h0 of the Be-doped layer ranges from 20 nm to 35 nm. The method includes: Step A, growing multiple Be-doped calibration structures with different doped material layer thicknesses using a molecular beam epitaxy system at a first temperature, and measuring the doping concentration of the corresponding Be-doped calibration structures. The doped material layer of the Be-doped calibration structure is of the same material type as the Be-doped layer, and the thickness of the doped material layer is greater than or equal to 75 nm. The first temperature is determined based on empirical values. Based on the determined initial temperature; Step B: Use the preset model y=a / x+b to fit the data to obtain the fitting parameters a and b, where x represents the thickness of the doped material layer of the Be-doped calibration structure, and y represents the measured doping concentration corresponding to x; Step C: Calculate y1=a / h0+b and compare y1 and N0; Step D: Adjust the value of the first temperature according to the comparison result in Step C, and repeat Steps A to C under the new first temperature condition until the absolute value of (y1-N0) / N0 is less than the preset threshold, and determine the Be source furnace temperature when growing the Be-doped layer in the semiconductor device structure based on the final value of the first temperature. This application establishes the correspondence between the doping thickness of doped material layers of different thicknesses and the measured doping concentration through a preset model, so that the doping process parameters corresponding to the expected doping concentration of the base layer can be directly determined using the measured results of the doped calibration structure. This avoids the problem of the actual doping concentration of the base region deviating from the expected value due to the different transient responses of different Be source furnaces when changing Be source furnaces, and improves the performance stability of different batches of epitaxial materials and devices. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the method for determining beryllium doping process parameters in molecular beam epitaxy provided in an embodiment of the present invention is shown. Figure 2 A schematic diagram of the Be-doped calibration structure provided in an embodiment of the present invention is shown; Figure 3 A schematic diagram showing the relationship between Be doping concentration and doping growth time provided in an embodiment of the present invention is shown. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] When different batches of beryllium doping are grown using different Beryllium source furnaces (e.g., when changing molecular beam epitaxy equipment), the transient responses of different Beryllium source furnaces differ. This causes a change in the correspondence between the actual doping concentration of the Beryllium-doped base layer and the measured doping concentration of the conventional doping calibration structure (the thickness of the conventional doping calibration structure is greater than the thickness of the base layer). In this case, even if the measured doping concentration obtained using the doping calibration structure is consistent with that of previous batches, the actual doping concentration of the corresponding grown base layer will still deviate compared to before, resulting in changes in device performance parameters. This necessitates re-establishing the correspondence between device parameters and calibration results, increasing production and testing costs. Therefore, a novel method for determining beryllium doping process parameters is needed to ensure that the actual doping concentration of the base region remains stable across different batches or different beryllium doping source furnaces.

[0021] This invention provides a method for determining the process parameters of beryllium doping in molecular beam epitaxy. This method is used to determine the Be source furnace temperature when growing a Be-doped layer in a semiconductor device structure. The expected doping concentration of the Be-doped layer is a preset concentration N0, and the thickness h0 of the Be-doped layer ranges from 20 nm to 35 nm. Optionally, the Be-doped layer is a Be-doped InGaAs material layer. The semiconductor device structure can be, for example, an HBT structure on an InP substrate.

[0022] When the semiconductor device is an HBT device, the Be-doped layer is the base layer, and the expected doping concentration N0 of the Be-doped layer is typically greater than 1 × 10⁻⁶. 19 cm -3The thickness h0 of the Be-doped layer can be 20 nm, 35 nm, or any thickness between 20 nm and 35 nm, such as 25 nm or 30 nm. It should be noted that the preset concentration N0 and thickness h0 are designed by semiconductor device structure designers based on the functional requirements of the semiconductor device. The purpose of this application is to determine the relevant growth process parameters during molecular beam epitaxy (MBE) growth based on the already designed structure, so that the grown epitaxial material structure meets the functional requirements of the semiconductor device. To determine the Be source furnace temperature (corresponding to the preset concentration N0) for growing the Be-doped layer, calibration growth is first performed using a doping calibration structure. To ensure the accuracy of the Hall test (as a depletion layer exists during testing), the thickness of the doping calibration structure is typically greater than or equal to 75 nm. If the doping concentration is low, a thicker doping calibration structure is required. That is, the thickness of the doped material layer in the doping calibration structure must be greater than the thickness of the Be-doped layer in the semiconductor device structure. If there is no transient effect in the Be source furnace doping, and the concentration of the entire doped layer is ideally uniformly distributed, the source furnace temperature determined by the doping calibration structure can be directly applied to the growth of the Be-doped layer in the semiconductor device structure. However, due to the transient effect of the Be source furnace, directly applying the source furnace temperature determined by the doping calibration structure to the growth of the Be doped layer in the semiconductor device structure will lead to an actual Be doped layer concentration exceeding expectations. Furthermore, even using the same calibration results, the actual Be doped layer concentration in the semiconductor device structure will vary due to the typically different transient responses of different Be source furnaces. Therefore, a novel method for determining beryllium doping process parameters is needed.

[0023] Figure 1 A flowchart illustrating the method for determining beryllium doping process parameters in molecular beam epitaxy provided by an embodiment of the present invention is shown. Figure 1 As shown, the method includes: Step A: At the first temperature of the Be source furnace, multiple Be-doped calibration structures with different doped material layer thicknesses are grown using a molecular beam epitaxy system, and the doping concentration of the corresponding Be-doped calibration structures is measured.

[0024] The doped material layer of the Be-doped calibration structure is of the same material type as the Be-doped layer, the thickness of the doped material layer is greater than or equal to 75 nm, and the first temperature is an initial temperature determined according to empirical data. For example, the first temperature is the Be source furnace temperature determined according to empirical data that makes the expected doping concentration of any one of the plurality of Be-doped calibration structures approach or equal to the preset concentration N0. As described in the following text, during the doping process, the Be source furnace will exhibit a concentration overshoot in a short initial period of time, and then gradually stabilize. Therefore, at the same Be source furnace temperature, the average doping concentration of a thinner layer will be greater than the average doping concentration of a thicker layer. Since the thickness of the Be-doped calibration structure is greater than the thickness of the Be-doped layer in the semiconductor device structure, when selecting the initial value of the first temperature, a temperature slightly lower than the finally desired ideal temperature (the temperature of the Be source furnace when growing the Be-doped layer in the semiconductor device structure) can be selected, so as to complete the calibration process more quickly. For example, optionally, in step A, the first temperature is the Be source furnace temperature determined according to the pre-obtained relationship curve between the Be doping concentration and the Be source furnace temperature that makes the expected doping concentration of any one of the plurality of Be-doped calibration structures equal to m×N0, where m is a preset coefficient, and m is in the range of 0.7<m<0.9. It should be noted that the pre-obtained relationship curve between the Be doping concentration and the Be source furnace temperature is obtained in the following manner: on the premise of fixing other growth process parameters, only the temperature of the Be source furnace is changed, and multiple epitaxial growths are performed respectively to obtain a plurality of epitaxial wafers, and concentration tests (for example, by means of Hall test or SIMS test) are performed on the plurality of epitaxial wafers to obtain the corresponding doping concentrations, thereby obtaining multiple sets of datasets of Be source furnace temperature and Be doping concentration; preprocessing the data in the dataset, converting the Be source furnace temperature Ts into the corresponding thermodynamic temperature Tr, where Tr=Ts+273.15, calculating the independent variable x=1 / Tr and the dependent variable y=ln(Ns), where Ns represents the Be doping concentration in the dataset, performing least squares linear fitting y=A+B*x, where * represents the multiplication sign, so as to obtain the fitting coefficients A and B, and further the model N(Ti)=e can be utilized A+B / Ti to calculate the Be doping concentration N(Ti) corresponding to any Be source furnace temperature Ti, and the relationship curve corresponding to the model is taken as the relationship curve between the Be doping concentration and the Be source furnace temperature.

[0025] It should be noted that for the purpose of distinction, the term "Be-doped layer" is used in the present application to refer to the Be-doped material layer in the functional complete semiconductor device structure, for example, the Be-doped base layer in the semiconductor device structure; the term "doped material layer" is used to refer to the Be-doped material layer in the Be-doped calibration structure that is only used for calibrating Be doping. Figure 2A schematic diagram of the Be-doped calibration structure provided in an embodiment of the present invention is shown, as follows: Figure 2 As shown, the Be-doped calibration structure, from bottom to top, includes a substrate 201, a buffer layer 202, and a Be-doped material layer 203. As previously indicated, the doped material layer of the Be-doped calibration structure is made of the same material as the Be-doped layer. That is, for example, if the Be-doped layer in the semiconductor device structure is a Be-doped GaAs layer, the doped material layer 203 of the Be-doped calibration structure is also a Be-doped GaAs layer. In this case, the buffer layer 202 corresponds to an undoped GaAs layer, and the substrate 201 corresponds to a semi-insulating GaAs substrate. Similarly, if the Be-doped layer in the semiconductor device structure is a Be-doped InGaAs layer, the doped material layer 203 of the Be-doped calibration structure is also a Be-doped InGaAs layer. In this case, the buffer layer 202 corresponds to an undoped InGaAs layer, and the substrate 201 corresponds to a semi-insulating InP substrate.

[0026] The thickness of the doped material layer in the Be-doped calibration structure can range from, for example, 75 nm to 300 nm. Optionally, in step A, the thicknesses of the plurality of Be-doped calibration structures are 75 nm, 150 nm, and 300 nm, respectively.

[0027] In the process of growing multiple Be-doped calibration structures with different doped material layer thicknesses using a molecular beam epitaxy system, the only difference between each Be-doped calibration structure is the thickness of the doped material layer 203; all other process parameters are the same, thus obtaining multiple calibration samples. These calibration samples are then tested to obtain the doping concentration of each sample. In practice, the doping concentration of the Be-doped calibration structures is measured using a Hall effect meter.

[0028] Step B: Use the preset model y=a / x+b to fit the data to obtain the fitting parameters a and b.

[0029] Where x represents the thickness of the doped material layer in the Be-doped calibration structure, and y represents the measured doping concentration corresponding to x.

[0030] Optionally, the growth rate V of the Be-doped layer B The range is 0.5 μm / h ≤ V B ≤1 μm / h. Optionally, the growth rate of the doped material layer is the same as that of the Be-doped layer.

[0031] During molecular beam epitaxy (MBE) doping, an initial concentration overshoot occurs when the Be source furnace baffle is first opened. This is a typical phenomenon caused by a combination of factors, including transient surface adsorption and surface Be enrichment. For typical MBE growth rates, the epitaxial layer thickness corresponding to this overshoot is usually less than 10 to 15 nm, after which the concentration stabilizes. The transient characteristics (overshoot) of different source furnaces are generally different, and empirical parameters for the transient characteristics of different source furnaces cannot be directly applied to another source furnace. Generally, the highest concentration at the overshoot point is typically about 20%–40% higher than the steady-state concentration after stabilization. Assume the Be source furnace temperature is T. 10 The corresponding stable doping concentration is N. 10 In the molecular beam epitaxy system, the Be source furnace temperature is set to T. 10 The substrate is stabilized at this temperature for a period of time. Then, the Be source furnace baffle is opened, and a doped material layer of a certain thickness (e.g., 200 nm) is grown on the substrate. During growth, the Be source temperature remains stable. After growth, SIMS (secondary ion mass spectrometry) can be used to determine the doping concentration distribution of the doped material layer at different depths. Based on the SIMS test results, a curve showing the relationship between doping concentration and growth time (which can be calculated using thickness and growth rate) can be plotted, yielding results such as... Figure 3 The diagram shown is shown in the image.

[0032] like Figure 3 As shown, during molecular beam epitaxy (MBE) doping growth, the horizontal axis represents the doping growth time, and the vertical axis represents the corresponding instantaneous doping concentration. Given a fixed growth rate, the doping growth time corresponds one-to-one with the growth thickness. The doped material layer begins growth at time t0 (at which point the Be source furnace baffle is open). Between time t0 and time t1, the doping concentration experiences a certain amount of overshoot. As mentioned earlier, at time t1, the thickness of the grown doped material layer is typically less than 10 to 15 nm. From time t1 onwards, the instantaneous doping concentration remains stable. Since the doping concentration obtained by the Hall effect measurement is the average concentration of the entire doped layer, assuming the Be source furnace temperature remains constant, let's assume the growth time of the doped material layer for the first sample is from time t0 to time t2, corresponding to a total doped material layer thickness of h2. Let's assume the growth time of the doped material layer for the second sample is from time t0 to time t3, corresponding to a total doped material layer thickness of h3. Obviously, h3 > h2, indicating that the measured doping concentration of the second sample will be less than that of the first sample. For Figure 3 The doping concentration curve shown assumes a total doping dose of P from time t0 to time t1 (assuming the thickness of the doped material layer corresponding to this time period is S1). From time t1 to any time t... x (t) xDuring the period >t1), since the instantaneous doping concentration is stable, it can be assumed that the doping concentration per unit thickness is K starting from time t1. Furthermore, it is assumed that at time t... x The thickness of the doped material layer that has been grown at time t is x. x The cumulative total doping dose (calculated from time t0) is equal to the total dose from time t0 to time t1 plus the dose from time t1 to time t2. x The total dose between time t1 and time t2. x Between these times, the doping concentration remains stable (equal to K). Therefore, from time t1 to time t... x The total dose between time t1 and time t2 is equal to the dose from time t1 to time t3. x The thickness of the growth between the two sections multiplied by the doping concentration K within that section, since time t x Let x be the thickness of the doped material layer that has grown at time t1, and S1 be the thickness of the doped material layer that has grown at time t2. Therefore, from time t1 to time t... x The total thickness grown between these points is equal to (x-S1), and thus from time t1 to time t... x The total dose between time t0 and time t1 is equal to (x-S1)×K. Since the total dose between time t0 and time t1 is P, at time t... x The cumulative total doping dose (calculated from time t0) corresponding to time t0 is equal to P + (x - S1) × K. Therefore, the theoretical doping concentration corresponding to a doped material layer thickness of x is y = [P + (x - S1) × K] / x. Note that this formula applies only at time t0. x When the value is greater than t1, the equation is transformed to obtain: y=(P-S1×K) / x+K. For the same Be source furnace and the same Be source furnace temperature, P, S1, and K are all constants. Therefore, let a=P-S1×K and b=K, then the above equation can be simplified to y=a / x+b, thus establishing a relationship model between the doping concentration y and the thickness x of the doped material layer. Here, a and b are model parameters, and a and b can be determined by parameter fitting after obtaining multiple sets of x and y values.

[0033] Step C: Calculate y1 = a / h0 + b, and compare y1 and N0.

[0034] After the model parameters a and b are determined in step B, the model can be used to calculate the corresponding doping concentration y1 when the thickness is h0. Since the preset concentration is N0, if y1=N0, the calibration is completed, and the corresponding first temperature at this time is the temperature of the Be source furnace when growing the Be-doped layer in the semiconductor device structure. If y1<N0, the value of the first temperature needs to be increased; if y1>N0, the value of the first temperature needs to be decreased. The core idea of this method is to establish a relationship model between the doping concentration and the growth thickness, obtain the test data of the thicker doped material layer and fit to obtain the parameters of the relationship model, so that the doping concentration corresponding to the thinner doped material layer can be calculated through the model, which not only avoids the measurement error caused by directly growing the thinner doped material layer, but also avoids the error introduced by directly taking the test data of the thicker doped material layer as the data of the thinner doped material layer (that is, the error introduced by not considering the transient response of the Be source furnace). Through this method, the actual doping concentration corresponding to the thinner doped material layer (with a thickness of 20 nm to 35 nm) at the first temperature can be reliably determined.

[0035] Step D: Adjust the value of the first temperature according to the comparison result in step C, and repeat steps A to C under the new first temperature condition until the absolute value of (y1-N0) / N0 is less than the preset threshold, and the temperature of the Be source furnace when growing the Be-doped layer in the semiconductor device structure is determined according to the final value of the first temperature.

[0036] The preset threshold can be determined according to the concentration control accuracy requirement for the Be-doped layer in actual operation. For example, the preset threshold can be 5% or 3%. For example, when the concentration control accuracy requirement is ±5%, the preset threshold can be set to 5%; when the concentration control accuracy requirement is ±3%, the preset threshold can be set to 3%. It should be understood that if the absolute value of the calculated (y1-N0) / N0 is already less than the preset threshold when the first temperature is the initial temperature, there is no need to perform steps A to C again, and the temperature of the Be source furnace when growing the Be-doped layer in the semiconductor device structure can be directly determined according to the value of the first temperature, which is an ideal situation. Usually, after the growth test and calculation are performed at the initial temperature, it is necessary to adjust the value of the first temperature according to the comparison result of step C, and repeat steps A to C under the new first temperature condition. For switching between different epitaxial systems and different Be source furnaces, after relevant empirical data are accumulated, usually the initial temperature only needs to be adjusted once, and then after repeating steps A to C, the desired result can be obtained, without further adjustment of the Be source furnace temperature and growth test.

[0037] Optionally, the value of the first temperature can be adjusted based on the comparison result in step C. Specifically, this includes: calculating N0 / y1, and then calculating and determining the specified doping concentration N based on the pre-obtained relationship curve between the Be doping concentration and the Be source furnace temperature. z It becomes N0 / y1×N z At that time, the change in Be source furnace temperature ΔT is used as the first temperature, and then the sum of the first temperature and ΔT is used as the adjusted value to specify the doping concentration N. z This indicates the measured doping concentration of the Be-doped calibration structure with the thinnest doped material layer among the multiple Be-doped calibration structures described in step A.

[0038] Among the multiple Be-doped calibration structures, the Be-doped calibration structure with the thinnest doped material layer is closest to the thickness of the Be-doped layer in the semiconductor device structure. Therefore, when calculating the value of the first temperature adjustment, the specified doping concentration N is used. z The change in Be source furnace temperature ΔT corresponding to a multiple of N0 / y1 can be approximated as a multiple of N0 / y1 increase in the doping concentration y1 of the Be doped layer, thus obtaining the expected doping concentration as N0 / y1×y1= N0.

[0039] Optionally, the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure is determined based on the final value of the first temperature, including: using the final value of the first temperature as the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure; or, based on the final y1 and N0, and historical data on the influence of adjusting the value of the first temperature on y1, the final value of the first temperature is corrected again, and the corrected first temperature is used as the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure.

[0040] Since the final first temperature value already makes the absolute value of (y1-N0) / N0 less than the preset threshold, it can be directly used as the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure. Furthermore, based on accumulated historical data, the first temperature can be fine-tuned again, and this finely-tuned first temperature can be used as the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure. Since this fine-tuning is done when the absolute value of (y1-N0) / N0 is already less than the preset threshold, there is no need for further calibration structure growth verification after the correction. Instead, the finely-tuned temperature can be directly applied to the growth of the Be-doped layer in the complete semiconductor device structure.

[0041] Specifically, for InP-based HBT devices with a Be-doped base region, the base region doping concentration directly determines the base region sheet resistance, which is directly related to the device's current gain. In the first molecular beam epitaxy system, for a given HBT device structure and its expected current gain, a conventional Be doping concentration calibration method is used (e.g., the test concentration of a Be-doped calibration structure with a doped layer thickness of 200 nm is directly used as the base region concentration). After multiple experiments and current gain tests, it is determined that when the Be-doped calibration structure has a doping concentration of Z0, the current gain of the corresponding device is the expected current gain (it should be understood that the actual doping concentration of the base region is usually not equal to Z0 at this time; in the process of multiple experiments, other process conditions may have been changed to meet the expected current gain condition). When the device structure is subsequently grown using a second molecular beam epitaxy system (at this time, due to...), The system was changed, resulting in a different Be source furnace than before. The conventional Be doping concentration calibration method was used to obtain the Be source furnace temperature corresponding to the calibrated doping concentration Z0, and this temperature was applied to device growth (other process conditions were completely consistent with the final determined process conditions in the first molecular beam epitaxy system). However, the current gain of the obtained device was reduced by approximately 9% compared to the expected value. This indicates that in the second molecular beam epitaxy system, although the calibrated doping concentration corresponding to the thicker calibration structure was consistent with that in the first molecular beam epitaxy system, the actual doping concentration of the thinner layer in the device was higher than in the first molecular beam epitaxy system. In the second molecular beam epitaxy system, the initial concentration overshoot of the Be source furnace doping concentration was greater. To verify the effectiveness of the method in this application, firstly, in a first molecular beam epitaxy system, the Be source furnace temperature Tz corresponding to the calibration doping concentration Z0 using conventional methods (calibration structure doped layer thickness of 200 nm) is obtained. This condition corresponds to the expected device current gain obtained in the first molecular beam epitaxy system. Then, using Tz as the first temperature, Be-doped calibration structures with thicknesses of 75 nm, 150 nm, and 300 nm are grown respectively, and the corresponding doping concentrations are measured. A preset model y = a / x + b is used for data fitting to obtain the fitting parameters a and b, and y is calculated. z =a / h0+b, the obtained y z The value is greater than Z0. In the second molecular beam epitaxy system, the preset concentration y is obtained by using the calibration method provided in this application (steps A to D above). z The Be source furnace temperature T corresponding to the time (so that the actual doping concentration is consistent with that in the first molecular beam epitaxy system during thin-layer doping) b and in that T bThe same device structure was grown under the same conditions (other process conditions were completely consistent with the final process conditions determined in the first molecular beam epitaxy system). After testing, the current gain of the obtained device differed from the expected value by less than 3%. This error is sufficient to meet the actual requirements. Compared with the conventional calibration method, the performance deviation was significantly reduced, thus verifying the effectiveness of the method provided in this application.

[0042] In summary, this application establishes a correlation between the doping thickness and the measured doping concentration of doped material layers of different thicknesses through a pre-defined model. This allows for the direct determination of the doping process parameters corresponding to the expected doping concentration of the base region layer using the measured results of the doped calibration structure. This avoids the problem of the actual doping concentration of the base region deviating from the expected value due to the different transient responses of different Be source furnaces when changing Be source furnaces, thereby improving the performance stability of different batches of epitaxial materials and devices.

[0043] 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 the process parameters of beryllium doping in molecular beam epitaxy, characterized in that, The method is used to determine the Be source furnace temperature when growing a Be-doped layer in a semiconductor device structure. The expected doping concentration of the Be-doped layer is a preset concentration N0, and the thickness h0 of the Be-doped layer ranges from 20 nm to 35 nm. The method includes: Step A: At the first temperature of the Be source furnace, multiple Be-doped calibration structures with different doped material layer thicknesses are grown using a molecular beam epitaxy system, and the doping concentration of the corresponding Be-doped calibration structure is measured. The doped material layer of the Be-doped calibration structure is of the same material as the Be-doped layer, and the thickness of the doped material layer is greater than or equal to 75 nm. The first temperature is an initial temperature determined based on empirical data. Step B: Use the preset model y=a / x+b to fit the data to obtain the fitting parameters a and b, where x represents the thickness of the doped material layer of the Be-doped calibration structure, and y represents the measured doping concentration corresponding to x. Step C: Calculate y1 = a / h0 + b, and compare y1 with N0; Step D: Adjust the value of the first temperature based on the comparison result in step C, and repeat steps A to C under the new first temperature condition until the absolute value of (y1-N0) / N0 is less than a preset threshold. Then, determine the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure based on the final value of the first temperature. Adjusting the value of the first temperature based on the comparison results in step C specifically includes: calculating N0 / y1, and then calculating and determining the specified doping concentration N based on the pre-obtained relationship curve between the Be doping concentration and the Be source furnace temperature. z It becomes N0 / y1×N z At that time, the change in Be source furnace temperature ΔT is used as the first temperature, and then the sum of the first temperature and ΔT is used as the adjusted value to specify the doping concentration N. z This indicates the measured doping concentration of the Be-doped calibration structure with the thinnest doped material layer among the multiple Be-doped calibration structures described in step A.

2. The method for determining the process parameters of beryllium doping in molecular beam epitaxy according to claim 1, characterized in that, The doping concentration of the Be-doped calibration structure was measured using a Hall effect meter.

3. The method for determining the process parameters of beryllium doping in molecular beam epitaxy according to claim 1, characterized in that, The thickness of the doped material layer in the Be-doped calibration structure ranges from 75 nm to 300 nm.

4. The method for determining the process parameters of beryllium doping in molecular beam epitaxy according to claim 3, characterized in that, In step A, the thicknesses of the plurality of Be-doped calibration structures are 75 nm, 150 nm, and 300 nm, respectively.

5. The method for determining the process parameters of beryllium doping in molecular beam epitaxy according to claim 1, characterized in that, In step A, the first temperature is the Be source furnace temperature determined based on a pre-obtained relationship curve between the Be doping concentration and the Be source furnace temperature, such that the expected doping concentration of any of the plurality of Be doped calibration structures is equal to m × N0, where m is a preset coefficient and the range of m is 0.

7. <m<0.9。 6. The method for determining the process parameters of beryllium doping in molecular beam epitaxy according to claim 1, characterized in that, Determining the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure based on the final value of the first temperature includes: using the final value of the first temperature as the Be source furnace temperature for growing the Be-doped layer in the semiconductor device structure; or Based on the final values ​​of y1 and N0, and historical data on the impact of adjusting the value of the first temperature on y1, the final value of the first temperature is revised again, and the revised first temperature is used as the Be source furnace temperature when growing the Be doped layer in the semiconductor device structure.

7. The method for determining the process parameters of beryllium doping in molecular beam epitaxy according to claim 1, characterized in that, The Be-doped layer is a Be-doped InGaAs material layer.

8. The method for determining the process parameters of beryllium doping in molecular beam epitaxy according to claim 1, characterized in that, The growth rate V of the Be-doped layer B The range is 0.5 μm / h ≤ V B ≤1 μm / h.

9. The method for determining the process parameters of beryllium doping in molecular beam epitaxy according to claim 1, characterized in that, The growth rate of the doped material layer is the same as that of the Be-doped layer.

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