CN115831743B - Molecular beam epitaxial growth method of HBT device - Google Patents
Molecular beam epitaxial growth method of HBT device Download PDFInfo
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Abstract
The invention provides a molecular beam epitaxial growth method of an HBT device, and relates to the technical field of semiconductor manufacturing. The method comprises the following steps: depositing and growing a collector region layer; and when the gallium source furnace is heated from the first temperature, depositing a growing base region layer on the collector region layer, and heating the gallium source furnace in a piecewise linear heating mode. In the process of epitaxially growing the base region layer with continuously graded components, the temperature rising mode of the gallium source furnace is set to be a piecewise linear temperature rising mode, a piecewise target temperature value is selected according to a logarithmic function relation, the piecewise linear temperature rising mode is used for realizing the approximate simulation of the logarithmic temperature rising mode, and compared with the mode of carrying out temperature step or direct linear temperature rising on the gallium source furnace from a first temperature to a second temperature, the method can obviously reduce temperature overshoot possibly occurring in the short-time rapid temperature rising process of the gallium source furnace, thereby obviously improving the abnormal component change of the base region layer InGaAs material caused by the temperature overshoot and being beneficial to improving the performance of an HBT device.
Description
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to a molecular beam epitaxial growth method of an HBT device.
Background
In recent years, heterojunction Bipolar Transistor (HBT) devices have been widely used in the fields of microwave and millimeter wave power gain, ultra-high speed switching, digital integrated circuits, and optical fiber communications. HBTs have a number of advantages: high frequency and high speed, high power density, high power gain and good linearity. HBTs are vertical transport devices, some of whose main device targets are mostly determined by the device epitaxial layer structure. Due to the development of Molecular Beam Epitaxy (MBE) technology, the thickness of the epitaxial layer has been able to be controlled with accuracy on the order of atomic layers, so that the device characteristics of HBTs can be precisely adjusted.
InP/InGaAs material-based HBT devices have been widely studied and used because of their superior characteristics over conventional Si-based HBT devices.
The base layer in HBT device structures is typically very thin to reduce base transit time and thereby increase device current gain. For InGaAs material base layers, to further improve the performance of HBT devices, the base layer may be designed as a compositionally continuously graded layer to create a built-in potential within the base layer to enhance carrier injection and thus further increase current gain.
However, the molecular beam epitaxy of the base layer is very short because of the very thin base layer, and growing an InGaAs material base layer that meets the desired continuous grading of composition presents challenges.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a molecular beam epitaxial growth method of an HBT device, which aims to solve the problem of epitaxial growth of an InGaAs material base region layer with continuously graded components.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the invention provides a molecular beam epitaxial growth method of an HBT device, which comprises an n-type collector region layer and a p-type base region layer arranged on the collector region layer, wherein the collector region layer is In 0.53 Ga 0.47 An As layer, wherein the In component at the interface of the base layer close to the collector region layer is 0.53, the In component at the interface of the base layer far away from the collector region layer is y, wherein y is a preset fixed value, y is more than or equal to 0.43 and less than or equal to 0.47, and the base layer is In with the In component continuously gradually changed from 0.53 to y from bottom to top m Ga 1-m An As layer, m represents In, the thickness h of the base layer is In the range of 25 nm-50 nm, the total time S for depositing and growing the base layer is In the range of 100 seconds-300 seconds, and the method comprises the following steps:
depositing a growth collector layer, wherein the temperature of a gallium source furnace of the molecular beam epitaxy equipment is constant for growing In during the process of depositing the growth collector layer 0.53 Ga 0.47 A first temperature of the As layer;
while the gallium source furnace is heated from the first temperature, a base region layer is deposited and grown on the collector region layer, and the gallium source furnace is heated in a piecewise linear heating mode as follows: dividing the total time S for depositing and growing the base layer into N time periods, wherein N is an integer greater than or equal to 2, and in any ith time period of the N time periods, the gallium source furnace is linearly increased from the initial temperature at the beginning of the ith time period to the ith target temperature T at the end of the ith time period i The corresponding time at the end of the ith period is t i ，i=1,2,...,N，t N =s, and nth target temperature T N Equal to In for growing In composition y y Ga 1-y A second temperature of the As layer, which is higher than the first temperature, assuming that the starting time of the 1 st period is t 0 Let t be 0 =0, and the starting temperature of period 1 is the 0 th target temperature T 0 Then the 0 th target temperature T 0 Equal to the first temperature, for j=0, 1,2, any one of N, time t j Corresponding target temperature T j All satisfy the following functional relationship:
wherein the coefficient isaA constant greater than 0, a basebIs a constant that is greater than 1,xthe time of day is indicated as such,f(x) Indicating time of dayxCorresponding target temperature, coefficientaSum base numberbOne of them is preset, and the other is obtained by calculation.
Optionally, the base in the functional relationshipbSet as irrational number e, the functional relationship is expressed as
At this time, the liquid crystal display device,aobtained by calculation of the formula:
alternatively, n=3.
Alternatively, t 1 And t 2 Is obtained by solving the equation set consisting of the following equation (1) and equation (2):
alternatively, the system of equations consisting of equation (1) and equation (2) is solved numerically by iterative computation as follows:
wherein n represents the number of iterations, t 1,n Representing t obtained after n iterative calculations 1 The value of t 2,n Representing t obtained after n iterative calculations 2 Is used as a reference to the value of (a),
t 1 iterative initial value t 1,0 T 2 Iterative initial value t 2,0 The following relationship is satisfied:
0< t 1,0 < t 3 and 0 is< t 2,0 < t 3 。
Alternatively, the process may be carried out in a single-stage,
and->
。
Optionally, the number of iterations n in the iterative calculation satisfies the following range: 16<n<40。
Alternatively, the number of iterations n=20.
Optionally, y is more than or equal to 0.44 and less than or equal to 0.46, and the temperature of an indium source furnace of the molecular beam epitaxy device is constant during the process of depositing and growing the base region layer on the collector region layer.
The beneficial effects of the invention include:
the molecular beam epitaxial growth method of the HBT device provided by the invention comprises the following steps: depositing a growth collector layer, wherein the temperature of a gallium source furnace of the molecular beam epitaxy equipment is constant for growing In during the process of depositing the growth collector layer 0.53 Ga 0.47 A first temperature of the As layer; while the gallium source furnace is heated from the first temperature, a base region layer is deposited and grown on the collector region layer, and the gallium source furnace is heated in a piecewise linear heating mode as follows: dividing the total time S for depositing and growing the base region layer into N time periods, wherein N is an integer greater than or equal to 2, and gallium is in any ith time period of the N time periodsThe source furnace is linearly increased from the initial temperature at the beginning of the ith period to the ith target temperature T at the end of the ith period i The corresponding time at the end of the ith period is t i ，i=1,2,...,N，t N =s, and nth target temperature T N Equal to In for growing In composition y y Ga 1-y A second temperature of the As layer, which is higher than the first temperature, assuming that the starting time of the 1 st period is t 0 Let t be 0 =0, and the starting temperature of period 1 is the 0 th target temperature T 0 Then the 0 th target temperature T 0 Equal to the first temperature, for j=0, 1,2, any one of N, time t j Corresponding target temperature T j All satisfy the following functional relationship:
wherein the coefficientsaA constant greater than 0, a basebIs a constant that is greater than 1,xthe time of day is indicated as such,f(x) Indicating time of dayxCorresponding target temperature, coefficientaSum base numberbOne of them is preset, and the other is obtained by calculation. In the process of continuously gradually changing the base region layer by epitaxial growth components, the temperature rising mode of the gallium source furnace is set to be a piecewise linear temperature rising mode, and a piecewise target temperature value is selected according to a logarithmic function relation, so that the logarithmic temperature rising mode that the temperature is approximately simulated In a logarithmic change relation with time by the piecewise linear temperature rising mode is realized, compared with the mode that the temperature of the gallium source furnace is stepped from a first temperature or is directly linearly raised to a second temperature, the temperature overshoot of the gallium source furnace In the short-time rapid temperature rising process can be obviously reduced, the abnormal component change of the base region layer InGaAs material caused by the temperature overshoot is obviously improved, the continuous gradual smooth transition of In components is realized, and the performance of an HBT device is favorably improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic flow chart of a molecular beam epitaxy growth method of an HBT device according to an embodiment of the present invention;
fig. 2 shows a schematic structural diagram of an HBT device according to an embodiment of the present invention;
fig. 3 is a schematic diagram showing an optimization mode of a gallium source furnace target temperature changing with time according to an embodiment of the invention;
fig. 4 shows a graph of a time-dependent change in target temperature of a gallium source furnace provided by an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
InP/InGaAs material-based HBT devices have been widely studied and used because of their superior characteristics over conventional Si-based HBT devices. The base layer in HBT device structures is typically very thin to reduce base transit time and thereby increase device current gain. For InGaAs material base layers, to further improve the performance of HBT devices, the base layer may be designed as a compositionally continuously graded layer to create a built-in potential within the base layer to enhance carrier injection and thus further increase current gain. However, the molecular beam epitaxy of the base layer is very short because of the very thin base layer, and growing an InGaAs material base layer that meets the desired continuous grading of composition presents challenges. Therefore, it is desirable to provide a molecular beam epitaxial growth method for HBT devices to achieve high quality epitaxial growth of InGaAs material base layers with continuously graded composition.
Fig. 1 is a schematic flow chart of a molecular beam epitaxy growth method of an HBT device according to an embodiment of the present invention; fig. 2 shows a schematic structural diagram of an HBT device according to an embodiment of the present invention.
The embodiment of the invention provides a molecular beam epitaxial growth method of an HBT device, and as shown in fig. 2, the structure of the HBT device comprises an n-type collector region layer and a p-type base region layer 203 arranged on the collector region layer 202. It should be appreciated that the structure of the HBT device may further comprise a first structural layer 201 disposed between the substrate 200 and the n-type collector layer 202, the first structural layer 201 may be, for example, a single material layer or a stacked layer of multiple material layers, the first structural layer 201 may be, for example, a buffer layer, or the first structural layer 201 may be, for example, a stacked layer of a buffer layer and a sub-collector layer, depending on the device structure requirements; similarly, the structure of the HBT device may further include a second structural layer 204 disposed on the base layer 203, and the second structural layer 204 may be, for example, a single material layer or a stacked layer of a plurality of material layers, the second structural layer 204 may be, for example, an emitter layer, or the second structural layer 204 may be, for example, a stacked layer of an isolation layer and an emitter layer, depending on the device structure requirements. The present invention is not particularly limited to the first structural layer 201 and the second structural layer 204. The substrate 200 may be an InP substrate or a GaAs substrate.
As shown in fig. 1, the molecular beam epitaxial growth method of the HBT device provided by the embodiment of the present invention includes:
and 101, depositing and growing a collector region layer.
After depositing and growing the first structural layer 201 on the substrate 200, a grown collector layer 202 is deposited on the first structural layer 201. As can be seen from the above description, the collector region layer 202 is In 0.53 Ga 0.47 And an As layer. In the molecular beam epitaxy apparatus, the beam current rate of the element is controlled by controlling the temperature of the source furnace of the corresponding element, and the higher the temperature of the source furnace is, the higher the beam current rate of the element is. Through a pre-calibration test, the realization of In can be known 0.53 Ga 0.47 The indium source furnace temperature and the gallium source furnace temperature required by the proportion of In and Ga In As. Assume that In is implemented 0.53 Ga 0.47 The temperature of the gallium source furnace required for the composition ratio of In to Ga In As is the first temperature, so that the temperature of the gallium source furnace of the molecular beam epitaxy apparatus is constant for growing In during the deposition and growth of the collector region layer 202 0.53 Ga 0.47 A first temperature of the As layer. It should be appreciated that the temperature of the indium source furnace is also constant during deposition of the grown collector layer 202.
Since the base region layer 203 is In with continuously graded In composition m Ga 1-m As layer, and In m Ga 1-m The In composition of the As material continuously gradually changes from 0.53 to y, and 0.43.ltoreq.y.ltoreq.0.47, that is, the In composition of the base layer 203 gradually decreases from 0.53 and finally decreases to y. In order to realize the gradual decrease of the In component In the base region layer 203, the temperature of the gallium source furnace can be gradually increased In the process of depositing and growing the base region layer 203, and the beam flow rate of gallium is gradually increased along with the gradual increase of the temperature of the gallium source furnace, so that the In can be realized m Ga 1-m The gradual increase In Ga component and the corresponding decrease In component of the As material. It should be appreciated that the temperature of the indium source furnace may remain unchanged or may gradually decrease while the temperature of the gallium source furnace increases. To realize In m Ga 1-m The In composition of the As material continuously gradually changes from 0.53 to y, the initial temperature of the gallium source furnace is a first temperature corresponding to the In composition of 0.53, and the final target temperature at the end of the growth of the base layer after the gallium source furnace is raised is a second temperature corresponding to the In composition y (As described below). Obviously, the second temperature is higher than the first temperature.
Alternatively, 0.44.ltoreq.y.ltoreq.0.46, for example, y may be preset to 0.45, and the temperature of the indium source furnace of the molecular beam epitaxy apparatus is constant during deposition of the growth base layer 203 on the collector layer 202.
It should be appreciated that the first temperature and the second temperature of the gallium source furnace described herein are pre-obtained, and specifically, for example, the first temperature and the second temperature of the gallium source furnace described herein are both obtained through pre-experimental tests at a specific indium source furnace temperature, and thus, the difference between the second temperature and the first temperature may be predetermined, typically, in the order of ten degrees celsius to tens of degrees celsius.
As described hereinabove, deposition growthThe total time S of the base layer 203 is limited to a range of 100 seconds +.s.ltoreq.300 seconds, and therefore, it is necessary to raise the temperature of the gallium source furnace by about ten degrees celsius to tens of degrees celsius in this time range. In the molecular beam epitaxy apparatus, the temperature of the gallium source furnace is sensed by a thermocouple and controlled by a PID controller, and during the temperature rising process, a target temperature of the gallium source furnace is set, and then the controller controls the heating assembly so that the actual temperature of the gallium source furnace reaches the current target temperature. In the molecular beam epitaxy equipment, a conventional heating mode comprises two modes of step heating and linear heating, wherein the step heating means that the current target temperature is directly set to be the final expected temperature, and then the source furnace is quickly heated to the final expected temperature under the control of a controller; the linear temperature rise means that the current target temperature is linearly increased to the final desired temperature within a certain period of time, and at the same time, the source furnace is heated to the current target temperature under the control of the controller, and the actual temperature of the source furnace is finally heated to the final desired temperature as the current target temperature is linearly increased. Under the step heating mode, although the gallium source furnace can be heated quickly In a short time, obvious overshoot occurs after the gallium source furnace temperature is raised to the final target temperature, and the overshoot of the gallium source furnace temperature can cause the flow rate of the gallium element beam to be excessively high In a short time, thereby causing In the base region layer 203 m Ga 1-m The composition variation of the As material is not smooth, which negatively affects the built-in potential of the base layer 203, thereby eventually degrading HBT device performance. The temperature overshoot can be improved by using a linear temperature rise method, but for some HBT device structures, the second structure layer 204 on the base layer 203 is In with a component of y y Ga 1-y As layer, after the growth of the base layer 203, the temperature of the gallium source furnace is stabilized for growth of In y Ga 1-y A second temperature of the As layer, in which case, since the maximum period of time allowed for the linear temperature increase process is the growth time S of the base layer 203, the rate of change of the target temperature will be changed from a fixed slope of the linear temperature increase period to zero directly near the end point of the linear temperature increase process, a certain amount of temperature overshoot will still be caused in PID control of the gallium source furnace temperature, and if the temperature increase time of the linear temperature increase process is less than the growth time S of the whole base layer 203, a certain amount of temperature overshoot will be caused in the base regionThe unevenness of the In composition variation is caused inside the layer 203, and if the temperature rise time of the linear temperature rise process corresponds to the growth time S of the entire base layer 203, the unevenness of the In composition variation is caused at the interface between the base layer 203 and the second structural layer 204. To further improve this temperature overshoot to further optimize the smooth transition of the InGaAs material composition in the base layer 203 to grow a continuously graded composition InGaAs material base layer, an optimized temperature ramp is required to further suppress the above-mentioned temperature overshoot.
In the process of depositing and growing the base region layer 203 on the collector region layer 202, the gallium source furnace is heated in a piecewise linear heating mode as follows: dividing the total time S for depositing and growing the base layer into N time periods, wherein N is an integer greater than or equal to 2, and in any ith time period of the N time periods, the gallium source furnace is linearly increased from the initial temperature at the beginning of the ith time period to the ith target temperature T at the end of the ith time period i The corresponding time at the end of the ith period is t i ，i=1,2,...,N，t N =s, and nth target temperature T N Equal to In for growing In composition y y Ga 1-y A second temperature of the As layer, which is higher than the first temperature, assuming that the starting time of the 1 st period is t 0 Let t be 0 =0, and the starting temperature of period 1 is the 0 th target temperature T 0 Then the 0 th target temperature T 0 Equal to the first temperature. Note that, for any one of j=0, 1,2,..n, when j takes a different value, the target temperature T j Also the values of (c) are different and as j increases, T j The value of (2) also increases.
For j=0, 1, 2.,. N, time t j Corresponding target temperature T j All satisfy the following functional relationship:
wherein the coefficient isaA constant greater than 0, a basebIs a constant that is greater than 1,xthe time of day is indicated as such,f(x) Indicating time of dayxCorresponding target temperature, coefficientaSum base numberbOne of them is in advanceSetting, the other is obtained by calculation.
Due to the Nth target temperature T N (i.e., the second temperature) is known, the target temperature T N Corresponding time t N The target temperature T is known =s 0 Equal to the first temperature is also known and the following holds:
in the above formula onlyaAndbtwo unknowns, thus, when the coefficients areaSum base numberbOne of them is a coefficient after being presetaSum base numberbThe other of (2) may be obtained by solving the above equation by calculation.
Optionally, the base in the functional relationshipbSet as irrational number e, the functional relationship is expressed as
At this time, the liquid crystal display device,aobtained by calculation of the formula:
similarly, it can be preset thataFor example, set upa=1, then b can be obtained by calculation of:
in the above formula, there is only one unknown number of b, for example, the value of b can be obtained by calculating in a numerical solution manner.
Theoretically, the rate of change of the logarithmic function is continuously graded over time. If the target temperature of the gallium source furnace temperature is continuously gradually increased in a logarithmic function manner (namely, the target temperature of the gallium source furnace temperature is in a logarithmic function relationship with time), the change rate of the target temperature of the gallium source furnace temperature is also continuously gradually increased, and the target temperature cannot appearThe step jump of the change rate can inhibit the temperature overshoot in the temperature PID control of the gallium source furnace. However, in the actual operation of the molecular beam epitaxy equipment, it is difficult to realize that the temperature of the gallium source furnace is completely raised according to the logarithmic function, but the piecewise linear temperature raising mode can be adopted to approximate the temperature raising mode of the analog logarithmic function, so that the overshoot In the temperature raising process of the gallium source furnace can be obviously restrained, and In the base region layer is improved m Ga 1-m A smooth transition of the As material composition.
It should be appreciated that after deposition of the grown base layer 203, the second structural layer 204 may be further grown according to structural requirements to finally complete molecular beam epitaxial growth of the HBT device epitaxial wafer.
In summary, in the process of continuously gradually growing the base layer by the epitaxial growth component, the temperature rising mode of the gallium source furnace is set to be a piecewise linear temperature rising mode, and the piecewise target temperature value is selected according to the logarithmic function relation, so that the logarithmic temperature rising mode that the piecewise linear temperature rising mode is used for simulating the logarithmic change relation of the temperature along with time is realized, compared with the mode that the temperature of the gallium source furnace is stepped from the first temperature or is directly and linearly raised to the second temperature, the temperature overshoot possibly occurring In the short-time rapid temperature rising process of the gallium source furnace can be obviously reduced, the abnormal component change of the base layer InGaAs material caused by the temperature overshoot is obviously improved, the continuous gradual smooth transition of the In component is realized, and the performance of the HBT device is favorably improved.
For the piecewise linear temperature increase mode of the gallium source furnace described in the above description, the larger the value of N, the more logarithmic mode can be approached by the piecewise linear mode, and at the same time, the higher the complexity of the control process of the molecular beam epitaxy apparatus, the range of 3 to 5 can be set in consideration of the convenience of actual operation and the length of the total time period of the piecewise linear temperature increase process, for example, in which case further suppression of temperature overshoot can still be achieved with respect to the conventional step temperature increase and linear temperature increase modes of the apparatus itself. For example, n=3 may be set.
In the case of n=3, i.e. to use three linear increases in temperatureFitting logarithmic heating. Fig. 3 shows a schematic diagram of an optimization mode of a gallium source furnace target temperature changing with time according to an embodiment of the invention. In fig. 3, a curve 1 represents a logarithmic warming curve, and a curve 2 represents a piecewise linear warming curve composed of three line segments. On the curve 1, a point Q0 is a start point, a point Q3 is an end point, and a point Q1 and a point Q2 are two intermediate points. At points Q0, Q1, Q2 and Q3, respectively, curve 1 and curve 2 coincide. In practical application, the positions of the point Q0 and the point Q3 are determined, for the above heating process of the gallium source furnace, the point Q0 corresponds to the start time 0 and the first temperature, the point Q3 corresponds to the end time S and the second temperature, the positions of the intermediate points Q1 and Q2 can be selected, different intermediate points Q1 and Q2 are selected, and the fitting degrees of the curve 1 and the curve 2 are different. Therefore, in the case of the position determination of the points Q0 and Q3, it is necessary to select the appropriate intermediate points Q1 and Q2 so that the curves 1 and 2 reach a best fit, since the logarithmic function is a convex function, the three line segments of the curve 2 are all located under the curve 1, in which case the best fit corresponds to the minimum total area of the areas A1, A2 and A3. The area A1 is an area surrounded by the curve 1 and the curve 2 between the point Q0 and the point Q1; the area A2 is an area surrounded by the curve 1 and the curve 2 between the point Q1 and the point Q2; the area A3 is an area surrounded by the curve 1 and the curve 2 between the point Q2 and the point Q3. Since the area of the area enclosed by the curve 1 and the lower and right coordinate axes is fixed between the point Q0 and the point Q3, in order to minimize the total area of the areas A1, A2 and A3, it is necessary that the area enclosed by the curve 2 and the lower and right coordinate axes is maximized, the area enclosed by the curve 2 and the lower and right coordinate axes is constituted by one triangle and two trapezoids, and the abscissa t of the point Q1 and the point Q2 1 And t 2 As independent variables, the area of the area surrounded by the curve 2, the lower coordinate axis and the right coordinate axis is used as the dependent variables to establish an area function, and the abscissa t corresponding to the best fitting can be obtained by solving the maximum value of the area function 1 And t 2 Thereby knowing the positions of the intermediate points Q1 and Q2.
For simplicity of solution, for the base in the functional relationshipbIn the case of irrational number e, the functional relationship is expressed as
In this case, for the case of n=3, solving the best fit with reference to fig. 3 and the above description, the abscissa t can be known 1 And t 2 The corresponding solution is a best fit when the following two equations are satisfied simultaneously:
it will be appreciated that t in the above formula 3 Is a known number (i.e., S).
Thus, for the basebIn the case of irrational number e and n=3, the time t of two intermediate points of piecewise linear heating up 1 And t 2 Is obtained by solving the equation set consisting of the following equation (1) and equation (2):
alternatively, the system of equations consisting of equation (1) and equation (2) is solved numerically by iterative computation as follows:
wherein n represents the number of iterations, t 1,n Representing t obtained after n iterative calculations 1 The value of t 2,n Representing t obtained after n iterative calculations 2 It will be appreciated that t 1,(n+1) Representing t obtained after n+1 iterative calculations 1 The value of t 2,(n+1) Representing t obtained after n+1 iterative calculations 2 Is a value of (2).
t 1 Iterative initial value t 1,0 T 2 Iterative initial value t 2,0 The following relationship is satisfied:
0< t 1,0 < t 3 and 0 is< t 2,0 < t 3 。
At t 3 (i.e., S) is 129 seconds, t 1,0 Is 9, t 2,0 29, the above numerical iterative solution calculation is performed, and the time t obtained by the corresponding calculation at different iteration times is shown in the following table 1 1 And t 2 As can be seen, t after 30 iterative calculations 1 The value of (2) is stabilized at 11.57825, t 2 Is stable at 49.2755; it can also be seen that t after undergoing 16 to 20 iterative calculations 1 And t 2 The values of (2) have reached good accuracy. In practice, in order to reduce the amount of computation, alternatively,
and->
. Optionally, the number of iterations n in the iterative calculation satisfies the following range: 16<n<40. Alternatively, the number of iterations n=20.
Table 1 numerical iterative calculation values
| Number of iterations | t 3 | t 2 | t 1 |
| 0 | 129 | 29 | 9 |
| 1 | 129 | 45.78455 | 7.526409 |
| 2 | 129 | 43.58784 | 10.90584 |
| 3 | 129 | 48.40134 | 10.47815 |
| 4 | 129 | 47.83292 | 11.41067 |
| 5 | 129 | 49.05979 | 11.30143 |
| 6 | 129 | 48.9184 | 11.53694 |
| 7 | 129 | 49.22247 | 11.50985 |
| 8 | 129 | 49.18763 | 11.56809 |
| 9 | 129 | 49.26248 | 11.56142 |
| 10 | 129 | 49.25392 | 11.57575 |
| 11 | 129 | 49.27231 | 11.57411 |
| 12 | 129 | 49.27021 | 11.57763 |
| 13 | 129 | 49.27473 | 11.57723 |
| 14 | 129 | 49.27421 | 11.5781 |
| 15 | 129 | 49.27532 | 11.578 |
| 16 | 129 | 49.27519 | 11.57821 |
| 17 | 129 | 49.27546 | 11.57819 |
| 18 | 129 | 49.27543 | 11.57824 |
| 19 | 129 | 49.2755 | 11.57823 |
| 20 | 129 | 49.27549 | 11.57825 |
| 21 | 129 | 49.27551 | 11.57824 |
| 22 | 129 | 49.27551 | 11.57825 |
| 23 | 129 | 49.27551 | 11.57825 |
| 24 | 129 | 49.27551 | 11.57825 |
| 25 | 129 | 49.27551 | 11.57825 |
| 26 | 129 | 49.27551 | 11.57825 |
| 27 | 129 | 49.27551 | 11.57825 |
| 28 | 129 | 49.27551 | 11.57825 |
| 29 | 129 | 49.27551 | 11.57825 |
| 30 | 129 | 49.27551 | 11.57825 |
Fig. 4 shows a graph of a time-dependent change in target temperature of a gallium source furnace provided by an embodiment of the present invention. As shown in fig. 4, data 1 represents a graph of gallium source furnace temperature over time under logarithmic heating conditions; data 2 indicates the position of two intermediate points specified directly: t is t 1 Equal to 9, t 2 29, adopting piecewise linear temperature rise, and a curve chart of gallium source furnace temperature change along with time; data 3 represents the initial values of the iterative calculations described above, respectively 9 and 29, calculated from Table 1 to obtain t 1 Has a value of 11.57825, t 2 The value of (2) is 49.27551, the temperature of the gallium source furnace is raised in a piecewise linear manner, and the temperature of the gallium source furnace is changed along with time. As can be seen from fig. 4, data 3 fits better with data 1 relative to data 2. That is, in the case where n=3, t obtained by the iterative calculation as above is employed 1 And t 2 Better fitting of piecewise linear temperature rise and logarithmic temperature rise can be obtained, so that the abnormal components of the base region layer InGaAs material caused by temperature overshoot can be improved, continuous gradual smooth transition of In components can be realized, and the performance of the HBT device can be improved.
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 the same, but not limit the scope of the present invention, and all equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of the present invention.
Claims (9)
1. A molecular beam epitaxial growth method of an HBT device is characterized In that the structure of the HBT device comprises an n-type collector region layer and a p-type base region layer arranged on the collector region layer, wherein the collector region layer is In 0.53 Ga 0.47 An As layer, the In composition of the base layer at the interface near the collector layer is 0.53, and the In composition of the base layer at the interface far from the collector layerThe composition is y, wherein y is a preset fixed value, y is more than or equal to 0.43 and less than or equal to 0.48, and the base region layer is In with the composition gradually changed from 0.53 to y from bottom to top m Ga 1-m An As layer, m represents the composition of In, the thickness h of the base layer is In the range of 25 nm-50 nm, the total time S for depositing and growing the base layer is In the range of 100 seconds-300 seconds, and the method comprises:
depositing and growing the collector region layer, wherein the temperature of a gallium source furnace of the molecular beam epitaxy equipment is constant for growing In the process of depositing and growing the collector region layer 0.53 Ga 0.47 A first temperature of the As layer;
while the gallium source furnace is heated from the first temperature, depositing and growing the base region layer on the collector region layer, wherein the gallium source furnace is heated in a piecewise linear heating mode as follows: dividing the total time S for depositing and growing the base layer into N time periods, wherein N is an integer greater than or equal to 2, and in any ith time period of the N time periods, the gallium source furnace is linearly increased from the initial temperature at the beginning of the ith time period to the ith target temperature T at the end of the ith time period i The corresponding time at the end of the ith period is t i ，i=1,2,...,N，t N =s, and nth target temperature T N Equal to In for growing In composition y y Ga 1-y A second temperature of the As layer, which is higher than the first temperature, assuming that the starting time of period 1 is t 0 Let t be 0 =0, and the starting temperature of the 1 st period is the 0 th target temperature T 0 The 0 th target temperature T 0 Equal to the first temperature, for j=0, 1,2, any one of N, time t j Corresponding target temperature T j All satisfy the following functional relationship:
wherein the coefficient isaA constant greater than 0, a basebIs a constant that is greater than 1,xthe time of day is indicated as such,f(x) Indicating time of dayxTime-corresponding targetTemperature, coefficient ofaSum base numberbOne of them is preset, and the other is obtained by calculating the following equation:
2. the method of molecular beam epitaxy of HBT devices according to claim 1, wherein the base in said functional relationshipbSet as irrational number e, the functional relationship is expressed as
At this time, the liquid crystal display device,aobtained by calculation of the formula:
3. the molecular beam epitaxial growth method of HBT device according to claim 2 wherein n=3.
4. A molecular beam epitaxial growth method of HBT device according to claim 3 wherein t 1 And t 2 Is obtained by solving the equation set consisting of the following equation (1) and equation (2):
5. the molecular beam epitaxial growth method of the HBT device according to claim 4 wherein the system of equations consisting of equation (1) and equation (2) is solved numerically by iterative calculation as follows:
wherein n represents the number of iterations, t 1,n Representing t obtained after n iterative calculations 1 The value of t 2,n Representing t obtained after n iterative calculations 2 Is used as a reference to the value of (a),
t 1 iterative initial value t 1,0 T 2 Iterative initial value t 2,0 The following relationship is satisfied:
0< t 1,0 < t 3 and 0 is< t 2,0 < t 3 。
6. The molecular beam epitaxy growth method of an HBT device according to claim 5, wherein,
and->
。
7. The molecular beam epitaxial growth method of HBT device according to claim 5 wherein the number of iterations n in said iterative calculation satisfies the following range: 16<n<40。
8. The molecular beam epitaxial growth method of HBT device of claim 7 wherein the number of iterations n=20.
9. The molecular beam epitaxy growth method of HBT device according to claim 1, wherein y is 0.45.ltoreq.y.ltoreq.0.47, and the temperature of an indium source furnace of the molecular beam epitaxy apparatus is constant during deposition growth of the base layer on the collector layer.
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