CN117646198A - Automatic control method and system for pressure of atomic-level-precision CVD equipment - Google Patents
Automatic control method and system for pressure of atomic-level-precision CVD equipment Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 61
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- 239000010408 film Substances 0.000 claims description 13
- 238000005070 sampling Methods 0.000 claims description 9
- 238000000427 thin-film deposition Methods 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 abstract description 14
- 239000004065 semiconductor Substances 0.000 abstract description 5
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- 239000007789 gas Substances 0.000 description 24
- 238000005229 chemical vapour deposition Methods 0.000 description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 15
- 239000002041 carbon nanotube Substances 0.000 description 15
- 229910021393 carbon nanotube Inorganic materials 0.000 description 15
- 238000000231 atomic layer deposition Methods 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 9
- 230000001276 controlling effect Effects 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000000151 deposition Methods 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000005240 physical vapour deposition Methods 0.000 description 2
- 239000012495 reaction gas Substances 0.000 description 2
- 238000004092 self-diagnosis Methods 0.000 description 2
- 238000007736 thin film deposition technique Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
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Abstract
The invention discloses an automatic control method and system for pressure of atomic-level precision CVD equipment, and belongs to the technical field of semiconductor manufacturing. According to the method, the butterfly valve experience opening angle is introduced in the film deposition process, so that the target pressure can be quickly approached, and the response time is greatly improved. Moreover, the probability of failure of an automatic adjusting program can be avoided to a great extent, the situation of failure of automatic adjustment is easy to occur in direct adjustment of high pressure adjustment (20 kPa), pressure running and collapse are caused, and the introduced experience value can reach the vicinity of target pressure rapidly, so that large-angle adjustment is avoided. Furthermore, the method and the device can achieve higher control precision by adopting two different algorithms of a periodic discontinuous angle control algorithm and a continuous angle control algorithm for automatic control according to different pressure values, and can avoid fluctuation of pressure in a long time.
Description
Technical Field
The invention relates to an automatic control method and system for pressure of atomic-level precision CVD equipment, and belongs to the technical field of semiconductor manufacturing.
Background
Thin film deposition is one of the core processes of previous fabrication throughout the semiconductor fabrication process. Conventional thin film deposition techniques are classified into Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD). With the advent of the leading edge field of "atomic scale, near atomic scale fabrication", a higher precision thin film deposition technique, i.e., atomic layer deposition (Atomic Layer Deposition, ALD), has emerged on the basis of conventional Chemical Vapor Deposition (CVD).
Atomic layer deposition is a technique for depositing material materials in the form of monoatomic films on the surface of a substrate on a chemical vapor phase by layer basis. Is an important tool in the fields of semiconductor manufacture and nanotechnology, and provides key support for high-performance and high-reliability device manufacture. However, the atomic level accuracy cannot be achieved by the general CVD apparatus, mainly because the pressure control accuracy cannot be achieved. Pressure is a critical parameter in ALD deposition processes, directly determining the free path of motion of the feedstock molecules. Whether the pressure of the cavity can be accurately and stably controlled directly influences the quality of the manufacturing materials. Most of the pressure control systems of the CVD equipment at present are realized by a method of screwing a valve by hand and visually checking a pressure gauge, and the efficiency is low and the precision is poor. The system of automatic control is adopted partly, mostly adopts needle valve, combination valve to realize high accuracy control, and its often structure is complicated, adopts the less needle valve of aperture moreover, and though realized high accuracy pressure control, sacrifice the gas velocity of flow, lead to the pressure control inefficiency, and the time that many materials grow fast can concentrate on the first few seconds of letting in gas, if the pressure can not accurate control this moment, can influence the effect of deposit greatly. In addition, chemical vapor deposition processes vary in pressure from vacuum to atmospheric pressure, and most pressure control systems have difficulty meeting such large ranges.
Disclosure of Invention
In order to realize high precision, high efficiency and automatic pressure control in a wide range in the film deposition process, the invention provides an automatic pressure control method and system for CVD equipment with atomic-level precision, a butterfly valve is driven by a stepping motor, and rapid and accurate pressure control is realized by matching with an experience angle and a control algorithm under different pressures.
The automatic control method of the pressure of the CVD equipment with atomic level precision is realized based on a pressure gauge, a butterfly valve and a stepping motor, wherein the pressure gauge is used for acquiring the internal pressure of the ALD equipment or the CVD equipment, the butterfly valve is connected with a vacuumizing pipeline, and the opening angle of the butterfly valve is controlled by the stepping motor so as to achieve the purpose of controlling the internal pressure of the ALD equipment or the CVD equipment, and the automatic control method specifically comprises the following steps:
step 1, obtaining the temperature and the gas flow rate required by the film deposition process;
typically, the thin film deposition process includes a plurality of stages, such as a pretreatment stage, a reaction stage, a constant temperature stage, etc., each of which has certain requirements for temperature and gas flow rate. The gas flow rate here refers to the volume of gas flowing through the reaction gas delivery pipe per unit time.
Step 2, acquiring an angle-pressure experience curve and an angle-speed experience curve corresponding to each temperature under the gas flow; the angle-pressure experience curve is a curve of pressure changing along with the opening angle of the butterfly valve, and the angle-speed experience curve is a curve of pressure changing speed along with the opening angle of the butterfly valve;
the method for acquiring the angle-pressure experience curve comprises the following steps: and (3) maintaining a certain temperature, and measuring the change condition of pressure along with the change of the opening angle of the butterfly valve under a certain gas flow.
The acquisition method of the angle-speed empirical curve comprises the following steps: and (3) maintaining a certain temperature and a certain gas flow, setting a sampling period, and measuring the change condition of the change rate of the pressure along with the change of the opening angle of the butterfly valve in the sampling period.
Step 3, determining target pressure required by each stage of the film deposition process, reading current gas flow and temperature, and determining butterfly valve experience opening angles corresponding to the target pressure required by each stage according to the angle-pressure experience curves;
and determining the opening angle of the butterfly valve corresponding to the target pressure required in each stage of the film deposition process according to the angle-pressure experience curve, namely, the empirical opening angle, and rapidly opening the butterfly valve to the empirical opening angle, so that the actual pressure value can rapidly reach the vicinity of the target pressure value.
And 4, aiming at pressure control of each stage of the thin film deposition process, rapidly adjusting the butterfly valve to an empirical opening angle, and selecting a corresponding algorithm to automatically control the pressure according to the pressure change rate corresponding to the butterfly valve opening empirical angle and the target pressure.
In the actual deposition process, when the pressure reaches a certain valueIn this case, the time required for increasing the pressure of a given value is much longer than the time required for decreasing the same pressure value, will +.>And the pressure value is recorded as a pressure threshold value, and different control algorithms are adopted for controlling the pressure value which is larger than and smaller than the pressure threshold value.
Optionally, the step 4 includes:
setting a pressure threshold, and when the target pressure is greater than or equal to the set pressure threshold, adopting a periodic discontinuous angle control algorithm to automatically control the pressure; and when the target pressure is smaller than the set pressure threshold value, adopting a continuous angle control algorithm to automatically control the pressure.
Optionally, the periodic discontinuous angle control algorithm logic is:
setting a pressure sampling periodT and pressure rate threshold ++>The method comprises the steps of carrying out a first treatment on the surface of the According to the variation trend of the angle-speed experience curve, the pressure variation speed gradually increases to a certain value and then decreases along with the variation of the opening angle of the butterfly valve, namely, the pressure variation speed has a maximum value.
S1, acquiring a pressure sampling periodRate of pressure change within T->；
S2, judging the pressure change rateWhether the absolute value of (2) exceeds the set pressure change rate threshold value +.>；
S2.1, if the pressure change rateIs greater than a set pressure change rate threshold +.>Further according to the degree to which the absolute value of the rate of pressure change exceeds the set threshold value of the rate of pressure change, and the rate of pressure change +>Determining the stepping angle and direction of the butterfly valve;
s2.2, if the pressure change rateIs not exceeding the set pressure change rate threshold +.>The current pressure value P is further collected, and the current pressure value P, the target pressure and the pressure change rate are judged>To determine the stepping angle and direction of the butterfly valve;
s3, reading the pressure after adjusting the opening angle of the butterfly valve, calculating a difference value with the target pressure, judging whether the difference value is in an error range, and if the difference value is in the error range, maintaining the current opening angle of the butterfly valve; if the difference is not in the error range, continuing to sample the pressure change rate in the next period, and repeating the steps.
Optionally, the pressure change rate thresholdDetermined from the angle-rate empirical curve.
Optionally, the pressure change rate thresholdThe method comprises the following steps: />P max Wherein->，/>P max Is the maximum rate in the angle-rate empirical curve.
Optionally, the absolute value of the pressure change rate exceeds the set pressure change rate threshold in S2.1, and the pressure change rateDetermining the stepping angle and direction of the butterfly valve, comprising:
1) When the pressure changes at a rateIs greater than +.>P max 50% and->When the value is positive, the butterfly valve is at a stepping angleForward stepping;
2) When the pressure changes at a rateIs greater than +.>P max 70% and->When the value is positive, the butterfly valve is at a stepping angleForward stepping;
3) When the pressure changes at a rateIs greater than +.>P max 80% and->When the value is positive, the butterfly valve is at a stepping angleForward stepping;
the stepping angle satisfies；
In the three cases, if the pressure change rate isWhen the value is negative, the butterfly valve reversely steps at a corresponding stepping angle; wherein, the butterfly valve is opened in forward stepping and closed in reverse stepping.
Optionally, determining the stepping angle and direction of the butterfly valve in S2.2 includes:
1) If the current pressure value P is smaller than the target pressure and the pressure change rate is equal to or higher than the target pressurePositive value, the current angle of the butterfly valve is maintained or the butterfly valve is opened by a stepping angle +>Reversely stepping;
2) If the current pressure value P is smaller than the target pressure and the pressure change rate is equal to or higher than the target pressureNegative value, then step angle +.>Reversely stepping;
3) If the current pressure value P is greater than the target pressure and the pressure change ratePositive value, step angle +>Forward stepping;
4) If the current pressure value P is greater than the target pressure and the pressure change rateNegative, the current angle of the butterfly valve is maintained or the butterfly valve is opened by a stepping angle +>Forward stepping;
the stepping angle satisfiesAnd->，/>。
Optionally, the continuous angle control algorithm is a PID control algorithm.
The application also provides an automatic control system for the pressure of the atomic-level-precision CVD equipment, which comprises a pressure gauge, a butterfly valve and a stepping motor, wherein the pressure gauge is used for acquiring the internal pressure of the ALD equipment or the CVD equipment, the butterfly valve is connected with a vacuumizing pipeline, the stepping motor is used for controlling the opening angle of the butterfly valve to realize pressure control, and the system adopts the method to realize pressure control.
Optionally, the system further comprises a controller, and the pressure gauge and the stepping motor are electrically connected with the controller; the controller is configured to execute the periodic discontinuous angle control algorithm and the continuous angle control algorithm.
The invention has the beneficial effects that:
by introducing the empirical opening angle of the butterfly valve in the film deposition process, the target pressure can be quickly approached, and the response time is greatly improved. And the probability of failure of an automatic adjusting program can be avoided to a great extent, and the situation of failure of automatic adjustment is easy to occur for direct adjustment of high pressure adjustment (20 kPa), so that pressure collapse is caused. The method can reach the vicinity of the target pressure rapidly by introducing an empirical value, and large-angle adjustment is avoided. Furthermore, the method and the device can achieve higher control precision by adopting two different algorithms of a periodic discontinuous angle control algorithm and a continuous angle control algorithm for automatic control according to different pressure values, and can avoid fluctuation of pressure in a long time.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of an automatic pressure control method provided by the invention.
FIG. 2 is a schematic diagram of hardware connections of an automatic pressure control system according to an embodiment of the present invention.
FIG. 3 is a graph of angle versus pressure experience for a gas flow of 0 at ambient temperature 25 ℃.
FIG. 4 is a graph of angle versus velocity experience for a gas flow of 0 at room temperature of 25 ℃.
Fig. 5 is a graph showing the effect of pressure control on the pretreatment stage in the carbon nanotube deposition process using the method of the present application.
Fig. 6 is a graph showing the effect of the method of the present application on the pressure control process for the steps 310-350s in the pretreatment stage of the carbon nanotube deposition process.
Fig. 7 is a graph showing the effect of the method of the present application on the 300 th to 800 th seconds of the pressure control process for the pretreatment stage in the carbon nanotube deposition process.
Fig. 8 is a graph showing the effect of pressure control on the reaction stage in the carbon nanotube deposition process using the method of the present application.
Fig. 9 is a graph showing the effect of the method of the present application on the pressure control process 165-200s for the reaction stage in the carbon nanotube deposition process.
Fig. 10 is a graph showing the effect of the method of the present application on the 100 th to 700 th s of the pressure control process for the reaction stage in the carbon nanotube deposition process.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
Embodiment one:
the present embodiment provides an automatic control method of pressure of an atomic-level-precision CVD apparatus, which is used to realize pressure control in an ALD apparatus or a CVD apparatus in a thin film deposition process, as shown in fig. 1. The method is realized based on a pressure gauge, a butterfly valve and a stepping motor, as shown in fig. 2, wherein the pressure gauge is used for acquiring the internal pressure of ALD equipment or CVD equipment, the butterfly valve is connected with a vacuumizing pipeline, the opening angle of the butterfly valve is controlled by the stepping motor so as to achieve the purpose of controlling the internal pressure of the ALD equipment or the CVD equipment, in fig. 2, after a pressure signal acquired by the pressure gauge is transmitted to a controller, the controller selects a corresponding algorithm according to the pressure value to calculate and obtain a control electric signal to be transmitted to the stepping motor, the stepping motor converts the corresponding control electric signal into a corresponding angular displacement pulse signal, and the butterfly valve is controlled to rotate by the corresponding angle according to the pulse signal so as to realize opening or closing.
As shown in fig. 1, the method includes:
step 1, acquiring the temperature and the gas flow rate required by the film deposition process, wherein the gas flow rate is the volume of gas flowing in a reaction gas conveying pipeline in unit time in the film deposition process, namely the volume of gas input into an ALD device or a CVD device in unit time;
and 2, acquiring an angle-pressure experience curve and an angle-speed experience curve corresponding to each temperature under the gas flow, wherein the angle-pressure experience curve is a curve of pressure changing along with the opening angle of the butterfly valve, and the angle-speed experience curve is a curve of pressure changing along with the opening angle of the butterfly valve.
Fig. 3 and 4 are respectively angle-pressure experience curves and angle-rate experience curves corresponding to a gas flow rate of 0 at normal temperature of 25 ℃.
Step 3, determining target pressure required by each stage of the film deposition process, reading current gas flow and temperature, and determining butterfly valve experience opening angles corresponding to the target pressure required by each stage according to the angle-pressure experience curves;
the film depositing process includes pre-treatment stage, reaction stage, heat preservation stage, etc. and the temperature and the required target pressure are different.
Step 4, aiming at pressure control of each stage in the thin film deposition process, rapidly adjusting a butterfly valve to an empirical opening angle, and selecting a corresponding algorithm to automatically control the pressure according to the pressure change rate corresponding to the butterfly valve opening empirical angle and the target pressure, wherein the specific algorithm is as follows:
setting a pressure threshold, and when the target pressure is greater than or equal to the set pressure threshold, adopting a periodic discontinuous angle control algorithm (corresponding to algorithm 1 in fig. 1) to automatically control the pressure; when the target pressure is smaller than the set pressure threshold value, adopting a continuous angle control algorithm (corresponding to algorithm 2 in fig. 1) to automatically control the pressure; the pressure threshold is determined empirically (during actual deposition, when the pressure reaches a certain valueIn this case, the time required for increasing the pressure of a given value is significantly longer than the time required for decreasing the same pressure value>I.e., the pressure threshold), typically the pressure threshold P is 20kPa.
The periodic discontinuous angle control algorithm logic is as follows:
setting a pressure sampling periodT and pressure rate threshold ++>The pressure change rate threshold value +.>Maximum value of the velocity +.f can be based on the angle-velocity empirical curve>P max Determination of->P max ，/>The specific values are determined by the skilled person.
S1, acquiring a pressure sampling periodRate of pressure change within T->；
S2, judging the pressure change rateWhether the absolute value of (2) exceeds the set pressure change rate threshold value +.>；
S2.1, if the pressure change rateIs greater than a set pressure change rate threshold +.>Further according to the degree to which the absolute value of the rate of pressure change exceeds the set threshold value of the rate of pressure change, and the rate of pressure change +>The stepping angle and the stepping direction of the butterfly valve can be determined by the positive and negative values of the butterfly valve, and the stepping angle and the stepping direction can be set in multiple steps, and can be specifically set by technicians; such as:
1) When the pressure changes at a rateIs greater than +.>P max 50% and->When the value is positive, the butterfly valve is at a stepping angleForward stepping;
2) When the pressure changes at a rateIs greater than +.>P max 70% and->When the value is positive, the butterfly valve is at a stepping angleForward stepping;
3) When the pressure changes at a rateIs greater than +.>P max 80% and->When the value is positive, the butterfly valve is at a stepping angleForward stepping;
the stepping angle satisfies。
In the three cases, if the pressure change rate isWhen the value is negative, the butterfly valve reversely steps at a corresponding stepping angle; wherein, the butterfly valve is opened in forward stepping and closed in reverse stepping.
In one implementation of the method, in one implementation,，/>，/>。
s2.2, if the pressure change rateIs not exceeding the set pressure change rate threshold +.>The current pressure value P is further collected, and the current pressure value P, the target pressure and the pressure change rate are judged>Positive and negative of (2):
1) If the current pressure value P is smaller than the target pressure and the pressure change rate is equal to or higher than the target pressurePositive value, the current angle of the butterfly valve is maintained or the butterfly valve is opened by a stepping angle +>Reversely stepping;
2) If the current pressure value P is smaller than the target pressure and the pressure change rate is equal to or higher than the target pressureNegative value, then step angle +.>Reversely stepping;
3) If the current pressure value P is greater than the target pressure and the pressure change ratePositive value, step angle +>Forward stepping;
4) If the current pressure value P is greater than the target pressure and the pressure change rateNegative, the current angle of the butterfly valve is maintained or the butterfly valve is opened by a stepping angle +>Forward stepping.
Wherein the method comprises the steps ofAnd->，/>。
In one implementation of the method, in one implementation,，/>
the continuous angle control algorithm comprises:
i.e., the existing PID control algorithm, reference is made to patent CN112695297a for an introduction to a method for controlling chamber pressure in a semiconductor process or CN116931610a for an introduction to a method and apparatus for rapid response of pressure control.
Specifically, under the butterfly valve control scene of the application, the target pressure is taken as input, the real-time pressure is monitored, the output analog quantity is used for regulating and controlling the angle adjusting speed, and as the butterfly valve control system is sensitive to angle adjustment, the maximum adjusting speed is controlled within 0.1 degrees/s, for example, the output analog quantity is-10000 to 10000, which corresponds to forward rotation 0.1 degrees/s to reverse rotation 0.1 degrees/s. The control angle is smoothly and rapidly adjusted by adjusting suitable PID parameters including, but not limited to, parameter self-diagnosis in Siemens STEP 7-MicroWIN SMART software PLC wizard modules. Reading the pressure after adjusting the opening angle of the butterfly valve, calculating the difference value between the pressure and the target pressure, judging whether the difference value is within an error range, and if the difference value is within the error range, maintaining the current opening angle of the butterfly valve; if the difference is not within the error range, the PID adjustment is continued.
S3, reading the pressure after adjusting the opening angle of the butterfly valve, calculating a difference value with the target pressure, judging whether the difference value is in an error range, and if the difference value is in the error range, maintaining the current opening angle of the butterfly valve; if the difference value is not in the error range, continuing to sample the pressure change rate in the next period, and repeating the process.
Example two
The embodiment provides a pressure automatic control method, taking a carbon nanotube deposition process as an example for explanation, the method includes:
step 1, obtaining the temperature and the gas flow rate required by the carbon nano tube deposition process;
the stages required to adjust the pressure in the production process of the carbon nanotubes are 800 ℃, 500sccm of argon and hydrogen mixed gas pretreatment stage and 800 ℃ and 600sccm of ethanol gas reaction stage.
And 2, acquiring an angle-pressure experience curve and an angle-speed experience curve under the gas flow, wherein the angle-pressure experience curve is a curve of pressure changing along with the opening angle of the butterfly valve, and the angle-speed experience curve is a curve of pressure changing speed changing along with the opening angle of the butterfly valve.
Step 3, determining target pressure required by each stage of the film deposition process, reading current gas flow and temperature, and determining butterfly valve experience opening angles corresponding to the target pressure required by each stage according to the angle-pressure experience curves;
in the production process of the carbon nano tube, the pressure is controlled to be 50kPa when the temperature is 800 ℃, the pressure is controlled to be 2kPa when the temperature is 500sccm of argon and hydrogen gas mixture is 600sccm of ethanol, and the empirical opening angles of 800 ℃, 50kPa and 800 ℃ and 2kPa are obtained according to the empirical curve corresponding to the angle-pressure.
Step 4, rapidly adjusting the butterfly valve to an empirical opening angle, and selecting a corresponding algorithm to automatically control the pressure according to the pressure change rate corresponding to the butterfly valve opening empirical angle and the target pressure;
the pressure threshold value P=20kPa, so that the target pressure 50kPa in the pretreatment stage in the production process of the carbon nano tube is larger than the pressure threshold value, and the pressure is automatically controlled by adopting a periodic discontinuous angle control algorithm; and in the reaction stage, the target pressure 2kPa is smaller than a pressure threshold value, and a continuous angle control algorithm is adopted to automatically control the pressure.
Setting a pressure sampling period of a carbon nano tube deposition process for a pretreatment stage with a target pressure of 50kPaPressure change rate threshold->An empirical opening angle corresponding to 50kPa, which is 7.930 ° according to an angle-pressure empirical curve at 800 ℃, is read =0.3 kPa/s, and a pressure change rate is detected after rotation to the empirical angle +>= +0.03kPa/s, its absolute value does not exceed the pressure change rate threshold +.>Further collecting the current pressureThe force value P is 48.3kPa, which is smaller than the target pressure 50kPa, and the pressure change rate +.>Positive value, the current angle of the butterfly valve is maintained.
Step 4, reading the pressure after adjusting the opening angle of the butterfly valve, calculating a difference value with the target pressure, judging whether the difference value is in an error range, and if the difference value is in the error range, maintaining the current opening angle of the butterfly valve; if the difference value is not in the error range, continuing to sample the pressure change rate in the next period, and repeating the step 4.
And after 8S of step control, the pressure reaches 49.8kPa, and the difference value between the pressure and the target pressure is smaller than the set error range of 0.2kPa, the current butterfly valve opening angle is maintained until the pressure exceeds 50.2kPa, and the opening angle is reduced by an angle of 0.001 degrees.
Fig. 5 to 7 are graphs showing the effect of pressure control at the pretreatment stage in the production process of carbon nanotubes, and it can be seen from fig. 6 that the butterfly valve is rapidly opened to an empirical opening angle at t=317 s, and the pressure value in the system is 50.2kPa at t=321 s, i.e. within the error allowable range, i.e. 4s, so that the pressure can be controlled within the target pressure value error allowable range; as can be seen from FIG. 7, the pressure fluctuation range is 49.5kPa to 50.5kPa, i.e., the pressure can be controlled within the 1% fluctuation range. For the reaction stage with the target pressure of 2kPa, adopting a continuous angle control algorithm to automatically control the pressure:
the continuous angle control algorithm comprises:
the target pressure is taken as input, the real-time pressure is monitored, and an output analog quantity is output to regulate and control the angle adjustment speed, for example, the output analog quantity is-10000 to 10000, which corresponds to forward rotation 0.1 degrees/s to reverse rotation 0.1 degrees/s. The angular adjustment is controlled by adjusting suitable PID parameters including, but not limited to, parameter self-diagnosis in PID, etc. Reading the pressure after adjusting the opening angle of the butterfly valve, calculating the difference value between the pressure and the target pressure, judging whether the difference value is within an error range, and if the difference value is within the error range, maintaining the current opening angle of the butterfly valve; if the difference is not within the error range, the PID adjustment is continued.
The condition is suitable for adjusting the 2kPa link in the production of the carbon nano tube, the read experience angle is 7.930 degrees, the PID control can be automatically started after the rotation to the experience angle, and the angle is continuously adjusted. And when the pressure difference value is within the error range, the PID control is automatically stopped.
Fig. 8 to 10 are graphs showing the effect of controlling the pressure during the reaction stage in the production process of the carbon nanotubes, and it can be seen from fig. 9 that the butterfly valve is rapidly opened to the empirical opening angle at t=166 s, and the pressure value in the system at t=174 s is 1980Pa, i.e. within the error allowable range, i.e. 8s, so that the pressure can be controlled within the error allowable range of the target pressure value. As can be seen from FIG. 10, the pressure fluctuation range is 1980Pa-2020Pa, i.e., the pressure can be controlled within a fluctuation range of 1%.
Through multiple experiments, the method can adjust the system pressure within 10 seconds to the allowable error range.
Some steps in the embodiments of the present invention may be implemented by using software, and the corresponding software program may be stored in a readable storage medium, such as an optical disc or a hard disk.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (10)
1. An automatic control method for pressure of an atomic-level-precision CVD device, which is characterized by being realized based on a pressure gauge, a butterfly valve and a stepping motor, and comprising the following steps:
step 1, obtaining the temperature and the gas flow rate required by the film deposition process;
step 2, acquiring an angle-pressure experience curve and an angle-speed experience curve corresponding to each temperature under the gas flow; the angle-pressure experience curve is a curve of pressure changing along with the opening angle of the butterfly valve, and the angle-speed experience curve is a curve of pressure changing speed along with the opening angle of the butterfly valve;
step 3, determining target pressure required by each stage of the film deposition process, reading current gas flow and temperature, and determining butterfly valve experience opening angles corresponding to the target pressure required by each stage according to the angle-pressure experience curves;
and 4, aiming at pressure control of each stage of the thin film deposition process, rapidly adjusting the butterfly valve to an empirical opening angle, and selecting a corresponding algorithm to automatically control the pressure according to the pressure change rate corresponding to the butterfly valve opening empirical angle and the target pressure.
2. The method according to claim 1, wherein the step 4 comprises:
setting a pressure threshold, and when the target pressure is greater than or equal to the set pressure threshold, adopting a periodic discontinuous angle control algorithm to automatically control the pressure; and when the target pressure is smaller than the set pressure threshold value, adopting a continuous angle control algorithm to automatically control the pressure.
3. The method of claim 2, wherein the periodic discontinuous angle control algorithm logic is:
setting a pressure sampling periodT and pressure rate threshold ++>；
S1, acquiring a pressure sampling periodRate of pressure change within T->；
S2, judging the pressure change rateWhether the absolute value of (2) exceeds the set pressure change rate threshold value +.>；
S2.1, if the pressure change rateIs greater than a set pressure change rate threshold +.>Further according to the degree to which the absolute value of the rate of pressure change exceeds the set threshold value of the rate of pressure change, and the rate of pressure change +>Determining the stepping angle and direction of the butterfly valve;
s2.2, if the pressure change rateIs not exceeding the set pressure change rate threshold +.>The current pressure value P is further collected, and the current pressure value P, the target pressure and the pressure change rate are judged>To determine the stepping angle and direction of the butterfly valve;
s3, reading the pressure after adjusting the opening angle of the butterfly valve, calculating a difference value with the target pressure, judging whether the difference value is in an error range, and if the difference value is in the error range, maintaining the current opening angle of the butterfly valve; if the difference is not in the error range, continuing to sample the pressure change rate in the next period, and repeating the steps.
4. A method according to claim 3, wherein the rate of pressure change thresholdDetermined from the angle-rate empirical curve.
5. The method of claim 4, wherein the rate of pressure change thresholdThe method comprises the following steps: />P max Wherein->，/>P max Is the maximum rate in the angle-rate empirical curve.
6. The method according to claim 5, wherein the absolute value of the rate of change of pressure exceeds the set threshold of the rate of change of pressure, and the rate of change of pressure in S2.1Determining the stepping angle and direction of the butterfly valve, comprising:
1) When the pressure changes at a rateIs greater than +.>P max 50% and->When the valve is positive, the butterfly valve is at a stepping angle +.>Forward stepping;
2) When the pressure changes at a rateIs greater than +.>P max 70% and->When the valve is positive, the butterfly valve is at a stepping angle +.>Forward stepping;
3) When the pressure changes at a rateIs greater than +.>P max 80% and->When the valve is positive, the butterfly valve is at a stepping angle +.>Forward stepping;
the stepping angle satisfies；
In the three cases, if the pressure change rate isWhen the value is negative, the butterfly valve reversely steps at a corresponding stepping angle; wherein, the butterfly valve is opened in forward stepping and closed in reverse stepping.
7. The method of claim 6, wherein determining the step angle and direction of the butterfly valve in S2.2 comprises:
1) If the current pressure value P is smaller than the target pressure and the pressure change rate is equal to or higher than the target pressurePositive value, the current angle of the butterfly valve is maintained or the butterfly valve is opened by a stepping angle +>Reversely stepping;
2) If the current pressure value P is smaller than the target pressure and the pressure change rate is equal to or higher than the target pressureNegative value, then step angle +.>Reversely stepping;
3) If the current pressure value P is greater than the target pressure and the pressure change ratePositive value, step angle +>Forward stepping;
4) If the current pressure value P is greater than the target pressure and the pressure change rateNegative, the current angle of the butterfly valve is maintained or the butterfly valve is opened by a stepping angle +>Forward stepping;
the stepping angle satisfiesAnd->，/>。
8. The method of claim 7, wherein the continuous angle control algorithm is a PID control algorithm.
9. An automatic pressure control system of an atomic-level-precision CVD device, which is characterized by comprising a pressure gauge, a butterfly valve and a stepping motor, wherein the pressure gauge is used for acquiring the internal pressure of the ALD device or the CVD device, the butterfly valve is connected with a vacuumizing pipeline, the stepping motor is used for controlling the opening angle of the butterfly valve to realize pressure control, and the system adopts the method of any one of claims 1-8 to realize pressure control.
10. The system of claim 9, further comprising a controller, wherein the pressure gauge and the stepper motor are each electrically connected to the controller; the controller is configured to execute the periodic discontinuous angle control algorithm and the continuous angle control algorithm.
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