Feed-forward suppression method for starting interference of etching machine

Abstract

The invention provides a feedforward suppression method for starting interference of an etching machine, the control input of the etching machine is a heat source controlled by a heater, the heater is controlled by a feedforward controller, and the suppression method comprises the following steps: determining a disturbance transfer function between measured input disturbance and cavity output; determining a heater transfer function between the heater and the cavity output; measuring actual disturbance introduced to the etching machine when the radio frequency power supply is started; the heater is controlled according to a feed-forward control transfer function in the feed-forward controller, wherein the feed-forward control transfer function is represented by a ratio of the perturbation transfer function to the heater transfer function. According to the invention, the problem of heat source interference caused by etching starting is solved, and the temperature difference in the process cavity before and after starting is within the threshold range.

Description

Technical Field

[0001] The invention belongs to the technical field of etching, and in particular relates to a feedforward suppression method for ignition interference of an etcher. Background Art

[0002] In the chip manufacturing process, etching uniformity is an important indicator, and temperature is precisely the basic factor that determines uniformity. When the etching process temperature is stable, the etching result is uniform in depth. When the temperature of the hot plate fluctuates greatly, over-etching will occur, affecting the etching uniformity, which will directly affect the entire wafer or batch of silicon wafers. Therefore, the key to the etching machine process is to suppress the temperature disturbance in the etching process.

[0003] like Figures 1 to 3 During the etching process, high-energy particles are required to bombard the surface of the wafer, and the bombardment process causes great interference to the temperature of the hot plate. Ordinary PID control is mainly used to suppress small interference from the surrounding environment. When the interference is large, PID control cannot suppress the interference in time, causing the temperature of the hot plate to exceed the process allowable range for a long time. Through the analysis of the control principle, it can be seen that PID control is a control algorithm based on the feedback control principle. This algorithm is widely used because it does not need to know the specific model of the control system and has relatively high control accuracy. However, this feedback control algorithm only suppresses interference when it is detected, so the algorithm has inherent defects in control timeliness; and some systems have obvious inertia links, delay links, etc., so these systems need a certain amount of time from the occurrence of interference to the detection of interference, and it also takes time from intervention to the effect, so the timeliness of control cannot be guaranteed. Summary of the invention

[0004] The purpose of the present invention is to provide a feedforward suppression method for the ignition interference of an etcher, which solves the heat source interference caused by the etching ignition and realizes that the temperature difference in the process chamber before and after the ignition is within the threshold range. The technical solution adopted is as follows:

[0005] A feedforward suppression method for ignition interference of an etcher, wherein the control input of the etcher is a heat source controlled by a heater, and the heater is controlled by a feedforward controller, and the suppression method comprises the following steps:

[0006] determining a disturbance transfer function between a measured input disturbance and a cavity output;

[0007] determining a heater transfer function between the heater and a cavity output;

[0008] Measure the actual disturbance introduced into the etcher when the RF power is ignited;

[0009] The heater is controlled according to a feedforward control transfer function in the feedforward controller, wherein the feedforward control transfer function is represented by a ratio of the disturbance transfer function to the heater transfer function.

[0010] Preferably, the determination of the disturbance transfer function specifically comprises the following steps:

[0011] Applying an input disturbance of known ignition power to the etcher and recording the cavity output;

[0012] The input disturbance is the temperature at the RF power source after the RF power source is ignited; the cavity output is the temperature of the hot plate;

[0013] defining the disturbance transfer function as a ratio of a first incremental change to a second incremental change;

[0014] wherein the first incremental change is an incremental change of the output disturbance before applying the input disturbance relative to the output disturbance after applying the input disturbance;

[0015] The second incremental change is an incremental change of the input disturbance relative to the output disturbance after applying the input disturbance.

[0016] Preferably, the temperature of the heat plate in the cavity involved in the output disturbance is acquired by a temperature sensor on the heat plate.

[0017] Preferably, the disturbance transfer function is:

[0018] Preferably, the determination of the heater transfer function specifically comprises the following steps:

[0019] Applying an input disturbance of known ignition power to the etcher, and recording an output disturbance of the cavity output;

[0020] defining the heater transfer function as a ratio of the first incremental change to the third incremental change;

[0021] The third incremental change is a change in the input amount of the heater before applying the input disturbance relative to after applying the input disturbance to the etcher.

[0022] Preferably, the heater transfer function is:

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] By detecting the disturbance, the control can be carried out, so the intervention can be started when the disturbance occurs, which greatly improves the timeliness. By combining feedforward control with feedback control, the control can not only meet the control accuracy, but also ensure the timeliness of large disturbance suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of wafer etching;

[0026] Figure 2 Schematic diagram of the hot plate and ignition effect in wafer etching;

[0027] Figure 3 The effect diagram of hot plate temperature control;

[0028] Figure 4 This is the structural diagram of the feedforward suppression system for the ignition interference of the etcher;

[0029] Figure 5 It is a simulation diagram of the MV1 value output by the PID controller before ignition and the MV2 value output by the heater after ignition in this embodiment. DETAILED DESCRIPTION

[0030] The feedforward suppression method for the ignition interference of the etcher of the present invention will be described in more detail below in conjunction with the schematic diagram, wherein the preferred embodiment of the present invention is shown, and it should be understood that those skilled in the art can modify the present invention described herein and still achieve the advantageous effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation of the present invention.

[0031] A feedforward suppression method for the ignition interference of an etcher, wherein the control input of the etcher is a heat source controlled by a heater, and the heater is controlled by a feedforward controller. That is, the temperature control of the hot plate of the etcher is controlled by a PLC to control the heater to increase the temperature, and the PLC controller controls the temperature increase process through PID setting, and there is heat interference generated by the ignition effect during the temperature increase process.

[0032] The inhibition method comprises the following steps:

[0033] Determine the measured input disturbance n and cavity output y 2 The disturbance transfer function G n (S);

[0034] Determine the heater and chamber output 2 Heater transfer function G(S);

[0035] Measure the actual disturbance introduced into the etcher when the RF power is ignited;

[0036] The heater is controlled according to a feedforward control transfer function in a feedforward controller, wherein the feedforward control transfer function D n (S) is expressed as the ratio of the disturbance transfer function to the heater transfer function.

[0037] Disturbance transfer function Gn The determination of (S) specifically includes the following steps:

[0038] Apply an input disturbance of known ignition power to the etcher and record the cavity output;

[0039] The input disturbance is the temperature T at the RF power source after the RF power source is started. 3 ; Cavity output is the temperature of the hot plate inside the cavity.

[0040] The specific steps of "applying an input disturbance of known starting power p to the etcher" are:

[0041] The RF power supply is started, and its start-up time t is the same as the start-up time in the process of determining the heater transfer function G(S).

[0042] Therefore, the energy generated by the RF power supply = pt.

[0043] Temperature T 3 , measured by the temperature sensor at the RF power supply.

[0044] defining a disturbance transfer function as the ratio of the first incremental change to the second incremental change;

[0045] The first incremental change is the output disturbance (temperature T of the hot plate in the cavity) before the input disturbance is applied. 0 ) relative to the output disturbance after applying the input disturbance (the temperature of the hot plate in the cavity T 1 ) incremental changes;

[0046]

[0047] The temperature of the heat disk in the cavity before applying the input disturbance is T 0 :

[0048] That is, during the sampling time, the temperature of the hot plate in the cavity will fluctuate during the PID controller adjustment process. The average value of the floating value is the temperature T. 0 .

[0049] The temperature T of the heat plate in the cavity after applying the input disturbance 1 :

[0050] That is, during the sampling time, the composite control system formed by the PID controller and the feedforward controller will cause the temperature of the hot plate in the cavity to fluctuate during the adjustment process. The average value of the floating value is the temperature T. 1 .

[0051] The second incremental change is the input disturbance relative to the applied input disturbance (temperature T 3 ) is the incremental change in the output disturbance after .

[0052]

[0053] The independent variable in the disturbance transfer function is defined as: sampling time interval, which is set to 100ms.

[0054] The temperature of the heat plate in the cavity is acquired by a temperature sensor in the cavity.

[0055] Through MATLAB neural network learning, the output-input mapping relationship in the disturbance transfer function is established, and finally the following disturbance transfer function is established:

[0056] The disturbance transfer function is:

[0057] The determination of the heater transfer function G(S) specifically includes the following steps:

[0058] Apply an input disturbance of known ignition power to the etcher and record the output disturbance of the cavity output;

[0059] The heater transfer function is defined as the ratio of the first incremental change to the third incremental change.

[0060] The third incremental change is the change in the amount of input to the heater before the input disturbance is applied relative to the amount of input to the etcher after the input disturbance is applied.

[0061] The "heater input" is referred to as u.

[0062] That is, applying an input disturbance (temperature T 3 ), the heater input (equal to MV1 value) is B 0 ;

[0063] Apply input disturbance (temperature T 3 ) after which the heater input (MV2 value) is B 1 ;

[0064]

[0065] in, Figure 5 The definition of MV value in is: the operating amount output to the heater, as a percentage.

[0066] The independent variable in the heater transfer function is defined as: sampling time interval, which is set to 100ms.

[0067] Through MATLAB neural network learning, the output-input mapping relationship in the heater transfer function is established, and finally the following heater transfer function is established:

[0068] The heater transfer function is:

[0069] The feedforward control transfer function is:

[0070] like Figure 5 As shown in the figure, under the feedforward-feedback compound control, the MV1 value output by the PID controller and the MV2 value input by the heater are sampled again and it is found that, under the same process temperature value before and after starting, the difference in MV after steady state is basically a constant. This constant value is the required feedforward compensation amount.

[0071] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A feedforward suppression method for ignition interference of an etcher, characterized in that: The control input of the etcher is a heat source controlled by a heater, the heater is controlled by a feedforward controller, and the suppression method comprises the following steps: determining a disturbance transfer function between a measured input disturbance and a cavity output; determining a heater transfer function between the heater and a cavity output; Measure the actual disturbance introduced into the etcher when the RF power is ignited; The heater is controlled according to a feedforward control transfer function in the feedforward controller, wherein the feedforward control transfer function is represented by a ratio of the disturbance transfer function to the heater transfer function.

2. The feedforward suppression method for ignition interference of an etcher according to claim 1, characterized in that: The determination of the disturbance transfer function specifically comprises the following steps: Applying an input disturbance of known ignition power to the etcher and recording the cavity output; The input disturbance is the temperature at the RF power source after the RF power source is ignited; the cavity output is the temperature of the hot plate; defining the disturbance transfer function as a ratio of a first incremental change to a second incremental change; wherein the first incremental change is an incremental change of the output disturbance before applying the input disturbance relative to the output disturbance after applying the input disturbance; The second incremental change is an incremental change of the input disturbance relative to the output disturbance after applying the input disturbance.

3. The feedforward suppression method for ignition interference of an etcher according to claim 2, characterized in that: The temperature of the heat plate in the cavity involved in the output disturbance is obtained by a temperature sensor on the heat plate.

4. The feedforward suppression method for ignition interference of an etcher according to claim 2, characterized in that: The disturbance transfer function is:

5. The feedforward suppression method for ignition interference of an etcher according to claim 2, characterized in that: The determination of the heater transfer function specifically comprises the following steps: Applying an input disturbance of known ignition power to the etcher, and recording an output disturbance of the cavity output; defining the heater transfer function as a ratio of the first incremental change to the third incremental change; The third incremental change is a change in the input amount of the heater before applying the input disturbance relative to after applying the input disturbance to the etcher.

6. The feedforward suppression method for ignition interference of an etcher according to claim 5, characterized in that: The heater transfer function is:

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