Pulse bias signal generation method and semiconductor process device

Abstract

Provided in the present application are a pulse bias signal generation method and a semiconductor process device, which are applied to the technical field of semiconductor process devices. The method comprises: acquiring a target IEDF, wherein the target IEDF records a plurality of single-peak IEDFs, and an ion fraction and an ion energy peak value which correspond to each single-peak IEDF; on the basis of the ion energy peak value corresponding to each single-peak IEDF and a negative jump amplitude of a pulse bias signal, determining a pulse duty cycle of pulses contained in a pulse train corresponding to each single-peak IEDF; then, according to each pulse duty cycle, creating a pulse train corresponding to a corresponding single-peak IEDF, so as to obtain a signal sequence; and finally, according to the negative jump amplitude, repeatedly outputting the signal sequence, so as to output a pulse bias signal. Compared with the prior art, a shorter time is required for adjusting a duty cycle in the present application, and the rapid switching of a pulse bias signal can be realized, thereby controlling ion energy to be distributed according to a target IEDF, thus meeting the actual process requirements.

Description

A method for generating pulse bias signals and semiconductor process equipment Technical Field

[0001] This application relates to the field of semiconductor process equipment technology, specifically to a pulse bias signal generation method and semiconductor process equipment. Background Technology

[0002] Ion energy distribution is a key parameter determining the quality of plasma etching processes, and is typically represented by the ion energy distribution function (IEDF). With the continuous development of semiconductor technology, controlling ion energy to conform to an arbitrary IEDF distribution to meet the requirements of different semiconductor processes has become one of the most important research topics for those skilled in the art.

[0003] Existing technologies control ion energy to exhibit a single-peak IEDF distribution by adjusting the waveform of a pulse bias signal. Theoretically, by providing pulse bias signals with different negative voltage transition amplitudes, ion energy can be controlled to follow an arbitrary IEDF distribution. However, in existing technologies, the negative transition amplitude of the pulse bias signal is provided by a DC power supply. Adjusting the DC power supply output voltage requires a relatively long time, and the negative transition amplitude cannot be rapidly modulated. This results in the actual energy distribution deviating significantly from the theoretically defined two independent single-peak IEDFs. Therefore, existing technologies cannot control ion energy to follow the expected IEDF distribution, making it difficult to meet practical process requirements. Summary of the Invention

[0004] In view of this, this application aims to provide a pulse bias signal generation method and semiconductor process equipment to control ion energy according to the expected IEDF distribution to meet actual process requirements.

[0005] According to a first aspect of this application, a method for generating a pulse bias signal is provided, comprising the following steps:

[0006] Obtain the target ion energy distribution function (IEDF), wherein the target IEDF includes multiple single-peak IEDFs and the ion quantity percentage and ion energy peak value corresponding to each single-peak IEDF;

[0007] For each of the single-peak IEDs, based on the peak ion energy of the single-peak IED and the negative jump amplitude value of the pulse bias signal, the pulse duty cycle of the pulses contained in the corresponding pulse train is determined. The pulse bias signal includes multiple pulse trains, each pulse train corresponds to each of the single-peak IEDs, and each pulse train includes multiple pulses, with the negative jump amplitude value of each pulse being the same.

[0008] A pulse train corresponding to the corresponding single-peak IEDF is created according to the duty cycle of each pulse to obtain a signal sequence, wherein the proportion of the number of pulses contained in each pulse train in the signal sequence is consistent with the proportion of the ion content of the corresponding single-peak IEDF.

[0009] The signal sequence is repeatedly output according to the negative jump amplitude value to output the pulse bias signal.

[0010] In some embodiments, a pulse train corresponding to a single-peak IEDF is created according to each pulse duty cycle to obtain a signal sequence, including:

[0011] Based on the ion content ratio of each single-peak IEDF, the number of pulses contained in the pulse train corresponding to each single-peak IEDF is determined respectively.

[0012] The corresponding pulse trains are determined according to the number of pulses and pulse duty cycle of each single-peak IEDF to obtain the signal sequence.

[0013] In some embodiments, based on the ion content ratio of each of the single-peak IEDFs, the number of pulses contained in the pulse train corresponding to each single-peak IEDF is determined, including:

[0014] Obtain the total number of pulses contained in each pulse train in the signal sequence;

[0015] The number of pulses corresponding to each single-peak IEDF is obtained by multiplying the ion content ratio of each single-peak IEDF by the total number of peaks.

[0016] In some embodiments, obtaining the total number of pulses contained in each pulse train in the signal sequence includes:

[0017] Obtain a preset cycle frequency and target parameters, wherein the preset cycle frequency is the frequency at which the signal sequence is repeatedly output, and the target parameters include ion concentration and electron temperature;

[0018] Based on the preset cycle frequency, the target parameter, and the negative jump amplitude value, the total number of pulses contained in each pulse train in the signal sequence is determined.

[0019] In some embodiments, determining the total number of pulses contained in each pulse train in the signal sequence based on the preset cycle frequency, the target parameter, and the negative jump amplitude value includes:

[0020] Based on the target parameters and the negative jump amplitude value, the target frequency is determined, wherein the pulse bias signal output according to the target frequency enables ions to reach the wafer surface after multiple pulse cycles.

[0021] The quotient of the target frequency and the preset cycle frequency is determined to be the total number of pulses contained in each pulse train in the signal sequence.

[0022] In some embodiments, determining the target frequency based on the target parameter and the negative jump amplitude value includes:

[0023] Obtain a preset number of cycles, which is the number of pulse cycles required for ions to reach the wafer surface;

[0024] The time for ions to cross the sheath within the process chamber is determined based on the target parameters and the negative jump amplitude value.

[0025] The reference frequency is determined based on the time and the preset number of cycles;

[0026] Determine any frequency greater than or equal to the reference frequency as the target frequency.

[0027] In some embodiments, the process of determining the pulse duty cycle of the pulse train corresponding to any of the single-peak IEDFs includes:

[0028] The pulse duty cycle of the pulse train is calculated using the following formula:

[0029] Where m represents the pulse duty cycle;

[0030] E p The peak ion energy represents the single-peak IEDF.

[0031] e represents the electron charge;

[0032] V out This represents the negative jump amplitude value.

[0033] In some embodiments, before determining the pulse duty cycle of the corresponding pulse train based on the peak ion energy of the single-peak IEDF and the negative jump amplitude value of the pulse bias signal for each of the single-peak IEDFs, the method further includes: determining the negative jump amplitude value of the pulse bias signal based on each of the peak ion energy values, including:

[0034] The maximum value among the ion voltages required to generate each of the aforementioned ion energy peaks is used as the reference voltage value;

[0035] Determine any amplitude greater than or equal to the reference voltage value as the negative jump amplitude of the pulse bias signal.

[0036] In some embodiments, repeatedly outputting the signal sequence according to the negative jump amplitude value to output a pulse bias signal includes:

[0037] Control the DC power supply to output DC voltage according to the negative jump amplitude value;

[0038] In addition, driving signals are repeatedly output according to the pulse duty cycle of each pulse train in the signal sequence, so that the switch array converts the DC voltage into a corresponding pulse bias signal according to each pulse duty cycle.

[0039] Secondly, this application provides a semiconductor process apparatus, including: a bias power supply, a bias electrode, and a controller, wherein...

[0040] The bias electrode is disposed in the wafer carrier device of the process chamber;

[0041] The bias power supply includes a DC power supply and a switching array, wherein...

[0042] The output terminal of the DC power supply is connected to the input terminal of the switch array, and the output terminal of the switch array is connected to the bias electrode.

[0043] The controller is connected to the control terminals of the DC power supply and the switch array, respectively. The controller includes a memory and a processor. The memory is used to store instructions, and the processor is used to execute the pulse bias signal generation method as described in any of the first aspects of this application according to the instructions stored in the memory.

[0044] Based on the above, the pulse bias signal generation method provided in this application first obtains a target IEDF, which records multiple single-peak IEDFs and the ion quantity ratio and ion energy peak value corresponding to each single-peak IEDF. Based on the ion energy peak value corresponding to each single-peak IEDF and the negative jump amplitude value of the pulse bias signal, the pulse duty cycle of the pulses contained in the pulse train corresponding to each single-peak IEDF is determined. Then, a pulse train corresponding to the single-peak IEDF is created according to each pulse duty cycle to obtain a signal sequence. Finally, the signal sequence is repeatedly output according to the negative jump amplitude value to obtain a pulse bias signal that controls the ion distribution according to the target IEDF. This application repeatedly outputs pulse trains with the same negative jump amplitude value according to the signal sequence, that is, only the duty cycle of the output pulse bias signal needs to be adjusted to provide a pulse bias signal. Compared with the prior art, which controls the ion energy distribution by adjusting the negative jump amplitude value of the pulse bias signal, the time required to adjust the duty cycle is shorter, and the pulse bias signal can be switched rapidly to control the ion energy distribution according to the target IEDF, thereby meeting the actual process requirements. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1a is a waveform diagram of a pulse bias signal in the prior art.

[0047] Figure 1b shows a single-peaked IEDF obtained by controlling ions according to the pulse bias signal shown in Figure 1a.

[0048] Figure 2a is a waveform diagram of another pulse bias signal in the prior art.

[0049] Figure 2b shows the multi-peaked IEDF obtained by controlling the ions according to the pulse bias signal shown in Figure 2a.

[0050] Figure 2c shows the ideal IEDF corresponding to the pulse bias signal shown in Figure 2a.

[0051] Figure 3 is a structural block diagram of a semiconductor process equipment provided in this application.

[0052] Figure 4 is a flowchart of a pulse bias signal generation method provided in this application.

[0053] Figure 5 is a schematic diagram of a target IEDF.

[0054] Figures 6a-6c are waveform diagrams of a pulse bias signal generation method provided in this application.

[0055] Figures 7a-7c are another waveform diagram of the pulse bias signal generation method provided in this application.

[0056] Figure 8 is a flowchart of a signal sequence generation method provided in this application.

[0057] Figure 9 is a waveform diagram of a signal sequence provided in this application. Detailed Implementation

[0058] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0059] For anisotropic plasma etching processes, key parameters determining process quality include the type, quantity, and energy distribution of ions interacting with the wafer surface. The ion energy distribution is typically represented by the Ion Energy Distribution Function (IEDF). With the continuous development of semiconductor technology, the requirements for controlling the etching profile are becoming increasingly stringent (e.g., high aspect ratio etching). Therefore, how to control ion energy according to an arbitrary IEDF distribution to meet the requirements of different semiconductor processes has become one of the most important research topics for those skilled in the art.

[0060] Related technologies control ion energy to exhibit a single-peak IEDF distribution by adjusting the waveform of the pulse bias signal. As shown in Figure 1a, the waveform of the adjusted pulse bias signal includes four parts: a positive transition, a positive voltage, a negative transition, and a negative voltage ramp. By using the pulse bias signal shown in Figure 1a, the ion energy can be controlled to exhibit a single-peak IEDF distribution as shown in Figure 1b. Furthermore, the negative transition amplitude (Vout) of the pulse bias signal in related technologies determines the peak ion energy corresponding to the single-peak IEDF. Based on this, theoretically, by repeatedly providing pulse bias signals with different negative voltage transition amplitudes, the ion energy can be controlled to exhibit an IEDF distribution of any shape.

[0061] However, the inventors discovered that in related technologies, the negative jump amplitude of the pulse bias signal is provided by a DC power supply. Adjusting the DC power supply output voltage takes a long time, and the negative jump amplitude cannot be rapidly modulated. For example, providing a pulse bias signal as shown in Figure 2a, which includes a pulse bias signal with a negative jump amplitude of Vout1 and a pulse bias signal with a negative jump amplitude of Vout2, the ideal IEDF should be a bimodal IEDF as shown in Figure 2c. However, in actual control, the energy distribution effect is as shown in Figure 2b, which is clearly far from the theoretical two independent single-peak IEDF shown in Figure 2c. This is because the actual process of switching the negative jump amplitude from Vout1 to Vout2 is a gradual transition from Vout1 to Vout2. During this transition, a lot of ion energy outside the set range may be generated, resulting in the energy distribution effect shown in Figure 2b. Therefore, it is evident that related technologies cannot control ion energy to distribute according to the expected IEDF, making it difficult to meet actual process requirements. Furthermore, the frequency of the pulse bias signal in related technologies is typically 100kHz to 1MHz. For higher frequency pulse bias signals, there is currently no corresponding scheme for controlling the ion energy distribution.

[0062] To address the aforementioned technical problems, this application provides a semiconductor process apparatus, including: a controller 10, a process chamber 70, an upper electrode system, and a lower electrode system. Referring to FIG3, the lower electrode system includes, for example, a bias power supply 20 and a bias electrode 30. The bias power supply 20 includes a DC power supply 210 and a switch array 220. In some embodiments, the bias power supply 20 further includes a drive signal generation circuit 230. The upper electrode system includes, for example, an RF power supply 40, an impedance matching circuit 50, and a coupling coil 60. Those skilled in the art will understand that for inductively coupled plasma (ICP) equipment, the upper electrode system includes a coupling coil; for capacitively coupled plasma (CCP) equipment, the upper electrode system includes an upper electrode plate, such as a flow equalizer. A wafer carrier 710 is disposed within the process chamber 70 opposite to the coupling coil 60. The wafer carrier 710 may include, for example, an electrostatic chuck or a mechanical chuck, and is used to carry the wafer 80 to be processed.

[0063] In the example in Figure 3, the output of the RF power supply 40 is connected to the impedance matching circuit 50, which is connected to the coupling coil 60. After the RF power supply 40 is started, it can apply RF power to the coupling coil 60 through the impedance matching circuit 50, thereby generating plasma inside the process chamber 70.

[0064] In the bias power supply 20, the output terminal of the drive signal generation circuit 230 is connected to the control terminal of the switch array 220, the input terminal of the switch array 220 is connected to the output terminal of the DC power supply 210, and the output terminal of the switch array 220 is connected to the bias electrode 30, which is disposed inside the wafer carrier device 710. The controller 10 is connected to both the DC power supply 210 and the control terminal of the drive signal generation circuit 230. It should be noted that if the control signal output by the controller 10 is sufficient to drive the switch array 220, the drive signal generation circuit 230 can be omitted, that is, the output terminal of the controller 10 is directly connected to the control terminal of the switch array 220. Furthermore, as in some embodiments, the controller 10 is also connected to the radio frequency power supply 40.

[0065] The controller 10 controls the operation of the RF power supply 40 and applies RF power to the coupling coil 60 through the impedance matching circuit 50, thereby generating plasma inside the process chamber 70. Further, the controller 10 executes the pulse bias signal generation method provided in this application, controlling the lower electrode system to provide a pulse bias signal to the wafer 80 carried by the wafer carrier 710, thereby controlling the plasma in the process chamber 70 to be distributed according to the target IEDF. It should be noted that the process of the controller 10 controlling the upper electrode system to generate plasma can be implemented with reference to related technologies, and this application does not limit it in this regard.

[0066] Based on the basic structure of the aforementioned semiconductor process equipment, the pulse bias signal generation method provided in this application, after acquiring a target IDF that records multiple single-peak IDFs and the ion quantity ratio and ion energy peak value corresponding to each single-peak IDF, determines the pulse duty cycle of the pulse train corresponding to each single-peak IDF based on the ion energy peak value corresponding to each single-peak IDF and the negative jump amplitude value of the pulse bias signal. Then, a pulse train corresponding to the corresponding single-peak IDF is created according to each pulse duty cycle to obtain a signal sequence. Finally, the signal sequence is repeatedly output according to the negative jump amplitude value to obtain a pulse bias signal that controls the ion distribution according to the target IDF. The method provided in this application only needs to adjust the duty cycle of the output pulse bias signal to provide a pulse bias signal. Compared with the prior art, the method provided in this application does not need to control the ion energy distribution by adjusting the negative jump amplitude value of the pulse bias signal, and the time required to adjust the duty cycle is shorter. It can achieve rapid switching of the pulse bias signal, thereby controlling the ion energy distribution according to the target IDF and meeting the actual process requirements.

[0067] Referring to Figure 4, the pulse bias signal generation method provided in this application includes the following steps:

[0068] S100: Obtain the target IEDF.

[0069] The target IEDF mentioned in the embodiments of this application refers to the IEDF required to meet certain process requirements, which is also the ideal effect of ion energy distribution control. As mentioned above, related technologies have been able to control single-peak IEDFs. Therefore, the embodiments of this application mainly describe the case of a target IEDF including multiple single-peak IEDFs. Furthermore, the target IEDF also records the ion quantity ratio and ion energy peak value corresponding to each of its included single-peak IEDFs. Of course, according to the pulse bias signal generation method provided in this application, a pulse bias signal that can control the ion distribution to a single-peak IEDF can also be generated, which is also within the scope of protection of this application.

[0070] Based on the above, taking the high selectivity etching of multilayer mask structures as an example, it is necessary to control the ion energy according to the target IEDF distribution shown in Figure 5. The target IEDF in Figure 5 includes four single-peak IEDFs. From right to left in Figure 5, the peak ion energies of the four single-peak IEDFs are 240 eV, 210 eV, 180 eV, and 150 eV, respectively, and the ion content percentages corresponding to the four single-peak IEDFs are 10%, 20%, 30%, and 40%, respectively. The role of the various information recorded in the target IEDF will be discussed in subsequent sections and will not be elaborated here.

[0071] S110: For each single-peak IEDF, determine the pulse duty cycle of the corresponding pulse train based on the peak ion energy of the single-peak IEDF and the negative jump amplitude of the pulse bias signal.

[0072] The inventors discovered that the ion energy acting on the wafer surface can be expressed by formula (1): E p =eV out (1-m) (1)

[0073] Where m represents the pulse duty cycle of the pulse train;

[0074] E p The peak ion energy represents the single-peak IEDF.

[0075] e represents the electron charge;

[0076] V out This indicates the negative jump amplitude value.

[0077] Based on formula (1), it can be seen that in the negative jump amplitude value V out Under certain conditions, the peak ion energy E p Since it directly corresponds to the pulse duty cycle m, formula (1) can be appropriately modified to calculate the pulse duty cycle of the pulse train corresponding to each single-peak IEDF. The modified formula (2) is shown below.

[0078] Based on the above, in some embodiments, multiple single-peak IEDs recorded in the target IED are respectively regarded as target single-peak IEDs, and the ion energy peak of the target single-peak IED is carried into E. p Substitute the negative jump amplitude value into V out The calculated result is the pulse duty cycle m of the pulse train corresponding to the target single-peak IEDF.

[0079] In some embodiments, before performing S110, the negative jump amplitude value of the pulse bias signal can be determined based on the peak energy of each ion.

[0080] It is understandable that the pulse bias signal includes positive transitions (i.e., rising edges) and negative transitions (i.e., falling edges), where the voltage drop value corresponding to the transition from high level to low level is the negative transition amplitude.

[0081] In practical applications, it is sufficient to ensure that the maximum ion energy generated by the pulse bias signal is greater than the maximum ion energy peak value in the target IEDF. Based on this, the maximum value among the ion voltages required to generate each ion energy peak value is used as the reference voltage value, and any amplitude greater than or equal to the reference voltage value is used as the negative jump amplitude value of the pulse bias signal. The pulse bias signal generated based on this negative jump amplitude value can meet the actual process requirements. Under the premise of meeting the above basic requirements, this application does not limit the specific value of the negative jump amplitude value.

[0082] Following the example shown in Figure 5, the peak ion energies of the four single-peak IEDs are 240 eV, 210 eV, 180 eV, and 150 eV, respectively. The largest peak ion energy is 240 eV, corresponding to an ion voltage of 240 V. Therefore, 240 V is the aforementioned reference voltage. Based on this, any amplitude greater than or equal to 240 V, such as 300 V or 290 V, can be used as the negative jump amplitude value. In this application, the negative jump amplitude value of the pulse bias signal is the negative jump amplitude value of each pulse in the pulse train corresponding to each single-peak IED. In other words, the negative jump amplitude value of each pulse in the pulse bias signal generated according to the pulse bias signal generation method provided in this application is the same. The entire control process does not require adjusting the negative jump amplitude value of the pulse bias signal, and there is no gradual transition process of the negative jump amplitude value. Consequently, many ion energies outside the set range are not generated. Therefore, the ion energy can be controlled to follow the target IED distribution to meet the actual process requirements.

[0083] S120: Create pulse trains corresponding to the single-peak IEDF according to the duty cycle of each pulse to obtain the signal sequence.

[0084] The signal sequence described in this application includes pulse trains corresponding to each single-peak IED in the target IED, and for any single-peak IED, the signal sequence includes at least one corresponding pulse. Based on the aforementioned steps, it is known that the duty cycles of the pulse bias signals required to control ions according to different single-peak IED distributions are different. Therefore, when constructing the signal sequence, it is necessary to determine the corresponding pulse train for each single-peak IED in the target IED according to the pulse duty cycle determined in the aforementioned steps.

[0085] Furthermore, the proportion of pulses in the pulse train corresponding to each single-peak IEDF in the signal sequence is consistent with the proportion of ions in the target IEDF corresponding to that single-peak IEDF. In other words, the proportion of pulses in each pulse train in the signal sequence determines the proportion of ions in each single-peak IEDF in the target IEDF.

[0086] Using the example shown in Figure 5, the proportion of ions in each single-peak IEDF is 40%, 30%, 20%, and 10%, respectively. Correspondingly, in the signal sequence, the proportion of the number of pulses contained in the pulse train corresponding to each single-peak IEDF is also 40%, 30%, 20%, and 10%.

[0087] The above are the two basic requirements for constructing a signal sequence. The specific implementation methods for constructing a signal sequence will be discussed in subsequent content and will not be detailed here.

[0088] S130: Repeat the output signal sequence according to the negative jump amplitude value to output a pulse bias signal.

[0089] After obtaining the signal sequence, the pulse trains within the obtained signal sequence are repeatedly output according to the negative jump amplitude value. That is, after outputting the pulse train with the first pulse duty cycle, the negative jump amplitude value is kept constant, the pulse duty cycle is switched, and the pulse train with the second pulse duty cycle is output, until all the pulse trains in the output signal sequence are output. Then, the signal sequence is output again according to the above content. By repeating this process, the pulse bias signal that controls the ions to be distributed according to the target IEDF can be obtained.

[0090] As shown in Figure 3, the controller 10 controls the operation of the RF power supply 40 and applies RF power to the coupling coil 60 through the impedance matching circuit 50, thereby generating plasma inside the process chamber 70. Further, the controller 10 controls the DC power supply 210 to output a DC voltage according to the negative jump amplitude value. Simultaneously, it controls the drive signal generation circuit 230 to repeatedly output drive signals according to the pulse duty cycle of each pulse train in the signal sequence. This drives the switch array 220 to convert the DC voltage into corresponding pulses according to each pulse duty cycle, obtaining a pulse bias signal. Finally, the obtained pulse bias signal is output to the bias electrode 30 located inside the wafer carrier device 710 to control the ion energy during the process of ions reaching the wafer surface, thereby controlling the ions to distribute according to the target IEDF.

[0091] Further research by the inventors revealed that after outputting a pulsed bias signal to the bias electrode, the electrode and the wafer act as a capacitor. When the pulsed bias signal is at a high level, the wafer surface also senses a high level. This high level on the wafer surface, combined with the plasma inside the process chamber, creates an accelerating electric field that attracts electrons to the wafer surface, causing a decrease in surface voltage. When the pulsed bias signal is at a low level, the wafer surface voltage becomes negative, attracting ions to the surface. Because the velocity of ions is much lower than that of electrons, the voltage drop on the wafer surface caused by electrons is much greater than the voltage rise caused by ions. A stable voltage waveform is only formed on the wafer surface after multiple pulse cycles.

[0092] Therefore, the key to the repetitive output signal sequence is to ensure that the final output pulse bias signal can control the ions to reach the wafer surface after multiple pulse cycles. If the ions undergo multiple pulse cycles before reaching the wafer surface, they will no longer be affected in real time by the sheath voltage waveform formed on the wafer surface, but rather by the average sheath voltage. In this case, the ions will be accelerated to the wafer surface with an approximately constant sheath voltage within 100% of the pulse cycle. This effect is extremely effective in improving the control accuracy of ion energy distribution. Of course, this is also the key premise for this application to control the ion energy distribution by adjusting the pulse duty cycle. Unlike the pulsed bias signals provided in related technologies, when controlling ion movement, the time it takes for ions emitted from the plasma to cross the sheath and reach the wafer surface is generally several hundred ns. This means that ions can reach the wafer surface in about 1 / 4 of a pulse cycle. Due to the short time, the ions can be affected in real time by the sheath voltage waveform formed on the wafer surface. For the periodic sheath voltage waveform that the ions respond to in real time, the ion energy of the ions that bombard the wafer surface depends on the phase of the ions entering the sheath. That is, the ions will be accelerated to the wafer surface with a constant sheath voltage within about 80% of the pulse cycle. The negative voltage jump amplitude of the pulse bias signal (i.e., the voltage amplitude on the wafer surface) determines the specific effect of the ion energy distribution. Therefore, changing the frequency and duty cycle of the pulse bias signal in related technologies will not change the corresponding ion energy distribution.

[0093] In summary, the pulse bias signal generation method provided in this embodiment repeatedly outputs pulse bias signals with the same negative jump amplitude value according to the signal sequence. That is, only the duty cycle of the output pulse train needs to be adjusted to provide the pulse bias signal, without adjusting the negative jump amplitude value corresponding to each pulse train. Compared with the prior art, which controls the ion energy distribution by adjusting the negative jump amplitude value, the time required to adjust the duty cycle is shorter, and the pulse bias signal can be switched rapidly, thereby controlling the ion energy to be distributed according to the target IEDF and meeting the actual process requirements.

[0094] In the pulse bias signal generation method provided in the above embodiments, the duty cycle of the pulse train is determined based on the peak ion energy and the negative jump amplitude. Furthermore, the duty cycles of pulse trains corresponding to different single-peak IEDs are different. When outputting the pulse bias signal, the duty cycle needs to be adjusted to output different pulse bias signals. It can be understood that for any pulse in the pulse train, the duty cycle is equal to the ratio of the pulse width to the pulse period. Based on this, adjusting the duty cycle naturally corresponds to two implementation methods: one is to keep the pulse period constant and adjust the pulse width; the other is to keep the pulse width constant and adjust the pulse period.

[0095] Taking a target IEDF that includes two single-peak IEDFs as an example, the ion content of one single-peak IEDF is 25%, and the ion content of the other single-peak IEDF is 75%.

[0096] Figures 6a to 6c show the waveform relationship when the pulse period remains constant and the pulse width is adjusted. Figure 6a shows the waveform of the pulse bias signal. As can be seen from Figure 6a, the signal sequence includes four pulse bias signals with the same pulse period. The first three pulse bias signals correspond to the first pulse width, and the last pulse bias signal corresponds to the second pulse width. In Figure 6b, the solid line represents the voltage waveform induced on the wafer surface when the pulse bias signal shown in Figure 6a is applied, and the dashed line represents the average sheath voltage waveform actually experienced by the ions. Correspondingly, Figure 6c shows the control result of the ion energy distribution, i.e., the curve corresponding to the target IEDF.

[0097] Accordingly, Figures 7a to 7c show the waveform relationship when the pulse width remains constant and the pulse period is adjusted. Figure 7a is a waveform diagram of the pulse bias signal. As can be seen from Figure 7a, the signal sequence includes four pulse bias signals with the same pulse width. The first three pulse bias signals correspond to the first pulse period, and the last pulse bias signal corresponds to the second pulse period. In Figure 7b, the solid line represents the voltage waveform induced on the wafer surface when the pulse bias signal shown in Figure 7a is applied, and the dashed line represents the average sheath voltage waveform actually experienced by the ions. Correspondingly, Figure 7c shows the control result of the ion energy distribution, i.e., the curve corresponding to the target IEDF.

[0098] Understandably, given a fixed pulse duty cycle, it is also possible to adjust both the pulse width and pulse period simultaneously.

[0099] As can be seen from the above, the pulse bias signal generation method provided in this application can not only adjust the ion energy by adjusting the negative jump amplitude, but also adjust the ion energy distribution by adjusting the pulse width and pulse period of the pulse bias signal. This increases the selectable parameters for adjusting the ion energy distribution and reduces the difficulty of realizing arbitrary-shaped IEDFs. Furthermore, as shown in Figure 6a or Figure 7a, the pulse bias signal provided in this application is a standard pulse signal and does not include the negative voltage ramp of the shaped pulse bias signal shown in Figure 1a. This helps to reduce the difficulty of outputting the pulse bias signal.

[0100] As mentioned earlier, controlling ions to reach the wafer surface after multiple pulse cycles via pulse bias signals is key to controlling ion energy distribution by adjusting the pulse duty cycle of the pulse bias signals in this application. Therefore, determining the number of pulse bias signals within the signal sequence and ensuring that the pulse bias signals ensure ions reach the wafer surface after multiple pulse cycles is crucial for further improving the accuracy of ion energy distribution control. Based on this, this application provides a method for determining the signal sequence, as shown in Figure 8. This method includes the following steps.

[0101] S1301: Based on the ion content ratio of each single-peak IEDF, determine the number of pulses contained in the pulse train corresponding to each single-peak IEDF.

[0102] In some embodiments, the target parameters within the process chamber can be obtained first.

[0103] In this application, the target parameters within the process chamber mainly include ion concentration and electron temperature. In practical applications, the ion concentration and electron temperature within the process chamber can be obtained using a Langmuir probe, or other plasma diagnostic equipment. This application does not limit the specific method for obtaining the aforementioned target parameters.

[0104] As mentioned earlier, the proportion of each pulse bias signal in the signal sequence is consistent with the proportion of ions in the corresponding single-peak IEDF. The proportion of ions in each single-peak IEDF is already known through the target IEDF. Based on this, the total number of pulse bias signals included in the signal sequence can be determined, and thus the number of pulse bias signals corresponding to each single-peak IEDF can be obtained.

[0105] Therefore, the first step is to determine the total number of pulse bias signals in the signal sequence based on the aforementioned target parameters and negative jump amplitude value. Specifically, the preset cycle frequency is first determined. This preset cycle frequency is the frequency of the repeated output signal sequence. The setting of the preset cycle frequency mainly considers the performance parameters of the bias power supply in the semiconductor process equipment shown in Figure 3 and related process requirements. This application does not limit the specific value of the preset cycle frequency. As a preferred frequency range, the preset cycle frequency can be selected in the range of 10Hz-10kHz.

[0106] Then, based on the ion concentration, electron temperature, and negative jump amplitude, the target frequency is determined. The pulse bias signal output according to this target frequency will enable the ions to reach the wafer surface after multiple pulse cycles. The quotient of the target frequency and the preset cycle frequency is calculated, and the total number of pulse bias signals in the signal sequence is recorded. The specific process of determining the target frequency will be explained with specific examples in the following sections.

[0107] After obtaining the total number of pulse bias signals in the signal sequence, the product of the ion content ratio of each single-peak IEDF and the obtained total number is calculated to obtain the number of pulses in the pulse train corresponding to the corresponding single-peak IEDF.

[0108] S1302: Determine the corresponding pulse train according to the number of pulses and pulse duty cycle corresponding to each single peak IEDF to obtain the signal sequence.

[0109] Having completed the aforementioned steps, we have obtained the pulse duty cycle of the pulse bias signal corresponding to each single-peak IEDF, as well as the number of pulses in the signal sequence. For each single-peak IEDF, we generate a pulse bias signal with the corresponding number of pulses according to the pulse duty cycle of that single-peak IEDF, thus obtaining the signal sequence. The determination of the pulse duty cycle can be achieved by adjusting at least one of the pulse width and pulse period, as described above, and will not be repeated here.

[0110] After obtaining the signal sequence, a pulse bias signal can be output as described above to control the ions to distribute according to the target IEDF, which will not be repeated here.

[0111] The following section describes in detail the process of outputting a pulse bias signal using the method provided in this application, taking the control of ion energy according to the IEDF distribution shown in Figure 5 as an example.

[0112] Step S1: Obtain the target IEDF.

[0113] As shown in Figure 5, the target IEDF includes four single-peak IEDFs. From left to right in Figure 5, the peak ion energies of the four single-peak IEDFs are 150 eV, 180 eV, 210 eV and 240 eV, respectively. The ion content of the four single-peak IEDFs is 40%, 30%, 20% and 10%, respectively.

[0114] Step S2: Determine the negative jump amplitude value of the pulse bias signal based on the peak energy of each ion.

[0115] The peak ion energies of the four single-peak IEDFs are 240 eV, 210 eV, 180 eV and 150 eV, respectively. The largest peak ion energy is 240 eV, which corresponds to an ion voltage of 240 V. Based on this, any amplitude greater than or equal to 240 V, such as 300 V, can be used as the negative jump amplitude.

[0116] Step S3: For each single-peak IEDF, determine the pulse duty cycle of the corresponding pulse bias signal based on the peak ion energy and negative jump amplitude of the single-peak IEDF.

[0117] The negative jump amplitude is 300V. According to formula (2), the pulse duty cycle of the pulse bias signal corresponding to each single-peak IED is calculated. Then, the pulse duty cycle of the pulse bias signal of the single-peak IED with an ion energy peak value of 240eV is 0.2, the pulse duty cycle of the pulse bias signal of the single-peak IED with an ion energy peak value of 210eV is 0.3, the pulse duty cycle of the pulse bias signal of the single-peak IED with an ion energy peak value of 180eV is 0.4, and the pulse duty cycle of the pulse bias signal of the single-peak IED with an ion energy peak value of 150eV is 0.5.

[0118] Step S4: Determine the time it takes for ions to cross the sheath in the process chamber based on the ion concentration, electron temperature, and negative jump amplitude value within the process chamber.

[0119] As mentioned earlier, the ion concentration and electron temperature within the process chamber can be obtained using Langmuir probes or other plasma diagnostic equipment, which will not be detailed here.

[0120] The time it takes for ions to cross the sheath is calculated using the following formula:

[0121] Where, τ i Indicates the time it takes for ions to cross the sheath;

[0122] k represents the Boltzmann constant;

[0123] T e Indicates electron temperature;

[0124] n0 represents the ion concentration;

[0125] ε0 represents the vacuum permittivity;

[0126] M represents the ion mass;

[0127] V out This indicates the negative jump amplitude value.

[0128] Step S5: Determine the reference frequency based on the time it takes for ions to cross the sheath and the preset number of cycles.

[0129] As mentioned above, the key to the method provided in this application is to ensure that ions need to pass through multiple pulse cycles to reach the wafer surface when passing through the sheath. The preset number of cycles mentioned in this step refers to the number of pulse cycles required for ions to reach the wafer surface.

[0130] Based on the above, the reference frequency can be calculated using the following formula:

[0131] Among them, f min Indicates the reference frequency;

[0132] τi Indicates the time it takes for ions to cross the sheath;

[0133] N represents the preset number of cycles. As a preferred implementation, to ensure that ions need to pass through multiple pulse cycles to reach the wafer surface when passing through the sheath, the preset number of cycles should be greater than or equal to 5.

[0134] Step S6: Determine any frequency greater than or equal to the reference frequency as the target frequency.

[0135] Assuming that the reference frequency calculated according to formula (4) is 10MHz, based on this, 10MHz or other frequencies greater than 10MHz can be selected as the target frequency.

[0136] Step S7: Based on the target frequency and the preset cycle frequency of the signal sequence, determine the total number of pulses contained in each pulse train in the signal sequence.

[0137] As mentioned earlier, the preset cycle frequency can be selected in the range of 10Hz-10kHz. For example, if the preset cycle frequency is 10kHz, then the ratio of the target frequency (10MHz) to the preset cycle frequency is 1000, which is the total number of pulses contained in each pulse train in the signal sequence.

[0138] Step S8: Calculate the product of the ion content ratio of each single-peak IEDF and the total number of peaks to obtain the number of pulses corresponding to the corresponding single-peak IEDF.

[0139] As mentioned earlier, in the target IEDF shown in Figure 5, the ion content of the four peak IEDFs from left to right is 40%, 30%, 20%, and 10%, respectively. Correspondingly, in the signal sequence, the percentage of pulse bias signals corresponding to the four single-peak IEDFs is also 40%, 30%, 20%, and 10%.

[0140] By calculating the product of the ion content ratio of each single-peak IED and the total number of peaks, we find that the pulse bias signal of the single-peak IED with an ion energy peak of 150 eV has 400 pulses, the pulse bias signal of the single-peak IED with an ion energy peak of 180 eV has 300 pulses, the pulse bias signal of the single-peak IED with an ion energy peak of 210 eV has 200 pulses, and the pulse bias signal of the single-peak IED with an ion energy peak of 240 eV has 100 pulses.

[0141] Step S9: Determine the corresponding pulse train according to the number of pulses and pulse duty cycle corresponding to each single peak IEDF to obtain the signal sequence.

[0142] The final signal sequence obtained by following the steps described above is shown in Figure 9.

[0143] Step S10: Repeat the output signal sequence according to the preset cycle period (i.e., 10kHz) to output a pulse bias signal.

[0144] In summary, the pulse bias signal generation method provided in this application repeatedly outputs a signal sequence composed of pulse bias signals with different pulse duty cycles. By adjusting the pulse duty cycle (i.e., pulse width and / or pulse period) of the pulse bias signal, the pulse bias signal can be rapidly adjusted. This solves the problem in the prior art where the adjustment of the negative jump amplitude of the pulse bias signal is time-consuming and cannot accurately control the ion energy distribution. It enables the distribution control of IEDFs of arbitrary shapes, significantly improves the control accuracy of ion energy distribution, and meets process requirements.

[0145] In some embodiments, this embodiment also provides a computer-readable storage medium, such as a floppy disk, optical disk, hard disk, flash memory, USB flash drive, SD (Secure Digital Memory Card), MMC (Multimedia Card), etc., in which one or more instructions for implementing the above steps are stored. When these one or more instructions are executed by one or more processors, the processors execute the pulse bias signal generation method described above. For specific implementation details, please refer to the foregoing description; further elaboration is not provided here.

[0146] In addition to the methods and apparatus described above, embodiments of this application may also be computer program products, which include computer program instructions that, when executed by a processor, cause the processor to perform the steps in the pulse bias signal generation methods according to various embodiments of this application as described above.

[0147] Computer program products can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of this application. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0148] Those skilled in the art will understand that the contents disclosed herein can be varied and modified in many ways. For example, the various devices or components described above can be implemented in hardware, or in software, firmware, or a combination of some or all of the three.

[0149] Furthermore, while this disclosure makes various references to certain elements of systems according to embodiments of this disclosure, any number of different elements may be used and operated on clients and / or servers. Elements are merely illustrative, and different aspects of the system and method may use different elements.

[0150] This disclosure uses flowcharts to illustrate the steps of a method according to embodiments of this disclosure. It should be understood that the preceding or following steps are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes.

[0151] Those skilled in the art will understand that all or part of the steps in the above methods can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium, such as a read-only memory. Optionally, all or part of the steps in the above embodiments can also be implemented using one or more integrated circuits. Accordingly, each module / unit in the above embodiments can be implemented in hardware or as a software functional module. This disclosure is not limited to any particular combination of hardware and software.

[0152] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It should also be understood that terms such as those defined in a common dictionary should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and not as having an idealized or highly formalized meaning, unless expressly defined herein.

[0153] The foregoing description is intended to illustrate the present disclosure and should not be construed as limiting it. While several exemplary embodiments of the present disclosure have been described, those skilled in the art will readily understand that many modifications may be made to the exemplary embodiments without departing from the novel teachings and advantages of the present disclosure. Therefore, all such modifications are intended to be included within the scope of the present disclosure as defined by the claims. It should be understood that the foregoing description is intended to illustrate the present disclosure and should not be construed as limiting it to the specific embodiments disclosed, and modifications to the disclosed embodiments and other embodiments are intended to be included within the scope of the appended claims. The present disclosure is defined by the claims and their equivalents.

Claims

1. A method of generating a pulsed bias signal, characterized by, The method comprises the following steps: acquiring a target ion energy distribution function (IEDF), wherein the target IEDF comprises a plurality of single-peak IEDFs, and each single-peak IEDF corresponds to an ion amount proportion and an ion energy peak value; for each single-peak IEDF, determining a pulse duty cycle of a pulse included in a corresponding pulse train based on the ion energy peak value of the single-peak IEDF and a negative jump amplitude of a pulse bias signal, wherein the pulse bias signal comprises a plurality of pulse trains, each pulse train corresponds to each single-peak IEDF, and each pulse train comprises a plurality of pulses, and the negative jump amplitude of each pulse is a same value; creating a pulse train corresponding to each single-peak IEDF according to the pulse duty cycle, to obtain a signal sequence, wherein the number proportion of the number of pulses included in each pulse train in the signal sequence is consistent with the ion amount proportion of the corresponding single-peak IEDF; and repeatedly outputting the signal sequence according to the negative jump amplitude, to output the pulse bias signal.

2. The method of claim 1, wherein, The method of creating a pulse train corresponding to each single-peak IEDF according to the pulse duty cycle to obtain a signal sequence comprises the following steps: determining the number of pulses included in each pulse train corresponding to each single-peak IEDF based on the ion amount proportion of each single-peak IEDF; determining a corresponding pulse train according to the number of pulses corresponding to each single-peak IEDF and the pulse duty cycle, to obtain a signal sequence.

3. The method of claim 2, wherein, The method of determining the number of pulses included in each pulse train corresponding to each single-peak IEDF based on the ion amount proportion of each single-peak IEDF comprises the following steps: acquiring a total number of pulses included in each pulse train in the signal sequence; calculating the product of the ion amount proportion of each single-peak IEDF and the total number, to obtain the number of pulses corresponding to each single-peak IEDF.

4. The method of claim 3, wherein, The method of acquiring the total number of pulses included in each pulse train in the signal sequence comprises the following steps: acquiring a preset cycle frequency and target parameters, wherein the preset cycle frequency is a frequency of repeatedly outputting the signal sequence, and the target parameters comprise an ion concentration and an electron temperature; determining the total number of pulses included in each pulse train in the signal sequence based on the preset cycle frequency, the target parameters and the negative jump amplitude.

5. The method of claim 4, wherein, The method of determining the total number of pulses included in each pulse train in the signal sequence based on the preset cycle frequency, the target parameters and the negative jump amplitude comprises the following steps: determining a target frequency based on the target parameters and the negative jump amplitude, wherein a pulse bias signal output according to the target frequency can enable ions to reach a wafer surface after a plurality of pulse periods; determining the quotient of the target frequency and the preset cycle frequency as the total number of pulses included in each pulse train in the signal sequence.

6. The method of claim 5, wherein, The method of determining a target frequency based on the target parameters and the negative jump amplitude comprises the following steps: acquiring a preset period number, wherein the preset period number is the number of pulse periods required for ions to reach a wafer surface; determining a time for ions to pass through a sheath in a process chamber according to the target parameters and the negative jump amplitude; and determining the target frequency based on the time for ions to pass through the sheath and the negative jump amplitude. determining a reference frequency according to the time and the preset number of periods; determining any frequency greater than or equal to the reference frequency as a target frequency.

7. The method according to any one of claims 1 to 6, characterized in that, The process of determining the pulse duty cycle of the pulse train corresponding to any of the unimodal IEDFs comprises: The pulse duty cycle of the pulse train is calculated according to the following formula: wherein m represents the pulse duty cycle of the pulse train; E p represents the ion energy peak value of a single peak IEDF; e represents the electronic charge; V out represents the negative step magnitude.

8. The method according to any one of claims 1 to 6, characterized in that, Before determining the pulse duty cycle of the corresponding pulse train based on the ion energy peak value of each unimodal IEDF and the negative jump amplitude of the pulse bias signal, the method further comprises the following steps: determining the negative jump amplitude of the pulse bias signal based on the ion energy peak value, comprising the following steps: determining the maximum value of the ion voltage required to generate each ion energy peak value as a reference voltage value; determining any amplitude greater than or equal to the reference voltage value as the negative jump amplitude of the pulse bias signal.

9. The method according to any one of claims 1 to 6, characterized in that, The repeating output of the signal sequence according to the negative jump amplitude to output the pulse bias signal comprises the following steps: controlling the direct current power supply to output a direct current voltage according to the negative jump amplitude; and repeatedly outputting the driving signal according to the pulse duty cycle of each pulse train in the signal sequence so that the switch array converts the direct current voltage into the corresponding pulse bias signal according to the pulse duty cycle.

10. A semiconductor process apparatus, characterized by, comprising: a bias power supply, a bias electrode, and a controller, wherein the bias electrode is arranged in a wafer support device of a process chamber; the bias power supply comprises a direct current power supply and a switch array, wherein the output end of the direct current power supply is connected to the input end of the switch array, and the output end of the switch array is connected to the bias electrode; the controller is connected to the control end of the direct current power supply and the switch array, respectively, and the controller comprises a memory and a processor, the memory is used to store instructions, and the processor is used to execute the pulse bias signal generation method according to the instructions stored in the memory as claimed in any one of claims 1 to 9.

Images