Plasma process method and plasma processing equipment

Abstract

The invention provides a plasma process method and plasma processing equipment, belongs to the field of plasma processing, and in order to ensure the morphology consistency of an etching structure, the plasma process method specifically comprises the steps of introducing reaction gas, putting a substrate into a reaction cavity, exciting plasma and then executing an etching step and a modification step. Wherein the sum of the power of the source radio frequency for exciting the plasma and the power of the bias radio frequency for controlling the direction is recorded as net power, so that the net power of the etching step is smaller than the net power of the modification step, the etching step is used for promoting the etching depth, and the modification step is used for trimming the side wall morphology of the etching structure. According to the process method and the equipment applying the process method, when deep hole etching is carried out, good consistency of upper and lower feature sizes can be ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of plasma etching, and in particular to the technical field of a plasma process method and a plasma processing equipment. Background Art

[0002] Micromachining of semiconductor substrates is a well-known technology that can be used to manufacture, for example, semiconductors, flat panel displays, light emitting diodes (LEDs), solar cells, etc. An important step in micromachining manufacturing is a plasma treatment process step, which is performed inside a reaction chamber into which a process gas is input. A radio frequency source is inductively and / or capacitively coupled to the reaction chamber to excite the process gas to form and maintain a plasma.

[0003] As the demand for data storage and logic processing capabilities gradually increases, the aspect ratio (the ratio of the height of a hole or groove to its radial width) of the structure formed on the substrate is also getting higher and higher. In the process of using plasma etching to form a high aspect ratio structure, the difference in the upper and lower radial dimensions of the high aspect ratio structure needs to be controlled within a small range. However, in the existing process, when the high aspect ratio etching is carried out to a certain extent, the radial dimensions of the uppermost and lowermost parts will have a large difference, resulting in defects such as bowing and bending. Summary of the invention

[0004] In order to solve the above technical problems and improve the top-bottom consistency when etching a high aspect ratio structure, the present invention provides a plasma process method for etching a substrate, comprising:

[0005] After the substrate is moved into the reaction chamber, a reaction gas is introduced, and a bias radio frequency is applied after exciting plasma using a source radio frequency to perform a first processing stage and a second processing stage, wherein the first processing stage etches the substrate downward to a first depth, and the second processing stage etches downward to a second depth based on the first depth, and the second depth is greater than the first depth;

[0006] The first processing stage comprises a first etching step and a first modification step;

[0007] The second processing stage comprises a second etching step and a second modification step;

[0008] In the first etching step, the sum of the source RF power and the bias RF power applied to the reaction chamber is a first etching net power, and in the first modification step, the sum of the source RF power and the bias RF power applied to the reaction chamber is a first modification net power, and the first etching net power is less than the first modification net power; and

[0009] In the second etching step, the sum of the source RF power and the bias RF power applied to the reaction chamber is the second etching net power. In the second modification step, the sum of the source RF power and the bias RF power applied to the reaction chamber is the second modification net power. The second etching net power is less than the second modification net power.

[0010] Optionally, the substrate temperature in the first processing stage is lower than the substrate temperature in the second processing stage.

[0011] Optionally, during the etching process of the substrate, the temperature of the substrate is less than 20°C.

[0012] Optionally, the source radio frequency and / or bias radio frequency is in pulse mode.

[0013] Optionally, the duty cycle of the pulse mode is 5% to 90%.

[0014] Optionally, in the first processing stage, the first etching step and the first modification step are cycled alternately, and / or

[0015] In the second processing stage, the second etching step and the second modification step are cycled alternately.

[0016] Optionally, the duration range of the first etching step and the first modification step is 100 ms to 100 s, and / or the duration range of the second etching step and the second modification step is 100 ms to 100 s.

[0017] Optionally, the duration of the first processing stage ranges from 10s to 1000s, and / or the duration of the second processing stage ranges from 10s to 1000s.

[0018] Optionally, the source RF and / or bias RF is in continuous mode, the duration range of the first etching step and the first modification step is: 100ms~100s, and / or the duration range of the second etching step and the second modification step is: 100ms~100s.

[0019] Optionally, the first etching step and the first modification step use the same reaction gas, and / or the second etching step and the second modification step use the same reaction gas.

[0020] Optionally, the reaction gas is one or more of hydrocarbon fluorine gas, oxygen, hydrogen bromide, carbonyl fluoride, nitrogen trifluoride, hydrogen, and phosphorus trifluoride.

[0021] Optionally, the substrate includes an overlapping layer of silicon oxide and silicon nitride; or an overlapping layer of silicon oxide and polysilicon; or a silicon oxide layer.

[0022] Optionally, the process method forms a hole with an aspect ratio greater than 40 on the substrate.

[0023] Optionally, the longitudinal etching rate of the first etching step is greater than the longitudinal etching rate of the first modification step; the longitudinal etching rate of the second etching step is greater than the longitudinal etching rate of the second modification step; the lateral etching rate of the first etching step is less than the lateral etching rate of the first modification step; and the lateral etching rate of the second etching step is less than the lateral etching rate of the second modification step.

[0024] Optionally, the net power of the second etching step is greater than the net power of the first etching step, and the net power of the second modification step is greater than the net power of the first modification step.

[0025] Optionally, the duration of the second modification step is greater than the duration of the first modification step.

[0026] Optionally, the net power range of the first etching step and the second etching step is 3000W-8000W; the net power range of the first modification step and the second modification step is 8000W-14000W.

[0027] Furthermore, the present invention also provides a plasma process method for processing a substrate, comprising:

[0028] The substrate is moved onto a base in a reaction chamber, and then a reaction gas is introduced, a source radio frequency is used to excite plasma, and then a bias radio frequency is applied, and an etching step and a modification step are performed cyclically;

[0029] In the etching step, the sum of the source RF power and the bias RF power applied to the reaction chamber is the net etching power. In the modification step, the sum of the source RF power and the bias RF power applied to the reaction chamber is the net modification power. The net etching power is less than the net modification power.

[0030] Optionally, after the etching step and the modifying step are cyclically performed at least once, the temperature of the substrate is increased and the etching step and the modifying step are continuously cyclically performed.

[0031] Optionally, the duration of the etching step is in the range of 100 ms to 100 s, and / or the duration of the modification step is in the range of 100 ms to 100 s.

[0032] Optionally, the cycle is performed for a time range of 10s to 1000s, and then the temperature of the base is increased and the etching step and the modification step are continued to be performed in a cycle.

[0033] Optionally, during substrate processing, the temperature of the susceptor is less than -30°C.

[0034] Optionally, the temperature of the base is increased in the range of 1°C to 40°C.

[0035] Furthermore, the present invention also provides a plasma processing device, comprising:

[0036] A reaction chamber, wherein a reaction space is formed inside the reaction chamber for performing plasma processing;

[0037] An air inlet structure connected to a plurality of air sources for introducing reaction gas into the reaction space;

[0038] RF source, including source RF and bias RF;

[0039] A base, which is located inside the reaction chamber, and the upper surface of the base is used to carry the substrate;

[0040] A controller, used to control the processing equipment to execute any one of the process methods according to claims 1-23.

[0041] Optionally, the base is provided with a temperature regulator, and the adjustment range of the temperature regulator is -80°C to 30°C.

[0042] One of the above technical solutions has the following advantages or beneficial effects: the etching depth is quickly advanced in the longitudinal direction through the etching step, and the side wall protection layer of the target structure is radially trimmed through the modification step; by utilizing the cycle of the etching step and the modification step, the trimming result of the modification step can assist the progress of the next etching step, and the etching step can progress downward faster than without the modification step; by controlling the execution time of the etching step and the modification step, the upper and lower consistency of the morphology and the etching efficiency are taken into account, and the etching of the target structure is completed within an optimized time length; at the same time, in some technical solutions, the control of the substrate temperature is introduced. When the modification step and the etching step are cycled a certain number of times, the substrate temperature is increased. Compared with maintaining a constant temperature condition throughout the entire process stage, the net power is reduced when etching a target of the same depth. While ensuring that the etching and modification effects remain unchanged, the pressure range of the components in the chamber is reduced to prevent discharge from damaging the components or the substrate. In some technical solutions, when moving from one processing stage to another, as the etching depth increases, the net power of the etching step and the modification step is increased accordingly, so that the same etching effect can be obtained in the deep part of the hole as in the shallow part. Combined with temperature adjustment, the degree of increase in net power can be reduced. In some processing stages, the net power of the corresponding step can even be kept unchanged by adjusting the temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 A schematic diagram of a structure in which a portion is etched on a substrate using a process method;

[0045] Figures 2A-2D A schematic diagram of the structure formed during the etching of a substrate by the process method of the present invention;

[0046] Figure 3 It is a schematic diagram of the structure of applying the process method of the present invention to another etching object;

[0047] Figures 4A-4D Schematic diagram of the process steps of different embodiments of the present invention;

[0048] Figure 5 A schematic diagram of the structure of a plasma treatment device using the process method of the present invention;

[0049] Figure 6 It is a radio frequency schematic diagram of embodiment 1;

[0050] Figure 7 This is a radio frequency schematic diagram of the second embodiment. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Figure 1The schematic diagram is a structure diagram of a part of a substrate being etched using a process method, wherein the substrate includes a substrate 110, which is usually a silicon material, and a layer 120 to be etched formed on the substrate 110. After plasma is generated, a hole or other structure of shape needs to be formed in the layer 120 to be etched. The hole is used as a representative for explanation below. A mask layer 130 is provided on the layer 120 to be etched. The mask layer 130 is made into a certain pattern after the previous process such as the photolithography process, resulting in a part of the layer 120 to be etched being exposed and can be bombarded by plasma and etched away, while the part covered by the mask layer 130 is exempted from the bombardment and is retained, and finally the required hole is formed. In theory, the boundary of the retained part of the layer 120 to be etched strictly corresponds to the boundary of the mask layer 130, but in the actual plasma processing process, due to the lateral movement of particles, the side wall of the hole will be over-etched, and finally the lateral size of the hole will be larger than the expected value, resulting in the failure of subsequent filling and other process results. Therefore, in the actual plasma etching process, in addition to requiring the particles to move downward to react with the layer to be etched 120, it is also necessary to form a protective layer 140 on the side wall of the hole. The essence of the protective layer 140 is some hydrocarbon polymers, which can prevent the free radicals in the plasma from reacting with the side wall of the hole to produce lateral etching. However, the problem that follows is that the uniformity of the thickness of the protective layer 140 in the vertical direction cannot be guaranteed. In fact, without changing the process, the protective layer 140 near the top is thicker, and the thickness gradually increases over time, which will eventually cause the opening of the hole to be blocked, preventing the plasma from further etching downward.

[0053] The present invention provides a plasma process method for etching a substrate, such as Figure 2A As shown, the substrate includes a substrate 110, a layer to be etched 120 and a mask layer 130. The steps of an embodiment of the process method are as follows: Figure 4A As shown, the process includes moving the substrate into the reaction chamber and then introducing the reaction gas, which is selected according to the material of the different layers to be etched 120, and finally achieving high selectivity etching with the mask layer 130. Then, the reaction gas is excited to form plasma using source radio frequency, which usually has a higher frequency to accelerate the collision of particles in the reaction gas to form plasma, and then bias radio frequency is applied to perform the first processing stage 410 and the second processing stage 420, which usually has a lower frequency and is used to form an electric field to make the charged particles move toward the substrate and react physically or chemically with the layer to be etched 120 to perform the etching process, wherein the depth to be etched in the second processing stage 420 is greater than the depth to be etched in the first processing stage 410, that is, at the end of the first processing stage 410, the hole etched in the layer to be etched 120 has a first depth, and the second processing stage 420 continues to etch downward on the basis of the first processing stage 410, and at the end of the second processing stage 420, the hole etched in the layer to be etched 120 has a second depth, and the second depth is greater than the first depth.

[0054] Among them, the first processing stage 410 includes a first etching step and a first modification step; the sum of the effective powers of the source RF power and the bias RF power within a period of time is recorded as the net power, then the first etching step has a first etching net power, and the first modification step has a first modification net power. The difference between the first etching step and the first modification step is that the first etching net power is less than the first modification net power.

[0055] In the first etching step, Figure 2A-2B As shown, as the reaction time progresses, the plasma will form a protective layer 140 on the side wall of the hole. However, the closer to the hole mouth, the more polymer is deposited, resulting in a thicker protective layer 140 at this position. The first etching net power is increased to the first modification net power. In the same time, the energy obtained by the particles in the plasma is enhanced, with higher isotropic kinetic energy, and a stronger bombardment can occur in the lateral direction, resulting in the surface polymer of the protective layer 140 being bombarded away. Similarly, because the particles move from top to bottom, the polymer closer to the top is easier to be bombarded away, and finally the protective layer 140 is modified to obtain the following Figure 2C The etching results are shown.

[0056] Next, the second processing stage 420 is performed, which includes a second etching step and a second modification step. The second etching step has a second etching net power, and the second modification step has a second modification net power, wherein the second etching net power is less than the second modification net power. After the second etching step is performed continuously on the basis of the first processing stage 410, the following is formed. Figure 2D As shown in the etching result, the unevenness of the protective layer 140 occurs again near the hole mouth. At this time, the second etching net power is increased to the second modification net power to perform the second modification step, bombarding the excess polymer at the hole mouth to modify the morphology of the protective layer 140.

[0057] In summary, during the process, lateral etching and vertical etching always exist at the same time, such as Figure 2A-2B As shown by the arrow vector, the direction of the arrow represents the etching direction, and the length of the arrow represents the etching rate. However, by adjusting the net power, the longitudinal etching rate of the first etching step and the second etching step is greater than the longitudinal etching rate of the first modification step and the second modification step, and the lateral etching rate of the first etching step and the second etching step is less than the lateral etching rate of the first modification step and the second modification step. The first etching step and the second etching step mainly play the role of etching the substrate downward, and the first modification step and the second modification step mainly play the role of flattening the sidewall protection layer of the hole.

[0058] In some embodiments, the material of the substrate 110 may be sapphire, silicon carbide, germanium, gallium, etc., which can be used as a material for semiconductor processes, in addition to silicon; the layer to be etched 120 may be the same material, such as silicon dioxide, silicon nitride, single crystal silicon, polycrystalline silicon, or the above materials after doping, or may be an alternating stack of any two of silicon dioxide, silicon nitride, and polycrystalline silicon, such as Figure 3 In one embodiment shown, the layer to be etched 120 is an alternating stack of silicon dioxide layers 121 and silicon nitride layers 122 .

[0059] Because when using plasma for etching, as the etching depth increases, in addition to the polymer in the plasma being deposited on the side wall of the hole to form the protective layer 140, the byproducts of the reaction between the material of the etched layer 120 and the plasma are extracted from the hole and are also deposited on the side wall of the hole to form a part of the protective layer 140. At this time, compared with the modification step in the previous stage, the net power value of the modification step in the next stage can be increased, thereby improving the bombardment effect and modifying the protective layer 140 in the same time. However, too high net power will increase the risk of damage to various components in the chamber, and put forward higher requirements on the design of the chamber and the material of the components, which is not conducive to the cost reduction and mass production promotion of the product. In some other embodiments of the present invention, the substrate temperature of the second processing stage 420 is set higher than the substrate temperature of the first processing stage 410. When the substrate temperature is increased, the byproducts of the reaction and the energy obtained by the polymer in the plasma have higher activity, that is, lower viscosity. However, because the depth of the hole etched in the second processing stage 420 is deeper, the byproducts are more difficult to be extracted, and more are accumulated in the hole, resulting in a larger amount of raw materials for forming the protective layer 140. Therefore, although the viscosity is reduced, the thickness of the protective layer 140 can still be maintained at a certain value, which is sufficient to protect the sidewalls. Therefore, in the second processing stage 420, although the etching depth increases, it is not necessary to significantly increase the net RF power to achieve a sufficient modification effect. In some embodiments, the temperature of the substrate is increased, but the temperature of the substrate needs to be controlled to be always less than 20°C. Excessive temperature will significantly reduce the protective effectiveness of the protective layer.

[0060] In some other embodiments, the difference from the above embodiments is that, Figure 4BAs shown, the first processing stage 410 of the present invention includes a plurality of first etching steps and a first modification step performed alternately. Similarly, the second processing step 420 may also include a plurality of second etching steps and a second modification step performed alternately. In one embodiment, the bias RF and / or the source RF is in a pulse mode, and the duty cycle of the pulse mode may be between 5% and 90%. The pulse mode here is a pulse modulated on the basis of the inherent frequency of the RF power supply, that is, the frequency of the RF power supply itself is temporarily ignored, and the RF is modulated into a pulse, and the real electromagnetic mode will be a pulse mode after the frequency of the RF itself and the modulated frequency are superimposed. In the first processing stage or the second processing stage, when the pulse mode is in a low power position, it corresponds to the first etching step or the second etching step, and when the pulse RF is in a high power position, it corresponds to the first modification step or the second modification step. In the processing stage (first processing stage or second processing stage), the steps (first etching step, second etching step, first modification step or second modification step) can also each include multiple pulsed radio frequency cycles, and the difference between different steps can be adjusted by adjusting the net power of the pulse cycle in each step. The net power calculation of the pulsed radio frequency can be determined by the product of the high and low power values ​​and the corresponding duty cycle. In this embodiment, the sum of the time of the etching step and the modification step is the period of the pulse mode, but according to the actual process requirements, the time between different steps can be different, and the pulse period in each step can also be adjusted. The time range for each step is 100ms-100s. The time for each stage is 10s-1000s.

[0061] In other embodiments, the difference from the above embodiments lies in that the bias RF and / or source RF is in pulse mode, but each step contains multiple pulse cycles. For example, the cycle of the pulse mode can be set between 0.5ms and 100ms, and the time range for each step is between 100ms and 100s. The pulse modes included in different steps have the same maximum and minimum power values, and the net power is changed by adjusting the duty cycle of the pulses between different steps. For example, in the same processing stage, the maximum and minimum powers of the etching step and the modification step are the same, but the duty cycle of the maximum power of the modification step is larger. Therefore, when calculating the net power, the modification step obtains a larger net power.

[0062] In other embodiments, the difference from the above embodiments is that the source RF and / or bias RF can also be a continuous mode, and its waveform can be sinusoidal, linear or fixed. Correspondingly, the duration of each step is 100ms to 100s. The duration of each stage is 10s-1000s. When calculating the net power, compared with the pulse mode, the duty cycle is not required to participate in the calculation. Compared with the pulse mode, the continuous mode lasts longer for the same step, so the instantaneous maximum power of the continuous mode is smaller than that of the pulse mode to reduce the risk of damage to the chamber components. According to different process requirements, the duration and net power values ​​between different steps can be different.

[0063] In other embodiments, the difference from the above embodiments is that, in order to finally obtain a hole with a sufficient aspect ratio, for example, a hole with an aspect ratio greater than 40, Figure 4C As shown, the present invention may include multiple processing stages, such as the third processing stage 430, or continue to add three or more processing stages. The third processing stage 430 also includes a third etching step and a third modification step or an alternating cycle of the two. In order to reduce the risk of damage to the chamber due to high net power, the temperature of the processing stage (the first processing stage, the second processing stage, the third processing stage or the subsequent processing stage) can be gradually increased. And ensure that the temperature of the substrate is always less than 20°C.

[0064] In some embodiments, the gas used for plasma treatment may be one or more of carbon-hydrogen-fluorine gas, oxygen, hydrogen bromide, carbonyl fluoride, nitrogen trifluoride, hydrogen, and phosphorus trifluoride. The carbon-hydrogen-fluorine gas used may be one or more of CH2F2, CH3F, C2HF5, C3HF5, C3H2F4, C3H2F6, C4H2F6, and C4F8.

[0065] In some embodiments, the frequency range of the source RF is 13 MHz-120 MHz, and the power range is 500 W-8000 W; the frequency range of the bias RF is 50 kHz-2 MHz, and the power range is 1000 W-34000 W. The net power range of the etching step is 3000 W-8000 W, and the net power range of the modification step is 8000 W-14000 W.

[0066] The present invention also provides another plasma process method, such as Figure 4DAs shown, the difference from the above embodiment is that the substrate is moved onto the base of the reaction chamber, and then the reaction gas is introduced, and the bias radio frequency is applied after the source radio frequency is used to excite the plasma, and the etching step and the modification step are cyclically performed; in the etching step, the sum of the source radio frequency power and the bias radio frequency power applied to the reaction chamber is the net etching power, and in the modification step, the sum of the source radio frequency power and the bias radio frequency power applied to the reaction chamber is the net modification power, and the net etching power is less than the net modification power. The etching step mainly plays the role of pushing the depth of the hole downward, and the modification step mainly plays the role of trimming the morphology of the protective layer so that the protective layer does not hinder the downward etching. After the etching step and the modification step are cyclically performed at least once, for example, after performing the etching step-modification step-etching step-modification step, the temperature of the base is increased and the etching step and the modification step are continuously cyclically performed. Among them, the temperature adjustment value of each heating operation of the base is 1°C to 40°C, and the temperature of the base is always kept below -30°C. In this way, it can be ensured that the etching step and the modification step can be coordinated with the temperature, and finally a hole with a good sidewall morphology is obtained. If the adjustment value is too large or too small, the thickness of the protective layer will deviate from the threshold, affecting the interaction with the etching step and the modification step.

[0067] Embodiment 1

[0068] like Figure 6 As shown, in this embodiment, both the source RF and the bias RF are in pulse mode, the frequency of the source RF is 60 MHz, the maximum power is 5000 W, and the minimum power is 500 W. The waveform is as shown in FIG. Figure 6 As shown by the solid line; the frequency of the biased RF is 400KHz, the maximum power is 30000W, and the minimum power is 1000W. Its waveform is as follows Figure 6 As shown by the dotted line. The temperature of the base is -60°C. In the first etching step, the duty cycle of the source RF is 25%, and the duty cycle of the bias RF is 5%. In the first etching step, the net power value is 5000*25%+500*(1-25%)+30000*5%+1000*(1-5%)=4075, in W; in the first modification step, the duty cycle of the source RF is 30%, and the duty cycle of the bias RF is 21%. In the same way, the net power value can be calculated to be 8940W; in the second etching step, the duty cycle of the source RF is 25%, and the duty cycle of the bias RF is 8%. In the same way, the net power can be calculated to be 4945W; in the second modification step, the duty cycle of the source RF is 30%, and the duty cycle of the bias RF is 25%. In the same way, the net power can be calculated to be 10100W.

[0069] The following data is obtained:

[0070]

[0071] In this embodiment, in the same processing stage, the net power value of the modification step is greater than the net power value of the etching step. As the etching depth increases, the total net power of the etching step and the modification step increases in the adjacent processing stages because the etching rate and the modification rate need to be increased accordingly after the depth increases from top to bottom to obtain better morphological consistency of the etching target in unit time. The pore size difference (CD difference) between the top and bottom of the etched hole is 40nm, which is significantly improved compared to the prior art that does not change the net power.

[0072] In this embodiment, the change of net power is achieved by changing the duty cycle. In other embodiments, it can also be achieved by changing the maximum or minimum value of the RF power. In addition, in this embodiment, the bias RF and the source RF have substantially the same phase. In other embodiments, they can also have different phases, which has no effect on the calculation of net power. When the phases are the same, the synchronized phases are more likely to couple energy to the plasma within a certain period of time.

[0073] Embodiment 2

[0074] like Figure 7As shown, the difference between this embodiment and the embodiment is that both the source RF and the bias RF use continuous RF, the frequency of the source RF is 60MHz; the frequency of the bias RF is 400KHz. In the first etching step, the power of the source RF is 1000W, the power of the bias RF is 3000W, then the net power value is the sum of the power of the source RF and the bias RF, 4000W; in the first modification step, the power of the source RF is 2000W, the power of the bias RF is 7000W, then the net power value can be calculated to be 9000W in the same way; in the second etching step, the power of the source RF is 1000W, the power of the bias RF is 4000W, then the net power can be calculated to be 5000W in the same way; in the second modification step, the power of the source RF is 2000W, the power of the bias RF is 8000W, then the net power can be calculated to be 10000W in the same way. In this embodiment, in the first processing stage, when switching from the first etching step to the second etching step, the power of the source RF and the bias RF are increased at the same time, but the power of the bias RF is increased to a greater extent, because the source RF is mainly used to maintain the stability of the plasma, and the bias RF is mainly used to give the charged particles the directionality of movement toward the substrate. In order to maintain the basic stability of the plasma density, the power of the source RF changes less, and the adjustment of the bias RF power has less effect on the plasma density. In other embodiments, the power of the source RF can also be greatly changed without affecting the overall etching result. At the same time, in the second processing stage, the power of the bias RF is increased in the second etching step compared to the first etching step in the first processing stage, and the second modification step is increased compared to the first modification step in the first processing stage, because when the etching depth increases, the ability of downward etching and the ability of lateral modification need to be increased accordingly, so the corresponding power is also higher than that of the first stage.

[0075] The following data is obtained:

[0076]

[0077] The use of continuous RF can obtain the same net power value as pulsed RF in the corresponding step by controlling the power values ​​of source RF and bias RF. However, in the corresponding step, the instantaneous power value of continuous RF can be reduced accordingly compared with the pulse mode to reduce the burden on the equipment. At the same time, in some cases, such as the specification limitations of the RF source, the RF source can also provide basically the same etching results.

[0078] Embodiment 3

[0079] The difference between this embodiment and the first embodiment is that the temperature of the base is changed at different processing stages to obtain the following data:

[0080]

[0081] As the etching depth increases, the reaction substances in the hole are more difficult to be discharged and are easily deposited on the side walls, hindering the etching process. By increasing the temperature of the base from -60°C to -50°C, the kinetic energy of different particles is increased, and their viscosity is reduced, making it easier to discharge out of the hole. In this way, even if the net power is maintained unchanged in the same processing stage, good consistency of the upper and lower apertures can be obtained. The aperture difference (CD difference) between the upper and bottom of the etched hole can be reduced to 30nm

[0082] Embodiment 4

[0083] The difference between this embodiment and the third embodiment is that there are multiple processing stages, in each processing stage, the etching step and the modification step are cyclically performed, and the temperature of adjacent processing stages is increased, and the time of different steps is adjusted. The following data are obtained:

[0084] In the first processing stage, the temperature of the base is set to -50°C, and the entire processing stage lasts for 600 seconds. In this processing stage, the first etching step and the first modification step are cyclically performed, and the net power of the first etching step is 4000W, which lasts for 3 seconds, and the net power of the first modification step is 9000W, which lasts for 3 seconds; in the second processing stage, the temperature of the base is set to -40°C, and the entire processing stage lasts for 600 seconds. In this processing stage, the second etching step and the second modification step are cyclically performed, and the net power of the second etching step is 5000W, which lasts for 3 seconds, and the net power of the second modification step is 10000W, which lasts for 5 seconds; in the third processing stage, the temperature of the base is set to -30°C, and the entire processing stage lasts for 600 seconds. In this processing stage, the third etching step and the third modification step are cyclically performed, and the net power of the third etching step is 5000W, which lasts for 3 seconds, and the net power of the second modification step is 10000W, which lasts for 9 seconds. As the etching depth increases, the trimming of the sidewall becomes increasingly difficult, and the modification time needs to be extended. In other embodiments, according to the etching requirements, the number of processing stages can be further increased, and the base temperature between each processing stage is different. Through the above parameters and steps, an etching result with a CD difference of 30nm can be finally achieved in a hole structure with an aspect ratio of more than 60.

[0085] Figure 5A schematic diagram of the structure of a capacitively coupled plasma (CCP) etching device is shown. The capacitively coupled plasma etching device is a device that generates plasma in a reaction chamber by capacitive coupling by an RF power source applied to an electrode plate and is used for etching. It includes a reaction chamber 500, and the interior of the reaction chamber 500 forms a reaction space for performing plasma treatment. In some embodiments, the reaction chamber 500 includes a roughly cylindrical reaction chamber side wall 501 made of a metal material, and an opening 502 is provided on the reaction chamber side wall for accommodating the entry and exit of a substrate. An air intake structure is provided at the upper part of the reaction chamber, which connects a gas source 523 and a reaction space, and is used to input a reaction gas into the reaction chamber. Specifically, the air intake structure includes a gas shower head 522 and a mounting substrate 521 connecting the shower head 522 and the top wall of the reaction chamber. In the reaction chamber, a base 511 is also arranged opposite to the gas shower head. The gas shower head 522 also serves as the upper electrode of the reaction chamber. An electrostatic chuck is arranged above the base 521 and also serves as the lower electrode of the reaction chamber. The area between the upper electrode and the lower electrode is the reaction area. At least one RF power source 515 is applied to one of the upper electrode or the lower electrode through a matching network 516 to generate an RF electric field between the upper electrode and the lower electrode. The RF source may include a source RF and a bias RF. The source RF is used to dissociate the reaction gas into plasma. The plasma contains a large number of active particles such as electrons, ions, excited atoms, molecules and free radicals. The above active particles can undergo a variety of physical and chemical reactions with the surface of the substrate to be processed, so that the morphology of the substrate surface changes, that is, the etching process is completed. The bias RF is used to control the movement direction of the plasma. Among them, a controller 510 is used to execute the steps of the above process method.

[0086] In some embodiments, a temperature regulator is provided inside the base 511, specifically, it may include a fluid channel 514 and its circulation structure, which can be passed through a coolant circulation to cool down or heat up the base, and the controlled temperature range of the base is -80°C to 30°C. The temperature regulator and the gas source are jointly regulated by the controller 510 to switch different process steps.

[0087] An exhaust pump 541 is also provided below the reaction chamber 500 to discharge the reaction byproducts from the reaction chamber and maintain the vacuum environment of the reaction chamber. An electrostatic electrode 512 is provided inside the electrostatic chuck to generate electrostatic suction to support and fix the substrate W to be processed during the process. A heating device 513 is provided below the electrostatic chuck to control the temperature of the substrate during the process. A focusing ring 531 and an edge ring 532 are provided around the base, and the focusing ring and the edge ring are used to adjust the electric field or temperature distribution around the substrate to improve the uniformity of substrate processing. A protective ring 533 is provided radially outside the focusing ring 531. A plasma confinement ring 542 is provided around the protective ring 533, and an exhaust channel is provided on the plasma confinement ring. By reasonably setting the depth and width ratio of the exhaust channel, the plasma is confined to the reaction area between the upper and lower electrodes while the reaction gas is discharged, so as to avoid leakage of plasma to the non-reaction area and damage to the components in the non-reaction area. A lifting ring 543 is provided above the plasma confinement ring 542, which is used to protect the side wall from plasma bombardment. A middle grounding ring is provided below the plasma confinement ring 542, and the middle grounding ring is used to provide electric field shielding for the plasma confinement ring; a lower grounding ring 535 is provided below the middle grounding ring, and the middle grounding ring and the lower grounding ring 535 are electrically connected to form a radio frequency grounding loop in the reaction chamber. A shielding ring 534 is provided between the lower grounding ring and the base, and is used to shield the radio frequency signal applied to the base in the base, so as to realize electrical isolation between the base and the lower grounding ring.

[0088] The plasma processing equipment disclosed in the present invention is not limited to the above-mentioned CCP type plasma processing device, and can also be applied to other plasma processing devices, which will not be described in detail here.

[0089] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A plasma process for etching a substrate, characterized in that: include: After the substrate is moved into the reaction chamber, a reaction gas is introduced, and a bias radio frequency is applied after exciting plasma using a source radio frequency to perform a first processing stage and a second processing stage, wherein the first processing stage etches the substrate downward to a first depth, and the second processing stage etches downward to a second depth based on the first depth, and the second depth is greater than the first depth; The first processing stage comprises a first etching step and a first modification step; The second processing stage comprises a second etching step and a second modification step; In the first etching step, the sum of the source RF power and the bias RF power applied to the reaction chamber is a first etching net power, and in the first modification step, the sum of the source RF power and the bias RF power applied to the reaction chamber is a first modification net power, and the first etching net power is less than the first modification net power; and In the second etching step, the sum of the source RF power and the bias RF power applied to the reaction chamber is the second etching net power. In the second modification step, the sum of the source RF power and the bias RF power applied to the reaction chamber is the second modification net power. The second etching net power is less than the second modification net power.

2. The plasma processing method according to claim 1, characterized in that: The substrate temperature in the first process stage is lower than the substrate temperature in the second process stage.

3. The plasma processing method according to claim 2, characterized in that: During the etching process of the substrate, the temperature of the substrate is less than 20°C.

4. The plasma processing method according to claim 1, characterized in that: The source radio frequency and / or the bias radio frequency are in pulse mode.

5. The plasma processing method according to claim 4, characterized in that: The duty cycle of the pulse mode is 5% to 90%.

6. The plasma processing method according to claim 1, characterized in that: In the first processing stage, the first etching step and the first modification step are cycled alternately, and / or In the second processing stage, the second etching step and the second modification step are cycled alternately.

7. The plasma processing method according to claim 4, characterized in that: The duration of the first etching step and the first modification step is in the range of 100ms to 100s, and / or the duration of the second etching step and the second modification step is in the range of 100ms to 100s.

8. The plasma processing method according to claim 1, characterized in that: The duration of the first processing stage ranges from 10s to 1000s, and / or the duration of the second processing stage ranges from 10s to 1000s.

9. The plasma processing method according to claim 1, characterized in that: The source RF and / or bias RF are in continuous mode, the duration of the first etching step and the first modification step is in the range of 100ms to 100s, and / or the duration of the second etching step and the second modification step is in the range of 100ms to 100s.

10. The plasma processing method according to claim 1, characterized in that: The first etching step and the first modification step use the same reaction gas, and / or the second etching step and the second modification step use the same reaction gas.

11. The plasma processing method according to claim 10, characterized in that: The reaction gas is one or more of hydrocarbon fluorine gas, oxygen, hydrogen bromide, carbonyl fluoride, nitrogen trifluoride, hydrogen, and phosphorus trifluoride.

12. The plasma processing method according to claim 1, characterized in that: The substrate includes an overlapping layer of silicon oxide and silicon nitride; or an overlapping layer of silicon oxide and polysilicon; or a silicon oxide layer.

13. The plasma processing method according to claim 12, characterized in that: The process method forms a hole with a depth-to-width ratio greater than 40 on the substrate.

14. The plasma processing method according to claim 1, characterized in that: The longitudinal etching rate of the first etching step is greater than the longitudinal etching rate of the first modification step; the longitudinal etching rate of the second etching step is greater than the longitudinal etching rate of the second modification step; the lateral etching rate of the first etching step is less than the lateral etching rate of the first modification step; The lateral etching rate of the second etching step is less than the lateral etching rate of the second modification step.

15. The plasma processing method according to claim 1, characterized in that: The net power of the second etching step is greater than the net power of the first etching step, and the net power of the second modification step is greater than the net power of the first modification step.

16. The plasma processing method according to claim 1, characterized in that: The duration of the second modification step is greater than the duration of the first modification step.

17. The plasma processing method according to claim 1, characterized in that: The net power range of the first etching step and the second etching step is 3000W-8000W; the net power range of the first modification step and the second modification step is 8000W-14000W.

18. A plasma process for processing a substrate, characterized in that: include: The substrate is moved onto a base in a reaction chamber, and then a reaction gas is introduced, a source radio frequency is used to excite plasma, and then a bias radio frequency is applied, and an etching step and a modification step are performed cyclically; In the etching step, the sum of the source RF power and the bias RF power applied to the reaction chamber is the net etching power. In the modification step, the sum of the source RF power and the bias RF power applied to the reaction chamber is the net modification power. The net etching power is less than the net modification power.

19. The process according to claim 18, characterized in that: After the etching step and the modifying step are cyclically performed at least once, the temperature of the substrate is increased and the etching step and the modifying step are cyclically performed continuously.

20. The process according to claim 18, characterized in that: The duration of the etching step is in the range of 100 ms to 100 s, and / or the duration of the modification step is in the range of 100 ms to 100 s.

21. The process according to claim 19, characterized in that: The cycle is carried out for a time range of 10s to 1000s, and then the temperature of the base is increased and the etching step and the modification step are continued to be carried out in a cycle.

22. The process according to claim 19, characterized in that: During the substrate processing, the temperature of the susceptor is less than -30°C.

23. The process according to claim 19, characterized in that: The temperature of the base is increased in the range of 1°C to 40°C.

24. A plasma processing device, characterized in that: include: A reaction chamber, wherein a reaction space is formed inside the reaction chamber for performing plasma processing; An air inlet structure connected to a plurality of air sources for introducing reaction gas into the reaction space; RF source, including source RF and bias RF; A base is located inside the reaction chamber, and the upper surface of the base is used to support the substrate; a controller is used to control the processing equipment to execute any one of the process methods as claimed in claims 1-23.

25. The plasma processing apparatus according to claim 24, wherein: The base is provided with a temperature regulator, and the regulating range thereof is -80°C to 30°C.

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