Substrate surface flow distribution control system and method

Abstract

The invention relates to the technical field of semiconductor manufacturing, and provides a substrate surface flow distribution control system. The system comprises a reaction cavity in which a base is arranged, and the base is configured to bear a substrate; gas flows into the reaction cavity from the gas inlet end; gas flows out of the reaction cavity from the exhaust end, the exhaust end comprises a plurality of control zones, and the control zones are configured to adjust gas flow distribution on the surface of the substrate through mass flow distribution under the condition that the pressure of the reaction cavity is not changed. According to the invention, the plurality of control subareas are arranged at the exhaust end, so that the distribution of the flow flowing through the surface of the substrate can be accurately controlled on the premise that the pressure of the reaction cavity is constant based on mass flow distribution, thereby better controlling the reaction process of the semiconductor process and improving the film forming uniformity.

Description

Technical Field

[0001] The present invention generally relates to the field of semiconductor manufacturing technology. Specifically, the present invention relates to a substrate surface flow distribution control system and method. Background Art

[0002] In order to ensure the stability of semiconductor processes, maintaining stable airflow on the substrate surface is an important step. Figure 1 FIG. 1 shows a schematic diagram of a semiconductor reaction chamber in the prior art. Figure 1 As shown, semiconductor process systems usually use three methods to control vacuum / pressure in semiconductor process steps, including: controlling the pumping speed by changing the speed of the mechanical blower; controlling the pumping speed by adjusting the ballast gas feed flow between the process chamber and the pump; and controlling the pumping speed by adjusting the vacuum conductivity of the vacuum downstream front line using a throttle valve. Table 1 shows a comparison of the three control methods of blower speed control (Blower Speed ​​Control), ballast gas control (Ballast Gas Control) and downstream control (Downstream Control). As shown in Table 1, these three methods all have their own shortcomings.

[0003] Table 1

[0004]

[0005] Figure 2A -D shows a schematic diagram of a vacuum control valve in the prior art. Figure 2A In the gate valve shown, the movement position of the raft plate is linearly related to the output of the motor rotation, and the raft opening is crescent-shaped, which has a large nonlinear relationship with the rotation of the raft plate or the motor. Figure 2B In the gate valve shown, the movement position of the raft is linearly related to the output of the motor rotation, and the raft opening presents a cosine relationship and a nonlinear relationship with the raft or motor rotation. Figure 2C In the butterfly valve shown, the movement position of the raft is three-dimensional in space, which is related to the nonlinear rotation of the motor. When the raft is closed at nearly 0°, the relationship between the flow rate and the position of the motor is unstable or uncertain, or it can be expressed as over-response. When the valve body is in a fully open state at nearly 90°, the change in the opening angle has almost no effect on the flow rate, or it can be expressed as under-response. Therefore, some measures must be taken to make the valve work in the middle section close to 45°. Figure 2D In the vertically symmetrical structure valve shown in the figure, the movement position of the raft is linearly related to the output of the motor rotation, and the raft opening is cylindrical and linearly related to the motor output. In addition, some valves use a double-acting air linear cylinder controlled by a pilot valve, and its structure is similar to Figure 2DThe opening of the valve is similar to the cylindrical opening of the cylinder, and the opening of the valve is proportional to the stroke of the cylinder, showing a linear relationship. Due to the structural limitations of the existing vacuum control valve, it is difficult to ensure the pressure stability in the reaction chamber during the valve adjustment process. Summary of the invention

[0006] In order to at least partially solve the above problems in the prior art, the present invention provides a substrate surface flow distribution control system, comprising:

[0007] a reaction chamber, wherein a susceptor is disposed therein, and the susceptor is configured to carry a substrate;

[0008] an air inlet end, wherein the gas flows into the reaction chamber from the air inlet end; and

[0009] An exhaust end, wherein the gas flows out of the reaction chamber from the exhaust end, and the exhaust end includes a plurality of control partitions, and the plurality of control partitions are configured to adjust the gas flow distribution on the substrate surface by mass flow distribution when the pressure of the reaction chamber remains unchanged.

[0010] In one embodiment of the present invention, it is provided that the gas flow distribution on the substrate surface is adjusted by the multiple control partitions through mass flow distribution under the condition that the pressure of the reaction chamber remains unchanged, including:

[0011] The gas on the substrate surface forms an asymmetric mass flow field through mass flow distribution by multiple control partitions to offset the asymmetry of the semiconductor film forming or etching process and improve the uniformity of the semiconductor film forming or etching process results.

[0012] In one embodiment of the present invention, it is provided that the air inlet end comprises:

[0013] a showerhead disposed above the susceptor, wherein gas flows from the showerhead into the reaction chamber and flows from above the substrate toward the substrate; and

[0014] An inlet end mass flow meter is connected to the shower head, and the inlet end mass flow meter is configured to monitor the flow rate of the gas flowing into the reaction chamber.

[0015] In one embodiment of the present invention, it is provided that when the gas flows in and out in a direction horizontal to the substrate, the gas on the substrate surface is superimposed with peaks and troughs 180 degrees in opposite phase by mass flow distribution by multiple control partitions to improve the uniformity of the semiconductor film forming or etching process results; or

[0016] When the gas flows into the shower head from above the substrate and flows out from around the substrate, the gas on the substrate surface forms a non-radial flow field through mass flow distribution by multiple control partitions to offset the non-radial nature of the semiconductor film forming or etching process and improve the uniformity of the semiconductor film forming or etching process results.

[0017] In one embodiment of the present invention, it is provided that flow correction is performed on a plurality of control partitions of the exhaust end by means of the intake end mass flow meter.

[0018] In one embodiment of the present invention, it is provided that the system also includes a process detection device, and the process monitoring device is configured to determine that the etching or plasma ashing process reaction is completed when it is detected that the intake mass flow rate and other important process parameters at the intake end remain unchanged and the exhaust flow rate at the exhaust end changes suddenly.

[0019] In one embodiment of the present invention, it is provided that the process monitoring device is further configured to determine that the system needs maintenance when it is detected that the intake air flow rate and the exhaust air flow rate deviate from the daily benchmark.

[0020] In one embodiment of the present invention, it is provided that gas is introduced into the gas inlet end by a push method, and gas is exhausted by a pull method at the gas exhaust end, so as to adjust the gas flow distribution on the substrate surface by a push-pull method.

[0021] In one embodiment of the present invention, the plurality of control partitions are arranged around the susceptor, wherein the gas flows from the center of the substrate to the periphery of the substrate and flows out of the reaction chamber from the plurality of control partitions.

[0022] In one embodiment of the present invention, it is provided that the exhaust end further comprises:

[0023] An exhaust pump is connected to the plurality of control partitions, and is configured to evacuate gas so that the gas flows out of the reaction chamber from the plurality of control partitions.

[0024] In one embodiment of the present invention, it is provided that the control partition includes:

[0025] A flux valve, wherein the mass flow rate of the gas flowing through the control zone is controlled by controlling the opening of the flux valve;

[0026] a first pressure sensor disposed upstream of the flux valve, the first pressure sensor being configured to monitor the pressure on the reaction chamber side of the flux valve; and

[0027] A second pressure sensor is disposed downstream of the flux valve, the second pressure sensor being configured to monitor the pressure on the exhaust pump side of the flux valve.

[0028] In one embodiment of the present invention, it is provided that according to the flux area k of the flux valve of the i-th control zone i , the pressure on the reaction chamber side P chamber i And the pressure P on the exhaust pump side pump i Adjust the gas flow Q through the i-th control zone i, where when the gas flows in the form of viscous flow, the gas flow rate Q through the i-th control partition is i It is expressed as the following formula:

[0029]

[0030] Among them, k i represents the flux area of ​​the flux valve in the i-th control zone, P chamber i represents the pressure on the reaction chamber side of the i-th control zone, P pump i represents the pressure on the exhaust pump side of the i-th control zone; and\or

[0031] When the gas flows in the form of molecular flow, the flow rate Q of the gas passing through the i-th control partition is i It is expressed as the following formula:

[0032] Q i =k i ×(P chamber i -P pump i ).

[0033] In one embodiment of the present invention, it is provided that the control partition includes:

[0034] A flux valve, wherein the mass flow of the gas flowing through the control zone is controlled by controlling the opening of the flux valve; and

[0035] A differential pressure sensor, a first end of which is arranged upstream of the flux valve and a second end of which is arranged downstream of the flux valve, is configured to monitor the pressure difference between the reaction chamber side of the flux valve and the exhaust pump side of the flux valve.

[0036] In one embodiment of the present invention, it is provided that according to the flux area k of the flux valve of the i-th control zone i And the pressure difference ΔP between the reaction chamber side and the exhaust pump side of the i-th control zone i Adjust the gas flow Q through the i-th control zone i , where when the gas flows in the form of viscous flow, the gas flow rate Q through the i-th control partition is i It is expressed as the following formula:

[0037]

[0038] Among them, k i represents the flux area of ​​the flux valve in the i-th control zone, P chamber i represents the pressure on the reaction chamber side of the i-th control zone, P pump i Indicates the pressure on the exhaust pump side of the i-th control zone, ΔP i represents the pressure difference between the reaction chamber side and the exhaust pump side of the i-th control zone; and\or

[0039] When the gas flows in the form of molecular flow, the flow rate Q of the gas passing through the i-th control partition is i It is expressed as the following formula:

[0040] Q i =k i ×(P chamber i -P pump i ) = k i ×ΔP i .

[0041] In one embodiment of the present invention, a plurality of control zones are connected to the exhaust pump via a main pipe, wherein the main pipe is provided with a main pipe control valve, wherein the flux area k of the flux valve of the i-th control zone is i , the pressure difference ΔP between the reaction chamber side and the exhaust pump side of the i-th control zone i And the pressure P of the main control valve main vlv Adjust the gas flow Q through the i-th control zone i , expressed as the following formula:

[0042] Q i =k i ×2P main vlv ×ΔP i .

[0043] In one embodiment of the present invention, it is provided that the flux valve comprises a gate valve, a butterfly valve, a vertically symmetrical valve, a diaphragm valve, a bellows valve, a piezoelectric actuator, a solenoid electromagnetic actuator, a piezoelectric piston valve, a piezoelectrically controlled air pilot valve or a double-acting cylinder driven mass flow control valve.

[0044] The present invention also provides a method for controlling flow distribution on a substrate surface, comprising the following steps:

[0045] placing a substrate on a susceptor in the reaction chamber;

[0046] Allowing gas to flow into the reaction chamber from the gas inlet end; and

[0047] The gas is made to flow out of the reaction chamber from the plurality of control partitions at the exhaust end, wherein the gas flow distribution on the substrate surface is adjusted by the plurality of control partitions through mass flow distribution under the condition that the pressure of the reaction chamber remains unchanged.

[0048] In one embodiment of the present invention, it is provided that the exhaust mass flow rates of the plurality of control zones are used as process recipe parameters in the reaction chamber.

[0049] The present invention has at least the following beneficial effects: by setting up multiple control partitions at the exhaust end, the present invention can accurately control the flow distribution flowing through the substrate surface based on mass flow distribution under the premise of constant pressure in the reaction chamber, thereby better controlling the reaction process of the semiconductor process and improving film formation uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] To further illustrate the advantages and features of various embodiments of the present invention, a more detailed description of various embodiments of the present invention will be presented with reference to the accompanying drawings. It will be understood that these drawings only depict typical embodiments of the present invention and are therefore not to be considered as limiting the scope thereof. In the accompanying drawings, for clarity, identical or corresponding parts will be represented by identical or similar reference numerals.

[0051] Figure 1 The figure shows a schematic diagram of the principle of a semiconductor reaction chamber in the prior art.

[0052] Figure 2A -D shows a schematic diagram of a vacuum control valve in the prior art.

[0053] Figure 3A -D shows a schematic diagram of the pumping method around the reaction chamber in one embodiment of the present invention.

[0054] Figure 4 A control schematic diagram of a substrate surface flow distribution control system in one embodiment of the present invention is shown.

[0055] Figure 5 A schematic diagram of film formation on a substrate is shown.

[0056] Figure 6 A schematic diagram of airflow on a substrate surface in one embodiment of the present invention is shown.

[0057] Figure 7 A schematic diagram showing a principle of controlling the uniformity of film formation on a substrate surface based on mass flow rate in one embodiment of the present invention.

[0058] Figure 8 A schematic diagram of a horizontal laminar flow system in the prior art is shown.

[0059] Fig.9A -C shows a schematic diagram of a system for controlling gas flow at the edge of a substrate in the prior art.

[0060] Fig.10 A schematic diagram of a horizontal laminar flow system in one embodiment of the present invention is shown.

[0061] Fig.11A A schematic diagram of a piezoelectric actuator in one embodiment of the present invention is shown.

[0062] Fig. 11B A schematic diagram of a piezoelectric piston valve in one embodiment of the present invention is shown.

[0063] Fig. 12A A schematic structural diagram of a piezoelectrically controlled air pilot valve in an embodiment of the present invention is shown.

[0064] Fig. 12B A schematic structural diagram of a double-acting cylinder driving a mass flow control valve in one embodiment of the present invention is shown.

[0065] Fig.13 A schematic flow chart of a method for adjusting flow distribution on a substrate surface based on mass flow control in one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0066] It should be noted that the components in the figures may be shown exaggeratedly for the sake of illustration and are not necessarily true to scale. In the figures, identical or functionally identical components are provided with the same reference numerals.

[0067] In the present invention, unless otherwise specified, "arranged on...", "arranged above..." and "arranged above..." do not exclude the existence of an intermediate between the two. In addition, "arranged on or above..." merely indicates the relative positional relationship between two components, and in certain cases, such as after reversing the product direction, it can also be converted into "arranged below or below...", and vice versa.

[0068] In the present invention, each embodiment is only intended to illustrate the aspects of the present invention and should not be construed as limiting.

[0069] In the present invention, unless otherwise specified, the quantifiers "a", "an" and "an" do not exclude the presence of a plurality of elements.

[0070] It should also be noted that in the embodiments of the present invention, for the sake of clarity and simplicity, only a portion of the parts or components may be shown, but those of ordinary skill in the art will understand that under the teachings of the present invention, the required parts or components may be added according to the needs of the specific scenario. In addition, unless otherwise specified, the features in different embodiments of the present invention may be combined with each other. For example, a feature in the second embodiment may be used to replace a corresponding or functionally identical or similar feature in the first embodiment, and the resulting embodiment also falls within the disclosure scope or recorded scope of the present application.

[0071] It should also be noted that within the scope of the present invention, the terms "same", "equal", "equal to" and the like do not mean that the values ​​of the two are absolutely equal, but allow a certain reasonable error, that is, the terms also cover "substantially the same", "substantially equal", "substantially equal to". By analogy, in the present invention, the terms "perpendicular to", "parallel to" and the like indicating directions also cover the meanings of "substantially perpendicular to" and "substantially parallel to".

[0072] In addition, the numbering of the steps of the methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps can be executed in different orders.

[0073] The present invention will be further described below in conjunction with specific embodiments with reference to the accompanying drawings.

[0074] The present invention sets a plurality of control partitions at the exhaust end of the system, and controls the fluid flowing through the substrate surface more accurately under the premise of constant pressure in the reaction chamber by mass flow distribution, so that the semiconductor process can be better controlled and better uniformity can be obtained. The system includes a plurality of control partitions and a main pipe valve for controlling the front stage pressure, wherein each control partition has a flux valve and a pressure sensor for controlling the opening.

[0075] Figure 3A -D shows a schematic diagram of the pumping method around the reaction chamber. Figure 3A The system shown has multiple pendulum valves and gate valves, where air is taken in from a showerhead at the top of the reaction chamber and air is pumped from the surrounding of the reaction chamber. Figure 3B The system shown has 8 pumping speed control zones, where air is taken in from a showerhead at the top of the reaction chamber and air is pumped from all around the reaction chamber. Figure 3C The system shown in -D has 5×2 pumping speed control zones, where gas is pumped from the horizontal side of the reaction chamber.

[0076] Figure 4 FIG. 2 shows a control schematic diagram of a substrate surface flow distribution control system in one embodiment of the present invention. Figure 4 As shown, there is a pressure gauge before and after the mass flow control valve Valve i, namely Pchamber i located upstream of the valve and P pump i located downstream. In viscous flow, Qi = ki*(P 2 chamber iP 2pump i). In molecular flow, Qi = ki*(Pchamber iP pump i) (for example, when the etching machine uses a molecular pump). Here, "viscous flow" means that when the gas pressure is high and the flow rate is low, the inertial force of the gas is small, the internal friction plays a major role, the gas near the pipe wall hardly flows, and the maximum flow rate is at the center of the pipe, also known as laminar flow. "Molecular flow" means that the pipe pressure is very small and the mean free path of the gas molecules is much larger than the pipe diameter. The internal friction of the gas no longer exists, and the gas molecules leave the pipe freely and independently by thermal motion. In addition, the flow state between viscous flow and molecular flow is called viscous-molecular flow.

[0077] Under reasonable design, multiple Pchamber i are basically the same, and multiple P pump i are also basically the same, so the flow distribution of each valve is equivalent to adjusting ki (i.e., the passage area or opening aperture of the valve), that is, the flow Qi is proportional to ki, and ki represents the flux area of ​​valvei. In a simplified embodiment of the present invention, the pressure gauges before and after the valve valve can be eliminated, and open-loop control is performed simply by adjusting Ki through the opening of the valve. At this time, it is assumed that each valve valvei has the same structure. The opening of each valve is ki% (0<ki<100). Then the proportion of the flow allocated to valve i to the total flow is Wi=ki / (∑ki)*100%, and ∑wi=100%.

[0078] The two ends of the differential pressure gauge can be arranged before and after the mass flow control valve Valve i, namely P chamber i upstream of the valve and P pump i downstream. At this time, the pressure of the differential pressure gauge Preading = ΔP. In viscous flow, Qi = ki*(P 2 chamber iP 2 pump i). In molecular flow, Qi=ki*(Pchamber iP pump i)=ki*ΔP=ki*Preading. Therefore, N differential pressure gauges and 1 absolute pressure gauge can be used to control N partitions, greatly reducing costs. In molecular flow, control can be completed using N differential pressure gauges. At the same time, the differential pressure gauge is more accurate than the pressure difference measured by subtracting two absolute pressure gauges.

[0079] Transform the viscous flow formula, Qi=ki*(P 2 chamber iP 2pump i)=ki*(Pchamber i+Ppump i)*(Pchamber iP pump i)=ki*(2Ppumpi+ΔP)*ΔP, when ΔP<<Ppump, Qi=ki*2Ppump*ΔP. Since PΔP<<Ppump, the accuracy of Qi is mainly determined by the measurement accuracy of ΔP. Therefore, an absolute pressure gauge with lower accuracy can be used to reduce the cost. At the same time, the pressure difference measured by subtracting two absolute pressure gauges is more accurate than that by a differential pressure gauge.

[0080] In addition, a pressure control valve Valve main can be added to the main pipe above the pump, through which the main pipe valve pressure Pmain vlv can be controlled, that is, the original formula becomes Qi = ki * 2Pmainvlv * ΔP, that is, under a given Qi condition, Pmain can be changed to adapt to different pressure gauge configurations. For example, when the selected differential pressure gauge has a higher pressure difference measurement accuracy, pushing up the pressure of the main pipe control valve will help the absolute pressure gauge to obtain higher measurement accuracy, thereby making the flow control accuracy higher.

[0081] The existence of the main control valve Valve main helps to control the working condition of Valve i and make the control better. Due to the working principle of valve i, most valves have an optimal response opening. For example, when the butterfly valve is close to the fully open angle, the flow rate has almost no response to the valve rotation angle. However, when the angle is close to the fully closed angle, the flow rate changes dramatically and shows an over-response. In the middle section of the valve angle, the flow rate response is close to linear. Adding the pressure control valve Valve main to control Pmainvalve can make valve i work in the linear response area and greatly improve the flow control accuracy. In the control algorithm of the entire system, the working condition of the valve (rotation angle or stroke) can be judged to adjust (push up or down) Pmain valve so that the valve works in the middle section. If Pmainvalve does not exist. Valve i works at an inappropriate pressure, that is, the valve is in an extreme working condition close to fully open or fully closed. When the valve needs to respond to adjust the flow, due to the inappropriate valve opening, it is very likely to have an over-response or under-response.

[0082] In non-process state, the inlet flow rate of the equipment is controlled by a mass flow meter. The MFC at the inlet naturally forms a correction system for correcting the outlet flow rate. The principle is to use the gas closest to the ideal gas, such as inert gas, H2N2, etc. for flow correction. Usually, the cavity is large and the gas that initially enters the cavity needs time to build up pressure. After the initial pressure is established, there may be compression or local turbulence. That is, it takes a certain amount of stabilization time for the cavity flow rate to stabilize, that is, Q shower head = Q exhaust i. Since Qi = ki*(P 2 chamber iP 2 pump i) or Qi=ki*(Pchamber iP pump i), so ki can be calculated. Where Ki is a function of the actuator stroke, such as; Ki=f(x), in the case of using a servo motor, it is a function of the encoder step length, in the case of using a stepper motor, it is a function of the number of pulses, in the case of some other actuators using analog quantities, it is a function of the current or power supply, in the case of a double-acting cylinder controlled by a pilot valve stroke, it is a function of the pilot valve output pressure, or other valve actuator input variables, thus obtaining the valve Ki=fi(x) from 0%-100% opening, where x is the valve actuator input variable.

[0083] By opening Valve 1-Valve n one by one, the Ki diagram of all valves i can be obtained. This eliminates the need to calibrate Valve i with an expensive flow calibration system in the factory. Alternatively, valve i can be calibrated again on site. In addition, since the chamber needs to be purged frequently in almost all semiconductor chambers, the data collection of these purging processes can be used as a daily online calibration for the accuracy and reliability of the gas flow system of the big data monitoring equipment.

[0084] An optimized complete gas system should include the air flow distribution system of the sprinkler (or injector) (usually composed of mass flow meters, various manual and automatic valves, filters, etc.), a multi-channel (n>1) mass flow exhaust distribution system including valve i (pressure sensors or pressure difference sensors upstream and downstream of the valve), and a main pipe pressure control valve for controlling the main pipe pressure. And these air intake systems are coordinated through a general controller to calibrate these sensors and mass flow and each other, as well as collect big data.

[0085] In most semiconductor processes, the precursor and other reactive gases undergo chemical reactions, and their mass flow rate will change greatly, that is, Q shower head ≠ Q exhaust. Therefore, it is impossible to determine the flow rate by a simple upstream mass flow meter. Therefore, a method is needed to measure Q exhaust so as to further distribute the Mass Flow. For etching and plasma ashing processes, the completion of etching, etching to the stop layer or PR etching is inevitably accompanied by a drastic change in Q exhaust. That is, the sudden change of Q exhaust can be used as the endpoint detection of etching or ashing when the intake flow remains unchanged. In place of traditional grating endpoint detection. In addition, Q gas in / Q exhaust can also be used as a very important indicator for online process monitoring. When Q gas n / Q exhaust is abnormal and deviates from the daily benchmark, it means that the system needs maintenance or care.

[0086] The flow distribution process of the substrate surface based on mass flow control includes: configuring the gas flow (Setting Flow), wherein the standard starting condition Qexhaust total is measured, all Pi chambers are set to the same and specified process pressure Pprocess, and all proportional control valves Vi are controlled according to Pi=Pprocess. Qi and Qexhaust total=∑qi are calculated according to Pi and Pi down. That is, under this condition, the flow entering the pump is Qexhaust total. Setting the recipe parameters (Recipe parameter setting), wherein the mass flow is distributed according to the wafer process results obtained under the standard starting condition, or the contour map, and the setting value is Qi=Qtotal*Ki, Ki is the flow proportional coefficient corresponding to each control valve, and ∑ki=100%, Qi=Qtotal*Ki is used to adjust the working condition of Zone i to minimize Non-uniformity.

[0087] In the past 10 years, LAM research has been the most favored by various manufacturers, and the most efforts have been invested in the base with multiple temperature zones (>100 zones) adjustment (for etching equipment, the base is a multi-temperature zone electrostatic chuck). This method has its disadvantages: it is known that silicon has a relatively high heat transfer coefficient at room temperature (300K). It is generally believed to be about 148-151W / Km, higher than most metals. Therefore, the temperature difference established in the multi-zone base becomes very small when transferred to the silicon substrate. Silicon carbide has a higher heat transfer coefficient. At the same time, designing a temperature-controlled base with >100 zones is very difficult and costly. It has a very low cost-effectiveness, and the ability to adjust the process results is very limited.

[0088] Therefore, the exhaust assists the air intake device to assist in adjusting the process results by using the so-called push & pull method. That is, the shower head / injector performs air intake (push), and the multi-channel exhaust mechanism distributes the mass flow of the exhaust gas in proportion (pull), thereby achieving more precise control of the transmission process flowing over the substrate surface.

[0089] In fact, in the design of semiconductor cavities, plasma coils, plasma substrates, and heaters are usually designed in a so-called radial circular symmetry form. Various process parameters such as temperature, density, and process results such as thickness are presented in various annular circular symmetry forms. When adjusting the process results, the overall process results are usually decomposed into a radial symmetric result and a non-radial symmetric result superimposed on each other. The process of process parameter optimization is actually to achieve consistency of process results by superimposing a physical or chemical field that is opposite and offset to the above-mentioned non-radial through parameter adjustment.

[0090] In fact, in the design of the prior art, exhaust is almost the only important aspect that has not been actively controlled by effective physical means. The prior art only controls the pressure of the chamber, and the gas freely flows over the substrate surface and enters the exhaust device). Through the multi-zone active mass flow control of the present invention, the consistency of fluid transmission can be greatly improved, that is, the radial symmetry of the fluid flow background can be achieved.

[0091] Furthermore, when the fluid mass flow rate is evenly distributed radially, it still shows inconsistency. At this time, more fluid can be forced to flow through by proportionally distributing the mass flow rate of the exhaust gas. Figure 5 Figure 2 shows a schematic diagram of film formation on a substrate. Figure 5As shown in the figure, the three circled areas indicate that the film layer may be too thin or the etching rate is lower. Compared with other areas, more reactants such as free radicals need to be transported to increase the growth or etching rate. Therefore, it is necessary to increase the mass flow rate of the partitions corresponding to the three circles to achieve a more uniform radial process result.

[0092] Figure 6 The schematic diagram of the airflow on the surface of a substrate in one embodiment of the present invention is shown. Assuming that the exhaust control system has 12 partitions, located at 1-12 o'clock, the airflow on the substrate corresponds to the radial part of the basic or process flow radial mass flow, the flow at 7 o'clock and 8 o'clock increases, and the flow at 10 o'clock and 11 o'clock minus the flow in the opposite direction, forming a non-radial mass flow field, which is used to offset the non-radial nature of the process, and finally obtain a very uniform radial process contour map. Figure 7 FIG. 1 shows a schematic diagram of a method for controlling the uniformity of film formation on a substrate surface based on mass flow in one embodiment of the present invention. Figure 7 As shown, the final process formula, when Qtotal and other process variables remain unchanged, Qexhaust i = Qtotal*WFi (WFi is the mass flow percentage allocated to valve i in Zone i) ∑WFi = 100%.

[0093] Figure 8 Schematic diagram of a horizontal laminar flow system in the prior art is shown. This system is usually used for silicon or other CVD epitaxy applications, such as Figure 8 As shown in the figure, the current exhaust control technology makes all the gases concentrate at one point and exhaust. Due to fluid mechanics effects, such as no slip at the solid boundary and low pressure area, a very significant low-speed area appears at the edge of the substrate, making the growth rate at the edge lower than that in the center. In this case, it is impossible to adjust the growth rate at the edge of the substrate to an acceptable range through the traditional method of using multiple injection ports.

[0094] Fig.9A -C shows a schematic diagram of a system for controlling the gas flow at the edge of a substrate in the prior art. Fig.9A-C shows a method, which provides a side injection port perpendicular to the first injection port to control the gas flow at the edge of the substrate, thereby optimizing the uniformity of growth deposition. The disadvantage of this method is that it is not a global methodological solution. A systematic, global technical route can help solve it. For example, since there is only one pump outlet, the streamlines of all fluids finally flow to the only outlet, so that the low-pressure area must exist. More or less, it affects the uniformity of the process. In addition, side injection cannot be used to improve the uniformity of the center part.

[0095] Fig.10 FIG. 2 shows a schematic diagram of a horizontal laminar flow system in one embodiment of the present invention. Fig.10 As shown, in a horizontal laminar flow system, since the substrate is usually rotated to improve uniformity. Therefore, the uniformity contour map of the substrate usually presents good concentric circles. That is, it is only necessary to study the distribution of substrate uniformity along the diameter or radius (left-right symmetry). And it presents u, n, w, m or more complex (if there are enough injectors) wave shapes. Similar to the above method, the process result (red curve) can be regarded as a straight uniform background, superimposed with the non-uniform result of a wave. That is, under the original process conditions, an inverse flow can be provided at the outlet exhaust, that is, the flow rate in the low growth rate area is increased and the flow rate in the high growth rate area is reduced. In other words, an inverse trough is superimposed on the original peak, or an inverse peak is superimposed on the trough to obtain a more uniform process result and optimize the growth deposition or etching uniformity.

[0096] In the present invention, compared with the traditional design (NW / KF DN 100-400mm (4″-16″) caliber), the original flow is distributed to multiple valves. Therefore, it is possible to further choose to use multiple valves with smaller calibers, so some of the original fluxes (calibers) are too small, which rarely appear in the pressure control valves (high-resolution diaphragm valves, or bellows valves) or actuators (piezoelectric actuators or solenoid electromagnetic actuators (solenoidactuators) with very short strokes resulting in insufficient flux. These two types of actuators have higher response speeds and lower costs than motor actuators with servo motors and lead screws or reducers (the cost and control complexity of motors + servos are far higher than those of piezoelectric and solenoid actuators)) can be used in the present invention. At the same time, valves with smaller calibers usually have smaller raft masses and respond faster, so that the accuracy of flow control is greatly improved. Fig.11A FIG. 1 shows a schematic diagram of a piezoelectric actuator in one embodiment of the present invention, Fig. 11BThe schematic diagram of a piezoelectric piston valve in one embodiment of the present invention is shown. In addition, the present invention can also use a piezoelectric diaphragm valve. Traditionally, due to the very short stroke of the pressure actuator, the pressure valve has a very small caliber and is rarely used in exhaust port control. In the present invention, due to the use of more partitions, the flow caliber requirement for a single valve is reduced, so it is possible to use a piezoelectric actuator with a faster response and a shorter stroke.

[0097] In the present invention, the air pilot valve can also be used to control the left and right pressure difference of the double-acting cylinder to control the cylinder to stop at a specified position (proportional control cylinder or servo control cylinder). This servo cylinder is often equipped with a distance scale or position encoder that can output accurate position signals, so as to achieve accurate stroke control like a servo motor, thereby further accurately controlling the opening of the valve and completing accurate control of mass flow. Compared with the motor, the cylinder also has the advantage of faster response. At the same time, since multiple complex servo motor controllers are not required, the design complexity and cost of its electronic control part are also greatly reduced. Fig. 12A A schematic structural diagram of a piezoelectrically controlled air pilot valve in an embodiment of the present invention is shown. Fig. 12B The schematic diagram of the structure of a double-acting cylinder driving a mass flow control valve in one embodiment of the present invention is shown. The piezoelectric pilot valve controls the cylinder movement speed by controlling the air flow rate, and controls the cylinder's stop position by controlling the pressure difference on both sides of the double-acting cylinder (usually the cylinder has a distance scale to measure the stop position). This pneumatic system that can accurately control speed and position is collectively called a servo cylinder. The piezoelectric pilot valve controls the position of the single-acting cylinder with a spring through pressure, thereby accurately controlling the flow of the valve.

[0098] Fig.13 FIG. 1 is a flow chart showing a method for adjusting the flow distribution on the substrate surface based on mass flow control in one embodiment of the present invention. Fig.13As shown, in one embodiment of the present invention, a method for adjusting the flow distribution on the surface of a substrate by mass flow control is also proposed, and the method includes the following steps: power-on self-test of the equipment; injecting a calibration gas of a specified flow rate through an upstream mass flow meter; opening the exhaust valve of Zone i one by one, confirming and correcting the ki of the zone so that QMFC=Q zone i; opening the upstream mass flow meter to inject the process gas to implement the recipe, and perform processes such as CVD or Etch; measuring the flow Qi of each Zone i, Total Q=∑Qi, and drawing a contour map of the process; for processes such as Etch that require endpoint detection, measuring the mutation points of Qi and TotalQ, so that the process of this step is stopped and the next step process is entered; according to the contour map of the process results, calculating the uneven part in the process contour map; according to the uneven part of the contour map of the process results, calculating the reverse uneven exhaust flow required by the exhaust fluid to offset the process unevenness; Zone i The exhaust flow rate percentage Qi / Qtotal% is used as a recipe parameter; different Qi / Qtotal% are tested to optimize the process result; and different Qi / Qtotal% are tested to optimize the process result.

[0099] Although various embodiments of the present invention are described above, it should be understood that they are presented as examples only and not as limitations. It is obvious to those skilled in the relevant art that various combinations, modifications and changes can be made thereto without departing from the spirit and scope of the present invention. Therefore, the breadth and scope of the present invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should only be defined according to the attached claims and their equivalents.

Claims

1. A substrate surface flow distribution control system, characterized in that: include: a reaction chamber, wherein a susceptor is disposed therein, and the susceptor is configured to carry a substrate; An air inlet end, wherein the gas flows into the reaction chamber from the air inlet end; as well as An exhaust end, wherein the gas flows out of the reaction chamber from the exhaust end, and the exhaust end includes a plurality of control partitions, and the plurality of control partitions are configured to adjust the gas flow distribution on the substrate surface by mass flow distribution when the pressure of the reaction chamber remains unchanged.

2. The substrate surface flow distribution control system according to claim 1, characterized in that: The gas flow distribution on the substrate surface is adjusted by multiple control partitions through mass flow distribution under the condition that the pressure of the reaction chamber remains unchanged, including: The gas on the substrate surface forms an asymmetric mass flow field through mass flow distribution by multiple control partitions to offset the asymmetry of the semiconductor film forming or etching process and improve the uniformity of the semiconductor film forming or etching process results.

3. The substrate surface flow distribution control system according to claim 2, characterized in that: The air inlet end comprises: a showerhead disposed above the susceptor, wherein gas flows from the showerhead into the reaction chamber and flows from above the substrate toward the substrate; and An inlet end mass flow meter is connected to the shower head, and the inlet end mass flow meter is configured to monitor the flow rate of the gas flowing into the reaction chamber.

4. The substrate surface flow distribution control system according to claim 2 or 3, characterized in that: When the gas flows in and out in a direction horizontal to the substrate, the gas on the substrate surface is distributed by mass flow rate through multiple control partitions so that the gas presents a superposition of 180-degree opposite peaks and troughs to improve the uniformity of the semiconductor film formation or etching process results; or When the gas flows into the shower head from above the substrate and flows out from around the substrate, the gas on the substrate surface forms a non-radial flow field through mass flow distribution by multiple control partitions to offset the non-radial nature of the semiconductor film forming or etching process and improve the uniformity of the semiconductor film forming or etching process results.

5. The substrate surface flow distribution control system according to claim 3, characterized in that: The mass flow meter at the air intake end is used to perform flow correction on the multiple control partitions at the exhaust end.

6. The substrate surface flow distribution control system according to claim 1, characterized in that: It also includes a process monitoring device, which is configured to determine that the etching or plasma ashing process reaction is completed when it is detected that the intake mass flow rate and other important process parameters at the intake end remain unchanged and the exhaust flow rate at the exhaust end changes suddenly.

7. The substrate surface flow distribution control system according to claim 6, characterized in that: The process monitoring device is also configured to determine that the system needs maintenance when it is detected that the intake air flow rate and the exhaust air flow rate deviate from the daily benchmark.

8. The substrate surface flow distribution control system according to claim 1, characterized in that: The gas is introduced into the gas in a push manner at the gas inlet end, and is exhausted in a pull manner at the gas exhaust end, so as to adjust the gas flow distribution on the substrate surface in a push-pull manner.

9. The substrate surface flow distribution control system according to claim 3, characterized in that: The plurality of control partitions are arranged around the susceptor, wherein the gas flows from the center of the substrate to the periphery of the substrate and flows out of the reaction chamber from the plurality of control partitions.

10. The substrate surface flow distribution control system according to claim 9, characterized in that: The exhaust end also includes: An exhaust pump is connected to the plurality of control partitions, and is configured to evacuate gas so that the gas flows out of the reaction chamber from the plurality of control partitions.

11. The substrate surface flow distribution control system according to claim 10, characterized in that: The control partition includes: A flux valve, wherein the mass flow rate of the gas flowing through the control zone is controlled by controlling the opening of the flux valve; a first pressure sensor disposed upstream of the flux valve, the first pressure sensor being configured to monitor the pressure on the reaction chamber side of the flux valve; and A second pressure sensor is disposed downstream of the flux valve, the second pressure sensor being configured to monitor the pressure on the exhaust pump side of the flux valve.

12. The substrate surface flow distribution control system according to claim 11, characterized in that: According to the flux area k of the flux valve of the i-th control zone i , the pressure on the reaction chamber side P chamber i And the pressure P on the exhaust pump side pump i Adjust the gas flow Q through the i-th control zone i , where when the gas flows in the form of viscous flow, the gas flow rate Q through the i-th control partition is i It is expressed as the following formula: Among them, k i represents the flux area of ​​the flux valve in the i-th control zone, P chamber i represents the pressure on the reaction chamber side of the i-th control zone, P pump i represents the pressure on the exhaust pump side of the i-th control zone; and\or When the gas flows in the form of molecular flow, the flow rate Q of the gas passing through the i-th control partition is i It is expressed as the following formula: Q i =k i ×(P chamber i -P pump i )。 13. The substrate surface flow distribution control system according to claim 11, characterized in that: The control partition includes: A flux valve, wherein the mass flow of the gas flowing through the control zone is controlled by controlling the opening of the flux valve; and A differential pressure sensor, a first end of which is arranged upstream of the flux valve and a second end of which is arranged downstream of the flux valve, is configured to monitor the pressure difference between the reaction chamber side of the flux valve and the exhaust pump side of the flux valve.

14. The substrate surface flow distribution control system according to claim 13, characterized in that: According to the flux area k of the flux valve of the i-th control zone i And the pressure difference ΔP between the reaction chamber side and the exhaust pump side of the i-th control zone i Adjust the gas flow Q through the i-th control zone i , where when the gas flows in the form of viscous flow, the gas flow rate Q through the i-th control partition is i It is expressed as the following formula: Among them, k i represents the flux area of ​​the flux valve in the i-th control zone, P chamber i represents the pressure on the reaction chamber side of the i-th control zone, P pump i Indicates the pressure on the exhaust pump side of the i-th control zone, ΔP i represents the pressure difference between the reaction chamber side and the exhaust pump side of the i-th control zone; and\or When the gas flows in the form of molecular flow, the flow rate Q of the gas passing through the i-th control partition is i It is expressed as the following formula: Q i =k i ×(P chamber i -P pump i )=k i ×ΔP i 。 15. The substrate surface flow distribution control system according to claim 13, characterized in that: A plurality of control zones are connected to the exhaust pump via a main pipe, wherein the main pipe is provided with a main pipe control valve, wherein the flux area k of the flux valve of the i-th control zone is i , the pressure difference ΔP between the reaction chamber side and the exhaust pump side of the i-th control zone i And the pressure P of the main control valve mainvlv Adjust the gas flow Q through the i-th control zone i , expressed as the following formula: Q i =k i ×2P main vlv ×ΔP i 。 16. The substrate surface flow distribution control system according to any one of claims 11 and 13, characterized in that: The flux valve includes a gate valve, a butterfly valve, a vertically symmetrical valve, a diaphragm valve, a bellows valve, a piezoelectric actuator, a solenoid electromagnetic actuator, a piezoelectric piston valve, a piezoelectrically controlled air pilot valve or a double-acting cylinder-driven mass flow control valve.

17. A method for controlling flow distribution on a substrate surface, characterized in that: The following steps are involved: placing a substrate on a susceptor in the reaction chamber; Allowing gas to flow into the reaction chamber from the gas inlet end; and The gas is made to flow out of the reaction chamber from the plurality of control partitions at the exhaust end, wherein the gas flow distribution on the substrate surface is adjusted by the plurality of control partitions through mass flow distribution under the condition that the pressure of the reaction chamber remains unchanged.

18. The substrate surface flow distribution control according to claim 17, characterized in that: The exhaust mass flow rates of the multiple control zones are used as process recipe parameters in the reaction chamber.

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