Methods of forming trench structures, removing byproducts within trenches, and wafer carrier devices

Abstract

The application discloses a method for forming a groove structure, removing byproducts in the groove, and a wafer supporting device. The wafer supporting device comprises at least one wafer slot for supporting a wafer, and the bottom surface of each wafer slot is an inclined surface relative to the horizontal plane. After the wafer with a groove pattern is placed on the wafer supporting device, the wafer is transmitted into a process chamber, and the wafer is in an inclined state in the process chamber. One side wall of the groove can face the incoming etching gas, and the contact area between the etching gas and the side wall is large. When the wafer is etched for the first time, byproducts on the side wall of the groove can be effectively removed. The wafer is rotated by a preset angle, and the other side wall of the groove faces the incoming etching gas. When the wafer is etched for the second time, byproducts on the other side wall of the groove can be effectively removed. The above two etching processes can reduce the height difference of the stripe protrusions formed on the side wall of the groove in the process of etching to form the groove, effectively reduce the roughness of the side wall of the groove, and weaken the micro-groove defects at the bottom of the groove.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor process, in particular to a method for forming a trench structure and removing by-products in the trench and a wafer carrying device. BACKGROUND

[0002] The demand for some semiconductor devices is increasing, for example, the demand for lithium niobate optical modulators in optical modules is rapidly increasing, but the processing cost is still high, which makes it difficult to be widely used, and the core of limiting mass production is etching process. Since the halogen compounds of Li in the etching by-products of lithium niobate wafers have a boiling point above 1000℃, they are difficult to volatilize and deposit on the crystal surface, which seriously affects the roughness of the etched sidewall.

[0003] In lithium niobate optical modulators and other semiconductor devices, the waveguide loss of optical modulation is mainly related to the sidewall roughness and the sidewall angle. The larger the roughness, the greater the waveguide loss. Therefore, the trench roughness has an important influence on the performance of the semiconductor device. In the prior art, some schemes use Cl (chlorine) and F (fluorine) to etch lithium niobate wafers and other materials. The sidewall roughness after etching is obvious. Although some other schemes improve the smoothness of the surface of the related wafer to a certain extent, the sidewall angle of the trench is low, which cannot form effective structure patterns (such as optical waveguide patterns), and still easily affects the performance of the obtained device. It can be seen that the traditional trench etching scheme is difficult to obtain a trench structure with good performance. SUMMARY

[0004] In view of this, the present application provides a method for forming a trench structure and removing by-products in the trench and a wafer carrying device to solve the problem that the traditional trench etching scheme is difficult to obtain a trench structure with good performance.

[0005] The present application provides a wafer carrying device, which comprises at least one wafer slot for carrying a wafer. The bottom surface of each wafer slot is an inclined surface relative to the horizontal plane, and the angle of the inclined surface relative to the horizontal plane is an acute angle.

[0006] Optionally, the angle is 3-10°.

[0007] Optionally, the depth of the wafer slot is 0.2-0.8mm.

[0008] Optionally, the wafer carrying device is a tray, the thickness of the tray is 1-5mm, and the remaining thickness of the tray at the bottom surface of the wafer slot is greater than or equal to 0.6mm.

[0009] The present application also provides a method for removing by-products in a trench for a wafer with a trench pattern, which comprises:

[0010] placing the wafer with the trench pattern on a wafer supporting device, the wafer supporting device being any of the above wafer supporting devices;

[0011] performing a first etching on the wafer;

[0012] rotating the wafer by a preset angle;

[0013] performing a second etching on the wafer.

[0014] Optionally, the preset angle is an integer multiple of 180°.

[0015] Optionally, the etching gas used in the first etching and the second etching comprises at least one of Ar, He and N2.

[0016] Optionally, the process parameters of the first etching and the second etching comprise: the etching pressure ranges from 1 to 4 mTorr.

[0017] Optionally, the process parameters of the first etching and the second etching comprise: the upper radio frequency power ranges from 200 to 500 w, and the lower radio frequency power ranges from 20 to 200 w.

[0018] Optionally, the process parameters of the first etching and the second etching comprise: the etching time ranges from 30 to 60 s.

[0019] The application further provides a method for forming a trench structure, the method comprising:

[0020] etching a trench on a wafer surface;

[0021] removing the by-products on the sidewall of the trench by any of the above methods for removing by-products in the trench.

[0022] Optionally, the etching a trench on a wafer surface comprises: introducing an etching gas into a process chamber; loading a radio frequency power to the process chamber to generate plasma under a first chamber pressure; reducing the chamber pressure to a second chamber pressure by a stepwise pressure reduction under a glow state, the second chamber pressure being less than the first chamber pressure; and etching the wafer to form a trench.

[0023] Optionally, the first chamber pressure ranges from 10 to 50 mTorr, the second chamber pressure ranges from 1 to 5 mTorr, and the stepwise pressure reduction time ranges from 3 to 10 s.

[0024] In the above-mentioned method for forming a trench structure and removing by-products in the trench and wafer carrying device, the bottom surface of the wafer groove is an inclined surface relative to the horizontal plane. After the wafer with the trench is placed in the wafer groove, the wafer is in an inclined state. In the process of etching to form the trench, the stripe protrusions formed on the sidewall of the trench can be better bombarded by etching gas. The top end of the stripe protrusion has a high etching rate under the bombardment of the etching gas, and the bottom of the stripe protrusion has a low etching rate. After etching, the degree of surface roughness is reduced, so that the height difference of the stripe protrusion is reduced, and the roughness of the sidewall of the trench is reduced. For the trench bottom surface, the micro-groove formed in the process of etching to form the trench has a low etching rate at the bottom due to the change of the bombardment angle of the etching gas, and it is difficult for the reflected particles to enter the micro-groove again, so that the micro-groove phenomenon is reduced and not aggravated again. It can be seen that the performance of the obtained trench related structure can be optimized from multiple aspects. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 is a schematic diagram of the sidewall of the trench in a conventional etching scheme;

[0027] Figure 2 is a top view of a wafer carrying device in an embodiment of the present application;

[0028] Figure 3 is a schematic diagram of an inclined surface in an embodiment of the present application;

[0029] Figure 4 is a schematic diagram of a wafer carried by a wafer carrying device in an embodiment of the present application;

[0030] Figure 5 is a schematic diagram of a tray in an embodiment of the present application;

[0031] Figure 6 is a flowchart of a method for removing by-products in a trench in an embodiment of the present application;

[0032] Figure 7 is a flowchart of a method for forming a trench structure in an embodiment of the present application;

[0033] Figure 8 is a schematic diagram of a process chamber in an embodiment of the present application;

[0034] Figure 9 is a schematic diagram of plasma bombardment during conventional etching;

[0035] Figure 10 is a schematic diagram of modification of plasma bombardment and trench sidewall in etching in an embodiment of the present application;

[0036] Figure 11 is a schematic diagram of the result after etching a lithium niobate wafer using a conventional scheme;

[0037] Figure 12 is a schematic diagram of the result after etching a lithium niobate wafer using the method of forming a trench structure according to the present application. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application. In the case of no conflict, each of the following embodiments and its technical features can be combined with each other.

[0039] In a conventional etching trench scheme, the wafer is usually placed horizontally in the process chamber, and the wafer is etched by plasma to form a trench on the wafer surface, as shown in Figure 1 (a) and (b) of FIG. 1, due to the influence of factors such as residual by-products, a striation protrusion similar to Figure 1 (b) of FIG. 1 is formed on the trench sidewall. The cross section of the striation protrusion is, for example, triangular, resulting in a high roughness of the trench sidewall. In addition, in the process of removing by-products in the trench by physical bombardment using inert gases such as Ar, as shown in Figure 1 (a), Ar ions will rebound at the corner of the trench to form a secondary etching, which aggravates the subtrench defect. Moreover, the conventional physical bombardment mainly removes by-products at the bottom of the trench. Since the angle between the trench sidewall and the etching direction is low, the sidewall by-products cannot be effectively removed, and even the striation protrusion of the trench sidewall can be aggravated, further reducing the smoothness of the trench sidewall.

[0040] Based on the above problems, the first aspect of the present application provides a wafer carrying device. The wafer carrying device includes at least one wafer slot for carrying a wafer. In some examples, the above-mentioned wafer slot can also be referred to as a wafer slot. Wherein, the wafer carrying device can only include one wafer slot, for example Figure 2 The wafer carrying device shown in (a) of FIG. 2 can be a carrying seat or the like device including only one wafer slot; the wafer carrying device can also include a plurality of wafer slots, for example Figure 2 The wafer carrying device shown in (b) of FIG. 2 can be a tray or the like device including a plurality of symmetrically distributed wafer slots. Specifically, referring to Figure 3As shown, the bottom surface of each wafer slot is an inclined surface with respect to the horizontal plane, and the angle of inclination of the inclined surface with respect to the horizontal plane is an acute angle. After the wafer with the trench is placed in the wafer slot, the wafer is in an inclined state, and the posture of the wafer can be referred to as Figure 4 As shown, when the wafer is in the inclined state shown in (a) of FIG. 6, Figure 4 As shown, when the wafer is in the inclined state shown in (a) of FIG. 6, Figure 4 As shown, when the wafer is in the inclined state shown in (a) of FIG. 6,

[0041] Optionally, the size of the wafer slot is in the range of 2-6 inches, so as to be compatible with wafers of 6 inches and below.

[0042] In some embodiments, the angle of inclination of the inclined surface can be determined according to the angle between the trench side wall and the trench bottom surface, the smaller the angle between the trench side wall and the trench bottom surface, the smaller the angle of inclination of the inclined surface, and the larger the angle between the trench side wall and the trench bottom surface, the larger the angle of inclination of the inclined surface, so as to ensure the stability of the wafer placed in the wafer slot on the basis of maximizing the contact area between the etching gas and the trench side wall. Specifically, the angle of inclination of the inclined surface is in the range of 3-10°, for example, if the angle between the trench side wall and the trench bottom surface is 65°, the angle of inclination of the inclined surface can be 3° or 4°, if the angle between the trench side wall and the trench bottom surface is 80°, the angle of inclination of the inclined surface can be 9° or 10°, and so on. The angle of inclination in the range of 3-10° can better stabilize the wafer placed in the wafer slot while maximizing the contact area between the etching gas and the corresponding trench side wall of the wafer.

[0043] Optionally, the depth of the wafer slot is in the range of 0.2-0.8 mm, which can refer to the maximum depth of the wafer slot (e.g. the depth of the lowest part of the bottom surface of the wafer slot), and the depth in this range can better stabilize the wafer in the wafer slot.

[0044] In some examples, the wafer carrying device is a tray, which can have only one wafer slot or multiple wafer slots, which can be symmetrically distributed as shown in Figure 5 Fig. 1 (b), for example. Figure 5 Fig. 1 (a) is a top view of the tray, and Fig. 1 (b) is a longitudinal sectional view. The diameter of the tray can range from 210 mm to 220 mm, which can be designed as 8 inches to be applied to 6 inches and below wafer etching process. In other examples, the wafer carrying device can be a carrying base in a process chamber.

[0045] Optionally, the thickness of the tray is 1-5 mm, which can provide a relatively stable platform. The remaining thickness of the tray at the bottom surface of the wafer slot is greater than or equal to 0.6 mm, which can reduce the probability of debris at the wafer slot.

[0046] Optionally, the tray is a Si tray based on the advantages of good thermal conductivity and low price of Si (silicon), which can timely conduct heat during etching to prevent the wafer from being cracked due to thermal stress, and facilitate mass production.

[0047] In the above wafer carrying device, the bottom surface of the wafer slot is an inclined surface relative to the horizontal plane. After the wafer with a groove is placed in the wafer slot, the wafer is in an inclined state. The stripe protrusions on the sidewall of the groove can be better hit by the etching gas. The top end of the stripe protrusion has a fast etching rate under the hit of the etching gas, and the bottom of the stripe protrusion has a slow etching rate, thereby reducing the height difference of the stripe protrusion and the roughness of the sidewall of the groove. For the groove bottom surface, the micro-groove formed during the etching process to form the groove has a low etching rate at the bottom, and the reflected particles are difficult to enter the micro-groove again, which can reduce the micro-groove phenomenon and prevent it from being aggravated again. It can be seen that the inclined etching of the wafer with a groove based on the above wafer carrying device can optimize the performance of the obtained groove-related structure from multiple aspects.

[0048] The second aspect of the present application provides a method for removing by-products in a groove for a wafer with a groove pattern. Referring to Figure 6 Fig. 2, the method for removing by-products in a groove includes steps S110-S140.

[0049] S110, placing a wafer with a groove pattern on a wafer carrying device. The wafer carrying device is the wafer carrying device described in any of the above embodiments. The wafer carried by the wafer carrying device can refer to Fig. 1 (a) or (b), and the wafer is in an inclined state. One side of the sidewall of the groove can face the incident etching gas to a certain extent, and the contact area between the etching gas and the sidewall is increased. Figure 4

[0050] ​Optionally, when the wafer carrying device is a tray, the robot can carry the tray carrying the wafer into the carrying base in the process chamber; when the wafer carrying device is a carrying base, the robot can grab the wafer to extend into the process chamber, the pin needle is raised so that the robot releases the wafer onto the pin needle, the robot exits after releasing the wafer, and the pin needle carrying the wafer is lowered so that the wafer falls into the wafer groove of the carrying base.

[0051] S120, performing first etching on the wafer to remove the byproducts on the sidewall of the trench facing the direction of the etching gas injection. In an optional embodiment, the first etching is mainly physical bombardment.

[0052] S130, rotating the wafer by a preset angle so that the other sidewall of the trench faces the injected etching gas to a certain extent. Optionally, if the trench pattern (such as the bottom pattern or the top view pattern) is a relatively regular shape such as a rectangle or a long strip, the preset angle is an integer multiple of 180°, so that the wafer can be rotated from the posture shown in (a) to the posture shown in (b) according to the preset angle, so that the byproducts on the sidewall of the trench can be removed when the wafer is in the posture shown in (a), and the byproducts on the other sidewall of the trench can be removed when the wafer is in the posture shown in (b). Figure 4 Figure 4 Figure 4 Figure 4

[0053] Specifically, the process of rotating the wafer by a preset angle includes: taking out the wafer carrying device from the process chamber, rotating the wafer by a preset angle, and then putting the wafer carrying device after the wafer rotation into the process chamber.

[0054] S140, performing second etching on the wafer to remove the byproducts on the other sidewall of the trench.

[0055] The method for removing the byproducts in the trench by tilting etching on the wafer can increase the contact area between the etching gas and the sidewall of the etched trench, the stripe protrusion on the sidewall of the trench can be better bombarded by the etching gas, the top end of the stripe protrusion can be etched at a high rate under the bombardment of the etching gas, the bottom of the stripe protrusion can be etched at a low rate, so that the height difference of the stripe protrusion can be reduced, and the roughness of the sidewall of the trench can be reduced; for the trench bottom, the micro-groove formed in the process of etching to form the trench can be reduced because the bottom of the micro-groove is etched at a low rate and the reflected particles are difficult to enter the micro-groove again, and the micro-groove phenomenon can be reduced without being aggravated again.

[0056] ​​​​Optionally, the etching gas used in the first etching and the second etching is a physical etching gas, which includes at least one of an inert gas and N2 (nitrogen), wherein the inert gas can include Ar (argon) and He (helium) and the like; for example, the physical etching gas can use Ar, so that the corresponding plasma has a higher etching efficiency, for another example, the physical etching gas can use N2, so that the corresponding plasma has a higher etching precision, for another example, the physical etching gas can use a mixed gas of Ar and N2, so as to take into account the etching efficiency and the etching precision. When the by-products in the trench are removed by physical bombardment, the etching speed is low (for example, the etching rate of Ar is between 5-15 nm / min), and only a slight etching of the wafer is performed in the process of cleaning the by-products on the sidewall of the trench, for example, the etching depth of the sidewall of the trench can be controlled within 10 nm, and the bottom surface Ra (roughness) can be reduced by 1-3 nm. Such low-speed etching does not change the original structure of the wafer and does not cause damage to the wafer.

[0057] Specifically, the process and parameters used in the first etching and the second etching are the same, for example, both etching processes can include: introducing a physical etching gas into a process chamber, loading a radio frequency power into the process chamber to ionize the physical etching gas to generate a corresponding plasma to etch the wafer. The process parameters of the first etching and the second etching include: the upper radio frequency power (SRF) ranges from 200-500w, and the lower radio frequency power (BRF) ranges from 20-200w; and / or, the etching time ranges from 30-60s; wherein the etching time can be determined according to the target depth of the trench, and the target depth is large, and the etching time can be relatively long, for example, if the target depth is less than or equal to 300nm, the etching time can be set to 50s or 60s and the like, and if the target depth is greater than 300nm, the etching time can be relatively extended according to the increasing amplitude of the target depth.

[0058] Further, the process parameters of the first etching and the second etching can also include: the etching pressure ranges from 1-4mTorr, and the etching pressure in this range can provide a low-pressure etching environment, which is suitable for etching wafers of lithium niobate and the like. Etching such wafers in a low-pressure environment can quickly dissociate the by-products generated in the etching process, which is helpful for the discharge of the by-products.

[0059] In some embodiments, the bottom of the wafer is coated with a heat transfer medium such as pump oil to improve the heat conduction performance in the etching process. After the wafer with the trench pattern is placed on the wafer carrying device, the method for removing the by-products in the trench can further include: transferring the wafer carrying device into the process chamber, electrostatically adsorbing the wafer carrying device, and introducing He (helium) into the bottom of the wafer carrying device to uniformly heat, so as to prepare a uniform and stable chamber environment in advance.

[0060] The above-described method for removing byproducts in trenches involves placing a wafer with a trench pattern on a wafer carrier device with an inclined wafer trench and then introducing it into a process chamber. This tilts the wafer within the chamber, allowing one sidewall of the trench to face the incoming etching gas, increasing the contact area between the etching gas and the sidewall. During the first etching operation, byproducts on that sidewall are effectively removed. Then, the wafer is rotated by a preset angle so that the other sidewall faces the incoming etching gas, allowing for a second etching operation that effectively removes byproducts from the other sidewall. These two etching processes effectively reduce the roughness of the trench sidewalls and weaken micro-groove defects at the bottom of the trench. Therefore, this method for removing byproducts in trenches can optimize trench performance in wafers from multiple perspectives.

[0061] A third aspect of this application provides a method for forming a trench structure, with reference to... Figure 7 As shown, the method for forming the trench structure includes steps S210 and S220.

[0062] S210 etches trenches on the wafer surface.

[0063] S220, the trench is modified using the method for removing by-products in the trench as described in any of the above embodiments, so as to remove by-products from the sidewalls of the trench.

[0064] Specifically, etching trenches on the wafer surface includes: introducing etching gas into a process chamber; applying radio frequency power to the process chamber at a first chamber pressure to generate plasma; gradually reducing the pressure of the process chamber while maintaining the ignition state to a second chamber pressure, the second chamber pressure being less than the first chamber pressure; and etching the wafer to form trenches.

[0065] The process chamber may include a plasma process chamber employing an ICP coil, wherein the ICP coil may be a three-dimensional structure, such as a reference... Figure 8 As shown, the use of a three-dimensional ICP coil allows byproducts generated during subsequent etching to deposit on the inner wall of the cavity, minimizing their impact on the RF power feed and avoiding etching instability caused by byproduct interference in planar coils. The three-dimensional ICP coil can be a belt structure with 1, 3, or 5 turns. In some examples, the process chamber for trench formation is different from the process chamber for trench modification. In other examples, the process chamber for trench formation is the same as the process chamber for trench modification, and different wafer carriers can be used for trench formation and trench modification.

[0066] Specifically, the etching gas used to form the trench can include a chemical etching gas and an auxiliary etching gas. Optionally, the chemical etching gas is a halogen chemical etching gas, which can be any one of CF4 (carbon tetrafluoride), CHF3 (trifluoromethane), BCl3 (boron trichloride), and Cl2 (chlorine). Optionally, the auxiliary etching gas can be a physical bombardment gas including Ar.

[0067] The first chamber pressure is 10-50 mTorr, and the chamber pressure in this range enables the process chamber to have ignition conditions, and the plasma source can be successfully ignited. The second chamber pressure is 1-5 mTorr to provide a low-pressure etching environment, rapidly dissociate byproducts in the etching process, and facilitate the discharge of byproducts.

[0068] Optionally, the above-mentioned process chamber is provided with an etching gas, and the process chamber is loaded with a radio frequency power at the first chamber pressure, including: the process chamber is provided with a chemical etching gas at a first flow rate and an auxiliary etching gas at a second flow rate; the pressure in the process chamber is adjusted to the first chamber pressure, and the upper radio frequency power is loaded for ignition, and the lower radio frequency power is loaded for auxiliary ignition. The second flow rate is 5-20 times the first flow rate, for example, the first flow rate can be 2-7 sccm, and the second flow rate can be 10-150 sccm. Here, the upper radio frequency power and the lower radio frequency power are loaded at the same time, and the lower radio frequency power is used to assist ignition, which can make the ignition process more reliable. The upper radio frequency power during ignition can be 300-1200 W.

[0069] Optionally, the above-mentioned process chamber is provided with a PV valve for adjusting the internal pressure; the PV valve can be used to adjust the pressure in the process chamber according to the preset opening degree. Optionally, the preset opening degree of the PV valve can be determined according to the amount of gas, and the value range can be 200-400, so that the pressure in the process chamber is gradually lowered to 1-5 mTorr within the gradual pressure reduction time, realizing gradual pressure reduction, which can effectively avoid the radio frequency extinction phenomenon when the pressure in the process chamber is lowered to below 5 mTorr (such as 1-2 mTorr), so as to realize stable ultra-low pressure etching of the wafer in the process chamber, and rapidly dissociate byproducts during etching to promote the discharge of byproducts.

[0070] Optionally, the radio frequency power used to form the trench includes a lower radio frequency power of 50-500 W, and the lower radio frequency power is less than 80% of the upper radio frequency power.

[0071] In some examples, the etching depth can be monitored using detection systems such as LEP (Laser-to-Edge Detection) or IEP (Integrated Electro-Optical Detection) during the formation of the trench structure. Specifically, the etching depth during trench formation is 70%-90% of the target trench depth, reserving some depth for the finishing etching process. The finishing etching process can continue etching to the bottom of the trench to reach 10%-30% of the target depth, which, while completing the remaining etching depth, can also weaken microgroove defects at the bottom of the trench.

[0072] In some examples, the method for forming trench structures described above is illustrated using the etching of lithium niobate wafers as an example. This method can be used to etch waveguide devices, where the raised ridges between the resulting trenches can serve as waveguides. BCl3 is used as the chemical etching gas and Ar as the auxiliary etching gas during trench formation. The corresponding process formulations are shown in Table 1. In Table 1, the initialization steps represent the initial stabilization process before ignition. In the pressure control method, Pressure indicates direct adjustment to the target gas pressure, and Position indicates gradual adjustment to the target gas pressure. During the trench formation process, as... Figure 1 As shown, the trench sidewalls will form a similar Figure 1 The stripes shown in (b) are raised, and microgroove defects are easily formed at the bottom of the groove.

[0073] Table 1

[0074] Step Initialization Ignition Ignition stabilization Etching Duration (s) 5 5 5 20 Gas pressure (mTorr) 20 20 / 3 SRF (w) 0 200 470 470 BRF (w) 0 20 0 150 Ar (sccm) 50 50 50 50 BCl3(sccm) 4 4 4 4 Pressure control mode Pressure Pressure Position Pressure PV valve opening 0 0 300 0

[0075] The modification etching process can adopt the process formulation shown in Table 2. In Table 2, the etching gas includes Ar. The initialization step refers to the initial stabilization process before ignition. In the pressure control method, Pressure represents direct adjustment to the target gas pressure, and Position represents gradual adjustment to the target gas pressure.

[0076] Table 2

[0077] Step Initialization Ignition Ignition stabilization Etching Duration (s) 5 5 5 20 Gas pressure (mTorr) 20 20 / 2 SRF (w) 0 200 400 200 BRF (w) 0 20 0 20 Ar (sccm) 50 50 30 30 [N2 (sccm)] 0 0 0 0 Pressure control mode Pressure Pressure Position Pressure PV valve opening 0 0 200 0

[0078] The inventors also compared and analyzed the method of tilting the wafer in an inclined wafer trench for etching during the modification etching process of this application with the method of placing the wafer in a horizontal wafer trench for conventional etching. The analysis process is as follows:

[0079] In conventional etching methods, the rebound of etching gases (such as Ar) at the corners of the trenches can easily lead to secondary etching, potentially exacerbating the trenching effect of microgrooves and worsening the microgroove problem at the bottom of the trenches. Figure 9As shown. In this conventional etching method, the etching gas bombardment mainly cleans up the by-products at the bottom of the trench, while the contact area between the trench sidewall and the corresponding plasma is small. The plasma cannot effectively clean up the by-products on the sidewall, and may even aggravate the sidewall striations. It can be seen that the conventional etching method is difficult to reduce the roughness of the trench sidewall, and may even increase the roughness at that location.

[0080] In tilted etching, the contact area between the trench sidewalls and the corresponding plasma increases, allowing the stripes on the trench sidewalls to be better bombarded by the etching gas. Figure 10 As shown in (a), increasing the angle between the etching direction and the stripe protrusions on the trench sidewall allows for more effective etching of the stripe protrusions. The top of the stripe protrusions etches rapidly under the bombardment of the etching gas, while the bottom of the stripe protrusions etches slowly, resulting in a reduced surface undulation after etching. Figure 10 As shown in (b), this reduces the roughness of the trench sidewalls. For the trench bottom, the microgrooves formed during the etching process have a low etching rate at the bottom due to the change in the etching gas bombardment angle, and the reflected particles are unlikely to re-enter the microgrooves, thus mitigating the microgrooving phenomenon and preventing secondary aggravation. Furthermore, for lithium niobate wafers, which have strong LN bond energies, Ar bombardment etching is used at a low etching rate (between 5-15 nm / min). During the process of cleaning byproducts from the trench sidewalls and optimizing the roughness of the trench bottom, only the original structure of the wafer is slightly etched. For example, the etching depth for the trench sidewalls can be controlled within 10 nm, reducing the bottom surface roughness by 1-3 nm. This low-speed etching does not alter other structures of the lithium niobate wafer and does not cause related structural damage.

[0081] Furthermore, the inventors observed the results obtained by etching lithium niobate wafers using conventional methods to form trenches, and by first etching trenches on the surface of the lithium niobate wafer and then modifying the etching of the trenched lithium niobate wafer using an inclined etching method. They found that after etching the lithium niobate wafer using the conventional etching method, there were obvious byproduct residues on the sidewalls of the trenches, such as... Figure 11 As shown in (a), the bottom surface of the trench has a high roughness and slight microgrooves, such as Figure 11 As shown in (b). Using the method for forming trench structures provided in this application, trenches are first formed by etching on the surface of a lithium niobate wafer, and then the byproducts on the trench sidewalls are cleaned using two tilting etching processes. After etching is completed, the byproducts on the trench sidewalls are significantly reduced, as shown in (b). Figure 12 As shown in (a), the angle between the trench sidewall and the bottom surface did not change significantly; this angle was greater than 60°, and the microgroove problem at the bottom did not worsen; in fact, it was mitigated to some extent. Figure 12 As shown in (b).

[0082] It can be seen that the method for forming a trench structure provided by the application can effectively clean by-products on the trench sidewall, optimize the roughness thereof, weaken defects on the trench bottom, maintain the angle between the trench sidewall and the bottom, avoid damage to other related structures, and improve the performance of the obtained wafer product.

[0083] Although the application has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art based on the foregoing description and accompanying drawings. The application includes all such modifications and alterations and is limited only by the scope of the following claims. In particular, with reference to the various functions performed by the foregoing components (individually and collectively referred to as "components"), the terms used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the component (e.g., that is functionally equivalent), whether or not the function is structurally identical to the structure shown in the exemplary implementations of the specification.

[0084] That is, the above only describes the embodiments of the application, and does not limit the patent scope of the application, and any equivalent structure or equivalent process transformation using the content of the specification and drawings of the application, such as the mutual combination of technical features between embodiments, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the application.

[0085] In addition, in the description of the application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application. In addition, for structural elements with the same or similar properties, the same or different reference numerals can be used to identify them. In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features with "first", "second" can explicitly or implicitly include one or more features. In the description of the application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0086] In this application, the use of the singular includes the plural unless specifically stated otherwise. In this application, the use of "or" means "and / or" unless stated otherwise. In this application, the use of "an" includes "one or more". In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at least a third" unless context clearly states otherwise. In this application, the use of "another" means "at least a second" or "at

Claims

1. A wafer carrier device, characterized in that, The wafer carrier includes at least one wafer trench for carrying the wafer, and the bottom surface of each wafer trench is an inclined surface relative to the horizontal plane. The inclination angle of the inclined surface relative to the horizontal plane is 3-10°, so as to reduce the roughness of the trench sidewall and alleviate the microgroove phenomenon at the bottom of the trench during the removal of by-products in the trench of the wafer.

2. The wafer carrier device according to claim 1, characterized in that, The depth of the wafer trench is 0.2-0.8 mm.

3. The wafer carrier device according to claim 1, characterized in that, The wafer carrier is a tray; the thickness of the tray is 1-5mm, and the remaining thickness of the tray on the bottom surface of the wafer slot is greater than or equal to 0.6mm.

4. A method for removing byproducts from trenches, used on wafers with trench patterns, characterized in that, The method includes: The wafer with the grooved pattern is placed on a wafer carrier device, wherein the wafer carrier device is any one of claims 1 to 3; The wafer is first etched; Rotate the chip by a preset angle; The wafer is then subjected to a second etching.

5. The method for removing by-products from trenches according to claim 4, characterized in that, The preset angle is an integer multiple of 180°.

6. The method for removing by-products from trenches according to claim 4, characterized in that, The etching gases used for the first and second etching processes include at least one of Ar, He, and N2.

7. The method for removing by-products from trenches according to claim 4, characterized in that, The process parameters for the first etching and the second etching include: etching pressure ranging from 1 to 4 mTorr; and / or upper RF power ranging from 200 to 500 W, lower RF power ranging from 20 to 200 W; and / or etching time ranging from 30 to 60 s.

8. A method for forming a trench structure, characterized in that, The method includes: Trenches are formed by etching on the wafer surface; The byproducts on the sidewalls of the trench are removed by the method for removing byproducts in the trench as described in any one of claims 4-7.

9. The method for forming a trench structure according to claim 8, characterized in that, The etching of trenches on the wafer surface includes: Etching gas is introduced into the process chamber; Under the first chamber pressure, radio frequency power is applied to the process chamber to generate plasma; While maintaining the ignition state, the process chamber is gradually depressurized to reduce the chamber pressure to a second chamber pressure, which is lower than the first chamber pressure. The wafer is etched to form trenches.

10. The method for forming a trench structure according to claim 9, characterized in that, The pressure in the first chamber is 10-50 mTorr, the pressure in the second chamber is 1-5 mTorr, and the pressure drop time is 3-10 s.

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