Selective removal of Si3N4 by wet chemical method

Abstract

A system for processing a substrate and a method for processing a substrate are disclosed. The system for processing a substrate includes a processing chamber configured to receive a substrate, wherein the substrate is exposed to an etchant in the processing chamber to remove a portion of the substrate and create access to the substrate. By-products in the etchant; a by-product removal unit for converting the by-products into precipitates and removing the precipitates, thereby removing the by-products. After removing the by-products, the etchant solution is recycled back to the processing chamber.

Description

[0001] Related Applications

[0002] This application is a national stage application of PCT / US2020 / 019097, which was filed on February 20, 2020 and claims priority to and the benefit of U.S. Provisional Application No. 62 / 808,646, filed on February 20, 2019, the entire content of which is incorporated herein by reference. Technical Field

[0003] The present disclosure generally relates to semiconductor design and manufacturing. Specifically, the present invention relates to a method for removing a dielectric layer from an integrated circuit device. Background Art

[0004] Integrated circuits are the foundation of the information industry. The development and application of technologies such as 5G, artificial intelligence, the Internet of Things, and autonomous driving all rely on integrated circuits such as processors and memories. The pursuit of higher performance and lower cost integrated circuits has led to integrated circuits with higher integration densities. This poses challenges to various semiconductor manufacturing equipment such as wet etching equipment.

[0005] During the manufacturing process of an integrated circuit (IC) device, a dielectric layer is typically used to assist the manufacturing process. After the assisting manufacturing process, the silicon nitride layer must be removed.

[0006] Several processes for removing a silicon nitride layer from an IC device that is selective to silicon oxide are known, i.e., removing the silicon nitride without significantly eroding the silicon oxide. In one removal process, a substrate containing a silicon nitride layer is immersed in water at a high temperature (100 °C). Other removal processes use phosphoric acid (H3PO4). At low temperatures, phosphoric acid cannot significantly etch silicon nitride because it cannot significantly erode silicon nitride. Higher temperatures not only accelerate the etching rate of silicon nitride but also accelerate the corrosion of silicon oxide. As a result, it is difficult to etch a silicon nitride structure using phosphoric acid.

[0007] In view of the above, there is a need for an effective or cost-effective method for selectively removing silicon nitride. Summary of the Invention

[0008] According to a first aspect, a method for removing a dielectric material from a semiconductor device structure may include a processing chamber and a by-product removal section. The processing chamber may be configured to receive the semiconductor device structure. The semiconductor device structure may be exposed to an etchant in the processing chamber to remove a portion of the structure and generate by-products that enter the etchant. The by-product removal section may be configured to convert the by-products into precipitates and remove the precipitates, thereby continuously removing the by-products.

[0009] In certain aspects, the by-product removal section includes a precipitation accelerator supply section.

[0010] In some aspects, the precipitation accelerator supply section includes a filter configured to remove precipitates.

[0011] In some aspects, the by - product removal section further includes a precipitation chamber disposed on the upstream side of the filter. The precipitation accelerator supply section is configured to supply a precipitation accelerator to the precipitation chamber.

[0012] In some aspects, the system includes an etchant treatment section. The etchant treatment section is configured to prepare an etchant.

[0013] In some aspects, the etchant treatment section is configured to store the etchant.

[0014] In some aspects, the etchant treatment section includes a chemical reagent supply section for supplying chemical reagents.

[0015] In some aspects, the etchant treatment section includes a chamber for mixing and storing chemical reagents.

[0016] In some aspects, for example, the diameter of the filter does not exceed about 0.22 microns.

[0017] According to a second aspect, a method of removing dielectric material from a semiconductor device structure includes the steps of introducing an etchant into a processing chamber to remove a portion of the semiconductor device structure and generate by - products; converting the by - products into precipitates; and removing the precipitates, thereby continuously removing the by - products.

[0018] In some aspects, converting the by - products into precipitates includes the step of supplying a precipitation accelerator to the etchant.

[0019] In some aspects, removing the precipitates includes filtering out the precipitates.

[0020] In some aspects, the etchant includes a phosphoric acid - containing solution.

[0021] In some aspects, a portion of the substrate includes silicon nitride.

[0022] In some aspects, the by - products include silicic acid.

[0023] In some aspects, the precipitation accelerator includes one or more of the following: hydrogen fluoride, water, amino acids, amines, or inorganic salts containing Ca or Mg, etc.

[0024] In some aspects, the precipitation accelerator causes the by - products to precipitate on the precipitation accelerator. The precipitation accelerator includes one or more of the following: molecular sieves, silicate powders, quartz, or siloxanes.

[0025] In some aspects, the present invention includes real - time monitoring of the by - product concentration.

[0026] In some aspects, the present invention includes real - time monitoring of the by - product concentration.

[0027] In some aspects, the precipitation promoter is introduced proportionally.

[0028] In some aspects, the amount of the precipitation promoter introduced is not proportional.

[0029] In some aspects, the precipitation promoter causes a change in the by-product temperature, either higher or lower.

[0030] According to a third aspect, a method for removing a dielectric material from a semiconductor device structure includes exposing the semiconductor device structure to a solution that exhibits a positive etch selectivity to the dielectric material (such as silicon nitride); chemically removing the dielectric material from the semiconductor device structure such that the solution exhibits a negative etch selectivity to silicon oxide.

[0031] In some aspects, the method further includes converting the silicon nitride into a by-product.

[0032] In some aspects, the method further includes converting the by-product into a precipitate.

[0033] In some aspects, the method further includes removing the precipitate from the solution.

[0034] In some aspects, the method further includes monitoring the composition of the solution in real time.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS These and other advantages of the present invention can be easily understood with reference to the following description and drawings, wherein:

[0036]

[0037] Figure 1 A system for processing a substrate according to an embodiment of the present disclosure is shown;

[0038] Figure 2 is a schematic cross-sectional view of a substrate to be processed according to an embodiment of the present invention.

[0039] Figure 3 A system for processing a substrate according to an embodiment of the present disclosure is shown;

[0040] Figure 4 A by-product removal portion according to an embodiment of the present invention is shown;

[0041] Figure 5 A system for processing a substrate according to an embodiment of the present disclosure is shown;

[0042] Figure 6A A connection manner of an etchant processing portion according to an embodiment of the present invention and a first circulation pipeline is shown;

[0043]

[0044] Figure 6B ​​Shows the etchant treatment section according to another embodiment of the present invention and the connection manner with the first circulation pipeline;

[0045] Figure 6C Schematic diagram of the etching solution treatment section according to another embodiment of the present invention and the connection manner with the first circulation pipeline.

[0046] Figure 7 Shows a system for processing a substrate according to an embodiment of the present disclosure; and

[0047] Figure 8 Shows a flowchart of a method for processing a substrate according to an embodiment of the present disclosure. Detailed Description of the Invention

[0048] The following preferred embodiments of the present disclosure may be described with reference to the accompanying drawings. In the following description, well-known functions or structures are not described in detail because they may obscure the present disclosure with unnecessary details. For the present disclosure, the following terms and definitions shall apply.

[0049] References to "one embodiment" or "an embodiment" throughout the specification mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the claimed subject matter. Thus, the phrases "in one embodiment" or "an embodiment" appearing throughout this specification do not necessarily all refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in one or more embodiments.

[0050] The process steps described below may not form a complete process flow for manufacturing IC devices. Only the process steps necessary for understanding the present invention are disclosed.

[0051] Wet etching technology is one of the key technologies in semiconductor manufacturing technology. When etching a substrate, in order to precisely control the etching rate and obtain the etching selectivity for a specific material, in addition to meeting reaction process conditions such as temperature, it is usually also necessary to keep the content or concentration of various components in the etching solution or the etching solution within the error range. For example, on the one hand, as the etching reaction proceeds, the active components in the etching solution will gradually be consumed. Therefore, it is necessary to monitor the components of the etching solution in real time and timely replenish the consumed effective components. On the other hand, various etching by-products will be generated during the etching reaction. If these by-products cannot be removed in a timely manner, these by-products will have potential adverse effects on the etching process. Unfortunately, the current design work of wet etching equipment mainly focuses on the former, and the latter has not received enough attention. This results in a general lack of the ability to remove etching by-products in related etching equipment. However, with the continuous improvement of the integration and complexity of integrated circuits, the lack of this ability will not only reduce the recovery rate of the etching solution, but also make it difficult to form very fine semiconductor device structures.

[0052] ​

[0053] In particular, current NAND memories are typically constructed with a 3D structure. Key steps in forming the 3D structure include: forming a stack composed of alternatingly stacked silicon nitride layers and silicon dioxide layers on a semiconductor substrate such as silicon. Forming trenches through the stack to reach the substrate by dry etching techniques. The structure of the 3D NAND is related to the following U.S. patents. Patent Application Serial No.: 16 / 517,600, filed on July 21, 2019, claiming priority and benefiting from PCT Application No.: PCT / US18 / 14408, filed on January 19, 2018, claiming priority and benefiting from U.S. Provisional Application No. 62 / 448,677, filed on January 20, 2017. Construction of a 3D ferroelectric oxide memory device. Patent Application Serial No.: 16 / 517,598, which claims priority and benefits from the PCT application number. PCT / US18 / 14416, filed on January 19, 2018, claiming U.S. Provisional Application No.: 62 / 448,677, filed on January 20, 2017. The above applications are co-owned with this application and are incorporated herein by reference in their entirety.

[0054] The silicon nitride material layer is selectively removed by an etching solution with phosphoric acid as the main etchant. Specifically, the silicon nitride layer in the stack is removed through the trenches formed in the stack and silicon, thereby removing the nitride. For 3D NAND memories, the main method to increase the storage density is to increase the number of layers of the 3D structure, that is, the number of silicon nitride layers and silicon dioxide layers. However, increasing the number of silicon nitride layers and silicon dioxide layers not only means an increase in the amount of silicon nitride to be removed, but also means an increase in the etching depth due to the increase in the aspect ratio. In this case, the influence of etching by-products cannot be ignored. Etching silicon nitride with a phosphoric acid solution forms

[0055] the main etching by-product is silicic acid, which exists in the form of orthosilicic acid (Si(OH)4) and the phosphoric acid solution. The inventors have found in practice that as the number of layers of the 3D structure increases, the orthosilicic acid that enters (e.g., dissolves) the phosphoric acid solution is more likely to polymerize and eventually precipitate beyond its solubility limit during the etching process. This phenomenon will prevent further silicon nitride etching and even cause

[0056] particle contamination on the surface of the structure, making it difficult to form the desired high aspect ratio structure. Currently, the etching equipment of the related technology cannot solve or alleviate the above problems.

[0057] Embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0058] Figure 1 Shown is a system 1 for processing a substrate according to an embodiment of the present disclosure. As shown. Refer to Figure 1, System 1 for processing a substrate includes a processing chamber 10 and a by-product removal section 20. The processing chamber 10 is configured to receive a substrate 100, where the substrate 100 is exposed to an etchant to remove a portion of the by-products. The substrate 100 generates by-products that enter (e.g., dissolve, etc.) into the etchant. The by-product removal section 20 is used to convert the generated by-products into precipitates and remove the precipitates, thereby removing the by-products.

[0059] Through the above system, the etching by-products with potential adverse effects in the etching solution can be removed or reduced in a timely manner during the etching process, thereby ensuring that the etching process can proceed well. As described above, this is particularly important for selectively removing silicon nitride during the manufacturing process of 3D NAND memories. According to an embodiment of the present disclosure, the etchant may include a phosphoric acid solution. The removed portion of the substrate 100 includes silicon nitride.

[0060] Figure 2 A cross-sectional view of the substrate 100 to be processed according to an embodiment of the present disclosure is shown. The substrate 100 is particularly suitable for manufacturing 3D NAND memories. As shown. Referring to Figure 2 , the substrate 100 may include a substrate 101 (e.g., a silicon substrate) and a stack 102 on the substrate 101. The stack 102 includes a silicon dioxide layer 1021 and a silicon nitride layer 1022 alternately stacked on the substrate 101. The substrate 100 also includes a hole 103 extending through the stack 102. During the etching process, the substrate 100 is disposed in the processing chamber 10 and exposed to the etchant or etching solution entering the hole 103, thereby removing each silicon nitride layer 1022 in the stack 102.

[0061] Figure 3 A system for processing a substrate according to an embodiment of the present disclosure is illustrated. As Figure 3 shown, the processing chamber 10 and the by-product removal section 20 are disposed in a first circulation pipeline 50 for circulating the etching solution in a first circulation direction A. The first circulation pipeline 50 includes a first pipeline 51 and a second pipeline 52. The first pipeline 51 may be configured to guide the etching solution from the processing chamber 10 to the by-product removal section 20, and the second pipeline 52 is configured to convey the etchant from the by-product removal section back to the processing chamber 1020. Through this system configuration, the etchant can be circulated between the processing chamber 10 and the by-product removal section 20, so that it can be recycled, which increases the processing capacity and material utilization rate. In addition, as shown. As Figure 3 shown, a pump P and a valve V are provided in the new circulation loop 50 as needed to control the flow rate and flow velocity of the etching solution. It should be understood that other additional devices (not shown), such as heating gases, various sensors, pressure gauges, etc., may also be provided in the first circulation pipeline 50, and the embodiments of the present invention do not limit this.

[0062] Figure 4Shows a by-product removal section according to an embodiment of the present invention. As Figure 4 shown, the by-product removal unit 20 includes a precipitation accelerator supply unit 21 and a filter 22. The precipitation accelerator supply unit 21 is configured to supply, upstream of the filter 22, for example, in the first circulation direction A, a precipitation accelerator for converting etch by-products into precipitates. The filter 22 is configured to remove the generated precipitates.

[0063] In the case where the etchant is a phosphoric acid solution and the material layer to be etched is a silicon nitride layer, as described above, the etch by-product that easily forms a precipitate is silicic acid, which exists in the form of orthosilicic acid in the phosphoric acid solution. Optionally, the precipitation accelerator may include at least one of the following: hydrogen fluoride, H2O, amino acids, amines, inorganic salts containing Ca, Mg, etc. For example, when the precipitation accelerator is hydrogen fluoride, the reaction to produce a precipitate is represented by the following formula:

[0064]

[0065] The precipitation accelerator may include a solid structure that causes silicic acid to precipitate on the surface of the solid structure. Such a solid structure may include, but is not limited to, SiO2 in powder or lump form, or molecular sieves, etc.

[0066] The precipitation accelerator may heat or cool the by-products to accelerate precipitation.

[0067] Figure 5 Shows a system for processing a substrate according to an embodiment of the present disclosure. As shown in the figure. Referring to Figure 5 , the substrate processing system further includes an etchant processing unit 30 connected to the first circulation pipeline 50. The etchant processing unit 30 is configured to perform at least one of the following functions: 1) prepare and store the etchant; 2) supply the prepared etchant to the first circulation line; 3) supply chemical reagents to the first circulation pipeline to adjust the etchant. It should be understood that the etchant processing unit 30 can be connected to any suitable position in the first circulation pipeline 50 according to actual needs. Although the etchant processing section 30 is Figure 2 shown as being connected

[0068] to the second pipeline 52 (i.e., the downstream side of the by-product removal section 20). As Figure 5 shown, the etchant processing unit 30 can be connected to the first pipeline 51 (i.e., the upstream side of the by-product removal unit). However, considering that the etch by-products and the precipitation accelerator may have a potential impact on the chemicals from the etchant processing section 30, it is advantageous to connect the etch processing section 30 to the second wiring 52.

[0069] Figures 6A-6C Shows an etchant processing unit and its connection to the first circulation loop according to various embodiments of the present invention. As shown in the figure. Referring toFigures 6A-6C The etchant treatment unit 30 includes a chemical agent supply unit 31 for supplying chemical agents and a cavity 32 for mixing and storing chemical agents. It should be understood that the cavity 32 of the etchant treatment section 30 is not necessary. In the absence of the cavity 32, the chemical reagent supply unit 30 can directly supply chemical reagents to the circulation path 50. According to an embodiment of the present disclosure, for etching silicon nitride, the chemical reagents provided by the chemical reagent supply section 31 may include, but are not limited to, phosphoric acid, water, and various additives. The additives may include, for example, a silicon dioxide etching inhibitor (a silicon compound, such as H2SiO3, etc.), a silicon nitride etching promoter (a fluorine compound, such as NH4F, NH4HF2, etc.). At room temperature, the various additives can be liquid, solid, or gas.

[0070] According to an embodiment of the present disclosure, as Figure 1 shown. Referring to Figure 6A FIG., the cavity 32 may include a cavity provided in the first circulation pipeline 50 (specifically provided in the second circulation pipeline 52). According to an embodiment of the present disclosure, as Figure 1 shown. As Figure 6B shown, the cavity 32 includes a first cavity 32a and a second cavity 32b. The first cavity 32a is provided with the first circulation pipeline 50 (specifically the second pipeline 52). The second chamber 32b may be connected to the first chamber 32a and may be provided in the supply pipeline 60 that does not form the first circulation pipeline 50. The chemical agent supply unit 31 is configured to extend into the first cavity 32a and the second cavity 32b, and at least one of the first cavity 32a or the second cavity 32b provides chemical reagents. According to an embodiment of the present disclosure, the cavity 32 may be provided in the supply pipeline 60 that does not form the first circulation pipeline 50. As Figure 6C shown, the cavity 32 includes a first cavity 32a and a second cavity 32b provided in the supply pipeline 60. The first cavity 32a is connected to the second pipeline 52, and the second cavity 32b is connected to the first cavity 32a. In addition, as shown in FIG. Figure 6C shown, the chemical agent supply unit 31 is configured to supply chemical agents to at least one of the first cavity 32a and the second cavity 32b. In addition, as shown in the figure. Referring to Figure 6B and 6C FIG., the cavity 32 may have a separate circulation pipeline 70 so that the chemicals supplied to the cavity 32 can be sufficiently stirred and mixed. In addition, the cavity 32 may have a heater and various sensors (not shown).

[0071] Figure 7 FIG. shows a system for processing a substrate according to an embodiment of the present disclosure. As Figure 7As shown, the substrate processing system 1 further includes a third line 81. One end of the third line 81 is connected to the first line 51, and the other end of the third line 81 is connected to a part of the second line. Downstream of the etchant processing unit 30. The third line portion 81 is configured to remove the etchant from the second line. The pipeline 52 leads back to the first pipeline 51. After introducing the third pipeline 81, the third pipeline 81, the by-product removal section 20, and the etchant processing section 30 can form a second circulation pipeline 80 that circulates in the second cycle, which enables the etchant solution to be circulated and processed by the by-product removal section 20 and the etchant solution processing section 30 before entering the processing chamber 10. With this configuration, the etchant solution can be fully processed and stabilized before being introduced into the processing chamber 10.

[0072] In another aspect of the present disclosure, a method for processing a substrate is provided. Figure 8 A flowchart of a method for processing a substrate according to an embodiment of the present disclosure is shown. The method for processing a substrate includes: introducing an etchant solution into a processing chamber to remove a part of the substrate and generate by-products entering the etchant solution (step S101); converting the by-products into precipitates and removing the precipitates, thereby removing the by-products (step S102). According to an embodiment of the present disclosure, converting the by-products into precipitates includes supplying a precipitation promoter to the etchant solution after use to generate precipitates. According to an embodiment of the present invention, the etchant solution includes a phosphoric acid-containing solution, a part of the substrate includes silicon nitride (such as Figure 2 the silicon nitride layer 1022 therein), the by-products include silicic acid, and the precipitation promoter includes hydrogen fluoride. Optionally, the substrate processing method may further include the step of reintroducing the etchant solution into the processing chamber after removing the by-products.

[0073] In another aspect of the present disclosure, a method for removing a dielectric material from a semiconductor device structure may include the step of exposing the semiconductor device structure to a solution that exhibits a positive etch selectivity for silicon nitride; chemically removing the silicon nitride from the semiconductor device structure such that the solution exhibits a negative etch selectivity for silicon oxide.

[0074] The method uses an etchant such as an acid solution that exhibits a positive etch selectivity or the ability to etch one material (i.e., silicon nitride) faster than a second material (i.e., silicon oxide).

[0075] Positive etch selectivity means that the acid solution etches the dielectric layer (e.g., silicon nitride) at a faster rate than silicon oxide. The acid solution used contains phosphoric acid. The acid solution may contain any concentration of phosphoric acid in water as long as the acid solution exhibits a positive etch selectivity. The phosphoric acid concentration ranges from about 50% to about 100%, more preferably 85%. The phosphoric acid solution may optionally contain additional reagents such as buffers and / or other acids such as fluoboric acid and sulfuric acid.

[0076] Negative etch selectivity means that the acid solution etches silicon oxide at a slower rate than silicon nitride.

[0077] The method may further include the steps of converting silicon nitride into a by-product; converting the by-product into a precipitate; removing the precipitate from the solution; and monitoring the composition of the solution in real time, as described above.

[0078] Although various embodiments have been described with reference to specific arrangements of components, features, etc., these are not intended to be exhaustive of all possible arrangements or features, and in fact many other embodiments, modifications, and variations can be determined by those skilled in the art. Accordingly, it should be understood that the present invention may thus be practiced in a manner different from that specifically described above.

[0079] It should be understood that a process including converting a portion of a semiconductor device into a soluble by-product, removing the by-product from the process chamber, and preparing an etchant for the process chamber in real time can be widely applied to any suitable semiconductor processing involving a liquid solution and is not limited to the semiconductor removal embodiments described in the present invention only by way of example, such as NAND, or dielectric materials, such as silicon nitride.

Claims

1. A system for removing material from a semiconductor device structure, comprising: A processing chamber configured to receive the semiconductor device structure, wherein the semiconductor device structure is exposed to an etchant in the processing chamber to remove a portion of the structure and generate by-products that enter the etchant; A by-product removal section for converting the by-products into precipitates and removing the precipitates, thereby continuously removing the by-products; And a circulation line for reintroducing the etchant into the processing chamber after the by-products are removed; The by-product removal section includes a precipitation promoter supply section and a filter, wherein the filter is configured to remove the precipitates; The precipitation promoter includes a solid structure on which the by-products precipitate; The solid structure includes molecular sieve, silica, silicate or siloxane.

2. The system according to claim 1, wherein the by-product removal section further includes a precipitation chamber provided on the upstream side of the filter, and the precipitation promoter supply section is configured to supply the precipitation promoter to the precipitation chamber.

3. The system according to claim 1, further comprising an etchant treatment section, wherein the etchant treatment section is configured to prepare the etchant.

4. The system according to claim 3, wherein, The etchant treatment section is further configured to store the etchant.

5. The system according to claim 3, wherein the etchant treatment section includes a chemical reagent supply section for supplying chemical reagents.

6. The system according to claim 5, wherein the etchant treatment section includes a chamber for mixing and storing the chemical reagents.

7. A method for removing material from a semiconductor device structure, comprising: Introducing an etchant into a processing chamber to remove a portion of the semiconductor device structure and generate by-products; Converting the by-products into precipitates; And removing the precipitates, thereby continuously removing the by-products; Wherein converting the by-products into precipitates includes providing a precipitation promoter to the etchant; The precipitation promoter includes a solid structure on which the by-products precipitate; The solid structure includes molecular sieve, silica, silicate or siloxane.

8. The method according to claim 7, wherein Removing the precipitates includes filtering out the precipitates.

9. The method according to claim 7, wherein The etchant includes a phosphoric acid-containing solution.

10. The method according to claim 7, wherein the material includes silicon nitride.

11. The method according to claim 7, wherein the precipitation promoter further includes one or more of the following: hydrogen fluoride, water, amino acid, amine or an inorganic salt containing Ca or Mg.

Images