Semiconductor structure and manufacturing method thereof
By forming a photoresist layer and performing an etching process during semiconductor manufacturing, a spacer structure is formed, which solves the leakage problem caused by voids or gaps in the semiconductor structure, improves the process yield, and protects the bit line structure.
Patent Information
- Application Number
- CN202411349021.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-07-30
- Filing Date
- 2024-09-26
- Publication Date
- 2026-01-30
AI Technical Summary
In semiconductor structures, gaps or gaps between cell contacts and bit lines can cause leakage current, affecting process yield.
By forming a photoresist layer and performing a planarization process during semiconductor manufacturing, etching an oxide layer to expose spacers, depositing a dielectric layer and forming a spacer structure, etching away excess layers, and forming cell contacts and landing pads, the generation of voids or gaps is avoided.
It effectively prevents leakage between the bit line structure and the cell contacts, improves process yield, protects the bit line structure from damage, and improves the overall performance of the semiconductor structure.
Smart Images
Figure CN121442684A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a semiconductor structure and a method of manufacturing the same. BACKGROUND
[0002] As electronic devices become lighter and thinner, semiconductor devices such as dynamic random access memory (DRAM) become more highly integrated. In addition, the performance of DRAM is improved by shortening the pitch between semiconductor structures in the DRAM. Due to the reduction in the size of the semiconductor structures, in addition to increasing the difficulty of the process, elements in the semiconductor structures are prone to leakage due to too close a pitch.
[0003] Therefore, in the semiconductor manufacturing process, how to reduce leakage to improve the process yield of the semiconductor structure becomes an important issue. SUMMARY
[0004] Embodiments of the present disclosure provide a method of manufacturing a semiconductor structure, comprising the following steps. A substrate is provided, and the substrate comprises a plurality of active regions and a plurality of insulating regions, wherein each insulating region is located between two adjacent active regions. A plurality of bit line contacts are formed in each active region, respectively, and a plurality of bit line structures are formed in each bit line contact, respectively. A first oxide layer covering the bit line structures is deposited. A second oxide layer is deposited on the first oxide layer. A photoresist layer is formed to completely cover the second oxide layer. An upper portion of the second oxide layer is removed to expose an upper portion of the first oxide layer.
[0005] In some embodiments, removing the upper portion of the second oxide layer comprises the following steps. After the photoresist layer is formed, a planarization process is performed on the photoresist layer until a top surface of the second oxide layer is exposed. An upper portion of the second oxide layer is etched to expose the upper portion of the first oxide layer.
[0006] In some embodiments, the method further comprises the following steps. After the first oxide layer is deposited, a two-contact spacer is formed, wherein each of the two-contact spacers is located on opposite sides of each bit line contact and surrounded by the first oxide layer, respectively.
[0007] In some embodiments, the method further comprises the following steps. The photoresist layer is removed. A top portion of the first oxide layer located on each bit line structure is etched until each of the two-contact spacers is exposed. After the top portion of the first oxide layer is etched, each bit line structure is shortened in height.
[0008] In some embodiments, after the top portion of the first oxide layer is etched, the top portion of the first oxide layer and each bit line structure are rounded.
[0009] In some embodiments, after etching the top of the first oxide layer, the stepped profile of the top of the second oxide layer located on the exposed upper portion of the first oxide layer becomes a smooth tapered profile of the top of the second oxide layer located on the exposed upper portion of the first oxide layer.
[0010] In some embodiments, the method further includes the following steps: After removing the photoresist layer, a first dielectric layer is conformally deposited on each bit line structure, the exposed two-contact spacer, a portion of the active region, and a portion of the insulating region. A sacrificial layer is deposited on the first dielectric layer to completely cover each bit line structure. The top of each bit line structure, the top of the first oxide layer, the top of the first dielectric layer, and the top of the sacrificial layer are removed.
[0011] In some embodiments, after removing the top of each bit line structure, the top surface of each bit line structure, the top surface of the first oxide layer, and the top surface of the first dielectric layer are coplanar.
[0012] In some embodiments, the method further includes the following steps: After removing the top of each bitline structure, the sacrificial layer is removed. A plurality of cell contacts are formed, with each cell contact located between two adjacent bitline structures. The bottom of each cell contact contacts each active region.
[0013] In some embodiments, the method further includes the step of partially removing the upper portion of the first dielectric layer, the upper portion of the first oxide layer, and the upper portion of each bit line structure during the formation of the cell contact. The top of the first dielectric layer, the top of the second oxide layer, the top of the first oxide layer, and the top of each bit line structure collectively form a rocket shape.
[0014] In some embodiments, the method further includes the following steps: forming a plurality of landing pads on each unit contact; and forming a second dielectric layer on each bitline structure to separate each landing pad from one another.
[0015] Other embodiments of the present invention also provide a semiconductor structure. The semiconductor structure includes a substrate, a bit line structure disposed above the substrate, a spacer structure disposed on and extending along the sidewall of the bit line structure, and a bit line contact disposed in each active region and contacting the bottom of a second spacer. The substrate includes a plurality of active regions and a plurality of insulating regions adjacent to the active regions. The spacer structure includes a first spacer surrounding the sidewall of the bit line structure and a second spacer surrounding the lower portion of the sidewall of the first spacer.
[0016] In some embodiments, the semiconductor structure further includes two contact spacers disposed on opposite sides of the bit line contacts.
[0017] In some embodiments, the first spacer surrounds each of the two contact spacers.
[0018] In some embodiments, the spacer structure further includes a third spacer surrounding the upper portion of the sidewall of the first spacer, the sidewall of the second spacer, and the upper portion of each of the two-contact spacers.
[0019] In some embodiments, the top of the third spacer, the top of the second spacer, the top of the first spacer, and the top of the bit line structure together form a slope.
[0020] In some embodiments, the semiconductor structure further includes a landing pad disposed on top of the bit line structure and covering the slope.
[0021] In some embodiments, the bit line structure includes a bottom cover layer disposed on a bit line contact, a conductive layer disposed on the bottom cover layer, and a top cover layer disposed on the conductive layer. A first spacer surrounds the upper portion of the top cover layer, and the first spacer and a second spacer surround the lower portion of the top cover layer.
[0022] In some embodiments, the height of the lower part of the top cover layer is greater than the height of the upper part of the top cover layer.
[0023] In some embodiments, the semiconductor structure further includes two-cell contacts disposed on opposite sides of the bit line contacts. Each of the two-cell contacts partially contacts the active region. Attached Figure Description
[0024] The following embodiments are read in conjunction with the accompanying drawings to clearly understand the viewpoint of this invention. It should be noted that, according to industry standard practice, the various features are not drawn to scale. In fact, for the sake of clear discussion, the dimensions of the various features may be arbitrarily enlarged or reduced.
[0025] Figures 1 to 3 This is a view of a method for manufacturing a semiconductor structure according to some embodiments of the present invention during the formation of a photoresist layer;
[0026] Figures 4 to 6 This is a view of a method for manufacturing a semiconductor structure according to some embodiments of the present invention during the etching of the upper portion of a second oxide layer;
[0027] Figures 7 to 9 This is a view of a method for manufacturing a semiconductor structure according to some embodiments of the present invention during the formation of spacer structures on the sidewalls of each bit line structure; and
[0028] Figure 10 and Figure 11 This is a view of a method for manufacturing a semiconductor structure according to some embodiments of the present invention during the formation of a plurality of unit contacts and a plurality of landing pads. Detailed Implementation
[0029] Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings. Where possible, the same reference numerals are used in the drawings and description to refer to the same or similar parts.
[0030] Furthermore, for ease of description, spatially related terms such as "above," "over," "below," and "between" may be used in this invention to describe the relationship or function of one element or feature to another, as shown in the accompanying drawings. In addition to the orientations depicted in the drawings, the spatially related terms are intended to cover different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or in other directions), and the spatially related descriptors used in this invention can be interpreted accordingly.
[0031] The terms “including,” “having,” and “comprising” used in this invention are open-ended terms, meaning including but not limited to.
[0032] It should be noted that when the following attached figures (e.g.) are used... Figures 1 to 11 When describing and illustrating a series of operations or steps, the order in which these operations or steps are described should not be limited. For example, some operations or steps may be performed in a different order than in this invention, or some operations or steps may occur simultaneously, or some operations may be omitted, and / or some operations or steps may be repeated. Furthermore, the actual operations or steps in the process stages may differ in the formation of the semiconductor structure (e.g., Figure 11 Additional operations or steps are performed before, during, or after the semiconductor structure 100 to form the semiconductor structure 100. Therefore, the present invention can be briefly described as a portion of these additional operations or steps. Furthermore, unless otherwise stated, the following figures (e.g.) Figures 1 to 11 The same interpretation discussed can be directly applied to other figures.
[0033] In prior art, gaps or seams exist between the cell contacts and the bit line structure, leading to storage-bit-line leakage (SBLEK). Furthermore, SBLEK worsens with subsequent processing. Therefore, embodiments of the present invention provide a semiconductor structure and a method for manufacturing the same to solve the leakage problem caused by gaps or seams between the cell contacts and the bit line structure.
[0034] Please see Figures 1 to 3 . Figures 1 to 3 This is a view of a method for manufacturing a semiconductor structure according to some embodiments of the present invention during the formation of a photoresist layer. Figure 1In this embodiment, substrate 110 includes a plurality of active regions 112 and a plurality of insulating regions 114. Each insulating region 114 is located between adjacent active regions 112 to isolate the plurality of active regions 112 from each other. In some embodiments, substrate 110 may include silicon, such as crystalline silicon, polycrystalline silicon, or amorphous silicon. Substrate 110 may include elemental semiconductors, such as germanium. In some embodiments, substrate 110 may include alloy semiconductors, such as silicon germanium, silicon germanium carbide, indium gallium phosphide, or other suitable materials. In some embodiments, substrate 110 may include compound semiconductors, such as silicon carbide (SiC), gallium arsenide (GaAs), indium phosphide (InP), indium arsenide (InAs), or other suitable materials. Furthermore, in some embodiments, substrate 110 may optionally have a semiconductor-on-insulator (SOI) structure.
[0035] Next, each of the plurality of bit line contacts BC is formed in each active region 112. Then, each of the plurality of bit line structures BL is formed on each of the plurality of bit line contacts BC. Furthermore, each bit line structure BL includes a bottom cover layer 132 on each bit line contact BC, a conductive layer 134 on the bottom cover layer 132, and a top cover layer 136 on the conductive layer 134.
[0036] Furthermore, two recesses (not shown) are formed on opposite sides of each bitline contact BC. In some embodiments, each of the two recesses exposes the sidewall of each bitline contact BC. A first oxide layer 122 is deposited over the substrate 110 and in the two recesses, covering each bitline structure BL. In some embodiments, the first oxide layer 122 comprises a low-k dielectric material, and the low-k dielectric material has, for example, a low dielectric constant (3.5). In some embodiments, the first oxide layer 122 comprises SiCO. In some embodiments, an insulating layer 120 is formed between the first oxide layer 122 and the substrate 110. In some embodiments, a spacer material layer 124A is formed on the first oxide layer 122 in each of the two recesses. In some embodiments, the spacer material layer 124A comprises SiN. Subsequently, a second oxide layer 142 is deposited on the top surface of the first oxide layer 122 and each of the two spacer material layers 124A. By forming a first oxide layer 122 embedded in the substrate 110 and surrounding each of the two spacer material layers 124A, gaps or slots between each bit line structure and the subsequently formed cell contacts can be avoided.
[0037] exist Figure 2 In this process, a photoresist layer 150 is formed to completely cover the second oxide layer 142. Subsequently, in Figure 3In the process, a planarization process is performed to remove the top of the photoresist layer 150 until the top surface TP of the second oxide layer 142 is exposed.
[0038] Please see Figures 4 to 6 . Figures 4 to 6 This is a view of a method for manufacturing a semiconductor structure according to some embodiments of the present invention during the etching of the upper portion of a second oxide layer. Figure 4 In this process, the upper portion of the photoresist layer 150 is removed to expose the upper portion of the second oxide layer 142. In some embodiments, the upper portion of the photoresist layer 150 is removed by an etching-back process.
[0039] exist Figure 5 In this process, the upper portion of the second oxide layer 142 is removed to expose the upper portion of the first oxide layer 122 on each bit line structure BL. In some embodiments, the upper portion of the second oxide layer 142 on each bit line structure BL is removed by a wet etching process. In some embodiments, the wet etching process is performed using a dilute hydrofluoric acid (DHF) etchant. In some embodiments, such as Figure 5 As shown in the enlarged view 500 of the dashed box, after removing the upper part of the second oxide layer 142, a stepped profile SW is formed at the exposed upper part of the first oxide layer 122.
[0040] exist Figure 6 In the middle, remove the photoresist layer 150 (e.g.) Figure 5 (As shown). Next, the upper portion of the first oxide layer 122 located on each bit line structure BL is removed until a portion of each of the two spacer material layers 124A is exposed to form two contact spacers 124 respectively, and the top of the first oxide layer 122 and each bit line structure BL are rounded. Therefore, after removing the photoresist layer 150, each bit line structure BL is at a height SH1 (as shown). Figure 5 The top of the first oxide layer 122 is shortened. In some embodiments, the top of the first oxide layer 122 is removed by an etching process, such as a dry etching process or a wet etching process, and the top cover layer 136 is substantially not damaged during the removal of the top of the first oxide layer 122. Therefore, the height SH1 is substantially equal to the thickness of the top of the first oxide layer 122. In some embodiments, such as Figure 6 As shown in the enlarged view 600 of the dashed frame, after etching the top of the first oxide layer 122, the stepped profile SW at the top of the second oxide layer 142 located on the exposed upper part of the first oxide layer 122 (as shown in the image). Figure 5The first oxide layer 122 is replaced by a smooth, tapered profile ST at the top of the second oxide layer 142 located on the exposed upper portion of the first oxide layer 122. In some embodiments, the height H1 measured from the top surface of the top cover layer 136 to the top surface of the conductive layer 134 is approximately 120 nanometers (nm). In some embodiments, the height H2 measured from the top of the second oxide layer 142 (after removing the top of the first oxide layer 122) to the top surface of the conductive layer 134 is approximately 45 nm. In some embodiments, the thickness of the first oxide layer 122 on the sidewall of each bit line structure BL is approximately between 3 nm and 4 nm, and preferably, the thickness T1 of the first oxide layer 122 on the sidewall of each bit line structure BL is 3.5 nm.
[0041] Please see Figures 7 to 9 . Figures 7 to 9 This is a view of a method for manufacturing a semiconductor structure according to some embodiments of the present invention, during the formation of spacer structures on the sidewalls of each bit line structure. Figure 7 In this process, after removing the top of the first oxide layer 122, a first dielectric layer 160 is conformally deposited on each bit line structure BL, each of the two exposed contact spacers 124, a portion of the plurality of active regions 112, and a portion of each insulating region 114. In some embodiments, the first dielectric layer 160 comprises a nitride. The first dielectric layer 160 is configured to protect the first oxide layer 122 and the second oxide layer 142. Specifically, the first dielectric layer 160 is configured such that no gaps or seams are created between each bit line structure BL and each of the two unit contacts, such that the thickness of the first dielectric layer 160 covering each of the two contact spacers 124 is sufficient to prevent damage to the first oxide layer 122 during subsequent etching configured to form the unit contacts (described later). In some embodiments, the thickness T2 of the first dielectric layer 160 on each bit line structure BL is between about 5 nm and 8 nm. In some embodiments, the thickness T3 of the first dielectric layer 160 covering each of the two contact spacers 124 is about 5 nm.
[0042] exist Figure 8 In this process, a sacrificial layer 170 is deposited on the first dielectric layer 160 to completely cover each bit line structure BL (not shown). In some embodiments, the sacrificial layer 170 comprises a nitride. Then, the top of each bit line structure BL, the top of the first oxide layer 122, the top of the first dielectric layer 160, and the top of the sacrificial layer 170 are removed. In some embodiments, the top of each bit line structure BL, the top of the first oxide layer 122, the top of the first dielectric layer 160, and the top of the sacrificial layer 170 are removed by an etching process (e.g., an etch-back process). Therefore, after the etching process, each bit line structure BL is at a height of SH2 (e.g., ...). Figure 7The height SH2 is shortened. In some embodiments, the height SH2 is approximately 20 nm. Therefore, after the etching process, the height H1' measured from the top surface of the top capping layer 136 to the top surface of the conductive layer 134 is approximately 100 nm. Furthermore, after the etching process, the top surface of each bit line structure BL, the top surface of the first oxide layer 122, the top surface of the first dielectric layer 160, and the top surface of the sacrificial layer 170 are coplanar. Through the sacrificial layer 170 and the etching process, the first oxide layer 122 on the sidewalls of each bit line structure BL is not lost during the shortening of each bit line structure BL.
[0043] exist Figure 9 In this process, the sacrificial layer 170 is removed to expose the first dielectric layer 160. In some embodiments, the sacrificial layer 170 is removed by an etching process (e.g., a dry etching process or a wet etching process). Furthermore, after removing the sacrificial layer 170, the top of the first dielectric layer 160 on each bit line structure BL is lost.
[0044] Please see Figure 10 and Figure 11 . Figure 10 and Figure 11 This is a view of a method for manufacturing a semiconductor structure according to some embodiments of the present invention during the formation of a plurality of unit contacts and a plurality of landing pads. Figure 10 In this embodiment, multiple openings (not shown) are formed on opposite sides of each bitline contact BC in the substrate 110 to expose the sides of each of the two contact spacers 124, respectively. In some embodiments, the openings are formed by an etching process (e.g., a dry etching process or a wet etching process). Subsequently, a conductive material is formed in each opening to completely cover each bitline structure BL. Then, the top portion of the conductive material is removed by an etch-back process (e.g., a RIE process) to form multiple unit contacts CC, each unit contact CC being adjacent to each of the two contact spacers 124. Specifically, each unit contact CC is formed on opposite sides of the conductive layer 134 of each bitline structure BL. Furthermore, during the removal of the top portion of the conductive material, the top of each bitline structure BL is raised to a height SH3 (e.g., ...). Figure 9 Remove.
[0045] Additionally, during the formation of the unit contact CC, the upper portion of the first dielectric layer 160, the upper portion of the first oxide layer 122, and the upper portion of each bit line structure BL are partially removed. In some embodiments, after the partial removal of the upper portion of the first dielectric layer 160, the upper portion of the first oxide layer 122, and the upper portion of each bit line structure BL during the formation of the unit contact CC, the top of the first dielectric layer 160, the top of the second oxide layer 142, the top of the first oxide layer 122, and the top of each bit line structure BL collectively form a rocket shape. In some embodiments, after the formation of the unit contact CC, the top of the first dielectric layer 160, the top of the second oxide layer 142, the top of the first oxide layer 122, and the top of each bit line structure BL collectively form a slope SL. Furthermore, after removing the sacrificial layer 170, a spacer structure SP including the first oxide layer 122, the second oxide layer 142, and the first dielectric layer 160 is formed. In this way, by removing the top of the conductive material and the top of each bit line structure BL, damage to the top of the first oxide layer 122 on each bit line structure BL can be avoided when removing the sacrificial layer.
[0046] exist Figure 11 In this process, a landing pad material is formed on each unit contact CC, with the top surface of the landing pad material higher than the top surface of each bitline structure BL. Subsequently, the landing pad material is etched to form multiple openings (not shown), and multiple landing pads LP are formed on top of each bitline structure BL, covering the slope SL. In some embodiments, during the formation of the openings, a portion of each bitline structure BL and each spacer structure SP may be removed. Then, a second dielectric layer 180 is formed in each opening to separate each landing pad LP from one another.
[0047] like Figure 11 As shown, an embodiment of the present invention also provides a semiconductor structure 100. The semiconductor structure 100 includes a substrate 110, a bit line structure BL disposed above the substrate 110, and a spacer structure SP disposed on and extending along the sidewalls of the bit line structure BL. The substrate 110 includes a plurality of active regions 112 and a plurality of insulating regions 114, each insulating region 114 being located between adjacent active regions 112 to separate the active regions 112 from each other. The spacer structure SP includes a first spacer 122 surrounding the sidewalls of the bit line structure BL and a second spacer 142 surrounding the lower portion of the sidewalls of the first spacer 122. Additionally, the semiconductor structure 100 includes bit line contacts BC disposed in each active region 112 and contacting the bottom of the second spacer 142. Furthermore, the top surface of the first spacer 122 is higher than the top surface of the second spacer 142.
[0048] In some embodiments, the semiconductor structure 100 further includes two contact spacers 124 disposed on opposite sides of the bit line contact BC. In some embodiments, a first spacer 122 surrounds each contact spacer 124. In some embodiments, the spacer structure SP further includes a third spacer 160 surrounding the upper portion of the sidewall of the first spacer 122, the sidewall of the second spacer 142, and the upper portion of each of the two contact spacers 124. In some embodiments, the top of the third spacer 160, the top of the second spacer 142, the top of the first spacer 122, and the top of the bit line structure BL collectively form a slope SL. In other words, the slope SL refers to a curved surface formed on the common top surface of each bit line structure BL, the first oxide layer 122, and the first dielectric layer 160. In some embodiments, the semiconductor structure 100 further includes a landing pad LP disposed on the top of the bit line structure BL and covering the slope SL.
[0049] Furthermore, the bit line structure BL includes a bottom cover layer 132 disposed on the bit line contact BC, a conductive layer 134 disposed on the bottom cover layer 132, and a top cover layer 136 disposed on the conductive layer 134. A first spacer 122 surrounds the upper portion of the top cover layer 136, and a first spacer 122 and a second spacer 142 surround the lower portion of the top cover layer 136. In some embodiments, the height H3 of the lower portion of the top cover layer 136 (e.g., ...) Figure 10 (e.g., greater than the height H4 of the upper part of the top cover layer 136) Figure 10 In some embodiments, the semiconductor structure 100 further includes two unit contacts CC disposed on opposite sides of the bit line contact BC, each of the two unit contacts CC partially contacting each active region 112.
[0050] In summary, the embodiments of the present invention can prevent gaps or slits from forming between each bit line structure and each of the two unit contacts, thereby improving the leakage current problem of the semiconductor structure. Furthermore, damage to the top of each bit line structure during manufacturing can be avoided, thus preventing damage to the semiconductor structure.
[0051] While some embodiments of the invention have been described in considerable detail, other embodiments are also possible. Therefore, the spirit and scope of the claims should not be limited to the embodiments described herein.
[0052] The foregoing summary outlines the features of several embodiments of the present invention, enabling those skilled in the art to more readily understand the invention. Those skilled in the art should understand that the present invention can be readily used as a basis for changes or designs to other structures or processes to achieve the same objectives and / or obtain the same advantages as the embodiments of the present invention. Those skilled in the art will also understand that equivalent structures described above do not depart from the spirit and scope of the present invention, and that modifications, substitutions, and alterations can be made without departing from the spirit and scope of the present invention.
[0053] [Symbol Explanation]
[0054] 100: Semiconductor Structure
[0055] 110:Substrate
[0056] 112: Active Zone
[0057] 114: Insulation Zone
[0058] 120: Insulation layer
[0059] 122: First oxide layer / first spacer
[0060] 124: Contact spacer
[0061] 124A: Spacer material layer
[0062] 132: Bottom Cover Layer
[0063] 134: Conductive layer
[0064] 136: Top Covering Layer
[0065] 142: Second oxide layer / second spacer
[0066] 150: Photoresist layer
[0067] 160: First dielectric layer / Third spacer
[0068] 170: Sacrifice Layer
[0069] 180: Second dielectric layer
[0070] 500, 600: Enlarged View
[0071] BC: Bit line contact
[0072] BL: Bitline Structure
[0073] CC: Unit Contact
[0074] H1,H1',H2,H3,H4,SH1,SH2,SH3: Height
[0075] LP: Landing mat
[0076] SL: slope
[0077] SP: Spacer Structure
[0078] ST: Smooth tapered profile
[0079] SW: Stepped Profile
[0080] TP: Top surface
[0081] T1, T2, T3: Thickness.
Claims
1. A method of fabricating a semiconductor structure, characterized by, comprising: providing a substrate, and the substrate comprises a plurality of active regions and a plurality of insulating regions, wherein each of the insulating regions is located between two adjacent ones of the plurality of active regions; forming each of a plurality of bitline contacts in each of the active regions, respectively, and forming each of a plurality of bitline structures in each of the bitline contacts, respectively; depositing a first oxide layer covering the plurality of bitline structures; depositing a second oxide layer on the first oxide layer; forming a photoresist layer to completely cover the second oxide layer; and removing an upper portion of the second oxide layer to expose an upper portion of the first oxide layer.
2. The method of claim 1, wherein, removing the upper portion of the second oxide layer comprises: after forming the photoresist layer, performing a planarization process on the photoresist layer until a top surface of the second oxide layer is exposed; and etching the upper portion of the second oxide layer to expose the upper portion of the first oxide layer.
3. The method of claim 1, wherein, further comprising: after depositing the first oxide layer, forming two-contact spacers, wherein each of the contact spacers is located on opposite sides of each of the bitline contacts and is surrounded by the first oxide layer.
4. The method of claim 3, wherein, further comprising: removing the photoresist layer; and etching a top portion of the first oxide layer located on each of the bitline structures until each of the contact spacers is exposed, wherein after etching the top portion of the first oxide layer, each of the bitline structures is highly shortened.
5. The method of claim 4, wherein, after etching the top portion of the first oxide layer, the top portion of the first oxide layer and each of the bitline structures are rounded.
6. The method of claim 4, wherein, after etching the top portion of the first oxide layer, a stepped profile of a top portion of the second oxide layer located on the exposed upper portion of the first oxide layer becomes a smooth tapered profile of the top portion of the second oxide layer located on the exposed upper portion of the first oxide layer.
7. The method of claim 4, wherein, further comprising: after removing the photoresist layer, conformally depositing a first dielectric layer on each of the bitline structures, the exposed plurality of contact spacers, a portion of the plurality of active regions, and a portion of the plurality of insulating regions; depositing a sacrificial layer on the first dielectric layer to completely cover each of the bitline structures; and removing a top portion of each of the bitline structures, the top portion of the first oxide layer, a top portion of the first dielectric layer, and a top portion of the sacrificial layer.
8. The method of claim 7, wherein, after removing the top portion of each of the bitline structures, a top surface of each of the bitline structures, a top surface of the first oxide layer, and a top surface of the first dielectric layer are coplanar.
9. The method of claim 7, wherein, further comprising: after removing the top portion of each of the bitline structures, removing the sacrificial layer; and forming a plurality of cell contacts, and each of the cell contacts is located between two adjacent ones of the plurality of bitline structures, wherein a bottom portion of each of the cell contacts contacts each of the active regions.
10. The method of claim 9, wherein, further comprising: during forming the plurality of cell contacts, partially removing an upper portion of the first dielectric layer, the upper portion of the first oxide layer, and an upper portion of each of the bitline structures, wherein the top of the first dielectric layer, the top of the second oxide layer, the top of the first oxide layer, and the top of each of the bit line structures collectively form a rocket shape.
11. The method of claim 10, wherein, Further comprising: forming a plurality of landing pads on each of the cell contacts; and forming a second dielectric layer on each of the bit line structures to separate each of the landing pads from each other.
12. A semiconductor structure, characterized by Comprising: a substrate comprising a plurality of active regions and a plurality of insulating regions adjacent to the plurality of active regions; a bit line structure disposed above the substrate; a spacer structure disposed on and extending along sidewalls of the bit line structure, wherein the spacer structure comprises: a first spacer surrounding the sidewalls of the bit line structure; and a second spacer surrounding a lower portion of sidewalls of the first spacer, wherein a top surface of the first spacer is higher than a top surface of the second spacer; and a bit line contact disposed in each of the active regions and contacting a bottom portion of the second spacer.
13. The semiconductor structure of claim 12, wherein, Further comprising: a two-contact spacer disposed on opposite sides of the bit line contact.
14. The semiconductor structure of claim 13, wherein, The first spacer surrounds each of the contact spacers.
15. The semiconductor structure of claim 13, wherein, The spacer structure further comprises: a third spacer surrounding an upper portion of the sidewalls of the first spacer, sidewalls of the second spacer, and an upper portion of each of the contact spacers.
16. The semiconductor structure of claim 15, wherein, a top portion of the third spacer, a top portion of the second spacer, a top portion of the first spacer, and a top portion of the bit line structure collectively form a ramp.
17. The semiconductor structure of claim 16, wherein, Further comprising: a landing pad disposed on the top portion of the bit line structure and covering the ramp.
18. The semiconductor structure of claim 13, wherein, The bit line structure comprises: a bottom cap layer disposed on the bit line contact; a conductive layer disposed on the bottom cap layer; and a top cap layer disposed on the conductive layer, wherein the first spacer surrounds an upper portion of the top cap layer, and the first spacer and the second spacer surround a lower portion of the top cap layer.
19. The semiconductor structure of claim 18, wherein, A height of the lower portion of the top cap layer is greater than a height of the upper portion of the top cap layer.
20. The semiconductor structure of claim 18, wherein, Further comprising: a two-cell contact disposed on opposite sides of the bit line contact, wherein each of the cell contacts respectively partially contacts each of the active regions.