阅读说明：本技术 电容孔形成方法 (Method for forming capacitor hole ) 是由 鲍锡飞 方锦国 于 2020-05-26 设计创作，主要内容包括：一种电容孔形成方法,通过在支撑层上形成两层厚度较薄并且材料不相同的第一材料层和第二材料层作为过刻蚀调节层,在硬掩膜层形成刻蚀孔并对硬掩膜层进行过刻蚀时,能在第二材料层中形成一定的过刻蚀深度,并能使得刻蚀孔在第一材料层停住,从而能矫正和调节刻蚀孔的刻蚀深度,使得过刻蚀硬掩膜层后形成的刻蚀孔能具有相同的深度或者深度相差很小,后续沿刻蚀孔刻蚀所述支撑层在支撑层中形成暴露连接垫表面的电容孔时,不会由于刻蚀孔深度的不一而影响电容孔的刻蚀,使得形成的若干电容孔暴露出相应的连接垫的时间点基本相同或者相差很小,防止形成电容孔时对部分电容孔的侧向刻蚀,使得若干电容孔的尺寸较为均匀,提高DRAM的性能。(A method for forming capacitor holes includes forming two first material layers and two second material layers with different materials on support layer as over-etching regulation layer, forming etching holes on hard mask layer and over-etching hard mask layer, forming a certain over-etching depth in second material layer and stopping etching holes on first material layer for correcting and regulating etching depth of etching holes to let etching holes formed after over-etching hard mask layer have same depth or small depth difference, etching support layer along etching holes to form capacitor holes exposing connection pad surface in support layer without influencing etching of capacitor holes due to different depths of etching holes to let time points of formed capacitor holes exposing corresponding connection pads be same or small difference and preventing side etching of capacitor holes when capacitor holes are formed, the sizes of the capacitor holes are uniform, and the performance of the DRAM is improved.)

1. A method of forming a capacitor hole, comprising:

providing a semiconductor substrate, wherein a plurality of connecting pads are formed in the semiconductor substrate;

forming a support layer on the semiconductor substrate;

forming an over-etching depth adjusting layer on the supporting layer, wherein the over-etching depth adjusting layer comprises a first material layer positioned on the supporting layer and a second material layer positioned on the first material layer, the materials of the first material layer and the second material layer are different and are different from the materials of a subsequently formed hard mask layer, and the thicknesses of the first material layer and the second material layer are smaller than the thickness of the subsequently formed hard mask layer;

forming a hard mask layer on the over-etching depth adjusting layer;

etching the hard mask layer to form a plurality of etching holes, over-etching the hard mask layer when the hard mask layer is etched to form the etching holes, forming a certain over-etching depth in the second material layer, and stopping the etching holes in the first material layer;

and etching the first material layer and the support layer along the etching holes, and forming a plurality of capacitor holes exposing the surfaces of the corresponding connecting pads in the support layer.

2. The method for forming a via for a capacitor of claim 1, wherein the hard mask layer is etched such that the etch selectivity of the hard mask layer with respect to the second material layer is greater than the etch selectivity of the hard mask layer with respect to the first material layer when the plurality of etch vias are formed.

3. The method for forming a capacitor hole according to claim 2, wherein the hard mask layer is etched, and when a plurality of etching holes are formed, an etching selection ratio of the hard mask layer to the second material layer is greater than 2:1, an etching selection ratio of the hard mask layer to the first material layer is greater than 7:1, and an etching selection ratio of the second material layer to the first material layer is greater than 3: 1.

4. The method for forming a capacitor hole according to claim 3, wherein the hard mask layer is etched, and when a plurality of etching holes are formed, an etching selection ratio of the hard mask layer to the second material layer is 3:1-4:1, an etching selection ratio of the hard mask layer to the first material layer is 8:1-10:1, and an etching selection ratio of the second material layer to the first material layer is 4:1-6: 1.

5. The method of claim 1 or 3, wherein the first material layer and the second material layer have a thickness of 1/20-1/40 of a thickness of the hard mask layer.

6. The method for forming a capacitor hole according to claim 5, wherein the hard mask layer is made of polysilicon, the second material layer is made of silicon nitride or silicon carbonitride, and the first material layer is made of silicon oxide.

7. The method as claimed in claim 6, wherein the hard mask layer has a thickness of 700 nm and 900 nm, the second material layer has a thickness of 10 nm to 20nm, and the first material layer has a thickness of 10 nm to 20 nm.

8. The method of claim 7, wherein etching the hard mask layer is performed by anisotropic dry etching.

9. The method of claim 8, wherein said anisotropic dry etch uses an etch gas comprising Cl₂。

10. The method of forming a capacitor hole of claim 1, wherein said support layer is a single layer or a multi-layer stack structure.

11. The method of forming a capacitor hole of claim 10, wherein when the support layer has a single-layer structure, a single-sided capacitor is formed in the capacitor hole after the capacitor hole is formed.

12. The method of forming a capacitor hole of claim 10, wherein when the support layer is a multi-layer stack structure including a plurality of sacrificial layers and sub-support layers alternately stacked, a first electrode layer is formed on an inner wall of the capacitor hole after the capacitor hole is formed; and removing the sacrificial layer between the capacitor holes, filling a capacitor dielectric layer and a second electrode layer positioned on the capacitor dielectric layer at the position where the sacrificial layer is removed and in the capacitor holes, and forming a plurality of double-sided capacitors.

Technical Field

The invention relates to the field of memory manufacturing, in particular to a method for forming a capacitor hole of a DRAM (dynamic random access memory).

Background

Dynamic Random Access Memory (DRAM) is a semiconductor Memory device commonly used in computers, and is composed of many repetitive Memory cells. Each memory cell generally includes a capacitor and a transistor, a gate of the transistor is connected to a word line, a drain of the transistor is connected to a bit line, and a source of the transistor is connected to the capacitor, and a voltage signal on the word line can control the transistor to be turned on or off, so that data information stored in the capacitor can be read through the bit line or written into the capacitor through the bit line for storage.

The prior art provides a method for forming a DRAM, which includes: providing a semiconductor substrate; forming a groove type transistor in the semiconductor substrate, wherein the groove type transistor comprises a grid electrode positioned in the semiconductor substrate and a source electrode and a drain electrode positioned on two sides of the grid electrode; forming a dielectric layer covering the trench transistor on the semiconductor substrate, wherein a connecting pad connected with the source electrode is formed in the dielectric layer; forming a support layer on the dielectric layer; etching the supporting layer, and forming a plurality of capacitor holes in the supporting layer, wherein each capacitor hole exposes the surface of a corresponding connecting pad; forming a first electrode layer on the inner wall surface of the capacitor hole; forming a capacitance dielectric layer on the first electrode layer; and forming a second electrode layer on the capacitance dielectric layer.

However, the sizes of the capacitor holes formed in the foregoing method may be non-uniform, which affects the performance of the DRAM.

Disclosure of Invention

The technical problem to be solved by the invention is how to improve the uniformity of the size of the capacitor hole in the DRAM.

The invention provides a method for forming a capacitor hole, which comprises the following steps:

providing a semiconductor substrate, wherein a plurality of connecting pads are formed in the semiconductor substrate;

forming a support layer on the semiconductor substrate;

forming an over-etching depth adjusting layer on the supporting layer, wherein the over-etching depth adjusting layer comprises a first material layer positioned on the supporting layer and a second material layer positioned on the first material layer, the materials of the first material layer and the second material layer are different and are different from the materials of a subsequently formed hard mask layer, and the thicknesses of the first material layer and the second material layer are smaller than the thickness of the subsequently formed hard mask layer;

forming a hard mask layer on the over-etching depth adjusting layer;

etching the hard mask layer to form a plurality of etching holes, over-etching the hard mask layer when the hard mask layer is etched to form the etching holes, forming a certain over-etching depth in the second material layer, and stopping the etching holes in the first material layer;

and etching the first material layer and the support layer along the etching holes, and forming a plurality of capacitor holes exposing the surfaces of the corresponding connecting pads in the support layer.

Optionally, when the hard mask layer is etched to form a plurality of etching holes, an etching selection ratio of the hard mask layer to the second material layer is greater than an etching selection ratio of the hard mask layer to the first material layer.

Optionally, when the hard mask layer is etched to form a plurality of etching holes, an etching selection ratio of the hard mask layer to the second material layer is greater than 2:1, an etching selection ratio of the hard mask layer to the first material layer is greater than 7:1, and an etching selection ratio of the second material layer to the first material layer is greater than 3: 1.

Optionally, when the hard mask layer is etched to form a plurality of etching holes, the etching selection ratio of the hard mask layer to the second material layer is 3:1-4:1, the etching selection ratio of the hard mask layer to the first material layer is 8:1-10:1, and the etching selection ratio of the second material layer to the first material layer is 4:1-6: 1.

Optionally, the thickness of the first material layer and the second material layer is 1/20-1/40 of the thickness of the hard mask layer.

Optionally, the hard mask layer is made of polysilicon, the second material layer is made of silicon nitride or silicon carbide nitride, and the first material layer is made of silicon oxide.

Optionally, the thickness of the hard mask layer is 700-900 nm, the thickness of the second material layer is 10-20nm, and the thickness of the first material layer is 10-20 nm.

Optionally, the hard mask layer is etched by anisotropic dry etching.

Optionally, the etching gas used in the anisotropic dry etching includes Cl₂。

Optionally, the support layer is a single-layer or multi-layer stacked structure.

Optionally, when the supporting layer is of a single-layer structure, after the capacitor hole is formed, a single-sided capacitor is formed in the capacitor hole.

Optionally, when the supporting layer is a multilayer stacked structure, the multilayer stacked structure includes a plurality of sacrificial layers and sub-supporting layers stacked alternately, and after the capacitor hole is formed, a first electrode layer is formed on an inner wall of the capacitor hole; and removing the sacrificial layer between the capacitor holes, filling a capacitor dielectric layer and a second electrode layer positioned on the capacitor dielectric layer at the position where the sacrificial layer is removed and in the capacitor holes, and forming a plurality of double-sided capacitors.

Compared with the prior art, the technical scheme of the invention has the following advantages:

the capacitor hole forming method of the DRAM of the invention is characterized in that after a supporting layer is formed on a semiconductor substrate, an over-etching depth adjusting layer is formed on the supporting layer, the over-etching depth adjusting layer comprises a first material layer positioned on the supporting layer and a second material layer positioned on the first material layer, the materials of the first material layer and the second material layer are different and are different from the materials of a hard mask layer formed subsequently, the thicknesses of the first material layer and the second material layer are both smaller than the thickness of the hard mask layer formed subsequently, then the hard mask layer is formed on the over-etching depth adjusting layer, two first material layers and two second material layers which are thinner and different in material are formed on the supporting layer as the over-etching adjusting layer, when an etching hole is formed on the hard mask layer and the hard mask layer is over-etched, a certain over-etching depth can be formed in the second material layer, the etching holes can be stopped on the first material layer, so that the etching depth of the etching holes can be corrected and adjusted, the etching holes formed after the hard mask layer is over-etched can have the same depth or have small depth difference, when the supporting layer is etched along the etching holes to form the capacitor holes exposing the surfaces of the connecting pads in the supporting layer, the etching of the capacitor holes cannot be influenced due to the different depths of the etching holes, the time points of the formed capacitor holes exposing the corresponding connecting pads are basically the same or have small difference, the lateral etching of part of the capacitor holes when the capacitor holes are formed is prevented, the sizes of the capacitor holes are uniform, and the performance of the DRAM is improved.

Furthermore, when the hard mask layer is etched to form a plurality of etching holes, the etching selection ratio of the hard mask layer relative to the second material layer is larger than that of the hard mask layer relative to the first material layer, so that when the hard mask layer is over-etched, the etching rates of the second material layer and the first material layer are sequentially reduced, the control and formation of the bottom positions of the plurality of etching holes are facilitated, and the etching holes formed after the hard mask layer is over-etched can have the same depth or have small depth difference.

Further, the thickness of the first material layer and the second material layer is 1/20-1/40 of the thickness of the hard mask layer, and the hard mask layer is etched subsequently, when a plurality of etching holes are formed, the etching selection ratio of the hard mask layer to the second material layer is 3:1-4:1, the etching selection ratio of the hard mask layer to the first material layer is 8:1-10:1, the etching selection ratio of the second material layer to the first material layer is 4:1-6:1, by setting the specific thickness and specific etching selection ratio of the first material layer and the second material layer relative to the hard mask layer, thereby correcting and adjusting the etching depth of the etching hole more simply and efficiently in the process of forming the etching hole, the etching holes formed after the hard mask layer is over-etched can have the same depth or have small depth difference.

Drawings

FIGS. 1-6 are schematic structural diagrams illustrating a capacitor hole forming process of a DRAM according to an embodiment of the present invention.

Detailed Description

As mentioned in the background, the sizes of the capacitor holes formed in the foregoing method are not uniform (for example, the sizes of some capacitor holes are larger, and the sizes of some capacitor holes are smaller), which affects the performance of the DRAM.

After research on the existing DRAM forming process, it is found that, after a support layer (generally made of silicon nitride or silicon oxide) is formed, a hard mask layer (generally made of polysilicon) is also formed on the support layer, and in order to ensure the blocking performance of the hard mask layer when the support layer is etched, the thickness of the hard mask layer is generally thicker (greater than 800 nm); after forming a hard mask layer, forming a graphical mask layer on the hard mask layer; the hard mask layer is etched by taking the patterned mask layer as a mask, a plurality of etching holes are formed in the hard mask layer, and the hard mask layer can be etched through only by enough over etching (over etching) when the hard mask layer is etched, so that part of the supporting layer can be etched when the hard mask layer is over etched, and the bottoms of the etching holes are positioned in the supporting layer, but the existing over etching process is easy to cause that the depths of the bottoms of the etching holes formed in the supporting layer are different (the depths of the bottoms of the etching holes in the supporting layer are different, namely, on one hand, plasma etching is adopted when the hard mask layer is etched, the plasma concentration distributed above the middle of a wafer is larger than the plasma concentration distributed above the edge of the wafer in an etching chamber, and on the other hand, in order to form a small-size capacitor hole, the patterned mask layer is usually formed by adopting a double patterning process, specifically, a plurality of discrete first mask patterns distributed along a first direction are formed on the hard mask layer through a double-pattern process; forming a plurality of discrete second mask patterns distributed along a second direction on the first mask pattern through a double-pattern process, wherein an included angle is formed between the first direction and the second direction, the first mask pattern and the second mask pattern form the graphical mask layer, and when the first mask pattern and the second mask pattern are formed through the double-pattern process, due to the difference of etching selection ratios, over-etching openings with different depths are formed on the surface of the hard mask layer, and the over-etching openings with different depths are conducted into the supporting layer when the hard mask layer is etched). The bottom of the etching hole is different in depth in the supporting layer, in one case, when the supporting layer is subsequently etched along the plurality of etching holes to form a plurality of capacitor holes, some capacitor holes (the capacitor holes formed by etching along the etching holes with the deeper depth) will expose the surface of the corresponding connection pads first, some capacitor holes (the capacitor holes formed by etching along the etching holes with the shallower depth) will expose the surface of the corresponding connection pads later, the etching plasma still moves towards the capacitor holes because the etching process of the capacitor holes with the exposed connection pads first is continued, and the etching plasma will not consume the etching plasma, so the etching plasma will etch the supporting layer on the side of the capacitor holes, the size of the capacitor holes with the exposed connection pads first will be further increased, and finally, when all the capacitor holes are formed, the size of some capacitor holes will be larger, so that the size of the formed plurality of capacitor holes will be non-uniform, when a capacitor structure is subsequently formed in the capacitor hole, the performance of the capacitor structure is affected, thereby affecting the performance of the DRAM. Under the other condition, when the etching time is the same, some capacitor holes are etched to the bottom and are connected with the connecting pads, and some capacitor holes cannot be etched to the bottom and cannot be connected with the connecting pads, so that some capacitors cannot achieve the effect of storing charges, and the performance of the whole device is affected. The invention provides a method for forming a capacitor hole of a DRAM, which comprises the steps of forming a support layer on a semiconductor substrate, forming an over-etching depth adjusting layer on the support layer, wherein the over-etching depth adjusting layer comprises a first material layer positioned on the support layer and a second material layer positioned on the first material layer, the materials of the first material layer and the second material layer are different and are different from the materials of a hard mask layer formed subsequently, the thicknesses of the first material layer and the second material layer are both smaller than the thickness of the hard mask layer formed subsequently, then forming the hard mask layer on the over-etching depth adjusting layer, forming two first material layers and two second material layers which are thinner and different in material on the support layer as the over-etching adjusting layer, and forming an etching hole on the hard mask layer and performing over-etching on the hard mask layer, forming a certain over-etching depth in the second material layer, the etching holes can be stopped on the first material layer, so that the etching depth of the etching holes can be corrected and adjusted, the etching holes formed after the hard mask layer is over-etched can have the same depth or have small depth difference, when the supporting layer is etched along the etching holes to form the capacitor holes exposing the surfaces of the connecting pads in the supporting layer, the etching of the capacitor holes cannot be influenced due to the different depths of the etching holes, the time points of the formed capacitor holes exposing the corresponding connecting pads are basically the same or have small difference, the lateral etching of part of the capacitor holes when the capacitor holes are formed is prevented, the sizes of the capacitor holes are uniform, and the performance of the DRAM is improved.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In describing the embodiments of the present invention in detail, the drawings are not to be considered as being enlarged partially in accordance with the general scale, and the drawings are only examples, which should not be construed as limiting the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.

Referring to fig. 1, a semiconductor substrate 200 is provided, and a plurality of connection pads 220 are formed in the semiconductor substrate 200.

The semiconductor substrate 200 serves as a platform for subsequent processes. In an embodiment, the semiconductor base 200 includes a semiconductor substrate 201 and at least one dielectric layer 202 on the semiconductor substrate, and the connection pad 220 is located in the dielectric layer 202.

The material of the semiconductor substrate may be silicon (Si), germanium (Ge), or silicon germanium (GeSi), silicon carbide (SiC); or silicon-on-insulator (SOI), germanium-on-insulator (GOI); or may be other materials such as group iii-v compounds such as gallium arsenide. In this embodiment, the semiconductor substrate 201 is made of silicon. The semiconductor substrate is doped with certain impurity ions according to needs, and the impurity ions can be N-type impurity ions or P-type impurity ions.

A plurality of groove type transistors are formed in the semiconductor substrate, and each groove type transistor comprises an active region; the active region is divided into a drain region and at least one source region by the groove, specifically, when the number of the grooves is one, the active region is divided into the source region and the drain region which are respectively positioned at two sides of the groove by the groove, when the number of the grooves is two, the two grooves are parallel to each other, and the active region is divided into the drain region which is positioned between the two grooves and the two source regions which are respectively positioned at the outer sides of the two grooves by the two grooves; a gate structure or Word Line (WL) located in the trench. The drain region of the trench transistor is subsequently connected with a bit line, and the source region of the trench transistor is subsequently connected with a capacitor. The connection pads 220 formed in the dielectric layer are connected to the corresponding source regions, and specifically, the connection pads 220 may be connected to the corresponding source regions through metal connection structures.

The dielectric layer 202 may be a single-layer or multi-layer (2 or more) stacked structure, and the material of the dielectric layer may be silicon nitride, silicon oxynitride, silicon oxide, FSG (fluorine-doped silicon dioxide), BSG (boron-doped silicon dioxide), PSG (phosphorus-doped silicon dioxide), or BPSG (boron-phosphorus-doped silicon dioxide), low-k material, other suitable materials, and/or combinations thereof

Referring to fig. 2, a support layer 205 is formed on the semiconductor substrate 200.

The support layer 205 is used to define and support the subsequently formed capacitor structure.

In this embodiment, the support layer 205 is a multi-layer stacked structure, and the multi-layer stacked structure includes a plurality of sacrificial layers 203 and sub-support layers 204 stacked alternately. In this embodiment, a multilayer stack structure having four layers, that is, two sacrificial layers 203 and two sub-support layers 204 is taken as an example, and the bottom layer in the multilayer stack structure is one sacrificial layer 203, and the top layer is one sub-support layer 204.

The purpose of having a sacrificial layer in the support layer 205 is to subsequently remove the sacrificial layer, where the sacrificial layer is removed and in the capacitor hole, a double-sided capacitor can be formed. The sacrificial layer 203 and the sub-support layer 204 are made of different materials, the sacrificial layer 203 can be made of one of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide and silicon carbonitride, and the support layer 204 can be made of one of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide and silicon carbonitride. In this embodiment, the sub-support layer 204 is made of silicon nitride, and the sacrificial layer 203 is made of silicon oxide.

In other embodiments, the supporting layer may be a single-layer structure, and after capacitor holes are formed in the supporting layer, a single-sided capacitor structure is formed in the capacitor holes.

In one embodiment, the thickness of the support layer 205 is 2000 nm to 3000 nm. In this embodiment, the thickness of the support layer 205 is 2800 nm.

Referring to fig. 3, an over-etching depth adjustment layer 208 is formed on the support layer 205, the over-etching depth adjustment layer 208 includes a first material layer 206 on the support layer 205 and a second material layer 207 on the first material layer 206, the materials of the first material layer 206 and the second material layer 207 are different and are different from the material of the hard mask layer to be formed subsequently, and the thicknesses of the first material layer 206 and the second material layer 207 are smaller than the thickness of the hard mask layer to be formed subsequently; a hard mask layer 209 is formed on the over-etch depth adjustment layer 208.

An over-etching depth adjusting layer 208 is formed on a support layer 205, the over-etching depth adjusting layer 208 comprises a first material layer 206 and a second material layer 207 positioned on the first material layer 206, the materials of the first material layer 206 and the second material layer 207 are different and are different from the material of a formed hard mask layer 209, the thicknesses of the first material layer 206 and the second material layer 207 are smaller than the thickness of the formed hard mask layer 209, and by forming the first material layer and the second material layer which are thinner and different in material as the over-etching adjusting layer, when an etching hole is formed in the hard mask layer 209 and the hard mask layer is over-etched, a certain over-etching depth can be formed in the second material layer, and the etching hole can stop in the first material layer, so that the etching depth of the etching hole can be corrected and adjusted, and the etching holes formed after the hard mask layer 209 are over-etched can have the same depth or have a small depth difference, when the supporting layer is etched along the etching holes to form the capacitor holes exposing the surfaces of the connecting pads in the supporting layer, the etching of the capacitor holes cannot be influenced due to different depths of the etching holes, so that the time points of the formed plurality of capacitor holes exposing the corresponding connecting pads are basically the same or have small difference, the lateral etching of partial capacitor holes when the capacitor holes are formed is prevented, the sizes of the plurality of capacitor holes are uniform, and the performance of the DRAM is improved.

In an embodiment, a patterned photoresist layer 210 is further formed on the hard mask layer 209, and the patterned photoresist layer 210 is used as a mask for subsequent etching of the hard mask layer 209.

In another embodiment, a plurality of discrete first mask patterns arranged along a first direction are formed on the hard mask layer 209, a plurality of discrete second mask patterns arranged along a second direction are formed on the first mask patterns, an included angle is formed between the first direction and the second direction, and the hard mask layer is etched by using the first mask patterns and the second mask patterns as masks.

In an embodiment, when the hard mask layer 209 is subsequently etched to form a plurality of etching holes, an etching selection ratio of the hard mask layer 209 to the second material layer 207 is greater than an etching selection ratio of the hard mask layer 209 to the first material layer 206, so that when the hard mask layer is over-etched, etching rates of the second material layer and the first material layer are sequentially reduced, which is more beneficial to controlling and forming the bottom positions of the plurality of etching holes, and the etching holes formed after over-etching the hard mask layer 209 can have the same depth or have a small depth difference.

In a specific embodiment, the thicknesses of the first material layer 206 and the second material layer 207 are 1/20-1/40, which may be 1/20, 1/30, and 1/40 of the thickness of the hard mask layer 209, and when the hard mask layer 209 is subsequently etched to form a plurality of etching holes, an etching selection ratio of the hard mask layer 209 to the second material layer 207 is greater than 2:1, and may be 3:1-4:1, and specifically may be 3:1, 4:1, an etching selection ratio of the hard mask layer 209 to the first material layer 206 is greater than 7:1, and may be 8:1-10:1, and specifically may be 8:1, 9:1, and 10:1, and an etching selection ratio of the second material layer 207 to the first material layer 206 is greater than 3:1, and may be 4:1-6:1, and specifically may be 4:1, 5:1, 6:1, by setting the specific thickness and specific selection ratio of the first material layer 206 and the second material layer 207 relative to the hard mask layer, the etching depth of the etching hole can be corrected and adjusted more simply and efficiently in the process of forming the etching hole, so that the etching holes formed after the hard mask layer 209 is over-etched can have the same depth or have small depth difference.

In order to enable the hard mask layer 209 to have sufficient mask blocking capability during subsequent etching of the support layer, the thickness of the hard mask layer 209 is generally thicker (greater than 500 nm), and the thicknesses of the second material layer 207 and the first material layer 206 cannot be too thick or too thin, if the thicknesses are too thick, a high aspect ratio in an etching hole forming process of the patterned hard mask layer 209 is increased, etching difficulty is increased, if the thicknesses are too thin, the second material layer 207 cannot function as a stop layer to a certain extent, and the etching difficulty is also increased, so that the etching holes formed after the hard mask layer 209 is over-etched can keep the same depth or have a small difference in depth, and difficulty is increased very little, in this embodiment, the material of the hard mask layer 209 is polysilicon, the material of the second material layer 207 is silicon nitride or silicon carbide nitride, the material of the first material layer 206 is silicon oxide, and the thickness of the hard mask layer 209 is 700 nm and 900 nm, may be 700 nm, 800 nm, 900 nm, the thickness of the second material layer 207 is 10-20nm, may be 10 nm, 15 nm, 20nm, the thickness of the first material layer is 10-20nm, may be 10 nm, 15 nm, 20 nm.

Referring to fig. 4, the hard mask layer 209 is etched to form a plurality of etching holes 211, and when the hard mask layer 209 is etched to form the etching holes 211, the hard mask layer 209 is over-etched to form a certain over-etching depth in the second material layer 207, and the etching holes 211 are stopped in the first material layer 206.

The hard mask layer 209 is etched by anisotropic dry etching. In this embodiment, the anisotropic dry etching is an anisotropic plasma etching process, and the etching gas used in the anisotropic dry etching includes Cl₂。

Referring to fig. 5, the first material layer 206 and the support layer 205 are etched along the etching holes 211, and a plurality of capacitor holes 212 exposing surfaces of the corresponding connection pads 220 are formed in the support layer 205.

And an anisotropic dry etching process is adopted for etching the first material layer 206 and the support layer 205.

In this embodiment, the gas used for etching the first material layer 206 and the support layer 205 includes CF₄、C₄F₈And CHF₃One or more of them.

Referring to fig. 6, the hard mask layer 209 and the over-etch adjusting layer 208 are removed.

In one embodiment, the hard mask layer 209 and the over-etch adjusting layer 208 may be removed by a separate etching process or a planarization process. In another embodiment, the hard mask layer 209 and the over-etching adjustment layer 208 may also be removed by a planarization process during the subsequent formation of the first electrode layer.

In this embodiment, after the capacitor hole 212 is formed, the method further includes: forming a first electrode layer on an inner wall of the capacitor hole; and removing the sacrificial layer between the capacitor holes, filling a capacitor dielectric layer and a second electrode layer positioned on the capacitor dielectric layer at the position where the sacrificial layer is removed and in the capacitor holes, and forming a plurality of double-sided capacitors.

In other embodiments, when the support layer is a single-layer structure, after forming the capacitor hole, forming a single-sided capacitor in the capacitor hole, the single-sided capacitor including a first electrode layer on an inner wall of the capacitor hole; a capacitor dielectric layer located on the first electrode layer; and the second electrode layer is positioned on the capacitance dielectric layer.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.