阅读说明：本技术 eflash器件的控制栅刻蚀方法 (Control gate etching method of eflash device ) 是由 白宇 于 2020-11-25 设计创作，主要内容包括：本申请涉及半导体集成电路制造技术领域,具体涉及一种eflash器件的控制栅刻蚀方法。包括：提供一eflash器件的存储区结构,存储区结构由下至上依次层叠的栅介质层、多晶硅浮栅、多晶硅间介质层、多晶硅控制栅和掩模层；在掩模层上开设刻蚀窗口；在刻蚀窗口的周壁上形成侧墙,通过侧墙定义出控制栅刻蚀图案；根据控制栅刻蚀图案进行干法刻蚀,刻蚀去除控制栅刻蚀图案位置处的多晶硅控制栅,使得刻蚀停止面位于多晶硅间介质层中；根据控制栅刻蚀图案进行湿法刻蚀,刻蚀去除在栅刻蚀图案位置处,剩余的多晶硅间介质层；使得多晶硅控制栅的刻蚀周面光滑。本申请可以解决相关技术中控制栅的顶端出现尖角,从而对产品的良率产生不利影响的问题。(The application relates to the technical field of semiconductor integrated circuit manufacturing, in particular to a control gate etching method of an eflash device. The method comprises the following steps: providing a storage region structure of an eflash device, wherein the storage region structure comprises a gate dielectric layer, a polysilicon floating gate, an inter-polysilicon dielectric layer, a polysilicon control gate and a mask layer which are sequentially stacked from bottom to top; opening an etching window on the mask layer; forming a side wall on the peripheral wall of the etching window, and defining a control gate etching pattern through the side wall; performing dry etching according to the control gate etching pattern, and etching to remove the polysilicon control gate at the position of the control gate etching pattern so that the etching stop surface is positioned in the inter-polysilicon dielectric layer; performing wet etching according to the control gate etching pattern, and etching to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern; so that the etched peripheral surface of the polysilicon control gate is smooth. The method and the device can solve the problem that sharp corners appear at the top end of the control gate in the related technology, so that adverse effects are generated on the yield of products.)

1. A control gate etching method of an eflash device is characterized by comprising the following steps:

providing a storage region structure of an eflash device, wherein the storage region structure comprises a gate dielectric layer, a polysilicon floating gate, an inter-polysilicon dielectric layer, a polysilicon control gate and a mask layer which are sequentially stacked from bottom to top;

opening an etching window on the mask layer;

forming a side wall on the peripheral wall of the etching window, and defining a control gate etching pattern through the side wall;

performing dry etching according to the control gate etching pattern, and etching to remove the polysilicon control gate at the position of the control gate etching pattern so that the etching stop surface is positioned in the inter-polysilicon dielectric layer;

performing wet etching according to the control gate etching pattern, and etching to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern; so that the etched peripheral surface of the polysilicon control gate is smooth.

2. The method for etching the control gate of the eflash device as claimed in claim 1, wherein the inter-poly dielectric layer comprises a first oxide layer, a nitride layer and a second oxide layer which are sequentially stacked from bottom to top;

the step of performing dry etching according to the control gate etching pattern to remove the polysilicon control gate at the position of the gate etching pattern by etching so that the etching stop surface is positioned in the inter-polysilicon dielectric layer comprises the following steps:

and performing dry etching according to the control gate etching pattern, and etching to remove the polysilicon control gate at the position of the gate etching pattern, so that the etching stop surface is positioned in the nitride layer of the inter-polysilicon dielectric layer.

3. The method for etching the control gate of the eflash device as claimed in claim 1, wherein the step of performing wet etching according to the control gate etching pattern to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern comprises:

and carrying out wet etching on the control gate etching pattern by using non-hydrofluoric acid etching liquid, and etching to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern.

4. The method for etching the control gate of the eflash device as claimed in claim 1, wherein the step of opening the etching window on the mask layer comprises:

defining an etching window pattern on the mask layer through a photoetching process;

and etching the mask layer according to the etching window pattern to form the etching window.

5. The method for etching the control gate of the eflash device as claimed in claim 1, wherein the step of forming the sidewall on the peripheral wall of the etching window and defining the control gate etching pattern through the sidewall comprises:

depositing a silicon dioxide layer to enable the silicon dioxide layer to cover the residual mask layer, the peripheral wall of the etching window and the polysilicon control gate at the position of the etching window;

defining a side wall pattern on the silicon dioxide layer through a photoetching process;

and etching to remove the silicon dioxide layer outside the side wall pattern, so that a side wall is formed on the peripheral wall of the etching window.

6. The method for etching the control gate of the eflash device as claimed in claim 1, wherein the mask layer has a thickness of 3000 angstroms to 4000 angstroms.

7. The method for etching the control gate of the eflash device as claimed in claim 1, wherein the polysilicon control gate has a thickness of 500 angstroms to 700 angstroms.

8. The method for etching the control gate of the eflash device as claimed in claim 1, wherein the thickness of the inter-poly dielectric layer is 120 angstroms to 160 angstroms.

9. The method for etching the control gate of the eflash device as claimed in claim 1, wherein the storage region structure is located on a channel region of the eflash device substrate layer.

Technical Field

The application relates to the technical field of semiconductor integrated circuit manufacturing, in particular to a control gate etching method of an eflash device.

Background

Embedded Flash memory cells (Embedded Flash) have occupied an increasingly important position in the field of non-volatile memories due to their performance advantages of low cost, low power consumption, fast access speed, and the like. With the development of technology, data storage media applications are also exclusively applied to flash memory type memories from some traditional non-volatile memories, and mass solid-state storage devices with flash memories as main storage media have become one of the mainstream schemes for data storage today.

In general, the eflash memory structure comprises a floating gate and a control gate which are laminated together, and a composite dielectric layer is formed between the floating gate and the control gate. The control of the read operation, the write operation and the erase operation of the eflash is realized by applying different operating voltages to electrodes such as a control gate of the eflash. The storage content of eflash depends on the state of the floating gate storing electrons in the storage structure, if the floating gate is in a state without electrons, the data in eflash is 1, and if the floating gate is in a state with electrons, the data in eflash is 0.

In the manufacturing process of eflash in the related technology, the control gate needs to be etched to manufacture a word line, an etching window is formed at a position needing to be etched and removed before the control gate is etched, the control gate material and the surface layer of the composite dielectric layer at the position of the etching window are removed through dry etching, and then the residual composite dielectric layer at the position of the etching window is further removed through hydrofluoric acid, so that the control gate is etched.

Fig. 1 shows a schematic cross-sectional structure of a device after etching a control gate by a related art, which includes a floating gate 110 and a control gate 130 stacked together, and a composite dielectric layer 120 is formed between the floating gate 110 and the control gate 130. The related art method of etching the control gate may cause the top end of the control gate to have a sharp corner as shown in part a of fig. 1, thereby adversely affecting the yield of the product.

Disclosure of Invention

The application provides a control gate etching method of an eflash device, which can solve the problem that sharp corners appear at the top end of a control gate in the related technology, so that adverse effects are generated on the yield of products.

The application provides a control gate etching method of an eflash device, which comprises the following steps:

providing a storage region structure of an eflash device, wherein the storage region structure comprises a gate dielectric layer, a polysilicon floating gate, an inter-polysilicon dielectric layer, a polysilicon control gate and a mask layer which are sequentially stacked from bottom to top;

opening an etching window on the mask layer;

forming a side wall on the peripheral wall of the etching window, and defining a control gate etching pattern through the side wall;

performing dry etching according to the control gate etching pattern, and etching to remove the polysilicon control gate at the position of the control gate etching pattern so that the etching stop surface is positioned in the inter-polysilicon dielectric layer;

performing wet etching according to the control gate etching pattern, and etching to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern; so that the etched peripheral surface of the polysilicon control gate is smooth.

Optionally, the inter-polysilicon dielectric layer includes a first oxide layer, a nitride layer and a second oxide layer, which are sequentially stacked from bottom to top;

the step of performing dry etching according to the control gate etching pattern to remove the polysilicon control gate at the position of the gate etching pattern by etching so that the etching stop surface is positioned in the inter-polysilicon dielectric layer comprises the following steps:

and performing dry etching according to the control gate etching pattern, and etching to remove the polysilicon control gate at the position of the gate etching pattern, so that the etching stop surface is positioned in the nitride layer of the inter-polysilicon dielectric layer.

Optionally, the step of performing wet etching according to the control gate etching pattern to etch and remove the remaining inter-polysilicon dielectric layer at the position of the gate etching pattern includes:

and carrying out wet etching on the control gate etching pattern by using non-hydrofluoric acid etching liquid, and etching to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern.

Optionally, the step of forming an etching window on the mask layer includes:

defining an etching window pattern on the mask layer through a photoetching process;

and etching the mask layer according to the etching window pattern to form the etching window.

Optionally, the step of forming a side wall on the circumferential wall of the etching window and defining a control gate etching pattern through the side wall includes:

depositing a silicon dioxide layer to enable the silicon dioxide layer to cover the residual mask layer, the peripheral wall of the etching window and the polysilicon control gate at the position of the etching window;

defining a side wall pattern on the silicon dioxide layer through a photoetching process;

and etching to remove the silicon dioxide layer outside the side wall pattern, so that a side wall is formed on the peripheral wall of the etching window.

Optionally, the thickness of the mask layer is 3000 angstroms to 4000 angstroms.

Optionally, the thickness of the polysilicon control gate is 500 to 700 angstroms.

Optionally, the thickness of the inter-polysilicon dielectric layer is 120 to 160 angstroms.

Optionally, the storage region structure is located on a channel region of the eflash device substrate layer.

The technical scheme at least comprises the following advantages: firstly, forming an etching window on the mask layer; forming a side wall on the peripheral wall of the etching window, and defining a control gate etching pattern through the side wall; performing dry etching according to the control gate etching pattern, and etching to remove the polysilicon control gate at the position of the control gate etching pattern so that the etching stop surface is positioned in the inter-polysilicon dielectric layer; performing wet etching according to the control gate etching pattern, and etching to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern; the etching circumferential surface of the polycrystalline silicon control gate can be smooth, so that a sharp corner is prevented from being formed at the top end of the control gate and the like, and the yield of products is improved.

Drawings

In order to more clearly illustrate the detailed description of the present application or the technical solutions in the prior art, the drawings needed to be used in the detailed description of the present application or the prior art description will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic cross-sectional view of a device after a control gate is etched in the related art;

FIG. 2 is a flowchart illustrating a control gate etching method for an eflash device according to an embodiment of the present application;

fig. 3a to fig. 3e show a schematic cross-sectional structure diagram of a device after completion of each step in a control gate etching method for an eflash device according to an embodiment of the present application.

Detailed Description

The technical solutions in the present application will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; the connection can be mechanical connection or electrical connection; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

In addition, the technical features mentioned in the different embodiments of the present application described below may be combined with each other as long as they do not conflict with each other.

Fig. 2 shows a flowchart of a control gate etching method for an eflash device according to an embodiment of the present application, and fig. 3a to fig. 3e show a schematic cross-sectional structure diagram of the eflash device after completion of each step in the control gate etching method for the eflash device according to the embodiment of the present application. Referring to fig. 2, the control gate etching method of the eflash device includes the following steps:

step S1: providing a storage region structure of an eflash device, wherein the storage region structure comprises a gate dielectric layer, a polysilicon floating gate, an inter-polysilicon dielectric layer, a polysilicon control gate and a mask layer which are sequentially stacked from bottom to top.

Referring to fig. 3a, a schematic cross-sectional view of the storage area structure of the eflash device provided in step S1 is shown. The storage region structure is positioned on a channel region of the substrate layer of the eflash device and comprises a gate dielectric layer 210, a polysilicon floating gate 220, an inter-polysilicon dielectric layer 230, a polysilicon control gate 240 and a mask layer 250 which are sequentially stacked from bottom to top, wherein the thickness range of the gate dielectric layer 210 can be 800 angstroms to 100 angstroms, the thickness range of the polysilicon floating gate 220 can be 200 angstroms to 400 angstroms, the thickness range of the inter-polysilicon dielectric layer 230 can be 120 angstroms to 160 angstroms, the thickness of the polysilicon control gate 240 is 500 angstroms to 700 angstroms, and the thickness of the mask layer 250 is 3000 angstroms to 4000 angstroms.

Step S2: and opening an etching window on the mask layer.

Optionally, defining an etching window pattern on the mask layer by a photolithography process; and etching the mask layer according to the etching window pattern to form the etching window. Referring to fig. 3b, which shows a schematic cross-sectional structure of the device after step S2 is completed, it can be seen from fig. 3b that the etching window 251 is opened, so that the polysilicon control gate 240 at the position of the etching window 251 is exposed.

Step S3: and forming a side wall on the peripheral wall of the etching window, and defining a control gate etching pattern through the side wall.

The method comprises the following steps of: depositing a silicon dioxide layer on the surface of the device after the step S2 is finished, so that the silicon dioxide layer covers the residual mask layer, the peripheral wall of the etching window and the polysilicon control gate at the position of the etching window; covering photoresist on the surface of the silicon dioxide, and defining a side wall pattern through a photoetching process, namely covering the developed residual photoresist on the position of the side wall; and then etching to remove the silicon dioxide layer outside the side wall pattern, so that the silicon dioxide layer on the peripheral wall of the etching window is reserved to form the side wall. Referring to fig. 3c, it can be seen from fig. 3c that the sidewall 252 is located on a sidewall of the remaining mask layer 250, i.e. a peripheral wall of an etching window, which is further defined by the sidewall to form a control gate etching pattern 253 after the step S3 is completed.

And step S4, performing dry etching according to the control gate etching pattern, and removing the polysilicon control gate at the position of the control gate etching pattern by etching so that the etching stop surface is positioned in the interpoly dielectric layer.

Referring to fig. 3d, which shows a schematic cross-sectional structure of the device after step S4 is completed, it can be seen that the control gate etching pattern 253 defines the portion of the polysilicon control gate 240 that needs to be removed by etching. The dry etch etches down from the upper surface of the polysilicon control gate 240 at the location of the control gate etch pattern 253 to the middle of the interpoly dielectric layer 230.

Step S5: performing wet etching according to the control gate etching pattern, and etching to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern; so that the etched peripheral surface of the polysilicon control gate is smooth.

Fig. 3e is a schematic cross-sectional structure diagram of the device after the step S5 is completed, and as shown in fig. 3e, after the control gate structure is etched, the etched peripheral surface B of the polysilicon control gate 240 is smooth and has no sharp corners, where the etched peripheral surface B of the polysilicon control gate 240 refers to a surface of the polysilicon control gate 240 formed by etching, and since the etching in the steps S4 and S5 is from top to bottom, the etched surface is located on the peripheral side of the polysilicon control gate 240, that is, the etched peripheral surface B of the polysilicon control gate 240 is formed.

In the embodiment, an etching window is firstly formed on the mask layer; forming a side wall on the peripheral wall of the etching window, and defining a control gate etching pattern through the side wall; performing dry etching according to the control gate etching pattern, and etching to remove the polysilicon control gate at the position of the control gate etching pattern so that the etching stop surface is positioned in the inter-polysilicon dielectric layer; performing wet etching according to the control gate etching pattern, and etching to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern; the etching circumferential surface of the polycrystalline silicon control gate can be smooth, so that a sharp corner is prevented from being formed at the top end of the control gate and the like, and the yield of products is improved.

In this embodiment, the interpoly dielectric layer includes a first oxide layer, a nitride layer and a second oxide layer sequentially stacked from bottom to top; the step S4: and performing dry etching according to the control gate etching pattern, and etching to remove the polysilicon control gate at the position of the gate etching pattern so that the etching stop surface is positioned in the inter-polysilicon dielectric layer, wherein the step comprises the following steps:

and performing dry etching according to the control gate etching pattern, and etching to remove the polysilicon control gate at the position of the gate etching pattern, so that the etching stop surface is positioned in the nitride layer of the inter-polysilicon dielectric layer.

In this embodiment, step S5: the step of performing wet etching according to the control gate etching pattern to etch and remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern comprises the following steps:

and carrying out wet etching on the control gate etching pattern by using non-hydrofluoric acid etching liquid, and etching to remove the residual inter-polysilicon dielectric layer at the position of the gate etching pattern.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of this invention are intended to be covered by the scope of the invention as expressed herein.