Harc etching chemistry for semiconductors

Abstract

A method for etching a wafer includes: providing a wafer; forming a patterned mask on the surface of the wafer; and etching the mask using an etching gas. The wafer includes an oxide-containing material layer. The mask contains a material that is at least partially metallic. The etching gas is selected from the group consisting of CF4, CHF3, and NF3. Therefore, improved selectivity and a satisfactory etch rate (ER) can be achieved between the mask and the wafer.

Description

Cross-references to related applications

[0001] This application claims the benefit of U.S. non-provisional application No. 18 / 607,202, filed March 15, 2024, which is incorporated herein by reference in its entirety. Technical Field

[0002] This application generally relates to the field of etching semiconductor wafers. Background Technology

[0003] The semiconductor industry has experienced rapid growth due to the continuous increase in the integration density of various electronic components, such as transistors, diodes, resistors, capacitors, etc. In most cases, the increase in integration density comes from the iterative reduction of the minimum feature size, which allows more components to be integrated into a given area. Summary of the Invention

[0004] As described herein, a method may include: providing a wafer; forming a patterned mask on the surface of the wafer; and selectively etching the mask and the wafer beneath the mask using an etching gas selected from the group consisting of CF4, CHF3, and NF3. The wafer includes an oxide-containing material layer. The mask comprises a material that is at least partially metallic.

[0005] In some embodiments, the oxide-containing material layer may include an oxide layer situated on top of a nitride layer. In some embodiments, the oxide-containing material layer comprises a stack of oxide layers and nitride layers alternating one another. In some embodiments, the material that is at least partially metallic includes a tungsten-containing material. In some embodiments, the tungsten-containing material includes tungsten silicide (WSix).

[0006] An etchant for etching a wafer using a mask may include a gas selected from the group consisting of CF4, CHF3, and NF3. The mask includes at least a pattern and is made of a material that is at least partially metallic.

[0007] In some embodiments, the wafer includes an oxide-containing material layer. In some embodiments, the oxide-containing material layer includes an oxide layer situated on a nitride layer. In some embodiments, the oxide-containing material layer includes a stack of oxide layers and nitride layers alternating one another. In some embodiments, the material that is at least partially metallic includes a tungsten-containing material. In some embodiments, the tungsten-containing material includes tungsten silicide (WSix).

[0008] In another general aspect, a method includes: forming a patterned mask on a wafer; and selectively etching the mask and the wafer beneath the mask using an etching gas selected from the group consisting of CF4, CHF3, and NF3. The mask comprises a material that is at least partially metallic.

[0009] In some embodiments, the wafer includes an oxide-containing material layer. In some embodiments, the oxide-containing material layer includes an oxide layer situated on top of a nitride layer. In some embodiments, the oxide-containing material layer includes a stack of oxide and nitride layers alternating one another. In some embodiments, the material, at least partially metallic, includes a tungsten-containing material. In some embodiments, the tungsten-containing material includes tungsten silicide (WSix). In some embodiments, the etching gas consists of CF4. In some embodiments, the etching gas consists of CHF3. In some embodiments, the etching gas consists of NF3.

[0010] The described technology may be implemented in the form of hardware, methods or processes, or a tangible computer medium for performing the process. Attached Figure Description

[0011] A better understanding of all aspects of this disclosure will be achieved by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, in accordance with industry standard practice, the various features are not drawn to scale. In fact, for clarity of discussion, the dimensions of the various features may be arbitrarily increased or decreased.

[0012] Figure 1 It is a cross-sectional view showing a wafer being etched (before etching) by an etching gas using a mask, according to some embodiments.

[0013] Figure 2 It is a cross-sectional view showing a wafer etched (after etching) by an etch gas using a mask according to some embodiments.

[0014] Figure 3 This paper presents a comparison between etching an ONO wafer according to some embodiments and etching an ONO wafer using an ACL mask with C4F6 as the etching gas.

[0015] Figure 4 This is a flowchart illustrating a method for etching a wafer using an etching gas via a mask, according to some embodiments. Detailed Implementation

[0016] The following disclosure provides numerous different embodiments or examples for implementing various features of the provided subject matter. Specific examples of components and arrangements are described below to simplify this disclosure. Of course, these are merely examples and not intended to be limiting. For example, in the following description, forming a first feature on or over a second feature may include embodiments in which the first and second features are formed in direct contact. There are also embodiments in which additional features may be formed between the first and second features such that the first and second features may not be in direct contact. Furthermore, reference numerals and / or letters may be repeated in various examples in this disclosure. Such repetition is for simplicity and clarity and does not, in itself, define the relationship between the various embodiments and / or configurations discussed.

[0017] Furthermore, for ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” “upper,” “top,” and “bottom” are used herein to describe the relationship between one element or feature and another, as shown in the accompanying drawings. In addition to the orientations depicted in the drawings, the spatial relative terms are intended to encompass different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and therefore the spatial relative descriptions used herein will also be interpreted accordingly.

[0018] In the fabrication of semiconductor devices, such as 3D NAND memory, high aspect ratio contact (HARC) etching is typically required. For example, HARC etching of a wafer using an amorphous carbon layer (ACL) mask can attempt to maintain sufficient selectivity between the ACL mask and the wafer to achieve the desired high aspect ratio using polyfluorocarbon (FC) gases (such as C4F6 and C4F8) as etchants. However, these polyfluorocarbon gases can lead to slower etch rates (ER) and undesirable contact deformation, which can negatively impact device performance and thus necessitate improved HARC etching chemistry.

[0019] Figure 1 This is a cross-sectional view 100 showing a wafer 10 being etched (before etching) by an etching gas 30 using a mask 20, according to some embodiments. In some embodiments, the mask 20 is formed on the wafer 10 before the etching process is performed on the wafer 10.

[0020] In some embodiments, wafer 10 includes an oxide-containing material layer. In some embodiments, the oxide-containing material layer of wafer 10 includes an oxide layer (referred to as an "ON" layer) situated on a nitride layer, and in other embodiments, the oxide-containing material layer of wafer 10 includes a stack of oxide layers and nitride layers alternating on top of each other (referred to as an "ONO" layer).

[0021] In some embodiments, the mask 20 includes one or more patterns such that some areas of the top surface of the wafer 10 are exposed, while other areas of the top surface of the wafer 10 are covered by the mask 20 and thus protected. The pattern of the mask 20 can be formed using processes such as photolithography, etching (e.g., wet etching or plasma dry etching), and (chemical mechanical polishing) CMP processes.

[0022] In some embodiments, mask 20 is a hard mask comprising a material that is at least partially metallic. In some embodiments, the material of mask 20 that is at least partially metallic includes a tungsten (W)-containing material. In some embodiments, the tungsten-containing material of mask 20 includes tungsten silicide (WSix).

[0023] Figure 2 Is with Figure 1 The cross-sectional view 100 corresponds to the cross-sectional view 200, which shows, according to some embodiments, the wafer 10 being etched (wet etched) (after etching) by using an etch gas 30 with a mask 20 acting as a photomask on the wafer 10.

[0024] In some embodiments, the etching gas 30 is selected from CF4, CHF3, NF3, etc., or combinations thereof. In some embodiments, the etching gas 30 is CF4. In some embodiments, the etching gas 30 is CHF3. In some embodiments, the etching gas 30 is NF3. In some embodiments, the etching gas 30 is any combination of CF4, CHF3, NF3, etc.

[0025] At least a portion of the mask 20 is made of a metallic material (e.g., WSi). x This provides better etch resistance and allows the use of a wider variety of gaseous chemicals that utilize leaner fluorocarbon (FC) or hydrofluorocarbon (HFC) gases (such as CF4, CHF3, and NF3) as etching gases. This is in contrast to mask 20, which is at least partially metallic (such as WSi). x In collaboration, these leaner etching formulations can produce higher etching rates and less contact deformation while maintaining satisfactory selectivity between the mask and the wafer to be partially etched.

[0026] Figure 3This paper demonstrates a comparison between etching of ONO wafers using a WSix mask with CHF3 and NF3 (more depleted chemicals) as etching gases, as shown in some embodiments such as 300A, and etching of ONO wafers using a conventional ACL mask with C4F6 as the etching gas, as shown in 300B. Using more easily etchable ACL masks, such as the more depleted chemicals (e.g., CF4, CHF3, and NF3) applied according to some embodiments, is not feasible. Experimental results show that such more depleted etching chemicals (e.g., using CHF3 and NF3 as etching gases) according to some embodiments exhibit advantages for etching ONO wafers using a WSix mask. x The feasibility of partially etching the ONO layer using a mask, compared to etching the ONO wafer using an ACL mask with a richer chemical substance (such as C4F6) as the etching gas, can provide improved etch profiles, faster etch rates, and better mask selectivity.

[0027] It should be noted that etching ONO wafers using a conventional ACL mask with a less enriched etch chemical (e.g., C4F6) as the etch gas can produce greater selectivity, according to some embodiments, compared to etching ONO wafers using a WSix mask with a less enriched etch chemical (e.g., CF4, CHF3, and NF3) as the etch gas. The less enriched etch chemical discussed herein does not contain deposit-rich FC gases (e.g., C4F6), which reduces polymer-driven deformation, reduces profile warping when using a WSix mask to maintain high-quality device performance during process integration, produces improved etch rate (ER), and consumes less energy. For example, the selectivity for etching ONO wafers using a WSix mask with CHF3 and NF3 as the etch gas is 37.2, while the selectivity for etching ONO wafers using an ACL mask with C4F6 as the etch gas is 8.7. For example, the etching efficiency (ER) of ONO wafers using a 300 nm WSix mask with CHF3 and NF3 as etching gases is 9.9, while the ER of ONO wafers using a 2.5 μm ACL mask with C4F6 as etching gas is 8.8. Thinner masks can accelerate the etching rate compared to thicker masks, and ACL can promote some carbon-based deposition, which may slow down the etching rate. Since the WSix mask is metal-based and inherently carbon-free, this carbon-based deposition can be avoided by using this mask.

[0028] Figure 4 This illustrates the corresponding embodiments according to some examples. Figure 1 and Figure 2 The flowchart illustrates a method 400 for etching wafer 10 using etching gas 30 and mask 20. It should be understood that, for additional embodiments of this method, [further details may be needed]. Figure 4 Additional operations are provided before, during, and after the processes discussed herein, and some of the operations described below may be substituted or eliminated. The order of operations / processes may be interchangeable, and at least some of the operations or processes may be performed in a different order.

[0029] refer to Figure 1 and Figure 4 In operation 410, a wafer 10 is provided. In some embodiments, the wafer 10 includes an oxide-containing material layer. In some embodiments, the oxide-containing material layer includes an oxide layer (referred to as an "ON" layer) situated on a nitride layer, and in other embodiments, the oxide-containing material layer includes a stack of oxide layers and nitride layers alternating on top of each other (referred to as an "ONO" layer).

[0030] refer to Figure 1 and Figure 4 In operation 420, a mask 20 having one or more patterns is formed on wafer 10. The pattern of mask 20 can be formed using, for example, photolithography, etching, and (chemical mechanical polishing) CMP processes, such that some areas of the top surface of wafer 10 are exposed, while other areas of the top surface of wafer 10 are covered by mask 20 and thus protected. In some embodiments, mask 20 is a hard mask comprising a material that is at least partially metallic. In some embodiments, the material that is at least partially metallic includes a tungsten-containing material. In some embodiments, the tungsten-containing material includes tungsten silicide (WSix).

[0031] refer to Figure 2 and Figure 4 In operation 430, a hole 40 with a high aspect ratio is formed in the wafer 10 by selectively etching the mask 20 and the wafer 10 beneath the mask 20 using an etching gas 30. In some embodiments, the etching gas 30 is selected from CF4, CHF3, NF3, etc., or combinations thereof. In some embodiments, the etching gas 30 is CF4. In some embodiments, the etching gas 30 is CHF3. In some embodiments, the etching gas 30 is NF3. In some embodiments, the hole 40 with a high aspect ratio is filled with a conductive material (not shown), such as Cu, thereby forming a HARC.

[0032] By using a material that is at least partially metallic (such as WSix) as the material of the mask 20 when etching the ON layer or ONO layer 10 and using a less metallic etching chemical (such as CF4, CHF3, and NF3) as the etching gas 30, the etching profile is improved, the etching selectivity between the mask 20 and the wafer 10 is increased, and the etching rate is also improved, thereby significantly improving device yield and performance.

[0033] The content described and illustrated herein are examples and variations thereof. The terminology, descriptions, and figures used herein are illustrative only and are not intended to be limiting. Many variations are possible within the spirit and scope of this subject matter, which is intended to be defined by the appended claims 1 to 20 and their equivalents, wherein, unless otherwise indicated, all terms shall be understood in their broadest reasonable sense.

Claims

1. A method comprising: A wafer is provided, wherein the wafer includes an oxide-containing material layer; A mask comprising at least a pattern is formed on the surface of the wafer, wherein the mask comprises at least partially a metallic material; and The mask and the wafer beneath it are selectively etched using an etching gas selected from the group consisting of CF4, CHF3 and NF3.

2. The method as described in claim 1, wherein, The oxide-containing material layer includes an oxide layer located on top of a nitride layer.

3. The method as described in claim 1, wherein, The oxide-containing material layer comprises a stack of oxide layers and nitride layers that alternate one on top of the other.

4. The method of claim 1, wherein, The material that is at least partially metallic includes tungsten-containing materials.

5. The method of claim 4, wherein, The tungsten-containing material includes tungsten silicide (WSix).

6. An etchant for etching a wafer using a mask, comprising: The gas is selected from the group consisting of CF4, CHF3, and NF3. The mask includes at least a pattern and is made of a material that is at least partially metallic.

7. The etchant as claimed in claim 6, wherein, The wafer includes an oxide-containing material layer.

8. The etchant as claimed in claim 7, wherein, The oxide-containing material layer includes an oxide layer located on top of a nitride layer.

9. The etchant as claimed in claim 7, wherein, The oxide-containing material layer comprises a stack of oxide layers and nitride layers that alternate one on top of the other.

10. The etchant of claim 6, wherein, The material that is at least partially metallic includes tungsten-containing materials.

11. The etchant of claim 10, wherein, The tungsten-containing material includes tungsten silicide (WSix).

12. A method comprising: A mask comprising at least a pattern is formed on a wafer, wherein the mask comprises a material that is at least partially metallic; and The mask and the wafer beneath it are selectively etched using an etching gas selected from the group consisting of CF4, CHF3 and NF3.

13. The method of claim 12, wherein, The wafer includes an oxide-containing material layer.

14. The method of claim 13, wherein, The oxide-containing material layer includes an oxide layer located on top of the nitride layer.

15. The method of claim 12, wherein, The oxide-containing material layer comprises a stack of oxide layers and nitride layers that alternate one on top of the other.

16. The method of claim 12, wherein, The material that is at least partially metallic includes tungsten-containing materials.

17. The method of claim 16, wherein, The tungsten-containing material includes tungsten silicide (WSix).

18. The method of claim 12, wherein, The etching gas consists of CF4.

19. The method of claim 12, wherein, The etching gas consists of CHF3.

20. The method of claim 12, wherein, The etching gas consists of NF3.

Images