Method for manufacturing ultra-thin metal gate

Abstract

The application provides a manufacturing method of an ultra-thin metal gate, which comprises the following steps: providing a substrate, wherein a floating gate structure is formed on the substrate, the floating gate structure comprises a storage area and a non-storage area; forming a first thin film covering the floating gate structure and a first composite thin film layer on the first thin film; forming a photoresist layer covering an oxide layer on the substrate, opening the photoresist layer by lithography so that the first composite thin film layer on the non-storage area is exposed; etching the exposed first composite thin film layer; etching the first composite thin film layer in the storage area; removing the photoresist layer, and then forming a second composite thin film layer covering the first thin film and the remaining first composite thin film layer on the substrate; etching the first thin film, the remaining first composite thin film layer and the second composite thin film layer. The application forms a multi-layer protective layer on the titanium nitride layer, protects the titanium nitride layer in the subsequent high-temperature process steps, makes the titanium nitride layer continuous, and improves the performance of the device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for manufacturing an ultrathin metal gate. Background Technology

[0002] Existing technologies use vertical TIN (titanium nitride) as the floating gate material, and horizontal electric field-guided write operations and voltage-coupled erase operations at the tip of the TIN can greatly improve write and erase efficiency. However, using TIN metal as the floating gate structure (such as...) Figure 1 As shown in the figure, after subsequent high-temperature process steps, TIN discontinuity is likely to occur, which will have an adverse effect on the storage of the entire circuit.

[0003] Therefore, a method for manufacturing an ultrathin metal gate is needed to protect the TIN in subsequent high-temperature process steps, ensuring TIN continuity and improving device performance. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for manufacturing an ultrathin metal gate, which solves the problem that in the prior art, when using TIN metal material as a floating gate structure, TIN discontinuity is easily caused after subsequent high-temperature process steps, which has an adverse effect on the storage of the entire circuit.

[0005] To achieve the above and other related objectives, the present invention provides a method for manufacturing an ultrathin metal grid, comprising:

[0006] Step 1: Provide a substrate on which a floating gate structure is formed, the floating gate structure including a storage region and a non-storage region;

[0007] Step 2: Form a first thin film covering the floating grid structure and a first composite thin film layer on the first thin film;

[0008] Step 3: Form a photoresist layer covering the oxide layer on the substrate, and use photolithography to open the photoresist layer to expose the first composite thin film layer on the non-storage area;

[0009] Step 4: Etch the exposed first composite film layer so that the first composite film layer on the floating gate structure in the storage region is retained;

[0010] Step 5: Etch the first composite film layer in the storage region to remove the first composite film layer outside the sidewalls and bottom trenches of the floating gate structure in the storage region;

[0011] Step 6: Remove the photoresist layer, and then form a second composite film layer on the substrate covering the first film and the remaining first composite film layer;

[0012] Step 7: Etch the first thin film and the remaining first and second composite thin film layers, so that the first thin film and the remaining first and second composite thin film layers outside the sidewall of the floating gate structure in the storage area are removed, and the second composite thin film layer outside the sidewall of the floating gate structure in the non-storage area is removed.

[0013] Preferably, the substrate in step one is a silicon substrate.

[0014] Preferably, the floating gate structure is formed after the floating gate tunneling oxide layer is formed on the substrate in step one.

[0015] Preferably, the material of the first thin film in step two is hafnium dioxide.

[0016] Preferably, the thickness of the first film in step two is 20 to 30 angstroms.

[0017] Preferably, the first composite thin film layer in step two comprises a titanium nitride layer and a first oxide layer stacked from bottom to top.

[0018] Preferably, the thickness of the first oxide layer in step two is about 20 to 40 angstroms.

[0019] Preferably, the thickness of the titanium nitride layer in step two is about 20 to 40 angstroms.

[0020] Preferably, the deposition temperature of the titanium nitride layer in step two is 390 degrees Celsius to 410 degrees Celsius.

[0021] Preferably, in step four, the first oxide layer is removed by wet etching, and then the titanium nitride layer is removed by dry etching.

[0022] Preferably, the etching in step five is wet etching.

[0023] Preferably, the second composite thin film layer in step six is ​​a second oxide layer and a silicon nitride layer stacked from bottom to top.

[0024] Preferably, the thickness of the second oxide layer in step six is ​​about 20 to 30 angstroms.

[0025] Preferably, the thickness of the silicon nitride layer in step six is ​​about 20 to 30 angstroms.

[0026] Preferably, the etching in step seven is dry etching.

[0027] As described above, the method for manufacturing the ultrathin metal grid of the present invention has the following beneficial effects:

[0028] This invention forms a multilayer protective layer on the titanium nitride layer, which protects the titanium nitride layer in subsequent high-temperature process steps, making the titanium nitride layer continuous and improving the performance of the device. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a floating gate in the prior art;

[0030] Figure 2 The diagram shown illustrates the formation of the first thin film and the first composite thin film layer according to the present invention.

[0031] Figure 3 The diagram shown is a photolithography schematic of the present invention.

[0032] Figure 4 The diagram shows the etching of the first composite thin film layer according to the present invention.

[0033] Figure 5 The diagram shows a schematic of the continued etching of the first composite thin film layer according to the present invention.

[0034] Figure 6 The diagram shown illustrates the formation of the second composite thin film layer according to the present invention.

[0035] Figure 7 The diagram shows the etching of the second composite thin film layer according to the present invention.

[0036] Figure 8 The diagram shown is a schematic representation of the process flow of this invention. Detailed Implementation

[0037] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0038] Please see Figure 8 The present invention provides a method for manufacturing an ultrathin metal grid, comprising:

[0039] Step 1, please refer to Figure 2 A substrate 10 is provided, on which a floating gate structure 11 is formed, the floating gate structure 11 including a memory region and a non-memory region;

[0040] In one optional embodiment, the substrate 10 in step one is a silicon substrate 10, and the floating gate structure 11 can be formed on the silicon substrate 10, or the floating gate structure 11 can be formed on the epitaxial layer after the epitaxial layer is formed on the silicon substrate 10.

[0041] In one alternative implementation, after the floating gate tunnel oxide layer is formed on the substrate 10 in step one, the floating gate structure 11 is then formed, which is the fabrication of FLOTOX (floating gate tunnel oxide transistor).

[0042] Step 2, please refer to Figure 2 A first thin film 12 covering the floating grid structure 11 and a first composite thin film layer 13 on the first thin film 12 are formed.

[0043] In one alternative embodiment, the material of the first thin film 12 in step two is hafnium dioxide.

[0044] In one alternative implementation, the thickness of the first film 12 in step two is 20 to 30 angstroms.

[0045] In an optional embodiment, the first composite thin film layer 13 in step two includes a titanium nitride layer 131 and a first oxide layer 132 stacked from bottom to top, wherein the first oxide layer 132 is used to protect the titanium nitride layer 131 in subsequent processes.

[0046] In one alternative embodiment, the thickness of the first oxide layer 132 in step two is approximately 20 to 40 angstroms.

[0047] In one alternative embodiment, the thickness of the titanium nitride layer 131 in step two is approximately 20 to 40 angstroms.

[0048] In one alternative embodiment, the deposition temperature of the titanium nitride layer 131 in step two is between 390 degrees Celsius and 410 degrees Celsius.

[0049] Step 3, please refer to Figure 3 A photoresist layer 14 covering the composite thin film layer 13 is formed on the substrate 10. Photolithography opens the photoresist layer 14 to expose the first composite thin film layer 13 on the non-storage area. The exposed first composite thin film layer 13 is the part that needs to be etched away.

[0050] Step four, please refer to Figure 4 The first composite thin film layer 13 is etched to expose the first composite thin film layer 13, so that the first composite thin film layer 13 on the floating gate structure 11 in the storage region is retained.

[0051] In one alternative embodiment, in step four, the first oxide layer 132 is removed by wet etching, followed by the removal of the titanium nitride layer 131 by dry etching.

[0052] Step 5, please refer to Figure 5 The first composite thin film layer 13 in the storage region is etched to remove the first composite thin film layer 13 outside the sidewalls and bottom trenches of the floating gate structure 11 in the storage region.

[0053] In one optional implementation, the etching in step five is wet etching. Specifically, a mixed cleaning solution of HF, H2O2 and H2O can be used, and the cleaning time is about 100 seconds.

[0054] Step Six, please refer to Figure 6 The photoresist layer 14 can be removed by ashing and wet washing. Then, a second composite film layer 15 covering the first film 12 and the remaining first composite film layer 13 is formed on the substrate 10. The second composite film layer 15 is used to protect the first composite film layer 13.

[0055] In an optional embodiment, the second composite thin film layer 15 in step six is ​​a second oxide layer 151 and a silicon nitride layer 152 stacked from bottom to top.

[0056] In one alternative implementation, the thickness of the second oxide layer 151 in step six is ​​approximately 20 to 30 angstroms.

[0057] In one alternative implementation, the thickness of the silicon nitride layer 152 in step six is ​​approximately 20 to 30 angstroms.

[0058] Step 7, please refer to Figure 7 The first thin film 12 and the remaining first and second composite thin film layers (13, 15) are etched, so that the first thin film 12 and the remaining first and second composite thin film layers (13, 15) outside the sidewall of the floating gate structure 11 in the storage region are removed, and the second composite thin film layer 15 outside the sidewall of the floating gate structure 11 in the non-storage region is removed. That is, the first thin film 12 and the first and second composite thin film layers (13, 15) are retained on the sidewall of the floating gate structure 11 in the storage region, which protects the subsequent titanium nitride layer 131. After the subsequent high-temperature process steps, the titanium nitride layer 131 is relatively continuous.

[0059] In one alternative implementation, the etching in step seven is dry etching.

[0060] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0061] In summary, this invention forms a multi-layered protective layer on the titanium nitride layer, protecting the titanium nitride layer during subsequent high-temperature processing steps, ensuring the continuity of the titanium nitride layer, and improving device performance. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0062] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for manufacturing an ultrathin metal grid, characterized in that, At least including: Step 1: Provide a substrate on which a floating gate structure is formed, the floating gate structure including a storage region and a non-storage region; Step 2: Form a first thin film covering the floating gate structure and a first composite thin film layer on the first thin film, wherein the first composite thin film layer is a titanium nitride layer and a first oxide layer stacked from bottom to top; Step 3: Form a photoresist layer covering the first composite thin film layer on the substrate, and use photolithography to open the photoresist layer to expose the first composite thin film layer on the non-storage area; Step 4: Etch the exposed first composite film layer so that the first composite film layer on the floating gate structure in the storage region is retained; Step 5: Etch the first composite film layer in the storage region such that the first composite film layer located on the sidewall of the floating gate structure in the storage region is retained, while the first composite film layer located on the top of the floating gate structure and the bottom between the floating gate structures is removed. Step 6: Remove the photoresist layer, and then form a second composite film layer covering the first film and the remaining first composite film layer. The second composite film layer is a second oxide layer and a silicon nitride layer stacked from bottom to top. Step 7: Etch the first thin film, the remaining first composite thin film layer, and the second composite thin film layer, such that in the storage region, the first thin film, the remaining first composite thin film layer, and the second composite thin film layer on the sidewall of the floating gate structure are retained, while the first thin film, the remaining first composite thin film layer, and the second composite thin film layer located at the bottom between the floating gate structures are removed, and in the non-storage region, the first thin film and the second composite thin film layer located at the bottom between the floating gate structures are removed.

2. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The substrate mentioned in step one is a silicon substrate.

3. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: After forming the floating gate tunneling oxide layer on the substrate in step one, the floating gate structure is then formed.

4. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The material of the first thin film in step two is hafnium dioxide.

5. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The thickness of the first film in step two is 20 to 30 angstroms.

6. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The thickness of the first oxide layer in step two is 20 to 40 angstroms.

7. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The thickness of the titanium nitride layer in step two is 20 to 40 angstroms.

8. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The deposition temperature of the titanium nitride layer in step two is 390 degrees Celsius to 410 degrees Celsius.

9. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: In step four, the first oxide layer is removed by wet etching, and then the titanium nitride layer is removed by dry etching.

10. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The etching described in step five is wet etching.

11. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The thickness of the second oxide layer in step six is ​​20 to 30 angstroms.

12. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The thickness of the silicon nitride layer in step six is ​​20 to 30 angstroms.

13. The method for manufacturing an ultrathin metal grid according to claim 1, characterized in that: The etching described in step seven is dry etching.

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