A method for improving virtual pattern dish A method for improving virtual pattern dish

Abstract

The present application relates to a method for improving virtual pattern dish, and belongs to the technical field of semiconductor manufacturing process, which solves the problem of dish defect in the prior art that in the CMP, the film with high polishing rate is polished in the area with low pattern density of the stop layer. The method for improving virtual pattern dish comprises the following steps: providing a semiconductor substrate with a substrate pattern, and the substrate pattern is a transition area; forming a first stop layer only on the substrate pattern; forming a deposition film layer on the substrate, and the deposition film layer forms a groove in the transition area; the top surface of the deposition film layer on the groove is flush with the top surface of the substrate pattern; forming a second stop layer above the deposition film layer, and the bottom surface of the second stop layer above the groove is flush with the top surface of the substrate pattern, and the top surface of the second stop layer above the groove is flush with the top surface of the first stop layer; and the polishing rate of the first stop layer and the second stop layer is less than that of the deposition film layer. The method realizes the complete planarization processing without dish when the virtual pattern is made.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a method for improving virtual pattern trapping. Background Technology

[0002] Chemical Mechanical Planarization (CMP) utilizes the chemical etching effect of polishing slurry and the mechanical cutting action of polishing machinery to achieve a sufficiently smooth and flat wafer surface. Since its initial introduction into integrated circuits, CMP has been widely used in various stages of the polishing process, playing a crucial role in improving the yield of integrated circuit devices and chips. CMP is indispensable and irreplaceable in achieving global wafer surface planarization. However, due to the extremely complex mechanism of CMP, the cyclical action of chemical reactions, fluid lubrication, and mechanical cutting on the wafer surface makes controlling the planarity extremely difficult. Furthermore, the polishing rates differ in different regions of different materials during the CMP process, requiring selective control, which also presents a challenge.

[0003] The entire CMP process varies depending on the grinding requirements of different materials. The grinding process must use a grinding slurry with a specific film selectivity. When the stop layer is exposed at a low grinding rate, a certain period of deep CMP is performed to complete the entire CMP process. However, in areas with low stop layer density or no stop layer, the deposited film is ground down at a high grinding rate, resulting in... Figure 1 The defective disc trap shown is an undesirable feature.

[0004] Existing technologies use a CMP virtual media layer to prevent disk trapping during the CMP process. The virtual pattern is created by covering a photomask to achieve virtual pattern creation, and then removed through exposure and etching processes. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a method for forming virtual patterns in CMP, in order to solve the problem that in existing CMP, when polishing slurries with a film-to-material selectivity are used, the film with a high polishing rate is polished in areas with low stop layer pattern density, resulting in disc-shaped defects.

[0006] This invention provides a method for improving virtual pattern trapping, comprising: A semiconductor substrate with substrate patterns formed thereon is provided, wherein the substrate patterns are transition regions; A first stop layer is formed only on the substrate pattern; A deposited film layer is formed on a substrate, wherein a trench is formed in the transition region of the deposited film layer toward the substrate, and the top surface of the deposited film layer on the trench is made flush with the top surface of the substrate pattern by etching. A second stop layer is formed above the deposited film layer, such that the bottom surface of the second stop layer above the trench is flush with the top surface of the substrate pattern, and the top surface of the second stop layer above the trench is flush with the top surface of the first stop layer. The grinding rates of the first stop layer and the second stop layer are lower than those of the deposited film layer.

[0007] Furthermore, after forming a second stop layer above the deposited film, the process also includes: Remove the second stop layer above the substrate pattern; Remove the deposited film layer above the substrate pattern and above the transition region that is higher than the first stop layer, as well as the second stop layer on the trench side; Remove the deposited film layer above the bottom surface of the trench that is higher than the top surface of the substrate pattern; Remove the first stop layer and the second stop layer above the bottom of the trench, as well as the deposited film layer above the top surface of the substrate pattern, to expose the top of the substrate pattern.

[0008] Furthermore, the method for removing the second stop layer above the substrate pattern is depth CMP.

[0009] Furthermore, the method for removing the first stopping layer is CMP.

[0010] Furthermore, the first stop layer and the second stop layer are made of silicon nitride layers.

[0011] Furthermore, the material of the deposited film is a silicon oxide layer.

[0012] Furthermore, the method for removing the first stop layer and the second stop layer is either dry etching or wet etching.

[0013] Furthermore, the thickness of the first stop layer is 1 nm or more, and the thickness of the second stop layer is 1 nm or more.

[0014] Furthermore, the CMP uses a polishing slurry with a high polishing ratio.

[0015] Furthermore, the grinding ratio of the grinding fluid to the deposited layer film and the stop layer is 10:1 or higher.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) In contrast, the prior art does not provide protection at the trenches of the deposited film. In this invention, a second stop layer is covered on the deposited film. The second stop layer provides good protection for the deposited film at the trenches during the grinding process, preventing the formation of disc-shaped defects at the trenches.

[0017] (2) The prior art fills the trench with FCVD, which has high fluidity, by using a large amount of deposit and completing the filling of the trench through long-term chemical deposition; the present invention uses silicon nitride with low fluidity as the second stop layer, which requires less material for deposition, takes less time for deposition, and has higher production efficiency.

[0018] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0019] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0020] Figure 1 This is a schematic diagram illustrating the disc-shaped defects that occur after grinding with a polishing slurry having a film-to-mass ratio using existing technology. Figure 2 Schematic diagram of trench formation for depositing film above the first stop layer; Figure 3 A schematic diagram of the deposition of a second stop layer on the deposition film above the pattern and trenches; Figure 4 A diagram illustrating the removal of the second stop layer above the pattern during CMP. Figure 5 A schematic diagram showing the process of grinding the deposited film above the pattern to the contact surface between the top of the first stop layer and the deposited film during CMP. Figure 6 To continue CMP, the first stop layer above the pattern is completely removed, and grinding is performed until the top of the pattern contacts the first stop layer. (See diagram for reference.)

[0021] Figure label: 1-Pattern; 2-First stop layer; 3-Deposited film layer; 4-Second stop layer; 5-Trench; 6-Dish trap defect. Detailed Implementation

[0022] The entire CMP process varies depending on the grinding requirements of different materials. The grinding process must utilize a grinding slurry with a specific film selectivity. When the stop layer is exposed at a low grinding rate, a certain period of deep CMP is performed to complete the entire process. However, in areas with low stop layer density or no stop layer, the deposited film is ground down at a high grinding rate, resulting in… Figure 1 The defect shown is a bad disc trap 6.

[0023] The method for improving virtual pattern trapping provided by the present invention includes: A semiconductor substrate with substrate patterns formed thereon is provided, and the substrate patterns are transition regions; A first stop layer is formed only on the substrate pattern; A deposited film layer is formed on the substrate, and a trench is formed in the transition region of the deposited film layer towards the substrate. The top surface of the deposited film layer on the trench is made flush with the top surface of the substrate pattern by etching. A second stop layer is formed above the deposited film layer, such that the bottom surface of the second stop layer above the trench is flush with the top surface of the substrate pattern, and the top surface of the second stop layer above the trench is flush with the top surface of the first stop layer. The grinding rates of the first stop layer and the second stop layer are lower than those of the deposited film layer.

[0024] Existing technologies for treating trenches formed by film deposition employ two methods: "filling" and "photomask." The "filling" method uses silica with good flowability for chemical deposition, completely filling the trench area after a long deposition period. After filling, CMP (chemical mechanical polishing) is performed. Because the trench area is fully filled with silica, both the trench and patterned areas are simultaneously polished by the polishing slurry during the polishing process, thus preventing dent defects in the trench area. The "photomask" method, on the other hand, covers the patterned area with a photomask. When CMP is about to polish the photomask, CMP is stopped, and the photomask is removed using exposure and etching processes, directly avoiding polishing and thus preventing dent defects caused by polishing the trench area.

[0025] Considering that photomask preparation and removal require cumbersome exposure and etching processes, this invention avoids photomasks and the corresponding complex exposure and etching processes. Instead, it directly employs CMP (Chemical Motion Processing) to prevent dish defects by designing a second stop layer to alter the grinding rate during CMP. Furthermore, unlike existing technologies that fill the trench areas before grinding, this invention retains the trench areas and uniformly covers the deposited film in both patterned and unpatterned trench areas with a low-rate stop layer, effectively protecting the trench areas. By eliminating the need to fill the trench areas, the chemical deposition materials used for filling are significantly reduced, lowering processing costs. Additionally, filling trench areas requires substantial time for chemical deposition; this invention eliminates the need for trench filling, greatly saving time and improving production efficiency.

[0026] Specifically, after the formation of the second stop layer above the deposited film, the process also includes: Remove the second stop layer above the substrate pattern; Remove the deposited film layer above the substrate pattern and above the transition region that is higher than the first stop layer, as well as the second stop layer on the trench side; Remove the deposited film layer above the bottom surface of the trench, which is higher than the top surface of the substrate pattern; Remove the first stop layer and the second stop layer above the bottom of the trench to expose the top of the substrate pattern.

[0027] Specifically, the method for removing the second stop layer above the substrate pattern is depth CMP.

[0028] Specifically, the method for removing the first stopping layer is CMP.

[0029] Specifically, the method for removing the deposited film layer above the bottom surface of the trench and above the top surface of the substrate pattern is etching.

[0030] Since chemical deposition occurs simultaneously across the entire wafer surface area, during the chemical deposition process to cover the trench area with the second stop layer, the deposited film in the pattern area will also be covered by the second deposited film. Therefore, in the CMP process, deep CMP is first performed to remove all the second stop layer above the pattern, and then CMP is continued to grind the deposited film above the pattern down to the contact surface between the top of the first stop layer and the deposited film.

[0031] Because the upper surface of the deposited film in the trench area is covered by a second stop layer, when CMP continues, the pattern is covered by a first stop layer with a low grinding rate, and the surface of the deposited film in the trench area is also covered by a second stop layer with a low grinding rate. During CMP, the second stop layer effectively protects the deposited film in the trench area. Therefore, the first stop layer above the pattern is completely removed, and grinding is performed down to the contact surface between the top of the pattern and the first stop layer. The deposited film in the trench area is not damaged, thus avoiding the formation of dish defects.

[0032] To achieve complete planarization of the patterned and unpatterned regions after the stop layer is removed, the top surface of the deposited film layer in the transition region is flush with the top surface of the substrate pattern, forming a trench. This achieves complete planarization of the patterned and transition regions after the first stop layer covering the patterned region and the second stop layer covering the deposited film in the unpatterned substrate region are removed simultaneously.

[0033] In one possible implementation, the thickness of the second stop layer covering the trench area is equal to the thickness of the first stop layer covering the pattern.

[0034] Specifically, the first and second stop layers are made of silicon nitride layers.

[0035] Existing technologies use silicon oxide layers to fill and level trenches. Silicon oxide layers have good fluidity, making trench filling easy, and also offer a high grinding rate. After filling the trenches with the silicon oxide layer, existing technologies grind both the patterned and trench areas, resulting in similar grinding ratios for both regions, thus allowing for simultaneous grinding. Unlike existing technologies, this invention, to prevent the first and second stop layers from being unable to be removed simultaneously during CMP due to differences in thickness and grinding rate, thus hindering complete planarization of both patterned and unpatterned areas, uses a second stop layer with the same thickness as the first stop layer covering the pattern. Both the first and second stop layers are made of the same silicon nitride layer.

[0036] In one possible implementation, the deposited film is made of silicon oxide.

[0037] The primary function of the deposited film is to cover the patternless transition region, raising its height to be flush with the pattern height. Therefore, silicon oxide is chosen because it has better fluidity and is easily removed by subsequent processes such as photolithography. Studies have shown that using silicon nitride as the deposited film makes subsequent removal extremely difficult. If CMP is used to remove the deposited film to expose the pattern, it will completely destroy the pattern. Therefore, silicon nitride cannot be effectively removed using this method. Thus, the deposited layer is made of silicon oxide.

[0038] Specifically, the methods for removing the first and second stop layers are dry etching or wet etching.

[0039] Specifically, the thickness of the first stop layer is 1 nm or more, and the thickness of the second stop layer is 1 nm or more.

[0040] A high polishing ratio allows the deposited film to be polished rapidly, while the stop layer is either barely polished or polished very quickly. This allows the stop layer to protect the deposited film covering the patterned and trench areas during CMP. An excessively thick stop layer leads to waste and reduced production efficiency; therefore, a thinner stop layer is better. However, an excessively thin stop layer may be removed during CMP, rendering it ineffective. Therefore, the thickness of both the first and second stop layers is chosen to be greater than 1 nm.

[0041] Specifically, CMP uses a high-grinding-ratio grinding fluid.

[0042] Specifically, the grinding ratio of the grinding fluid to the deposited film and the stop layer is 10:1 or higher.

[0043] The CMP process requires that the deposited film be rapidly polished, while the stop layer is either barely polished or polished very quickly, in order to utilize the stop layer to protect the deposited film in the patterned and trenched areas covered by the stop layer during the CMP process. Therefore, the polishing slurry must be selected with a high selectivity, and the polishing ratio of the polishing slurry to the deposited film and the stop layer should be greater than 10:1.

[0044] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0045] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the term "connected" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the terms "top," "bottom," "above," "below," and "on" used throughout the description refer to the relative positions of components of the device, such as the relative positions of the top and bottom substrates inside the device. It is understood that the device is multifunctional, regardless of its spatial orientation.

[0046] The working surface of this invention can typically be a plane or a curved surface, and can be inclined or horizontal. For ease of explanation, the embodiments of this invention are placed on a horizontal surface and used on a horizontal surface, thereby defining "height" and "vertical".

[0047] Example 1 One specific embodiment of the present invention discloses a method for forming virtual patterns.

[0048] In this embodiment, the pattern is created using a photolithography-defined and etching process to produce a patterned area with a substrate and a base area without a pattern, i.e., a trench area.

[0049] The substrate in this embodiment is a silicon substrate.

[0050] There are multiple trench regions, with the same or different widths, ranging from 600nm to 900nm.

[0051] A first stop layer, consisting of a silicon nitride layer, is formed on the surface of a silicon substrate. A photoresist pattern is formed using photolithography to open up the trench formation area. The first stop layer and the substrate are then etched sequentially to form the desired patternless substrate area, i.e., the trench area. The photoresist pattern is then removed to obtain the desired trench area. Figure 1 The pattern 1 shown is covered with a first stop layer 2, wherein the height of the pattern 1 is 200 nm and the thickness of the first stop layer 2 is 10 nm.

[0052] Next, a deposited film layer is formed, such as Figure 2 As shown, a chemical deposition method is used to deposit a film layer 3 in the unpatterned area, i.e., the trench area 5. The film layer 3 is a silicon oxide layer. The target thickness of the film layer 3 in the trench area 5 is 200 nm. That is, after deposition, the trench area 5 is covered with the film layer 3. After etching, the thickness of the film layer 3 in the trench area 5 is 200 nm.

[0053] While the deposition film 3 is deposited in the trench region 5, the deposition film 3 is also deposited on the top of the pattern region. That is, while the trench region 5 is covered by the deposition film 3, the top of the first stop layer 2 in the pattern region is also covered by the deposition film 3.

[0054] After deposition is complete, a baking process is performed.

[0055] The deposition of film layer 3 was carried out using a high-density plasma HDPCVD process.

[0056] Then, a second stopping layer is formed, such as Figure 3 As shown, a second stop layer 4 is deposited in the trench region 5 using a chemical deposition method. The second stop layer 4 is a silicon nitride layer, and the thickness of the second stop layer 4 deposited in the trench region 5 is 100 nm.

[0057] While the second stop layer 4 is deposited in the trench region 5, the second stop layer 4 is also deposited above the pattern region. That is, while the deposited film layer 3 in the trench region 5 is covering the second stop layer 4, the deposited film layer 3 in the pattern region is also covered by the second stop layer 4.

[0058] The deposition of the second stop layer 4 was carried out using a horizontal vertical flow enhanced plasma PEVCD process.

[0059] Next, chemical mechanical grinding is performed, such as... Figure 4 As shown, during CMP, a polishing slurry containing cerium dioxide was used, with a polishing powder diameter ranging from 10 nm to 100 nm. The polishing ratio of the polishing slurry to the deposited film and the stop layer was 20:1.

[0060] First, CMP grinds and removes the entire second stop layer 4 above the pattern area.

[0061] Then, chemical mechanical grinding is performed, such as... Figure 5 As shown: CMP continues until it stops at the highest point of the first stop layer 2. At this point, the pattern area is covered by the first stop layer 2, and the groove area is covered by the remaining part of the second stop layer 4. The second stop layer effectively prevents the formation of disc-shaped defects in the groove area during CMP.

[0062] Next, as Figure 6 As shown, after CMP is completed, the portion of the deposited film layer 3 located above the height of pattern 1, i.e., above 700nm, is subjected to a reverse etching process using wet etching.

[0063] The deposited film layer 3, which is above the bottom surface of the trench and above the top surface of pattern 1, is removed by etching. A reverse etching process is performed on the first stop layer 2 above the cover pattern 1 and the portion of the second stop layer 4 covering the trench region 5. The reverse etching process uses dry etching to completely remove the silicon nitride layer of the first stop layer 2 and the second stop layer 4.

[0064] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving virtual pattern trapping, characterized in that, include: A semiconductor substrate with substrate patterns formed thereon is provided, wherein the substrate patterns are transition regions; A first stop layer is formed only on the substrate pattern; A deposition film is formed on a substrate using a high-density plasma process. The deposition film forms trenches in the transition region that are directed toward the substrate. Etching is used to make the top surface of the deposition film on the trench flush with the top surface of the substrate pattern. A second stop layer is formed above the deposited film layer using a horizontal-vertical flow enhanced plasma process, such that the bottom surface of the second stop layer above the trench is flush with the top surface of the substrate pattern, and the top surface of the second stop layer above the trench is flush with the top surface of the first stop layer; the thickness of the second stop layer is equal to the thickness of the first stop layer, and both the first and second stop layers are made of the same material, silicon nitride layers. The second stop layer above the substrate pattern was removed using CMP. CMP is used to remove the deposited film layer above the substrate pattern and above the transition region that is higher than the first stop layer, as well as the second stop layer on the side of the trench; The deposited film layer above the bottom surface of the trench and above the top surface of the substrate pattern is removed by etching; The first stop layer and the second stop layer above the bottom of the trench are removed by etching to expose the top of the substrate pattern; Wherein, the thickness of the first stop layer is 1 nm or more, and the thickness of the second stop layer is 1 nm or more; the polishing rate of the first stop layer and the second stop layer is less than that of the deposited film layer; The CMP uses a high-grinding-ratio polishing slurry, wherein the polishing ratio of the polishing slurry to the deposited film layer and the first stop layer is 10:1 or higher.

2. The method for improving virtual pattern trapping according to claim 1, characterized in that, The method for removing the second stop layer above the substrate pattern is depth CMP.

3. The method for improving virtual pattern trapping according to claim 1, characterized in that, The deposited film is made of silicon oxide.

4. The method for improving virtual pattern trapping according to claim 1, characterized in that, The method for removing the first and second stop layers is either dry etching or wet etching.

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