Contact hole structure forming method, contact hole structure and power device

Abstract

The invention discloses a contact hole structure forming method, a contact hole structure and a power device. The contact hole structure forming method comprises the steps that a first dielectric layer, a buffer dielectric layer and a second dielectric layer are sequentially formed on the surface of a substrate; forming a transition contact hole structure of which the bottom enters the substrate on the surface of the second dielectric layer by adopting photoetching and dry etching processes; and removing the residual photoresist by adopting a wet photoresist removing process to form a final contact hole structure, and enabling the side wall of the final contact hole structure to have opening degrees which are reduced layer by layer at the positions of the second dielectric layer, the buffer dielectric layer and the first dielectric layer. The buffer dielectric layer is arranged, so that the abrupt change degree of steps generated at the side wall can be effectively relieved, a metal hole filling process window is improved, the gap defect generated after metal filling is avoided, and the performance of the device is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor integrated circuit technology, and in particular to a method for forming a contact hole structure, the contact hole structure, and a power device. Background Technology

[0002] refer to Figure 1 Currently, when fabricating contact holes on power devices, an interlayer dielectric layer structure with two dielectric layers, USG (undoped glass) layer 11 and PSG (phosphate glass) layer 12, is typically formed on the surface of substrate 10. Then, a photoresist pattern 14 is formed on the surface of PSG layer 12 using a photolithography process. Using the photoresist pattern 14 as a mask, a contact hole 13 that enters the substrate 10 is formed on the surface of PSG layer 12 through a dry etching process.

[0003] refer to Figure 2 Then, a wet stripping process is generally used to remove the remaining photoresist. The wet stripping process usually uses SPM solution (a mixture of sulfuric acid and hydrogen peroxide) in combination with SC1 solution (a mixture of ammonia and hydrogen peroxide). However, because the etching rate of the two films USG layer 11 and PSG layer 12 by SC1 solution is significantly different, that is, the lateral etching rate of PSG layer 12 is greater than that of USG layer 11, a protruding "T"-shaped step 15 appears on the sidewall of the contact hole 13 after cleaning, forming a contact hole structure that is wide at the top and narrow at the bottom.

[0004] refer to Figure 3 When filling the contact hole 13 with contact hole metal 16, chemical vapor deposition is generally used. This process is characterized by the metal filler preferentially growing from the sidewalls. However, due to the presence of the "T"-shaped step 15, the top opening of the contact hole 16 is prone to premature closure during filling. This results in insufficiently filled gaps 17 forming in the middle region of the lower contact hole 13, thus affecting the performance of the power device.

[0005] Although reducing the etching amount during wet stripping can improve the degree of abrupt change in the "T" step, the plasma bombardment during dry etching to form contact holes can cause severe polymer contamination within the contact holes. Therefore, when the etching amount during wet stripping is reduced, it can lead to new problems such as difficulty in completely removing contamination defects and the formation of buried layer defects after metal filling, which in turn affects the product yield. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects in the prior art and to provide a method for forming a contact hole structure, as well as a contact hole structure and a power device.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] This invention provides a method for forming a contact hole structure, comprising:

[0009] Provide substrate;

[0010] A first dielectric layer, a buffer dielectric layer, and a second dielectric layer are sequentially formed on the surface of the substrate;

[0011] A transition contact hole structure that enters the substrate from the bottom is formed on the surface of the second dielectric layer using photolithography and dry etching processes.

[0012] A wet photoresist stripping process is used to remove the remaining photoresist, forming the final contact hole structure, and the sidewalls of the final contact hole structure have progressively smaller openings at the second dielectric layer, the buffer dielectric layer, and the first dielectric layer.

[0013] Furthermore, during the wet stripping process, the wet solution is used to etch the second dielectric layer, the buffer dielectric layer, and the first dielectric layer on the sidewall of the transition contact hole structure with progressively decreasing etching amounts, thereby forming the final contact hole structure with progressively smaller openings. This is achieved by using the buffer dielectric layer to mitigate the abrupt change in the step between the second dielectric layer and the first dielectric layer on the sidewall caused by the difference in etching rates.

[0014] Furthermore, the first dielectric layer includes a USG layer, the second dielectric layer includes a PSG layer, and the wet etching solution includes SPM solution and SC1 solution. By selecting the material of the buffer dielectric layer, the etching rate of the wet etching solution on the buffer dielectric layer is made to be less than the etching rate on the second dielectric layer, but greater than the etching rate on the first dielectric layer.

[0015] Furthermore, the buffer medium layer includes a USG-doped layer.

[0016] Furthermore, the buffer medium layer includes a USG layer doped with a Group VA element, and by adjusting the doping concentration of the Group VA element, the etching amount of the wet process solution on the buffer medium layer is intermediate between the etching amount on the second medium layer and the etching amount on the first medium layer.

[0017] Furthermore, it also includes: using a chemical vapor deposition process to fill the final contact hole structure with contact hole metal.

[0018] The present invention also provides a contact hole structure, wherein the contact hole structure is formed on a substrate, and a first dielectric layer, a buffer dielectric layer and a second dielectric layer are sequentially formed on the surface of the substrate, and the contact hole structure enters the substrate from the surface of the second dielectric layer through the buffer dielectric layer and the first dielectric layer in sequence;

[0019] The sidewalls of the contact hole structure have progressively smaller openings at the second dielectric layer, the buffer dielectric layer, and the first dielectric layer.

[0020] Furthermore, the first dielectric layer includes a USG layer, the second dielectric layer includes a PSG layer, the buffer dielectric layer includes a USG layer doped with a Group VA element at a doping concentration of 5% to 20%, and the contact hole structure is filled with contact hole metal.

[0021] Furthermore, the doping concentration is 10%.

[0022] The present invention also provides a power device including the contact hole structure described above.

[0023] As can be seen from the above technical solution, the present invention adds a buffer dielectric layer between the existing double dielectric layers (first dielectric layer and second dielectric layer) used to form the contact hole structure on the substrate. During the wet resist removal process after dry etching, the wet solution produces a progressively decreasing etching amount on the second dielectric layer, the buffer dielectric layer, and the first dielectric layer, corresponding to the formation of a final contact hole structure with a progressively smaller opening. This changes the morphology of the contact hole after wet resist removal from the previous "T" shape to a "Y" shape. By setting the buffer dielectric layer, the abrupt change in the step between the second dielectric layer and the first dielectric layer at the sidewall caused by the difference in etching rate is effectively mitigated. Therefore, when the contact hole structure is subsequently filled with metal, the metal filling process window can be improved, thereby improving the gap problem generated after metal filling. Attached Figure Description

[0024] Figures 1-3 This is a schematic diagram of a conventional process for forming contact holes on power devices.

[0025] Figure 4 This is a flowchart of a method for forming a contact hole structure according to a preferred embodiment of the present invention.

[0026] Figures 5-9 According to a preferred embodiment of the present invention Figure 4 A schematic diagram of the process steps for forming a contact hole structure using this method.

[0027] Figure 10 This is a schematic diagram of a contact hole structure according to a preferred embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0029] like Figures 1-3 As shown, in existing methods for fabricating contact holes in power devices, an interlayer dielectric layer structure with two dielectric layers, USG layer 11 and PSG layer 12, is typically formed on the surface of substrate 10. After dry etching of the contact hole, when the remaining photoresist is removed using a wet photoresist stripping process, the wet photoresist stripping process usually uses SPM solution combined with SC1 solution (standard solution No. 1). Since the lateral etching rate of SC1 solution on PSG layer 12 is greater than that on USG layer 11, abrupt "T"-shaped step 15 is formed on the contact hole sidewall after cleaning, resulting in a contact hole structure that is wide at the top and narrow at the bottom. When metal is filled into the contact hole, the metal filler preferentially grows from the sidewall. Therefore, the presence of the "T"-shaped step 15 leads to premature closure of the top opening during metal filling, which can easily cause gap 17 defects due to insufficient filling and affect the performance of the power device.

[0030] Furthermore, although reducing the etching amount during wet resist removal can improve the degree of abrupt change in the "T" step, the bombardment of plasma during dry etching to form contact holes can cause severe polymer contamination within the contact holes. Therefore, when the etching amount during wet resist removal is reduced, it can lead to new problems such as difficulty in completely removing contamination defects and the formation of buried layer defects after metal filling, which in turn affects the product yield.

[0031] To address the aforementioned problems, this invention provides a method for forming a contact hole structure and a contact hole structure. The aim is to improve the abruptness of the "T"-shaped step and enhance the integrity of the metal filling by improving the process and structure, while ensuring that polymer contamination can be cleaned.

[0032] A method for forming a contact hole structure according to the present invention includes:

[0033] Provide substrate;

[0034] A first dielectric layer, a buffer dielectric layer, and a second dielectric layer are sequentially formed on the surface of the substrate;

[0035] A transition contact hole structure that enters the substrate from the bottom is formed on the surface of the second dielectric layer using photolithography and dry etching processes.

[0036] A wet photoresist stripping process is used to remove the remaining photoresist, forming the final contact hole structure, and the sidewalls of the final contact hole structure have progressively smaller openings at the second dielectric layer, the buffer dielectric layer, and the first dielectric layer.

[0037] A contact hole structure of the present invention is formed on a substrate, wherein a first dielectric layer, a buffer dielectric layer and a second dielectric layer are sequentially formed on the surface of the substrate, and the contact hole structure enters the substrate from the surface of the second dielectric layer through the buffer dielectric layer and the first dielectric layer in sequence; wherein the sidewall of the contact hole structure has an opening that gradually decreases at the second dielectric layer, the buffer dielectric layer and the first dielectric layer.

[0038] This invention adds a buffer dielectric layer between the existing double dielectric layers (first dielectric layer and second dielectric layer) used to form contact hole structures on a substrate. During the wet resist removal process after dry etching, the wet solution produces progressively decreasing etching amounts on the second dielectric layer, the buffer dielectric layer, and the first dielectric layer, corresponding to the formation of a final contact hole structure with progressively smaller openings. This transforms the contact hole morphology after wet resist removal from the previous "T" shape to a "Y" shape. By setting the buffer dielectric layer, the abrupt change in the step between the second and first dielectric layers at the sidewalls caused by the difference in etching rates is effectively mitigated. Therefore, during subsequent metal filling of the contact hole structure, the metal filling process window can be improved, thereby mitigating the gap problem after metal filling.

[0039] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] refer to Figure 4 A method for forming a contact hole structure according to the present invention includes the following steps:

[0041] Step S1: A first dielectric layer, a buffer dielectric layer, and a second dielectric layer are sequentially formed on the surface of the substrate.

[0042] like Figure 5As shown, taking the fabrication of contact holes on power devices as an example, a substrate 20 is used, such as a silicon substrate. Some or all of the front-end processes can be completed on the silicon substrate.

[0043] First, a dielectric deposition process is used to sequentially form a first dielectric layer 23, a buffer dielectric layer 21, and a second dielectric layer 22 on the surface of the substrate 20 to form an interlayer dielectric layer on the surface of the substrate 20.

[0044] In some embodiments, a first dielectric layer 23, a buffer dielectric layer 21, and a second dielectric layer 22 of the required thickness are sequentially formed on the upper surface of the substrate 20 using spin coating, physical vapor deposition, or chemical vapor deposition processes.

[0045] In some embodiments, the first dielectric layer 23 includes a USG layer (undoped glass layer) 231; the second dielectric layer 22 includes a PSG layer (phosphate glass layer) 221; and the buffer dielectric layer 21 includes a doped USG layer 211 (a film layer formed by doping on the basis of USG film).

[0046] In some embodiments, the buffer medium layer 21 includes a doped USG layer 211 doped with a certain concentration of group VA elements, that is, by doping a certain concentration of group VA elements on the basis of the USG film, a doped USG layer 211 as the buffer medium layer 21 is formed.

[0047] Group VA elements include nitrogen, phosphorus, arsenic, antimony, and bismuth.

[0048] In this embodiment, a chemical vapor deposition process is used to sequentially form a USG first dielectric layer 23 of the required thickness, a USG buffer dielectric layer 21 doped with 5% to 20% arsenic, and a PSG second dielectric layer 22 on the upper surface of the silicon substrate 20. Preferably, the arsenic doping concentration in the buffer dielectric layer 21 is about 10%.

[0049] Step S2: Using photolithography and dry etching processes, a transition contact hole structure is formed on the surface of the second dielectric layer 22, with the bottom extending into the substrate 20.

[0050] like Figure 6 As shown, a photoresist layer is formed on the surface of the second dielectric layer 22 of the PSG. Then, a photolithography process is used to form a contact hole photoresist pattern 24 on the surface of the second dielectric layer 22.

[0051] like Figure 7As shown, a dry etching process is then used, with the photoresist pattern 24 as a mask, to form a transition contact hole structure 25 that enters the substrate 20 at its bottom on the surface of the second dielectric layer 22. It can be seen that the transition contact hole structure 25 formed by dry etching has flat sidewalls, and no step morphology appears at the sidewalls of the first dielectric layer 23, the buffer dielectric layer 21, and the second dielectric layer 22.

[0052] When dry etching is used to form the transition contact hole structure 25, the bombardment of plasma will cause serious polymer contamination in the transition contact hole structure 25. This needs to be removed by the subsequent wet desmearing process to avoid the formation of buried layer defects after metal filling, which would affect the product yield.

[0053] Step S3: Use a wet photoresist removal process to remove the remaining photoresist, forming the final contact hole structure, and make the sidewalls of the final contact hole structure have progressively smaller openings at the second dielectric layer 22, the buffer dielectric layer 21 and the first dielectric layer 23.

[0054] like Figure 8 As shown, a wet photoresist removal process is then used to remove the remaining photoresist after dry etching to form the final contact hole structure 28, and also to remove polymer contamination caused by dry etching.

[0055] During the wet photoresist stripping process, while effectively removing residual photoresist and polymer contaminants, the wet etching solution produces progressively decreasing etching rates on the second dielectric layer 22, buffer dielectric layer 21, and first dielectric layer 23 located on the sidewalls of the transition contact hole structure 25. This results in the final contact hole structure 28 having a progressively smaller opening at the second dielectric layer 22, buffer dielectric layer 21, and first dielectric layer 23. Thus, by providing the buffer dielectric layer 21, the difference in etching rates produced by the wet etching solution on the second dielectric layer 22, buffer dielectric layer 21, and first dielectric layer 23 can be utilized to maintain the original step 27 (see reference) between the second dielectric layer 22 and the first dielectric layer 23. Figure 2 (The T-shaped step 15 in the middle is understood to be a new transition step 26 between the two, which can mitigate the abrupt change of the original step 27 between the second medium layer 22 and the first medium layer 23 at the side wall, thereby improving the metal filling process window and improving the gap problem after metal filling.)

[0056] In some embodiments, the wet etching solution includes SPM solution (a mixture of sulfuric acid and hydrogen peroxide) and SC1 solution (a mixture of ammonia and hydrogen peroxide) (i.e., SPM solution combined with SC1 solution). Furthermore, by selecting the material of the buffer dielectric layer 21, for example using a USG layer 211 doped with a Group VA element as the buffer dielectric layer 21, the etching rate of the wet etching solution on the buffer dielectric layer 21 is lower than the etching rate on the PSG second dielectric layer 22, but higher than the etching rate on the USG first dielectric layer 23.

[0057] Furthermore, by adjusting the doping concentration of the Group VA element to, for example, between 5% and 20%, the etching amount of the wet etching solution on the buffer dielectric layer 21 is between the etching amount on the second dielectric layer 22 and the etching amount on the first dielectric layer 23. For example, by adjusting the doping concentration of the Group VA element to around 10%, the etching amount of the wet etching solution on the buffer dielectric layer 21 is between the etching amount on the second dielectric layer 22 and the etching amount on the first dielectric layer 23.

[0058] Depend on Figure 8 As can be seen, due to the presence of the added buffer medium layer 21, the morphology of the final contact hole structure 28 after wet desmearing and cleaning changes from an approximately "T" shape (see reference) to the shape before the buffer medium layer 21 was formed. Figure 2 The original second medium layer 22 and the first medium layer 23 were transformed into an approximate "Y" shape when the buffer medium layer 21 was formed. That is, a transition step 26 was added to the step surface between the original second medium layer 22 and the first medium layer 23, so that the overall abrupt change of the step formed on the side wall of the final contact hole structure 28 was significantly buffered.

[0059] The principle underlying this invention is as follows:

[0060] In current methods for fabricating contact holes in power devices, an interlayer dielectric structure consisting of a USG layer and a PSG layer is typically formed on the substrate surface. After dry etching of the contact holes, a wet stripping process is used to remove the remaining photoresist. This process usually employs a combination of SPM solution and SC1 solution (standard solution #1). Since SC1 solution has a higher lateral etching rate on the PSG layer than on the USG layer, this results in abrupt "T"-shaped step sidewall morphology after cleaning, creating a contact hole structure that is wide at the top and narrow at the bottom. During metal filling of the contact holes, the metal filler preferentially grows from the sidewalls. The presence of the "T"-shaped step leads to premature closure of the top opening during metal filling, potentially causing gap defects due to insufficient filling and affecting the performance of the power device (see reference). Figures 1-3 ).

[0061] Therefore, in order to improve the above problems, the present invention adds a sandwich structure of a buffer medium layer 21 between the first medium layer 23 and the second medium layer 22. This is used to generate a progressively decreasing etching amount on the second medium layer 22, the buffer medium layer 21 and the first medium layer 23 by using wet descaling solution during subsequent wet descaling, thereby forming a final contact hole structure 28 with a progressively smaller opening, so that the morphology of the contact hole after wet descaling is changed from the previous "T" shape to a "Y" shape.

[0062] Specifically, a stepped structure is present between the second dielectric layer 22 and the buffer dielectric layer 21, and between the buffer dielectric layer 21 and the first dielectric layer 23, located on the sidewall of the final contact hole structure 28. This creates a three-layer stepped structure arranged sequentially from the surface of the second dielectric layer 22 downwards along the axis of the contact hole structure, consisting of the second dielectric layer 22, the buffer dielectric layer 21, and the first dielectric layer 23. Specifically, the distances a between the sidewall of the second dielectric layer 22 and the axis of the contact hole structure, b between the sidewall of the buffer dielectric layer 21 and the axis of the contact hole structure, and c between the sidewall of the first dielectric layer 23 and the axis of the contact hole structure decrease sequentially, with a > b > c.

[0063] It should be noted that, as Figure 2 In the existing contact hole structure shown, the buffer dielectric layer 21 of the present invention is not present between the PSG layer 12 (equivalent to the second dielectric layer 22) and the USG layer 11 (equivalent to the first dielectric layer 23). Therefore, according to the existing contact hole structure, the abruptness of the "T"-shaped step 15 generated between the PSG layer 12 and the USG layer 11 will be very obvious (i.e., the step surface is relatively wide). Figure 8 In the final contact hole structure 28 of the present invention shown, since a buffer dielectric layer 21 is added between the second dielectric layer 22 and the first dielectric layer 23 as a sandwich structure, the original step 27 between the second dielectric layer 22 and the first dielectric layer 23 (equivalent to Figure 2 A new transition step 26 is formed on the "T"-shaped step 15 generated between the PSG layer 12 and the USG layer 11, such that (ab) < (ac) and (bc) < (ac), thus mitigating the lateral abruptness of the step originally generated between the second medium layer 22 and the first medium layer 23.

[0064] By setting a buffer medium layer 21, the overall abrupt change of the step generated at the sidewall between the second medium layer 22 and the first medium layer 23 can be significantly mitigated. This improves the metal filling process window and optimizes the metal filling effect when the contact hole structure is filled with metal, thus improving the gap problem generated after metal filling.

[0065] This invention employs a USG layer 211 doped with a Group VA element as a buffer dielectric layer 21. Compared to an undoped USG film, the etching rate of the wet etching solution on the doped USG film is greater than that on the undoped USG film. This results in a higher etching rate of the wet etching solution on the buffer dielectric layer 21 than on the first dielectric layer 23. Simultaneously, the etching rate of the wet etching solution on the buffer dielectric layer 21 is lower than that on the second dielectric layer 22, thereby reducing the lateral width of the steps formed between the second dielectric layer 22 and the buffer dielectric layer 21, and between the buffer dielectric layer 21 and the first dielectric layer 23.

[0066] Furthermore, when the doping concentration of the buffer medium layer 21 is within a certain range, the etching rate of the wet etching solution will increase as the doping concentration increases.

[0067] Experiments revealed that when the doping concentration of the buffer dielectric layer 21 is approximately 5% to 20%, the etching rate of the wet etching solution on the buffer dielectric layer 21 is lower than that on the second dielectric layer 22, but higher than that on the first dielectric layer 23. This means that the etching amount of the wet etching solution on the buffer dielectric layer 21 is between the etching amounts on the second dielectric layer 22 and the first dielectric layer 23.

[0068] Further experimental verification showed that when the doping concentration of the buffer dielectric layer 21 was around 10%, the wet resist removal effect was optimal. This not only ensured that polymer contaminants generated by the preceding dry etching process were thoroughly cleaned, but also ensured that the etching amount of the wet etching on the buffer dielectric layer 21 was between that of the second dielectric layer 22 and the first dielectric layer 23. Therefore, by adjusting the doping concentration of the Group VA element, the etching amount of the wet etching solution on the buffer dielectric layer 21 could be positioned between that of the second dielectric layer 22 and the first dielectric layer 23, achieving the best buffering effect against abrupt changes in the original step 27.

[0069] Step S4: Fill the final contact hole structure 28 with contact hole metal.

[0070] like Figure 9 As shown, finally, a metal filling process is used to fill the final contact hole structure 28 with contact hole metal 29.

[0071] In some embodiments, a chemical vapor deposition process is used to fill the final contact hole structure 28 with contact hole metal 29. In this case, based on the improved step abruptness of the final contact hole structure 28, the process window for metal filling can be improved, thus mitigating gap problems that may arise in the final contact hole structure 28 after the contact hole metal 29 is filled.

[0072] After removing excess contact hole metal 29 from the surface of the second dielectric layer 22 through a planarization process, such as chemical mechanical polishing, a conductive contact hole structure is formed (see reference). Figure 10 ).

[0073] The following detailed description of a contact hole structure according to the present invention, in conjunction with specific embodiments and accompanying drawings, provides a further detailed explanation.

[0074] refer to Figure 10 A pre-filling contact hole structure 28 of the present invention is formed on a substrate 20. A first dielectric layer 23, a buffer dielectric layer 21, and a second dielectric layer 22 are sequentially formed on the surface of the substrate 20, thereby forming an interlayer dielectric layer on the surface of the substrate 20. The contact hole structure 28 is formed on the surface of the second dielectric layer 22, and extends downwards from the surface of the second dielectric layer 22, sequentially passing through the second dielectric layer 22, the buffer dielectric layer 21, and the first dielectric layer 23, before entering at the bottom and stopping in the substrate 20.

[0075] The sidewalls of the contact hole structure 28 have progressively smaller openings at the second dielectric layer 22, the buffer dielectric layer 21, and the first dielectric layer 23. In other words, there is a stepped structure between the second dielectric layer 22 and the buffer dielectric layer 21, and between the buffer dielectric layer 21 and the first dielectric layer 23, located on the sidewalls of the contact hole structure 28. This creates a three-layer stepped structure arranged sequentially from the surface of the second dielectric layer 22 downwards along the axis of the contact hole structure 28, consisting of the second dielectric layer 22, the buffer dielectric layer 21, and the first dielectric layer 23. Specifically, the distances a between the side of the second dielectric layer 22 and the axis of the contact hole structure 28, b between the side of the buffer dielectric layer 21 and the axis of the contact hole structure 28, and c between the side of the first dielectric layer 23 and the axis of the contact hole structure 28 decrease sequentially, with a > b > c (refer to...). Figure 8 ).

[0076] It should be noted that, as Figure 2 In the existing contact hole structure shown, the buffer dielectric layer 21 of the present invention is not present between the PSG layer 12 (equivalent to the second dielectric layer 22) and the USG layer 11 (equivalent to the first dielectric layer 23). Therefore, according to the existing contact hole structure, the abruptness of the step 15 generated between the PSG layer 12 and the USG layer 11 will be very obvious. Figure 10 In the contact hole structure 28 of the present invention shown, since a buffer dielectric layer 21 is added between the second dielectric layer 22 and the first dielectric layer 23 as a sandwich structure, the original step (equivalent to) between the second dielectric layer 22 and the first dielectric layer 23 is eliminated. Figure 2 A new transition step is formed on step 15, which is generated between PSG layer 12 and USG layer 11 (see reference). Figure 8The transition step 26 and the original step 27 are arranged such that (ab) < (ac) and (bc) < (ac), thus mitigating the lateral abruptness of the step originally generated between the second medium layer 22 and the first medium layer 23.

[0077] When the contact hole structure 28 is filled with contact hole metal 29 using a chemical vapor deposition process (refer to step S4 and...), Figure 9 By utilizing the contact hole sidewall structure of the present invention, the phenomenon of premature sealing closure of the metal filler that preferentially grows from the sidewall at the top opening of the contact hole can be effectively avoided, thereby avoiding gap defects caused by insufficient metal filling and improving the performance of the device.

[0078] In some embodiments, the contact hole structure 28 is filled with contact hole metal 29 to form a conductive contact hole structure 281. The conductive contact hole structure 281 can be formed by filling the contact hole structure 28 with contact hole metal 29 and removing excess contact hole metal 29 from the surface of the second dielectric layer 22.

[0079] In some embodiments, substrate 20 may be, for example, a silicon substrate. Some or all of the front-end processes may be performed on the silicon substrate.

[0080] In some embodiments, the first dielectric layer 23 includes a USG layer 231; the second dielectric layer 22 includes a PSG layer 221; and the buffer dielectric layer 21 includes a doped USG layer 211 (a film layer formed by doping on the basis of the USG film).

[0081] Furthermore, the buffer dielectric layer 21 includes a doped USG layer 211 doped with Group VA elements at a concentration of 5% to 20%. Group VA elements include nitrogen, phosphorus, arsenic, antimony, and bismuth. Preferably, the doping concentration of the buffer dielectric layer 21 is 10%.

[0082] In some embodiments, (ab) = (bc). That is, the step width between the second dielectric layer 22 and the buffer dielectric layer 21 is approximately equal to the step width between the buffer dielectric layer 21 and the first dielectric layer 23.

[0083] A contact hole structure 28 of the present invention can be formed using the contact hole structure forming method of the present invention described above. Wherein, Figure 10 The contact hole structure 28 shown corresponds to Figure 8 The final contact hole structure 28 in the process.

[0084] A power device of the present invention includes, for example, the above-described examples. Figure 10The contact hole structure 28. The contact hole structure 28 can prevent gaps from being formed when the contact hole metal 29 is filled into the contact hole structure 28 by chemical vapor deposition process, thereby improving the integrity of the metal filling when forming the conductive contact hole structure 281, and thus improving the performance of the power device.

[0085] In some embodiments, the power device includes a MOSFET or an IGBT; the MOSFET includes a trench gate MOSFET or an SGT MOSFET.

[0086] In summary, this invention adds a buffer dielectric layer 21 between the existing double dielectric layers (first dielectric layer 23 and second dielectric layer 22) on the substrate 20 for forming contact hole structures. During the wet resist removal process after dry etching, the wet solution produces progressively decreasing etching amounts on the second dielectric layer 22, the buffer dielectric layer 21, and the first dielectric layer 23, corresponding to the formation of a final contact hole structure 28 with progressively smaller openings. This transforms the contact hole morphology after wet resist removal from the previous "T" shape to a "Y" shape. By setting the buffer dielectric layer 21, the abrupt change in the step between the second dielectric layer 22 and the first dielectric layer 23 at the sidewall caused by the difference in etching rates is effectively mitigated. Therefore, when filling the contact hole structure 28 with the contact hole metal 29, the metal filling process window can be improved, thereby reducing the gap problem after metal filling.

[0087] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A method for forming a contact hole structure, characterized in that, include: Provide substrate; A first dielectric layer, a buffer dielectric layer, and a second dielectric layer are sequentially formed on the surface of the substrate; A transition contact hole structure with its bottom entering the substrate is formed on the surface of the second dielectric layer using photolithography and dry etching processes. A wet photoresist stripping process is used to remove the remaining photoresist, forming the final contact hole structure, and the sidewalls of the final contact hole structure have progressively smaller openings at the second dielectric layer, the buffer dielectric layer, and the first dielectric layer.

2. The method for forming a contact hole structure according to claim 1, characterized in that, When performing the wet stripping process, the wet solution is used to etch the second dielectric layer, the buffer dielectric layer, and the first dielectric layer on the sidewall of the transition contact hole structure with progressively decreasing etching amounts, thereby forming the final contact hole structure with progressively smaller openings. By setting the buffer dielectric layer, the abrupt change in the step between the second dielectric layer and the first dielectric layer at the sidewall caused by the difference in etching rates is mitigated.

3. The method for forming a contact hole structure according to claim 2, characterized in that, The first dielectric layer includes a USG layer, the second dielectric layer includes a PSG layer, and the wet etching solution includes SPM solution and SC1 solution. By selecting the material of the buffer dielectric layer, the etching rate of the wet etching solution on the buffer dielectric layer is made to be less than the etching rate on the second dielectric layer, but greater than the etching rate on the first dielectric layer.

4. The method for forming a contact hole structure according to claim 3, characterized in that, The buffer medium layer includes a USG-doped layer.

5. The method for forming a contact hole structure according to claim 4, characterized in that, The buffer medium layer includes a USG layer doped with a Group VA element, and by adjusting the doping concentration of the Group VA element, the etching amount of the wet process solution on the buffer medium layer is intermediate between the etching amount on the second medium layer and the etching amount on the first medium layer.

6. The method for forming a contact hole structure according to claim 1, characterized in that, Also includes: The final contact hole structure is filled with contact hole metal using a chemical vapor deposition process.

7. A contact hole structure, characterized in that, The contact hole structure is formed on a substrate, and a first dielectric layer, a buffer dielectric layer, and a second dielectric layer are sequentially formed on the surface of the substrate. The contact hole structure enters the substrate from the surface of the second dielectric layer through the buffer dielectric layer and the first dielectric layer in sequence. The sidewalls of the contact hole structure have progressively smaller openings at the second dielectric layer, the buffer dielectric layer, and the first dielectric layer.

8. The contact hole structure according to claim 7, characterized in that, The first dielectric layer includes a USG layer, the second dielectric layer includes a PSG layer, the buffer dielectric layer includes a USG layer doped with a Group VA element at a doping concentration of 5% to 20%, and the contact hole structure is filled with contact hole metal.

9. The contact hole structure according to claim 8, characterized in that, The doping concentration is 10%.

10. A power device comprising the contact hole structure according to any one of claims 7-9.

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