Preparation method for leveling metal material layer
By forming a metal material layer in the holes and/or trenches and pretreating it, combined with the dry etching process, the problem of CMP grinding dependence on pattern density is solved, and the flatness and device yield of the metal material layer are significantly improved.
Patent Information
- Application Number
- CN202311577282.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-23
- Publication Date
- 2025-05-23
AI Technical Summary
In the prior art, during the planarization of metal layers of fill holes and/or trenches, the grinding effect is strongly dependent on pattern density, resulting in poor surface flatness of the metal layer and affecting yield.
After the metal material layer is formed in the holes and/or trenches, pretreatment is performed to reduce surface unevenness, and then the metal material layer and substrate are removed to a preset thickness using a dry etching process to avoid the dependence of CMP grinding on pattern density.
The flatness of the metal material layer is significantly improved through the dry etching process, reducing process difficulty and complexity, improving device yield and reducing cost.
Smart Images
Figure CN120033079A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of integrated circuit semiconductor manufacturing, and in particular to a preparation method for planarizing a metal material layer. Background Art
[0002] Chemical Mechanical Polishing (CMP) is a chemical mechanical polishing technology that uses the mechanical grinding of abrasive particles and the chemical action of oxidants to remove chemical reactants on the surface of the polished part, obtain a smooth surface to achieve ultra-precision damage-free surface processing, and meet the circuit flatness requirements at 0.35μm. It is mainly used for ultra-precision surface processing. The polishing step is a process that combines chemical corrosion and mechanical friction. The workpiece to be processed is fixed on the grinding head facing down and fixed on the rotating machine. The surface of the rotating machine is covered with a polishing pad, and an abrasive slurry with small abrasive particles flows onto the table. The surface material of the workpiece to be processed is invaded by abrasive particles, polished, and then washed away by the abrasive slurry. Due to the rotational friction of the two tracks and the combined action of the abrasive slurry, the surface of the workpiece is polished.
[0003] CMP is usually used in the manufacture of semiconductor devices to flatten or polish the material layer deposited on the surface of the wafer. As the technology node extends from 0.13μm to 22nm, the process has increasingly stringent requirements for uniformity, flatness, and defect control. Especially in the planarization process of CMP for hole filling and / or trenches of some metal materials, CMP has very high requirements for pattern loading and is highly dependent on pattern density. Different pattern densities will produce different grinding effects, and it is very easy to produce a grinding effect with high and low drops on the surface, affecting the yield. Summary of the invention
[0004] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a preparation method for planarizing a metal material layer, which is used to solve the problem that in the prior art, during the CMP process for planarizing a metal layer that fills holes and / or grooves, the grinding effect of CMP is highly dependent on the density of the filled hole and / or groove pattern, resulting in poor surface flatness of the metal layer after grinding, affecting the yield.
[0005] In order to achieve the above-mentioned object and other related objects, the present invention provides a preparation method for planarizing a metal material layer, the preparation method comprising the following steps:
[0006] Providing a substrate having a plurality of holes and / or grooves formed therein;
[0007] forming a metal material layer on the substrate and in the holes and / or grooves, wherein the metal material layer at least fills the holes and / or grooves, and the surface of the metal material layer is uneven;
[0008] trimming the surface of the metal material layer to improve the flatness of the surface of the metal material layer;
[0009] Using a dry etching process to remove the metal material layer on the trimmed surface of the substrate;
[0010] The metal material layer and the substrate are removed to a preset thickness using a dry etching process.
[0011] Optionally, the material of the metal material layer is one of tungsten, cobalt, copper, aluminum, titanium, tantalum and their nitrides.
[0012] Optionally, a cushion oxide layer is formed on the surface of the substrate.
[0013] Optionally, before forming the metal material layer on the substrate and in the holes and / or grooves, the method further includes forming an adhesion layer on the substrate and in the holes and / or grooves.
[0014] Furthermore, the adhesion layer includes a titanium nitride layer or a tantalum nitride layer.
[0015] Optionally, a CMP process or an atomic layer etching process is used to trim the surface of the metal material layer.
[0016] Furthermore, the surface of the metal material layer is trimmed by controlling the trimming time.
[0017] Furthermore, the free radicals used in the atomic layer etching process include F or Cl.
[0018] Optionally, the substrate is a semiconductor substrate or a dielectric substrate.
[0019] Optionally, in the step of removing the metal material layer and the substrate to a preset thickness by using a dry etching process, an etching selectivity ratio of etching the metal material layer to the substrate is 1.1:1 to 1:1.1.
[0020] As described above, the preparation method for planarizing the metal material layer of the present invention is to pre-treat the metal material layer after forming the metal material layer in the hole and / or groove, so as to perform the first step of processing the unevenness of its surface, reduce the sharpness of its high and low unevenness, and improve the flatness of the surface of the metal material layer, and then use the dry etching process to etch the trimmed metal material layer. Since dry etching is insensitive to the pattern load, and the surface of the metal material layer has been pre-treated to improve its surface flatness, the surface flatness of the metal material layer is greatly improved after dry etching. Finally, the metal material layer and the substrate of the preset thickness are etched back by dry etching, which can further improve the flushness and flatness of the metal material layer and the substrate surface. The preparation method avoids the dependence of CMP grinding on the density of the hole filling and / or groove pattern, and the dry etching process parameters are easier to control than CMP grinding, so while improving the flushness and flatness of the metal material layer and the substrate surface, the process difficulty and complexity are effectively reduced, the device yield is improved, and the cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figures 1 to 4 The cross-sectional structure schematic diagram of an example of the prior art is a process of filling a groove in a substrate with metal tungsten and then performing CMP polishing.
[0022] Figures 5 to 9 It is a schematic diagram of the cross-sectional structure after each step in the preparation method for planarizing the metal material layer of the present invention is completed.
[0023] Description of Reference Numerals
[0024] 10 Base
[0025] 11 Silicon dioxide layer
[0026] 12 Silicon Nitride Layer
[0027] 13 Tungsten metal layer
[0028] 14 Depression
[0029] 15 Groove
[0030] 20 Base
[0031] 21 holes and / or grooves
[0032] 22 Metal material layer
[0033] 23 Bump
[0034] 24 Depression DETAILED DESCRIPTION
[0035] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.
[0036] See also Figures 1 to 9 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.
[0037] like Figures 1 to 4 FIG. 1 is a schematic diagram of a cross-sectional structure of an example process in which a groove in a substrate is filled with metal tungsten and then subjected to CMP polishing.
[0038] like Figure 1 As shown, firstly, a silicon dioxide layer 11 and a silicon nitride layer 12 as an etching stop layer are formed on a silicon material substrate 10;
[0039] like Figure 1 As shown, the silicon nitride layer 12, the silicon dioxide layer 11 and the substrate 10 are then etched in sequence to form a groove 15 of a desired layout;
[0040] like Figure 2 As shown, a tungsten metal layer 13 is then deposited on the surface of the structure so that the tungsten metal layer 13 fills the groove 15. Based on the limitations of the existing deposition process, the surface of the substrate with holes is filled, and the surface of the formed metal layer is uneven. The surface of the tungsten metal layer 13 in the area where the groove 15 is located is concave, and the surface of the tungsten metal layer 13 in the area where the substrate 10 is located is convex;
[0041] like Figure 3 and Figure 4 As shown, the tungsten metal layer 13 is finally ground by a CMP process, so as to obtain a tungsten metal layer 13 that is flush with the surface of the substrate 10 and has a smooth surface.
[0042] However, in practice, the surface morphology of the tungsten metal layer 13 obtained after the CMP process is uneven. Figure 3 and Figure 4As shown, the surface of the tungsten metal layer 13 has a height difference and a depression 14. This is mainly because CMP is very sensitive to the pattern load. The surface morphology of the tungsten metal layer formed after the holes and / or grooves with different layout densities are filled is different. During the CMP grinding process, the uneven surface will cause the grinding liquid to gather in different states. The grinding is faster where the grinding liquid gathers more, and the grinding is slower where the grinding liquid gathers less. Therefore, the CMP grinding parameters need to be adjusted for tungsten metal layers with different surface morphologies. CMP grinding requires adjusting complex parameters such as grinding liquid, grinding pad, and grinding pressure, which greatly increases the difficulty of the process. It often happens that Figure 3 and Figure 4 The uneven grinding surface shown has a serious impact on the improvement of yield.
[0043] Based on this, this embodiment provides a preparation method for planarizing a metal material layer, and the preparation method comprises the following steps:
[0044] S1. Providing a substrate, wherein a plurality of holes and / or grooves are formed in the substrate:
[0045] S2, forming a metal material layer on the substrate and in the hole, wherein the metal material layer at least fills the hole and / or the groove, and the surface of the metal material layer is uneven;
[0046] S3, trimming the surface of the metal material layer to improve the flatness of the surface of the metal material layer;
[0047] S4, removing the metal material layer on the trimmed surface of the substrate by a dry etching process;
[0048] S5. Use a dry etching process to remove the metal material layer and the substrate to a preset thickness.
[0049] In the preparation method for planarizing the metal material layer of the present embodiment, after forming the metal material layer in the hole and / or the groove, the metal material layer is first pre-treated to perform the first step of processing on the unevenness of its surface, so as to reduce the sharpness of its high and low unevenness and improve the flatness of the surface of the metal material layer, and then the trimmed metal material layer is etched by a dry etching process. Since dry etching is insensitive to the pattern load, and the surface of the metal material layer has been pre-treated to improve its surface flatness, the surface flatness of the metal material layer is greatly improved after dry etching. Finally, the metal material layer and the substrate of a preset thickness are etched back by dry etching, so that the flushness and flatness of the metal material layer and the substrate surface can be further improved. The preparation method avoids the dependence of CMP grinding on the density of the hole filling and / or groove pattern, and the dry etching process parameters are easier to control than CMP grinding, so while improving the flushness and flatness of the metal material layer and the substrate surface, the process difficulty and complexity are effectively reduced, the device yield is improved, and the cost is reduced.
[0050] The preparation method for planarizing the metal material layer of this embodiment is described in detail below with reference to specific drawings.
[0051] like Figure 5 As shown, step S1 is first performed to provide a substrate 20 in which a plurality of holes and / or grooves 21 are formed.
[0052] The material of the substrate 20 is set according to the structure to be prepared, and can be a semiconductor material, a dielectric material, etc. For example, when the structure to be prepared is a trench metal gate, the material of the substrate 20 is generally selected as a semiconductor material, such as a common silicon material, and the hole formed at this time is a blind hole. Of course, other material layers (such as a gate dielectric layer) may also be formed on the sidewalls and bottom of the blind hole, which is not the focus of improvement of this embodiment and will not be described in detail here; for another example, when the structure to be prepared is a conductive contact hole or a conductive contact groove, the material of the substrate 20 is generally selected as a dielectric material, such as a common silicon dioxide material, and the hole formed at this time is a through hole or a through groove, and of course, the bottom of the substrate 20 is connected to a front-end device layer.
[0053] In addition, it should be noted that the distribution of the several holes and / or grooves 21 formed in the substrate 20 on the substrate 20 can be uniform or uneven; there can be only several holes, only several grooves, or both holes and grooves; the caliber and depth of the several holes and / or grooves 21 can be the same or different. The specific selection is based on actual needs. The several holes and / or grooves 21 can be divided into real holes and / or grooves and virtual holes and / or grooves from the perspective of device function. The real holes and / or grooves are subsequently filled with metal and serve as the functional structure of the device, while the virtual holes and / or grooves are not used as the functional structure of the device after being filled with metal, which may provide quality assurance during the device preparation process.
[0054] As a preferred example, a cushion oxide layer may also be formed on the surface of the substrate 20 to protect the substrate 20 in subsequent process steps. The layer may be formed by a thermal oxidation process, low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD) or atomic layer chemical vapor deposition (ALCVD) or other processes.
[0055] As an example, the method for forming the holes and / or grooves 21 includes: coating a photoresist layer on the substrate 20, and when a pad oxide layer is formed on the substrate 20, coating the photoresist layer on the pad oxide layer; patterning the photoresist layer to form a patterned photoresist layer, the patterned photoresist layer having a window that can define the position of the holes and / or grooves; etching the substrate 20 based on the patterned photoresist layer to form the holes and / or grooves 21. It should be noted here that the number, formation position, depth and other parameters of the holes and / or grooves 21 are selected according to the specific device needs, and no excessive restrictions are made here.
[0056] like Figure 6 As shown, step S2 is then performed to form a metal material layer 22 on the substrate 20 and in the holes and / or grooves 21, wherein the metal material layer 22 at least fills the holes and / or grooves 21, and the surface of the metal material layer 22 is uneven, having protrusions 23 and corresponding depressions 24. The uneven surface of the metal material layer 22 is an objective phenomenon existing in the existing deposition process.
[0057] The metal material layer 22 may be deposited by conventional deposition processes, such as CVD processes. Metal CVD has excellent step coverage and can fill contact holes with high aspect ratios without gaps.
[0058] The material of the metal material layer 22 is selected according to actual needs. For example, when a metal gate needs to be prepared, the material of the metal material layer 22 can be tungsten, titanium, cobalt, copper, aluminum, tantalum and their nitrides; when a conductive contact hole needs to be prepared, the material of the metal material layer 22 can be tungsten, copper, aluminum and other metal good conductors.
[0059] As an example, before forming the metal material layer 22, a step of forming an adhesion layer in the substrate 20 and the holes and / or grooves 21 is also included. For example, the adhesion layer may be a single layer of a titanium nitride adhesion layer or a tantalum nitride adhesion layer, or a stack of titanium / titanium nitride or a stack of tantalum / tantalum nitride. The role of the adhesion layer is to improve the adhesion between the metal material layer 22 and the surface material layer of the substrate 20 to prevent the metal material layer 22 from falling off. The specific material is selected according to the selection of the metal material layer 22 and the surface material layer of the substrate 20. For example, when the material of the metal material layer 22 is tungsten and the surface material layer of the substrate 20 is oxide, the adhesion layer is selected as a stack of titanium / titanium nitride.
[0060] like Figure 7 As shown, step S3 is then performed to trim the surface of the metal material layer 22 to improve the flatness of the surface of the metal material layer 22 .
[0061] It should be noted that the purpose of this step is to trim the surface of the metal material layer 22 so that the surface is flatter than before the trimming, but it does not necessarily have to be absolutely flat. Figure 7 The surface morphology of the metal material layer 22 is only an ideal state. In practice, there will still be some unevenness on the surface of the metal material layer 22. This trimming step lays the foundation for the subsequent dry etching step, so that the subsequent dry etching process has a relatively flat etching surface, reduces the impact of the surface unevenness on the dry etching endpoint, and improves the etching accuracy.
[0062] As an example, a CMP process or an atomic layer etching process (ALE) may be used to trim the surface of the metal material layer 22. For example, the surface of the metal material layer 22 may be trimmed by controlling the trimming time according to the material of the metal material layer 22 and the parameters selected by the CMP process or the atomic layer etching process.
[0063] As a preferred example, an atomic layer etching process is selected to trim the surface of the metal material layer 22. The atomic layer etching process is a technology for removing atomic layers of materials by a self-limiting reaction. It has high etching accuracy and low etching damage. Its working principle is mainly to first adsorb reactive gas molecules (free radicals) on the surface of the substrate, and then use light, electron beam or ion beam to excite the gas molecules so that the gas molecules react with the atoms on the surface of the substrate, thereby removing an atomic layer on the surface of the substrate, and repeating the adsorption-excitation-reaction cycle to achieve etching of an atomic layer of the desired thickness. In this embodiment, an atomic layer etching process is selected to trim the surface of the metal material layer 22. Since the surface of the metal material layer 22 is uneven, the reactive free radicals that lead to the surface of the metal material layer 22 will be adsorbed according to the surface morphology of the metal material layer 22, such as Figure 6 As shown, at the protrusion 23, the reactive free radicals are adsorbed not only on the top surface of the protrusion 23 but also on the side surface of the protrusion 23, that is, the entire surface of the protrusion 23 fully adsorbs the reactive free radicals, which will effectively increase the etching reaction area. The etching rate at the protrusion 23 is faster than that at the recess 24, so the unevenness of the surface of the metal material layer 22 is better, and a metal material layer 22 with higher flatness can be obtained.
[0064] As an example, the free radicals used in the atomic layer etching process are generally F or Cl, which can react with the metal material to form gaseous or liquid etching byproducts that are easy to remove.
[0065] like Figure 8 As shown, step S4 is then performed to remove the metal material layer 22 on the surface of the trimmed substrate 20 using a dry etching process.
[0066] The dry etching process is insensitive to the pattern load, and its parameter adjustment is easy to control. After trimming the metal material layer 22, a metal material layer 22 with a relatively flat surface can be obtained. At this time, the dry etching process can easily remove the metal material layer 22 on the surface of the substrate 20 and the removal effect is better.
[0067] The parameters of the dry etching process and the etching ions used are selected according to the material of the metal material layer 22 and are not excessively limited here.
[0068] like Fig. 9 As shown, step S5 is finally performed to remove the metal material layer 22 and the substrate 20 to a preset thickness using a dry etching process to further improve the levelness and flatness of the metal material layer 22 and the surface of the substrate 20 .
[0069] Here, it is preferably selected that the etching selectivity ratio of the dry etching for the metal material layer 22 and the substrate 20 is 1.1:1 to 1:1.1, for example, it can be 1.1:1, 1:1, 1:1.1; optimally, the etching selectivity ratio of the selective etching for the metal material layer 22 and the substrate 20 is 1:1 to achieve synchronous etching of the two.
[0070] In summary, the present invention provides a preparation method for planarizing a metal material layer. After forming a metal material layer in a hole and / or a groove, the metal material layer is first pretreated to perform a first step of processing on the unevenness of its surface, thereby reducing the sharpness of its high and low unevenness and improving the flatness of the surface of the metal material layer. Then, the trimmed metal material layer is etched using a dry etching process. Since dry etching is insensitive to the pattern load, and the surface of the metal material layer has been pretreated to improve its surface flatness, the surface flatness of the metal material layer is greatly improved after dry etching. Finally, the metal material layer and the substrate of a preset thickness are etched back by dry etching, so that the flushness and flatness of the metal material layer and the substrate surface can be further improved. The preparation method avoids the dependence of CMP grinding on the density of the hole filling and / or groove patterns, and the dry etching process parameters are easier to control than CMP grinding. Therefore, while improving the flushness and flatness of the metal material layer and the substrate surface, the process difficulty and complexity are effectively reduced, the device yield is improved, and the cost is reduced. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.
[0071] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A method for preparing a flat metal material layer, It is characterized in that The preparation method comprises the following steps: Providing a substrate having a plurality of holes and / or grooves formed therein; forming a metal material layer on the substrate and in the holes and / or grooves, wherein the metal material layer at least fills the holes and / or grooves, and the surface of the metal material layer is uneven; trimming the surface of the metal material layer to improve the flatness of the surface of the metal material layer; Using a dry etching process to remove the metal material layer on the trimmed surface of the substrate; The metal material layer and the substrate are removed to a preset thickness using a dry etching process.
2. The method for preparing a flat metal material layer according to claim 1, Features: The material of the metal material layer is one of tungsten, cobalt, copper, aluminum, titanium, tantalum and nitrides thereof.
3. The method for preparing a flat metal material layer according to claim 1, Features: A cushion oxide layer is formed on the surface of the substrate.
4. The method for preparing a flat metal material layer according to claim 1, Features: Before forming the metal material layer on the substrate and in the holes and / or grooves, the method further includes forming an adhesion layer on the substrate and in the holes and / or grooves.
5. The method for preparing a flat metal material layer according to claim 4, Features: The adhesion layer includes a titanium nitride layer or a tantalum nitride layer.
6. The method for preparing a flat metal material layer according to claim 1, Features: The surface of the metal material layer is trimmed by using a CMP process or an atomic layer etching process.
7. The method for preparing a flat metal material layer according to claim 6, Features: The surface of the metal material layer is trimmed by controlling the trimming time.
8. The method for preparing a flat metal material layer according to claim 6, Features: The free radicals used in the atomic layer etching process include F or Cl.
9. The method for preparing a flat metal material layer according to claim 1, Features: The substrate is a semiconductor substrate or a dielectric substrate.
10. The method for preparing a flat metal material layer according to claim 1, Features: In the step of removing the metal material layer and the substrate to a preset thickness by using a dry etching process, an etching selectivity ratio of etching the metal material layer to the substrate is 1.1:1 to 1:1.1.