Semiconductor device preparation method
By forming a staggered triangular cone structure on the surface of the single crystal silicon wafer, the problems of complex process and high cost caused by anti-reflective coatings in the prior art are solved, and the effect of effectively eliminating standing wave effect and improving lithography accuracy is achieved. .
Patent Information
- Application Number
- CN202311005011.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-09
- Publication Date
- 2025-02-18
AI Technical Summary
In the prior art, spin-coated organic anti-reflection coating or CVD deposited inorganic anti-reflection layer is used to reduce the standing wave effect caused by the diffraction effect formed by the substrate reflected light and the incident light of the photolithography machine, resulting in complex process. and manufacturing costs increase.
By placing a single crystal silicon wafer with a crystalline direction in an acid liquid and an alkali liquid for soaking, a staggered triangular cone structure is formed, which acts as a natural anti-reflection layer to reduce the standing wave effect.
Effectively eliminate standing wave effect, improve lithography accuracy, reduce device preparation costs, and simplify process flow.
Smart Images
Figure CN119480621A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of integrated circuit manufacturing, and in particular to a method for preparing a semiconductor device. Background Art
[0002] With the rapid development of semiconductor technology, the integration of devices is increasing day by day and the characteristic size of devices is shrinking day by day, so that the fabrication process of the interposer layer (Interposer layer) of the back-end encapsulation is increasingly transitioning to the front-end process, and the photoresist opening size is getting smaller and smaller in photolithography, and the wavelength of the photolithography machine is getting shorter and shorter. A certain degree of standing wave effect occurs in the exposure process of photoresist (also called photoresist, in this specification, photoresist and photoresist can be used interchangeably), causing the photolithography precision to decrease, thus causing the production yield to decrease. Specifically, the cause of the standing wave effect is that when the photoresist is exposed, light is irradiated on the substrate through the photoresist, and at the interface of the photoresist and the substrate, light can be reflected, and these reflected lights and incident lights can form interference, so that the distribution of light intensity along the glue depth direction is uneven, and constructive and destructive stripes occur in the exposure area in the photoresist thus. After the photoresist is developed, the sidewall will produce wavy unevenness and form the standing wave effect.
[0003] To solve the standing wave effect, the current mainstream method in the industry is to spin-coat a layer of anti-reflective coating before spin-coating photoresist in the lithography process, or to use CVD technology to deposit a layer of SiN as an anti-reflective coating, so as to reduce the standing wave effect caused by the diffraction effect formed by the reflected light from the substrate and the incident light from the lithography machine.
[0004] However, this approach has many shortcomings, such as:
[0005] 1) Since the raw material cost of the spin-coated anti-reflection layer is extremely high, the cost of the entire process is increased to a certain extent;
[0006] 2) Since the anti-reflective layer is different from the photoresist and will not dissolve in the developer like the photoresist, in the subsequent etching process, an additional step of etching the anti-reflective coating will be added, increasing the instability of the process;
[0007] 3) Compared with the anti-reflection layer formed by spin coating, the inorganic anti-reflection layer deposited by CVD process also increases the process steps of subsequent CMP process and thin film process, and also increases the steps of subsequent etching process.
[0008] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention
[0009] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a method for preparing a semiconductor device, which is used to solve the problems of complicated process and increased manufacturing cost caused by the method of preparing an organic anti-reflection coating in the form of spin coating or an inorganic anti-reflection layer deposited by CVD in the prior art to reduce the standing wave effect caused by the diffraction effect formed by the substrate reflected light and the incident light of the lithography machine.
[0010] To achieve the above object and other related objects, the present invention provides a method for preparing a semiconductor device, comprising the steps of:
[0011] S1: Prepare <111> Single crystal silicon wafer with different crystal orientations;
[0012] S2: Soak the single crystal silicon wafer in an acid solution with a mass fraction of 25% to 50% for 15s to 60s, and then clean it;
[0013] S3: soaking the cleaned single crystal silicon wafer in an alkali solution with a mass fraction of 40% to 50% for 60 seconds to 150 seconds, thereby forming a staggered triangular pyramid structure on the surface of the single crystal silicon wafer, and then cleaning;
[0014] S4: forming a photoresist layer on the surface of the single crystal silicon wafer having the triangular pyramid structure;
[0015] S5: exposing and developing the photoresist layer to form a plurality of openings in the photoresist layer to expose the single crystal silicon wafer;
[0016] S6: etching the single crystal silicon wafer according to the opening to form a plurality of grooves in the single crystal silicon wafer, and then removing the remaining photoresist layer;
[0017] S7: depositing a thin film in the trench.
[0018] Optionally, the acid solution includes hydrofluoric acid and / or hydrochloric acid.
[0019] Optionally, the alkali solution includes several of NH4OH, KOH and NaOH.
[0020] Optionally, the step S2 is performed by soaking in an acid solution for 30 seconds, and the step S3 is performed by soaking in an alkaline solution for 120 seconds.
[0021] Optionally, step S5 includes post-baking the photoresist layer at a temperature of 70° C.-90° C. after exposing it, and then developing it.
[0022] Optionally, the post-bake process further includes a step of introducing alkaline gas to neutralize excess photoacid generated on the top of the photoresist layer after exposure.
[0023] Optionally, step S7 includes the steps of first forming a seed layer on the inner surface of the groove and then forming a main layer.
[0024] More optionally, the material filled in the trench includes silicon or copper.
[0025] Optionally, the photoresist layer has more than two layers, and the absorption coefficient of the bottom photoresist layer is greater than the absorption coefficient of the upper photoresist layer.
[0026] Optionally, the cleaning in steps S2 and S3 is performed by using deionized water for 60 seconds.
[0027] As described above, the semiconductor device preparation method of the present invention has the following beneficial effects: the semiconductor device preparation method provided by the present invention can effectively eliminate the standing wave effect and improve the lithography accuracy through improved process and flow design, which helps to improve the device preparation yield and reduce the production cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 The flowchart of the semiconductor device manufacturing method provided by the present invention is shown.
[0029] Figure 2 The SEM image shows the surface morphology of a conventional single crystal silicon wafer.
[0030] Figure 3 The SEM image shows the surface morphology of the single crystal silicon wafer after being processed in the present invention.
[0031] Figure 4 The SEM image shows the sidewall morphology of the photoresist layer in the present invention after development.
[0032] Figure 5 The SEM image shows the sidewall morphology of the photoresist layer after development in the prior art. DETAILED DESCRIPTION
[0033] 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. For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general proportion, and the schematic diagram is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.
[0034] For ease of description, spatially relative terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
[0035] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.
[0036] It should be noted that the diagrams provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the diagrams only show the components related to the present invention rather than the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed arbitrarily, and the layout of the components may also be more complicated. In order to make the diagrams as concise as possible, not all structures are marked in the drawings.
[0037] like Figure 1 As shown, the present invention provides a method for preparing a semiconductor device, the method comprising the steps of:
[0038] First, execute step S1, prepare <111> Single crystal silicon wafer with different crystal orientations.
[0039] The single crystal silicon wafer can be formed by conventional crystal pulling and cutting process or by epitaxial process. When it is formed by conventional crystal pulling and cutting process, its surface may have defects such as fine cracks, so it can be ground if necessary. If it is formed by epitaxial process, this step is to perform epitaxial process such as vapor phase epitaxy on the substrate to form a single crystal silicon wafer with <111> The substrate may be pre-formed with other structures, such as transistors. Of course, the single crystal silicon wafer may also be a bare silicon wafer, and this embodiment may be used to prepare a silicon adapter board.
[0040] After the single crystal silicon wafer is prepared, step S2 is performed to immerse the single crystal silicon wafer in an acid solution with a mass fraction of 25%-50% for 15s-60s, and then clean it.
[0041] After soaking in acid, the natural oxide film and impurities such as metal particles on the surface of the single crystal silicon wafer are completely removed. After this preliminary treatment, the roughness of the surface of the single crystal silicon wafer will increase. The acid used in this embodiment can be hydrofluoric acid and / or hydrochloric acid commonly used in semiconductor factories. That is, the acid can be a single component acid or a mixture of several acids, as long as the mass percentage concentration of the acid is within the range of 25%-50%. Preferably, at least hydrofluoric acid is included. In a more preferred example, the mass fraction of the acid is 30%-40%, and the soaking time is 30s. After soaking in the acid for a preset time, the silicon wafer is rinsed with deionized water to remove the acid and other impurity particles remaining on the surface of the silicon wafer. The rinsing time is preferably greater than 30s, and more preferably 60s.
[0042] After ensuring that all impurities on the surface of the silicon wafer are removed, execute step S3, soak the cleaned single crystal silicon wafer in an alkali solution with a mass fraction of 40%-50% for 60s-150s, thereby forming a staggered triangular pyramid structure on the surface of the single crystal silicon wafer, and then clean it. This step is a very critical step in this embodiment. The concentration of the alkali solution and the soaking time have a very large influence on the morphology of the final triangular pyramid structure, and the morphology of the triangular pyramid structure determines its ability to absorb light. It will not work if the concentration of the alkali solution is too high or too low, or the soaking time is too short or too long. The parameters of this step must be strictly followed. In a better example, the alkali solution includes several of NH4OH, KOH and NaOH. For example, if it is soaked in an alkali solution of KOH+isopropanol or NaOH+isopropanol for 120s, a structure such as Figure 3 The thin layer shown (the maximum height of the triangular pyramid does not exceed 2μm) is a triangular pyramid structure with staggered heights. If the immersion time is too long and the corrosion effect is too strong, the surface of the single crystal silicon wafer will form triangular pyramids that are too dense and too high, which will not only easily lead to uneven thickness of the subsequent photoresist layer, but also reduce the light absorption capacity, and the improvement of the standing wave effect is not obvious.
[0043] After soaking in the alkali solution for a preset time, the single crystal silicon wafer is rinsed with deionized water for more than 30 seconds, for example, 60 seconds, to ensure that there is no alkali solution residue.
[0044] Next, step S4 is performed to form a photoresist layer on the surface of the single crystal silicon wafer having the triangular pyramid structure.
[0045] As an example, the method of forming the photoresist layer is preferably to adopt spin coating but is not limited thereto, and the thickness of the spin coating should not be too large or too small. The photoresist can be a positive photoresist or a negative photoresist. In one example, the thickness of the photoresist layer is 3μm-5μm. The photoresist layer can be continuously coated with only one material. In another example, the photoresist layer is more than 2 layers, and the absorption coefficient of the bottom photoresist layer is greater than the absorption coefficient of the upper photoresist layer. For example, an organic dye with a good absorption coefficient can be added to the bottom photoresist layer, and the dye can be dissolved in the solvent in the photoresist layer, and no additional removal process is required later. Adding a dye with a good absorption coefficient to the bottom photoresist layer can reduce the reflection intensity, and also help to improve the standing wave effect, and ensure the exposure accuracy of the bottom of the pattern, while the dye does not need to be added to the upper photoresist layer. In some other examples, different exposure energies can be used for exposure of photoresist layers of different materials. For example, if a pattern with a high aspect ratio is to be prepared, the photoresist layer may be divided into two layers, and the exposure energy of the upper photoresist layer is greater than the exposure energy of the lower photoresist layer.
[0046] Next, step S5 is performed to expose and develop the photoresist layer to form a plurality of openings in the photoresist layer to expose the single crystal silicon wafer.
[0047] In a preferred example, step S5 includes, after the photoresist layer is exposed, using a hot plate to post-bake the single crystal silicon wafer formed with the photoresist layer, and then developing it. The post-bake temperature is preferably 70°C-90°C, and the post-bake time is 30s-60s. In a further example, the post-bake process also includes the introduction of alkaline gas to neutralize the excessive photoacid generated at the top of the photoresist layer after exposure, so as to improve the top morphology of the photoresist layer and avoid the formation of a T-shaped top, so as to improve the photolithography morphology and improve the photolithography accuracy. The alkaline gas is, for example, ammonia, and the ammonia flow rate is, for example, less than or equal to 2sccm. Ammonia can be transported to the post-bake oven together with an inert gas such as nitrogen. During the exposure process, part of the reflected light is absorbed by the triangular pyramid structure previously formed on the surface of the single crystal silicon wafer, and the remaining reflected light becomes messy and has no fixed angle due to the presence of the triangular pyramid, so it cannot interfere with the incident light, thereby avoiding the formation of standing waves.
[0048] Next, step S6 is performed to etch the single crystal silicon wafer according to the opening to form a plurality of grooves in the single crystal silicon wafer. The method for etching the single crystal silicon wafer can adopt an existing etching process, such as dry etching using fluorine-containing gases such as CF4, or wet etching, without specific limitation. After the etching is completed, the residual photoresist is removed. After this step, the pattern in the photoresist layer is transferred to the single crystal silicon wafer.
[0049] Next, step S7 is performed to deposit a thin film in the trench.
[0050] The method of depositing the thin film and the material of the thin film are determined according to the needs. For example, if a transfer plate is prepared, a conductive material layer needs to be filled in the groove in this step, such as filling a conductive polysilicon material or filling a metal copper. In a preferred example, this step includes the steps of forming a seed layer on the inner surface of the groove first, and then forming a main layer, for example, first using a chemical vapor deposition process to form a copper seed layer on the inner surface of the groove, and then using a physical vapor deposition copper process or an electroplating copper process to completely fill the rest of the groove. In another example, an adhesion layer such as titanium and / or titanium nitride can also be formed on the inner surface of the groove first, and then a main conductive material layer is formed. In some other examples, for example, in some power device preparation processes, it is necessary to form several isolation grooves in a silicon substrate. In this step, a silicon oxide layer can be formed on the inner surface of the groove by a thermal oxidation process, and then a chemical vapor deposition process is used to fill the groove with an insulating material. The type of semiconductor device prepared in this embodiment is not strictly limited, or the present invention is suitable for preparing various types of semiconductor devices. In particular, the denser the device integration, the higher the requirements for lithography accuracy, and the more suitable the present invention is.
[0051] After the trench is filled, other film layers and / or structures may be prepared according to the device preparation requirements, which will not be elaborated one by one.
[0052] The present invention makes full use of <111> The unique properties of single-crystal silicon wafers with different crystal orientations. Silicon has a cubic crystal structure and its surface morphology is Figure 2 As shown. The atomic density of single crystal silicon on the wafer is <111> , <110> , <100> Three types, whose density is determined by <111> arrive <100> Decrease successively, so the etching rate in the same etching solution is <100> arrive <111> In this embodiment, the surface of the single crystal silicon wafer is first cleaned with an acid solution of a specific concentration to remove the natural oxide film, metal particles and other organic or inorganic pollutants on the surface of the single crystal silicon wafer, and then the surface of the single crystal silicon wafer is wet-etched with an alkali solution of a specific concentration. Since the etching rates of each crystal face of the single crystal silicon wafer are different, the following will eventually be formed: <111> There is a triangular structure under the microscopic level of the surface, as shown in the following figure: Figure 3 For example, if the alkali solution used is NaOH, the chemical reaction equation is:
[0053] Si+2NaOH+H2O→Na2SiO3+2H2↑
[0054] The present invention forms a layer of triangular pyramid structures on the surface of the single crystal silicon wafer that can greatly absorb incident light through corrosion with acidic and alkaline solutions of specific concentrations. These triangular pyramid structures can act as anti-reflection layers. Therefore, in this embodiment, there is no need to prepare an additional anti-reflection layer. In other words, in this embodiment, there is no need to form an anti-reflection layer of other materials on the surface of the substrate before applying the photoresist. Accordingly, there is no need to add a separate process for removing the anti-reflection layer in the subsequent process. Since this layer of triangular pyramid structures with staggered arrangements that can absorb incident light is formed on the surface of the single crystal silicon wafer, the side wall morphology of the subsequent photoresist layer formed on its surface after exposure and development is as follows: Figure 4 As shown in FIG. 1 , it can be seen that the boundary between the exposure area and the non-exposure area of the photoresist layer is very clear, the side wall is close to vertical, and the standing wave phenomenon basically disappears. However, the side wall of the single crystal silicon wafer without the triangular pyramid structure of the present invention is as shown in FIG. 1 after exposure and development. Figure 5 As shown, it can be seen that the boundary between the exposure area and the non-exposure area is not obvious, and due to the presence of reflected light, wavy stripes are formed on the side wall of the photoresist layer.
[0055] The semiconductor device preparation method provided by the present invention can effectively eliminate the standing wave effect, improve the lithography accuracy, and help improve the device preparation yield through improved process and flow design. Compared with the prior art, the preparation method of the present invention has a lower production threshold. Because most of the methods in the prior art that use spin-coating anti-reflective coating to improve the standing wave effect require high temperature for curing, the requirements for equipment are higher. In addition, in the prior art, most of the anti-reflective coatings will not remain in the entire product, and need to be removed after the pattern transfer is completed through processes such as etching, and the chemicals for spin-coating anti-reflective coatings in the prior art are different from photoresists, are insoluble in inorganic solvents, and need to be ashed, which increases the overall cost. In the present application, the triangular pyramid structure is left in the wafer as a substrate and does not require additional removal.
[0056] In addition, for the production of the transfer layer and the advanced packaging process, the solution provided by the present invention can eliminate the standing wave effect, so that the temperature of PEB (Post Exposure Bake) in the photolithography process has a large adjustment space, which can directly increase the process window of the photolithography process. Because PEB is a heating step after exposure and before development, its main purpose is to evaporate the residual solvent in the photoresist layer, and it can improve the standing wave effect to a certain extent. Although the temperature range of PEB for photoresist layers of different materials is different, most of the prior art is between 90-110°C. When the post-bake exceeds a certain temperature, the photoresist will detach, and this step will also affect the CD size after the final development. Generally speaking, the adjustable space of this temperature is very small, because if the temperature is low, the improvement of the standing wave effect will be unacceptably low, and if the temperature is high, it may cause the photoresist to detach. However, in the present invention, because a triangular pyramid structure is formed as an "anti-reflection layer", it is not necessary to consider the impact of low temperature on the CD size, and the post-baking temperature can be appropriately lowered compared to the prior art, which provides a lot of room for adjustment for the entire photolithography process. Of course, the post-baking temperature cannot be reduced indefinitely, otherwise the post-baking will be meaningless. The inventor has found through a large number of experiments that in this embodiment, the post-baking temperature can be reduced by 10-20°C compared to the post-baking temperature in the prior art, for example, between 70°C and 90°C.
[0057] It should be particularly noted that the parameters of each step in this embodiment are the optimal parameters obtained by the inventor of this case through a large number of experiments. The steps constitute an indivisible whole. Although the mechanism of interaction between the steps is not completely clear, it has been confirmed through a large number of experiments by the inventor that the preparation of semiconductor devices based on this scheme can basically eliminate the standing wave effect.
[0058] In summary, the semiconductor device manufacturing method provided by the present invention comprises the steps of: S1: preparing <111> S2: soaking the single crystal silicon wafer in an acid solution with a mass fraction of 25%-50% for 15s-60s, and then cleaning it; S3: soaking the cleaned single crystal silicon wafer in an alkali solution with a mass fraction of 40%-50% for 60s-150s, thereby forming a staggered triangular pyramid structure on the surface of the single crystal silicon wafer, and then cleaning it; S4: forming a photoresist layer on the surface of the single crystal silicon wafer with the triangular pyramid structure; S5: exposing and developing the photoresist layer to form a plurality of openings in the photoresist layer to expose the single crystal silicon wafer; S6: etching the single crystal silicon wafer according to the openings to form a plurality of grooves in the single crystal silicon wafer, and then removing the residual photoresist layer; S7: depositing a thin film in the groove. The improved process and flow design of the present invention can effectively eliminate the standing wave effect, improve the photolithography accuracy, and help to improve the device preparation yield and reduce the production cost. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.
[0059] 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 ideas disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A method for preparing a semiconductor device, characterized in that: Includes steps: S1: Prepare <111> Single crystal silicon wafer with different crystal orientations; S2: Soak the single crystal silicon wafer in an acid solution with a mass fraction of 25% to 50% for 15s to 60s, and then clean it; S3: soaking the cleaned single crystal silicon wafer in an alkali solution with a mass fraction of 40% to 50% for 60s to 150s, thereby forming a staggered triangular pyramid structure on the surface of the single crystal silicon wafer, and then cleaning; S4: forming a photoresist layer on the surface of the single crystal silicon wafer having the triangular pyramid structure; S5: exposing and developing the photoresist layer to form a plurality of openings in the photoresist layer to expose the single crystal silicon wafer; S6: etching the single crystal silicon wafer according to the opening to form a plurality of grooves in the single crystal silicon wafer, and then removing the remaining photoresist layer; S7: depositing a thin film in the trench.
2. The method for preparing a semiconductor device according to claim 1, characterized in that: The acid solution includes hydrofluoric acid and / or hydrochloric acid.
3. The method for preparing a semiconductor device according to claim 1, wherein: The alkali solution includes several kinds of NH4OH, KOH and NaOH.
4. The method for preparing a semiconductor device according to claim 1, wherein: In step S2, the samples are soaked in an acid solution for 30 seconds, and in step S3, the samples are soaked in an alkaline solution for 120 seconds.
5. The method for preparing a semiconductor device according to claim 1, wherein: Step S5 includes exposing the photoresist layer, post-baking at a temperature of 70° C. to 90° C., and then developing.
6. The method for preparing a semiconductor device according to claim 5, characterized in that: The post-bake process also includes a step of introducing alkaline gas to neutralize the excessive photoacid generated on the top of the photoresist layer after exposure.
7. The method for preparing a semiconductor device according to claim 1, wherein: Step S7 includes the steps of first forming a seed layer on the inner surface of the groove and then forming a main layer.
8. The method for preparing a semiconductor device according to claim 7, characterized in that: The material filled in the trench includes silicon or copper.
9. The method for preparing a semiconductor device according to claim 1, wherein: The photoresist layer has more than two layers, and the absorption coefficient of the bottom photoresist layer is greater than the absorption coefficient of the upper photoresist layer.
10. The method for preparing a semiconductor device according to claim 1, wherein: The cleaning in steps S2 and S3 is performed by using deionized water for 60 seconds.