Substrate etching method and plasma device
By alternately performing etching stages with different flow ratios, the morphology of the conductive layer is accurately controlled, which solves the problem of difficult to control the metal gate morphology in the prior art, and achieves an efficient and accurate etching effect.
Patent Information
- Application Number
- CN202311660225.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-05
- Publication Date
- 2025-06-06
AI Technical Summary
The prior art is difficult to accurately control the morphology of the metal gate, and it is impossible to obtain a metal gate with a vertical structure.
By alternately performing the first etching stage and the second etching stage, the flow ratio of the etching gas and the passivation gas is regulated to achieve precise control of the morphology of the conductive layer. The flow rate of the etching gas and the passivation gas in the first etching stage is relatively large, focusing on longitudinal etching; the flow rate of the second etching stage is relatively small, focusing on side wall protection.
Accurate control of the recessed structure is achieved, and an ideal recessed structure with vertical side walls is obtained, which improves the efficiency and accuracy of the etching process.
Smart Images
Figure CN120109017A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductors, and in particular to a substrate etching method and a plasma device. Background Art
[0002] The metal gate etched by the existing etching technology often presents a non-vertical structure, that is, the angle between the sidewall and the bottom surface of the recessed structure etched on the metal material is much greater than 90 degrees, making the bottom of the recessed structure an inverted trapezoid. Even by optimizing the etching gas flow ratio or plasma intensity, it is still impossible to accurately control the morphology of the metal gate and obtain a metal gate with a vertical structure. Summary of the invention
[0003] The purpose of the present invention is to precisely control the morphology of the conductive layer after etching by utilizing the first etching stage and the second etching stage which are performed alternately.
[0004] In order to achieve the above object, the present invention provides a substrate etching method, comprising the following steps:
[0005] Providing a substrate and placing it in the reaction chamber, the substrate comprising a base layer, a conductive layer to be etched and a mask layer from bottom to top;
[0006] Introducing a mixed gas consisting of an etching gas and a passivation gas into the reaction chamber, igniting plasma, and etching the conductive layer;
[0007] Regulating the flow composition ratio of the mixed gas to alternately perform the first etching stage and the second etching stage;
[0008] In any of the first etching stages, a flow ratio of the etching gas to the passivation gas is greater than a flow ratio of the etching gas to the passivation gas in any of the second etching stages.
[0009] Optionally, the conductive layer is any one or more of W, TaN, TiN, and HfO.
[0010] Optionally, after the conductive layer is etched, a metal gate is formed.
[0011] Optionally, the conductive layer is W, and the etching gas is NF 3 , the passivation gas is N 2 .
[0012] Optionally, the flow rate of the etching gas is 10 sccm-60 sccm, and the flow rate of the passivation gas is 10 sccm-50 sccm.
[0013] Optionally, the conductive layer is TiN, and the etching gas is Cl 2 , the passivation gas is N2 .
[0014] Optionally, the flow rate of the etching gas is 5 sccm-70 sccm, and the flow rate of the passivation gas is 10 sccm-50 sccm.
[0015] Optionally, in any two of the first etching stages, the flow ratio of the etching gas to the passivation gas is the same or different; in any two of the second etching stages, the flow ratio of the etching gas to the passivation gas is the same or different.
[0016] Optionally, in the first etching stage, the flow ratio of the etching gas to the passivation gas is not less than 2:1; in the second etching stage, the flow ratio of the etching gas to the passivation gas is less than 2:1. Optionally, in the first etching stage and the second etching stage, the etching gas and the passivation gas are simultaneously and continuously introduced into the reaction chamber.
[0017] Optionally, the etching times of any two of the first etching stages or the etching times of any two of the second etching stages are the same or different.
[0018] Optionally, the etching time of any first etching stage is greater than the etching time of any second etching stage.
[0019] Optionally, the etching time of the first etching stage is 1-5s;
[0020] The etching time of the second etching stage is 1-5s.
[0021] Optionally, in the first etching stage, the flow rate of the etching gas remains unchanged, and the flow rate of the passivation gas remains unchanged;
[0022] In the second etching stage, the flow rate of the etching gas remains unchanged, and the flow rate of the passivation gas remains unchanged.
[0023] Optionally, in the same first etching stage and / or the second etching stage, the etching gas and / or the passivation gas are introduced in a continuously changing form.
[0024] Optionally, the first etching stage and the second etching stage are alternately performed 10-20 times.
[0025] Optionally, the etching gas is used to etch the conductive layer to form a recessed structure in the conductive layer; and the passivation gas is used to form a protective layer on the sidewall of the recessed structure.
[0026] Optionally, the angle between the side wall and the bottom surface of the recessed structure is 80°-90°.
[0027] Optionally, a lateral dimension variation of the recessed structure at various locations is less than 10%.
[0028] The present invention also provides a plasma device, comprising:
[0029] Reaction chamber;
[0030] A base, located in the reaction chamber and used for carrying a substrate;
[0031] A radio frequency source, used to excite the gas in the reaction chamber into plasma;
[0032] A controller is configured to execute the substrate etching method as described above.
[0033] The beneficial effects of the present invention include at least:
[0034] (1) The present invention divides the etching process of the substrate into an alternating first etching stage and a second etching stage according to the different flow ratios of the etching gas and the passivation gas. In the first etching stage, the flow ratio of the etching gas to the passivation gas is relatively large. At this time, the speed at which the etching gas generates gaseous products is accelerated, and the speed at which the passivation gas generates solid products on the side walls of the recessed structure is slowed down, so that the solid products are not easy to accumulate in the recessed structure, and the etching gas can continue to etch downward. In the second etching stage, the flow ratio of the etching gas to the passivation gas is smaller than that in the first etching stage. At this time, compared with the first etching stage, the speed at which the passivation gas generates solid products on the side walls of the recessed structure is accelerated, and the speed at which the etching gas generates gaseous products is slowed down. In the second etching stage, the etching level is weakened, and the protection of the side walls of the recessed structure is strengthened. In the alternating process of vertical etching and sidewall protection, it is only necessary to control the cycles and duration of the two etching stages to achieve independent segmentation of anisotropic and isotropic etching, achieve precise control of the recessed structure, and obtain an ideal recessed structure with vertical sidewalls.
[0035] (2) In the first etching stage and the second etching stage of the present invention, etching gas and passivation gas are continuously introduced into the reaction chamber at the same time. At any time, the mixed gas always has the behavior of longitudinally etching the recessed structure, so that the etching continues and the efficiency of the entire etching process is improved; it also always has the behavior of forming solid products on the sidewalls of the recessed structure to protect the sidewalls, so that the sidewalls are always protected and the etching gas does not excessively widen the width of the recessed structure. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Figure 1 Schematic diagram of the structure of the substrate to be etched.
[0037] Figure 2 Schematic diagram of the structure of a metal gate prepared in a comparative example of the present invention.
[0038] Figure 3 The present invention provides a flow chart of the etching method for a substrate.
[0039] Figure 4 Schematic diagram of the structure of the metal gate prepared in Examples 1-3 of the present invention.
[0040] Figure 5 This is a time-gas flow curve diagram of Example 1 of the present invention.
[0041] Figure 6 This is a time-gas flow curve diagram of Example 2 of the present invention.
[0042] Figure 7 This is a time-gas flow curve diagram of Example 3 of the present invention.
[0043] In the figure, 1-base layer, 2-conductive layer, 3-silicon nitride mask layer, 4-photoresist mask layer. DETAILED DESCRIPTION
[0044] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0045] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.
[0046] like Figure 1 As shown, the substrate to be etched includes a base layer 1, a conductive layer 2 to be etched, and a mask layer from bottom to top. The mask layer includes a silicon nitride mask layer 3 formed on the surface of the conductive layer to be etched, and a patterned photoresist mask layer 4 formed on the surface of the silicon nitride mask layer 3. The silicon nitride mask layer 3 is first etched downward using the photoresist mask layer 4 as a mask, and then the conductive layer 2 is continuously etched, so that the pattern on the photoresist mask layer 4 is transferred to the conductive layer 2, and a recessed structure is formed in the conductive layer 2.
[0047] Theoretically, the etching gas is affected by the electric field in the vertical direction and is introduced in a direction perpendicular to the conductive layer. Under the shielding of the mask layer, only the longitudinal dimension (depth) of the recessed structure continues to increase, and the lateral dimension (width) of the recessed structure can be kept consistent with the mask layer. In practice, the etching gas will inevitably bombard the sidewalls of the recessed structure, widening the width of the recessed structure. Therefore, a mixed gas composed of etching gas and passivation gas is usually introduced into the reaction chamber.
[0048] The etching gas is used to etch the conductive layer. The etching gas continuously bombards the material of the conductive layer to generate low-boiling-point gaseous products. The gaseous products are discharged from the substrate, and a recessed structure is etched in the conductive layer. The passivation gas is used to form sidewall protection. The passivation gas combines with the conductive layer material of the sidewall of the recessed structure to generate a high-boiling-point solid product attached to the sidewall as a protective layer for the sidewall. The solid product is stable in nature and is not easy to react with the etching gas, so that the etching gas is not easy to etch the sidewall of the recessed structure, keeping the lateral size of the recessed structure stable. Most of the etching gas bombards the bottom surface of the recessed structure along the longitudinal direction.
[0049] However, the inventors have found that it is difficult to etch the sidewalls of the recessed structure vertically using conventional etching techniques, especially the Figure 2 The bottom shown is an inverted trapezoidal concave structure. Figure 2 In the embodiment, the angle between the side wall and the bottom surface of the concave structure is greater than 90°, and the lateral dimension of the concave structure gradually increases from the bottom surface upward.
[0050] This is because, as the etching position gradually approaches the base layer, the amount of etching gas reaching the bottom decreases, and the rate at which the etching gas combines with the material of the conductive layer to generate gaseous products is lower than the rate at which the passivation gas combines with the material of the conductive layer to generate solid products, so solid products are more likely to form. Solid products gradually accumulate in the recessed structure, making it difficult for the etching gas to enter the bottom of the recessed structure and react with the conductive layer, and the generated gaseous products are also difficult to be discharged from the recessed structure. Therefore, as etching continues, more and more solid products accumulate in the recessed structure, making it more difficult for the etching gas to etch the recessed structure, thereby forming a recessed structure with an inverted trapezoidal bottom.
[0051] However, it is difficult to find the balance point of the generation rate of gaseous products and solid products by optimizing the etching gas flow ratio or plasma intensity. Limited by the hardware conditions for controlling the gas flow and the selectable gas types, if the trapezoidal defect is avoided by reducing the amount of passivation gas under the above gas ratio, it is possible to lean towards over-etching defects, resulting in insufficient retention of the conductive layer 2. Moreover, the etching process is complicated. Even if the balance point can be found and the flow ratio of the etching gas is determined before the etching begins, as the etching continues, the etching depth gradually increases, and the balance point may change, so that the flow ratio of the etching gas determined initially cannot adapt to subsequent changes, and the morphology of the metal gate cannot be accurately controlled, and a metal gate with a vertical structure cannot be obtained.
[0052] Based on this, Figure 3 As shown, the present invention provides a substrate etching method, comprising the following steps:
[0053] Step S1: providing a substrate and placing it into a reaction chamber, wherein the substrate comprises, from bottom to top, a base layer, a conductive layer to be etched, and a mask layer.
[0054] In some embodiments, the base layer is a silicon substrate, and the mask layer includes a silicon nitride mask layer formed on the surface of the conductive layer to be etched, and a patterned photoresist mask layer formed on the surface of the silicon nitride mask layer.
[0055] Step S2: introducing a mixed gas consisting of an etching gas and a passivation gas into the reaction chamber, igniting plasma, and etching the conductive layer.
[0056] The flow composition ratio of the mixed gas is regulated to alternately perform the first etching stage and the second etching stage; in any of the first etching stages, the flow ratio of the etching gas to the passivation gas is greater than the flow ratio of the etching gas to the passivation gas in any of the second etching stages. The first etching stage and the second etching stage of the present invention are performed in an alternating cycle, and in each cycle, the flow ratio of the etching gas to the passivation gas in the first etching stage is greater than the flow ratio of the etching gas to the passivation gas in the second etching stage; and in the next cycle, the flow ratio of the etching gas to the passivation gas in the first etching stage can be less than the flow ratio of the etching gas to the passivation gas in the first etching stage in the previous cycle, but still greater than the flow ratio of the etching gas to the passivation gas in the second etching stage in the previous cycle.
[0057] In the first etching stage, the flow ratio of the etching gas to the passivation gas is relatively large. At this time, the speed at which the etching gas generates gaseous products is accelerated, and the speed at which the side wall of the recessed structure of the passivation gas generates solid products is slowed down, making it difficult for the solid products to accumulate in the recessed structure, and the etching gas can continue to etch downward. In the first etching stage, because the reaction between the conductive layer 2 and the etching gas is more active, a certain amount of passivation gas is required for adjustment, rather than only etching gas.
[0058] However, as the first etching stage proceeds, when the etching progress approaches the mask coverage size, the side walls of the recessed structure cannot be adequately protected due to the small flow rate of the passivation gas, causing the etching gas to bombard the side walls of the recessed structure, widening the lateral size of the recessed structure and easily forming a recessed structure with a roughly equilateral triangle at the bottom, that is, the angle between the side wall and the bottom of the recessed structure is much less than 90°, and a vertical side wall still cannot be obtained.
[0059] Therefore, after the first etching stage is performed for a period of time, the second etching stage is performed alternately. In the second etching stage, the flow ratio of the etching gas to the passivation gas is less than that in the first etching stage. At this time, the speed at which the passivation gas generates solid products on the sidewalls of the recessed structure is accelerated, and the speed at which the etching gas generates gaseous products is slowed down. In the second etching stage, the etching level is weakened and the sidewall protection of the recessed structure is strengthened. In the second etching stage, in order to prevent the sidewall protection layer from being excessively deposited, a portion of the etching gas is required as a balance. At the same time, the presence of the etching gas can also ensure the progress of etching. After the second etching stage is performed for a period of time, when the solid products accumulated on the sidewalls increase and affect the longitudinal etching of the etching gas, the first etching stage is performed alternately again.
[0060] In the present invention, the etching of the substrate is divided into an alternating first etching stage and a second etching stage, and the flow rates of the etching gas and the passivation gas are controlled in the first etching stage and the second etching stage, respectively. The first etching stage focuses on the longitudinal etching of the recessed structure, and the second etching stage focuses on the sidewall protection of the recessed structure. In the alternating process of longitudinal etching and sidewall protection, after determining the flow rate ratio, it is only necessary to control the cycle and duration of the two etching stages, thereby avoiding switching between the two extreme states of over-etching and over-protection when the flow rates of the etching gas and the passivation gas are adjusted separately, that is, it is possible to achieve precise control of the recessed structure and obtain an ideal recessed structure with vertical sidewalls.
[0061] In some embodiments, the conductive layer is any one or more of tungsten (W), tantalum nitride (TaN), titanium nitride (TiN), and hafnium oxide (HfO). After the conductive layer is etched, the remaining portion is used as a metal gate in a logic semiconductor unit.
[0062] In some embodiments, the conductive layer is W, and the etching gas is NF3 , the passivation gas is N 2 . Etching gas NF 3 The W conductive layer generates tungsten fluoride, the passivation gas N 2 The tungsten nitride is formed with the W conductive layer. The flow rate of the etching gas is 10 sccm-60 sccm, and the flow rate of the passivation gas is 10 sccm-50 sccm.
[0063] In some embodiments, the conductive layer is TiN, and the etching gas is Cl 2 , the passivation gas is N 2 . Etching gas Cl 2 With TiN conductive layer to generate TiCl 4 The flow rate of the etching gas is 5 sccm-70 sccm, and the flow rate of the passivation gas is 10 sccm-50 sccm.
[0064] In some embodiments, the flow ratio of the etching gas to the passivation gas is the same or different in any two of the first etching stages; the flow ratio of the etching gas to the passivation gas is the same or different in any two of the second etching stages. The same flow ratio includes that the flow rates of the etching gas and the passivation gas are exactly the same in value, and also includes that the flow rates of the etching gas and the passivation gas are doubled or reduced, but the ratio remains unchanged.
[0065] In some embodiments, in the first etching stage, the flow ratio of the etching gas to the passivation gas is not less than 2:1; in the second etching stage, the flow ratio of the etching gas to the passivation gas is less than 2:1. Theoretically, when the flow rates of the etching gas and the passivation gas are the same, that is, the flow ratio of the etching gas to the passivation gas is 1:1, it is the balance point between the etching of the etching gas and the sidewall protection of the passivation gas. But as mentioned above. When the etching position gradually approaches the base layer, the rate at which the etching gas combines with the material of the conductive layer to generate gaseous products is lower than the rate at which the passivation gas combines with the material of the conductive layer to generate solid products, and the etching gas becomes more difficult to etch the recessed structure, and solid products are more likely to form. In fact, when the flow ratio of the etching gas to the passivation gas is greater than 1:1, the etching stage may still appear to focus on the sidewall protection of the recessed structure. The inventors have found through experimental verification that, in the actual etching process, the flow ratio of the etching gas to the passivation gas is limited to 2:1. When the flow ratio of the etching gas to the passivation gas is greater than or equal to 2:1, the etching stage is mainly based on etching; when the flow ratio of the etching gas to the passivation gas is less than 2:1, the sidewall protection is mainly used in the etching stage.
[0066] In some embodiments, in the first etching stage and the second etching stage, the etching gas and the passivation gas are simultaneously and continuously introduced into the reaction chamber. Therefore, in any time period of the entire etching process of the present invention, etching gas and passivation gas are introduced. The present invention defines that the flow ratio of etching gas and passivation gas in different etching stages is different, and further defines whether the etching stage is mainly for etching or sidewall protection. At any time, the mixed gas always has the behavior of longitudinally etching the recessed structure, so that the etching continues and the efficiency of the entire etching process is improved; there is also always the behavior of forming solid products on the sidewalls of the recessed structure to protect the sidewalls, so that the sidewalls are always protected and the etching gas does not excessively widen the width of the recessed structure.
[0067] In some embodiments, the etching time of any two of the first etching stages or the etching time of any two of the second etching stages are the same or different. The etching time of any first etching stage or any second etching stage of the present invention can be set to a fixed value or dynamically adjusted according to the state of the sidewall of the recessed structure as required by the etching.
[0068] In some embodiments, the etching time of the first etching stage is 1-5 s; the etching time of the second etching stage is 1-5 s.
[0069] In some embodiments, the etching time of any of the first etching stages is greater than the etching time of any of the second etching stages, so that the sidewall protection of the conductive layer 2 is sufficient to maintain the etching morphology and will not affect the etching progress.
[0070] In some embodiments, in the first etching stage, the flow rate of the etching gas remains unchanged, and the flow rate of the passivation gas remains unchanged; in the second etching stage, the flow rate of the etching gas remains unchanged, and the flow rate of the passivation gas remains unchanged, so as to reduce the variables affecting the etching results and reduce the difficulty of regulation.
[0071] In other embodiments, the etching gas and / or the passivation gas are introduced in a continuously changing form. In any first etching stage or second etching stage, the flow rate of the etching gas or the passivation gas may not be set to a fixed value, as long as the flow rate ratio of the etching gas to the passivation gas is greater in the first etching stage, and the flow rate ratio of the etching gas to the passivation gas is less than that in the first etching stage in the second etching stage, so as to fine-tune the flow rate change to cope with the difference in etching results caused by changes in other conditions.
[0072] In some embodiments, during the entire conductive layer etching process, the first etching stage and the second etching stage are alternately performed 10-20 times.
[0073] By using the substrate etching method provided by the present invention, the finally obtained recessed structure is as follows Figure 4As shown, the angle between the side wall and the bottom surface is 80°-90°, and the bottom of the recessed structure is close to a right angle, which significantly improves the trapezoidal defect; and the lateral dimension variation of the recessed structure at various locations is less than 10%, and the variation range of the lateral dimension at different positions of the recessed structure is small, and the side wall is basically in a vertical state.
[0074] The present invention also provides a plasma device, comprising: a reaction chamber; a base located in the reaction chamber and used to support a substrate; a radio frequency source, used to excite the gas in the reaction chamber into plasma; and a controller, which is configured to execute the above-mentioned substrate etching method.
[0075] The following is through Example 1-Example 3 and Figure 5-Figure 7 The substrate etching method of the present invention is introduced. Figure 5-Figure 6 In the figure, the horizontal solid line represents the etching gas, and the horizontal dotted line represents the passivation gas; Figure 7 In the figure, the solid line represents the etching gas, and the dotted line represents the passivation gas.
[0076] Example 1
[0077] In this embodiment, the conductive layer to be etched is W, the thickness of the conductive layer is 50 nm, and the etching gas is NF 3 , the passivation gas is N 2 .
[0078] like Figure 5 It is a schematic diagram of two cycles. In this embodiment, a first etching stage and a second etching stage constitute one cycle. The total etching time of each cycle is 1 second. There are 10 cycles in total, and the total etching time is 20 seconds.
[0079] In any first etching stage, the flow rate of the etching gas remains unchanged, and the flow rate of the passivation gas remains unchanged; the flow rate of the etching gas is 50 sccm, the flow rate of the passivation gas is 10 sccm, and the flow ratio of the etching gas to the passivation gas is 5:1; in any second etching stage, the flow rate of the etching gas is the same, and the flow rate of the passivation gas is the same; the flow rate of the etching gas is 30 sccm, the flow rate of the passivation gas is 20 sccm, and the flow ratio of the etching gas to the passivation gas is 3:2.
[0080] Example 2
[0081] The conductive layer of this embodiment is W, the thickness of the conductive layer is 50nm, and the etching gas is NF 3 , the passivation gas is N 2 .
[0082] like Figure 6 As shown, in this embodiment, a first etching stage and a second etching stage constitute a cycle, the total etching time of each cycle is 2 seconds, and a total of 10 cycles are repeated, with a total etching time of 20 seconds.
[0083] According to the different flow compositions of etching gas and passivation gas, each etching cycle specifically includes four etching processes. The first etching stage can be divided into etching process I, etching process II and etching process III. In etching process I, the flow rate of etching gas is 50sccm, the flow rate of passivation gas is 10sccm, and the flow ratio of etching gas to passivation gas is 5:1; in etching process II, the flow rate of etching gas is 30sccm, the flow rate of passivation gas is 20sccm, and the flow ratio of etching gas to passivation gas is 3:2; in etching process III, the flow rate of etching gas is 40sccm, the flow rate of passivation gas is 20sccm, and the flow ratio of etching gas to passivation gas is 2:1; the second etching stage includes etching process IV. In any second etching stage, the flow rate of the etching gas is the same and the flow rate of the passivation gas is the same; in etching process IV, the flow rate of the etching gas is 20 sccm, the flow rate of the passivation gas is 30 sccm, and the flow ratio of the etching gas to the passivation gas is 2:3.
[0084] Example 3
[0085] The conductive layer of this embodiment is TiN, the thickness of the conductive layer is 20nm, and the etching gas is Cl 2 , the passivation gas is N 2 .
[0086] like Figure 7 As shown, in this embodiment, a first etching stage and a second etching stage constitute a cycle, the total etching time of each cycle is 2 seconds, and a total of 10 cycles are repeated, with a total etching time of 20 seconds.
[0087] In this embodiment, the etching gas and the passivation gas are introduced in a continuously changing form, and the time-etching gas pulse flow curve is a sine wave, and the time-passivation gas pulse flow curve is a cosine wave. In any first etching stage, the peak value of the etching gas is 55 sccm, and the trough value of the passivation gas is 10 sccm; in any second etching stage, the trough value of the etching gas is 5 sccm, and the peak value of the passivation gas is 35 sccm.
[0088] Comparative Example
[0089] The conductive layer to be etched is W, the thickness of the conductive layer is 50nm, and the etching gas is NF 3 , the passivation gas is N 2 The etching gas was always kept at a flow rate of 10 sccm and the passivation gas was kept at 50 sccm to be introduced into the reaction chamber for a total time of 20 s.
[0090] The morphology of the metal gate obtained in Example 1-3 is as follows Figure 4 As shown, the morphology of the metal gate obtained in the comparative example is as follows Figure 2 shown.
[0091] In summary, the present invention provides a substrate etching method, wherein a mixed gas composed of an etching gas and a passivation gas is introduced into the reaction chamber, plasma is ignited, and the conductive layer is etched; the first etching stage and the second etching stage are performed alternately by adjusting the flow composition ratio of the mixed gas; wherein the flow ratio of the etching gas to the passivation gas in the first etching stage is relatively large, and longitudinal etching behavior is dominant; the ratio of the etching gas to the passivation gas in the second etching stage is smaller than that in the first etching stage, and sidewall protection behavior is dominant. In the alternating process of longitudinal etching and sidewall protection, it is only necessary to control the cycle and duration of the two etching stages to achieve independent segmentation of anisotropic and isotropic etching, achieve precise control of the recessed structure, and obtain an ideal recessed structure with vertical sidewalls.
[0092] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.
Claims
1. A substrate etching method, It is characterized in that The steps include: Providing a substrate and placing it in the reaction chamber, the substrate comprising a base layer, a conductive layer to be etched and a mask layer from bottom to top; Introducing a mixed gas consisting of an etching gas and a passivation gas into the reaction chamber, igniting plasma, and etching the conductive layer; Regulating the flow composition ratio of the mixed gas to alternately perform the first etching stage and the second etching stage; In any of the first etching stages, a flow ratio of the etching gas to the passivation gas is greater than a flow ratio of the etching gas to the passivation gas in any of the second etching stages.
2. The substrate etching method according to claim 1, It is characterized in that The conductive layer is any one or more of W, TaN, TiN and HfO.
3. The substrate etching method according to claim 2, It is characterized in that After the conductive layer is etched, a metal gate is formed.
4. The substrate etching method according to claim 2, It is characterized in that The conductive layer is W, and the etching gas is NF 3 , the passivation gas is N 2 .
5. The substrate etching method according to claim 4, It is characterized in that The flow rate of the etching gas is 10 sccm-60 sccm, and the flow rate of the passivation gas is 10 sccm-50 sccm.
6. The substrate etching method according to claim 2, It is characterized in that The conductive layer is TiN, and the etching gas is Cl 2 , the passivation gas is N 2 .
7. The substrate etching method according to claim 6, It is characterized in that The flow rate of the etching gas is 5 sccm-70 sccm, and the flow rate of the passivation gas is 10 sccm-50 sccm.
8. The substrate etching method according to claim 1, It is characterized in that In any two of the first etching stages, the flow ratio of the etching gas to the passivation gas is the same or different; in any two of the second etching stages, the flow ratio of the etching gas to the passivation gas is the same or different.
9. The substrate etching method according to claim 1, It is characterized in that In the first etching stage, the flow ratio of the etching gas to the passivation gas is not less than 2:1; in the second etching stage, the flow ratio of the etching gas to the passivation gas is less than 2:
1.
10. The substrate etching method according to claim 1, It is characterized in that In the first etching stage and the second etching stage, the etching gas and the passivation gas are simultaneously and continuously introduced into the reaction chamber.
11. The substrate etching method according to claim 1, It is characterized in that The etching times of any two of the first etching stages or the etching times of any two of the second etching stages are the same or different.
12. The substrate etching method according to claim 1, It is characterized in that The etching time of any first etching stage is greater than the etching time of any second etching stage.
13. The substrate etching method according to claim 1, It is characterized in that The etching time of the first etching stage is 1-5s; The etching time of the second etching stage is 1-5s.
14. The substrate etching method according to claim 1, It is characterized in that In the first etching stage, the flow rate of the etching gas remains unchanged, and the flow rate of the passivation gas remains unchanged; In the second etching stage, the flow rate of the etching gas remains unchanged, and the flow rate of the passivation gas remains unchanged.
15. The substrate etching method according to claim 1, It is characterized in that In the same first etching stage and / or the second etching stage, the etching gas and / or the passivation gas is introduced in a continuously changing manner.
16. The substrate etching method according to claim 1, It is characterized in that The first etching stage and the second etching stage are alternately performed 10-20 times.
17. The substrate etching method according to claim 1, It is characterized in that The etching gas is used to etch the conductive layer to form a recessed structure in the conductive layer; the passivation gas is used to form a protective layer on the side wall of the recessed structure.
18. The substrate etching method according to claim 16, It is characterized in that The included angle between the side wall and the bottom surface of the recessed structure is 80°-90°.
19. The substrate etching method according to claim 16, It is characterized in that The transverse dimension variation of the concave structure at various locations is less than 10%.
20. A plasma device, It is characterized in that include: Reaction chamber; A base, located in the reaction chamber and used for carrying a substrate; A radio frequency source, used to excite the gas in the reaction chamber into plasma; A controller configured to execute the substrate etching method according to any one of claims 1 to 19.