Deep trench etching method
Through the two-stage etching method, the ratio and bias duty cycle of oxygen flow to sulfur hexafluoride gas and the problem of the difficulty in etching deep trenches in the prior art is solved, and efficient deep trench formation and surface protection are achieved. Improved the morphological quality of the deep grooves.
Patent Information
- Application Number
- CN202411183533.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-27
- Publication Date
- 2024-12-10
AI Technical Summary
The existing single-step steady-state etching method is difficult to meet the needs of deeper and higher depth-to-face ratios, and the process parameter window becomes narrower, making it difficult to maintain an ideal trench morphology.
Using a two-stage etching method, the first stage forms a deep trench primary structure under the ratio of specific oxygen flow to sulfur hexafluoride gas flow and bias duty cycle, and the second stage gradually adjusts the gas ratio and bias duty cycle to A deep trench structure is formed, which utilizes an increase in oxygen flow to protect the silicon surface and reduce plasma energy.
A high etching rate and efficiency are achieved, the deep groove surface is protected, the double slope problem is avoided, and the smoothness of the morphology of the deep groove side wall is improved.
Smart Images
Figure CN119108275A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of semiconductor integrated circuit manufacturing, and in particular to a deep trench etching method. Background Art
[0002] Single-step steady-state etching method: referred to as SSP etching, is widely used in dry etching of silicon deep trenches due to its high process stability and the advantage of maintaining a high etching rate. In the deep trench etching process, SSP etching mainly uses SF6 and O2 gases as plasma sources, and adjusts factors such as gas, RF bias and chamber pressure to make the etching have better morphology adjustment capabilities.
[0003] As the market demands for semiconductor device performance increase, the development of trenches with higher aspect ratios will become the main focus in the future. However, the current etching method is only suitable for trench etching below 52μm, and can no longer meet the development needs of deeper trenches and higher performance devices. As the trench depth increases, the etching time increases and the plasma energy increases, SSP faces severe challenges.
[0004] However, during the entire etching process of the related SSP technology, the etching parameters are kept constant, and the ideal groove depth and surface morphology are obtained through time superposition. During the etching process, the requirements for depth, angle, and sidewall morphology determine that the single-step method parameter setting needs to seek a balance point, but as the groove aspect ratio increases, the process parameter window becomes narrower and it is even difficult to etch a groove with an ideal morphology. Summary of the invention
[0005] The present application provides a deep trench etching method, which can solve the problem of rough sidewall morphology of deep trenches etched in related technologies.
[0006] In order to solve the technical problem described in the background technology, the present application provides a deep trench etching method, the deep trench etching method comprising:
[0007] Providing a semiconductor substrate, and performing a first-stage etching on the semiconductor substrate in a first etching gas atmosphere, under a first bias voltage, and according to a first bias voltage duty cycle to form a deep trench primary structure; a first ratio exists between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere;
[0008] The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle, so as to form a deep trench structure.
[0009] Optionally, the step of providing a semiconductor substrate, performing a first-stage etching on the semiconductor substrate to form a deep trench primary structure in a first etching gas atmosphere, under a first bias voltage, and according to a first bias voltage duty cycle; wherein the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere have a first ratio, comprises:
[0010] The provided semiconductor substrate is subjected to first-stage etching to form a deep trench primary structure in a first etching gas atmosphere in which the ratio of oxygen flow to sulfur hexafluoride gas flow is in the range of 50% to 65%, under a first bias voltage and according to a first bias voltage duty cycle.
[0011] Optionally, the step of providing a semiconductor substrate, performing a first-stage etching on the semiconductor substrate to form a deep trench primary structure in a first etching gas atmosphere, under a first bias voltage, and according to a first bias voltage duty cycle; wherein the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere have a first ratio, comprises:
[0012] A semiconductor substrate is provided. In a first etching gas atmosphere, under a first bias voltage, and with a first bias duty ratio ranging from 70% to 100%, the semiconductor substrate is subjected to a first stage of etching to form a deep trench primary structure. A first ratio exists between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere.
[0013] Optionally, the step of providing a semiconductor substrate, performing a first-stage etching on the semiconductor substrate to form a deep trench primary structure in a first etching gas atmosphere, under a first bias voltage, and according to a first bias voltage duty cycle; wherein the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere have a first ratio, comprises:
[0014] A semiconductor substrate is provided. In a first etching gas atmosphere, at a first bias voltage in a range of 250V to 290V, and according to a first bias voltage duty cycle, the semiconductor substrate is subjected to a first stage of etching to form a deep trench primary structure. A first ratio exists between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere.
[0015] Optionally, the step of performing a second-stage etching on the deep trench primary structure, in which, in the second-stage etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle to form the deep trench structure, comprises:
[0016] The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to a second ratio in the range of 65% to 85%, the bias voltage is gradually increased from the first bias voltage to a second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to a second bias duty cycle, so as to form a deep trench structure.
[0017] Optionally, the step of performing a second-stage etching on the deep trench primary structure, in which, in the second-stage etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle to form the deep trench structure, comprises:
[0018] The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to a second ratio, the bias voltage is gradually increased from the first bias voltage to a second bias voltage in the range of 290V to 330V, and the bias duty cycle is gradually decreased from the first bias duty cycle to a second bias duty cycle to form a deep trench structure.
[0019] Optionally, the step of performing a second-stage etching on the deep trench primary structure, in which, in the second-stage etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle to form the deep trench structure, comprises:
[0020] The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to a second ratio, the bias voltage is gradually increased from the first bias voltage to a second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to a second bias duty cycle in the range of 40% to 65%, so as to form a deep trench structure.
[0021] Optionally, the step of performing a second-stage etching on the deep trench primary structure, in which, in the second-stage etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle to form the deep trench structure, comprises:
[0022] The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually and linearly increased from the first ratio to the second ratio, the bias voltage is gradually and linearly increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually and linearly decreased from the first bias duty cycle to the second bias duty cycle, so as to form a deep trench structure.
[0023] The technical solution of the present application includes at least the following advantages: a higher etching rate in the first stage etching and a higher etching efficiency. Since the second stage etching is based on the first stage etching, the ratio of oxygen flow rate is increased, so that oxygen forms an oxide with the exposed silicon surface after the first stage etching to block the second stage etching process, protect the surface of the deep groove, and obtain a higher etching selectivity relative to the hard mask layer. In addition, a higher second bias voltage in the second stage etching can weaken the energy of the plasma, and a smaller second bias voltage duty cycle can reduce the time that the plasma continues to bombard the deep groove, thereby reducing the etching rate and improving the protection of the sides of the deep groove. And the etching parameters in the second stage etching are gradually transitioned from the etching parameters in the first stage etching to prevent the problem of double slope caused by a sudden change in the etching parameters. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0025] Figure 1 A flow chart of a deep trench etching method provided by an embodiment of the present application is shown;
[0026] Figure 2 A schematic diagram of a cross-sectional structure of the device after step S1 is completed is shown;
[0027] Figure 3 A schematic diagram of the cross-sectional structure of the device after step S2 is completed is shown;
[0028] Figure 4 A schematic diagram showing the change of bias voltage during etching process is shown;
[0029] Figure 5 A schematic diagram of the bias duty cycle in the first stage of etching is shown. DETAILED DESCRIPTION
[0030] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.
[0031] In the description of the present application, it should be noted that the terms "center", "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 application 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 application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.
[0032] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0033] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.
[0034] Figure 1 A flowchart of a deep trench etching method provided by an embodiment of the present application is shown. Figure 1 It can be seen that the deep trench etching method includes the following steps:
[0035] Step S1: providing a semiconductor substrate, and performing a first-stage etching on the semiconductor substrate in a first etching gas atmosphere, under a first bias voltage, and according to a first bias voltage duty cycle to form a deep trench primary structure; a first ratio exists between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere.
[0036] Figure 2 The schematic diagram of the cross-sectional structure of the device after step S1 is completed is shown. Figure 2As can be seen in the figure, after the first stage etching, the semiconductor substrate 100 forms a deep trench primary structure 110. The depth of the deep trench primary structure 110 is S1. By controlling the etching time of the first stage etching, the depth S1 of the deep trench primary structure 110 can account for 10% to 50% of the target depth of the deep trench.
[0037] Step S2: performing a second stage of etching on the deep trench primary structure. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle, so as to form a deep trench structure.
[0038] Figure 3 The schematic diagram of the cross-sectional structure of the device after step S2 is completed is shown. Figure 3 It can be seen that after the second stage of etching, Figure 1 The deep trench primary structure 110 shown continues to extend downward to form a deep trench structure 120 .
[0039] It should be noted that the first stage etching has a higher etching rate and maintains a higher etching efficiency. Since the second stage etching is based on the first stage etching, the ratio of oxygen flow rate is increased, so that oxygen and the exposed silicon surface after the first stage etching are formed into oxide to block the second stage etching process, protect the surface of the deep groove, and obtain a higher etching selectivity relative to the hard mask layer. The smaller second bias duty cycle can reduce the time that the plasma continues to bombard the deep groove to reduce the etching rate and improve the protection of the side of the deep groove. And the etching parameters in the second stage etching are gradually transitioned from the etching parameters in the first stage etching to prevent the problem of double slope caused by a sudden change in the etching parameters.
[0040] In addition, in the later stage of the second stage etching, it is necessary to ensure better plasma directivity, and use a higher bias voltage to improve plasma directivity, so as to better achieve the etching effect on the deep trench. Among them, in the later stage of the second stage etching, other parameters remain unchanged, and the bias voltage is higher than the first bias voltage in the first stage to improve the directivity of plasma bombardment.
[0041] Figure 4 The schematic diagram of the change of bias duty cycle during the etching process is shown. Figure 4 It can be seen that in the first stage of etching, the bias voltage is the first bias duty cycle, and in the second stage of etching, the bias voltage gradually increases from the first bias duty cycle to the second bias duty cycle.
[0042] Figure 5The schematic diagram of the bias duty cycle in the first stage of etching is shown. Figure 5 It can be seen that the pulse time length of the first bias Bias1 is T2, the cycle length is T1, and the duty cycle of the first bias is T2 / T1.
[0043] Exemplarily, a provided semiconductor substrate is subjected to a first stage etching to form a deep trench primary structure in a first etching gas atmosphere in which the ratio of oxygen flow rate to sulfur hexafluoride gas flow rate is in a range of 50% to 65%, under a first bias voltage and according to a first bias voltage duty cycle.
[0044] Exemplarily, a semiconductor substrate is provided, and in a first etching gas atmosphere, under a first bias voltage, and with a first bias duty cycle ranging from 70% to 100%, the semiconductor substrate is subjected to a first-stage etching to form a deep trench primary structure; a first ratio is present between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere.
[0045] Exemplarily, a semiconductor substrate is provided, and in a first etching gas atmosphere, at a first bias voltage in a range of 250 V to 290 V, the semiconductor substrate is etched in a first stage to form a deep trench primary structure according to a first bias voltage duty cycle; the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere have a first ratio
[0046] Exemplarily, the deep trench primary structure undergoes second-stage etching, during which the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate gradually increases from the first ratio to a second ratio in the range of 65% to 85%, the bias voltage gradually increases from the first bias voltage to the second bias voltage, and the bias duty cycle gradually decreases from the first bias duty cycle to the second bias duty cycle to form a deep trench structure.
[0047] Exemplarily, the deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to a second ratio, the bias voltage is gradually increased from the first bias voltage to a second bias voltage in the range of 290V to 330V, and the bias duty cycle is gradually decreased from the first bias duty cycle to a second bias duty cycle to form a deep trench structure.
[0048] Exemplarily, the deep trench primary structure is subjected to a second-stage etching. In the second-stage etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to a second ratio, the bias voltage is gradually increased from the first bias voltage to a second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to a second bias duty cycle in the range of 40% to 65%, so as to form a deep trench structure.
[0049] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.
Claims
1. A deep trench etching method, characterized in that: The deep trench etching method comprises: Providing a semiconductor substrate, and performing a first-stage etching on the semiconductor substrate in a first etching gas atmosphere, under a first bias voltage, and according to a first bias voltage duty cycle to form a deep trench primary structure; a first ratio exists between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere; The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle, so as to form a deep trench structure.
2. The deep trench etching method according to claim 1, characterized in that: The step of providing a semiconductor substrate, performing a first-stage etching on the semiconductor substrate in a first etching gas atmosphere, under a first bias voltage, and according to a first bias voltage duty cycle to form a deep trench primary structure; and the step of having a first ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere comprises: The provided semiconductor substrate is subjected to first-stage etching to form a deep trench primary structure in a first etching gas atmosphere in which the ratio of oxygen flow to sulfur hexafluoride gas flow is in the range of 50% to 65%, under a first bias voltage and according to a first bias voltage duty cycle.
3. The deep trench etching method according to claim 1, characterized in that: The step of providing a semiconductor substrate, performing a first-stage etching on the semiconductor substrate in a first etching gas atmosphere, under a first bias voltage, and according to a first bias voltage duty cycle to form a deep trench primary structure; and the step of having a first ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere comprises: A semiconductor substrate is provided. In a first etching gas atmosphere, under a first bias voltage, and with a first bias duty ratio ranging from 70% to 100%, the semiconductor substrate is subjected to a first stage of etching to form a deep trench primary structure. A first ratio exists between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere.
4. The deep trench etching method according to claim 1, characterized in that: The step of providing a semiconductor substrate, performing a first-stage etching on the semiconductor substrate in a first etching gas atmosphere, under a first bias voltage, and according to a first bias voltage duty cycle to form a deep trench primary structure; and the step of having a first ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere comprises: A semiconductor substrate is provided. In a first etching gas atmosphere, at a first bias voltage in a range of 250V to 290V, and according to a first bias voltage duty cycle, the semiconductor substrate is subjected to a first stage of etching to form a deep trench primary structure. A first ratio exists between the oxygen flow rate and the sulfur hexafluoride gas flow rate in the first etching gas atmosphere.
5. The deep trench etching method according to claim 1, characterized in that: The step of performing a second-stage etching on the deep trench primary structure, wherein in the second-stage etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle to form a deep trench structure, comprises: The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to a second ratio in the range of 65% to 85%, the bias voltage is gradually increased from the first bias voltage to a second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to a second bias duty cycle, so as to form a deep trench structure.
6. The deep trench etching method according to claim 1, characterized in that: The step of performing a second-stage etching on the deep trench primary structure, wherein in the second-stage etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle to form a deep trench structure, comprises: The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to a second ratio, the bias voltage is gradually increased from the first bias voltage to a second bias voltage in the range of 290V to 330V, and the bias duty cycle is gradually decreased from the first bias duty cycle to a second bias duty cycle to form a deep trench structure.
7. The deep trench etching method according to claim 1, characterized in that: The step of performing a second-stage etching on the deep trench primary structure, wherein in the second-stage etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle to form a deep trench structure, comprises: The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to a second ratio, the bias voltage is gradually increased from the first bias voltage to a second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to a second bias duty cycle in the range of 40% to 65%, so as to form a deep trench structure.
8. The deep trench etching method according to claim 1, characterized in that: The step of performing a second-stage etching on the deep trench primary structure, wherein in the second-stage etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually increased from the first ratio to the second ratio, the bias voltage is gradually increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually decreased from the first bias duty cycle to the second bias duty cycle to form a deep trench structure, comprises: The deep trench primary structure is subjected to a second stage of etching. In the second stage of etching, the ratio between the oxygen flow rate and the sulfur hexafluoride gas flow rate is gradually and linearly increased from the first ratio to the second ratio, the bias voltage is gradually and linearly increased from the first bias voltage to the second bias voltage, and the bias duty cycle is gradually and linearly decreased from the first bias duty cycle to the second bias duty cycle, so as to form a deep trench structure.