Trench filling method of semiconductor

Abstract

The invention provides a trench filling method for a semiconductor, which comprises the following steps: S1, according to a relation curve of different pressures of process gases and corresponding growth rates, acquiring a process parameter corresponding to the condition that the slope of the relation curve is less than zero; s2, forming a groove on the substrate; s3, introducing a first process gas and a second process gas, performing a chemical vapor deposition process according to the process parameters to form a polycrystalline silicon thin film, and filling the groove with the polycrystalline silicon thin film; wherein the process parameters are kept unchanged in the chemical vapor deposition process; the first process gas is DCS, and the second process gas is HCL. According to the method provided by the invention, no gap is generated in the polycrystalline silicon film filled in the groove.

Description

Technical Field

[0001] The present invention relates to the technical field of thin film growth, and particularly to the technical field of trench thin film filling of semiconductors. Background Art

[0002] In the process of semiconductor chip manufacturing, there are many trenches or deep holes that need to be filled. After filling the trenches or deep holes with the existing thin film process, it is easy to cause gaps, especially in deep trenches, and this phenomenon is more obvious. As shown in Figure 1 (a) of Figure 1 Figure 1 , since the reactants are gradually consumed in the deep trench or deep hole structure from the opening 201, the middle part 202 to the lower part 203 region, the concentration of the reactants will gradually decrease. Therefore, the growth rate of the thin film will gradually decrease from the opening 201 to the lower part 203, and the final filling effect will be as shown in

[0003] (a) of Figure 1 Figure 1 , and gaps are formed in the thin film. This gap defect usually affects the function of microelectronic chips. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for filling trenches of semiconductors to solve the above problems.

[0005] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0006] The present invention provides a method for filling trenches of semiconductors, including:

[0007] S1. According to the relationship curve between the different pressures of the process gas and the corresponding growth rate, obtain the process parameters corresponding to the slope of the relationship curve being less than zero;

[0008] S2. Form trenches on the substrate;

[0009] S3. Introduce the first process gas and the second process gas, and perform a chemical vapor deposition process according to the process parameters to form a polysilicon thin film, and the polysilicon thin film fills the trenches;

[0010] Wherein, the process parameters remain unchanged during the chemical vapor deposition process; the first process gas is DCS, and the second process gas is HCL.

[0011] Optionally, the process parameters include temperature, chamber pressure, and the partial pressure ratio of the first process gas and the second process gas.

[0012] Optionally, the temperature ranges from 850 to 1000 °C.

[0013] Optionally, the pressure ranges from 10 to 200 torr.

[0014] Optionally, the partial pressure ratio ranges from 0.6 to 0.9.

[0015] Optionally, the polysilicon thin film is polysilicon.

[0016] Optionally, the sidewall of the trench is one of silicon dioxide, silicon nitride, or silicon oxynitride.

[0017] Optionally, the trench is a deep trench isolation trench.

[0018] Optionally, the trench is an inverted V-shaped trench.

[0019] Optionally, the trench is a bowl-shaped trench.

[0020] Optionally, the maximum width of the trench ≤ 1.8 times the width of the trench opening.

[0021] Optionally, the depth-to-width ratio of the trench ranges from 15 to 25.

[0022] Optionally, the chemical vapor deposition process is carried out in a reduced-pressure epitaxial device.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The process provided by the present invention can perfectly fill the trench, especially irregular trenches such as inverted V-shaped trenches and bowl-shaped trenches, without forming gaps.

[0025] 2. During the process of the present invention, the process parameters remain unchanged, so there will be no problem of overcharge of temperature or pressure, and at the same time, the time for switching between different temperatures and different pressures is saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for description will be briefly introduced below. Obviously, the drawings in the following description are an embodiment of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts:

[0027] Figure 1 is a schematic diagram of the prior art;

[0028] Figure 2Schematic diagram of the trench filling process of the present invention;

[0029] Figure 3 Experimental graph of the relationship curve of the present invention;

[0030] Figure 4 Cross-section of the trench of the present invention;

[0031] Figure 5 Schematic diagram of the filling process of the present invention applied to the filling of deep trench isolation trenches;

[0032] Figure 6 Diagram of the trench filled by the filling process of the present invention;

[0033] Figure 7 Schematic diagram of the reduced pressure epitaxial equipment of the present invention. Detailed implementation manners

[0034] The following further elaborates in detail on the solution proposed by the present invention in conjunction with the accompanying drawings and specific implementation manners. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are in a very simplified form and all use non-precise scales, only for conveniently and clearly assisting in explaining the purpose of the implementation manners of the present invention. In order to make the purpose, features, and advantages of the present invention more obvious and understandable, please refer to the accompanying drawings. It should be known that the structures, scales, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have a substantial technical meaning. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed by the present invention.

[0035] Figure 2 The schematic diagram of the trench filling process of the present invention is shown. As Figure 2 shown, the present invention discloses a method for filling trenches in a semiconductor, including:

[0036] S1. According to the relationship curve between the different pressures of process gases and the corresponding growth rates, obtain the process parameters corresponding to the slope of the relationship curve being less than zero;

[0037] S2. Form trenches on the substrate;

[0038] S3. Introduce a first process gas and a second process gas, and perform a chemical vapor deposition process according to the process parameters to form a polysilicon thin film, and the polysilicon thin film fills the trenches;

[0039] Among them, the process parameters remain unchanged during the chemical vapor deposition process, that is, in step S3, when the growth chemical vapor deposition process is carried out, the process parameters are invariant with time; the first process gas is DCS, and the second process gas is HCL. The polysilicon thin film is polysilicon.

[0040] The present invention discovers that for polysilicon thin films deposited with DCS and HCL as process gases under some special process parameters, the following phenomenon exists: under some process parameters, as the pressure of DCS decreases, the film growth rate increases instead. Therefore, gaps and defects will not occur when filling trenches under these process parameters.

[0041] Among them, in step S1, it further includes: first obtaining a relationship curve. Figure 3 The experimental graph showing the relationship curve Figure 3 where the abscissa is the pressure of the process gas (normalized value), the ordinate is the growth rate (normalized value), and groups B1, B2, B3, and B4 correspond to different temperature conditions. As Figure 3 shown, the relationship curve can be obtained through experiments. Obtaining the relationship curve includes:

[0042] S11. Under the same process parameters, introduce the first process gas and the second process gas, deposit different polysilicon thin films on the wafer surface corresponding to different pressures, and respectively obtain the growth rates of the different polysilicon thin films to obtain the relationship curve; among them, the process parameters include temperature, chamber pressure, and the partial pressure ratio of the first process gas and the second process gas.

[0043] S12. Change the process parameters and repeat step S11. Preferably, the process parameters are changed by the method of controlling variables.

[0044] In step S11, specifically, in a reduced-pressure epitaxial device, place the wafer, introduce the first process gas and the second process gas, change the pressure of the process gas, and through multiple experiments, each experiment uses a different pressure to deposit a polysilicon thin film on the wafer surface, obtain the growth rates corresponding to different pressures, and obtain the relationship curve; among them, the wafer is a non-pattern wafer; the sampling points of the pressure are 3 - 5, that is, select different 3 - 5 pressures; the pressure is the partial pressure, preferably, the partial pressure is the partial pressure of DCS.

[0045] Through Figure 3It can be seen that taking the C11 curve in Group B1 as an example: under the same process parameters (temperature of 850 °C, partial pressure ratio of 0.65, chamber pressure of 10 torr), the first process gas (DCS) and the second process gas (HCL) are introduced. In the first experiment, polysilicon thin film is deposited on the wafer surface at the first pressure, and the growth rate corresponding to the first pressure can be obtained, namely point A11; in the second experiment, polysilicon thin film is deposited on the wafer surface at the second pressure, and the growth rate corresponding to the second pressure can be obtained, namely point A12; in the third experiment, polysilicon thin film is deposited on the wafer surface at the third pressure, and the growth rate corresponding to the third pressure can be obtained, namely point A13. The partial relationship curve is obtained by fitting the three points A11, A22, and A33.

[0046] In step S12, specifically, the process parameters are changed by the method of controlling variables to repeat step S11. The process parameters specifically include changing the temperature, chamber pressure, and partial pressure ratio, that is, changing one of the process parameters to repeat step S11. Continue to refer to Figure 3 Group B1 in. The partial pressure ratio is changed to 2, and other process parameters remain unchanged. Step S11 is repeated to obtain the relationship curve C12. Similarly, by analogy, more relationship curves C21, C22, C31, C32, C33, C41, C42, C43, and C44 can be obtained.

[0047] Optionally, the range of the temperature is 850 - 1000 °C. The range of the chamber pressure is 10 - 200 torr. The range of the partial pressure ratio is 0.6 - 0.9.

[0048] In step S2, semiconductor processing is started. First, a trench is formed on the surface. Optionally, the maximum width of the trench ≤ 1.8 times the width of the trench opening, and the aspect ratio of the trench ranges from 15 - 25. The filling of the above trenches is difficult. Preferably, the trench is an inverted V-shaped trench, as shown in Figure 4 (a) of. From the opening 201 to the middle 203 and then to the lower part 203 of the inverted V-shaped trench, the width of the trench gradually increases; or the trench is a bowl-shaped trench, as shown in Figure 4 (b) of. The width of the middle 203 of the bowl-shaped trench is greater than the width of the opening 201 and the lower part 203. The process of the present invention can make the growth rate of the polysilicon thin film in the lower part 203 of the trench greater than the growth rate of the polysilicon thin film in the opening 201. Therefore, no gap exists in the formed film, and the trench can be perfectly filled. Further preferably, step S2 further includes: screening a set of process parameters according to the aspect ratio of the trench. According to the method of step S1, multiple sets of process parameters that meet the conditions can be obtained (see Figure 3) That is, multiple sets of process parameters with a slope less than zero. Select a suitable set of process parameters according to the aspect ratio of the trench. The filling effect of the trench is better, and at the same time, the growth rate is fast, saving costs. Preferably, the chamber pressure is 10 - 50 torr, the temperature is 850 - 950 °C, and the partial pressure ratio is 0.6 - 0.9.

[0049] Specifically, the screening includes: determining whether the aspect ratio < 20:1. If so, in the process parameters, the chamber pressure is selected as 40 - 50 torr, the temperature is selected as 900 - 950 °C, and the partial pressure ratio is selected as 0.8 - 0.9.

[0050] Determine whether the aspect ratio ≥ 20:1. If so, in the process parameters, the chamber pressure is selected as 10 - 40 torr, the temperature is selected as 850 - 900 °C, and the partial pressure ratio is selected as 0.7 - 0.8. Preferably, it further includes: further determining whether the maximum width of the trench ≥ 1.4 times the width of the trench opening. If so, the partial pressure ratio is selected as 0.6 - 0.7, and the process parameters corresponding to the growth rate of the lower part of the trench being 1.5 times the growth rate of the trench opening are selected.

[0051] In step S3, specifically, a first process gas and a second process gas are introduced into the reduced-pressure epitaxial equipment, and a polysilicon thin film is formed by chemical vapor deposition according to the process parameters.

[0052] The above process method is applied to deep trench isolation trenches, and the phenomenon of negative slope is more obvious and easier to occur. Figure 5 Shows a schematic diagram applied to the filling of deep trench isolation trenches, as Figure 5 shown, including the following steps:

[0053] Deposit a mask 303 on the surface of the substrate 301. Among them, the substrate 301 is a silicon substrate, and the mask 303 is silicon nitride. The substrate 301 includes a plurality of device regions 302.

[0054] Etch the substrate 301 to form a trench 304, as Figure 5 shown in (a). Among them, the trench 304 is the Figure 4 trench in. The trench 304 is formed between the device regions 302 for forming deep trench isolation.

[0055] Deposit an oxide layer 305, as Figure 5 shown in (b). Among them, the oxide layer 305 is located on the inner surface of the trench 304 and the surface of the mask 303, and the oxide layer 305 is one of silicon dioxide, silicon nitride, or silicon oxynitride.

[0056] Etch the oxide layer 305 at the bottom of the trench 304 and the oxide layer 305 on the surface of the mask 303, as Figure 5 shown in (c). That is, an oxide layer 305 is formed only on the sidewalls of the trench.

[0057] A chemical vapor deposition process is performed to form a polysilicon thin film 306, and the polysilicon thin film fills the trench 304, as shown in Figure 5 (d) thereof. Among them, the polysilicon thin film 306 is polysilicon.

[0058] Figure 6 A diagram showing a trench filled by using the thin film growth method of the present invention, and the trench is a bowl-shaped trench. As shown in Figure 6 (a) thereof shows a slice with incomplete trench filling. It can be seen that the growth rate at the lower part of the trench is greater than the growth rate at the opening of the trench, so the generation of gaps is avoided. Figure 6 (b) thereof shows a slice with completed filling, and the result shows that the trench is completely filled and there are no cracks.

[0059] Figure 7 A schematic diagram of a reduced-pressure epitaxial device is shown, as shown in Figure 7As shown, the reduced-pressure epitaxial growth apparatus 100 is applied to the process method of the present invention. The reduced-pressure epitaxial growth apparatus includes a chamber, an intake pipeline 102, a gas injection plug 110, a heating assembly 106, a temperature measuring instrument 108, a rotary support assembly, an outlet plug 134, an exhaust connection member 158, and an exhaust pipeline 103. The chamber includes a wall portion 112 (i.e., a side wall), a bushing assembly (including an upper ring body 114 and a lower ring body 116), an upper dome 118, a lower dome 120, an upper flange 122, and a lower flange 124. The wall portion 112 is generally annular, and its inner surface is a cylindrical shape penetrating up and down. The wall portion 112 is made of a metal material. The upper ring body 114 and the lower ring body 116 are both ring bodies formed of quartz and are disposed on the inner surface of the wall portion 112. The upper dome 118 is generally circular or pot-lid-shaped formed of quartz, and the lower dome 120 is generally conical funnel-shaped formed of quartz. The upper ring body 114 is disposed above the lower ring body 116 to form a bushing assembly, and a gas inlet and a gas outlet are respectively formed at two opposite sides of the bushing assembly for the entry and discharge of process gas. The upper dome 118 is disposed above the upper ring body 114, and the upper dome 118 is fixed above the wall portion 112 through the upper flange 122. The lower dome 120 is disposed below the lower ring body 116, and the lower dome 120 is fixed below the wall portion 112 through the lower flange 123. The heating assembly 106 is disposed above and below the chamber, and the emitted infrared light can penetrate the upper dome 118 and the lower dome 120 and enter the chamber to provide heating energy for the chamber. The rotary support assembly includes a base 123, a rotary support shaft 124, a lifting support frame 126, and a pin 128. The base 123 is horizontally disposed inside the reaction chamber and is used to horizontally carry a wafer 130 (or a substrate) to be processed. Specifically, the base 123 is disposed at the center of the ring body of the bushing assembly and is located between the gas inlet and the gas outlet. The upper surface of the base 123 and the gas inlet and the gas outlet are at the same horizontal plane. The rotary support shaft 124 is used to support the rotation and lifting of the base 122, and the lifting support frame 126 is used to support the pin 128 when the rotary support shaft 124 descends, so as to separate the substrate 130 from the base 123 during the transfer of the substrate. The temperature measuring instrument 108 is disposed above and below the chamber and is used to monitor the temperature near the substrate 130. The reduced-pressure epitaxial growth apparatus 100 further includes a preheating ring 132 and a pump. The preheating ring 132 is disposed around the base 123 and is used to preheat the process gas entering the chamber.The intake pipeline 102 is connected to the gas inlet through the gas injection plug 110 and is used to introduce the process gas into the chamber. The gas injection plug 110 is inserted into the gap of the wall portion 112 in the intake direction. The heating component 106 heats and decomposes the process gas, which is deposited on the surface of the substrate 130, thereby forming a polysilicon thin film on the substrate 130. The outlet plug 134 is inserted into the gap of the wall portion 112 in the outlet direction. One end of the outlet plug 134 is connected to the gas outlet of the bushing assembly, and the other end of the outlet plug 134 is connected to the exhaust connection member 136. The gas outlet of the exhaust connection member 158 is connected to the exhaust pipeline 103, and the pump is connected to the exhaust pipeline 103 and is used to discharge the gas in the reaction chamber. Process waste gas enters the exhaust pipeline 103 from the outlet plug 134 through the exhaust connection member 136 and is discharged from the chamber through the pump. The pump is also used to provide negative pressure for the reaction chamber.

[0060] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element. In addition, the term "connected" in this text means that A and B are directly connected, or means that A and B are indirectly connected. Indirect connection is such that A and B are connected through C, or even through more components such as C and D. The connection between A and B can be integral or separate, detachable or fixed. The term "optional" in this text means that this technical feature can be combined or not combined with any feature in the text.

[0061] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A trench filling method for a semiconductor, characterized in that, Including: S1. Obtain the process parameters corresponding to the slope of the relationship curve being less than zero according to the relationship curve between the different pressures of the process gas and the corresponding growth rates; S2. Form grooves on the substrate; S3. Introduce the first process gas and the second process gas, and perform a chemical vapor deposition process according to the process parameters to form a polysilicon film, and the polysilicon film fills the grooves; Wherein, the process parameters remain unchanged during the chemical vapor deposition process; The first process gas is DCS, and the second process gas is HCL.

2. The trench filling method of a semiconductor according to claim 1, wherein, The process parameters include temperature, chamber pressure, and the partial pressure ratio of the first process gas and the second process gas.

3. The trench filling method of a semiconductor according to claim 2, wherein, The range of the temperature is 850 - 1000 °C.

4. The trench filling method of a semiconductor according to claim 2, wherein, The range of the pressure is 10 - 200 torr.

5. The trench filling method for a semiconductor according to claim 2, characterized in that, The range of the partial pressure ratio is 0.6 - 0.

9.

6. The trench filling method for a semiconductor according to any one of claims 1-5, characterized in that The polysilicon film is polysilicon.

7. The trench filling method of a semiconductor according to any one of claims 1-5, characterized in that, The side walls of the grooves are one of silicon dioxide, silicon nitride, or silicon oxynitride.

8. The trench filling method for a semiconductor according to any one of claims 1-5, characterized in that, The grooves are deep trench isolation grooves.

9. The trench filling method of a semiconductor according to claim 1, characterized in that, The grooves are inverted V-shaped grooves.

10. The trench filling method for a semiconductor according to claim 1, wherein The grooves are bowl-shaped grooves.

11. The trench filling method of a semiconductor according to claim 9 or 10, characterized in that, The maximum width of the grooves ≤ 1.8 times the width of the groove openings.

12. The trench filling method of a semiconductor according to claim 9 or 10, characterized in that, The range of the depth-to-width ratio of the grooves is 15 - 25.

13. The trench filling method of a semiconductor according to any one of claims 1-5, characterized in that, The chemical vapor deposition process is carried out in a reduced-pressure epitaxial device.

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