WO2015074621A1

WO2015074621A1 - Etching method for controlling micro-loading effect of depth of shallow trenches

Info

Publication number: WO2015074621A1
Application number: PCT/CN2014/092156
Authority: WO
Inventors: 符雅丽; 李国荣; 杨盟
Original assignee: 北京北方微电子基地设备工艺研究中心有限责任公司
Priority date: 2013-11-25
Filing date: 2014-11-25
Publication date: 2015-05-28
Also published as: CN104658882B; CN104658882A; TW201521112A; TWI609423B

Abstract

An etching method for controlling the micro-loading effect of the depth of shallow trenches comprises the following steps: etching the mask layers on the wafer entering a process chamber, until the openings on the wafer contact with the Si substrate of the wafer; feeding deposition gases into the process chamber to carry out deposition reaction, in order to deposit a layer of polymer-like film preventing from thickness etching; feeding inert gases into the process chamber and processing the polymer-like film under the condition of plasma excitation; carrying out a shallow trenching etching process on the wafer till the predetermined depth. It can effectively reduce or eliminate the micro-loading effect of etching depth during the etching of the trenches, need no additional processes with simple operation and relatively short elapsed-time, and furthermore can adjust with great flexibility by controlling the process parameter, such as time, for special equipment process.

Description

Etching method for controlling micro-load effect of shallow trench depth

Technical field

The present invention relates to the field of semiconductor device manufacturing, and more particularly to an etching method for controlling the shallow micro-load effect of shallow trenches.

Background technique

Generally, for the trench etching of different opening sizes on the wafer, there is a certain difference in the depth after the etching is completed. The micro-loading effect is the rate of volatilization of the by-product of the etching process. Caused by the difference in etching aspect ratio. In recent years, with the advancement of semiconductor process nodes, the control requirements for the deep load effect of trench etching have become higher and higher. Especially for Shallow Trench Isolation-ETching (STI-ET), this loading effect affects the electrical results of semiconductor devices. Due to the existence of the basic physical principles of reactant consumption and diffusion, this loading effect is difficult to eradicate by simple adjustment of the process parameters of the ordinary etching process, especially when the node continues to shrink, the load effect continues to increase, giving The etching process poses great challenges. After the trench etching of the wafer in the conventional technology, the micro load effect is as shown in FIG. 1 , wherein in the wafer 100, the photoresist 101, the mask layer 102, and the silicon oxide layer are sequentially in order from top to bottom. 103, the base silicon 104, and the wafer 100 further includes a small opening area 110 and a large opening area 120.

In response to the above problems in the conventional process, an improvement scheme has been proposed. After the shallow trench etching is performed to a certain depth, the load effect is compensated by selectively growing silicon in the large opening region 120, and then shallow trench etching is performed to reach the target depth. However, this modification scheme is complicated, and includes not only an etching process but also a series of processes such as epitaxial growth, and in particular, the method of selectively performing epitaxial growth is too cumbersome. In this way, the processing cycle is greatly extended and the production cost is increased.

In summary, how to provide a simple and effective way to reduce the micro-loading effect of trench etching The eclipse method is an urgent problem to be solved.

Summary of the invention

Based on this, it is necessary to provide an etching method capable of effectively reducing the micro-loading effect of the wafer trench etching depth.

An etching method for controlling shallow trench depth micro-loading effect provided for the purpose of the present invention includes the following steps: mask etching a wafer entering a process chamber until an opening on the wafer contacts Substrate silicon to the wafer; depositing a deposition gas into the process chamber to perform a deposition reaction, depositing a polymer-like film layer on the wafer that blocks the subsequent etching; The inert gas is introduced into the process chamber, and the polymer film layer is processed under plasma excitation conditions; the wafer is subjected to a shallow trench etching process to a predetermined depth.

Wherein, the polymer-like film layer which blocks the subsequent etching is a polymer-like film layer having carbon and hydrogen components.

Wherein, the polymer-like film layer which blocks the subsequent etching is a SiO ₂ -based film layer.

Wherein, in the step of depositing a deposition gas into the process chamber, performing a deposition reaction, and depositing a polymer-like film layer for blocking the subsequent etching on the wafer, the polymer The thickness of the film layer is from 10 angstroms to 300 angstroms.

Wherein, after the step of performing the shallow trench etching process on the wafer up to the preset depth, the method further comprises the step of: removing the photoresist remaining in the wafer by ashing.

Wherein, the deposition gas is CH ₄ or a combination of SiH ₄ and O ₂ .

Wherein, the inert gas is Ar and/or He.

Wherein, the thickness of the polymer-like film layer is controlled by the deposition time.

Wherein the inert gas is introduced into the process chamber, and the polymer film layer is treated under plasma excitation conditions, including the steps of: introducing an inert gas into the process chamber; Treating the polymer film layer under excitation conditions; The point detection method captures the moment when the small-sized open area of the wafer exposes the base silicon, ends the current step, and completes the step of processing the polymer-like film layer.

The process condition of performing a mask etching process on the wafer entering the process chamber until the opening on the wafer contacts the base silicon of the wafer is: source power It is 400-700W, the bias power is 100-300W, the air pressure is 3mt~10mt, the etching time is 10~40s per step, the main gas is CF ₄ and CH ₂ F ₂ , the flow rate is 50-350sccm, and the auxiliary gas is O. ₂ , Ar, He, the auxiliary gas flow rate other than oxygen is 50 ~ 150sccm, oxygen flow rate is 5 ~ 30scc;

The process condition of the process step of depositing a deposition gas into the process chamber to perform a deposition reaction and depositing a polymer-like film layer for blocking the subsequent etching on the wafer is: source power 100 to 1000W, bias power is 0W ~ 50W, deposition gas flow is 10 ~ 500sccm, process pressure is 1 ~ 100mT, process time is 10 ~ 60s;

The process conditions for introducing the inert gas into the process chamber and treating the polymer film layer under plasma excitation conditions are: source power is 100-1000 W, bias power is 50 W ~300W, Ar flow rate is 10 ~ 500sccm, He flow is 10 ~ 500sccm, process pressure is 1 ~ 100mT, process time is 10-60s;

The process conditions for performing the shallow trench etching process on the wafer to a predetermined depth are: source power is 700-1200 W, bias power is 100-200 W, air pressure is 10 mt ～ 25 mt, etching time It is 70 to 100 s, the main gas is HBr, the flow rate is 300-500 sccm, and the auxiliary gas is at least one of Cl ₂ , NF ₃ , SF ₆ , N ₂ , O ₂ , and HeO ₂ , and the flow rate is 5-50 sccm.

Wherein, the process conditions of the process step of depositing a deposition gas into the process chamber, performing a deposition reaction, and depositing a polymer-like film layer for blocking the subsequent etching on the wafer are: The source power is 300-700W, the bias power is 0W, the deposition gas flow rate is 100-200sccm, the process gas pressure is 10-30mT, and the process time is 10-30s;

The process condition of the process step of injecting an inert gas into the process chamber to treat the polymer-like film layer under plasma excitation conditions is: source power is 300 to 700 W, bias power is 100 W to 200 W, Ar flow rate is 100 to 200 sccm, He flow rate is 100 to 200 sccm, process gas pressure is 5 to 20 mT, and process time is 10-20 s.

The process conditions of the process step of removing the photoresist from the wafer by the ashing process are: source power is 700-1200 W, bias power is 0 W, air pressure is 10 mt to 30 mt, and etching time is 80 ～. At 120 s, the gas is O ₂ and the flow rate is 200 to 500 sccm.

Advantageous effects of the present invention include:

The invention provides an etching method for controlling the micro-load effect of shallow trench depth, which can be used to form a trench by adding a deposition step of a polymer-like film layer and a modification step of the deposited polymer-like film layer. Etching the opposite effect of the microloading effect effectively reduces or eliminates the etch depth microloading effect in the trench etch. Moreover, the etching method for controlling the micro-load effect of shallow trench depth provided by the invention does not need to add an additional process, is simple in operation, and has a short time; and can be adjusted and controlled by process parameters such as time for specific equipment processing, and has high flexibility. . At the same time, this method can help balance the difference in critical dimensions of different opening areas of the wafer to a certain extent.

DRAWINGS

1 is a schematic view of a wafer after conventional trench etching;

2 is a flow chart of a specific embodiment of an etching method for controlling a micro-load effect of a shallow trench depth according to the present invention;

3 is a schematic view showing the structure of a wafer when step S100 is performed by the method shown in FIG. 2;

4 is a schematic structural view of a wafer when step S200 is performed by the method shown in FIG. 2;

FIG. 5 is a schematic structural view of a wafer when step S300 is performed by using the method shown in FIG. 2;

6 is a schematic structural view of a wafer when step S400 is performed by the method shown in FIG. 2;

7 is a flow chart of another embodiment of an etching method for controlling shallow trench depth microloading effects of the present invention.

detailed description

In order to make the object, the technical solution and the advantages of the present invention more clearly, the etching method for controlling the shallow groove depth micro-load effect provided by the embodiment of the present invention will be described below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The etching method for controlling the shallow trench depth micro-load effect provided by the embodiment of the present invention, as described in FIG. 2, includes the following steps:

S100, performing mask etching on the wafer entering the process chamber until the opening on the wafer contacts the base silicon of the wafer. As shown in FIG. 3, the mask layer 102 of the wafer 100 entering the process chamber is etched, and the opening on the wafer 100 is etched to contact the base silicon to complete the etching of the mask layer 100. As shown in the figure, in the wafer 100, from top to bottom, there are a photoresist layer 101, a mask layer 102, a silicon oxide layer 103, and a base silicon 104, wherein the mask layer 102 is a SIN type hard mask layer. . The wafer 100 further includes a small opening area 110 and a large opening area 120.

S200, a deposition gas is introduced into the process chamber to perform a deposition reaction, and a polymer-like film layer that blocks the subsequent etching is deposited on the wafer. As shown in FIG. 4, above the photoresist layer 101 on the surface of the wafer 100, after the mask layer 102 is etched, over the exposed regions (the small opening regions 110 and the large opening regions 120) are exposed above the base silicon, and on the opening sidewalls. A layer of polymer-like film 105 is deposited on the polymer film layer 105, which is a polymer-like film layer which has a certain barrier effect on subsequent etching.

Here, the total contact area of the small opening area 110 (ie, all the small opening areas) in the small opening area 110 and the large opening area 120 of the same opening area during the deposition of the polymer-like film layer 105 (ie, all small opening areas) The sum of the areas of the bottom of the layer 110 and the sidewalls of the polymer-depositable polymer film layer 105 is greater than the total contact area of the large opening region 120 (i.e., the bottom of the large opening region 120 and the sidewalls of the depositable polymer) The sum of the areas of the film layers 105). Cause Thus, the thickness of the polymer-like film layer 105 deposited in the large opening region 120 is greater than the thickness of the polymer-like film layer 105 deposited by the small opening region 110. Thereby playing a complementary role in the subsequent trench etching. Moreover, the deposition does not occur only at the bottom of the opening. According to the bias value of the plasma reaction conditions during the deposition process, the sidewalls of the opening are also deposited with a polymer film layer 105 of different thickness. Generally, the larger the opening area, the side wall thereof The thicker the deposited polymer-like film layer 105 will be. This difference also balances the loading effect of the opening size of the trench etching process to some extent.

S300, an inert gas is introduced into the process chamber, and the polymer-like film layer is treated under plasma excitation conditions. As shown in FIG. 5, after the polymer-based film layer 105 is treated under an inert gas atmosphere under plasma excitation conditions, the polymer-like film layer 105 at all positions of the wafer 100 is thinned or disappears. It should be noted here that the treatment is to modify the polymer-like film layer 105 to make the film layer thin or disappear. It is primarily a physical bombardment where the rate of consumption of the deposited polymer-like film layer 105 is approximately the same at different openings. Therefore, after the treatment of this step, the thickness of the polymer-like film layer 105 deposited in the large opening region 120 is still greater than the thickness of the polymer-like film layer 105 deposited in the small opening region 110. And after the treatment of this step, the thickness of the deposited deposit is proportional to the size of the opening. At the same time, a small amount of other auxiliary gas may be added in the step for processing, such as O ₂ , N ₂ , H ₂ and the like.

S400, performing a shallow trench etching process on the wafer to a preset depth. After the two-step process of S300 and S400 described above, the process of shallow trench etching of the wafer 100 is continued until a predetermined depth is reached. The preset depth is an etch depth set according to actual needs of the semiconductor device. It should be noted here that due to the blocking of the polymer-like film layer 105, the etching speed of the large opening region 120 may be slowed relative to the original state, so that the small opening region 110 and the large opening region 120 may be etched. The depth is the same or similar, as shown in Figure 6.

The etching method for controlling the micro-load effect of the shallow trench depth provided by the embodiment of the present invention can be performed by adding a deposition step of the polymer-like film layer and a step of modifying the deposited layer. The opposite result of the trench etch microloading effect, thereby effectively reducing or eliminating the etch depth microloading effect in the trench etch. Moreover, the etching method for controlling the shallow micro-load effect of the shallow trench provided by the embodiment of the invention does not need to add an additional process, is simple in operation, has a short time, and can be adjusted and controlled by time and other process parameters for specific equipment processing, and flexibility. Big. At the same time, this method can help balance the difference in key dimensions of different opening areas of the wafer to a certain extent.

In one embodiment, the polymer-like film layer that blocks the subsequent etching is a polymer-like film layer having carbon and hydrogen components. The polymer-like film layer 105 whose main component is carbon and hydrogen is equivalent to a photoresist, which acts as a barrier to subsequent etching, thereby equivalent to a slowing of the etching rate, and a polymer film deposited due to the large opening region 120. The thickness of the layer is large, so the effect of slowing down the etching speed of the large opening region 120 is more pronounced.

In an embodiment of the invention, the polymer-like film layer which has a certain blocking effect on the subsequent etching is a SiO ₂ -based film layer. Like the polymer-like film layer whose main components are carbon and hydrogen, the SiO ₂ -type film layer can also play a role in relatively slowing the etching speed of the large opening region 120.

In one embodiment, the polymer-like film layer 105 has a thickness of 10 angstroms to 300 angstroms. In one embodiment, the etching method for controlling the shallow trench depth micro-loading effect, as shown in FIG. 7, further includes the following steps: S500, removing the photoresist remaining in the wafer by ashing.

In one embodiment, the deposition gas is CH ₄ or a combination of SiH ₄ and O ₂ . When the gas CH _{4 is} used for deposition, a polymer-like film layer mainly composed of carbon and hydrogen can be formed. When a combination of SiH ₄ and O ₂ gas is used as a deposition gas, a SiO ₂ -type film layer can be formed, which can be relatively reduced. The effect of the etch rate in the slow open area. It should be noted here that other gas combinations which can produce a similar deposited film layer are also applicable in other embodiments of the invention, such as other carbon and hydrogen containing gases.

In one embodiment, the inert gas is Ar and/or He.

In one embodiment, the thickness of the polymer-like film layer is controlled by deposition time. It should be noted here that the deposition time of the polymer-like polymer can be obtained through preliminary experiments. The TEM slice analysis can be performed after the trench etching is completed by presetting a short deposition time to verify the difference in depth at different opening sizes. If the difference is still large, the deposition time needs to be increased. This is repeated until the depth difference is reduced to an acceptable range. This is a simple process test that can be directly performed by a person skilled in the art according to the description, and will not be described in detail herein.

In other embodiments of the invention, the thickness of the polymer-like film layer can also be adjusted and controlled by other parameters of the processing process or a combination of parameters, such as source power, gas pressure, and gas flow rate.

In other embodiments of the invention, the treatment of the polymer-like polymer can also be controlled by other parameters or combinations of parameters of the processing process, such as process time, source power, gas pressure, and gas flow rate.

Preferably, in one embodiment, step S300 includes the following steps:

S310, introducing an inert gas into the process chamber;

S320, treating the polymer film layer under plasma excitation conditions;

S330, using an endpoint detection method to capture the instant that the small-sized open area of the wafer exposes the base silicon, ending the current step, and completing the step of processing the polymer-like film layer.

The embodiment of the invention can accurately grasp the time of the polymer-like treatment, make the process processing more accurate, and at the same time reduce the cost and improve the production efficiency.

In one embodiment of the present invention, the etching process for mask etching of a wafer entering a process chamber until the opening on the wafer contacts the base silicon of the wafer The process conditions of the step (ie, step S100) are: source power is 400-700 W, bias power is 100-300 W, air pressure is 3 mt to 10 mt, etching time is 10-40 s, and main gas is CF ₄ and CH. ₂ F ₂ , the flow rate is 50-350 sccm, the auxiliary gas is O ₂ , Ar, He, the auxiliary gas flow rate other than oxygen is 50-150 sccm, and the oxygen flow rate is 5-30 sccm.

Performing a process step of depositing a deposition gas into the process chamber to perform a deposition reaction, depositing a polymer-like film layer blocking the subsequent etching on the wafer (ie, step S200) The process conditions are: the source power is 100-1000W, and the bias power is 0W-50W. The deposition gas flow rate is 10 to 500 sccm, the process gas pressure is 1 to 100 mT, and the process time is 10 to 60 s.

The process step of introducing an inert gas into the process chamber to process the polymer-like film layer under plasma excitation conditions (ie, step S300) is: source power is 100-1000W The bias power is 50W to 300W, the Ar flow rate is 10 to 500 sccm, the He flow rate is 10 to 500 sccm, the process gas pressure is 1 to 100 mT, and the process time is 10-60 s.

The process conditions for performing the shallow trench etching process on the wafer to a predetermined depth (ie, step S400) are: source power is 700-1200 W, bias power is 100-200 W, and air pressure is 10 mt. ～25mt, etching time is 70-100s, main gas is HBr, flow rate is 300-500sccm, auxiliary gas is at least one of Cl ₂ , NF ₃ , SF ₆ , N ₂ , O ₂ , HeO ₂ , flow rate is 5-50 sccm.

In one embodiment of the present invention, the deposition gas is introduced into the process chamber to perform a deposition reaction, and a polymer-like film layer for blocking subsequent etching is deposited on the wafer. The process conditions of the process step (ie, step S200) are: source power is 300-700 W, bias power is 0 W, deposition gas flow is 100-200 sccm, process gas pressure is 10-30 mT, and process time is 10-30 s.

The process condition that the inert gas is introduced into the process chamber to process the polymer-like film layer under plasma excitation conditions (ie, step S300) is: source power is 300-700W The bias power is 100 W to 200 W, the Ar flow rate is 100 to 200 sccm, the He flow rate is 100 to 200 sccm, the process gas pressure is 5 to 20 mT, and the process time is 10-20 s.

In one embodiment of the present invention, the process condition of removing the photoresist ashing removal of the wafer (ie, step S500) is as follows: the source power is 700-1200 W, and the bias power is 0W, the gas pressure is 10 mt to 30 mt, the etching time is 80 to 120 s, the gas is oxygen, and the flow rate is 200 to 500 sccm.

The above-mentioned embodiments are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. Should be pointed out It is to be understood that those skilled in the art can make various modifications and improvements without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Claims

An etching method for controlling a micro-load effect of a shallow trench depth, comprising the steps of:

Performing mask etching on the wafer entering the process chamber until the opening on the wafer contacts the base silicon of the wafer;

Depositing a deposition gas into the process chamber to perform a deposition reaction, depositing on the wafer a layer of a polymer-like film that blocks the subsequent etching;

Introducing an inert gas into the process chamber to treat the polymer-like film layer under plasma excitation conditions;

The wafer is subjected to a shallow trench etch process up to a predetermined depth.
The etching method for controlling shallow trench depth micro-loading effect according to claim 1, wherein the polymer-like film layer which blocks the subsequent etching is a polymer film having carbon and hydrogen components. Floor.
The etching method for controlling the shallow trench depth micro-loading effect according to claim 1, wherein the polymer-like film layer that blocks the subsequent etching is a SiO 2 -based film layer.
The etching method for controlling the shallow trench depth micro-loading effect according to claim 2 or 3, wherein a deposition gas is introduced into the process chamber, a deposition reaction is performed, and deposition is performed on the wafer. In the step of a polymer-like film layer which blocks the subsequent etching, the polymer-like film layer has a thickness of 10 angstroms to 300 angstroms.
The etching method for controlling shallow trench depth micro-loading effect according to claim 4, wherein the step of performing a shallow trench etching process on the wafer up to a preset depth further comprises the following steps:

The photoresist remaining in the wafer is removed by ashing.
The etching method for controlling shallow trench depth micro-loading effect according to claim 4, wherein the deposition gas is CH 4 or a combination of SiH 4 and O 2 .
The etching method for controlling shallow trench depth microloading effect according to claim 4, wherein the inert gas is Ar and/or He.
The etching method for controlling shallow trench depth micro-loading effect according to claim 4, wherein the thickness of the polymer-like film layer is controlled by deposition time.
The etching method for controlling shallow trench depth micro-loading effect according to claim 4, wherein an inert gas is introduced into the process chamber, and the polymer film layer is applied under plasma excitation conditions. Processing, including the following steps:

Introducing an inert gas into the process chamber;

Treating the polymer-like film layer under plasma excitation conditions;

The end point detection method is used to grab the instant that the small-sized open area of the wafer exposes the base silicon, and the current step is completed to complete the step of treating the polymer-like film layer.
The etching method for controlling the shallow trench depth microloading effect according to claim 7, wherein

The process conditions for performing a mask etch process on the wafer entering the process chamber until the opening on the wafer contacts the base silicon of the wafer are:

The source power is 400-700W, the bias power is 100-300W, the air pressure is 3mt~10mt, the etching time is 10~40s per step, the main gas is CF 4 and CH 2 F 2 , the flow rate is 50-350sccm, auxiliary gas O 2 , Ar, He, the auxiliary gas flow rate other than oxygen is 50 ~ 150sccm, oxygen flow rate is 5 ~ 30scc;

Depositing a deposition gas into the process chamber, performing a deposition reaction, sinking on the wafer The process conditions for the process steps of stacking a polymer-like film layer that blocks the subsequent etching are:

The source power is 100-1000W, the bias power is 0W-50W, the deposition gas flow rate is 10-500sccm, the process gas pressure is 1-100mT, and the process time is 10-60s;

The process conditions of the process step of introducing an inert gas into the process chamber and treating the polymer-like film layer under plasma excitation conditions are:

The source power is 100-1000W, the bias power is 50W-300W, the Ar flow rate is 10-500sccm, the He flow rate is 10-500sccm, the process air pressure is 1-100mT, and the process time is 10-60s;

The process conditions for performing the shallow trench etching process on the wafer up to a preset depth are:

The source power is 700-1200W, the bias power is 100-200W, the air pressure is 10mt~25mt, the etching time is 70-100s, the main gas is HBr, the flow rate is 300-500sccm, and the auxiliary gas is Cl 2 , NF 3 , SF. 6. At least one of N 2 , O 2 , and HeO 2 having a flow rate of 5 to 50 sccm.
The etching method for controlling the shallow trench depth micro-load effect according to claim 10, wherein

The process conditions for introducing a deposition gas into the process chamber to perform a deposition reaction and depositing a polymer-like film layer for blocking the subsequent etching on the wafer are:

The source power is 300-700W, the bias power is 0W, the deposition gas flow rate is 100-200sccm, the process gas pressure is 10-30mT, and the process time is 10-30s;

The process conditions of the process step of introducing an inert gas into the process chamber and treating the polymer-like film layer under plasma excitation conditions are:

The source power is 300-700 W, the bias power is 100 W-200 W, the Ar flow rate is 100-200 sccm, the He flow rate is 100-200 sccm, the process gas pressure is 5-20 mT, and the process time is 10-20 s.
The etching method for controlling shallow trench depth micro-loading effect according to claim 5, wherein the process condition of the process step of removing the photoresist from the wafer is removed for:

The source power is 700-1200 W, the bias power is 0 W, the air pressure is 10 mt to 30 mt, the etching time is 80-120 s, the gas is O 2 , and the flow rate is 200-500 sccm.