WO2015021932A1

WO2015021932A1 - Substrate etching method

Info

Publication number: WO2015021932A1
Application number: PCT/CN2014/084373
Authority: WO
Inventors: 蒋中伟
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: 2013-08-16
Filing date: 2014-08-14
Publication date: 2015-02-19
Also published as: TWI532095B; TW201515085A; CN104370268A; CN104370268B

Abstract

A substrate etching method includes the following steps: step of a round corner basic shape etching: feeding etching gas into a reaction chamber and turning on an excitation power supply and a bias voltage power supply, thereby forming the corner basic shape of a groove sidewall top on the boundary of a mask-covered area and a non mask-covered area on the substrate; step of a groove depth etching: keeping feeding the etching gas to the reaction chamber while keeping the excitation power supply and the bias voltage power supply on or keeping the excitation power supply on alone, thereby etching the groove to a predetermined depth so that the projection of the groove on the plane perpendicular to the groove length presents such a shape that the sidewall top of the groove is a round angle. The etching gas is gas mixture comprising at least one of fluorocarbon type or hydrofluorocarbons type gas, oxygen, and fluorine type gas free of carbon and hydrogen. The substrate etching method not only forms a sidewall profile having a smooth round angle on the top of the sidewall, but also increases the etching degree and the etching ratio.

Description

Substrate etching method

The present invention relates to the field of semiconductors, and in particular, to a substrate etching method. Background technique

In recent years, MEMS (Micro-Electro-Mechanical System) devices and MEMS devices have been increasingly used in automotive and consumer electronics, as well as TSV (Through Silicon Via) technology in the future. With broad prospects in the field of packaging, dry plasma deep silicon etching processes are becoming one of the most sought-after processes in MEMS processing and TSV technology.

Etching trenches on a substrate is a common etch process, and the etched topography requirements for trenches are different for different applications. For example, in the field of packaging, it is often necessary to obtain a trench topography having inclined sidewalls according to process requirements; and, in order to ensure the performance and stability of the device, it is usually required to have a certain topography on the top of the sidewall. Referring to Figure 1, there is shown a trench topography of a slanted sidewall in the prior art. As shown in Fig. 1, the size of the opening of the mask on the substrate is smaller than the size of the opening of the substrate, and the side walls of the groove are inclined.

The existing substrate etching method mainly includes the following steps:

Rounded corner topography etching step: for forming a top fillet on the sidewall of the trench at a position where the mask meets the substrate;

Trench deep etching step: The trench is etched on the substrate to a predetermined depth. In the above-described rounded basic topography etching step, the etching gas is a mixed gas of at least one of C _x H _y F _z gas (hydrocarbon-based gas) and HBr gas, wherein x, y, z Both are positive integers. In the above trench deep etching step, the etching gas is mixed with at least one of C _x F _y gas (carbon fluoride-based gas) and HBr, He and 0 ₂ , wherein x, y Both are positive integers.

The above substrate etching method inevitably has the following problems in practical applications: First, the etching depth of the substrate etching method is 4000~500θΑ, and the etching depth is small, so that the etching depth is not required to be satisfied. Process.

Second, the etching process of the above substrate etching method is 200-500 nm/min, and the etching rate is low, so that the production efficiency is low, and the demand for large-scale production cannot be satisfied.

Third, in the above-mentioned rounded basic topography etching step, a smooth rounded corner is obtained at the top of the sidewall by depositing reaction by-products of the C _x H _y F _z gas at the interface between the mask and the substrate. This deposition method is only applicable to a process in which the size of the opening of the trench is substantially equal to the size of the opening of the mask, and the process of the mask opening size shown in FIG. 1 is smaller than the size of the opening of the trench (the so-called "undercut phenomenon"). In other words, the reaction by-products of the C _x H _y F _z gas cannot be deposited on the top of the sidewall due to the blocking of the mask, so that a rounded rounded corner cannot be obtained at the top of the sidewall. Summary of the invention

The present invention aims to at least solve one of the technical problems existing in the prior art, and proposes a substrate etching method which can not only obtain a groove top shape having rounded rounded corners on the sidewall, but also can improve etching depth and Etching rate.

To achieve the object of the present invention, a substrate etching method is provided, which comprises the following steps: a rounded basic topography etching step, an etching gas is introduced into the reaction chamber, and an excitation power source and a bias power source are turned on to Etching the intersection of the covered area of the mask and the uncovered area to form a basic topography of the fillet at the top of the trench sidewall;

The trench deep etching step continues to pass the etching gas into the reaction chamber, and keeps the excitation power source and the bias power source turned on, or only keeps the excitation power source turned on, so that the trench reaches a predetermined depth, and the trench is vertical The projection in the plane of the length direction of the groove exhibits a form: that is, the top of the side wall of the groove is rounded;

Wherein the etching gas is at least one of a fluorocarbon or a hydrofluorocarbon gas, A mixed gas of oxygen and a fluorine-based gas containing no carbon or hydrogen.

Wherein, the fluorine-based gas containing no carbon and hydrogen includes SF ₆ or NF ₃ .

Preferably, the fluorocarbon-based gas comprises C4F ₈ and/or C ₅ F ₈ and/or C ₂ F ₆ .

Preferably, the hydrofluorocarbon-based gas comprises CH ₃ F and/or CH ₂ F ₂ .

Wherein, in the rounded basic topography etching step, the content of the fluorocarbon or hydrofluorocarbon gas in the reaction chamber is the sum of the content of the oxygen and the fluorine-containing gas containing no carbon and hydrogen The ratio is between 1:1 and 1:10.

Preferably, in the rounded basic topography etching step, the content of the fluorocarbon or hydrofluorocarbon gas in the reaction chamber is equal to the content of the oxygen and the fluorine-containing gas containing no carbon and hydrogen. The ratio of the sum is between 1:3 and 1:5.

Wherein the ratio of the content of the fluorocarbon or hydrofluorocarbon gas in the reaction chamber to the sum of the content of the oxygen and the fluorine-containing gas containing no carbon and hydrogen in the trench deep etching step Between 15: 1 and 2: 1.

Preferably, in the trench deep etching step, the content of the fluorocarbon or hydrofluorocarbon gas in the reaction chamber is the sum of the content of the oxygen and the fluorine-containing gas containing no carbon and hydrogen. The ratio is between 10:1 and 5:1.

Wherein, the flow rate of the fluorine-containing gas containing no carbon and hydrogen is 100 to 2000 sccm.

The flow rate of the fluorocarbon or hydrofluorocarbon gas is 100 to 2000 sccm.

Wherein, in the rounded basic topography etching step, the chamber pressure of the reaction chamber is 10 to 120 mT.

Preferably, in the rounded basic topography etching step, the chamber pressure of the reaction chamber is 40 to 90 mT.

Wherein, in the trench deep etching step, the chamber pressure of the reaction chamber is 120-250 mT.

Preferably, in the trench deep etching step, the chamber pressure of the reaction chamber is

150~200mT. The bias power output of the bias power source ranges from 15 to 50 W in the rounded basic topography etching step; and the excitation power output of the excitation power source ranges from 500 to 5000 W.

Preferably, in the rounded basic topography etching step, the bias power output of the bias power source ranges from 20 to 30 W.

The bias power output of the bias power source ranges from 0 to 15 W in the trench depth etching step; and the excitation power output of the excitation power source ranges from 500 to 5000 W.

Preferably, in the trench depth etching step, the bias power supply output bias power ranges from 0 to 10 W.

Wherein, the flow rate of the oxygen is 10 to 100 sccm.

Preferably, the flow rate of the oxygen gas is 30 to 70 sccm.

Preferably, helium gas or argon gas is supplied as an auxiliary gas while an etching gas is introduced into the reaction chamber.

The invention has the following beneficial effects:

The substrate etching method provided by the present invention uses a mixed gas of at least one of a fluorocarbon and/or a hydrofluorocarbon gas, oxygen, and a fluorine gas containing no carbon and hydrogen. As an etching gas, a fluorine-based gas containing no carbon and hydrogen can enhance isotropic etching, and a fluorocarbon or hydrofluorocarbon gas can enhance anisotropic etching, which makes the basic shape of the rounded corner In the etching step, the top of the sidewall can be directly etched by introducing a relatively high proportion of fluorocarbon or hydrofluorocarbon gas into the reaction chamber and a relatively low proportion of fluorine and gas containing no carbon and hydrogen. The groove has a rounded rounded corner, which is not only suitable for requiring the groove opening size and the mask opening as compared with the prior art in which the reaction byproduct produced by the etching gas is deposited on the top of the sidewall to obtain a rounded corner. The process is basically equivalent in size, and is also applicable to a process requiring a mask opening size smaller than the size of the trench opening, so that the substrate etching method provided by the present invention has a wider application range. Moreover, in the trench deep etching step, a relatively low proportion of fluorocarbon or hydrofluorocarbon gas is introduced into the reaction chamber, and a relatively high ratio is not Fluorine-containing gases containing carbon and hydrogen can achieve higher etching depths and etching rates, thereby improving process efficiency. DRAWINGS

1 is a cross-sectional view showing a groove shape of a slanted side wall in the prior art;

2 is a flow chart of a substrate etching method according to an embodiment of the present invention;

3A is a schematic diagram of a process of etching a fillet basic topography in a substrate etching method according to an embodiment of the present invention;

3B is a schematic diagram of a process of a trench deep etching step in a substrate etching method according to an embodiment of the present invention;

Fig. 4 is an electron micrograph of a trench topography obtained by the substrate etching method provided by the embodiment of the invention.

detailed description

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the substrate etching method provided by the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

2 is a flow chart of a substrate etching method according to an embodiment of the present invention. 3A is a schematic diagram of a process of etching a fillet basic topography in a substrate etching method according to an embodiment of the present invention; FIG. 3B is a process of a trench deep etching step in a substrate etching method according to an embodiment of the present invention; schematic diagram. Please refer to Figure 2, Figure 3A and Figure 3B together. The substrate etching method includes the following steps:

Rounded basic shape etching step: an etching gas is introduced into the reaction chamber, and an excitation power source and a bias power source are turned on to etch a trench at a boundary between a region covered by the mask on the substrate and an uncovered region. The basic topography of the fillet at the top of the sidewall is shown as circled area I in Figure 3A. Trench deep etching step: continue to pass the etching gas into the reaction chamber, and keep the excitation power supply and the bias power supply turned on (or turn off the bias power supply and only keep the excitation power on), so that the trench reaches a predetermined depth, and The etch correction is continued on the fillet basic topography area such that the projection of the groove in a plane perpendicular to the length of the groove exhibits a form: that is, the top of the trench sidewall is rounded, that is, A smooth transition between the sidewall of the trench and the upper surface of the substrate. Wherein, the angle between the sidewall of the trench and the bottom wall of the trench may be an obtuse angle, a right angle or an acute angle according to the process requirements.

Wherein, the etching gas used in the above two steps is a mixed gas of the following three types of gases: the first type of gas is at least one of a fluorocarbon and/or a hydrofluorocarbon gas, and the second type The gas is oxygen, and the third gas is a fluorine-based gas containing no carbon or hydrogen. Preferably, the fluorocarbon-based gas comprises C ₄ F ₈ and/or C ₅ F ₈ and/or C ₂ F ₆ ; the hydrofluorocarbon-based gas comprises CH ₃ F and/or CH ₂ F ₂ ; The fluorine-based gas includes SF ₆ or NF ₃ .

Since the third type of gas (ie, a fluorine-based gas containing no carbon and hydrogen) can enhance isotropic etching, the first type of gas (ie, fluorocarbon or hydrofluorocarbon) can enhance anisotropic engraving Etching, which allows a relatively high proportion of fluorocarbon or hydrofluorocarbon gases to be introduced into the reaction chamber during the etch step of the fillet basic morphology, and a relatively low proportion of fluorine and carbon-free fluorine. The gas-like gas can directly etch the rounded rounded corners at the top of the sidewall of the trench, which is not only applicable in the prior art, because the reaction by-products generated by the etching gas are deposited on the top of the sidewall to obtain rounded corners. The process of the substrate etching method provided by the embodiment of the present invention has a wider application range, and the process of the trench opening is substantially equal to the size of the mask opening, and is also applicable to a process in which the opening size of the mask is smaller than the size of the opening of the trench. Of course, the content of fluorocarbon or hydrofluorocarbon gases should not be too high to prevent the formation of a rough etched topography. In practical applications, the ratio of the content of the first type of gas in the reaction chamber to the sum of the contents of the second type of gas and the third type of gas may be between 1:1 and 1:10, preferably, Between 1:3 and 1:5.

Preferably, in the rounded basic topography etching step, the anisotropic etching can be further enhanced by using a lower chamber pressure and/or a higher bias power to obtain a specific process. The required inclined side walls (for example, the process requires that the angle between the bottom wall and the side wall of the groove be an obtuse angle). In practical applications, the chamber pressure of the reaction chamber may be 10 to 120 mT, preferably 40 to 90 mT; and the bias power output of the bias power source may range from 15 to 50 W, preferably from 20 to 30 W.

In the trench deep etching step, a relatively low proportion of the first type of gas (ie, fluorocarbon or hydrofluorocarbon gas) and a relatively high proportion of the third type gas are introduced into the reaction chamber ( That is, a fluorine-based gas containing no carbon and hydrogen) can obtain a higher etching depth and an etching rate, so that the trench can be quickly etched to a predetermined etching depth to improve process efficiency. In practical applications, the ratio of the content of the first type of gas in the reaction chamber to the sum of the contents of the second type of gas and the third type of gas is between 15:1 and 2:1, preferably, 10: 1 and 5: 1 between. Further, the content of the fluorine-containing gas containing no carbon and hydrogen should not be too high to prevent the inclination angle of the side wall from being excessively large.

Preferably, in the trench deep etching step, the isotropic etching is further enhanced by using a higher chamber pressure and/or a lower bias power, so that the etching rate can be increased. In practical applications, the chamber pressure of the reaction chamber may be 120 to 250 mT, preferably 150 to 200 mT; and the bias power output of the bias power source may range from 0 to 15 W, preferably from 0 to 10 W.

Preferably, in the rounded basic topography etching step and the trench deep etching step, the flow rate of the fluorine-containing gas containing no carbon and hydrogen may be 100 to 2000 sccm; the flow rate of the fluorocarbon or hydrofluorocarbon gas may be It is 100~2000sccm.

Preferably, in the rounded basic topography etching step and the trench deep etching step, higher excitation power can be used to further increase the etching rate. Preferably, the excitation power output of the excitation power source ranges from 500 to 5000W.

Preferably, in the rounded basic topography etching step and the trench deep etching step, an etching gas is introduced into the reaction chamber, and a non-etching gas such as helium or argon may be introduced. The reacting gas acts as an auxiliary gas. With the aid of the auxiliary gas, not only the reaction chamber can be adjusted The total gas content inside, and also the distribution of the etching gas uniformity, can improve the flexibility of process control and process uniformity.

In addition, in the rounded basic topography etching step and the trench deep etching step, by using oxygen as one of the etching gases, the sidewall tilt angle can be adjusted (which corresponds to the trench sidewall and the trench low wall). The role of the angle between. The flow rate of oxygen may be 10 to 100 sccm; preferably, 30 to 70 sccm.

A specific example of the substrate etching method provided by the present invention will now be described in detail. Specifically, the substrate etching method includes the following steps:

Rounded basic shape etching step: an etching gas is introduced into the reaction chamber, and an excitation power source and a bias power source are turned on to etch a trench at a boundary between a region covered by the mask on the substrate and an uncovered region. The topography of the top of the sidewall is substantially topographical, as shown by the circled area in Figure 3A. Wherein, the etching gas is a mixed gas of SF ₆ , C ₄ F ₈ and 0 ₂ , and the flow rate of SF ₆ is 800 sccm, the flow rate of C ₄ F ₈ is 200 sccm, and the flow rate of 0 ₂ is 60 sccm; The excitation power is 2500W; the bias power of the bias power supply is 20W; the chamber pressure of the reaction chamber is lOOmT; the etching time is 2min.

Trench deep etching step: continue to pass the etching gas into the reaction chamber, turn off the bias power supply, keep the excitation power turned on, so that the trench reaches a predetermined depth, and continue to correct the fillet basic topography area, Projecting the trench in a plane perpendicular to the length of the trench exhibits a morphology such that the top of the trench sidewall is rounded, that is, the sidewall of the trench is rounded between the upper surface of the substrate Transition, and the angle between the sidewall of the trench and the bottom wall of the trench is an obtuse angle, as shown in Figure 3B. Wherein, the flow rate of SF ₆ is 800 sccm, the flow rate of C ₄ F ₈ is lOOsccm, the flow rate of 0 ₂ is 50 sccm, the excitation power of the excitation power supply is 2500 W, the monthly chamber pressure of the reaction chamber is 200 mT, and the etching time is 5 min. .

Referring to FIG. 4, there is shown an electron micrograph of the trench topography obtained by the substrate etching method provided by the embodiment of the invention. As shown in FIG. 4, the sidewall of the trench is inclined, and the top of the sidewall has a rounded rounded corner, and the total process time for etching the trench is 8 min. This shows that The substrate etching method provided in this embodiment can not only obtain the groove shape with the sidewall inclined and the rounded top of the sidewall, but also can improve the etching depth and the etching rate. Exemplary embodiments, however, the invention is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and scope of the invention. These modifications and improvements are also considered to be within the scope of the invention.

Claims

letter of request

1. A substrate etching method, characterized in that it includes the following steps:

Basic fillet morphology etching steps: Pour etching gas into the reaction chamber, and turn on the excitation power supply and bias power supply to etch to form a trench at the junction of the mask-covered area and the uncovered area on the substrate. The basic shape of the fillet at the top of the side wall;

Trench depth etching step: Continue to introduce etching gas into the reaction chamber, and keep the excitation power supply and bias power supply on, or just keep the excitation power supply on, so that the trench reaches the predetermined depth and the trench is vertically The projection in the plane along the length of the trench has the following shape: that is, the top of the trench sidewall is rounded;

Wherein, the etching gas is a mixed gas of at least one of fluorocarbon or hydrocarbon-fluorine gas, oxygen, and fluorine gas that does not contain carbon and hydrogen.

2. The substrate etching method according to claim 1, wherein the fluorine gas containing no carbon and hydrogen includes SF ₆ or NF ₃ .

3. The substrate etching method according to claim 1, wherein the fluorocarbon gas includes C ₄ F ₈ and/or C ₅ F ₈ and/or C ₂ F ₆ .

4. The substrate etching method according to claim 1, wherein the hydrocarbon and fluorine gas includes CH ₃ F and/or CH ₂ F ₂ .

5. The substrate etching method according to claim 1, characterized in that, in the etching step of the rounded basic shape, the content of the fluorocarbon or hydrocarbon fluorine gas in the reaction chamber is equal to the content of the fluorocarbon or hydrofluorocarbon gas in the reaction chamber. The ratio of the sum of the contents of oxygen and fluorine gases without carbon and hydrogen is between 1:1 and 1:10.

6. The substrate etching method according to claim 5, wherein the rounded corners are substantially In the morphology etching step, the ratio of the content of the fluorocarbon or hydrocarbon fluorine gas in the reaction chamber to the sum of the content of the oxygen and the fluorine gas that does not contain carbon and hydrogen is between 1:3 and 1 :5 between.

7. The substrate etching method according to claim 1, wherein in the trench depth etching step, the content of the fluorocarbon or hydrofluorocarbon gas in the reaction chamber is equal to the oxygen content. The ratio to the sum of the contents of fluorine gases that do not contain carbon and hydrogen is between 15:1 and 2:1.

8. The substrate etching method according to claim 7, wherein in the trench depth etching step, the content of the fluorocarbon or hydrofluorocarbon gas in the reaction chamber is equal to the oxygen content. The ratio to the sum of the contents of fluorine gases that do not contain carbon and hydrogen is between 10:1 and 5:1.

9. The substrate etching method according to claim 1, wherein the flow rate of the fluorine gas that does not contain carbon and hydrogen is 100~2000 sccm.

10. The substrate etching method according to claim 1, wherein the flow rate of the fluorocarbon or hydrofluorocarbon gas is 100~2000 sccm.

11. The substrate etching method according to claim 1, characterized in that, in the etching step of the rounded basic topography, the chamber pressure of the reaction chamber is 10~120mT.

12. The substrate etching method according to claim 11, characterized in that, in the step of etching the basic rounded corner topography, the chamber pressure of the reaction chamber is 40~90mT.

13. The substrate etching method according to claim 1, wherein in the trench depth etching step, the chamber pressure of the reaction chamber is 120~250mT.

14. The substrate etching method according to claim 13, characterized in that, at the depth of the trench In the etching step, the chamber pressure of the reaction chamber is 150~200mT.

15. The substrate etching method according to claim 1, wherein in the step of etching the basic rounded corner shape, the bias power output by the bias power supply ranges from 15 to 50 W; The excitation power output by the excitation power supply ranges from 500 to 5000W.

16. The substrate etching method according to claim 15, wherein in the step of etching the basic rounded corner shape, the bias power output by the bias power supply ranges from 20 to 30W.

17. The substrate etching method according to claim 1, wherein in the trench depth etching step, the bias power output by the bias power supply ranges from 0 to 15 W; the excitation power supply The output excitation power ranges from 500 to 5000W.

18. The substrate etching method according to claim 17, wherein in the trench depth etching step, the bias power output by the bias power supply ranges from 0 to 10 W.

19. The substrate etching method according to claim 1, wherein the flow rate of oxygen is 10~100 sccm.

20. The substrate etching method according to claim 19, characterized in that the flow rate of the oxygen is 30~70 sccm.

21. The substrate etching method according to claim 1, wherein while the etching gas is introduced into the reaction chamber, helium or argon is introduced as an auxiliary gas.