WO2016074581A1

WO2016074581A1 - High aspect ratio shallow trench isolation etching method

Info

Publication number: WO2016074581A1
Application number: PCT/CN2015/093757
Authority: WO
Inventors: 符雅丽
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: 2014-11-13
Filing date: 2015-11-04
Publication date: 2016-05-19
Also published as: TWI612579B; CN105655283A; TW201618182A

Abstract

A high aspect ratio shallow trench isolation etching method is provided. The method comprises an etching step comprising a plurality of depth-etching sub-steps, said plurality of depth-etching sub-steps being used for etching the depth of a shallow trench; in each depth-etching sub-step the variable numerical value used for the process parameter representing the amount of reaction byproduct deposit accumulation changes in accordance with a first rule that decreases said amount of accumulation; alternatively, in each depth-etching sub-step the variable numerical value used for the process parameter representing the amount of reaction byproduct deposit changes in accordance with a second rule that alternately increases and decreases said amount of accumulation. The high aspect ratio shallow trench isolation etching method provided simplifies the etching steps without requiring any etching equipment modifications, but still allows for ideal trench etching contours to be achieved. The invention therefore economizes procedure time and reduces etching costs.

Description

High aspect ratio shallow trench isolation etching method

Technical field

The present invention relates to the field of microelectronics, and in particular to a shallow trench isolation etching method with high aspect ratio.

Background technique

In recent years, as the integration degree of semiconductor devices has increased, the size of individual components has become smaller and smaller. For process nodes of 32 nm and below, shallow trench isolation etching is required to have a higher aspect ratio (depth of trenches / The diameter of the trench), which has a higher requirement for the etching process for etching shallow trenches on the substrate, to obtain a trench etched topography having an ideal aspect ratio.

At present, the substrate is usually etched by a continuous etching method, that is, the total etching depth of the substrate etching is performed in one step, and the excitation power, the flow rate of the etching gas (for example, HeO), and the like are adjusted. Parameters to improve the smoothness of the sidewall profile of the trench. However, in the substrate etching process, especially when etching a substrate having a process node of 32 nm or less, the reaction by-products generated by the reaction rapidly accumulate on the sidewalls of the hard mask layer of the trench. As a result, the opening size of the substrate trench is reduced, thereby reducing the amount of plasma entering the trench, thereby causing the critical dimension of the substrate trench (such as the trench width) to be sharply reduced as the etching depth increases. Thus, a trench etched topography having an ideal aspect ratio cannot be obtained. In addition, since the by-products accumulated on the sidewalls of the hard mask layer increase the charge accumulated on the hard mask layer, the electric field generated by the charges causes the plasma to be etched from the original vertical direction. The direction toward the sidewall of the trench is deviated, causing a recessed etched topography on the sidewall of the trench, as shown in FIG.

In order to obtain an ideal trench etched morphology, another etching method is used. As shown in FIG. 2, the etching method mainly includes the following steps:

(a) An etching process using a hydrogen halide gas. The substrate 102 exposing the mask 101 is etched to a predetermined depth as shown in Fig. 2(a).

(b) An etching process using a fluorine-containing gas. That is, the etching gas is replaced with a fluorine-containing gas, and the substrate 102 is further etched as shown in Fig. 2(b).

(c) Protective film forming step. A protective film 103 is formed on the substrate 102 by sputtering, and a protective film 103 is deposited on the top of the mask 101 and the sidewalls and the bottom of the trench 104 as shown in Fig. 2(c).

(d) Protective film removal step. Only the protective film 103 on the side wall 104a of the trench 104 is left, and the remaining protective film 103 is removed as shown in Fig. 2(d).

(e) Steps (b), (c), and (d) are repeated until the trench 104 of the substrate 102 reaches the etch depth required for the process, as shown in Figure 2(e).

Although the above etching method can obtain a groove etching morphology having a desired aspect ratio to some extent, it inevitably has the following problems in practical applications:

First, since the above etching method requires a step of forming a protective film by sputtering in the etching process, and the process is accompanied by the cycles of steps (b), (c), and (d), the entire etching is performed. Repeated execution during the process results in a longer etch process.

Second, since the protective film forming process in the above etching method is performed by sputtering, and conventional etching equipment usually does not have a sputtering function, a special design of a conventional etching device is required. This leads to an increase in the manufacturing cost of the equipment.

Summary of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a high aspect ratio shallow trench isolation etching method, which can not only obtain the ideal trench etching morphology, but also can not only The etching step is simplified, and no modification to the etching apparatus is required, thereby saving process time and reducing the manufacturing cost of the apparatus.

To achieve the object of the present invention, a high aspect ratio shallow trench isolation etching method is provided, comprising an etching step, the etching step comprising a plurality of deep etching sub-steps, the plurality of deep etching sub-steps For etching the depth of the trench, wherein the value of the process parameter used in each deep etching sub-step to change the deposition amount of the reaction by-product is such that the reaction by-product deposit can be The first regular change in the amount of accumulation reduction; or the value of the process parameter used in each deep etching substep to change the amount of deposit accumulation of reaction by-products is such that the amount of deposits of the reaction by-products is increased. And reducing the second regular change between the two processes.

Wherein, the etching step further comprises a trench formation sub-step, the trench formation sub-step prior to the plurality of deep etching sub-steps, the trench formation sub-step for forming on the substrate The groove is shaped.

The first rule is: in the plurality of deep etching sub-steps, the value of the process parameter used in each deep etching sub-step is relative to the adjacent previous deep etching sub-step The value of the process parameters employed is a step-by-step variable.

The first rule is: in the plurality of deep etching sub-steps, the value of the process parameter used at the beginning of each deep etching sub-step is opposite to the end of the same deep etching sub-step The value of the process parameter used is changed by a unit variable, and the value of the process parameter initially used in each depth etching substep is the same as the end of the adjacent previous deep etching substep. The values of the process parameters used are the same.

The first rule is: in the plurality of deep etching sub-steps, the value of the process parameter used in each deep etching sub-step is first relative to the initial value of the same deep etching sub-step Recursively a unit recursive variable, and then keeps changing the value after a unit recursive variable until the end of the deep etching substep, the value of the process parameter used at the beginning of each depth etching substep and the adjacent The values of the process parameters used at the end of the last deep etch substep are the same.

Wherein, the process parameter includes at least one of a flow rate of a regulating gas, a susceptor temperature, and a chamber pressure that can change a deposit accumulation amount of a reaction by-product.

Preferably, the progressive unit recursive variables between the two adjacent deep etch sub-steps are the same.

Preferably, the process time of each deep etching sub-step is the same.

Preferably, the process time used in each deep etching sub-step ranges from 5 to 10 s.

Preferably, the conditioning gas comprises a conditioning gas that increases the amount of deposits of the reaction by-products; the flow rate of the conditioning gas used in the first deep etching sub-step ranges from 5 to 30 sccm.

Preferably, the temperature of the susceptor used in the first deep etching sub-step ranges from 50 to 60 °C.

Preferably, the chamber pressure used in the first deep etching sub-step ranges from 10 to 45 mT.

The second rule is: in the plurality of deep etching sub-steps, the value of the process parameter used in each adjacent two deep etching sub-steps is between two fixed amounts alternately.

Preferably, the process parameters include a flow rate of a conditioned gas that can change a deposit accumulation amount of the reaction by-product; and, for a conditioned gas that can increase a deposit accumulation amount on the reaction by-product, the first depth is engraved The flow rate of the conditioned gas used in the eclipse step is a larger fixed amount of the two fixed amounts; for the conditioned gas which can reduce the deposit accumulation amount of the reaction by-product, the first deep etchant The flow rate of the conditioned gas used in the step is a smaller fixed amount of the two fixed amounts.

Preferably, the values of the process parameters used in each of the two adjacent deep etching sub-steps are alternately fixed by the same amount.

The second rule is: in the plurality of deep etching sub-steps, the value of the process parameter used in each of the deep etching sub-steps is initially at the end of the same deep etching sub-step The value of the process parameter used is changed by a unit variable, and the values of the process parameters used in the initial steps of each depth etching sub-step are the same, and the end of each depth etching sub-step is adopted. The values of the process parameters are the same.

The second rule is: in the plurality of deep etching sub-steps, the value of the process parameter used in each deep etching sub-step is first relative to the initial value of the same deep etching sub-step Recursively a unit recursive variable, and then keeps changing the value of a unit recursive variable until the end of the deep etching substep, the values of the process parameters used in the initial depth etching substeps are the same, The values of the process parameters used at the end of the deep etch substep are the same.

Preferably, the plasma is always in an illuminating state from the beginning to the end of the etching step.

Preferably, the conditioning gas comprises any one of nitrogen, helium, argon, fluorine-containing gas and oxygen or a combination of at least two gases.

The invention has the following beneficial effects:

The high aspect ratio shallow trench isolation etching method provided by the present invention divides an etching step into a trench formation sub-step and a plurality of depth etching sub-steps for forming a trench prototype on a substrate, The plurality of deep etching sub-steps are used to etch the depth of the trench, and the values of the process parameters used in each deep etching sub-step to change the deposition amount of the reaction by-products may be The first regular variation of the deposit accumulation amount of the by-products can make the effect of the reaction by-product deposition layer blocking the etching reaction on the sidewalls of the trench gradually weaken as the etching time increases; or, each depth is engraved The value of the process parameter used in the eclipse step to change the amount of deposits of the by-products of the reaction is a second rule that alternates between the two processes of increasing and decreasing the amount of deposits of reaction by-products. The etch-based process and the deposition-based process are alternated throughout the etching process. By means of the various deep etching sub-steps following one of the above rules, rapid deposition of reaction by-products on the sidewalls of the mask and the top of the trench sidewalls can be avoided, and an ideal etched morphology with smooth sidewalls and no inflection points is finally obtained. At the same time, the high aspect ratio shallow trench isolation etching method provided by the present invention only needs to adjust specific process parameters without adding additional steps, which is simpler than the prior art, and requires no etching. Any modification of the etch equipment can reduce the manufacturing cost of the equipment.

DRAWINGS

1 is an electron micrograph of a trench etched morphology obtained by an existing substrate etching process;

2(a) is a schematic view showing a trench etched morphology obtained by using an etching process containing a hydrogen halide gas by another etching method;

2(b) is a schematic view showing a trench etched morphology obtained after an etching process using a fluorine-containing gas by another conventional etching method;

2(c) is a schematic view showing a trench etched morphology obtained after a protective film forming process using another conventional etching method;

2(d) is a schematic view showing a trench etched morphology obtained after a protective film removal process using another conventional etching method;

2(e) is a schematic view showing a trench etched morphology finally obtained by another etching method;

3A is a flow chart showing a high aspect ratio shallow trench isolation etching method according to a first embodiment of the present invention;

3B is a schematic view showing a trench etched morphology obtained by completing each of the deep etching sub-steps in FIG. 3A;

4 is a flow chart showing a high aspect ratio shallow trench isolation etching method according to a second embodiment of the present invention;

FIG. 5 is a flow chart showing a high aspect ratio shallow trench isolation etching method according to a third embodiment of the present invention; FIG.

6A is a flow chart showing a high aspect ratio shallow trench isolation etching method according to a fourth embodiment of the present invention;

6B is a schematic view showing a trench etched morphology obtained by completing each of the deep etching sub-steps in FIG. 6A;

7 is a flow chart showing a high aspect ratio shallow trench isolation etching method according to a fifth embodiment of the present invention;

FIG. 8 is a flow chart of a shallow trench isolation etching method for high aspect ratio according to a sixth embodiment of the present invention.

detailed description

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the high aspect ratio shallow trench isolation etching method provided by the present invention will be described in detail below with reference to the accompanying drawings.

The high aspect ratio shallow trench isolation etching method provided by the present invention comprises an etching step for etching a trench on a surface to be etched of a substrate. In the etching step, the substrate is etched by introducing an etching gas and a regulating gas into the reaction chamber, and turning on the upper electrode power source (for example, a radio frequency power source), and applying the upper electrode power source to the reaction chamber. The upper electrode power is such that the etching gas in the reaction chamber is excited to form a plasma; the lower electrode power is turned on, and the lower electrode power source applies a lower electrode power to the substrate, so that the plasma etches the substrate until the substrate is to be inscribed A trench having a predetermined etch depth is etched on the etched surface. It should be noted that the etching gas refers to a gas capable of performing etching alone, and the flow rate thereof is generally large. compare to, The etching effect of the conditioned gas is limited, and it mainly serves as an auxiliary, and the flow rate is generally small.

The etching step includes a plurality of deep etching sub-steps for etching the depth of the trench. Wherein, the value of the process parameter used in each deep etching sub-step to change the deposit amount of the reaction by-product is changed according to the first rule that can reduce the deposition amount of the reaction by-product, and the etching can be performed along with the etching With the increase of time, the effect of the reaction by-product deposition layer on the sidewall of the trench to block the etching reaction is gradually weakened; or, the value of the process parameter used in each deep etching sub-step to change the deposition amount of the reaction by-product According to the second regular variation of the deposition amount of the reaction by-product deposit between the two processes of increasing and decreasing, the etching-based process and the deposition-based process can be made throughout the etching process. process alternately. The deposit of the reaction by-product refers to a macromolecular substance which is easily deposited in the reaction by-product, which accumulates on the surface of the etching trench during the etching process.

Wherein, the etching step further comprises a trench forming sub-step, the trench forming sub-step is preceded by a plurality of deep etching sub-steps, and the trench forming sub-step is for forming a trench prototype on the substrate. The so-called trench prototype refers to a shallow groove formed in advance at a corresponding position on the substrate in order to facilitate etching to form a groove on the substrate.

By means of the various deep etching sub-steps following one of the above rules, rapid deposition of reaction by-products on the sidewalls of the mask and the top of the trench sidewalls can be avoided, and an ideal etched morphology with smooth sidewalls and no inflection points is finally obtained. At the same time, the high aspect ratio shallow trench isolation etching method provided by the present invention only needs to adjust specific process parameters without adding additional steps, which is simpler than the prior art, and requires no etching. Any modification of the etch equipment can reduce the manufacturing cost of the equipment.

Six specific embodiments of the high aspect ratio shallow trench isolation etching method provided by the present invention are described in detail below.

Specifically, FIG. 3A is a shallow trench isolation with high aspect ratio according to a first embodiment of the present invention. FIG. 3B is a schematic flow chart of the etching process obtained by completing each of the deep etching sub-steps in FIG. 3A. FIG. Referring to FIG. 3A and FIG. 3B together, in the high aspect ratio shallow trench isolation etching method provided in this embodiment, the trench formation sub-step is used to form a trench prototype on the substrate, and multiple deep etching The sub-step is used to etch the depth of the trench, and the value of the process parameter used in each deep etching sub-step to change the deposition amount of the reaction by-product is reduced according to the deposition amount of the reaction by-product. The first rule is: the first rule is: in the plurality of deep etch sub-steps, the value of the process parameter used in the next deep etch sub-step is relative to the adjacent previous deep etch sub-step The value of the process parameter is changed by a unit variable.

As shown in FIG. 3A, the etching step includes a trench formation sub-step S0 and n depth etching sub-steps for forming a trench prototype on the substrate 1, respectively S1, S2, S3, ... ..., Sn, n are positive integers, and n depth etching sub-steps are used to etch the depth of the trench formed on the substrate 1. Wherein, the value of the process parameter used in the deep etching sub-step S1 to change the deposit amount of the reaction by-product is equal to M; the process of the deep etching step S2 to change the deposit amount of the reaction by-product The value of the parameter is equal to M+x or Mx, that is, the value of the process parameter used in the deep etching sub-step S2 is relative to the value of the process parameter used in the deep etching sub-step S1 x (increasing or decreasing one unit) The value of the process parameter used in the deep etching sub-step S3 to change the deposit amount of the reaction by-product is equal to M+2x or M-2x, that is, the process parameters used in the deep etching sub-step S3 The value of the process is relative to the value of the process parameter used in the deep etching sub-step S2 by the value x; and so on, the value of the process parameter used in the deep etching sub-step Sn to change the deposit amount of the reaction by-product is equal to M+(n-1)x or M-(n-1)x, that is, the value of the process parameter used in the deep etching sub-step Sn relative to the process parameter used in the deep etching sub-step S(n-1) The value is incremented by x.

As shown in FIG. 3B, on the surface of the substrate 1 to be etched, there are sequentially arranged from bottom to top. The patterned oxide layer 3 and mask layer 2. Before performing the deep etching sub-steps S1 to Sn, the high aspect ratio shallow trench isolation etching method further includes a sub-step S0 of forming a trench prototype on the substrate 1 for first etching on the substrate 1. Etching a certain depth on the etched surface. The depth etching sub-steps S1 to Sn are then sequentially performed. In the deep etching sub-step S1, the value of the process parameter which can change the deposit amount of the reaction by-product is equal to M. Under this condition, the deposition amount of the reaction by-product is the largest, so that the deposition effect is greater than the etching effect. After the deep etching sub-step S1 is completed, a reaction by-product deposition layer 4 is formed on the sidewall of the trench for blocking the lateral progress of the etching reaction to realize anisotropic etching. In the deep etching sub-step S2, the value of the process parameter is incrementally x with respect to the value of the process parameter used in the deep etching sub-step S1, that is, the deposition amount of the reaction by-product is reduced, thereby causing deposition. The weakening, and further, after the completion of the deep etching substep S2, the thickness of the reaction byproduct deposition layer 4 is thinned due to being consumed. By analogy, as the etching depth increases, the deposition is gradually weakened, and the thickness of the reaction byproduct deposition layer 4 is gradually consumed until it is completely consumed after the deep etching substep Sn is completed. Preferably, the successive unit recursive variables between the two adjacent deep etching sub-steps are the same, that is, the above x is a fixed value, which can be implemented by a compiler to automatically control each deep etching sub-step. The numerical value of the process parameters is changed so that automatic control can be achieved. Similarly, the process time of each deep etching sub-step can be the same to facilitate automatic control, and preferably, the process time of each deep etching sub-step takes a value ranging from 5 to 10 s.

It can be seen from the above that by changing the value of the process parameter of the deposition amount of the reaction by-product used in each deep etching substep by the above-mentioned first rule of the present embodiment, the deposit of the reaction by-product can be avoided. The amount of accumulation rapidly increases at the top of the sidewall, while ensuring that the accumulation of by-products of the reaction is insufficient to hinder the plasma from entering the bottom of the trench, and to prevent the plasma from deviating from the original vertical direction, resulting in a corner of the sidewall of the trench, and finally obtaining the side. The ideal etched surface with smooth walls and no inflection points.

4 is a flow chart of a shallow trench isolation etching method for high aspect ratio according to a second embodiment of the present invention, and a schematic diagram of a trench etched morphology obtained by each deep etching substep is similar to FIG. 3B. Referring to FIG. 4 and FIG. 3B together, in the high aspect ratio shallow trench isolation etching method provided in this embodiment, the trench formation sub-step is used to form a trench prototype on the substrate, and multiple deep etching The sub-step is used to etch the depth of the trench, and the value of the process parameter used in each deep etching sub-step to change the deposition amount of the reaction by-product is reduced according to the deposition amount of the reaction by-product. The first rule is changed. In the plurality of deep etching sub-steps, the value of the process parameter used in each of the deep etching sub-steps is used at the end of the same deep etching sub-step. The value of the process parameter is changed by a unit variable, and the value of the process parameter used in each of the deep etching substeps is the same as the value of the process parameter used at the end of the adjacent previous deep etching substep.

As shown in FIG. 4, the etching step includes a trench formation sub-step S0 and n depth etching sub-steps for forming a trench prototype on the substrate 1, respectively S1, S2, S3, ... ..., Sn, n are positive integers, and n depth etching sub-steps are used to etch the depth of the trench formed on the substrate 1. Wherein, the initial value of the process parameter used in the deep etching sub-step S1 to change the deposit accumulation amount of the reaction by-product is equal to M, and the end value is equal to M+x or Mx, that is, the value of the process parameter used is in the depth. The etching step S1 is linearly increased or decreased; the initial value of the process parameter used in the deep etching sub-step S2 to change the deposition amount of the reaction by-product is equal to M+x or Mx, and the end value is equal to M+2x or M-2x, that is, the value of the process parameter used in the deep etching sub-step S2 is linearly increased or decreased in the deep etching sub-step S2, and the deep etching sub-step S2 and deep etching The slope of the linear change of the sub-step S1 is the same, and the initial value of the process parameter used in the deep etching sub-step S2 is the same as the value of the process parameter used at the end of the deep etching sub-step S1; the deep etching sub-step S3 is adopted The initial value of the process parameter that can change the amount of deposits of reaction by-products is equal to M+2x or M-2x, and the end value is equal to M+3x or M-3x, that is, the value of the process parameter used in the deep etching sub-step S3 is linearly increased or decreased in the deep etching sub-step S3, the deep etching sub-step S3 and the deep etching sub-step S2 The slope of the linear change is the same, the initial value of the process parameter used in the deep etching sub-step S3 is the same as the value of the process parameter used at the end of the deep etching sub-step S2; and so on, the deep etching sub-step Sn The initial value of the process parameter used to change the deposit accumulation amount of the reaction by-product is equal to M+(n-1)x or M-(n-1)x, and the end value is equal to M+nx or M-nx, ie, depth The value of the process parameter used in the etching sub-step Sn is linearly increased or decreased in the deep etching sub-step Sn, and the linear variation of the deep etching sub-step Sn and the deep etching sub-step S(n-1) The slope of the process parameter is the same as that of the process parameter used at the end of the deep etching sub-step S(n-1).

As shown in FIG. 3B, an oxide layer 3 and a mask layer 2 having a pattern are sequentially disposed on the surface to be etched of the substrate 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the high aspect ratio shallow trench isolation etching method further includes a sub-step S0 of forming a trench prototype on the substrate 1 for first etching on the substrate 1. Etching a certain depth on the etched surface. The depth etching sub-steps S1 to Sn are then sequentially performed. In the deep etching sub-step S1, the initial value of the process parameter which can change the deposit amount of the reaction by-product is equal to M, and the end value is equal to M+x or Mx, and under this condition, the sediment accumulation amount of the reaction by-product The maximum, so that the deposition effect is greater than the etching effect, and after the deep etching sub-step S1 is completed, a reaction by-product deposition layer 4 is formed on the sidewall of the trench for blocking the lateral progress of the etching reaction to achieve various directions. Hetero-etching. In the deep etching sub-step S2, the initial value of the process parameter is the same as the end value of the process parameter used in the deep etching sub-step S1, and the end value of the process parameter in the deep etching sub-step S2 is relative to the depth etchant. The initial value of the process parameter in step S2 is gradually changed x, that is, the deposition amount of the reaction by-product is decreased, thereby weakening the deposition, and further, after the deep etching sub-step S2 is completed, the reaction by-product deposition layer 4 is The thickness is thinned due to being consumed. By analogy, as the etching depth increases, the deposition is gradually weakened, and the thickness of the reaction byproduct deposition layer 4 is gradually consumed until it is completely consumed after the deep etching substep Sn is completed. Preferably, the successive unit recursive variables between the two adjacent deep etching sub-steps are the same, that is, the above x is a fixed value, which can be automatically controlled by the compiler to perform each of the deep etching sub-steps. The linear control of the initial and end values of the process parameters used enables automated control. Similarly, the process time of each deep etching sub-step can be the same to facilitate automatic control, and preferably, the process time of each deep etching sub-step takes a value ranging from 5 to 10 s.

It can be seen from the above that the reaction value can be avoided by making the initial value and the end value of the process parameters of the deposition amount of the reaction by-products which are used in each deep etching substep to be changed according to the above first rule of the present embodiment. The amount of deposits of the product rapidly increases at the top of the sidewall, while ensuring that the accumulation of by-products of the reaction is insufficient to hinder the plasma from entering the bottom of the trench, and to avoid the plasma from deviating from the original vertical direction, resulting in a corner of the sidewall of the trench. Finally, the ideal etched appearance with smooth sidewalls and no inflection points is obtained.

FIG. 5 is a flow chart of a shallow trench isolation etching method for high aspect ratio according to a third embodiment of the present invention, and a schematic diagram of a trench etched morphology obtained by each deep etching substep is similar to FIG. 3B. Referring to FIG. 5 and FIG. 3B together, in the high aspect ratio shallow trench isolation etching method provided in this embodiment, the trench formation sub-step is used to form a trench prototype on the substrate, and multiple deep etching The sub-step is used to etch the depth of the trench, and the value of the process parameter used in each deep etching sub-step to change the deposition amount of the reaction by-product is reduced according to the deposition amount of the reaction by-product. The first rule is changed. In the plurality of deep etching sub-steps, the value of the process parameter used in each deep etching sub-step is firstly changed relative to the initial value of the same deep etching sub-step. A unit recursive variable, and then keeps the value after a unit recursion variable until the end of the deep etching substep, each depth etch The value of the process parameters used in the initial step is the same as the value of the process parameters used at the end of the previous previous deep etch substep.

As shown in FIG. 5, the etching step includes a trench formation sub-step S0 and n depth etching sub-steps for forming a trench prototype on the substrate 1, respectively S1, S2, S3, ... ..., Sn, n are positive integers, and n depth etching sub-steps are used to etch the depth of the trench formed on the substrate 1. Wherein, the initial value of the process parameter used in the deep etching sub-step S1 to change the deposit amount of the reaction by-product is equal to M, and the value of the process parameter linearly changes with respect to the initial value of the process parameter for a period of time. The variable is incremented to obtain the intermediate value M+x or Mx, and then the intermediate value is maintained until the end of the deep etching sub-step S1, and the end value is equal to M+x or Mx, that is, the value of the used process parameter is in the depth etchant. The step S1 is linearly increased or decreased first, and then the value of the process parameter after the linear change (ie, the intermediate value) is maintained until the deep etching sub-step S1 ends; the deep etching sub-step S2 can change the reaction by-product. The initial value of the process parameter of the sediment accumulation is equal to M+x or Mx. During a period of time, the value of the process parameter changes linearly with respect to the initial value of the process parameter by a unit variable, and the intermediate value M+2x or M-2x is obtained. And then maintaining the intermediate value until the end of the deep etch sub-step S1, resulting in an end value equal to M+2x or M-2x, ie, the number of process parameters used The value is linearly increased or decreased in the deep etching sub-step S2, and then the value of the process parameter after the linear change (ie, the intermediate value) is maintained until the deep etching sub-step S2 ends; the deep etching sub-step S3 is used. The initial value of the process parameter that can change the sediment accumulation amount of the reaction by-product is equal to M+2x or M-2x. During a period of time, the value of the process parameter linearly changes with respect to the initial value of the process parameter by one unit variable, and the middle is obtained. The value M+3x or M-3x, and then the intermediate value is maintained until the end of the deep etching sub-step S3, and the end value is equal to M+3x or M-3x, that is, the value of the used process parameter is in the depth etching sub-step S3 is linearly increased or decreased first, and then the value of the process parameter after linear change (ie, the intermediate value) is maintained until the depth etching substep S3 ends; and so on, the initial value of the process parameter used in the deep etching sub-step Sn to change the deposit accumulation amount of the reaction by-product is equal to M+(n-1)x or M-(n-1)x, During a period of time, the value of the process parameter is linearly changed with respect to the initial value of the process parameter by a unit variable, and the intermediate value M+nx or M-nx is obtained, and then the intermediate value is maintained until the depth etching step Sn ends, and the end is obtained. The value is equal to M+nx or M-nx, that is, the value of the process parameter used is linearly increased or decreased in the deep etching sub-step Sn, and the value of the process parameter after the linear change is maintained (ie, the intermediate value). Until the deep etching sub-step Sn ends.

As shown in FIG. 3B, an oxide layer 3 and a mask layer 2 having a pattern are sequentially disposed on the surface to be etched of the substrate 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the high aspect ratio shallow trench isolation etching method further includes a sub-step S0 of forming a trench prototype on the substrate 1 for first etching on the substrate 1. Etching a certain depth on the etched surface. The depth etching sub-steps S1 to Sn are then sequentially performed. In the deep etching sub-step S1, the initial value of the process parameter which can change the deposit amount of the reaction by-product is equal to M, the intermediate value is equal to M+x or Mx, and the end value is equal to M+x or Mx, under this condition The deposition amount of the reaction by-product is the largest, so that the deposition effect is greater than the etching effect, and after the deep etching sub-step S1 is completed, the reaction by-product deposition layer 4 is formed on the sidewall of the trench for blocking engraving. The etch reaction proceeds laterally to achieve an anisotropic etch. In the deep etching sub-step S2, the initial value of the process parameter is the same as the end value of the process parameter used in the deep etching sub-step S1, and the end value of the process parameter in the deep etching sub-step S2 is relative to the depth etchant. The initial value change x of the process parameter in step S2, that is, the deposition amount of the reaction by-product is reduced, thereby weakening the deposition, and further, the thickness of the reaction by-product deposition layer 4 after the deep etching sub-step S2 is completed. Thinned due to being consumed. By analogy, as the etching depth increases, the deposition is gradually weakened, and the thickness of the reaction byproduct deposition layer 4 is gradually consumed until it is completely consumed after the deep etching substep Sn is completed. Preferably, The unit recursive variables changed between the two adjacent deep etching sub-steps are the same, that is, the above x is a fixed value, which can be automatically controlled by the compiler to control the process parameters used in each deep etching sub-step. The initial value, the intermediate value and the end value change, so that automatic control can be achieved. Similarly, the process time of each deep etching sub-step can be the same to facilitate automatic control, and preferably, the process time of each deep etching sub-step takes a value ranging from 5 to 10 s.

It can be seen from the above that the initial value, the intermediate value and the end value of the process parameters which can change the deposition amount of the reaction by-products used in each deep etching substep can be avoided according to the above first rule of the embodiment. The amount of deposits of reaction by-products rapidly increases at the top of the sidewalls, while ensuring that the accumulation of by-products of the reaction is insufficient to hinder the plasma from entering the bottom of the trenches, and to prevent the plasma from deviating from the original vertical direction, resulting in trench sidewalls. The corners appear, and the ideal etched appearance with smooth sidewalls and no inflection points is obtained.

Of course, the embodiment is not limited thereto, and other changes may be performed. For example, each deep etching sub-step may be divided into two deep etching sub-steps, and the deep etching sub-step S1 is taken as an example, and the process will be The initial value of the parameter is linearly changed to obtain the intermediate value of the process parameter as a deep etch sub-step S11, which is maintained from the intermediate value of the process parameter to the end of the deep etch sub-step S1 as another deep etch sub-step S12.

Of course, in the first to third embodiments described above, in the etching step, the trench formation sub-step S0 of forming the trench prototype on the substrate 1 may not be performed, but the deep etching sub-step is directly performed. A trench prototype is formed on the substrate, and the depth of the trench formed on the substrate 1 is etched.

In the above first to third embodiments, the process parameters include at least one of a flow rate of the regulating gas, a susceptor temperature, and a chamber pressure that can change the deposit accumulation amount of the reaction by-product, that is, the above may be separately made The value of any one of the process parameters is changed according to the first rule, and the at least two process parameters may be simultaneously changed according to the first rule.

For regulating the flow rate of the gas, some gases may act to increase the amount of deposits, such as N ₂ , and some gases may act to reduce the amount of deposits, such as NF ₃ , due to the different gases. Therefore, by passing the conditioning gas into the reaction chamber simultaneously with the etching gas which is mainly used for etching, and in the plurality of deep etching substeps, the flow rate of the regulating gas used in the next deep etching substep is By reducing the flow rate of the modulating gas used in the adjacent previous deep etch substep by a unit variable, a reduction in the amount of deposit by-products can be achieved. Further, for a conditioned gas that can increase the amount of deposit accumulation, the variation rule can be: the flow rate of the conditioned gas used in each deep etch substep relative to the adjustment of the adjacent previous deep etch substep The flow rate of the gas is reduced by one unit variable to reduce the amount of deposits of reaction by-products. For a conditioned gas that reduces the amount of deposit buildup, the variation rule may be: the flow rate of the conditioned gas used in each deep etch substep relative to the flow rate of the conditioned gas used in the adjacent previous deep etch substep A unit transfer variable is added to reduce the amount of deposits of reaction by-products. Of course, in practical applications, only a regulating gas that can reduce or increase the amount of deposit accumulation can be introduced, or a combination of adjusting gases that can reduce and increase the amount of deposits can be simultaneously introduced, and according to each regulating gas. The role of the decision to develop their own rules of change.

The above conditioning gas includes any one of nitrogen, helium, argon, oxygen, and fluorine-containing gas or a combination of at least two gases. Preferably, the unit recursive variable ranges from 1 to 2 sccm; for the regulating gas that can increase the deposit accumulation amount, the flow rate of the regulating gas used in the first deep etching sub-step ranges from 5 to 30 sccm.

The high aspect ratio shallow trench isolation etching method provided by the present embodiment will be further described below by taking the regulating gas as N ₂ as an example. Specifically, since N ₂ can increase the amount of deposits during the trench etching process, if the flow rate of N ₂ is gradually reduced, the deposition of reaction by-products on the upper and side walls of the trench will gradually The weakening prevents the deposit buildup from growing too fast on the upper and side walls of the trench.

Based on the above principle flow, carrying out the etching depth of each sub-step, each sub-step of etching depth of the flow rate of N ₂ is employed with respect to the etching depth adjacent a substep employed N ₂ Reduce one unit recursive variable. Specifically, taking the process time of each deep etching sub-step as 5 s as an example, during the first 5 s etching duration, the flow rate of N _{2 is} the largest, so that the etching is completed. Thereafter, a deposit of a certain amount of reaction by-products is deposited on the upper and side walls of the trench to prevent lateral progression of the etching reaction. During the second 5 s etching duration, the flow rate of N ₂ is reduced relative to the flow rate of the first 5 s etching time, thereby reducing the amount of deposits of reaction by-products, thereby causing reaction by-products. The accumulation effect is weakened, and physical bombardment and chemical action result in an increase in the consumption of deposits, so that after the completion of the second 5s etching time, the thickness of the reaction byproduct deposition layer 4 is thinned by being consumed. By continuing to reduce the flow rate of N ₂ following the above rules, the deposition of reaction by-products can be made weaker, so that the amount of deposits on the upper surface of the trench does not rapidly increase, and the degree of accumulation will not be sufficient to hinder the plasma. The body enters the bottom of the trench or changes the direction of the plasma, causing the etching morphology to bend to both sides, and finally the ideal etching morphology with smooth sidewalls and no inflection points can be obtained.

Preferably, the unit recursive variable ranges from 1 to 2 parameter units, but in practical applications, for different regulating gases, the above unit recursive variables may be set according to specific conditions, as long as the groove of the substrate 1 can be used. The groove may be subjected to a primary-order relationship of the etching and deposition processes. For example, for Ar, the unit bias is preferably 10 sccm; for example, for NF ₃ , the unit bias is preferably 2 sccm.

For the susceptor temperature, the relationship with the deposition amount of the reaction by-product is: the higher the susceptor temperature, the more easily the reaction by-products are volatilized, and the less the deposition amount of the reaction by-products; The lower the amount of deposits of reaction by-products, the more. Therefore, in the plurality of deep etching substeps, the base used in the deep etching substep is The seat temperature is varied in accordance with the first rule provided in the first to third embodiments, and the amount of deposit accumulation of reaction by-products can be reduced. In practical applications, the substrate is usually heated by a susceptor for carrying the substrate, so that the temperature of the susceptor can be adjusted by adjusting the heating power of the susceptor. Preferably, the temperature of the susceptor used in the first deep etching sub-step ranges from 50 to 60 ° C; the value of the unit recursion ranges from 1 to 2 ° C.

For the chamber pressure, the relationship with the amount of deposits of reaction by-products is: the higher the chamber pressure, the longer the reaction by-product stays in the reaction chamber, and the more the deposition of reaction by-products On the contrary, the lower the chamber pressure, the shorter the reaction by-product stays in the reaction chamber, and the less the deposition amount of reaction by-products. Therefore, in a plurality of deep etching sub-steps, deposit accumulation of reaction by-products can be achieved by changing the chamber pressure employed in the deep etching sub-step according to the first rule provided in the first to third embodiments. The amount is reduced. Preferably, the chamber pressure used in the first deep etching substep ranges from 10 to 45 mT; the unit recursive value ranges from 1 to 2 mT.

6A is a flow chart of a shallow trench isolation etching method for a high aspect ratio according to a fourth embodiment of the present invention, and FIG. 6B is a schematic diagram of a trench etching morphology obtained by each depth etching substep in FIG. 6A. Referring to FIG. 6A and FIG. 6B together, in the high aspect ratio shallow trench isolation etching method provided in this embodiment, the trench formation sub-step is used to form a trench prototype on the substrate, and multiple deep etching The sub-step is used to etch the depth of the trench, and the value of the process parameter used in each deep etching sub-step to change the deposition amount of the reaction by-product is such that the deposition amount of the reaction by-product is increased. And reducing the second regular variation between the two processes, the second rule is: in the plurality of deep etching sub-steps, the values of the process parameters used in each of the two adjacent deep etching sub-steps are different The two fixed amounts alternate between each other.

As shown in FIG. 6A, the etching step includes a trench formation sub-step S0 and n deep etching sub-steps for forming a trench prototype on the substrate 1, respectively S1, S2, S3, S4, . ....., Sn, n is a positive integer, and n deep etching sub-steps are used to etch the depth of the trench formed on the substrate 1. Wherein, the value of the process parameter used in the deep etching sub-step S1 to change the deposit accumulation amount of the reaction by-product is equal to A (one of the fixed values); and the deep etching step S2 can change the reaction by-product The value of the process parameter of the sediment accumulation amount is equal to B (the other fixed value); the value of the process parameter used in the deep etching sub-step S3 to change the deposition amount of the reaction by-product is equal to A; the deep etchant The value of the process parameter used in step S4 to change the deposit accumulation amount of the reaction by-product is equal to B; and so on, the deposition of the sediment which can change the reaction by-product used in the deep etching sub-step S(n-1) The value of the process parameter is equal to A; the value of the process parameter used in the deep etching sub-step Sn to change the deposit accumulation amount of the reaction by-product is equal to B.

As shown in FIG. 6B, a patterned oxide layer 3 and a mask layer 2 are sequentially disposed on the surface to be etched of the substrate 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the high aspect ratio shallow trench isolation etching method further includes a sub-step S0 of forming a trench prototype on the substrate 1 for first etching on the substrate 1. Etching a certain depth on the etched surface. The depth etching sub-steps S1 to Sn are then sequentially performed. In the deep etching sub-step S1, the value of the process parameter which can change the deposit amount of the reaction by-product is equal to A. Under this condition, the sediment accumulation amount of the reaction by-product is an increasing process, that is, deposition It is larger than the etching effect, so that after the deep etching sub-step S1 is completed, a reaction by-product deposition layer 4 is formed on the sidewall of the trench for blocking the lateral progress of the etching reaction to realize anisotropic etching. In the deep etching sub-step S2, the value of the process parameter is changed from the value A of the process parameter used in the original deep etching sub-step S1 to the value B. Under this condition, the deposition amount of the reaction by-product is A reduced process, i.e., the deposition is less than the etching, so that after the deep etching sub-step S2 is completed, the thickness of the reaction by-product deposit layer 4 is thinned due to being consumed. By analogy, the reaction by-products are alternately cycled multiple times between the two processes of increasing and decreasing, and are finally completely consumed after completing the deep etching sub-step Sn. Preferably, each phase The values of the process parameters used in the two deep etching sub-steps of the neighbor are alternately fixed, that is, each adjacent two deep etching sub-steps alternate between two fixed values of A and B, which is the same The automatic control of the alternating values of the process parameters used in each of the two adjacent deep etching sub-steps can be achieved by a compiler to achieve automatic control. Similarly, the process time of each deep etching sub-step can be the same to facilitate automatic control, and preferably, the process time of each deep etching sub-step takes a value ranging from 5 to 10 s.

It can be seen from the above that the deposition of reaction by-products can also be avoided by making the value of the process parameter of the deposition amount of the reaction by-product which is used in each deep etching substep to be changed according to the above second rule of the present embodiment. The amount of material accumulation rapidly increases at the top of the sidewall, while ensuring that the accumulation of by-products of the reaction is insufficient to hinder the plasma from entering the bottom of the trench, and to prevent the plasma from deviating from the original vertical direction, resulting in a corner of the sidewall of the trench, which is finally obtained. The ideal etched topography with smooth sidewalls and no inflection points.

Preferably, the process parameters include a flow rate of the conditioned gas that can change the amount of deposits of the by-products of the reaction. Some gases may act to increase the amount of deposits of the deposits, such as N ₂ , while some gases may It acts to reduce the amount of deposits, such as NF ₃ . Therefore, for the conditioned gas which can increase the deposit accumulation amount of the reaction by-product, the flow rate of the conditioned gas used in the first deep etch sub-step is a larger fixed amount of the two fixed amounts, and a regulating gas for reducing the deposit accumulation amount of the reaction by-product, the flow rate of the regulating gas used in the first deep etching sub-step is a smaller fixed amount of the two fixed amounts, so as to be able to be on the groove first Deposits of a certain amount of reaction by-products are deposited on the ports and sidewalls to prevent lateral progression of the etching reaction.

The above conditioning gas may include any one of nitrogen, helium, argon, oxygen, and fluorine-containing gas or a combination of at least two gases. Preferably, both fixed amounts are in the range of 5 to 30 sccm. It should be noted that the response speed of the flow rate of the regulating gas is compared. The susceptor temperature or chamber pressure is faster and thus more suitable for frequent alternating between two fixed amounts. In addition, when the flow rate of the gas is gradually adjusted according to the second rule, the difference between the two fixed amounts should be appropriately increased compared with the unit recursive variable in the first rule to ensure that the reaction by-products are increased and decreased. The effect of alternating between processes is obvious.

Based on the above principle, in performing the above-mentioned respective depth etching sub-steps, the flow rate of N ₂ used in each adjacent two deep etching sub-steps may be alternated between two fixed amounts, preferably at 15 sccm and The 8 sccm is alternated, and the flow rate of N ₂ used in the first deep etching sub-step is 15 sccm. Specifically, taking the process time of each deep etching sub-step as 5 s as an example, during the first 5 s etching duration, the flow rate of N ₂ is 15 sccm, thereby completing the segment. After the etch, the upper and side walls of the trench will deposit a certain amount of deposits of reaction by-products that prevent the lateral progression of the etch reaction. During the second 5s etching duration, the flow rate of N ₂ is replaced by the original 15 sccm to 8 sccm, that is, the flow rate used for the first 5 s etching time is decreased, thereby causing deposition of reaction by-products. The amount of accumulation is reduced, which in turn reduces the accumulation of reaction by-products, while physical bombardment and chemical action result in more and more consumption of deposits, so that after the completion of the second 5s etching time, the reaction by-product deposition layer 4 The thickness is thinned due to being consumed. During the third 5 s etching duration, the flow of N ₂ was again restored to 15 sccm, thereby depositing thicker deposits of reaction by-products on the sidewalls of the trench. By alternating the flow of N ₂ between the two fixed amounts following the above rules, an ideal etched profile with smooth sidewalls and no inflection points can be obtained.

In practical applications, for different conditioning gases, the above two fixed amounts may be set according to specific conditions. For example, for Ar, the flow rate is preferably between 50 sccm and 80 sccm; for NF ₃ , the flow rate is preferably 5 sccm and 10 sccm. .

FIG. 7 is a flow chart of a shallow trench isolation etching method for high aspect ratio according to a fifth embodiment of the present invention, and a schematic diagram of a trench etched morphology obtained by each deep etching substep is similar to FIG. 6B. Referring to FIG. 7 and FIG. 6B together, in the high aspect ratio shallow trench isolation etching method provided in this embodiment, the trench formation sub-step is used to form a trench prototype on the substrate, and multiple deep etching The sub-step is used to etch the depth of the trench, and the value of the process parameter used in each deep etching sub-step to change the deposition amount of the reaction by-product is such that the deposition amount of the reaction by-product is increased. And reducing the second regular variation between the two processes, the second rule is: in the plurality of deep etching sub-steps, the value of the process parameter used in each of the deep etching sub-steps is initially the same as the same The value of the process parameter used at the end of the deep etching substep is changed by a unit variable, and the values of the process parameters used at the beginning of each depth etching substep are the same, and the process used at the end of each depth etching substep is used. The values of the parameters are the same.

As shown in FIG. 7, the etching step includes a trench formation sub-step S0 and n depth etching sub-steps for forming a trench prototype on the substrate 1, respectively S1, S2, S3, S4, . ...,., Sn, n is a positive integer, and n depth etching sub-steps are used to etch the depth of the trench formed on the substrate 1. Wherein, the initial value of the process parameter used in the deep etching sub-step S1 to change the deposit amount of the reaction by-product is equal to A, and the end value is equal to Ax or A+x, that is, the value of the process parameter used is in the depth. The etching step S1 is linearly reduced; the initial value of the process parameter used in the deep etching sub-step S2 to change the deposit accumulation amount of the reaction by-product is equal to A, and the end value is equal to Ax or A+x, that is, The value of the process parameter used in the deep etching sub-step S2 is linearly reduced in the deep etching sub-step S2, and the linear etching of the deep etching sub-step S2 and the deep etching sub-step S1 is oblique. The rate is the same, the initial value of the process parameter used in the deep etching sub-step S2 is the same as the initial value of the process parameter used in the deep etching sub-step S1; the deposition of the reaction by-product which is used in the deep etching sub-step S3 The initial value of the process parameter of the material accumulation amount is equal to A, and the end value is equal to Ax or A+x, that is, the value of the process parameter used in the deep etching sub-step S3 is linearly reduced in the deep etching sub-step S3. The deep etching sub-step S3 has the same slope as the linear change of the deep etching sub-step S2, and the initial value of the process parameter used in the deep etching sub-step S3 is the same as the initial value of the process parameter used in the deep etching sub-step S2. And so on, the initial value of the process parameter used in the deep etching sub-step Sn to change the deposition amount of the reaction by-product is equal to A, and the end value is equal to Ax or A+x, that is, the deep etching sub-step Sn The value of the process parameter used is linearly reduced in the deep etching sub-step Sn, and the slope of the linear variation of the deep etching sub-step Sn and the deep etching sub-step S(n-1) is the same, deep The initial value of the process parameter used in the etch sub-step Sn is the same as the initial value of the process parameter used in the deep etch sub-step S(n-1).

As shown in FIG. 6B, a patterned oxide layer 3 and a mask layer 2 are sequentially disposed on the surface to be etched of the substrate 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the high aspect ratio shallow trench isolation etching method further includes a sub-step S0 of forming a trench prototype on the substrate 1 for first etching on the substrate 1. A certain depth is etched on the etched surface, and then the deep etch sub-steps S1 to Sn are sequentially performed. In the deep etching sub-step S1, the initial value of the process parameter which can change the deposition amount of the reaction by-product is equal to A, and the initial value is linearly changed to obtain the end value, and the end value is equal to Ax or A+x. The deposit accumulation amount of the reaction by-product is a decreasing process, that is, the deposition effect at the beginning of the deep etching sub-step 1 is greater than the etching effect, and the deposition effect is less than the etching effect at the end, thereby completing the deep etching sub-step In the process of S1, a reaction by-product deposition layer 4 is formed on the sidewall of the trench for blocking the lateral progress of the etching reaction to realize anisotropic etching, and then, as the etching action is enhanced and the deposition is weakened , the thickness of the reaction byproduct deposition layer 4 is eliminated Consumption is thinning. In the deep etching sub-step S2, the initial value of the process parameter which can change the deposit amount of the reaction by-product is equal to A, and the initial value is linearly changed to obtain the end value, and the end value is equal to Ax or A+x, that is, the depth engraving The initial value of the process parameter of the etch sub-step S2 is equal to the initial value of the process parameter of the deep etch sub-step S1, the end value of the process parameter of the deep etch sub-step S2 and the end value of the process parameter of the deep etch sub-step S1 Equally, under this condition, the process of increasing the deposition amount of the reaction by-product from the increase to the reduction is the same as the deep etching sub-step S1. Preferably, the initial values of the process parameters of each deep etching sub-step are equal, and the end values of the process parameters of each deep etching sub-step are equal, that is, the initial value of the process parameters of each deep etching sub-step is equal to A, the initial value. The end value is obtained by linear change, and the end value is equal to Ax or A+x. This can also be achieved by compiling the program to automatically control the change of the value of the process parameters used in each deep etching sub-step, thereby realizing automatic control. Similarly, the process time of each deep etching sub-step can be the same to facilitate automatic control, and preferably, the process time of each deep etching sub-step takes a value ranging from 5 to 10 s.

It can be seen from the above that the deposition of reaction by-products can also be avoided by making the values of the process parameters of the deposition amount of the reaction by-products used in the respective deep etching substeps variable according to the above second rule of the present embodiment. The amount of material accumulation rapidly increases at the top of the sidewall, while ensuring that the accumulation of by-products of the reaction is insufficient to hinder the plasma from entering the bottom of the trench, and to prevent the plasma from deviating from the original vertical direction, resulting in a corner of the sidewall of the trench, which is finally obtained. The ideal etched topography with smooth sidewalls and no inflection points.

Based on the above principle, the flow rate of N ₂ used in each deep etching substep can be linearly changed from an initial value to an end value, preferably N ₂ of each depth etching substep. The initial value of the flow rate is 15 sccm, and the end value is 8 sccm. Specifically, the process time taken for each deep etching sub-step is 5 s, for example, during the first 5 s etching duration. The initial flow rate of N ₂ is 15 sccm, so that a certain amount of deposition of reaction by-products will be deposited on the upper and side walls of the trench, preventing the lateral progress of the etching reaction, and then linearly changing the flow rate of N ₂ to 8 sccm, that is, The flow rate is reduced, so that the deposition amount of reaction by-products is reduced, and the accumulation of reaction by-products is weakened, and physical bombardment and chemical action result in more and more consumption of deposits, so that reaction by-product deposition layer 4 The thickness is thinned by being consumed, that is, in this deep etching sub-step (i.e., the process of the first 5 s etching duration), a deposition-based process is performed first, and then. The etching-based process is gradually carried out. During the second 5 s etching duration, the initial flow of N ₂ was again restored to 15 sccm, thereby depositing thicker deposits of reaction byproducts on the sidewalls of the trench. By linearly changing the flow rate of N ₂ to the end value following the above rules, an ideal etched profile with smooth sidewalls and no inflection points can be obtained.

In practical applications, the initial value and the end value may be set according to specific conditions for different adjusting gases. For example, for Ar, the flow rate preferably varies linearly between 50 sccm and 80 sccm; for NF ₃ , the flow rate is preferably 5 sccm. Linear change between 10sccm and 10sccm.

FIG. 8 is a flow chart of a high aspect ratio shallow trench isolation etching method according to a sixth embodiment of the present invention, and a schematic diagram of a trench etched morphology obtained by each deep etching substep is similar to FIG. 6B. Referring to FIG. 8 and FIG. 6B together, in the high aspect ratio shallow trench isolation etching method provided by the embodiment, the trench formation sub-step is used to form a trench prototype on the substrate, and multiple deep etching Substeps are used to etch the depth of the trenches, each depth etching substep The value of the process parameter used to change the deposit accumulation amount of the reaction by-product is changed according to a second rule that alternates between the deposition amount of the reaction by-product and the process of increasing and decreasing. Therefore, in the plurality of deep etching sub-steps, the value of the process parameter used in each deep etching sub-step is first changed with respect to the initial value of the same deep etching sub-step by a unit-recursive variable, and then kept changing. The value after a unit recursive variable is up to the end of the deep etch sub-step, and the values of the process parameters used at the beginning of each deep etch sub-step are the same, and the values of the process parameters used at the end of each deep etch sub-step are the same.

As shown in FIG. 6B, the etching step includes a trench formation sub-step S0 and n deep etching sub-steps for forming a trench prototype on the substrate 1, respectively S1, S2, S3, S4, . ...,., Sn, n is a positive integer, and n depth etching sub-steps are used to etch the depth of the trench formed on the substrate 1. Wherein, the initial value of the process parameter used in the deep etching sub-step S1 to change the deposit amount of the reaction by-product is equal to A, and the value of the process parameter is linearly changed by one unit with respect to the initial value of the process parameter for a period of time. The variable is incremented to obtain the intermediate value A+x or Ax, and then the intermediate value is maintained until the end of the deep etching sub-step S1, and the end value is equal to A+x or Ax, that is, the value of the used process parameter is in the depth etchant. The step S1 is linearly increased or decreased first, and then the value of the process parameter after the linear change (ie, the intermediate value) is maintained until the deep etching sub-step S1 ends; the deep etching sub-step S2 can change the reaction by-product. The initial value of the process parameter of the sediment accumulation amount is equal to A. During a period of time, the value of the process parameter is linearly changed with respect to the initial value of the process parameter by a unit variable, and the intermediate value A+x or Ax is obtained, and then the intermediate value is maintained. Until the end of the deep etching sub-step S2, the end value is equal to A+x or Ax, that is, the value of the used process parameter is in the depth The etchant step S2 linearly increases or decreases first, and then maintains the value of the process parameter after the linear change (ie, the intermediate value) until the deep etch sub-step S2 ends; the deep etch sub-step S3 can change the reaction pair The initial value of the process parameter for the sediment accumulation of the product is equal to A, and the value of the process parameter is relative for a period of time. Linearly changing a unit recursion variable from the initial value of the process parameter to obtain the intermediate value A+x or Ax, and then maintaining the intermediate value until the end of the deep etching sub-step S3, the end value is equal to A+x or Ax, ie, The value of the process parameter is linearly increased or decreased in the deep etching sub-step S3, and then the value of the process parameter after the linear change (ie, the intermediate value) is maintained until the depth etching sub-step S3 ends; and so on, the depth The initial value of the process parameter used in the etching sub-step Sn to change the deposit amount of the reaction by-product is equal to A, and the value of the process parameter linearly changes with respect to the initial value of the process parameter for a period of time, a unit variable, Obtaining the intermediate value A+x or Ax, and then maintaining the intermediate value until the end of the deep etching sub-step Sn, the end value is equal to A+x or Ax, that is, the value of the used process parameter is in the deep etching sub-step Sn The linear increase or decrease is followed by the value of the process parameter after the linear change (ie, the intermediate value) until the end of the deep etching sub-step Sn.

As shown in FIG. 6B, a patterned oxide layer 3 and a mask layer 2 are sequentially disposed on the surface to be etched of the substrate 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the high aspect ratio shallow trench isolation etching method further includes a sub-step S0 of forming a trench prototype on the substrate 1 for first etching on the substrate 1. A certain depth is etched on the etched surface, and then the deep etch sub-steps S1 to Sn are sequentially performed. In the deep etching sub-step S1, the initial value of the process parameter which can change the deposit amount of the reaction by-product is equal to A, and the initial value is linearly changed to obtain the intermediate value A+x or Ax, and then the intermediate value is maintained until the depth is carved. The etchant step S1 ends, and the end value is equal to Ax or A+x. Under this condition, the deposition amount of the reaction by-product is a decreasing process, that is, the deposition effect at the beginning of the deep etching sub-step 1 is greater than the engraving. At the end of the etch, the deposition is less than the etching, so that during the completion of the deep etching sub-step S1, a reaction by-product deposition layer 4 is formed on the sidewall of the trench for blocking the lateral progress of the etching reaction. Anisotropic etching is performed, and then, as the etching action is enhanced and the deposition is weakened, the thickness of the reaction byproduct deposition layer 4 is consumed. Thinning. In the deep etching sub-step S2, the initial value of the process parameter which can change the deposit amount of the reaction by-product is equal to A, and the initial value is linearly changed to obtain the intermediate value A+x or Ax, and then the intermediate value is maintained until the depth is carved. The etch step S2 ends, and the end value is obtained, and the end value is equal to Ax or A+x, that is, the initial value of the process parameter of the deep etch sub-step S2 is equal to the initial value of the process parameter of the deep etch sub-step S1, and the depth is The end value of the process parameter of the etch sub-step S2 is equal to the end value of the process parameter of the deep etch sub-step S1, under which the process of depositing the deposition amount of the reaction by-product from increasing to decreasing and the step of deep etching are performed. S1 is the same. By analogy, the initial values of the process parameters of the respective deep etching sub-steps are equal, and the end values of the process parameters of the respective deep etching sub-steps are equal, that is, the initial values of the process parameters of the respective deep etching sub-steps are equal to A, initial The value is linearly changed to obtain the intermediate value A+x or Ax, and then the intermediate value is maintained until the end of the deep etching substep, and the end value is obtained, and the end value is equal to Ax or A+x, which can also be automatically controlled by the compiler. The value of the process parameters used in each of the deep etching sub-steps is changed to achieve automatic control. Similarly, the process time of each deep etching sub-step can be the same to facilitate automatic control, and preferably, the process time of each deep etching sub-step takes a value ranging from 5 to 10 s.

The high aspect ratio shallow trench isolation etching method provided by the present embodiment will be further described below by taking the regulating gas as N ₂ as an example. Specifically, since N ₂ can increase the amount of deposit accumulation during the trench etching process, if the flow rate of N ₂ is gradually reduced, the deposition of reaction by-products on the upper and side walls of the trench will gradually The weakening prevents the deposit buildup from growing too fast on the upper and side walls of the trench.

In the fifth embodiment and the sixth embodiment, preferably, the process parameters include a flow rate of the regulating gas which can change the amount of deposit accumulation of the reaction by-product, and some gases may increase the deposit accumulation due to different gases. The effect of the amount, such as N ₂ , and some gases can act to reduce the amount of deposits, such as NF ₃ . Therefore, for the conditioned gas which can increase the deposit accumulation amount of the reaction by-product, the initial value of the flow rate of the conditioned gas used in each deep etching sub-step should be greater than the end value of the flow rate of the conditioned gas, and the reaction can be reduced. The adjustment gas of the sediment accumulation amount of the by-product, the initial value of the flow rate of the regulating gas used in each deep etching sub-step should be less than the end value of the flow rate of the regulating gas, so as to be able to first pass the upper mouth and the side wall of the groove A deposit of a certain amount of reaction by-products is deposited thereon to prevent lateral progress of the etching reaction.

In the fifth embodiment and the sixth embodiment, the conditioning gas may include any one of nitrogen gas, helium gas, argon gas, fluorine-containing gas, and oxygen gas or a combination of at least two gases. It should be noted that since the response speed of the flow rate of the regulating gas is faster than the susceptor temperature or the chamber pressure, it is more suitable for the case of frequent linear changes in the initial value and the end value. In addition, when the flow rate of the gas is gradually adjusted according to the second rule, the difference between the initial value and the end value should be appropriately increased compared with the unit recursive variable in the first rule to ensure that the reaction by-products increase and decrease. The effect of alternating between processes is obvious.

Of course, in the fourth to sixth embodiments described above, in the etching step, the trench formation sub-step S0 of forming the trench prototype on the substrate 1 may not be performed, but the deep etching sub-step is directly performed. A trench prototype is formed on the substrate, and the depth of the trench formed on the substrate 1 is etched.

In the above first to sixth embodiments, preferably, the upper electrode used in the etching step The power range is from 600 to 1200W. The power of the lower electrode used in the etching step ranges from 100 to 300 W. The etching gas used in the etching step includes chlorine gas and hydrogen bromide gas. The flow rate of the etching gas ranges from 50 to 350 sccm.

Further preferably, the plasma is always in an illuminating state from the beginning to the end of the etching step. That is, in the process of performing a plurality of deep etching substeps, the upper electrode power supply and the lower electrode power source are always turned on after the current deep etching substep is completed, and before the next deep etching substep is performed. In order to ensure that the plasma continues to glow, so that the entire etching step is continuous.

The reason for this setting is that due to the frequent switching of the germination and the annihilation in the prior art, the charged particles suspended in the chamber are easily dropped after the annihilation, and the plasma is also relatively unstable during the initiation and extinction processes. The state (the initial reflection power is easy to be high) causes the deposition or desorption of reaction by-products on the sidewall of the chamber to be unstable, thereby causing the particles to fall easily, thereby causing the particles to fall during the entire etching process. The substrate is contaminated, thereby reducing the yield of the product; and in the first to sixth embodiments described above, the plasma is always in the illuminating state, which can effectively avoid the above problems, thereby improving the yield of the product.

In the above embodiments, only the values of the process parameters are changed according to the sequential progress of the respective deep etching sub-steps, and no transition step or additional steps are added, and the etching gas and the adjusting gas are simultaneously etched to make the total The etching time is shortened compared to the total etching time of the single-step etching. Therefore, the high aspect ratio shallow trench isolation etching method provided by the above various embodiments of the present invention has the advantages of simple etching step, flexible adjustment mode, and no modification to the etching apparatus, thereby reducing the manufacturing cost of the device.

Of course, in practical applications, after completing each deep etching sub-step, the upper electrode power supply and the lower electrode power supply may also be turned off, and then turned back on when performing the next deep etching sub-step.

It will be understood that the above embodiments are merely illustrative of the principles of the present invention. An exemplary embodiment is used, 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

A high aspect ratio shallow trench isolation etching method, comprising: an etching step, the etching step comprising a plurality of deep etching sub-steps, wherein the plurality of deep etching sub-steps are used for Etching the depth of the trench, wherein

The value of the process parameter used in each deep etching substep to change the deposit amount of the reaction by-product varies according to a first rule that reduces the amount of deposit accumulation of the reaction by-product; or

The value of the process parameter used in each deep etching substep to change the deposit accumulation amount of the reaction by-product is such that the deposition amount of the reaction by-product is alternated between the two processes of increasing and decreasing. The rules change.
The high aspect ratio shallow trench isolation etching method according to claim 1, wherein the etching step further comprises a trench formation sub-step, the trench formation sub-step in the plurality of Prior to the deep etching sub-step, the trench formation sub-step is used to form a trench prototype on the substrate.
The high aspect ratio shallow trench isolation etching method according to claim 1, wherein the first rule is: in the plurality of depth etching substeps, each depth etching substep The value of the process parameter employed is progressively changed by one unit variable relative to the value of the process parameter employed by the adjacent previous deep etch substep.
The high aspect ratio shallow trench isolation etching method according to claim 1, wherein the first rule is: in the plurality of depth etching substeps, each depth etching substep is initial The value of the process parameter used in the time is changed by one unit variable with respect to the value of the process parameter used at the end of the same deep etching substep, and each depth etching substep The value of the process parameter employed at the beginning of the step is the same as the value of the process parameter employed at the end of the adjacent previous deep etch substep.
The high aspect ratio shallow trench isolation etching method according to claim 1, wherein the first rule is: in the plurality of depth etching substeps, each depth etching substep The value of the process parameter used is first changed with respect to the initial value of the same deep etching substep by a unit variable, and then the value after one unit variable is changed until the end of the deep etching substep, each The values of the process parameters used in the initial depth etch sub-step are the same as the values of the process parameters used at the end of the adjacent previous deep etch sub-step.
The high aspect ratio shallow trench isolation etching method according to any one of claims 3 to 5, wherein the process parameter includes a flow rate of a regulating gas that changes a deposition amount of a reaction by-product, At least one of a susceptor temperature and a chamber pressure.
The high aspect ratio shallow trench isolation etching method according to claim 6, wherein the successive unit recursive variables between the adjacent two deep etching substeps are the same.
The high aspect ratio shallow trench isolation etching method according to claim 1, wherein each of the deep etching substeps adopts the same process time.
The high aspect ratio shallow trench isolation etching method according to claim 8, wherein the process time used in each of the deep etching substeps ranges from 5 to 10 s.
A high aspect ratio shallow trench isolation etching method according to claim 6, wherein said conditioning gas comprises a regulating gas which increases a deposition amount of deposits of said reaction by-product;

The flow rate of the conditioned gas used in the first deep etching substep is in the range of 5 to 30 sccm.
The high aspect ratio shallow trench isolation etching method according to claim 6, wherein the temperature of the susceptor used in the first deep etching substep ranges from 50 to 60 °C.
The high aspect ratio shallow trench isolation etching method according to claim 6, wherein the chamber pressure used in the first deep etching substep ranges from 10 to 45 mT.
The high aspect ratio shallow trench isolation etching method according to claim 1, wherein the second rule is: in the plurality of depth etching substeps, each adjacent two depths are engraved The values of the process parameters employed in the eclipse step alternate between two different fixed amounts.
A high aspect ratio shallow trench isolation etching method according to claim 13, wherein said process parameter includes a flow rate of a regulating gas which changes a deposition amount of said reaction by-product; and

For the conditioned gas which can increase the deposit accumulation amount of the reaction by-product, the flow rate of the conditioned gas used in the first deep etch sub-step is a larger fixed amount of the two fixed amounts; The regulating gas for reducing the deposit accumulation amount of the reaction by-product, the flow rate of the regulating gas used in the first deep etching substep is a smaller fixed amount of the two fixed amounts.
The high aspect ratio shallow trench isolation etching method according to claim 13 or 14, wherein the values of the process parameters used in each of the two adjacent deep etching substeps are alternately fixed. .
The high aspect ratio shallow trench isolation etching method according to claim 1, wherein the second rule is: in the plurality of depth etching substeps, each depth etching substep is initial The value of the process parameter used in the time is changed by a unit variable with respect to the value of the process parameter used at the end of the same deep etching substep, and the respective depth etching substeps are initially used. The values of the process parameters are the same, and the values of the process parameters used at the end of each depth etching substep are the same.
The high aspect ratio shallow trench isolation etching method according to claim 1, wherein the second rule is: in the plurality of deep etching substeps, each depth etching substep The value of the process parameter used is first changed with respect to the initial value of the same deep etching substep by a unit recursion variable, and then the value after the unit recursion variable is changed until the end of the deep etching substep, the respective The values of the process parameters used in the initial step of the deep etching sub-step are the same, and the values of the process parameters used at the end of each depth etching sub-step are the same.
The high aspect ratio shallow trench isolation etching method according to claim 1, wherein the plasma is always in an illuminating state from the beginning to the end of the etching step.
The high aspect ratio shallow trench isolation etching method according to claim 6 or 14, wherein the conditioning gas comprises any one of nitrogen, helium, argon, fluorine-containing gas and oxygen or At least two gas combinations.