CN1731564A - Method for etching holes with different aspect ratios - Google Patents

Abstract

The invention discloses a method for etching holes with different depth-width ratios. An etching stop layer is formed on the lower surface of a substrate, and a mask pattern is formed on the upper surface of the substrate. The mask pattern includes a plurality of sacrificial block patterns respectively disposed on a first hole predetermined region and a second hole predetermined region. An etching process is then performed to etch the substrate that is not masked by the mask pattern to the etch stop layer. Finally, the etching stop layer is removed, and the substrate shielded by the sacrificial block patterns is removed together.

Description

Method for etching holes with different aspect ratios

technical field

The present invention relates to a method for etching holes with different aspect ratios, especially an etching method using sacrificial block patterns.

Background technique

The etching process is one of the most common techniques in the semiconductor process, and its purpose is to remove unnecessary films or semiconductor substrates to form desired structures or patterns. The principle of etching is to use the chemical reaction between the etching solution and the film, or to use plasma to physically and chemically bombard the film to achieve the purpose of removing the film. In the case of using a mask pattern, such as a photoresist pattern, the pattern of each thin film layer can be defined by an etching process, and then the desired element can be produced.

With the development of micro-electro-mechanical devices, because micro-electro-mechanical devices often have different structures than semiconductor devices, such as needing to etch through the wafer, the yield of the etching process becomes more important. Especially when holes with different aspect ratios have to be produced due to structural design requirements, the yield rate will be affected due to the inconsistency of the etching conditions of each hole during the etching process. This is the so-called aspect ratio dependent etching (ARDE) )Phenomenon.

Please refer to FIGS. 1 to 4. FIGS. 1 to 4 are schematic diagrams of conventional methods for etching holes with different aspect ratios, wherein FIG. 1 is a top view of a substrate 10, and FIGS. 2 to 4 are substrates 10 Sectional view along the 1-1' direction. First, as shown in FIG. 1 and FIG. 2 , a substrate 10 is firstly provided, and an etching stop layer 12 is formed on the bottom surface of the substrate 10 , and a photoresist pattern 14 is formed on the upper surface of the substrate 10 . The photoresist pattern 14 is used to define a first predetermined hole region 16 and a second predetermined hole region 18 in the substrate 10 .

As shown in FIG. 3 , an etching process is then carried out, using the photoresist pattern 14 as a hard mask, removing the substrate 10 not covered by the photoresist pattern 14 so as to be respectively in the first hole predetermined area 16 A first hole 20 and a second hole 22 are formed with the second predetermined hole region 18 . Wherein, since the first hole 20 and the second hole 22 have different aspect ratios, the etching rate is different. As shown in Figure 3, when the substrate 10 in the first hole predetermined area 16 has been etched through and stopped at the etch stop layer 12, the substrate 10 in the second hole predetermined area 18 has not been completely etched due to the slow etching rate. remove.

As shown in FIG. 4, since the etching rate of the second predetermined hole area 18 is relatively slow, the etching process must continue until the substrate 10 is etched through to form the second hole 22. The bottom 10 has been etched through, and if the etching process continues, the first hole 20 will be over-etched to cause poor sidewall conditions, or form a bottom enlarged hole 24 , thereby causing structural deviation of the MEMS device.

From the above, it can be seen that when the existing etching process forms holes with different aspect ratios, the problem of over-etching will be caused due to the different etching rates. In view of this, the applicant proposes an improved invention based on these shortcomings and many years of experience through careful observation and research, in order to increase production capacity and yield.

Contents of the invention

Therefore, the main purpose of the present invention is to provide a method for etching holes with different aspect ratios, so as to solve the insurmountable problems in the prior art.

According to a preferred embodiment of the present invention, a method of etching holes with different aspect ratios is disclosed. Firstly, a substrate is provided, and an etching stop layer is formed on the lower surface of the substrate. Then a mask pattern is formed on the upper surface of the substrate to define at least one first hole predetermined area and at least one second hole predetermined area on an upper surface of the substrate, and the mask pattern also includes multiple The sacrificial block patterns are respectively located on the first predetermined hole area and the second hole predetermined area. An etching process is then performed to etch the substrate not covered by the mask pattern until the etch stop layer. Finally, the etching stop layer is removed, and the substrate covered by the sacrificial block patterns is also removed.

Since the method of the present invention utilizes a plurality of sacrificial block patterns as a hard mask and performs an etching process, holes with the same aspect ratio are formed at positions not covered by the sacrificial block patterns during the etching process, and then the etching stop layer is removed. At the same time, the sacrificial block pattern and the covered substrate can be removed together, so that the problem caused by the large difference in the aspect ratio of the hole to be formed in the etching process can be avoided, thereby improving the yield of the etching process .

In order to enable your examiners to further understand the characteristics and technical content of the present invention, please refer to the following detailed description and accompanying drawings of the present invention. However, the accompanying drawings are only for reference and auxiliary description, and are not intended to limit the present invention.

Description of drawings

1 to 4 are schematic diagrams of existing methods for etching holes with different aspect ratios;

5 to 8 are schematic diagrams of a method for etching holes with different aspect ratios according to a preferred embodiment of the present invention;

9 and 10 are schematic diagrams of a method for etching holes with different aspect ratios according to another preferred embodiment of the present invention.

Explanation of reference signs

10 substrate 12 etch stop layer

14 photoresist pattern 16 first hole predetermined area

18 Reserved area for the second hole 20 The first hole

22 Second Hole 24 Reaming

50 substrate 52 etch stop layer

54 mask pattern 54A sacrificial block pattern

56 The first hole reservation area 58 The second hole reservation area

60 First Hole 62 Second Hole

70 substrate 72 etch stop layer

74 photoresist pattern 74A sacrificial block pattern

76 The first hole reservation area 78 The second hole reservation area

80 The third hole reservation area

Detailed ways

Please refer to FIG. 5 to FIG. 8, FIG. 5 to FIG. 8 is a schematic diagram of a method for etching holes with different aspect ratios according to a preferred embodiment of the present invention, wherein FIG. 5 is a top view of a substrate 50, and FIG. 6 to FIG. 8 is a cross-sectional view of the substrate 50 along the 5-5' direction. As shown in FIGS. 5 and 6 , a substrate 50 is first provided, and an etch stop layer 52 is formed on the bottom surface of the substrate 50 respectively, and a mask pattern 54 is formed on the upper surface of the substrate 50 to form a mask pattern 54 on the substrate 50. A first hole predetermined area 56 and a second hole predetermined area 58 are defined in . The mask pattern 54 further includes a plurality of sacrificial block patterns 54A located on the first predetermined hole area 56 and the second predetermined hole area 58 respectively. Wherein in this embodiment, the material of the mask pattern 54 is selected photoresist, and utilizes the photolithography process to be formed, but the material of the mask pattern 54 also can choose non-photoresist material according to the situation, for example Silicon oxide or nitrogen silicon compound to increase the masking effect. In addition, the function of the sacrificial block pattern 54A is to make the first predetermined hole region 56 and the second predetermined hole region 58 have the same etching conditions when the subsequent etching process is performed.

As shown in FIG. 7 and FIG. 8, an etching process, such as a reactive ion etching (RIE) process is performed, using the mask pattern 54 and the sacrificial block pattern 54A as a hard mask to etch away the unmasked The mold pattern 54 and the sacrificial block pattern 54A cover the substrate 50 until the etch stop layer 52 . It should be noted that since the sacrificial block pattern 54A makes the first predetermined hole region 56 and the second predetermined hole region 58 have the same line width, in fact, when the etching process is performed, the first predetermined hole region 56 and the second predetermined region 58 have the same line width. A plurality of holes with similar aspect ratios are formed in the predetermined hole region 58 , so that the etching rate will not be affected due to the different aspect ratios, thereby affecting the yield of the etching process.

Since the substrate 50 covered by the sacrificial block pattern 54A is connected to the etch stop layer 52, when the etch stop layer 52 is removed, the sacrificial block pattern 54A and the substrate 50 covered by it can be removed together to form a The first hole 60 and a second hole 62 . Finally, the mask pattern 54 on the upper surface of the substrate 50 is removed, that is, the fabrication of the first hole 60 and the second hole 62 is completed, as shown in FIG. 8 . Wherein in this embodiment, the etch stop layer 52 can be selected photoresist, benzocyclobutene (Benzocyclobutene, BCB), polyimide (polyimide), silicon dioxide, metal, tape, UV tape or wax Materials that can be easily removed by wet etching, heating or lighting.

It can be seen from the above-mentioned embodiments that the special feature of the present invention is that a plurality of sacrificial block patterns are used as hard masks and an etching process is performed, so that holes with the same aspect ratio are formed at positions not covered by the sacrificial block patterns during the etching process, Then, when removing the etching stop layer, the sacrificial block pattern and the substrate covering it are removed together, so that the problems caused by the large difference in the aspect ratio of the holes to be formed during the etching process can be avoided. . However, it is worth noting that the size, distribution, and configuration density of the sacrificial block patterns are adjusted according to the mask pattern density and the parameters of the etching process, that is, when the mask patterns on the substrate have different pattern densities (pattern densities) , the present invention can properly adjust the size, distribution, and configuration density of the sacrificial block patterns in each hole, so as to avoid the micro-loading effect (micro-loading effect) from affecting the uniformity of etching. For example, if the density of a plurality of first holes in a certain region to be formed on the substrate is higher than the density of a plurality of second holes in another region, the sacrificial block pattern provided in each predetermined region of the first holes The disposition density of the sacrificial block pattern should be lower than the disposition density of the sacrificial block patterns in the predetermined regions of the second holes, so that the overall etching conditions on the substrate are similar.

In addition, if the aspect ratio of some holes to be formed (hereinafter referred to as the third hole) is much lower than that of other holes, the third hole can also be used as a benchmark, and the sacrificial block pattern is used to make other holes with larger aspect ratios, such as the first hole. The first or second hole has the same etching conditions as the third hole. Please refer to FIG. 9 and FIG. 10. FIG. 9 and FIG. 10 are schematic diagrams of a method for etching holes with different aspect ratios according to another preferred embodiment of the present invention, wherein FIG. 9 is a top view of a substrate 70, and FIG. 10 is A cross-sectional view of the substrate 70 along the 7-7' direction. As shown in FIGS. 9 and 10 , a substrate 70 is first provided, and an etch stop layer 72 is formed on the bottom surface of the substrate 70 respectively, and a mask pattern 74 is formed on the upper surface of the substrate 70 to form a mask pattern 74 on the substrate 70. A first predetermined hole area 76 , a second predetermined hole area 78 , and a third predetermined hole area 80 are defined in . The mask pattern 74 further includes a plurality of sacrificial block patterns 74A located on the first predetermined hole area 76 and the second predetermined hole area 78 respectively. Since the aspect ratio of the third predetermined hole area 80 is much lower than that of the first predetermined hole area 76 and the second predetermined hole area 78, the method of this embodiment is based on the line width of the third predetermined hole area 80, and The first predetermined hole region 76 and the second predetermined hole region 78 have the same etching conditions as the third predetermined hole region 80 by using the sacrificial block pattern 74A. Under the same etching conditions, the subsequent etching process can be carried out, and the detailed steps of the etching process have been disclosed in detail in the previous preferred embodiment, and will not be repeated here.

In addition, the above two preferred embodiments are applied in the case of etching through the substrate, and if the method of the present invention is intended to be applied in the case of not etching through the substrate, it is not necessary to form an etch stop layer on the bottom surface of the substrate, and After etching the substrate in the holes with different aspect ratios to a predetermined depth, an isotropic etching process is used to remove the substrate covered by the sacrificial block patterns in the holes, and the sacrificial block patterns are also removed, so that Holes with different aspect ratios can be etched.

Compared with the prior art, the method of the present invention uses multiple sacrificial block patterns as hard masks and performs an etching process, so that holes with the same aspect ratio are formed at positions not covered by the sacrificial block patterns during the etching process, and then When removing the etch stop layer, the sacrificial block pattern and the substrate covered are removed together, so that the problems caused by the large difference in the aspect ratio of the holes to be formed during the etching process can be avoided, and then Improve the yield of etching process.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the patent of the present invention.

Claims (17)

1. A method of etching holes with different aspect ratios, comprising: providing a substrate; forming an etch stop layer on the lower surface of the substrate; A mask pattern is formed on an upper surface of the substrate to define at least one first hole predetermined area and at least one second hole predetermined area on the upper surface of the substrate, and the mask pattern also includes a plurality of The sacrificial block patterns are respectively located on the first predetermined hole area and the second predetermined hole area; performing an etching process, etching the substrate not covered by the mask pattern until the etch stop layer; and The etching stop layer is removed, and the sacrificial block patterns and the substrate covered by the sacrificial block patterns are removed together. 2. The method of claim 1, wherein an area of the first predetermined hole area is not equal to an area of the second predetermined hole area. 3. The method as claimed in claim 1, wherein the sacrificial block patterns are used to make the first predetermined hole region and the second predetermined hole region have the same etching conditions. 4. The method as claimed in claim 3, wherein the sacrificial block patterns make the first predetermined hole region and the second predetermined hole region have the same line width when performing the etching process. 5. The method according to claim 1, wherein the size, distribution, and arrangement density of the sacrificial block patterns are adjusted according to the density of the mask pattern and the parameters of the etching process. 6. The method of claim 1, further comprising a step of removing the mask pattern. 7. The method according to claim 1, wherein the mask pattern further defines at least a third hole predetermined area on the upper surface of the substrate, and the third hole predetermined area does not include any sacrificial block pattern . 8. A method of etching holes with different aspect ratios, comprising: A substrate is provided, and an upper surface of the substrate includes at least one first predetermined hole region and at least one second predetermined hole region; A mask pattern is formed on the upper surface of the substrate, the mask pattern exposes the first hole predetermined area and the second hole predetermined area, and the mask pattern also includes a plurality of sacrificial block patterns located on the first hole On a predetermined hole area and the second hole predetermined area; performing an etching process using the mask pattern as a mask to etch the substrate not masked by the mask pattern; and The sacrificial blocks and the substrate covered by the sacrificial blocks are removed. 9. The method of claim 8, wherein an area of the first predetermined hole area is larger than an area of the second predetermined hole area. 10. The method as claimed in claim 8, wherein the sacrificial block patterns make the first predetermined hole region and the second predetermined hole region have the same etching conditions. 11. The method as claimed in claim 10, wherein the sacrificial block patterns make the first predetermined hole region and the second predetermined hole region have the same line width when performing the etching process. 12. The method according to claim 8, wherein the size, distribution, and configuration density of the sacrificial block patterns are adjusted according to the density of the mask pattern and the parameters of the etching process. 13. The method of claim 8, further comprising forming an etch stop layer on a lower surface of the substrate before performing the etching process. 14. The method of claim 13, wherein the etching process etches through the substrate and stops at the etch stop layer. 15. The method of claim 14, wherein the sacrificial block patterns and the substrate masked by the sacrificial block patterns are removed together when the etch stop layer is removed. 16. The method of claim 8, further comprising a step of removing the mask pattern. 17. The method of claim 8, wherein the upper surface of the substrate includes at least one third hole predetermined area, and the third hole predetermined area does not include any sacrificial block pattern.

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