CN104078329A - Method for forming self-aligned multiple graphs - Google Patents

Abstract

A method for forming self-aligned multiple patterns, comprising: a part of the surface of the layer to be etched has several discrete first sacrificial layers, the surface of the layer to be etched is exposed between adjacent first sacrificial layers, and the surface of the first sacrificial layer is Having a second sacrificial layer; removing part of the second sacrificial layer along the sidewall surface of the second sacrificial layer, and exposing part of the surface of the first sacrificial layer; forming a mask on the layer to be etched, the first sacrificial layer and the surface of the second sacrificial layer film; etching back the mask film, forming a second mask on the surface of the first sacrificial layer on both sides of the second sacrificial layer, and forming a first mask on the surface of the layer to be etched on both sides of the first sacrificial layer; After the first mask and the second mask, remove the second sacrificial layer; after removing the second sacrificial layer, use the second mask as a mask to etch the first sacrificial layer until the layer to be etched is exposed, and etch The etched first sacrificial layer forms a third mask. The method for forming self-alignment multiple patterns of the present invention is simple, and the formed self-alignment multiple patterns are accurate.

Description

Method for forming self-aligned multiple patterns

technical field

The invention relates to the technical field of semiconductor manufacturing, in particular to a method for forming self-aligned multiple patterns.

Background technique

With the continuous progress of semiconductor technology, the process nodes of semiconductor devices are continuously reduced. However, due to the limitation of the precision of the existing photolithography process, the mask pattern formed by the existing photolithography process is difficult to meet the demand for continuous reduction of the feature size of semiconductor devices, which hinders the development of semiconductor technology.

In order to further reduce the size of the semiconductor device on the basis of the existing photolithography process, a multi-patterning process is proposed in the prior art. Among them, the self-aligned quadruple patterning process (SaDDP, Self-aligned Double Double Patterning) has application prospects because it can form smaller-sized masks. 1 to 4 are schematic cross-sectional structural diagrams of the process of forming a mask using a self-aligned quadruple patterning process in the prior art, including:

Please refer to FIG. 1, a first sacrificial layer 101 is formed on the surface of the layer to be etched 100, and the formation process of the first sacrificial layer 101 is: a first sacrificial film is formed on the surface of the layer to be etched 100; Several discrete photoresist layers are formed on part of the surface; the first sacrificial film is etched using the photoresist layer as a mask until the layer 100 to be etched is exposed.

Referring to FIG. 2, a second sacrificial film (not shown) is deposited on the surface of the layer to be etched 100 and the first sacrificial layer 101; the second sacrificial film is etched back until the first sacrificial layer 101 is exposed. A second sacrificial layer 102 is formed on the surface of the layer to be etched 100 on both sides of the first sacrificial layer 101 .

Please refer to FIG. 3 , after forming the second sacrificial layer 102 , remove the first sacrificial layer 101 (as shown in FIG. 2 ); after removing the first sacrificial layer 101 , deposit a mask film on the surface of the second sacrificial layer 102 (not shown); etch back the mask film until the second sacrificial layer 102 is exposed, and form a mask layer 103 on the surface of the layer to be etched 100 on both sides of the second sacrificial layer 102 .

Referring to FIG. 4 , after the mask layer 103 is formed, the second sacrificial layer 102 (as shown in FIG. 3 ) is removed. Subsequently, the mask layer 103 can be used to etch the layer 100 to be etched.

However, the existing self-aligned quadruple patterning process is complicated, which will increase the process time and cost.

For more information about the multiple patterning process, please refer to the US patent document with publication number US2012085733A1.

Contents of the invention

The problem to be solved by the present invention is to provide a method for forming self-aligned multiple patterns, which can simplify the method for forming self-aligned multiple patterns and save costs.

In order to solve the above problems, the present invention provides a method for forming self-aligned multiple patterns, including: providing a layer to be etched, a part of the surface of the layer to be etched has a number of discrete first sacrificial layers, adjacent to the first sacrificial layer The surface of the layer to be etched is exposed between the layers, and the surface of the first sacrificial layer has a second sacrificial layer; part of the second sacrificial layer is removed along the side wall surface of the second sacrificial layer, so that the second sacrificial layer The size of the layer is reduced, and part of the surface of the first sacrificial layer is exposed; a mask film is formed on the surface of the layer to be etched, the first sacrificial layer, and the second sacrificial layer; the mask film is etched back until the exposed As far as the surface of the first sacrificial layer and the surface of the second sacrificial layer, a second mask is formed on the surface of the first sacrificial layer on both sides of the second sacrificial layer, and a first mask is formed on the surface of the layer to be etched on both sides of the first sacrificial layer; After forming the first mask and the second mask, the second sacrificial layer is removed.

Optionally, further comprising: after removing the second sacrificial layer, using the second mask as a mask, etching the first sacrificial layer until the layer to be etched is exposed, and the etched second A sacrificial layer forms the third mask.

Optionally, the process of removing part of the thickness along the sidewall surface of the second sacrificial layer is a plasma dry etching process, and the parameters of the plasma dry etching process are: the gas pressure is 0 millitorr to 50 millitorr Torr, the bias voltage is 0 volts to 100 volts, and the total flow rate of etching gas is 100 standard ml/min to 500 standard ml/min.

Optionally, the material of the second sacrificial layer is different from that of the first sacrificial layer, and the material of the second sacrificial layer is polysilicon, amorphous carbon, silicon oxide or silicon nitride.

Optionally, when the material of the second sacrificial layer is polysilicon, the etching gas includes hydrogen bromide and oxygen, and the volume ratio of hydrogen bromide and oxygen is 1:1-30:1; when the second When the material of the second sacrificial layer is silicon oxide, the etching gas includes tetracarbon hexafluoride and helium, and the volume ratio of tetracarbon hexafluoride and helium is 1:1 to 40:1; when the second When the material of the sacrificial layer is silicon nitride, the etching gas includes fluoromethane and helium, and the volume ratio of the fluoromethane to helium is 1:1˜40:1.

Optionally, it also includes: before reducing the size of the second sacrificial layer, forming several overlapping sacrificial layers on the surface of the second sacrificial layer, the size of the several overlapping sacrificial layers is the same as that of the first sacrificial layer and the second sacrifice layer. The sacrificial layers are the same, the materials of the several sacrificial layers are all different, and the materials of the several sacrificial layers are different from the first sacrificial layer or the second sacrificial layer; , so that the size of each sacrificial layer is smaller than the size of the sacrificial layer below the sacrificial layer, and exposes part of the surface of the sacrificial layer located under the sacrificial layer, and the sacrificial layer exposes part of the second sacrificial layer The surface of the sacrificial layer; the mask film is also formed on the sidewalls and top surfaces of the several overlapping sacrificial layers; when the mask film is etched back, the top surface of some overlapping sacrificial layers is also exposed, respectively in each A fourth mask is formed on both sides of the sacrificial layer and on the surface of the sacrificial layer below the layer; the sacrificial layer at the top is removed, and several overlapping sacrificial layers, the second sacrificial layer and the sacrificial layer are etched with the fourth mask. The first sacrificial layer is until the layer to be etched is exposed.

Optionally, the number of overlapping sacrificial layers is 1 to 4 layers, and the material of the several overlapping sacrificial layers is polysilicon, amorphous carbon, silicon oxide or silicon nitride; The partial thickness process is a plasma dry etching process, and the parameters of the plasma dry etching process are: the gas pressure is 0 mTorr to 50 mTorr, the bias voltage is 0 V to 100 V, the total flow rate of the etching gas 100 standard ml/min to 500 standard ml/min; when the material of the sacrificial layer is polysilicon, the etching gas includes hydrogen bromide and oxygen, and the volume ratio of hydrogen bromide and oxygen is 1:1 to 30 : 1; when the material of the sacrificial layer is silicon oxide, the etching gas includes tetracarbon hexafluoride and helium, and the volume ratio of tetracarbon hexafluoride and helium is 1:1 to 40:1; When the material of the sacrificial layer is silicon nitride, the etching gas includes fluoromethane and helium, and the volume ratio of the fluoromethane to helium is 1:1˜40:1.

Optionally, the method for forming the first sacrificial layer and the second sacrificial layer is: depositing a first sacrificial film on the surface of the layer to be etched; depositing a second sacrificial film on the surface of the first sacrificial film; A patterned layer is formed on the surface of the film, and the patterned layer defines the positions and shapes of several first sacrificial layers and second sacrificial layers; using the patterned layer as a mask, etching the second sacrificial film and the first sacrificial layer Sacrifice the film until the layer to be etched is exposed to form a first sacrificial layer and a second sacrificial layer.

Optionally, the formation process of the patterned layer is a photolithography process, a nano-printing process or an directed self-assembly process.

Optionally, the process of etching the second sacrificial film and the first sacrificial film is an anisotropic dry etching process.

Optionally, before reducing the size of the second sacrificial layer, the thickness of the second sacrificial layer is thinner than that of the first sacrificial layer.

Optionally, the material of the mask film, the first sacrificial layer or the second sacrificial layer is polysilicon, amorphous carbon, silicon oxide or silicon nitride, and the material of the mask film is the same as that of the first sacrificial layer or the second sacrificial layer. The materials of the two sacrificial layers are different.

Optionally, the process for removing the second sacrificial layer is a dry etching process or a wet etching process.

Optionally, the formation process of the mask film is an atomic layer deposition process or a chemical vapor deposition process.

Optionally, the thickness of the mask film is smaller than the thickness removed along the sidewall surface of the second sacrificial layer.

Optionally, the layer to be etched is a semiconductor substrate.

Optionally, the method further includes: providing a semiconductor substrate, the layer to be etched is located on the surface of the semiconductor substrate.

Optionally, further comprising: a device layer located between the semiconductor substrate and the layer to be etched, the device layer including a semiconductor device and a dielectric layer electrically isolating the semiconductor device.

Optionally, the layer to be etched is a polysilicon layer, a metal layer or a dielectric layer.

Optionally, the semiconductor substrate is a silicon substrate.

Optionally, after forming the third mask, the layer to be etched is etched using the first mask and the third mask as masks.

Compared with the prior art, the technical solution of the present invention has the following advantages:

The surface of the layer to be etched has a first sacrificial layer, and the surface of the first sacrificial layer has a second sacrificial layer; part of the thickness is thinned from the side wall surface of the second sacrificial layer, so that the size of the second sacrificial layer is reduced, and Part of the surface of the first sacrificial layer is exposed; subsequently, only a mask film needs to be formed on the surface of the layer to be etched, the first sacrificial layer, and the second sacrificial layer, and the mask film is etched by an etch-back process once, That is, it is possible to simultaneously form a first mask on the surface of the layer to be etched on both sides of the first sacrificial layer, and form a second mask on the surface of the first sacrificial layer on both sides of the second sacrificial layer, and then form a self-aligned quadruple pattern. The self-aligned quadruple pattern is formed only by one deposition process and one etch-back process, the formation method is simple, the process steps are simplified, raw materials are saved, and costs are reduced.

Further, the process of thinning part of the thickness from the sidewall surface of the second sacrificial layer is a plasma dry etching process, and in the plasma dry etching process, by adjusting the pressure, bias ( bias) and the total gas flow rate, so that the etching rate of the etching process in the direction parallel to the surface of the layer to be etched is greater than the etching rate in the direction perpendicular to the surface of the layer to be etched, so that the etching process can start from the first Part of the second sacrificial layer is removed from the sidewall surface of the second sacrificial layer; meanwhile, the size reduction of the second sacrificial layer perpendicular to the surface of the layer to be etched is small. If the size of the etched second sacrificial layer parallel to the surface of the layer to be etched is smaller than that of the first sacrificial layer, only one layer of mask film can be formed subsequently, and the first mask film can be formed at the same time only through one etch-back process. film and a second mask, and then form a self-aligned quadruple pattern.

Further, the thickness of the second sacrificial layer is thinner than that of the first sacrificial layer, then the height of the first mask subsequently formed on both sides of the first sacrificial layer is higher than that of the second mask formed on both sides of the second sacrificial layer. The height of the mask is high; after removing the second sacrificial layer and etching the first sacrificial layer with the second mask as a mask, it can be ensured that the first mask has a sufficient height and size so that The first mask can subsequently be used as a mask for etching the layer to be etched, thereby ensuring the stability of the etched pattern.

Further, several overlapping sacrificial layers are formed on the surface of the second sacrificial layer, and before forming the mask film, part of the thickness is removed along the sidewall surface of each sacrificial layer, so that the size of the sacrificial layer is smaller than that of the sacrificial layer located in the layer. The size of the sacrificial layer under the sacrificial layer, and make the mask film also cover the sidewalls and top surfaces of the several overlapping sacrificial layers; A fourth mask is formed on both sides, and the fourth mask can form a self-aligned multiple pattern together with the first mask and the second mask, and is used to etch the layer to be etched, so that the formed device size smaller.

Description of drawings

1 to 4 are schematic cross-sectional structural diagrams of the process of forming a mask using a self-aligned quadruple patterning process in the prior art;

5 to 10 are schematic cross-sectional structure diagrams of the formation process of the self-aligned multiple patterns described in the first embodiment of the present invention;

11 to 13 are schematic cross-sectional structure diagrams of the formation process of the self-aligned multiple patterns according to the second embodiment of the present invention.

Detailed ways

As mentioned in the background, the existing self-aligned quadruple patterning process is relatively complicated and the process cost is high.

The inventors of the present invention have found through research that, when forming a self-aligned quadruple pattern in the prior art, please continue to refer to FIG. The second sacrificial layer 102 . Please continue to refer to FIG. 3 , and then the first sacrificial layer 101 is removed, and a mask layer 103 is formed on the surface of the layer to be etched 100 on both sides of the second sacrificial layer 102 by using a self-alignment process again. Wherein, after two self-alignment processes to form the second sacrificial layer 102 and the mask layer 103 respectively, that is, two deposition processes and an etch-back process are required, which not only complicates the process steps, but also causes waste of raw materials. Not conducive to promotion in production. Moreover, the second sacrificial layer 102 is formed on both sides of the first sacrificial layer 101 using a deposition process and an etch-back process. The size and shape of the second sacrificial layer 102 are difficult to ensure, and it is easy to The mask layer 103 on both sides of the sacrificial layer 102 has poor morphology and inaccurate dimensions, resulting in unstable performance of the formed semiconductor device.

After further research by the inventors of the present invention, a first sacrificial layer is formed on the surface of the layer to be etched, and the surface of the first sacrificial layer has a second sacrificial layer; after part of the thickness is reduced from the surface of the second sacrificial layer, the Part of the surface of the first sacrificial layer is exposed; after that, only one deposition process and an etch-back process are required to form a first mask on the surface of the layer to be etched on both sides of the first sacrificial layer, and to form a mask on both sides of the second sacrificial layer. The second mask is formed on the surface of the first sacrificial layer on the side; wherein, the second mask is used as a mask for etching the first sacrificial layer, and the etched first sacrificial layer forms a third mask, and the first mask The self-aligned quadruple pattern formed by the film and the third mask. The formation process of the self-aligned quadruple pattern is simple, and only one deposition process and one etching-back process are used, which can simplify process steps and save costs.

In order to make the above objects, features and advantages of the present invention more comprehensible, specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

first embodiment

5 to 10 are schematic cross-sectional structure diagrams of the forming process of the self-aligned multiple patterns described in this embodiment.

Please refer to FIG. 5 , a layer to be etched 200 is provided, a first sacrificial film 201 is deposited on the surface of the layer to be etched 200; a second sacrificial film 202 is deposited on the surface of the first sacrificial film 201; Several discrete patterned layers 203 are formed on the surface, and the surface of the second sacrificial film 202 is exposed between adjacent patterned layers 203. The patterned layer 203 defines several first sacrificial layers (not shown) and The location and shape of the second sacrificial layer (not shown).

A quadruple self-alignment pattern is subsequently formed on the surface of the layer to be etched 200, and the layer 200 to be etched is etched using the formed quadruple self-alignment pattern as a mask to form a desired semiconductor structure .

In one embodiment, a semiconductor substrate (not shown) is also provided, and the layer to be etched 200 is formed on the surface of the semiconductor substrate; the layer to be etched 200 is a polysilicon layer, a metal layer or a dielectric layer, The material of the metal layer includes copper, tungsten or aluminum, and the material of the dielectric layer includes silicon oxide, silicon nitride, silicon oxynitride or amorphous carbon. In addition, a device layer (not shown) can be formed between the semiconductor substrate and the layer to be etched 200 , and the device layer includes a semiconductor device and a dielectric layer electrically isolating the semiconductor device. Wherein, the semiconductor substrate is a silicon substrate, a silicon germanium substrate, a silicon carbide substrate, a silicon-on-insulator (SOI) substrate, a germanium-on-insulator (GOI) substrate, a glass substrate or a III-V compound substrate. bottom (such as gallium nitride or gallium arsenide, etc.); the semiconductor device includes transistors, resistors, capacitors, memories, etc., to form a chip or integrated circuit; the dielectric layer surrounds the semiconductor device for electrical isolation In the semiconductor device, the material of the dielectric layer is one or more of silicon oxide, silicon nitride, silicon oxynitride and low-K dielectric material. Subsequently, the layer 200 to be etched is etched using the self-aligned multiple pattern formed in this embodiment as a mask, and the etched layer 200 to be etched is used as a part of a chip or an integrated circuit; or, the etched The layer to be etched 200 can also be used as a mask for etching the semiconductor substrate or device layer.

In another embodiment, the layer to be etched is a semiconductor substrate, and the semiconductor substrate is used to provide a working platform for subsequent processes, and the semiconductor substrate is a silicon substrate, a silicon germanium substrate, a silicon carbide substrate substrate, silicon-on-insulator (SOI) substrate, germanium-on-insulator (GOI) substrate, glass substrate or III-V compound substrate (such as gallium nitride or gallium arsenide, etc.). Subsequently, the self-aligned multiple pattern formed in this embodiment is used as a mask for etching the semiconductor substrate.

The first sacrificial film 201 is used to form a first sacrificial layer, and the second sacrificial film 202 is used to form a second sacrificial layer. The materials of the first sacrificial film 201 and the second sacrificial film 202 are different, so that the subsequent selective plasma dry etching process can be used to reduce the size of the second sacrificial layer, while the shape and size of the first sacrificial layer are different. will be affected, so that only one deposition process and one etch-back process can be used to simultaneously form a mask layer on both sides of the first sacrificial layer and the second sacrificial layer. The material of the first sacrificial film 201 or the second sacrificial film 202 is polysilicon, amorphous carbon, silicon oxide or silicon nitride, and the formation process of the first sacrificial film 201 or the second sacrificial film 202 is a deposition process, relatively Preferably a chemical vapor deposition process.

In addition, the thickness of the first sacrificial film 201 is thicker than that of the second sacrificial film 202, the thickness of the first sacrificial film 201 is 1000 angstroms to 2000 angstroms, and the thickness of the second sacrificial film 202 is 800 angstroms to 2000 angstroms. 1500 angstroms; the thickness of the first sacrificial layer formed subsequently is thicker than that of the second sacrificial layer, and the height of the second mask formed on both sides of the second sacrificial layer subsequently is higher than that of the first mask formed on both sides of the first sacrificial layer The height is low; when the second sacrificial layer is subsequently removed, and the first sacrificial layer is etched using the second mask as a mask to form a third mask, it can be ensured that the first mask has sufficient height and size as a The mask of the layer 200 to be etched is etched.

The formation process of the patterned layer 203 is a photolithography process, a nano-printing process or an directed self-assembly process. Due to the limited accuracy of the existing patterning process, when the size of the patterned layer 203 is guaranteed to be accurate, the size of the patterned layer 203 cannot be further reduced, thereby limiting the feature size of the formed semiconductor device, which is not conducive to the device. further integration. In this embodiment, four masks with precise dimensions can be formed within the region where a single patterned layer 203 is accurately formed, and the layer 200 to be etched is etched with the masks, and the size of the formed semiconductor structure is reduced, and The size is accurate, which is conducive to the reduction of semiconductor devices and stable performance. In this embodiment, the formation process of the patterned layer 203 is a photolithography process, that is, the formed patterned layer 203 is a photoresist layer. The formation process of the photoresist layer is as follows: using a spin coating process to form a photoresist film on the surface of the second sacrificial film 202; using an exposure process to pattern the photoresist film to form a patterned layer 203; wherein, the The size of the patterned layer 203 is limited by the accuracy of the exposure process. Therefore, if the photolithography process cannot be used to form a patterned layer 203 with a smaller size and precise size, then the patterned layer 203 is used as a mask to etch and form The graphic size of is limited and cannot be reduced further.

Please refer to FIG. 6, using the patterned layer 203 as a mask, etch the second sacrificial film 202 and the first sacrificial film 201 (refer to FIG. 5) until the layer 200 to be etched is exposed. Several discrete first sacrificial layers 201a are formed on part of the surface of the layer 200, the surface of the layer 200 to be etched is exposed between adjacent first sacrificial layers 201a, and the surface of the first sacrificial layer 201a has a second sacrificial layer 202a.

The process of etching the second sacrificial film 202 and the first sacrificial film 201 is an anisotropic dry etching process, which can etch to form the first sacrificial layer 201a and the first sacrificial layer 201a whose sidewalls are perpendicular to the surface of the layer 200 to be etched. The second sacrificial layer 202a. The formed first sacrificial layer 201a and the second sacrificial layer 202a have the same size; and the patterns of the first sacrificial layer 201a and the second sacrificial layer 202a are defined by the patterned layer 203, so the dimensional accuracy of the patterned layer 203 determines The dimensional accuracy of the first sacrificial layer 201a and the second sacrificial layer 202a is improved. A first mask is subsequently formed on both sides of the first sacrificial layer 201a, that is, the first sacrificial layer 201a is used to define the position of the subsequently formed first mask.

Referring to FIG. 7 , part of the thickness is removed along the sidewall surface of the second sacrificial layer 202 a to reduce the size of the second sacrificial layer 202 a and expose part of the surface of the first sacrificial layer 201 a.

After the size of the second sacrificial layer 202a is reduced, part of the surface of the first sacrificial layer 201a is exposed, and only one deposition process and one etch-back process are required to form the first sacrificial layer 201a on both sides of the first sacrificial layer 201a. mask, and simultaneously form a second mask on both sides of the second sacrificial layer 202b, that is, form a self-aligned quadruple pattern. The manufacturing process of the self-aligned quadruple pattern is simplified, which can save material and cost.

It should be noted that before removing part of the second sacrificial layer 202a, the patterned layer 203 (as shown in FIG. 6 ) is removed; in this embodiment, the patterned layer 203 is a photoresist layer, and the removed The process of the photoresist layer is a pickling process or an ashing process.

The process of removing part of the second sacrificial layer 202a from the sidewall surface of the second sacrificial layer 202a is a plasma dry etching process, and the plasma dry etching process is performed in a direction parallel to the surface of the layer 200 to be etched. The etching rate on the surface of the layer to be etched 200 is faster than the etching rate in the direction perpendicular to the surface of the layer to be etched 200, so as to reduce the size of the second sacrificial layer 202a parallel to the direction of the layer to be etched 200, while the first The thickness dimension of the second sacrificial layer 202a perpendicular to the direction of the layer to be etched 200 is less reduced.

Specifically, by adjusting the gas pressure, bias voltage and the total amount of gas in the etching process, the free path (free path) of the plasma used for etching is reduced; and the plasma free path is reduced, that is, the plasma The scattering probability increases the plasma density in the direction parallel to the surface of the layer to be etched 200 , thereby achieving the purpose of increasing the etching rate in the direction parallel to the surface of the layer to be etched 200 .

In addition, the etching process is selective to the second sacrificial layer 202a and the first sacrificial layer 201a, and the size of the first sacrificial layer 201a will not be reduced while etching the sidewall of the second sacrificial layer 202a , the precise size of the first sacrificial layer 201a is maintained, so that the position of the subsequently formed first mask is precise. Moreover, the etching rate of the etching process is easy to control, so the thickness of the second sacrificial layer 202a removed by etching can be precisely controlled; and before the etching process, the pattern size of the second sacrificial layer 202a is determined by the pattern Layer 203 is precisely defined, and the thickness of the removed second sacrificial layer 202a can be precisely controlled, so the size of the etched second sacrificial layer 202a can still be kept accurate, and the subsequent formation of the second sacrificial layer 202a on both sides The position of the second mask is precise.

The parameters of the plasma dry etching process are as follows: the air pressure is 0 mTorr to 50 mTorr, the bias voltage is 0 V to 100 V, and the total flow rate of etching gas is 100 NmL/min to 500 NmL/min. In one embodiment, when the material of the second sacrificial layer 202a is polysilicon, the etching gas includes hydrogen bromide and oxygen, and the volume ratio of hydrogen bromide and oxygen is 1:1˜30:1. In another embodiment, when the material of the second sacrificial layer 202a is silicon oxide, the etching gas includes tetracarbon hexafluoride (C ₄ F ₆ ) and helium, and the tetracarbon hexafluoride and helium The gas volume ratio is 1:1 to 40:1. In other embodiments, when the material of the second sacrificial layer 202a is silicon nitride, the etching gas includes monofluoromethane (CH ₃ F) and helium, and the volume ratio of monofluoromethane to helium is 1 :1～40:1.

Referring to FIG. 8 , a mask film 204 is formed on the surface of the layer to be etched 200 , the first sacrificial layer 201 a and the second sacrificial layer 202 a.

The mask film 204 is used to form a first mask on both sides of the first sacrificial layer 201a and a second mask on both sides of the second sacrificial layer 202a. The material of the mask film 204 is polysilicon, amorphous carbon, silicon oxide or silicon nitride, and the material of the mask film 204 is different from that of the first sacrificial layer 201a or the second sacrificial layer 202a, so as to ensure subsequent When the mask film 204 is etched back, it will not affect the topography of the first sacrificial layer 201a or the second sacrificial layer 202a; the thickness of the mask film 204 is smaller than that along the second sacrificial layer 202a The thickness dimension removed from the side wall surface can expose the surface of the first sacrificial layer 201a when the mask film 204 is etched back later, so that the second mask formed on the surface of the first sacrificial layer and the second mask formed on the first sacrificial layer can be exposed. There is a certain distance between the first masks on the sidewalls of the sacrificial layer 201a, and the formed first mask and second mask can form a self-aligned quadruple mask pattern.

The formation process of the mask film 204 is a deposition process, preferably an atomic layer deposition process or a chemical vapor deposition process; the atomic layer deposition process or chemical vapor deposition process can accurately control the thickness of the mask film 204, The thickness of the mask film 204 is 10 nanometers to 30 nanometers; and the thickness of the mask film determines the size of the subsequently formed first mask and the second mask, so the subsequently formed first mask and the second mask The size of the second mask can be precisely controlled. The parameters of the deposition process are determined by the material used for the mask film 204 in the specific process, and should not be too limited, and will not be described here.

Please refer to FIG. 9 , etch back the mask film 204 (as shown in FIG. 8 ) until the surfaces of the first sacrificial layer 201 a and the second sacrificial layer 202 a are exposed. A second mask 204b is formed on the surface of the sacrificial layer 201, and a first mask 204a is formed on the surface of the layer to be etched 200 on both sides of the first sacrificial layer 201a.

The etch-back process is an anisotropic dry etching process, and the parameters of the anisotropic dry etching process depend on the material and thickness of the specific mask film 204 and should not be too limited. I won't go into details. In the anisotropic dry etching process, the plasma of the etching gas is bombarded in a direction perpendicular to the surface of the layer to be etched 200, which can remove the surface of the layer to be etched 200, as well as the first sacrificial layer 201a and the second sacrificial layer 201a. The mask film 204 on the top surface of the sacrificial layer 202a is formed to form the first mask 204a and the second mask 204b.

The first mask 204a and the second mask 204b are formed by only one patterning process, that is, within the area where only one patterned layer 203 (as shown in FIG. 5 ) can be accurately formed, two patterns with precise dimensions can be formed. A first mask 204a and two second masks 204b, a total of four patterns as etching masks, that is, self-aligned quadruple patterns; the formed first mask 204a and second mask 204b are guaranteed In the case of high precision, the size is reduced, which can meet the development needs of the integration and miniaturization of semiconductor devices.

Secondly, before forming the mask film 204, the size of the second sacrificial layer 202a is reduced and part of the surface of the first sacrificial layer 201a is exposed by using a plasma dry etching process. Therefore, after the mask film 204 is formed, only one pass The etch-back process can simultaneously remove the mask film 204 on the top surfaces of the first sacrificial layer 201a and the second sacrificial layer 202a, thereby simultaneously forming two first masks 204a and two second masks 204b. Therefore, the self-aligned multiple patterning of this embodiment can be completed by only one deposition process and one etch-back process, which can reduce process steps and save costs.

Please refer to FIG. 10, after forming the first mask 204a and the second mask 204b, remove the second sacrificial layer 202a (as shown in FIG. 9); after removing the second sacrificial layer 202a, use the The second mask 204b is a mask, etch the first sacrificial layer 201a (as shown in FIG. 9 ) until the layer 200 to be etched is exposed, and the etched first sacrificial layer 201a forms a third mask 201b .

The process of removing the second sacrificial layer 202a is a dry etching process or a wet etching process. Since the etching speed of the wet etching process is relatively fast, the wet etching process is preferably used here; in addition, when the When the material of the second sacrificial layer 202a is amorphous carbon, the process of removing the second sacrificial layer 202a can also be an ashing process. After removing the second sacrificial layer 202a, the first sacrificial layer 201a at the bottom of the second sacrificial layer 202a is exposed, so as to subsequently form a third mask 201b.

The process of etching the first sacrificial layer 201a is an anisotropic dry etching process, which can form a third mask 201b whose sidewalls are perpendicular to the surface of the layer to be etched 200, so that the third mask 201b The pattern is consistent with the pattern of the second mask 204b, and under the condition that the size of the second mask 204b is accurate, the size of the third mask 201b is accurate; the third mask 201b and the first mask The film 204a is located on the surface of the layer 200 to be etched, and determines the pattern of the layer 200 to be etched, so that the size of the pattern obtained by etching the layer 200 to be etched can be precise.

In addition, because the thickness of the first sacrificial layer 201a is thicker than that of the second sacrificial layer 202a, and the height of the first mask 204a is determined by the thickness of the first sacrificial layer 201a, the height of the second mask 204b is determined by the thickness of the first sacrificial layer 204a. The thickness of the second sacrificial layer 202a is determined, so the height of the first mask 204a is higher than that of the second mask 204b. After removing the second sacrificial layer 202a and etching the first sacrificial layer 201a, it can be ensured that the first mask 204a still has a sufficient height dimension to etch the layer 200 to be etched.

It should be noted that after the third mask 201b is formed, the layer to be etched 200 is etched using the first mask 204a and the third mask 201b as masks; the layer to be etched is etched The process of 200 is an anisotropic dry etching process, so that the layer to be etched 200 forms a required pattern to form a semiconductor device.

In this embodiment, a second sacrificial layer is formed on the surface of the first sacrificial layer, and the size of the second sacrificial layer is smaller than that of the first sacrificial layer, and part of the surface of the first sacrificial layer is exposed; A mask film is formed on the surface of the etching layer, the first sacrificial layer and the second sacrificial layer, and the mask film is etched by an etch-back process, that is, the first mask can be formed on both sides of the first sacrificial layer, and the A second mask is formed on both sides of the second sacrificial layer. Secondly, after the second sacrificial layer is formed by etching the patterned layer as a mask, it is etched from the sidewall surface of the second sacrificial layer by using a plasma dry etching process to reduce the size. The reduced size of the second sacrificial layer is easily controlled by the etching process, and the size of the second sacrificial layer is precise, thereby making the positions of the first mask and the second mask precise. However, the size of the first mask and the second mask is controlled by the thickness of the mask film, so the position and size of the formed first mask and the second mask are precise.

second embodiment

11 to 13 are schematic cross-sectional structure diagrams of the formation process of the self-aligned multiple patterns according to the second embodiment of the present invention.

Please refer to FIG. 11 , a layer to be etched 300 is provided, and several discrete first sacrificial layers 301a are formed on a part of the surface of the layer to be etched 300, and the surface of the layer to be etched 300 is exposed between adjacent first sacrificial layers 301a, so The first sacrificial layer 301a has a second sacrificial layer 302a on its surface, and the second sacrificial layer 302a has a third sacrificial layer 330 on its surface.

The size of the third sacrificial layer 330 is consistent with that of the first sacrificial layer 301a and the second sacrificial layer 302a, the material of the third sacrificial layer 330 is polysilicon, amorphous carbon, silicon oxide or silicon nitride, and the first The material of the third sacrificial layer 330 is different from that of the first sacrificial layer 301a or the second sacrificial layer 302a.

The formation process of the first sacrificial layer 301a, the second sacrificial layer 302a and the third sacrificial layer 330 is: depositing a first sacrificial film on the surface of the layer to be etched 300; depositing a second sacrificial film on the surface of the first sacrificial film; A third sacrificial film is deposited on the surface of the second sacrificial film; several discrete patterned layers are formed on a part of the surface of the third sacrificial film, and the surface of the third sacrificial film is exposed between adjacent patterned layers; The patterned layer is a mask, and the third sacrificial film, the second sacrificial film and the first sacrificial film are etched until the layer 300 to be etched is exposed.

The materials and structures of the layer to be etched 300 , the first sacrificial layer 301 a and the second sacrificial layer 302 a are the same as those described in the first embodiment, and will not be repeated here.

Please refer to FIG. 12 , remove part of the thickness along the side wall surface of the second sacrificial layer 302a, so that the size of the second sacrificial layer 302a is reduced, and expose part of the surface of the first sacrificial layer 301a; along the side of the third sacrificial layer 330 Part of the thickness of the wall surface is removed to reduce the size of the third sacrificial layer 330 and expose part of the reduced size surface of the second sacrificial layer 302a.

The process of removing part of the thickness along the sidewall surface of the third sacrificial layer 330 and the process of removing part of the thickness along the sidewall surface of the second sacrificial layer 302a are the same as those described in the first embodiment along the sidewall of the second sacrificial layer 202a. The process of removing part of the thickness from the surface is the same, and will not be repeated here.

Please refer to FIG. 13 , a mask film is formed on the surface of the layer to be etched 300, the first sacrificial layer 301a, the second sacrificial layer 302a, and the third sacrificial layer 330; the mask film is etched back until exposed The etching layer 300, the first sacrificial layer 301a, the second sacrificial layer 302a and the surface of the third sacrificial layer 330, form the fourth mask 304c on the surface of the second sacrificial layer 302a on both sides of the third sacrificial layer 330, A second mask 304b is formed on the surface of the first sacrificial layer 301a on both sides of the second sacrificial layer 302a, and a first mask 304a is formed on the surface of the layer to be etched 300 on both sides of the first sacrificial layer 301a.

The formation process and the etch-back process of the mask film are the same as those described in the first embodiment, and will not be repeated here. It should be noted that the thickness of the mask film needs to be smaller than the thickness removed along the sidewall surface of the third sacrificial layer, so that the fourth mask 304c formed on both sides of the third sacrificial layer and There is a certain distance between the second masks 304b, so as to form a self-aligned sextuple pattern.

The third sacrificial layer 330 is subsequently removed, and the second sacrificial layer 302a is etched with the fourth mask 304c until the first sacrificial layer 301a is exposed; after that, the second sacrificial layer 302a is etched with the fourth mask 304c and the second mask The film 304b etches the first sacrificial layer 301a until the surface of the layer to be etched 300 is exposed; wherein, the etched second sacrificial layer 302a and the first sacrificial layer 301a between the fourth mask and the layer to be etched 300 A fifth mask is formed. Subsequently, the layer to be etched 300 is etched by using the first mask 304a, the third mask 302b and the fifth mask, and the pattern size after etching can be further reduced.

The first mask, the second mask and the fifth mask formed in this embodiment together form a self-aligned sextuple pattern, which can further reduce the size of the etched semiconductor structure.

In summary, the surface of the layer to be etched has a first sacrificial layer, and the surface of the first sacrificial layer has a second sacrificial layer; part of the thickness is thinned from the side wall surface of the second sacrificial layer, so that the second sacrificial layer The size is reduced, and part of the surface of the first sacrificial layer is exposed; subsequently, it is only necessary to form a mask film on the surface of the layer to be etched, the first sacrificial layer, and the second sacrificial layer, and use an etch-back process to etch all The above mask film, that is, a first mask can be formed on the surface of the layer to be etched on both sides of the first sacrificial layer at the same time, a second mask can be formed on the surface of the first sacrificial layer on both sides of the second sacrificial layer, and then a self-aligning Quadruple graphics. The self-aligned quadruple pattern is formed only by one deposition process and one etch-back process, the formation method is simple, the process steps are simplified, raw materials are saved, and costs are reduced.

Further, the process of thinning part of the thickness from the sidewall surface of the second sacrificial layer is a plasma dry etching process, and the etching rate of the plasma dry etching process in the direction parallel to the surface of the layer to be etched, Greater than the etching rate perpendicular to the direction of the surface of the layer to be etched, part of the second sacrificial layer can be thinned from the sidewall, and at the same time, the thickness reduction of the second sacrificial layer in the direction perpendicular to the surface of the layer to be etched is small; thus, The size of the etched second sacrificial layer parallel to the surface of the layer to be etched can be smaller than that of the first sacrificial layer; subsequently, only one layer of mask film can be formed, and the second sacrificial layer can be formed simultaneously by only one etch-back process. A mask and a second mask are used to form a self-aligned quadruple pattern.

Further, the thickness of the second sacrificial layer is thinner than that of the first sacrificial layer, then the height of the first mask subsequently formed on both sides of the first sacrificial layer is higher than that of the second mask formed on both sides of the second sacrificial layer. The height of the mask is high; after the second sacrificial layer is removed, it can be ensured that the first mask has a sufficient height as a mask for etching the layer to be etched, thereby ensuring the stability of the etched pattern.

Further, several overlapping sacrificial layers are formed on the surface of the second sacrificial layer, and before forming the mask film, part of the thickness is removed along the sidewall surface of each sacrificial layer, so that the size of the sacrificial layer is smaller than that of the sacrificial layer located in the layer. The size of the sacrificial layer under the sacrificial layer, and make the mask film also cover the sidewalls and top surfaces of the several overlapping sacrificial layers; A fourth mask is formed on both sides, and the fourth mask can form a self-aligned multiple pattern together with the first mask and the second mask, and is used to etch the layer to be etched, so that the formed device size smaller.

Although the present invention is disclosed above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention should be based on the scope defined in the claims.

Claims (20)

1. a formation method for autoregistration multiple graphics, is characterized in that, comprising:

Layer to be etched is provided, and the part surface of described layer to be etched has some the first discrete sacrifice layers, exposes layer to be etched surface between adjacent the first sacrifice layer, and described the first sacrificial layer surface has the second sacrifice layer;

Sidewall surfaces along described the second sacrifice layer is removed segment thickness, the size of described the second sacrifice layer is dwindled, and expose part the first sacrificial layer surface;

Form mask film in described layer to be etched, the first sacrifice layer and the second sacrificial layer surface;

Return mask film described in etching, until expose the first sacrifice layer and the second sacrificial layer surface, form the second mask in the first sacrificial layer surface of the second sacrifice layer both sides, form the first mask on the layer to be etched surface of the first sacrifice layer both sides;

After forming the first mask and the second mask, remove described the second sacrifice layer.

2. the formation method of autoregistration multiple graphics as claimed in claim 1, it is characterized in that, also comprise: after removing described the second sacrifice layer, taking described the second mask as mask, the first sacrifice layer described in etching is until expose layer to be etched, the first sacrifice layer formation the 3rd mask after etching.

3. the formation method of autoregistration multiple graphics as claimed in claim 1, it is characterized in that, the technique of removing segment thickness along the sidewall surfaces of the second sacrifice layer is plasma dry etch process, the parameter of described plasma dry etch process is: air pressure is 0 millitorr～50 millitorr, bias voltage is 0 volt～100 volts, and etching gas total flow is 100 standard ml/min～500 standard ml/min.

4. the formation method of autoregistration multiple graphics as claimed in claim 3, is characterized in that, the material of described the second sacrifice layer is different from the material of the first sacrifice layer, and the material of described the second sacrifice layer is polysilicon, amorphous carbon, silica or silicon nitride.

5. the formation method of autoregistration multiple graphics as claimed in claim 4, is characterized in that, in the time that the material of described the second sacrifice layer is polysilicon, etching gas comprises hydrogen bromide and oxygen, and the volume ratio of described hydrogen bromide and oxygen is 1:1～30:1; In the time that the material of described the second sacrifice layer is silica, etching gas comprises hexafluoroization four carbon and helium, and the volume ratio of described hexafluoroization four carbon and helium is 1:1～40:1; In the time that the material of described the second sacrifice layer is silicon nitride, etching gas comprises a fluoromethane and helium, and the volume ratio of a described fluoromethane and helium is 1:1～40:1.

6. the formation method of autoregistration multiple graphics as claimed in claim 1, it is characterized in that, also comprise: before dwindling the second sacrifice layer size, form some sacrifice layers that overlap in described the second sacrificial layer surface, the size of described some overlapping sacrifice layers is all consistent with the first sacrifice layer and the second sacrifice layer, the material of described some sacrifice layers is all different, and some sacrifice layers are different from the material of the first sacrifice layer or the second sacrifice layer; Before forming mask film, sidewall surfaces along each layer of sacrifice layer is removed segment thickness, make the size of every layer of sacrifice layer all be less than the size that is positioned at one deck sacrifice layer under this layer of sacrifice layer, and expose the partial sacrifice layer surface that is positioned at one deck under this layer of sacrifice layer, and described sacrifice layer exposes part the second sacrificial layer surface; Described mask film is also formed at sidewall and the top surface of described some overlapping sacrifice layers; While returning described in etching mask film, also expose some overlapping sacrifice layer top surfaces, respectively every layer of sacrifice layer both sides, the sacrificial layer surface that is positioned at one deck under this layer forms the 4th mask; Removal is positioned at the sacrifice layer at top, and with the some overlapping sacrifice layers of described the 4th mask etching, the second sacrifice layer and the first sacrifice layer until expose layer to be etched.

7. the formation method of autoregistration multiple graphics as claimed in claim 6, is characterized in that, described some overlapping sacrifice layers are 1～4 layer, and the material of described some overlapping sacrifice layers is polysilicon, amorphous carbon, silica or silicon nitride; The technique of removing segment thickness along the sidewall surfaces of each layer of sacrifice layer is plasma dry etch process, the parameter of described plasma dry etch process is: air pressure is 0 millitorr～50 millitorr, bias voltage is 0 volt～100 volts, and etching gas total flow is 100 standard ml/min～500 standard ml/min; In the time that the material of described sacrifice layer is polysilicon, etching gas comprises hydrogen bromide and oxygen, and the volume ratio of described hydrogen bromide and oxygen is 1:1～30:1; In the time that the material of described sacrifice layer is silica, etching gas comprises hexafluoroization four carbon and helium, and the volume ratio of described hexafluoroization four carbon and helium is 1:1～40:1; In the time that the material of described sacrifice layer is silicon nitride, etching gas comprises a fluoromethane and helium, and the volume ratio of a described fluoromethane and helium is 1:1～40:1.

8. the formation method of autoregistration multiple graphics as claimed in claim 1, is characterized in that, the formation method of described the first sacrifice layer and the second sacrifice layer is: in layer surface deposition to be etched the first sacrificial film; In first sacrificial film surface deposition the second sacrificial film; Form patterned layer on described the second sacrificial film surface, described patterned layer has defined position and the shape of some the first sacrifice layers and the second sacrifice layer; Taking described patterned layer as mask, the second sacrificial film and the first sacrificial film described in etching until expose layer to be etched, form the first sacrifice layer and the second sacrifice layer.

9. the formation method of autoregistration multiple graphics as claimed in claim 8, is characterized in that, the formation technique of described patterned layer is photoetching process, nano print technique or directed self-assembly process; The technique of described etching the second sacrificial film and the first sacrificial film is anisotropic dry etch process.

10. the formation method of autoregistration multiple graphics as claimed in claim 1, is characterized in that, before dwindling the size of described the second sacrifice layer, and the thin thickness of Thickness Ratio first sacrifice layer of described the second sacrifice layer.

The 11. formation methods of autoregistration multiple graphics as claimed in claim 1, it is characterized in that, the material of described mask film or the first sacrifice layer is polysilicon, amorphous carbon, silica or silicon nitride, and the material of described mask film is different from the material of the first sacrifice layer or the second sacrifice layer.

The 12. formation methods of autoregistration multiple graphics as claimed in claim 1, is characterized in that, the technique of removing the second sacrifice layer is dry etch process or wet-etching technology.

The 13. formation methods of autoregistration multiple graphics as claimed in claim 1, is characterized in that, the formation technique of described mask film is atom layer deposition process or chemical vapor deposition method.

The 14. formation methods of autoregistration multiple graphics as claimed in claim 1, is characterized in that, the thickness of described mask film is less than the gauge of removing along the sidewall surfaces of described the second sacrifice layer.

The 15. formation methods of autoregistration multiple graphics as claimed in claim 1, is characterized in that, described layer to be etched is Semiconductor substrate.

The 16. formation methods of autoregistration multiple graphics as claimed in claim 1, is characterized in that, also comprise: Semiconductor substrate is provided, and described layer to be etched is positioned at described semiconductor substrate surface.

The 17. formation methods of autoregistration multiple graphics as claimed in claim 16, it is characterized in that, also comprise: the device layer between described Semiconductor substrate and layer to be etched, described device layer comprises the dielectric layer of semiconductor device and the described semiconductor device of electricity isolation.

The 18. formation methods of autoregistration multiple graphics as claimed in claim 16, is characterized in that, described layer to be etched is polysilicon layer, metal level or dielectric layer.

19. as described in claim 15 or 16 the formation method of autoregistration multiple graphics, it is characterized in that, described Semiconductor substrate is silicon substrate.

The 20. formation methods of autoregistration multiple graphics as claimed in claim 2, is characterized in that, after forming the 3rd mask, and taking described the first mask and the 3rd mask as mask, layer to be etched described in etching.