TWI449103B - Method of fomring patterns - Google Patents

Description

Method of forming a pattern

The present invention relates to a method of forming a pattern, and more particularly to a method of preventing a hard mask from adhering to an etching reactant when forming a pattern.

Integral circuits or MEMS systems are fabricated using a semiconductor substrate, such as a germanium wafer, and repeatedly subjected to hundreds of different processes such as thin film deposition, oxidation, lithography, etching, and doping. In the lithography and etching process, a film is formed that forms a patterned photoresist on the substrate, and a pattern of the transferred photoresist is etched to the underlying film. However, as the critical size shrinks, the resolution of the lithography system needs to be improved. One of the methods used today is to increase the numerical aperture to achieve higher resolution, although the increased numerical aperture allows for higher resolution. However, the depth of focus of the image projected into the photoresist is reduced, resulting in thinning of the patterned photoresist layer. Therefore, most of the patterned photoresist during etching is consumed during etching, resulting in poor etching performance.

Therefore, in the etching process, a hard mask is currently used instead of the photoresist because the hard mask has higher etching resistance than the photoresist material, so when the hard mask is used as a mask to etch the film on the substrate, the hard mask is used. The cover is less likely to be worn during etching and affects the pattern of the film. The hard mask can be a composite layer such as tantalum nitride, tantalum oxynitride and tantalum oxide. 1 to 2 are schematic views showing a conventional method of patterning a hard mask. As shown in FIG. 1, a material layer 10 to be etched is covered with a hard mask 12, including a hafnium oxide layer 14, a hafnium oxynitride layer 16 and a tantalum nitride layer 18, which are covered from bottom to top, and then utilized micro The shadow and etching process, before forming a patterned photoresist (not shown) on the surface of the hard mask 12, and then patterning the hard mask 12, and then removing the patterned photoresist, can be formed as shown in FIG. Patterned hard mask 20.

Since the chemical and physical properties of the various material layers in the hard mask 12 are different, there are different etch rates and the accompanying etching by-products and residues are different, so the outline of the patterned hard mask 20 will A pattern irregularity may occur at the opening due to the difference in etching rate of each layer and etching by-products, so that the pattern of the patterned hard mask 20 cannot be accurately transferred onto the material layer 10 to be etched after etching.

In view of this, the present invention provides a method of forming a pattern which can avoid the above problems. According to a preferred embodiment of the present invention, the present invention provides a method of forming a pattern by first providing a material layer to be etched, the material layer being a dielectric layer to be formed into a metal interconnect, and then forming a pattern on the material layer. A hard mask, wherein the patterned hard mask can be a multi-layer or single-layer structure, and then a pre-processing process can be performed, and the pre-processing process can include a nitridation process, an oxidation process, or an actinic radiation process, and then reuse The treated patterned hard mask acts as a mask to etch the layer of material.

In accordance with another preferred embodiment of the present invention, the hard mask is comprised of any combination of a tantalum nitride layer, a hafnium oxynitride layer, a titanium nitride layer, and a titanium metal layer. After treatment with a nitridation process, the surface of the titanium metal layer is converted to titanium nitride.

According to still another preferred embodiment of the present invention, the distance between the two electrodes of the machine used for etching is between 26 mm and 33 mm.

According to still another preferred embodiment of the present invention, the operating power during etching is 50 watts to 150 watts.

According to still another preferred embodiment of the present invention, nitrogen gas is introduced as a transport gas during etching.

The invention is characterized in that the surface property of the patterned hard mask is changed by pretreatment, so that when the material layer is etched, the patterned hard mask does not adversely react with the etching gas to generate an adherent, resulting in patterning. The hard mask deforms and causes etch residues to accumulate on the patterned hard mask.

Another feature of the present invention is that there are several ways to avoid patterning hard mask deformation that can be used alone or in combination to enhance the effect.

3 to 6 illustrate a method of forming a pattern of the present invention. As shown in FIG. 3, first, a material layer 30 to be etched is provided, for example, including a dielectric layer 34 and a low dielectric material layer 36. The material layer 30 to be etched is located above a metal interconnect layer 32. One of the metal interconnects 37 is located in the metal interconnect layer 32. For example, the metal interconnects 37 can be single damascene metal or dual damascene metal traces, or other conductive components such as metal plugs. Then, a hard mask layer 35 is formed in sequence, the hard mask layer 35 includes at least one metal atom-containing material, and the hard mask layer 35 may be composed of a selective oxynitride layer 40, a selective titanium metal layer 42, and titanium nitride. Layer 44, selective yttria layer 46 and selective yttria layer 48 are layered from a bottom-up stack of composite material layer 30, followed by patterned photoresist (not shown), and patterned By patterning the hard mask layer 35 and then removing the patterned photoresist, a patterned hard mask 38 as in FIG. 4 can be formed. It is worth noting that the selective yttrium oxide layer 48, the selective yttria layer 46, the titanium nitride layer 44 and the selective titanium metal layer 42 in the hard mask 35 are etched through during etching until exposure The selective ruthenium oxynitride layer 40 is removed, and the selective ruthenium oxynitride layer 40 is only partially removed, that is, the low dielectric material layer 36 under the selective ruthenium oxynitride layer 40 is not exposed. It is still shielded by the ruthenium oxynitride layer 40, so the low dielectric material layer 36 is not adversely affected during the step of removing the photoresist. Moreover, the material of the hard mask 35 may be any combination of the above materials or the above materials and other materials in consideration of factors such as stress, antireflection ability, adhesion, etching resistance, and the like. For example, different hard mask materials can have different stress types such as tensile stress and shrinkage stress, so that the total stress of the hard mask material does not cause excessive stretching or shrinkage on the layer of material to be etched below, thus reducing delamination risks of.

According to another preferred embodiment of the present invention, the material layer 30 to be etched may also comprise a semiconductor material, a conductive material or a work function material, etc., and the pattern to be created may be a via, a trench, a line or a block. . The titanium metal layer 42 in the patterned hard mask 38 can be changed to yttrium, lanthanum, rare earth elements or transition metal elements according to different process requirements, and the titanium nitride layer 44 can also be made of other metal nitrides or metal oxides. Instead of, for example, tantalum nitride, aluminum oxide, and the like. In addition, an organic material such as a photoresist may be further included in the patterned hard mask 38, and the material composition of the patterned hard mask 38 may be other multilayer structures or a single layer structure. In addition, the method of the present invention can be applied to various etching processes in a semiconductor process that require the use of a hard mask. The embodiments exemplified below are applications for fabricating metal interconnects, while others such as gate definition or dual damascene processes The method of the invention can also be used. When the material of the patterned hard mask 38 comprises a photosensitive material such as a photoresist, the patterned hard mask 38 is formed by patterning the hard mask 35 by using a combination of a lithography process, that is, an exposure and development step. This is achieved and the step of removing the photoresist is not required after patterning the hard mask 35.

As shown in FIG. 5, after the patterned hard mask 38 is formed, a pretreatment 50 is performed, such as performing a nitridation process, and nitriding the surface of the patterned hard mask 38 exposed in the space to form a patterned hard mask 38', a selective yttria layer 40 exposed in the patterned hard mask 38, a selective titanium metal layer 42, a titanium nitride layer 44, a selective yttria layer 46, and The selective ruthenium oxide layer 48 is bonded to nitrogen to form a nitride after the treatment, and it is particularly noteworthy that the nitridation process is mainly for the purpose of patterning the hard mask 38 to be exposed to titanium in the space. The metal layer 42, that is, the side wall surface of the titanium metal layer 42, forms titanium nitride 52. Further, the upper surface and the side wall surface of the yttrium oxynitride layer 40 are simultaneously nitrided. The nitriding process uses a plasma machine, which is preferably operated at a frequency of 2,7 million Hz or 60 megahertz for a 10 to 15 second reaction.

Finally, as shown in FIG. 6, the selective yttria layer 40 in the patterned hard mask 38' is first etched, and after exposing the material layer 30, the pre-processed patterned hard mask 38' is used. To mask, the material layer 30 is etched to complete the pattern transfer. Since the nitride of the patterned hard mask 38' and the surface of the patterned hard mask 38' is consumed during the etching process, only a portion of the patterned hard mask 38' remains in Fig. 6. The step of etching the material layer 30 may be performed in-situ after the nitriding treatment of the patterned hard mask 38, or ex-situ.

The foregoing pretreatment 50 can be changed to an oxidation process according to different process requirements or using an actinic radiation process such as ultraviolet light irradiation or other processes that can change the surface characteristics (chemical or physical properties) of the patterned hard mask 38, for example, In other words, the critical dimension of the patterned hard mask 38' after the oxidation treatment can be reduced; and the bond in the formed patterned hard mask 38' after the ultraviolet light irradiation is changed, so that the hardness is increased to A better masking effect is provided in subsequent etching steps.

Figure 7 is a schematic diagram showing the deformation of the patterned hard mask, in which the same elements are denoted by the same symbols. In the conventional step of etching the material layer, fluorocarbon is usually used as an etching gas, such as carbon tetrafluoride. After trifluoromethane, hexafluoroethane or the like, after the fluorocarbon is ionized, a plasma is formed, which contains a fluoride ion, a fluorocarbon radical, or the like. However, the conventional process does not pretreat the patterned hard mask before etching the material layer, and therefore, as shown in Fig. 7, when the plasma etching is performed, the surface of the untreated titanium metal layer 42 is combined. The fluoride ion reacts to form a by-product of the titanium fluoride protrusion 54 or the like adhered to the surface of the titanium metal layer 42, and then an etching residue such as the fluorocarbon polymer 56 is deposited on the patterned hard mask 38. The sidewalls cause deformation of the patterned hard mask 38, changing the size of the opening to be defined, thereby seriously affecting the etching effect. Different from the prior art, the present invention utilizes pretreatment to convert the surface of the titanium metal layer 42 into titanium nitride, thereby reducing the possibility of the titanium metal layer reacting with the etching gas, so that the titanium fluoride protrusion can be effectively avoided. 54.

FIG. 8 is a schematic view showing a bowl-shaped profile after a conventional material layer is etched, wherein the same elements are denoted by the same symbols. In the conventional step, since the etching rate of the patterned hard mask and the material layer are too large, a bowl-like profile is formed after etching, if the patterned hard mask 38 is used in FIG. An example consisting of a selective ruthenium oxynitride layer 40, a selective titanium metal layer 42, titanium nitride 44, a selective ruthenium oxyhydroxide 46, and a selective ruthenium oxide 48, prior to pretreatment 50 The etch rate of the selective ruthenium oxynitride layer 40 is lower than that of the dielectric material 36. Therefore, during etching, the low dielectric material 36 is etched more, and the ruthenium oxynitride layer 40 is etched less, thereby causing A bowl-shaped outline 62, as indicated by a circle, in Figure 8. Such as the first As shown in FIG. 5, in the present invention, the quality of the patterned hard mask 38' formed after the pretreatment 50 is changed, so that the etching rate of the patterned hard mask 38' and the material layer 30 are brought closer, especially The selective ruthenium oxynitride layer 40 in the patterned hard mask 38' is nitrided to cause an etch rate of the nitrided selective ruthenium oxynitride layer 40 and the low dielectric material 36 in the material layer 30. Nearly, therefore, a smooth profile 60 as indicated by the circle in Figure 5 can be formed after etching.

In addition, the present invention further provides three ways to avoid the formation of titanium fluoride protrusions, which are described as follows: increasing the distance between the two electrodes of the plasma machine for etching and reducing the power of the plasma machine during etching. Alternatively, a carrier gas such as nitrogen, argon or helium may be introduced during etching. Increasing the distance between the electrodes and reducing the power of the etching plasma, the purpose of which is to reduce the electric field between the electrodes. When the electric field is lowered, the amount of fluoride ions in the reaction chamber is lowered, thereby reducing the fluoride ion and the titanium metal layer. reaction. In addition, the purpose of introducing the gas is to allow some of the surface of the titanium metal layer to react to form a nitrogen-containing compound, such as titanium nitride, so that the titanium metal layer does not react with the etching gas, thereby avoiding formation of fluorination. Titanium bumps. According to the study by the inventors, the distance between the two electrodes is maintained between 26 mm and 33 mm, or the operating power of the machine is adjusted between 50 watts and 150 watts and the operating frequency is 2 megahertz, 2,000. 7 million Hz or 60 megahertz, or a feed gas of 20-50 minutes per minute (sccm) during etching, can effectively avoid the formation of titanium fluoride protrusions. The above three methods can be used alone, in combination with each other, or even with a pretreatment process. For example, the patterned hard mask can be nitrided before etching, and then the etching gas can be used in the etching process to avoid The effect of titanium fluoride protrusion formation is better.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

10‧‧‧Material layer to be etched

12‧‧‧ Hard mask

14, 48‧‧ ‧ yttrium oxide layer

16‧‧‧Nitrogen oxide layer

40, 46‧‧‧ 氮 氮 氮 layer

18‧‧‧矽 nitride layer

20‧‧‧ patterned hard mask

30‧‧‧Material layer

32‧‧‧Metal interconnect layer

34‧‧‧ dielectric layer

35‧‧‧hard mask layer

36‧‧‧Low dielectric material layer

38‧‧‧Metal plug

38, 38'‧‧‧ patterned hard mask

42‧‧‧Titanium metal layer

44‧‧‧Titanium nitride layer

50‧‧‧Pretreatment

52‧‧‧Titanium nitride

54‧‧‧Titanium fluoride bumps

56‧‧‧Fluorocarbon polymer

60‧‧ ‧ smooth contour

62‧‧‧ bowl outline

Figures 1 through 2 illustrate a conventional method of patterning a hard mask.

3 to 5 illustrate a method of forming a pattern of the present invention.

Figure 6 is a schematic diagram showing the deformation of the patterned hard mask.

Figure 7 is a schematic view showing the shape of the bowl after the material layer is etched.

Figure 8 is a schematic view showing a bowl-shaped profile of a material layer after etching in the prior art.

30. . . Material layer

34. . . Dielectric layer

32. . . Metal interconnect layer

36. . . Low dielectric material layer

37. . . Metal plug

38’. . . Patterned hard mask

42. . . Titanium layer

44. . . Titanium nitride layer

40, 46. . . Niobium oxynitride layer

48. . . Cerium oxide layer

50. . . Pretreatment

52. . . Titanium nitride

Claims (20)

A method of forming a pattern comprising: providing a layer of material overlying a mask layer, wherein the mask layer is a composite layer; etching the portion of the mask layer to form a patterned mask, wherein the patterned mask Masking the layer of material; performing a pretreatment to change the properties of the patterned mask; after the pre-treating, etching the patterned mask to expose the layer of material; and after exposing the layer of material, The patterned mask acts as a mask to pattern the layer of material. The method of forming a pattern according to claim 1, wherein the pretreatment is selected from the group consisting of a nitridation process, an oxidation process, and an actinic radiation process. The method of forming a pattern according to claim 1, wherein the material layer comprises a semiconductor material. The method of forming a pattern as described in claim 1, wherein the material layer comprises a work function material. The method of forming a pattern according to claim 1, wherein the patterned mask comprises a metal, a metal nitride or a metal oxide. The method of forming a pattern according to claim 5, wherein the patterned mask further comprises a dielectric material. The method of forming a pattern according to claim 5, wherein the patterned mask further comprises an organic material. A method of forming a pattern as described in claim 7 wherein the layer of material is in-situ patterned after completion of the pretreatment. The method of forming a pattern as described in claim 1, wherein one of the chemical and physical properties of the patterned mask is changed after the pretreatment. The method of forming a pattern as described in claim 9, wherein the chemical property comprises a bonding manner of a surface of the patterned mask. A method of forming a pattern comprising: providing a material layer overlying a mask layer comprising at least one metal atom-containing material, wherein the mask layer is a composite material layer; etching the portion of the mask layer to form a pattern a mask, wherein the patterned mask shields the layer of material; performing a pretreatment to change surface characteristics of the patterned mask; after the pre-treating, etching the patterned mask to expose the layer of material; After the material layer is exposed, an etching process is performed, using the patterned mask as Masking, etching the layer of material. The method of forming a pattern according to claim 11, wherein the pretreatment is selected from the group consisting of a nitridation process, an oxidation process, and an actinic radiation process. The method of forming a pattern according to claim 12, wherein after the pretreatment, the surface of the metal atom-containing material in the patterned mask forms the nitride containing the metal atomic material and the metal One of the oxides of atomic materials. The method of forming a pattern according to claim 13, wherein the metal atom-containing material is selected from the group consisting of titanium nitride, titanium, niobium, tantalum, rare earth elements, and transition metal elements. The method of forming a pattern as described in claim 11, wherein the etching process is performed in-situ after the pretreatment is completed. The method of forming a pattern according to claim 11, wherein the etching process is performed by plasma etching using a machine. The method of forming a pattern according to claim 16, wherein the distance between the two electrodes of the machine is between 26 mm and 33 mm. A method of forming a pattern as described in claim 16 wherein the machine is Operating power is 50 watts to 150 watts, and the operating frequency of the machine includes 2 megahertz, 27 megahertz or 60 megahertz. A method of forming a pattern as described in claim 11, wherein the etching process is performed while introducing nitrogen gas. The method of forming a pattern according to claim 11, wherein the patterned mask comprises a ruthenium oxide layer, a ruthenium oxynitride layer, a titanium nitride layer and a titanium metal layer.