TW201332018A - Etching method for organic substance layer - Google Patents

Abstract

This invention provides an etching method for an organic substance layer such as the bottom photoresist material layer. The etching method includes: placing a substrate to be etched in a plasma reaction chamber in which the substrate includes the etching object, i.e. an organic substance material layer; injecting reaction gas into the plasma reaction chamber; and adding radio-frequency power to the reaction gas to ignite plasma to etch the substrate. The reaction gas comprises main etching gas and diluted gas, wherein the main etching gas is selected from CO2 and the diluted gas is chosen from one of Ar, N2, CO or the compound thereof. The flow amount of the diluted gas should be less than the flow amount of the main etching gas.

Description

Organic layer etching method

The present invention relates to a plasma etching method for an organic layer, and more particularly to an etching method for an organic layer under a low critical dimension (CD) requirement.

In the field of semiconductor device fabrication, various reaction chambers that utilize plasma for processing are ubiquitous. With higher processing precision and smaller critical dimensions, the industry's critical dimensions have now reached below 45 nm, such as the 22 nm CPU. However, the existing method for obtaining a processed pattern by irradiating a photoresist by an optical method has a minimum critical dimension of only about 45 nm, and it is costly to obtain a higher-precision pattern, and has no economic value. In order to obtain a smaller critical dimension processing capability under the existing lithography technology, the prior art widely adopts a critical dimension reduction technique, that is, forming a hole or a groove having a trapezoidal profile by etching on the basis of a large mask, and finally A mask with a smaller critical dimension is obtained. The key to adopting this technology is to obtain a method that can accurately control the etching result, so that the pattern size can be uniformly reduced during the etching process, and the final pattern conversion distortion is not deformed. Such a critical dimension reduction technique can be applied to etching of a plurality of material layers, such as an insulating material layer, usually a germanium-containing inorganic substance such as APL, SiO2, SiN, or the like. These material layers are relatively hard to control the shape of the channel formed by etching. However, in order to reduce the processing steps and directly obtain a high-precision patterned mask, it is now also possible to add a thick layer of organic material under the conventional photoresist, directly through etching. A method of forming a low critical size mask. It is much more difficult to etch on such a material layer because these material layers are similar to photoresist and are softer organic material layers, so they are also called bottom photo resist (BPR). The sidewalls of these material layers are easily broken during etching to form a gap causing pattern distortion. Existing etching methods often use etching gases such as HBr/O2, CO/O2, and N2/H2 to etch these BPR layers, but it is difficult to obtain accurate etching patterns using these gases and associated etching techniques. Therefore, there is a need in the industry for an etching method that can precisely etch such an organic material layer to form a low critical dimension pattern.

The summary of the present invention is intended to provide a basic understanding of the invention, and is not intended to Its sole purpose is to present some concepts of the invention in a simplified

The present invention provides an organic layer etching method, the etching method includes: placing a substrate to be etched into a plasma reaction chamber, the substrate includes etching a target organic material layer; and introducing a reaction gas into the plasma reaction chamber; Applying radio frequency electric energy to the reaction gas to ignite the plasma, and etching the substrate; wherein the reactive gas comprises a main etching gas and a diluent gas, wherein the main etching gas is selected from the group consisting of CO2, and the diluent gas is selected from the group consisting of Ar and N2. One of the COs or a mixture thereof, the dilution gas flow rate is less than the main etching gas flow rate. Wherein the etch target organic material layer comprises a layer of organic mask material, and no pattern is formed above the organic mask material layer a layer of machine material having a first critical dimension. Wherein the pattern of the patterned inorganic material layer is obtained by mask etching of a photoresist having a first critical dimension pattern located thereon. Wherein the organic mask material layer forms a pattern having a second critical dimension at the bottom of the material layer by etching, wherein the second critical dimension is smaller than the first critical dimension.

The present invention further etches the underlying second inorganic material layer with the organic mask material layer having the second critical dimension pattern as a mask.

According to a feature of the invention, the organic mask material layer has a thickness greater than 100 nm.

According to an embodiment of the invention, the flow rate of the main etching gas to the dilution gas flow ratio is greater than 3:2 and less than or equal to 3:1, or greater than 5:3 and less than or equal to 5:2.

According to an embodiment of the invention, the reaction gas further comprises a sidewall passivation gas COS, and the other flow rate of the COS gas is smaller than the gas flow rate of the diluent gas. The flow ratio of the COS gas flow to the main etch gas is less than 1:10. According to a feature of the invention, the gas pressure after the introduction of the reaction gas into the reaction chamber is 10-20 mt.

Other features, objects, and advantages of the present invention will become more apparent from To explain and clarify the gist of the present invention. The drawings do not depict all of the technical features of the specific embodiments, nor the actual size and true proportions of the components.

Embodiments of the present invention provide a method of applying to a plasma processing chamber Systems and methods for controlling RF power to minimize reflected power and effectively apply RF power to plasma. Various embodiments enable automatic adjustment of the RF power without the need to modify the verified technology menu. This automatic adjustment can be accomplished by adjusting the frequency matching and RF matching network parameters.

Figure 1 shows a plasma reaction chamber 1 which is etched in accordance with the present invention. The reaction chamber 1 includes a base 33 to which a radio frequency power source is connected. The pedestal 33 is also connected to the lower electrode as a low frequency RF power. After the plasma is ignited, the energy of the plasma is adjusted by adjusting the power of the low frequency RF power source. The base 33 includes a substrate holding device 34, which may be an electrostatic chuck or a mechanical chuck. The substrate to be processed 30 is fixed above the substrate holding device 34. The periphery of the substrate 30 also includes an edge ring 36 for controlling the temperature at the edge of the substrate, the electric field distribution, etc., and also protecting the underlying device from plasma corrosion that is ignited in the reaction chamber. The top of the reaction chamber opposite the susceptor also includes a gas diffusion device 40 coupled to a gas source 50, which may be a conventional gas shower head or other gas jet head. In addition to the capacitively coupled (CCP) plasma reaction chamber shown in Figure 1, the etching method of the present invention can also be used in an inductively coupled (ICP) plasma reaction chamber. The main difference compared with the capacitive coupling type is that the ICP ionizes the reaction gas by passing the RF power through the insulating material window around the reaction space into the reaction space around the coil of the reaction chamber. Other reaction chamber structures capable of ionizing the reaction gas can be used in the etching method of the present invention, and since they have little influence on the main feature points of the method of the present invention, they will not be described herein.

2 shows an etchant layer structure according to an embodiment of the present invention. schematic diagram. The etch target layer 20 of the present invention is usually an insulating material layer, such as SiO2, low-K material, etc., and the etch target layer is covered with a thick underlayer photoresist layer 13 (BPR), and the intermediate mask layer 12 is The TEOS material layer, as well as the uppermost photoresist layer 10 (PR) and the photoresist are immediately adjacent to the anti-reflective layer 11 (BARC).

At the beginning of the process, the enlarged target pattern is first obtained by a conventional method using a photolithography technique. A hole or a groove is formed, and the lower anti-reflection layer 11 and the intermediate mask layer 12 are etched using this pattern to form a first pattern 100, as shown in FIG. Finally, the intermediate mask layer is used as a mask to etch the pattern 100 into the underlying organic material layer 13. The thickness selection of the BPR material layer 13 is determined according to the need to narrow the critical dimension. It is usually much thicker than a conventional photoresist layer and can reach more than 100 nm, such as 150 nm or even 200 nm. The underlying photoresist layer (BPR), although also referred to as a photoresist layer, is not completely identical in material to the overlying photoresist layer 10, such as a bottom photoresist layer (BPR) that does not require the addition of a photosensitive material. Both are called photoresists, which only show that the materials used are similar. The relatively soft organic materials do not mean the same. When the organic material layer 13 is etched using the intermediate mask layer, as shown in FIG. 3, a trapezoidal cross-sectional structure is formed in the organic material layer to finally form the pattern 101 of the critical dimension required.

In the first embodiment of the present invention, the reactant gas is introduced into the reaction chamber when the organic material layer 13 is etched by the intermediate mask layer 12. The reaction gas includes a main etching gas such as CO2 for reacting a radical which is desorbed from the oxygen ion or oxygen by the radio frequency electric field to react with the organic layer, and the formed gas is removed after the oxidation. In order to protect the sidewalls, a sidewall passivation gas such as COS is also provided. COS can form a stable bond with the carbon atoms on the sidewall of the organic layer. The chemical bond prevents it from being oxidized by the main etching gas, thereby preventing the sidewall from being etched to form an arc structure. Passivation gas can also act to slow the etch rate. In addition to the passivation gas, a diluent gas such as N2 may be added, and the overall etching rate and gas concentration may be adjusted by adjusting the amount of the dilution gas. By injecting the above-mentioned processing gas into the reaction chamber to a gas pressure of 20 mt or less, the magnitude of the applied radio frequency power depends on the thickness of the etched organic layer and the material of the upper intermediate mask layer. 100-1000W, 60Mhz RF power is a typical application. The low frequency (2/13 Mhz) power connected to the lower electrode 33 is less than 250 W. The etching method and effect of the present invention will be described below by way of specific embodiments. In the first embodiment of the present invention, the flow rate of the CO2 gas into the main etching gas is 250 sccm, the gas flow rate of the dilution gas N2 is 100 sccm, and the flow rate of the sidewall passivation gas COS is 25 sccm for a certain time, so that the gas pressure reaches 15 mt to 600 W. A 60 Mhz RF electric field was applied to the plasma reaction chamber such that the reaction gas generated and maintained the plasma for 75 seconds. The etching effect obtained by etching using the method disclosed in the first embodiment of the present invention is as shown in FIG. 5a, and the hole formed by etching after etching the sidewall by the method of the present invention can be clearly seen. A section with a slight trapezoidal shape. An ideal etching effect on the underlying organic material layer is obtained: not only the sidewalls are not curved, but also the under-via size is uniformly scaled down by the through-holes formed by the upper lithography technique. By thus etching the organic material layer 13, the critical dimension of 45 nm above the opening becomes 30 nm or less at the bottom of the opening, or any size between the two, and the specific information can be designed according to the design needs. Come choose.

Another embodiment of the present invention, wherein the process gas is introduced, It can be 250 sccm of main etching CO2 gas, 150 sccm of diluted gas argon (Ar) and 25 sccm of sidewall passivated COS gas, so that the pressure in the reaction chamber reaches 20 mt. A 60 Mhz RF electric field of 600 W power was applied to the plasma reaction chamber so that the reaction gas generated and maintained the plasma for 30 seconds. The etching results as shown in Fig. 5b are obtained after etching in the manner of this embodiment of the invention. It can be seen from Fig. 5b that the holes formed by etching of the lower BPR organic material layer also have a slight trapezoidal sidewall, and the sidewalls are well protected from lateral etching.

In the third embodiment of the present invention, the processing gas introduced therein may also be a main etching gas CO2 gas of 250 sccm, a dilution gas CO flow rate of about 150 sccm, and a COS gas of 20 sccm, so that the gas pressure in the reaction chamber reaches 10 mt. A 60 Mhz RF electric field of 600 W power was applied to the plasma reaction chamber for 90 seconds. After etching by the method disclosed in the third embodiment of the present invention, the etching result as shown in FIG. 5c is obtained. It can be seen from Fig. 5c that the holes formed by etching of the lower BPR organic material layer also have a slight trapezoidal sidewall, and the sidewalls are well protected from lateral etching.

In a fourth embodiment of the present invention, the process gas introduced therein comprises a main etching CO 2 gas flow rate of 400 sccm, a dilution gas N2 gas of 200 sccm reaches a gas pressure of 20 mt, and a 60 Mhz RF electric field of 600 W power is applied to the plasma reaction chamber for 30 times. second. After etching by the method disclosed in the fourth embodiment of the present invention, the etching result as shown in FIG. 5d is obtained. It can be seen from Fig. 5d that the holes formed by etching of the lower BPR organic material layer also have a slight trapezoidal sidewall, and the sidewalls are well protected from lateral etching. Compared with the foregoing several embodiments, the main etching gas flow rate and the dilution gas flow rate are greatly increased, but due to the main etching gas and the thinning The ratio of both of the released gases is still close to 2:1 as in the previous embodiment, so that the etching purpose of the present invention can be substantially achieved even without COS sidewall protection. Since the main etching gas is CO2, the etching effect on the organic material itself is not very strong, and after dilution by a large amount of dilution gas, a relatively good sidewall shape can be obtained even if a sidewall passivation gas such as COS is not introduced. This not only reduces the difficulty of debugging the etching process, but also reduces the cost of gas use. Both CO2 and N2 are common gases, while COS is much more expensive than the former two. Therefore, the present invention not only has an etching effect better than the prior art, but also simplifies the process and saves costs.

In summary, the etching method of the present invention can achieve the etching purpose of the present invention as long as the overall ratio of the etching gas to the dilution gas flow rate is in the range of 5:3 to 5:2. The above gas flow ratio is only given a specific preferred embodiment, and it has been experimentally verified that even if the flow ratio of the above gas is in the range of 3:2 to 3:1, the above etching purpose can be substantially achieved, and it is better than the prior art. Side wall shape.

The gas flow pressure and power parameters used in the above etching are obtained based on the capacitive coupling type reaction chamber, and the present invention can also be applied to a voltage coupled type reaction chamber (ICP). The parameters thereof will be very different, but basic. The inventive concept is the same, and the ratio of the gas flow rate used will be similar to that described in the above embodiment of the present invention. Even the same capacitive coupling type (CCP) plasma reaction chamber will be slightly different, and as long as it conforms to the idea of the present invention, it is within the scope of the invention as long as the gas use and flow ratio are the same as defined in the patent scope of the present invention.

The terms and expressions used in the description of the present specification are intended to describe the invention and not to be construed as a limitation. In addition, those skilled in the art Other implementations can be readily conceived from the understanding of the specification and the practice of the invention. Various aspects and/or components of the various embodiments described herein can be employed individually or in combination. It is to be understood that the specification and examples are by way of example only, and the scope of the invention

1‧‧‧reaction chamber

10‧‧‧Photoresist layer

100‧‧‧ graphics

101‧‧‧ graphics

11‧‧‧Anti-reflection layer

12‧‧‧Intermediate mask

13‧‧‧Organic material layer

20‧‧‧ etching target layer

30‧‧‧Substrate

33‧‧‧Base

34‧‧‧Substrate fixture

36‧‧‧Edge ring

40‧‧‧Gas diffuser

50‧‧‧ gas source

Figure 1 shows a graphical representation of a plasma reaction chamber of the present invention.

2 is a schematic view showing the structure of an etched material layer according to an embodiment of the present invention.

3 is a schematic view showing the structure of a material layer after forming a patterned mask layer by photolithography according to an embodiment of the present invention.

4 is a schematic view showing an etching structure of a material layer after etching an organic material layer through a mask layer according to an embodiment of the present invention.

5a-5d are cross-sectional views showing a material layer after etching an organic material layer by the etching methods of the first to fourth embodiments of the present invention.

10‧‧‧Photoresist layer

100‧‧‧ graphics

101‧‧‧ graphics

11‧‧‧Anti-reflection layer

12‧‧‧Intermediate mask

13‧‧‧Organic material layer

20‧‧‧ etching target layer

Claims (11)

An organic layer etching method comprises: placing a substrate to be etched into a plasma reaction chamber, the substrate comprising etching a target organic material layer; introducing a reaction gas into the plasma reaction chamber; and applying radio frequency electric energy to the reaction gas to ignite The substrate is etched by the plasma; wherein the reactive gas comprises a main etching gas and a diluent gas, wherein the main etching gas is selected from the group consisting of CO2, and the diluent gas is selected from one of Ar, N2, CO or a mixture thereof. Wherein the dilution gas flow rate is less than the main etching gas flow rate. The organic layer etching method according to claim 1, wherein the etching target organic material layer comprises a layer of an organic mask material, and a patterned inorganic material layer above the organic mask material layer, the graphic The layer of inorganic material has a first critical dimension. The method for etching an organic layer according to claim 2, wherein the pattern of the patterned inorganic material layer is etched by using a photoresist having the first critical dimension pattern as a mask thereon. . The organic layer etching method according to claim 2, wherein the organic mask material layer forms a pattern having a second critical dimension at the bottom of the material layer by etching, wherein the second critical dimension is smaller than the first A critical dimension. The organic layer etching method according to claim 4, wherein the underlying second inorganic material layer is etched by using the organic mask material layer having the second critical dimension pattern as a mask. An organic layer etching method as described in claim 2, The thickness of the organic mask material layer is greater than 100 nm. The organic layer etching method according to claim 1, wherein the ratio of the flow rate of the main etching gas to the dilution gas flow rate is greater than 3:2 and less than or equal to 3:1. The organic layer etching method according to claim 7, wherein the ratio of the flow rate of the main etching gas to the dilution gas flow rate is greater than 5:3 and less than or equal to 5:2. The organic layer etching method according to claim 1, wherein the reaction gas further comprises a sidewall passivation gas COS, and the other flow rate of the COS gas is smaller than a gas flow rate of the diluent gas. The organic layer etching method according to claim 9, wherein the ratio of the flow rate of the COS gas to the main etching gas is less than 1:10. The organic layer etching method according to claim 1, wherein the gas pressure after the reaction gas is introduced into the reaction chamber is 10-20 mt.