TW201331985A - Etching method of organic substance layer - Google Patents

Abstract

An etching method of organic substance layer, such as a bottom photo resist material layer, is provided. The mentioned etching method includes: placing a substrate to be etched into a plasma reaction chamber, wherein the mentioned substrate comprises thereon an etching target organic substance material layer; directing reaction gas into the plasma reaction chamber; exerting the radiofrequency electrical energy onto the reaction gas to ignite the plasma body to perform the etching towards the mentioned substrate; wherein the mentioned reaction gas comprises main etching gas, dilution gas, and sidewall protection gas, in which the main etching gas molecule is O2, the dilution gas is selected from one of the Ar, N2, or CO, or the mixture of the mentioned gases, and the sidewall protection gas is COS. The flow rate of the dilution gas is greater than that of the mentioned main etching gas, while the flow rate of the sidewall protection gas is smaller than that 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 optically irradiating the photoresist can achieve a minimum critical dimension of only about 45 nm, and a higher precision lithography machine is required to obtain a low-size graphic, which has a great cost, and does not have 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 thicker organic material under the conventional photoresist. Material layer, a method of directly forming a low critical size mask by etching. 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 processes. 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 invention discloses an organic layer etching method. The etching method comprises: placing a substrate to be etched into a plasma reaction chamber, wherein the substrate comprises 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 reaction gas includes a main etching gas, a diluent gas, and a sidewall shielding gas, wherein the main etching gas molecule is O2, and the diluent gas is selected From one of Ar, N2, CO or a mixture of the three, the sidewall shielding gas is COS, the dilution gas flow rate is greater than the main etching gas flow rate, and the sidewall shielding gas flow rate is smaller than the main etching gas flow rate. The etching target material The layer includes a layer of organic mask material and a layer of inorganic material patterned over the layer of organic mask material, the patterned layer of inorganic 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. 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. And etching the underlying second inorganic material layer with the organic mask material layer having the second critical dimension pattern as a mask. The flow ratio of the dilution gas to the main etching gas O2 in the reaction gas in the reaction chamber may be 5:1 to 10:1, or 5:1 to 8:1. The ratio of the flow rate of the diluent gas in the reaction gas to the side wall shielding gas COS in the reaction chamber may be between 20:1 and 6:1.

According to an embodiment of the invention, the organic mask material layer has a thickness greater than 100 nm. The radio frequency power is applied as 100-1000 W of radio frequency power, and the etching time lasts for more than 30 seconds.

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 system and method for controlling radio frequency power applied to a plasma processing chamber to minimize reflected power and effectively apply radio frequency power to the plasma. Various embodiments Automatic adjustment of RF power without the need to modify the validated 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 is a schematic view showing the structure of an etched material layer according to an embodiment of the present invention. The etch target layer 20 of the present invention is usually an insulating material layer, such as SiO2, low-K material, etc., which are respectively covered on the etch target layer. There is a thicker underlayer photoresist layer 13 (BPR), an intermediate mask layer 12 such as a TEOS material layer, and an uppermost photoresist layer 10 (PR) and an anti-reflective layer 11 (BARC) immediately below the photoresist. .

At the beginning of the process, the enlarged target pattern is first obtained by a conventional method using a photolithography technique. Holes or trenches are formed, and the lower anti-reflection layer 11 and the intermediate mask layer 12 are etched using this pattern to form the 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 O2 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. The COS can combine with the carbon atoms on the sidewall of the organic layer to form a stable chemical bond, preventing 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 down the etch rate use. In addition to the passivation gas, a diluent gas such as N2, Ar, CO, or the like may be added, and the overall etching rate and gas concentration can be adjusted by adjusting the amount of the dilution gas. By injecting the above-mentioned process 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, 60 Mhz 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 process and effect of the present invention will be described below by way of specific examples. In the first embodiment of the present invention, the processing gas introduced therein includes a main etching gas O2 flow rate of 30 sccm, a dilution gas CO gas of 200 sccm, and a sidewall passivation gas COS flow rate of 20 sccm, reaching a gas pressure of 10 mt, and a 60 Mhz radio frequency of 600 W power. An electric field was applied to the plasma reaction chamber for 30 seconds. The etching effect is shown in Figure 5.

The use of oxygen as the main etching gas for the organic layer can easily cause the sidewalls to be etched to form an isotropically etched curved sidewall. Therefore, the present invention adds a large amount of diluent gas in addition to the main etching gas, and the flow rate of the diluent gas is much larger than the main etching gas O2, reaching 20:3, and then a small amount of the sidewall shielding gas can be used to accurately etch the organic layer. Ensure the etch rate. The etching target of the present invention can still be achieved between the ratio of the diluent gas and the main etching gas between 5:1 and 8:1 and even between 5:1 and 10:1. Correspondingly, the flow ratio of the dilution gas to the side wall shielding gas COS can be selected between 20:1 and 6:1. The etching effect as shown in Fig. 5 can still be achieved by using these gas flow ratios.

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), and the parameters thereof will be very different, but The basic inventive idea 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, other implementations will be readily apparent to those skilled in the <RTIgt; 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‧‧‧plasma reaction chamber

10‧‧‧Photoresist layer

11‧‧‧Anti-reflection layer

12‧‧‧Intermediate mask

13‧‧‧Photoresist layer

20‧‧‧ etching target layer

100‧‧‧ graphics

101‧‧‧ graphics

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.

FIG. 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.

Figure 5 is a cross-sectional view showing a material layer after etching an organic material layer by an etching method of an embodiment of the present invention.

11‧‧‧Anti-reflection layer

12‧‧‧Intermediate mask

13‧‧‧Photoresist layer

20‧‧‧ etching target layer

100‧‧‧ graphics

101‧‧‧ graphics

Claims (10)

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, a diluent gas and a sidewall shielding gas, wherein the main etching gas molecule is O2, and the diluent gas is selected from one of Ar, N2 and CO Or a mixture of the gases, the sidewall shielding gas is COS, the dilution gas flow rate is greater than the main etching gas flow rate, and the sidewall shielding 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. The organic layer etching method according to claim 2, wherein the organic mask material layer has a thickness greater than 100 nm. The organic layer etching method according to claim 1, wherein a flow ratio of the diluent gas to the main etching gas O2 in the reaction gas into the reaction chamber is 5:1 to 10:1. The method for etching an organic layer according to claim 7, wherein a flow ratio of the diluent gas to the main etching gas O2 in the reaction gas into the reaction chamber is 5:1 to 8:1. The method for etching an organic layer according to claim 7, wherein a ratio of a flow rate of the diluent gas to the reaction gas COS in the reaction chamber is between 20:1 and 6:1. . The organic layer etching method according to claim 1, wherein the radio frequency electric energy is applied to 100-1000 W of radio frequency electric energy, and the etching time is longer than 30 seconds.