Blank mask with backside conductive layer and photomask manufactured therewith

Abstract

A blank mask having a back-side conductive layer and a photomask manufactured therefrom are disclosed. The blank mask includes a conductive layer attached to the back side of a substrate, and the conductive layer includes a first layer, a second layer, and a third layer sequentially stacked on the back side of the substrate. The first and third layers are made of a material containing chromium (Cr) and oxygen (O), and the second layer is made of a material containing chromium (Cr) but not oxygen (O). A blank mask with a conductive layer is provided, the conductive layer having the characteristics of low sheet resistance, high adhesion to the substrate, and low stress applied to the substrate.

Description

Technical Field

[0001] This disclosure relates to a blanking mask and a photomask, and more specifically, to a blanking mask having a conductive layer on the back side of a substrate and a photomask fabricated using the blanking mask. Background Technology

[0002] Blank masks have various types of structures where thin films are stacked on a substrate. Any type of blank mask, such as a reflective blank mask used for extreme ultraviolet (EUV) light, has a conductive layer on the back side of the substrate. Figure 1 This is a side cross-sectional view of a standard blank mask.

[0003] The blank mask comprises: a substrate 110, on the front side of which various types of thin films (not shown), such as reflective and absorbing films, are formed; and a conductive layer 120 is formed on the back side of the substrate 110. The conductive layer 120 is used to improve the adhesion between the electron chuck and the blank mask and to prevent particle generation due to friction between the electron chuck and the blank mask. The conductive layer 120 is typically made of a chromium (Cr)-based material.

[0004] The conductive layer 120 needs to possess characteristics such as low sheet resistance, high adhesion to the substrate 110, and low stress applied to the substrate 110. With high sheet resistance, a risk of dielectric breakdown exists because a high voltage is required to achieve high adhesion to the electron chuck. With low adhesion to the conductive layer 120, there may be a problem of reduced alignment during clamping due to slippage of the blank mask. Furthermore, the conductive layer 120, made of a Cr-based material, applies tensile stress to the back side of the substrate 110, thereby generating compressive stress on the front side of the substrate 110. The compressive stress applied to the substrate 110 increases the flatness value of the substrate 110, resulting in increased coverage. Summary of the Invention

[0005] This disclosure provides a blank mask having a conductive layer that has the characteristics of low sheet resistance, high adhesion to the substrate, and low stress applied to the substrate.

[0006] According to one aspect of this disclosure, a blank mask includes a conductive layer attached to the back side of a substrate, wherein the conductive layer includes a first layer, a second layer, and a third layer sequentially stacked on the back side of the substrate, wherein the first and third layers are made of a material containing chromium (Cr) and oxygen (O), and the second layer is made of a material containing chromium (Cr) but not oxygen (O).

[0007] At least one of the first, second, and third layers may be made of a material that further contains nitrogen (N).

[0008] At least one of the first, second, and third layers may be made of a material that further contains carbon (C).

[0009] The first and third layers can be made of CrCON, and the second layer can be made of CrCN.

[0010] The first layer can be made of 20 atomic% to 70 atomic% of chromium (Cr), 30 atomic% to 80 atomic% of oxygen (O), and 0 atomic% to 50 atomic% of nitrogen and carbon. The second layer can be made of 40 atomic% to 100 atomic% of chromium (Cr) and 0 atomic% to 60 atomic% of nitrogen and carbon. The third layer can be made of 20 atomic% to 70 atomic% of chromium (Cr), 30 atomic% to 80 atomic% of oxygen (O), and 0 atomic% to 50 atomic% of nitrogen and carbon.

[0011] At least one of the first, second, and third layers may be made of a material further comprising at least one element selected from the group consisting of: hydrogen (H), boron (B), aluminum (Al), silver (Ag), cobalt (Co), copper (Cu), iron (Fe), hafnium (Hf), indium (In), molybdenum (Mo), nickel (Ni), niobium (Nb), silicon (Si), tantalum (Ta), titanium (Ti), zinc (Zn), and zirconium (Zr).

[0012] The content of the element can be 15 atomic percent or less than 15 atoms.

[0013] The first layer may have a root mean square (RMS) surface roughness of 0.5 nanometers or less.

[0014] The first layer can have a thickness of 10 nanometers to 100 nanometers.

[0015] The second layer can have a sheet resistance of 100Ω / Y or less than 100Ω / Y.

[0016] The second layer can have a thickness of 10 nanometers to 60 nanometers.

[0017] The third layer may have a root mean square (RMS) surface roughness of 0.5 nanometers or less.

[0018] The third layer can have a thickness of 1 nanometer to 30 nanometers.

[0019] According to this disclosure, a photomask is provided that is manufactured using a blank mask configured as described above.

[0020] According to this disclosure, a blank mask having a conductive layer is provided, the conductive layer having the characteristics of low sheet resistance, high adhesion to the substrate, and low stress applied to the substrate. Attached Figure Description

[0021] The above and other aspects, features, and advantages of certain embodiments of this disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0022] Figure 1 This is a side cross-sectional view of a standard blank mask.

[0023] Figure 2 This is a side cross-sectional view of a blank mask according to the present disclosure.

[0024] Explanation of icon numbers

[0025] 110, 210: Substrate;

[0026] 120, 220: Conductive layer;

[0027] 221: First layer / layer;

[0028] 222: Second layer / layer;

[0029] 223: Third layer / layer. Detailed Implementation

[0030] Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings.

[0031] Figure 2 This is a side cross-sectional view of a blank mask according to the present disclosure. The present disclosure illustrates a reflective blank mask for extreme ultraviolet (EUV) light. However, the present disclosure is not limited thereto and applies to all types of blank masks with conductive layers.

[0032] The blank mask includes: a substrate 210, on the front side of which various types of thin films (not shown), such as reflective and absorbent films, are formed; and a conductive layer 220 is formed on the back side of which the substrate 210 is formed.

[0033] Substrate 210 is a glass substrate for a reflective blank mask exposed to EUV light, and is configured to have a reflective blank mask with a wavelength of 0 ± 1.0 × 10⁻⁶. -7 / ℃ and preferably 0±0.3×10 -7 A low thermal expansion material (LTEM) substrate with a low coefficient of thermal expansion in the range of / ℃ to prevent pattern deformation due to heat and stress during exposure. SiO2-TiO2 type glass, multi-component glass ceramics, or similar materials can be used as the substrate material 210.

[0034] Substrate 210 needs to have high flatness to increase the accuracy of reflected light during exposure. Flatness is represented by the total indicated reading (TIR) ​​value, and preferably, substrate 210 has a low TIR value. In a region of 132 square millimeters or 142 square millimeters, the flatness of substrate 210 is 100 nanometers or less, and preferably 50 nanometers or less.

[0035] Various types of thin films are formed on the front side of substrate 210. Figure 2 On the upper surface of the mask. In the case of a reflective blank mask used for EUV, thin films, such as reflective films and absorbent films, are formed.

[0036] The conductive layer 220 is formed on the back side of the substrate 210. Figure 2 The conductive layer 220 is located on the lower surface of the substrate. It is configured to comprise three layers: a first layer 221, a second layer 222, and a third layer 223. In addition to the three layers 221, 222, and 223, the conductive layer 220 of this disclosure may also include additional layers. Furthermore, each of layers 221, 222, and 223 may be configured to comprise multiple sublayers, and in this case, the sublayers may be configured to have different compositions and / or composition ratios. Additionally, each of layers 221, 222, and 223 may be formed in a continuous film whose composition and / or composition ratio continuously change.

[0037] The conductive layer 220 has a thickness of 21 nanometers to 190 nanometers. Furthermore, the conductive layer 220 is configured to have a sheet resistance of 100 Ω / Y or less and a root mean square (RMS) surface roughness of 0.5 nanometers or less. Additionally, the conductive layer 220 is configured to have a flatness of 150 nanometers or less, exhibiting compressive stress.

[0038] The first layer 221 is a layer in contact with the substrate 210 and is made of a material containing chromium (Cr) and oxygen (O). The first layer 221 may further contain nitrogen (N) and may further contain carbon (C). Preferably, the first layer 221 is made of CrCON.

[0039] The oxygen (O) contained in the first layer 221 increases the adhesion between the substrate 210 and the first layer 221, and also increases the compressive stress of the first layer 221 to reduce the tensile stress caused by the Cr material. In addition, the carbon (C) contained in the first layer 221 further reduces the tensile stress of the first layer 221 and relatively reduces the sheet resistance, thereby achieving a smooth adhesion to the electron chuck.

[0040] The nitrogen (N) contained in the first layer 221 is used to reduce the surface roughness of the first layer 221 by ensuring its amorphous morphology. That is, by containing nitrogen (N), the first layer 221 becomes amorphous and has excellent surface smoothness. The first layer 221 is controlled to have a root mean square (RMS) surface roughness of 0.5 nm or less. When the RMS surface roughness is 0.5 nm or greater, the adhesion between the first layer 221 and the substrate 210 can be reduced. Therefore, by controlling the RMS surface roughness to 0.5 nm or less, the adhesion between the first layer 221 and the substrate 210 can be enhanced. This prevents the first layer 221 from peeling off and prevents particle generation. The RMS surface roughness of the first layer 221 is preferably 0.4 nm or less, and most preferably 0.3 nm or less.

[0041] Preferably, the first layer 221 has a thickness of 10 nanometers to 100 nanometers. When the thickness of the first layer 221 is 10 nanometers or less, it is difficult to ensure sufficient adhesion and sufficient compressive stress. When the thickness of the first layer 221 is 100 nanometers or greater, the time required to form the first layer 221 increases and the thickness of the first layer 221 increases beyond what is required, but without increasing additional compressive stress or adhesion, thus increasing the risk of peeling. More preferably, the thickness of the first layer 221 is 20 nanometers to 90 nanometers, and most preferably, it is 30 nanometers to 80 nanometers.

[0042] The second layer 222 is formed on the first layer 221 and is made of a material that does not contain oxygen (O) but contains chromium (Cr). The first layer 221 may further contain nitrogen (N) and may further contain carbon (C). Preferably, the first layer 221 is made of CrCN.

[0043] The second layer 222 does not contain oxygen (O), and therefore serves to reduce the overall resistance of the conductive layer 220. Preferably, the second layer 222 has a sheet resistance of 100 Ω / Y or less. The carbon (C) contained in the second layer 222 relatively reduces the sheet resistance, and therefore serves to achieve a smooth adhesion to the electronic chuck.

[0044] The second layer 222 has a thickness of 10 nanometers to 60 nanometers. When the thickness of the second layer 222 is 10 nanometers or less, the total resistance of the conductive layer 220 cannot be sufficiently reduced. When the thickness of the second layer 222 is 60 nanometers or greater, the additional resistance reduction effect is minimal, and the time required to form the second layer 222 increases, and the thickness of the second layer 222 increases beyond what is required, thus increasing the risk of peeling. The thickness of the second layer 222 is more preferably 20 nanometers to 50 nanometers, and most preferably 25 nanometers to 45 nanometers.

[0045] The third layer 223 is formed on the second layer 222 and is made of a material containing chromium (Cr) and oxygen (O). The third layer 223 may further contain nitrogen (N) and may further contain carbon (C). Preferably, the third layer 223 is made of CrCON.

[0046] The oxygen (O) contained in the third layer 223 is used to increase the adhesion between the electron chuck and the third layer 223. The carbon (C) contained in the third layer 223 relatively reduces the sheet resistance, and therefore, achieves a smooth adhesion to the electron chuck.

[0047] The nitrogen (N) contained in the third layer 223 is used to reduce the surface roughness of the third layer 223 by ensuring its amorphous morphology. That is, by containing nitrogen (N), the third layer 223 becomes amorphous and has excellent surface smoothness. The third layer 223 is controlled to have a root mean square (RMS) surface roughness of 0.5 nm or less. When the RMS surface roughness is 0.5 nm or greater, it is difficult to ensure adhesion between the third layer 223 and the electron chuck. By controlling the RMS surface roughness to 0.5 nm or less, it is possible to enhance the adhesion between the third layer 223 and the electron chuck. Therefore, particle generation caused by friction between the electron chuck and the conductive layer 220 can be suppressed while the substrate 210 (on which the conductive layer 220 is formed) is adsorbed by the electron chuck. The root mean square (RMS) surface roughness of the third layer 223 is preferably 0.4 nm or less, and most preferably 0.3 nm or less.

[0048] The third layer 223 has a thickness of 1 nanometer to 30 nanometers. When the thickness of the third layer 223 is 1 nanometer or less, it is difficult to ensure adhesion to the electronic chuck. When the thickness of the third layer 223 is 30 nanometers or greater, no additional adhesion effect is ensured, and the time required to form the third layer 223 increases. The thickness of the third layer 223 is more preferably 3 nanometers to 20 nanometers, and most preferably 5 nanometers to 15 nanometers.

[0049] At least one of the first, second, and third layers may further contain at least one element selected from the group consisting of: hydrogen (H), boron (B), aluminum (Al), silver (Ag), cobalt (Co), copper (Cu), iron (Fe), hafnium (Hf), indium (In), molybdenum (Mo), nickel (Ni), niobium (Nb), silicon (Si), tantalum (Ta), titanium (Ti), zinc (Zn), and zirconium (Zr). By setting the content of these elements to 15 atomic% or less, the crystal structure of the first layer 221 to the third layer 223 may be amorphous and its surface may be further smoothed.

[0050] Simultaneously, the entire conductive layer 220 can be formed as a continuous film. In this case, the conductive layer 220 is configured such that, in the direction away from the substrate 210, from a point adjacent to the substrate 210 to the midpoint, the oxygen (O) content decreases and the nitrogen (N) content increases, and is configured such that, from the midpoint to the opposite side of the substrate 210, the oxygen (O) content increases and the nitrogen (N) content decreases. Therefore, a second layer 222 made of chromium or a chromium compound and not containing oxygen (O) is disposed in the middle region of the conductive layer 220 in the thickness direction.

[0051] Specifically, the composition ratio of each conductive layer is preferably configured as follows: The first layer 221 of the conductive layer 220 may be made of 20 atomic% to 70 atomic% of chromium (Cr), 30 atomic% to 80 atomic% of oxygen (O), and 0 atomic% to 50 atomic% of nitrogen and carbon; the second layer may be made of 40 atomic% to 100 atomic% of chromium (Cr) and 0 atomic% to 60 atomic% of nitrogen and carbon; and the third layer may be made of 20 atomic% to 70 atomic% of chromium (Cr), 30 atomic% to 80 atomic% of oxygen (O), and 0 atomic% to 50 atomic% of nitrogen and carbon.

[0052] Example 1

[0053] A conductive layer with a three-layer structure primarily composed of Cr was formed on the back side of a SiO2-TiO2-type transparent substrate using a DC magnetron reactive sputtering apparatus. All three layers of the conductive layer were formed using Cr as the target material.

[0054] A first layer of CrCON film with a thickness of 41 nm was formed by injecting Ar:N2:CO2 = 6 sccm:10 sccm:6 sccm as the process gas and using a processing power of 1.4 kW. A second layer of CrCN film with a thickness of 30 nm was formed by injecting Ar:N2:CH4 = 5 sccm:5 sccm:0.8 sccm as the process gas and using a processing power of 1.0 kW. A third layer of CrCON film with a thickness of 9 nm was formed by injecting Ar:N2:CO2 = 3 sccm:5 sccm:7.5 sccm as the process gas and using a processing power of 1.4 kW.

[0055] The sheet resistance of the conductive layer, measured using a 4-point probe, was 15.6 Ω / Y. The root mean square (RMS) surface roughness (RMS) measured using atomic force microscopy (AFM) was 0.26 nm. The flatness of the back side of the substrate, measured using a flatness meter, was 180 nm with compressive stress. Therefore, it was confirmed that there were no issues with bonding to the electronic chuck and that there were no issues with using the conductive layer from Example 1 as the conductive layer.

[0056] A 40-layer reflective film was formed by alternately stacking Mo and Si layers on the front side of a substrate with a conductive layer. After mounting Mo and Si targets on an ion beam deposition-low defect density (IBD-LDD) apparatus, the reflective film was formed by alternately forming Mo and Si layers in an Ar atmosphere. Specifically, the reflective film was formed by forming a Mo layer with a thickness of 2.8 nm, followed by forming a Si layer with a thickness of 4.2 nm, and repeating this process 40 times, based on a Mo-Si layer cycle. The top layer of the reflective film was formed of Si to suppress surface oxidation.

[0057] The reflection coefficient of the reflective film at 13.5 nm was measured using an EUV reflectometer, and the reflection coefficient was 67.7%. The surface roughness was measured using an AFM device, and the surface roughness was 0.125 nm Ra.

[0058] A 2.5 nm thick RuN capping film was formed on the reflective film using an IBD-LDD device and a Ru target in a nitrogen atmosphere. As a result of measuring the reflectance coefficient in the same manner as the reflective film after capping film formation, a reflectance coefficient of 66.8% at a wavelength of 13.5 nm was confirmed, indicating almost no loss of reflectance.

[0059] An absorption film was formed on the cover film using a DC magnetron sputtering apparatus. Specifically, an absorption film consisting of a Ta film with a thickness of 50 nm was formed on the cover film using a Ta target, Ar = 8 sccm as the process gas, and a process power of 0.7 kW. The absorption film exhibited a reflectance coefficient of 2.2% relative to a wavelength of 13.5 nm.

[0060] When measured using a flatness meter, the flatness of the front side of the substrate was 178 nanometers, thus confirming that the flatness was either the desired value or less.

[0061] The blank mask for EUV is fabricated by spin-coating a 100-nanometer-thick resist film 109 onto an absorbent film.

[0062] Example 2

[0063] In Example 2, the composition of the second layer of the conductive layer was changed from CrCN to CrN. To form the second layer, a CrN film with a thickness of 32 nm was formed by injecting Ar:N2 = 5 sccm:5 sccm as the process gas and using a processing power of 1.0 kW. The other processes were the same as in Example 1. The sheet resistance of the conductive layer, measured using a 4-point probe, was 20.2 Ω / Y, and the root mean square (RMS) surface roughness value, measured using atomic force microscopy (AFM), was 0.28 nm. Therefore, it was confirmed that there were no problems when combined with the electron chuck and that there were no problems when using the conductive layer from Example 2 as the conductive layer.

[0064] When measuring the flatness of the conductive layer using a flatness meter, a value of 190 nm was obtained, with the stress being compressive stress. When measured using the flatness meter, the flatness of the front side of the substrate after the absorption film formation process was completed was 216 nm, thus confirming that the flatness was either the desired value or less.

[0065] Example 3

[0066] In Example 3, the composition of the first layer was changed from CrCON to CrCO. To form the first layer, an Ar:CO2 = 6 sccm: 6 sccm process gas was injected, and a process power of 1.4 kW was used to form a CrCO film with a thickness of 39 nm. Other processes were the same as in Example 1. The sheet resistance of the conductive layer, measured using a 4-point probe, was 21.6 Ω / Y, and the root mean square (RMS) surface roughness was 0.27 nm when measured using atomic force microscopy (AFM). Therefore, it was confirmed that there were no problems when combined with the electron chuck and when using the conductive layer from Example 3 as the conductive layer.

[0067] When measuring the flatness of the conductive layer using a flatness meter, a value of 190 nm was obtained, with the stress being compressive stress. When measured using the flatness meter, the flatness of the front side of the substrate after the absorption film formation process was completed was 203 nm, thus confirming that the flatness was less than the desired value.

[0068] Comparative Example 1

[0069] In Comparative Example 1, the conductive layer was formed from a single CrN layer. To form the conductive layer, a CrN film with a thickness of 60 nanometers was formed by injecting a processing gas of Ar:N2 = 5 sccm:5 sccm and a processing power of 1.0 kW. The sheet resistance of the conductive layer, measured using a 4-point probe, was 20.1 Ω / Y, and the root mean square (RMS) surface roughness value, measured using atomic force microscopy (AFM), was 0.2 nanometers. Therefore, it was confirmed that there were no problems when combined with the electron chuck and that there were no problems when using the conductive layer of Comparative Example 1 as the conductive layer.

[0070] When measuring the flatness of the conductive layer using a flatness meter, a value of 240 nm was obtained, with the stress being tensile stress. When measured using the flatness meter, the flatness of the front side of the substrate after the absorption film formation process was completed was 715 nm, thus confirming that the flatness is greater than the required value.

[0071] The present disclosure has been specifically described above with reference to the accompanying drawings, but this structure is for illustrative and interpretative purposes only and is not intended to limit the meaning or scope of the disclosure as described in the claims. Therefore, those skilled in the art will understand that various modifications and equivalent structures based on the described structure are possible. Consequently, the actual technical scope of the present disclosure should be defined by the spirit of the appended claims.

Claims

1. A blank mask, comprising: Substrate; as well as A conductive layer is attached to the back side of the substrate. The conductive layer comprises a first layer, a second layer, and a third layer sequentially stacked on the back side of the substrate. The first layer and the third layer are made of a material containing chromium (Cr) and oxygen (O), and The second layer is made of a material that does not contain oxygen (O) but contains chromium (Cr); The first and third layers are made of CrCON, and the second layer is made of CrCN; The first layer has a thickness of 10 nanometers to 100 nanometers; The second layer has a thickness of 10 nanometers to 60 nanometers; The third layer has a thickness of 1 nanometer to 30 nanometers; The first layer is made of a total of 20 atomic% to 70 atomic% chromium (Cr), 30 atomic% to 80 atomic% oxygen (O), and 0 atomic% to 50 atomic% nitrogen and carbon. The second layer is made of 40 atomic% to 100 atomic% chromium (Cr) and 0 atomic% to 60 atomic% nitrogen and carbon. The third layer is made of a total of 20 atomic% to 70 atomic% chromium (Cr), 30 atomic% to 80 atomic% oxygen (O), and 0 atomic% to 50 atomic% nitrogen and carbon.

2. The blank mask according to claim 1, wherein at least one of the first layer, the second layer and the third layer is made of a material further containing nitrogen (N).

3. The blank mask according to claim 1, wherein at least one of the first layer, the second layer and the third layer is made of a material further containing carbon (C).

4. The blank mask according to any one of claims 1 to 3, wherein at least one of the first layer, the second layer and the third layer is made of a material further comprising at least one element selected from the group consisting of: hydrogen (H), boron (B), aluminum (Al), silver (Ag), cobalt (Co), copper (Cu), iron (Fe), hafnium (Hf), indium (In), molybdenum (Mo), nickel (Ni), niobium (Nb), silicon (Si), tantalum (Ta), titanium (Ti), zinc (Zn) and zirconium (Zr).

5. The blank mask according to claim 4, wherein the content of said element is 15 atomic% or less than 15 atoms.

6. The blank mask according to any one of claims 1 to 3, wherein the first layer has a root mean square surface roughness of 0.5 nanometers or less.

7. The blank mask according to any one of claims 1 to 3, wherein the second layer has a sheet resistance of 100 Ω / Y or less than 100 Ω / Y.

8. The blank mask according to any one of claims 1 to 3, wherein the third layer has a root mean square surface roughness of 0.5 nanometers or less.

9. A photomask manufactured using the blank mask as described in claim 1.

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