Radiation Filters for Radiation Sensors

Abstract

A radiation filter for reducing the transmission of radiation of harmful wavelengths. The radiation filter comprises zirconium and SiN3. The radiation filter may form part of a radiation sensor comprising: a passivation layer arranged to receive radiation transmitted by the radiation filter, a photodiode arranged to receive radiation transmitted by the passivation layer, and a circuit element connected to the photodiode. The radiation sensor may be used as part of an extreme ultraviolet lithography apparatus or lithography tool to perform optical measurements.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 18201678.2 filed on October 22, 2018, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a radiation filter and a radiation sensor comprising the radiation filter. The radiation sensor may form part of a lithographic apparatus such as an extreme ultraviolet lithographic apparatus or a lithographic tool. Background Art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern to a substrate. A lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern at a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) disposed on a substrate.

[0005] To project a pattern on a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on a substrate. A lithographic apparatus using extreme ultraviolet (EUV) radiation with a wavelength in the range of 4-20 nm (e.g., 6.7 nm or 13.5 nm) can form smaller features on a substrate than a lithographic apparatus using radiation with a wavelength of, for example, 193 nm.

[0006] Lithographic equipment typically includes a radiation sensor for performing various optical measurements (e.g., measuring optical aberrations of different optical elements and / or measuring the alignment between a projected image and a previously formed pattern on a substrate, etc.). Known radiation sensors are typically designed to detect wavelengths of radiation across the visible portion of the electromagnetic spectrum. EUV radiation can be difficult to detect without damaging the known radiation sensor. A known radiation sensor configured for use with an EUV lithographic equipment is provided with a conversion layer (e.g., a scintillator) and a light guide (e.g., a fiber optic board). The conversion layer is configured to convert EUV radiation into visible radiation so that the known radiation sensor can safely detect the converted radiation. The light guide is configured to guide the visible radiation from the conversion layer toward a detection element (e.g., a camera) of the known radiation sensor. The presence of the conversion layer and / or the light guide and / or any adhesive used to connect these features together and / or to the detection element reduces the accuracy of measurements made using the known radiation sensor.

[0007] It would be desirable to provide, for example, a method that obviates or mitigates one or more problems of the prior art, whether identified herein or elsewhere. Summary of the invention

[0008] According to a first aspect of the present invention, there is provided a radiation filter for reducing the transmission of radiation of harmful wavelengths, the radiation filter comprising zirconium and SiN3.

[0009] The radiation filter comprising zirconium and SiN3 advantageously transmits incident EUV radiation while reducing the transmission of other forms of radiation, such as DUV radiation, visible radiation and / or infrared radiation. This makes the radiation filter particularly advantageous when used for EUV radiation measurement purposes, for example when used to perform measurements in an EUV lithography process.

[0010] The radiation filter may include a first layer comprising zirconium and a second layer comprising SiN3.

[0011] The first layer may be disposed on the second layer.

[0012] The radiation filter may comprise a third layer comprising silicon.

[0013] The third layer may be disposed on the first layer.

[0014] The radiation filter may comprise a third layer comprising SiN 3. The first layer may be located between the second layer and the third layer.

[0015] The radiation filter may include a fourth layer including silicon. The fourth layer may be disposed on the third layer.

[0016] The third layer may have a thickness of about 5 nm or more. The third layer may have a thickness of about 100 nm or less.

[0017] The third layer may have a thickness of about 5 nm or more. The third layer may have a thickness of about 200 nm or less.

[0018] The fourth layer may have a thickness of about 10 nm or more. The fourth layer may have a thickness of about 500 nm or less.

[0019] The first layer may have a thickness of about 10 nm or more. The first layer may have a thickness of about 500 nm or less.

[0020] The second layer may have a thickness of about 5 nm or more. The second layer may have a thickness of about 100 nm or less.

[0021] The radiation filter may further comprise an anti-reflection layer for increasing the transmission of at least one wavelength of radiation through the radiation filter.

[0022] The anti-reflection layer may include at least one of SiON, CrO, CrN, CrON, SiN 3 , SiO 2 , and Al 2 O 3 .

[0023] The radiation filter may further comprise a protective layer for reducing damage to the radiation filter caused by hydrogen radicals.

[0024] The protection layer may include at least one of SiN and SiO 2 .

[0025] According to a second aspect of the present invention, there is provided a radiation sensor, which comprises the radiation filter of the first aspect of the present invention, and further comprises: a passivation layer arranged to receive radiation transmitted by the radiation filter, a photodiode arranged to receive radiation transmitted by the passivation layer, and a circuit element connected to the photodiode.

[0026] A radiation sensor comprising the radiation filter of the first aspect of the invention advantageously reduces or avoids the need for at least one of a conversion layer, a light guide and an adhesive, thereby simplifying the design of the radiation sensor and improving the transmittance, resolution and efficiency of the radiation sensor compared to known radiation sensors. The radiation sensor also advantageously experiences reduced blurring compared to known radiation sensors, thereby improving the accuracy of measurements performed using the radiation sensor. It has been found that the radiation sensor provides improved passivation and pinning (i.e., suppressing charge trapping) compared to known radiation sensors.

[0027] The passivation layer may include boron.

[0028] The radiation sensor may further include an adhesive layer. The adhesive layer may include silicon. The adhesive layer may be located between the passivation layer and the photodiode.

[0029] The photodiode may be a CMOS photodiode.

[0030] According to a third aspect of the present invention, there is provided a lithographic apparatus arranged to project a pattern from a patterning device onto a substrate, the lithographic apparatus comprising the radiation sensor of the second aspect of the present invention.

[0031] It has been found that a lithographic apparatus comprising a radiation sensor having a radiation filter has sufficient radiation hardness to relatively high doses of EUV radiation over the lifetime of the lithographic tool (e.g., many years). The lithographic apparatus according to the third aspect of the invention advantageously reduces the amount of time to perform lithographic measurements compared to known lithographic apparatuses, thereby increasing the throughput and availability of the lithographic apparatus.

[0032] According to a fourth aspect of the present invention, there is provided a lithography tool for performing optical measurements, the lithography tool comprising the radiation sensor of the second aspect of the present invention.

[0033] According to a fifth aspect of the present invention there is provided a method of filtering radiation, the method comprising passing the radiation through the radiation filter of the first aspect of the present invention.

[0034] According to a sixth aspect of the present invention, there is provided a method of performing optical measurements, the method comprising: directing radiation towards an object; collecting radiation that interacts with the object; passing the collected radiation through a radiation filter according to the first aspect; and detecting the filtered radiation.

[0035] According to a seventh aspect of the present invention, a method for manufacturing a radiation sensor is provided, the method comprising: providing a substrate; forming an epitaxial layer on the substrate; forming a photodiode in the epitaxial layer; forming a circuit element connected to the photodiode; forming a passivation layer on the epitaxial layer; and forming a radiation filter comprising zirconium and SiN3 on the passivation layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0037] - Figure 1 A lithographic system according to an embodiment of the present invention is shown, the lithographic system comprising a lithographic apparatus, a radiation source and a radiation sensor comprising a radiation filter;

[0038] - Figure 2 schematically illustrates a cross-sectional view of a portion of a radiation sensor including a radiation filter according to an embodiment of the present invention;

[0039] - Figure 3 schematically illustrates a cross-sectional view of a portion of a radiation sensor including a radiation filter having a silicon layer according to an embodiment of the present invention;

[0040] - Figure 4 schematically illustrates a cross-sectional view of a portion of a radiation sensor including a radiation filter having a plurality of SiN 3 layers according to an embodiment of the present invention;

[0041] - Figure 5 schematically illustrates a cross-sectional view of a portion of a radiation sensor comprising a radiation filter having a plurality of layers comprising SiN 3 and a layer comprising silicon according to an embodiment of the present invention;

[0042] - Figure 6 schematically shows a cross-sectional view of a portion of a radiation sensor according to an embodiment of the present invention, the radiation sensor comprising a radiation filter having an anti-reflection layer and a protective layer 44;

[0043] - Figure 7 schematically illustrates a method of manufacturing a backside illuminated radiation sensor including a radiation filter according to an embodiment of the invention; and

[0044] - Figure 8A method of manufacturing a front-illuminated radiation sensor comprising a radiation filter according to an embodiment of the invention is schematically illustrated. DETAILED DESCRIPTION

[0045] Figure 1 A lithographic system according to an embodiment of the invention is shown, the lithographic system comprising a radiation source SO and a lithographic apparatus LA comprising a radiation sensor 20 having a radiation filter 24. The radiation source SO is configured to generate an EUV radiation beam B and to provide the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g. a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

[0046] The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA. Furthermore, the illumination system IL may comprise a faceted field mirror arrangement 10 and a faceted pupil mirror arrangement 11. The faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11 together provide a desired cross-sectional shape and a desired intensity distribution for the EUV radiation beam B. In addition to or instead of the faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11, the illumination system IL may comprise other mirrors or arrangements.

[0047] After being so conditioned, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B' is generated. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. To this end, the projection system PS may include a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B' so as to form an image having features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although in Figure 1 The projection system PS is shown with only two mirrors 13, 14, but the projection system PS may comprise a different number of mirrors (eg six or eight mirrors).

[0048] The substrate W may include a previously formed pattern. In this case, the lithographic apparatus LA aligns the image formed by the patterned EUV radiation beam B′ with the pattern previously formed on the substrate W.

[0049] A relative vacuum, ie a small amount of gas (eg hydrogen) at a pressure well below atmospheric pressure, may be provided in the radiation source SO, in the illumination system IL and / or in the projection system PS.

[0050] The radiation source SO may be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a free electron laser (FEL), or any other radiation source capable of generating EUV radiation.

[0051] The lithographic apparatus comprises a radiation sensor 20 having a radiation filter 24 according to an embodiment of the invention. The radiation sensor 20 may be configured to detect a wavefront of radiation passing through the projection system PS, thereby determining optical aberrations of the projection system PS. The radiation sensor 20 may, for example, comprise a shearing interferometer.

[0052] Known radiation sensors are typically designed to detect wavelengths of radiation across the visible portion of the electromagnetic spectrum. EUV radiation may be difficult to detect without damaging the known radiation sensor. A known radiation sensor configured for use with an EUV lithography device is provided with a conversion layer (e.g., a scintillator) and a light guide (e.g., a fiber optic plate). The conversion layer is configured to convert EUV radiation into visible radiation so that the known radiation sensor can safely detect the converted radiation. The light guide is configured to guide the visible radiation from the conversion layer toward a detection element (e.g., a camera) of the known radiation sensor. The conversion layer is connected to the light guide via an adhesive layer. The light guide is connected to the camera via an adhesive layer. The presence of the conversion layer, the light guide, and the adhesive layer reduces the accuracy of measurements made using the known radiation sensor. For example, the adhesive layer may introduce significant blurring of an image passing through the adhesive into the camera and / or reduce the intensity of the radiation reaching the camera. Blurring of the image may introduce measurement errors and / or reduce the resolution of the known radiation sensor.

[0053] Figure 1 The radiation sensor 20 shown does not include the conversion layers, light guides, and adhesive layers discussed above with respect to known radiation sensors. This advantageously avoids the problems of blurring and transmission losses associated with known radiation sensors, thereby improving the accuracy and / or resolution of the radiation sensor 20 compared to known radiation sensors. The increase in radiation transmission through the radiation sensor 20 increases the efficiency of the radiation sensor. The increased efficiency of the radiation sensor 20 may in turn reduce the amount of time required to perform measurements made using the radiation sensor, thereby increasing the throughput of the lithographic apparatus LA. The radiation sensor 20 also advantageously has a simpler design due to the reduced number of components therein.

[0054] An important consequence of removing these components from the radiation sensor 20 is that the radiation sensor detects EUV radiation directly (i.e., EUV radiation is no longer converted into lower energy photons before being detected). Since the energy of the photons to be detected is relatively high, EUV radiation may damage components of the radiation sensor. Known radiation sensors typically include a silicon oxide passivation layer that forms a boundary with a silicon layer (e.g., a CMOS image sensor). EUV photons can interact with the silicon oxide layer in a variety of ways, thereby reducing the optical and / or electrical responsiveness of the radiation sensor. For example, EUV photons can contribute to the generation of charge carriers (e.g., electrons, holes, etc.) in the silicon oxide passivation layer. The generated charge carriers can accumulate and / or contribute to the generation of defects at the boundary between the silicon layer and the silicon oxide layer, and / or in the gate region of transistors located near the pixels of the known radiation sensor. These defects may cause adverse effects of the known radiation sensor, such as measurement noise, dark current, reduced optical responsiveness, fixed pattern noise, etc. The above-mentioned adverse effects may cause, for example, the known radiation sensor to be unsuitable for use within one month. EUV lithography equipment tends to use relatively high doses of EUV radiation (e.g., about 6 kJcm -2 ), and tend to have a long service life (e.g., many years). Known radiation sensors are not adequately resistant to such high doses of EUV radiation over such long periods of time. Known radiation sensors will have to be repaired and / or replaced regularly, adversely affecting the throughput of the lithographic apparatus and increasing the maintenance costs of the lithographic apparatus.

[0055] Figure 2 A cross-sectional view of a portion of a radiation sensor 20 including a radiation filter 24 according to an embodiment of the present invention is schematically shown. The radiation filter 24 includes zirconium and SiN3. The radiation filter 24 includes a first layer 26, the first layer 26 including zirconium, and a second layer 28, the second layer 28 including SiN3. The first layer 26 is disposed on the second layer 28. The first layer 26 may be deposited on the second layer 28 using, for example, sputtering deposition. The first layer 26 may have a thickness 23 of about 10 nm or more. The first layer 26 may have a thickness 23 of about 500 nm or less. For example, the first layer 26 may have a thickness of about 100 nm. The second layer 28 may have a thickness 25 of about 5 nm or more. The second layer 28 may have a thickness 25 of about 100 nm or less.

[0056] The radiation filter 24 is configured to reduce the transmission of radiation of harmful wavelengths passing through the radiation filter 24 while allowing the transmission of radiation of desired wavelengths. The radiation filter 24 of the present invention is configured to transmit EUV radiation while filtering out other types of radiation (e.g., visible radiation, deep ultraviolet (DUV) radiation, and / or infrared radiation). Zirconium can be configured to block incident DUV radiation and visible radiation while transmitting incident EUV radiation. For example, if the first layer 26 including zirconium has a thickness of about 100 nm, the first layer 26 can transmit about 0% of the incident DUV radiation, 0.1% of the incident visible radiation, and about 70% of the incident EUV radiation. SiN3 can be configured to be used as a capping layer for zirconium to reduce and / or prevent oxidation of zirconium while also transmitting incident EUV radiation. For example, if the second layer including SiN3 has a thickness of about 10 nm, the second layer 28 can transmit about 90% of the incident EUV radiation.

[0057] The radiation sensor 20 further includes a passivation layer 30. The passivation layer 30 is disposed on the radiation filter 24. Figure 2 In the example of , the passivation layer 30 is disposed on the first layer 26 including zirconium. The passivation layer 30 may include boron. The boron may be pure boron (i.e., undoped boron). The boron may be formed at a relatively low temperature (e.g., between about 400° C. and about 450° C.) to avoid damaging other components of the radiation sensor 20 due to high temperatures during the manufacture of the radiation sensor 20. The passivation layer 30 may have a thickness 27 greater than about 2 nm. The passivation layer 30 may have a thickness 27 less than about 10 nm.

[0058] The radiation sensor 20 also includes a photodiode 32. The photodiode 32 is arranged to receive radiation transmitted by the passivation layer 30. The photodiode 32 may be a PIN photodiode. The photodiode 32 may be a CMOS photodiode. The photodiode 32 is formed in and / or on the epitaxial layer 34. The photodiode 32 may have a thickness of, for example, about 4 μm. It should be understood that these figures are schematic and that the relative size of the radiation filter 24 has been increased compared to the size of the photodiode 32 in order to improve the clarity of these figures. The epitaxial layer 34 is disposed on the passivation layer 30. The epitaxial layer 34 and / or the photodiode 32 may include silicon. For example, a boron silicon junction may be formed between the passivation layer 30 and the epitaxial layer 34.

[0059] The radiation sensor 20 also includes a circuit element 36. A conductive path 37 exists between the circuit element 36 and the photodiode 32, so that a current generated by the interaction between the incident radiation and the photodiode 32 is received by the circuit element 36. The current generated by the photodiode 32 may propagate to the circuit element 36 through the epitaxial layer 34, for example, by means of charge migration. In the figure, the conductive path 37 has been represented by two thick lines to clearly indicate that the charge generated by the photodiode 32 reaches the circuit element 36. It is understood that the charge may not completely pass through the radiation sensor along the lines representing the conductive path 37. The circuit element 36 may include, for example, metal interconnects, transistors, vias, etc. Deep implantation may be used to isolate different pixels (e.g., different photodiodes 32) of the radiation sensor 20 from each other.

[0060] Figure 3 Schematically shows a cross-sectional view of a portion of a radiation sensor 20 according to an embodiment of the present invention, the radiation sensor 20 comprising a radiation filter 24 having a silicon layer 38. The radiation filter 24 and Figure 2 is the same as shown except that it now also includes a third layer comprising silicon 38. Figure 3 In an example of , the third layer 38 is disposed on the first layer 26. The third layer 38 may have a thickness 29 of about 5 nm or more. The third layer 38 may have a thickness 29 of about 200 nm or less. The third layer, the third layer including silicon 38 may assist in bonding the radiation filter 24 and the passivation layer 30 including boron. That is, the third layer, the third layer including silicon 38 may act as an adhesive layer. The third layer, the third layer including silicon 38 may reduce the transmission of incident DUV radiation while allowing the transmission of incident EUV radiation. For example, if the third layer, the third layer including silicon 38 has a thickness 29 of about 50 nm, the third layer 28 may transmit about 90% of the incident EUV radiation. As another example, if the third layer, the third layer including silicon 38 has a thickness of about 200 nm, the third layer 28 may transmit about 70% of the incident EUV radiation.

[0061] Figure 4 Schematically shows a cross-sectional view of a portion of a radiation sensor 20 according to an embodiment of the present invention, the radiation sensor 20 comprising a radiation filter 24 having a plurality of SiN3 layers 28, 40. The radiation filter 24 and Figure 23. The first layer 26 is located between the second layer 28 and the third layer 40. The third layer 40 including SiN3 may have a thickness 31 of about 5 nm or more. The third layer 40 including SiN3 may have a thickness 31 of about 100 nm or less. For example, if the third layer 40 including SiN3 has a thickness of about 10 nm, the third layer 40 may transmit about 90% of the incident EUV radiation. The third layer 40 including SiN3 may be configured to act as a capping layer and / or reduce undesirable diffusion of silicon and / or zirconium.

[0062] Figure 5 Schematically shows a cross-sectional view of a portion of a radiation sensor 20 according to an embodiment of the present invention, the radiation sensor 20 comprising a radiation filter 24 having a plurality of layers 28, 40 comprising SiN3 and a layer 42 comprising silicon. Figure 2 The radiation filter shown is the same except that it now also includes a third layer 40, the third layer 40 includes SiN3; and a fourth layer 42, the fourth layer 42 includes silicon. The first layer 26 including zirconium is located between the second layer 28 including SiN3 and the third layer 40 including SiN3. The fourth layer 42 is disposed on the third layer 40. The third layer 40 can have a thickness of about 5 nm or more. The third layer 40 can have a thickness of about 100 nm or less. For example, if the third layer 40 including SiN3 has a thickness of about 10 nm, the third layer 40 can transmit about 90% of the incident EUV radiation. The fourth layer 42 can have a thickness of about 10 nm or more. The fourth layer 42 can have a thickness of about 500 nm or less. For example, if the fourth layer 42 including silicon has a thickness of about 50 nm, the fourth layer 42 can transmit about 90% of the incident EUV radiation. The third layer 40 including SiN3 can be configured to act as a capping layer and / or reduce harmful diffusion of silicon and / or zirconium. The fourth layer 42 including silicon can assist in bonding the radiation filter 24 and the passivation layer 30 including boron. That is, the fourth layer 42 including silicon can act as an adhesive layer. The fourth layer 42 including silicon can reduce the transmission of incident DUV radiation while allowing the transmission of incident EUV radiation.

[0063] Figure 6 Schematically shows a cross-sectional view of a portion of a radiation sensor 20 according to an embodiment of the present invention, the radiation sensor 20 comprising a radiation filter 24 having an anti-reflection layer 42 and a protective layer 44. The radiation filter 24 and Figure 54. The protective layer 44 is the same as shown, except that it now also includes an anti-reflective layer 42 and a protective layer 44. The protective layer 44 is configured to reduce damage to the radiation filter caused, for example, by hydrogen radicals, while also transmitting incident EUV radiation. The protective layer 44 can be configured to reduce the transmission of non-EUV radiation such as DUV radiation and visible radiation. The protective layer can, for example, include SiN and / or SiO2. The protective layer 44 can have a thickness 33 of, for example, about 100 nm or more. The protective layer 44 can have a thickness of, for example, about 1 μm or less.

[0064] The anti-reflective layer 42 is configured to increase the transmission of at least one wavelength of radiation through the radiation filter. For example, the anti-reflective layer 42 can be configured to increase the transmission of EUV radiation to the photodiode 32. The anti-reflective layer 42 can, for example, include at least one of SiON, CrO, CrN, CrON, SiN3, SiO2, and Al2O3. The anti-reflective layer 42 can have a thickness 35 of, for example, about 1 μm or less.

[0065] The above about Figure 2-6 The radiation sensor 20 has a higher efficiency than known radiation sensors and has improved stability and lifetime compared to known radiation sensors, including when continuously exposed to high doses of EUV radiation (up to about 6 kJcm -2 ). The boron-silicon bond at the interface between the passivation layer 30 and the epitaxial layer 34 is very strong and stable even under very high doses of high energy radiation (such as EUV radiation) and / or high energy particles (e.g., hydrogen radicals). The passivation layer including boron 30 may behave like a semi-metal layer and reduce the risk of charging due to exposure to high doses of high energy radiation or particles. The boron atoms at the boron-silicon junction may play the role of passivating dangling bonds at the silicon surface. The boron-silicon junction may help form a p-type semiconductor layer near the silicon surface, thereby forming an internal electric field that may reduce the number of photogenerated charge carriers reaching the silicon surface and negatively affect the performance of the radiation sensor.

[0066] The degradation and radiation hardness of the radiation sensor 20 have been tested at different doses of EUV radiation (i.e., radiation at a wavelength of about 13.5 nm). Compared to known radiation sensors including a silicon oxide passivation layer and lacking a radiation filter according to the present invention, the radiation sensor 20 is more stable and radiation hard and can withstand very high doses of high energy radiation (e.g., up to about 100 kJcm -2 ) successfully operated. In contrast, the optical responsivity of known radiation sensors is -2 The EUV radiation dropped by about 6% after exposure to 10Jcm -2The EUV radiation dropped by about 34% after exposure to about 100 Jcm -2 The optical response of known radiation sensors was found to decrease by about 92% after exposure to about 100 Jcm -2 The EUV radiation can then be neglected.

[0067] The radiation sensor 20 may be a two-dimensional pixel array or a one-dimensional pixel array sensor. The radiation sensor 20 may be manufactured using CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor) manufacturing technology.

[0068] A use Figures 2 to 6 A method for performing optical measurement with any of the radiation sensors 20 may include directing radiation to an object such as a grating. The radiation that interacts with the object may then be collected using, for example, a lens and / or a reflector. The collected radiation may then pass through a radiation filter 24 of the radiation sensor 20. The radiation that has been filtered by the radiation filter 24 may then be detected by a photodiode 32 of the radiation sensor 20. The photodiode 32 may generate a current based on the filtered radiation received and provide the current to a circuit element 36. There is a conductive path 37 between the circuit element 36 and the photodiode 32 so that the current generated by the interaction between the incident radiation and the photodiode 32 is received by the circuit element 36. The circuit element 36 may be configured to generate a measurement signal based on the received current. For example, the measurement signal may be provided to a memory device and / or a processor for storage and / or analysis.

[0069] A method of forming a radiation sensor 20 including a radiation filter 24 according to an embodiment of the present invention involves forming an epitaxial layer on a substrate (e.g., a silicon-on-insulator substrate), forming a photodiode (e.g., a CMOS photodiode) in the epitaxial layer, forming a circuit element (e.g., a metal interconnect) connected to the photodiode in the epitaxial layer, forming a passivation layer on the epitaxial layer, and forming a radiation filter including zirconium and SiN3 on the passivation layer. Figure 7 and Figure 8 Two different methods of making alternative versions of radiation sensor 20 including radiation filter 24 according to the present invention are discussed in greater detail.

[0070] Figure 7 A method of manufacturing a backside illuminated radiation sensor including a radiation filter according to an embodiment of the invention is schematically illustrated.The backside illuminated radiation sensor is configured to receive incident radiation at a photodiode without the radiation having to pass through circuit elements of the radiation sensor.

[0071] The first step S1 comprises providing a substrate 46. The substrate 46 may, for example, comprise a silicon-on-insulator wafer.

[0072] The second step S2 includes: forming an epitaxial layer 34 on the substrate 46. The epitaxial layer 34 may be a p-doped epitaxial layer with a doping concentration of about 1×10 14 atoms / m3 or more. The epitaxial layer 34 may be a p-doped epitaxial layer having a doping concentration of about 1×10 16 The epitaxial layer 34 may have a thickness of about 10 μm or more. The epitaxial layer 34 may have a thickness of about 50 μm or less.

[0073] The third step S3 comprises forming a photodiode 32 in the epitaxial layer 34. The photodiode 32 may be a PIN photodiode. The photodiode 32 may be a CMOS photodiode. Other implantations may be performed to form other structures and / or features of the radiation sensor, such as a floating diffusion region, a transfer gate, etc.

[0074] The fourth step S4 comprises forming a circuit element 36 connected to the photodiode 32. The circuit element 36 may, for example, comprise metal interconnects, transistors, vias, etc. The circuit element 36 may be formed in and / or on the epitaxial layer 34 using, for example, standard submicron CMOS processing techniques. The circuit element 36 may, for example, comprise multiple layers of metal interconnects. There is a conductive path 37 between the circuit element 36 and the photodiode 32 so that a current generated by the interaction between the incident radiation and the photodiode 32 is received by the circuit element 36. The current generated by the photodiode 32 may, for example, propagate to the circuit element 36 by means of charge migration through the epitaxial layer 34.

[0075] A fifth step S5 comprises attaching a support layer 48 to the circuit element 36 and turning over the radiation sensor 20. The support layer 48 may, for example, comprise a handle wafer.

[0076] The sixth step S6 includes backside thinning and / or grinding of the substrate 46 to reach the epitaxial layer 34 . The sixth step S6 may be performed using physical and / or chemical etching / grinding to reach the desired thickness of the epitaxial layer 34 .

[0077] The seventh step S7 includes: forming a passivation layer 30 on the epitaxial layer 34. The passivation layer 30 may include boron. The boron may be pure boron (i.e., undoped boron). Boron may be deposited on the epitaxial layer 34 using chemical vapor deposition. Boron may be formed under relatively low temperature conditions (e.g., between about 400° C. and about 450° C.) to avoid damaging other components of the radiation sensor 20 due to high temperatures during the manufacture of the radiation sensor 20. For example, the deposition of boron may involve providing a mixture of diborane gas and hydrogen gas. The thickness of the passivation layer 30 may depend on the intended use of the radiation sensor 20. The passivation layer 30 may have a thickness greater than about 2 nm. The thickness of the passivation layer 30 may be less than about 10 nm. The minimum thickness of the passivation layer 30 may depend at least in part on reducing the presence of pinholes and / or forming a properly uniform passivation layer. The maximum thickness of passivation layer 30 may depend at least in part on the desired absorption of incident radiation and / or charged particles by the passivation layer, and / or the amount of time required to form the passivation layer (ie, generally, thicker passivation layers take longer to form via deposition).

[0078] The seventh step S7 may optionally include: cleaning the surface of the epitaxial layer 34 to reduce the presence of metal and / or organic contaminants, native oxides, etc. Cleaning the surface of the epitaxial layer 34 may include, for example, performing hydrogen fluoride vapor etching, then rinsing the surface of the epitaxial layer with a dilute hydrogen fluoride solution, and drying the surface in a manner (e.g., Marangoni drying technique) that can reduce the appearance of watermarks. After cleaning, the radiation sensor 20 may be transported to a deposition tool in a short time (e.g., less than about 5 minutes) to reduce the risk of contamination. The deposition tool may keep the radiation sensor in a protective environment (e.g., an environment including a dry and inert atmosphere (such as nitrogen)). The boron layer 30 may then be deposited on the epitaxial layer 34 using a deposition tool. The deposition on the active region of the photodiode 32 may be selective and / or uniform.

[0079] The eighth step S8 comprises forming a radiation filter 24 comprising zirconium and SiN3 on the passivation layer 30. For example, the radiation filter 24 comprising zirconium and SiN3 may be deposited on the passivation layer 30 via layer deposition such as sputtering deposition. The radiation filter 24 formed on the passivation layer may be about Figures 2 to 6 Any radiation filter 24 described.

[0080] Figure 8 A method of manufacturing a front-illuminated radiation sensor 20 including a radiation filter 24 according to an embodiment of the invention is schematically illustrated. The front-illuminated radiation sensor is configured to receive incident radiation at a photodiode 32 after the radiation has passed through circuit elements 36 of the radiation sensor 20.

[0081] A first step S9 comprises providing a substrate 46. The substrate 46 may, for example, comprise a silicon-on-insulator wafer.

[0082] The second step S10 includes forming an epitaxial layer 34 on the substrate 46. The epitaxial layer 34 may be a p-doped epitaxial layer having a doping concentration of about 1×10 14 atoms / m3 or more. The epitaxial layer 34 may be a p-doped epitaxial layer having a doping concentration of about 1×10 16 The epitaxial layer 34 may have a thickness of about 10 μm or more. The epitaxial layer 34 may have a thickness of about 50 μm or less.

[0083] The third step S11 includes forming a photodiode 32 in the epitaxial layer 34. The photodiode 32 may be a PIN photodiode. The photodiode 32 may be a CMOS photodiode. Other implantations may be performed to form other structures and / or features of the radiation sensor, such as a floating diffusion region, a transfer gate, etc.

[0084] The fourth step S12 comprises forming a circuit element 36, which is connected to the photodiode 32. The circuit element 36 may, for example, comprise metal interconnects, transistors, vias, etc. The circuit element 36 may be formed in and / or on the epitaxial layer 34 using, for example, standard submicron CMOS processing techniques. The circuit element 36 may, for example, comprise multiple layers of metal interconnects. There is a conductive path 37 between the circuit element 36 and the photodiode 32 so that the current generated by the interaction between the incident radiation and the photodiode 32 is received by the circuit element 36. The current generated by the photodiode 32 may, for example, propagate to the circuit element 36 by means of charge migration through the epitaxial layer 34.

[0085] The fifth step S13 includes forming a passivation layer 30 on the epitaxial layer 34. The passivation layer 30 may include boron. The boron may be pure boron (i.e., undoped boron). Boron may be deposited on the epitaxial layer 34 using chemical vapor deposition. Boron may be formed at a relatively low temperature (e.g., between about 400° C. and about 450° C.) to avoid damaging other components of the radiation sensor 20 due to high temperatures during the manufacture of the radiation sensor 20. For example, boron deposition may involve providing a mixture of diborane gas and hydrogen gas. The thickness of the passivation layer 30 may depend on the intended use of the radiation sensor 20. The passivation layer 30 may have a thickness greater than about 2 nm. The thickness of the passivation layer 30 may be less than about 10 nm. The minimum thickness of the passivation layer 30 may depend at least in part on reducing the presence of pinholes and / or forming a suitably uniform passivation layer. The maximum thickness of passivation layer 30 may depend at least in part on the desired absorption of incident radiation and / or charged particles by the passivation layer, and / or the amount of time required to form the passivation layer (ie, generally, thicker passivation layers take longer to form via deposition).

[0086] The fifth step S13 may optionally include cleaning the surface of the epitaxial layer 34 to reduce the presence of metal and / or organic contaminants, native oxides, etc. Cleaning the surface of the epitaxial layer 34 may include, for example, performing hydrogen fluoride vapor etching, then rinsing the surface of the epitaxial layer with a dilute hydrogen fluoride solution, and drying the surface in a manner (e.g., Marangoni drying technique) that can reduce the appearance of watermarks. After cleaning, the radiation sensor 20 may be transported to a deposition tool in a short time (e.g., less than about 5 minutes) to reduce the risk of contamination. The deposition tool may keep the radiation sensor 20 in a protective environment (e.g., an environment including a dry and inert atmosphere (such as nitrogen)). The boron layer 30 may then be deposited on the epitaxial layer 34 using a deposition tool. The deposition on the active region of the photodiode 32 may be selective and / or uniform.

[0087] The sixth step S14 includes forming a radiation filter 24 including zirconium and SiN3 on the passivation layer 30. The radiation filter 24 formed on the passivation layer 30 may be about Figures 2 to 6 Any radiation filter as described.

[0088] It should be understood that the terms "first", "second", "third" and "fourth" as used herein are merely intended to distinguish and identify different layers of the radiation filter. The terms "first", "second", "third" and "fourth" as used herein are not intended to limit the present invention by conveying any spatial order of the layers of the radiation filter. For example, the terms "first", "second", "third" and "fourth" are not intended to indicate the order of the layers with which incident radiation interacts when the radiation filter is used. The terms "first", "second", "third" and "fourth" as used herein are not intended to limit the present invention by conveying any temporal order of the layers. For example, the terms "first", "second", "third" and "fourth" are not intended to indicate the temporal order in which the layers are formed when manufacturing the radiation filter.

[0089] Although the radiation filter 24 comprising zirconium and SiN3 has been described above with respect to the radiation sensor 20 for detecting optical aberrations of a lithographic apparatus, it should be understood that the radiation filter can be applied to any type of radiation sensor and / or any other optical device or surface. For example, the radiation filter can be applied to an alignment sensor for measuring the alignment between a substrate and a mask, a topography sensor for measuring the height of a surface of a substrate, etc.

[0090] Although specific reference may be made herein to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications. Other possible applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0091] Although specific reference may be made herein to embodiments of the invention in the context of lithographic equipment, embodiments of the invention may be used in other equipment. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus for measuring or processing an object such as a wafer (or other substrate) or a mask (or other pattern forming device). These apparatus may generally be referred to as lithographic tools. Such lithographic tools may use vacuum conditions or ambient (non-vacuum) conditions. A radiation sensor may form part of a lithographic tool for performing optical measurements.

[0092] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention is not limited to optical lithography and may be used in other applications (eg imprint lithography) where the context permits.

[0093] Although specific embodiments of the present invention have been described above, it should be understood that the present invention may be practiced in a manner other than that described. The above description is intended to be illustrative rather than restrictive. Therefore, it will be clear to those skilled in the art that modifications may be made to the described invention without departing from the scope of the claims set forth below.

[0094] Items

[0095] 1. A radiation filter for reducing the transmission of radiation of harmful wavelengths, the radiation filter comprising zirconium and SiN3.

[0096] 2. The radiation filter of clause 1, wherein the radiation filter comprises: a first layer comprising zirconium; and a second layer comprising SiN3.

[0097] 3. The radiation filter according to clause 2, wherein the first layer is arranged on the second layer.

[0098] 4. The radiation filter according to clause 2 or 3, wherein the radiation filter comprises a third layer comprising silicon.

[0099] 5. The radiation filter according to clause 4, wherein the third layer is arranged on the first layer.

[0100] 6. The radiation filter according to clause 2 or 3, wherein the radiation filter comprises a third layer, the third layer comprising the SiN3, and wherein the first layer is located between the second layer and the third layer.

[0101] 7. The radiation filter of clause 6, wherein the radiation filter comprises a fourth layer, the fourth layer comprising silicon, and wherein the fourth layer is disposed on the third layer.

[0102] 8. The radiation filter according to clause 6 or 7, wherein the thickness of the third layer is between about 5 nm and about 100 nm.

[0103] 9. The radiation filter according to clause 4 or 5, wherein the thickness of the third layer is between about 5 nm and about 200 nm.

[0104] 10. The radiation filter of clause 7, wherein the fourth layer has a thickness between about 10 nm and about 500 nm.

[0105] 11. The radiation filter of any of clauses 2 to 10, wherein the first layer has a thickness between about 10 nm and about 500 nm.

[0106] 12. The radiation filter of any of clauses 2 to 11, wherein the second layer has a thickness between about 5 nm and about 100 nm.

[0107] 13. The radiation filter according to any of clauses 1 to 12, further comprising an anti-reflection layer for increasing the transmission of at least one wavelength of radiation through the radiation filter.

[0108] 14. The radiation filter according to clause 13, wherein the antireflection layer comprises at least one of SiON, CrO, CrN, CrON, SiN3, SiO2 and Al2O3.

[0109] 15. The radiation filter according to any of clauses 1 to 14, further comprising a protective layer for reducing damage to the radiation filter caused by hydrogen radicals.

[0110] 16. The radiation filter according to clause 15, wherein the protective layer comprises at least one of SiN and SiO2.

[0111] 17. A radiation sensor comprising a radiation filter according to any one of items 1 to 16, and further comprising: a passivation layer arranged to receive radiation transmitted by the radiation filter; a photodiode arranged to receive radiation transmitted by the passivation layer; and a circuit element connected to the photodiode.

[0112] 18. The radiation sensor of clause 17, wherein the passivation layer comprises boron.

[0113] 19. The radiation sensor of clause 18, further comprising an adhesive layer comprising silicon located between the passivation layer and the photodiode.

[0114] 20. The radiation sensor of any of clauses 17 to 19, wherein the photodiode is a CMOS photodiode.

[0115] 21. A lithographic apparatus arranged to project a pattern from a patterning device onto a substrate, the lithographic apparatus comprising a radiation sensor according to any of clauses 17 to 20.

[0116] 22. A lithography tool for performing optical measurements, the lithography tool comprising a radiation sensor according to any of clauses 17 to 20.

[0117] 23. A method of filtering radiation comprising passing the radiation through a radiation filter according to any of clauses 1 to 16.

[0118] 24. A method of performing optical measurements, comprising: directing radiation towards an object; collecting radiation that interacts with the object; passing the collected radiation through a radiation filter according to any one of clauses 1 to 16; and; detecting the filtered radiation.

[0119] 25. A method for manufacturing a radiation sensor, comprising: providing a substrate; forming an epitaxial layer on the substrate; forming a photodiode in the epitaxial layer; forming a circuit element connected to the photodiode; forming a passivation layer on the epitaxial layer; and forming a radiation filter including zirconium and SiN3 on the passivation layer.

Claims

1. A radiation filter for reducing the transmission of radiation of harmful wavelengths, the radiation filter comprising: a first layer comprising zirconium; and A second layer, the second layer comprises SiN3, wherein the first layer is disposed on the second layer. 2 . The radiation filter of claim 1 , wherein the radiation filter comprises a third layer comprising silicon, wherein the third layer is disposed on the first layer.

3. The radiation filter according to claim 1, wherein the radiation filter comprises a third layer, the third layer comprises the SiN3, and wherein the first layer is located between the second layer and the third layer, wherein the radiation filter comprises a fourth layer, the fourth layer comprises silicon, and wherein the fourth layer is disposed on the third layer.

4. The radiation filter of claim 2, wherein the third layer has a thickness between about 5 nm and about 200 nm.

5. The radiation filter of claim 3, wherein the third layer has a thickness between about 5 nm and about 100 nm.

6. The radiation filter of claim 3, wherein the fourth layer has a thickness between about 10 nm and about 500 nm.

7. The radiation filter according to any one of claims 1 to 6, wherein the thickness of the first layer is between about 10 nm and about 500 nm, and / or wherein the thickness of the second layer is between about 5 nm and about 100 nm.

8. The radiation filter according to any one of claims 1 to 6, further comprising an anti-reflection layer for increasing the transmission of at least one wavelength of radiation through the radiation filter.

9. The radiation filter according to claim 8, wherein the anti-reflection layer comprises at least one of SiON, CrO, CrN, CrON, SiN3, SiO2 and Al2O3.

10. The radiation filter according to any one of claims 1 to 6, further comprising a protective layer for reducing damage to the radiation filter caused by hydrogen radicals.

11. The radiation filter of claim 10, wherein the protective layer comprises at least one of SiN and SiO2.

12. A radiation sensor comprising the radiation filter according to any one of claims 1 to 11, and further comprising: a passivation layer arranged to receive radiation transmitted by the radiation filter; a photodiode arranged to receive radiation transmitted by the passivation layer; as well as, A circuit element is connected to the photodiode.

13. The radiation sensor of claim 12, wherein the passivation layer comprises boron, the radiation sensor further comprising an adhesive layer comprising silicon between the passivation layer and the photodiode.

14. The radiation sensor of claim 12 or 13, wherein the photodiode is a CMOS photodiode.

15. A lithographic apparatus arranged to project a pattern from a patterning device onto a substrate, the lithographic apparatus comprising a radiation sensor according to any one of claims 12 to 14.

16. A lithography tool for performing optical measurements, the lithography tool comprising a radiation sensor according to any one of claims 12 to 14.

17. A method of filtering radiation comprising passing the radiation through a radiation filter according to any one of claims 1 to 11.

18. A method of performing optical measurement, comprising: directing radiation toward an object; collecting radiation interacting with the object; passing the collected radiation through a radiation filter according to any one of claims 1 to 11; as well as; The filtered radiation is detected.

19. A method of manufacturing a radiation sensor, comprising: providing a substrate; forming an epitaxial layer on the substrate; forming a photodiode in the epitaxial layer; forming a circuit element connected to the photodiode; forming a passivation layer on the epitaxial layer; as well as, A radiation filter is formed on the passivation layer, the radiation filter comprising: a first layer comprising zirconium; and A second layer, the second layer comprises SiN3, wherein the first layer is disposed on the second layer.

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