JP2010080504A - Reflection type photomask blank, reflection type photomask, and inspection method and inspection device of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type photomask blank by which contrast between a pattern opened part and a pattern non-opened part of a reflection type photomask can be increased, and a pattern can be inspected easily, and to provide the reflection type photomask, and an inspection method and an inspection device of the same. <P>SOLUTION: The reflection type photomask blank includes a substrate, a reflection film formed on the substrate, a luminescent layer formed on the reflection film and emitting light when a voltage is applied, an absorber formed on the luminescent layer and absorbing exposure light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reflective photomask blank, a reflective photomask, an inspection method thereof, and an inspection apparatus applicable to photolithography, which are used in a semiconductor device manufacturing process.

  Photolithography using visible light (g-line, h-line) or ultraviolet light (i-line, KrF, ArF) is widely used for patterning of wiring and semiconductors such as semiconductor integrated circuits and display devices. Development of lithography using extreme ultraviolet light (EUV) as a next-generation light source is also in progress.

  There are two types of photomasks, transmissive and reflective. The transmissive type is formed by forming a light shielding body that shields exposure light on a substrate transparent to the exposure light, and shaping or patterning the light shielding body into the shape of a semiconductor circuit pattern. On the other hand, as shown in FIG. 3, which is a schematic sectional view of a conventional general reflection type photomask structure, the reflection type has a reflection film 302 composed of at least one layer that reflects exposure light on a substrate 301. An absorber 304 that absorbs exposure light is disposed thereon, and the absorber 304 is patterned into a semiconductor circuit pattern. In some cases, a back surface conductive film 300 for an electrostatic chuck may be provided below the substrate 301. Similarly, a reflective film protective layer 303 may be provided on the reflective film 302.

  In the inspection of the pattern formed on the reflective photomask, it is a general method to irradiate the photomask with inspection light and analyze the light reflected on the mask and compare it with design data or the actual good mask. . Therefore, in the photomask to be inspected, as shown in FIG. 3, a portion where the absorber 304 is not patterned and does not exist, a portion where the absorber 304 exists, that is, a pattern opening 310, and a pattern non-opening 311 A high contrast is required between the two. In order to cope with this, an antireflection film 305 for inspection light is provided on the exposure light absorber 304 which is the pattern non-opening 311.

  However, as the circuit pattern becomes finer and the area of the pattern opening becomes smaller, the reflection intensity of the inspection light from the pattern opening decreases, and the contrast between the opening and the non-opening depends on the pattern shape. Often, it was impossible to get enough. This is because the absolute amount of light reflected by the pattern opening decreases as the area of the pattern opening decreases. When the brightness of the inspection light is increased to increase the brightness from the pattern opening, the brightness of the light reflected from the pattern non-opening also increases, and thus the contrast cannot be improved.

  In addition, in the conventional inspection method using reflected light, although the antireflection film is formed on the absorber, it is a method of suppressing the reflected light by shifting the phase. It was dependent on the wavelength. In other words, since the wavelength of the inspection light is limited, there is a problem that the inspection cannot be performed depending on the inspection apparatus. Further, the effect of antireflection depends on the film thickness of the antireflection film. Therefore, it has been difficult to completely suppress reflection from variations in film thickness and film characteristics at the time of manufacture, that is, to suppress the reflectance of the non-opening portion to the inspection light to 0%.

  The present invention provides a reflective photomask blank, a reflective photomask, and a method for inspecting the same, which can increase the contrast between the pattern opening and the non-opening of the reflective photomask and can easily inspect the pattern. And an inspection apparatus.

  The invention according to claim 1 of the present invention is formed on a substrate, a reflective film formed on the substrate, a light emitting layer that emits light by applying a voltage formed on the reflective film, and the light emitting layer. A reflective photomask blank comprising an absorber that absorbs exposure light.

  The invention according to claim 2 of the present invention is formed on a substrate, a reflective film formed on the substrate, a light emitting layer that emits light by applying a voltage formed on the reflective film, and the light emitting layer. A reflective photomask blank comprising an absorber that absorbs exposure light, and a light-shielding body that shields light emitted from the light-emitting layer above or below the absorber.

  The invention according to claim 3 of the present invention is formed on a substrate, a reflective film formed on the substrate, a light emitting layer that emits light by applying a voltage formed on the reflective film, and the light emitting layer. A reflective photomask blank comprising: an absorber that absorbs exposure light and shields light emitted from the light emitting layer.

  The invention according to claim 4 of the present invention is the reflective photomask blank according to any one of claims 1 to 3, wherein the absorber is patterned and formed. It is.

  According to claim 5 of the present invention, a defect is applied to the reflective photomask by applying a voltage to the light emitting layer of the reflective photomask according to claim 4 and detecting electromagnetic waves radiated from the light emitting layer. This is a reflection type photomask inspection method characterized by inspection.

  The invention according to claim 6 of the present invention comprises a mechanism for applying a voltage and a mechanism for detecting electromagnetic waves using the inspection method for a reflective photomask according to claim 5. The present invention is a reflection type photomask inspection apparatus characterized by inspecting defects.

  According to one embodiment of the present invention, when the light emitting layer located under the absorber is caused to emit light, the patterned absorber or light shielding body shields electromagnetic waves radiated from the light emitting layer along the shape of the pattern. Therefore, it is not necessary to provide an antireflection film that is necessary for the inspection using the conventional reflected light, and the pattern shape can be inspected without irradiating the inspection light.

  Furthermore, according to one embodiment of the present invention, in the conventional pattern inspection method using reflected light, the inspection light has to reciprocate the pattern opening, whereas the light passing through the pattern opening is only the return path, More light can be obtained from the opening due to the shorter path.

In addition, according to an embodiment of the present invention, the patterned absorber that absorbs exposure light shields electromagnetic waves radiated from the light emitting layer into the shape of the absorber pattern. By designing a little thicker, variations in film thickness and material manufacturing can be canceled, and electromagnetic waves radiated from the non-opening can be made almost zero. The contrast can be increased.

  Therefore, according to the present invention, since the contrast between the pattern opening and the non-opening in the reflective photomask can be increased, the pattern can be easily inspected.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. The present invention is not limited to the following embodiment.

  FIG. 1 is a schematic cross-sectional view showing an example of a reflective photomask blank and a reflective photomask of the present invention. As shown in FIG. 1, the reflective photomask blank of the present invention includes at least a reflective film 102 that reflects exposure light formed on a substrate 101, a light emitting layer 110 formed on the reflective film 102, and light emission. And an absorber 108 that absorbs exposure light formed on the layer 110.

  More specifically, a flat substrate having a very small thermal expansion coefficient is preferably used as the substrate 101. When the substrate 101 needs to be electrostatically chucked in the course of exposure or inspection, the back surface conductive film 100 is provided on the back surface of the substrate 101.

  The reflective film 102 that reflects the exposure light may be a single layer, but may be preferably a multilayer film depending on the wavelength of the exposure light, and is not uniquely limited. A material and a layer structure are selected so that the reflectance of exposure light to be used is as high as possible.

  The light emitting layer 110 is usually composed of a plurality of film groups. That is, at least the lower electrode 103, the lower dielectric 104, the phosphor 105, the upper dielectric 106, and the upper electrode 107 are included.

All the film groups constituting the light emitting layer 110 are required to be transparent to the exposure light. Here, “transparent to exposure light” means that the exposure light irradiated to the reflective photomask and reflected in the shape of the pattern has such a luminance that the resist on the non-exposed object can be exposed. This transparency varies depending on the wavelength used for exposure, and also varies depending on the sensitivity of the resist and the required throughput, so that it is not uniquely limited. When the reflective film 102 has a single-layer structure, the reflective film 102 may also serve as the lower electrode 103. As an example, when KrF light having a wavelength of 248 nm is used as exposure light, the material of the reflective film 102 can be Al, and this can be used as a lower electrode. Similarly _Si 3 _{N 4} in the lower dielectric 104, the phosphor 105 ZnS, the upper dielectric 106 may be used as the _Si 3 _{N 4.} The upper electrode 107 is required to be transparent enough to transmit electromagnetic waves radiated from the light emitting layer 110 in addition to the above-described transparency to exposure light. As an example, when ZnS is used for the phosphor 105, ITO or the like can be used.

  The absorber 108 is required to be made of a material having a large extinction coefficient with respect to the wavelength of exposure light. In addition, because of the necessity of patterning, a material having good processing characteristics is selected by dry etching or other methods.

  The light shield 109 is required to be made of a material that shields electromagnetic waves emitted from the light emitting layer 110. A material having a large extinction coefficient with respect to the wavelength of the electromagnetic wave emitted from the light emitting layer 110 is required. Similarly to the absorber 108, a material having good processing characteristics is selected by dry etching or other methods because of the necessity of patterning.

  The absorber 108 may include the effect of the light shield 109. In that case, the light shield 109 can be omitted.

  Various known film forming techniques can be used for forming the above thin film. Among these, sputtering or pulsed laser deposition (PLD) is preferable because a high-quality film can be formed. In order to provide a point for applying a voltage for causing the light emitting layer 110 to emit light, the lower electrode 103 and the upper electrode 107 are partially masked so that they can be accessed from the upper surface of the photomask.

  By using such a method, the reflective photomask blank of the present invention is completed.

  The patterning of the absorber 108 can be performed by general photolithography, charged particle beam lithography, nanoimprinting, or the like, and is not particularly limited. The same applies to the light shield 109 when the light shield 109 is present. In the case where the light shield 109 is present, the absorber 108 including the light shield 109 is patterned to complete the reflective photomask of the present invention.

  By applying a voltage to the lower electrode 103 and the upper electrode 107 connected to the light emitting layer 110 of the completed photomask, an electromagnetic wave is emitted from the light emitting layer 110, and the electromagnetic wave is emitted from the upper patterned light shield 109 (the absorber 108 is a light shield). In the case of serving also as 109, the absorber 108) is formed into a circuit pattern shape and is emitted from the upper surface of the mask. By inspecting this electromagnetic wave, pattern defects can be evaluated.

  FIG. 2 shows an example of an inspection apparatus that implements the inspection method of the present invention.

  In order to facilitate the inspection of the photomask of the present invention, a probe 202 for applying a voltage to the photomask is provided in the inspection apparatus. The method is not particularly limited, but a method of providing the probe 202 on a part of the XY stage 204 is simple.

  The probe 202 is designed so that a voltage sufficient to cause the light emitting layer 110 to emit light can be applied. In FIG. 2, the light emitting layer power source 205 corresponds to this. The voltage value at this time is appropriately selected depending on the configuration of the light emitting layer 110. Electromagnetic waves are radiated from the light emitting layer 110 of the mask by applying the voltage to the probe 202 by applying the voltage to the lower electrode 103 and the upper electrode 107 of the mask. The inspection apparatus is provided with a mechanism for detecting this electromagnetic wave and evaluating pattern defects. As in the example shown in FIG. 2, the image sensor 203 detects light, and the analysis computer 201 analyzes and evaluates it. As a detection method, an appropriate method is selected depending on the wavelength of the electromagnetic wave. In any case, a known detection method can be used.

  The inspection apparatus is completed by incorporating a mechanism for detecting electromagnetic waves radiated from the probe 202 and the light emitting layer 110 described above.

  As described above in detail, according to the present invention, a reflective photomask blank and a reflective type that can take a large contrast between the pattern opening and the non-opening and can easily inspect the pattern. A photomask, an inspection method thereof, and an inspection apparatus can be provided.

It is a schematic sectional drawing which shows an example of the reflective photomask blank and reflective photomask of this invention. It is the schematic which shows an example of the test | inspection apparatus which implement | achieves the test | inspection method of this invention. It is a schematic sectional drawing which shows the conventional general reflection type photomask structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Back surface conductive film 101 ... Substrate 102 ... Reflective film 103 ... Lower electrode 104 ... Lower dielectric 105 ... Phosphor 106 ... Upper dielectric 107 ... Upper electrode DESCRIPTION OF SYMBOLS 108 ... Absorber 109 ... Light-shielding body 110 ... Light emitting layer 201 ... Analysis computer 202 ... Probe 203 ... Image sensor 204 ... XY stage 205 ... Light emission Power supply 300 for layer ... Back surface conductive film 301 ... Substrate 302 ... Reflective film 303 ... Reflective film protective layer 304 ... Absorber 305 ... Antireflection film 310 ... Pattern opening 311 ... Pattern non-opening

Claims (6)

A substrate,
A reflective film formed on the substrate;
A light emitting layer that emits light by applying a voltage formed on the reflective film;
An absorber that absorbs exposure light formed on the light emitting layer;
A reflective photomask blank comprising: A substrate,
A reflective film formed on the substrate;
A light emitting layer that emits light by applying a voltage formed on the reflective film;
An absorber that absorbs exposure light formed on the light emitting layer;
A light-shielding body that shields light emitted from the light-emitting layer on an upper part or a lower part of the absorber;
A reflective photomask blank comprising: A substrate,
A reflective film formed on the substrate;
A light emitting layer that emits light by applying a voltage formed on the reflective film;
An absorber that absorbs exposure light formed on the light emitting layer and shields light emitted from the light emitting layer;
A reflective photomask blank comprising:   The reflective photomask blank according to any one of claims 1 to 3, wherein the absorber is formed by patterning.   A reflection photomask is inspected for defects by applying the voltage to the light emitting layer of the reflective photomask according to claim 4 and detecting an electromagnetic wave radiated from the light emitting layer. Type photomask inspection method.   A defect of the reflection type photomask is inspected using the reflection type photomask inspection method according to claim 5, comprising a mechanism for applying the voltage and a mechanism for detecting the electromagnetic wave. Reflective photomask inspection equipment.