JP2006324384A - Etch selectivity measuring method and etch selectivity measurement device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etch selectivity measuring method and an etch selectivity measuring device which can determine the etch selectivity of an etched object against an etching mask under the environment wherein the etched object is actually etched. <P>SOLUTION: From the diffracted lights reflected by the etched object 6 and a diffraction grating pattern 7, the height H1 of the diffraction grating pattern 7 before etching, the distance from the long wavelength semiconductor laser for measurement-side surface of the diffraction grating pattern 7 after etching to the bottom face of a trench, and the depth of the trench, are found. Based on these data, a difference between the height of the diffraction grating pattern 7 before and after etching is calculated. From the calculated difference in height and the depth of the trench, the etch selectivity of the etched object 6 against the etching mask 5 can be derived. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an etching selectivity measuring method and an etching selectivity measuring apparatus.

  In dry etching, control of the etching selectivity is important because it affects the shape of the pattern after etching. For this reason, usually, a condition satisfying a desired etching selectivity is obtained from a plurality of preliminary experiments, and a pattern having a predetermined aspect ratio is formed by performing dry etching under this condition.

  However, in such a method, the same condition obtained from the preliminary experiment is used for a certain pattern and a pattern to be formed next to this pattern. That is, when a plurality of patterns are sequentially formed, all of the plurality of patterns are formed under the same conditions. Therefore, even if a pattern having an aspect ratio other than a predetermined value is formed, the next pattern is formed under the same conditions as that pattern, so that a pattern having an aspect ratio other than the predetermined value is formed again.

  That is, the above-described method has a problem that a desired aspect ratio may not be obtained because the environment in which the preliminary experiment is performed does not necessarily match the environment in which the pattern is actually formed.

  Conventionally, there is a method for measuring the etching depth of a pattern in an environment where the pattern is actually formed, but there is no method for measuring the etching selectivity of the pattern to the etching mask in the environment where the pattern is actually formed. It was.

A method for measuring the etching depth of the pattern during etching is described in, for example, Japanese Patent Application Laid-Open No. 7-58081 (Patent Document 1) and Japanese Patent Application Laid-Open No. 8-248617 (Patent Document 2).
JP-A-7-58081 JP-A-8-248617

  Accordingly, an object of the present invention is to provide an etching selectivity measuring method and an etching selectivity measuring apparatus capable of obtaining an etching selectivity of an etching object with respect to an etching mask in an environment in which the etching object is actually etched. It is in.

In order to solve the above problems, the etching selectivity measurement method of the present invention is:
Laser light is emitted toward the surface of the diffraction grating pattern that is a part of the etching mask formed on the surface of the etching object, and the light intensity of the laser light reflected by the etching object and the diffraction grating pattern Based on the step of obtaining the height of the diffraction grating pattern before etching,
After etching the object to be etched and forming a groove in the vicinity of the diffraction grating pattern of the object to be etched, laser light is emitted toward the surface of the diffraction grating pattern after etching, and after etching Determining the distance from the surface of the diffraction grating pattern after etching to the bottom surface of the groove based on the light intensity of the laser beam reflected by the object to be etched and the diffraction grating pattern;
After removing the etching mask including the diffraction grating pattern, laser light is emitted toward the surface of the etching object, and the groove is formed based on the light intensity of the laser light reflected by the etching object. A process for determining depth;
Based on the height of the diffraction grating pattern before etching, the distance from the surface of the diffraction grating pattern after etching to the bottom of the groove, and the depth of the groove, the height of the diffraction grating pattern before etching and the etching And a step of obtaining a difference from the height of the diffraction grating pattern later.

  According to the etching selectivity measurement method of the above configuration, the etching is performed based on the height of the diffraction grating pattern before etching, the distance from the surface of the diffraction grating pattern after etching to the bottom surface of the groove, and the depth of the groove. The difference between the height of the previous diffraction grating pattern and the height of the diffraction grating pattern after etching is obtained. Therefore, the etching selectivity of the etching object with respect to the etching mask in an environment where the etching object is actually etched can be derived using the difference and the depth of the groove.

  In the etching selectivity measuring method according to one embodiment, the wavelength of the laser beam is in the range of 500 nm to 800 nm.

  According to the etching selectivity measurement method of the above embodiment, since the wavelength of the laser beam is in the range of 500 nm to 800 nm, the light intensity of the reflected laser can be easily detected.

  Further, when the wavelength of the laser beam is less than 500 nm, an angle formed by the reflected laser beam with respect to the emission direction of the laser beam, that is, a diffraction angle is increased. For example, the diffraction angle of the first-order diffracted light that is the reflected laser light is approximately 90 degrees. Therefore, it becomes difficult to detect the light intensity of the reflected laser light.

  Further, when the wavelength of the laser beam is set to a value exceeding 800 nm, the diffraction angle of the laser beam is further increased, so that it becomes more difficult to detect the light intensity of the reflected laser beam.

  In the etching selectivity measurement method according to an embodiment, the reflected laser light is first-order diffracted light.

  According to the etching selectivity measurement method of the above embodiment, since the reflected laser light is first-order diffracted light, the detection accuracy of the light intensity of the laser light can be increased.

  In the etching selectivity measurement method according to an embodiment, the laser beam emission direction is substantially perpendicular to the surface of the etching object.

  According to the etching selectivity measurement method of the above embodiment, since the laser beam emission direction is substantially perpendicular to the surface of the etching target, the reflected laser is reflected even when the etching target rotates, for example, during etching. It is possible to eliminate the change of the light intensity due to the rotation.

Moreover, the etching selectivity measuring apparatus of the present invention is
A light source that emits laser light toward the surface of a diffraction grating pattern that is a part of an etching mask formed on the surface of the object to be etched;
A light receiving unit that receives the laser light reflected by the etching object and the diffraction grating pattern, and outputs a signal corresponding to the light intensity of the received laser light;
An arithmetic unit is provided for obtaining a difference between the height of the diffraction grating pattern before etching and the height of the diffraction grating pattern after etching based on the signal.

  According to the etching selectivity measuring apparatus having the above-described configuration, the calculation unit obtains the difference between the height of the diffraction grating pattern before etching and the height of the diffraction grating pattern after etching, and this difference and the depth of the groove are used. It is possible to derive the etching selectivity of the etching object with respect to the etching mask in the environment where the etching object is actually etched.

  It is preferable that the light source is a pulsed light source because the laser excitation effect on etching can be sufficiently reduced.

  In the etching selectivity measuring apparatus according to one embodiment, the etching selectivity is managed so as not to deviate from a desired value.

  According to the etching selectivity measurement apparatus of the above embodiment, a desired aspect ratio can be reliably obtained by managing the etching selectivity so that it does not deviate from a desired value. That is, the etching object can be reliably etched into a desired shape.

  In the etching selectivity measuring apparatus according to one embodiment, the arithmetic unit receives the signal via a differentiation circuit.

  According to the etching selectivity measuring apparatus of the above embodiment, since the arithmetic unit receives the signal through the differentiating circuit, the etching selectivity of the etching object with respect to the etching mask can be set even if the change in the light intensity of the laser beam is small. It can be accurately derived by the etching process.

  According to the etching selectivity measurement method of the present invention, based on the height of the diffraction grating pattern before etching, the distance from the surface of the diffraction grating pattern after etching to the bottom of the groove, and the depth of the groove, Since the difference between the height of the diffraction grating pattern and the height of the diffraction grating pattern after etching is obtained, this difference and the depth of the groove are used to perform etching on the etching mask in the environment where the etching target is actually etched. The etching selectivity of the object can be derived.

  According to the etching selectivity measurement apparatus of the present invention, the calculation unit obtains the difference between the height of the diffraction grating pattern before etching and the height of the diffraction grating pattern after etching, and using this difference and the depth of the groove, It is possible to derive the etching selectivity of the etching object with respect to the etching mask in an environment where the etching object is actually etched.

  Hereinafter, the etching selectivity measurement method of the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 shows a schematic configuration diagram of an etching selectivity measuring apparatus according to an embodiment of the present invention.

  The etching selectivity measuring apparatus receives the first-order diffracted light from the long-wavelength semiconductor laser 1 for measurement that emits laser light having a wavelength of 500 nm to 800 nm toward the substrate 12 and the first-order diffracted light from the substrate 12. A photodiode 2 that outputs a signal corresponding to the light intensity of the light, and an arithmetic unit 3 that receives a signal output from the photodiode 2 via a differentiating circuit 4. The long wavelength semiconductor laser 1 for measurement is an example of a light source. The photodiode 2 is an example of a light receiving unit.

  The measurement long wavelength semiconductor laser 1 is fixed to the chamber 10 of the etching apparatus so that the emission direction of the laser light is substantially perpendicular to the surface of the substrate 12 on the measurement long wavelength semiconductor laser 1 side. A substrate holder 11 is disposed in the chamber 10 so as to be rotatable in the direction of the arrow in the figure, and the substrate 12 is held by the substrate holder 11.

  The calculation unit 3 detects the light intensity of the first-order diffracted light received by the photodiode 2 based on the signal from the photodiode 2. Moreover, the said calculating part 3 has the recorder 8 which memorize | stores various data.

  As shown in FIG. 2, the substrate 12 has a device formation region A for forming a semiconductor device such as a semiconductor laser and an etching selectivity measurement region B for measuring an etching selectivity. .

  In the etching selectivity measurement region B, as shown in FIG. 3A, an etching target 6 is formed on the substrate 12, and a diffraction grating pattern 7 is formed on the etching target 6. The diffraction grating pattern 7 is constituted by a part of the etching mask 5.

  Note that reference numeral 13 in FIG. 1 denotes a quartz window provided on the side wall of the chamber 10.

  The etching selectivity measuring apparatus having the above configuration measures the etching selectivity as follows.

  First, before the etching of the etching target 6 is started, the long wavelength semiconductor laser 1 for measurement is pulsed or continuously oscillated, and laser light is emitted from the long wavelength semiconductor laser 1 for measurement toward the diffraction grating pattern 7. Then, the first-order diffracted light from the etching object 6 and the diffraction grating pattern 7 shown in FIG. 3A is received by the photodiode 2. As a result, a signal corresponding to the light intensity of the first-order diffracted light is input from the photodiode 2 to the arithmetic unit 3 via the differentiation circuit 4. Then, the arithmetic unit 3 obtains the height H1 of the diffraction grating pattern 7 that has not been etched based on the signal from the photodiode 2 and stores it in the recorder 8.

  Next, the etching of the etching target 6 is started, an etching gas is supplied into the chamber 10, and a part of the etching target 6 is exposed until the surface of the substrate 12 on the long wavelength semiconductor laser 1 side for measurement is exposed. Etch. That is, the groove 9 shown in FIG. 3B is formed in the vicinity of the diffraction grating pattern 7 of the etching target 6. 2 indicates the shape of the diffraction grating pattern 7 that is not etched.

  Next, the measurement long wavelength semiconductor laser 1 is pulsed or continuously oscillated, and laser light is emitted from the measurement long wavelength semiconductor laser 1 toward the etched diffraction grating pattern 7 to perform etching. The first-order diffracted light from the etched object 6 and diffraction grating pattern 7 is received by the photodiode 2. As a result, a signal corresponding to the light intensity of the first-order diffracted light is input from the photodiode 2 to the arithmetic unit 3 via the differentiation circuit 4. Then, the arithmetic unit 3 obtains the distance H2 from the surface of the etched diffraction grating pattern 7 on the long-wavelength semiconductor laser 1 side to the bottom surface of the groove 9 based on the signal from the photodiode 2. Store in the recorder 8.

  Next, as shown in FIG. 3C, after removing the diffraction grating pattern 7 together with the etching mask 5, the measurement long wavelength semiconductor laser 1 is pulse-oscillated or continuously oscillated, and etching is performed from the measurement long wavelength semiconductor laser 1. Laser light is emitted toward the etched object 6, and the first-order diffracted light from the etched object 6 and the substrate 12 subjected to the etching is received by the photodiode 2. As a result, a signal corresponding to the light intensity of the first-order diffracted light is input from the photodiode 2 to the arithmetic unit 3 via the differentiation circuit 4. Then, the arithmetic unit 3 obtains the depth H3 of the groove 9 based on the signal from the photodiode 2 and stores it in the recorder 8.

  Next, the calculation unit 3 calculates the height H1 of the diffraction grating pattern 7 before etching and the distance H2 from the surface on the measurement long wavelength semiconductor laser 1 side of the diffraction grating pattern 7 after etching to the bottom surface of the groove 9. Based on the depth H3 of the groove 9, the difference (= (H1 + H3) −H2) between the height of the diffraction grating pattern 7 before etching and the height of the diffraction grating pattern 7 after etching is obtained.

で導き出す。 Finally, the calculation unit 3 performs etching on the etching mask 5 based on the difference between the height of the diffraction grating pattern 7 before etching and the height of the diffraction grating pattern 7 after etching, and the depth H3 of the groove 9. The etching selectivity of the object 6 is derived. Specifically, the etching selectivity is

Derived by.

  Thus, the height H1 of the diffraction grating pattern 7 before etching, the distance H2 from the surface on the long-wavelength semiconductor laser 1 side for measurement of the diffraction grating pattern 7 after etching to the bottom surface of the groove 9, and the groove 9 Based on the depth H3, the etching selectivity of the etching object 6 with respect to the etching mask 5 in an environment where the etching object 6 is actually etched can be derived.

  The measurement long wavelength semiconductor laser 1 is fixed to the chamber 10 of the etching apparatus so that the emission direction of the laser light is substantially perpendicular to the surface of the substrate 12 on the measurement long wavelength semiconductor laser 1 side. Therefore, it is not necessary to adjust the incident angle of the laser beam with respect to the etching object 6 and the diffraction grating pattern 7.

  Further, even if the substrate is rotated during the etching in order to improve the uniformity of the etching, the emission direction of the laser light of the measurement long wavelength semiconductor laser 1 is on the surface of the substrate 12 on the measurement long wavelength semiconductor laser 1 side. On the other hand, since it is substantially perpendicular to the etching mask 5, it is possible to prevent an adverse effect on the measurement of the etching selectivity of the etching object 6 with respect to the etching mask 5.

  Further, the height H1 of the diffraction grating pattern 7 before etching, the distance H2 from the surface on the measurement long wavelength semiconductor laser 1 side of the diffraction grating pattern 7 after etching to the bottom surface of the groove 9, and the depth of the groove 9 If the etching selectivity obtained based on H3 differs from the desired value, the desired aspect ratio can be reliably obtained at the next etching by changing the supply amount of the etching gas into the chamber 10 or the like. be able to.

  In the above embodiment, the first-order diffracted light is received by the photodiode 2, but the second-order or higher-order diffracted light may be received by the photodiode 2.

  When the etching selectivity of the etching object 6 with respect to the etching mask 5 is measured using first-order or higher-order diffracted light, the wavelength of incident light (laser light emitted from the long-wavelength semiconductor laser 1 for measurement) is in the visible light range. It is preferable to set within.

  It is preferable that the laser beam emitted from the long-wavelength semiconductor laser 1 for measurement is a pulsed laser beam because the laser excitation effect can be sufficiently reduced with respect to etching.

  In the above embodiment, the etching selectivity measurement region B is provided outside the device formation region A. However, the etching selectivity measurement region B may be provided within the device formation region A.

  In the above embodiment, the etching selectivity measurement region B is provided on the same substrate 12 as the device formation region A. However, the etching selectivity measurement region B may be provided on a substrate 12 different from the device formation region A. . That is, it is possible to prepare an etching selectivity monitoring substrate only for obtaining the etching selectivity of the etching object 6 with respect to the etching mask 5 and to form only the etching selectivity measuring region B on the etching selectivity monitoring substrate. Good. When the etching selectivity monitoring substrate is used, it is preferable to perform etching simultaneously on the substrate on which the device formation region A is formed and the etching selectivity measurement B is not formed, and the etching selectivity monitoring substrate.

  In the above embodiment, the etching object 6 on the substrate 12 is etched. However, the diffraction grating pattern 7 is formed on the surface of the substrate 12 on the measurement long wavelength semiconductor laser 1 side, and the substrate 12 is etched. May be. In this case, the substrate 12 is an example of an object to be etched.

  The present invention is not limited to the production of a semiconductor laser, for example, and can be applied to various manufacturing processes in which a substrate, a semiconductor layer, and the like are etched in a shape having a predetermined aspect ratio with good controllability.

  By the way, as shown in FIG. 5, the diffraction angle of the diffraction grating pattern 6 is determined by the grating interval d, and the diffraction efficiency is determined by the groove depth and shape of the grating. The light intensity of the diffracted light is given by the following equation.

とすると、出射光強度は

で示される。 Width α
Number of slits M in the light incident range
Incident light intensity I ₀
θ _n : angle of Nth order diffracted light θ ₀ : angle of incident light

Then, the emitted light intensity is

Indicated by

  In actual etching, when the etching selection ratio of the etching target 6 to the etching mask 5 is low, the grating spacing d is constant and the width α is small as shown in FIG. Get smaller. On the contrary, when the etching selectivity of the etching object 6 with respect to the etching mask 5 is high, the light intensity of the diffracted light becomes relatively large as shown in FIG. 4A.

According to another embodiment of the present invention, a SiO ₂ film is formed by a P-CVD (plasma chemical vapor deposition) method or the like on a GaAs semiconductor substrate used in a laser or the like for this etching. A resist is applied to the substrate, the pattern is transferred by an exposure machine such as a stepper, and developed to form a resist pattern on the substrate.

  Next, when etching is performed by a RIE (reactive ion etching) apparatus, the intensity of the first-order diffraction pattern obtained by aligning the optical axis of the light receiving portion is monitored before the etching according to the present invention.

θ＝２４．７°
の位置に回折パターンが出現することになる（図５参照）。 Therefore, when the etching is started, the pattern intensity of the reflected light changes as described above. If the amount of change is recorded and correlated with the actual pattern angle, the in-situ etching selectivity can be measured, albeit indirectly. Assuming that a diffraction pattern having a period of about d = 1.60 × 10 ⁻⁶ m is formed on a part of the substrate as a diffraction pattern, when a red semiconductor laser having a wavelength of 670 nm is used as a measurement light source, the first-order diffraction pattern is

θ = 24.7 °
A diffraction pattern appears at the position (see FIG. 5).

  Further, according to the present invention, the etching selectivity of the etching object 6 with respect to the etching mask 5 can be accurately obtained even when a substrate having no layer structure, a substrate having a large absorption, or a substrate having a low refractive index is used.

FIG. 1 is a schematic configuration diagram of an etching selectivity measuring apparatus according to an embodiment of the present invention. FIG. 2 is a schematic perspective view of the substrate used in the etching selectivity measurement method according to the embodiment of the present invention. FIG. 3A is a schematic diagram for explaining the etching selectivity measurement method of the above embodiment. FIG. 3B is a schematic diagram for explaining the etching selectivity measurement method of the embodiment. FIG. 3C is a schematic diagram for explaining the etching selectivity measurement method of the embodiment. FIG. 4A is a schematic diagram for explaining the etching selectivity measurement method of the above embodiment. FIG. 4B is a schematic diagram for explaining the etching selectivity measurement method of the above embodiment. FIG. 5 is a schematic view for explaining an etching selectivity measuring method according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measurement long wavelength semiconductor laser 2 Photodiode 3 Operation part 4 Differentiation circuit 5 Etching mask 6 Etching object 7 Diffraction grating pattern

Claims (7)

Laser light is emitted toward the surface of the diffraction grating pattern that is a part of the etching mask formed on the surface of the etching object, and the light intensity of the laser light reflected by the etching object and the diffraction grating pattern A step of determining the height of the diffraction grating pattern before etching based on
After etching the object to be etched and forming a groove in the vicinity of the diffraction grating pattern of the object to be etched, laser light is emitted toward the surface of the diffraction grating pattern after etching, and after etching Determining the distance from the surface of the diffraction grating pattern after etching to the bottom surface of the groove based on the light intensity of the laser beam reflected by the object to be etched and the diffraction grating pattern;
After removing the etching mask including the diffraction grating pattern, laser light is emitted toward the surface of the etching object, and the groove is formed based on the light intensity of the laser light reflected by the etching object. A process for determining depth;
Based on the height of the diffraction grating pattern before etching, the distance from the surface of the diffraction grating pattern after etching to the bottom of the groove, and the depth of the groove, the height of the diffraction grating pattern before etching and the etching And a step for obtaining a difference from the height of the diffraction grating pattern later. In the etching selectivity measurement method according to claim 1,
An etching selectivity measuring method, wherein the wavelength of the laser beam is in a range of 500 nm to 800 nm. In the etching selectivity measurement method according to claim 1,
An etching selectivity measurement method, wherein the reflected laser light is first-order diffracted light. In the etching selectivity measurement method according to claim 1,
The method of measuring an etching selectivity, wherein an emission direction of the laser beam is substantially perpendicular to a surface of the etching object. A light source that emits laser light toward the surface of a diffraction grating pattern that is a part of an etching mask formed on the surface of the object to be etched;
A light receiving unit that receives the laser light reflected by the etching object and the diffraction grating pattern, and outputs a signal corresponding to the light intensity of the received laser light;
An etching selectivity measuring apparatus comprising: an arithmetic unit that obtains a difference between the height of the diffraction grating pattern before etching and the height of the diffraction grating pattern after etching based on the signal. In the etching selectivity measuring apparatus according to claim 5,
An etching selectivity measuring apparatus, wherein the etching selectivity is managed so as not to deviate from a desired value. In the etching etching selectivity measurement apparatus according to claim 5,
The etching selection ratio measuring apparatus, wherein the arithmetic unit receives the signal via a differentiation circuit.

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