JP4761934B2 - Semiconductor substrate with alignment mark and method of manufacturing alignment mark - Google Patents

Description

The present invention relates to a semiconductor substrate with an alignment mark and a method for manufacturing the alignment mark, and more particularly to a semiconductor substrate with an alignment mark provided with an alignment mark used for position detection during processing on a transparent semiconductor substrate and a method for manufacturing the alignment mark.

In the manufacturing process of semiconductor elements and semiconductor integrated circuits, a resist pattern is formed by transferring a pattern formed on a photomask or the like using an exposure apparatus onto a semiconductor substrate coated with photoresist or the like by so-called photolithography technology. Then, processing by dry etching or the like is repeated using this resist pattern as a mask.

In particular, in recent years, since the patterns to be formed have become increasingly fine, when manufacturing semiconductor elements and semiconductor integrated circuits having desired performance, it is required to improve processing alignment accuracy. .

For this alignment, for example, an alignment mark for position information detection is formed on the semiconductor substrate, and the position of the semiconductor substrate is specified by the exposure apparatus detecting this alignment mark. A method of performing predetermined position control necessary for the machining process based on the detection result is frequently used.

FIG. 5 shows an example of a cross-sectional shape of an alignment mark portion in a semiconductor substrate with an alignment mark. The example shown in FIG. 5 has a shape called a so-called engraving marker, and has a configuration in which a plurality of concave engravings 52 are arranged in a predetermined direction on a semiconductor substrate 51 serving as a base. Then, in a relatively initial stage in a series of processes for manufacturing a semiconductor element, for example, it is formed in advance together with processing by etching or the like for element formation.

When processing a semiconductor substrate by photolithography, the alignment of the semiconductor substrate is performed with a predetermined accuracy in an exposure apparatus. Various methods for specifying the substrate position have been devised. In the case of a semiconductor substrate with an alignment marker, for example, as described below, there is a method using reflected light from the alignment marker.

That is, a dedicated alignment light source that emits laser light or the like is provided, and the irradiation light from this alignment light source is irradiated to an alignment mark provided on the semiconductor substrate via a lens, a beam splitter, or the like, and reflected light from the surface. Is received by an alignment detector via a lens, a beam splitter, or the like, and the position of the alignment mark is detected. Then, based on the detection result, the stage on which the semiconductor substrate is placed is controlled to move in the X, Y, Z, and θ directions to adjust the position.

An example of aligning a semiconductor substrate by the above-described method is disclosed in, for example, Patent Document 1.
JP 2003-289029 A (page 8, FIG. 7)

By the way, in the manufacture of a semiconductor element, a transparent substrate such as glass, sapphire, or silicon carbide is used as a base semiconductor substrate. Further, when a high frequency device is formed, a transparent thin film such as gallium nitride or aluminum gallium nitride is laminated on the transparent substrate. Then, an alignment mark 52 as shown in FIG. 5 is formed on a transparent semiconductor substrate including the laminated thin film layer, and the manufacturing process by the photolithography technique is performed while specifying the position of the alignment mark 52. The desired semiconductor element is formed by proceeding.

However, when the semiconductor substrate to be processed is transparent, the conventional engraved alignment mark in which the concave engravings 52 are arranged in a predetermined direction as illustrated in FIG. 5 for alignment is irradiated from the alignment light source. The emitted laser light is only slightly reflected by scattering on the substrate surface, and most of it is transmitted through the semiconductor substrate. For this reason, there has been a problem that sufficient reflected light cannot be obtained on the alignment detector side, and the position of the semiconductor substrate and the predetermined position on the substrate cannot be detected and specified stably.

For a transparent semiconductor substrate, there is a method using a so-called metal marker formed of a metal film instead of the engraved marker as described above. However, this requires a unique process for forming a metal marker by metal vapor deposition, which increases the number of manufacturing processes and complicates the process.

The present invention has been made in order to solve the above-described problems. An alignment mark provided with an alignment mark that realizes good position detection even for a transparent substrate when positioning a semiconductor substrate is performed. It is an object of the present invention to provide a method for manufacturing an attached semiconductor substrate and an alignment mark.

In order to achieve the above object, a semiconductor substrate with an alignment mark of the present invention is a semiconductor substrate with an alignment mark having a carved alignment mark at a predetermined position on the surface, and a plurality of the alignment marks are provided at predetermined intervals. A second-stage concave engraving is further provided on the bottom surface of the first-stage engraving engraved in a concave shape, and the bottom surface of the second-stage engraving is provided from the bottom surface of the first-stage engraving. The distance to the surface of the semiconductor substrate with the alignment mark having the alignment mark is λ / 2n or more in advance when a photosensitive material with a refractive index n is applied to the surface of the semiconductor substrate and irradiated with an exposure light source with a wavelength λ. It is characterized by.

The method for manufacturing an alignment mark according to the present invention is a method for manufacturing an alignment mark of a semiconductor substrate with an alignment mark having an engraved alignment mark on the surface, wherein a first photoresist is applied on the semiconductor substrate. 1 photoresist layer is formed,
The second photoresist layer is formed by applying a second photoresist having a slower dissolution rate to the release agent than the first photoresist on the first photoresist layer, and the first and second photoresist layers are formed. A semiconductor substrate on which a photoresist layer is formed is exposed to a mask pattern of the alignment mark, the mask pattern is developed to form a resist film other than the alignment mark formation site, and the alignment mark formation site The second photoresist layer is removed by the release agent, an opening having a shape in which the opening of the first photoresist layer is larger than the opening of the second photoresist layer is formed, and the opening is formed by ECR etching. The semiconductor substrate is etched to form a first concave engraving and the progress of this etching The opening of the opening is narrowed by deforming the resist film of the second photoresist layer at the periphery of the opening so as to cover the periphery of the concave engraving, and a predetermined amount is further applied to the narrowed opening. ECR etching is continued to a depth to form a second concave engraving, and the resist film is peeled off after completion of the ECR etching.

According to the present invention, a semiconductor substrate with an alignment mark provided with an alignment mark capable of realizing good position information detection even for a transparent substrate during positioning of the semiconductor substrate, and the alignment mark A manufacturing method can be obtained.

The best mode for carrying out the semiconductor substrate with an alignment mark and the method for manufacturing the alignment mark according to the present invention will be described below with reference to FIGS.

FIG. 1 is a plan view showing an embodiment of a semiconductor substrate with alignment marks according to the present invention. In the example shown in FIG. 1, the case where a plurality of semiconductor elements are formed on the semiconductor substrate 1 with the alignment mark is modeled.

That is, as shown in FIG. 1A, a plurality of element formation regions 3 for forming semiconductor elements are provided on a semiconductor substrate 2 which is a base of a semiconductor substrate 1 with alignment marks. In each of these element formation regions 3, as shown in FIG. 1B, an alignment mark 4 for detecting position information in the X direction and an alignment mark 5 for detecting position information in the Y direction are formed. Has been. Each of these alignment marks 4 and 5 is formed in an engraved shape, and a plurality of square engravings 6 are arranged at predetermined intervals in the X direction and the Y direction, respectively.

FIG. 2 is a cross-sectional view showing a model of a cross section along the AA plane of the alignment mark 4 in FIG. 1B which is one alignment mark on the semiconductor substrate 1 with the alignment mark. The Y-direction alignment mark 5 also has a similar cross section.

As illustrated in FIG. 2, the alignment mark 4 includes five engravings 6 formed by engraving the base semiconductor substrate 2 and arranged at a predetermined interval. These engravings 6
In each of these, a concave engraving 62 is provided on the bottom surface 61 of the first engraving engraved in a concave shape, and the cross-sectional shape thereof has a two-step shape. Here, the depth to the bottom surface 61 of the first engraving is about 1 μm.

Further, the distance d from the bottom surface 61 of the first level engraving to the bottom surface of the second level engraving 62
Is set in advance to have the following value range. That is, in the process of forming the semiconductor element on the semiconductor substrate 1 with the alignment mark, when the refractive index of the photosensitive material applied to the surface is n and the wavelength of the exposure light source is λ, d is λ / 2
n or more.

Next, during the process of processing the semiconductor substrate 1 with the alignment mark having the alignment mark having the above-described structure, for example, the alignment mark 4 is irradiated with the irradiation light from the alignment light source, and the position information is detected by the reflected light. The case where it does is demonstrated.
For example, laser light having a wavelength of 633 nm is used as irradiation light from the alignment light source.

Each of the engravings 6 constituting the alignment mark 4 is formed in two steps as shown in the sectional view of FIG. For this reason, as compared with the case of the conventional alignment mark as illustrated in FIG. 5, reflection due to scattering is likely to occur when the alignment light source is irradiated. Therefore, not only when the semiconductor substrate 2 as a base is opaque, but also when it is transparent, it is possible to obtain a more stable reflected light than before, and it is possible to detect good position information.

Further, for example, when performing photo-etching or the like in a processing step of forming a semiconductor element on the semiconductor substrate 1 with the alignment mark, a wavelength is applied after a photosensitive material having a refractive index n is applied to the substrate surface including the alignment mark. Irradiation light of λ is emitted from the exposure light source. In this case, since the distance d from the bottom surface 61 of the first stage engraving to the bottom surface of the second stage engraving 62 is set to λ / 2n or more, the bottom surface 61 of the first stage engraving. The optical path difference in the photosensitive material between the light reflected from the light and the light reflected from the bottom surface of the second engraving 62 becomes one wavelength or more of the irradiation light. Therefore, even when the semiconductor substrate 2 as a base is transparent, sufficiently stable reflected light can be detected at a distance where the intensity of the reflected light is increased due to this optical path difference, and good position information can be detected. Can do.

Next, a method for manufacturing an alignment mark of the semiconductor substrate 1 with an alignment mark according to the present invention will be described with reference to FIGS. As illustrated in the cross-sectional view of FIG. 2, the alignment mark includes five engravings 6 formed in a two-step shape by engraving the semiconductor substrate 2 serving as a base, and arranged at a predetermined interval. In the following description, one of these engravings 6 will be taken and its manufacturing method will be described.

3 and 4 are cross-sectional views showing an embodiment of the method of manufacturing the engraving 6 in the order of steps.
First, as shown in FIG. 3A, a first photoresist is applied on a semiconductor substrate 2 to be a base, and a first photoresist layer 7 is formed. Furthermore, a second photoresist layer 8 is formed on the upper layer by applying a second photoresist having a slower dissolution rate with respect to the release agent than the first photoresist.

Next, the mask pattern of the alignment mark is exposed on the upper surface of the semiconductor substrate on which the first photoresist layer 7 and the second photoresist layer 8 are formed, and then developed.
Then, as shown in FIG. 3B, in addition to the alignment mark forming portion 9, the resist film 10
Form.

Next, the two photoresist layers 7 and 8 at the alignment mark forming portion 9 are removed with a release agent. Immediately after the start of removal at this time, as shown in FIG. 3C, the first photoresist layer 7 and the second photoresist layer 8 are both peeled off in the same manner. Here, when the peeling is further continued, the peeling of the first photoresist layer 7 proceeds with the lapse of time due to the difference in dissolution rate of the two layers of the photoresist with respect to the release agent, and FIG.
), An opening 11 having a shape in which the opening of the first photoresist layer 7 is larger than the opening of the second photoresist layer 8 is formed.

Subsequently, the base semiconductor substrate 2 is etched from the opening 11 by ECR etching to form the engraving 12 as shown in FIG. The engraving 12 formed here is the first engraving, and the depth to the bottom surface 61 is, for example, about 1 μm.

Further, by the heating during the ECR etching, the resist film formed by the second photoresist layer 8 overhanging the opening 11 is gradually dropped as the ECR etching proceeds, and is engraved as shown in FIG. 4B. ECR is modified to cover the periphery of 12
Narrow the opening to be etched.

Then, ECR etching is continued for the narrowed opening 13 until a predetermined depth set in advance is reached, thereby forming a second engraving 62 as shown in FIG. The depth d to the bottom surface of the second-stage engraving 62 at this time is, for example, the refractive index of the photosensitive material applied to the surface in the process of forming the semiconductor element on the semiconductor substrate 1 with this alignment mark. n, where λ is the wavelength of the exposure light source to be irradiated, the value is λ / 2n or more.

Thereafter, as shown in FIG. 4D, all resist films are peeled off with an organic solvent or the like to obtain a desired engraving 6.

As described above, in the semiconductor substrate 1 with the alignment mark shown in the present embodiment, each engraving 6 constituting the engraved alignment marks 4 and 5 is further provided on the bottom surface 61 of the first engraving. It is formed in a two-step staircase shape with a second-stage carving 62. Thereby, it is easy to generate reflection due to scattering when irradiated with an alignment light source or the like, and sufficiently stable reflected light can be obtained, so that it is possible to realize good position information detection even for a transparent substrate. it can.

The depth d of the second-stage engraving 62 is determined by the semiconductor substrate 1 with the alignment mark.
On the basis of the characteristic values of the exposure light source and the photosensitive material used when performing photo-etching or the like in the process of forming a semiconductor element or the like on the top, λ / 2n or more is set in advance. Thereby, the optical path difference between the reflected light from the bottom surface of the first engraving and the reflected light from the bottom surface of the second engraving with respect to the exposure light source is set to one wavelength or more of the exposure light source, and the intensity is increased. Since sufficiently stable reflected light can be obtained at a long distance, it is possible to realize good position information detection even for a transparent semiconductor substrate.

The top view which shows one Example of the semiconductor substrate with an alignment mark which concerns on this invention. Sectional drawing which models and shows the cross section along the AA surface of FIG.1 (b). Sectional drawing which shows the process of the 1st step in one Example of the manufacturing method of the alignment mark which concerns on this invention. Sectional drawing which shows the process of the 2nd step in one Example of the manufacturing method of the alignment mark which concerns on this invention. Sectional drawing which shows an example of the cross-sectional shape of the site | part of the alignment mark in the conventional semiconductor substrate with an alignment mark.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate with an alignment mark 2 Semiconductor substrate used as a base 3 Element formation region 4, 5 Alignment mark 6, 12, 62 Engraving 7 First photoresist layer 8 Second photoresist layer 9 Alignment mark formation part 10 Resist film 11, 13 Opening 61 The bottom of the first stage engraving

Claims (3)

A semiconductor substrate with an alignment mark having an engraved alignment mark at a predetermined position on the surface,
The alignment mark is further provided with a second-stage concave engraving on the bottom surface of the first-stage engraving engraved into a plurality of recesses arranged at predetermined intervals ,
The distance from the bottom surface of the first-stage engraving to the bottom surface of the second-stage engraving is such that a photosensitive material having a refractive index n is applied to the surface of the semiconductor substrate with the alignment mark having the alignment mark and has a wavelength λ. A semiconductor substrate with an alignment mark, which is set to λ / 2n or more in advance when irradiating an exposure light source for exposure . A method of manufacturing an alignment mark of a semiconductor substrate with an alignment mark having a carved alignment mark on a surface,
Applying a first photoresist on a semiconductor substrate to form a first photoresist layer;
The second photoresist layer is formed by applying a second photoresist having a slower dissolution rate to the release agent than the first photoresist on the first photoresist layer,
Exposing the mask pattern of the alignment mark to the semiconductor substrate on which the first and second photoresist layers are formed,
Developing the mask pattern to form a resist film other than the alignment mark formation site,
The first and second photoresist layers at the alignment mark formation site are removed by the release agent, and the opening of the first photoresist layer is larger than the opening of the second photoresist layer. Form the
The semiconductor substrate is etched from the opening by ECR etching to form a first concave engraving, and as the etching proceeds, the second photo on the periphery of the opening is covered so as to cover the periphery of the concave engraving. Narrowing the opening of the opening by deforming the resist film of the resist layer,
ECR etching is continued to a predetermined depth for the narrowed opening to form a second concave engraving.
A method of manufacturing an alignment mark, comprising peeling off the resist film after the ECR etching is completed. The depth of ECR etching with respect to the narrowed opening is determined by applying a photosensitive material having a refractive index n to the surface of a semiconductor substrate with an alignment mark having the alignment mark and irradiating an exposure light source with a wavelength λ. 3. The method of manufacturing an alignment mark according to claim 2 , wherein λ / 2n is set in advance.

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