JP2002208557A - Exposure mask for alignment of crystal surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust an angle of rotation of an exposure mask with respect to the crystal orientation of a wafer by creating, on the wafer, alignment marks corresponding to the crystal surface of the wafer when forming a resist pattern with the angle of rotation of the crystal surface of the wafer correctly aligned, in such a case as in the manufacture of a semiconductor laser, and then detecting these marks by an aligner or the like. SOLUTION: In an exposure mask for a first mask process, a plurality of mark patterns are formed as marks used when aligning the masks in mask processes on and after the second mask process, with each mark pattern having the same shape but differing in an angle of rotation by increment of 0.1 deg. or smaller. The angle of rotation of each mark pattern has an angle range of ±0.3 deg. or larger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure mask,
Particularly, in a process of forming a resist for processing a waveguide stripe in a manufacturing process of a semiconductor laser or the like, it is suitable to be used in a first mask process in a case where a resist pattern is formed by accurately adjusting a rotation angle with respect to a crystal plane of a wafer. The present invention relates to a structure of an exposure mask for crystal plane alignment.

[0002]

2. Description of the Related Art Conventionally, with respect to a method of manufacturing an optical device using a crystal plane alignment exposure mask, as described in, for example, Japanese Patent Application Laid-Open No. 7-169673, a deviation angle from a desired crystal plane is smaller than a predetermined angle. Forming a photosensitive resin on a circular wafer having an orientation flat (hereinafter abbreviated as orientation flat) surface processed as described above;
A step of aligning an exposure mask for a first mask process with the circular wafer on which the photosensitive resin is formed, and after exposing and developing the photosensitive resin on the circular wafer, Measuring the amount of misalignment at the time of mask alignment with the first mask, and selecting a wafer that can be used in a subsequent step and an unusable wafer in accordance with the measurement result, wherein the first mask The process exposure mask has two scale patterns in which a plurality of linear patterns are arranged at predetermined intervals on both sides of the reference line pattern, and the reference line pattern of each scale pattern is located on a straight line. The measurement of the amount of misalignment between the exposure mask for the first mask process and the circular wafer is performed using one of the two scale patterns transferred onto the photosensitive resin. A positional shift amount between, the other of the two scale pattern, was performed by measuring the difference between the positional shift amount between the orientation flat portion.

Further, the exposure mask for the first mask step has a marker pattern used for mask alignment in a mask step after the second mask step in addition to the two scale patterns. In the mask process after the process, the exposure mask and the circular wafer are aligned using the marker portion on the circular wafer to which the marker pattern has been transferred.

[0004]

In the prior art, an exposure mask for a first mask process is exposed on a circular wafer having an orientation flat surface processed so that a deviation angle from a desired crystal plane is not more than a predetermined angle. 2 formed by transferring onto a conductive resin
The angle shift amount between the exposure mask for the first mask process and the circular wafer was measured using the two scale patterns. Further, the exposure mask for the first mask process is formed by the second mask.
In addition to the two scale patterns, the mask pattern has a mark pattern used when performing mask alignment in a mask step after the second mask step. In the mask step after the second mask step, the mark pattern on the circular wafer is transferred. The alignment between the exposure mask and the circular wafer is performed by using the mark portion.

However, when the first mask step and the second mask step are performed by, for example, a reduction projection exposure apparatus, in the first mask step, the angle of the orientation flat of the circular wafer is changed by mechanical means, that is, a probe such as a pin. In general, the angle deviation of the exposure mask for the first mask process with respect to the orientation flat of the circular wafer is about 0.2 ° with respect to a desired angle.

In an ordinary semiconductor laser fabrication process, the angle deviation of the active layer processing pattern or the like with respect to the crystal plane of the wafer must be at least 0.1 ° or less.
Regarding the angle of the active layer processing pattern or the like with respect to the orientation flat, the deviation from the desired angle needs to be at least 0.1 ° or less.

[0007] As described in the above-mentioned publication, if sorting is performed based on an angle shift at the time of mask alignment between an exposure mask and a circular wafer, more than half of the wafers may be unusable in subsequent steps. Unusable wafers are
There is a possibility that it can be reused by re-exposing and developing, but it is unknown whether it can be used by re-executing it once, and it was very inefficient in the manufacturing process.

An object of the present invention is to provide a second masking process even when the angle of the exposure mask for the first masking process with respect to the orientation flat of the circular wafer is deviated from the desired angle by 0.1 ° or more in the first masking process. In the subsequent mask step, it is an object to provide a crystal plane alignment photomask capable of adjusting the angle of the exposure mask with respect to the orientation flat of the circular wafer so that the deviation from the desired angle is at least 0.1 ° or less. .

[0009]

An object of the present invention is to transfer a mask pattern to a resist by light or an electron beam,
Of the exposure masks used in the mask step of obtaining a desired resist pattern by developing, the same shape as a mark used when performing mask alignment in the mask steps after the second mask step in the exposure mask for the first mask step. This is achieved by providing a plurality of mark patterns that differ only in the rotation angle.

Another object of the present invention is to provide an exposure mask for a first mask process, which is used in a mask process for obtaining a desired resist pattern by transferring and developing a mask pattern on a resist by light or an electron beam. The rotation angles of a plurality of mark patterns having the same shape but different rotation angles provided as marks used for mask alignment in a mask step after the second mask step have at least a step of 0.1 ° or less. Achieved by having

Another object of the present invention is to provide an exposure mask for a first mask process, which is used in a mask process for obtaining a desired resist pattern by transferring a mask pattern onto a resist by light or an electron beam and developing the mask pattern. Among them, the rotation angles of a plurality of mark patterns having the same shape but different rotation angles provided as marks used for mask alignment in a mask process after the second mask process are 1
At least ±
This is achieved by having an angle range of 0.3 ° or more.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a plan view showing a part of a crystal plane alignment exposure mask according to one embodiment of the present invention, and FIG. FIG. 4 is an enlarged plan view of FIG. FIG. 2 is an explanatory view showing a method of forming a resist pattern in which the rotation angle with respect to the orientation flat is adjusted using the crystal plane alignment exposure mask according to the present embodiment, and FIG. 2A shows a first mask step. FIG. 3B shows a second mask step. FIG. 3 is a schematic view showing a part of a semiconductor laser device manufactured using a crystal plane alignment exposure mask according to an embodiment of the present invention.

Here, the exposure mask for crystal plane alignment of this embodiment is set and used in a reduction projection exposure apparatus having a reduction ratio of 1: 5 using i-line as an exposure light source.

Exposure mask 100 for the first mask process of FIG.
A mark pattern having the same shape but a different rotation angle is used as a mark for aligning the mask and the wafer in at least one or more of the second mask process and the subsequent mask processes in the exposure region 1 of FIG. Nine are provided. That is, using the alignment mark 2 for the second mask process with a rotation angle of 0 ° as a reference for the rotation angle, a pattern other than the number 0 included in the square frame of the alignment mark 2 for the second mask process with a rotation angle of 0 ° is After rotating about the rotation reference point 11, it is translated in parallel with the rotation angle and drawn with the number of the rotation angle. Alignment mark 4, alignment mark 5 for a second mask process with a rotation angle of + 0.3 °, alignment mark 6 for a second mask process with a rotation angle of + 0.4 °, for a second mask process with a rotation angle of −0.1 ° Alignment mark 7, alignment mark 8 for second mask process with rotation angle of -0.2 °, alignment mark 9 for second mask process with rotation angle of -0.3 °, second mask process with rotation angle of -0.4 ° A matching mark 10 is provided.

In the exposure area 1 of the exposure mask for the first mask process shown in FIG. 1, alignment marks 2 to 10 for the second mask process are provided.
In addition to the above, there is provided an angle shift measuring scale pattern 12 in which a plurality of linear patterns are arranged at intervals of 5 μm. The above is the configuration of the exposure mask for crystal plane alignment of this embodiment.

A film is formed on an n-type (100) InP 3-inch semiconductor substrate processed so that the angle of deviation of the orientation flat surface from the original crystal plane (01-1--) plane is 0.02 ° or less. 0.1 μm thick InGaAsP (composition wavelength 1.
30 μm) active layer, 0.1 μm-thick p-type InP spacer layer, 10 nm-thick InGaAsP (composition wavelength 1.1
0 μm) etch stop layer and 2.0 μm thick p
InP cladding layer, p-type InGaAs with a thickness of 0.8 μm
An s cap layer is sequentially formed.

After an SiO ₂ film is formed on the semiconductor laser substrate 101 on which the above-described multilayer growth has been performed, a photoresist is applied and, as shown in FIG. 2, used as an exposure mask for the first mask step of the above-mentioned reduction projection exposure apparatus. A photoresist pattern is formed using the crystal plane alignment exposure mask according to the present embodiment.

When exposing the photoresist, FIG.
As shown in (A), in at least two or more shots of the reduced projection exposure shots, that is, in the orientation flat angle shift measurement shot 102, the linear pattern array of the angle shift measurement scale pattern 12 provided in the exposure mask. Of the InP semiconductor substrate. Further, the exposure shot is not provided on the whole surface of the InP semiconductor substrate, but the orientation flat angle deviation measurement shot 102 on the orientation flat as described above, and about 2 to 4 mark shots 103 required as alignment marks for the second mask process.
Keep only.

Of the two orientation flat angle shift measurement shots 102, the position shift amount of the angle shift measurement scale pattern 12 transferred to one shot from the orientation flat portion and the scale pattern 1 transferred to the other shot
The difference between the position of the shot and the orientation flat is measured by measuring the difference between the position 2 and the amount of displacement from the orientation flat portion.

Based on the above angle deviation, the alignment mark 3 for the second mask process with a rotation angle of + 0.1 ° transferred to the mark shot 103 and the alignment mark for the second mask process with a rotation angle of 0.2 ° 4, alignment mark 5 for the second mask process with a rotation angle of + 0.3 °, alignment mark 6 for the second mask process with a rotation angle of + 0.4 °, alignment mark 7 for the second mask process with a rotation angle of −0.1 ° Alignment mark 8 for the second mask step with a rotation angle of -0.2 °, alignment mark 9 for the second mask step with a rotation angle of -0.3 °, and alignment for the second mask step with a rotation angle of -0.4 ° A mark is selected from the marks 10 so that the shot arrangement of the reduced projection exposure for the orientation flat in the second mask process is most appropriate. Thus, in the second mask step, the angle of the resist pattern with respect to the orientation flat is set to ± 0.05 ° with respect to a desired value.
Can be adjusted within.

As shown in FIG. 2B, without removing the resist used in the first mask step, a mesa processing exposure mask was used as an exposure mask for the second mask step.
A resist pattern formed by an exposure shot in the second mask process, that is, a mesa processing resist pattern 104 is formed in a portion other than where the resist pattern is formed in the first mask process, and is wet-etched or dry-etched using a mixed gas of methane and hydrogen As a result, p-type InGa
The width of the As cap layer and the p-type InP cladding layer is 1.7
It is processed into a stripe structure having a rectangular cross section of μm.

Here, the alignment mark for the second mask process is selected so that the stripe direction, that is, the cavity length direction is closest to the [011] direction of the semiconductor laser substrate 101. In the semiconductor laser substrate 101 used in this embodiment, the original crystal plane (01-1) is used.
−) Since the orientation angle of the orientation flat surface with respect to the surface is processed to be 0.02 ° or less, the deviation angle from the [011] direction in the resonator length direction should be kept within 0.07 °. Can be.

After a 1.0 μm thick SiO ₂ film is formed on the entire surface of the substrate, a p-type InGaAs cap layer is formed by wet etching using a resist pattern aligned using the alignment mark formed in the second mask process as a mask. A contact window is processed thereon to form an electrode isolation insulating layer.

After a p-electrode is formed on the p-type InGaAs cap layer and the electrode isolation insulating layer, the back surface is polished until the thickness of the InP semiconductor substrate becomes 150 μm, and an n-electrode is formed on the back surface.

Finally, in a cleavage step, an element having a stripe structure 201 having a cavity length of 900 μm and an n-electrode 202 is cut out as shown in FIG. 3 to form an emission end face 203 and a rear end face 204, and one side as the rear end face A high reflection film 205 having a reflectance of 70% is formed on the end face.

In the cavity length direction of the semiconductor laser manufactured by the above-described process, the angle formed between the emission end face 203 and the rear end face 204 formed by the cleavage step and the cavity length direction is controlled to 90 ° ± 0.07. I have. The deviation angle of the outgoing beam with respect to the cavity length direction is larger than the angle between the normal line to the outgoing end face and the cavity length direction due to the difference in the refractive index between the optical waveguide portion and air, but within ± 2 °. Can be suppressed.

When a semiconductor laser is used as a component of an optical communication device, an information processing device, or the like, it is necessary to couple the lens to a lens system. Since it is within ± 2 °, if the index mark used for coupling with the lens system is formed on the substrate in an accurate positional relationship to the stripe pattern, the coupling efficiency between the semiconductor laser and the lens system will be significantly reduced. I will not let you.

[0028]

As described above, by using the crystal plane alignment exposure mask of the present invention as the first step exposure mask, the first mask step exposure mask for the circular wafer orientation flat is used in the first mask step. Even when the angle deviates by 0.1 ° or more from the desired angle, the angle of the exposure mask with respect to the orientation flat of the circular wafer is set to at least 0 in the mask step after the second mask step. .1 ° or less.

That is, a plurality of mark patterns having the same shape but different rotation angles are provided in the exposure mask for the first mask process as marks used for mask alignment in the mask process after the second mask process. The rotation mask of the plurality of mark patterns has a step of at least 0.1 ° or less and a range of at least ± 0.3 ° or more, so that the first mask process exposure mask for the orientation flat of the circular wafer is formed. Is 0.1 ° or more from the desired angle.
By aligning the exposure mask for the second mask process with the mark pattern whose rotation angle with respect to the orientation flat is closest to the desired one among a plurality of mark patterns having different rotation angles in the following increments, a mask process after the second mask process is performed. In this case, the angle of the exposure mask with respect to the orientation flat of the circular wafer can be adjusted to a desired angle by at least 0.1 ° or less. Thereby, the angle shift of the exposure mask with respect to the crystal plane of the wafer can be reduced.

In the first masking step of the manufacturing process of a semiconductor laser or the like, only the mark pattern used for mask alignment in the masking step after the second masking step is formed, and the actual element pattern is formed after the second masking step. Then, the angle of the exposure mask for the first mask process with respect to the orientation flat of the circular wafer is 0.
Even when the angle is shifted by 1 ° or more, the angle of the exposure mask with respect to the orientation flat of the circular wafer can be adjusted to at least 0.1 ° or less in the mask process after the second mask process. Can make a deviation from a desired angle with respect to the orientation flat 0.1 ° or less.

Therefore, by using the exposure mask for the crystal plane alignment of the present invention as the exposure mask for the first mask step, the mask for the first mask step and the circular wafer can be aligned after the first mask step. It is not necessary to sort unusable wafers in the subsequent steps according to the angle shift amount of the above, and the efficiency of the manufacturing process of the semiconductor laser or the like can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a part of a crystal plane alignment exposure mask according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a method for forming a resist pattern in which the rotation angle with respect to the orientation flat according to one embodiment of the present invention is adjusted.

FIG. 3 is a schematic view of a laser device manufactured using an exposure mask according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exposure area, 2 ... Alignment mark for 2nd mask process of rotation angle 0 °, 3 ... Alignment mark for 2nd mask process of rotation angle + 0.1 °, 4 ... Second mask process of rotation angle + 0.2 ° Alignment mark for the second mask process with a rotation angle of + 0.3 °, alignment mark for the second mask process with a rotation angle of + 0.4 °, second alignment mark with a rotation angle of −0.1 ° Alignment mark for mask process, 8 ... Alignment mark for second mask process with rotation angle of -0.2 °, 9 ... Alignment mark for second mask process with rotation angle of -0.3 °, 10 ... Rotation angle -0.4 ° second alignment mark for the mask process, 11 ... rotation reference point, 12
... scale pattern for measuring angle deviation, 101 ... substrate for semiconductor laser, 102 ... shot for measuring orientation flat angle deviation,
103: mark shot, 104: mesa processing resist pattern, 201: stripe structure, 202: n-electrode,
203: emission end face, 204: rear end face, 205: high reflection film.

Claims (3)

[Claims] An exposure mask for transferring a mask pattern to a resist by light or an electron beam and developing the mask pattern to obtain a desired resist pattern, wherein a second mask is provided in the exposure mask for the first mask process. An exposure mask for crystal plane alignment, comprising a plurality of mark patterns having the same shape but different rotation angles as marks used for mask alignment in a mask step after the step. 2. The exposure mask for crystal plane alignment according to claim 1, wherein the exposure mask is provided as a mark used when aligning a mask in a mask process after a second mask process.
A rotation angle of a plurality of mark patterns having the same shape but different rotation angles has an interval of at least 0.1 ° or less. 3. A crystal plane alignment exposure mask according to claim 1, wherein said exposure mask is provided as a mark used when aligning a mask in a mask step after a second mask step.
A rotation angle of a plurality of mark patterns having the same shape but different rotation angles has an angle range of at least ± 0.3 ° or more with respect to one reference mark pattern for crystal plane alignment. Exposure mask.