JP2002050569A - Method for forming pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that conventionally the limit in formation of a grating pattern by using, for example, an electron beam exposure system by a grating pattern needs a pitch of integer times as large as the positioning minimum unit, because a positioning minimum unit of an exposure system decided according to a resolution of a digital/analog converter in the case of forming the pattern on a substrate by using a exposure system. SOLUTION: The method for forming the pattern comprises the steps of repeatedly exposing to an electron beam exposure, by using a projection mask 1 mounting a partial region of an array pattern to form an overall array pattern. The method also comprises the steps of arraying n pieces of unit patterns 2 of the repeating pattern in a projection mask at an arraying pitch p, and deciding n so that a product of the n and the p becomes an integer times as large as a positioning minimum unit of the exposure system. Thus, the pitch of the patterns capable of being exposed can be changed in units of 1/n of the positioning minimum unit of the exposure system. A plurality of projection mask are utilized, to enable a change of the pitch at a fine unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method, and more particularly to a pattern forming method using a projection mask and a projection exposure apparatus.
For example, a method of forming a periodic pattern that requires a fine periodic pattern such as a distributed feedback semiconductor laser or a surface acoustic wave device, or that requires a very fine pitch change on a substrate, and using the method. It relates to the structure of the element.

[0002]

2. Description of the Related Art A large-capacity optical communication system using wavelength division multiplexing requires a set of distributed feedback semiconductor lasers having slightly different transmission wavelengths. For this purpose, a large number of elements in which the pitch of the grating of the distributed feedback semiconductor laser is slightly changed are required.

Conventionally, a two-beam interference exposure method has been used to form this. This method divides a laser beam having high coherence into two optical paths and irradiates the substrate with light at a fixed angle from two directions. By precisely controlling the irradiation angle, the pitch of the formed grating can be minutely changed.

However, this method has a disadvantage that only gratings having the same pitch can be formed on an exposure substrate, and a part of a continuous grating pattern required by a specific element is conscious of a shift in pitch. I couldn't do that.

To solve this problem, Japanese Patent Laid-Open Publication No. Hei 8-22
An electron beam exposure method as disclosed in Japanese Patent No. 7838 was used. By using an electron beam, it has become possible to mix grating patterns with a plurality of pitches on a substrate or to make a pitch shift in a part of a periodic pattern. Further, this method discloses a method of forming a line pattern that does not pass through the grid points by superposing and exposing a plurality of line patterns passing through grid points where the electron beam can be positioned on the substrate.

However, in order to form a line pattern that does not lie on a grid point in the above-described method, it is necessary to precisely control the exposure amount ratio of a plurality of line exposures to perform the overexposure.
For this reason, in order to form one grating pattern, a large number of combinations of line exposures are required, which has a problem in terms of productivity.

Further, for example, the minimum grid point interval that can be positioned is 2 nm, and the required grating period is 24 nm.
In the case of 0.1 nm, it is necessary to expose and synthesize a line pattern passing through adjacent grid points at an exposure amount ratio of 19: 1.

More recently, there has been a demand to change the pitch of the grating in units of 0.05 nm. In this case, it is necessary to control the exposure ratio in units of 1/40. An electron beam exposure apparatus has a minimum exposure time and an exposure amount variable step determined by an electric circuit, and there is a problem that the exposure amount cannot be controlled when a highly sensitive electron beam resist is used. For this reason, it is necessary to reduce the current value of the electron beam or to use a low-sensitivity electron beam resist, and there is a disadvantage that productivity is further reduced.

[0009]

Conventionally, a method of forming a grating pattern such as a distributed feedback type semiconductor laser that requires a fine pitch change or a pattern that requires a discontinuous pitch shift in the middle of a constant pitch grating has been proposed. Although known, it was of low productivity as described above. In order to reduce communication costs, it is necessary to realize such a grating pattern with high productivity and high yield.

It is an object of the present invention to provide a pattern forming method capable of changing the pitch in fine units that are not limited to the smallest step unit that can be positioned by the projection exposure apparatus. This also provides a method of manufacturing a set of distributed feedback semiconductor lasers having slightly different oscillation wavelengths required for the wavelength division multiplexing transmission system with high productivity and low cost.

[0011]

In order to solve the above-mentioned problems, in the method of the present invention, a plurality of projection exposures are performed by using a projection mask equipped with a periodic pattern partial area pattern and a projection exposure apparatus. Then, the entire pattern is formed.

The position where the projection exposure apparatus exposes the pattern on the substrate is controlled through a digital / analog converter, so that there is a minimum grid point that can be positioned, and the mask pattern is located at an intermediate position between the grid points. A reference position (a position determined by the exposure apparatus, such as the center or lower left of the mask pattern) cannot be arranged.

However, the pattern arranged on the projection mask is reduced (or equalized or enlarged) by the projection magnification of the projection exposure apparatus and is exposed on the substrate. The positions of the patterns arranged other than the reference positions are not limited to the lattice points of the exposure apparatus. Therefore, it is possible to mount a grating pattern of an integral multiple of a unit equal to or smaller than the minimum step unit determined by the exposure apparatus on the projection mask.

However, it is not desirable that there is a pitch change at a boundary between a plurality of projection exposure patterns. Therefore, assuming that the number of gratings arranged in the projection mask is p and the grating pitch at the time of projecting and exposing the substrate is p, n · p must be an integral multiple of the minimum unit of the exposure apparatus.

[0015] However, since the pattern mounted on the projection mask is also formed by exposing with a certain exposure apparatus, it is not always possible to obtain a pattern arranged at an arbitrary position.

Exposure on a substrate to be exposed by changing the pitch of the periodic pattern in units smaller than the minimum step unit of the projection exposure apparatus is achieved by using a reduced projection type exposure apparatus. If the projection magnification of the projection exposure apparatus is 1 / r, a pattern having a pitch change of 1 / r times the minimum step unit of the projection exposure apparatus can be obtained. Further, by forming the pattern of the projection mask by reduced projection exposure, it is possible to change the pitch in finer increments. By combining these two methods, it is possible to change the pitch in finer increments.

When a plurality of exposure patterns are connected by using a projection mask having a partial area of the whole pattern to form the whole pattern, a connection error between the exposure patterns becomes a problem. There are various causes for this connection error,
The main factors are fluctuation factors such as the position of the electron beam fluctuating due to the noise of the internal electric circuit system, disturbance noise, or magnetic field fluctuation, and fixed displacement caused by distortion of the deflection electron lens or nonlinearity of the digital / analog converter. .

The connection error due to the time-varying cause is as follows:
It is reduced by averaging the overlapped exposures by shifting the time. Further, the fixed connection error due to the deflection position can be reduced by overlappingly exposing the same pattern at different deflection positions.

Further, even if the position is shifted by a distance equal to or less than the dimension of the unit pattern and the overlapping exposure is performed, averaging of the temporal variation of the exposure position, that is, reduction of the connection error can be achieved without changing the arrangement pitch. In this case, the following new effects can be obtained. That is, if the pattern to be exposed is a one-dimensional array pattern, and the array direction is X and the other direction is Y, the Y direction is a continuous pattern. It can be practically eliminated.

On the other hand, if the overlapping exposure is performed by shifting the position in the X direction by a distance equal to or less than the dimension of the unit pattern, it becomes possible to shift the position of the center of gravity of the exposed pattern by the exposure ratio of each pattern. This method is different from the method described in the above-mentioned Japanese Patent Application Laid-Open No. Hei 8-227838 in that the exposure position of the entire exposure pattern can be shifted including a line that does not pass through a grid point that can be positioned on the substrate. It is possible.

The above-described effects can be maximized by using an electron beam exposure apparatus having a partial batch exposure function as the exposure means. As disclosed in Japanese Patent Application Laid-Open No. 62-260322, a partial batch electron beam exposure apparatus mounts (a plurality of) patterns repeatedly used in an LSI or the like as a stencil mask in an electron optical system. A required pattern is selected by deflecting the electron beam and reduced and projected on a substrate.

The advantage of using an electron beam exposure apparatus is that, since the reduction ratio can be increased, the pitch of the grating pattern after exposure can be reduced even if the unit of position in forming the pattern on the projection mask is coarse. The point is that it can be changed finely. For example, an electron beam exposure apparatus that creates a projection mask has a position increment unit of 2 nm.
When the reduction ratio of the exposure partial batch electron beam exposure apparatus is 1/25, the pitch can be changed in units of 0.08 nm. Further, a photomask is created by an electron beam exposure apparatus having a step unit of 2 nm, and a pattern of a projection mask is formed by performing optical reduction projection exposure to 1/5 using this mask. Is 0.0
The pitch can be changed in units of 2 nm.

Another advantage of using the partial batch electron beam exposure apparatus is that the exposure reduction ratio can be easily and widely changed by changing the set value of the exposure lens. (In the optical reduction projection exposure apparatus, since a fixed optical lens is used, the changeable reduction ratio is several ppm.
(Ppm is in parts per million). Therefore, a pitch change of about 1% required for a distributed feedback semiconductor laser using a projection mask formed at one kind of pitch is as follows:
It can be easily performed without affecting other electro-optical characteristics.

Further, by using an electron beam exposure apparatus capable of exposing while the stage is continuously moving, and by using it together with the overlay exposure, the deflection position of the electron beam deflector is automatically adjusted. Since the exposure can be performed at the same position on the substrate by changing, the connection error between the exposure patterns due to the non-linearity of the deflector can be reduced.

In the case of a distributed feedback semiconductor laser, it is known that stable oscillation can be obtained by adopting a structure in which the pitch is shifted by an amount corresponding to １ ／ wavelength in the middle of a grating having a constant pitch. Fluctuations in the pitch of the grating lead to broadening of the spectrum of the oscillating wavelength, so that high precision is required. However, the error allowed in the amount by which the pitch is shifted is somewhat large.

Generally, a deflector of an electron beam exposure apparatus is
In order to deflect the electron beam in a wide range and at high speed, there are two or three stages, and a deflector (main deflector) that deflects widely and a deflector (sub-deflector) that deflects narrowly and quickly, and in some cases, a narrower area. It has a deflector (sub-sub-deflector) that deflects at high speed. Where the range covered by these deflectors is switched, a connection error may occur in the exposure pattern. By making the above-mentioned pitch-shifted position coincide with the position at which the coverage of these deflectors is switched, it is possible to minimize the influence on the element characteristics.

From the above, more specifically, the present invention provides a method for forming an entire pattern area in which unit patterns are regularly arranged at a predetermined pitch or a partial area in which unit patterns are regularly arranged at a predetermined pitch. Using a mask on which a pattern constituting a part of the entire pattern area formed by arranging a plurality of patterns, a step of forming a desired pattern on a substrate by a projection exposure apparatus, and The pattern formation characterized in that the arrangement pitch of the unit patterns constituting the above is substantially equal to an integral multiple of a unit equal to or less than a minimum step unit that can be positioned when the projection exposure apparatus exposes the pattern onto the substrate. Provide a way.

Further, according to the present invention, in the above structure, the arrangement pitch of the unit patterns formed on the substrate is changed by changing a projection magnification of the projection exposure apparatus. A method of forming is provided.

Further, the present invention provides a pattern forming method according to the above structure, wherein a desired pattern is formed on the substrate by exposure including a plurality of overlapping exposures using the same mask.

Further, the present invention relates to a pattern area in which unit patterns are regularly arranged at a predetermined pitch, and a pattern area starting from a position shifted by a desired amount from the predetermined pitch and regularly arranged at the predetermined pitch. Forming a pattern on the substrate using an electron beam exposure apparatus, and wherein the electron beam exposure apparatus deflects the electron beam within a wide area on the substrate; and A second deflector that deflects in a narrow area on the substrate, and exposes the regular array pattern of the predetermined pitch at least in an area where the second deflector can be exposed; And a position on the substrate at which the deflection position of the deflector switches, and a position at which the pitch is shifted.

Still further, according to the present invention, in the above-mentioned structure, the electron beam exposure apparatus has a pitch substantially equal to an integral multiple of a unit smaller than a minimum step unit that can be positioned when exposing a pattern on the substrate. A pattern forming method is provided, wherein the regularly arranged pattern is formed by projecting and exposing a plurality of times using a mask having a repetitive pattern mounted thereon.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the first embodiment, and is an example of a plane pattern of a projection mask when the present invention is carried out using a projection mask and an electron beam exposure apparatus having a partial batch exposure function. FIG. In this example, the structure of the projection mask is the same as that shown in JP-A-6-132204, and is a stencil mask having an opening in silicon having a thickness of 10 μm.

FIG. 2 is a schematic view of the electron beam exposure apparatus used. An electron beam 4 accelerated by an electron source 3 at an acceleration voltage of 50 kV is formed in a first opening 5 and converged by a condenser lens 6. The deflector 7 is used to select a specific mask area from a mask plate 10 on which a plurality of projection masks similar to those shown in FIG. 1 are mounted. The electron beam is shaped by the shaping lens 8 and selectively irradiates a specific mask area 9 as shown in FIG.

Here, the electron beam formed into the mask pattern is reduced by the reduction lens 11 and is exposed to the silicon wafer 15 as the substrate to be exposed through the objective lens 12 to form a latent image 16. (The latent image becomes a resist pattern in a later developing step.) At this time, the movable stage 17
The exposure position on the wafer is determined by the main deflector 14 and the sub deflector 13.

The current density of this device is 10 A / cm 2,
The projection magnification is 1/25, the minimum positioning unit is 2 nm, and the maximum electron beam size that can be exposed in one transfer is 5 μm square on the exposure substrate. For this reason, the 125 μm square area indicated by rectangle 1 in FIG. 1 has the largest size on the mask. In this embodiment, openings 2 having a width d = 2.5 μm and a length 50 μm are formed in this region with a pitch p = 6.025 μm and an arrangement number n = 20. Aperture length up to 125μ
m is possible, but the reason for limiting to 50 μm is to limit the current value passing through the entire opening. It is known that, when the current value of the formed electron beam is large, the beam is blurred due to the repulsion by the Coulomb force between the electrons. In the case of the apparatus used in this embodiment, since the current density on the wafer is 10 A / cm 2,
The current passing through the entire m-square is 2500 nA, but it is approximately 500 nA in order to expose a fine pattern with high accuracy.
Exposure was desired with the following total current values.

The current passing through the mask shown in FIG.
0 nA, and high-precision exposure is possible. When this mask pattern is exposed on a substrate, the width is 2 μm and the pitch is 24 μm.
20 grating patterns of 0.1 nm are formed. This pitch indicates that the pitch can be changed with a fineness of 1/20 of the minimum positioning unit of 2 nm of the electron beam writing apparatus.

FIG. 3 shows electron beam exposure data used for exposure. The pattern 18 formed by one exposure is called one shot. This is data for forming an entire pattern 19 by exposing 11 shots at a pitch of 0.5 μm in the X direction and 166 shots at a pitch of 4.802 μm in the Y direction.
In the X direction, a quadruple-exposed region is formed with a width of 4 μm. The reason for the quadruple exposure shifted in the X direction is to make the connection between shots substantially invisible by other shots and to average the fluctuation of the exposure position of the electron beam.

A positive type electron beam resist ZEP520 (trade name of Zeon Corporation) was applied to a substrate of a 2-inch InP (indium phosphorus) wafer at a thickness of 0.2 μm. Exposure 2
15000 chips were exposed at 0 μC / cm 2 with the exposure pattern shown in FIG. 3 as one chip. A quadruple-exposed region with a width of 4 μm has an exposure amount of 80 μC / cm 2.
As a result of development with xylene for 60 seconds, a grating pattern having a pitch of 240.1 nm was formed smoothly over a width of 4 μm and a length of about 800 μm.

As described above, even when the exposure pitch was an integral multiple of the minimum step unit of 2 nm of the exposure apparatus, a grating pattern of 0.1 nm unit could be formed well. The time required for exposure of this one wafer was about 6 minutes. Wafer loading / unloading,
The time for irradiating the wafer with the electron beam excluding the alignment and the like was about 2 minutes, which proved the high productivity of this method.

When the exposure data shown in FIG. 3 is used, a width of 1.times.
A defective resolution area of 5 μm is formed, but there is no problem if the defective resolution area is arranged at a position other than the active area when applied to a distributed feedback semiconductor laser. If the poor resolution area becomes a problem, it can be eliminated by performing solid-fill exposure in an area including this area. Further, since this region has a resolution defect due to an insufficient exposure amount due to the single exposure to the triple exposure, the width is set to 1 in FIG.
The problem can also be solved by using a mask having a thickness of 2.5 μm to perform overlapping exposure to compensate for the shortage.

Here, the mask plate 10 on which the projection mask of FIG. 2 is mounted will be described in more detail with reference to FIG. An opening 20 of 125 μm square is formed at the center of the mask plate, and is used for a variable shaped beam. In the periphery, a projection mask 21 having a pattern formed by an opening in an area of 125 μm square similar to that shown in FIG.
Are arranged. The 21 masks may have different patterns, or a plurality of the same masks may be used as spares.

As described above, which mask is used is shown in FIG.
Can be electrically selected by the deflector 7. Therefore, there is no problem in forming grating patterns having different pitches in the same wafer. Here, if the opening areas of the 21 projection masks are made approximately equal, the degree of beam blur due to the Coulomb repulsion described above becomes equal, so that the optimal exposure condition does not change. In particular, it is effective in exposing the same wafer using a plurality of masks. The opening area can be easily adjusted by adjusting the width d and the length of the unit pattern 2 in FIG.

FIG. 5 shows a second embodiment of the present invention, and is a plan view of a projection mask for forming a 199.96 nm grating pattern using two projection masks. The electron beam exposure apparatus used for the exposure is the apparatus shown in FIG. One projection mask area 22
And the lower left position of the opening pattern 23 having a width d = 1.5 μm and a length 62.5 μm is arranged so as to coincide with a point A (lower left) which is a reference point of the projection mask, and the pitch is 4.9 in the Y direction.
25 lines were arranged at 99 μm.

In another projection mask area 24, 22
The lower left position of the same opening pattern as that of the mask
4 were shifted from the reference point B in the Y direction by a distance s = 25 nm, and 25 of them were arranged in the Y direction at a pitch of 4.999 μm.

To manufacture these projection masks, first,
A reticle magnified 4 times was prepared and reduced to 1/4 by an optical reduction projection exposure apparatus to form a pattern. Since the minimum positioning unit is 2 nm in drawing a 4 × reticle, a position rounding error of 0.5 nm of ４ in the projection exposure mask and 0.02 nm of 1/25 in the wafer after exposure (the starting point of the pattern or When the end point is not on the drawable positioning grid point, an error that occurs when the end point is replaced with an adjacent drawable positioning grid point is included.

However, in this embodiment, since the arrangement position unit on the projection mask is 1 nm and combined with a 4 × reticle, no rounding error occurs. However, such rounding errors do not accumulate and do not affect the array pitch, so it is possible to further reduce the array position unit on the projection mask. FIG. 6 shows drawing data when the two projection masks shown in FIG. 5 are exposed on a substrate. A pattern 25 using the projection mask 22 shown in FIG. 5 is shifted and superposed 16 times in the X direction at a pitch of 0.5 μm, and the projection mask 24 shown in FIG. Pattern 26 using
Are shifted 16 times in the X direction at a pitch of 0.5 μm.

As shown in FIG. 6, patterns 25 and patterns 26 are alternately arranged at positions separated by 4.998 μm and 5.000 μm, respectively. As a result, even if an electron beam exposure apparatus having a minimum positioning unit of 2 nm is used, 9.9 is obtained.
A grating pattern having a pitch of 199.96 nm in units of 98 μm is formed in units of 50 lines.

It is also possible to change the pitch in smaller units by using three or more projection masks.

FIG. 7 shows a third embodiment of the present invention. The projection mask area 27 has a width d = 1.5 μm,
Twenty opening patterns 28 having a pitch p = 5.0 μm are formed.

Under the standard lens setting conditions of the electron optical system shown in FIG. 2, an electron beam formed to 1/25 of the present mask is irradiated on the substrate to be exposed. What sets this projection magnification is the reduction lens 11 in FIG. This lens can be digitally set by a control computer, and its output is converted into a current by a digital / analog converter and passed to the excitation coil of the reduction lens. Digitally, 65536 steps can be set, but 1/2
The set value giving 5 was 55000. Since the current value of the electromagnetic coil, which is an analog output, can be changed by the power supply voltage, it is convenient to adjust the current change amount per unit of digital setting in advance so as to be an integral multiple of a desired magnification.

In the electron beam exposure apparatus used in the present embodiment, the magnification can be changed by 50 ppm (ppm is 1 / 1,000,000) per unit of the digital set value when the projection magnification is around 1/25. That is, a magnification change of 0.01 nm is possible for a pitch of 200 nm. In the present embodiment, an example in which the grating pitch is changed in units of 0.025 nm using an exposure apparatus having a minimum unit of exposure positioning of 2 nm by combining a fine pitch change by changing a projection magnification and an exposure position shift by minute shift overlapping exposure is described. FIG.
FIGS. 3B and 3D show exposure data PT1 for exposing a position on a substrate to be exposed using the mask shown in FIG. 3A, and FIGS. Exposure data PT2 and PT3 for exposing the pattern by +2 nm and -2 nm in the Y direction, respectively.

FIG. 8 shows exposure data for exposing these exposure data on the InP wafer 29. Assuming that the deviation of the set value of the reduction lens from the standard value is f unit, f =
At 0, the grating pitch is 200 nm,
The PT1 that has been exposed four times at the same position is arranged in the Y direction at a shot pitch p1 = 4 μm. At f = 25 units, the grating pitch is 200.025 nm. At this time, as shown in FIG. 8, a grating having a smooth pitch is formed by a combination of the overlapping exposure of PT1 and PT2. The position in the Y direction is 4 * p1 + 2 nm = 1
The drawing position comes on the grid of the minimum positioning unit of the drawing apparatus every 6.002 μm. In the figure, the position of the fifth shot is shifted in the X direction for easy viewing.

Similarly, when f is deflected in the negative direction, PT1
And PT3, a grating pattern with a smooth pitch is formed. Thus, f = −
Change from 250 units to f = + 250 units to 0.02
21 types of grating patterns having different pitches in 5 nm units were formed on the same wafer.

In this embodiment, at most 4 overlapping exposures, 1/1/2 nm of the minimum positioning unit of the electron beam exposure apparatus is used.
The grating pitch can be changed by 80 units.
This is the greatest effect that it is possible to expose a line that does not pass through the positioning grid point by using the projection mask.

FIG. 9 shows the fourth embodiment, and shows a method for solving the problem that the pitch of the grating fluctuates due to the non-linearity of the deflecting lens of the electron beam exposure apparatus. In the electron beam exposure apparatus used in this embodiment, the deflection range (field) of the main deflector is 1000 μm,
Deflection range (subfield) by sub deflector is 80 μm
It is. The projection mask used is the same as the mask 27 of FIG.

As shown in FIG. 9 (a), the exposure data 30 in the subfield has an exposure pattern of the mask 27 having a pitch of 4 .mu.
6 were arranged in the Y direction at m. This subfield is shown in FIG.
They are arranged at a pitch of 8 μm in the Y direction as shown in FIG. Although the figure is shifted in the X direction for easy viewing, the position in the X direction is actually the same.

As a result, patterns exposed at different field positions and subfield positions are superposed three times at the center of the entire pattern. At the upper end and the lower end of the entire pattern, an insufficient area of the overlap exposure occurs. Therefore, the auxiliary subfields 31, 32, 33, and 34 partially arranged in the subfield are overlap exposed and 3
This is performed so that the overlapping exposure is performed twice. Since the center position of the subfield is always positioned by the main deflector, the non-linearity of the digital / analog converter is averaged by the superposition exposure at different main deflection positions and subdeflection positions.

FIG. 10 shows a fifth embodiment of the present invention, in which a shift is made in the middle of a fixed grating pitch using three projection masks. The electron beam exposure apparatus used is the one shown in FIG. 2 as in the previous embodiments, and the minimum positioning unit is 2 nm. As shown in FIG. 10A, an opening 36 having a width d = 2 μm and a length 100 μm in the first projection mask region 34 is set at the origin C at the lower left of the mask region and the pitch p = 6.
N = 20 pieces were arranged at 01 μm.

In the second mask area 37 for projection, the opening 36 of the same shape is shifted from the origin D at the lower left corner of the mask area by a distance s = 1.05025 μm in the Y direction as shown in FIG. N = 20 at a pitch p = 6.01 μm from the position
This book was arranged.

Further, in the third projection mask area 38, an opening 36 of the same shape is provided in the Y direction from the origin E located at the lower left of the mask area at a distance 2s = 3.00 as shown in FIG.
From the position shifted by 5 μm, n = 20 at a pitch p = 6.01 μm.

As shown in FIG. 10D, the exposure data used for this electron beam exposure is obtained by forming a pattern 39 in the Y direction at a pitch p * n / 25 = 48 using a projection mask 35.
38 shots at 08 nm, 76 shots of the pattern 40 using the projection mask 37 while maintaining the same pitch, and 38 shots of the pattern 41 using the projection mask 38 while maintaining the same pitch. .

Using this exposure data, a grating pattern was formed on the InP substrate. Since the production of the distributed feedback semiconductor laser includes a step of cleaving the substrate at the center of the grating region, one laser element is shifted by 60.1 nm from the center of the grating pattern having a pitch of 240.4 nm. Is formed.

In this embodiment, three projection masks are used, but a first mask can be used instead of the third projection mask. In this case, a region having a pitch of p + s and a region of p-s are formed in the entire shape of the grating region. After cleavage at the center of the grating, a laser device having two structures is formed, but the characteristics are the same.

It is also possible to shift the pitch by shifting the drawing position in the middle of the grating using only the first projection mask. In this case, the pitch is shifted by 2 nm. In order to perform finer pitch shift using only the first projection mask, it is effective to combine with the shift overlapping exposure method used in the third embodiment.

FIG. 11 shows a sixth embodiment, which is an access optical communication system equipped with a distributed feedback semiconductor laser manufactured by using the pattern forming method of the present invention. Using a mask substrate equivalent to the projection mask substrate shown in FIG. 4, 16 types of stencil masks for forming a grating pattern having different pitches were prepared using 16 of the 21 openings. In fabricating a distributed feedback semiconductor laser, the same mask was used on the same InP wafer by using the mask.
Grating patterns having different pitches were formed. These semiconductor lasers are
3 was installed.

The transmitting / receiving module 42 includes the optical module 4
3 and a driving stage 44 and a receiving amplification stage 45. By mounting a semiconductor laser manufactured from the same wafer as the transmission / reception module, the characteristics can be easily controlled. While the optical signal is transmitted through the fiber 46, it is split into 16 at the electric dividing stage 47, so that a significant reduction in system cost can be realized.

[0068]

According to the present invention, when performing reduced projection exposure using a mask on which a partial area of the entire area of a regular array pattern is mounted, a pattern that does not fall on a grid point determined in advance by the minimum positioning unit of the exposure apparatus is used. Is mounted on a mask, a pattern in which the pitch is changed in fine units smaller than the minimum positioning unit of the exposure apparatus can be realized with high productivity.

When the number of arrangements of the regular patterns to be mounted in the mask is n and the arrangement pitch on the substrate to be exposed is p, the arrangement pattern to be mounted in the mask is n * p, the minimum positioning of the exposure apparatus. When the number is set to be an integral multiple of the unit, the pitch shift of the pattern after exposure can be eliminated, so that a highly accurate array pattern can be obtained. At this time, when a plurality of masks are used in combination, the value of n * p can be increased, so that a finer pitch change can be realized.

By exposing the exposure pattern to the same position on the substrate to be exposed a plurality of times, the temporal fluctuation of the exposure position of the exposure apparatus can be averaged, so that a highly accurate array pattern can be realized.

When the exposure pattern is a one-dimensional arrangement pattern, the regular arrangement direction is X, and the other direction is Y, and the overlapping direction is shifted in the Y direction, thereby performing the temporal exposure position of the exposure apparatus. Since connection errors between exposure shots in addition to fluctuations can be averaged, a more accurate array pattern can be obtained.

Further, in the case of the one-dimensional array pattern, when the overlapping exposure is carried out by shifting the pattern width in the X direction below the pattern width, it is possible to shift the position of the center of gravity of the exposure pattern in accordance with each exposure amount ratio. In this case, since overlay exposure can be performed including a pattern that does not fall on a grid point determined by the minimum positioning unit of the exposure apparatus, fine pitch change of the array pattern can be performed with a small number of overlaps.

If reduction projection exposure is used for these projection exposures, an enlarged mask is used, so that the pitch of the pattern formed on the mask can be changed in finer units. At this time, by using the electron beam exposure apparatus, the reduction magnification can be made very large as compared with the optical reduction projection exposure method, and it is effective because the accuracy between shots can be made high.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of the present invention, and is a plan view showing a projection mask for an electron beam exposure apparatus.

FIG. 2 is a schematic view showing an electron beam exposure apparatus having a partial batch exposure function using a projection mask.

3 is a diagram showing exposure data for exposing a grating pattern using the projection mask of FIG. 1 and the electron beam exposure apparatus of FIG. 2;

FIG. 4 is a view showing a mask plate on which a plurality of projection masks used in the electron beam exposure apparatus of FIG. 2 are mounted.

FIG. 5 is a view showing two projection masks used in a second embodiment of the present invention.

FIG. 6 is a view showing exposure data for exposing a grating whose pitch can be finely changed using the projection mask of FIG. 5;

FIGS. 7A and 7B are diagrams for explaining a third embodiment of the present invention, wherein FIG.
Is a projection mask for graying exposure, (b),
FIGS. 3C and 3D are views showing exposure data for performing fine shift overlapping exposure using FIG.

FIG. 8 shows an example of using the projection mask and the exposure data of FIG.
FIG. 4 is a diagram showing exposure data for forming a grating pattern on a P wafer.

FIG. 9 is a view for explaining a fourth embodiment of the present invention, and is a view showing exposure data for reducing pitch fluctuation due to non-linearity of a deflecting lens of an electron beam exposure apparatus by averaging.

FIG. 10 is a diagram for explaining a fifth embodiment of the present invention. FIG. 10 is a plan view showing a planar structure of a projection mask for shifting a certain grating pitch in the middle by using three projection masks, and exposure using the same. FIG.

FIG. 11 is a diagram for explaining a sixth embodiment of the present invention, showing an example of a multi-wavelength optical communication system equipped with a distributed feedback semiconductor laser manufactured by the method of the present invention.

[Explanation of symbols]

1 ... A region indicating the maximum range of the projection mask that can be exposed,
Reference numeral 2 denotes an aperture of a unit pattern for forming a grating pattern, 3 denotes an electron source, 4 denotes an electron beam, 5 denotes a first opening for shaping an electron beam, 6 denotes a condenser lens, and 7 denotes a plurality of deflectors for projection. Deflector for selecting one of the masks, 8: molded lens, 9: one projection mask area, 10: mask plate on which a plurality of projection masks are mounted, 11: reduction lens, 12: objective Lens: 13: sub deflector, 14: main deflector, 15: substrate to be exposed (wafer), 16: exposed latent image pattern, 17: movable stage, 18: using the projection mask shown in FIG. Exposure data for exposing in one shot, entire area formed by repeatedly exposing 19 ... 18, 20 ... opening for forming a variable shaping beam, 21 ... projection mounted on mask plate 10 mask One region, one region of the projection mask for 22 ... grating formation, 23 ...
Opening indicating unit pattern of grating pattern, 2
4 ... Projection mask area at a position different from 22 in the mask plate, 25 ... Exposure data for one-shot exposure using projection mask 22, 26 ... 1 using projection mask 24
Exposure data for shot exposure, 27: mask area for projection used in the third embodiment, 28: unit opening pattern of grating used in the third embodiment, 29: InP (indium phosphorus) wafer, 30: electron beam Exposure data for exposing in a range (subfield) that can be exposed by the sub deflector of the exposure apparatus, a point indicating the center position of the subfield at 30 '... 30, and exposure data of 31, 32, 33, 34 ... 30 Auxiliary exposure data for supplementing an underexposure area generated during the overexposure, 35... A projection mask area for forming a grating, 36... A unit pattern opening of the grating pattern, and 37. The opening pattern of the mask pattern forming mask areas 38... Grating pattern formation mask area arranged starting from a position shifted by 2 s, 39... Exposure data for exposing projection mask 35, 40... Exposure data for exposing projection mask 37, 41. Exposure data for exposing the mask 38 for exposure, 42 ... Transmission / reception module, 43 ... Optical module, 4
4 drive stage, 45 reception amplification stage, 46 optical fiber, 4
7 ... Electric division stage.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ken Sudo 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory of Hitachi, Ltd. (72) Inventor Jiro Yamamoto 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Hitachi, Ltd. Central Research Laboratory (72) Inventor Mitsuhiro Sawada 5-2-1, Josuihoncho, Kodaira-shi, Tokyo Co., Ltd. Semiconductor Group, Hitachi, Ltd. (72) Inventor Hajime Hayakawa 6-16, Shinmachi, Ome-shi, Tokyo 3 shares Hitachi, Ltd. Device Development Center (72) Inventor Yasuo Seino 1 Nishiyokote-cho, Takasaki-shi, Gunma 1 F-term (reference) 2H097 AA03 AB05 CA16 GB01 LA17 LA20 5F056 AA06 AA20 AA22 AA27 CB14 CC13 DA22 FA07 FA08

Claims (5)

[Claims] 1. An entire pattern area in which unit patterns are regularly arranged at a predetermined pitch, or an entire pattern area formed by arranging a plurality of partial areas in which unit patterns are regularly arranged at a predetermined pitch. Using a mask on which a pattern constituting a part is mounted, the projection exposure apparatus has a step of forming a desired pattern on a substrate, and the arrangement pitch of unit patterns constituting the pattern is substantially reduced. Wherein the projection exposure apparatus uses an integral multiple of a unit equal to or less than a minimum step unit that can be positioned when exposing a pattern onto the substrate. 2. The pattern forming method according to claim 1, wherein an arrangement pitch of said unit patterns formed on said substrate is changed by changing a projection magnification of said projection exposure apparatus. 3. A pattern forming method according to claim 1, wherein a desired pattern is formed on said substrate by exposure including a plurality of overlapping exposures using the same mask. 4. A pattern including a pattern region in which unit patterns are regularly arranged at a predetermined pitch and a pattern starting from a position shifted by a desired amount from the predetermined pitch and being regularly arranged at the predetermined pitch, Forming a first deflector for deflecting the electron beam within a wide area on the substrate; and forming a narrow beam on the substrate with a first deflector. A second deflector that deflects the light in the region, and exposes the regular array pattern at the predetermined pitch at least in the region where the second deflector can be exposed; A pattern forming method, wherein a position on the substrate at which a deflection position is switched matches a position at which the pitch is shifted. 5. The method according to claim 1, wherein the electron beam exposure apparatus uses a mask on which a repetitive pattern having a pitch of an integral multiple of a unit equal to or less than a minimum step unit that can be positioned when exposing the pattern onto the substrate is used. 5. The pattern forming method according to claim 4, wherein the regular array pattern is formed by performing a plurality of projection exposures.