JP2902489B2 - Variable shape charged particle beam exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam exposure method, and more particularly to a charged particle beam exposure method suitable for exposing a plurality of patterns at regular intervals.

[0002]

2. Description of the Related Art In recent years, the pattern of a semiconductor device has been miniaturized in order to increase the speed and integration of the semiconductor device. In order to expose such a fine pattern, a high-resolution exposure means is required. Development of a charged particle beam exposure apparatus using charged particles such as electrons having a wavelength much shorter than that of light has been continued to realize high-resolution exposure means.

[0003] A charged particle beam can be focused on an extremely small spot, and high resolution can be realized. However, when a large area is drawn with a small spot, the time required for exposing a unit area increases. I will. Therefore,
A variable-shaped charged particle beam exposure technique for shaping a charged particle beam into an arbitrary rectangular shape or the like and exposing a certain area at a time has been developed.

FIG. 5 shows a conventional variable shape electron beam exposure technique. As shown in FIG. 5A, an electron beam is shaped into an arbitrary variable rectangular pattern 101, and a photoresist layer applied on a semiconductor wafer or the like is exposed.

As shown in FIG. 5B, a variable rectangular pattern is formed by passing an electron beam 103 through masks 104 and 106 having two rectangular openings. It is assumed that the electron beam 103 has a circular cross section at first, as shown in the upper right part of the figure. This electron beam is applied to a mask 104
By irradiating one corner of the opening provided in the above, a fan-shaped electron beam cross section 105 having two right sides is formed. The electron beam having such a cross-section is applied to another mask 1.
06 to form an electron beam having an arbitrary rectangular cross section 107.

An arbitrary rectangular electron beam formed as described above is irradiated on the photoresist layer. According to the design of the semiconductor device, the rectangular cross section of the electron beam is changed into a desired shape, and is successively exposed.

In an electron beam exposure apparatus,
Although the position accuracy of the beam cross section is extremely high at the reference point, a displacement occurs as the distance from the reference point increases. The reference point is usually set at one end of the rectangle.

In the rectangular pattern shown in FIG. 5A, although the positional accuracy of the reference point (0, 0) at the left end is high, the position at the right end has a displacement of dx depending on the value of the length p10 of the long side of the rectangle. Will happen. Since the displacement dx depends on the length p10 of the pattern, changing the rectangular pattern also changes the displacement dx.

FIG. 6 is a diagram for explaining a quantum point contact device. FIG. 6A is a plan view of a semiconductor device having two quantum point contacts. On a semiconductor substrate 110, three Schottky electrodes 111,
112, 113 are formed, between which quantum point contacts are formed.

FIG. 6B schematically shows a cross-sectional shape of the quantum point contact device shown in FIG. An electron transit layer 117 of an intrinsic semiconductor having a relatively narrow band gap is epitaxially grown on the semiconductor substrate 115,
Furthermore, an electron supply layer 118 having a high impurity concentration and a wide band gap is epitaxially grown thereon. The electrons in the electron supply layer 118 are supplied to the electron transit layer having a narrower band gap, and form a two-dimensional electron gas 120 near the interface. Schottky electrodes 111, 112, and 113 are formed on the electron supply layer 118, and depletion layers 121, 122, and 123 are formed thereunder. Then 2
The two-dimensional electron gas 120 is rejected by the depletion layers 121, 122, and 123, and is localized in a narrow space between the Schottky electrodes.

When the voltage applied to the Schottky electrodes 111, 112, 113 is adjusted, the depletion layers 121, 122, 1
23 further grows and narrows the width of the two-dimensional electron gas 120. Eventually, the width of the two-dimensional electron gas 120 becomes extremely narrow, forming a one-dimensional electron gas. In such a state, the electron gas 120 forms a new quantum state,
In the figure, the two-dimensional electron gas extending on the back side and the front side of the drawing is connected in a point-like manner (point contact). Such a state is called a quantum point contact.

In the quantum point contact device,
The distance between the Schottky electrodes is an important parameter. For example, as shown in the figure, two quantum point contacts are formed in parallel, a two-dimensional electron gas is supplied from one side, and two electron waves are emitted to the other side. Occurs. Schottky electrodes 111, 112,
Adjusting the voltage applied to 113 changes the quantum state allowed at each quantum point contact.

If the distance between the Schottky electrodes 111, 112 and 113 to be formed at equal intervals becomes non-uniform, even if a predetermined bias voltage is applied, the expected quantum You will not be able to get the status. Then, a desired interference state may change or interference may not occur.

FIG. 6C shows an example of a pattern for forming such a quantum point contact device. The pattern of the electron beam for forming the Schottky electrodes 111, 112, 113 is changed to 111a, 112a, 113a.
Indicated by

As described above, the deformable electron beam has extremely high positional accuracy at the reference point (0, 0), but the positional accuracy decreases as the distance from the reference point increases, and the distance-dependent displacement dx occurs. It is assumed that the long patterns 111a and 113a generate displacements dx1 and dx3 at the end opposite to the reference point, and the central short pattern 112a generates a displacement dx2. Then, the distance between the Schottky electrodes, which should be formed at the same interval x0, is different from (x0-dx1) on one side and (x0-dx2) on the other side as shown in the figure.

The displacement dx depends on the pattern length in a complicated shape, and it is extremely difficult to control this amount accurately.
For example, if the interval to be formed is 500 nm and the displacement d
If the difference of x is 50 nm, a fatal error occurs for the quantum point contact device.

[0017]

As described above,
In the variable shape charged particle beam exposure technique according to the related art, the position of a reference point of a pattern can be accurately controlled, but the accuracy of a position apart from the reference point must be reduced. Since the amount of displacement at a position distant from the reference point depends on the distance from the reference point or the like in a complicated manner, it becomes difficult to position the pattern end with good reproducibility when the size of the pattern changes.

An object of the present invention is to provide a variable-shaped charged particle beam exposure method capable of forming a predetermined interval between patterns of different sizes with good reproducibility.

[0019]

FIG. 1 is a diagram illustrating the principle of the present invention. As shown in FIG. 1A, a long pattern 1
And a short pattern 2 are formed at an interval q. It is assumed that the charged particle beam exposure apparatus performs positioning using the lower left end of each pattern as a reference point. Then, in the x direction, the right end of each pattern is the pattern length p1, p2
Produces a displacement dx1 for the long pattern 1 and a displacement dx2 for the short pattern 2.

FIG. 1B shows one form of a pattern created by the present invention. A long pattern 1 is formed by a second pattern 4 having the same length as the short pattern 2 and a first pattern 3 corresponding to the remaining portion.

In the configuration shown in FIG. 1B, an interval g equal to or less than a predetermined value is provided between the first pattern 3 and the second pattern 4. FIG. 1C shows another form of the pattern created by the present invention. Long pattern 1
Is formed by the second pattern 4 having the same length as the short pattern 2 and the first pattern 5 which forms the remaining portion of the long pattern and overlaps the second pattern. The first pattern 5 and the second pattern 4 have an overlapping portion s. The overlapping portion s is selected such that the first pattern 5 does not project to the right of the right end of the second pattern 4.

Although the case where the left end of each pattern is the reference position has been described above, the right end of each pattern may be the reference position. This case will be described with reference to FIGS.

FIG. 1D shows a target pattern.
The target pattern is a pattern in which a long pattern 6 and a short pattern 2 are arranged at an interval q. Due to the nature of the charged particle beam exposure apparatus, the right end of each pattern is accurately positioned as a reference position, and displacements dx2 and dx6 depending on the pattern lengths p2 and p6 occur at the left end of each pattern.

FIG. 1E shows one form of a pattern created according to the present invention. A long pattern 6 is formed by a second pattern 8 having the same length as the short pattern 2 and a first pattern 7 corresponding to the remaining portion. An interval g equal to or less than a predetermined value is provided between the first pattern 7 and the second pattern 8.

FIG. 1F shows another form of the pattern created by the present invention. In this configuration, the second pattern 8 forming the long pattern 6 and the first pattern 9
Have an overlapping portion s.

Although the case where two patterns are formed has been described, three or more patterns can be formed. In particular, the present invention is effective when three or more patterns are formed at equal intervals.

[0027]

In the variable shape charged particle beam exposure, the pattern displacement dx depends on the pattern length p.
When is small, it becomes small. When the end of the long pattern is formed by another short pattern, the positional accuracy of the end of the pattern can be improved.

Even if the remaining portion of the long pattern and the other short pattern used at the end are separated by a very small distance that can be neglected in terms of the function of the device to be formed, even if they are overlapped, the function of the device will not be affected.

When a short pattern and a long pattern are formed, the length of the gap can be controlled with good reproducibility by forming the end of the long pattern with another short pattern equivalent to the short pattern.

When short patterns are repeatedly arranged, uniform gaps can be formed.

[0031]

FIG. 2 shows a variable shape charged particle beam exposure method according to an embodiment of the present invention. FIG. 2A is a plan view of a target pattern. A long pattern 11, a short pattern 12, and a long pattern 13 are arranged with a gap q1. The long patterns 11 and 13 on both sides have length p
1, p3, and the central short pattern 12 has a length p2. Of these patterns, in particular, the gap q1 between the patterns
It is important to create evenly. For example,
4 is a Schottky electrode pattern of a quantum point contact device.

FIG. 2B shows an example of a pattern created to form the pattern shown in FIG. In order to form the long pattern 11, the length p of the short pattern 12
Expose a short pattern 15 having the same length p2 as 2 at the end to form the remaining part of the long pattern 11,
Another pattern 14 having a gap equal to or less than a predetermined length is exposed.

That is, the long pattern 11 is disassembled so that the displacement on the left side of the pattern becomes equal between the long pattern 11 and the short pattern 12, and the end of the long pattern 11
And a short pattern 15 equivalent to the above. Since the short patterns 12 and 15 have the same pattern length p2, the displacement at the right end of each pattern is also equal to dx2. Since the left end of each pattern is a reference position, its positioning accuracy is extremely high. Therefore, equal gaps are formed between the patterns 12 and 15 and between the patterns 13 and 12.

FIG. 2C is a sectional view showing the structure of a quantum point contact device in which equal gaps are formed as described above. An electron supply layer 22 is formed on the electron transit layer 21, and electrodes 14, 15, 12, and 13 having a pattern as shown in FIG. 2B are formed on the surface thereof. These electrodes form a Schottky contact with the semiconductor surface and form depletion layers 26, 27, 24, 25 thereunder. Left 2
Since the two patterns 14 and 15 are designed with a gap equal to or less than a predetermined length, the depletion layers 26 and 27 overlap,
Prohibits the presence of two-dimensional electron gas. Therefore, the two-dimensional electron gas flows between the electrodes 12 and 15 and between the electrodes 12 and 13.
Only allowed between

The gap between the electrodes 12 and 15, the electrodes 12 and 13
Are uniformly formed, so that when the bias voltage applied to the Schottky electrode is adjusted to form a one-dimensional electron gas, the quantum state in both gaps becomes uniform.

In order to form the long pattern 11,
A pattern 15 having the same pattern length as the short pattern 12 and a pattern partially overlapping the pattern 15 can also be used.

FIG. 3 is a view showing a variable-shaped charged particle beam exposure method according to another embodiment of the present invention. FIG. 3A shows a plan configuration of the pattern, and FIG. 3B shows a cross-sectional structure of the device. The relatively long pattern 31 and the short pattern 32 form an equivalently long pattern 33, and the length of the central short pattern 35 and the length of the short pattern 32 are made equal. Another long pattern 38 is formed by a short pattern 36 having the same length as the central short pattern 35 and a relatively long pattern 37.

With such a configuration, the three short patterns 32, 35, and 36 at the center can be formed into patterns having equivalent dimensions, and the distance therebetween can be made uniform with high precision.

In the case of the configuration shown in FIG. 3A, the reference position of the pattern may be on the right side or on the left side. FIG. 3 (B)
Shows a cross-sectional configuration of a quantum point contact device having such an electrode pattern. An electron supply layer 22 is formed epitaxially on the electron transit layer 21, and Schottky electrodes 31, 32, 35, 36, 37 are formed on the surface thereof.
Are formed. Three central Schottky electrodes 32,
35, 36 are formed at equal intervals, and the Schottky electrodes 31, 37 at both ends are Schottky electrodes 32, 36 on the inner side.
And a gap not more than a predetermined distance. With such an electrode arrangement, depletion layers 41, 42, 45, 46, 47 are formed in the semiconductor. The depletion layers 41, 42 and 46, 47 at both ends overlap each other because the Schottky electrodes 31, 32 and the Schottky electrodes 36, 37 are separated by a gap equal to or less than a predetermined distance, and the depletion layers continue also in the electrode gap. 43 and 48 are formed.

Thus, the Schottky electrodes 3 on both sides are
1, 32 and 36, 37 are functionally
It works equally well with one continuous long Schottky electrode.
Further, the gap between the Schottky electrodes 32 and 35 forming the quantum point contact, and the Schottky electrode 3
Since the gap between 5, 36 forms these Schottky electrodes with the same length, the same length can be achieved with extremely high precision.

FIG. 4 is a view for explaining a variable shape electron beam exposure method according to another embodiment of the present invention. FIG. 4 (A)
Shows a case where a long pattern L1 and short patterns S1, S2, S3, S4, S5... Arranged at equal intervals are exposed. The long pattern L1 is replaced with the short patterns S1, S
2 are formed by a short pattern 52 having the same length as that of..

In such a configuration, the gap between the patterns is the short pattern 52 and the equivalent short pattern S
1, S2,..., The gap is extremely homogeneously formed with good reproducibility.

FIG. 4B shows another embodiment for creating an equivalent pattern. In this embodiment, the point that the long pattern L1 is formed by the short pattern 52 and the long pattern 51 is the same as that of FIG. 4A, but the long pattern 51 and the short pattern 52 are not continuous, and a gap is provided therebetween. Is formed. This gap is chosen to be negligible due to the nature of the device to be made.

For example, according to the patterns shown in FIGS. 4A and 4B, a quantum point contact device in which a large number of quantum point contacts are arranged at equal intervals can be produced.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example,
Although the quantum point contact device has been described as a device to be formed, the present invention can be applied to other semiconductor devices and the like in which patterns having different lengths need to be accurately arranged. The shape of the pattern to be exposed is arbitrary. It will be apparent to those skilled in the art that various changes, improvements, combinations, and the like can be made.

[0046]

As described above, according to the present invention,
The gap between the long pattern and the short pattern can be created with high reproducibility.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention. FIG. 1 (A),
(D) is a plan view showing a target pattern, FIG.
(B), (C), (E), (F) is a plan view showing the form of a pattern created to realize a target pattern.

FIG. 2 shows an embodiment of the present invention. 2A is a plan view of a target pattern, FIG. 2B is a plan view of a pattern to be created, and FIG. 2C is a cross-sectional view of a device created using the pattern.

FIG. 3 shows another embodiment of the present invention. FIG. 3A is a plan view showing a Schottky electrode pattern, and FIG. 3B is a cross-sectional view of a quantum point contact device having the Schottky electrode.

FIG. 4 shows another embodiment of the present invention. FIG. 4 (A),
(B) is a plan view of a pattern for arranging a long pattern and a plurality of short patterns at equal intervals.

FIG. 5 shows a conventional technique. FIG. 5A shows an example of a variable rectangular pattern, and FIG. 5B is a schematic diagram for explaining shaping of a cross-sectional shape of an electron beam.

FIG. 6 shows a quantum point contact device. FIG.
6A is a plan view, FIG. 6B is a cross-sectional view, and FIG. 6C is a conceptual diagram for explaining exposure of the Schottky electrode shown in FIG. 6A.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Long pattern 2 Short pattern 3, 4 Pattern for jointly forming a pattern equivalent to long pattern 1 4 Pattern having the same length as short pattern 2 3 Pattern separated from short pattern 4 5 Short pattern Patterns overlapping 4 6 Long patterns 7 and 8 Patterns for jointly creating a pattern equivalent to the long pattern 8 8 Patterns having the same length as the short pattern 2 7 Patterns separated from the short pattern 8 9 Pattern overlapping with short pattern 8

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027

Claims (3)

(57) [Claims] 1. A variable shape charging device for exposing a relatively long pattern (1, 6) and a relatively short pattern (2) with a variable shape charged particle beam to form a gap (q) of a predetermined length therebetween. In the particle beam exposure method, the first pattern (3, 5, 7, 9) and the second pattern (4, 8) having the same size as the relatively short pattern (2) near the end thereof are variable. Exposing the relatively long pattern (1, 6) as a whole by exposing with a charged particle beam having a shape; and exposing the relatively short pattern (2) at a predetermined distance from the second pattern (4, 8). And b) exposing. 2. The method according to claim 1, wherein the second pattern (4, 8) is connected to the first pattern.
2. The variable shape charged particle beam exposure method according to claim 1, wherein the exposure is performed at a very small distance (g) that is negligible in function of a device to be formed from the pattern (3, 7). 3. The method according to claim 1, wherein the second pattern (4, 8) is the first pattern.
2. The variable shape charged particle beam exposure method according to claim 1, wherein the exposure is performed in contact with or partially overlapping an end of the pattern.