JPH0352213B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing a hard mask, and in particular to a method for manufacturing a hard mask that can manufacture a hard mask having a conductive thin film without defects. be.

[Technical Background of the Invention] Among photomasks used in the manufacture of semiconductor devices, all master masks are currently patterned using an electron beam exposure method. Master masks that have patterns with higher precision and higher density than masks have come to be manufactured. However, the conventional master mask manufacturing method has problems as described below.

[Problems with Background Art] Conventionally, in a hard mask manufacturing method using an electron beam exposure method, pattern formation on a mask blank has been performed as shown in FIG. 1st
The figure shows a mask manufacturing method using a chrome hard mask blank.
2 is a glass substrate, 2 is a chromium (Cr) layer deposited on the glass substrate 1, 3 is a chromium oxide layer formed on the surface of the chromium layer 2, and 4 is a resist deposited on the chromium oxide layer 3. A blank plate 5 consisting of a glass substrate 1, a chromium layer 2, and a chromium oxide layer 3 is mounted on a transport cassette 6 and supported on an X-Y table (not shown) of an electron beam exposure apparatus. ing. 7 is a grounding electrode that also serves as a flattening pin (for horizontality detection);
is pressed against the outer peripheral edge surface of the resist layer 4 to level the surface of the blank board and electrically ground the resist layer 4. The surface of the resist layer 4 on the inner circumference side from the grounding electrode 7 is the actual pattern area where pattern formation is performed, and the electron beam is applied thereto.
By irradiating with EB, a latent image of a circuit pattern is formed on the resist layer 4.

In the conventional method as shown in FIG. 1, since the grounding electrode 7 is pressed onto the resist layer 4,
The following problems occurred.

(a) When the electron beam is irradiated, charges are accumulated in the chromium oxide layer 3 and the chromium layer 2, but because the grounding electrode 7 is in contact only with the resist layer 4, the blank plate cannot be completely grounded. During drawing, the influence of accumulated charge gradually increases,
As a result, distortion often occurs in the drawn pattern.

Also, when drawing patterns with minute dimensions,
Since the blank board was not completely grounded, the proximity effect was greater than in the case where the grounding was perfect due to the influence of residual charge, making it impossible to form accurate patterns.

(b) Since the grounding electrode 7 is pressed against the resist layer 4, resist may adhere to the tip of the grounding electrode 7. If the next blank board is patterned with the resist still attached to the tip of the grounding electrode 7, the following problems may occur when the grounding electrode 7 is also used as a flattening pin for the blank board. is likely to occur.
That is, as shown in FIG. 2, for example, while the resist piece 4a remains attached to the tip of one of the two grounding electrodes 7a and 7b,
When patterning the next blank plate 50, the horizontal alignment of the blank plate 50 will be distorted, so the axis _Y0 of the lens system of the electron beam exposure device 8
is tilted by an angle θ as shown in the figure with respect to the direction of the axis _Y1 of the blank plate 50, and as a result, the focus of the electron beam shifts and the long and short dimensions of the mask become out of order. In this way, the attached resist piece 4a
For example, as shown in FIG.
This corresponds to a case where the electron beam is irradiated in the vertical direction with the blank plate 5 tilted relative to the other side. In this case, the maximum amount of inclination of the blank plate 5 with respect to the cassette 6 is defined as R, the x and y directions are determined on the blank plate 5 as shown in the figure, and nine measurement points are placed on the blank plate 5 as shown in Fig. 4. Tori, R=500μm
The results of measuring the variation in the short dimension in the case of
FIG. 6 shows the results of measuring the long dimension (total pitch). In FIGS. 5 and 6, the x mark indicates the dimension in the x direction at each point, and the ○ mark indicates the dimension in the y direction, and the design dimension is 10 μ in both the x and y directions. Also,
The horizontal straight line L in FIG. 6 represents the true value (distance between B ₁ B ₂ or A ₀ C ₀ ; 90000,00μ)).

As is clear from FIGS. 5 and 6, when the blank plate 5 is tilted in the x direction, it is inevitable that the short and long dimensions in the same direction will be out of alignment. If the short and long dimensions are deviated in this way, accurate pattern formation becomes impossible and pattern defects are likely to occur.

(c) In order to prevent pattern defects caused by resist adhesion to the grounding electrode as described above, it has conventionally been necessary to keep the tip of the grounding electrode 7 clean at all times, but this reduces work efficiency. ,
The work could not be automated.

(d) When the grounding electrode is separated from the resist layer, the resist layer peels off, and the peeled resist pieces fly into the pattern area and adhere thereto, thereby damaging the pattern and causing mask defects. Something happened.

[Object of the Invention] An object of the present invention is to solve the problem of plane alignment accuracy of the conventional method and to provide an improved hard mask manufacturing method.

[Summary of the Invention] In the method of the present invention, when performing electron beam exposure, areas where a resist layer is not formed are provided in advance on the outer edge surface of a mask blank, and the surface of the mask blank exposed at the areas where the resist layer is not formed is exposed. This method is characterized in that the plane of the mask blank is leveled by bringing at least three leveling pins into contact with each other, and then electron beam exposure is performed. According to the method of the present invention, the flattening pin directly contacts the surface of the mask blank without intervening a resist layer, and resist does not adhere to the tip of the flattening pin even after repeated use. The plane alignment will not be distorted, and as a result, the focus of the electron beam will not shift and the short or long dimensions of the mask will not be distorted.

[Embodiments of the Invention] FIG. 7 shows the method of the present invention, and in FIG. 7, parts labeled with the same reference numerals as in FIG. 1 represent the same parts as in FIG. 1.

In the method of the present invention, prior to performing electron beam exposure, the resist layer 4 on the surface of the blank plate 5 is preliminarily deposited at a pattern formation location 10 as shown in FIG.
(i.e., the actual pattern area) by peeling off at least one place on the outside.
As shown by the shaded line in the figure, a resist layer-free area 9 is formed at the corner of the blank plate 5, and the chromium oxide layer 3 exposed at the resist-layer-unformed area 9 is flattened as shown in FIG. While pressing the pin 7, the surface of the resist layer 4 is irradiated with an electron beam EB to expose the circuit pattern.

In the method of the present invention, since the tip of the flattening pin 7 does not come into contact with the resist layer, peeling of the resist layer and adhesion of the resist layer to the flattening pin 7 do not occur.
Furthermore, since the peeled resist pieces do not re-adhere within the pattern area, all causes of defects due to peeling of the resist layer are eliminated.

As shown by the shaded line in FIG. 8, one method for forming the resist layer-unformed area 9 is to spin-coat the resist using a spinner and simultaneously apply the resist to a point on the inscribed circumference of the resist-layer-unformed layer 9 (outside the pattern area). When a resist is spin-coated while dropping resist thinner onto the resist layer 11, only a circular resist layer is left, and no resist layer is formed in the areas 9 where the resist layer is not formed. In order to sharpen the periphery of the resist layer, it is preferable to inject the resist thinner in the tangential direction of the inscribed circle 11 at an angle of about 30° to the horizontal plane of the blank plate. In addition, it is preferable to drip the resist thinner at the same time as the resist spin coating in order to avoid increasing the number of steps.
This is possible even before the resist is exposed to EB, that is, after the resist is baked.

Location 9 where resist layer is not formed as shown in Figure 8
When the resist layer is formed, a relatively large area where the resist layer is not formed is obtained at the four corners, so instead of a pin-shaped flattening pin, a flattening pin with a large contact area can be used to ensure flatness. be able to.

[Effects of the Invention] As is clear from the above explanation, according to the method of the present invention, peeling of the resist layer due to the planar pin does not occur at all, so the occurrence of defocus of the electron beam due to peeling of the resist layer is avoided. On the other hand, it is possible to omit the work of keeping the flattening pin clean, and as a result, the occurrence of defective products can be prevented and the work can be simplified. Furthermore, since the work of cleaning the flattening pins is no longer necessary, the work can be automated, making it possible to increase the efficiency of the hard mask manufacturing process.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional hard mask manufacturing method, and FIGS. 2 to 6 are diagrams for explaining the problem when a resist piece adheres to the tip of a flattening pin in the method of FIG. FIG. 7 is a schematic diagram for explaining the method of the present invention, and FIG. 8 is a schematic plan view of a mask blank used in the method of the present invention. DESCRIPTION OF SYMBOLS 1...Glass substrate, 2...Chromium layer, 3...Chromium oxide layer, 4...Resist layer, 5...Blank plate (mask blank), 6...Cassette, 7...
Plane pin, 9... portion where resist layer is not formed, 1
1... Location where resist thinner is dripped.

Claims (1)

[Claims] 1. When forming a resist pattern on the surface of a hard mask blank by electron beam exposure, a resist layer-unformed area is prepared in advance at a location other than the planned pattern formation location on the hard mask blank, and the resist pattern is not formed on the hard mask blank. A flattening pin that is fastened to the base of the device and supports the exposed surface of the hard mask blank on a plane perpendicular to the axis of the lens system of the device is brought into contact with the surface of the area where the resist layer is not formed, and the hard mask blank is A method for manufacturing a hard mask characterized by flattening and performing electron beam exposure.