JP2009237289A - Halftone phase shift mask and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of a halftone phase shift mask and a method for manufacturing the mask, the halftone phase shift mask having a region comprising a phase shift layer and a region comprising a light shielding layer on the phase shift layer, in which a pattern having a large area but requiring no high accuracy such as a mask identification mark is formed in a short period of time without influencing the accuracy of other high accuracy pattern. <P>SOLUTION: The halftone phase shift mask has a structure where a pattern recognized by a difference in the reflectance depending on the presence or absence of a light shielding layer on a phase shift layer is used as an identification mark of the mask, and the mask is manufactured by the manufacturing method for simultaneously forming the identification mark with other patterns of the light shielding layers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a halftone phase shift mask used for manufacturing a semiconductor product, and more particularly to a mark structure for identifying a halftone phase shift mask and a manufacturing method thereof.

  Manufacturing a semiconductor product requires a large number of photomasks. In an exposure process for making one type of semiconductor, about 20 photomasks are used for forming circuits such as transistors, capacitors, resistors, and wiring. It is necessary to select a necessary item from the stock of the photomask and confirm that it is a desired mask before putting it into actual use, and an identification mark for this purpose is attached to the photomask.

  This identification mark is used to display management information such as the photomask manufacturing number, lot number, manufacturing date, etc., and is attached to the outer peripheral portion itself or coded and not used for circuit formation of the photomask substrate. The For these identification marks, a pattern size that can be optically read by a barcode method or can be directly observed with a microscope is sufficient (Patent Document 1).

  On the other hand, a photomask is obtained by forming a circuit pattern or its inverted pattern with a light-shielding metallic chromium (hereinafter referred to as Cr) on a quartz substrate. This photomask is set away from the photosensitive resist coated on the wafer, irradiated with ultraviolet rays by an exposure device, and the circuit pattern is transferred to the photosensitive resist by the same action as a photographic negative film. It is manufactured by an etching method.

  However, circuit patterns to be formed have been miniaturized due to higher integration and higher speed of semiconductors. In the photomask configuration including the simple Cr light-shielding film and the quartz substrate as described above, the light diffraction limit (With light, resolution less than half that wavelength cannot be reached), it has become difficult to transfer a fine pattern to a photosensitive resist. Therefore, a phase shift method has been developed as a technique for lowering the diffraction limit, and a photomask having a structure corresponding thereto has been provided as a phase shift mask.

  There are halftone type and Levenson type phase shift masks, but the former lays a part that changes the phase of light (hereinafter referred to as a shifter layer) on the mask substrate, and the phase changes through the shifter. This technique improves the resolving power by utilizing the interference between the transmitted light and the light that does not pass through the shifter and whose phase has not changed. When the phase difference is set to 180 degrees, the light amplitudes cancel each other at the shifter opening boundary, and the light intensity is reduced.

  Accordingly, in the standard halftone phase shift mask, a shifter pattern having a certain degree of transparency is formed on the quartz substrate instead of the light shielding Cr pattern. The shifter may be formed by laminating a plurality of materials as well as a single material in order to adjust the phase. A light-shielding zone is necessary around the transfer area to prevent unnecessary exposure. The light shielding layer is formed on the shifter layer, and is removed as necessary. In general, the pattern of the light shielding layer to be removed (hereinafter referred to as a light shielding band pattern) does not require high dimensional accuracy, position accuracy, and resolution accuracy. Further, the light shielding material of the light shielding layer may have a structure in which a plurality of films are laminated.

  For the formation of the shifter layer pattern, an electron drawing device with a high acceleration voltage is generally used because of dimensional accuracy, position accuracy, resolution accuracy, etc. In general, a low-cost drawing machine such as a laser drawing machine or a low-precision electronic drawing machine is used.

The known literature is shown below.
JP 2000-99619 A

  The identification mark provided outside the transfer area of the photomask is a rough pattern that does not require pattern resolution and accuracy. Nevertheless, until now, drawing has been performed with an accuracy that can be said to be excessive, simultaneously with a main pattern corresponding to a semiconductor circuit, using an expensive electron beam drawing apparatus for a long time.

  In a vector type electron beam lithography system, when the current density is high, the maximum shot size of the electron beam is small in order to avoid the influence of Coulomb repulsion between electrons. As a result, if there is an identification mark having a large area to be drawn, there is a problem that the number of electron beam shots increases, drawing time increases, and photomask productivity decreases. If the photomask manufacturing period is long, short delivery is difficult.

  In addition, a pattern with a large opening such as an identification mark has a problem in that it affects the dimensional accuracy of a fine pattern such as a circuit pattern due to scattered electrons, a loading effect, and the like.

  With regard to the problem of increased drawing time for high-area patterns, the efficiency can be improved by changing the drawing conditions such as rough pattern exposure, maximum shot size, and number of passes for fine pattern parts that require high accuracy. The drawing machine has a function that can shorten the drawing time by improving or dividing the pattern to be drawn into several parts and optimizing the drawing conditions and order. However, a sufficient effect is not obtained.

  The present invention has been made in view of such circumstances, and when forming a pattern having a large area and not requiring high accuracy such as an identification mark of a photomask, other fine features that require high accuracy are required. It is an object of the present invention to provide a halftone phase shift mask having an identification mark that can be easily formed in a short time without affecting pattern formation, and a method for manufacturing the same.

  A first aspect of the invention for achieving the above object is a halftone phase shift mask having a light shielding layer, which is recognized due to a difference in reflectance depending on the presence or absence of the light shielding layer on the shifter layer. Is a half-tone type phase shift mask characterized in that it is used as an identification mark of the mask.

  The present invention uses the difference in reflectance between the light shielding layer and the shifter layer on the substrate as an identification mark. Even from the transparent substrate side, the reflectance differs depending on the presence or absence of the light-shielding layer on the shifter layer, so that both can be distinguished and can function as an identification mark. At this time, even if a part of the identification mark includes only the transparent substrate, there is no problem as long as it can function as the identification mark. The structure of the identification mark of this patent includes a structure in which a transparent substrate is included in a part of the identification mark.

  According to a second aspect of the present invention, there is provided a manufacturing method characterized in that the shading band pattern and the identification pattern are performed in the same lithography process in the manufacturing process of the halftone phase shift mask.

The present invention does not form an identification pattern at the same time as a main pattern that requires high accuracy using a high-cost, low-throughput high-precision drawing machine. By performing simultaneously with the formation, it is possible to suppress a reduction in dimensional accuracy in the main pattern portion and reduce the drawing time of the high-precision drawing machine, so that the drawing cost can be reduced and the productivity can be improved.
In addition, since the identification pattern is formed simultaneously with the formation of the light-shielding band pattern, the identification pattern can be formed without newly adding processes.

  As described above, according to the present invention, by making the identification mark utilizing the fact that the light reflectance varies depending on the presence or absence of the light shielding layer on the shifter layer, the light shielding band pattern and the identification mark portion can be exposed simultaneously, Since the drawing time of the high-cost drawing machine used for drawing the main pattern is shortened, the drawing cost can be reduced. In addition, the photomask manufacturing period can be shortened and productivity can be improved. Further, since a large pattern such as an identification mark and a fine pattern such as a circuit pattern are not formed at the same time, the dimensional accuracy of the fine pattern portion is not lowered.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  A transparent substrate 1 is coated with a shifter layer 2 using molybdenum silicon as a shifter material, a light shielding layer 3 using Cr as a light shielding material, and a positive electron beam drawing resist 4 thereon. And blanks (FIG. 1 (a)).

  Next, after the electron beam drawing of the alignment pattern 5 necessary for the overwriting with the main pattern 10 is performed, a post-baking process is performed and a developing process is performed (FIG. 1B).

Next, dry etching is performed using the resist as a mask to remove the light shielding layer and the shifter layer in the opening. Subsequently, the resist is peeled off to obtain a pattern composed of two layers, a shifter layer and a light shielding layer (FIG. 1C).
Next, a positive i-line resist 6 is coated (FIG. 1D).

Using a laser drawing apparatus having an exposure wavelength of i-line, overwriting was performed to form the light-shielding band pattern 9 and the identification mark pattern 8, and then development processing was performed. (FIG. 1 (e)).
In addition, in other words, these steps may be overdrawing using an electron beam resist and using an electron beam drawing apparatus.

Next, dry etching is performed to remove unnecessary light shielding layers 7 and form identification marks 11. Finally, the resist was stripped and washed. By these steps, the identification mark 11 made of the light shielding layer 3 can be obtained on the shifter layer 2 (FIG. 1 (f)).
At this time, a top view and a partial cross-sectional view of the manufactured mask have a structure as shown in FIG.

(A)-(f) is a figure which illustrates typically the manufacturing process of the halftone type phase shift mask which becomes this invention by a partial cross section. It is a figure which illustrates typically the position and partial sectional view of a mask identification mark.

Explanation of symbols

1, quartz substrate 2, shifter layer 3, light shielding layer 4, electron beam resist 5, alignment pattern 6, photosensitive resist 7, unnecessary light shielding layer 8 on shifter pattern, identification mark pattern 9, light shielding band pattern 10, main Pattern part 11, identification mark

Claims (2)

  A halftone phase shift mask having a region composed of a phase shift layer and a region composed of a light shielding layer on the phase shift layer, and caused by a difference in reflectance caused by the presence or absence of the light shielding layer on the phase shift layer A halftone phase shift mask, wherein a recognized pattern is used as an identification mark of the mask.   A method for manufacturing a halftone phase shift mask, comprising the step of simultaneously performing the identification mark pattern according to claim 1 or a part of the identification mark and the pattern of the light shielding layer in the same photolithography process.