TW201405241A - Gray-tone mask, manufacturing method thereof and method of forming trench on substrate by using the same - Google Patents

Abstract

The present invention provides a gray-tone mask, which includes a first pattern and a second pattern. The first pattern has a first width, and the second pattern has a second width. The second pattern has a graded density. The present invention further provides a method of making the gray-tone mask, and a method of forming a trench by using the gray-tone mask.

Description

Gray-scale reticle and manufacturing method thereof, and method for forming ditch by using gray-scale reticle

The present invention relates to a structure of a reticle and a method of forming the same, and more particularly to a structure of a excimer laser gray scale reticle and a method of forming the same.

In the modern information society, micro-processing systems composed of integrated circuits (ICs) have long been widely used in all aspects of life, such as automatic control of household appliances, mobile communication devices, electronic computers, etc. The use of integrated circuits. With the increasing advancement of technology and the various imaginations of electronic products in human society, the integrated circuit has also developed in the direction of more yuan, more precision and smaller.

In the semiconductor process, in order to smoothly transfer the pattern of integrated circuits to the semiconductor wafer, the circuit pattern must first be designed on a mask layout, and then the mask pattern output according to the mask layout. (photomask pattern) to make a mask, and then transfer the pattern on the mask to the semiconductor wafer through a lithography process. A new patterning technique called excimer laser has been developed. The English word for excimer lasers is Excimer Laser, and the word Excimer is the combination of Excited Dimer, which is the excited dimer. The principle of excimer laser is applied in a mixed gas with a high voltage current to briefly excite the elements in the mixed gas to form a high energy unstable dimer. This dimer then emits laser light which ablate the patterned component in the semiconductor component.

In conventional excimer lasers, there are still many problems to be overcome, the most notable of which are "refractive angle limitation" and "plume effect". Please refer to FIG. 1 , which is a schematic diagram showing the influence of the refraction angle limit on the ablation depth in the prior art. As shown in FIG. 1, the laser light 100 produces a refraction phenomenon as it passes through the reticle 102 and is then focused on the substrate 104 for ablation. As the target line becomes thinner (the more the left side in Figure 1 represents the thinner the line width), the shape of the trench formed will gradually change from a U-shaped channel to a V-shaped ditch. In some finer line patterns, when the ablation depth is below the intersection of the two sides of the laser light 100 (as in point A of Figure 1), the laser light 100 is difficult to focus, causing a slow ablation rate, often requiring increased ablation. Time can reach the predetermined depth, but this often affects the depth of other thick line graphics.

On the other hand, in larger sized lines, the depth of the pattern is often affected by the smoke column effect. The smoke column effect means that in the pattern of large area or thick line, when ablation is performed, a large amount of fine powder is generated on the interface, and the fine powder will absorb a part of the laser energy, so that the rate of ablation is reduced, thereby causing The graphics depth is insufficient.

Therefore, whether the "smoke effect" or the "refraction angle limit" will cause the ablation depth to be inconsistent with the original design, it will reduce the quality of the component and become a problem to be solved.

The present invention thus proposes a gray scale mask and a method of forming the same. Using the present invention The grayscale reticle can form a pattern line of consistent depth.

According to an embodiment of the present invention, the present invention provides a gray scale mask comprising a first pattern and a second pattern. The first pattern has a first line width and the second pattern has a second line width, wherein the second pattern has a gray scale density.

According to another embodiment of the present invention, the present invention provides a method of forming a gray scale mask. A substrate is first provided and a mask is provided, the mask having a first pattern having a first line width and a second pattern having a second line width. Then, a direct laser ablation process is performed with the photomask to form a first trench corresponding to the first pattern in the substrate and has a first depth, and a second trench corresponds to the second pattern and has a second depth. Finally, a gray scale mask is provided, the gray scale mask having a first pattern and a second pattern, wherein the second pattern has a gray scale density.

According to another embodiment of the present invention, the present invention also provides a method of forming a trench on a substrate. First, after forming a gray scale mask by the foregoing method, another direct laser ablation process is performed by using a gray scale mask to form a fourth trench corresponding to the first pattern in the other substrate, and a fifth trench corresponding to The second pattern, wherein the fourth trench and the fifth trench both have a predetermined depth.

The gray-scale reticle and the forming method thereof provided by the invention compensate the gray-scale pattern by measuring the depth of the trench, and can effectively eliminate the influence of the smoke column effect, the refraction angle limit, or other factors.

The present invention will be further understood by those skilled in the art to which the present invention pertains. The effect.

The main feature of the present invention is to propose a structure of a gray scale reticle and a method for forming the same, and in particular, a gray scale reticle suitable for use in a quasi-molecular laser ablation process. The excimer laser ablation process of the present invention is a direct laser ablation (LDA) process, which refers to excimer lasers (such as KrF excimer lasers) on a semiconductor substrate or a glass substrate. Processes such as drilling, patterning, etc. are directly performed on a circuit board or other kinds of substrates to form various laser embedded circuits.

Please refer to FIG. 2 to FIG. 5 , which are schematic diagrams showing the steps of fabricating a gray scale mask according to the present invention, wherein FIG. 2 to FIG. 4 are schematic cross-sectional views, and FIG. 5 is a plane of the gray scale mask. schematic diagram. As shown in FIG. 2, a substrate 300 and a mask 302 are first provided. The surface of the substrate 300 may have any material suitable for excimer laser ablation, such as ABF (Ajinomoto Build-up Film), benzocyclobutene (BCB), liquid crystal polymer (LCP). ), photosensitive or non-photosensitive organic resins such as polyimide (PI), polyphenylene ether (PPE), polytetrafluoroethylene (PTFE), or various epoxy resins and glass fibers. And other materials. In a preferred embodiment of the invention, the material on the surface of the substrate 300 is ABF, which provides the best ablation effect. The mask 302 includes a first pattern 304, a second pattern 306, and a first The three patterns 308 have a first line width w1, a second line width w2, and a third line width w3. In an embodiment of the invention, the first pattern 304 is a thin line pattern having a first line width w1 between 3 micrometers (μm) and 8 micrometers, for example 5 micrometers; and the second pattern 306 has a medium line The pattern has a second line width w2 between 8 microns and 40 microns, for example 15 microns; the third pattern 308 has a pattern of thick lines having a third line width w3 of greater than 40 microns, such as 150 microns.

As shown in FIG. 3, a direct laser ablation process is performed using the reticle 302 such that the laser light 316 passes through the opaque portion of the reticle 302 (ie, the first pattern 304, the second pattern 306, and the third pattern 308). Whereas ablation is performed on the surface of the substrate 300, a first trench 310, a second trench 312, and a third trench 314 are formed in the substrate 300. The first trench 310 corresponds to the first pattern 304 and has a first depth d1, the second trench 312 corresponds to the second pattern 306 and has a second depth d2, and the third trench 314 corresponds to the third pattern 308 and has a third Depth d3. As described above, since the pattern of the thin line is prone to have a refractive angle limit when ablated, the resulting depth is shallower than the pattern of the middle line, for example, the first generated by the first pattern 304. The trench 310 may have a smaller depth than the second trench 312 generated by the second pattern 306, that is, d1 < d2. On the other hand, since the pattern of the thick line is prone to smoke column phenomenon when ablated, the depth generated will be shallower than that of the middle line pattern, and the depth of the first trench 314 generated by the third pattern 308 will be It is smaller than the second trench 312 generated by the second pattern 306, that is, d3 < d2. However, the magnitude relationship between the first depth d1 and the third depth d3 is not necessarily different from each other. Hereinafter, for convenience of explanation, the third depth d3 is larger than the first depth d1 as an example, that is, d1 < d3 < d2. The first depth d1 is, for example, 8 micrometers, The second depth d2 is, for example, 16 microns, and the third depth d3 is, for example, 12 microns.

As shown in FIGS. 4 and 5, a gray scale mask 320a is formed according to the relationship between the first depth d1, the second depth d2, and the third depth d3. The gray scale mask 320a and the mask 302 have substantially the same pattern, that is, the first pattern 304, the second pattern 306, and the third pattern 308, but in particular, at least one of the patterns has gray Order density. The gray scale density of this embodiment is determined by the relationship between the first depth d1, the second depth d2, and the third depth d3. In one embodiment of the invention, the gray scale density is determined by the following formula: gray scale density = (1 - predetermined depth / measured depth)

For example, in this embodiment, the deepest second depth d2 is a predetermined depth, and then the grayscale density of other graphics is calculated. For example, the desired light transmittance of the second pattern 306 is d1/d2, that is, 8/16 = 0.5, and 1-0.5 = 0.5, that is, a gray density of 50% is obtained. Similarly, the desired light transmittance of the third pattern 308 is d1/d3, that is, 8/12 = 0.75, and 1-0.75 = 0.25, that is, a gray density of 25% is obtained. The first pattern 304 maintains a 100% transmittance, that is, a gray density of 0%. As a result, the laser light 316 has only 50% intensity after passing through the second pattern 306, and the laser light 316 has only 75% intensity after passing through the third pattern 308. Finally, as shown in FIG. 4, another direct laser ablation process can be performed by using the gray scale mask 320a, that is, a fourth trench 310a and a fifth trench 312a can be formed on the substrate 300 of the same material. And a sixth trench 314a, the fourth trench 310a corresponds to the first pattern 304, and the fifth trench 312a corresponds to the second pattern 306, the sixth The ditch 314a corresponds to the third pattern 308, and the ditch depths of the fourth ditch 310a, the fifth ditch 312a and the sixth ditch 314a are the same, that is, both are d1. Through the foregoing steps, the influence of the smoke column effect, the refraction angle limit, or other factors can be effectively eliminated, and even if the pattern line width on the reticle is different, a pattern having the same depth can be formed in the substrate.

Please refer to FIG. 6, which is a schematic diagram of a gray scale mask according to another embodiment of the present invention. As shown in FIG. 6, the foregoing embodiment uses the first depth d1 as a predetermined depth. In other embodiments, a desired depth d' smaller than the first depth d1 may be selected as a reference, for example, the desired depth d' is 4. Micron. Similarly, the first pattern 304 has a gray scale density of 1-4/8, that is, 25%; the second pattern 306 has a gray scale density of 1-4/16, that is, 75%; and the third pattern 308 has a density of 1st. 4/12, that is, 67%, forms a gray scale mask 312b such as Fig. 6. Similarly, the seventh trench 310b, the eighth trench 312b, and the ninth trench 314b can be formed by using the gray scale mask 320b, and the ditch depths of all three are d'.

Please refer to FIG. 7 , which is a schematic diagram showing the steps of forming a trench by using a gray scale mask according to still another embodiment of the present invention. The foregoing embodiment has the trenches formed to have the same depth by selecting a predetermined depth. In the present embodiment, the trenches formed can also have different depths. For example, if it is desired to form a tenth trench 310c corresponding to the first pattern 304 on another substrate, assuming that the predetermined depth of the tenth trench 310c is d10, the grayscale of the first graphic 304 on the grayscale mask 320c The density is 1-(d10/d1); if the predetermined depth of the eleventh trench 312c is d11, the gray scale density of the second pattern 304 on the gray scale mask 320c is 1-(d11/d1); The predetermined depth of the second trench 314c is d12, and the gray scale density of the third pattern 308 on the gray scale mask 320c is 1-(d12/d1). Then, through the gray scale mask 320c, the tenth trench 310c having a depth of d10, the eleventh trench 312c having a depth of d11, and the twelfth portion having a depth of d12 can be formed on the other substrate via a direct ablation process. Ditch 314c.

It should be noted that the gray scale reticle 320a, 320b, 320c of the present invention is different from the conventional gray scale reticle with different thickness or different materials to form different transmittance regions. As shown in Fig. 5, the excimer laser gray scale mask 320a of the present invention comprises a transparent substrate 321 and an opaque material 323 disposed thereon. In a region other than the first graphic 304, the second graphic 306, and the third graphic 308, the substrate 321 is completely covered by the opaque material 323, and in the first graphic 304, the second graphic 306, and the third graphic 308, The opaque dots 322 are uniformly distributed, and the ratio of the area of the opaque dots 322 to the pattern determines the transmittance of the pattern. For example, in the third graphic 308, as shown in the enlarged area of the right half of FIG. 5, the dot 322 is completely opaque, and in the third pattern 308, the area other than the dot 322 is 100% transparent. Light, and all of the dots 322 occupy an area of 25% in the third pattern 308. By varying the density of the dots 322 on the reticle, the light transmittance in different regions of the reticle can be varied. In a preferred embodiment of the present invention, the transparent substrate 321 may comprise various light transmissive inorganic materials or organic materials such as glass, quartz, plastic, resin, acryl, other suitable materials, or a combination of the foregoing materials, but The present invention is not limited thereto, and the opaque material 323 constituting the dots 322 is, for example, a metal chrome, an opaque resin, or a material such as graphite. The dots 322 can comprise any simple geometric shape, such as a circle, a rectangle, a diamond, or a combination of the above. The method of forming the dots 322 can be, for example, a photo-etching-process (PEP) process or an ink jet printing process. Or laser processing, etc., can also be other processes suitable for forming a reticle.

In another embodiment of the present invention, the method of the present invention for forming excimer laser gray scale masks 320a, 320b, 320c may further comprise a regression step. Please refer to FIG. 8 , which is a representation of the regression step of the present invention. As shown in Fig. 8, if there are too many patterns on the mask 302 and the depth of the formed trenches cannot be measured one by one, only a plurality of patterns of different line widths can be selected for measurement. For example, five or more graphs may be selected, and the ablation trench depth is measured, with the x-axis as the width and the y-axis as the ablation depth, resulting in a distribution as shown in FIG. Then, for example, the data is subjected to a regression step, and a regression line (y = ax ² + bx + c) such as a quadratic curve with an opening downward can be obtained. Subsequently, when designing the gray scale density of the excimer laser gray scale masks 320a, 320b, 320c, the equation can be used to obtain a calculated depth of different line width patterns, and as described above, a predetermined depth is selected as Benchmark, and match the formula: gray scale density = (1 - predetermined depth / measured depth)

The gray scale density of different patterns can be obtained, so that a large amount of time for measuring the depth of the trench can be omitted.

In addition, it must be noted that the excimer laser gray scale mask of the present invention is particularly used in a patterning process of excimer lasers, such as a KrF excimer laser (248 nm) patterning process. On other types of reticle, since the laser is not directly ablated through the reticle, there is no problem of the angle of refraction and the effect of the smoke column. The embodiment is not the same as the present invention.

In summary, the excimer laser gray scale mask and the forming method thereof are compensated by measuring the depth of the trench to compensate the gray scale pattern, and the smoke column effect or the refraction angle limit can be effectively eliminated, or even The influence of other factors.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

100‧‧‧Laser light

102‧‧‧Photomask

104‧‧‧Substrate

300‧‧‧Base

302‧‧‧Photomask

304‧‧‧ first graphic

310c‧‧‧The Tenth Ditch

312c‧‧‧11th ditches

314c‧‧‧12th ditches

316‧‧‧Laser light

320a‧‧‧ Grayscale mask

321‧‧‧Transparent substrate

306‧‧‧ second graphic

308‧‧‧ third graphic

310‧‧‧First ditches

312‧‧‧Second ditches

314‧‧‧ Third Ditch

310a‧‧‧fourth ditches

312a‧‧‧ Fifth Ditch

314a‧‧‧ Sixth Ditch

310b‧‧‧ seventh ditches

312b‧‧‧ eighth ditches

314b‧‧‧The Ninth Ditch

320b‧‧‧ Grayscale mask

320c‧‧‧ Grayscale mask

322‧‧‧ outlets

323‧‧‧ opaque material

W1‧‧‧first width

W2‧‧‧second width

W3‧‧‧ third width

D1‧‧‧first depth

D2‧‧‧second depth

D3‧‧‧ third depth

D’‧‧‧Desired depth

FIG. 1 is a schematic view showing the influence of the refraction angle limit on the ablation depth in the prior art.

2 to 5 are schematic views showing the steps of fabricating a gray scale mask according to the present invention.

FIG. 6 is a schematic view showing a gray scale mask in another embodiment of the present invention.

FIG. 7 is a schematic view showing a gray scale reticle in still another embodiment of the present invention.

Figure 8 is a representation of the regression step of the present invention.

300‧‧‧Base

304‧‧‧ first graphic

306‧‧‧ second graphic

308‧‧‧ third graphic

320a‧‧‧ Grayscale mask

310a‧‧‧fourth ditches

312a‧‧‧ Fifth Ditch

314a‧‧‧ Sixth Ditch

316‧‧‧Laser light

W1‧‧‧first width

W2‧‧‧second width

W3‧‧‧ third width

D1‧‧‧first depth

D2‧‧‧second depth

D3‧‧‧ third depth

Claims (15)

A gray scale mask comprising: a first pattern having a first line width; and a second pattern having a second line width, wherein the second pattern has a gray scale density. The gray scale reticle of claim 1, wherein the second pattern is uniformly covered with a plurality of dots. The gray scale reticle of claim 2, wherein the dots comprise an opaque material. The gray scale reticle of claim 1, wherein the second pattern has a light transmittance of less than 100%. The gray scale reticle of claim 1, wherein the first line width is not equal to the second line width. A method of forming a trench in a substrate, comprising: performing a direct ablation process on the gray scale mask according to any one of claims 1 to 5 to form a fourth trench in a substrate Corresponding to the first figure, and a fifth ditch corresponding to the second figure, wherein the fourth ditch and the fifth ditch have the same depth. A method of forming a trench in a substrate, comprising: performing a direct ablation process by using the gray scale mask according to any one of claims 1 to 5 to form a tenth trench in a substrate Corresponding to the first pattern, and an eleventh ditches corresponding to the second pattern, wherein the tenth ditches and the eleventh ditches have different depths. A method for fabricating a gray scale mask, comprising: providing a substrate; providing a photomask having a first pattern having a first line width, and a second pattern having a second line width; The cover performs a direct laser ablation process to form a first trench in the substrate corresponding to the first pattern and having a first depth, and a second trench corresponding to the second pattern and having a second depth; A gray scale mask is formed, the gray scale mask having the first pattern and the second pattern, wherein the second pattern has a second gray scale density. The method for fabricating a gray scale reticle according to claim 8, wherein the second gray scale density = (1 - a second predetermined depth / the second depth). The method for fabricating a gray scale reticle according to claim 9, wherein the first pattern of the gray scale reticle has a first gray scale density, and the first gray scale density=(1-一第a predetermined depth / the first depth). The method for fabricating a gray scale mask as described in claim 8 further comprises a regression step. A method of forming a trench in a substrate, comprising: forming the gray scale mask by a method for fabricating a gray scale mask as described in claim 10; performing another direct laser ablation with the gray scale mask The process is such that a fourth trench is formed in the other substrate to correspond to the first pattern, and a fifth trench corresponds to the second pattern. A method of forming a trench in a substrate as described in claim 12, wherein the first predetermined depth is equal to the second predetermined depth. A method of forming a trench in a substrate as described in claim 13 wherein the first predetermined depth is equal to the second predetermined depth equal to the first depth. A method of forming a trench in a substrate as described in claim 10, wherein the first predetermined depth is not equal to the second predetermined depth.