CN103513508B - Gray-scale photomask and manufacturing method, and trench formation method with gray-scale photomask - Google Patents

Abstract

The present invention discloses a grayscale photomask, comprising a first pattern and a second pattern. The first pattern has a first line width, the second pattern has a second line width, and the second pattern has a grayscale density. The present invention also provides a method for making the grayscale photomask, and a method for forming a trench on a substrate using the grayscale photomask.

Description

Gray-scale photomask and manufacturing method, and trench formation method with gray-scale photomask

technical field

The present invention relates to a structure of a photomask and a method for forming the same, in particular to a structure of an excimer laser grayscale photomask and a method for forming the same.

Background technique

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 automatically controlled household appliances, mobile communication equipment, electronic calculators, etc. use of integrated circuits. With the advancement of technology and the various imaginations of electronic products in human society, integrated circuits are also developing in a more diverse, more sophisticated, and smaller direction.

In the semiconductor process, in order to smoothly transfer the pattern of the integrated circuit to the semiconductor chip, the circuit pattern must first be designed on a photomask layout, and then the photomask output according to the photomask layout A photomask pattern is used to make a photomask, and then the pattern on the photomask is transferred to the semiconductor chip through a photolithography process. At present, a new patterning technology has been developed, called excimer laser. The English of excimer laser is Excimer Laser, and the word Excimer is the combination of Excited Dimer, that is, the excited dimer. The principle of the excimer laser is to apply a high-voltage current to the mixed gas to briefly excite the elements in the mixed gas to form high-energy unstable dimers. The dimer then emits laser light, which can ablate patterned components in semiconductor components.

In existing 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 of the influence of the limit of refraction angle on the ablation depth in the prior art. As shown in FIG. 1 , when the laser light 100 passes through the photomask 102 , a refraction phenomenon occurs, and then it is focused on the substrate 104 for ablation. And as the target line gets thinner (the left side in Figure 1 means the thinner the line width), the shape of the ditch formed will gradually change from a U-shaped ditch to a V-shaped ditch. In the pattern of some thinner lines, when the ablation depth is below the intersection point of both sides of the laser 100 (as shown in point A in Figure 1), the laser 100 is difficult to focus and the ablation speed is slow, and it is often necessary to increase the ablation time. Reach the predetermined depth, but this often affects the depth of other thick line graphics.

On the other hand, in larger-sized lines, the pattern depth is often affected by the smoke plume effect. The smoke column effect means that in large-area or thick-line graphics, a large amount of micropowder debris will be generated on the interface during ablation. These micropowder debris will absorb part of the laser energy, reducing the ablation rate, resulting in graphics Not enough depth.

Therefore, whether it is the "smoke column effect" or the "refraction angle limit", the resulting ablation depth will not meet the original design, so the quality of the components will be reduced, and it has become an urgent problem to be solved.

Contents of the invention

The present invention provides a gray-tone mask (Gray-Tone mask, also called a gray-tone mask) and a forming method thereof. Utilizing the grayscale photomask of the present invention can form pattern circuits with consistent depth.

According to an embodiment of the present invention, the present invention provides a grayscale photomask, which includes a first pattern and a second pattern. The first pattern has a first line width, the second pattern has a second line width, and the second pattern has a gray scale density.

According to another embodiment of the present invention, the present invention provides a method for forming a grayscale photomask. Firstly, a base is provided, and a photomask is provided. The photomask has a first pattern with a first line width, and a second pattern with 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 and having a first depth, and a second trench corresponding to the second pattern and having a second depth in the substrate. Finally, a grayscale photomask is provided. The grayscale photomask has a first pattern and a second pattern, wherein the second pattern has a grayscale density.

According to another embodiment of the present invention, the present invention also provides a method for forming a trench on a substrate. Firstly, after forming a gray scale photomask by the aforementioned method, another direct laser ablation process is performed on the gray scale photomask to form a fourth trench corresponding to the first pattern and a fifth trench in another substrate Corresponding to the second pattern, both the fourth ditch and the fifth ditch have a predetermined depth.

The gray-scale photomask and its forming method proposed by the present invention compensate the gray-scale pattern by measuring the depth of the formed trench, which can effectively eliminate the influence of smoke column effect, refraction angle limit, or other factors.

Description of drawings

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

FIG. 2 to FIG. 5 are schematic diagrams of steps for fabricating a grayscale photomask according to the present invention.

FIG. 6 is a schematic diagram of a grayscale photomask in another embodiment of the present invention.

FIG. 7 is a schematic diagram of a grayscale photomask in another embodiment of the present invention.

Fig. 8 is a representation diagram of the regression steps of the present invention.

Wherein, the reference signs are explained as follows:

100 Laser 310c Tenth Ditch

102 Photomask 312c Eleventh trench

104 Base plate 314c Twelfth trench

300 base 316 laser

302 photomask 320a grayscale photomask

304 First graphics 321 Transparent substrate

306 second pattern 320b grayscale photomask

308 third pattern 320c grayscale photomask

310 First Ditch 322 Outlets

312 Second trench 323 Opaque material

314 3rd ditch w1 1st width

310a 4th trench w2 2nd width

312a Fifth Ditch w3 Third Width

314a Sixth Ditch d1 First Depth

310b Seventh Ditch d2 Second Depth

312b Eighth Ditch d3 Third Depth

314b Ditch Ninth d’ Desired Depth

detailed description

In order to enable those of ordinary skill in the technical field of the present invention to further understand the present invention, several preferred embodiments of the present invention are specifically listed below, and in conjunction with the attached drawings, the composition of the present invention and the desired effect are described in detail. .

The main feature of the present invention is to provide a gray-scale photomask structure and its forming method, especially a gray-scale photomask suitable for excimer laser ablation process. The excimer laser ablation process referred to in the present invention is a direct laser ablation (laser direct ablation, LDA) process, which refers to using an excimer laser (such as the excimer laser of KrF) on a semiconductor substrate, a glass substrate, a circuit board, etc. Or other types of substrates, such as drilling, patterning, etc., are directly performed to form various laser embedded circuits (laserembedded circuits).

Please refer to FIG. 2 to FIG. 5 , which are schematic diagrams showing steps of making a grayscale photomask according to the present invention, wherein FIG. 2 to FIG. 4 are schematic cross-sectional views, and FIG. 5 is a schematic plan view of the grayscale photomask. As shown in FIG. 2 , firstly, a substrate 300 and a photomask 302 are provided. The surface of the substrate 300 can have any material suitable for excimer laser ablation, such as ABF (Ajinomoto Build-up Film), benzocyclobutene (benzocyclobutene, BCB), liquid crystal molecular polymer (liquid crystal polymer, LCP) , polyimide (polyimide, PI), polyphenol ether (polyphenylene ether, PPE), polytetrafluoroethylene (polytetrafluoroethylene, PTFE) and other photosensitive or non-photosensitive organic resins, or various epoxy resins and glass fibers can also be mixed Material. In a preferred embodiment of the present invention, the material on the surface of the substrate 300 is ABF, which can obtain a preferred ablation effect. The photomask 302 includes a first pattern 304 , a second pattern 306 and a third pattern 308 , which sequentially have a first line width w1 , a second line width w2 and a third line width w3 . In one embodiment of the present invention, the first pattern 304 is a thin line pattern, and its first line width w1 is between 3 microns (μm) and 8 microns, for example, 5 microns; the second pattern 306 has a medium line width The second line width w2 of the pattern is between 8 microns and 40 microns, such as 15 microns; the third pattern 308 has a pattern of thick lines, and the third line width w3 is greater than 40 microns, such as 150 microns.

As shown in FIG. 3 , the photomask 302 is used to carry out a direct laser ablation process, so that the laser light 316 passes through the light-transmitting part of the photomask 302 (that is, the places of the first pattern 304, the second pattern 306 and the third pattern 308 ) and perform ablation on the surface of the substrate 300 to form a first trench 310 , a second trench 312 and a third trench 314 in the substrate 300 . Wherein, the first ditch 310 corresponds to the first pattern 304 and has a first depth d1, the second ditch 312 corresponds to the second pattern 306 and has a second depth d2, the third ditch 314 corresponds to the third pattern 308 and has a third depth d3. As mentioned above, since the pattern of thin lines is likely to have the phenomenon of limited refraction angle during ablation, the resulting depth will be shallower than that of the pattern of medium lines. For example, the first pattern 304 produced by the first The depth of the ditch 310 is smaller than that of the second ditch 312 generated by the second pattern 306 , ie, d1<d2. On the other hand, since the pattern of thick lines is prone to smoke column effect during ablation, the resulting depth will be shallower than that of the pattern of medium lines. The depth of the first trench 314 generated by the third pattern 308 will be lower. smaller than the second trench 312 generated by the second pattern 306, ie, d3<d2. However, the relationship between the first depth d1 and the third depth d3 is not necessarily the same. In the following, for convenience of description, it is taken as an example that the third depth d3 is greater than the first depth d1, that is, d1<d3<d2. The first depth d1 is, for example, 8 microns, the second depth d2 is, for example, 16 microns, and the third depth d3 is, for example, 12 microns.

As shown in FIG. 4 and FIG. 5 , a grayscale photomask 320 a is formed according to the relationship among the first depth d1 , the second depth d2 and the third depth d3 . The grayscale photomask 320a has substantially the same pattern as the photomask 302, that is, it also has the first pattern 304, the second pattern 306 and the third pattern 308, but in particular, at least one of these patterns has Gray scale density. The grayscale density of this embodiment is determined by the relationship among the first depth d1, the second depth d2 and the third depth d3. In one embodiment of the present invention, the grayscale density is determined by the following formula:

Grayscale density=(1-predetermined depth/measured depth)

For example, in this embodiment, the deepest second depth d2 is used as the predetermined depth, and then the grayscale densities of other graphics are calculated. For example, the expected 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 scale density of 50%. Similarly, the expected 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 scale density of 25%. The first pattern 304 maintains a light transmittance of 100%, that is, a gray scale density of 0%. In this way, the laser 316 only has 50% intensity after passing through the second pattern 306 , and the laser 316 only has 75% intensity after passing through the third pattern 308 . Finally, as shown in FIG. 4 , another direct laser ablation process can be performed using the grayscale photomask 320a, that is, a fourth trench 310a, a fifth trench 312a and A sixth ditch 314a, the fourth ditch 310a corresponds to the first pattern 304, the fifth ditch 312a corresponds to the second pattern 306, the sixth ditch 314a corresponds to the third pattern 308, and the fourth ditch 310a, the fifth ditch 312a and the sixth ditch The ditch depths of 314a are all the same, that is, they are all d1. Through the aforementioned steps, the effects of smoke column effect, limit of refraction angle, or other factors can be effectively eliminated, and patterns with the same depth can be formed in the substrate even if the line widths of the patterns on the photomask are different.

Please refer to FIG. 6 , which is a schematic diagram of a grayscale photomask according to another embodiment of the present invention. As shown in Figure 6, the aforementioned embodiment is based on the first depth d1 as the predetermined depth. In other embodiments, a desired depth d' smaller than the first depth d1 can also be selected as a reference, for example, the desired depth d' is 4 Micron. Similarly, the grayscale density of the first graphic 304 is 1-4/8, or 25%; the grayscale density of the second graphic 306 is 1-4/16, or 75%; the grayscale density of the third graphic 308 is 1-4/8, or 25%. 4/12, that is, 67%, to form, for example, the grayscale photomask 312b in FIG. 6 . Similarly, the seventh trench 310b, the eighth trench 312b and the ninth trench 314b can be formed by using the grayscale photomask 320b, and the depth of the three trenches is d'.

Please refer to FIG. 7 , which is a schematic diagram showing steps of forming trenches by using a grayscale photomask in another embodiment of the present invention. In the foregoing embodiments, a predetermined depth is selected so that the formed trenches have the same depth. In this embodiment, however, the trenches formed may 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 pattern 304 on the grayscale photomask 320c The step density is 1-(d10/d1); if the predetermined depth of the eleventh ditch 312c is d11, the gray-scale density of the second pattern 304 on the gray-scale photomask 320c is 1-(d11/d1); if The predetermined depth of the twelfth trench 314c is d12, and the grayscale density of the third pattern 308 on the grayscale photomask 320c is 1-(d12/d1). Then, through the grayscale photomask 320c, the tenth trench 310c with a depth of d10, the eleventh trench 312c with a depth of d11, and the tenth trench 312c with a depth of d12 can be formed on another substrate through a direct ablation process. Two ditches 314c.

It should be noted that the grayscale photomasks 320a, 320b, and 320c of the present invention are different from grayscale photomasks in the prior art that have regions with different light transmittances formed with different thicknesses or different materials. As shown in FIG. 5 , the excimer laser grayscale photomask 320 a of the present invention includes a transparent substrate 321 and an opaque material 323 disposed thereon. In areas other than the first figure 304, the second figure 306 and the third figure 308, the substrate 321 is completely covered by the opaque material 323, while in the first figure 304, the second figure 306 and the third figure 308, then Opaque dots 322 are evenly distributed, and the ratio of the area of all opaque dots 322 to the figure determines the light transmittance of the figure. For example, in the third figure 308, as shown in the enlarged area on the right half of FIG. , and the area occupied by all dots 322 in the third pattern 308 is 25%. By changing the density of dots 322 on the photomask, the light transmittance of different regions on the photomask can be changed. In a preferred embodiment of the present invention, the transparent substrate 321 may comprise various light-transmitting inorganic materials or organic materials, such as glass, quartz, plastic, resin, acrylic, other suitable materials, or a combination of the aforementioned materials, but Not limited thereto, the opaque material 323 constituting the dots 322 is, for example, metal chrome, opaque resin or graphite. The dots 322 may comprise any simple geometric shape, such as circles, rectangles, rhombuses, or combinations thereof. The method of forming dots 322 can be, for example, photolithography and etching process (photo-etching-process, PEP) process, ink jet coating (ink jet printing) process or laser process, etc., and can also be other suitable methods for forming photomasks. Membrane process.

In another embodiment of the present invention, the method for forming the excimer laser grayscale photomask 320a, 320b, 320c of the present invention may further include a regression step. Please refer to FIG. 8 , which is a representation diagram of the regression steps of the present invention. As shown in FIG. 8 , if there are too many patterns on the photomask 302 and the depths of the formed trenches cannot be measured one by one, only a few patterns with different line widths can be selected for measurement. For example, five or more patterns can be selected to measure the trench depth after ablation, with the x-axis as the width and the y-axis as the ablation depth to obtain the distribution as shown in FIG. 8 . Then, for example, a regression step is performed on these data, and a regression line (y=ax2+bx+c) such as a downward-opening quadratic curve can be obtained. When designing the grayscale densities of the excimer laser grayscale photomasks 320a, 320b, and 320c, this equation can be used to obtain a calculation depth of different line width patterns, and as mentioned above, a predetermined depth can be selected As a benchmark, and with the formula:

Grayscale density=(1-predetermined depth/measured depth)

The grayscale density of different graphics can be obtained, so that a lot of time for measuring the depth of the trench can be omitted.

In addition, it must be noted that the excimer laser grayscale photomask of the present invention is especially used in the patterning process of excimer laser, such as the patterning process of KrF excimer laser (248nm). On other types of photomasks, since the substrate is not directly ablated by laser light passing through the photomask, there will be no problems of refraction angle limit and smoke column effect. The principles and implementation methods are different from those of the present invention.

To sum up, the excimer laser gray-scale photomask and its forming method proposed in the present invention compensate the gray-scale pattern by measuring the depth of the formed ditch, which can effectively eliminate the smoke column effect or the limit of the refraction angle, and even other The influence of the factor.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. A method for making a grayscale photomask, characterized in that it comprises: provide a base; providing a photomask having a first pattern with a first linewidth and a second pattern with a second linewidth; performing a direct laser ablation process with the photomask to form a first trench corresponding to the first pattern and having a first depth, and a second trench corresponding to the second pattern and having a second depth in the substrate depth; and A grayscale photomask is formed, the grayscale photomask has the first pattern and the second pattern, wherein the second pattern has a second grayscale density. 2 . The method for fabricating a grayscale photomask according to claim 1 , wherein the second grayscale density=(1−a second predetermined depth/the second depth). 3. The method for fabricating a grayscale photomask according to claim 2, wherein the first pattern of the grayscale photomask has a first grayscale density, and the first grayscale density=( 1-a first predetermined depth/the first depth). 4. A method of forming a trench in a substrate, comprising: The gray-scale photomask is formed by the method for manufacturing a gray-scale photomask as claimed in claim 3; and Another direct laser ablation process is performed with the grayscale photomask to form a fourth trench corresponding to the first pattern and a fifth trench corresponding to the second pattern in another substrate. 5. The method for forming a trench in a substrate according to claim 4, wherein the first predetermined depth is equal to the second predetermined depth. 6. The method for forming a trench in a substrate according to claim 5, wherein the first predetermined depth is equal to the second predetermined depth and is equal to the first depth. 7. The method for fabricating a grayscale photomask according to claim 3, wherein the first predetermined depth is not equal to the second predetermined depth.