Method of etching trapezoidal grooves and method of forming metal lines on a substrate

Abstract

The present application relates to a method for etching trapezoidal grooves and a method for forming metal lines on a substrate. The method for etching trapezoidal grooves comprises the following steps: providing a substrate; forming a photoresist on the surface of the substrate; shielding the photoresist with a first mask plate to perform a first exposure; removing the first mask plate, shielding the photoresist with a second mask plate to perform a second exposure; and then developing the area subjected to the second exposure to obtain trapezoidal grooves; wherein the exposure area subjected to the second exposure is surrounded by the exposure area subjected to the first exposure, and the dose of the first exposure is less than that of the second exposure. The method of the present application only needs to form a single layer of photoresist, and the phenomenon of covering the sidewall of the photoresist does not occur when sputtering metal in the groove, thereby avoiding the problem of incomplete peeling.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor production process, in particular to a method for etching trapezoidal groove and a method for forming metal line on substrate. BACKGROUND

[0002] The stripping process is a process often used in semiconductor device manufacturing, and as the pattern size decreases, the line width of the stripped pattern is also required to be higher and higher. In order to achieve a pattern stripping process below 100 nm, electron beam exposure becomes a necessary choice. In the electron beam stripping process (such as the process flow shown in Figure 1 ), the use of double-layer resist is a common means, and usually one layer of resist is MMA and the other layer is PMMA. The use of double-layer resist is mainly to form a trapezoidal groove (TEM image as Figure 2 ), to prevent the phenomenon of incomplete stripping caused by the deposition of metal film on the resist sidewall during sputtering. However, this method has the problem that the resist coating step is complicated and the material cost is high.

[0003] Therefore, the present application is proposed. SUMMARY

[0004] The main purpose of the present application is to provide a method for etching trapezoidal groove and a method for forming metal line on substrate, which only needs to form a single layer of resist, and the phenomenon of covering the resist sidewall does not occur when sputtering metal in the groove, thereby avoiding the problem of incomplete stripping.

[0005] In order to solve the above technical problems, the present application provides the following technical solutions.

[0006] The method for etching trapezoidal groove comprises:

[0007] providing a substrate;

[0008] forming a resist on the surface of the substrate;

[0009] shielding the resist with a first mask plate to perform first exposure;

[0010] removing the first mask plate, shielding the resist with a second mask plate to perform second exposure;

[0011] then developing the area of the second exposure to obtain a trapezoidal groove;

[0012] wherein the exposure area of the second exposure is surrounded by the exposure area of the first exposure, and the dose of the first exposure is less than the dose of the second exposure.

[0013] The method for forming metal line on substrate comprises:

[0014] A trapezoidal groove is formed on a substrate using the method described above;

[0015] A metal is sputtered into the trapezoidal groove;

[0016] The photoresist is peeled off.

[0017] Compared with the prior art, the present application achieves the following technical effects:

[0018] The area difference and dose difference of the two exposures make the photoresist that is completely exposed trapezoidal, so that a trapezoidal groove is formed after development, and the shape obtained is regular and uniform. Specifically, during the first exposure process, a part of energy is deposited in the photoresist in advance, but it is not enough to make the photoresist completely photosensitive. Through the second exposure, the photoresist in the exposed area of the second mask plate is completely photosensitive, and due to the scattering caused by the arrival of the electron beam or ultraviolet light to the substrate, the photoresist beside the bottom of the second mask plate also receives a certain energy, which is superimposed with the energy of the first exposure, resulting in the bottom being soluble in the developing solution. BRIEF DESCRIPTION OF DRAWINGS

[0019] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the application.

[0020] Figure 1 A process flow chart for etching a trapezoidal groove in the prior art;

[0021] Figure 2 A SEM image of the trapezoidal groove obtained in the prior art;

[0022] Figure 3 A process flow chart for etching a trapezoidal groove in the present application;

[0023] Figures 4-6 A structure diagram formed by each step when the process shown in Figure 3

[0024] Figure 7 A SEM image of the trapezoidal groove obtained in the present application. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood, however, that the description is merely exemplary and is not intended to limit the scope of the present disclosure. Also, in the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concept of the present disclosure.

[0026] ​Various structural diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These diagrams are not drawn to scale, in which certain details are shown in a somewhat exaggerated manner for the purpose of clarity and understanding, and certain details can be omitted. The shapes of various regions, layers, and the relative sizes and positional relationships between them shown in the drawings are merely exemplary, and in actuality can be deviated due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, and relative positions can be additionally designed according to actual needs by those skilled in the art.

[0027] In the context of the present disclosure, when a layer / element is referred to as being located "on" another layer / element, the layer / element can be directly located on the other layer / element, or there can be an intermediate layer / element between them. In addition, if a layer / element is located "on" another layer / element in one orientation, it can be located "under" the other layer / element when the orientation is reversed.

[0028] Although the prior art has solved the problem of sputtering covering photoresist sidewalls to some extent, the photoetching coating process is complex and has high material cost. Therefore, the present application provides another exposure method, which is as follows.

[0029] First, a substrate is provided, and two mask plates are prepared: a first mask plate and a second mask plate, the exposure window areas of the two mask plates are different in size, the exposure window of the first mask plate is larger, and when covering the substrate, the exposure window of the first mask plate completely covers the exposure window of the second mask plate. The substrate can be any substrate known to those skilled in the art for carrying a cross-wire structure, such as silicon-on-insulator (SOI), bulk silicon, silicon carbide, germanium, germanium silicon, gallium arsenide, or germanium-on-insulator, and the corresponding top semiconductor material is silicon, germanium, germanium silicon, or gallium arsenide, and the common one is a silicon substrate.

[0030] Then a single layer of photoresist is formed on the surface of the substrate. The photoresist is a positive photoresist and can be any material, such as PMMA, PMAA, PCEA, etc., and PMMA is preferred. The thickness of the photoresist is determined according to the shape requirements of the groove. The exposure dose and the light source are related to the type of photoresist.

[0031] Next, the first mask plate is used to shield the photoresist, and the first exposure is performed. At this time, the exposure is a low-dose exposure, which only deposits a part of the energy, and the energy is not enough to make the photoresist completely photosensitive. The light source is preferably an electron beam.

[0032] Then the first mask plate is removed.

[0033] Then a second mask is applied to shield the photoresist, and a second exposure is performed. At this time, the exposure is a high-dose exposure, greater than the dose of the first exposure, and the exposed area is smaller than the first exposure, in the center of the first exposed area, so that the middle area is cumulatively exposed and can be developed. At the same time, the first exposure will scatter to the bottom of the photoresist (referring to the area where the photoresist and the substrate are critical), and at this time the bottom will also be cumulatively exposed due to scattering after the second exposure, so that it can also be dissolved in the developer, and finally the exposed area is developed, and a trapezoidal groove is formed as a matter of course. Among them, the light source of the second exposure is also an electron beam. Taking PMMA photoresist as an example, the dose of the first exposure and the dose of the second exposure are preferably 1 uC / m 2 , 3 uC / m 2 , respectively, and a more regular trapezoidal groove can be formed. Taking a common Josephson junction as an example, the groove suitable for sputtering metal lines is a trapezoidal groove, and the width of the widest part is 400-450 nm. To adapt to this, the thickness of the photoresist during preparation is preferably between 150-180 nm, and the width of the exposed area of the first exposure is preferably more than 200 nm wider than the width of the exposed area of the second exposure.

[0034] Finally, according to the needs, sputter the required material in the trapezoidal groove, such as common metals such as aluminum, titanium, tungsten, etc.

[0035] Based on the above process, taking the formation of a groove with a widest width of 400-450 nm and PMMA photoresist as an example, the following examples are provided.

[0036] Example

[0037] The process shown in Figure 3 is used:

[0038] First step, coat PMMA photoresist 102 on substrate 101 to obtain the structure shown in Figure 4 .

[0039] Second step, place the first mask 103, which has a large exposure window, as shown in Figure 5 , and perform a first low-dose exposure with an electron beam as the light source, with a dose of 1 uC / m 2 .

[0040] Third step, remove the first mask and place the second mask 104, which has a small exposure window, as shown in Figure 6 (the boundary line 103a of the first exposure area is drawn with a dashed line in the figure), and perform a second high-dose exposure with an electron beam as the light source, with a dose of 3 uC / m 2 .

[0041] Fourth step, remove the second mask plate, add developing solution to develop the exposed area, clean and get the trapezoidal groove, the morphology under the electron microscope is shown in Figure 7

[0042] Fifth step, according to the need, sputter the appropriate material in the trapezoidal groove.

[0043] The above describes the embodiments of the present disclosure. However, these embodiments are only for illustrative purposes, and are not intended to limit the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, which should all fall within the scope of the present disclosure.​

Claims

1. A method of etching trapezoidal grooves, characterized by, The method comprises: providing a substrate; forming a photoresist on the surface of the substrate; shielding the photoresist with a first mask plate and performing a first exposure; removing the first mask plate, shielding the photoresist with a second mask plate and performing a second exposure; then developing the area exposed in the second exposure to obtain a trapezoidal groove; wherein the exposure area of the second exposure is surrounded by the exposure area of the first exposure, and the dose of the first exposure is less than that of the second exposure; in the first exposure process, a part of energy is deposited in the photoresist in advance, but it is not enough to make the photoresist completely photosensitive; through the second exposure, the photoresist in the exposed area of the second mask plate is completely photosensitive, and due to the scattering caused by the arrival of the electron beam or ultraviolet light to the substrate, the photoresist beside the bottom of the second mask plate also receives a certain energy, which is superimposed with the energy of the first exposure to make the bottom soluble in the developing solution.

2. The method of claim 1, wherein, The photoresist is PMMA.

3. The method of claim 2, wherein, The dose of the first exposure, the dose of the second exposure are 1 uC / m 2 , 3 uC / m 2 , respectively.

4. The method of claim 1, wherein, The substrate is a silicon substrate.

5. The method of claim 1, wherein, The width of the widest part of the trapezoidal groove is 400-450 nm, and the thickness of the photoresist is between 150-180 nm.

6. The method of claim 5, wherein, The width of the exposure area of the first exposure is more than 200 nm wider than the width of the exposure area of the second exposure.

7. A method of forming metal lines on a substrate, characterized by, The method comprises: forming a trapezoidal groove on a substrate by the method of any one of claims 1-6; then sputtering metal into the trapezoidal groove; stripping the photoresist.

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