CN116564800A - A method of forming trenches with different depths on the surface of semiconductor at one time - Google Patents

Abstract

The invention belongs to the technical field of semiconductor device etching, and particularly relates to a method for forming grooves with different depths on the surface of a semiconductor at one time, which comprises the steps of forming a first mask material and a second mask material with slope structures at designated positions on the surface of a etched material, forming a photoresist layer on the second mask material through a photoetching process, and forming a series of windows according to design; etching the second mask material through the series of windows until the first mask material is exposed; and selecting etching conditions of dry etching to enable the etching conditions to have etching effects on the first mask material and the etched material, then performing next etching until a plurality of series grooves with different depths are formed on the etched material, and finally removing all mask materials. The method can form a plurality of series grooves with different depths by one-time photoetching and dry etching technology, has high efficiency and reduces the labor and time cost.

Description

A method of forming trenches with different depths on the surface of semiconductor at one time

technical field

The invention belongs to the technical field of etching for semiconductor device preparation, in particular to a method for forming a series of grooves with different depths on the surface of a semiconductor at one time.

Background technique

In the process of preparing semiconductor devices, it is often necessary to form fine groove structures of different sizes and depths on the surface of semiconductor materials or on the surfaces of different functional materials. These groove structures play a key role in device performance.

For example, in the design of high-power silicon carbide MOSFET devices, it is usually necessary to design a series of terminal structures to ensure the normal operation of the device. One such design is to etch a series of trenches around the active region with gradually varying trench depths to improve device performance.

These fine groove structures are often formed by photolithography process plus dry etching process. One of the methods used in dry etching process is to use plasma under the action of reactive gas to make exposed through physical action and chemical reaction. In the plasma beam the semiconductor surface is removed and etched to form trench structures. This method is called ion beam etching, and its main features are high efficiency and strong directionality. This method also requires the cooperation of photolithography to produce patterns on the mask material, that is, the surface to be etched is exposed to the plasma beam, and the part that does not need to be etched is protected by the mask material.

The specific process is as follows: a layer of photoresist is coated on the surface of the semiconductor, which is characterized in that the part irradiated by light can be dissolved by a specific chemical solvent, but the part not irradiated by light cannot (and vice versa). The light passes through the photoresist plate, on which it has been designed to form light-transmitting and non-transmittable patterns and irradiates on the photoresist layer so that the designed pattern on the photoresist plate is transferred to the photoresist layer, and then through the method of wet etching Form the surface windows that need to be etched and removed on the mask, and finally form the required trench structure in the semiconductor by dry or wet etching. As shown in Figure 1, the current method of forming a series of trenches with different depths is: first photolithography plus dry etching to form trenches with the first depth, and second photolithography plus dry etching to form trenches with For the trenches of the second depth, by analogy, a series of trenches of different depths are formed by multiple times of photolithography and multiple times of etching.

However, when this method is applied to a large number of required series of trenches, multiple repetitions of photolithography and etching are required, and there is a technical problem of very low efficiency.

Contents of the invention

In order to solve the above technical problems, the present invention provides a method for forming grooves with different depths on the semiconductor surface at one time, which can form multiple series of grooves with different depths by one-time photolithography plus dry etching technology, with high efficiency and less manpower. and time costs are greatly reduced.

A method of forming grooves with different depths on the semiconductor surface at one time in the present invention that solves the above technical problems includes the following steps:

S1: forming a first mask material with a slope structure whose thickness gradually decreases at a designated position on the surface of the etched material;

S2: forming a second mask material with uniform thickness and the same slope on the first mask material;

S3: Form a photoresist layer with uniform thickness and the same slope on the second mask material, and form a series of windows according to the design on the specific slope area of the photoresist layer through the photolithography process, and partially expose a second mask material;

S4: Etching away the exposed positions on the second mask material, transferring the series of windows to the second mask material, and partially exposing the first mask material;

S5: Etching the first mask material and the material to be etched until a series of trenches with different depths are etched on the material to be etched, then removing the first mask material and the second mask material.

The first mask material in S1 is formed by imprinting.

In the optimized solution, the first mask material is a material suitable for imprinting, the first mask material can be an organic polymer, and when the etched material is etched by dry etching, the first mask Materials can also be etched.

The method for forming the second mask material in S2 is formed by any other method that can form a thin film with uniform thickness.

The second mask material can be silicon dioxide or metal. Since the etching rate of the second mask material is much lower than that of the first mask material and the material to be etched, it is ensured that the slope structure will not be destroyed before the entire etching is completed.

In the optimized scheme, the angle of the slope structure is ≤45 degrees. The slope of the mask material plays the role of adjusting the etching front.

In S4 and S5, the series of windows are transferred to the second mask material and the first mask material by dry or wet etching.

In S5, the series of windows are transferred to the material to be etched by dry etching. Continue to transfer the design pattern to the semiconductor surface after dry etching, remove the mask material, and form multiple series of grooves with different depths on the semiconductor surface.

In said S4, the selection of the second mask material should meet the following conditions: the etching rate of the second mask material is much lower than the etching rate of the first mask material and the material to be etched; wherein, the first mask material The comparison of the etching rate of the material, the material to be etched and the second mask material should be under the same etching method.

In said S5, the selection of the first mask material should meet the following conditions: the etching rate of the first mask material in the direction perpendicular to the surface is equal to the etching rate of the material to be etched, and the first mask material in the direction parallel to the surface The etching rate in the surface direction is lower than the etching rate of the material to be etched; wherein, the etching rate of the first mask material and the material to be etched should be compared by the same etching method.

In the present invention, the dry etching method is used to effectively etch the etched material and the first mask material. Due to the existence of the slope, there is a height difference in the window area formed thereon, so the etching front reaches the etched There is a time difference on the surface of the material, and the grooves finally formed on the etched material have different depths.

The present invention provides a method for forming grooves with different depths on the semiconductor surface at one time, which overcomes the technical problem that if the number of series of grooves is relatively large, repeated photolithography and etching are required, and the efficiency is very low. The method of the present invention only Multiple series of grooves with different depths are formed by one-time photolithography plus dry etching technology, which has high efficiency and greatly reduces labor and time costs.

Description of drawings

Fig. 1 is traditional ion beam etching process flow chart among the present invention;

Figure 2(a) is a schematic diagram of forming the first mask material in the present invention;

Figure 2(b) is a schematic diagram of forming the first mask material and the second mask material in the present invention;

Figure 2(c) is a schematic diagram of the etched photoresist layer in the present invention;

Fig. 3 is the etched schematic diagram of the second mask material and photoresist layer in the present invention;

Fig. 4 is the schematic diagram that removes photoresist layer among the present invention;

5 is a schematic diagram of etching of the first mask material, the second mask material and the etched material in the present invention;

6 is a schematic diagram of removing the first mask material and the second mask material in the present invention;

The specific identification in the figure is:

1-first mask material, 2-etched material, 3-second mask material, 4-slope structure, 5-series windows, 6-slope angle, 7-series grooves, 8-photoresist layer .

Detailed ways

Below in conjunction with specific embodiment, do further elaboration among the present invention:

Example 1

As shown in Fig. 2(a), firstly, a first mask material 1 with a slope structure 4 is formed at a designated position on the surface of the etched material 2; one of the methods for forming the first mask material 1 is the embossing method, The slope angle 6 of the slope structure 4 can be set to be less than or equal to 45 degrees.

Wherein, the specified position is the position of the groove to be etched during device design, which is related to the structure of the device at that time and determined for actual needs.

As shown in FIG. 2( b ), a second mask material 3 is then formed on the first mask material 1 . Forming the second mask material 3 is formed by other methods, and the other methods are conventional methods. The embossing method is to place the sheet material between the upper and lower molds, and the thickness of the material is changed under pressure, and the extruded A forming method in which the pressed material is filled in the convex and concave parts of the mold cavity with undulating fine lines, and the undulating bulges and characters or patterns are formed on the surface of the workpiece, which is also a conventional method.

The second mask material 3 can be silicon dioxide or metal. Since the etching rate of the second mask material 3 is much lower than that of the first mask material 1 and the material to be etched 2, it can be ensured that the slope structure 4 will not be destroyed before the entire etching is completed.

As shown in FIG. 2( c ), a layer of photoresist layer 8 is formed on the second mask material 3 , and then a series of windows 5 are formed on the photoresist layer 8 according to the design through a photolithography process.

In this example, the mask material has two layers, which are respectively the first mask material 1 of the first layer and the second mask material 3 of the second layer, and a layer of light is formed on the second layer of the second mask material 3. The resist layer 8 is the third layer, and a series of windows 5 are opened on the third layer by photolithography to partially expose the second mask material 3;

As shown in Figure 3, after wet or dry etching, the exposed part of the second mask material 3 is etched, the pattern of the series of windows 5 is transferred to the first mask material 1, and the local area of the first mask material 1 exposed.

The selection of the second mask material 3 should meet the following conditions: the etching rate of the second mask material 3 is much lower than the etching rate of the first mask material 1 and the etched material 2; wherein, the first mask material 1. The etching rate of the material to be etched 2 and the second mask material 3 should be compared under the same etching method, and the etching method is a dry etching method or a wet etching method.

As shown in FIG. 4, the photoresist layer 8 of the third layer is removed.

As shown in Figures 5 and 6, the series of windows 5 are transferred to the first mask material 1 through wet or dry etching, and dry etched to the etched material 2, and finally the first mask is removed. Membrane material 1 and second mask material 3 . The selection of the first mask material 1 should meet the following conditions: the etching rate of the first mask material 1 in the direction perpendicular to the surface is equal to the etching rate of the etched material 2, and the first mask material 1 is parallel to the surface. The etching rate in the direction is less than the etching rate of the etched material 2; wherein, the etching rate comparison between the first mask material 1 and the etched material 2 should be under the same etching method, and the etching method is dry etching method or wet etching method.

A series of windows 5 are designed on the first mask material 1 with a slope structure 4. When the front edge of the groove at the thickest part of the first mask material 1 reaches the surface of the material 2 to be etched, the window 5 has already been formed on the material 2 to be etched. A series of grooves 7 of different depths are formed inside.

Example 2

On the basis of the content of embodiment 1, the etching method of setting the first mask material 1 and the second mask material 3, and the material to be etched 2 is a dry etching method, so that it can effectively etch the material to be etched. In addition to the etching material 2, the first mask material 1 can also be effectively etched.

The first mask material 1 is etched by dry etching. Since the thickness of the first mask material 1 in the vertical direction is different, the front edge of the thinnest etched trench reaches the edge of the etched material 2 during the dry etching process. surface, other parts of the trench front are still inside the first mask material 1 . When the front edge of the groove at the thickest point reaches the surface of the etched material 2, the groove at the thinnest point has entered the inside of the etched material 2 to form a series of grooves with different depths inside the etched material 2 7.

The slope angle 6 of the slope structure 4 can be set to be less than 45 degrees. Due to the existence of the slope structure 4, there is a height difference in the window region formed thereon, so there is a time difference for the etching front to reach the surface of the etched material 2, as shown in FIG. 5; remove the first mask material 1 and the second mask The membrane material 3 and finally the series of trenches 7 formed on the etched material 2 have different depths. As shown in FIG. 6 , the etching conditions of the dry etching method do not need to be set in advance, but can be determined according to the specific material to be etched and the mask material.

Among the present invention, the etched material 2 can be an existing semiconductor material, the first mask material 1 can be an organic polymer, and the second mask material 3 can be silicon dioxide, but the thickness of the silicon dioxide must ensure that the entire etching If it is not completely etched away during the etching process, the second mask material 3 can also be some metal material.

In the present invention, dry or wet etching is a conventional technique, and the method of forming the series of windows 5 is also a conventional photolithography technique.

In the present invention, after forming the first mask material 1 and the second mask material 3 with the slope structure 4 at the specified position on the surface of the material 2 to be etched, a photolithographic mask material 3 is formed on the second mask material 3 by a photolithography process. The adhesive layer 8 forms the series of windows 5 as designed. Etch the second mask material 3 through the series of windows 5 until the first mask material 1 is exposed; the etching conditions of the dry etching method are selected so that it has the same effect on the first mask material 1 and the etched material 2 Etching action, and then carry out the next step of etching until the required series of grooves 7 are formed on the etched material 2, and finally all the mask materials are removed. The method of the present invention can form a plurality of serial grooves 7 with different depths by one-time photolithography plus dry etching technology, which has high efficiency and reduces manpower and time costs.

The above implementation/test examples are merely examples for clear description, and are not intended to limit the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (8)

1. A method of forming trenches having different depths at a time in a semiconductor surface, comprising: the method comprises the following steps:

s1: forming a first mask material (1) with a slope structure (4) at a designated position on the surface of the etched material (2);

s2: forming a second mask material (3) with the same slope on the first mask material (1);

s3: forming a photoresist layer (8) with the same slope on the second mask material (3), and forming a series of windows (5) on the slope area of the photoresist layer (8) as required to locally expose the second mask material (3);

s4: transferring the series of windows (5) onto the second mask material (3), locally exposing the first mask material (1);

s5: and etching the first mask material (1) and the etched material (2) until the first mask material (1) and the second mask material (3) are removed after the series of grooves (7) with different depths are etched on the etched material (2).

2. A method of forming trenches having different depths at a time in a semiconductor surface according to claim 1, wherein: the inclination angle of the slope structure (4) is less than or equal to 45 degrees.

3. A method of forming trenches having different depths at a time in a semiconductor surface according to claim 1, wherein: the method for forming the first mask material (1) in the step S1 is an imprinting method.

4. A method of forming trenches having different depths at a time in a semiconductor surface according to claim 3, wherein: the first mask material (1) is an organic polymer.

5. A method of forming trenches having different depths at a time in a semiconductor surface according to claim 1, wherein: and in S4 and S5, transferring the series of windows (5) onto the second mask material (3) and the first mask material (1) by a dry etching method or a wet etching method.

6. A method of forming trenches having different depths at a time in a semiconductor surface as recited in claim 5, wherein: in the steps S4 and S5, the conditions to be satisfied for selecting the second mask material (3) are: the etching rate of the second mask material (3) is far smaller than the etching rates of the first mask material (1) and the etched material (2); wherein, the etching rates of the first mask material (1), the etched material (2) and the second mask material (3) are compared under the same etching method.

7. A method of forming trenches having different depths at a time in a semiconductor surface according to claim 1, wherein: and in the step S5, transferring the series of windows (5) onto the etched material (2) by a dry etching method.

8. A method of forming trenches having different depths in a semiconductor surface at a time as claimed in claim 6 or 7, wherein: in the S4 and S5, the conditions to be satisfied for selecting the first mask material (1) are: the etching rate of the first mask material (1) in the direction vertical to the surface is equal to the etching rate of the etched material (2), and the etching rate of the first mask material (1) in the direction parallel to the surface is smaller than the etching rate of the etched material (2); wherein, the etching rate of the first mask material (1) and the etched material (2) is compared under the same etching method.