CN115159449A

CN115159449A - Method for improving etching defect

Info

Publication number: CN115159449A
Application number: CN202210876118.5A
Authority: CN
Inventors: 张振兴; 周真
Original assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corp
Current assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corp
Priority date: 2022-07-25
Filing date: 2022-07-25
Publication date: 2022-10-11

Abstract

The invention provides a method for improving etching defects, which comprises the steps of providing a substrate, wherein a first metal layer and a second metal layer formed on the first metal layer are formed on the substrate; forming a photoresist layer on the second metal layer, opening part of the photoresist layer by photoetching to expose the second metal layer below the photoresist layer, and adjusting the temperature of a photoresist removing machine table to form an intermetallic compound at the contact surface of the first metal layer and the second metal layer; removing the exposed second metal layer by wet etching, and then drying the substrate to remove the solution on the first metal layer and the second metal layer; removing the photoresist layer by using an ashing process so as to remove the residual solution on the first metal layer and the second metal layer; the substrate is cleaned and then dried. According to the invention, baking heat treatment is carried out before the metal layer is etched, and thermal stress is released; and after etching, drying treatment is enhanced, residual acid liquor in the cavity generated by the reaction between the metal layers is removed, and further etching reaction of the residual acid liquor is prevented, so that the rat bite defect is improved.

Description

Method for improving etching defect

Technical Field

The invention relates to the technical field of semiconductors, in particular to a method for improving etching defects.

Background

MEMS sensors, i.e. Micro Electro Mechanical Systems (MEMS), are a leading-edge research field of multidisciplinary intersection developed on the basis of microelectronics. Over forty years of development, it has become one of the major scientific and technological fields of world attention. It relates to various subjects and technologies of electronics, machinery, materials, physics, chemistry, biology, medicine and the like, and has wide application prospect. Hundreds of products have been developed including miniature pressure sensors, acceleration sensors, micro-inkjet printheads, digital micro-mirror displays, with MEMS sensors representing a significant proportion. MEMS sensors are new types of sensors manufactured using microelectronics and micromachining techniques. Compared with the traditional sensor, the sensor has the characteristics of small volume, light weight, low cost, low power consumption, high reliability, suitability for batch production, easiness in integration and realization of intellectualization. At the same time, feature sizes on the order of microns make it possible to perform functions that some conventional mechanical sensors cannot achieve.

For an MEMS accelerometer product, in the prior art, a layer of photoresist is formed on an aluminum layer on a substrate, a pattern on the aluminum layer is defined by photolithography, then the photoresist layer is opened to remove the exposed aluminum layer by wet etching, then the substrate after wet etching is subjected to an ashing process and aqueous cleaning, and the wet etching of aluminum in a metal etching station is prone to cause a "mouse-bite defect" as shown in fig. 1 and 2, which reduces the critical dimension of line width and results in a loss of product yield.

In order to solve the above problems, a new method for improving etching defects is required.

Disclosure of Invention

In view of the above disadvantages of the prior art, the present invention provides a method for improving etching defects, which is used to solve the problem that wet etching of aluminum in a metal etching stage in the prior art is prone to cause "mouse-bite defects", which will reduce critical dimensions of line widths and result in loss of product yield.

To achieve the above and other related objects, the present invention provides a method for improving etching defects, comprising:

providing a substrate, wherein a first metal layer and a second metal layer formed on the first metal layer are formed on the substrate;

step two, forming a photoresist layer on the second metal layer, opening part of the photoresist layer by photoetching to expose the second metal layer below the photoresist layer, and then adjusting the temperature of a photoresist removing machine table to form an intermetallic compound on the contact surface of the exposed second metal layer and the first metal layer below the exposed second metal layer;

removing the exposed second metal layer by wet etching, and then drying the substrate to remove the solution on the first metal layer and the second metal layer;

removing the photoresist layer by using an ashing process to remove the residual solution on the first metal layer and the second metal layer;

and step five, cleaning the substrate, and then drying the substrate.

Preferably, the substrate in the first step is a silicon substrate.

Preferably, the material of the first metal layer in the first step is titanium.

Preferably, the material of the second metal layer in the first step is aluminum.

Preferably, the intermetallic compound in step two is TiAL3.

Preferably, the photoresist removing machine in the second step is a deep ultraviolet light processing machine.

Preferably, the temperature of the deep ultraviolet light processing machine in the second step is adjusted to be 150 to 180 ℃.

Preferably, the solution is removed in step three by means of an isopropanol vapor dryer, after which nitrogen is fed into the isopropanol vapor dryer to remove the gases therein.

Preferably, the temperature of the electric furnace used in the ashing process in step four is 250 degrees celsius.

Preferably, the gases introduced into the electric furnace used in the ashing process in step four are H2N2 and O2.

Preferably, in step four, the gas is introduced into the electric furnace at 200 to 400SCCM of H2N2 and 2500 to 3500SCCM of O2.

Preferably, the power of the electric furnace used in the ashing process in step four is 1000 to 1400 watts.

As described above, the method for improving etching defects of the present invention has the following beneficial effects:

the invention carries out baking heat treatment before the metal layer is etched, and releases thermal stress; and after etching, drying treatment is enhanced, residual acid liquor in the cavity generated by the reaction between the metal layers is removed, and further etching reaction of the residual acid liquor is prevented, so that the rat bite defect is improved.

Drawings

FIG. 1 is a schematic diagram of a rat bite defect in the prior art;

FIG. 2 is a schematic diagram showing a rat bite defect in the prior art;

FIG. 3 is a schematic view of the improvement of rat bite defect of the present invention;

FIG. 4 is a schematic process flow diagram of the present invention.

Detailed Description

The following embodiments of the present invention are provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

Referring to fig. 4, the present invention provides a method for improving etching defects, including:

in an embodiment of the present invention, the substrate in the first step is a silicon substrate.

In an embodiment of the invention, in the first step, the material of the first metal layer is titanium.

In an embodiment of the invention, in the first step, the material of the second metal layer is aluminum.

Forming a photoresist layer on the second metal layer by using a photoresist removing machine, opening part of the photoresist layer by photoetching, exposing, erecting a film, developing, baking and the like to expose the second metal layer below the photoresist layer, transferring the substrate after photoetching into the photoresist removing machine, and forming an intermetallic compound at the contact surface of the first metal layer and the second metal layer at the exposed part by adjusting the temperature of the photoresist removing machine, namely before etching the second metal layer, releasing the thermal stress of the metal layer by baking heat treatment;

in an embodiment of the present invention, in the second step, the intermetallic compound is TiAL3, and is formed by reacting a titanium metal layer with an aluminum metal layer.

In the embodiment of the present invention, the photoresist removing machine in the second step is a deep ultraviolet curing (UV curing) machine, and the UV curing machine is a machine that uses a UV light source to cure the UV coating, and performs a chemical reaction with the photosensitizer in the UV coating, and performs an instant drying and curing.

In the embodiment of the invention, the temperature of the deep ultraviolet light processing machine is adjusted to be 150 to 180 ℃ in the second step.

Removing the exposed second metal layer by wet etching, wherein drying is the last step of wet cleaning, greatly influences the yield of the wafer, because a cavity is formed by the reaction between the metal layers, acid liquor remained in the cavity can be continuously etched to form a rat bite defect, and then the substrate is subjected to enhanced drying treatment, so that the solution on the first metal layer and the solution on the second metal layer are removed, and the acid liquor is prevented from continuously reacting;

in the embodiment of the invention, the wet cleaning with a particle size of 0.35 μm or less in the wafer factory adopts a drying method of heating isopropyl alcohol vapor mist, which is generally called IPA drying method. IPA drying removes water molecules using intermolecular forces. The isopropanol is atomized to form mist, and molecules of the mist can easily enter a channel of the device under the carrying of hot nitrogen, so that water molecules in the channel are taken away to achieve the drying effect. The method not only greatly reduces the occurrence of the residual phenomenon of water vapor, but also reduces the adsorption of particles on the surface of the wafer, the solution is removed by using an isopropanol vapor dryer in the third step, then nitrogen is introduced into the isopropanol vapor dryer to discharge the gas in the isopropanol vapor dryer, hot N2 and IPA pass through an IPA atomizer to quickly form IPA vapor to be sprayed on the surface of the wafer to achieve drying, and the method has enough IPA concentration to form IPA vapor blocks, has no high temperature danger and is quicker to dry.

Removing the photoresist layer by using an ashing process, and simultaneously adjusting parameters of an electric furnace in the ashing process to remove the residual solution on the first metal layer and the second metal layer in the step;

in the embodiment of the present invention, the temperature of the electric furnace used in the ashing process in step four is 250 degrees celsius.

In the embodiment of the present invention, the gases introduced into the electric furnace used in the ashing process in step four are H2N2 and O2.

In the embodiment of the invention, H2N2 with 200 to 400SCCM and O2 with 2500 to 3500SCCM are introduced into the electric furnace in the fourth step.

In an embodiment of the present invention, the power of the electric furnace used in the ashing process in step four is 1000 to 1400 watts.

And step five, cleaning the substrate, and then drying the substrate.

In an embodiment of the present invention, the substrate after the wet cleaning may be subjected to a drying process in an electric furnace.

It should be noted that the drawings provided in this embodiment are only for schematically illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings and not drawn according to the number, shape and size of the components in actual implementation, and the form, quantity and proportion of each component in actual implementation may be arbitrarily changed, and the component layout may be more complicated.

In summary, the invention performs the baking heat treatment before the metal layer is etched to release the thermal stress; and after etching, drying treatment is enhanced, residual acid liquor in the cavity generated by the reaction between the metal layers is removed, and further etching reaction of the residual acid liquor is prevented, so that the rat bite defect is improved. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A method for improving etching defects, comprising:

and step five, cleaning the substrate, and then drying the substrate.

2. The method for improving etching defects according to claim 1, wherein: the substrate in the first step is a silicon substrate.

3. The method for improving etching defects according to claim 1, wherein: in the first step, the first metal layer is made of titanium.

4. A method for improving etching defects according to claim 3, wherein: in the first step, the second metal layer is made of aluminum.

5. The method for improving etching defects according to claim 4, wherein: in the second step, the intermetallic compound is TiAL3.

6. The method for improving etching defects according to claim 1, wherein: and in the second step, the photoresist removing machine is a deep ultraviolet light processing machine.

7. The method for improving etching defects according to claim 1, wherein: and in the second step, the temperature of the deep ultraviolet light treatment machine is adjusted to be 150-180 ℃.

8. The method for improving etching defects according to claim 1, wherein: in the third step, the solution is removed by using an isopropanol vapor dryer, and then nitrogen is introduced into the isopropanol vapor dryer to exhaust the gas in the isopropanol vapor dryer.

9. The method for improving etching defects according to claim 1, wherein: the temperature of the electric furnace used in the ashing process in step four is 250 degrees celsius.

10. The method for improving etching defects according to claim 1, wherein: and in the fourth step, the gas introduced into the electric furnace used in the ashing process is H2N2 and O2.

11. The method for improving etching defects as set forth in claim 10, wherein: in step four, 200 to 400SCCM of H2N2 and 2500 to 3500SCCM of O2 are introduced into the electric furnace.

12. The method for improving etching defects according to claim 1, wherein: the power of the electric furnace used in the ashing process in step four was 1000 to 1400 watts.