阅读说明：本技术 一种金属电极结构的实现方法 (Method for realizing metal electrode structure ) 是由 张宏伟 栗锐 陈征 柏松 杨勇 费晨曦 于 2020-12-28 设计创作，主要内容包括：本发明公开了一种金属电极结构的实现方法,该方法包括：通过金属化方法形成钛铝双层金属,其中钛金属设于底层,位于衬底表面,铝金属设于顶层,位于钛金属表面；涂覆光刻胶,并光刻出掩膜图形；基于单片式湿法喷雾腐蚀系统,使用特定的腐蚀液,控制腐蚀过程的转速、喷淋压力、喷淋区域与喷淋时间等参数,逐层腐蚀铝金属、钛金属,然后再次腐蚀铝金属,使铝金属的侧蚀继续增大,露出底层钛的边界,最终形成底层钛边缘超出顶层铝边缘至少0.1um的电极结构；相比于传统的槽式腐蚀,得到了更好的稳定性、均匀性与形貌；相比于一般的多层金属腐蚀结果,避免了因为底层金属侧蚀带来的缝隙,消除了器件的可靠性隐患；相比于干法刻蚀,避免了腔体沾污、衬底损伤以及等离子体损伤等问题。(The invention discloses a method for realizing a metal electrode structure, which comprises the following steps: forming titanium-aluminum double-layer metal by a metallization method, wherein the titanium metal is arranged on the bottom layer and positioned on the surface of the substrate, and the aluminum metal is arranged on the top layer and positioned on the surface of the titanium metal; coating photoresist and photoetching a mask pattern; based on a single-chip wet spray corrosion system, using a specific corrosive liquid, controlling parameters such as the rotating speed, the spraying pressure, the spraying area, the spraying time and the like in the corrosion process, corroding aluminum metal and titanium metal layer by layer, then corroding the aluminum metal again to enable the side corrosion of the aluminum metal to continue to increase and expose the boundary of bottom titanium, and finally forming an electrode structure with the bottom titanium edge exceeding the top aluminum edge by at least 0.1 um; compared with the traditional groove type corrosion, better stability, uniformity and appearance are obtained; compared with the common multilayer metal corrosion result, the method avoids gaps caused by the side corrosion of the bottom metal, and eliminates the hidden trouble of reliability of the device; compared with dry etching, the method avoids the problems of cavity contamination, substrate damage, plasma damage and the like.)

1. A method for realizing a metal electrode structure is characterized by comprising the following steps:

(1) coating photoresist on the surface of the metal, and photoetching to form a mask; the metal electrode is composed of titanium metal and aluminum metal;

(2) transferring the photoetched wafer into a single-chip spray corrosion system, and sealing a cavity;

(3) spraying aluminum corrosive liquid to corrode aluminum metal;

(4) washing the aluminum corrosive liquid remained on the surface of the wafer by using deionized water;

(5) spraying diluted hydrofluoric acid to corrode titanium metal;

(6) washing the diluted hydrofluoric acid remained on the surface of the wafer by using deionized water;

(7) spraying aluminum corrosive liquid to corrode aluminum metal again;

(8) washing the aluminum corrosive liquid remained on the surface of the wafer by using deionized water;

(9) spin-drying and dehydrating the wafer;

(10) opening the cavity and transferring the corroded wafer out;

(11) and removing the photoresist on the surface of the wafer by using an organic solution.

2. The method of claim 1, wherein the titanium metal is in the bottom layer and has a thickness of 50-500 nm; the aluminum metal is on the top layer, and the thickness is 1-10 um.

3. The method of claim 2, wherein the resulting electrode structure has a bottom titanium metal edge that extends at least 0.1um beyond a top aluminum metal edge.

4. The manufacturing method according to claim 1, wherein the photoresist is a positive photoresist.

5. The manufacturing method of claim 1, wherein the aluminum etching solution is a mixed solution of phosphoric acid, nitric acid, acetic acid and deionized water, wherein the molar ratio of the components is, phosphoric acid: nitric acid: acetic acid: water 1-60: 1-40: 1-30: 1-80.

6. The manufacturing method according to claim 1, wherein the diluted hydrofluoric acid is a mixed solution of hydrofluoric acid and deionized water, wherein the molar ratio of each component is hydrofluoric acid: 1-30 parts of water: 170.

7. the production method according to claim 1, wherein the liquid ejection time in the step (3) is 10 to 500 seconds, the liquid ejection time in the step (5) is 10 to 500 seconds, and the liquid ejection time in the step (7) is 1 to 300 seconds.

8. The manufacturing method according to claim 1, wherein the aluminum etchant temperature is controlled to 40-90 ℃ and the diluted hydrofluoric acid temperature is controlled to 10-50 ℃.

9. The method of claim 1, wherein the wafer rotation speed is 0 to 2500R/min.

10. The method of claim 1, wherein the nozzles for the solution, deionized water, and nitrogen are positionable and operable.

Technical Field

The invention relates to the field of wet etching process in semiconductor device manufacturing, in particular to a method for realizing a metal electrode structure.

Background

On semiconductor devices, metallization processes are often used to deposit thin films of conductive metals on the chip for a variety of purposes. There are several main requirements to consider whether a metal material is qualified: conductivity, adhesion, deposition difficulty, planarization, reliability, corrosion resistance, and stress, all of which are well behaved by titanium and aluminum. Titanium metal is widely used in schottky contact, ohmic contact, barrier metal, metal interconnection, contact metal, alloy components and the like because of its characteristics of large work function, small contact resistance, good adhesion and the like. Aluminum metal is one of the most important materials in the semiconductor manufacturing industry at present due to its low resistivity, low cost and process compatibility, and is widely used in the fields of metal interconnection, electrode thickening, metal soldering, surface passivation, ohmic contact and the like. Titanium-aluminum double-layer metal is a common metal electrode structure as a barrier metal of a schottky diode, a thickened metal of the barrier metal, and a thickened metal of an MOSFET ohmic metal. Therefore, the patterning of the titanium-aluminum metal is a key technology with wide demand in the semiconductor process.

Wet etching is a widely used process in semiconductor device fabrication and plays an important role in metal or dielectric rinsing, residue removal, and large-scale pattern etching applications. Compared with dry etching, wet etching can have extremely high selection ratio for lower layer materials, does not bring plasma damage to devices, and has relatively simple basic conditions. The monolithic wet spray etching is an improved wet etching method with higher precision, and has several advantages over the conventional immersion etching, mainly the significant improvement of process uniformity and precision. The single-chip operation mode is characterized in that the equipment accurately controls the solution proportion, the temperature and the mechanical operation, and water is sprayed and washed in time after corrosion, so that the uniformity and controllability of the corrosion are guaranteed; the pollution degree from the corrosive liquid and the tank body is obviously reduced. Furthermore, spray erosion systems are often closed, increasing the safety of personnel operations.

In the established process, the titanium-aluminum metal lamination layer needs to be patterned layer by layer, and finally a structure with the edge of the bottom layer of titanium metal exceeding the edge of the top layer of aluminum metal by at least 0.1um is formed. The process requires good uniformity, controllability and cleanliness, and the uniformity in and among the chips is less than 5 percent; the corrosion of the width line of more than 20um can be realized; the metal edge is neat and has no undercutting; gaps caused by the fact that bottom layer metal is over-etched do not exist between layers, and therefore potential safety hazards of devices are introduced.

The conventional wet etching adopts a groove type soaking mode, the service life of a solution is often difficult to control along with the change of process conditions and the volatilization of a solvent, the process conditions cannot be solidified, the manual regulation is possibly extremely relied on, or the problems of incomplete corrosion, over corrosion and the like are easily caused, so that the product loss is caused; cleanliness of the tank-type equipment cannot be guaranteed, and contamination which is difficult to clean is easy to accumulate in the tank body or the pipeline for a long time and is attached to the surface of the wafer in the corrosion process, so that process abnormity is caused; on the other hand, due to the difference of solution exchange at different positions in the groove, the uniformity in the wafer, among the wafers and among batches is difficult to meet the requirement of 5%, corrosion in some thin lines even can not be realized, and the groove type corrosion mode is difficult to meet for the process with high stability requirement or high line precision requirement; the dry etching introduces the problems of cavity contamination, substrate damage, plasma damage and the like, and brings irreversible damage to the device. Therefore, the titanium-aluminum metal corrosion process with higher precision and good controllability is significant to be found.

Disclosure of Invention

The invention aims to provide a method for realizing a metal electrode structure, which can continuously corrode two layers of metal, simultaneously ensure better wet corrosion uniformity, controllability and cleanliness, present better metal side wall appearance and form a device structure with higher reliability.

In order to achieve the above object, the present invention provides a method for implementing a metal electrode structure, comprising the following steps:

step 1: coating photoresist on the surface of the metal electrode, and photoetching to form a mask;

step 2: transferring the photoetched wafer into a single-chip spray corrosion system, and sealing a cavity;

and step 3: spraying aluminum corrosive liquid to corrode aluminum metal;

and 4, step 4: washing the aluminum corrosive liquid remained on the surface of the wafer by using deionized water;

and 5: spraying diluted hydrofluoric acid to corrode titanium metal;

step 6: washing the diluted hydrofluoric acid remained on the surface of the wafer by using deionized water;

and 7: spraying aluminum corrosive liquid to corrode aluminum metal;

and 8: washing the aluminum corrosive liquid remained on the surface of the wafer by using deionized water;

and step 9: spin-drying and dehydrating the wafer;

step 10: opening the cavity and transferring the corroded wafer out;

step 11: and removing the photoresist on the surface of the wafer by using an organic solution.

Further, the metal electrode is composed of titanium metal and aluminum metal.

Furthermore, the titanium metal is arranged at the bottom layer, the thickness of the titanium metal is 50-500nm, and the aluminum metal is arranged at the top layer, and the thickness of the aluminum metal is 1-10 um.

Further, the finally obtained electrode structure is that the edge of the bottom layer titanium metal exceeds the edge of the top layer aluminum metal by at least 0.1 um.

Further, the photoresist is positive photoresist.

Further, the aluminum corrosive liquid is a mixed solution of phosphoric acid, nitric acid, acetic acid and deionized water, wherein the molar ratio of each component is as follows: nitric acid: acetic acid: water 1-60: 1-40: 1-30: 1-80.

The diluted hydrofluoric acid is a mixed solution of hydrofluoric acid and deionized water, wherein the molar ratio of each component is hydrofluoric acid: 1-30 parts of water: 170.

further, the liquid spraying time in the step 3 is 10-500 seconds, the liquid spraying time in the step 5 is 10-500 seconds, and the liquid spraying time in the step 7 is 1-300 seconds.

Further, the temperature of the aluminum corrosive liquid is controlled to be 40-90 ℃, and the temperature of the diluted hydrofluoric acid is controlled to be 10-50 ℃.

Further, the rotating speed of the wafer is 0-2500R/min.

Further, the nozzles for the solution, deionized water and nitrogen are positionable and operable.

Compared with the prior art, the invention has the beneficial effects that:

(1) the uniformity is good. The position of the solution nozzle in the corrosion process moves, and various corrosion uniformity can be controlled within 5% by matching with different rotating speeds of the wafer in solutions with different viscosities;

(2) the controllability is strong. The reaction of titanium with hydrofluoric acid is extremely severe, and the use of low-concentration hydrofluoric acid, coupled with a long etching time and the above-mentioned uniformity, allows to control the fluctuations in the etching result to a minimum. In addition, the spray corrosion system accurately controls the solution proportion, the temperature and the mechanical operation, and water is sprayed for washing in time after corrosion, so that the controllability of the corrosion process is improved; the fluctuation of the edge position of the aluminum metal, the fluctuation of the sheet inside and between sheets is within +/-2 um, and the fluctuation of the edge position of the titanium metal is within +/-1 um;

(3) the cleanliness is high. The trench etch tends to accumulate contamination and to stick back to the wafer surface, resulting in die loss. The single-chip spray corrosion mode ensures that the solution is used for one time, the loss amount is controllable, and the contamination is greatly reduced;

(4) no hidden trouble of reliability. After the bottom layer titanium metal is corroded, due to the existence of side corrosion, the edge of titanium can retract into the edge of aluminum metal to form a gap, and if solution or contamination enters the gap, great reliability hidden danger which cannot be detected is brought. Finally, aluminum corrosion is added, and titanium is exposed to at least 0.1um, so that the hidden danger of gap structure and reliability can be eliminated;

(5) the metal appearance is good. The aluminum metal is rough and has larger thickness, the appearance with irregular edges is very easy to appear in the longer corrosion process, the yield loss is brought, the higher corrosion temperature is used for controlling the higher corrosion rate, and the poor appearance of the metal edges caused by the factors such as photoresist deformation or uniformity and wettability in the corrosion process is avoided by matching the control of the spray flow and the rotating speed.

Drawings

Fig. 1 is a schematic flow chart of a method for implementing a metal electrode structure according to an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of a metal electrode finally obtained according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more comprehensible, the technical solutions in the embodiments of the present invention are described in detail below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are not all embodiments of the present invention, but only some embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any inventive step, are within the scope of the present invention.

Fig. 1 is a schematic flow chart of a wet etching method for a titanium-aluminum double-layer metal electrode single sheet according to an embodiment of the present invention, and as shown in fig. 1, the wet etching method for a titanium-aluminum double-layer metal electrode single sheet according to the present invention includes the following steps:

in step 101, the surface of the substrate is already made into a titanium-aluminum double-layer metal by a metallization evaporation process: the titanium is positioned at the bottom layer and has the thickness of 180 nm; the aluminium is located the top layer, and thickness is 5 um. Coating AZ1500 photoresist on the surface of the aluminum, and photoetching positive photoresist to obtain square array glue blocks with the width of 50um and the interval of 20um, and exposing aluminum metal in a region to be corroded;

in step 102, the wafer is transferred into a single-chip spray etching system, the surface to be etched faces upwards, and a cavity door is closed;

in step 103, pre-spraying aluminum etching solution for 15 seconds;

in step 104, spraying and corroding aluminum metal by using aluminum corrosive liquid heated to 75 ℃ at the flow rate of 290mL/min, wherein the corrosion time is 300 seconds, and the rotating speed of a wafer is 200R/min;

in the step 105, deionized water with the flow rate of 700mL/min is used for washing for 80 seconds, aluminum corrosive liquid on the surface of the wafer is washed clean, and the rotating speed of the wafer is 100R/min;

in step 106, pre-spraying diluted hydrofluoric acid for 15 seconds;

in step 107, spraying and corroding titanium metal at a flow rate of 520mL/min by using diluted hydrofluoric acid with the temperature of 22 ℃, wherein the corrosion time is 150 seconds, the wafer rotating speed is 150R/min, and a titanium structure on the surface of the substrate 201 is formed, such as 202 in FIG. 2;

in step 108, deionized water with the flow rate of 700mL/min is used for washing for 40 seconds, and the diluted hydrofluoric acid on the surface of the wafer is washed clean, wherein the rotating speed of the wafer is 150R/min;

in step 109, aluminum metal is spray-etched by using an aluminum etching solution heated to 60 ℃ at a flow rate of 200mL/min, the etching time is 60 seconds, the wafer rotation speed is 150R/min, and an aluminum structure on the titanium surface is formed, as shown in 203 in FIG. 2;

in the step 110, deionized water with the flow rate of 700mL/min is used again for washing for 80 seconds, the aluminum corrosive liquid on the surface of the wafer is washed clean, and the rotating speed of the wafer is 100R/min;

in step 111, the wafer is rotated at a high speed at a rotating speed of 2000R/min for spin-drying for 120 seconds;

in step 112, hot nitrogen heated to 80 ℃ is sprayed on the surface of a wafer rotating at a low speed of 400R/min at a flow rate of 1L/min after passing through isopropanol, and the wafer is dehydrated;

in step 113, opening the cavity, and transferring the corroded and dehydrated wafer out of the single-chip corrosion system;

in step 114, the wafer is soaked with DMF solution heated to 60 deg.C for 20 minutes to remove the photoresist on the wafer surface.

In the above step, the aluminum etching solution is a mixed solution of phosphoric acid, nitric acid, acetic acid and deionized water, wherein the molar ratio of each component is as follows: nitric acid: acetic acid: water 1-60: 1-40: 1-30: 1-80; the diluted hydrofluoric acid is a mixed solution of hydrofluoric acid and deionized water, wherein the molar ratio of each component is hydrofluoric acid: 1-30 parts of water: 170; the spray nozzle for spraying the aluminum corrosive liquid, the spray nozzle for spraying the diluted hydrofluoric acid, the spray nozzle for spraying the deionized water and the spray nozzle for spraying the hot nitrogen have the movement tracks of reciprocating from the edge of the wafer to the radial 3/4 position of the wafer, the movement speed is 4 cm/s, in the pre-spraying in the step 103 and the step 106, the spray nozzle is far away from the wafer, and the solution cannot touch metal on the surface of the wafer.

The above description is only one specific example of the present invention and should not be construed as limiting the invention in any way. It will be apparent to persons skilled in the relevant art that various modifications and changes in form and detail can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.