HSQ exposure optimization method

Abstract

The invention relates to the technical field of micro-nano device preparation, in particular to an HSQ exposure optimization method which comprises the following steps: S1, sample preparation: spin-coating electron beam photoresist on the surface of a substrate to obtain a sample; s2, exposure: carrying out electron beam exposure on the sample, and after exposure, putting the sample into a developing solution for developing to obtain an electron beam photoresist mask; s3, optimization: putting the developed sample into a reactive ion etching machine, setting an optimization menu, and then starting optimization; s4, etching: putting the optimized sample into an inductively coupled plasma etching machine, and starting etching after setting an etching menu; and S5, photoresist removal: putting the etched sample into a photoresist removal solution for photoresist removal. According to the method, the overexposure phenomenon of the electron beam photoresist mask is optimized, the influence is eliminated, and the mask can be continuously used, so that the subsequent etching process and the chip preparation effect are not influenced, and the quality of a device is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-nano device preparation, and more specifically, to a HSQ exposure optimization method. Background Art

[0002] Hydrogenated siloxane (HSQ) is a negative resist commonly used in electron beam lithography. It is widely used in the field of micro-nano processing because of its extremely high resolution, which can reach the sub-10 nanometer level. The proximity effect in electron beam lithography is caused by the scattering of electrons in the resist and substrate, which changes the direction of their movement, resulting in exposure of nearby areas that were not originally intended to be exposed, while some areas that are intended to be exposed do not receive sufficient exposure, causing changes in the pattern and affecting the resolution. The proximity effect is related to the conditions of the incident electron beam, the resist and the substrate. Its influence can be analyzed by simulating the scattering process of electrons in the resist and the substrate and the distribution of electron deposition energy in the resist. During the electron beam exposure process of HSQ, when the electron beam deposition energy reaches a certain amount, the Si-H and Si-O bonds in the box-shaped unit can be disconnected to form a three-dimensional network structure, which can significantly reduce the dissolution rate of HSQ in the developer. The pre-baking process also promotes the transformation of HSQ from a box-shaped structure to a network structure, thereby improving the sensitivity. Of course, the contrast will also decrease. This structural change directly affects the quality of the HSQ mask.

[0003] In summary, in practical applications, due to the small spacing of some device structure designs and the proximity effect in electron beam exposure, overexposure often occurs during HSQ exposure. This overexposure may cause adhesion between structures, thus affecting the quality of the HSQ mask, and further affecting the subsequent etching process and the final effect of chip preparation. Summary of the invention

[0004] The purpose of the present invention is to overcome the disadvantage that overexposure often occurs during HSQ exposure in the prior art, and to provide a HSQ exposure optimization method that can effectively eliminate the influence of the overexposure phenomenon and improve the quality of the HSQ mask.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A HSQ exposure optimization method is provided, comprising the following steps:

[0007] S1. Sample preparation: spin coating electron beam photoresist on the substrate surface to obtain a sample;

[0008] S2. Exposure: The sample is subjected to electron beam exposure, and after exposure, it is placed in a developer to develop to obtain an electron beam photoresist mask;

[0009] S3. Optimization: Place the developed sample into the reactive ion etcher, set the optimization menu and start the optimization;

[0010] S4. Etching: Place the optimized sample into the inductively coupled plasma etcher, set the etching menu, and start etching;

[0011] S5. Degumming: Place the etched sample into the degumming solution for degumming.

[0012] In a HSQ exposure optimization method of the present invention, in step S2, there is structural adhesion in the electron beam photoresist mask due to electron beam overexposure, and after the electron beam photoresist mask is optimized in step S3, the structural adhesion is eliminated in the electron beam photoresist mask. The present invention optimizes the overexposure phenomenon of the electron beam photoresist mask, eliminates the influence, ensures that the mask can continue to be used, and improves the quality of the HSQ mask, thereby not affecting the subsequent etching process and chip preparation effect.

[0013] In the present invention, in step S1, the electron beam photoresist is HSQ photoresist. Hydrogenated siloxane (HSQ) is a negative resist commonly used in electron beam lithography. Because it has an extremely high resolution and can reach the sub-10 nanometer level, it is widely used in the field of micro-nano processing. The present invention optimizes the overexposure phenomenon that often occurs during HSQ exposure to eliminate the influence of overexposure and adhesion between structures, so that HSQ photoresist can be better used and the quality of subsequent etching process and chip preparation is improved.

[0014] Preferably, in step S1, the substrate comprises gallium arsenide. Gallium arsenide has high electron mobility and direct bandgap characteristics, which makes it suitable for high-speed and photoelectric conversion applications. In particular, it performs well in radio frequency and optoelectronic devices. As a substrate material, gallium arsenide has a wide range of applications and importance in semiconductor device manufacturing, especially in the fields of high frequency, high speed, optoelectronics and microwaves.

[0015] Preferably, in step S2, the beam current of the electron beam exposure is 0.7nA-0.9nA, and the dose is 750μC / cm 2 ~850μC / cm 2 .

[0016] Preferably, in step S2, TMAH developer is used, and the developing time is 1.5min to 2.5min. The main component of tetramethylammonium hydroxide (TMAH) aqueous solution is water, accounting for more than 99%. It is widely used for development in photolithography. Whether it is I-line, 248nm, 193nm, 193nm immersion or EUV, TMAH aqueous solution is used as developer. Sometimes, in order to avoid the collapse of the photoresist lines, a small amount of surfactant can be added to the TMAH aqueous solution.

[0017] Preferably, in step S3, the optimization menu includes gas, gas ratio, cavity gas pressure and radio frequency voltage.

[0018] Preferably, in step S3, the gas is trifluoromethyl and argon, trifluoromethyl: argon = 1:3, the chamber pressure is 25mTorr to 35mTorr, and the RF voltage is 150W to 250W. This mixing ratio helps to achieve a good etching effect, because the trifluoromethyl provides the active groups required for etching, while argon acts as a diluent to help control the etching rate and uniformity. The RF voltage is set between 150W and 250W. This power range can provide sufficient energy to excite the gas and form a plasma while avoiding excessive damage to the sample. Adjustment of the RF voltage will affect the density of the plasma and the energy of the ions, thereby affecting the etching rate and selectivity.

[0019] Preferably, in step S4, the etching recipe includes gas, gas ratio, chamber gas pressure and radio frequency voltage.

[0020] Preferably, in step S4, the gas is silicon tetrachloride, argon, and nitrogen, silicon tetrachloride: argon: nitrogen = 2:15:1, the chamber pressure is 4mTorr to 6mTorr, and the RF voltage is 90W to 110W. Silicon tetrachloride: argon: nitrogen = 2:15:1, this ratio helps to balance chemical etching and physical etching to achieve the desired etching effect;

[0021] Preferably, in step S5, the degumming liquid includes hydrofluoric acid. Hydrofluoric acid has a strong cleaning ability and can effectively remove photoresist and other substances. Especially in the fields of integrated circuits, liquid crystal displays, and semiconductors, hydrofluoric acid is widely used for cleaning, etching, and corroding and thinning chips.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides an HSQ exposure optimization method. After the electron beam photoresist mask is optimized by the present invention, structural adhesion is eliminated in the electron beam photoresist mask. The present invention optimizes the overexposure phenomenon of the electron beam photoresist mask, eliminates the influence, ensures that the mask can continue to be used, thereby not affecting the subsequent etching process and chip preparation effect, and improving the quality of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a process of HSQ exposure optimization method;

[0025] Figure 2 A schematic diagram of the preparation process of a HSQ exposure optimization method;

[0026] Figure 3 It is a schematic diagram of the effects of the present invention before, during and after optimization;

[0027] Figure 4 It is a schematic diagram of the effect after etching and de-resisting using the method of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0029] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0030] Embodiment 1

[0031] This embodiment is a first embodiment of a HSQ exposure optimization method. Figure 1 As shown, the following steps are included:

[0032] S1. Sample preparation: spin coating electron beam photoresist on the substrate surface to obtain a sample;

[0033] S2. Exposure: The sample is subjected to electron beam exposure, and after exposure, it is placed in a developer to develop to obtain an electron beam photoresist mask;

[0034] S3. Optimization: Place the developed sample into the reactive ion etcher, set the optimization menu and start the optimization;

[0035] S4. Etching: Place the optimized sample into the inductively coupled plasma etcher, set the etching menu, and start etching;

[0036] S5. Degumming: Place the etched sample into the degumming solution for degumming.

[0037] In step S1, the electron beam photoresist is HSQ photoresist. Hydrogenated siloxane (HSQ) is a negative resist commonly used in electron beam lithography. Because it has an extremely high resolution and can reach the sub-10 nanometer level, it is widely used in the field of micro-nano processing. The present invention optimizes the overexposure phenomenon that often occurs during HSQ exposure to eliminate the influence of overexposure and eliminate adhesion between structures, so that HSQ photoresist can be better used and the quality of subsequent etching process and chip preparation is improved.

[0038] In step S2, the beam current of the electron beam exposure is 0.7nA to 0.9nA, and the dose is 750μC / cm 2 ~850μC / cm 2 . Using TMAH developer, the development time is 1.5min to 2.5min. The main component of tetramethylammonium hydroxide (TMAH) aqueous solution is water, accounting for more than 99%. It is widely used in the development of photolithography. Whether it is I-line, 248nm, 193nm, 193nm immersion or EUV, TMAH aqueous solution is used as the developer. Sometimes, in order to avoid the collapse of the photoresist lines, a small amount of surfactant can be added to the TMAH aqueous solution.

[0039] In step S3, the optimization menu includes gas, gas ratio, chamber pressure and RF voltage. The gases are trifluoromethyl and argon, trifluoromethyl: argon = 1:3, the chamber pressure is 25mTorr~35mTorr, and the RF voltage is 150W~250W. This mixing ratio helps to achieve good etching effects, because trifluoromethyl provides the active groups required for etching, while argon acts as a diluent to help control the etching rate and uniformity. The RF voltage is set between 150W and 250W. This power range can provide sufficient energy to excite the gas and form a plasma while avoiding excessive damage to the sample. Adjustment of the RF voltage affects the density of the plasma and the energy of the ions, which in turn affects the etching rate and selectivity.

[0040] In step S4, the etching menu includes gas, gas ratio, chamber pressure and RF voltage. The gas is silicon tetrachloride, argon and nitrogen, silicon tetrachloride: argon: nitrogen = 2:15:1, the chamber pressure is 4mTorr~6mTorr, and the RF voltage is 90W~110W. Silicon tetrachloride: argon: nitrogen = 2:15:1, this ratio helps to balance chemical etching and physical etching to achieve the desired etching effect.

[0041] In the HSQ exposure optimization method of this embodiment, in step S2, there is structural adhesion in the electron beam photoresist mask due to electron beam overexposure, and after the electron beam photoresist mask is optimized in step S3, the structural adhesion is eliminated in the electron beam photoresist mask. The present invention optimizes the overexposure phenomenon of the electron beam photoresist mask, eliminates the influence, and ensures that the mask can continue to be used, thereby not affecting the subsequent etching process and chip preparation effect.

[0042] Embodiment 2

[0043] This embodiment is a second embodiment of a HSQ exposure optimization method. This embodiment is similar to the first embodiment, except that: Figure 2 As shown, the following steps are included:

[0044] Step S1. Sample preparation: Spin-coating HSQ electron beam photoresist on the surface of a gallium arsenide substrate to obtain a sample; Gallium arsenide has high electron mobility and direct bandgap characteristics, which makes it suitable for high-speed and photoelectric conversion applications. In particular, it performs well in radio frequency and optoelectronic devices. As a substrate material, gallium arsenide has a wide range of applications and importance in semiconductor device manufacturing, especially in the fields of high frequency, high speed, optoelectronics and microwaves.

[0045] Step S2. Exposure: The sample is subjected to electron beam exposure, and after exposure, it is placed in a developer to develop and obtain a HSQ electron beam photoresist mask. The electron beam exposure parameters are a beam current of 0.8 nA and a dose of 800 μC / cm 2 ; The developing solution is TMAH and the developing time is 2 min.

[0046] Step S3. Optimization: Place the developed sample into a reactive ion etcher, and start optimization after setting the optimization menu; the optimization menu includes gas and ratio, chamber pressure, and RF voltage; the gas is trifluoromethyl and argon, the ratio is 1:3, the chamber pressure is 30mTorr, and the RF voltage is 200W.

[0047] Step S4. Etching: Place the optimized sample into the inductively coupled plasma etcher, set the etching menu, and start etching. The etching menu includes gas and ratio, chamber pressure, and RF voltage; the gas is silicon tetrachloride, argon, and nitrogen, the ratio is 2:15:1, the chamber pressure is 5mTorr, and the RF voltage is 100W.

[0048] Step S5. Degumming: placing the etched sample into a degumming solution for degumming.

[0049] like Figure 3As shown, before the optimization process, there is structural adhesion in the HSQ electron beam photoresist mask due to electron beam overexposure. During the optimization process, the structural adhesion caused by electron beam overexposure gradually disappears. After the HSQ electron beam photoresist mask is optimized by S3, the structural adhesion is eliminated in the HSQ electron beam photoresist mask.

[0050] This embodiment optimizes the overexposure of the HSQ mask to eliminate the structural adhesion caused by electron beam overexposure, ensuring that the mask can continue to be used, thereby not affecting the subsequent etching process and chip preparation effect, and improving the quality of the chip.

[0051] Embodiment 3

[0052] This embodiment is a third embodiment of a HSQ exposure optimization method, and this embodiment is similar to the first embodiment, except that in step S5, the degumming solution includes hydrofluoric acid. Hydrofluoric acid has a strong cleaning ability and can effectively remove photoresist and other substances. In particular, in the fields of integrated circuits, liquid crystal displays, and semiconductors, hydrofluoric acid is widely used for chip cleaning, etching, and corrosion thinning.

[0053] like Figure 4 As shown, after the etching and de-resisting in this embodiment, the structural adhesion phenomenon caused by electron beam overexposure in the HSQ electron beam photoresist mask is completely eliminated, ensuring that the mask can continue to be used, thereby not affecting the subsequent etching process and chip preparation effect, and improving the quality of the chip.

[0054] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A HSQ exposure optimization method, characterized in that: The following steps are involved: S1. Sample preparation: spin coating electron beam photoresist on the substrate surface to obtain a sample; S2. Exposure: The sample is subjected to electron beam exposure, and after exposure, it is placed in a developer to develop to obtain an electron beam photoresist mask; S3. Optimization: Place the developed sample into the reactive ion etcher, set the optimization menu and start the optimization; S4. Etching: Place the optimized sample into the inductively coupled plasma etcher, set the etching menu, and start etching; S5. Degumming: Place the etched sample into the degumming solution for degumming.

2. The HSQ exposure optimization method according to claim 1, characterized in that: In step S1, the electron beam photoresist is HSQ photoresist.

3. The HSQ exposure optimization method according to claim 1, characterized in that: In step S1 , the substrate includes gallium arsenide.

4. The HSQ exposure optimization method according to claim 1, characterized in that: In step S2, the beam current of the electron beam exposure is 0.7nA to 0.9nA, and the dose is 750μC / cm 2 ~850μC / cm 2 .

5. The HSQ exposure optimization method according to claim 1, characterized in that: In step S2, TMAH developer is used, and the developing time is 1.5 min to 2.5 min.

6. The HSQ exposure optimization method according to claim 1, characterized in that: In step S3, the optimization menu includes gas, gas ratio, cavity gas pressure and radio frequency voltage.

7. The HSQ exposure optimization method according to claim 6, characterized in that: In step S3, the gases are trifluoromethyl and argon, trifluoromethyl:argon=1:3, the cavity pressure is 25mTorr-35mTorr, and the radio frequency voltage is 150W-250W.

8. The HSQ exposure optimization method according to claim 1, characterized in that: In step S4, the etching recipe includes gas, gas ratio, chamber pressure and radio frequency voltage.

9. The HSQ exposure optimization method according to claim 8, characterized in that: In step S4, the gases are silicon tetrachloride, argon, and nitrogen, silicon tetrachloride: argon: nitrogen = 2: 15:1, the cavity pressure is 4mTorr~6mTorr, and the RF voltage is 90W~110W.

10. The HSQ exposure optimization method according to claim 1, characterized in that: In step S5, the degumming solution includes hydrofluoric acid.

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