Photoresist-removing liquid and photoresist-removing method

Abstract

The present invention discloses a photoresist-removing solution comprising of an N-containing compound and an organic substance in a mass ratio of 1:(0.5-150). The N-containing compound includes at least one of the followings: tetraalkylammonium hydroxide, ammonia, liquid ammonia, and a mixture of ammonia and water; wherein the tetraalkylammonium hydroxide has the general formula (I): ##STR00001##
wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4 is an alkyl with 1 to 4 carbons, respectively. The organic substance is an organic substance having at least one electron-withdrawing functional group. The present invention mixes a specific kind of N-containing compound and a specific kind of organic substance in a certain ratio, and preferably adds a certain amount of water, so that the removal liquid in the present application has an extremely excellent photoresist-removing effect.

Claims

1. A photoresist-removing method, comprising: using a removal liquid to remove photoresist, wherein the removal liquid comprises an N-containing compound and an organic substance in a mass ratio of 1:(0.5-150), and the N-containing compound including at least one of the following: a tetraalkylammonium hydroxide, ammonia, liquid ammonia, and a mixture of ammonia and water; wherein the tetraalkylammonium hydroxide has the general formula (I): ##STR00003## wherein R1, R2, R3, R4 is an alkyl with 1 to 4 carbons, respectively; wherein the organic substance is an organic substance with at least one electron-withdrawing functional group; mixing the removal liquid with a gas to form a gas-liquid mixture; and spraying the gas-liquid mixture on a surface of the photoresist.

2. The photoresist-removing method of claim 1, wherein the gas is a mixture of one or more of ammonia, oxygen, nitrogen, air or ozone.

3. The photoresist-removing method of claim 1, wherein the gas is air or oxygen, and the gas is partially or completely converted into ozone by an ozone generating device before being mixed with the removal liquid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an SEM image of test wafer A of the present invention before testing;

(2) FIG. 2 is a cross-sectional view of FIG. 1;

(3) FIG. 3 is an SEM image of the same position of FIG. 1 after spraying for 1 minute using the formulation of Example 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) The invention is further illustrated by the following examples, which are merely illustrative of the invention, and the invention is not limited to the following examples.

(5) In the following examples, the used chemical liquids are all electronic grades, wherein the mass concentration of ammonia water (mixture of ammonia and water) is 25-28%. For the convenience of calculation, the mass concentration of ammonia water in the following embodiments is 28% for calculation. In the following embodiments, the test wafer for testing the removal effect is prepared by applying a 1 micron thick positive photoresist currently used on the entire surface of the wafer by means of a rotating or sliding device (model AZ701, AZ Electronics Materials), which is pre-baked at a temperature of approximately 150° C. using a hot plate or an oven, exposed using photomasks with different patterns according to different wafers, developed, dried, post-baked, plasma etched, and then the test wafer is finally obtained; the test wafer is cut into squares having a width of about 1.5 cm according to different patterns, and the wafer mainly having a large-sized structure is the test wafer A, and the test is performed. The SEM image of wafer A before testing is shown in FIGS. 1-2. The wafer with long thin strip structure is the test wafer B, and the wafer with short thick strip structure is the test wafer C, and the removal effect test is performed separately.

Embodiment 1

(6) Acetone and ammonia were mixed according to the mass ratio of Table 1, and several sets of removal liquids were obtained (Examples 1-14, the specific ratios are shown in Table 1).

(7) TABLE-US-00001 TABLE 1 Acetone-Ammonia Water Removal Mixtures in Different Ratios Ammonia in Acetone Ammonia water ammonia Water Example (wt. %) (wt. %) (wt. %) 1 100 0 0 2 98.21 1.79 0.50 3 96.43 3.57 1.00 4 94.64 5.36 1.50 5 91.07 8.93 2.50 6 87.50 12.5 3.50 7 85.00 15 4.20 8 82.14 17.86 5.00 9 64.29 35.71 10.00 10 46.43 53.57 15.00 11 28.57 71.43 20.00 12 21.40 78.6 22.00 13 13.90 86.1 24.10 14 0.00 00 28.00

(8) The removal effects of the removal solutions obtained in the above Examples 1-14 were tested by several processes. (In the test table for removal effect: evaluation from residual area, x—indicates almost no removal effect (residual >95%); Δ—indicates effect but not completely removed; ◯—indicates no visible residual photoresist under 160 times microscope).

(9) The specific method is listed hereafter.

(10) Method 1: 14 test wafers A, test wafers B, and test wafers C were respectively taken, immersed in the removal liquid of the above Examples 1-14 at normal temperature, and shaken slightly, taken out after 1 minute, and blown dry with nitrogen. The final removal effect is shown in Table 2 by visual observation and microscopic observation.

(11) TABLE-US-00002 TABLE 2 Removal effect of immersion method Example Test wafer A Test wafer B Test wafer C 1 x x x 2 x x x 3 x x x 4 x x x 5 x x x 6 Δ Δ Δ 7 Δ Δ Δ 8 Δ Δ Δ 9 Δ Δ Δ 10 Δ Δ Δ 11 Δ Δ Δ 12 Δ Δ Δ 13 Δ Δ Δ 14 x x x

(12) As shown in Table 2, the above removal solution and Method 1 did not remove the photoresist completely. In fact, Examples 9, 10, 11 and 12 work best, with only a small amount (<5%) of photoresist residual while the removal solutions of Examples 3 and 4 only enable lithography layer of the test wafer to be cracked and slightly thinned (residual area >99%).

(13) If the immersion time is extended, the photoresist can be completely removed as the immersion time of the removal liquid using the removal liquids of Examples 8-12 reaches 3 minutes.

(14) Method 2: The removal solution prepared in Examples 1-14 was mixed with oxygen through a mixing device, and then sprayed onto the test wafer A, the test wafer B, and the test wafer C at normal temperature for 1 minute; the wafers were dried using nitrogen gas and observed by naked eye and microscope. The final removal effect is shown in Table 3. In the experiment, the oxygen pressure was 10 psi, and the liquid pressure of the removal solution was 7 psi. The solution was sprayed through a 1/16 inch tube.

(15) The above mentioned mixing device and mentioned mixing method can be referred to the description of the gas-liquid mixing device in another patent application of the applicant (WO/2016/023414).

(16) TABLE-US-00003 TABLE 3 i. Removal effect of spray method (1 minute) Example Test wafer A Test wafer B Test wafer C 1 ∘ Δ Δ 2 ∘ Δ Δ 3 ∘ Δ Δ 4 ∘ Δ Δ 5 ∘ Δ Δ 6 ∘ Δ Δ 7 ∘ Δ Δ 8 ∘ ∘ ∘ 9 ∘ ∘ ∘ 10 ∘ ∘ ∘ 11 ∘ ∘ ∘ 12 ∘ ∘ ∘ 13 ∘ ∘ ∘ 14 Δ Δ Δ

(17) It can be seen from Table 3 that the spray method can be better applied in the test wafer A mainly for the large-sized structure. For the test wafer B and the test wafer C that have smaller structures, the removal efficiency will deteriorate when the ammonia gas concentration is too low (Examples 1-7) or the acetone content is too low (Example 14). In the embodiment 14, the partial block photoresists detached from the surface of the wafer is reattached to the original photoresist at other positions again, indicating that the individual ammonia molecules or ammonia water in the removal liquid have a stripping effect and a dissolving effect on the photoresist. FIG. 3 is an SEM image of the formulation of Example 11 after 1 minute spraying.

(18) When the oxygen in Method 2 is replaced with air or nitrogen, the removal effect is not significantly different from oxygen. However, when ozone was used instead of oxygen (using oxygen as a raw material and directly used to prepare ozone by a 5 g/L ozone generator), the removal liquid of Example 7 was used, and the photoresist residuals on the test wafer B and the test wafer C were not observed, indicating that the addition of ozone significantly contributes to the removal of the removal solution.

(19) Utilizing the formulation of Examples 8-13 therein, the spray time of Method 2 was shortened to 35 s, and the results are shown in Table 4.

(20) TABLE-US-00004 TABLE 4 ii. Removal effect of spray method (35 s) Example Test wafer A Test wafer B Test wafer C 8 ∘ Δ Δ 9 ∘ Δ Δ 10 ∘ Δ Δ 11 ∘ Δ ∘ 12 ∘ ∘ ∘ 13 ∘ Δ Δ

(21) As shown in Table 4, under the shortening time, the removal effect of the removal liquid of Example 12 (acetone 21.40 wt. %, ammonia water 78.60 wt. %) was the best. In Example 12, by conversion, it was found that the mass ratio of acetone to ammonia was about 1:1.

(22) Further, the removal liquid of Example 12 is directly flowed (ie, not mixed with oxygen or other gas, but directly sprayed) onto the surface of the test wafer in 35 seconds, which is dried by nitrogen then; it is found by microscopy that the photoresist on the wafer A (large pattern) and the test wafer C (short thick strip) were both removed well with no residue observed, and there was a very small amount of residue on the test wafer B (long strip).

(23) For further illustrating the effect of water in the present invention, several sets of comparative examples are provided herein (Comparative Examples 1-8, specific ratios shown in Table 5).

(24) TABLE-US-00005 TABLE 5 iii. acetone-ammonia water-water mixture removal liquid Acetone Ammonia water Example (wt. %) (wt. %) (wt. %) 1 21.4 5 73.6 2 21.4 15 63.6 3 5 5 90 4 15 15 70 5 26.2 5 68.8 6 23.4 15 61.6 7 5 22 73 8 15 22 63

(25) In the above table, the mass percentage of ammonia is calculated by multiplying the mass percentage of ammonia by 28%, and the mass percentage of water is the mass percentage of ammonia multiplied by 72% plus the mass percentage of water added separately.

(26) The removal liquid in the above comparative example was sprayed onto the surface of the test wafer A by the method 2, and after drying for 1 minute, it was blown with nitrogen and observed under a microscope. All the comparative solutions were not effective in removing the photoresist, and no significant change was observed in Comparative Examples 3, 4, 7, and 8. Comparative Example 1 showed little change, and only a small amount of cracks were observed (residual area >99%), the photoresist in Comparative Example 5 has more thinning phenomenon, and the majority of Comparative Example 6 is removed (residual area <60%), and the remaining portion is thinned, the similar parts of Comparative Example 2 and Comparative Example 6 were removed and the remaining parts were thinned. It can be seen that under this experimental condition, after adding excess water, the mass concentration of acetone or ammonia is reduced, so that the removal effect of the removal liquid is degraded.

Embodiment 2

(27) The photoresist-removing liquid containing tetraalkylammonium hydroxide is further illustrated by the following examples 15-21. The proportions of the components in the above examples are shown in Table 6; in tetraalkylammonium hydroxide.

(28) TABLE-US-00006 TABLE 6 Tetraalkylammonium hydroxide-organic- water mixed removal liquid Tetraalkylammonium hydroxide Water Ethanol Example (wt. %) (wt. %) (wt. %) 15 25 60 00 16 7.5 40 30 17 15 30 40 18 3 26 55 19 0.5 24 70 20 1.5 22 90 21 0 8 95

(29) The above seven groups of photoresist-removing liquids were applied by spraying (mix nitrogen and removal liquid) for 3 min to remove the photoresist. The method was consistent with the examples, and the specific effects were as follows:

(30) TABLE-US-00007 TABLE 7 Removal effect of tetraalkylammonium hydroxide- organic-water mixed removal solution Example Test wafer A Test wafer B Test wafer C 15 Δ x x 16 Δ x x 17 Δ x x 18 ∘ ∘ ∘ 19 Δ Δ Δ 20 Δ Δ x 21 x x x

(31) It can be seen from Table 7 that only when the tetraalkylammonium hydroxide, water and organic substance are within a certain range, the effect is better. On this basis, the tetraalkylammonium hydroxide in the mixture can achieve the desired photoresist-removing effect at a lower concentration. At very low concentrations (Example 19), the photoresist was removed, but the effect was weak. With the reduction of organic substance and even the absence of organic substance (Example 15), the removal ability of the mixture was also significantly weakened.

(32) It should be noted that the above Examples 15-21 are only a brief introduction to the photoresist-removing liquids containing tetraalkylammonium hydroxide, wherein tetramethylammonium hydroxide can also use tetraalkylammonium hydroxide with 2-4 carbons, the weight ratio of organic substances can also be adjusted according to different photoresists, and the specific photoresist-removing method is not limited to the spray method, and the above immersion method, etc. can also be used for photoresist-removing. Utilizing the spray method, the gases such as oxygen, ozone, ammonia, etc. can also be selected.

(33) In the present invention, the optimum ratio of the components and the optimum conditions of the process in the chemical formulation will vary depending on the composition and structure of the photoresist and the manufacturing process.

(34) The above embodiments are merely illustrative of the technical concept and the features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the present invention and to implement the present invention, and the scope of the present invention is not limited thereto. Equivalent variations or modifications made in accordance with the spirit of the invention are intended to be included within the scope of the invention.