AQUEOUS ALKALINE PRE-TREATMENT SOLUTION FOR USE PRIOR TO DEPOSITION OF A PALLADIUM ACTIVATION LAYER, METHOD AND USE THEREOF

Abstract

The invention relates to an aqueous alkaline pre-treatment solution for use prior to deposition of a palladium activation layer on a substrate in manufacturing an article with an integrated circuit and a method and use thereof, wherein the solution comprises: at least one hydroxycarboxylic acid or salt thereof according to the general formula (I)

[RCH.sub.2—(RCH).sub.n—COO.sup.−].sub.m M.sup.m+  (I)

wherein n is integer from 2 to 4 and m is 1 or 2, R is independently H or OH with proviso that at least one R is OH, and wherein M.sup.m+ with m: 1 is hydrogen, ammonium or alkali metal; or M.sup.m+ with m: 2 is earth alkali metal, at least one polyoxyethylene sorbitan fatty acid ester, at least one sulphonated fatty acid or a salt thereof.

Claims

1. Aqueous alkaline pre-treatment solution for comprising: at least one hydroxycarboxylic acid or salt thereof according to the general formula (I)
[RCH.sub.2—(RCH).sub.n—COO.sup.−].sub.m M.sup.m+  (I) wherein n is integer from 2 to 4 and m is 1 or 2, R is independently H or OH with proviso that at least one R is OH, and wherein M.sup.m+ with m: 1 is hydrogen, ammonium or alkali metal; or M.sup.m+ with m: 2 is earth alkali metal, at least one polyoxyethylene sorbitan fatty acid ester, at least one sulphonated fatty acid or a salt thereof.

2. Aqueous alkaline pre-treatment solution according to claim 1 wherein the concentration of the at least one hydroxycarboxylic acid or salt thereof is from 200 to 400 mg/L.

3. Aqueous alkaline pre-treatment solution according to claim 1 wherein the concentration of the at least one polyoxyethylene sorbitan fatty acid ester is from 0.4 to 1.2 mg/L.

4. Aqueous alkaline pre-treatment solution according to claim 1 wherein the sulphonated fatty acid is selected from the group consisting of unsaturated branched or unbranched C16 to C20 fatty acids or mixtures thereof.

5. Aqueous alkaline pre-treatment solution according to claim 1 wherein the concentration of the at least one sulphonated fatty acid is from 4 to 12 mg/L.

6. Aqueous alkaline pre-treatment solution according to claim 1 wherein the solution has a pH from 8-12.

7. Method for pre-treatment of a substrate for subsequent deposition of a palladium activation layer on said substrate in manufacturing an article with an integrated circuit comprising the steps in the following order: (i) providing the substrate having at least one conductive metal layer surface and at least one non-conductive surface; (ii) providing the aqueous alkaline pre-treatment solution according to claim 1; (iii) treating the substrate with the pre-treatment solution by bringing the substrate into contact with the aqueous pre-treatment solution.

8. Method of claim 7, wherein the method further comprises the step: (iv) treating the substrate of step (iii) with a palladium activation solution wherein a palladium ion layer is deposited onto the surfaces of the treated substrate of step (iii).

9. Method of claim 8 wherein the method further comprises the step: (v) treating a substrate of step (iv) with palladium reduction solution wherein the deposited palladium ion layer in step (iv) is transformed into a metallic palladium layer.

10. Method according to claim 7 wherein the at least one conductive metal layer surface is a copper layer surface.

11. Method according to claim 8 wherein the palladium ion layer is deposited onto the at least one non-conductive surface of the treated substrate of step (iii).

12. Method of using of the aqueous pre-treatment solution according to claim 1 for subsequent deposition of a palladium ion layer on a substrate in manufacturing an article with an integrated circuit wherein the solution is applied directly before applying a palladium activation solution in order to minimize a palladium particle formation while forming the palladium ion layer.

13. Method of using the aqueous pre-treatment solution according to claim 1 for subsequent deposition of a metal layer in manufacturing an article with an integrated circuit.

14. Method of using the aqueous pre-treatment solution according to claim 1 for metallization of at least one recessed structure of the at least one non-conductive surface in manufacturing an article with an integrated circuit.

15. Method according to claim 14, wherein the at least one recessed structure is selected from the group consisting of blind micro vias (BMVs), through hole vias (THVs), through glass vias (TGVs), through silicon vias (TSVs), buried vias, and mixtures of any of the aforementioned.

Description

EXAMPLES

[0061] The invention will now be illustrated by reference to the following non-limiting examples. The relative ratio of the used compounds of the present invention within the examples were found as preferable useful, but are not considered as limiting.

[0062] I. Backlight Test: Investigation of metal or metal alloy coverages of surfaces in recessed structures

[0063] The coverage of the surfaces of recessed structures with metal or metal alloy in the process can be assessed using an industry standard Backlight Test, in which a plated coupon is sectioned, so as to allow areas of incomplete coverage to be detected as bright spots when viewed over a strong light source [confer US 2008/0038450 A1, incorporated herein by reference in its entirety]. The quality of the metal or metal alloy deposit is determined by the amount of light that is observed under a conventional optical microscope.

[0064] The results of the backlight measurement are given on a scale from D1 to D10, wherein D1 means the worst result and D10 the best result. Reference samples showing results from D1 to D10 are shown in FIG. 3 of WO 2013/050332 (incorporated herein by reference).

[0065] The following substrates as coupons were used in different tests: Coupons based on the materials DE104, DE117, IS410 and 185 HR (from Isola), R-1755C (from Matsushita/Panasonic), NP140, NP140 TL and NP170 (from Nan Ya), S1141 (from Shengy), KB6160A (from Kingboard) and IT-185-TC (from lteq) were utilized. The hole diameter in the coupons was 1 mm. If necessary, the substrates were subjected to a desmear and cleaning treatment which is known in the art before applying the solutions of the Inventive Examples or Comparative Examples.

[0066] After applying the solutions of the Inventive Examples or Comparative Examples all coupons were used directly in the process described in the following Table I. The substrates were immersed in the given order for the time and temperature as given in Table into the solutions.

TABLE-US-00001 TABLE I Process for depositing copper on substrates. Treatment corresponds to t [s] T [° C.] Palladium activation solution Step (iv) 40 45 Neoganth ® U Activator Palladium reduction solution Step (v) 30 30 Neoganth ® P WA Electroless copper solution Step (vi) 600 32 e.g. Printoganth ® U Plus

[0067] Neoganth® U Activator Bath [0068] palladium ion concentration: 300 mg/L [0069] pH: 10

[0070] Neoganth P-WA Bath [0071] Neoganth P-WA concentration: 6 mL/L [0072] pH: 8

[0073] Electroless Copper Bath [0074] copper ion concentration: 2.25 g/L [0075] nickel ion concentration: 0.5 g/L [0076] Formaldehyde concentration 4 g/L [0077] NaOH concentration: 14 g/L [0078] Tartrate concentration: 19 g/L [0079] cyanide concentration: 0,006 g/L

Inventive Example 1

[0080] In the following example, the coupons based of material ISOLA IS410 were tested with different conditions (see Table II) for temperature [° C.]/amount [ml] of stock solution/pH value (e.g. 30/150/10 shows a coverage result of D8.5.)

[0081] The coupons were pre-treated with the aqueous alkaline pre-treatment solution of the present invention, wherein 120 mL (Inventive Example 1a), 150 mL (Inventive Example 1b) and 180 mL (Inventive Example 1c) of the stock solutions were provided and diluted with alkaline water to a total volume of 1 L to get the inventive aqueous alkaline pre-treatment solution, and applied according to the conditions of Table II. The stock solution has the following composition and conditions: [0082] Concentration: [0083] Gluconate: 1,9 g/L [0084] polyoxyethylene sorbitan monostearate : 0.005 g/L [0085] Sulphonated monopalmitoleate acid: 0.046 g/L [0086] Temperature: 35° C. [0087] pH: 10

[0088] The coupons were subsequently treated according to the process in Table I above.

[0089] The results of the backlight measurement are given on a scale from D1 to D10, wherein D1 means the worst result and D10 the best result, D7-D10 are desired results.

[0090] It can be seen that the pre-treatment solution shows excellent results in the given working ranges according to pH, concentrations and also according to working temperature.

TABLE-US-00002 TABLE II Coverage results Dx Test on IS410 Ø: 1.0 mm 30/150/10 8.5 20/180/11 8.1 20/180/9 8.3 20/150/11 8.4 20/120/10 8.3 20/120/11 8.1 20/150/10 8.3 20/150/9 8.1 20/180/10 8.4 20/120/9 7.9 30/180/10 8.4 30/150/11 9.0 30/180/11 8.1 30/150/9 9.3 30/120/11 8.1 30/180/9 8.9 30/120/10 8.1 30/150/10 8.6 30/120/9 8.5 40/180/10 8.7 40/150/9 9.0 40/150/10 8.2 40/120/10 8.2 40/120/11 8.4 40/120/9 8.2 40/180/9 8.3 40/150/11 8.2 40/180/11 8.4

Comparative Example 1

[0091] The following different coupons were pre-treated with an aqueous acidic pre-treatment solution of the following composition and conditions: [0092] Concentration: [0093] Sodium bisulfate: 0.7 g/L [0094] PEG 1200: 0.1 g/L [0095] derivative of benzenesulfonic acid: 0.18 g/L [0096] Temperature: 25° C. [0097] pH: 3

[0098] Backlight Test:

[0099] The backlight results are shown in Table III. The copper coverage was evaluated on the basis of the treated coupons. The backlight values were obtained from the backlight coupons. It can be seen, that the present invention is well working over a wide area of different base materials.

TABLE-US-00003 TABLE III Backlight values Comparative Inventive Test Example 1 Example 1b Isola 185 HR 7.0 6.1 CEM3 6.5 6.5 IT-158-TC 6.3 6.3 NP140 7.2 7.1 S1141 7.8 6.9 DE117 6.5 6.2 R1755C 6.6 5.3 NP170 6.4 7.4 DE104 6.1 6.9 NP140 TL 5.5 5.5 KB6160A 5.5 5.0 IS410 7.6 8.0

Comparative Example 2-5

[0100] The coupons ISOLA IS 410, having hole diameter of 1 mm, were subjected to a desmear and cleaning treatment which is known in the art and were then pre-treated with aqueous pre-treatment solutions of pH 10 containing different additives of the following: [0101] Comparative Example 2: fatty alcohol polyalkylene glycol ether concentration: 0.015 g/L [0102] Comparative Example 3: Potassium sorbate concentration: 0.02 g/L [0103] Comparative Example 4: Sulfosalicylic acid: 0.0243 g/L [0104] Comparative Example 5: PEG 1200 concentration: 0.1 g/L

[0105] After the pre-treatment step according to the Inventive Example 1b and the Comparative Example 2-5 all coupons were treated directly after the pre-treatment step in the same way as described above in Table I.

[0106] The backlight results for coupons are summarised in Table IV. The copper coverage was evaluated on the basis of the treated coupons. The backlight values were obtained from the backlight coupons ISOLA IS 410 of Inventive Example 1b and Comparative Examples 2-5.)

TABLE-US-00004 TABLE IV Backlight Result Inventive Example 1b 8.6 Comparative Example 2 - Fatty alcohol polyalkylene 8.3 glycol ether Comparative Example 3 - Potassium sorbate 5.6 Comparative Example 4 - Sulfosalicylic acid 6 Comparative Example 5 - PEG 1200 3.9

[0107] II. Foaming Behaviour of Pre Dip-Contaminated Activator Baths

[0108] Following substrate treatment with the so-called pre dip containing the pre-treatment solution, the substrate is directly transferred to the alkaline ionic palladium activation solution without rinsing. Thus, the palladium activation solution is directly contaminated with the components in the pre dip treatment solution.

[0109] Table V shows the foaming behaviour of an uncontaminated catalyst treatment solution, a catalyst treatment solution contaminated with pre dip according to the composition described in Comparative Example 1 and a catalyst treatment solution contaminated with pre dip according to the composition described in Inventive Example 1b. It can be seen that the catalyst treatment solution contaminated with pre dip according to the composition described in Inventive Example 1b displays significantly less foam than the catalyst treatment solution contaminated with pre dip according to the composition described in Comparative Example 1, thereby demonstrating the markedly improved foaming characteristics of Inventive Example 1b.

TABLE-US-00005 TABLE V Unused palladium activation solution with drag in of 100% water  5 ml Palladium activation solution with drag in of 100% Inventive 13 ml Example 1b Palladium activation solution with drag in of 100% Comparative 71 ml Example 1

[0110] III. Particle Formation in Pre Dip-Contaminated Palladium Activation Solution

[0111] Following the substrate treatment with the pre-treatment solution (pre dip), the substrate is directly transferred to the alkaline ionic palladium catalyst without rinsing. Thus, the catalyst is directly contaminated with the components in the pre dip treatment solution. Table VI depicts the particle formation behaviour of an uncontaminated catalyst treatment solution, a catalyst treatment solution contaminated with pre dip according to the composition described in Comparative Example 1 and a catalyst treatment solution contaminated with pre dip according to the composition described in Inventive Example 1 b. It can be seen that the catalyst treatment solution contaminated with pre dip according to the composition described in Inventive Example 1b contains significantly fewer particles than the catalyst treatment solution contaminated with pre dip according to the composition described in Comparative Example 1, thereby demonstrating the markedly improved particle formation characteristics of Inventive Example 1b.

TABLE-US-00006 TABLE VI Pre Dip-contaminated activator Particle Mean size Standard bath (1:10 diluted) amount/mL [μm] dev. [μm] Comparative example 1 168.2k   2.719 1.03 Inventive example 1b 68k 2.869 1.46 “Water-contaminated“ for 34k 3.107 1.14 comparison

[0112] IV. Electrical Reliability Test

[0113] In order to measure the effect on electrical reliability of a particular treatment solution, the so-called solder shock test, which is known in the art, is often used. In this test, suitable coupons with copper inner layers are desmeared, cleaned, activated, electrolessly plated, electrolytically reinforced and prepared for solder shocking as known in the art. The coupons are then subjected to solder shocking treatment according to the conditions required and examined under a microscope after appropriate sample embedding and cross-section preparation by grinding. The number of interconnect defects (ICDs), that is, the number of separations between the coupon copper inner layers and the deposited copper, are counted while viewing the samples through the microscope: the fewer the ICDs counted, the higher the electrical reliability of the system under investigation.

[0114] Table VII contains the solder shock test results of coupons treated with a pre dip solution according to Inventive Example 1b and coupons treated with a pre dip solution according to Comparative Example 1. For the following two tests, the solder bath temperature was used at 288° C. or at 326° C. and the following solder shocking procedure was applied in the given order: [0115] 1. Coupon floated on 288 or 326° C. solder surface for 10 s, [0116] 2. Coupon removed from 288 or 326° C. solder surface and allowed to cool on a non-conductive surface until room temperature is reached, [0117] 3. Coupon turned over and floated a new on 288 or 326° C. solder surface for 10 s, [0118] 4. Steps 2 and 3 repeated until coupon floated a total of 6 for 288° C. and 9 times for 326° C., [0119] 5. Embedding and cross-section preparation.

TABLE-US-00007 TABLE VII Coupon Sample ID 1 2 3 Total % ICDs 6× at 288° C. Comparative Example 1 1/287 0/274 0/287 1/848 0.12 Inventive example 1b 0/285 9/288 0/277 9/850 1.06 (after make-up) Inventive example 1b 0/255 0/262 0/261 0/778 0.00 (end of lifetime) ICDs 9× at 326° C. Comparative Example 1 36/282  41/284  28/285  105/851  12.34 Inventive example 1b 35/288  14/77  10/275  59/640  9.22 (after make-up) Inventive example 1b 0/265 1/276 1/268 2/809 0.25 (end of lifetime)

[0120] It can be seen in Table VII, that the solder shock test performance of Inventive Example 1 b is indistinguishable from that of Comparative Example 1 for 288° C. test conditions. According to even harder 326° C. test conditions it can be seen, that electrical reliability of the Inventive Example 1b was slightly better than of the Comparative Example 1 and was improved while running the solution over time.

[0121] With the testing of the Inventive Example 1b “real production conditions over time” were simulated, due to the direct drag-in inventive solution into the activator module containing the palladium activation solution. Thereby, the complete amount of the inventive solution plus a certain copper amount is transferred to and located in the palladium activation solution in a minimum of time. In order to simulate this sequence, a complete make-up amount of Inventive Example (150 ml/l) was poured at once into the palladium activation solution. Afterwards 100 ppm copper ions in form of dissolved CuSO.sub.4×5 H.sub.20 were added and the pH value of the palladium activation solution was adjusted according to the relevant technical data sheet (TDS).

[0122] The amount of 100 ppm copper ions refers to the TDS of all conventional pre dip solutions (pre-treatment solutions), wherein this amount of copper ions is set as limit.