Method for evaluating electroless plating

Claim 3

An evaluating method according to claim 1, further comprising the step of determining the Tafel slope β a of anodic reaction of the metal test piece, said step comprising: (i) instantaneously feeding the electrical double layer of the test piece with a charge qβ a whose absolute value is larger than that of charge q R , thereby changing the potential of the test piece to have a predetermined polarization potential η.sub.β.sbsb.a whose value is positive and higher than the polarization potential η R ; (ii) measuring, as function of time, the variation of the polarization potential η.sub.β.sbsb.a (t) of the test piece due to an electroless plating reaction, using the reference electrode; and (iii) calculating the Tafel slope β a of the test piece based on the polarization potential η.sub.β.sbsb.a (t) of the test piece measured as a function of time; said evaluation method also comprising the step of determining the Tafel slope β c of cathodic reaction of the test piece, said step comprising: (i) instantaneously feeding the electrical double layer of the test piece with a charge q.sub.β.sbsb.c whose absolute value is larger than that of the charge q R and whose polarity is opposite to that of the charge q.sub.β.sbsb.a, thereby changing the potential of the test piece to have a predetermined polarization potential η.sub.β.sbsb.c whose value is negative; (ii) measuring, as a function of time, the variation of the polarization potential η.sub.β.sbsb.c (t) of the test piece due to an electroless plating reaction, using the reference electode; and (iii) calculating a Tafel slope β c of the test piece based on the polarization potential η.sub.β.sbsb.c (t) of the test piece measured as a function of time, and said evaluation method also comprising the step of calculating the electroless plating current density I ELP of the test piece based on the reaction resistance R ELP , anodic Tafel slope β a and cathodic Tafel slope β c , the electroless plating current density I ELP being proportional to the rate of electroless plating V ELP ;, whereby the electroless plating is evaluated by evaluating the electroless plating current density I ELP .

Claim 4

A method according to claim 1, wherein the step of determining said initial polarization potential η R (O) includes the step of extrapolating the variation of the polarization potential η R (t) as a function of time.

Claim 5

A method according to claim 1, in which the step of calculating said reaction resistance R ELP includes the step of determining the differential capacitance C D of the electrical double layer of the test piece from the charge density, Δq=q/S, of the charge fed to the test piece per unit area and from the initial polarization potential η R (0).

Claim 6

A method according to claim 4 wherein the step of determining said differential capacitance includes the steps of dividing said charge density Δq by said initial polarization potential η R (0) and wherein the step of calculating said reaction resistance R ELP includes the step of measuring the slope of the logarithm of η R (t).

Claim 7

A method according to claim 2, in which the step of determining said Tafel slope β a of anodic reaction includes the steps of sampling, from the polarization potential η.sub.β.sbsb.a (t), polarization potentials η.sub.β.sbsb.a (t 1 ), η.sub.β.sbsb.a (t 2 ) and η.sub.β.sbsb.a (t 3 ) at times t 1 , t 2 , and t 3 respectively and using the following equation: ##EQU17##

Claim 8

A method according to claim 6, in which the step of sampling said polarization potentials includes the step of ensuring that η.sub.β.sbsb.a (t.sub.1)-η.sub.β.sbsb.a (t.sub.2)=η.sub.β.sbsb.a (t.sub.2)-η.sub.β.sbsb.a (t.sub.3)=Δη.sub.β.sbsb.a and wherein the step of obtaining Tafel slope β a includes the step of performing the following division: ##EQU18##

Claim 9

A method according to claim 2, in which the step of determining said Tafel slope β a of anodic reaction includes the steps of sampling the variation of the polarization potential η.sub.β.sbsb.a (t) to obtain polarization potentials η.sub.β.sbsb.a (t 1 ), η.sub.β.sbsb.a (t 2 ), η.sub.β.sbsb.a (t 3 ), . . . η.sub.β.sbsb.a (t n ) at times t 1 , t 2 , t 3 , . . . t n respectively such that η.sub.β.sbsb.a (t.sub.1)-η.sub.β.sbsb.a (t.sub.2)=η.sub.β.sbsb.a (t.sub.2)-η.sub.β.sbsb.a (t.sub.3)= . . . =η.sub.β.sbsb.a (t.sub.n -1)-η.sub.β.sbsb.a (t.sub.n)=Δη.sub.β.sbsb.a, and performing the following division: β.sub.a =Δη.sub.β.sbsb.a /logδ where ##EQU19##

Claim 10

A method according to claim 2, in which the step of determining said Tafel slope β c of cathodic reaction includes the steps of sampling the variation of the polarization potential η.sub.β.sbsb.c (t) to obtain polarization potentials η.sub.β.sbsb.c (t 1 ), η.sub.β.sbsb.c (t 2 ) and η.sub.β.sbsb.c (t 3 ) at times t 1 , t 2 and t 3 ,, respectively, and performing the following division. ##EQU20##

Claim 11

A method according to claim 9, in which the step of determining said Tafel slope β c includes the steps of sampling said polarization potential is carried out such that: η.sub.β.sbsb.c (t.sub.2)-η.sub.β.sbsb.c (t.sub.1)=η.sub.β.sbsb.c (t.sub.3)-η.sub.β.sbsb.c (t.sub.2)=Δη.sub.β.sbsb.c' and performing the following division: ##EQU21##

Claim 12

A method according to claim 2, in which the step of determining said Tafel slope β c of cathodic reaction includes the steps of sampling the variation of the polarization potentials η.sub.β.sbsb.c (t) to obtain polarization potentials η.sub.β.sbsb.c (t 1 ), η.sub.β.sbsb.c (t 2 ), η.sub.β.sbsb.c (t 3 ), . . . η.sub.β.sbsb.c (t n ) at times t 1 , t 2 , t 3 , . . . t n , respectively, such that η.sub.β.sbsb.c (t.sub.1)-η.sub.β.sbsb.c (t.sub.2)=η.sub.β.sbsb.c (t.sub.2)-η.sub.β.sbsb.c (t.sub.3)= . . . =η.sub.β.sbsb.c (t.sub.n -1)-η.sub.β.sbsb.c (t.sub.n)=Δη.sub.β.sbsb.c and performing the following division: β.sub.c =Δη.sub.β.sbsb.c /logδ where ##EQU22##

Claim 13

A method according to claim 1, in which said predetermined polarization potential η R is -30 mv ≦η R ≦30 mv .

Claim 14

A method according to claim 11, in which said predetermined polarization potential η R is -10 mv ≦η R ≦10 mv .

Claim 15

A method according to claim 2, in which said predetermined polarization potential η.sub.β.sbsb.a is 30 mV or more.

Claim 16

A method according to claim 13, in which the predetermined polarization potential η.sub.β.sbsb.a is +50 mV or more.

Claim 17

A method according to claim 2, in which said predetermined polarization potential η.sub.β.sbsb.c is -30 mV or less.

Claim 18

A method according to claim 15, in which the predetermined polarization potential η.sub.β.sbsb.c is -50 mV or less.

Claim 19

A method according to claim 2, including, after completion of any one of said steps, the step of applying a predetermined bias voltage to said test piece, thereby bringing the potential of the test piece back to said test piece's natural electroless deposition potential E ELP .

Claim 20

A method according to claim 2, in which the step of calculating said electroless deposition current density I ELP of the test piece includes the step of performing the following multiplication: I.sub.ELP =(K/2.3)/R.sub.ELP, where K=β.sub.a β.sub.c /(β.sub.a +β.sub.c).

Claim 21

A method according to claim 19, including the step of calculating the electroless deposition rate V ELP of the metal test piece by performing the following multiplication: V.sub.ELP =(M/n·F)·I.sub.ELP, where M denotes the atomic weight of the metal deposited on the test piece, n the valence of the deposited metal ion, and F the Faraday constant.

Claim 22

A method according to claim 20, including the step of calculating the weight W ELP of metal deposited on the test piece by performing the following multiplication: W.sub.ELP =(M/n·F)·Q.sub.ELP, where Q ELP denotes the quantity of electricity consumed to deposit the metal for a period T, Q ELP being expressed as follows: ##EQU23##

Claim 23

A method according to claim 3, including the step of detecting how the differential capacitance C D (t) of the electrical double layer of the test piece changes as time elapses, thus evaluating the surface condition of the metal film deposited on the test piece in accordance with the C D (t)-t relationship.