JPH0290639A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To minimize the mechanical damage to a semiconductor element by a method wherein the bonding pressure conforming to the history of the deformation resistance of a material used for lead and bump electrode is specified to perform the bonding process in compliance therewith. CONSTITUTION:Assuming the bonding times O-to, to-tp and tp-termination T to be termed stage 1, stage 2 and stage 3, the profile of bonding pressure P in the stage 1 conforms to the profile of deformation resistance in the elasticity region of material (epsilon<=epsilono). At this time, the elastic deformation 0-epsilono corresponds to the bonding time O-to-(epsilon=epsilon.t). Within the stage 2, the profile of bonding pressure after exceeding the yield stress Y of the material conforms to the profile of deformation resistance in the plasticity region of material (epsilon>epsilono). During the unloading process, the profile of the bonding pressure in the stage 3 conforms to the profile of deformation resistance in the elasticity region of material similar to the case in the stage 1 in consideration of the spring back after the plasticity deformation of the material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of inner lead bonding of a semiconductor device with protruding electrodes.

[Conventional technology]

As a conventional technique, bonding of film carrier type semiconductor devices, that is, TAB (Tape
ILB (I
nnerLead Bonding) is performed as follows.

That is, copper foil is laminated onto a polyimide tape with sprocket holes, a lead pattern corresponding to a bonding wire is formed on this by photo-etching, and then a TAB tape plated with gold, tin, or solder and an electrode for external extraction are formed. A semiconductor element (bellet) having a protruding electrode (hereinafter referred to as a bump) formed thereon is prepared.

Then, polyimide tape and leads of a tape carrier made of gold, tin, or solder-plated copper foil are superimposed on this bang, and bonding is performed from above by applying heat and pressure with a bonding tool.

Alternatively, a lead pattern is formed on the TAB tape, half-etching is performed on the lead tip by photo-etching, a bump is formed on the lead tip, and then plating is performed with at least one metal layer (for example, gold). This lead is superimposed on the external lead electrode of a normal semiconductor element, and bonding is performed by applying pressure and heating from above using a bonding tool.

By the way, the method of applying pressure during bonding is shown in Figure 2 (
Electronic Materials, May 1985, quoted from PI3) and Figure 3 (Ha oral Technical Rep.
ort 187°Vol, 33. No. Quoted from I P23) As can be seen, the bonding pressure (load)
adopted a discontinuous step load for the bonding time.

[Problem to be solved by the invention]

The conventional bonding pressurization method described above is a step loading method that involves rapid changes in pressure (load) with respect to the bonding time, that is, a dynamic load is applied.

The bump and the semiconductor element substrate are each forced to undergo rapid deformation behavior at a strain rate i (j=dε/dt, where ε is the strain generated inside the material and t is time). Generally, as a material undergoes plastic deformation, work hardening of the material progresses, and the deformation resistance against external load (bonding pressure in this case) increases nonlinearly. In addition, the stress-strain curve of the material with respect to changes in strain rate and temperature is shown in Figure 4 (
Plasticity and plastic working, 2nd edition, 1977. Ohmsha.

As is clear from the above (quoted from page 9), the history changes. That is, the mechanical properties of the material change.

For these reasons, the conventional bonding pressurization method, which has a high strain rate, produces dynamic transient stress particularly on the semiconductor element substrate below the bump, resulting in excessive mechanical damage, such as brittle fracture on the semiconductor element substrate below the bump. Alternatively, there is a drawback that minute cracks are generated and propagated due to cleavage fracture, and these cracks further grow to cause macroscopic destruction of the semiconductor element substrate, that is, defects such as bump peeling occur.

An object of the present invention is to provide a method for manufacturing a semiconductor device that solves the above problems.

[Differences between the invention and the prior art]

In contrast to the conventional semiconductor device manufacturing method (bonding pressure method) described above, the present invention improves the work hardening and deformation resistance of the materials used for the TAB tape leads and bumps against bonding pressure (external load). The difference is that it uses a bonding pressure method that is consistent with the history, making it possible to further reduce mechanical damage to semiconductor elements.

[Means to solve the problem]

In order to achieve the above object, the present invention provides bonding using a thermocompression bonding process to a semiconductor device having a protruding electrode on either the lead end of a film carrier tape or an external lead-out electrode pad provided on a semiconductor element. In the manufacturing method, a bonding pressure is set in accordance with the history of deformation resistance of the material used for the lead and the protruding electrode, and bonding is performed in accordance with this.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

(Example 1) FIG. 1 is a diagram showing the relationship between bonding pressure (load) and bonding time showing Example 1 of the present invention. The history of this curve is expressed by the following formula: P=F,・εt
(IP=Y+F・(#-t-j
−t, )” f2j=dε/dt=Δε/Δt
(3 At this time, P is the bonding pressure (kg
f/l112F is the work hardening coefficient of the material (for example, about 2 for copper)
5 to 27 kgf#g+g''), Y is the static yield stress of the material (for example, about 25 to 27 kof/nm2 for copper), t
where t is the bonding time, t is the time required for the material to reach the elastic limit strain ε under a constant strain rate of 1 expressed by equation (2) (that is, t4 = ε, /me) - n is the material E is the work hardening index of the material (for example, around 0.3 for copper), and E is the longitudinal elastic modulus of the material (for example, about 0.7 x 10' to 1 for copper).
Ox10'kgf/nu')

The bonding time from 0 to t is stage 1, t, to t.
The period from t to the end is called stage 2, and the period from t to the end is called stage 3. In stage 1, the bonding pressure profile is expressed by equations (1) and (3), and this is determined by the elasticity of the material. It conforms to the profile of deformation resistance within the range (ε≦ε,). At this time, the elastic strain is 0 to ε, and the bonding time is 0 to 1. (ε=j−t). In stage 2, the bonding pressure profile after exceeding the yield stress Y of the material is expressed by equations (2) and (3), which are expressed in the plastic region of the material (
It conforms to the profile of deformation resistance at ε〉ε, ). At this time, as in stage 1, the plastic strain ε, ~
ε, is the bonding time t, ~1. <ε=i·t). Stages 1 and 2 are the loading process,
The pressure load is achieved according to the degree of work hardening of the material.

Stage 3 is a process of unloading, and takes into account springback after plastic deformation of the material, and conforms to the profile of deformation resistance within the elastic range of the material, as in stage 1.

Equation (3) determines the strain rate, where Δε is the strain increment, Δt is the bonding time increment, and dε/
dt is described in accordance with the definition of differential theory. This strain rate can be easily determined by determining the optimal size in a high-speed compression test. That is, high-speed compression tests are performed on the material under various strain rates t near a predetermined bonding temperature, and the relationship between stress σ and strain ε, which is the history of the material's deformation resistance, corresponding to each strain rate is determined. Quantitatively determine the relationship between strain rate t, stress σ, and strain when there is no large difference by comparing the history of stress σ - strain ε when performing a quasi-static compression test from among these. The relationship between stress σ and strain ε is replaced by the bonding pressure-bonding time curve from the following formula (4), which is a modified version of formula (3).

(Example 2) FIG. 5 is a diagram showing the relationship between bonding pressure and bonding time in Example 2 of the present invention. This is a linear approximation using the piecewise polynomial shown below.

At bonding time, 0~t, stage 1, t,~
1+ to stage 2, t, ~t2 to stage 3, t2 to t
, is called stage 4, t3 to t is called stage 5, and t to the end is called stage 6. In stage 1, after applying the preload P, the deformation resistance in the elastic region is increased as in Example 1. Bonding pressure load is applied according to the profile. In stages 2 to 5, the bonding time t, ~t, is divided into several intervals, and each interval is linearly approximated by the corresponding linear polynomial, and each is determined in the following form. Stage 2 P
+=α+jt (4 stage 3 P2=α
2jt (5 stage 4 P3=αsit
(6 stage 5 P4=α<jt
(7 These are generally expressed as P in any interval 1, = α1th t (1 = 1.2. -m, i is the number of segments) (8
), and is used in conjunction with equation (3) of Example 1.

Stage 6 is the unloading process as in Example 1, and the slope of the bonding pressure with respect to time is set equal to the longitudinal elastic modulus of the material in consideration of springback after plastic deformation of the material. .

From the above, this embodiment has the advantage that the load control of the bonding pressure can be linearly controlled, making the control easier.

〔Effect of the invention〕

As explained above, the present invention performs a high-speed compression test on materials used in semiconductor devices (particularly bumps) at a temperature near the bonding temperature, so that the effect of strain rate does not significantly affect the deformation resistance of the material. Know the strain rate of time,
By setting a pressure curve of bonding pressure (load) and time t in accordance with the deformation resistance history of stress σ - strain ε at this time, and performing bonding according to this, the semiconductor device to be bonded by thermocompression bonding process. atiIl
This has the effect of reducing physical damage.

[Brief explanation of drawings]

Figures 1 and 5 are diagrams showing bonding pressure curves in the present invention, Figures 2 and 3 are diagrams showing conventional bonding pressure curves, and Figure 4 is a diagram showing the temperature and strain rate of the material (copper). FIG. 4 is a diagram showing changes in the history (σ−ε) of the deformation resistance of the material. Y... Yield stress of material E... Longitudinal elastic modulus of material F... Work hardening coefficient of material t... Strain rate (=dε/dt) P, Po, P+, Pt, Ps, P4・... Bonding pressure α l - α 2 , α 1 , α 4 ... Proportionality constant t in each piecewise polynomial, ... Bonding time t+, t2 . . . until the elastic limit strain ε is reached. ti...Arbitrary bonding segment time t in each piecewise polynomial,...Time at which the bonding pressure loading process ends n...Work hardening index of the material σ...Stress ε...Strain t...・Bonding time diagram Figure 4. Bonding temperature diagram Figure 4

Claims (1)

[Claims] (1) In a manufacturing method in which bonding is performed by a thermocompression bonding process to a semiconductor device having a protruding electrode on either the lead end of a film carrier tape or an external lead-out electrode pad provided on a semiconductor element,
A method for manufacturing a semiconductor device, characterized in that a bonding pressure is set in accordance with the history of deformation resistance of materials used for the leads and the protruding electrodes, and bonding is performed in accordance with this.